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2007

This is to certify that the
thesis entitled

FAT TRANSPORT PROPERTIES AND MECHANISMS
DURING COOKING OF GROUND MEAT

presented by

MITRA CHOWDARY TRIPURANENI

has been accepted towards fulfillment
of the requirements for the

MS. degree in Biosystems and Agricultural
Engineering

 

 

fiflm

" Mamo'fessor’s Signature

[OX/W

ate

MSU is an Affirmative Action/Equal Opportunity Institution

 

LIBRARY
Michigan State
University

 

 

 

-.-o—o—o-o-o-n—n-o-.-n-.—.--. -

PLACE IN RETURN BOX to remove this checkout from your record.
TO AVOID FINES return on or before date due.
MAY BE RECALLED with earlier due date if requested.

 

DATE DUE DATE DUE DATE DUE

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2/05 p:/CIRC/DateDue.indd-p.1

FAT TRANSPORT PROPERTIES AND MECHANISMS DURING COOKING OF
GROUND MEAT

By

Mitra Chowdary Tripuraneni

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Biosystems and Agricultural Engineering

2006

ABSTRACT

FAT TRANSPORT PROPERTIES AND MECHANISMS DURING COOKING OF
GROUND MEAT

By
Mitra Chowdary Tripuraneni

Ground meat is a porous medium in which water and fat co-exist. During
cooking, the porous structure of the ground meat matrix changes continuously, thereby
affecting the transport of water and fat out of the meat matrix. Porosity, pore-size
distributions, and effective permeability of water through the ground beef matrix were
determined for different endpoint temperatures and initial fat contents. Low fat (5.5%)

and high fat (14.5%) ground beef samples were formed into patties and cooked in a
moist-air convection oven (T dry bulb of 176.7°C and T dew point of 939°C) to center

temperatures of 45, 60, and 75°C. These samples were then analyzed at room temperature
for pore-size distributions and permeability. The viscosity and density of beef fat was
determined with respect to temperature (40, 50, 60, and 70°C).

The median pore diameters increased (P<0.05) with temperature. The
permeability of low fat samples (2.85 x10'14 to 1.53 x10'13 m2) was higher than that of the
high fat samples (7.19 x 10''5 to 9.21 x10'15 m2) for all cooking treatments. The viscosity
of beef fat decreased with temperature from 34.25 cP at 40°C to 14.36 cP at 70°C. The
hydraulic conductivity, the lipidic conductivity, and the tortuosity of the ground beef
matrix were also calculated. All these parameters are essential for describing and

modeling the fat transport mechanism during cooking of ground meat products.

T o my Parents

iii

ACKNOWLEDGEMENTS

I would like to express my sincere appreciation to Dr. Bradley Marks for his
guidance and patience during my research and studies. I am grateful to him for his
support and understanding throughout my study. I would also like to thank Dr. James
Steffe and Dr. Alden Booren for their invaluable comments and time throughout this
project and serving on my committee. I would like to thank the Department of
Biosystems & Agricultural Engineering for providing me the opportunity to perform my
research. My sincere appreciation goes to the members of our research team especially
Dr. Alicia Orta Ramirez for helping me with various things. I would also like to thank all
the members of the PMI facility for helping me with both the machines. Last but not the
least; I would like to thank my parents and my husband for their support and
encouragement throughout my M.S. program. Of course, this project would not have
been possible without the financial support from the National Research Initiative of the

USDA Cooperative State Research: Education and Extension Service.

iv

TABLE OF CONTENTS

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

LIST OF FIGURES ..... viii
LIST OF TABLES - xiii
KEY TO SYMBOLS - xviii
1. INTRODUCTION AND OBJECTIVES ...... l
1.1. Problem Statement
1.2. Objectives - 3
2. REVIEW OF LITERATURE ......
2.1. Introduction
2.2. Meat Fats: Fat loss during Cooking and Cooking Models
2.3. Ground Meat Matrix- Porous nature __ 14
2.4. Multi—phase Fluid Flow— Porous media 24
2.4.1. Porous Media .................................................................................................. 25
2.4.2. Multiphase Fluid F low- Models ...................................................................... 28
2.4.2.1. Relative Permeability: Theory ..................................................................... 29
2.4.2.2. Relative permeability: Measurement ........................................................... 31
2.5. Summary 33
3. MATERIALS AND EXPERIMENTAL METHODS _ - 34
3.1. Overview 34
3.2. Meat — Sample Preparation - - - 35
3.2.1. Meat ................................................................................................................ 35
3.2.2. Pre-treatment—Laboratory oven cooking ...................................................... 36
3.3. Shrinkage - 38
3.4. Porosity and Pore-size distribution 38
3.4.1. Liquid Extrusion Porosimeter: Theory ........................................................... 39
3.4.2. Liquid Extrusion Porosimeter: Measurement ................................................. 41
3.5. Permeability 45
3.6. Fluid Properties of Fats 48
3.6.1. Sample Preparation ......................................................................................... 49

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3.6.2. Viscosity ......................................................................................................... 49
3.6.3. Density ............................................................................................................ 51
3.7. Relative Permeability Measurement - - 51
3.7.1. Theory ............................................................................................................. 51
3.7.2. Fat Transport Solution .................................................................................... 52
RESULTS AND DISCUSSION 56
4.1. Overview 56
4.2. Meat 57
4.3. Shrinkage .......... 57
4.4. Porosity and Pore-size distribution 58
4.4.1. Cumulative Pore Volume ................................................................................ 59
4.4.2. Accessible Porosity ......................................................................................... 66
4.4.3. Pore-distribution ............................................................................................. 68
4.4.4. Median Pore Diameters ................................................................................... 80
4.4.5. Pore Surface Area ........................................................................................... 81
4.5. Permeability- 83
4.5.1. Room Temperature ......................................................................................... 83
4.5.2. Elevated Temperature ..................................................................................... 87
4.6. Fluid Properties of Fat -- 90
4.7. Conductivity ______ 92
4.8. Tortuosity 94
4.9. Relative Permeability of Fat 99
4.10. Summary 102
CONCLUSIONS 104
FUTURE WORK _- 107
APPENDICES 111
7.1. Pore-size distribution Results - 112
7.2. Permeability Results 132
7.3. Pore-size distribution Results—Tests for Fat and Grind 148
7.4. Viscosity Results 153
7.5. Fat Analysis 157
7.6. Relative Permeability Results _ 158

vi

8. BIBLIOGRAPHY ----- _- -160

 

vii

LIST OF FIGURES

Figure 2.1: Schematic of the ground meat porous structure in which water and fat are
distributed. ................................................................................................................ 25

Figure 3.1: General arrangement of the laboratory convection oven showing directions of
steam and airflow. ..................................................................................................... 36

Figure 3.2: Schematic representation of the flow diagram of the PMI Liquid Extrusion
Porosimeter. .............................................................................................................. 41

Figure 3.3: Sketch illustration of the principle of the PMI Liquid Extrusion Porosimeter.

................................................................................................................................... 42
Figure 3.4: Schematic diagram of the sample chamber assembly for the PMI Liquid

Extrusion Porosimeter ............................................................................................... 44
Figure 3.5: Schematic representation of the principle of the PMI Permeameter. ............. 45
Figure 3.6: Schematic representation of the PMI Permeameter flow diagram. ................ 46
Figure 3.7: Schematic diagram of the sample chamber assembly for the PMI

Permeameter. ............................................................................................................ 48

Figure 3.8: Schematic diagram of the concentric cylinder viscometer used for viscosity
measurements on beef fat .......................................................................................... 50

Figure 4.1: Shrinkage percentage of the low fat and high fat ground beef samples cooked
to different endpoint temperatures. ........................................................................... 58

Figure 4.2: Cumulative pore volume as a function of pore diameter for low fat and high
fat raw ground beef samples: means of 5 replicates. ................................................ 59

Figure 4.3: Cumulative pore volume as a function of pore diameter for low fat and high
fat ground beef samples cooked to endpoint temperature of 45°C: means of 5
replicates. .................................................................................................................. 60

Figure 4.4: Cumulative pore volume as a function of pore diameter for low fat and high
fat ground beef samples cooked to endpoint temperature of 60°C: means of 5
replicates. .................................................................................................................. 60

Figure 4.5: Cumulative pore volume as a function of pore diameter for low fat and high

fat ground beef samples cooked to endpoint temperature of 75°C: means of 5
replicates. .................................................................................................................. 61

viii

Figure 4.6: Accessible porosity as a function of endpoint temperature for low fat and high
fat ground beef samples cooked to different endpoint temperatures. ....................... 67

Figure 4.7: Pore volume fractions at particular diameters for low fat and high fat ground
beef samples tested raw at room temperature using the Liquid Extrusion
Porosimeter: means of 5 replicates. .......................................................................... 71

Figure 4.8: Pore volume fractions at particular diameters for low fat and high fat ground
beef samples cooked to 45°C and tested at room temperature using the Liquid
Extrusion Porosimeter: means of 5 replicates ........................................................... 71

Figure 4.9: Pore volume fractions at particular diameters for low fat and high fat ground
beef samples cooked to 60°C and tested at room temperature using the Liquid
Extrusion Porosimeter: means of 5 replicates ........................................................... 72

Figure 4.10: Pore volume fractions at particular diameters for low fat and high fat ground
beef samples cooked to 75°C and tested at room temperature using the Liquid
Extrusion Porosimeter: means of 5 replicates ........................................................... 72

Figure 4.11: (a) Pore volume fractions (at particular diameters) for low fat ground beef
samples tested at raw and cooked to endpoint temperatures of 45, 60, and 75°C:
means of 5 replicates. (b) Same plot as (a), plotted as line graph instead of bar chart.
................................................................................................................................... 73

Figure 4.12: Pore volume fractions (at particular diameters) for high fat ground beef
samples tested at raw, and cooked to endpoint temperatures of 45, 60, and 7 5°C:
means of 5 replicates. (b) Same plot as (a), plotted as x-y graph instead of bar chart.
................................................................................................................................... 74

Figure 4.13: Pore surface area of low fat and high fat ground beef samples tested at raw,
and cooked to endpoint temperatures of 45, 60, and 75°C: means of 5 replicates. .. 82

Figure 4.14: Permeability of low fat ground beef samples tested at raw, and cooked to
endpoint temperatures of 45, 60, and 75°C: means of 4 replicates. .......................... 84

Figure 4.15: Permeability of high fat ground beef samples tested at raw, and cooked to
endpoint temperatures of 45, 60, and 75°C: means of 4 replicates ........................... 84

Figure 4.16: Apparent viscosity of beef fat as a function of temperature determined using
a rotational viscometer: means of 3 replicates. ......................................................... 91

Figure 4.17: Density of beef fat as a function of temperature: means of 3 replicates. ..... 91

Figure 7.1: Permeability of raw low fat samples 1 through 4, tested at room temperature
using the PMI Permeameter. ................................................................................... 132

ix

Figure 7.2: Permeability of low fat samples 1 through 4, cooked to endpoint temperature
of 45°C and tested at room temperature using the PMI Permeameter. ................... 133

Figure 7.3: Permeability of low fat samples 1 through 4, cooked to endpoint temperature
of 60°C and tested at room temperature using the PMI Permeameter. ................... 134

Figure 7.4: Permeability of low fat samples 1 through 4, cooked to endpoint temperature
of 75°C and tested at room temperature using the PMI Permeameter. ................... 135

Figure 7.5: Permeability of raw high fat samples 1 through 4, tested at room temperature
using the PMI Permeameter. ................................................................................... 136

Figure 7.6: Permeability of high fat samples 1 through 4, cooked to endpoint temperature
of 45°C and tested at room temperature using the PMI Permeameter. ................... 137

Figure 7.7: Permeability of high fat samples 1 through 4, cooked to endpoint temperature
of 60°C and tested at room temperature using the PMI Permeameter. ................... 138

Figure 7.8: Permeability of high fat samples 1 through 4, cooked to endpoint temperature
of 75°C and tested at room temperature using the PMI Permeameter. ................... 139

Figure 7.9: Permeability of low fat samples 1 through 4, cooked to endpoint temperature
of 45°C and tested at 45°C using the PMI Permeameter. ....................................... 140

Figure 7.10: Permeability of low fat samples 1 through 4, cooked to endpoint temperature
of 60°C and tested at 60°C using the PMI Permeameter. ....................................... 141

Figure 7.11: Permeability of low fat samples 1 through 4, cooked to endpoint temperature
of 45°C and tested at 60°C using the PMI Permeameter. ....................................... 142

Figure 7.12: Permeability of low fat samples 1 through 4, cooked to endpoint temperature
of 60°C and tested at 45°C using the PMI Permeameter. ....................................... 143

Figure 7.13: Permeability of high fat samples 1 through 4, cooked to endpoint
temperature of 45°C and tested at 45°C using the PMI Permeameter. ................... 144

Figure 7.14: Permeability of high fat samples 1 through 4, cooked to endpoint
temperature of 60°C and tested at 60°C using the PMI Permeameter. ................... 145

Figure 7.15: Permeability of high fat samples 1 through 4, cooked to endpoint
temperature of 45°C and tested at 60°C using the PMI Permeameter. ................... 146

Figure 7.16: Permeability of high fat samples 1 through 4, cooked to endpoint
temperature of 60°C and tested at 45°C using the PMI Permeameter. ................... 147

Figure 7.17: Pore volume distributions (at particular diameters) of raw low fat, high fat
and re-ground high fat ............................................................................................. 149

Figure 7.18: Pore volume distributions (at particular diameters) of raw low fat, high fat
and low-high fat (low fat samples which were made to high fat by adding ground fat
tissues) ..................................................................................................................... 151

Figure 7.19: Pore volume distributions (at particular diameters) of low fat samples
cooked to endpoint temperatures of 45, 60, and 75°C in a convection oven at 60%
moisture by air volume. .......................................................................................... 152

Figure 7.20: Pore volume distributions (at particular diameters) of high fat samples
cooked to endpoint temperatures of 45, 60, and 75°C in a convection oven at 60%
moisture by air volume. .......................................................................................... 152

Figure 7.21: Apparent viscosity of beef fat at 40°C (sample 1), determined using a
rotational viscometer ............................................................................................... 153

Figure 7.22: Apparent viscosity of beef fat at 40°C (sample 2), determined using a
rotational viscometer ............................................................................................... 153

Figure 7.23: Apparent viscosity of beef fat at 50°C (sample 1), determined using a
rotational viscometer ............................................................................................... 154

Figure 7.24: Apparent viscosity of beef fat at 50°C (sample 2), determined using a
rotational viscometer ............................................................................................... 154

Figure 7.25: Apparent viscosity of beef fat at 60°C (sample 1), determined using a
rotational viscometer. .............................................................................................. 155

Figure 7.26: Apparent viscosity of beef fat at 60°C (sample 2), determined using a
rotational viscometer ............................................................................................... 155

Figure 7.27: Apparent viscosity of beef fat at 70°C (sample 1), determined using a
rotational viscometer ............................................................................................... 156

Figure 7.28: Apparent viscosity of beef fat at 70°C (sample 2), determined using a
rotational viscometer ............................................................................................... 156

Figure 7.29: Flow curve during relative permeability experiments at a pressure step of
0.86 psi (5928 Pa). .................................................................................................. 158

Figure 7.30: Flow curve during relative permeability experiments at a pressure step of 1.2
psi (8271 Pa). .......................................................................................................... 158

xi

Figure 7.31: Flow curve during relative permeability experiments at a pressure step of
1.54 psi (10615 Pa). ................................................................................................ 159

Figure 7.32: Flow curve during relative permeability experiments at a pressure step of
1.87 psi (12890 Pa). ................................................................................................ 159

xii

LIST OF TABLES

Table 4.1: Analysis of variance for the total cumulative pore volume of low fat ground
beef samples as affected by endpoint temperature. .................................................. 63

Table 4.2: Analysis of variance for the total cumulative pore volume of high fat ground
beef samples as affected by endpoint temperature. .................................................. 64

Table 4.3: Two-way Analysis of variance for the total cumulative pore volume of high fat
ground beef samples as affected by endpoint temperature and fat content. ............. 64

Table 4.4: Data from pore-size distribution tests on raw low fat sample 1 from the Liquid
Extrusion Porosimeter software. ............................................................................... 69

Table 4.5: Data from raw low fat sample 1 set where pore diameters were categorized
into groups. ............................................................................................................... 70

Table 4.6: Median pore diameters of low fat and high fat samples at different treatment
conditions determined using the Liquid Extrusion Porosimeter: means of 5

replicates. .................................................................................................................. 81

Table 4.7: Two-way Analysis of variance for median pore diameters of low fat and high
fat samples with respect to endpoint temperature and fat content. ........................... 81

Table 4.8: Two-way Analysis of variance for permeability of low fat and high fat samples
with respect to endpoint temperature and fat content. .............................................. 87

Table 4.9: Perrneabilities of the low fat and the high fat samples at elevated temperatures

of 45 and 60°C: means of 4 replicates. ..................................................................... 88
Table 4.10: Two-way Analysis of variance for permeability of the low fat and high fat

samples with respect to test temperature and fat content .......................................... 90
Table 4.11- Densities and viscosities of water and beef fat at various temperatures. ...... 93

Table 4.12- Hydraulic and lipidic conductivities of the low fat and high fat samples at
different treatment conditions. .................................................................................. 93

Table 4.13: Tortuosity of the low fat and high fat ground beef samples at different
treatment conditions .................................................................................................. 99

Table 4.14: Relative Permeability of beef fat within the low fat samples cooked and
tested at 60°C. ......................................................................................................... 101

xiii

Table 7.1: Data from pore-size distribution test on raw low fat sample 2 using the Liquid
Extrusion Porosimeter ............................................................................................. 112

Table 7.2: Data from pore-size distribution test on raw low fat sample 3 using the Liquid
Extrusion Porosimeter ............................................................................................. 112

Table 7.3: Data from pore-size distribution test on raw low fat sample 4 using the Liquid
Extrusion Porosimeter................................... .......................................................... 113

Table 7.4: Data from pore-size distribution test on raw low fat sample 5 using the Liquid
Extrusion Porosimeter ............................................................................................. 113

Table 7.5: Data from pore-size distribution test on low fat sample I cooked to endpoint
temperature of 45°C. ............................................................................................... 114

Table 7.6: Data from pore-size distribution test on low fat sample 2 cooked to endpoint
temperature of 45°C. ............................................................................................... 114

Table 7.7: Data from pore-size distribution test on low fat sample 3 cooked to endpoint
temperature of 45°C. ............................................................................................... 115

Table 7.8: Data from pore-size distribution test on low fat sample 4 cooked to endpoint
temperature of 45°C. ............................................................................................... 115

Table 7.9: Data from pore-size distribution test on low fat sample 5 cooked to endpoint
temperature of 45°C. ............................................................................................... 116

Table 7.10: Data from pore-size distribution test on low fat sample I cooked to endpoint
temperature of 60°C. ............................................................................................... 116

Table 7.11: Data from pore-size distribution test on low fat sample 2 cooked to endpoint
temperature of 60°C. ............................................................................................... 117

Table 7.12: Data from pore-size distribution test on low fat sample 3 cooked to endpoint
temperature of 60°C. ............................................................................................... 117

Table 7.13: Data from pore-size distribution test on low fat sample 4 cooked to endpoint
temperature of 60°C. ............................................................................................... 118

Table 7.14: Data from pore-size distribution test on low fat sample 5 cooked to endpoint
temperature of 60°C. ............................................................................................... 118

Table 7.15: Data from pore-size distribution test on low fat sample I cooked to endpoint
temperature of 75°C. ............................................................................................... 119

xiv

Table 7.16: Data from pore-size distribution test on low fat sample 2 cooked to endpoint
temperature of 75°C. ............................................................................................... 119

Table 7.17: Data from pore-size distribution test on low fat sample 3 cooked to endpoint
temperature of 75°C. ............................................................................................... 120

Table 7.18: Data from pore-size distribution test on low fat sample 4 cooked to endpoint
temperature of 75°C. .......................................................... 120

Table 7.19: Data from pore-size distribution test on low fat sample 5 cooked to endpoint
temperature of 75°C. ............................................................................................... 121

Table 7.20: Data from pore-size distribution test on raw high fat sample 1 using the
Liquid Extrusion Porosimeter. ................................................................................ 121

Table 7.21: Data from pore-size distribution test on raw high fat sample 2 using the
Liquid Extrusion Porosimeter. ................................................................................ 122

Table 7.22: Data from pore-size distribution test on raw high fat sample 3 using the
Liquid Extrusion Porosimeter. ................................................................................ 122

Table 7.23: Data from pore-size distribution test on raw high fat sample 4 using the
Liquid Extrusion Porosimeter. ................................................................................ 123

Table 7.24: Data from pore-size distribution test on raw high fat sample 5 using the
Liquid Extrusion Porosimeter. ................................................................................ 123

Table 7.25: Data from pore-size distribution test on high fat sample I cooked to endpoint
temperature of 45°C. ............................................................................................... 124

Table 7.26: Data from pore-size distribution test on high fat sample 2 cooked to endpoint
temperature of 45°C. ............................................................................................... 124

Table 7.27: Data from pore-size distribution test on high fat sample 3 cooked to endpoint
temperature of 45°C. ............................................................................................... 125

Table 7.28: Data from pore-size distribution test on high fat sample 4 cooked to endpoint
temperature of 45°C. ............................................................................................... 125

Table 7.29: Data from pore-size distribution test on high fat sample 5 cooked to endpoint
temperature of 45°C. ............................................................................................... 126

Table 7.30: Data from pore-size distribution test on high fat sample I cooked to endpoint
temperature of 60°C. ............................................................................................... 126

XV

Table 7.31: Data from pore-size distribution test on high fat sample 2 cooked to endpoint
temperature of 60°C. ............................................................................................... 127

Table 7.32: Data from pore-size distribution test on high fat sample 3 cooked to endpoint
temperature of 60°C. ............................................................................................... 127

Table 7.33: Data from pore-size distribution test on high fat sample 4 cooked to endpoint
temperature of 60°C. .......................................................... 128

Table 7.34: Data from pore-size distribution test on high fat sample 5 cooked to endpoint
temperature of 60°C. ............................................................................................... 128

Table 7.35: Data from pore-size distribution test on high fat sample I cooked to endpoint
temperature of 75°C. ............................................................................................... 129

Table 7.36: Data from pore-size distribution test on high fat sample 2 cooked to endpoint
temperature of 75°C. ............................................................................................... 129

Table 7.37: Data from pore-size distribution test on high fat sample 3 cooked to endpoint
temperature of 75°C. ............................................................................................... 130

Table 7.38: Data from pore-size distribution test on high fat sample 4 cooked to endpoint
temperature of 75°C. ............................................................................................... 130

Table 7.39: Data from pore-size distribution test on high fat sample 5 cooked to endpoint
temperature of 75°C. ............................................................................................... 131

Table 7.40: Data from pore-size distribution test on raw re-ground high fat sample 1
using liquid extrusion porosimeter .......................................................................... 148

Table 7.41: Data from pore-size distribution test on raw re-ground high fat sample 2
using liquid extrusion porosimeter .......................................................................... 148

Table 7.42: Data from pore-size distribution test on raw re-ground high fat sample 3
using liquid extrusion porosimeter .......................................................................... 149

Table 7.43: Data from pore-size distribution test on raw low-high fat (low fat samples
which were made to high fat by adding ground fat tissues) sample 1 using liquid
extrusion porosimeter .............................................................................................. 150

Table 7.44: Data from pore-size distribution test on raw low-high fat (low fat samples

which were made to high fat by adding ground fat tissues) sample 2 using liquid
extrusion porosimeter .............................................................................................. 150

xvi

Table 7.45: Data from pore-size distribution test on raw low-high fat (low fat samples
which were made to high fat by adding ground fat tissues) sample 3 using liquid
extrusion porosimeter .............................................................................................. 151

Table 7.46: Fat analysis of low fat and high fat samples after cooking to different

endpoint temperatures in a convection oven at different humidities (60 and 80%
moisture by volume), expressed as fatzprotein ratio (FzP) ...................................... 157

xvii

Letters

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KEY TO SYMBOLS

Cross-sectional area (m2)
Pore diameter ( pm)

Diameter of the patty after cooking (m)

Diameter of the patty before cooking (m)

Fat capillary diffusivity (cmz/s)

Initial dry-basis fat content (g fat/ g dry matter)
Hydraulic potential (m)

Hydraulic conductivity (m/s)

Sample thickness (m)

Effective path length (m)

Torque (N -m)

Pressure (N/mz)

Volume flow (m3/s)

Saturation

Temperature (°C)

Volumetric fluid flow rate (m3/s)

Volume (m3)

Volume of the pores (m3)

Bulk volume (m3)

Volume of the fluid (m3)

Total void volume (m3)

Volume of extruded liquid at a particular diameter (m3)
Total volume of extruded liquid (m3)

Volume fraction
Flow rate distribution over pore diameters (,um'l )
Gravitational acceleration (m/sz)

Elevation; height of the rotor (m)
ith phase.

Permeability (m2)
Relative permeability of the ith phase

Capillary pressure (N/mz)
Oil phase

Water, wetting fluid (water)
Non-wetting fluid (oil)
Distance along flow (m)

xviii

Time (s)

17 , v Flow velocity; volumetric flux (m/s)
Greek Symbols

6 Pore diameter (,um)

(1(6) Pore—size distribution

Afli

fithVCbQfiep

Volume fraction of pores in the ith class

Mobility of oil phase (m3.s/kg)
Tortuosity of the medium

Shear stress (N/mz)

Solid-liquid contact angle (degrees)
Surface tension of liquid (dynes/cm)

Fat apparent viscosity (cP)
Fluid Viscosity (cP)
Density (kg/m3)

Porosity

xix

1. INTRODUCTION AND OBJECTIVES

1.1. Problem Statement

Fat has a considerable influence on the sensory characteristics of meat products,
such as flavor, mouth feel, juiciness, and texture. At room temperature, most of the fat in
mammalian muscle tissue exists in solid form. As the meat temperature exceeds the
melting point of the fat during cooking, the fat melts and starts to move out of the meat
matrix. The fat released upon cooking stimulates salivation; therefore, meat with a high
amount of fat is perceived to be juicy and tender. Prior research suggests that there is
considerable fat loss during cooking of ground meat products (Dagerskog, 1979; Troutt et
a1. 1992; Young et a1. 1991; Sheridan and Shilton, 2002; Badiani et al. 2002; Watkins and
Marks, 2002). In addition to the impact on quality, fat loss during cooking reduces
cooking yields and therefore economic returns for commercial cooking systems.

Water-based cooking losses are mostly evaporative losses, but fat-based cooking
losses are mainly in the form of drip (Sheridan and Shilton, 2002). Thus, mass transfer
within the product will result in mass loss in two forms, as vapor and as drip from the
product. As the fat melts during cooking, it can flow and affect the energy balance within
the product. Because of this, fat plays an important role in mass transfer during cooking
of meat. However, many of the present heat and mass transfer cooking models neglect fat
transport. This is because fat losses were often considered to be minor, relative to water
losses. But, research also suggests that fat transport can contribute up to 6% yield losses
for ground beef (initially 17.5% fat) and up to 28% yield losses for ground pork patties

(initially 41.9% fat) cooked in a convection oven (Watkins and Marks, 2002). This

suggests that fat transport has a significant impact on the cooking losses; therefore, a
more thorough understanding of the fat transport mechanism during cooking of ground
meat products would help improve cooking models and aid in process improvement.

The ground meat matrix can be considered as a porous medium. Porosity and
permeability are the two most important properties of a porous medium. During cooking,
the porosity of the meat changes continuously (Murphy and Marks, 1999; Kova'csne et
a1. 2005). The changing matrix potential can influence the liquid holding capacity of
ground meat and increase the complexity of the heat and mass transfer process.
Therefore, an evaluation of the changes in the porous structure of the meat matrix, in
terms of the porosity and pore-size distributions during cooking of ground meat, is
important to understanding and modeling the fat transport mechanism.

Permeability is another important property of the porous medium. It is the ability
of the porous medium to permit flow. Because fat transport is a type of convective flow
through the medium, it is important to know the permeability of the ground meat matrix.
Most foods are porous in nature; however, permeability studies in food related research is
rare. Hence, it is important to evaluate the permeability of the meat matrix, to further
develop efficient cooking models that include fat transfer.

Research suggests that fat transport should also depend on the physical structure
and composition of the fat itself. Animal fats are complex fluids, which are solid at room
temperature. As the fat melts during cooking, it begins to transport out of the meat
matrix. Viscosity is a property that measures the resistance offered by a fluid to flow.
Hence, fat transport during cooking may also depend on the rheological properties of fat

such as viscosity.

It is essential to determine some of the basic properties defining the porous meat
structure and the fluid properties of the fat, before modeling the fat transport mechanism
during cooking. This will lead to a more mechanistic formulation for modeling fat
transport during cooking of meat products. Knowledge of these properties is the basis for
developing those cooking models that will help improve design and operation of

commercial cooking systems and thereby improve product yield.

1.2. Objectives

The porous structure of the ground meat significantly influences the many
transport processes that occur during cooking. These transport processes depend on the
material properties of the porous medium (ground meat) and the fluid properties of the
fluids (water and fat). Therefore, the overall goal of this research was to quantify the
effects of cooking on the porosity and permeability of ground beef and to determine the
lipidic conductivity of beef fat within the ground beef patty as a firnction of product
endpoint temperature. This conductivity is an important parameter, which is needed to
better describe the fat transport mechanism in the cooking models. Hence, knowledge of
these parameters will aid the effectiveness of future cooking models and will facilitate
optimizing the cooking process for product yield. Therefore, the specific objectives of

this study were to:

l.

