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LIBRARY
Michigan State
University

 

 

 

This is to certify that the
thesis entitled

COMPARISON OF DIFFERENT PACKAGING MATERIALS
TO DETERMINE THEIR EFFECT ON AVAILABILITY AND
EFFECTIVENESS OF 1-METHYLCYCLOPROPENE

presented by

LUIS C. RODRIGUEZ

has been accepted towards fulfillment
of the requirements for the

MS. degree in PACKAGING

 

 

WM

Major Professor’s Signature

7/97/200 7

Date

MSU is an affirmative-action, equal-amortunity emoloyer

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

 

DATE DUE

DATE DUE

DATE DUE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

6/07 p:/ClRC/DaleDue.indd-p.1

COMPARISON OF DIFFERENT PACKAGING MATERIALS TO DETERMINE
THEIR EFFECT ON AVAILABILITY AND EFFECTIVENESS OF
1-METHYLCYCLOPROPENE
By

Luis C. Rodriguez

A THESIS
Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of
MASTER OF SCIENCE
School of Packaging

2007

 

ABSTRACT

COMPARISON OF DIFFERENT PACKAGING MATERIALS TO DETERMINE

THEIR EFFECTS ON AVAILABILITY AND EFFECTIVENESS OF 1-MCP
By
Luis C. Rodriguez

The effects of corrugated board, high density polyethylene (HDPE), and
wood (Gmelina arboreus) materials on available concentration of the ethylene
action inhibitor 1-methylcyclopropene (1-MCP) was tested in sealed chambers at
different relative humidities. In addition, the ability of 1-MCP to suppress ripening

of banana in the presence of those materials was evaluated.

The concentration of 1-MCP declined in the chamber headspace in the
presence of the materials tested, but the rate at which 1-MCP gas was removed
differed markedly. The average percentage loss for HDPE and wood was
between 10-12% at the conditions tested, while for corrugated fiberboard it

ranged from 12% to 94%.

The loss of 1-MCP in the presence of corrugated board occurred more
readily at higher RH, while increasing the amount of material in the chamber
headspace and the initial concentration seem to play an important role in the rate

at which 1-MCP was depleted from the treatment chamber.

In these tests, corrugated fiberboard altered the dose response of
bananas because it affected the amount of 1-MCP present, thus markedly

reducing the effectiveness of the compound.

To my wife, Paula and our wonderful kids, Maria Paula and Luis Eduardo,

for their love and support

ACKNOWLEDGEMENTS

I would like to express my gratitude to both Dr. Bruce Harte, my major
professor, and Dr. Randolph Beaudry, who provided guidance and presented an
opportunity for me to pursue the MS. I am also thankful to the members of my
guidance committee: Dr. Gary Burgess, this work benefited greatly from his
knowledge and willingness to help, and Dr. Rafael Auras, for bringing insightful
suggestions into the proposed research.

I also want to thank the faculty and staff at the School of Packaging and the
Department of Horticulture. A special thanks goes to Dr. Susan Selke for her
constructive comments and suggestions.

I am deeply indebted to Dr. Deirdre Holcroft, R&D Manager of Agrofresh, for the
financial support that made possible the completion of my degree.

I thank my graduate fellows in the School of Packaging for their valuable
friendship.

I want to thank the many friends of the Comunidad Latinoamerica at MSU.
Special thanks goes to Irving and Romelia Widders, Oscar Castaneda and
family, Byron and Elena; for their friendship, precious help in getting started and
for being close by.

Finally, I wish to thank my Lord Jesus Christ for making my dreams and goals

come true.

 

TABLE OF CONTENTS

LIST OF TABLES ................................................................................. vii
LIST OF FIGURES ................................................................................ ix
Introduction .......................................................................................... 1
Chapter 1. Literature Review .................................................................... 4
1.1 Introduction ...................................................................................... 4
1.2 Regulatory status of 1-MCP ................................................................ 8
1.3 Current applications of 1-MCP ............................................................. 9
1.4 1-MCP benefits on tree fnJits ............................................................. 11
1.5 Factors that determine the response to 1-MCP as a postharvest

treatment ............................................................................................ 15
1.6 Conclusion .................................................................................... 17
Literature cited .................................................................................... 18

Chapter 2. Comparison of different packaging materials in concert with 1-MCP in

delaying ripening of bananas ................................................... 22
Abstract .............................................................................................. 22
2.1 Introduction .................................................................................... 24
2.2 Materials and Methods ..................................................................... 28
2.3 Results and Discussion .................................................................... 36
2.4 Conclusion ..................................................................................... 51
Literature cited .................................................................................... 52

Chapter 3. Comparison of corrugated board, HDPE, and wood relative to their
effect on the available concentration of 1-MCP over a period of time
of 24 h at 21°C and relative humidities of 50%, 80% and

