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This is to certify that the

thesis entitled

EVALUATION OF THE MOISTURE PERMEABILITY CHARACTERISTICS
OF CONFECTIONERY PRODUCT PACKAGES WITH A
COLD SEAL CLOSURE

presented by

MUHAMMAD A. ZIA

has been accepted towards fulfillment
of the requirements for

_MASIER_ degree in W

7
fiféta '3

Major professor

Datew

0-7639 MS U is an Affirmative Action/Equal Opportunity Institution

 

 

 

 

LIBHARY
Michigan State
University

 

 

 

PLACE IN RETURN BOX to remove this checkout from your record.
To AVOID FINES return on or before date due.
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DATE DUE DATE DUE DATE DUE

 

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6/01 cJCIRC/DateDue.p65-p. 15

EVALUATION OF THE MOISTURE PERMEABILITY CHARACTERISTICS
OF CONFECTIONERY PRODUCT PACKAGES WITH A COLD SEAL
CLOSURE

By

Muhammad A. Zia

A THESIS
Submitted to
Michigan State University

in the partial fulfillment of the requirement
for the degree of

MASTER OF SCIENCE

School of Packaging

2002

ABSTRACT

EVALUATION OF THE MOISTURE PERMEABILITY CHARACTERISTICS
OF CONFECTIONERY PRODUCT PACKAGES WITH A COLD SEAL
CLOSURE

BY

Muhammad A. Zia

The water vapor transmission rate and permeance constants were determined
for the seven commodity films. The moisture isotherm of the confectionery
product was developed at a temperature of 23°C, to allow the selection of storage
conditions, in which the product would gain moisture as well as lose moisture. The
extent of moisture uptake by a confectionery product packaged in the respective
commodity packaging structures was also evaluated over a storage period of 115
days, at ambient temperature and low (20 %) and high (75%) relative humidity
conditions. Hardness of the nougat phase was determined to evaluate the effect of
moisture and relative humidity. Based on the statistical analysis, no statistically
significant differences between the performance of the respective package film
structures were observed over the storage period. The moisture loss or gain of the
packaged product at the two different relative humidity conditions, was assumed
to pass through micro-voids in the cold seal closure area. The packaging structures
were found to have no significant effect on the hardness of the nougat phase of the
product over the storage conditions studied. The storage conditions however, had a

statistical significance difference on the hardness in all packaged products.

ACKNOWLEDGMENTS

I would like to express my deepest thanks and appreciation to my academic advisor,
Dr. Jack R. Giacin, who passed away prior to completion of this manuscript, for his
consistent encouragement, advice and inspiring guidance throughout my graduate
program.

Grateful appreciation is extended to Dr. Bruce Harte, for his inspiring guidance
and consistent encouragement, to complete this manuscript. I would like to express my
appreciation to Dr. Jerry Cash and Dr. James Steffe for serving on my guidance
committee and for their help throughout my study in Michigan State University.

Also, I would like to thank to all my friends in School of Packaging and
Department of food Science and human nutrition, Michigan State University, for their
help and encouragement through my research study.

Finally, a special thanks to my dear wife Lubna, my sons Zain and Qasim for their

love, encouragement and support.

iii

TABLE OF CONTENTS

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

LIST OF TABLES vii
LIST OF FIGURES viii
INTRODUCTION 1
LITERATURE REVIEW
The Mechanism of Water Vapor Transmission Through Polymeric Packaging
Materials 5
Permeation Theory 9
Permeability Measurement Methods 11
Gravimetric Method 12
Isostatic Method 13
Quasi-Isostatic Method 16
Water Vapor Transmission Rate Measurement 17
Confectionery Packaging 2]
Characteristics of seal 22
Heat seal 23
Cold Seal 25
Moisture Permeability Characteristics of Chocolate 29
Moisture Isotherm and Shelf life of Food Products 33

Texture Profile Analysis 37

 

iv

MATERIALS AND METHODS

Water Vapor Transmission Rates

 

Packaging Materials

 

 

Water Vapor Transmission Rate Measurements

Water Vapor Transmission Rate Measurement Using The
Gravimetric Method

 

Determination of Moisture Isotherm

 

Determination of Equilibrium Moisture Contents

 

Determination of Initial Moisture Contents

 

Determination of Moisture Content of a Packaged Confectionery Product

 

With Cold Seal Closure During Storage

Determination of Texture of a Packaged Confectionery Product With
Cold Seal Closure During Storage

 

 

Sample Preparation

Setting of Instron -—

 

Textural Measurements of Nougat Phase of Confectionery Bar-----—---

RESULTS AND DISCUSSION

 

Water Vapor Transmission Rates

Equilibrium Sorption Isotherm of the Product

 

Initial Moisture Contents

 

Equilibrium Moisture Isotherm

 

The Effect of Relative Humidity on Moisture Content of the Packaged

 

Confectionery Product, Packaged with Cold Seal Closures

The Effect of Relative Humidity on Texture of the Packaged Confectionery
Product, Packaged with Cold Seal Closures

 

Hardness of Nougat Phase

 

4O

40

40

42

42

45

45

46

47

47

48

49

51

56

56

56

63

71

71

SUMMARY AND CONCLUSIONS

 

BIBLIGRAPHY

 

vi

77

86

Tables

10

LIST OF TABLES

Test Conditions for WVTR Determinations using the Mocon
Permatran W3/31

 

Equilibrium Relative Humidifies for Saturated Salt Solution

 

Water Vapor Transmission Rate of Film Structures at Different Temperature

 

and Relative Humidity Conditions

The Permeance Values of Film Structures at Different Temperature
and Relative Humidity Conditions

 

Equilibrium Moisture Content of the Chocolate Phase of the Confectionery
Product as a Function of Relative Humidity (RH;

 

Equilibrium Moisture Content of the Nougat Phase of the Confectionery
Product as a Function of Relative Humidity (RH)

 

The Change in Moisture Content of Nougat Phase of the Confectionery
Product at Room Temperature (23°C) and 20 % Relative Humidity During
115 Days Storage Period

 

The Change in Moisture Content of Nougat Phase of the Confectionery
Product at Room Temperature (23°C) and High Relative Humidity During
115 Days Storage Period

 

The Change in Hardness (Newton) of Nougat Phase of the Confectionery
Product at Room Temperature (23°C) and 20 % Relative Humidity During
115 days Storage Period

 

The Change in Hardness (Newton) of Nougat Phase of the Confectionery
Product at Room Temperature (23°C) and High Relative Humidity During
115 days Storage Period

 

vii

41

43

54

55

59

6O

67

68

73

74

LIST OF FIGURES

Figures

1

Product at 23°C

Typical Texture Profile Analysis (TPA) Curve Using the Instron
Universal Testing Machine

 

Equilibrium Moisture Content of Chocolate Phase of the Confectionery

 

Equilibrium Moisture Content of Nougat Phase of the Confectionery
Product at 23°C

 

The Change in Moisture Content of the Nougat Phase of the Confectionery
Product at room temperature (23°C) and 20 % Relative Humidity During
115 Days Storage Period

 

The Change in Moisture Content of the Nougat Phase of the Confectionery
Product at room temperature (23°C) and High Relative Humidity During
115 Days Storage Period

 

The Change in Hardness (Newton) of Nougat Phase of the Confectionery
Product at room temperature (23°C) and 20 % Relative Humidity During
120 Days Storage Period

 

The Change in Hardness (Newton) of Nougat Phase of the Confectionery
Product at room temperature (23°C) and High Relative Humidity During
120 Days Storage Period

 

viii

Pages

50

61

62

69

70

75

76

LIST OF APPENDIXES

Appendixes Pages
Appendix I Analysis of Variance (ANOVA) for Water Vapor Transmission rate of
Packaging Film Structures at 378°C and 90 % Relative Humidity- 79

Appendix II Analysis of Variance (ANOVA) for Water Vapor Transmission rate of
Packaging Film Structures at 23°C and 80 % Relative Humidity--- 80

Appendix 111 Analysis of Variance (ANOVA) for Water Vapor Transmission rate of
Packaging Film Structures at 23°C and 30 % Relative Humidity-—- 81

Appendix IV Analysis of Variance (ANOVA) for Moisture Content of Product
Package System 82

 

Appendix V Analysis of Variance (ANOVA) for Hardness of Product
Package System 83

 

Appendix VI The data for Moisture Isotherm of Chocolate Phase of the
Confectionery Product 84

 

Appendix VII The data for Moisture Isotherm of Nougat Phase of the
Confectionery Product 85

 

INTRODUCTION

The quality or shelf life of a food product is determined by a number
of interactions between parameters related to the product itself and/or
associated with the external storage environment. The interaction between
moisture and the food product is critical, and moisture transfer in food
products, to include confectionery products, frequently leads to deleterious
changes in product quality. Moisture transfer can occur between a food
product and its environment, and/or within a non-homogeneous structured
food product. In either situation, moisture transfer results in a change of the
water activity (aw) and the moisture content of the product.

Preventing such undesirable effects are dependent on the nature of
the product, its sensitivity to the gain or loss of moisture, the package
system and the storage environment. Selecting a package system of
appropriate moisture barrier characteristics, in general, provides adequate
protection to prevent the gain or loss of moisture by the product and allows
maintenance of product quality. Implicit in this assumption is that the
package is hermetically sealed and that diffusion through the package
structure, as described by Fick’s First and Second Laws, is the principle
mechanism resulting in water vapor transfer through the package structure.

Alternatively, if the package system had serious leakage or sea]

integrity problems, the assumption that water vapor transfer is the result of

diffusion through the package structure is erroneous. In this case, a process
involving flow or transfer through micro-voids in the seal area would be the
principle mechanism of moisture gain or loss.

Precedence for a mechanism involving the flow or transfer of water
vapor through micro-voids in the package seal area, accompanied by a
concomitant change in the moisture content of the packaged product is
found in the studies recently reported by Lin (1995), who studied the extent
of toluene vapor uptake by a packaged confectionery product. The results
of these studies indicated that for a confectionery product packaged in a
series of commodity package structures, permeant flow or transfer through
micro-voids in the cold seal closure area was the predominant mechanism
of toluene ingression. Since cold seal closures are widely employed in the
packaging of confectionery products, evaluation of seal performance or seal
integrity for the cold seal closure warrants further investigation.

This study represents an extension of the studies reported by Lin
(1995) and considers the effect of storage conditions and package structure
on the quality of a chocolate based confectionery product, over a six month
storage period. The moisture content of the packaged products was
determined as a function of storage time and conditions (i.e. temperature
and relative humidity), due to its dominant role in product quality.

Two analytical procedures, namely moisture content determination

by the Karl Fischer method and texture Profile Analysis using the Instron

Universal Tensile Tester, were employed. The results of the tests were
applied to assess the relative performance of a series of commodity package
structures, sealed by a cold seal closure procedure, on the moisture content
change of a chocolate based confectionery product, where quality is
dependent upon the moisture content of the non-homogeneous product.

The results of the objective and subjective tests performed were
evaluated to establish a relationship between the change in moisture content
of the packaged product and the moisture barrier characteristics of the
respective package structures, as well as the affect of moisture content on
the texture of the packaged product. Further, by analyzing the numerical
consistency of the product water activity, information on the mechanism
associated with water vapor transfer was obtained.

The specific objectives of the study include:

0 Determination of the water vapor permeability of a series of commodity
packaging structures used for packaging confectionery products.

0 Development of a test system to allow determination of the change in
product moisture content of a packaged confectionery product stored at
conditions of constant temperature and relative humidity.