Analyze the changes in the ground beef microstructure, porosity, pore-size
distributions, and water permeability after convection cooking (30-80°C) of
ground beef.

Analyze the fat transport properties by determining the density, viscosity, and
lipidic conductivity of beef fat through the ground beef matrix.

Determine the relative permeability of beef fat with respect to water in a ground

beef matrix.

2. REVIEW OF LITERATURE

2.1. Introduction

Fat loss during cooking has a significant effect on the cooking yield of ground
meat products. Therefore, it is important to understand the fat transport mechanism that
occurs during cooking of ground meat products. The ground meat matrix is a porous
medium, where water and fat co-exist. Almost 70% of meat is comprised of water.
During cooking, water and fat losses combine to cause cooking losses. Water losses are
mostly by evaporation, but fat losses are mainly in the form of drip. Because meat cannot
be devoid of water, in order to fully understand the fat transport mechanism, a multi-
phase fluid flow model is needed. Two-fluid flows are mostly encountered in ground
water hydrology and petroleum engineering related works. This type of work is very
rarely found in food related research.

Because the present work is related to two fluids flowing in a porous meat matrix,
it has its roots from two different sources of literature. Therefore, this literature review is
divided into three sections: one discusses meat fats, cooking losses, and cooking models
from food related research; the second discusses the porous nature of ground meat and
the importance of determining porosity, permeability, and pore-size distributions; and the

third discusses porous medium properties and two-phase fluid flows, drawing on ground

water hydrology and petroleum engineering research.

2.2. Meat Fats: Fat loss during Cooking and Cooking Models

Meat fats usually encompass all the lipid species, including triglycerides,
phospholipids, sterols, and sterol esters, and other lipids in minute quantities if present.
Triglycerides predominate in meat fats, although small amounts of mono- and
diglycerides may be present (Dugan Jr, 1987). Saturated fatty acids and mono-
unsaturated fatty acids are dominant in meat fat triglycerides. Meat fats usually are rich in
stearic, palmitic, and oleic acids and contain small amounts of other acids (Dugan Jr,
1987). The fatty acid content varies in different animals and is influenced by factors such
as age, diet and environment (Dugan Jr, 1987).

Ground meat is mainly composed of water (~70%), the remaining being proteins
and fat. Meat with high fat content will have lower amounts of protein and water. During
cooking of ground meat patties, water and fat are lost in the form of cooking juices. Fat
loss during cooking may be influenced by many factors. During double-sided grilling of
beef patties, Dagerskog (1979) and Dagerskog and Bengtsson (1974) reported that fat
losses depended on initial fat content, but not on grill temperature. When cooking ground
beef patties (23.8% fat) to varying endpoint temperatures in a water bath, Pan and Singh
(2001) reported that holding time (the time for which the samples are held at a specific
temperature) had a significant effect on fat loss, supporting the importance of fat loss as a
transport process, not as a state variable. Other studies indicated that fats from different
species (e.g., beef, pork, turkey) show different melting profiles (Skala et al. 1989), and
thus behave differently during cooking. This suggests that fat loss also depends on the

physical and chemical structure of the fats.

Previous studies have also shown that fat contributes disproportionately to
cooking losses, relative to water. Dagerskog (1979) and Dagerskog and Bengtsson (1974)
reported that fat losses contributed to a high fraction of the yield loss during double-sided
grilling of beef patties (up to ~ 30% of the total yield loss for 14% fat patties). While
cooking ground beef patties containing 5-30% fat content, Troutt et a1. (1992) reported
that cooking losses were lowest for 5-20% fat patties, intermediate for 25% fat patties,
and highest for 30% fat patties. This suggests that cooking losses increase with fat
content. While cooking beef burger patties using far infrared radiation, Sheridan and
Shilton (2002) reported that fat content played a greater part in the rate of drip loss than
did heating method. Water-based cooking loss was mostly by evaporation, and fat-based
cooking loss was exclusively in drip. Generally, differences in fat levels of ground meat
products have affected the quality of cooked products.

When cooking ground meat patties in a convection oven, Watkins and Marks
(2002) reported that fat content has a significant effect on the cooking time for ground
turkey, ground beef, and ground pork. Fat transport contributed up to 6% yield losses for
ground beef (17.5% fat content) and up to 28% yield losses for ground pork patties
(41.9% fat content). Higher fat samples of ground beef and ground pork cooked faster
than the lower fat samples. However, in ground turkey the opposite was true. In another
study, while cooking ground pork patties of different fat levels (5, 10, 15, 20, and 25%
fat) in a microwave oven, Jeong et al. (2004) reported that total cooking losses and drip
losses were highest for 25% fat patties and lowest for 5% fat patties. Higher fat content
improved the heating rate, as low fat patties required longer heating times than did high

fat patties to reach the target center temperature. This was attributed to the low specific

heat capacity of fat compared to water. Also, the amount of air pockets in cooked patties
increased with increasing fat levels. They reported that the voids are caused by the
translocation of the rendered fat during cooking.

While cooking frozen ground beef burger patties in a double-sided pan fryer,
Kova’csne et al. (2004) reported that fat loss depended on the initial fat content of the
beef burgers. However, the higher fat content of the patties retarded the heating time
significantly. This was attributed to the low thermal conductivity of fat. Fat loss was
related to the shrinkage of meat patties during cooking, which in turn was affected by the
amount of connective tissue. These results are in direct opposition with the results from
the previous study, where Jeong et al. (2004) reported that higher fat content improved
the heating rate. However, it has to be noted that the basic principles (dielectric properties
and microwave frequencies) of microwave cooking are very different from pan-frying,
due to potentially different boundary conditions.

In a latter study by the same group (Kova'csne et al. 2005), the cooking
temperature did not affect the cooking losses. However, the initial fat content of the
patties and the patty diameter significantly affected the fat losses. The fat loss varied
considerably from 1.3% in the lean burger (6.7% fat) to 30.4% in the high fat meat (39%
fat). High fat contents of the patties resulted in higher radial shrinkage of the patties. The
porosity of the patties was influenced by the pan temperature, patty diameter, and fat
content. Several other studies (Young et al. 1991; Badiani et al. 2002) reported that there
is considerable fat loss during cooking.

While comparing fat holding capacity between beef burgers and emulsion

sausages, Andersson et al. (2000) reported that fat losses during cooking were greater for

beef burgers compared to emulsion sausages. This is attributed to the lack of stability in
the fat and a lack of a well-established protein network in the beef burgers. Because
emulsified products are more finely comminuted compared to beef burgers, the protein
structure is more widely dispersed and has a better fat holding capacity. On the other
hand, the structure of the beef burgers is mainly composed of more or less intact muscle
fibers and fiber bundles. These greater fat losses can be also attributed to the fact that the
structure of the beef burgers contains much larger pore sizes when compared to
emulsified products. Image analysis of these two products showed that fat in the beef
burgers is mostly in the form of fat cell aggregates and separate fat cells and only to a
minor extent in the form of small droplets, whereas fat in the emulsified products exists
in the form of small droplets and larger fat pools. Because emulsified fat is more stable
than fat encapsulated in the fatty tissue, the study reported that fat losses are mainly
related to the transportability of the fat from the inner to the outer part of the product.
Therefore, the major observation of this study was that frying/cooking losses depend on
both the properties of the fat and the properties of the surrounding protein network.

While studying the effect of animal fats and vegetable oils on the quality and
stability of beef patties, Dzudie et al. (2004) reported that cooking losses were highest for
patties containing vegetable oils when compared to patties containing beef and pork fats.
This suggests that fat transport is certainly dependent on the transportability of these fats,
which in turn depends on the nature and composition of these fats. Hence, the structure
of the porous ground meat matrix as well as the viscosity of the fat are important

properties that are essential in understanding the fat transport mechanism. All of the

above studies suggest that fat loss is a major component of cooking loss and that it can
and should be modeled as a transport process.

However, very little published literature has included fat loss as a transport
process during modeling of cooking processes. Pan et al. (2000) proposed a model for
contact cooking of hamburger patties that includes a fat transfer component. The water
and fat holding capacities were modeled as empirical functions of temperature and initial
concentration, but not time. Mass transfer of water and fat was assumed to be due to the

capillary flow of water and liquid fat partially resulting from protein denaturation and

phase change of fat.
_ (_§we(T_Two ))
mwe _ mwoe [2.1]
(-5 (T-T ))
_ fe f0
mfe “ mfoe [2.2]
where:
m

we and m fe are the water and fat concentrations at a specific temperature,

m

wo and m f0 are the initial water and fat concentrations,

5

we and 6f? are constants which were determined experimentally,

T W and T f0 are the temperatures at which water and fat transfer begin.

The water and fat transfer rates were determined using the following relations:

10

am
at

 

W : _Kw (mw — mwe) [2.3]

amf _

’67 '- _Kf (m; " m/e) [2.4]

where:

Kw and Kfare constants which were determined experimentally

The constants were determined by the experimental measurement of water and fat
holding capacities as a function of temperature. Thus, using these equations, models for
mass transfer of water and fat were solved via finite difference formulations. However,
the shrinkage of the meat patties and the resulting changes in the meat matrix during
cooking were not taken into account.

Mittal and Zhang (2001) used a diffusion model with a convective boundary
condition to describe moisture and fat transport during deep fat frying of meatballs. The
assumptions of their model were satisfactory for immersion frying, but not relevant to
oven cooking (i.e., air convection), due to a potentially large dimensional change of the
product and the lack of a convective boundary condition for fat transfer at the product
surfaces.

Shilton et al. (2002) also included fat in a model for cooking of beef patties by
far-infrared radiation. One-dimensional heat and mass transfer equations were used to
describe cooking. An evaporative boundary condition was used for mass transfer, and
values for the mass diffirsion coefficient were found using an empirical fit of the
experimental data. Because heat transfer in ground meat during cooking is not entirely by

conduction, the model was not accurate for meat containing high fat contents. Therefore,

11

a term for internal convection was included to improve the accuracy and effectively
model the cooking process. This resulted in a satisfactory prediction of experimental
results. They reported that heat transfer in ground beef patties is strongly influenced by
internal movement of melted fat by convection during the cooking process. This implies
that fat transport plays an important role in modeling the cooking process of ground meat
products. However, this approach did not directly account for the fundamental driving
forces for the fat transport, such as shrinkage of the product and the resulting increase in
internal pressure. Therefore, such a formulation is not easily extendible to other products
and processes.

Watkins and Marks (2002) described fat transport using a diffusion-based model.

The diffusion model was:

91:- 1%,) 61].3(D 61]
6t far ' “W“"ar 62 “Rf/"“62 [2'5]

where, Dam/a, is the capillary diffusivity of fat in the product.

According to Darcy’s law of capillary diffusion for transport of fluids through
porous media, the concentration gradient across the spatial dimension was used to
describe the fat transport mechanism. The capillary diffusivity is a function of the
material and the fluid properties. However, one of the assumptions of this study is that
there is no significant change in the porosity of the sample. This assumption may not be
true, because research suggests that porosity increases during cooking of ground meat
(Murphy and Marks, 1999; Kova'csne et al. 2005). This suggests that increasing pressure

due to shrinkage and changing matrix potential of the ground meat matrix causes the

12

more complex part of the cooking. Therefore, because capillary diffusivity is a function
of the material and the fluid properties, it is important to determine these changes with

respect to temperature.

While conducting fat holding capacity experiments, Tripuraneni et al. (2006)
reported that fat loss was a function of meat species, the initial fat content, and the
cooking temperature. The fat holding capacity was described as the ability of the meat
matrix to hold the fat during cooking. Fat holding capacity (FHC) was modeled as

empirical functions of initial fat content (F a) and cooking temperature (T):

FHC=fl0+A*T+fl2*T2+fli*fii+/3.*T*I%+e [2.61

Previous research has addressed the effects of temperature and time on the fat
holding capacity, and some of the work has described the heat and mass transfer models
of cooking, but none has effectively modeled the fat transport mechanism. Such a model
is particularly important to more accurately predict the yield of meat products during
cooking. Thus, a mechanistic model for fat transport will be a significant contribution to
the current state-of-the-art.

However, before such a model could be developed, there are some basic
properties that need to be studied. From the different studies cited above, it is evident that
fat transport depends not only on the physical properties of the fat, but also is a function
of the surrounding protein matrix. Apart from this, there is water, which is another fluid
available in the meat matrix. During cooking, both water and fat are lost. This increases

the complexity of the cooking models. This becomes a multi-phase fluid transport

13

problem, which involves a lot of parameters, like the porosity, pore-size distributions, and
permeability of the meat matrix and the hydraulic and the lipidic conductivity of water
and fat through the meat matrix. This is a relatively new approach in modeling the
cooking process. Since this type of research is very limited in foods, no such data on the
permeability and the conductivity of beef fat are available. Hence, this study aims at
determining those properties of the ground meat matrix that are essential in developing

precise cooking models.

2.3. Ground Meat Matrix- Porous nature

Meat tissues are complex structures, which are composed of bundles of muscle
fibers. These muscle fibers are the basic cellular units of living muscle and of meat, and
are comprised of myofibrillar (salt soluble), sarcoplasmic (water soluble), and connective
tissue (salt insoluble) proteins. The three major components of meat are water (70%),
proteins (20%), fat (3%), and ash (1%). Other compounds in meat include carbohydrates,
minerals, and vitamins. These compounds comprise about 1% of meat and have little
influence on the production of processed meat products (Hedrick et al. 1994).

Water is the largest component of meat and is available in three forms (1) bound,
(2) immobilized, and (3) free water. Bound water makes up approximately 4-5% of the
water in muscle, and is held very tightly by the proteins. Immobilized water is attracted to
the bound water molecules in layers that become successively weaker as the distance
from the reactive group on the protein becomes greater. The free water is that water
which is held only by surface forces. Fat is the most variable component in processed

meat. It is extremely important, because it directly affects flavor, texture, shelf life, and

14

profits. Proteins are the main structural units of the meat, mainly the myofibrillar
(contractile) proteins that form filamentous structures. These are salt soluble proteins, and
their ability to absorb enough water in the presence of salt makes them very important
part of the proteins in processed meat technology (Hedrick et al. 1994). The muscle
protein denaturation during cooking has a significant effect on many changes, such as
shrinkage, tissue hardening, color changes, and cooking losses.

The shrinkage of meat patties during cooking varies the pore structure of the meat
considerably. During moist air impingement cooking, Watkins and Marks (2002)
reported that patty diameter decreases roughly linearly with cooked temperature. During
pan-frying of beef burgers, Kova'csne et al. (2005) reported that shrinkage of the meat
patties is directly related to the fat losses. Hung et al. (1978) suggested that moisture
transport from meat during cooking is largely due to squeezing of the muscle fibers
during protein denaturation. The porous structure of the meat matrix, the phase change of
the fat (from solid to liquid as the meat temperature exceeds the melting point of the fat),
and the internal pressures exerted by the shrinkage of the muscle fibers during cooking,
all impact the fat transport out of the meat matrix.

Transport processes in the meat matrix are particularly influenced by the porous
structure of the meat patties (Farkas and Singh, 1991). Generally, most foods are porous
in nature. However, very little published literature has characterized the porous nature of
the food substances. In the meat industry, many studies have related the porous structure
of the meat to many factors such as, cooling rate, temperature distribution, percentage
weight loss, and pressure distribution within the porous cooked meat joints, but very little

research has studied the changes in the porosity and pore-size distributions during

15

cooking. McDonald and Sun (2000) studied the influence of porosity on the efficiency of
vacuum cooling of cooked beef products. They reported that the rate of vacuum cooling
was directly influenced by porosity. They also studied the effect of various processing
conditions, such as injection level, tumbling, and mincing during sample preparation on
the porosity of beef samples. They reported that porosity increased throughout
processing.

Porosity and pore-size distributions are important indicators of the microstructure
and physical characteristics of a product (Farkas and Singh, 1991; Datta and Zhang,
1999). McDonald et al. (2001) reported that moisture loss and development of porosity
during vacuum cooling had a significant effect on the therrnophysical properties (thermal
conductivity, specific heat capacity, and thermal diffusivity) of cooked beef products.

Wang and Sun (2002) developed three-dimensional mathematical models solved
via the finite element method to study heat and mass transfer through porous cooked meat
joints. They reported that porosity and pore sizes had a significant impact on the cooling
rate, temperature distribution, percentage weight loss, and pressure distribution within the
porous cooked meat joints. Rahman eta]. (2002) characterized the pore formation during
various methods of drying in tuna products. Dried tuna produced by three methods of
drying (air, vacuum, and freeze-drying) was investigated using a mercury porosimeter.
They reported that pore-size distributions were completely different for the three methods
of drying and that the porosity of freeze-dried samples was much higher than those of air-
dried and vacuum-dried samples.

Ngadi et al. (2001) also used a mercury porosimeter to measure the changes in

porosity and pore-size distributions during cooking of SPF (soy-protein flour) and TSP

16

(textured soy-protein) extended ground beef patties. Mercury intrusion porosimetry
(MIP) is a technique that is used to estimate capillary pressures in porous materials. The
method consists of injecting mercury at increasing pressure into a sample, which has been
previously evacuated. Recording mercury pressures and saturations allows generation of
a capillary pressure-saturation curve. These data can be used to determine porosity and
pore-size distributions of core samples.

These experiments were good for a preliminary examination of how the meat
structure changes with cooking temperature. However, the main drawback of this
technique was the requirement of a dry sample. To satisfy this condition, the samples
were oven dried prior to analysis. This technique (MIP) determines the porosity,
cumulative pore volume, cumulative pore surface area, and pore diameters, and their
distribution. They reported that average porosities of SPF and TSP extended samples
were from 24 to 34% and from 4 to 22%, respectively. Increasing the cooking
temperature and extender concentration resulted in an increase in total pore surface area.

The pore diameters up to 0.01 pm were effectively measured, and a majority of them (up
to 80%) were larger than 10 gm.

In a more recent study, Kassama and Ngadi (2005) investigated the effect of
frying oil temperature and frying times on the pore-structure of deep-fat-fried chicken
meat. The same mercury porosimeter technique was utilized in this study, except that the
samples in this study were freeze-dried prior to analysis. This is a much better technique,
as freeze drying preserves the structural integrity of the samples, compared to oven
drying. They reported that porosity and pore sizes decreased with frying time. This was

attributed to the blockage of the pores due to oil uptake during frying. However, the most

17

important factor that has to be noticed in these two studies is that the porosity, pore
diameters, and their distribution were significantly affected by the sample treatment
conditions.

In an extended part of the above study, Kassama and Ngadi (2005) modeled the
moisture transfer during deep fat frying of chicken meat using Fick’s law of diffusion.
The relationship between moisture loss and pore formation was investigated as a function
of frying oil temperature and time. Pore formation was significantly (P<0.01) affected by
temperature and time and influenced moisture diffusivity and oil uptake. This suggests
that porosity and pore-size distributions are important in determining the microstructure
and physical characteristics of a product.

Also, permeability is another very important property of a porous medium.
Permeability of a porous medium is the measure of the ease with which a fluid may flow
through the material by an applied pressure gradient. A porous medium may be
permeable to one or more fluids. It depends on the characteristic properties of the porous
medium and the fluids. Ground meat can be considered as a porous medium, in which
water and fat co-exist. Also, development of internal pressure, due to shrinkage of the
muscle fibers, may be the fundamental driving force for fat transport. Therefore,
studying the permeability of the meat matrix and the conductivity of the fat through the
meat matrix are important in presenting a detailed view of the transport mechanisms
undergoing during cooking.

Permeability is referred to as the ability of the fluids (water and fat) to pass
through the ground meat matrix. Very little published research has included permeability

of fluids through food products. Goedeken and Tong (1993) determined the permeability

l8

of air through porous pre-gelatinized flour dough as a function of porosity (0.10-0.60),
moisture content (1 5-50%), and fat content (0-6%). They reported that permeability was
directly affected by porosity, but not by the moisture content and fat content. The
permeability values ranged from 2 x 10"4 m2 at a porosity of 0.1 to 2.3 x 10'” m2 at a
porosity of 0.6.

Feng et al. (2004) investigated the intrinsic and relative permeabilities by flow of
humid air in unsaturated apple tissues (10-15mm thick). The intrinsic permeability was
determined as a function of porosity. The permeability increased with increase in
porosity, with values ranging from 8.89 x 10'13 to 4.57 x.10‘ll m2 for porosity ranging
from 0.33 to 0.77.

Ni and Datta (1999) worked on multi-phase porous media models during
microwave heating of biomaterials, and developed heat and mass transfer models for
potato baking and deep fat frying. They also modeled the heat and mass transfer process
during baking of a potato slab. They measured the water permeability of raw potato slabs
(15 mm diameter & 2 mm thickness) and the gas permeability of baked potato skin (0.5
mm thick) using a capillary flow porometer. They reported an average water permeability
of 5 x 10”° m2 for the potato slabs and an average gas permeability of 5 x 10'16 m2 for the
potato skins. The measured permeability was very sensitive to applied pressures. These
data were used to model the heat and mass transfer during baking of potato slabs using a
multi-phase porous media model.

Datta (2005) has investigated the hydraulic permeability through raw whole

muscle beef tissues (12 mm thick) and potato slabs (2.5 and 5 mm thick). The hydraulic

19

conductivity is described as the conductivity of water through the porous meat tissue

under an applied pressure head. It is given as:

_p__g_ 1
,u —872Aflii [2.7]

where:

K ,, is the hydraulic conductivity (m/s),

Afl, is the volume fraction of pores in the ith class having radius r, ,
,0 is the density of water (kg/m3),

,u is the viscosity of water (kg/ms), and

T is the tortuosity of the medium.

The hydraulic conductivity K], is a function of the fluid and the matrix properties.

The important fluid properties are density and viscosity of the fluid and, the important
matrix properties are the porosity, pore-size distributions, and tortuosity of the medium.
The matrix property on a whole can be included under the permeability or the intrinsic

permeability k, and is given as:

1 2
k = “—2 4.3.-'3- [2.8]
81 ,-
Therefore, the hydraulic conductivity is given as:

K. = kpg

2.9
fl [ ]

The permeability of whole muscle tissues was calculated from Darcy’s law, given by:

20

Vp
k=———
A(AP/L) [2'10]

where:

y is the viscosity of the fluid (kg/ms),
AP is the pressure head (N/mz),

V is the fluid flow rate (m3/s) at a pressure head of AP ,
A is the cross-sectional area of the porous material (m2), and
L is the thickness of the porous material (m).

The Darcy permeability for the pressure driven flow of water through Datta’s
samples ranged from 10''7 to 10'19 m2. The water permeability of potato was slightly
lower than that of meat tissues. Also, in the case of potato, permeability appears to
increase with pressure. That was not the case with beef tissues, where permeability
decreased with pressure. However, the permeability of ground meat patties may be
significantly different from the permeability of whole muscle tissues, because of the
differences in the pore diameters and general structure.

Kova'csne et al. (2006) determined the permeability of water and fat as a function
of the cooked endpoint temperature during pan-frying of beefburgers. The intrinsic
permeability of water in beefburgers (17 mm diameter and 10 mm thick) of different fat
contents pan-fried to center temperatures of 50, 60, 70, and 80°C was determined using
an air-driven pressure cell. Water above the sample was pressurized at a constant value
using air to reach target pressures of 2, 2.5, and 3 bars (29, 36.27, and 43.52 psi). The
intrinsic water permeability calculated on the basis of Darcy’s law was reported to be in

the range of 6.8 x 10''8 to 1.6 x 10'l° m2 for the temperatures ranging from 50 to 80°C.

21

Water permeability in beefburgers (22 mm diameter and 10 mm thick) was also
determined by process of centrifugation. After frying, the samples were placed in
centrifuge tubes and centrifirged for 5 min and 15 min at two different speeds of 150 and
500g. The water and fat losses on centrifugation'were calculated as a percentage of the
weight of the beefburger before centrifugation. The flux of the water and fat was

calculated by

V

Z:—
A.t

[2.11]

where:
V is the volume of water or fat (m3),
A is the cross-sectional area of the beefburger (m2), and

t is the duration of the time (s).

The permeability of water on centrifugation varied from 1.2 x 10''7 to 1.9 x 10'‘6
m2, and the permeability of fat on centrifugation varied from 8.4 x 10'17 to 5.1 x 10'15 m2
for temperatures ranging from 50°C to 80°C. The permeability of fat was reported to be
higher than that of water at all temperatures.

The centrifugation technique used here was similar to that used by Rochowiak et
al. (2006) in determining the water holding capacity of ground turkey and by Tripuraneni
et al. (2006) in determining the fat holding capacity of ground beef. However, this
concept of relating the water and fat losses during centrifugation to the permeability and
the relative permeability of water and fat in a ground meat matrix is quite vague. This
type of centrifugation technique is employed by various studies in literature to determine

the liquid holding capacity of the samples. Moreover, the determination of the relative

22

permeability of one phase with respect to another phase in any kind of sample is not so
simple. It requires parameters such as fluid saturations, capillary pressures, wettability,
interfacial tension and many other parameters (Scheidegger 1974). This type of work is
rarely found in food related research.

The study of Kova'csne et al. (2006) was very closely associated to the present
research, with the permeability of the beefburgers to fat and water being the common
goal. However, the cooking process in the two studies is quite different. The previous
study used frying as the method of cooking, and the present study is interested in oven
cooking. This research focuses on improving the cooking yields of cooked ground meat
patties, so the samples for analysis in this research were cooked in a laboratory
convection oven, to simulate industrial cooking practices. Due to the potential differences
between the two cooking methods, there might be differences in the permeabilities of
water and fat.

Also, cooking temperature may influence the permeability of beef patties;
however tests in the previous study were conducted only at room temperature. The
viscosities of water and fat vary with temperature, and the porous structure and pore
distributions of the meat matrix may change with temperature. Hence, the present study
is interested in controlling the temperature during testing in order to generate property
data directly relevant to the temperature that occurs during cooking.

Also, the present study is more interested in relating the changes in the porous
structure of the meat matrix to the permeability of the ground meat samples during
cooking. These relationships may help understand the complexities of meat patty cooking

and aid in the development of efficient cooking models based on two-fluid flow theories.

23

Therefore, determining the permeability of water and fat through an oven-cooked ground

meat matrix would be a significant contribution to the current state-of—the-art.

2.4. Multi-phase Fluid Flow- Porous media

Multi-phase flow in unsaturated porous media is of practical importance in many
industrial applications. This type of work is often encountered in ground water hydrology
and oil and petroleum reservoir engineering. The present study also involves
simultaneous flow of two immiscible fluids (water and fat) in the ground meat porous
medium domain (Figure 2.1). Water acts as the wetting fluid, and fat acts as a non-
wetting fluid. There is loss of both water and fat during cooking. Hence, to accurately
describe the fat transport mechanism, a multi-phase fluid transport model must be
developed.

However, an accurate description of the porous medium and its properties is
needed before the multi-phase fluid flows can be modeled. Hence, this section deals with

a brief description of porous media and properties.

24

Protein
Matrix

 

 

Figure 2.1: Schematic of the ground meat porous structure in which water and fat
are distributed.

2.4.1. Porous Media

The two most significant properties of a porous medium are: (1) porosity, which
is a measure of pore space, and (2) permeability, which is a measure of the ease with
which fluids may traverse the medium under the influence of a driving pressure.
However, there are many other properties of the porous medium, which are important in
modeling multi-phase flows. Here is a brief description of those properties from Collins

(1961) and outlined in the following 3 pages.

Porosity: The porosity of a porous material is the fraction of the bulk volume of the

material occupied by voids.

25

¢ = p [2.12]

where:

Vp is the volume of the pores (m3),

Vb is the bulk volume of the material (m3), and

¢ is the porosity

Permeability: Permeability of a porous medium is the measure of the ease with which a
fluid may flow through the material by an applied pressure gradient. It is called the fluid
conductivity of the porous medium.

Darcy’s law gives the equation that defines permeability (k). It is given by equation 2.10.

Pore-size distribution: Pore-size distribution is important in consolidated materials,
where grain-size distribution cannot be obtained. A pore-size can be defined by the pore
diameter. It is the distribution of the pore volume with respect to pore size. Specific pore
volume is the sum of volumes of all pores in the sample. Pore volume, specific surface

area, and mean pore diameter are correlated to each other.

Fluid Saturation: The void space of a porous medium may be partially filled with any
fluid (a liquid or a gas). The saturation of a porous medium with respect to a particular

fluid is defined as the fraction of the void volume of the medium filled by the particular

fluid.

26

S = —f- [2.13]

where:

S is the saturation,

Vf is the volume of the fluid in the medium (m3), and

Vv is the total volume of the voids in the medium (m3),

If two fluids, say w and nw are jointly filling the porous medium, then
SW + SW :1 [2.14]

where, w is the wetting fluid and nw refers to the non-wetting fluid.

Capillary Pressure: When two immiscible fluids are in contact in the interstices of a
porous medium, a discontinuity in pressure exists across the interface separating them. It

is given by

PC = Paw — P... [2.15]
pc is the capillary pressure (N/mz),
in is the pressure in the non-wetting phase (fat; N/mz), and

pw is the pressure in the wetting phase (water; N/mz),

Relative Permeability: When two immiscible fluids are simultaneously flowing through a
porous medium, the single-phase Darcy’s law can be extended to quantify multi-phase

flow problems by introducing a relative permeability for each phase. In an immiscible

27

two-phase flow, the flow of one fluid is assumed to behave as though it coexists with
another fluid in a stationary state. Hence, permeability can be defined for each fluid
through Darcy’s law. However, these permeabilities are independent of fluid flow rate

and fluid properties, but depend only on the fluid saturations within the porous medium.

Thus, if kw and knw are the permeabilities of the two fluids, the wetting and the non-

wetting fluid determined through Darcy’s law, they can be expressed as fractions of

single-phase permeability, k of the porous medium.