95% .................................................................................................. 54
Abstract ............................................................................................. 54
3.1 Introduction .................................................................................... 56
3.2 Materials and Methods ..................................................................... 58
3.4 Results and Discussion .................................................................... 64
3.5 Conclusion .................................................................................. 100
Literature cited ................................................................................... 101

 

APPENDICES .................................................................................... 102
APPENDIX A 1-MCP Calibration Curve .................................................. 103

APPENDIX B Model to describe permeability of 1-methylcyclopropene through
paperboard ......................................................................................................... 104

APPENDIX C Comparison of experimental and estimated concentration of 1-
MCP using the calculated k values ......................................................... 121

vi

 

LIST OF TABLES

Table 1.1 Fruits classified according to respiratory behavior and ethylene
production rates .................................................................................... 6

Table 1.2 Current products containing 1-MCP: Use site registration and
registration date in the USA .................................................................... 11

Table 1.3 Summary of the potential benefit of 1-MCP on tree fruits ............ 12

Table 2.1 Percent (%) 002 accumulated in 1.9 L glass jars after enclosing
fruit for 6 hr with and without packing materials .......................................... 37

Table 2.2 Constants a, b, c, and d and coefficient of determination for fit of
C02 data from Gran Naine bananas treated with 1-MCP at concentrations
between 5-60 nL L", with subsequent exposure to ethylene for 24 h at 20°C...40

Table 2.3 Degree of reduction in the Hue angle (H°) from its initial value of
120 at color stage 1, to when control fruit reached color grade 5 .................... 42

Table 2.4 Constants a, b, c, and d and coefficient of determination for fit of H°
data from Gran Naine bananas treated with 1-MCP at concentrations between 5-
60 nL L", with subsequent exposure to ethylene for 24 h at 20°C .................. 45

Table 3.1 Treatments used to test the effects of relative humidity, amount of
packaging material in the treatment chamber, and initial concentration on
availability of 1-MCP ............................................................................. 61

Table3.2 Values of k for the exponential model Ct = Coe'kt fit to the
concentration of 1 -MCP in the chambers containing HDPE boxes at different
relative humidities (RH), initial concentrations of gas 1 -MCP (10 and 20 (IL L")
and ratios of packaging material (R= kg/m3 ) .............................................. 75

Table 3.3 Values of k for the exponential model Ct = Coe'kt fit to the
concentration of 1 -MCP in the chambers containing corrugated! fiberboard boxes
at different relative humidities (RH), initial concentrations of 1 -MCP (10 and 20 uL
L'1 )and ratios of packaging material (R= kg/m3 ) ......................................... 75

Table 3.4 Best-fit for constants a, b and c and sum of squares of the errors
(SSE) for high density polyethylene (HDPE) and corrugated board (CB) for the
different relative humidities, initial concentrations of gas 1-MCP and ratios of
packaging material tested ......................................................................... 94

vii

Table 3.5 Calculated vs. Experimental k values for HDPE at the different RH,
initial 1-MCP concentrations and ratios (kg/m3) tested .................................. 95

Table 3.6 Calculated vs. Experimental k values for corrugated board at the
different RH, initial 1-MCP concentrations and ratios (kg/m3) tested ................ 95

Table B1. Concentration of 1-MCP (g/cc) in Chamber 2 after diffusing through a
paperboard membrane - Replicate 1 ...................................................... 107

Table 82. Concentration of 1-MCP (g/cc) in Chamber 2 after diffusing through a
paperboard membrane — Replicate 2 ...................................................... 108

Table B3. Best values of D and S within different ranges, using experimental
data from Replicate 1 .......................................................................... 114

Table B4. Best values of D and S within different ranges, using experimental
data from Replicate 2 .......................................................................... 115

Table B5. Predicted values of coefficients S, D and P for 1-MCP through
paperboard ....................................................................................... 118

viii

LIST OF FIGURES

Figure 2.1 Percent (%) 002 accumulation in 1.9 L glass jars after enclosing
fruit for 6 hr with and without packing materials .......................................... 39

Figure 2. 2 Reduction in Hue angle from its initial value of approximately 120°H
at color stage 1 of Gran Naine bananas treated with 1 -MCP at concentrations
between 5-60 nL L" .............................................................................. 44

Figure 2.3 Reduction in hue angle (°H) in Gran Naine bananas from an initial
value of approximately 120°H at color stage 1 as a function of 1-MCP treatment
and package composition on 2 lots of fruit ................................................. 48

Figure 2.4 Respiration rates as C02 production (mL/kg.h) inside 1.9 L glass
jars after enclosing fruit for 6 hr ............................................................... 50

Figure 3.1 Effects of wood (Gmelina arboreus), HDPE and corrugated board
on 1-MCP concentration at 20°C and 50% RH. Control was a 1-L empty jar....65