0 Evaluation of the relative performance of the package systems with
respect to variation in the moisture content of the packaged product, as a

function of storage time and conditions.

 

0 Evaluation of the quantitative relationship between the respective
package structures as regards product moisture content and the sensory
responses (i.e. texture profile) to product quality, as a function of

storage time and conditions.

LITERATURE REVIEW

The Mechanism of Water Vapor Transmission Through Polymeric Packaging
Materials

The deterioration of food quality during storage may be due in part to the
loss of moisture or flavor compounds from the packaged food product, or to the
uptake of moisture or volatile contaminants permeating from the external
environment. Therefore, measurement of the rate of permeation of water vapor
and organic vapors through polymeric packaging materials is of significant
importance.

Permeability is the phenomenon of transmission of a gas or water vapor
through a polymer. This process may be characterized by three basic steps, which
are summarized below:

1. Adsorption, the dissolution of a gas or vapor into the polymer matrix at
the high penetrant concentration surface.

2. Diffusion, the movement of a gas or water vapor penetrant through the
polymer bulk phase, along a concentration gradient.

3. Desorption, the desorption or evaporation of the penetrant from the low
concentration surface of the polymer membrane.

Mass transfer in polymeric packaging materials can be referred to as either
permeability, sorption or migration. When small molecules permeate through a

polymeric membrane, the rate of permeation is governed by the physical and

chemical nature of the penetrant and the polymer membrane, as well as external
factors, which include: temperature, vapor pressure, and relative humidity.

The permeability of a gas or vapor through a polymeric film is a function of
two fundamental parameters: the diffusion coefficient (D), and the solubility
coefficient (8). Functionally, the diffusion coefficient is a kinetic term and
describes how rapidly permeant molecules advance and the time required to reach
steady state. The solubility coefficient is a thermodynamic term, describing how
permeant molecules are sorbed by the barrier structure. The diffusion process is
the result of polymer molecules having a random kinetic agitation or heat motion.
Above the glass transition temperature (T3), polymer chain segments have
vibration, rotation, and translation properties, which continually create temporary
holes or voids within the polymer matrix. The holes allow penetrant molecules to
pass through the matrix under a concentration gradient. For polymer membranes
below T8, the rate of diffusion will be a function of the size and frequency of pre-
existing holes or the void volume between polymer chains. Whereas, solubility
involves the affinity of the permeant for the polymer (Bauer, 1984 and Imbalzano
et a1., 1991).

Permeation is a measure of the steady-state transfer of the permeant, which
is usually described by the permeability constant, P. The permeability constant can
be expressed in terms of two fundamental parameters: the diffusion coefficient (D)
and the solubility coefficient (S). Their relationship is described by Equation A.

P=DxS (A)

 

Where the diffusion coefficient (D) is a measure of the rate at which
penetrant molecules advance through the polymer, and the solubility coefficient
(S) describes the amount of permeant dissolved in the polymer matrix at
equilibrium conditions (Crank, 1968).

The mass transfer of organic volatiles is a major concern with polymeric
packaging films. There is potential loss of aroma/flavor compounds due to their
permeation through the film, or to their sorption by the polymeric packaging
material. Another reason for concern involves the possibility of contamination of
the food due to the permeation of organic vapor from the external environment
through the packaging film, with sorption by the product (Mohney et al., 1988;
Tou et al., 1990; and Franz, 1993).

To understand the sorption mechanism in food product /package systems,
it is necessary to assure quality control and prediction of product shelf life.
Measurement of the loss of product volatiles by permeation is also associated with
product shelf life. Sorption can be described as a function of sorbate concentration
by a sorption equilibrium isotherm that can be presented by Henry’s law or other
mathematical models. Specifically, Henry’s law describes the relationship between
the vapor pressure of the organic penetrate and the mole fraction of penetrant
sorbed by the polymer membrane at equilibrium.

The partition coefficient K is defined as the ratio of the equilibrium
concentration of a component in a fluid phase and the equilibrium concentration of

the component in a polymeric material. For a specific concentration, the partition

coefficient K provides a practical way to calculate the change in a component
concentration, either in the food or packaging material, from the time that the food
product and packaging material are contracted, up to the moment they reach
equilibrium, provided the initial concentrations are known.

Since sorption and migration are essentially the same mass transport
phenomenon, migration can also be described by a partition and diffusion
coefficient. The diffusion coefficient determines the dynamics of the sorption
process. The larger the value of D the shorter the time to reach equilibrium.
(Giacin, 1995).

Non-interactive molecules like oxygen, nitrogen, and carbon dioxide will
have little or no effect on polymer morphology, when sorbed into the polymer
matrix. However, organic vapors are comparable in size or larger than the polymer
chain segments associated with chain segmental mobility at temperatures above
T3. These organic penetrants diffuse by a complicated mechanism, which is
dependent upon the motions of both the polymer and diffusant molecules. Organic
molecules may also have a higher solubility in the polymer, which can result in
significant swelling of the polymer matrix by the sorbed organic molecules.
Organic molecules sorbed by the polymer can act like a plasticizer, lowering the
glass transition temperature (T8) and increasing the polymer’s segmental motions
at any temperature. This will results in further plasticization and swelling (Meares,

1965).

Permeation Theory

For non-interactive permeants, such as gases, the rate of transfer of a
diffiising substance can be expressed mathematically by Fick’s first and second
laws of diffusion, as described in equations B and C, respectively. The solubility

can be described by Henry’s law (Crank, 1975).

F = - D (dc/dx) (B)

dc/dt = d/dx (D dc/dx ) = D (dzc/dxz) (C)
where: F = flux (the rate of transfer of the diffusing substance per unit area)

D = diffusion coefficient

c = concentration of diffusing substance

x = direction of diffusion

t = time.

When organic permeants enter the permeant molecules the polymer, a
boundary layer is created. The boundary layer phase of the polymer is swollen and
the diffusion coefficient of the permeant in this phase is not equivalent to that of
the non-swollen phase. The diffusion coefficient in the swollen phase is larger
than in the non-swollen phase. Also in such cases, Fick’s laws of diffusion do not
apply, since the boundary phase is changing with time (Crosby, 1981 and
Maekawa, 1994).

Under low vapor concentration levels, the vapor pressure of the penetrant is

proportional to its concentration in the polymer. According to Henry’s law

(Equation D), the rate of transfer of a diffusing substance can be expressed in
terms of the permeant partial pressure between surfaces x = O to x = L by the
relationship:

C = S x Ap (D)
where: C = concentration of the penetrant in the polymer phase

S = solubility coefficient

AP = partial pressure of the penetrant in the gas phase.

At steady state, the diffusion flux (F) (equation E) of a permeant in a

polymer can be defined as the amount of penetrant which passes through a unit

surface area per unit time.

F = Q/A x t (E)

where : Q = quantity of diffusing substance transferring through the film.
A = area
t = time.

Also the diffusion flux (F) (equation F) of the permeant can be integrated
through the total thickness of the polymer between the two concentrations,
assuming that the diffusion coefficient (D) is constant and independent of
concentration.

F = D (C1-C2) /L (P)

where : C1, C2 = concentration of gas or vapor at the surfaces

x = O andx — L respectively (C ,> C 2)

L = film thickness.

10

From equations D, E and F the amount of penetrant which has transmitted at time
t can be calculated by substitution in to equations (G) and (H).
Q={D(C1-C2)xAxt}/L (G)
Q: {stuh-pz)xAxt}/L (H)
Using the definition of permeability:
P=DxS

The permeability constant can be determined by substitution in to Equation 1:

 

P=(QxL)/AxtX(Pi-P2) (I)

Permeability Measurement Methods

Permeability, diffusion and solubility coefficient values can be determined
by the following methods: (1) the gravimetric method (2) the isostatic method; and
(3) the quasi-isostatic method. Basically, each test method is designed to measure
the permeability by mounting the film in a hermetic environment between two test
cell chambers. A fixed and constant gas or vapor concentration is introduced into
the high concentration cell chamber. The permeant then diffuses through the
barrier membrane and is desorbed from the low concentration film surface into the
low concentration cell chamber, where it is then quantified using an appropriate

method of detection.

1]

Gravimetric Method

In this procedure, permeation values are determined by observing the
change in weight of a test cell or intact package system, as a result of the diffusion
process. An example is the method described in ASTM E-96 (ASTM, 1988),
where an aluminum dish containing desiccant is covered with a packaging
material, weighed and placed in a constant temperature and humidity chamber.
The samples are then weighed periodically, and the water vapor transmission rate
is determined by the weight gain over time.

Recently, an electrobalance method has been used to measure the sorption
and diffusion of organic vapors by polymeric materials (Berens and Hopfenberg,
1982; Choy et al., 1984). The experiments are carried out at equilibrium vapor
pressure, using an electrobalance, which continually records the gain or loss of
weight, by a test specimen, as a function of time. The Gravimeuic methods in
general have low sensitivity, especially for high barrier polymer films, and are
applicable over a limited vapor pressure range. However, application of the
electrobalance negates these limitations and provides for high sensitivity and
utility over a wide range of temperature and sorbate vapor pressure (Hernandez et
aL,1986)

More recently, the isostatic and quasi-isostatic procedures have become
widely employed for measuring permeability. Since organic vapor and aroma
permeability measurement involve complicated procedures, there is no standard

analytical technique. Also, there is very limited number of commercial instruments

12

 

available for measuring organic vapor permeability. To date, most research in this
area has been conducted using a permeation system of the investigator’s own
design (Blaskesley, 1974; Niebergall et al., 1979; Baner, 1987; Hernandez et al.,
1986; Hatzidimitriu et al., 1987; Liu et al. 1991; and Franz, 1993). Most of these
have been designed to measure the transmission rate of organic vapor through
barrier membranes by maintaining a constant partial pressure differential across

the test membrane.

Isostatic Method

The total pressure in both chambers of the permeation cell is kept constant
by maintaining the same atmospheric pressure in both chambers of the test cell.
The permeability measurement involves maintaining a constant permeant partial
pressure, or a concentration gradient between the two cell chambers. The permeant
which has permeated through the film and into the lower concentration chamber is
then conveyed by a carrier gas to a detector where it is quantified. The
permeability measurement involves determining the change in the ratio of [( AM /
At ) t/ (AM / At) co], as a function oftime.

Equation I, which was derived by Pasternak et al. (1970), describes the
transmission rate profile curve (Hernandez et al., 1986):

(AM/At)./ (AM / At ) .,= ( 4/(n)"2 ) (L2/4Dt) V’ exp ( -L2/4Dt) (J)

13

where: (AM / At), and (AM / At ) a, = the transmission rate of the penetrant at time
(t) and at steady state ( co ) respectively.
t = time
L = film thickness
D = diffusion coefficient.
A value of ( L2 / 4Dt) can then be calculated for each value of
[(AM / At ) I/ (AM / At ) ,0 ]. A straight line can be obtained by plotting (4Dt / L2)
as a function of time. From the slope of the straight line, the diffusion coefficient
(D) was obtained from Equation K.
D = [(slope) x (L2) 1 / 4 (K)
Ziegel et a1. (1969) derived Equation L, from a different expression for [(AM / At)t
/(AM / At) ,0] ( Hernandez et al., 1986), to solve for D.
D=L2/(7.199xt0,5) (L)
where : t0.5 = the time required to reach a rate of transmission (AM / At ) ,
value equal to half the steady state (AM / At ) a, value.
Finally, the permeability coefficient (P) can be calculated from data
obtained using the isostatic method by substituation into Equation M.
P: (AM/At),o x(L/A.Ap) (M)
Where : A = area of the film exposed to permeant in the permeation cell
L = film thickness

Ap = partial pressure gradient.