_ "W
krmw - [2.16]

knw _ k [2.17]

k is an intrinsic property of the pore structure and is also called the intrinsic permeability
of the porous medium. These relative permeabilities are each less than unity, but their

sum is not unity.

2.4.2. Multiphase Fluid F low- Models

In order to develop a multi-phase fluid transport model, first an accurate
description of multi-phase flow through porous media is important. In this context, multi-
phase flow is described as the simultaneous flow of two immiscible fluids through the
porous medium. Typically, multi-phase flows through porous media are modeled using
Continuum representations, where state variables are defined relative to local volume
averages (Bear, 1972). Several properties have to be specified in such models. They are

the fluid properties, such as viscosity and density, and the material properties, such as

28

porosity, relative permeability, and capillary pressure. The viscosity and density of the
fluid and the porosity of the material can be determined by simple laboratory
experiments. However, properties such as relative permeability and capillary pressure

cannot be measured directly.

2.4.2.1. Relative Permeability: Theory

As mentioned earlier, the definition of relative permeability can be derived from

the extension of Darcy’s law to multi-phase flow (Demond and Roberts, 1987).

k.
Vt =“ —" (VB—Pith) [2.18]
i
where,
V, = j , is the flow of the ith phase per unit area of the sample (m/s),

k,- is the effective permeability, the permeability of the porous medium to the ith phase
(mi),
.11,- is the viscosity of the ith phase (kg/ms),

P is the pressure (N/mz),

p is the density (kg/m3),

g is the gravitational acceleration (m/sz),
h is the elevation (m),

i is the ith phase.

29

Relative permeability to the ith phase can be defined as:

km k [2.19]

km- is the relative permeability of the ith phase.

Darcy’s law for multi-phase flow can then be written by substituting (2.19) into (2.18)

(Demond and Roberts, 1987):

k .
V- =- (VB-pawl)

l

 

[2.20]

i
so the equations for multi-phase flow can then be written by inserting Darcy’s law into

the continuity equation (Demond and Roberts, 1987; Watson et al. 1998):

 

a kkrmwpnw
E(¢pannw) : V l! (VR'W +th) [2’21]

5 Hey/9..
E(¢prw)=V. — (VP +th) [2.22]

where:

w and nw refer to the wetting and non-wetting phases, respectively,

km, and kmw are the relative permeability of the wetting and non-wetting phases,

SW and Snw are the phase saturations the wetting and non-wetting phases,

¢ is the porosity of the medium.

The state variables, fluid phase saturations and pressures, are related as follows

30

P — P... = P. [2.231

SW + Snw = 1 [2.24]

In this equation, many properties, such as viscosity, density, and porosity, can be
determined by simple experimental techniques, but the estimation of relative permeability

and local saturations are relatively difficult.

2.4.2.2. Relative permeability: Measurement

Relative permeability measurements are carried out using steady state or unsteady
state techniques. Steady state methods are based on the simultaneous injection of both
fluids, while unsteady state methods are based on immiscible displacement experiments
(Scheidegger, 1974).

The steady state methods are direct application of Darcy’s law. The two
immiscible fluids are injected simultaneously at constant flow rates or pressures into the
porous medium until the flow reaches equilibrium or steady state conditions. At this state,
the flow rates, pressure drops, and fluid saturations are measured and correlated using
Darcy’s law. The steady state methods attempt to maintain uniform saturation throughout
the medium. Therefore, these methods ofien introduce errors, because of saturation non-
uniformity (Ramakrishnan and Cappiello, 1990). The most important operational
problems encountered with this technique are capillary end effects, hysteresis, scaling
effects, and appreciably longer experimental times that are needed before a steady state

flow is achieved (Avraam and Payatakes, 1995).

31

The unsteady state or displacement method of measuring relative permeabilities
consists of monitoring the production history and pressure drop across the sample during
a laboratory displacement process. The relative permeability is obtained as the solution of
an inverse problem. The inverse problem consists in matching the measured production
history and pressure drop to the solutions of the multiphase flow equations using the
Buckley-Leverett approximation (Bear, 1972).

The most common methods employed in determining relative permeabilty are: (a)
the Pennyslyvania state method, (b) the single sample dynamic feed method, (0) the gas
drive method, ((1) the stationary liquid method, (e) the Hassler method, (1) the Hafford
technique, and (g) the dispersed feed method. Scheidegger (1974) has presented a
detailed account on these seven methods of determining relative permeabilty. The
stationary liquid method can only determine the relative permeability of gases. The
Pennyslyvania state method requires the sample to be sandwiched between two samples
of the similar material. Thus, it requires three samples, and this is done to minimize any
end effects. The secondary fluid or the non-wetting fluid should be gaseous in the single
sample dynamic feed and the gas drive methods. In the single sample dynamic feed,
Hafford, and dispersed feed methods, end-effects are reduced by flowing at sufficiently
high rate (Scheidegger 1974; Ramakrishnan and Cappiello, 1990).

The concept of relative permeability seems very simple, but the measurement and
interpretation of relative permeability versus saturation curves is not. There is evidence
that relative permeability may be a function of many more parameters than fluid
saturation (Scheidegger, 1974). Temperature, flow velocity, saturation history, wettability

changes, interfacial tension, intrinsic permeability, and the mechanical and chemical

32

behavior of the matrix material may all play roles in changing the functional dependence
of the relative permeability on saturation. Demond and Roberts (1987) best described the

influence of certain variables on relative permeability.

2.5. Summary

As discussed in the previous sections, two things have to be considered when
attempting to model the fat transport mechanism during cooking of ground meat
products. First, the ground meat is porous in nature, and second, water and fat coexist in
meat. Thus, this research is divided into two parts: (1) to study the influence of
temperature on the porous structure of ground meat, by analyzing the porosity, pore-size
distributions, and the permeability of the meat matrix as a function of temperature and fat
content and (2) to understand the fat transport mechanism by determining the
conductivity of fat through the ground meat matrix. This would give a better insight into

the fat transport mechanism and thereby aid the effectiveness of future cooking models.

33

3. MATERIALS AND EXPERIMENTAL METHODS

3.1. Overview

The main aim of this study was to underStand the complexities during cooking of
ground meat. The conductivity of water and fat during cooking are important in
developing improved cooking models. Conductivity measurements depend on the fluid
properties, as well as the material pr0perties of the ground meat. The important fluid
properties are viscosity and density. The critical material properties of the ground meat
are porosity and pore-size distributions. Therefore, this study was conducted to determine
these material and fluid properties during convection cooking of ground beef as function
of temperature.

The materials and the methods used to determine all these properties were
described in the following six sections. The first section (section 3.2) describes the raw
materials and the pre-treatment of the patties for further analysis. The second section
(section 3.3) describes the determination of shrinkage of the patties after cooking. The
third section (section 3.4) describes the determination of material properties of the ground
meat, such as porosity and pore-size distributions, and the fourth section (section 3.5)
describes the determination of permeability of the ground meat matrix as a function of
cooked temperature. The fifth section (section 3.6) describes the determination of the
fluid properties of beef fat, the density and viscosity. Later, in section 3.7, the

measurement of relative permeability of fat was described.

34

3.2. Meat — Sample Preparation

3.2. 1. Meat

Two lots of fresh ground beef were acquired from a local commercial supplier.
The two lots of ground beef were different in fat content (one low fat and the other high
fat). Two different fat contents were used in order to determine whether the fat content
affected the results of this study. The two lots were pre-ground prior to receiving and no
additional grind was conducted. Hence, the grind of the raw material was not controlled,
therefore; there were differences other than just fat content between the two lots.
However, the two lots of ground beef will be referred to as low fat and high fat samples
throughout the rest of this study.

The fat contents of the two lots were determined in triplicate using solvent
extraction (AOAC method 991.36: Solvent Extraction). Moisture determination was
carried out by oven drying the samples at 125°C for 4 h (AOAC Method 950.46 Air
Drying). The ground beef samples were then made into patties (~ 10 g each) by manually
pressing the meat into sterile plastic petri dishes (35 mm diameter x10 mm thickness).
This type of patty formation can induce lot of variability in between samples. Therefore,
in order to reduce that variability, all the patties were formed only by the author. The
patties were then bagged and frozen (-28 °C) until testing. Prior to testing, the samples

were tempered to 4°C by placing in the refiigerator overnight.

35

3.2.2. Pre-treatment—Laboratory oven cooking

Patties were cooked in a custom-built computer controlled laboratory convection
oven (Figures 3.1). The oven body is a stainless steel box (762 x 508 x 457 mm)
insulated with fiberglass. It consists of three elements: the conditioning chamber, the
steam generator and the sample chamber.

The steam generator is powered by a 750W immersion heater, which is used to
heat distilled water. The steam is then injected into the conditioning chamber via a
solenoid valve and a pressure-regulating valve (344,738 N/m2). The conditioning
chamber heats and conditions the cooking chamber to the desired temperature and
moisture content. It consists of four strip heaters (350 W each), which heat and condition
the air, which is circulated through the sample chamber via a 6 W centrifugal fan. The
cooking chamber is the smallest chamber (10 x 10 x 10 cm). A T-type thermocouple

monitors process temperature.

 

 

 

Steam

Generator Conditioning Chamber
with air heaters

 

 

 

 

 

 

 

 

 

 

 

 

Sample Chamber

Figure 3.1: General arrangement of the laboratory convection oven showing
directions of steam and airflow.

36

Air moisture content is monitored via a polymer sensor (Visala DRYCAP®) and a
dew point transmitter (Vaisala DMP246). All sensors, the heater, and the valve control
actuators are monitored and controlled by a laptop computer with a data acquisition and
control unit (B&B electronics, SDAIBB & SDDARB4). The oven can control temperature
up to 250°C and air moisture content up to 90% moisture by volume (dew point
temperature of 97.22°C), depending on the air temperature. The oven is capable of
precisely maintaining dry bulb temperature (i0.11°C) and air moisture content (i0.1%)
during the treatments. The approach velocity of the moist-air onto the product is ~1.3
m/s.

Both high fat and low fat patties were cooked at an air temperature of 176.7°C and
a dew point temperature of 939°C, which gives percent moisture by air volume of 80%.
Prior to heating, each patty was weighed to the nearest 0.0001 g. The patties were
supported on a wire mesh screen and then placed in the cooking chamber. A type T
thermocouple was inserted into the approximate center of the patty, and the patties were
cooked one at a time to center temperatures of 45, 60, or 75°C. Ten patties were cooked
at each condition. After cooking, the patties were removed from the oven, and surface
moisture (droplets) was removed by briefly dabbing with paper towels. The patties were
then weighed to the nearest 0.0001 g. Four patties cooked at each treatment condition
were analyzed for moisture (oven drying, AOAC Method 950.46 Air Drying) and fat
contents (AOAC method 991.36: Solvent Extraction). The rest of the samples for
porosity and pore-size distribution analyses were stored in the refrigerator (4°C). Prior to

analysis, the samples were thawed to room temperature of 23°C by leaving them on the

37

laboratory bench top for 2 h. All the samples cooked for pore-size distribution tests were

analyzed within two days of cooking.

3.3. Shrinkage

The shrinkage of the samples is an important property that affects many of the
mechanisms occurring during cooking. The shrinkage of the patties is caused by the
denaturation of the proteins during cooking. The shrinkage of the patties was calculated
by measuring (to the nearest 0.1 mm) the diameter of the patties before and after cooking,
using digital calipers. The patty diameter shrinkage was calculated as a percentage of the

original diameter.

b
Percentage Shrinkage = D a x 100 [3.1]
b

where:

D], is the diameter of the patty before cooking (m), and

D0 is the diameter of the patty after cooking (m).

3.4. Porosity and Pore-size distribution

Porosity and pore-size distributions were determined at room temperature using a
PMI Liquid Extrusion Porosimeter (Porous materials Inc, Ithaca, NY). This instrument
has the capability of determining pore diameters up to 0.05 microns. The principle of
operation is quite different from that of the mercury intrusion porosimeter (MIP). As
mentioned earlier, the principle of MIP is to force mercury into the evacuated pores of the

sample. Thus, porosity and pore-diameters are calculated from the pressure required to

38

force a certain quantity of mercury into the sample. However, the technique employed in
Liquid Extrusion Porosimeter (LEP) is quite different. Liquid is extruded from the
saturated sample under pressure, and porosity and pore diameters are calculated from the

pressure required to push a certain quantity of liquid from the sample.

3.4.1. Liquid Extrusion Porosimeter: Theory

A wetting liquid will spontaneously fill the pores of a porous medium, but
removal of the wetting liquid is not spontaneous and requires some work (Jena and
Gupta, 2002). Assuming that the pores are cylindrical, the pressure required to displace
the wetting liquid from the pores is given by the equation (Scheidegger 1974; Ngadi et al.

2001; Micromeritics, 2001; Jena and Gupta, 2002):

_ 4y c086
D

P [3.2]

where:

D is the pore diameter (pm ),

P is the applied pressure at which liquid is extruded out of the sample (N/mz),

y is the surface tension of liquid, (72 dynes/cm for water), and

6’ is the solid-liquid contact angle (~ 0 for low surface tension liquids).
This equation suggests that the applied gas pressure and pore diameters are
inversely related, which means, that smaller pores are measured at higher pressures.
The pore volume distribution of the samples is computed by the following

relationship (Jena and Gupta, 2002).

39

dV
dlogD

 

f = -( ) [33]

where, V is the pore volume corresponding to the amount of liquid extruded out of the

sample. This quantity gives the flow rate distribution over pore diameters. This flow
distribution (f) is designated as pore-size distribution of the samples (,um‘I ). Area under

the distribution function in any pore diameter range gives the percentage flow in the
selected diameter range. Because the increase in the percentage flow is determined
essentially by the increase in the number of pores and the pore diameter, a sharp increase
in pore-size distribution suggests that the number of pores of that diameter is large.

The pores in a porous material can be classified as through pores, blind pores and
closed pores. The through pores are the ones that are important in fluid flow, as they
extend from one surface to another. The blind pores only have an open end, and they do
not contribute to fluid flow. The closed pores cannot be accessed at all. The LEP
measures only through pores or pores that affect fluid flow. The through pore surface
area (A) of the samples is computed by the following relationship (N gadi et a1. 2001;

Micromeritics, 2001; Jena and Gupta, 2002):

_ lPdV
700819

A

 

[3.4]

The total extrusion volume, total pore surface area, average pore diameters and
porosity were determined using the LEP. The bulk volume is calculated from the weight

and bulk density of the sample and the porosity is calculated from equation 2.12.

40

3.4.2. Liquid Extrusion Porosimeter: Measurement

A schematic of the Liquid Extrusion Porosimeter (LEP) is shown below (Figure
3.2). The pressure regulator regulates the air supply to the machine. V1 is the air inlet
vent, V3 is the air outlet vent, and V9 is the liquid drain outlet. The LEP requires a fully
saturated sample, which is supported on a membrane (Millipore membrane filter). The
membrane is such that its pores are very small in diameter (0.45 ,um) compared to the
pores of the sample, and the membrane is also saturated with the same liquid. A gas
pressure is then applied uniformly on the sample from the top. As the pressure is
increased, liquid is extruded from the pores of the sample, and the extruded liquid passes

to a plastic weighing cup on the balance.

Pressure Guage

Pressure
Re . ulator

 

 

Sample
Chamber

 

Air Vent
Scale

V9

Figure 3.2: Schematic representation of the flow diagram of the PMI Liquid
Extrusion Porosimeter.

41

The pressure applied and the pore diameters measured are inversely related, i.e.,
smaller pore diameters are measured at higher pressures. The membrane pores are very
small in diameter compared to the pores of the sample; therefore, the pressure required to
remove liquid from the largest pore of the membrane is greater than the pressure required
to remove liquid from the smallest pore of interest in the sample. Hence, as the gas
pressure is increased, gas displaces liquid from the pores of the sample, but does not
remove any liquid from the pores of the membrane (Figure 3.3), which therefore remain
saturated. As the liquid wets the membrane, the liquid removed from the sample passes
through the liquid filled pores of the membrane to a balance.

The weight of the liquid is measured and is converted into volume using the
density of water. The volume of extruded liquid is reported as a function of pressure.
Thus, the pressure required to evacuate the pores and the volume of the liquid collected
are used to determine porosity and pore—size distributions of the sample. When the test is

done, the vent V9 is opened, and the extruded liquid from the balance drains out.

Gas Pressure

Sample

Membrane ————%

 

Liquid Flow

Figure 3.3: Sketch illustration of the principle of the PMI Liquid Extrusion
Porosimeter.

42

Water and fat co-exist in meat, i.e., there are two fluids. Therefore, to push only
one fluid out of the meat matrix for pore—size determination, the samples were first
tempered to room temperature. Because fat remains solid at room temperature, water was
pushed out of the samples for pore size determination. Both high fat and low fat samples
were used, and the treatment conditions were raw, and cooked to center temperature of
45, 60, and 75°C at 176.7°C oven temperature and 80% moisture by volume. Five
samples were treated at each condition. Therefore, a total of 40 samples were tested.

Because the LEP required saturated samples to begin with, all the samples (except
raw) were submerged in de-ionized tap water @H ~ 6.2 to 6.3) for 10 min before testing
to approximate this condition of saturation. The raw samples were so soft in texture that
they began to disintegrate when soaked for more than 5min. Hence; they were submerged
in water for only 5 min. The cooked samples had good texture to withstand 10 min in
water. Soaking for 10 min in water does not normally satisfy the condition of achieving
saturation; however, this was the best that can be done in a sample like ground meat. This
LEP technique is generally used for determining porosity and pore-size distributions in
materials like ceramics.

A schematic diagram of the sample chamber assembly is shown below (Figure
3.4). The sample chamber is attached to the machine. A hose (not shown in figure) is
attached from the sample chamber to the weighing cup on the balance. The extruded fluid
reaches the balance through this hose. The hole in the bottom of the sample chamber is
filled with water, and a screen is placed on top of it. On top of the screen, a wet
membrane (whose pores are much smaller than that of the pores of the sample) is placed.

Then a greased O-ring is placed on top of the membrane. The hollow plastic insert (35

43

mm diameter x 25 mm high), which holds the sample, is then placed on the O-ring. There
is another O-ring on top of the insert. These O-rings need to be greased for better contact
with the chamber, thus eliminating any chance of air leakage. After the insert is in place,
the saturated sample is then lowered slowly into the sample chamber, so that the bottom
of the sample is in contact with the membrane below. Thus the sample is placed in the
chamber, and then the machine test cycle is fully automated.

After soaking, the samples were inserted into the LEP as described above. The
machine is fiilly automated, and the extruded volume vs. applied pressure graph was
plotted as the samples were tested. The samples were tested using a pressure step of 0.1
psi (~ 689 Pa) until a maximum pressure of 1.25 psi (~ 8600 Pa) was reached. At this

maximum pressure, the pore diameters of 33 ,um were successfully measured. Because

this research is mostly focused on flow in a porous medium like meat, the diameters

below 35 um may not necessarily contribute to flow. Hence, they were not measured.

O-Ring

__ Plastic
Insert

 

 

—Sample

Membrane

Screen

 

__ Sample
Chamber

 

 

 

 

 

Figure 3.4: Schematic diagram of the sample chamber assembly for the PMI Liquid
Extrusion Porosimeter.

44

3.5. Permeability

According to Darcy’s law, flow of fluids through porous media is proportional to
the pressure gradient causing flow. The proportionality constant is described as the
permeability of the porous media and is normally a function of the viscosity of the fluid.
The permeability of ground meat was determined using a custom-built PMI Permeameter
(Porous materials Inc, Ithaca, NY). A head of liquid of known quantity is pressurized
using air at a constant value through the sample (Figure 3.5). As the pressure is increased,
the liquid is forced through the sample. The pressure and flow rate data are used to

compute the liquid permeability through the sample from equation 2.10.

Liquid Flow

 

 

 

 

Gas Pressure

Figure 3.5: Schematic representation of the principle of the PMI Permeameter.

A schematic of the Permeameter set-up is shown below (Figure 3.6). It consists of
a pressure regulator, sample chamber, penetrometer, and several valves. The sample is

placed in the sample chamber and is closed tight. The chamber is made of metal inserts,

45

and the two O-rings around the chamber fit the chamber thoroughly into the insert,
making it water proof. The pressure regulator regulates the air pressure to the system. The
penetrometer is a long and slender container, which is filled with the fluid prior to
starting the experiment. During the experiment, the air pressure pushes this fluid in the
penetrometer to force through the sample. The fluid flow rate through the sample is
determined from the drop in the height of the column of fluid in the penetrometer. Digital
sensors in the penetrometer measure this drop in the fluid column. The liquid is pushed
through the sample from bottom up, and the extruded liquid is drained out from an

opening, which leads to the liquid drain.

 

Penetrometer

Fill Valve

Valleep

 

 

 

I

 

 

 

Vent

->

-%O———

Pressure
Regulator

 

 

 

Isolation

 

 

 

 
 

Liquid Drain

Figure 3.6: Schematic representation of the PMI Permeameter flow diagram.

46

The low fat and high fat ground beef samples were used. The samples were
prepared in the same manner as described for the pore-distribution tests, except that
bigger petri dishes (60 mm diameter x 10 mm thick) were used. The samples were
cooked to the same end-point temperatures (45,60, and 75°C) in the laboratory scale
convection oven (T dry bun, 176.7°C and T dew point 93.9°C). Prior to testing, a cylinder with
a diameter of 34 mm and a height of 10 mm was excised from each sample by a sharp
edged steel cylinder from the middle portion of the cooked samples. This cylinder was
then inserted into the Permeameter chamber for permeability tests.

A schematic diagram of the sample chamber is shown below (Figure 3.7). The
sample chamber is a metal cylinder with an opening in the bottom. The spacing insert is
also a cylinder made of metal. It has two O-rings on the sides and one on the top and one
on the bottom. These O-rings are provided to ensure that there is no gap or space between
the sample insert and the camber, thus maintaining it waterproof. The inside of the
sample insert is hollow and a wire mesh screen is built in to hold the sample. The size of
the sample should be 34 mm diameter x 10 mm thick. The wire mesh screen fixes this
size of the sample.

Once the sample is in place, it fully occupies the insert, and there is no gap around
for water leakage. An adapter plate with a wire mesh screen is then placed on top of the
sample. The adapter plate has an O-ring on one side, and this O-ring should face up when
the plate is in place. On top of the adapter plate, the top of the sample chamber (not
shown in the figure) is placed and is tightened properly. Once everything is in place, the
machine is operated. When the automated test is run, first the water fills into the

penetrometer. The pressure step of 0.025 psi (172 Pa) was used, and a maximum pressure

47

of 3 psi (20,678 Pa) was applied in steps. The machine was set up to wait 10 seconds in

between pressure steps.

Adapter Plates

O
Sample

L
Spacing
U Insert

\
>O-Rings

Q
-.-_ __ __.--.--.__,-- --.-_,_-. __S_ample
Chamber

 

 

 

 

C)
C

 

C)

 

 

 

 

 

 

 

 

 

 

 

 

Figure 3.7: Schematic diagram of the sample chamber assembly for the PMI
Permeameter.

3.6. Fluid Properties of Fats

Meat fats are highly complex substances, due to the presence of triglycerides.
Hence, in order to fully understand the fat transport mechanism, it is important to
understand the nature of these fats. The transport of fat on melting depends on its
rheological properties. Therefore, viscosity of fats is an important factor that needs to be

considered.

48

3.6.1. Sample Preparation

Pure beef outer subcutaneous fat tissues were acquired from the Michigan State
University Meat Laboratory. Beef fat (tallow) was rendered from these tissues. It was

then cooled, vacuum packaged in 100 ml blocks, and frozen (-28°C) until use.

3.6.2. Viscosity

Viscosity is the measure of the resistance offered by a fluid to flow. A rotational
viscometer (Haake Viscotester, VT550) was used to determine the viscosity of beef fat.
This is a Searle type concentric cylinder viscometer (Figure 3.8). It consists of a two
concentric cylinders; the inner cylinder called the bob rotates at a preset speed, and the
outer cylinder called the cup is stationary. The substance to be measured is located in the
measuring gap of the two cylinders of the sensor system. When the rotor (bob) is rotated
at a preset speed, the substance to be measured exerts a resistance to this rotational
movement (due to its viscosity), which becomes apparent as a torque value (M) applied
on the measuring shaft of the system. The opposing torque is given by (Steffe, 1996):
M = 27rhr20' [3.5]
where:

M =torque response on the sensor (N -m),

h =height of the rotor (m),
r = any location in the fluid, r; S r S r2 , and

o: =shear stress (N/mz)

49

An MVI sensor, which is primarily used for viscosity measurements of medium
viscosity liquids, such as heavy oils, paints, varnishes, resins, emulsions, etc., working in
the medium shear rate range (Haake Instructional Manual, Viscotester, VT550), was
used, and the temperature of the fat was controlled using a water bath. The top and the
bottom surfaces of the rotors are recessed to minimize end effects on torque. An air
bubble is retained in the bottom recess, while the upper recess accommodates any excess
sample. The instrument is fully automated and can be used over a wide range of

temperatures.

 

Figure 3.8: Schematic diagram of the concentric cylinder viscometer used for
viscosity measurements on beef fat.

The apparent viscosity of beef fat was determined at 40, 50, 60, and 70°C. Melted
fat at particular temperatures was placed in the cup, which was temperature controlled.
The machine was automated and shear rates of 60 - 70 s‘1 were applied for 10 s and the

shear stress exerted by the sample was measured. The apparent viscosity (7]) of beef fat

50

was determined as the ratio of shear stress (a) to shear rate (7) from the following

equation.

n = °— [3.6]
7

3.6.3. Density

Atmospheric liquid density of fat was calculated by measuring the sample mass in
a graduated cylinder. A known amount of melted fat at each temperature (40, 50, 60 and

70°C) was weighed in a graduated cylinder for the density measurements.

3.7. Relative Permeability Measurement

3.7.1. Theory

The estimation of the relative permeability of each phase is the key to modeling
multi-phase fluid flow through porous media. Relative permeability experiments are
difficult to conduct in the laboratory. As mentioned earlier, relative permeability can be
estimated by steady state or unsteady state experiments. Despite the various refinements,
all these methods suffer from serious drawbacks. However, an attempt has been made to
determine the relative permeability of fat through ground meat matrix. This study makes
use of the steady state technique proposed by Ramakrishnan and Cappiello (1990) to

determine the relative permeability of fat and is in the following two pages.

51

3.7.2. Fat Transport Solution

A fully saturated sample is required, and it is injected with oil (melted fat) at
regular intervals. The inlet oil pressure should be maintained constant. If the injection
pressure is increased above the capillary pressure threshold or the break-through pressure
of the medium, the injected oil will span the medium and, therefore, flow of both water
and oil takes place at the opposite end. In order to maintain capillary equilibrium and
reduce any end-effects due to saturation gradients, the downstream side of the sample is
provided with a reservoir of water. Since fat is less dense than water, if the fat injection
takes place top-down then saturation cannot be maintained at the bottom end. Hence, fat
forced upward through the medium enables that both the water and fat are indeed

connected at the outlet (Ramakrishnan and Cappiello, 1990). This satisfies the boundary
condition of pc = 0.

The relative permeability for each phase, with the extension of Darcy’s law for

single-phase flow is given by (Ramakrishnan and Cappiello, 1990),

__ _ kkr,i (Si) Apt

Vi- — ,u. L [3-7]

 

where:

v,- is the Darcy velocity of phase i (m/s),
k is the intrinsic permeability of the medium (m2),

kni is the relative permeability of phase i,

,u, is the viscosity of phase i (Kg/ms),

52

S,- is the saturation of phase i,

p,- is the pressure of phase i (N/mz), and

L is the thickness of the medium (m).

For a fixed inlet oil pressure, steady state will be reached with progress in time. If
the wetting properties remain unaltered the displacement of the water corresponding to

the inlet oil pressure should be complete and hence, the water velocity will be zero. Thus,

for steady state conditions, pw = 0, Vw = Oand v0 = v. This implies that p0 = pc,

(Ramakrishnan and Cappiello, 1990). Therefore, the equation becomes

__ kkw (SW) dpc
#0 abc [3.8]

 

v:

w and 0 represent water and oil as the wetting and non-wetting phases.

where, x is the distance from the inlet face. As long as the saturation changes are

monotonic, kw , can be written as a function of pc (Ramakrishnan and Cappiello, 1990).

Then integrating the above equation (equation 3.8), we get,

0

vL=-j4.(pa)dp.

B) [3.9]

Here, 10 is the mobility of the oil phase at a capillary pressure pc and P0 is the

inlet oil pressure at the steady state of interest (Ramakrishnan and Cappiello, 1990).

53

dv x1

_ 0

d7 " L [3.10]

The mobility of the oil phase is related to the relative permeability of the oil phase from

the following equation.

kk

’10 = ’ [3.11]

#0

 

Thus, if a porous medium is completely saturated with the wetting phase, and the
non-wetting phase is injected successively at constant pressures until steady state is
reached at each of the pressures, the slope of the steady state velocity with respect to the
injection pressure is a direct measure of the relative permeability of the non-wetting
phase (Ramakrishnan & Cappiello, 1990).

According to this steady state technique proposed by Ramakrishnan and Cappiello
(1990), the determination of the relative permeability of the fat through ground meat
matrix was attempted. The Permeameter (Porous materials Inc, Ithaca, NY), which is
used to determine the permeability of the samples, is used again to determine this
property, the relative permeability of fat through meat matrix.