Figure 3.2 Effects of wood (Gmelina arboreus), HDPE and corrugated board
on 1-MCP concentration at 20°C, 80% RH. Control was a 1-L empty jar .......... 67

Figure 3.3 Effect of amount of HDPE and corrugated board and initial
concentration of 1-MCP on percentage (%) available 1-MCP at 20°C, 50%
RH .................................................................................................... 70

Figure 3.4 Effect of amount of HDPE and corrugated board and initial
concentration of 1-MCP on percentage (%) available 1-MCP at 20°C, 80%
RH .................................................................................................... 71

Figure 3.5 Effect of amount of HDPE and corrugated board and initial
concentration of 1-MCP on percentage (%) available 1-MCP at 20°C, 95%
RH .................................................................................................... 72

Figure 3. 6 Comparison of experimental and calculated concentration values of
1 -MCP in a sealed treatment chamber with a material ratio of 8 kg/m3 and an
initial concentration of 10 [IL L'1 held at 20°C and 50% RH for 24 h....... ........ 77

Figure 3. 7 Comparison of experimental and calculated concentration values of
1 -'MCP In a sealed treatment chamber with a material ratio of 8 kg/m3 and an
initial concentration of 20 uL L'1 held at 20°C and 50% RH for 24 h ................. 78

 

Figure 3. 8 Comparison of experimental and calculated concentration values of
1 -MCP In a sealed treatment chamber with a material ratio of 4 kg/m3 and an
initial concentration of 10 uL L" held at 20°C and 50% RH for 24 h ................. 79

Figure 3. 9 Comparison of experimental and calculated concentration values of
1 -MCP in a sealed treatment chamber with a material ratio of 4 kg/m3 and an
initial concentration of 20 pL L" held at 20°C and 50% RH for 24 h ................. 80

Figure 3.10 Comparison of experimental and calculated concentration values of
1 -MCP in a sealed treatment chamber with a material ratio of 8 kg/m3 and an
initial concentration of 10 pL L1 held at 20°C and 80% RH for 24 h ................. 81

Figure 3.11 Comparison of experimental and calculated concentration values of
1 -MCP in a sealed treatment chamber with a material ratio of 8 kg/m3 and an
initial concentration of 20 pL L" held at 20°C and 80% RH for 24 h ................. 82

Figure 3.12 Comparison of experimental and calculated concentration values of
1 -MCP in a sealed chamber treatment chamber with a material ratio of 4 kg/m3
and an initial concentration of 10 pL L" held at 20°C and 80% RH for 24 h ...... 83

Figure 3.13 Comparison of experimental and calculated concentration values of
1 -MCP in a sealed treatment chamber with a material ratio of 4 kg/m3 and an
initial concentration of 20 pl. L" held at 20°C and 80% RH for 24 h ................. 84

Figure 3.14 Comparison of experimental and calculated concentration values of
1 -MCP in a sealed treatment chamber with a material ratio of 8 kg/m3 and an
initial concentration of 10 pL L1 held at 20°C and 95% RH for 24 h ................. 85

Figure 3.15 Comparison of experimental and calculated concentration values of
1 -MCP in a sealed treatment chamber with a material ratio of 8 kg/m3 and an
initial concentration of 20 pL L1 held at 20°C and 95% RH for 24 h ................. 86

Figure 3.16 Comparison of experimental and calculated concentration values of
1 M-CP in a sealed treatment chamber with a material ratio of 4 kg/m3 and an
initial concentration of 10 uL L1 held at 20°C and 95% RH for 24 h ................. 87

Figure 3.17 Comparison of experimental and calculated concentration values of
1 -MCP in a sealed treatment chamber with a material ratio of 4 kg/m3 and an
initial concentration of 20 uL L" held at 20°C and 95% RH for 24 h ................. 88

Figure3. 18 Effect of relative humidity on experimental k values in a sealed
treatment chamber with a mass of corrugated board to air volume ratio (R) of 4 or
8 kg/m3 and initial concentration of 1 -MCP of 10 or 20 [IL L" applied at 20°C and
50%, 80%, and 95% RH for 24 h. The best fit equation is displayed next to its
corresponding curve ............................................................................. 90

Figure 3.19 Effect of amount of mass of corrugated board to air volume ratio (R)
on experimental k values at initial concentrations of 1-MCP of 10 or 20 UL L'
applied at 20°C and 50%, 80%, and 95% RH for 24 h; the mass of corrugated
board relative to air volume ratio (R) varied from 4 to 8 kgl. The best fit equation
is displayed next to its corresponding line .................................................. 91

Figure 3.20 Effect of initial concentrations of 1-MCP on experimental k values
when applied in a sealed treatment chamber with a mass of corrugated board to
air volume ratio (R) of 4 or 8 kg/m3 at 20°C and 50%, 80%, and 95% RH for 24 h.
The best fit equation is displayed next to its corresponding line ...................... 92