14

Various detector devices have been used in isostatic permeability studies.
Thermal conductivity detectors and therrnistors were used to measure single
permeants (Pasternak et al., 1970; Ziegel et al., 1969; Yasuda and Rosengren,
1970). Flame ionization detectors (FID) have been used for organic vapors and
provide the advantage of not being affected by the presence of the carrier gas and
water vapor (Zobel, 1982). When a complex mixture of organic permeants is
involved in the test, a gas chromatograph can be interfaced with a FID to separate
individual permeant first, before quantification (DeLassus, 1985). Other
techniques, based on either a photoionization detector or atmospheric pressure
ionization mass spectrometer, have been employed by Caldecourt et al. (1985).
Both detection systems were found to be very sensitive and useful in the
characterization of the permeability of barrier membranes to organic penetrants. In
some commercially available isostatic permeability testers, IR sensors and
coulumetric sensors are also used for detecting water vapor and oxygen,

respectively (MOCON; Operating Manuals, 1982; 1989).

15

Quasi- isostatic Method

The quasi-isostatic method is also known as the accumulation method. This
method involves measurement of accumulated gas or vapor, which has permeated
through a material as a firnction of time. In this method, one of the two chambers
adjacent to the film is closed to the external environment. The gas or vapor being
tested is allowed to flow through the high concentration cell chamber at
atmospheric pressure. At the same time, the gas permeates into the lower
concentration cell and aliquots are withdrawn from the low concentration cell for
quantification. Typically for organic penetrants, samples are taken and injected
directly into a gas chromatograph (GC), where a flame ionization detector is used
for quantification, at pre-determined time intervals (Bauer et al., 1984).

Using this method, the quantity of permeant accumulated increases as a
function of time. When the relationship between quantity accumulated per unit of
time is constant, a steady-state rate of diffusion has been reached. By extrapolating
the linear segment of the curve to the x-axis, the lag time (9) can be calculated
from the intersection of the projection of the steady state portion of the
transmission rate profile curve (Hernandez, et al., 1986 and Wangwiwatsilp,
1993). The diffusion coefficient is expressed by equation N.

D = L2 / 69 (N)
where : 9 = lag time
L = film thickness

and the permeability coefficient at steady state can be described by equation 0.

16

P=SlOpeXL/AXAp (O)
where : slope = straight line portion of the transmission rate curve (quantity / time)
L = film thickness
A = surface area

Ap = partial pressure.

Water Vapor Transmission Rate Measurement

The water vapor transmission rate (WVTR) is defined as the rate of water
vapor flow (Q/t), normal to the two surfaces, under steady state conditions,
through a unit area of a test film.

WVTR = Q/At

The WVTR does not take into account the thickness of the test material or
the driving force of permeant across the polymer. Therefore it is not a constant for
the test film, but is useful for comparative purposes. WVTR data are normally
reported at 38°C for films tested at 95% relative humidity. There are several
methods for measuring WVTR and water vapor permeability. Earlier methods
(ASTM E-96) were based on a Gravimetric procedure and measured the weight
increase by a desiccant sealed in an aluminum cup by the test film. In 1990,
ASTM introduced a new test standard (ASTM F 1249) based on the isostatic
method, which employed solid state electronics with pulse-modulated infra-red
sensors, which can detect down to one ppm water vapor.

MOCON® (Modern Controls Inc. Minneapolis, MN) manufactures and

17

markets an instrument, the Permatran-W 3/31, which meets the requirements of
ASTM F 1249. Test temperatures can be controlled from 10 to 40°C (: 0.5°C) and
relative humidity from 35% to 90% RH (j; 3%). The instrument can test at 100%
RH (: 3%) by inserting water saturated sponges in to the test cell.

Relative humidity is controlled by exposing pressurized dry nitrogen gas to
pure water (HPLC grade) in an enclosed chamber, when the equilibrium relative
humidity reaches 100%. The gas is then released to a lower pressure environment
which results in a reduction in the percent relative humidity. This two-pressure
method is used by the Permatran-W 3/31 to generate water vapor at the required
percent relative humidity. Test gas relative humidity is measured by a solid state
semi-conductor device, which is located in the outer chamber of both test cells.

Water vapor permeating across the film is transported by dry nitrogen gas
to a pressure modulated infrared detection system, intended for operation over a 5
to 50°C temperature range. The detector consists of a pump, a sensing chamber,
infrared source, a 2.6 micrometer infrared filter, a lead sulphide photo detector and
an amplifier. The pump varies the pressure and density of the gas mixture in the
sensing chamber, which consequently varies the absorption rate of infrared
radiation by the water vapor present. The infrared photo detector produces a low-
level electrical signal in response to the change in transmitted infrared radiation.
The amplifier produces a filtered DC signal in direct proportion to the water vapor
in the test cell and is therefore, proportional to the water vapor transmission rate of

the test film. The instrument must be calibrated using reference films of known

18

WVTR and at specific flow rates, generally at 10 cm3min'l and 100 cm3min". The
system must be operated using calibration flow rates, good barriers at the higher
flow rate and poor barriers at the lower flow rate.

An efficient process for measuring water vapor transmission rate of barrier
materials combines solid state electronics with patented pulse-modulated infra-red
to detect down to one part per million (ppm) of water vapor (Modern Controls Inc.
Minneapolis, MN). This instrumentation is capable of testing multiple samples
quickly and accurately and after six years of comparison testing with E-96,
became the basis for the newest ASTM water vapor transmission rate (WVTR)
standards in the United States (Demorest and Mayer, 1996). When determining
water vapor transmission rates of barrier materials, making direct measurements
under precise testing conditions is the most reliable method. It is now
recommended that the generated RH method can be employed to generate the
precise humidity desired. WVTR tests can be performed on all types of barrier
materials without factors such as salt inaccuracies, corrosion or assumed
humidifies being factors. The standard method of establishing a differential
gradient across a film surface is still the fastest way to measure permeability
(Demorest and Mayer, 1996). Modern test methods have been developed that
quickly and reliably measure the permeability, diffusion and solubility coefficients
for the various polymer/permeant combinations used in food and other packaging

(Demorest and Mayer, 1998).

19

MAS Technologies, Inc. (Zumbrota, MN) is another manufacture of
Permeability instruments. There products include the MAS 500 Isostatic Oxygen
Diffusion System, the MAS 1000 Moisture Permeation System and the MAS 2000
Organic Permeation System. The principle of both Modern Controls and MAS
Technologies permeability instruments is based on an isostatic procedure.
Typically, a film sample is mounted between two cell chambers. One of the cell
chambers holds the test gas to be used as the permeant, while the other chamber
holds carrier gas that flows through the cell to the detector. When the permeant
diffuses from the high concentration chamber into the low concentration chamber,
it flows directly to the detector for measurement.

The MAS 1000TM Moisture Permeation System is designed to test the
levels at which moisture will permeate. Diffusibility and solubility coefficient
values for the packaging material can also be determined. This system employs
mass transport theory within a unique software package, which allows for early
prediction of steady state permeation values. This highly sophisticated system
incorporate precise temperature and flow rate control and sensitivity in the 0.001
grams/ m2 /day region. The test RH level is fully controlled through software to
assure consistent and realistic measurements without the requirements of salt
solution preparation. The MAS 1000TM also incorporates a multiple zone cell to
provide the user with significant improvement in test flexibility. This allows the

user to select the appropriate test sensitivity level. Measurements requiring high

20

detector sensitivity may employ all zones, while low sensitivity measurements

may be conducted using a single zone.

Confectionery Packaging

The packaging requirements for chocolate confectionery products are
similar to other food products (Martin, 1987 and Anon, 1998) and are summarized
below:
1- Protection: The product should be protected by the package from the time of
manufacture to consumption. Water vapor, oxygen and undesirable environmental
odors need to be excluded and the product flavor kept inside the package.
2- Function: The package should be functional to facilitate the manufacture,
shipping, storage, display and use of the product.
3- Sales Appeal: The package must attract the shopper, appeal to emotions, inform
and trigger the sale.
Chocolate enrobed candy bars require that packaging material provide excellent
barrier, good print receptivity and ability to be sealed rapidly at temperatures low
enough to avoid melting of the chocolate coating. The printed glassine was the
most common packaging material used for confectionery packaging that did not
meet all these requirements; it kept the product clean and identified the brand but
provided little or no barrier; shelf life was less than three months (Jenkins and

Harrington, 1991). PVDC-coated cellophane laminations replaced glassine,

21

increased the shelf life and made attractive package (Jenkins and Harrington,
1991). The most widely used film construction currently in use is
"Lacquer/ink/whiteOPP/PVDO/cold seal”. This construction provides the oxygen
and moisture barrier, and the cold seal pattern enables the package to be sealed at
low temperatures below the melting point of chocolate (Jenkins and Harrington,
1991)

There are several common polymeric films/flexible materials used in
confectionery packaging structures. These include cellulose, high density
polyethylene (HDPE), polypropylene (PP), polyvinylidene chloride (PVDC),
polyethylene terephthalate (PET), aluminum foil, and paper / glassine. In
addition, a number of newer materials with excellent barrier properties are suitable

for confectionery packaging (Jenkins and Harrington, 1991).

Characteristics of Seal

Two major factors should be considered in the selection of adhesive
systems for package sealing. First, is the chemical nature of the adhesive
components, which acts as the binder. The second factor to consider is the way in
which the bond is formed, by loss of water or solvent, by loss of heat or by
chemical reaction. In practice, adhesives are widely used in forming multilayer
structures involving the combination of polymeric films or other non-polymeric

structures, as well as to seal fabricated package systems (Lazarus, 1990).

22

In general, the primary bonding associated with adhesives include three
types: covalent bonds, ionic bonds and metallic bonds. Three mechanisms for
adhesive bond formation (Lazarus, 1990) are summarized below:

Loss of carrier: The bond is formed when the carrier is lost through adsorption into
the substrate or by evaporation. Water based adhesives are preferred from an
environmental point of view, but removal of water requires more energy. Solvent
based adhesive systems are more common. Solvent based adhesives are preferred,
where two impermeable substrates are to be bonded such as lamination of plastic
films. It is easier to achieve good adhesion to plastic films with solvent based
types.

Loss of heat: The application of a molten adhesive, which solidifies on cooling,
has some advantages. This type adhesive has application with porous and
impermeable substrates and provides good adhesion. However, this molten
adhesive can not be applied to heat-sensitive substrates.

Chemical reaction: A liquid material is applied to the substrate and then reacted
chemically to create a solid. This technique is commonly used for structural
adhesives, where high bond strengths are needed. In many packaging applications

the substrates are relatively week and high strength adhesives are not required.

Heat Seal

The heat seal process requires is to reactivate a layer of thermoplastic
material or adhesive to react with an adherend by heat, enabling it to form a bond
with another adherend usually assisted by pressure (Booth, 1990).
Hot melt adhesives are thermoplastic and are amorphous, softening gradually over

a wide range of temperature. Adhesive performance can be best understood by

23

discussing the solid to liquid change in relation to adhesive application, and the
liquid to'solid change in relation to the formation of a good bond ( Kettleborough,
1990). The speed of bond formation on modern high-speed machinery depends on
several factors, such as the specific adhesive system, temperature, porosity and
surface characteristics of substrates, as well as application conditions, and the time
and extent of compression of the surfaces. It is essential to have a clear
understanding of practical adhesive application technology if bonding problems
are to be avoided and maximum production cost benefits obtained. If all factors
are carefully considered, the relatively high price of 100% solids hot melts may be
offset by various economic factors, including operational costs and performance
(Kettleborough, 1990).