The low fat ground beef samples were used for relative permeability
measurements. The samples were prepared similarly as for the permeability experiments.
The sample was assumed completely saturated with water, as it contained 70% water.
However, the samples were again immersed in water for 15 min prior to testing, in order
to approximate the condition of saturation. The sample chamber assembly was the same
as discussed for permeability experiments. However, because the relative permeability

experiments require thicker samples, a separate sample adaptor was used that can hold

54

samples of 34 mm diameter x 30 mm thick. Making and cooking a sample of that
thickness (30 mm thick) will increase the heterogeneity in the sample. Therefore, three
samples (each 10 mm thick) were stacked on top of each other to achieve 30 mm
thickness.

The Permeameter was maintained at 60°C, because beef fat is solid at low
temperatures. The samples were cooked to center temperatures of 60°C and tested for
relative permeability of oil. The saturated low fat ground beef samples were tested by
subjecting them to oil injection at successive pressure steps of 0.3 psi (2068 Pa) until a
maximum pressure of 5 psi (34464 Pa). At each pressure step, the pressure was held until

steady states are achieved.

55

4. RESULTS AND DISCUSSION

4.1. Overview

The experimental results for this study are grouped into three main sections. The
first section (section 4.2) describes the properties of the raw materials used for these
experiments. The second section (section 4.3) describes the results from the shrinkage
measurement of the samples after cooking. The third section (section 4.4) describes the
results of a set of experiments conducted to determine the material properties of the meat,
such as porosity and pore-size distributions. The pore-size distribution tests were
conducted using a Liquid Extrusion Porosimeter. Ground beef patties of two different fat
contents (low and high fat) were cooked to various end point temperatures and tested for
pore-size distributions. These experiments were intended to provide insight into the
differences in the pore-size distributions with respect to cooking treatment.

The fourth section (section 4.5) describes the results of a series of experiments
conducted to determine the permeability of the meat matrix. The same treatment
conditions that were used to determine pore-size distributions were repeated for
evaluating the permeability of ground beef. The permeability was measured using the
PMI Permeameter.

Section 4.6 describes results of a series of experiments conducted to determine the
fluid properties of fat. These are the density and viscosity of beef fat. The viscosity of fat
was determined using a rotational viscometer. The densities were determined using a
graduated cylinder. Later, the results from the above mentioned three tests, i.e., the pore-

size distribution tests, permeability tests, and the fat fluid property tests were used to

56

calculate the hydraulic and the lipidic conductivity, and the tortuosity of the ground meat
matrix (section 4.7 and section 4.8). Later in section 4.9, the results from the relative

permeability experiments were discussed.

4.2. Meat

Ground beef with two fat contents (low fat and high fat) was used for this study.
The fat contents of the two lots were 5.5 (i 0.25) and 14.5% (i 1.15) fat by mass,
respectively. Moisture contents were 71.9% (i 0.39) for the low fat ground beef and 66.3

% (i 0.51) for the high fat ground beef.

4.3. Shrinkage

The shrinkage of the patties was calculated as a percentage of the original
diameter of the patties using equation 3.1. The diameter of the low fat samples decreased
from 35 mm in raw samples to 31 mm in samples cooked to 75°C. The diameter of the
high fat samples decreased from 35 mm in raw samples to 28 mm in samples cooked to
75°C. In low fat samples, the shrinkage increased from 2.85% in samples cooked to 45°C
to ~ 11.42% in samples cooked to 75°C. In high fat samples, the shrinkage increased
from 5.71% in samples cooked to 45°C to ~ 20% in samples cooked to 75°C (Figure 4.1).

The high fat samples had more significant collapse in structure compared to the
low fat samples. This may be related to the interactions between the fat and the proteins
in the high fat samples. This significant shrinkage might cause internal pressures that

squeeze out water and fat from the meat matrix during cooking.

57

 

25

20 _.

15

104

% Shrinkage

 

 

 

 

 

 

 

Figure 4.1: Shrinkage percentage of the low fat and high fat ground beef samples
cooked to different endpoint temperatures.

4.4. Porosity and Pore-size distribution

Fat transport during cooking depends greatly on the material properties of the
meat as well as the fluid properties of the fat. Hence, two material properties of the meat
were determined using the Liquid Extrusion Porosimeter: porosity and pore-size
distributions. In these tests, both low fat and high fat ground beef patties (35 mm
diameter and 10 mm thickness) were cooked to center temperatures of 45, 60, or 75°C in
a convection oven (T my bulb of 176.7°C and T dew point of 93.9°C). Therefore, four
treatment conditions of raw and cooked to 45, 60, and 75°C were used, and the pore-

distribution tests were carried out at room temperature.

58

4.4.1. Cumulative Pore Volume

The liquid extrusion porosimeter determines pore-size distribution from the
amount of liquid extruded at a certain pressure. The volume of the extruded liquid is
related to the pore-distribution, accessible porosity, and the pore surface area of the
sample. A maximum of 1.25 psi (8616 Pa) pressure was applied on all the samples. The
cumulative pore volume is the total volume of the extruded liquid at a maximum pressure
of 1.25 psi (8616 Pa). All the samples were tested at room temperature. The plots
(Figures 4.2 to 4.5) show the cumulative pore volume extruded as a function of pore

diameter for both the low fat and high fat ground beef samples.

 

0.18
0.16 .
0.14 ,
0.12
0.1 ,
0.08 a
0.06 ~
0.04 -
0.02 ~

;_ 4: HF Raw

 

Cumulative Pore Volume (cc/g)

  

 

 

 

i T . _ ‘ .—
0 200 400 600 800 1000 1200 1400

Pore Diameter (microns)

 

Figure 4.2: Cumulative pore volume as a function of pore diameter for low fat and
high fat raw ground beef samples: means of 5 replicates.

59

 

0.14

 

l + LF cook45

0'12 " e. HF cook45

 

 

0.1 ,

0.08 -

 

0.06 ~ '
0.04 -
0.02 .

0 , T T ,‘W
0 200 400 600 800 1000 1200 1400 1600

Pore Diameter (microns)

Cumulative Pore Volume (cc/g)

 

 

 

 

Figure 4.3: Cumulative pore volume as a function of pore diameter for low fat and
high fat ground beef samples cooked to endpoint temperature of 45°C: means of 5
replicates.

 

 

 

 

0.12 , _,
:6 I -9— LF cook60
0
3 0.1« l HF cook60
g .. ,___-
a 0.084
e
>
g;- 0.06- . 0‘
[‘2’ 0.04 . x
‘6 ‘17, ”'1'- .
E 0.02 . .. i
3 ..,,.L\I'I H
0 rues:
0 . . . ‘ "guéetu—o—
o 200 400 600 800 1000 1200

Pore Diameter (microns)

Figure 4.4: Cumulative pore volume as a function of pore diameter for low fat and
high fat ground beef samples cooked to endpoint temperature of 60°C: means of 5
replicates.

60

 

0.08

0.07 — + LF coolafl

0.06 l l£§391875

0.05
0.04 l
0.03
0.02 .
0.01

 

Cumulative Pore Volume (cc/g)

 

 

 

A ._.._ ll -_
V TV v If

0 200 400 600 800 1000 1 200 1400

Pore Diameter (microns)

 

 

Figure 4.5: Cumulative pore volume as a function of pore diameter for low fat and
high fat ground beef samples cooked to endpoint temperature of 75°C: means of 5
replicates.

The cumulative pore volumes of extruded liquid for the low fat samples decreased
with cooking treatment temperature from 0.1428 cc/g in raw samples to 0.0751 cc/g in
samples cooked to 75°C. The cumulative pore volumes of extruded liquid for the high fat
samples also decreased with cooking treatment temperature from 0.1045 cc/g in raw
samples to 0.0481 cc/g in samples cooked to 75°C. The cumulative pore volume of
extruded liquid was greater for low fat samples compared to high fat samples at all
treatment conditions.

It must be noted that the pore distribution tests were carried out at room
temperature, and only water was extruded at room temperature. Therefore, because low
fat samples have considerably more moisture content compared to high fat samples, the

extruded cumulative pore volumes for all treatments are greater in low fat samples

61

compared to high fat samples. The moisture content of raw low fat and high fat samples
were 71.9% and 66.3% respectively.

Also, during cooking, water and fat are lost in the form of cooking losses.
Samples were analyzed for moisture and fat contents after cooking to different endpoint
temperatures. During cooking, the moisture content of the low fat samples decreased by
0.33, 1.37, and 5.57% when cooked to 45, 60, and 75°C center temperatures, respectively.
For the high fat samples, the moisture content during cooking decreased by 3.71, 2.94,
and 5.37% when cooked to 45, 60, and 75°C center temperatures, respectively. The drop
in fat contents was somewhat irregular (refer Appendix, section 7.5).

However, this explanation (amount of moisture in the samples) may not properly
explain the high cumulative pore volumes of low fat samples compared to high fat
samples. In order to satisfy the condition of saturation, all the cooked samples were
soaked in water for 10 min prior to testing. The water uptake of the samples afler
soaking was measured by weighing the samples before and after soaking. The water
uptake was approximately 0.114, 0.169, and 0.207 g for the low fat samples cooked to
45, 60, and 75°C respectively. The water uptake was approximately 0.212, 0.157, and
0.214 g for the high fat samples cooked to 45, 60, and 75°C respectively. The water
uptake was very little and not very different in the low fat and the high fat samples.

Therefore, the amount of water in the sample should not necessarily be a factor in
the low cumulative pore volumes of high fat samples. The protein structure and fat may
be responsible for this. Chemical interactions between proteins and fat, protein
denaturation, and, shrinkage of the patties may be different in low fat samples compared

to the high fat samples. Therefore, the high fat samples may be less permeable at all

62

cooking temperatures, compared to the low fat samples. Thus, the structure of the patties
is the most important factor that changes considerably during cooking.

The change in structure is related to shrinkage of the patties during cooking. As
discussed in the previous section, there was considerable shrinkage of the samples during
cooking. The high fat samples had significant shrinkage compared to the low fat samples.
This suggests that the interactions between the fat and proteins are responsible for the low
cumulative pore volumes of the high fat samples compared to the low fat samples.

The differences in the amount of extruded volume for the low fat samples at
different treatment conditions were significant only at the a = 0.10 level, whereas for
high fat samples, they were significant at the a = 0.05 level (Table 4.1 and 4.2). Two-
way analysis of variance confirmed the statistical significance (P<0.05) of the differences
in the extruded pore volumes with respect to endpoint temperature and fat content (Table

4.3). The interaction between endpoint temperature and fat content was not significant.

Table 4.1: Analysis of variance for the total cumulative pore volume of low fat
ground beef samples as affected by endpoint temperature.

 

Factor Sum of Squares Degrees of Mean F-Value P-Value
Freedom Squares

 

 

 

 

 

 

 

 

 

 

Temperature 0.011603 3 0.003868 2.560284 0.091335
Error 0.024171 16 0.001511
Total 0.035774 19

 

63

Table 4.2: Analysis of variance for the total cumulative pore volume of high fat
ground beef samples as affected by endpoint temperature.

 

Factor Sum of Squares Degrees of Mean F-Value P-Value
Freedom Squares

 

 

 

 

 

 

 

 

 

 

Temperature 0.009853 3 0.003284 14.43468 8.17E-05
Error 0.003641 16 0.000228
Total 0.013494 19

 

Table 4.3: Two-way Analysis of variance for the total cumulative pore volume of
high fat ground beef samples as affected by endpoint temperature and fat content.

 

 

 

 

 

 

Factor Sum of Squares Degrees of Mean F-Value P-Value
Freedom Squares

Temperature 0.020079 3 0.006693 7.701174 0.00052

Fat 0.015836 1 0.015836 18.22152 0.000164

Interaction 0.001377 3 0.000459 0.528166 0.666148

Error 0.02781 1 32 0.000869

Total 0.065 104 39

 

 

 

 

 

 

 

 

The cumulative pore volumes determined here are much less when compared to
the results from the work of Ngadi et al. (2001), who determined pore size distributions
in beef patties extended with soy protein. They reported cumulative pore volumes in the
range of 0.19 to 0.35 cc/g in the SPF (soy protein flour) extended samples and a
cumulative pore volume range of 0. 12 to 0.18 cc/g in the TSP (textured soy protein)
extended samples. They also reported a cumulative pore volume decrease with increase
in temperature. This was attributed to the collapse of the structure during protein
denaturation and other factors such as rate of moisture vaporization in products.

Kassama et al. (2005) reported a 24% cumulative pore volume decrease from 2.13

to 0.51 cc/g after deep fat frying of chicken meat for 360 s. Karathanos et al. (1996)

64

reported cumulative pore volumes greater than 5 cc/g in freeze dried carrots. The
cumulative pore volumes of the three studies mentioned above are much greater when
compared to the cumulative pore volumes of this study which are in the range of 0. 14 to
0.07 cc/g in low fat samples and 0.1 to 0.04 cc/ g in high fat samples. The main reason for
the large differences in the cumulative pore volumes of all these studies might be due to
the method of measuring pore diameters.

All the above three studies used mercury intrusion porosimetry to determine pore

diameters of up to 0.01 pm , but the present study used a liquid extrusion technique to
determine pore diameters up to 33 am. The techniques are different in that one is an

intrusion technique and the other is an extrusion technique. In an intrusion technique,
mercury is forced into the pores using very high pressures (greater than 228 MPa), but in
an extrusion technique, water is extruded out of the pores at very small pressures (less
than 0.01 MPa). Also, the intrusion technique is capable of measuring all blind pores, i.e.,
pores that have an inlet but no outlet, but the extrusion technique can only measure
through pores that extend all the way through the sample. This may explain the very large
difference between the cumulative pore volumes from the two techniques.

However, Ngadi et al. (2001) reported that the majority of the pores in the meat

patties extended with either TSP or SPF were greater than 10 pm. This suggests that
there are smaller numbers of pores less than 10 ,um , and their contribution to flow

certainly would be minimal.

65

4.4.2. Accessible Porosity

The liquid extrusion porosimeter determines pore-size distribution from the
amount of liquid extruded at a certain pressure. So, the amount of extruded liquid at a
certain pressure is the total accessible pore volume at that pressure. From this, the total
accessible pore volume can be related to the total accessible porosity or in a sense the
porosity of those pores that affect fluid flow of the sample. It should be noted that this
porosity is not the absolute porosity of the sample. The absolute porosity is the ratio of
the volume occupied by the total pore space in the sample to the bulk volume of the
sample. Normally, a gas is used to fill in all the pores of the sample to measure the total
pore space and relate to absolute porosity. But, the porosity defined here or determined
here is based on the volume of the fluid that is extruded out. Therefore, this should not be
confused with the absolute porosity of the samples.

Hence, the accessible porosity of the sample is defined as the ratio of the total

extruded pore volume to the bulk volume of the sample. It is given by:

V
p
% Accessible Porosity = V x 100 [4.2]
b

where:

Vp is the total extruded pore volume (m3), and

Vb is the bulk volume of the sample (m3).

Accordingly, the accessible porosity of the samples was determined from the
total extruded pore volume. It is shown in Figure 4.6 below. For each cooking treatment

the accessible porosity decreased with increase in the cooking temperature for both the

66

low fat and high fat samples. The accessible porosity of low fat samples decreased from
15.14% in raw to 7.64% in samples cooked to 75°C. The accessible porosity of high fat
samples decreased from 10.58% in raw to 5.17% in samples cooked to 75°C.

As stated above, the accessible porosity measured here is related to the total
extruded cumulative pore volume. The cumulative pore volume decreased with
temperature for both low fat and high fat samples. Hence, the decrease in accessible
porosity of the samples with respect to endpoint temperature was also attributed to the
significant changes caused by the shrinkage of the meat patties as discussed in the

previous section.

 

 

20
18 - DLF
16 . IHF

 

 

 

% Accessible Porosity
_L —L --l
O N h

 

 

 

 

 

owe-0:100

 

   

Raw cook 45 cook 60 cook 75

Figure 4.6: Accessible porosity as a function of endpoint temperature for low fat and
high fat ground beef samples cooked to different endpoint temperatures.

67

4.4.3. Pore-distribution

The liquid extrusion porosimeter determines pore-size distribution from the
amount of liquid extruded at a certain pressure. As described in the methods section, the
pressure applied on the sample was related to the pore diameters. This was a continuous
measurement, and, as the pressure was applied on the sample, water was extruded out of
the sample. A maximum of 1.25 psi (8616 Pa) was applied on the samples. This pressure

corresponds to pores ~ 33 ,um in diameter. The instrument gives the volume of water

extruded at certain pressures. A sample data sheet is given in Table 4.4.

68

Table 4.4: Data from pore-size distribution tests on raw low fat sample 1 from the
Liquid Extrusion Porosimeter software.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Pressure Pressure Diameter Cumulative Porosity % of Total Pore

PSIA Pa microns Pore Vol. °/o Pore Vol distributionl
cc/g dV/d logg

0.03 206.78 1392.7 0 0 0
0.034 234.35 1228.92 0.0005 0.054 0.226
0.038 261.92 1099.56 0.001 0.108 0.452 0.107
0.043 296.38 971.70 0.0017 0.183 0.769 0.135
0.048 330.84 870.48 0.0024 0.259 1.085 0.152
0.054 372.20 773.76 0.0034 0.367 1.538 0.203
0.06 413.56 696.38 0.0045 0.486 2.036 0.250
0.066 454.91 633.08 0.0058 0.627 2.624 0.326
0.074 510.05 564.63 0.0074 0.800 3.348 0.334
0.082 565.20 509.55 0.0093 1.005 4.208 0.443
0.091 627.23 459.15 0.01 15 1.243 5.203 0.505
0.101 696.16 413.69 0.0142 1.536 6.425 0.620
0.112 771.98 373.06 0.0175 1.892 7.918 0.764
0.124 854.69 336.96 0.0219 2.368 9.909 1.035
0.137 944.29 304.98 0.0265 2.866 1 1.99 1.105
0.152 1047.69 274.89 0.0317 3.428 14.343 1.198
0.168 1157.97 248.71 0.0375 4.056 16.968 1.388
0.185 1275.14 225.85 0.0438 4.737 19.819 1.565
0.204 1406.1 1 204.82 0.051 5.516 23.076 1.763
0.224 1543.96 186.53 0.0585 6.327 26.470 1.920
0.247 1702.49 169.16 0.067 7.247 30.316 2.082
0.273 1881.70 153.05 0.0756 8.177 34.208 2.058
0.301 2074.70 138.81 0.0844 9.129 38.190 2.158
0.332 2288.37 125.85 0.094 10.167 42.533 2.345
0.365 2515.83 114.47 0.1036 11.206 46.877 2.426
0.402 2770.86 103.93 0.1153 12.472 52.171 2.902
0.443 3053.46 94.319 0.1262 13.651 57.104 2.688
0.487 3356.74 85.79 0.1364 14.754 61.719 2.579
0.536 3694.48 77.953 0.1472 15.922 66.606 2.698
0.589 4059.80 70.93 0.1578 17.069 71.402 2.692
0.649 4473.36 64.38 0.168 18.172 76.01 2.518
0.713 4914.49 58.60 0.1789 19.351 80.95 2.775
0.787 5424.55 53.09 0.1882 20.357 85.158 2.255
0.865 5962.18 48.30 0.1964 21.244 88.86 2.078
0.951 6554.95 43.93 0.2039 22.055 92.262 1.895
1.046 7209.76 39.94 0.2104 22.758 95.203 1.635
1.15 7926.6 36.33 0.2165 23.418 97.963 1.541
1.239 8540.05 33.72 0.221 23.905 100 1.445

 

 

 

69

The pore-size distributions can be better described by grouping these data into
pore sizes of particular diameter range. The pore diameters were grouped into 10
categories. A sample data set is shown in Table 4.5. The volume fractions of the extruded
liquid were calculated as the ratio of the volume of extruded liquid at a particular

diameter to the total volume of extruded liquid. It is given as:

X f = _ [4.3]
where:

X f is the volume fraction of the extruded liquid at particular diameters,

Vd is the volume of extruded liquid at a particular diameter (m3), and

V, is the total volume of extruded liquid (m3).

Table 4.5: Data from raw low fat sample 1 set where pore diameters were
categorized into groups.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Diameter Volume
(microns) fractions
30-50 0.0296
50-90 0.0467
90-150 0.0457
150-230 0.0344
230-330 0.023
330-450 0.015
450—590 0.008
590-750 0.005
750-930 0.003
930-1 130 0.002

 

These data were plotted as histograms (Figures 4.7 to 4.12).

70

 

 

     

 

 

 

 

 

 

0.05
D LF raw
0.04 . “I HF raw
C
.9
<5 0.03 .
LL
G)
g 0.02 .
o
>
0.01 ,
o- jlleIIVJ

 

 

 

 

90- 150- 230- 330- 450- 590- 750- 930-
150 230 330 450 590 750 930 1130

Pore Diameter (microns)

Figure 4.7: Pore volume fractions at particular diameters for low fat and high fat
ground beef samples tested raw at room temperature using the Liquid Extrusion
Porosimeter: means of 5 replicates.

 

0.07

 

l E1 LF cook45 l
0'06 4 lg HF cook45]

0.05 « V—— n
0.04 4

0.03 ~

Volume Fraction

0.02 ~

0.01 .

   

 

 

 

  

 

 

 

 

 

30-50 50-90 90- 150- 230- 330- 450- 590- 750- 930-

150 230 330 450 590 750 930 1130
Pore Diameter (microns)

 

 

 

Figure 4.8: Pore volume fractions at particular diameters for low fat and high fat
ground beef samples cooked to 45°C and tested at room temperature using the
Liquid Extrusion Porosimeter: means of 5 replicates.

71

 

 

 

    

 

 

 

 

 

 

 

 

 

 

0.05
1:] LF cook60

0,04 _ I HF cook60
C
.o
8 0.03 «
(U .
it
o
g 0.02 .
T:
>

0.01 , .

0 f r T T r

 

 

 

 

 

 

 

 

30-50 50-90 90- 150- 230- 330- 450- 590- 750- 930-
150 230 330 450 590 750 930 1130

Pore Diameter (microns)

Figure 4.9: Pore volume fractions at particular diameters for low fat and high fat
ground beef samples cooked to 60°C and tested at room temperature using the
Liquid Extrusion Porosimeter: means of 5 replicates.

 

0.12

 

0 LF cook75
I HF cook75

 

 

0.1 .

 

0.08 .

0.06 ,

0.04 -

Volume Fraction

0.02 s

 

30-50 50-90 90- 150- 230- 330- 450- 590- 750- 930-

150 230 330 450 590 750 930 1130
Pore Diameter (microns)

 

 

 

Figure 4.10: Pore volume fractions at particular diameters for low fat and high fat
ground beef samples cooked to 75°C and tested at room temperature using the
Liquid Extrusion Porosimeter: means of 5 replicates.

72

  

     

(a) :ll Rawl i
0.05 ,. :22; ll45 l
: 5:5: 1
.g 0.04 1:160
9 [E75
0
g l
6 0.02 «
>
0.01 . H
0 l 555% it — - flfi

     

30—50 50-90 90- 150- 230- 30- 590- 750- 930-
150 230 330 450 590 750 930 1130

Pore Diameter (microns)

Volume Fraction

 

 

» 1

50-90 90- 150— 230-
150 230 330 450 590 750 930 1130
Pore Diameter (microns)

30-50

Figure 4.11: (a) Pore volume fractions (at particular diameters) for low fat ground
beef samples tested at raw and cooked to endpoint temperatures of 45, 60, and 75°C:
means of 5 replicates. (b) Same plot as (a), plotted as line graph instead of bar chart.

73

 

 

 

 
           

 

 

 

 

g .RaW'
3 I45 I
c a
.8 E 1360 l
o g :
s3 5753
a: i E l
E i E E
2 s é a
0 § E i =
>
30-50 50-90 90- 150- 230- 330- 450- 590- 750- 930—
150 230 330 450 590 750 930 1130
Pore Diameter (microns)
0-12 ' — —‘” *:;:
(b) 'x‘ l—o—RaW'
C:
.9
‘6
8
LL
0
E
3
B
>
0 i 7‘ _ f" 7—" "’T-i'Ti " “T'T‘T WT '_——TT___'1

30-50 50-90 90- 150- 230- 330- 450- 590- 750- 930-

150 230 330 450 590 750 930 1130
Pore Diameter (microns)

Figure 4.12: Pore volume fractions (at particular diameters) for high fat ground
beef samples tested at raw, and cooked to endpoint temperatures of 45, 60, and
75°C: means of 5 replicates. (b) Same plot as (a), plotted as x-y graph instead of bar
chart.

74

The pore distributions are quite different for both low fat and high fat samples for
each treatment conditions. At all treatment conditions, the high fat samples had large pore
diameters compared to the low fat samples. In raw low fat samples, most of the pores are
concentrated in the range below 300 um diameters, whereas in high fat samples, the
volume fractions were almost evenly distributed at all diameters. In raw low fat samples,
pores less than 195 pm in diameter occupied 80% of the total pore volume, whereas in
high fat samples, 80% of the total pore volume was occupied by pores less than 365 pm
in diameter.

In low fat samples cooked to 45°C, pores less than 246 pm in diameter occupied
80% of the total pore volume, whereas in high fat samples, 80% of the total pore volume
was occupied by pores less than 450 pm in diameter. In low fat samples cooked to 60°C,
pores less than 325 pm in diameter occupied 80% of the total pore volume, whereas in
high fat samples, 80% of the total pore volume was occupied by pores less than 540 pm
in diameter. In low fat samples cooked to 75°C, pores less than 330 pm in diameter
occupied 80% of the total pore volume, whereas in high fat samples 80% of the total pore
volume was occupied by pores less than 600 pm in diameter.

The pore diameters tended to increase with endpoint temperature. In both the
cases, low fat and high fat, the raw samples tended to have a more uniform pore
distribution, which is evident from the smooth line in Figures 4.14(b) and 4.15 (b). As the
cooking treatment temperature increased, the plots tended to have a peak in the middle of
the distribution indicating the largest extruded pore volumes, and thereby more pores in

that range.

75

In low fat samples, the raw ones tended to have a peak below 100 pm in

diameter, and as the cooking treatment temperature increased the peaks tended to shift to
the right roughly 230 to 330 ,um. In high fat samples, the raw ones tended to have a peak
below 100 ,um in diameter, and as the cooking’treatment temperature increased the peaks
tended to shift to the right roughly 330 to 450 ,um.

Also, as the cooking treatment temperature increased, the pore distributions
tended to have two peaks, thus indicating bimodal pore-distributions. The low fat samples
that were cooked to 60 and 75°C had bimodal distributions with two peaks at around 30-
50 um and 230-330 11m. The high fat samples that were cooked to 45°C had bimodal
distributions with two peaks at around 30-50 pm and 330-450 ,um. The high fat samples
that were cooked to 60°C also had bimodal distributions with two peaks at around 30-50
pm and 450-750 ,um. The high fat samples that were cooked to 60°C, had bigger pore
diameters compared to the rest of the samples. The high fat samples that were cooked to
75°C did not tend to have a bimodal distribution.

Also, as the cooking treatment temperature increased and the peaks tended to shift
to the right in both the low fat and high fat samples, there was a drop in the curve at
around 90-150 pm in low fat samples and 150-230 pm in high fat samples. This drop
suggests that there were fewer pores in this diameter range. The raw samples had a
smooth curve with a peak at 30-50 ,um.

This drop in the curve may be caused by the fat melting during cooking and, on
subsequent cooling to room temperature occupying some of these pores and blocking
them during pore-distribution tests. The drop in the curve was more significant in the

high fat samples that were cooked to 75°C. The volume fraction below 150 um was much

76

less in these samples, indicating fewer pores in this region. This greater drop in the curve
was evident even in the low fat samples that were cooked to 75°C. However, the drop in
the high fat samples was large compared to the low fat samples. Another possibility for
this drop in the curve may be related to the significant shrinkage of the meat patties
during cooking. The internal pressures exerted during cooking may squeeze the sample
and cause some of the pores to collapse.

The difference between the low fat and high fat samples was great with respect to
pore diameters. The high fat samples tended to have larger pore diameters at all treatment
conditions compared to the low fat samples. This may be due to two reasons. First, the
grind of the raw materials was not controlled in this study, i.e., the source of the meat was
not controlled. The two lots, low fat and high fat ground beef, were obtained from a local
grocery store and they were pre-ground. There was no additional grinding of the samples
Prior to analysis in this study. Hence, the grind of the samples was not properly
Controlled prior to analysis.

Secondly, these tests do not confirm whether the fat content of the two lots has an
effect on the pore-diameters. The fat content certainly had an effect on the cumulative
Dore volumes and the accessible porosity of the samples as discussed above. The
Shrinkage of the samples was significantly affected by the amount of fat and temperature.
The interactions of the fat and the proteins during cooking and denaturation cause
Shrinkage of the muscle fibers and give the texture/bind to the meat products. However,
this does not explain the effect of fat on the pore diameters.

Therefore, some additional tests were done to determine whether the grind and the

amount of fat had an influence on the pore diameters (see Appendix, section 7.3). The

77

high fat samples appeared to be more coarsely ground compared to the low fat samples.
Hence, a small portion of the high fat sample was reground using a 5 mm plate. These
samples were then formed into patties in Petri dishes and then tested raw for pore-size
distributions. The pore-distributions (see Appendix, section 7.3) were not appreciably
different from the original high fat ones.

Also, to test if the fat content influenced the pore- distributions, a small portion of
the low fat sample, which was originally around 5% fat, was mixed with ground fatty
tissues from beef obtained from the MSU meat laboratory to obtain samples that had15%
fat. That is, low fat samples (5% fat) were made into high fat samples (15% fat). The
samples were then formed into patties in Petri dishes and tested raw for pore-size
distributions. The pore-distributions (see Appendix, section 7.3) were not appreciably
different from the original low fat ones. Therefore, in raw samples, the fat content did not
have a great influence on the pore-diameters and their distribution.