Figure A1. 1-MCP calibration curve prepared using 1-butene: correlation
between target and actual levels of 1-MCP .............................................. 103

Figure B1. Setup of an experiment to determine the solubility of 1-MCP
through paperboard ............................................................................ 105

Figure B2. Variable in the experiment to determine the solubility of 1-MCP
through paperboard ............................................................................ 110

Figure B3. Glass system designed to validate the model to describe permeability
of 1-MCP through paperboard ............................................................... 116

Figure B4. Concentration of 1-MCP on chamber 2 after diffusing through a
paperboard membrane at different relative humidities and concentrations of 1-
MCP ................................................................................................ 117

Figure C1. Comparison of experimental and estimated concentration of 1-MCP
using the calculated k values (R = 8 kg/m3, Co = 10 uL L", 50%RH at
20°C) .................................................................................................................. 121

Figure CZ. Comparison of experimental and estimated concentration of 1-MCP
using the calculated k values (R = 8 kg/ m3, Co = 20 (IL L", 50%RH at
20°C) ............................................................................................... 122

Figure C3. Comparison of experimental and estimated concentration of 1-MCP
using the calculated k values (R = 4 kg/ m3, Co = 10 (IL L", 50%RH at
20°C) ............................................................................................... 123

Figure C4. Comparison of experimental and estimated concentration of 1-MCP
using the calculated k values (R = 4 kg/ m3, Co = 20 (IL L", 50%RH at
20°C) ............................................................................................... 124

Figure C5. Comparison of experimental and estimated concentration of 1-MCP
using the calculated k values (R = 8 kg/ m3, Co = 10 pL L", 80%RH at
20°C) ............................................................................................... 125

xi

 

Figure C6. Comparison of experimental and estimated concentration of 1-MCP
using the calculated k values (R = 8 kg/ m3, Co = 20 (IL L", 80%RH at
20°C) ............................................................................................... 126

Figure C7. Comparison of experimental and estimated concentration of 1-MCP
using the calculated k values (R = 4 kg/ m3, Co = 10 uL L", 80%RH at
20°C) ............................................................................................... 127

Figure CB. Comparison of experimental and estimated concentration of 1-MCP
using the calculated k values (R = 4 kg/ m3, Co = 20 (IL L", 80%RH at
20°C) ............................................................................................... 128

Figure 09. Comparison of experimental and estimated concentration of 1-MCP
using the calculated k values (R = 8 kg/ m3, Co = 10 uL L", 95%RH at
20°C) ............................................................................................... 129

Figure C10. Comparison of experimental and estimated concentration of 1-MCP
using the calculated k values (R = 8 kg/ m3, Co = 20 (IL L", 95%RH at
20°C) ............................................................................................... 130

Figure C11. Comparison of experimental and estimated concentration of 1-MCP
using the calculated k values (R = 4 kg/ m3, Co = 10 uL L", 95%RH at
20°C) ............................................................................................... 131

Figure C12. Comparison of experimental and estimated concentration of 1-MCP
using the calculated k values (R = 4 kg/ m3, Co = 20 (IL L", 95%RH at
20°C) ............................................................................................... 132

xii

INTRODUCTION

Postharvest losses in quantity and quality are a significant problem for
most horticultural crops. The magnitude of postharvest losses in fresh fruits and
vegetables is an estimated 5 to 25% in developed countries and 20 to 50% in
developing countries, depending upon the commodity, cultivar and handling
conditions. To reduce these losses, producers and handlers must understand the
biological and environmental factors involved in deterioration, and use
postharvest techniques that delay senescence and maintain the best possible
quality (Kader et al., 2002).

Traditionally, temperature, humidity control and modified atmospheres
have been used to maintain quality and delay over-ripening and senescence of

fruits and vegetables.

During the last decade the use of compounds that specifically target and
inhibit ethylene responsiveness have emerged as technologies which can be
used to delay senescence and deterioration of perishable fruits, vegetables,
potted plants, and cut flowers. Among these compounds, 1-methylcyclopropene

is the most promising ethylene action inhibitor (Sisler and Serek, 1997).

Postharvest applications with 1-methylcyclopropene (1-MCP) are done on
commodities already packaged and ready to be shipped for distribution and
commercialization. Even though the impact of 1-MCP on the postharvest biology

of several fruits, vegetables, and cut flowers has been studied, published data on

the equilibrium headspace concentrations of 1-MCP in the airspace of research
and commercial treatment chambers is lacking.