Hot melt adhesives can be based on a number of different chemical systems
but those based on vinyl acetate-ethylene copolymers represent the largest class.
These copolymers are readily available in different grades and have a high degree
of versatility and potential to tailor the formulation of the adhesive systems for
specific end use applications. These polymer systems offer excellent
machineability, setting and adhesion characteristics, coupled with good low
temperature flexibility, as well as very good compatibility with other formulating
constituents used in the manufacture of hot melts or heat seal adhesives. Other
types of polymers employed as hot melt adhesives include polyethylene,

polyamides, polyurethanes, and thermoplastic block copolymers (Coggin, 1990).

24

Hot melts are well known for their versatility and functionality, mainly in
applications related to packaging. There rapid green-strength development,
coupled with environmental durability, make them a highly cost effective product
for high speed production lines in packaging operations. They have limitations
which include: limited heat resistance due to the thermoplastic nature of the
adhesive system, susceptibility to solvent and plasticizer attack and bond failure
under high stress or load. A clean substrate surface is also a requirement for
effective bonding. Hot melts based upon ethylene-vinyl acetate copolymers are
dominant in this group with 50-55 % of the market volume. Polyolefins, such as
low density polyethylene and amorphous polypropylene account for 30-40% of the
market volume, while the remaining balance of 5-15% is made of “specialty” hot

melts (Kuzma, 1990).

Cold Seal

The term “cold seal” is used to describe the creation of an effective seal
without the use of heat. This technique requires two surfaces of cold seal
adhesives being bonded together under pressure alone. Booth (1990) defined cold
seal as “the ability of a non-tacky adhesive film to bond to itself under pressure at
room temperature”.

In the field of packaging, cold seal closures have been widely used for food
product packaging as well as for other heat sensitive products. Early applications

of this sealing technique were hindered, however, by the need to use organic

25

solvents, which were not suitable for food contact, in applying the cold seal
adhesive pattern. Now, with the development of new cold seal materials, which
are water based and rubber latex stabilized with alkali, the use of cold seal
adhesives has found considerable utility in the packaging of confectionery
products (Jones, 1985).

Cold seal adhesives were first introduced in the 1960’s for confectionery
packaging. Since then, their usage has increased significantly, and a wide range of
substrates have been evaluated (Stone, 1976, Anonymous, 1980 and Layfield,
1990). Cold seal adhesives are a blend of natural rubber latex and an acrylic resin
to reduce the self adhesion so that pressure is needed to form the bond. Biscuits,
chocolate and other heat sensitive foods are wrapped in films coated with cold seal
adhesive. This technique allows packing at very high speed with pressure so that
the contents remain unaffected (Lazarus, 1990). Natural rubber latex formulations
have wide use in cold seal applications because they form films that exhibit auto
adhesion and blocking resistance (Baetzold and Polance, 1998). Coextruded
polyester films are ideal for cold seal applications. They offer good adhesion for
metallizing or printing with either solvent-based or waterborne inks. Applications
include use for candy wrappers and other cold seal packages (Anonymous, 1991).
A metallized OPP film which uses a cost effective packaging material is suitable
for preventing moisture loss in low fat soft cookies. The OPP film Torayfan PC-l
fiom Toray Plastics is easily converted in to a variety of laminated structures. One

side of the film is highly corona treated, making it convertible with water-based

26

inks, adhesives, cold seal coatings and the other side is designed to be metallized
(Anonymous, 1993). A one side metallized heat-scalable OPP film designed
specifically for packaging applications is now available from ICI and sold under
the trade name Propafoil. It is already being used for the packaging of chocolate
biscuits, confectionery and ice cream. Propafoil can be used for heat seal and cold
seal coating applications (Tebbatt, 1983).

Cold seal adhesives are normally used on flexible film webs to replace a
laminated or extruded polyethylene layer as the sealing medium. This improves
the output and economy in the flexible packaging industry (Layfield, 1990). Cold
seal adhesives are based on a mixture of natural and synthetic rubber latexes,
combined with a number of lesser ingredients, such as antifoams, antifungicides,
and filling agents. The natural latex confers the characteristics of self adhesion.
Synthetic latexes are used to control the variable cohesive properties, to improve
stability, to increase resistance to oxidation, or to improve adhesion to difficult
substrates, and may also be used to reduce costs (Anonymous, 1980). From the
printers viewpoint the most desirable properties of cold seal adhesives are long
shelf life, low foaming, excellent printability, readily scalable and non blocking.
The application of cold seal adhesives in the confectionery industry is recognized
as revolutionary with respect to optimization of machine efficiency and reduction
of running costs (Layfield, 1990). According to Levine (1976) and Jones (1985),
the most important factors contributing to the dramatic grth in the use of cold

seal coated materials are:

27

1. Elimination of heat damage to heat sensitive products, such as chocolate. Heat
is not required in the bonding process, only contact pressure is required.

2. Less distortion and shrinkage of polypropylene packaging films.

3. Water based adhesive formulation eliminates solvent related concerns.

4. Elimination of temperature control equipment on the packaging line and lower
power consumption.

5. Easy machine maintenance and non-sticking of the coating to the product.

6. Faster than heat sealing.

Compared to heat sealing techniques, machine speeds can be doubled with
the use of a pattern cold seal. Cold seals are normally based on a type of natural
rubber latex and are widely categorized into two types, which can be described by
the nature of the dried film. "Hard" cold seals are essentially non pressure-
sensitive and usually exhibit low bond strength. The nature of the dried film is less
prone to blocking and stringing. "Soft" cold seals show a greater degree of
pressure sensitivity and will seal more readily. This characteristic has lead too
much higher seal strengths and in some cases to cause film tear. It has a higher
probability of blocking and stringing. The softer varieties of cold seals are usually
more tolerant to surface contamination. However, they exhibit a slight reduction in
seal strength (Layfield, 1990). In recent years, the trend with respect to cold seal
has been towards maximizing bond strength and obtaining 100% fiber tear on

single web films, especially low density pearlized polypropylene. Some fragile

28

products need an easy-open, peelable bond, this requirement necessitates a seal
strength in the region of lOOg/25mm (Layfield, 1990).

In addition to the well-established confectionery and biscuit markets, cold
seal adhesives may find use in other applications, such as medical packaging, tea
packaging or frozen food packaging. Also development of adhesive technology to
maintain performance with new films and inks/lacquers will be critical to the
industry (Stone, 1976 and Layfield, 1990). Advantages of cold seal films in biscuit
and confectionery packaging include reduced product damage, reduction in
packaging materials waste, ease of operation and start-up, reduced maintenance
costs, plant safety and energy savings (Matthews, 1980). Cold seal provides better
protection against moisture and costs are less when the packaging is made of
laminated material, since only a single film web is used with a cold seal pattern

application (Arnold, 1981).

Moisture Permeability Characteristics of Chocolate

The shelf life of a food product is determined by numerous, complex
interactions between parameters related to the product itself and/or associated with
the external environment. Among those factors, the interaction between moisture
and the food is critical. Moisture transfer in finished food products frequently
leads to deleterious changes in quality. Biquet and Labuza (1988) found that
moisture transfer can occur between a food and its environment and with in a non

homogeneous structured food system. In both cases, it results in a change of the

29

water activity (3,.) and the moisture content of the product as a function of time.
They also reported that chemical and enzymatic reactions in food, as well as the
microbial stability of food products, are strongly influenced by the water activity.
The use of adequate packaging material can control moisture exchange between a
food product and its surrounding. A more challenging problem is to prevent or
slow down moisture exchange within multi-component food products. The rate of
moisture exchange may be reduced by appropriate manipulation of certain
parameters.

In a study conducted by Biquet and Labuza, (1988) the moisture barrier
properties of a semi sweet dark chocolate film were determined at variable film
thicknesses, temperature and relative humidity in the intermediate moisture range.
They concluded that the chocolate film 0.6 mm (24 mil) thick was a better
moisture barrier than a 1 mil thick low density polyethylene film. The
mathematical packaging model for non-edible packaging materials worked well
for a typical outer barrier coated model system, while a new mathematical model
predicted well the moisture transfer within a bi-component system of different
initial aw, with the barrier between them. In peanut butter or cookies enrobed with
chocolate, the oil may migrate into the outer chocolate layer. This can cause the
chocolate to become soft and sticky. The crystal structure of the chocolate to
change causing "fat bloom," the enrobed material to become "dry," and the
product to undergo a flavor change (Brake and F ennema, 1993). Lipid migration

in chocolate enrobed cookies occurs rapidly during the early stages of storage and

30

diminishes with further storage (Wooton et al., 1970). It is difficult to maintain
low storage temperatures throughout the distribution system (Wacquez 1975).
Brake and Fennema, (1993) found that the shelf life of products susceptible to fat
migration can be extended by storing at low temperatures, using a thicker
chocolate coating, adding stabilizers or reducing fat content of the filling. Dry
films from cellulose derivatives are good lipid barriers, but films as thin as 0.005
mm have been detectable in the mouth (Nelson and Fennema, 1991). Sealing
enrobed centers with confectioner's glaze or similar sealant has been suggested to
inhibit fat transfer (Minson, 1990).

Designing a semi-solid, edible coating for use in confectionery products,
must satisfy several requirements: (1) the coating should be an effective barrier to
lipid migration; (2) it should not notably alter sensory properties; and (3) its water
activity must be similar to that of major components, preferably without drying.
Coatings containing hydrocolloids and sweetners were tested for lipid barrier and
sensory properties, adhesion to chocolate, viscosity, and aw. (Brake and Fennema,
1993)

For composite foods consisting of multilayers with different composition,
such as jelly-filled cookies, pizza, pies, chocolate coated products, snacks, candies,
etc. it is possible for moisture in one component to migrate to another (Cakebread,
1972) leading to deteriorating changes in product quality (Biquet and Labuza,
1988). The direction of moisture migration is not necessarily from the layer with

the higher moisture content but is related to the gradient in water activity (aw); i.e.

31

the transfer occurs from the phase with high aw to the phase with low aw (Salwin
and Slawson, 1959). In the past decade several authors have reported on how to
control moisture migration in composite products; mainly by separating the
different product components with an edible moisture barrier (Biquet and Labuza,
1988; Kamper and Fennema, 1985). As recently reviewed by Biquet and Labuza
(1988) plain chocolate has a low water activity (0.2—0.4 aw) and also good moisture
barrier properties. Because of these reasons many dry and semi-moist products,
which are coated with chocolate, have a considerable shelf life at room
temperature.

Larumbe et al (1991) studied the behavior of caramel jam-filled chocolate
coated candy during storage at room temperature and reported, that due to transfer
of moisture between components, the aw of the chocolate coating increased during
storage at 25°C. They also reported grth of fungi on the chocolate due to
increased aW and contamination of the chocolate surface. Debeaufort et al (1993)
conducted a study on the polarity, homogeneity, structure and the water vapor
permeability of model edible films, and reported an increase of water vapor

transmission rate with hydrophilicity and heterogeneity.