Therefore, after analyzing these two factors, it is still unclear whether these
factors were limiting the analysis of the results of this study. However, the pore
distributions tended to shifl to the right with cooking treatments in both the high fat and
low fat samples. This suggests that there is significant increase in the pore diameters or
the number of pores, with larger diameters tending to increase with endpoint temperature.

Pore-size distribution tests were also conducted on low fat and high fat samples
that were cooked at slightly different oven conditions. The same treatment conditions of
cooking to endpoint temperatures of 45, 60, and 75°C were employed. Both high fat and
low fat patties were cooked at an air temperature of 176.7°C and a dew point temperature

of 861°C, which gives percent moisture by air volume of 60%. Previously the samples

78

were cooked at a dew point temperature of 939°C, which gives percent moisture by air
volume of 80%. This was done to achieve different cooking humidities in the oven and to
test whether this factor has any influence on the pore-size distributions.

There was no difference in the pore distributions with respect to cooking
treatment conditions (45, 60, and 75°C) in the low fat samples cooked at 60% moisture
by air volume (refer Appendix, section 7.3). This behavior in the low fat samples is not
evident. The pattern in the pore distributions of the high fat samples cooked at 60%
moisture by air volume was similar to that of the high fat samples cooked at 80%

moisture by air volume, except that the peak tended to form at ~ 230—330 um in the
samples cooked at 60% moisture by air volume as opposed to the peak at 330-450 pm in

the samples cooked at 80% moisture by air volume (refer Appendix, section 7.3).

The accessible porosities and the cumulative pore volumes of the low fat samples
cooked to 45 and 60°C at 60% moisture by air volume were greater than in the samples
cooked at 80% moisture by air volume. However, the accessible porosities and the
cumulative pore volumes of the high fat samples cooked to 45, 60, and 75°C were not
appreciably different between the two oven cooking conditions.

Karathanos et al. (1996) analyzed the porous structure and the pore-size
distributions of agricultural plant products such as apple, potato, cabbage, and carrot.
Mercury intrusion porosimetry was used, and the materials were air-dried and freeze-

dried for analysis. They measured pore-diameters less than 1 pm. They reported two

discrete peaks in pore-size distribution for apples, potatoes, and cabbage and three peaks

for carrots.

79

Thus, pore-distributions for agricultural products vary, and they can be bimodal.
The pore-size distributions for ground beef in this study indicate that larger pores were
formed during cooking, and some of the smaller pores were getting blocked partly
because of the changes in structure caused during shrinkage and protein denaturation and

partly due to the melted fat that occupied some of the pores.

4.4.4. Median Pore Diameters

The median pore diameter is described as the diameter where half the total
amount of extruded volume was measured. The median pore diameter increased with
endpoint temperature for both low fat and high fat samples. The median pore diameters
were significantly (P<0.05) different for both low fat and high fat samples treated at
different treatment conditions (Table 4.6). In low fat samples, there was almost 70%
increase in the median pore diameter from raw to 75°C cooked ones and in the high fat
samples, there was more than 100% increase in the median pore diameter from raw to
75°C cooked ones. Two-way analysis of variance confirmed that the median pore
diameters were significantly affected by the sample treatment condition and the fat

content (Table 4.7).

80

Table 4.6: Median pore diameters of low fat and high fat samples at different
treatment conditions determined using the Liquid Extrusion Porosimeter: means of
5 replicates.

 

 

 

 

 

 

 

Median Pore Diameterimicrons)
Treatment Low Fat r31: Fat
Raw 98.37 129.01
Cooked 45°C 93.12 259.67
Cooked 60°C 117.30 172.23
Cooked 75°C 167.61 394.99

 

 

 

 

Table 4.7: Two-way Analysis of variance for median pore diameters of low fat and
high fat samples with respect to endpoint temperature and fat content.

 

 

 

 

 

 

 

Factor Sum of Squares Degrees of Mean F-Value P-Value
Freedom Squares

Temrature 1590982 3 53032.74 36.97 1.64E-10

Fat 143711.4 1 143711.4 100.17 2.22E-11

Interaction 64791.59 3 21597.2 15.05 2.7 6E-06

Error 45907.74 32 1434.617

Total 413509 39

 

 

 

 

 

 

 

4.4.5. Pore Surface Area

The pore surface area was measured from the total extruded pore volume using
the liquid extrusion porosimeter. As stated in the methods section, the pore surface area
or the through pore surface area (A) of the samples is computed using equation 3.4.
The pore surface area also decreased with endpoint temperature for both the low fat and
high fat samples (Figure 4.13). The pore surface area of the low fat samples decreased

with cooking treatment temperature by 55% from 72 cmz/g in raw ones to 32 cmZ/g in

81

samples cooked to 75°C. The pore surface area of the high fat samples decreased with
cooking treatment temperature by 82% from 47 cmz/g in raw ones to 8 cmz/g in samples
cooked to 75°C. Because the pore surface areas are calculated from the cumulative pore
volumes, the same explanation (shrinkage and changes in the structure of the patties due
to protein denaturation) holds for the decrease in pore surface area, with respect to

cooking treatment temperature.

 

100

 

DLF
30 . 1 IHF

 

 

 

 

 

604

 

40~

Pore Surface Area (cm 2lg)

204

 

 

 

 

 

 

 

   

Cook 45 Cook 60 Cook 75

Figure 4.13: Pore surface area of low fat and high fat ground beef samples tested at
raw, and cooked to endpoint temperatures of 45, 60, and 75°C: means of 5
replicates.

Karathanos et a1. (1996) reported pore surface areas of 1 mz/g while conducting
pore-size distribution tests on dehydrated apples, carrots, potatoes, and cabbages. Ngadi
et al. (2001) reported pore surface areas of TSP (textured soy protein) extended samples
to be in the range of 4 to 9 mz/g. Kassama et al. (2005) reported highest cumulative pore

surface area of 8.27 mz/g in deep fat fried chicken meat samples. The pore surface areas

82

of the samples in the present study were much less compared to the other studies
mentioned above. As explained during the analysis of cumulative pore volumes in section
4.3.1, the differences in the pore surface areas may be due the different techniques of

measurement (MIP and LEP) applied by the two studies.

4.5. Permeability

The permeability of ground beef samples was determined using a PMI
Permeameter. Both low fat and high fat samples were tested at treatment conditions of
raw, and cooked to center temperatures of 45, 60, or 75°C. Two sets of permeability
experiments were conducted: one set at room temperature and the other one at elevated

temperature. The results of these tests are described in the following two sections.

4.5.1. Room Temperature

Because fat exists as solid at room temperature, only water is pushed out of the
meat matrix by applying pressures at room temperature. Hence, this is the effective
permeability of water through the meat matrix (Figure 4.14 and 4.15). The permeability
of low fat samples is higher than that of the high fat samples at all treatment conditions.
The permeability values of the low fat samples ranged from 2.85 x10'14to 1.53 x10'13 m2.
The permeability values of the high fat samples ranged from 7.19 x 10'15 to 9.21 x10'15

m2. The highest permeability values were found for low fat samples cooked to 75°C.

83

2.5E-13

 

 

LF
s~ 25:u3

£5

g;‘L55su3

E

8 15=u3

5

83 55su1

0 . .5

 

 

20 30 40 50 60 70 80

Cook Temperature (°C)

Figure 4.14: Permeability of low fat ground beef samples tested at raw, and cooked
to endpoint temperatures of 45, 60, and 75°C:means of 4 replicates.

1xuai4
'125514
15514
8E45+
55515
45515
25515.4 HF
0 . . . .
20 30 40 50 60 70 80

 

Permeability (m 2)

 

 

 

Cook Temperature (°C)

Figure 4.15: Permeability of high fat ground beef samples tested at raw, and cooked
to endpoint temperatures of 45, 60, and 75°C:means of 4 replicates.

84

The error in the permeability values was large, as is evident from the above
figures. This is because of sample-to-sample variations. The permeability was sometimes
very different even in the samples that were given the same treatment. Also, the
permeability of the samples did not follow any particular trend with increasing pressures.
Datta (2005) reported swelling of the meat tissues (whole-muscle) during permeability
experiments, but no such swelling was seen in this study. This is because the sample
chamber assembly was made in such a way, that it holds just the sample. The sample was
constrained to the size of the chamber. Hence, no such swelling was seen. De-ionized
water with a pH of ~ 6.2 to 6.3 was used for all the permeability experiments.

The permeability of both the high fat and low fat ground beef samples was much
higher than the values reported by Kova'csne et al. (2006), which were in the range of 6.8
x 10'18 to 1.6 x 10'16 m2 for the ground beef samples cooked from 50 to 80°C. They
reported the highest permeability for lean meat samples cooked at 60°C. The differences
in the permeability values in these two studies may be because of the differences in the
method of cooking. Kova'csne et al. used a double-sided pan fiyer made of Teflon coated
aluminum to cook the samples. In this study, a convection oven was used to cook the
samples at 80% air moisture by volume. This high humidity was used to prevent drying
out of the samples and losing a lot of water. Pan-frying is entirely different from oven
cooking. In pan-frying, during the initial stages of cooking, there will be cooking losses,
but a crust is formed on the surfaces of the patty, which prevents further loss of water and
fat from the patties. But, in oven cooking no such crust is formed on the surface of the
patty. Therefore, the oven-cooked samples may be more permeable compared to the pan-

fried samples.

85

Also, Kova'csne et al. reported addition of salt to the beef burgers prior to
cooking. The addition of salt has a tremendous impact on the water holding capacity of
the meat matrix. It lowers the protein isoelectric point to a more acidic pH, thereby
affecting the water holding capacity and the binding capacity of the meat matrix. Hence,
this may also have a potential influence on the low permeabilities of the pan-fried
products in the study by Kova'csne et al. (2006).

However, the low fat samples are more permeable compared to the high fat
samples at all treatment conditions. This is confirmed by the two-way analysis of
variance (Table 4.8) that shows the significance (P<0.05) of fat content on permeability.
This also relates to the more cumulative pore volumes of the low fat samples compared to
the high fat samples during pore-distribution tests. This implies that the composition and
the structure of the samples may have a big impact on the permeability of the meat
matrix. Even though the high fat samples had larger pore diameters compared to the low
fat samples at all treatment conditions, the amount of extruded volume and the
permeability of the high fat samples was less compared to the low fat samples. This
suggests that chemical interactions between the proteins and the fat in the high fat patties
during cooking and protein denaturation may have given that dense structure to the high

fat samples, making them less permeable.

86

Table 4.8: Two-way Analysis of variance for permeability of low fat and high fat
samples with respect to endpoint temperature and fat content.

 

 

 

 

 

 

 

Factor Sum of Squares Degrees of Mean F-Value P-Value
Freedom Squares

Temperature 1 .6E-26 3 5 .33E-27 2.026335 0.137008

Fat 3.11E-26 1 3.11E-26 11.82142 0.002146

Interaction l .57E-26 3 5.24E-27 1.991694 0.142105

Error 6.32E-26 24 2.63E-27

Total 1.26E-25 31

 

 

 

 

 

 

 

4.5.2. Elevated Temperature

The permeability experiments were also conducted at 45 and 60°C. The samples
were prepared in the same way as for the room temperature permeability experiments.
Low fat and high fat samples were cooked to endpoint temperatures of 45 and 60°C and
then tested for permeability at those temperatures. The Permeameter can be temperature
controlled. It is continuously heated by circulating air. The entire machine heats up, and
the temperature is controlled with an accuracy of i3 °C. Opening and closing of the lid
during testing resulted in heat loss to the surrounding environment. However, the tests
were canied out at 45 (i3) and 60 (:3 )°C. The temperature of the Permeameter could
not be maintained at 75°C; hence, tests at 75°C were not conducted.

The permeabilities of the low fat and the high fat samples at elevated
temperatures are reported in the following table (Table 4.9). Both the low fat and high fat
samples cooked to 60°C and tested at 60°C had the highest permeability values. The
highest permeability values were found for low fat samples cooked to 60°C and tested at

60°C.

87

.1.

 

Table 4.9: Permeabilities of the low fat and the high fat samples at elevated
temperatures of 45 and 60°C: means of 4 replicates.

 

Permeability (m2)
Low Fat Hifigh Fat

Cooked 45°C Tested 45°C 2.35E-l3 (i2.66E-l3) 1.23E-l4 (i3.3E-15)

 

Treatment Test Temperature

 

 

Cooked 60°C Tested 60°C 8.82E- l 3 (i4.79E- 13) 3.34E-13 (i3.75E-13)

 

Cooked 45°C Tested 60°C 3.09E-l3 (i2.21E-13) 2.67E-15 (i2.l lE-15)

 

 

 

Cooked 60°C Tested 45°C 2.30E-13 (i2.4lE-13) 4.03E-14 (i2.36E-l4)

 

 

 

 

The difference between the permeability values at room temperature and at
elevated temperature for cook 60°C samples was more than an order of magnitude in both
the low fat and high fat samples. Because of the high temperature, the fat in the samples
also melts and is readily available to flow out of the meat matrix. The density and the
viscosity of water and fat at 60°C are less than that at room temperature. Also, the pore
size distribution tests confirm the presence of larger pores at higher temperatures.
Therefore, the structure of the patties also should have an effect on the high
permeabilities.

In order to confirm this, additional tests were done on both the low fat and high
fat samples. Both the samples were cooked to endpoint temperatures of 45 and 60°C and
tested vice versa. The 45°C-cooked samples were tested at 60°C, and the 60°C-cooked
samples were tested at 45°C. The permeability of the low fat samples cooked to 45°C and
tested at 60°C were not much different than the ones that were cooked to 45°C and tested
at 45°C. The high fat samples cooked to 45°C and tested at 60°C were less permeable

than the ones that were cooked to 45°C and tested at 45°C. Both the low fat and high fat

88

samples cooked to 60°C and tested at 45°C were less permeable than the ones that were
cooked to 60°C and tested at 60°C.

Both the low fat and high fat samples cooked to 60°C and tested at 60°C have the
highest permeability values, with the low fat ones being more permeable than the high fat
ones. The temperature 60°C has a significant effect on many complexities that occur
during cooking. During the determination of fat holding capacity of ground beef,
Tripuraneni et al. (2005) reported that largest changes in the fat holding capacity occurred
between 40 to 55°C in both the low fat (5.6% fat) and the high fat (15% fat) samples.
However, in the high fat samples, the fat holding capacity continued to decrease at
temperatures above 5 5°C. This supports the fact that by the time the meat temperature
reaches 60°C, one of the significant phases of the cooking has passed, and, therefore,
there can be a great change in the structure and the composition of the meat at 60°C. This
is evident from the pore-size distribution tests, where the pore diameters were bigger in
the samples cooked to 60°C than the ones cooked to 45°C.

The elevated temperature tests for permeability were carried out to evaluate how
the temperature and the structure of the meat were affecting the permeability of the meat
matrix in reality. Two-way analysis of variance confirmed that the test temperature and
the fat content had a significant effect on the permeability of the meat samples (Table
4.10). The median pore diameters of the high fat samples were greater than that of the
low fat samples at all treatment conditions. However, the permeability of the high fat
samples was low compared to the low fat samples at all treatment conditions. This
suggests that the structure of the meat patties has a significant effect on the permeability

of the samples. The permeability of the samples was greater when elevated temperature

89

was maintained during the test. Therefore, these tests confirm that both the structure and

temperature have an effect on the permeability of the meat matrix.

Table 4.10: Two-way Analysis of variance for permeability of the low fat and high
fat samples with respect to test temperature and fat content.

 

 

 

 

 

 

Factor Sum of Squares Degrees of Mean F—Value P-Value
Freedom Squares
Temperature 1.53E-24 1 1.53E-24 13.57603 0.002007
Fat 4.98E-25 1 4.98E-25 4.408369 0.051979
Interaction 3.18E-26 1 3.18E-26 0.281084 0.603272
Error 1.8lE-24 16 1.13E-25
Total 3.87E-24 19

 

 

 

 

 

 

 

 

4.6. Fluid Properties of Fat

Fat transport during cooking is very dependent on the rheological properties of the
meat fats. Density and viscosity of the fat are important in determining the fluid
conductivity through the ground meat porous structure. Particularly, viscosity is the
important parameter that characterizes the resistance to flow in materials. Hence the
viscosity of fat was determined as described in section 4 using a VT550 rotational
viscometer. The apparent viscosity of beef fat decreased with increasing temperature
from 34.25 cP at 40°C to 14.36 cP at 70°C (Figure 4.16). Also the viscosity of beef fat
was not appreciably different at different shear rates indicating a Newtonian behavior.
The density of beef fat also decreased slightly with temperature between 25 and 50°C

(Figure 4.17).

90

 

40
35
30
25
20 ~
15
10

Viscosity (cP)

 

 

 

3O 4O 50 60 70 80
Temperature (°C)

Figure 4.16: Apparent viscosity of beef fat as a function of temperature determined
using a rotational viscometer: means of 3 replicates.

 

890
880
870
860 l

850

Density (kg/m3)

E

 

 

 

830 . .
20 30 40 50 60 70 80

Temperature (°C)

Figure 4.17: Density of beef fat as a function of temperature: means of 3 replicates.

91

4.7. Conductivity

The transport mechanisms in a porous medium can be due to several different
mechanisms. The three major modes of transport are by molecular diffusion, capillary
diffusion, and convection (filtration or Darcy) flow) (Datta and Zhang, 1999). Darcy’s
law describes the movement of liquid in a porous medium. Darcy’s law defines the

hydraulic conductivity of the medium by:

V
K =
" [arr/as] ”-41

 

where:
v is the volumetric flux or specific discharge (m3/m2 s),
H is the hydraulic or water potential (m),

s is the distance along flow (m), and

K}, is the hydraulic conductivity (m/s)

The hydraulic conductivity is the ease with which a fluid can be transported
through a porous matrix. It is related to the permeability by equation 2.9. The
permeability from Darcy’s law is given by equation 2.10.

Therefore, once the permeability of the medium is known, the hydraulic
conductivity of the medium can be calculated by plugging in the density and viscosity of
the water in equation 2.9. The density and viscosity of fat is different from that of water.
Hence, if the density and viscosity of fat is used in the equation (2.9), the lipidic
conductivity of the medium can be calculated. Since fats are less dense and more viscous

compared to water, the lipidic conductivity is less than that of hydraulic conductivity.

92

The permeability experiments were carried out on both low fat and high fat
ground beef samples cooked to 45, 60, or 75°C center temperatures. Knowing the
densities and viscosities of water and fat at these temperatures, the hydraulic and the
lipidic conductivities of both the low fat and high fat ground beef samples can be
calculated.

The densities and viscosities of water and fat at temperatures of 45, 60, and 75°C

are listed in the following table (Table 4.11).

Table 4.11- Densities and viscosities of water and beef fat at various temperatures.

 

 

 

 

 

 

Temperature Water Beef Fat
(°C) Density (kg/m3) Viscosity (cP) Density (kg/m3) Viscosity (cP)
45 989.33 0.653 859.56 34.25
60 983.84 0.467 853.14 19.85
75 976.89 0.355 845.53 14.36

 

 

 

 

 

 

Therefore, using equation 2.9, the hydraulic and the lipidic conductivities of the

low fat and the high fat meat matrix were calculated (Table 4.12).

Table 4.12- Hydraulic and lipidic conductivities of the low fat and high fat samples
at different treatment conditions.

 

 

 

 

 

 

 

Treatment Hydraulic Conductivity (m/s) Lipidic Conductivity (m/s)
Low Fat High Fat Low Fat High Fat
Cooked 45°C 7.30E-07 1.06E-07 1.21E-08 1.77E-09
Cooked 60°C 1.95E-06 1.65E-07 3.99E-08 3.38E-09
Cooked 75°C 4.14E-06 2.48E-07 8.85E-08 5.31E-09

 

 

 

 

 

93

Both the hydraulic conductivity and the lipidic conductivity of the low fat samples
were greater compared to the high fat samples at all temperatures. Also, both the
hydraulic conductivity and the lipidic conductivity tended to increase with temperature.
This is because there is an increase in permeability of the meat matrix and decrease in
density and viscosity with temperature for both water and fat.

It must be noted that the effective permeability of the meat matrix that was
determined at room temperature on samples cooked to 45, 60, and 75°C endpoint
temperatures was used for hydraulic and lipidic conductivity calculations. This
permeability was a little higher when the same temperatures were maintained during
testing. The hydraulic and lipidic conductivities were greater in low fat samples
compared to the high fat samples. This is because of the higher permeability of the low
fat samples compared to the high fat samples. However, the fat content of the low fat
samples is less than that of the high fat samples. Hence, when these conductivity values
are further used in modeling the fat transport phenomenon, they should be used in

relation with the initial fat content of the products.

4.8. Tortuosity

The tortuosity of a porous medium is defined as the ratio of the effective path

length to the sample thickness.

 

_ L [4.5]

94

r is the tortuosity of the medium,
Le is the effective path length (m), and

L is the sample thickness (m).

Flow through porous media is so complex that many theories have evolved to
relate the different properties of the porous medium. Tortuosity is the parameter that
enables a link between the porosity, pore-size distribution, and the permeability of the
medium. Scheidegger (1974) presented a detailed report on how all these parameters are
linked. He presented different models, such as the capillaric models that are based on the
Hagen Poiseuille law and hydraulic radius models that are based on Kozeny theory.
Capillaric models are divided into straight capillaric model, parallel type models, and
serial type models to relate porosity, pore-size distribution, and the permeability of a
porous medium. The hydraulic radius models based on the Kozeny theory require a
parameter called the specific surface area of the channel of flow.

The introduction of all these parameters such as tortuosity, connectivity, and
specific surface area are important in transforming an ideal bundle of capillary tubes to a
real porous medium. However, the determination of these parameters is rather difficult.
Hence, with the available properties like porosity, pore-size distribution, and
permeability, this study makes use of two such models, the straight capillaric model
along with the parallel type model in order to determine the tortuosity of the ground meat
matrix. These models are utilized as described by Scheidegger (1974) and have been

outlined in the following two pages.

95

The straight capillaric models are constructed on the basis of representing the
porous medium by a bundle of straight, parallel capillaries of uniform diameterg‘ . The
Hagen-Poiseuille law gives the total volume-flow Q through a capillary:

_ .54 d_p
128p dx

 

Q:

[4.6]

where:

# is the viscosity (Kg/ms), and

d

j: is the pressure gradient along the capillary

If there are n such capillaries per unit area of cross-section of the model, the flow

per unit area V is given by

_ _ nag-4 d_p
12811 dx ”‘71

 

As the flow can also be expressed by Darcy’s law

kdp

V = _;—d_x_ [4.8]

it follows that

_ 71773-4
128

 

[4.9]

The pore volume of the model (assuming unit cross-sectional area) is equal to

1 --2
Z "71' X5 , the length being denoted by x; thus the porosity is

1 _
¢ = 11452 [4.10]

96

Solving these two equations, by eliminating n we get:

 

_2
k=¢°

32 [4.11]

In an actual porous medium (5 represents the average pore diameter. However,
this equation does not completely represent the connection between porosity and

permeability in a porous media. Hence, the factor 32 is commonly replaced by some

. 2 . . .
arbitrary factor 1' , where r is called the tortuosrty of the medium.

Therefore, the equation transforms to

¢52
k = 12 [4.12]

 

Now, this equation does not adequately represent the characteristics of a porous
medium. This model gives the permeability in one direction only. If all capillaries are
parallel, there can be no flow orthogonal to the capillaries. Moreover, 5 , which
represents the average pore diameter is kind of vague, because in an actual porous
medium, there are pores of different diameters. Therefore, average pore diameter cannot
account for the wide variability in the size of the pores of an actual porous medium. Thus,
assuming that there are one-third of the capillaries in each spatial dimension, the porosity

of the model is given by:

3 _
¢=Znfl52 [4.13]

Thus, the final model is given as:

_2
k = (M 2
967

 

[4.14]

97

However, 32 is still vague representing the average pore-diameter. It is quite

desirable to reduce 32 to some value calculated from the pore-size distribution. Thus,
assuming that all the capillaries permitting flow in a given direction are parallel to that

direction, but vary in pore diameter, leading from one face of the porous medium through

to the other, the 5‘2 is related to pore-size distribution by
‘2 _ 2
5 - [a a(5)db‘ [4.15]
0

where:
(1(5) is the pore-size distribution, and

6 is the pore diameter (,um ).

Thus, by using this theory of capillaric models, the tortuosity of the ground meat
matrix was calculated. Equation 4.15 was used to calculate the average pore diameter,
and then the tortuosity was calculated using equation 4.14. The pore diameters and the

pore-size distribution data obtained from the LEP were used to calculate average pore

diameter, 32. The average pore diameter, 32 , the average effective permeability of
water through the samples at room temperature and the accessible porosity of the samples
were plugged into equation 4.14 and the tortuosity of the medium was calculated.

The porosity, pore-size distributions, and the permeability are the important
parameters used to determine tortuostity. The tortuosity of both low fat and high fat
samples decreased as a function of cooking temperature. This may be related to the
significant shrinkage of the samples during cooking. The tortuosity values were reported

in the following table (Table 4.13).

98

 

Table 4.13: Tortuosity of the low fat and high fat ground beef samples at different
treatment conditions.

 

 

 

Tortuosity
Treatment Low Fat High Fat
Raw 1 .99 4. 162

 

Cooked 45°C 1.368 3.634

 

Cooked 60°C 0.954 2.788

 

Cooked 75°C 0.444 2.9425

 

 

 

 

 

The tortuosity values for the low fat cook 60 and 75°C ones were less than one.
This suggests that the capillaric model theory, on the basis of which the tortuosity
parameters were calculated, does not practically represent the ground meat porous
medium. Therefore, the relationship between the porosity, pore-size distributions, and the
permeability as described by equation 4.14, may be theoretically possible, but does not
represent the real porous medium in practice. Moreover, the porosity values in the
present study are not truly the absolute porosity of the samples, but only the total
accessible porosity. Hence, these porosities may be affecting the results of the tortuosity

values found.

4.9. Relative Permeability of Fat

The relative permeability of the fat was measured as described in the methods

section. The low fat samples that were cooked to 60°C were used. Three samples, each 34

99

mm x 10 mm thick, were stacked on top of one another in the sample chamber (34 mm x
30 mm). The Permeameter was set up at 60i3°C and pre-melted fat at 60°C was used. A
starting pressure of 0.3 psi (2068 Pa) was applied in steps of 0.3 psi (2068 Pa) until a
maximum pressure of 5 psi (34464 Pa) was reached.

The pressures at each pressure step were held until steady states were attained.
These steady state flow rates were sometimes reached quickly in a matter of seconds, but
sometimes did not (refer to Appendix: section 7.6). It should be noted that these tests
were conducted at 60°C, so, if the samples were held for longer periods of time, the
temperatures may cook the meat and introduce many different characteristics. Therefore,

the time at each pressure step was regulated for 60 s. The flow rate and the pressures

were used to calculate the mobility of the oil phase ( 40 ) using equation 3.10

(Ramakrishnan and Cappiello, 1990).

The mobility of the oil phase can be related to the relative permeability of the fat
by equation 3.11 (Ramakrishnan and Cappiello, 1990).

Therefore, applying equations 3.10 and 3.11, the relative permeability of the fat
was determined from the laboratory experiments. However, all the relative permeability
values turned out to be greater than 1(Table 4.14), which do not have any meaning. The
relative permeability is the ratio of the effective permeability to the intrinsic permeability
of the medium. The effective permeability is the permeability when two or more fluids
are occupying the porous medium. The intrinsic permeability is the permeability of the
medium at true saturation. Hence, the effective permeability is always less than the

intrinsic permeability of the medium.

100

Table 4.14: Relative Permeability of beef fat within the low fat samples cooked and

tested at 60°C.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Pressure (Pa) Flow (cc/s) Fat RP( km )
5462 0.0090
7833.56 0.0132 2.435
10143.3 0.0173 2.413
12452.35 0.0196 1.343
14702.81 0.0249 3.217
16960.17 0.0273 1.463
19200 0.0342 4.227
20143.22 0.0447 15.166
23442.07 0.0563 4.818
24463.57 0.0707 19.218
26506.56 0.0837 8.718
28560.6 0.0868 2.087
30600.83 0.0998 8.723
32670.7 0.1058 3.925
34677.17 0.1126 4.667

 

 

In the present study, the intrinsic permeability of the medium cannot be truly
determined, as it was impossible to get ground beef samples that are totally devoid of fat.
However, the low fat samples that were cooked to 60°C were submerged in water for 15
min to approximate the condition of saturation and were tested at room temperature to
determine the intrinsic permeability of the medium. This value turned out to be less than
that of the effective permeability of the medium. Sample to sample variations had a
significant effect on the permeability values. Some samples had high permeabilities
compared to the other samples in the same treatment condition. This was evident even in
the effective permeability of the samples reported in the permeability section.

The relative permeability values determined by Ramakrishnan and Cappiello
( 1990) were below one. Their experiments were conducted on a synthetic ceramic sample

(38 mm diameter x 75 mm thick) that is strongly water wet in nature. But the relative

101

permeabilities determined in the present study do not make any sense. This may be
because of the many violations of the underlying assumptions of the experimental
technique employed. First, the condition of saturation was not fully satisfied. The low fat
samples that had 5.47 i 0.25% fat were used. The samples were cooked to 60°C and then
soaked in water for 15 min to approximate the condition of saturation.

Second, three samples were stacked on top of one another for making a sample
which should be 30 mm thick. This had a major impact on the results, as fat was getting
in between the samples. Using one sample (30 mm thick) instead of three might reduce
some of these errors, but cooking a sample of that thickness might cause new problems of
changing the homogeneity of the sample. Also, as mentioned above, Ramakrishnan and
Cappiello (1990) used a sample that was 75 mm thick. But in this study, only 30 mm
thick samples were used. This may be major factor that was affecting the relative
permeability results.