The focus of this research is to investigate how the presence of packaging
materials might affect the concentration of 1-MCP, with the consequent reduction
in its potential effectiveness to delay ripening associated processes. To
accomplish this, the research project was divided into two main topics: 1)
determining how packaging material might compromise treatment dosages of 1-
MCP for climacteric fruits (bananas were used as the model system), 2)
evaluating the impact of (3) increased relative humidity in treatment chambers
containing wood, high density polyethylene, and corrugated fiberboard on the
initial concentration of 1-MCP over time, (b) increased amount of packaging
material in the treatment chamber on the initial concentration of 1-MCP over
time, and (c) increased levels of 1-MCP in the presence of various packaging

materials on the effective dose available in the treatment chamber over time.

Literature Cited

Kader, AA, 2002. Postharvest Technology of Horticultural Crops. Agriculture
and Natural Resources, Publication 3311. Third Edition. p.39.

Sisler, EC. and Serek, M., 1997. Inhibition of ethylene responses in plants at
receptor levels: recent developments. Physiologia Plantarum 100, 577-
582.

CHAPTER 1
LITERATURE REVIEW
1.1 Introduction

Plants produce hundreds of volatile compounds which can act as
regulators and coordinators in the growth and development of tissues and whole
plants. Ethylene (CzH4) is a volatile that has received considerably study as a
regulator of plant growth. This unsaturated two-carbon gas has been shown to
have biological and commercial importance (Abeles et al., 1992). Production of
ethylene varies with the type of tissue, the plant species, and the stage of
development. Fruits have two phases of comparatively high rates of ethylene
production. The first is associated with cell division and rapid growth; the second
phase is associated with ripening (Abeles et al., 1992).

The physiology and biochemistry of ethylene production in higher plants is
described in the literature (McKeon et al., 1995; Salisbury and Ross, 1992;
Abeles et al., 1992).

To synthesize ethylene in the plant, the amino acid methionine is
converted to S-adenosylmethionine (SAM), which is the precursor of 1-
aminocyclopropane-1-carboxilic acid (ACC), the immediate precursor of
ethylene. ACC synthase, which converts SAM to ACC, is the main control site of
ethylene biosynthesis. The conversion of ACC into ethylene is mediated by ACC
oxidase. The synthesis and activities of ACC synthase and ACC oxidase are

influenced by genetic factors and environmental conditions, including

temperature and concentrations of oxygen and carbon dioxide (Kader et al.,
2002)

Horticultural commodities are classified according to their respiration and
ethylene production rates. The terms climacteric and nonclimacteric are used to
describe fruits that show a large increase in carbon dioxide and ethylene
production rates coincident with ripening, and those that do not (table 1.1).
Although the term climacteric was originally applied to increased fruit respiration,
it subsequently included a rise in ethylene production (Abeles et al., 1992; Kader
etaL,2002)

Ethylene is known to induce ripening-associated processes such as
softening, color change, conversion of starch to sugars, loss of acidity, etc, in
climacteric fruits (Davies, 1995; Mauseth, 1991; Raven, 1992; Salisbury and
Ross, 1992).

Table 1.1 Fruits classified according to respiratory behavior and ethylene

production rates.

 

 

Climacteric fruits Nonclimacteric fruits
Apple Muskmelon Blackberry Lychee
Apricot Nectarine Cacao Okra
Avocado Papaya Carambola Olive
Banana Passion fruit Cashew apple Orange
Biriba Peach Cherry Pea
Blueberry Pear Cranberry Pepper
Breadfruit Persimmon Cucumber Pineapple
Cherirnoya Plantain Date Pomegranate
Durian Plum Eggplant Prickly pear
Feijoa Quince Grape Raspberry
Fig Rambutan Grapefruit Strawberry
Guava Sapodilla Jujube Summer squash
Jackfruit Sapote Lemon Tamarillo
Kiwifruit Soursop Lime Tangerine and
Mango Sweetsop Longan madarin
Mangosteen Tomato Loquat Watermelon

 

Adapted from Kader et al., 2002.

The role of ethylene in ripening has been confirmed by showing that
inhibitors of ethylene synthesis delay ripening. There are two classes of
inhibitors of ethylene action: (a) mild toxicants that block ethylene action by
slowing down cellular physiology (i.e. carbon dioxide, benzothiadiazole, ethylene
oxide), and, (b) competitive inhibitors that combine with the ethylene receptor (a
cell component that ethylene must bind to induce its physiological effects)
preventing the cell from responding to ethylene (Abeles et al., 1992).

The biological activity of ethylene analogues follows binding rules similar
to the binding of olefins to silver. This suggests that a metal is part of the
ethylene binding site. Ethylene can be considered a soft base and can be

expected to bind to metal ions, which are soft acids (Abeles et al., 1992).

In 1979, Sisler introduced the use of various volatile unsaturated ring
compounds as inhibitors of ethylene action. Since that time, it has been found
that many compounds interact with the ethylene receptor and modulate ethylene
responses (Sisler et al., 1999).