32

Moisture Isotherm and Shelf life of Food Products

The shelf life of most foods is affected by critical parameters such as
moisture content and water activity. Textural quality, chemical and biochemical
reactions and microbial grth rates are greatly affected by these parameters.
Water activity, which describes the availability of water to play a role in physical,
chemical and biochemical reactions, has been used to explain the influence of
moisture on reaction rates. Recently, the glass transition theory from polymer
science, has been introduced to food preservation, particularly for intermediate and
high moisture foods (Nelson and Labuza, 1994; Chirife and Pilar Buera, 1994).
The relationship between glass transition temperature and food stability has been
seen with increasing interest and is helping researchers to understand the influence
of water on food deterioration reactions.

Food product moisture content and equilibrium water activity of a food
product are related to each other by the food sorption isotherm. Several equations
have been used to mathematically describe sorption data representative of different
groups of food products. A review of the work devoted to the prediction of
moisture sorption behavior of mixed or multi-component products from individual
component's behavior is also presented .The control of moisture uptake or loss
during storage is one of the major protection functions of the food package. Fast
and reliable methods for shelf life prediction are of great interest as a tool for

package development. Mathematical models correlating the characteristics of the

33

product, the package properties, and the environmental conditions are less time
consuming and have lower cost than other shelf life determination techniques.

Most food sorption isotherms show a hysteresis behavior, i.e., the moisture
content is lower on equilibrium by adsorption than by desorption. This has
important implications with respect to food stability, since foods adjusted to the
desired aw by desorption rather than by adsorption, may deteriorate more rapidly
because of their higher moisture content. A number of equations or mathematical
models have been proposed to describe the moisture sorption behavior of foods.
Some are based on theoretical principles, while others are proposed due to their
curve fitting capability to experimental data. Chirife and Iglesias (1978) reviewed
the equations existing in the literature and compiled twenty-three equations,
discussing their origin, range of applicability and use. Some of these equations
were mathematically equivalent and some were limited to a specific range of aw or
type of foods. Boquet et al. (1978) and Boquet et al. (1979) evaluated equations
with two and three parameters for fitting experimental data of moisture sorption by
fruits, meats, milk products, proteins, starchy foods and vegetables.

In an attempt to include interaction parameters Nieto and Toledo (1989)
applied an empirical approach using a factorial design of 4 x 3 levels of
combinations of NaCl, non-fat dry milk and lard added to minced fish to produce
a fish sausage. Although good agreement was obtained between the experimental
and predicted values, the regression equation was limited to the factors and

respective levels used in the validation experiment.

34

Iglesias et al. (1979) assumed the additivity of the component's isotherms,
in calculating a mixture isotherm from the weight percentage of each component
multiplied by the amount of moisture it would sorb alone. The merit of this
approach lies in the use of a non-linear isotherm. The BET equation is used with
applicability in the range of aw from 0.05 to 0.40. Interest in the development of
shelf-life models for moisture sensitive products has been recognized for a long
time. However, most studies have focused on packages of single products. Based
on the concepts introduced by Heiss (1958), other studies on shelf-life modeling
have followed, eliminating some of the assumptions originally made and
increasing the complexity and applicability of the models.

Heiss (1958) discussed the relationship between moisture sorption
properties of foods, packaging film permeability, and the shelf-life of the product,
and developed a solution based on Fick's laws of diffusion. The model was
modified by Karel (1967), who assumed a linear isotherm and later by Labuza,
Mizrahi and Karel (1972) who introduced the non-linear isotherms. Clifford et al.
(1977) reported a shelf-life model taking into consideration the moisture in the
package head space, assuming a linear isotherm. Peppas and Khanna (1980)
developed a model using the Nernst-Plank diffusion equation combined with the
non-linear BET, Halsey, Oswin and Freundlich isotherm models. The model was
further extended to packaging systems where the polymeric film is appreciably
swollen by the diffusing water. Kim (1992) developed a model and a computer

program for predicting the shelf-life of a packaged pharmaceutical tablet, based on

35

the unsteady state mass transfer of water through the package and within the tablet
and used the method of finite differences to solve the model. The influence of
temperature on the system was introduced by Lee (1987), who considered its
effect on the permeability coefficient and by Kirloskar (1991) who considered the
effect of temperature on the sorption isotherm. Cardoso and Labuza (1983)
developed a dynamic mathematical model to predict moisture transfer for
packaged pasta under controlled, unsteady state conditions of temperature and
relative humidity. Although moisture transfer in composite foods has been studied
by several authors, very little work has been done for the case where the mixture is
packaged in a moisture permeable package. In multi-component foods, it is
assumed that the amount of water sorbed at any aW is equal to a weighted average
of the moisture each component would absorb alone. Hong et al. (1986) developed
a computer-aided model using the finite element method to predict moisture

transfer in a multi-component mixed system during storage.

36

Texture Profile Analysis

As described by Steffe (1996); “ Texture refers to the human sensation of food
derived from its rheological behavior during mastication and swallowing.
Obtaining a quantitative description of texture using instrumental data is very
complicated because no instrument can duplicate human capabilities. From an
engineering perspective, the mouth can be considered to be an intricate mechanical
system and chemical reactor that can crush, wet, enzymatically degrade,
pressurize, heat or cool, pump, chemically sample for taste, and sense force and
temperature. ” According to Brandt et al. (1963), texture profile is defined as the
organoleptic analysis of the texture complex of a food in terms of its mechanical,
geometrical, fat, moisture content, the degree of each present, and the order in
which they appear from first bite through complete mastication. Different texture
profile methods offer a means to help the food researcher obtain descriptive and
quantitative sensory data on the textural characteristics of food products.

Steffe (1996), in his review of texture profile analysis, described two methods to
evaluate food texture, sensory and instrumental. The sensory method of
developing a texture profile utilizes a human taste panel and provides the ultimate
test, which cannot be completely duplicated by any instrumental procedure.
Instrumental methods, however, are much less costly and time consuming than
sensory tests. Moreover, they often can be correlated to critical sensory attributes,
which allow some measure of consumer acceptability. It is, however, rare for

them to stand alone as a complete test. Friedman et al. (1963) reported good

37

correlation between the Texturometer and intensity of mechanical characteristics
of texture as perceived in the mouth. Friedman et al. (1963) and Szczesesnaik et
al. (1963) were poineers of Texture Profile Analysis using a General Food
Texturometer. Breene (1975) said that Bourne in 1968 was the first to apply the
Instron machine to objective texture profile analysis of a food. Steffe (1996)
reported that Boume in 1968 and 1974 adopted and extended, the technique to the
Instron Universal Tensile Tester, where a food sample is compressed, two times,
usually to 80 percent of its original height. Compression is achieved using parallel
plates where one plate is fixed and the other plate moves with a reciprocating
linear cyclical motion. Since this test is intended to reflect the human perception
of texture, the first and second compression cycles are referred to as the first bite
and second bite, respectively. Textural parameters such as fracturability, hardness,
adhesiveness, stringiness, springiness, cohesiveness, gumminess and chewiness
may be determined from the Texture Profile Curve using the Instron Universal
Tensile Tester. Harris et. al (1992) used an Instron Universal Testing Machine for
texture measurements of chocolate caramel rolls stored at 21°C and 38°C for 12
months. Guinot and Mathlouthi (1991), performed a study on the objective texture
measurements of sponge cake using a Universal Instron Testing Machine Model
1121. The Instron Universal Testing Machine can also be used to measure
hardness, fracturability, adhesiveness, cohesiveness, springiness, gumminess and
chewiness (Bryant, 1993). Green et al. (1981) used a Instron Universal Testing

Machine to measure the texture of cheddar cheese. Lee et al. (1985) studied the

38

changes in instrumental and sensory rheological parameters of chewing gum
during storage. They reported that texture was influenced to a great extent by the
moisture content of chewing gum while processing conditions and storage
temperature had little effect on texture change. Culioli and Sherman (1976) used
an Instron Universal Testing Machine to study the influence of cheese maturity,
test temperature, sample shape, sample height and surface area, on the force
compression behavior of Gouda cheese. Bertola et al. (1992) analyzed rheological
parameters during ripening of Tybo Argentino cheese. They applied the
compression test in two successive cycles to determine hardness, adhesiveness and

cohesiveness.

39

MATERIALS AND METHODS
Water Vapor Transmission Rates:
Packaging Materials:

Eight commercial barrier film structures were evaluated to determine their
water vapor transmission rates. All packaging films were coated with a 0.5 inch
wide pattern cold seal (PCS) on the non-printed side of the film. The eight film
structures evaluated included:

A 0.75 mil OPP/ink/adhesive/0.35 mil met PET/PCS
B 0.75 mil OPP/ink/adhesive/1.2 mil white opaque PP/PCS

Overlacquer/ink/1.2 mil white opaque PP/PCS

U ('1

Overlacquer/ink/1.2 mil white opaque PP/PCS

E Overlacquer/ink/1.2 mil white opaque PP/PCS

F Overlacquer/ink/primer/O.6 mil polyester/adhesive 0.35 mil PET/PCS
G Overlacquer/ink/l .2 mil CO-PET/white PP/ CO- PET/PCS

H Overlacquer/ink/primer/O.35 mil met PET/adhesive/1.2 mil white PP/PCS

Water Vapor Transmission Rate Measurement

Water vapor transmission rates and permeance of the film structures were
determined on a MOCON Permatran-W 3/31 - Water Vapor Transmission System
(Modern Controls, Inc. MN, USA).

A film sample, prepared using a special die, was placed within the test cell.

A 50 cm2 film surface separates the outer and inner cell chambers which are

40

clamped together during testing to provide a gas tight seal. During the testing
cycle, water vapor at a fixed and constant vapor pressure flowed through the outer
cell chamber at a pre-determined flow rate and nitrogen carrier gas transported the
water vapor permeated through the inner cell chamber to an infrared sensor which
quantifies the amount of water vapor in the carrier stream. A re-zeroing operation
is conducted at a pre-determined time interval between test runs to determine the
zero baseline and provide a more accurate transmission rate result. The

temperature controlled test cells can be operated between 5 and 50°C. Film

samples were tested at 23 and 378°C, at relative humidities of 35, 80 and 90%.

The test conditions are shown in Table 1.

 

 

 

 

 

 

 

 

Table 1. Test conditions for WVTR determination using the Mocon
Permatran-W 3/31.

Test parameters Values
Conditioning time (min) 00
Test cycle duration (min) 10
Re-zeroing cycle 05
Cell temperatures (°C) 23, 23, 37.8
Cell relative humidity (%) 35, 80, 90
Carrier gas flow rate (cm3 min") 100

 

 

 

41

Water Vapor Transmission Rate Measurement using Gravimetric Method
This method was used to determine the water vapor transmission rates of all
packaging film stocks at 23°C and 20 % RH. The standard ASTM E-96 method
(ASTM, 1988), was followed for this determination, where aluminum dishes
containing desiccant were covered with the packaging material, sealed with
paraffin wax, weighed and placed in a constant temperature at 23°C and 20 %
relative humidity chamber for a total of 27 days. The stored samples were weighed
periodically, at specific time intervals, until a constant moisture gain rate was
obtained. The net weight gain in grams (g) was plotted as a function of time
(days). The slope of the straight line portion of the graph was taken as the water
vapor transmission rate of the packaging film. From the water vapor transmission
rate and the partial pressure gradient, permeance constants for the packaging films

were determined.