Therefore, as mentioned above, all these factors had a great impact on the results
of this study. However, the concept of relative permeability is relatively new to the field
of food engineering. Moreover, it is an important property that is usefirl in many areas of
food research. Hence, future studies should implement this methodology again in a better

way to determine this property.

4.10. Summary

Thus, the basic properties that are essential for developing efficient cooking
models were determined successfully. The density and viscosity of beef fat decreased

with temperature. The lower values of viscosity mean the fluid has less resistance and

102

therefore can flow more easily. The median pore diameters increased with endpoint
temperature for both the low fat and high fat samples. The permeability of the low fat
samples was higher compared to the high fat samples. The determination of the relative
permeability of fat was attempted but could not be achieved. Knowledge of the changes
in the matrix properties, as well as the fluid properties, is essential when modeling the
heat and mass transfer during cooking of ground meat. This gives the opportunity to

develop improved cooking models for ready-to-eat meat and poultry products.

103

 

5. CONCLUSIONS

This study was conducted to analyze the changes in the structure of the ground
meat matrix during cooking, in terms of the porosity, permeability, and pore-size
distributions. These properties, along with the relationships between fat and proteins in
meat, are essential to understanding the fat transport mechanism and thereby aid future
cooking model improvements.

The basic properties that are essential for developing multi-phase fluid transport
models have been successfully determined. However, there are some uncontrollable
limitations in the way the tests were conducted. The samples were soaked for 10 min in
water to more closely (although perhaps still insufficiently) satisfy the requirement of a
saturated sample for pore-size distribution experiments. Applying vacuum during soaking
or vacuum saturation of the samples might have given a more thorough saturation. The
sample-to-sample variations in the same treatment condition were sometimes huge in all
the permeability experiments. This variability cannot be totally avoided or corrected,
because of the nature of a ground meat product. In spite of some limitations, all the basic

properties were determined. Therefore, the main conclusions of this study were:

1. The viscosity and density of beef fat decreased with temperature.

2. There was significant shrinkage of the high fat samples compared to the low fat

samples after all cooking treatments. This significant shrinkage might cause internal

pressures that may be the primary cause of fat transport out of the meat matrix.

104

3. The accessible porosities of both the low fat and high fat samples decreased with
endpoint temperature. This may be related to the shrinkage of the patties during

cooking and protein denaturation.

4. The pore distributions were quite different for each cooking treatment. High-fat
samples had significantly larger pore diameters at all cooking treatment temperatures
compared to the low-fat samples. Pore-distributions at higher temperatures of 60 and
75°C were bimodal. The median pore diameters increased with endpoint temperature

for both low fat and high fat samples.

5. The permeability of the low fat samples was higher compared to the high fat samples
at all treatment conditions. The highest permeability values were found for low fat
samples cooked to 75°C. The permeabilities of the low fat and the high fat samples
tested at elevated temperatures (45 and 60°C) were greater than those of the samples
tested at room temperature. The permeability of the high fat samples was less than
that of the low fat samples, even though the median pore diameters of the high fat
samples were greater than those of the low fat samples at all treatment conditions.
This is even evident from the low accessible porosities (or cumulative pore volumes)
of the high fat samples compared to the low fat samples. This suggests that the
interactions between the proteins and the fat in the high fat samples are changing the
structure of the high fat meat, making it less permeable. Therefore, all these results
suggest that permeability of the samples depended on both the temperature and the

structure of the meat during cooking.

105

6. The fluid and the material properties determined here are important properties, which
form the basis of fluid transport models. The permeability of the meat matrix, along
with the density and viscosity of water and fat at various treatment conditions, were
used to calculate the hydraulic and lipidic conductivities of the ground meat matrix.
The hydraulic and the lipidic conductivities were greater for low fat samples. The
lipidic conductivities were determined by using the water permeability of the meat
matrix. It is not the permeability of the fat in the meat; hence, they tend to be greater

in the low fat samples.

7. The pore volume distributions, along with permeability and the porosity values, were
used to determine the tortuosity of the ground meat matrix. However, the theoretical

equations still have some limitations in representing the actual porous medium.

8. The determination of the relative permeability of the fat was attempted but could not

be achieved due to some limitations as discussed in the previous section.

The changes in the structure of the meat patties with respect to cooking treatment
were successfully analyzed. These changes significantly influence the transport
mechanisms of water and fat through the meat. The hydraulic and the lipidic
conductivities were determined. The densities and viscosities of beef fat were determined
with respect to temperature. All these properties are useful in developing a multi-phase
fluid transport model that describes water and fat transport during cooking of ground

meat.

106

6. FUTURE WORK

Ground meat is a porous medium, in which water and fat co-exist. Cooking of
ground meat causes fats to melt and flow out of the meat matrix. Because water and fat
flow simultaneously, a two-fluid flow model would better describe the transport
mechanisms during cooking of ground meat products than do existing models. This
section deals with how the results from the present study should be further applied in
developing improved cooking models.

Porous media heat and mass transfer models are very complex, involving
numerous parameters. The basic properties, which are essential, are the fluid and matrix
properties that are integrated in the liquid and vapor permeability, porosity, capillary
diffusivity, and molecular diffusivity. The other important properties are the thermal
properties, such as specific heat, thermal conductivity, and density of the medium and
fluid. The present study focused on determining some of the essential properties that are
needed to develop precise cooking models for heat and mass transfer during cooking of
ground meat.

The present study has determined the material properties, such as porosity, pore-
size distribution, and liquid permeability of the ground meat matrix and the fluid
properties, such as density and viscosity of the fat. This study for the first time
determined the hydraulic conductivity and the lipidic conductivity of ground meat. These
parameters are not perfect, in a sense, owing to the underlying assumptions and the
difficulties posed by a porous medium.

The real porous medium is much more complex, with twisted, crooked, dead-

ending, or interconnected pores. The tortuosity and the connectivity are important

107

 

parameters that differentiate an ideal bundle of straight capillary tubes to a real porous
medium with twisted and crooked pores. The experimental data from this study have
been used to calculate the tortuosity parameter for ground beef samples, with respect to
different treatment conditions. However, the theoretical models failed to represent the
actual porous medium.

Fluid flow in a capillary porous medium can be due to several different
mechanisms, such as diffusion, bulk flow, or convective flow. Convective flow mainly
occurs through the pores and interstitial spaces of the porous medium. Fat transport
during cooking is a form of liquid transport, which can be described by Darcy’s law as
convection flow. The important parameters that are needed in applying Darcy’s law to
transport of fluids in a porous media are the permeability of the porous medium and the
conductivity of the fluids. These parameters (i.e., the hydraulic conductivity, the lipidic
conductivity, and the permeability of the porous medium) have been determined in this
study.

The present study evolved on the basis of two-fluid flow mechanisms for water
and fat through the ground meat porous matrix. In this study, the flow channels for water
and fat were assumed to be different, and the flow of both water and fat were assumed to
be simultaneous. Therefore, the two-fluid model makes sense. However, it is still unclear
whether the water and fat flow through different channels or the same channels, or if they
interact and flow together. It is important to understand this part of the transport
mechanism on the basis of which models should be developed. If the water and fat flow
through different channels, then a two-fluid flow model can best describe the transport

mechanism. Otherwise, alternative models have to be developed. Hence, a more thorough

108

understanding of the fluid transport during cooking is essential to develop effective
models for fat and water transport.

Multi-phase heat and mass transfer equations in porous media begin with
conservation equations for heat and mass of each phase (solid, liquid, and gas). Ni et al.,
(1999) have developed multi-phase porous media models for moisture transport in
intensive microwave heating of biomaterials. The total flux of vapor and air are
described by convective Darcy flow and diffusion, respectively. The total liquid flux is
given by Darcy’s law and expanded in terms of total pressure and capillary pressure.
Multi-phase porous media models have been developed on the basis of evaporation,
internal heat generation, and pressure driven flow. Because fat transport also depends on
convective flows and capillary pressures, these types of models should be developed to
represent the fat transport mechanism during cooking of ground meat.

Generally, multi-phase flow equations are derived from single phase Darcy
equations by introducing a relative permeability for each phase. The general equations for
two-phase flows are discussed in section 2 (review of literature) from equations 2.18 to
2.24. Therefore, as seen fiom these equations, many parameters are needed in modeling a
two-fluid flow phenomenon. Some of the parameters (density, viscosity porosity,
permeability, and conductivity) have been determined in this study. However, there are
other parameters, such as capillary pressures, fluid saturations, and relative permeabilities
of the two phases that are needed.

The present study made an attempt to determine the relative permeability of fat
during cooking of ground meat. However, this property was not successfully determined,

because of many limitations as described in the results section. As seen in this study,

109

determination of the tortuosity and the relative permeability parameters failed. Relative
permeability experiments are recognized as very difficult experiments, even in soil and
petroleum engineering research. This suggests the complexity of this parameter, and,
therefore, its determination in a sample like ground meat will be very challenging.

In spite of some limitations, the essential properties that are important in
developing precise cooking models have been determined. All the data reported in this
study are new and are essential for understanding fluid transport of water and fat during
cooking. Therefore, keeping in mind the complexity of some of these properties, the basic
groundwork for modeling must be laid out first. Later, any required parameters could be
determined from laboratory experiments. Image analysis might help identify some of the
parameters, such as tortuosity and connectivity. Image analysis would also identify water
and fat channels and the changes in the structure of the meat patties during cooking.

Therefore, the future work must understand the complexities of these models and
the complexity of meat patty cooking. Then, these properties can be used to improve

mechanistic models for mass transport during cooking.

110

7. APPENDICES

The data from the pore-size distribution and permeability tests are included in the
appendices. This section is divided into five sub-sections. The first section (section 7.1)
includes the pore-size distribution data from the experiments conducted using the Liquid
Extrusion Porosimeter. The second section (section 7.2) includes the permeability plots
for both the low fat and high fat samples tested at room temperature and elevated
temperatures using the PMI Permeameter.

The third section (section 7.3) includes data from the pore-size distribution tests
conducted on high fat and low fat samples to test if the grind and fat content had any
influence on the raw samples. The third section also includes pore-size distribution plots
for low fat and high fat samples cooked at 60% moisture by air volume. The fourth
section (section 7.4) includes plots from the experiments conducted to determine the
apparent viscosity of beef fat using the VT550 rotational viscometer. The fifth section
(section 7.5) has a brief note on the results of the fat content analysis on all the samples
after cooking to different endpoint temperatures. The last section (section 7.6) includes
the flow plots for the relative permeability experiments conducted using the PMI

Permeameter.

111

7.1. Pore-size distribution Results

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PressurelPressurelDiameterCumulative Porosity "/o of Total Pore

PSIA N/m2 microns Pore Vol. % Pore [Distributionl
M Volume dV/d logD

0.032 220.57 1305.7 0 ‘ 0 0
0.051 351.53 819.28 0.0013 0.134 0.72 0.064
0.071 489.38 588.5 0.0032 0.329 1.772 0.131
0.109 751.3 383.33 0.0086 0.884 4.762 0.287
0.162 1116.6 257.92 0.0191 1.964 10.58 0.603
0.218 1502.6 191.67 0.03 3.085 16.61 0.836
0.32] 2212.6 130.17 0.0504 5.183 27.91 1.2
0.518 3570.4 80.663 0.0908 9.338 50.28 1.922
0.627 4321.7 66.64 0.1113 11.45 61.63 2.444
0.759 5231.6 55.051 0.1328 13.66 73.53 2.562
0.919 6334.4 45.466 0.1539 15.83 85.22 2.512
1.01 1 6968.5 41.329 0.1634 16.8 90.48 2.267
1.235 8512.5 33.833 0.1806 18.57 100 1.957

 

 

 

Table 7.1: Data from pore-size distribution test on raw low fat sample 2 using the

Liquid Extrusion Porosimeter.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

lPressurelPressurelDiameterCumulativelPorosity % of Total Pore

PSIA N/m2 microns Pore Vol. % Pore [Distributio
cc/g Volume dV/dlgD_

0.031 213.67 1347.8 0 0 0
0.054 372.21 773.77 0.0015 0.161 0.89 0.064
0.075 516.95 557.11 0.0033 0.355 1.95 0.131
0.105 723.73 397.94 0.0069 0.742 4.07 0.255
0.156 1075.3 267.84 0.0163 1.753 9.62 0.566
0.21 1447.5 198.97 0.03 3.227 17.7 1.098
0.308 2123 135.66 0.0582 6.26 34.4 1.754
0.41 1 2832.9 101.66 0.0785 8.443 46.3 1.676
0.547 3770.3 76.386 0.0997 10.72 58.9 1.766
0.602 4149.4 69.408 0.107 11.51 63.2 1.815
0.728 5017.9 57.395 0.1221 13.13 72.1 1.892
0.968 6672.1 43.165 0.1455 15.65 85.9 1.956
1.286 8864 32.491 0.1694 18.22 100 2.004

 

 

 

 

 

 

 

 

 

Table 7.2: Data from pore-size distribution test on raw low fat sample 3 using the

Liquid Extrusion Porosimeter.

112

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PressurelPressurelDiameter umulativelPorosity% of Tota Pore
PSIA N/m2 microns Pore Vol. % Pore [Distributionl
cc/L Volume dV/d logL
0.034 234.35 1228.9 0 0 0
0.053 365.31 788.36 0.0007 0.075 1.2 0.038
0.074 510.06 564.64 0.0017 0.183 2.91 0.071
0.102 703.06 409.64 0.0036 0.388 6.15 0.141
0.151 1040.8 276.71 0.0089 0.958 15.2 0.322
0.204 1406.1 204.82 0.0163 1.755 27.9 0.586
0.301 2074.7 138.82 0.026 2.799 44.4 0.594
0.402 2770.9 103.94 0.0325 3.498 55.6 0.535
0.536 3694.5 77.954 0.0386 4.155 66 0.505
0.649 4473.4 64.381 0.0428 4.607 73.2 0.523
0.714 4921.4 58.52 0.0449 4.833 76.8 0.524
0.864 5955.3 48.36 0.0492 5.296 84.1 0.537
1.264 8712.4 33.056 0.0585 6.297 100 0.583

 

 

 

Table 7.3: Data from pore-size distribution test on raw low fat sample 4 using the
Liquid Extrusion Porosimeter.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IPressurelPressurelDiameterCumulative Porosi % of Total Pore

PSIA N/mz microns Pore Vol. % Pore 1Distributio
c_c/g Volume dV/d 10%

0.031 213.67 1347.8 0 0 0
0.053 365.31 788.36 0.0006 0.062 0.71 0.026
0.073 503.17 572.37 0.0016 0.165 1.89 0.071
0.11 758.2 379.85 0.0044 0.453 5.2 0.156
0.164 1130.4 254.78 0.011 1.133 13 0.377
0.22 1516.4 189.92 0.019 1.957 22.5 0.621
0.324 2233.2 128.96 0.0312 3.214 36.9 0.719
0.432 2977.6 96.721 0.041 1 4.233 48.6 0.785
0.523 3604.9 79.892 0.048 4.944 56.7 0.823
0.635 4376.9 65.801 0.0549 5.655 64.9 0.81 1
0.768 5293.6 54.405 0.0624 6.427 73.8 0.9
1.023 7051.2 40.844 0.0745 7.674 88.1 0.963
1.255 8650.3 33.293 0.0846 8.714 100 1.127

 

 

 

 

Table 7.4: Data from pore-size distribution test on raw low fat sample 5 using the
Liquid Extrusion Porosimeter.

113

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1Pressure1Pressure1DiameterCumulativelPorosity % of Total Pore

PSIA N/m2 microns Pore Vol. % Pore [Distributio
cc/g Volume dV/d logg

0.031 213.67 1347.8 0 0 0
0.054 372.21 773.77 0.0048 0.49 5.44 0.184
0.074 510.06 564.64 0.0075 0.76 8.5 0.182
0.116 799.55 360.2 0.0108 1.1 12.2 0.156
0.156 1075.3 267.84 0.0142 1.44 16.1 0.244
0.21 1447.5 198.97 0.0182 1.85 20.6 0.286
0.308 2123 135.66 0.0262 2.66 29.7 0.444
0.498 3432.6 83.902 0.0427 4.34 48.4 0.73
0.602 4149.4 69.408 0.0508 5.17 57.6 0.907
0.729 5024.8 57.316 0.0597 6.07 67.7 0.988
0.802 5527.9 52.099 0.0642 6.53 72.8 1.002
0.97 6685.9 43.076 0.0741 7.53 84 1.106
1.243 8567.6 33.615 0.0882 8.97 100 1.208

 

 

 

Table 7.5: Data from pore-size distribution test on low fat sample I cooked to
endpoint temperature of 45°C.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PressurelPressurelDlameterCumulativelPorosity % of Total Pore

PSIA N/m2 microns Pore Vol. % Pore istributionl
cc/g Volume dV/d IogD_

0.032 220.57 1305.7 0 0 0
0.051 351.53 819.28 0.0044 0.438 2.95 0.196
0.077 530.74 542.64 0.0113 1.124 7.58 0.348
0.105 723.73 397.94 0.0214 2.129 14.4 0.677
0.156 1075.3 267.84 0.0372 3.701 25 0.83
0.21 1447.5 198.97 0.0448 4.458 30.1 0.532
0.308 2123 135.66 0.0577 5.741 38.7 0.7
0.452 31 15.5 92.441 0.0761 7.572 51.1 0.997
0.548 3777.2 76.247 0.0874 8.696 58.7 1.22
0.603 4156.3 69.292 0.0938 9.333 63 1.391
0.73 5031.7 57.237 0.1071 10.66 71.9 1.447
0.971 6692.8 43.031 0.1289 12.83 86.5 1.589
1.233 8498.7 33.888 0.149 14.83 100 1.749

 

 

 

 

 

 

 

 

 

Table 7.6: Data from pore-size distribution test on low fat sample 2 cooked to
endpoint temperature of 45°C.

114

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ressurelPressurelDiameterCumulative Porosity% of Total Pore
PSIA N/m2 microns Pore Vol. % Pore [Distribution]
cc/g Volume dV/d logg
0.033 227.46 1266.2 0 0 0
0.051 351.53 819.28 0.0023 0.2337 1.94 0.112
0.071 489.38 588.5 0.0054 0.5486 4.55 0.199
0.107 737.52 390.5 0.0116 1.1786 9.78 0.321
0.159 1095.9 262.79 0.0215 2.1844 18.1 0.531
0.213 1468.1 196.17 0.0313 3.1801 26.4 0.712
0.317 2185 131.81 0.0445 4.5212 37.5 0.705
0.384 2646.8 108.81 0.0522 5.3035 44 0.853
0.512 3529.1 81.608 0.0646 6.5634 54.5 0.916
0.683 4707.7 61.176 0.0793 8.0569 66.9 1.084
0.825 5686.5 50.646 0.0902 9.1643 76.1 1.226
0.999 6885.8 41.825 0.1035 10.516 87.3 1.477
1.278 8808.9 32.694 0.1186 12.05 100 1.303

 

 

 

 

 

 

 

 

Table 7.7 : Data from pore—size distribution test on low fat sample 3 cooked to
endpoint temperature of 45°C.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ll’ressurelPressurelDiameterCumulativelPorosity°/o of Total Pore
PSIA N/m2 microns Pore Vol. % Pore istributionl
cc/g Volume dV/d IogD_
0.033 227.46 1266.2 0 0 0
0.051 351 .53 819.28 0.0009 0.095 0.8 0.043
0.07 482.49 596.9 0.0023 0.243 2.05 0.092
0.106 730.63 394.18 0.0067 0.708 5.98 0.22
0.159 1095.9 262.79 0.0177 1.869 15.8 0.564
0.234 1612.9 178.56 0.0361 3.813 32.2 0.99
0.313 2157.4 133.49 0.0469 4.953 41.8 0.772
0.418 2881.1 99.96 0.0577 6.094 51.5 0.776
0.505 3480.8 82.739 0.0658 6.949 58.7 0.891
0.61 1 421 1.4 68.385 0.0745 7.868 66.5 0.949
0.738 5086.8 56.617 0.0837 8.84 74.7 1.013
0.982 6768.6 42.549 0.0988 10.43 88.1 1.099
1.243 8567.6 33.615 0.1121 11.84 100 1.173

 

 

 

Table 7.8: Data from pore-size distribution test on low fat sample 4 cooked to
endpoint temperature of 45°C.

115

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

fi’ressurelPressurelDiameterCumulativelPorosity % of Total Pore

PSIA N/m2 microns Pore Vol. % Pore istributio
cc/g Volume dV/d logll‘

0.034 234.35 1228.9 0 0 0
0.052 358.42 803.53 0.0011 0.1 19 1.03 0.055
0.072 496.27 580.32 0.0027 0.293 2.53 0.105
0.108 744.41 386.88 0.0065 0.705 6.09 0.2
0.164 1130.4 254.78 0.017 1.843 15.9 0.537
0.22 1516.4 189.92 0.0292 3.165 27.4 0.887
0.325 2240.1 128.56 0.0415 4.499 38.9 0.673
0.434 2991.4 96.275 0.0521 5.648 48.8 0.783
0.526 3625.6 79.436 0.0601 6.515 56.3 0.889
0.636 4383.8 65.697 0.0693 7.512 64.9 1.034
0.77 5307.4 54.264 0.0793 8.596 74.3 1.117
0.933 6430.9 44.784 0.0897 9.723 84.1 1.157
1.238 8533.2 33.751 0.1067 11.57 100 1.283

 

 

 

Table 7.9: Data from pore-size distribution test on low fat sample 5 cooked to
endpoint temperature of 45°C.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PressurelPressurelDiameterCumulativelPorosity % of Total Pore

PSIA N/m2 microns Pore Vol. % Pore [Distributio
cc/g Volume dV/d logl

0.033 227.46 1266.2 0 0 0
0.051 351 .53 819.28 0.0048 0.48 4.64 0.209
0.071 489.38 588.5 0.0128 1.27 12.4 0.459
0.107 737.52 390.5 0.0243 2.42 23.5 0.532
0.161 1 109.7 259.52 0.0313 3.1 1 30.2 0.325
0.217 1495.7 192.55 0.0364 3.62 35.2 0.324
0.292 2012.7 143.09 0.0425 4.23 41.1 0.39
0.429 2957 97.397 0.0538 5.35 52 0.558
0.52 3584.2 80.353 0.0606 6.03 58.6 0.671
0.629 4335.5 66.428 . 0.068 6.76 65.7 0.738
0.762 5252.2 54.834 0.0765 7.61 73.9 0.841
0.923 6362 45.269 0.0855 8.5 82.6 0.891
1.1 17 7699.] 37.407 0.0946 9.41 91.4 0.906
1.348 9291.4 31 0.1035 10.3 100 0.899

 

Table 7.10: Data from pore-size distribution test on low fat sample I cooked to
endpoint temperature of 60°C.

116

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[PressurelPressurelDiameterCumulativelPorosity% of Total Pore

PSIA N/m2 microns Pore Vol. % Pore lDistributio
cc/g Volume dV/d logD_

0.033 227.46 1266.2 0 0 0
0.052 358.42 803.53 0 0 0 0
0.072 496.27 580.32 0.0009 0.09 0.85 0.051
0.108 744.41 386.88 0.0059 0.58 5.58 0.226
0.162 1 116.6 257.92 0.0185 1.83 17.5 0.569
0.217 1495.7 192.55 0.032 3.16 30.2 0.845
0.321 2212.6 130.17 0.0451 4.46 42.6 0.612
0.429 2957 97.397 0.055 5.44 52 0.625
0.519 3577.3 80.507 0.0623 6.16 58.9 0.701
0.629 4335.5 66.428 0.0706 6.98 66.7 0.79
0.762 5252.2 54.834 0.0795 7.86 75.1 0.849
0.921 6348.2 45.367 0.0892 8.82 84.3 0.937
1.253 8636.6 33.347 0.1058 10.5 100 0.987

 

 

 

 

 

 

 

 

 

Table 7.11: Data from pore-size distribution test on low fat sample 2 cooked to
endpoint temperature of 60°C.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

lPressure ressurelDiameterCumulativelPorosity% of Total Pore

PSIA N/m2 microns Pore Vol. % Pore [Distribution]
CC/j Volume dV/d logD_

0.033 227.46 1266.2 0 0 0
0.05 344.64 835.67 0.0031 0.33 3.05 0.146
0.077 530.74 542.64 0.0097 1.03 9.53 0.3
0.1 15 792.66 363.33 0.0237 2.51 23.3 0.685
0.155 1068.4 269.57 0.0362 3.84 35.6 0.821
0.229 1578.4 182.46 0.047 4.98 46.2 0.543
0.409 2819.1 102.16 0.0577 6.1 1 56.7 0.362
0.495 341 1.9 84.41 1 0.0625 6.62 61.4 0.493
0.545 3756.5 76.667 0.0653 6.92 64.1 0.571
0.66 4549.2 63.308 0.0718 7.61 70.5 0.666
0.797 5493.5 52.426 0.0795 8.42 78.1 0.801
0.964 6644.6 43.344 0.0882 9.35 86.6 0.897
1.247 8595.2 33.507 0.1018 10.8 100 1.036

 

 

 

Table 7.12: Data from pore-size distribution test on low fat sample 3 cooked to

endpoint temperature of 60°C.

117

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1Pressure1Pressure1DiameterCumulativelPorosity% of Total Pore
PSIA N/m’ microns Pore Vol. °/. Pore [Distributionl
cc/g Volume dV/d logg
0.033 227.46 1266.2 0 0 0
0.052 358.42 803.53 0.0019 0.19 1.47 0.076
0.073 503.17 572.37 0.0058 0.57 4.48 0.208
0.11 758.2 379.85 0.0176 1.72 13.6 0.521
0.15 1033.9 278.56 0.0321 3.14 24.8 0.846
0.222 1530.2 188.21 0.0592 5.78 45.7 1.25
0.328 2260.8 127.39 0.0674 6.59 52 0.38
0.438 3019 95.396 0.0757 7.4 58.5 0.519
0.53 3653.1 78.836 0.0825 8.06 63.7 0.645
0.642 4425.1 65.083 0.0907 8.86 70 0.774
0.776 5348.7 53.845 0.1003 9.8 77.5 0.916
0.939 6472.2 44.498 0.11 13 10.9 85.9 1.043
1.239 8540.1 33.723 0.1295 12.7 100 1.187

 

 

 

 

 

 

 

 

 

Table 7.13: Data from pore-size distribution test on low fat sample 4 cooked to

endpoint temperature of 60°C.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1Pressure1Pressure1D1ameterCumulativelPorosity °/o of Total Pore
PSIA N/m2 microns Pore Vol. % Pore [Distribution]
cc/g Volume dV/d logD_
0.032 220.57 1305.7 0 0 0
0.051 351.53 819.28 0.0009 0.09 0.7 0.036
0.07 482.49 596.9 0.004 0.39 3.09 0.184
0.117 806.45 357.12 0.0169 1.67 13.1 0.473
0.158 1089 264.45 0.0278 2.74 21.5 0.683
0.21 1 1454.4 198.03 0.0409 4.04 31.6 0.853
0.312 2150.5 133.92 0.0521 5.14 40.3 0.539
0.457 3150 91.43 0.0648 6.39 50.1 0.627
0.553 3811.7 75.558 0.0731 7.21 56.5 0.82
0.67 4618.1 62.363 0.0828 8.17 64 0.952
0.737 5079.9 56.694 0.0882 8.7 68.2 1.067
0.98 6754.8 42.636 0.107 10.6 82.8 1.243
1.304 8988.1 32.042 0.1293 12.8 100 1.471

 

 

 

 

 

 

 

 

 

Table 7.14: Data from pore-size distribution test on low fat sample 5 cooked to

endpoint temperature of 60°C.

118

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1Pressure1Pressure1DiameterCumulativelPorosity % of Total Pore
PSIA N/m2 microns Pore Vol. % Pore istributionl
cc/L Volume dV/d logD_
0.031 213.67 1347.8 0 0 0
0.055 379.1 759.7 0.00-14 0.13 3.16 0.04
0.076 523.85 549.78 0.0038 0.36 8.58 0.121
0.114 785.77 366.52 0.0116 1.09 26.2 0.314
0.153 1054.6 273.09 0.0233 2.19 52.6 0.65
0.227 1564.6 184.07 0.0298 2.8 67.3 0.269
0.334 2302.2 125.1 0.0313 2.94 70.7 0.063
0.49 3377.4 85.272 0.0326 3.07 73.6 0.055
0.54 3722.1 77.377 0.033 3.1 74.5 0.067
0.653 4500.9 63.987 0.0341 3.21 77 0.095
0.791 5452.1 52.823 0.0359 3.38 81 0.153
0.959 6610.1 43.57 0.0388 3.65 87.6 0.246
1.24 8546.9 33.696 0.0443 4.17 100 0.35

 

 

 

 

 

 

 

 

 

Table 7.15: Data from pore-size distribution test on low fat sample 1 cooked to
endpoint temperature of 75°C.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

lPressurelPressurelDiameter umulativelPorosig% of Total Pore
PSIA N/m2 microns Pore Vol. % Pore istributionl
cc/g Volume dV/d logl_)_
0.031 213.67 1347.8 0 0 0
0.054 372.21 773.77 0.0018 0.18 2.62 0.057
0.075 516.95 557.11 0.0045 0.45 6.54 0.144
0.1 14 785.77 366.52 0.0134 1.35 19.5 0.372
0.154 1061.5 271.32 0.0234 2.36 34 0.582
0.229 1578.4 182.46 0.0295 2.97 42.9 0.269
0.336 2315.9 124.36 0.0342 3.44 49.7 0.214
0.447 3081 93.475 0.039 3.93 56.7 0.294
0.493 3398.1 84.753 0.0409 4.12 59.4 0.339
0.542 3735.8 77.091 0.0432 4.35 62.8 0.425
0.657 4528.5 63.597 0.048 4.83 69.8 0.436
0.795 5479.7 52.558 0.0535 5.39 77.8 0.505
0.962 6630.8 43.434 0.0596 6 86.6 0.56
1.249 8609 33.453 0.0688 6.93 100 0.616

 

 

 

 

 

 

 

 

 

Table 7.16: Data from pore-size distribution test on low fat sample 2 cooked to
endpoint temperature of 75°C.