Recently, it has become apparent that cyclopropene (CP) and 1-
methylcyclopropene (1-MCP) are very effective blocking agents for the ethylene
receptor, and can inhibit the ethylene response for extended periods. Exposure
to as little as 0.5 nL L'1 of these compounds for 24 hours protects camations and
bananas from the effects of ethylene for about 12 days at 25°C. An analog, 3,3-
dimethylcyclopropene (3,3-DMCP), is also active, but requires about 1000 times
the treatment concentration, and protects for only 7 days. In contrast,
methylenecyclopropane, a compound whose double bond is outside the
cyclopropene ring, is an ethylene antagonist, mimicking the effects of ethylene
(Sisler et al., 1999).

These compounds act at a remarkably low concentration (Sisler et al.,
2001). After 24 h of exposure to as little as 0.7 nL L’1 cyclopropene or 1-
methylcyclopropene, is sufficient to block ripening of bananas at 24°C for 12
days. A concentration of 500 nL L'1 of 3,3-dimethylcyclopropene is required for
24 hours to block ripening for 7 days. It is not known why these large differences
in response occur.

Among the cyclopropenes, 1-methylcyclopropene (hereafter abbreviated

as 1-MCP) is the most promising ethylene action inhibitor (Sisler and Serek,

1997). Under normal environmental conditions it is a gas, stable at room

temperature and has a non toxic mode of action (US. EPA, 2006).

1.2 Regulatory status of 1-MCP

On September 27, 1997, the United States Environmental Protection
Agency (US EPA) received an application from Biotechnologies for Horticulture,
Inc. to register Ethleloc® containing 0.43% of 1-methylcyclopropene as a plant
growth regulator (US. EPA, 2006).

A notice of receipt of the application for registration of 1-
methylcyclopropene as a new active ingredient was published in the Federal
Register on March 10, 1999 (64 FR 11868) with a 30 day comment period. No
comments were received as a result of this publication (US. EPA, 2006).

In April, 2000, the Agency received a petition from AgroFresh lnc.,
proposing the establishment of an exemption from the requirement of regulations
for residues of the biochemical 1-MCP in or on all food commodities (US. EPA,
2006). A notice of filling was published in the Federal Register of June 21, 2000
(65 FR 38550).

The final rule establishing an exemption from the requirement of tolerance
for residues of 1-methylcyclopropene in or on fruits and vegetables when used as
a post harvest plant growth regulator, for the purpose of inhibiting the effects of
ethylene, was approved and published in the Federal Register on July 26, 2002
(67 FR 48796).

1.3 Current applications of 1-MCP

1-methylcyclopropene (1-MCP) has been shown to specifically, and
reversibly, suppress ethylene response and extend the postharvest shelf life and
quality of several fruits and vegetables. In particular, climacteric fruits such as
apple, tomato, and avocado are extremely responsive to 1-MCP (Huber et al.,
2003)

1-MCP works by blocking the ethylene binding site (Serek et al., 1994). It
was first utilized by the floral industry to keep flowers fresher longer (Reid et al.,
2001)

It is sold for fruit as SmartFreshTM by AgroFresh, a division of Rohm and
Haas; this is the sole commercial source of this compound (Sozzi and Beaudry,
2007)

1-MCP is formulated as a cyclodextrin powder. The cyclodextrin
molecules form a soluble molecular “cage” that releases the 1-MCP gas
molecules through aqueous dissolution (Blankenship and Dole, 2003).

1-MCP is currently available in four formulations from Agrofresh (Table
1.2). End-use products Ethleloc®, SmartFreshT", SmartTabsTM and EthlelocTM
sachets contain 0.14%, 3.3%, 0.63% and 0.014% of 1-MCP; respectively (US
EPA, 2006).

Two delivery systems are available for use with fruits: tablets or sachets
containing SmartFreshTM powder, sized to develop the appropriate treatment
concentrations. When the product is mixed with water or a buffer solution, it

releases the gas 1-MCP (Sozzi and Beaudry, 2007).

hTM exists in 27 countries and

Current registration for use of SmartFres
includes more than 24 different commodities including 23 fruit crops, of which 18
are tree fruits (Sozzi and Beaudry, 2007). The most common registrations are for
apple (22 countries), avocado (13 countries), tomato (13 countries), and melon (9
countries). The number of tree fruit registrations is greatest for the USA (12),
followed by Mexico (11).

Results obtained using 1-MCP in precommercial and commercial trials are

sometimes accessible only to the sponsoring company or organization (Sozzi

and Beaudry, 2007).

10

Table 1.2 Current products containing 1-MCP: Use site registration

registration date in the USA.

and

 

Product name 8. Use sites

Registration date

 

Ethylbloc ®

Use Sites

Fresh cut flowers and potted flowering, bedding,
nursery and foliage plants.