Determination of Moisture Isotherm

Equilibrium sorption isotherms were determined at room temperature 23°C
for both the chocolate and nougat component of the confectionery bar. The
equilibrium moisture content (EMC) is usually expressed as percent moisture on a
dry weight basis. The initial moisture content (IMC) of both the chocolate and
nougat component were measured with a high degree of accuracy by the Karl
Fischer titration method. In developing moisture sorption isotherm data, care was

taken to insure the relative humidity chambers employed were maintained at

42

constant temperature and relative humidity by monitoring periodically using a
Hygrodynamics (Newport Scientific, Inc. Jessup, MD, USA) instrument equipped
with temperature and RH sensors. The moisture sorption isotherms developed in
this study were determined by placing chocolate bars of known initial moisture
content in a series of eight relative humidity buckets maintained at constant room
temperature at 23°C i 2°C and determining the moisture content of chocolate and
nougat component of the confectionery bar at pre-determined intervals. The
relative humidity buckets were prepared and maintained from 8.6% to 75.3% RH
at temperature of 23°C : 2°C. The desired humidities in these buckets were
obtained by placing appropriate salt solutions into tightly closed plastic buckets.
The salt solutions employed and their corresponding relative humidities are

summarized in Table 2.

Table 2. Equilibrium relative humidities for saturated salt solutions.

 

 

 

 

 

 

 

 

 

Saturated salt solution % RH at 23°C % RH at 23°C

Expected Experimental
Lithium Chloride 12.0 8.6
Potassium Acetate 22.7 21.6
Magnesium Chloride 33.2 34.2
Potassium Nitrite 48.1 47.3
Sodium Nitrite 64.3 63.2
Sodium Chloride 75.8 71.2
Ammonium sulfate 80.3 75.3

 

 

 

 

43

Salt solutions were prepared by adding distilled water (slowly) to the chemically
pure salt in a crystallization dish with constant stirring and heating slightly until
about half the salt crystals were dissolved. The prepared salt solutions were
placed within the tightly closed buckets and allowed to equilibrate. The
relative humidity within each of these buckets was monitored periodically
using Hygrodynamics instrument. This procedure was used to assure that
constant relative humidity and temperature conditions were maintained. Three
replicate determinations for % moisture were made at each relative humidity
condition. The moisture content of the chocolate and nougat phase of the
confectionery bar were determined using a Brinkmann 720 KFS Titrino:
(Brinkmann Instruments, Inc. Westbury, NY, USA). Approximately 0.5 g of
sample was added to the Brinkmann titration vessel in the presence of Methanol
Solvent. The sample was then homogenized for 60 seconds with the attached
homogenizer and titrated with Hydranal Composite 5 Reagent. The percent
moisture content was recorded using a printer. The Instrument was calibrated
prior to running the test samples, to obtain accurate moisture values. This
procedure was repeated until no significant change in moisture content was

observed.

Determination of Equilibrium Moisture Contents

The equilibrium moisture content (EMC) at each relative humidity was
calculated using the following equations:

Wm = % moisture / 100 = g of water / g product

EMC = (Wm / Wp - Wm) 100 = g of water/ 100 g dry product.
Where: Wm is weight of moisture

W, is weight of product

The moisture sorption isotherm was obtained by plotting the average equilibrium
moisture content of the three replicates versus relative humidity at room

temperature (23°C i 2°C).

Determination of Initial Moisture Contents

Initial moisture contents of the product were determined using a Brinkmann
720 KFS Titrino: automatic titration system (Brinkmann Instruments, Inc.
Westbury, NY, USA). Approximately 0.5 g of sample was added to the
Brinkmann titration vessel in the presence of methanol solvent. The sample was
then homogenized for 60 seconds using a homogenizer and titrated with Hydranal
Composite 5 Reagent. The percent moisture content was recorded using a printer.
An average of seven samples was used to determine the moisture content of the

chocolate phase, and fifteen samples for the nougat phase.

45

Determination of Moisture Content of a Packaged Confectionery Product
with a Cold Seal Closure during Storage.

Samples of a chocolate type confectionery product packaged in the eight
packaging structures were supplied by a commercial manufacturer. The
confectionery products were manufactured in the dimension of 11cm x 3cm x 2cm
(Length x Width x height). Sealing of the respective barrier structures was carried
out with the same pattern cold seal adhesive and sealing conditions. For this study
two product storage conditions were selected.

0 20 % relative humidity and 23°C : 2°C
0 75 % relative humidity and 23° C : 2°C

The product was stored for 115 days in both conditions and moisture
determinations were performed at pre-determined time intervals of 0, 1, 2, 5, 10,
20, 30, 40, 55, 70, 85, 100 and 115 days, respectively. It should be noted that for
the storage stability studies carried out at high relative humidity conditions, the
environmental chamber was maintained at 75 % i 3 % relative humidity and a
temperature of 23°C j; 2°C over the 70 days storage period. Difficulty was
experienced with the relative humidity control of the environmental chamber and
highest relative humidity, which was to maintained at 60 %. Therefore, for the
final seven weeks of storage, the conditions were 23°C : 2°C and 60 % relative
humidity. Because of this problem these studies will be referred to as the high
relative humidity storage conditions, with an average relative humidity value of

67.5 %. Three samples for each wrapper type were selected randomly from the

46

humidity chamber and the moisture content of the nougat phase was determined
using the Brinkman’s 720 KFS Titrino: (Brinkmann Instruments, Inc. Westbury,
NY, USA). Each sample was discarded after use. The tests were performed at
room temperature (23°C : 2°C).

Determination of Texture of a Packaged Confectionery Product with a Cold
Seal Closure during Storage.

To determine the effect of storage conditions on the texture of the nougat
phase of the confectionery product, the packaged confectionery product was stored
for 120 days at the above condition of temperature and relative humidity. Texture
profile determinations (Hardness) were performed at pre-determined intervals of
time 0, 20, 40, 60, 90 and 120 days. Three chocolate bars for each wrapper type
were selected randomly from the humidity chamber. For this analysis, only the
nougat phase of the bar was used. Measurements were made on an Instron
Universal Testing Machine, model 1122 (Instron Corporation Canton, MA, USA).
Each sample was discarded after use. The test was performed at room temperature

(23°C i 2°C).

Sample Preparation
The nougat sample was prepared by peeling away the chocolate layer of the

candy bar after removing the packaging film wrapper at room temperature (23°C 1:

2°C). The nougat phase was cut into cubes of 15 mm (height) x 25 mm (width) x

47

25 mm (length), just prior to the test. A sharp knife was used for peeling away the
chocolate layer from the candy bar and for sample cutting. The test was performed

at a constant temperature of 23°C : 2°C.

Setting of the Instron

An Instron compression load cell (500 kg), fixed to the crosshead, was used
to perform the compression tests. Determination of the hardness was based on
force-displacement measurements using a plunger. The plunger, (0.5 inch
diameter), was attached to the moving crosshead, which was set to cycle mode at a
constant speed of 20 mm/min in both upward and downward directions. A flat
holding plate was used to hold the nougat sample on the stationary horizontal bed
plate of the machine, thus avoiding sticking of the nougat onto the plunger in its
upward movement. The penetration of the plunger into the nougat sample was set
at 11.25 mm, which corresponded to 75% of the height of the sample.

A bite was considered as a complete cycle of a downward plus upward
movement of the plunger, which penetrated and then removed from the sample. To
perform the tests, two bites were taken. The chart speed was set to 50 mm/min. A
typical texture profile analysis (TPA) curve from the Instron universal testing

machine is shown in Figure l.

48

Textural Measurements of Nougat Phase of Confectionery Bar

The nougat phase of the candy bars was analyzed for texture properties by
the Instron Universal Testing Machine, model 1122: (Instron Corporation Canton,
MA, USA) following the procedure described by Friedman, et al. (1963), with
related modifications as described below. The textural parameter; namely hardness
was defined as the maximum force exerted on the sample, and was measured from

the texture profile analysis (TPA) curve as the height of the first bite.

49

 

 

 

 

1;: Trim Bite Downward
7g T Second Bite Downward
M
o
“‘ A: Hardness
l A”
0 V DISTANCE
E; First Bite Upward
o
u. ‘i

 

 

 

Figure 1 Typical Texture Profile Analysis (TPA) Curve Using The Instron
Universal Testing Machine.

50

RESULTS AND DISCUSSION

Water Vapor Transmission Rates:

The water vapor transmission rates (WVTR) of the sample films were
determined at a temperature of 378°C, and 90 % relative humidity, and at 23°C
and relative humidities of 80%, 35%, and 20% respectively for all eight barrier
film structures. The WVTR of the film structures were determined using a
MOCON Permatran-W 3/31, for all conditions except for 23°C and 20 % relative
humidity. A gravimetric method was used for WVTR determinations at the above
mentioned conditions, since the Permatran -W 3/31 can not measure water vapor
transmission below 35 % relative humidity. The WVTR values were converted
into permeance values and are summarized in Tables 3-4, respectively. The
packaging structures used in this study are listed as follows.

A 0.75 mil OPP/ink/adhesive/0.35 mil met PET/PCS
0.75 mil OPP/ink/adhesive/1.2 mil white opaque PP/PCS

Overlacquer/ink/l .2 mil white opaque PP/PCS

U 0 w

Overlacquer/ink/1.2 mil white opaque PP/PCS

E Overlacquer/ink/1.2 mil white opaque PP/PCS

F Overlacquer/ink/primer/O.6 mil polyester/adhesive 0.35 mil PET/PCS
G Overlacquer/ink/1.2 mil CO-PET/white PP/ CO- PET/PCS

H Overlacquer/ink/primer/O.35 mil met PET/adhesive/1.2 mil white PP/PCS

51

As shown in Table 4, packaging structure H was found to have the lowest
permeance values and packaging structure F showed the highest permeance values
as compared to the other film structures. Temperature was found to have a
significant effect on the permeance values of all packaging structures, which is
expected from the Arrhenius relationship. At constant temperature (23°C) the
permeance values were similar over the relative humidity range evaluated (i.e. 20-
80 %). Since the respective film structures were not highly hydrophilic, they were
not expected to experience morphological changes as result of sorbed water.
Thus, these results were expected. From this study, the film structure, H
(Overlacquer/ink/primer/0.35 mil met PET/adhesive/ 1.2 mil white PP/PCS) was
found to have the best moisture barrier properties among the eight polymer
structures evaluated. The order of barrier properties for the packaging structures
evaluated, in order of decreasing moisture barrier performance, is as follows: H,
A, B, G, C, D, E and F.

To determine the statistical differences in the water vapor transmission rate
values data was analyzed using a one factor randomized complete block design
(MSTAT, Version 4.0, 1987) microcomputer statistical program. Analysis of
variance (ANOVA) showed, that there was a significant difference (p< 0.05)
between water vapor transmission rates of all film structures at all above

mentioned conditions. A detailed description of the statistical analysis is presented

in Appendix I-III.

52

Based on the statistical analysis, it was concluded that the film structures
had significantly different water vapor transmission rates from each other for all

conditions of relative humidity.

53

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 3: Water vapor transmission rate of film structures at different
temperature and relative humidity conditions.
SAMPLE 37.8°C 90%RH 23°C 80%RH 23°C 35%RH 23°C 20%RH
ID
gm/ 100in2day gm/ 100m2 day gm/ 100m2 day gm/ 100 in2 day
A 0.0531 0.01082 0.002517 0.0021
(0.001 5) (0.002) (0.0005) (0.0004)
B 0.1071 0.01816 0.006843 0.0042
(0.0007) (0.0009) (0.0004) (0.0010)
C 0.1957 0.02989 0.010590 0.0047
(0.0094) (0.0001) (0.0004) (0.0003)
D 0.2102 0.04027 0.014880 0.0088
(0.0033) (0.0006) (0.0003) (0.0004)
E 0.2511 0.05433 0.021560 0.0146
(0.0025) (0.0002) (0.0011) (0.0021)
F 0.7174 0.17850 0.084800 0.0452
(0.0079) (0.0090) (0.0025) (0.0022)
G 0.1864 0.02926 0.01 1520 0.0083
(0.0043) (0.0002) (0.0009) (0.0003)
H 0.0131 0.00382 0.001047 0.0010
(Control) (0.0010) (0.0009) (0.0006) (0.0002)

 

(1) The results reported are the average of 4 replicates.
(2) The values in parentheses are standard deviation.