119

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

lPressurelPressurelDiameterCumulativelPorosity% of Total Pore

PSIA N/m2 microns Pore Vol. % Pore istributlonl
cc/g Volume dV/d logD

0.031 213.67 1347.8 0 0 0
0.055 379.1 759.7 0.0012 0.124 1.94 0.038
0.076 523.85 549.78 0.0033 0.34 5.33 0.116
0.115 792.66 363.33 0.0108 1.113 17.4 0.324
0.155 1068.4 269.57 0.0223 2.299 36 0.69
0.23 1585.3 181.67 0.0309 3.186 49.9 0.39
0.34 2343.5 122.89 0.0353 3.639 57 0.202
0.497 3425.7 84.071 0.041 4.227 66.2 0.269
0.546 3763.4 76.526 0.0426 4.392 68.8 0.305
0.662 4563 63.1 17 0.0464 4.784 75 0.353
0.802 5527.9 52.099 0.0507 5.227 81.9 0.402
0.97 6685.9 43.076 0.0552 5.691 89.2 0.424
1.244 8574.5 33.588 0.0619 6.382 100 0.483

 

 

 

 

 

 

 

 

 

 

Table 7.17 : Data from pore-size distribution test on low fat sample 3 cooked to
endpoint temperature of 75°C.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

lPressurelPressurelDiameterCumulativelPorosity % of Total Pore
PSIA N/m2 microns Pore Vol. % Pore Distribution
cc/g__ Volume dV/d log];
0.032 220.57 1305.7 0 0 0
0.05 344.64 835.67 0.0006 0.06 0.67 0.024
0.071 489.38 588.5 0.0021 0.22 2.34 0.078
0.119 820.23 351.12 0.0109 1.14 12.1 0.31
0.16 1102.8 261.15 0.025 2.62 27.8 0.866
0.238 1640.5 175.56 0.0432 4.52 48.1 0.833
0.35 2412.4 1 19.38 0.0509 5.32 56.7 0.363
0.514 3542.8 81.291 0.0603 6.31 67.1 0.445
0.565 3894.4 73.953 0.063 6.59 70.2 0.519
0.622 4287.3 67.176 0.066 6.9 73.5 0.567
0.752 5183.3 55.563 0.0721 7.54 80.3 0.584
0.912 6286.1 45.815 0.0784 8.2 87.3 0.594
1.25 8615.9 33.427 0.0898 9.39 100 0.657

 

 

 

 

 

 

 

 

 

Table 7.18: Data from pore-size distribution test on low fat sample 4 cooked to
endpoint temperature of 75°C.

120

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PressurelPressurelDiameterCumulative orosi % of Total Pore
PSIA N/m2 microns Pore Vol. % Pore [Distributionl
cc/g Volume dV/d logD_
0.034 234.35 1228.9 0 0 0
0.052 358.42 803.53 0.0003 0.031 0.27 0.013
0.072 496.27 580.32 0.0017 0.174 1.53 0.082
0.11 758.2 379.85 0.0074 0.758 6.67 0.255
0.165 1 137.3 253.23 0.0225 2.304 20.3 0.706
0.222 1530.2 188.21 0.0346 3.543 31.2 0.773
0.359 2474.5 116.39 0.0477 4.884 43 0.517
0.479 3301.6 87.23 0.0584 5.98 52.7 0.703
0.526 3625.6 79.436 0.0627 6.42 56.5 0.871
0.638 4397.5 65.491 0.072 7.373 64.9 0.913
0.772 5321.2 54.123 0.0827 8.468 74.6 1.064
0.934 6437.8 44.736 0.0939 9.615 84.7 1.114
1.244 8574.5 33.588 0.1109 11.36 100 1.124

 

 

Table 7.19: Data from pore-size distribution test on low fat sample 5 cooked to
endpoint temperature of 75°C.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PressurelPressurelDiameter umulative orosi ‘% of Total Pore

PSIA N/m2 microns Pore Vol. % Pore [Distribution]
cc/g Volume dV/d logD_

0.033 227.46 1266.2 0 0 0
0.053 365.31 788.36 0.0061 0.65 6.39 0.302
0.073 503.17 572.37 0.0135 1.43 14.2 0.543
0.1 1 1 765.09 376.43 0.0222 2.35 23.3 0.487
0.151 1040.8 276.71 0.0292 3.1 30.6 0.534
0.225 1550.9 185.7 0.0394 4.18 41.3 0.6
0.333 2295.3 125.48 0.0506 5.36 53 0.671
0.488 3363.6 85.622 0.0621 6.58 65.1 0.706
0.538 3708.3 77.664 0.0651 6.9 68.2 0.722
0.651 4487.1 64.183 0.0709 7.52 74.3 0.714
0.788 5431.4 53.025 0.0771 8.17 80.8 0.762
0.952 6561.9 43.89 0.0838 8.88 87.8 0.832
1.267 8733.1 32.978 0.0954 10.1 100 0.953

 

 

 

 

 

 

 

 

 

Table 7.20: Data from pore-size distribution test on raw high fat sample 1 using the
Liquid Extrusion Porosimeter.

121

 

 

l

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ll’ressurelPressurelDiameterCumulativelPorosity % of Total Pore
PSIA N/m2 microns Pore Vol. % Pore [Distributionl
cc/g Volume dV/d log];
0.033 227.46 1266.2 0 0 0
0.052 358.42 803.53 0.0058 0.59 4.65 0.286
0.073 503. 17 572.37 0.0121 1.23 9.7 0.417
0.11 758.2 379.85 0.0268 2.72 21.5 0.805
0.163 1123.5 256.34 0.0391 3.96 31.3 0.702
0.242 1668 172.66 0.0526 5.33 42.1 0.767
0.359 2474.5 1 16.39 0.0686 6.96 55 0.911
0.479 3301.6 87.23 0.081 8.21 64.9 0.966
0.58 3997.8 72.04 0.0895 9.08 71.7 0.998
0.639 4404.4 65.389 0.0938 9.51 75.2 0.997
0.773 5328.1 54.053 0.1025 10.4 82.1 1.026
0.934 6437.8 44.736 0.1113 11.3 89.2 1.044
1.242 8560.7 33.642 0.1248 12.7 100 1.064

 

 

 

 

 

 

 

 

 

Table 7.21: Data from pore-size distribution test on raw high fat sample 2 using the
Liquid Extrusion Porosimeter.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PressurelPressurelDiameterCumulativelPorosity °/o of Total Pore
PSIA N/m2 microns Pore Vol. % Pore [Distribution]
cc/g Volume dV/d logy;
0.031 213.67 1347.8 0
0.054 372.21 773.77 0.0058 0 0 0.227
0.074 510.06 564.64 0.0114 0.57 6.83 0.386
0.1 12 771.98 373.07 0.0195 1.12 13.4 0.424
0.165 1137.3 253.23 0.0277 1.91 23 0.46
0.246 1695.6 169.85 0.0368 2.72 32.6 0.495
0.363 2502.1 115.11 0.0479 3.61 43.3 0.62
0.484 3336.1 86.329 0.0561 4.7 56.4 0.619
0.532 3666.9 78.54 0.0588 5.5 66.1 0.62
0.645 4445.8 64.78 0.0646 5.77 69.3 0.654
0.78 5376.3 53.568 0.07 6.34 76.1 0.617
0.943 6499.8 44.309 0.0754 6.86 82.4 0.618
1.268 8739.9 32.952 0.0849 7.39 88.8 0.697

 

 

 

Table 7.22: Data from pore-size distribution test on raw high fat sample 3 using the
Liquid Extrusion Porosimeter.

122

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1Pressure1Pressure1DiameterCumulativelPorosity % of Total Pore

PSIA N/m2 microns Pore Vol. % Pore [Distributionr
gg Volume dV/d logy

0.034 234.35 1228.9 0 0 0
0.053 365.31 788.36 0.0063 0.64 6.099 0.317
0.074 510.06 564.64 0.0122 1.23 1 1.81 0.395
0.112 771.98 373.07 0.0222 2.24 21.49 0.539
0.151 1040.8 276.71 0.0309 3.12 29.91 0.65
0.224 1544 186.53 0.0432 4.36 41.82 0.696
0.364 2508.9 1 14.79 0.0583 5.88 56.44 0.694
0.487 3356.7 85.797 0.0674 6.8 65.25 0.698
0.536 3694.5 77.954 0.0705 7.11 68.25 0.722
0.649 4473.4 64.381 0.0766 7.72 74.15 0.712
0.786 5417.7 53.159 0.0832 8.39 80.54 0.769
0.951 6555 43.936 0.0903 9.1 1 87.42 0.832
1.264 8712.4 33.056 0.1033 10.4 100 1.02

 

 

 

 

 

 

 

 

 

Table 7.23: Data from pore-size distribution test on raw high fat sample 4 using the
Liquid Extrusion Porosimeter.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ll’ressurelPressur iameterCumulativefi’orosity % of Total Pore
PSIA N/m2 microns Pore Vol. % Pore [Distributionl
cc/g Volume dV/d Iog_l_)_1
0.031 213.67 1347.8 0 0 0
0.055 379.1 759.7 0.0051 0.51 4.46 0.197
0.077 530.74 542.64 0.0093 0.93 8.14 0.276
0.1 15 792.66 363.33 0.0162 1.62 14.2 0.38
0.156 1075.3 267.84 0.0226 2.26 19.8 0.464
0.231 1592.2 180.88 0.0329 3.28 28.8 0.58
0.373 2571 l 12.02 0.0494 4.93 43.2 0.761
0.497 3425.7 84.071 0.0615 6.14 53.8 0.932
0.548 3777.2 76.247 0.0659 6.58 57.7 0.996
0.663 4569.9 63.022 0.0753 7.52 65.9 1.091
0.803 5534.8 52.034 0.0856 8.54 74.9 1.188
0.97 6685.9 43.076 0.0967 9.65 84.6 1.298
1.259 8677.9 33.188 0.1143 11.4 100 1.492

 

 

 

 

 

 

 

 

 

Table 7.24: Data from pore-size distribution test on raw high fat sample 5 using the
Liquid Extrusion Porosimeter.

123

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PressurelPressurelDiameterCumulativelPorosity % of Total Pore

PSIA N/m2 microns Pore Vol. % Pore [Distribution]
cc/g Volume dV/d logD_

0.032 220.57 1305.7 0 0 0
0.05 344.64 835.67 0 0 0 0
0.076 523.85 549.78 0.005 0.54 7.86 0.25
0.114 785.77 366.52 0.0191 2.07 30 0.727
0.154 1061.5 271.32 0.034 3.68 53.5 1.036
0.228 1571.5 183.26 0.0402 4.35 63.2 0.33
0.37 2550.3 1 12.93 0.0462 5 72.6 0.259
0.493 3398.1 84.753 0.0498 5.39 78.3 0.262
0.542 3735.8 77.091 0.051 1 5.53 80.3 0.287
0.657 4528.5 63.597 0.0537 5.81 84.4 0.283
0.794 5472.8 52.624 0.0564 6.1 88.7 0.298
0.96 6617 43.524 0.059 6.38 92.8 0.286
1.276 8795.1 32.746 0.0636 6.88 100 0.338

 

 

 

Table 7.25: Data from pore-size distribution test on high fat sample I cooked to
endpoint temperature of 45°C.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PressurelPressur iameterCumulativelPorosity% of Total Pore
PSIA l‘l/mz microns Pore Vol. % Pore istributionl
egg Volume dV/d logll
0.032 220.57 1305.7 0 0 0
0.051 351 .53 819.28 0.0014 0.14 1.705 0.058
0.071 489.38 588.5 0.0084 0.83 10.23 0.41
0.1 19 820.23 351.12 0.0359 3.54 43.73 1.032
0.162 1 1 16.6 257.92 0.0421 4.15 51.28 0.39
0.238 1640.5 175.56 0.0479 4.72 58.34 0.292
0.35 2412.4 1 19.38 0.0544 5.36 66.26 0.327
0.467 3218.9 89.472 0.0597 5.88 72.72 0.356
0.566 3901.3 73.822 0.0638 6.28 77.71 0.413
0.623 4294.2 67.068 0.0658 6.48 80.15 0.404
0.754 5197.1 55.416 0.0701 6.9 85.38 0.437
0.914 6299.9 45.715 0.0743 7.32 90.5 0.423
1.24 8546.9 33.696 0.0821 8.09 100 0.496

 

 

 

Table 7.26: Data from pore-size distribution test on high fat sample 2 cooked to
endpoint temperature of 45°C.

124

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PressurelPressurelDiameterCumulativelPorosity% of Total Pore
PSIA N/m2 microns Pore Vol. % Pore [Distributio
cc/g Volume dV/d 1%D_
0.032 220.57 1305.7 0 0 0
0.05 344.64 835.67 0.0025 0.27 2.55 0.121
0.071 489.38 588.5 0.0066 0.72 6.72 0.252
0.118 813.34 354.1 0.0322 3.53 32.8 1.088
0.158 1089 264.45 0.0457 5.01 46.5 0.998
0.234 1612.9 178.56 0.0542 5.94 55.2 0.467
0.344 2371.1 121.46 0.0635 6.96 64.7 0.521
0.503 3467 83.068 0.0738 8.09 75.2 0.585
0.553 381 1.7 75.558 0.0766 8.4 78 0.638
0.671 4625 62.27 0.0819 8.98 83.4 0.591
0.812 5596.9 51.457 0.087 9.54 88.6 0.577
0.982 6768.6 42.549 0.0923 10.1 94 0.602
1.22 8409.1 34.249 0.0982 10.8 100 0.587

 

 

 

Table 7.27: Data from pore-size distribution test on high fat sample 3 cooked to
endpoint temperature of 45°C.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PressurelPressurelDiameterCumulativelPorosity % of Total Pore

PSIA N/m2 microns Pore Vol. % Pore [Distributio
cc/g Volume dV/d logD_

0.033 227.46 1266.2 0 0 0
0.052 358.42 803.53 0.0045 0.46 5.898 0.197
0.072 496.27 580.32 0.0119 1.21 15.6 0.454
0.1 1 758.2 379.85 0.0286 2.9 37.48 0.786
0.149 1027 280.43 0.0343 3.47 44.95 0.375
0.223 1537.1 187.37 0.0413 4.18 54.13 0.346
0.362 2495.2 1 15.42 0.0501 5.08 65.66 0.362
0.483 3329.2 86.508 0.0556 5.63 72.87 0.381
0.531 3660 78.688 0.0574 5.81 75.23 0.379
0.643 4432 64.982 0.0609 6.17 79.82 0.365
0.777 5355.6 53.775 0.0647 6.55 84.8 0.401
0.94 6479.1 44.45 0.0685 6.94 89.78 0.398
1.271 8760.6 32.874 0.0763 7.73 100 0.516

 

 

 

Table 7.28: Data from pore-size distribution test on high fat sample 4 cooked to
endpoint temperature of 45°C.

125

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ll’ressurelPressurelbiameterCumulativelPorosity % of Total Pore

PSIA N/m2 microns Pore Vol. % Pore [Distributio
cc/g Volume dV/d logD_

0.033 227.46 1266.2 0 0 0
0.052 358.42 803.53 0.003 0.31 3.81 0.135
0.072 496.27 580.32 0.0082 0.85 10.4 0.327
0.11 758.2 379.85 0.024 2.5 30.5 0.763
0.163 1 123.5 256.34 0.0434 4.51 55.1 1.01
0.243 1674.9 171.95 0.0496 5.16 62.9 0.318
0.357 2460.7 1 17.04 0.0544 5.66 69 0.256
0.476 3280.9 87.78 0.0583 6.06 74 0.278
0.524 361 1.8 79.739 0.0596 6.2 75.6 0.277
0.635 4376.9 65.801 0.0628 6.53 79.7 0.341
0.768 5293.6 54.405 0.0665 6.92 84.4 0.398
0.93 6410.2 44.928 0.0707 7.35 89.7 0.449
1.238 8533.2 33.751 0.0788 8.2 100 0.58

 

 

 

 

 

 

 

 

 

Table 7.29: Data from pore-size distribution test on high fat sample 5 cooked to
endpoint temperature of 45°C.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ressurelPressurelDiamete CumulativelPorosity % of Total Pore
PSIA N/mz microns Pore Vol. % Pore istributio
cc/L Volume dV/d logD
0.033 227.46 1266.2 0 0 0
0.052 358.42 803.53 0.0008 0.09 1.148 0.036
0.07 482.49 596.9 0.0044 0.47 6.313 0.249
0.117 806.45 357.12 0.0198 2.14 28.41 0.617
0.158 1089 264.45 0.0279 3.01 40.03 0.555
0.234 1612.9 178.56 0.0339 3.66 48.64 0.315
0.377 2598.5 1 10.83 0.041 4.42 58.82 0.307
0.504 3473.9 82.903 0.0459 4.95 65.85 0.348
0.554 3818.6 75.421 0.0478 5.15 68.58 0.414
0.671 4625 62.27 0.0518 5.59 74.32 0.43
0.812 5596.9 51.457 0.0563 6.07 80.77 0.486
0.982 6768.6 42.549 0.0616 6.64 88.38 0.574
1.271 8760.6 32.874 0.0697 7.52 100 0.647

 

 

 

Table 7.30: Data from pore-size distribution test on high fat sample I cooked to

endpoint temperature of 60°C.

126

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PressurelPressurelDiameter umulativelPorosity% of Total Pore
PSIA N/m2 microns Pore Vol. % Pore [Distribution]
cc/L Volume dV/d logD_
0.032 220.57 1305.7 0 0 0
0.053 365.31 788.36 0.0063 0.64 11.45 0.237
0.072 496.27 580.32 0.0149 1.52 27.09 0.532
0.111 765.09 376.43 0.0207 2.12 37.64 0.254
0.164 1 130.4 254.78 0.025 2.56 45.45 0.209
0.244 1681.8 171.24 0.0289 2.96 52.55 0.186
0.359 2474.5 1 16.39 0.0332 3.4 60.36 0.211
0.479 3301.6 87.23 0.037 3.79 67.27 0.25
0.579 3990.9 72.165 0.0399 4.08 72.55 0.29
0.637 4390.6 65.594 0.0414 4.24 75.27 0.298
0.772 5321.2 54.123 0.0448 4.58 81.45 0.335
0.933 6430.9 44.784 0.0485 4.96 88.18 0.37
1.255 8650.3 33.293 0.055 5.63 100 0.415

 

 

 

 

Table 7.31: Data from pore-size distribution test on high fat sample 2 cooked to
endpoint temperature of 60°C.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PressurelPressurelDiameterCumulativell’orosity % of Total Pore
PSIA N/m2 microns Pore Vol. % Pore [Distribution]
cc/g Volume dV/d logg
0.033 227.46 1266.2 0 0 0
0.051 351 .53 819.28 0.0052 0.54 8.624 0.228
0.07 482.49 596.9 0.0112 1.15 18.57 0.362
0.106 730.63 394.18 0.0173 1.78 28.69 0.281
0.157 1082.2 266.14 0.0224 2.31 37.15 0.248
0.233 1606 179.33 0.0266 2.74 44.11 0.203
0.376 2591.7 111.13 0.033 3.4 54.73 0.255
0.503 3467 83.068 0.0378 3.89 62.69 0.315
0.553 3811.7 75.558 0.0397 4.09 65.84 0.383
0.669 461 1.2 62.456 0.0438 4.51 72.64 0.411
0.81 5583.1 51.584 0.0482 4.96 79.93 0.439
0.98 6754.8 42.636 0.0532 5.48 88.23 0.501
1.264 8712.4 33.056 0.0603 6.21 100 0.532

 

 

 

 

Table 7.32: Data from pore-size distribution test on high fat sample 3 cooked to
endpoint temperature of 60°C.

127

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PressurelPressurelDiameterCumulativelPorosity % of Total Pore
PSIA N/m2 microns Pore Vol. % Pore [Distribution]
cc/g Volume dV/d logD_
0.032 220.57 1305.7 0 0 0
0.052 358.42 803.53 0.0055 0.56 9.717 0.215
0.072 496.27 580.32 0.0122 1.25 21.55 0.39
0.109 751.3 383.33 0.0228 2.33 40.28 0.485
0.163 1 123.5 256.34 0.0262 2.68 46.29 0.16
0.241 1661.1 173.37 0.0299 3.06 52.83 0.179
0.354 2440 1 18.03 0.034 3.48 60.07 0.202
0.473 3260.2 88.337 0.0376 3.85 66.43 0.235
0.573 3949.5 72.92 0.0404 4.14 71.38 0.277
0.631 4349.3 66.218 0.0419 4.29 74.03 0.295
0.764 5266 54.69 0.0452 4.63 79.86 0.327
0.924 6368.9 45.22 0.0488 5 86.22 0.359
1.318 9084.6 31.702 0.0566 5.8 100 0.416

 

 

 

Table 7.33: Data from pore-size distribution test on high fat sample 4 cooked to
endpoint temperature of 60°C.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IPressurelPressurelDlameterCumulativelPorosity % of Total Pore

PSIA N/m2 microns Pore Vol. % Pore lDistributionl
cc/g Volume dV/d logD_

0.034 234.35 1228.9 0 0 0
0.054 372.21 773.77 0.0038 0.47 1 1.1 0.166
0.074 510.06 564.64 0.0079 0.98 23.1 0.263
0.11 758.2 379.85 0.0112 1.39 32.7 0.168
0.164 1 130.4 254.78 0.0138 1.71 40.4 0.131
0.242 1668 172.66 0.0164 2.04 48 0.135
0.356 2453.8 117.37 0.0196 2.43 57.3 0.167
0.476 3280.9 87.78 0.0221 2.74 64.6 0.174
0.524 3611.8 79.739 0.0231 2.87 67.5 0.21
0.633 4363.1 66.008 0.025 3.1 73.1 0.203
0.767 5286.7 54.476 0.0269 3.34 78.7 0.2
0.928 6396.4 45.025 0.0293 3.64 85.7 0.254
1.298 8946.7 32.191 0.0342 4.24 100 0.295

 

 

 

Table 7.34: Data from pore-size distribution test on high fat sample 5 cooked to
endpoint temperature of 60°C.

128

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PressurePressurelDiameterCumulativelPorosity % of Total Pore
PSIA N/m2 microns Pore Vol. % Pore [Distribution]
cc/L Volume dV/d logD_
0.032 220.57 1305.7 0 0 0
0.051 351.53 819.28 0.0047 0.55 9.98 0.155
0.077 530.74 542.64 0.0146 1.71 31 0.37
0.1 17 806.45 357.12 0.0373 4.36 79.2 0.836
0.157 1082.2 266.14 0.0433 5.06 91.9 0.314
0.231 1592.2 180.88 0.0435 5.09 92.4 0.008
0.375 2584.8 111.42 0.044 5.14 93.4 0.016
0.5 3446.4 83.567 0.0444 5.19 94.3 0.021
0.55 3791 75.97 0.0445 5.2 94.5 0.016
0.666 4590.5 62.738 0.0449 5.25 95.3 0.032
0.805 5548.6 51.905 0.0453 5.3 96.2 0.033
0.974 6713.5 42.899 0.046 5.38 97.7 0.057
1.251 8622.8 33.4 0.0471 5.51 100 0.068

 

 

 

Table 7.35: Data from pore-size distribution test on high fat sample I cooked to
endpoint temperature of 75°C.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

lPressurelPressurelDiameterCumulativ orosity % of Total Pore
PSIA N/m2 microns Pore Vol. % Pore [Distributionl
cc/J Volume dV/d logl
0.03 206.78 1392.8 0 0 0
0.053 365.31 788.36 0.0073 0.78 10.96 0.193
0.074 510.06 564.64 0.0171 1.84 25.68 0.441
0.1 12 771.98 373.07 0.0431 4.63 64.71 0.942
0.167 1 151.1 250.2 0.0585 6.29 87.84 0.579
0.225 1550.9 185.7 0.0591 6.35 88.74 0.03
0.363 2502.1 115.11 0.0602 6.47 90.39 0.035
0.484 3336.1 86.329 0.061 6.56 91.59 0.042
0.533 3673.8 78.393 0.0614 6.6 92.19 0.062
0.645 4445.8 64.78 0.0622 6.69 93.39 0.063
0.781 5383.2 53.5 0.0633 6.8 95.05 0.086
0.944 6506.7 44.262 0.0645 6.93 96.85 0.095
1.245 8581.4 33.561 0.0666 7.16 100 0.114

 

 

 

Table 7.36: Data from pore-size distribution test on high fat sample 2 cooked to
endpoint temperature of 75°C.

129

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

lPressurelPressurelDiameter umulativelPorosity% of Total Pore

PSIA N/m2 microns Pore Vol. % Pore [Distributio
cc/g Volume dV/d logg

0.031 213.67 1347.8 0 0 0
0.05 344.64 835.67 0.0035 0.37 7.81 0.122
0.076 523.85 549.78 0.0123 1.31 27.5 0.351
0.115 792.66 363.33 0.0315 . 3.35 70.3 0.775
0.155 1068.4 269.57 0.0362 3.85 80.8 0.263
0.229 1578.4 182.46 0.0374 3.97 83.5 0.051
0.374 2577.9 11 1.72 0.0387 4.11 86.4 0.044
0.498 3432.6 83.902 0.0398 4.23 88.8 0.064
0.549 3784.1 76.108 0.0402 4.27 89.7 0.069
0.664 4576.8 62.927 0.041 1 4.37 91.7 0.079
0.803 5534.8 52.034 0.042 4.46 93.8 0.079
0.973 6706.6 42.943 0.0432 4.59 96.4 0.104
1.249 8609 33.453 0.0448 4.76 100 0.107

 

 

 

Table 7.37 : Data from pore-size distribution test on high fat sample 3 cooked to
endpoint temperature of 75°C.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PressurelPressurelDiamete umulativelPorosity % of Total Pore
PSIA N/m2 microns Pore Vol. % Pore [Distributionl
cc/g Volume dV/d logg-
0.033 227.46 1266.2 0 0 0
0.052 358.42 803.53 0.0041 0.42 6.55 0.151
0.072 496.27 580.32 0.0111 1.14 17.7 0.361
0.11 758.2 379.85 0.0317 3.27 50.6 0.815
0.164 1 130.4 254.78 0.0529 5.45 84.5 0.89
0.242 1668 172.66 0.0542 5.59 86.6 0.056
0.356 2453.8 117.37 0.0555 5.72 88.7 0.056
0.474 3267.1 88.15 0.0566 5.84 90.4 0.064
0.523 3604.9 79.892 0.0571 5.89 91.2 0.085
0.633 4363.1 66.008 0.0581 5.99 92.8 0.088
0.767 5286.7 54.476 0.0592 6.1 94.6 0.096
0.928 6396.4 45.025 0.0605 6.24 96.6 0.1 14
1.242 8560.7 33.642 0.0626 6.45 100 0.121

 

 

 

Table 7.38: Data from pore-size distribution test on high fat sample 4 cooked to
endpoint temperature of 75°C.

130

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

lPressurelPressur iameter umulativelPorosity% of Total Pore

PSIA N/m2 microns Pore Vol. % Pore istributio
cc/L Volume dV/d logD_

0.031 213.67 1347.8 0 0 0
0.055 379.1 759.7 0 0 0 0
0.076 523.85 549.78 0.0014 0.141 7.07 0.061
0.1 14 785.77 366.52 0.0066 0.665 33.3 0.181
0.157 1082.2 266. 14 0.0116 1.169 58.6 0.22
0.232 1599.1 180.1 0.0191 1.925 96.5 0.271
0.376 2591.7 111.13 0.0198 1.996 100 0.02
0.502 3460.] 83.234 0.0198 1.996 100 0
0.552 3804.8 75.694 0.0198 1.996 100 0
0.667 4597.4 62.644 0.0198 1.996 100 0
0.807 5562.4 51.776 0.0198 1.996 100 0
0.975 6720.4 42.855 0.0198 1.996 100 0
1.126 7761.2 37.108 0.0198 1.996 100 0

 

 

 

 

 

 

 

 

 

Table 7.39: Data from pore-size distribution test on high fat sample 5 cooked to

endpoint temperature of 75°C.

131

7.2. Permeability Results

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

15-13 75-15
A Sam le1 A _ . SampleZ
a 8E-14 p a. 6515
E, 5 55-15
g 6E-14 :3‘ 45-15
.0 '5
a] 45-14 g 3545*
g g 2515
a 25-14 ‘ a 15-15]
0 0 I I
0 5000 10000 15000 20000 0 5000 10000 15000 20000
Pressure (Pa) Pressure (Pa)
SE43 0 15-13
g" - t Sample3 A Sample4
5 5513- l "5 85-14»
; 45-13 0 v
r: >~ - .
§ 35134 E 6514
E 2513 g 45'“:
33 15-13 E | ‘HflJL o 2E-14
CL
04 - 0
0 10000 20000 30000 0 5000 10000 15000 20000
Pressure (Pa) Pressure (Pa)

Figure 7.1: Permeability of raw low fat samples 1 through 4, tested at room
temperature using the PMI Permeameter.