April 22. 1999

 

SmartFreshTM

Use Sites

Post-harvest Fruits (apples, melons, tomatoes,
pears, avocadoes, mangoes, papayas, kiwifruit,
plums, apricots and persimmons

July 17, 2002

 

SmartFresh 1'“ SmartTabs

Use Sites

food commodities derived from: apples, melons,
tomatoes, pears, avocadoes, mangoes,
papayas, kiwifruit, plums, apricots and
persimmons

March 11, 2004

 

Manufacturing Use Product SF

January 30, 2004

 

Ethylbloc ® Sachet

Use Sites

Fresh cut flowers and potted flowering and
foliage plants

 

 

February 3, 2006

 

 

Source: US EPA, 2006.

1.4 1-MCP benefits on tree fruits

The potential benefit of 1-MCP for different tree fruit crops is described in

the literature (Table 1.3) in which respondents to an international survey ranked

the potential benefit of 1-MCP use as (1) no known benefit to fair benefit, (2)

good potential benefit, (3) very good potential benefit, or (4) excellent potential

benefit.

11

Table 1.3 Summary of the potential benefit of 1-MCP on tree fruits.

 

Potential benefit level Tree fruit crop (score)
Excellent Apple (3.92)

Very good Persimmon (3.25)
Kiwifruit (3)
Plum (3)
Avocado (2.56)
European and Asia Pears (2.5)

Good Mango (2.29)
Guava (2.20)
Papaya (2.20)
Banana and Plantain (2)
Cherirnoya (2)
Loquat (2)
Peach and Nectarine (1.7)

Fair/no benefit Pineapple (1.5)
Pomegranate (1 .5)
Apricot (1.4)
Lime (1 .4)
Berries (1)
Cherry ( 1)

Fig (1)

Grape (1)
Grapefruit (1 )
Lemon ( 1)
Mandarin (1)
Orange (1)

Benefits not anticipated Nuts and dried fruits - olive

Adapted from Sozzi and Beaudry, 2007.

12

A summary of the most relevant potential benefits of 1-MCP to different
tree fruits follows:

Apple (Ma/us domestica) was the first fruit to which 1-MCP could be
applied and then sold for human consumption. The effect of 1-MCP on this crop
has been widely studied in cultivars such as ‘Mclntosh’, ‘Empire’, ‘Delicious’,
‘Granny Smith’, ‘Fuji’, ‘Gala’, etc. 1-MCP suppresses ethylene production and
loss of tissue firmness in apples (Fan et al., 1999; Watkins et al., 2000; Reed,
2000). It also slows down the reduction in titratable acidity in most cultivars
evaluated (Fan et al., 1999; Watkins et al., 2000; Reed 2000). The effect on total
soluble solids is inconclusive because there have been reports that 1-MCP
decreases (Watkins et al., 2000), increases (Fan et al. 1999) or has no effect
(DeEll et al., 2002; Reed, 2002) on the total soluble solids of even the same
cultivars. Treatment with 1-MCP reduced by 50% the volatile formation from
Golden Delicious, Jonagold and Redchief Delicious fruit, relative to nontreated
fruit, in a manner similar to CA storage (Ferenczi et al., 2006).

1-MCP delays avocado (Persea amen'cana) ripening but renders it more
susceptible to decay (Hoffman et al., 2000). Softening in several cultivars of
avocado including Simmonds, Haas, Etinger, Reed and Fuerte was delayed by
1-MCP treatment through suppression of enzymes associated with the softening
process (Feng et al., 2000; Jeong et al., 2002).

1-MCP treatment of bananas (Musa acuminata) can affect ethylene
formation and respiration, volatile production, skin color, and pulp softening.

Without exogenous ethylene, 1-MCP delays the onset of the climacteric stage

13

whereas in the presence of exogenous ethylene, it does not affect the onset of
the climacteric, though treated fruit produce less ethylene and have a lower
respiration rate (Golding et al., 1998). It also delays and reduces volatile
production (Golding et al., 1999) and may induce uneven degreening (Jiang et al.
1999). 1-MCP treatment of mango (Mangifera indica) helps to maintain peel
color and external appearance by preventing oxidation of skin pigments (Silva et
al., 2004). 1-MCP treatment of papayas (Can'ca papaya) can effectively increase
the time to ripen approximately 3-fold (Hofman et al., 2001 ).

On pears (Pyrus communis), 1-MCP mainly affects texture and ethylene
production. The softening process in ‘Barlett’ pears that have started to ripen is
slowed and completely inhibited in ‘D’Anjou’ pears (Baritelle et al., 2001; Calvo
and Sozzy, 2004).