54

 

 

 

 

 

 

 

 

 

 

 

Table 4: The Permeance values of film structures at different temperature
and relative humidity conditions.
SAMPLE 37.8°C 90%RH 23°C 80%RH 23°C 35%RH 23°C 20%RH
ID
100 in day 100 in day 100 in day 100 in day
mmHg mmHg mmHg mmHg
A 0.0012 0.0006 0.00040 0.00024
B 0.0024 0.0011 0.00108 0.00098
C 0.0044 0.0018 0.00168 0.00110
D 0.0048 0.0024 0.00235 0.00209
E 0.0057 0.0032 0.00341 0.00345
F 0.0162 0.0146 0.01342 0.01073
G 0.0042 0.0017 0.00182 0.00167
H 0.0003 0.0002 0.00017 0.00025
(Control)

 

 

 

 

 

 

The permeance constants reported are the average of 4 replicates.

55

Equilibrium Sorption Isotherm of the product
Initial Moisture content

Equilibrium sorption isotherms were plotted at room temperature 23°C for
both the chocolate and nougat component of the confectionery bar. The initial
moisture content (IMC) of both the chocolate and nougat component were
measured with a high degree of accuracy by the Karl Fischer titration method.
The data obtained for initial moisture content of the chocolate phase and nougat

phase are given below.

Sample % Moisture Std. Dev.
Chocolate Phase 2.11 i 0.132
Nougat Phase 8.29 i 0.169

The chocolate phase values are averages of seven replicates and nougat
phase values are average of 15 replicates. The initial moisture content values
obtained, agreed well with the values reported by the manufacture of this product,

as a part of their quality control tests.

Equilibrium Moisture Isotherm
The moisture sorption isotherms developed in this study were determined
by placing chocolate bars of known initial moisture content in to a series of

eight relative humidity buckets maintained at a constant temperature of 23°C :1;

2°C. The moisture content of the chocolate and nougat components of the

56

confectionery bars were determined at pre-determined intervals. The relative
humidity buckets had humidities which ranged from 8.6% to 75.3%. In developing
moisture sorption isotherm data, care was taken to insure the relative humidity
chambers employed were maintained at constant temperature and relative
humidity by monitoring periodically with Hygrometer sensors: (Newport
Scientific, Inc. Jessup, MD, USA) containing both temperature and RH sensing
capacity. The numerical data for the equilibrium moisture content and the
associated relative humidity values for both phases of the product are summarized
in the Tables 5 and 6 respectively. The accumulated data of product moisture
content as a function of time is summarized in Appendix VI-VII. For better
illustration, the equilibrium moisture content data are presented graphically in
Figures 2 and 3 respectively, where the average equilibrium moisture content is
plotted as a function of relative humidity. The equilibrium moisture isotherm data
showed that at low relative humidity, the product looses moisture and at high
relative humidity, the product gains moisture, in both phases of the product. As
indicated from the results presented in Appendix VI-VII the product required a
storage period of 90 days to reach equilibrium. The very slow process of moisture
transfer into the nougat phase is attributed to the barrier characteristics of the
chocolate phase of the product. Similar results have been reported by Labuza and
Biquet (1988) in studies on chocolate. When only the nougat phase of the product
was exposed to the relative humidity conditions, equilibrium was attained within a

three week period, further supporting the moisture barrier role played by the

57

enrobed chocolate layer. The data obtained for these studies is summarized in

Appendix VIII.

58

Table 5: Equilibrium Moisture Content of the Chocolate Phase of
the Confectionery Product as a Function of Relative Humidity (RH).

 

 

 

 

 

 

 

 

RH % EMCa of Chocolate Phase“
g water /100 g dry wt.
8.6 1.456 (0.070)
21.6 1.549 (0.089 )
34.2 1.711 (0.179)
47.3 1.780 (0.075)
63.2 2.195 (0.053)
71.2 2.839 (0.058)
75.3 3.940 (0.068)

 

 

 

 

* Values are the average of 3 replicates analysis.
a . . . .
Equrlrbrrum morsture content
The values in parenthesis are standard deviation of % moisture.

59

Table 6: Equilibrium Moisture Content of the Nougat Phase of
the Confectionery Product as a Function of Relative Humidity (RH).

 

 

 

 

 

 

 

 

 

 

RH % EMC 3 of Nougat Phase“
iwater / 100 idry wt.
8.6 9.478 (0.087)
21.6 9.476 (0.176)
34.2 9.478 ( 0.209)
47.3 9.592 ( 0.202)
63.2 9.791 (0.308)
71.2 10.07 (0.259)
75.3 10.293 (0.094)

 

* Values are the average of 3 replicates analysis
a . . . .
Equrlrbrrum morsture content

The values in parenthesis are standard deviation of % moisture.

60

 

 

 

 

 

 

 

 

 

Figure 2: Equilibrium Moisture Content of Chocolate Phase of the
Confectionery Product at 23°C.

61

 

10.5

 

 

 

 

e
'9
8 104- 8
a, e
" e
g 9.5 .. . . . OEMC
2
ti
3 9*
O
8.5 % .L . . r 4 a
o 10 20 30 40 so so 70 80
RelativeHumtdltym

 

 

Figure 3: Equilibrium Moisture Content of Nougat Phase of the
Confectionery Product at 23°C.

62

 

The Effect of Relative Humidity on Moisture Content of the Packaged
Confectionery Product, Packaged with Cold Seal Closures

Based on the water vapor transmission rate and permenace values of the
respective packaging film structures, the following assumptions were made for
moisture uptake by the product/package system;

0 The seals were hermetic.

0 Moisture permeation occurs through the packaging film structures.

Samples of the chocolate confectionery product were packaged in the
eight material structures, and stored under two conditions, (I) 20 % :3 % relative
humidity and 23°C : 2°C; and (II) 75% :3 % relative humidity and 23°C : 2°C,
for 115 days. It is noted that for the storage stability studies carried out at high
relative humidity conditions, the environmental chamber was maintained at 75 %
i 3 % relative humidity and a temperature of 23°C : 2°C over the initial 70 days
storage period. At this time, difficulty was experienced with the relative humidity
controls of the environmental chamber and the highest relative humidity, which
could be maintained was 60 %. Therefore, for the final seven weeks of storage, the
storage conditions were at 23°C : 2°C and 60 % relative humidity. Because of this
problem, these studies are referred to as the high relative humidity storage
conditions, with an average relative humidity value of 67.5 %. The moisture
content of the nougat phase was determined at time intervals of 0, 1, 2, 5, 10, 20,
30, 40, 55, 70, 85, 100 and 115 days, respectively. Three package samples for each

Wrapper type were selected randomly from the humidity chamber and the

63

moisture content of the nougat phase was determined using the Brinkrnan 720
KFS Titrino, automatic titration system. The tests were performed at room
temperature (23°C i 2°C). The average values of % moisture, with a standard
deviation, in the nougat phase are summarized in Tables 7-8, respectively, for each
packaging structure, The change in moisture content at different time intervals
during storage is presented graphically in Figures 4-5 for better illustration. As
shown in Figures 4 and 5 an increase in moisture content over a storage period of
115 days was observed for product packaged in all of the treatment structures
stored at high relative humidity conditions, while a decrease in moisture content
over a storage period of 115 days was observed at 20 % relative humidity and 23
°C, for all packaged product.

Statistical analysis of the change in moisture content of confectionery
packaged product with time, was based on a three way factorial design, using three
way analysis of variance (ANOVA). The SAS (version 6.12, 1989)
microcomputer statistical program was used for this analysis. The statistical
analysis revealed that there was a significant effect of relative humidity and time
on moisture uptake for respective product package systems. The statistical analysis
also showed that the effect of relative humidity and time were not independent of
each other. Packaging film structures had no statistically significant effect (p<
0.05) on moisture gain or loss, However a significant interaction (p< 0.05)

between relative humidity and packaging film structure was observed. Analysis of

variance (ANOVA) for moisture uptake for the respective product/package
systems are presented in Appendix IV.

Based on the statistical analysis of the data for change in moisture content
of confectionery packaged product in all eight packaging structures and the data
for water vapor transmission rates of all eight film structures in sheet form, it can
be concluded that the moisture gain or loss by the product is through micro-voids
in the cold seal closure, rather than through permeation through the film
structures. This conclusion is based on the fact that there is a statistically
significant difference between the water vapor transmission rates of the respective
film structures used. There was no statistically significant difference between the
moisture content of the confectionery product packaged in the test packaging
structures. These results are similar to the results reported by Lin (1995) on the
permeability of organic vapors through a packaged confectionery product with a
cold seal closure. The assumption initially made was that the product package
system is hermetically sealed and that diffusion through the package structure, as
described by F ick’s First and second laws, is the principle mechanism resulting
in moisture ingression. Based on statistical analysis of the water vapor
transmission rates of the test film structures and the moisture uptake of the
packaged confectionery product, the assumption that moisture uptake through the
film structure appears not to be valid. Thus, as indicated above, mass transfer

through micro-voids in the cold seal closure area is the principle mechanism of

65

moisture ingression and not the result of diffusion through the package film

structure.

66

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70

The Effect of Relative Humidity on Texture of the Packaged Confectionery
Product, Packaged with Cold Seal Closures

To determine the effect of storage conditions on the texture of the nougat
phase of the confectionery product, the packaged confectionery product was stored
for 120 days at two conditions of temperature and relative humidity, and texture
characteristics were determined by obtaining a texture profile curve on an Instron
Universal Testing Machine, model 1122. The nougat phase of the candy bars was
analyzed for its texture properties. The textural characteristics; namely hardness

was determined from the texture profile curve at pre-determined time intervals of

O, 20, 40, 60, 90 and 120 days respectively.

Hardness of Nougat Phase

Hardness is defined as the maximum force exerted on the sample, and was
measured from the texture profile analysis (TPA) curve as the height of the first
bite (Friedman et a1 1963). The complete data for hardness during the storage
period is listed in Tables 9-10 and a plot of hardness, as a function of time
presented in Figures 6-7, for comparison between packaging structures. A slight
increase in hardness over a storage period of 120 days in all packaging structures
was observed at 20 % relative humidity and 23°C, while a slightly decrease in
moisture content over a storage period of 120 days in all packaging structures was

observed at high relative humidity storage conditions and 23°C. The change in

71

hardness values at different time intervals during storage is presented graphically
in Figures 6-7 for better illustration.

Statistical analysis showed that relative humidity and time had a
significant effect ( p< 0.05) on the hardness of the packaged product. However the
packaging structure had no statistically significant effect on hardness. Statistical
analysis indicated that relative humidity and packaging structure have a ( p< 0.05)
significant interaction. Similarly, packaging structure and time were dependent
upon each other. Relative humidity and time had significant interaction at ( p<
0.05). Analysis of variance (ANOVA) for hardness of the nougat phase of product

is given in appendix V.