132

 

 

 

 

 

 

 

 

 

 

  

 

 

 

 

6? Sample 1 g," ‘ Sam le 2
g 8543* 5 45-14 . p
g 6E-13 ~ g 35-14 .
5 s
8 4E-13 . 8 2E-14 —
cg: 2E-13 - E, 15-14 -
d (L
0 - ’ . 0 -.
0 5000 1000015000 20000 0 5000 1000015000 20000
Pressure (Pa) Pressure (Pa)
5E-14 1.2E-13
g," 4314 , Sample 3 p 1513 _ Sample4
‘E’ ‘8’ 8E 14
,1: 3E-14 « .3
’3 E 6E-14 1
- a (U
E 2E 14 E 4514 M
a "5'14 l g 2514 ~ ;.‘ 1‘
0 ‘ O _ a - -
0 5000 10000 15000 20000 0 5000 10000 15000 20000
Pressure (Pa) Pressure (Pa)

Figure 7.2: Permeability of low fat samples 1 through 4, cooked to endpoint
temperature of 45°C and tested at room temperature using the PMI Permeameter.

133

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2E-12 S I 1 1.2E-13
0 am e
a? p a? 15-13 _ Sample 2
g 1.5E-12 ~ E
2: l; 8E-14 .
5 15-12 1 % 615-14 -
g g 4E-14 ~
0 .- . . o -
0 5000 10000 15000 20000 0 5000 10000 15000 20000
Pressure (Pa) Pressure (Pa)
7E-13 315-13
,9 55-13 . Sample 3 0 (:2 Sample 4
.5, 55-13 ~ g 22:: J
g 4E-13 « :3:
g 3E‘13 1 2% 1.5E'13 “
g 25-13~ E 115-13*
ti.> 1E-13 ~ &‘ m n 3: 55-14 .
0 l 0 ~ .
0 5000 10000 15000 20000 0 5000 10000 15000 20000
Pressure (Pa) Pressure (Pa)

Figure 7.3: Permeability of low fat samples 1 through 4, cooked to endpoint
temperature of 60°C and tested at room temperature using the PMI Permeameter.

134

1.4E-12

A 1.2E-12 -
1E-12 ~
8E-13 a
6E-13 -
4E-13 L
2E-13 -

Permeability (m 2

2E-13 A

 

0 Sample 1

 

 

 

 

0 5000 1000015000 20000

Pressure (Pa)

 

Sample 3

 

 

 

5000 10000 15000 20000
Pressure (Pa)

O

7E-13

gr 6E-13 «
55-13 ~
4E-13 «
3E-13 ~
2E-13 —
1E-13 w
0 A

0

Permeability (m

5E-13
4E-13
35-13

1E-13
0

Permeability (m 2)

 

2E-13 4

 

Sample 2

 

 

50001000015000 20000

Pressure(Pa)

 

Sample 4

.4

.4

_‘

 

 

 

v

v

V T

0 5000 1000015000 20000
Pressure (Pa)

Figure 7.4: Permeability of low fat samples 1 through 4, cooked to endpoint
temperature of 75°C and tested at room temperature using the PMI Permeameter.

135

 

 

 

 

 

2E-13
p Sample1
g 1.5E-13
a
3 1E-13
(U
(D
g 5544
CL
0 l
0 10000 20000 30000
Pressure (Pa)
2.5E-14
A Sample3
“‘ 2E-14
E,
g 1.5E-14 a
g
a, 1E-14
E
o. 5E-15
0

 

 

0 5000 10000 15000 20000

Pressure (Pa)

1.2E-13

«A 15-131
E

3 85-14%

E 6E-14~
8

E 4E-144

31’ 2544+

0-

0

25-13

5 1.5543
3

1:; 12-134
8

E 55-14«
Q

 

 

Sample 2

 

5000 10000 15000 20000

Pressure (Pa)

 

 

0

Sample 4

 

5000 10000 15000 20000

Pressure (Pa)

Figure 7.5: Permeability of raw high fat samples 1 through 4, tested at room
temperature using the PMI Permeameter.

136

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3.5E-13 , 5E-14
97‘ - a a?“ m l
E 3E 13 T Sample1 E 4E-14a Sa pe2
g 2513 E 35'“
n ..
8 1.5E-13 « g 25-14 1
E 1E-13 E
33 55-14 J, 33 1544*
0 l 0 e
0 5000 10000 15000 20000 0 5000 10000 15000 20000
Pressure (Pa) Pressure (Pa)
1E-13 1.8E-14
A Sample 3 155.14 1 Sample4
“E 85-14 ~" 1.45-14
V g 125-14 -
> _ .
:3 6514 g 1E-14
4E-14 8 85-15
“g’ 6E-15 -
2E-15 a
0 4 ‘ 0 7 ,
0 5000 10000 15000 20000 0 5000 10000 15000 20000
Pressure (Pa) Pressure (Pa)

Figure 7.6: Permeability of high fat samples 1 through 4, cooked to endpoint
temperature of 45°C and tested at room temperature using the PMI Permeameter.

137

1.4E-14
1E-14 1
85-151
6E-154
4E-15~
25-15«
0 T a Y

0 5000 10000 15000 20000

Pressure (Pa)

 

Sample 1

)

T‘
N
m
_s
#1

 

Permeability (m 2

 

 

 

2.5E-14

 

2514 { Sample3

1.5E-14 ~
1E-14 a
5E-15 ,

Permeability (m 2)

 

 

 

0 f Y
0 5000 10000 15000 20000

Pressure (Pa)

2.5E-13

 

2E-13
1.5E-13 4
1 E13 ~

Permeability (m 2)

5E-14 «

 

0 r
0

3.5E-14

Permeability (m 2)

Sample 2

 

5000 10000 15000 20000
Pressure (Pa)

 

35-14 «
2.55-14 d
2514 4
1.5514 A
15-14 4
55-15 a

 

0

 

Sample 4

 

5000 10000 15000 20000

Pressure (Pa)

Figure 7.7: Permeability of high fat samples 1 through 4, cooked to endpoint

temperature of 60°C and tested at room temperature using the PMI Permeameter.

138

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1.4E-13 8E-14
é 1E-13~ g 6E-14-
g 8E-14 a 5
§ 6E-14« g 4514‘
g 4E-14 1 g 2544,
L1. 2E—14 « a
0 — 0
0 5000 10000 15000 20000 0 5000 10000 15000 20000
Pressure (Pa) Pressure (Pa)
2.5E-14 75-14
0? 2E-14 1 Sample 3 «1‘ 6E—14 Sample4
15, E, 55-14 a
g 1.5E-14 , ,1: 45-14 ,
E E
3 1E-14 1 8 35'14“
«E: g 2E-14 -
o. SE15 4 a. 15-14 ,
o I I T 0'
o 5000 10000 15000 20000 0 500° 10°00 15°00 20°00
pressure (pa) Pressure (Pa)

Figure 7.8: Permeability of high fat samples 1 through 4, cooked to endpoint
temperature of 75°C and tested at room temperature using the PMI Permeameter.

139

 

 

8E-13 2.5E-12

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A 7E-13 0 »
N a? - 1 Sam le2
E, 65-13 _ 4» Sample 1 E 2E 12 0 P
g 5543 * 2: 1.5542
3 4E-13 4 §
8 35-13 4 8 15421
,5, 25-134 E, 1
O. O. 5E-13 1

1E-13 4

0 ~ 1 r o l ,
0 5000 10000 15000 20000 0 5000 10000 15000
Pressure (Pa) Pressure (Pa)

1.4E'12 5E-13
o? 1.2E-12 Sample3 “1., Sample4
.5, 15-12 ~ $45-13-
g sis-13‘ gas-13,
25 =
g 6E-13 ~ g 25-13 1
g 4513 1 g
‘1 25-13— 83 1543‘

0 V I T r 0 d
0 5000 1000015000 20000 0 5000 10000 15000 20000
Pressure (Pa) Pressure (Pa)

Figure 7.9: Permeability of low fat samples 1 through 4, cooked to endpoint
temperature of 45°C and tested at 45°C using the PMI Permeameter.

140

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1.2E-12 1.6E-12

a? 1E-12 A 1.4E-12 «

5 35-131 é 1.2E-12 +

g 3. 1E-12 a

“g 6E-13 « E 35-13 a

g 4E-13 E 6E-13 A

‘1’ 4E-13 ~

0. 0! Sam le 2

E-1 , Sample1 p
2 3 °' 25-13
0 I f 0 . r T
0 5000 10000 15000 20000 0 5000 10000 15000 20000
Pressure (Pa) Pressure (pa)
13:}: 3.5512 ,

N" ‘ ' 1 N" 35-12 - 1 Sample4
E 1.25-12,

V E, 2.55-12 ~

g. 1E-12 2'

2‘5 era-13 , :3 25'12 “

g 6E‘13 , 8 1.5E'12 ‘

45-13 1 g 1E-12 ~ 1W
0. 2513 Sample 3 a. 515-13
0 1 T T 0 V. f f
0 5000 10000 15000 20000 0 5000 10000 15000 20000
Pressure (Pa) Pressure (Pa)

Figure 7.10: Permeability of low fat samples 1 through 4, cooked to endpoint
temperature of 60°C and tested at 60°C using the PMI Permeameter.

141

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3544 7E-13
A 7E-14 « A l
“' 6E14 Sample1 N 6E'13
I; 55'“ i 15, 55-13
22‘ ' 1 :3 45-13
3 4E-14 a 5
8 35-14, 8 35-13
1;, 25-14 . g 25-134
‘L 1E-14 W» °- 15-13‘ Samplez
0 T f I O 1 l’ l
0 5000 10000 15000 20000 0 5000 10000 15000 20000
Pressure (Pa) Pressure (Pa)
1E-12 1E-12
A A Sam le4 ‘
N era-13 a 1 Sample3 " 8E-134 p
E E
g 6E-13 a 3: 65-13 A
a E
g 4E-13 + g 4E-13 ~
g 2E-13 4 a) 2E-13 4
0 at T T 0 VV 1 r
0 5000 10000 15000 20000 0 5000 10000 15000 20000
Pressure (Pa) Pressure (Pa)

Figure 7.11: Permeability of low fat samples 1 through 4, cooked to endpoint
temperature of 45°C and tested at 60°C using the PMI Permeameter.

142

3.5E-13

 

3E-13 Sample 1
2.5E-13
2E-13
1.5E-13
1E-13
5E-14

0 MY“

Permeability (m 2)

 

 

 

0 5000 10000 15000 20000

Pressure (Pa)

 

Sample 3

 

 

0 5000 10000 15000 20000

Pressure (Pa)

 

Permeability (m 2)

4E-13

 

 

Sample 2

 

 

6E-14

)
(J!
m
—l
&

4E-14
35-14
25-14
15-14

Permeability (m 2

5000 10000 15000 20000

Pressure (Pa)

 

‘ Sample 4

 

 

 

0

5000 10000 15000 20000
Pressure (Pa)

Figure 7.12: Permeability of low fat samples 1 through 4, cooked to endpoint
temperature of 60°C and tested at 45°C using the PMI Permeameter.

143

 

 

 

0

1.2E-13

 

5000 10000 15000 20000

Sample 1

 

Pressure (Pa)

 

 

1E-13 ~
8E-14 r
6E-14 i
4E-14 1
2E-14 ~

Permeability (m 2)

 

o a

0

Sample 3

5000 10000 15000 20000

 

Pressure (Pa)

 

1E-13

A

Permeability (m 2

Permeability

8E—14 A
6E-14 1
4E-14 a
25-14 r

 

 

0 a
0

Sample 2

 

5000 10000 15000 20000
Pressure (Pa)

 

 

Sample 4

 

 

10000 20000 30000
Presure (Pa)

Figure 7.13: Permeability of high fat samples 1 through 4, cooked to endpoint
temperature of 45°C and tested at 45°C using the PMI Permeameter.

144

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1.4E-12 55-14
a? 125-12 0? 55-14 a 0 Sample 2
E 1E-12 a g 4314 q
{.5 8513 A g 3E 14
§ era-13 4 g '
g 4E-13« g 2544‘
0- 25-13 4 Sample1 ‘L 15444 i
O r I I 0 ‘ ‘ 1 V
0 5000 10000 15000 20000 0 10000 20000 30000
Pressure (Pa) Pressure (Pa)
2.5E-13 1E-12
~" 25-13 1 “7‘ 8E-13 —
5. E,
g 1.55-13 - g. 6E-13 a
a a
8 1E-13 a 8 4E-13 1
r, r,
0 T 0 fl T f
0 10000 20000 30000 0 5000 10000 15000 20000
Pressure (Pa) Pressure (Pa)

Figure 7.14: Permeability of high fat samples 1 through 4, cooked to endpoint
temperature of 60°C and tested at 60°C using the PMI Permeameter.

145

5E-14 15-14

 

 

    

 

 

 

 

 

 

 

 

 

 

 

 

 

 

eT‘ 4E-14 Sample1 g." 8E-15 J Sample2
E E
.é‘ 3E-14 , ,3: 615-15
:3 a
8 2E-14« g 4E-15
E E
33 1E-14 {‘1’ 2545
o - - , o ,
0 10000 20000 30000 5000 10000 15000 20000
Pressure (Pa) Pressure (Pa)
25-15 5E-13
A it." Sample4
N 4E-13 <
6155-15 Sample 3 E,
3 ,3 35-13
g "5'15 1 § 25-13
E
cg) 5546 a 115-13
CL
0 Y 0 t
5000 10000 15000 20000 25000 0 10°00 20°00 30°00
Pressure (Pa) Pressure (Pa)

Figure 7.15: Permeability of high fat samples 1 through 4, cooked to endpoint
temperature of 45°C and tested at 60°C using the PMI Permeameter.

146

Permeability (m 2)

Permeability (m 2)

 

5E-13
4E-13
3E-13
2E-13 1
1E-13 a

 

0

Sample 1

 

AA

 

0

8E-14

v 1 v “T v"

5000 10000 15000 20000
Pressure (Pa)

 

7E-14 a
6E-14 -
55-14

45-14 ~
3514 ~
2E-14 1
115-14 ]

 

0

Sample 3

 

 

5000 10000 15000 20000
Pressure (Pa)

Permeability (m 2)

 

A 3.5E-13
3E-13 ~
2.5E-13 -
25-13 1
1.5E-13 ~
1E-13 ~
5E-14 ~

 

014—“

0

2E-14 a

Sample 2

 

1

 

 

vv1

Pressure (Pa)

5000 10000 15000 20000

 

 

 

1

 

0

10000 20000
Pressure (Pa)

Sample 4

 

30000

Figure 7.16: Permeability of high fat samples 1 through 4, cooked to endpoint
temperature of 60°C and tested at 45°C using the PMI Permeameter.

147

7.3. Pore-size distribution Results—Tests for Fat and Grind

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Pressure1Pressure1DiameterCumulativelPorosity "/o of Total Pore

PSIA N/m2 microns Pore Vol. % Pore istributionl
cc/L Volume dV/d logD_

0.031 213.67 1347.8 0 O 0
0.054 372.21 773.77 0.0028 0.28 5.44 0.11 1
0.074 510.06 564.64 0.0049 0.48 9.51 0.146
0.1 1 1 765.09 376.43 0.009 0.89 17.5 0.222
0.165 1137.3 253.23 0.0138 1.37 26.8 0.265
0.245 1688.7 170.54 0.0194 1.92 37.7 0.31
0.36 2481.4 1 16.06 0.0255 2.52 49.5 0.347
0.479 3301.6 87.23 0.0302 2.99 58.6 0.361
0.528 3639.3 79.135 0.0318 3.15 61.7 0.36
0.639 4404.4 65.389 0.0352 3.48 68.3 0.39
0.773 5328.1 54.053 0.0387 3.83 75.1 0.403
0.935 6444.7 44.688 0.043 4.25 83.5 0.495
1.243 8567.6 33.615 0.0515 5.09 100 0.654

 

 

 

Table 7.40: Data from pore-size distribution test on raw re-ground high fat sample 1
using liquid extrusion porosimeter.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PressurelPressurdDiameterCumulativdPorosi % of Total Pore
PSIA N/m2 microns Pore Vol. % Pore lDistributionl
cc/g Volume dV/d log2_
0.033 227.46 1266.2 0 0 0
0.053 365.31 788.36 0.002 0.21 5.85 0.096
0.072 496.27 580.32 0.0039 0.4 l 1.4 0.141
0.12 827.12 348.19 0.008 0.82 23.4 0.183
0.163 1123.5 256.34 0.0108 1.11 31.6 0.208
0.24 1654.2 174.1 0.0149 1.53 43.6 0.241
0.352 2426.2 118.7 0.0191 1.97 55.8 0.25
0.47 3239.6 88.901 0.0224 2.3 65.5 0.26
0.569 3921.9 73.433 0.0246 2.53 71.9 0.262
0.689 4749.1 60.643 0.0267 2.75 78.1 0.25
0.834 5748.5 50.1 0.0288 2.96 84.2 0.251
1.009 6954.7 41.411 0.03l2 3.21 91.2 0.287
1.244 8574.5 33.588 0.0342 3.52 100 0.326

 

 

 

Table 7.41: Data from pore-size distribution test on raw re-ground high fat sample 2
using liquid extrusion porosimeter.

148

Table 7.42: Data from pore-size distribution test on raw re-ground high fat sample 3
using liquid extrusion porosimeter.

Volume Fraction

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Pressure1Pressure1DiameterCumulativeIPorosity% of Total Pore
PSIA N/m2 microns Pore Vol. % Pore istributionr
cc/g Volume dV/d logD_
0.031 213.67 1347.8 0 O 0
0.052 358.42 803.53 0.0025 0.26 6 0.] 11
0.072 496.27 580.32 0.005 0.52 12 0.176
0.11 758.2 379.85 0.0088 0.91 21.1 0.206
0.164 1 130.4 254.78 0.0136 1.41 32.6 0.275
0.243 1674.9 171.95 0.0186 1.93 44.6 0.291
0.355 2446.9 1 17 .7 0.0238 2.46 57.1 0.314
0.474 3267.1 88.15 0.0275 2.85 65.9 0.293
0.574 3956.4 72.793 0.0298 3.08 71.5 0.275
0.695 4790.4 60.12 0.0322 3.33 77.2 0.288
0.84 5789.9 49.742 0.0346 3.58 83 0.29
1.016 7003 41.125 0.0377 3.9 90.4 0.374
1.252 8629.7 33.373 0.0417 4.32 100 0.439

 

 

 

0.05 -

0.045 --
0.04 «
0.035 ~
0.03 ~
0.025 ~
0.02 -
0.015 ~
0.01 .
0.005 -

 

 

 

 

o A _.
30—50 50-90 90- 150- 230-

_—’ T ‘ "W ' _T‘ "7" Ta

—T~‘— ‘ 'T_" T l T

330- 450- 590- 750-
150 230 330 450 590 750 930 1130

Pore Diameter (microns)

Al .

930-

Figure 7.17 : Pore volume distributions (at particular diameters) of raw low fat, high
fat and re-ground high fat.

149

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1Pressure1PressurelDiameterCumulative1Porosity °/o of Total Pore

PSIA N/mz microns Pore Vol. % Pore [Distributionr
cc/g Volume dV/d logD_

0.032 220.57 1305.7 0 0 0
0.053 365.31 788.36 0.0015 0.14 2.56 0.063
0.072 496.27 580.32 0.0031 0.3 5.28 0.1 11
0.108 744.41 386.88 0.0058 0.56 9.88 0.142
0.162 1 1 16.6 257.92 0.0097 0.93 16.5 0.204
0.24] 1661.1 173.37 0.0153 1.47 26.1 0.3
0.356 2453.8 1 I737 0.0232 2.23 39.5 0.43
0.474 3267.1 88.15 0.0305 2.93 52 0.542
0.575 3963.3 72.667 0.0361 3.46 61.5 0.616
0.696 4797.3 60.034 0.0418 4.01 71.2 0.634
0.842 5803.7 49.624 0.0472 4.53 80.4 0.603
1.019 7023.7 41.004 0.0529 5.08 90.1 0.635
1.243 8567.6 33.615 0.0587 5.63 100 0.62

 

 

 

 

 

 

 

 

 

Table 7.43: Data from pore-size distribution test on raw low-high fat (low fat
samples which were made to high fat by adding ground fat tissues) sample 1 using
liquid extrusion porosimeter.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Pressure1PressurelDiameterCumuIativeIPorosity% of Total Pore
PSIA N/m2 microns Pore Vol. % Pore [Distributioni
egg Volume dV/d logD_
0.031 213.67 1347.8 0 0 0
0.054 372.21 773.77 0.0019 0.18 2.54 0.071
0.079 544.52 528.9 0.0037 0.35 4.95 0.098
0.1 19 820.23 351.12 0.0068 0.64 9.09 0.157
0.162 1 1 16.6 257.92 0.0099 0.93 13.2 0.208
0.239 1647.4 174.83 0.0157 1.47 21 0.309
0.353 2433.1 1 18.37 0.0248 2.32 33.2 0.484
0.471 3246.5 88.712 0.0357 3.34 47.7 0.784
0.57 3928.8 73.304 0.0434 4.06 58 0.837
0.689 4749.1 60.643 0.051 1 4.79 68.3 0.842
0.834 5748.5 50.1 0.0587 5.5 78.5 0.825
1.01 6961.6 41.37 0.0667 6.25 89.2 0.866
1.245 8581.4 33.561 0.0748 7 100 0.803

 

 

 

Table 7.44: Data from pore-size distribution test on raw low-high fat (low fat
samples which were made to high fat by adding ground fat tissues) sample 2 using
liquid extrusion porosimeter.

150

Table 7.45: Data from pore-size distribution test on raw low-high fat (low fat
samples which were made to high fat by adding ground fat tissues) sample 3 using

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PressurelPressurelDiameterCumulativelPorosity% of Total Pore

PSIA N/m2 microns Pore Vol. % Pore [Distributioni
cc/g Volume dV/d logD_

0.032 220.57 1305.7 0 0 0
0.05 344.64 835.67 0.0015 0.15 1.92 0.074
0.076 523.85 549.78 0.0034 0.34 4.36 0.1
0.105 723.73 397 .94 0.0054 0.54 6.92 0.136
0.157 1082.2 266.14 0.0094 0.94 12.1 0.219
0.233 1606 179.33 0.0151 1.5 19.4 0.318
0.379 2612.3 110.25 0.0262 2.61 33.6 0.503
0.505 3480.8 82.739 0.0366 3.65 46.9 0.799
0.556 3832.3 75.15 0.0408 4.06 52.3 0.963
0.673 4638.8 62.085 0.0496 4.94 63.6 1.016
0.816 5624.4 51.205 0.058 5.78 74.4 0.961
0.987 6803.1 42.334 0.0665 6.62 85.3 0.985
1.241 8553.8 33.669 0.078 7.77 100 1.107

 

 

 

liquid extrusion porosimeter.

Volume Fraction

 

0.06

0.05 q

0.04 .

0.03 »

0.02 ~

0.01 ,

 

 

 

 

 

l

l

T

T

30-50 50-90 90- 150- 230- 330- 450- 590- 750- 930-
150 230 330 450 590 750 930 1130
Pore Diameter (microns)

Figure 7.18: Pore volume distributions (at particular diameters) of raw low fat, high
fat and low-high fat (low fat samples which were made to high fat by adding ground
fat tissues).

151

 

0.05

0.04 4

 

0.03

0.02

Volume Fraction

0.01

 

 

 

 

0 T v - j T l T T F
30—50 50-90 90- 150- 230— 330- 450- 590- 750- 930-
150 230 330 450 590 750 930 1 130

Pore Diameters (microns)

Figure 7.19: Pore volume distributions (at particular diameters) of low fat samples
cooked to endpoint temperatures of 45, 60, and 75°C in a convection oven at 60%

moisture by air volume.

 

0.14 /
’——a—45
0.12
x --a-—60'
E 0.08~ ‘5.
LL ;
GE) 0.06(
2
O
> 0.04~
0.024
0 f f T f l l

 

 

 

 

30-50 50-90 90- 150- 230- 330- 450- 590- 750- 930-
150 230 330 450 590 750 930 1130

Pore Diameters (microns)

Figure 7.20: Pore volume distributions (at particular diameters) of high fat samples
cooked to endpoint temperatures of 45, 60, and 75°C in a convection oven at 60%

moisture by air volume.

152

7.4. Viscosity Results

 

 

 

 

40 O
O Q ..
00.9.90. 9......0 ’0‘
A30
0.
3
3‘
7,20
0
U
.9
>10
0 .
60 62 64 66 68 70

Shear rate (1/s)

Figure 7.21: Apparent viscosity of beef fat at 40°C (sample 1), determined using a
rotational viscometer.

40

 

35 O z. o oo o 3: o
304 0 °
25
20“
15*
10‘

Viscosity (cP)

 

 

 

60 62 64 66 68 70
Shear rate (1/s)

Figure 7.22: Apparent viscosity of beef fat at 40°C (sample 2), determined using a
rotational viscometer.

153

30

 

 

 

 

o o
. ° 9 o
0 o o
9.9, 20 9
3
.6 15 s
o
8
5 10 -
5
0 . . T
60 62 64 66 68 70
Shear rate (1/s)

Figure 7.23: Apparent viscosity of beef fat at 50°C (sample 1), determined using a
rotational viscometer.

 

 

 

 

30
25 . o o ’ °’ 0 0 °
- O o co
9 . . . o 3 °
6? 20 4 O O.
3
a
o
8
S 10
5 .
0 f m i l
60 62 64 66 68 70
Shear rate (1/s)

Figure 7.24: Apparent viscosity of beef fat at 50°C (sample 2), determined using a
rotational viscometer.

154

0)
O

 

 

 

 

25 - o
O

E 20 ~. . o .. . ' ° 0’
3 00 O O O. . z
5 ° 0
7, 15
0
8
5 1o-

5 s

o . . .

so 62 64 66 68 7o

Shear rate (1/s)

Figure 7.25: Apparent viscosity of beef fat at 60°C (sample 1), determined using a
rotational viscometer.

 

 

 

 

25
E ° ° 0 . O o. o
8 15 . ’
> 9 .
.g .
g 10 <
>

5 __

0 1 ! T l

60 62 64 66 68 70

Shear rate (1/s)

Figure 7.26: Apparent viscosity of beef fat at 60°C (sample 2), determined using a
rotational viscometer.

155

25

 

 

 

 

207 . 00
a; co . .
V 15 i O O

O O 9 O

a; 90 o . 3 . . . °’ ’
>

5

0 . .

60 62 64 66 68 7O

Shear rate (1/s)

Figure 7.27: Apparent viscosity of beef fat at 70°C (sample 1), determined using a
rotational viscometer.

 

 

 

 

20
o o
15 3
- o
E 9 O o 0 .° ° ’. . o . .
o o o
I . z
’5, 10 «
o
O
.‘L’
>
5 i
0 -
60 62 64 66 68 70
Shear rate (1/s)

Figure 7.28: Apparent viscosity of beef fat at 70°C (sample 2), determined using a
rotational viscometer.

156

7.5. Fat Analysis

After cooking, all the samples were analyzed for fat content. The loss of moisture
may be different from sample to sample and cooking treatment to treatment. Therefore,
the fat content was expressed on a dry basis asfat:protein ratio (Table 7.46). The results
show that the fat:protein of the low fat samples was not much affected by the different
treatment conditions. The results of the high fat samples show some irregularities, but
generally fat:protein decreased with increase in cooking temperature particularly in the
samples which were cooked at 60% moisture by air volume. These fat:protein analyses

were based on averages and also the fat and moisture analysis were not done on the same

samples. Therefore, this factor may have contributed to some irregularities.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Low Fat High Fat
Treatment
Initial F :P Final F:P Initial F :P Final F:P
Raw 0.242 0.242 0.749 0.749
Cooked 45°C (80% m/v) 0.242 0.246 0.749 0.873
Cooked 60°C (80% m/v) 0.242 0.248 0.749 0.709
Cooked 75°C (80% m/v) 0.242 0.28 0.749 0.784
Cooked 45°C (60% m/v) 0.242 0.249 0.749 0.692
Cooked 60°C (60% m/v) 0.242 0.249 0.749 0.577
Cooked 75°C (60% m/v) 0.242 0.288 0.749 0.584

 

Table 7.46: Fat analysis of low fat and high fat samples after cooking to different
endpoint temperatures in a convection oven at different humidities (60 and 80%
moisture by volume), expressed as fat:protein ratio (F:P)

157

 

7.6. Relative Permeability Results

 

.0
51’

P = 0.86 psi
0.32 -

p
o:

0.28 4

0.26 .

Penetrometer Drop (cm/s)

 

 

0.24

 

0 10 20 30 40 50 60 70
Time (s)

Figure 7.29: Flow curve during relative permeability experiments at a pressure step
of 0.86 psi (5928 Pa).

 

0.38
" 035. P = 1.20 psi

is:

0.32 ~

0.3 4
0.28 1
0.26 4

Penetrometer Drop (cm/s

 

 

0.24 . , . .

 

Time (s)

Figure 7.30: Flow curve during relative permeability experiments at a pressure step
of 1.2 psi (8271 Pa).

158

0.5

 

 

 

 

 

 

A P = 1.54 psi >
(D
E 0.45 ~
0.
9
o
5 0.4 -
m ’ 4
g L U U
‘53 0.35
C
OJ
0.
0.3 T7 r
0 10 20 30 40 50 60 70

Time (s)

Figure 7.31: Flow curve during relative permeability experiments at a pressure step
of 1.54 psi (10615 Pa).

0.54
Q52 . P = 1.87 psi

 

0.5 a >
0.48 .
0.46 ~

 

0.44 ~

Penetrometer Drop (cm/s)

 

0.42 ~ ”

 

 

 

0| 4 T l T T l l
0 1 0 2O 30 4O 50 60 70

Time (s)

Figure 7.32: Flow curve during relative permeability experiments at a pressure step
of 1.87 psi (12890 Pa).

159

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