72

 

Table 9: The change in hardness (Newton) of the nougat phase of the
confectionery product at room temperature (23°C) and 20%

relative humidity during 120 days storage period.

 

 

 

 

 

 

 

 

 

 

SAMPLE 0 DAY 20 DAYS 40 DAYS 60 DAYS 90 DAYS 120 DAYS
ID
A 14.37 12.08 13.39 16.00 16.98 23.51
(1.13) (1.50) (0.55) ((2.96) (2.08) (6.79)
B 1 1.10 16.00 17.96 15.02 16.00 24.49
@57) (4.83) (2.71) (0.57) (0.57) (0.98)
C 12.08 12.74 19.27 16.00 15.67 22.53
(2.26) (0.98) (2.47) (2.04) (0.98) (1.70)
D 12.08 15.35 19.59 16.97 16.98 25.47
(1.50) ((4.63) (1.92) (2.07) (1.13) (8.98)
E 16.65 13.39 13.72 14.37 15.68 35.27
(0.98) (2.04) (2.41) (1.13) (0.00) (3.92)
F 13.39 16.98 18.94 20.25 18.29 24.17
(2.83) (2.02) ((1.92) (1.13) (2.26) (2.99)
G 14.04 16.33 17.63 14.37 17.64 18.29
(0.57) (2.99) (0.00) (1.13) (0.00) (1.13)
H 16.98 14.04 20.57 16.00 19.59 19.92
(Control) (1.13) (2.83) (1.96) (0.57) (2.18) (2.47)

 

 

 

 

 

 

 

(1) The results reported are average of 3 replicates.
(2) The values in parentheses are standard deviation.

73

 

Table 10: The change in hardness (Newton) of the nougat phase of the
confectionery product at room temperature (23°C) and high

relative humidity during 120 days storage period.

 

 

 

 

 

 

 

 

 

 

SAMPLE ID 0 DAY 20 DAYS 40 DAYS 60 DAYS 90 DAYS 120 DAYS
A 14.37 12.74 16.00 11.10 12.41 11.10
(1.13) (0.00) (3.96) (1.13) (1.13) (1.13)
B 11.10 9.80 15.68 12.41 11.77 9.14
(0.57) (0.00) (1.96) (1.51) (1.98) (1.13)
c 12.08 10.12 15.68 13.39 11.43 11.10
(2.26) (2.04) (5.96) (2.26) (1.98) (2.26)
D 12.08 10.12 12.74 12.41 11.43 9.80
(1.50) (0.57) ((2.94) (3.71) Q50) (1.13)
E 16.65 10.78 13.72 12.41 10.45 10.45
(0.98) (0.98) (3.39) (1.13) (0.57) (1.96)
F 13.39 10.78 15.67 11.43 10.12 7.84
(2.83) £100) (3.39) (0.57) (2.47) (1.96)
G 14.04 12.08 16.33 10.78 11.76 8.49
(0.57) (0.57) (1.13) (0.98) (0.00) (1.13)
H 16.98 11.10 16.98 14.70 14.04 11.10
Q.13) (0.57) (2.26) (0.98) (0.57) (2.99)

 

 

 

 

 

 

 

(1) The results reported are average of 3 replicates.
(2) The values in parentheses are standard deviation.

74

 

 

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76

SUMMAY AND CONCLUSION

For a series of commodity film structures, permeance values were obtained
from permeability studies based on an isostatic procedure utilizing the Mocon’ s
Permatran W 3/31 WVTR. Permeability studies were carried out at two
temperatures to allow evaluation of the Arrehenius relationship. In addition, the
respective commodity film structures were used to package a confectionery
product with a cold seal closure technology. To evaluate the integrity of the cold
seal closure, with respect to water vapor ingression, storage stability studies were
carried out for a 115 day storage period at two relative humidity conditions.
Moisture isotherm of the confectionery product was developed at 23°C. A textural
parameter (Hardness) was measured to evaluate the effect of relative humidity and
moisture content in the nougat phase of the confectionery packaged product in
several packaging structures.

The temperature dependency of the transport process associated with the
respective barrier membranes, over the temperature range studied was found to
follow well the Arrehenius relationship.

The packaging film structure, “Overlacquer/ink/primer/O.35mil met
PET/adhesive/ 1.2 mil white PP/PCS” was found to exhibit the best water vapor
barrier properties among the eight polymer membranes evaluated, when tested in
film form. There were statistically significant differences between the water vapor

barrier properties of the respective polymer structures, in flat sheet form.

77

There was no statistically significant difference between the performance of the
product package system with regards moisture uptake. These findings indicate that
the barrier performance of the film structures showed significant differences, when
evaluated as flat film stock. This suggests that moisture uptake by the packaged
product is a result of moisture ingression through the sea] area as the predominant
mechanism and not the result of diffusion through the package structure. Statistical
analysis showed that there is no significant difference between the performance of
the product package system for texture (Hardness) of the nougat phase of the
confectionery packaged product over a storage period of 120 days within the same
storage conditions. However, relative humidity and time had a significant effect on

hardness of the confectionery packaged product.

78

 

Appendix I

Analysis of Variance (ANOVA) for Water Vapor Transmission Rate of Packaging
Film Structures at 37.8°C and 90 % Relative humidity.

 

 

Source of Degree of Sum of Square Mean Square F Value (I)
variance freedom df

Film Structure 7 1.3340 0.1910 9179.043“
Replication 3 0.000 0.000 2.2653
Error 2 1 0.000 0.0001

Total 31 1.335

 

M F Table Value :F 005 (3, 21) = 3.07 ; F005 (7, 21) = 2-49-
* = Significant difference at p S 0.05

79

Appendix II

Analysis of Variance (ANOVA) for Water Vapor Transmission Rate of Packaging
Film Structures at 23°C and 80 % Relative humidity.

 

 

Source of Degree of Sum of Square Mean Square F Value m
variance freedom df

Film Structure 7 0.088 0.013 1200.1340*
Replication 3 0.000 0.000 0.9788
Error 2 1 0.000 0.0001

Total 31 0.088

 

(1) F Table Value :F 005 (3. 21) = 3.07 ; F005 (7,21) = 2-49'
* = Significant difference at p S 0.05

80

Appendix 111

Analysis of Variance (ANOVA) for Water Vapor Transmission Rate of Packaging
Film Structures at 23°C and 30 % Relative humidity.

 

 

Source of Degree of Sum of Square Mean Square F Value (I)
variance freedom (If

Film Structure 7 0.021 0.003 35.9234“
Replication 3 0.000 0.000 0.6580
Error 2 1 0.002 0.0001

Total 31

 

(I) F Table Value :F (1059,21) = 3.07 ; F0.05 (7, 21) = 2-49-
* = Significant difference at p .<. 0.05

81

 

Appendix IV

Analysis of Variance (ANOVA) for Moisture Content for Product Package
Systems

 

 

Source of variance Degree of Sum of Mean F Value (1)
freedom (df) Square Square
RH l 9.29 9.29 91 .73*
Film 7 0.88 0.13 1.24
RH x Film 7 2.25 0.32 3.18"
Time 12 20.63 1.72 16.98*
RH x Time 12 16.30 1.36 13.42"
Film x Time 84 5.35 0.06 0.63
RH x Film x Time 84 8.73 0.10 1.03
Error 416 42.13 0.10
Total 623 105.58

 

(I) F Table Value 1F 0.05 (1,416) = 3.84 , F 0,05 (7,416) = 2-01; F0.05 (12,416) = 175; F005
(84,416)=1'26

* = Significant difference at p S 0.05

82

 

Appendix V

Analysis of Variance (ANOVA) for Hardness of Product Package Systems.

 

 

 

Source of variance Degree of Sum of Mean F Value?“
freedom (df) Square Square
RH 1 1731.37 1731.37 238.81*
Film 7 95.62 13.66 1.88
RH x Film 7 121.71 17.39 2.40*
Time 5 633.91 126.78 17.49*
RH x Time 5 1453.51 290.70 4010*
Film x Time 35 627.92 17.94 247*
RH x Film x Time 35 342.41 9.78 1.35
Error 192 1392.00 7.25
Total 287 6398.45

 

(I) F Table Value IF 0.05 (1,192) = 3.84 , F 0.05 (7,192) = 201; F 0.05 (5,192) = 2219 F005
(35.192) =1 -43

* = Significant difference at p S 0.05

83

The data for Moisture Isotherm of Chocolate Phase of the Confectionery Product.

Appendix: VI

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RH Moisture Moisture Moisture Moisture Moisture Moisture Moisture
% % % % % % % %
3/12/97 3/22/97 3/31/97 4/1 1l97 4/26/97 5/15/97 6/1/97
8.6 1.916 1.650 1.506 1.620 1.506 1.386 1.486
21.6 1.940 1.820 1.646 1.676 1.506 1.590 1.463
34.2 1.823 1.800 1.853 1.770 1.683 1.556 1.810
47.3 1.726 1.750 1.710 1.793 1.730 1.696 1.803
63.2 2.090 2.010 1.970 1.960 2.053 2.110 2.186
71.2 2.173 2.310 2.450 2.370 2.490 2.720 2.803
75.3 2.313 2.820 3.033 3.353 3.456 3.743 3.840
RH Std.Dev. Std.Dev. Std.Dev. Std.Dev. Std.Dev. Std.Dev. Std.Dev.
% i i i i j i i
8.6 0.023 0.070 0.166 0.113 0.040 0.055 0.106
21.6 0.026 0.080 0.090 0.049 0.089 0.026 0.421
34.2 0.125 0.113 0.113 0.105 0.023 0.049 0.145
47.3 0.119 0.087 0.088 0.104 0.036 0.037 0.064
63.2 0.225 0.165 0.045 0.030 0.057 0.079 0.045
71.2 0.235 0.131 0.026 0.060 0.262 0.135 0.135
75.3 0.140 0.180 0.332 0.101 0.176 0.301 0.190

 

84

 

Appendix: VII

The data for Moisture Isotherm of Nougat Phase of the Confectionery Product.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RH Moisture Moisture Moisture Moisture Moisture Moisture Moisture
% % % % % % % %
3/12/97 3/22/97 3/31/97 4/11/97 4/26/97 5/15/97 6l1/97
8.6 8.586 8.520 8.550 8.563 8.580 8.596 8.720
21 .6 8.426 8.676 8.420 8.486 8.463 8.530 8.780
34.2 8.240 8.716 8.810 8.383 8.586 8.510 8.806
47.3 8.076 8.830 8.730 8.276 8.610 8.270 8.896
63.2 8.440 8.610 8.460 8.463 8.700 8.483 9.136
71.2 8.006 8.886 8.590 8.573 8.740 8.966 9.333
75.3 8.410 8.796 8.590 8.470 8.920 9.266 9.400
RH Std.Dev. Std.Dev. Std.Dev. Std.Dev. Std.Dev. Std.Dev. Std.Dev.
% i .‘t i i i i 1
8.6 0.084 0.245 0.156 0.097 0.095 0.055 0.026
21.6 0.282 0.145 0.087 0.020 0.085 0.131 0.023
34.2 0.305 0.188 0.122 0.263 0.020 0.080 8.806
47.3 0.512 0.043 0.150 0.107 0.168 0.085 0.136
63.2 0.173 0.350 0.050 0.115 0.101 0.150 0.050
71.2 0.075 0.045 0.170 0.239 0.105 0.037 0.051
75.3 0.281 0.144 0.110 0.113 0.138 0.385 0.060

 

 

 

 

 

 

 

 

85

 

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