1-MCP slows the softening process in persimmon (Dispyros kaki) and
reduces the production of off-flavor compounds, acetaldehyde and ethanol
(Salvador et al., 2004).

1-MCP delays the ethylene and respiratory climacterics in plums (Prunus
domestica) (Abdi et al., 1998; Salvador et al., 2003). Aroma production of
‘Gulfruby’ and ‘Beauty’ plums is arrested by 1-MCP but can be restored by
propylene treatment (Abdi et al., 1998). It also reduces the production of off-
flavor compounds (Salvador et al., 2003), and delays changes in skin color,
softening and titratable acidity (Dong et al., 2002; Argenta et al., 2003; Valero et

aL,2004)

l4

1.5 Factors that determine the response to 1-MCP as a postharvest
treatment

Success of fruit response to 1-MCP treatment depends on six main factors
or sets of factors: (1) genotype (species and cultivar) and ripening physiology, (2)
preharvest environmental conditions and practices, (3) harvest date
(physiological age of fruit), (4) treatment conditions, (5) effect on susceptibility to
pathological disorders, and (6) the postharvest environment (Sozzi and Beaudry,
2007)

The effect of treatment conditions (time, concentration, temperature) is
described in the literature (Watkins, 2002; Blankenship and Dole, 2003).
Responses are usually “concentration x exposure” dependent in fruits such as
avocado, banana, guava, European pear, mango, peach and climacteric plums.
Concentration of 1-MCP may be a limiting factor, because high concentrations
can cause excessive delay in ripening or even prevent it, thus, selection of the
appropriate concentration depends on the species and cultivar (Sozzi and
Beaudry, 2007).

Indeed, findings from a study comparing 12 different fruits and vegetables
(Nanthachai et al., 2007) suggests that the rate of sorption differs markedly (up to
30-fold) between species. Interestingly, the authors also determined that most of
the 1-MCP applied must have been lost to one or more solid fractions of the plant
material excluding the physiologically active binding site.

The possibility that 1-MCP is absorbed by one or more of the insoluble dry

matter components suggests that materials that normally accompany

15

commodities inside refrigerated or controlled atmosphere facilities (treatment
rooms) may absorb a significant portion of the 1-MCP during the exposure
treatment time (Vallejo and Beaudry, 2006).

The loss of 1-MCP to non-target materials from fruit storage facilities was
first described in the literature by testing the sorptive capacity of oak, plywood,
high density polyethylene (HDPE) and polypropylene (PP) plastic bin material,
corrugated board, urethane insulation and cellulose- based fire retardant, which
are structural components of commercial treatment chambers (Vallejo and
Beaudry, 2006). Findings from this study show large differences in absorption of
1-MCP by the different materials. Of the bin and box construction materials,
those made from wood or wood fibre adsorbed significant quantities of 1-MCP
while plastic bin material absorbed little to no 1-MCP. Urethane insulation and
the fire retardant did not absorb 1-MCP. lmportantly, wetting of the wood and
corrugated board test samples dramatically increased absorption.

Probably, the most interesting result was related to a simulated CA
storage treatment in which apple was placed in the treatment chamber alone;
and in combination with a piece of wetted oak bin material. Inclusion of the
wooden bin material caused the 1-MCP concentration to be depleted by half
within the first 2 hours versus 12 hours if the wood was not included. The data
suggested that the loss of 1-MCP to non-target materials commonly encountered
in controlled atmosphere or regular atmosphere storage rooms is likely not of -
serious concern in situations when 1-MCP levels are near the maximum

recommended rate (i.e. apple and pears). However, under sub-saturating

16

concentrations, significant sorption by fruit, or sorption by corrugated board or
wood, might compromise 1-MCP efficacy (Vallejo and Beaudry, 2006).

Published data on headspace concentrations of 1-MCP in research or
commercial treatment chambers is lacking; 1-MCP has been treated as relatively
inert gas, the assumption being that when the material is added to an
experimental chamber, a small portion of the applied gas is bound to the
ethylene binding sites in the produce and the remainder of the material simply
stays in the airspace of the treatment chamber until it is vented (Sozzi and

Beaudry, 2007).

1.6 Conclusion

Traditionally, temperature and humidity control and modified atmospheres
are used for fruits and vegetables to maintain quality and delay ripening and
senescence. During the late 90’s and beginning of this century, the use of
compounds that specifically target and inhibit ethylene responsiveness have
emerged as alternative technologies for delaying senescence and deterioration
of perishable fruits, vegetables, potted plants, and cut flowers. 1-
methylcyclopropene (1-MCP) suppresses ethylene response and extends the
postharvest shelf life and quality of climacteric fruits. The impact of 1-MCP on
the postharvest biology of climacteric fruits is well characterized; however,
published data on the behavior of concentration of 1-MCP in the airspace of

research and commercial treatment chambers is lacking.

17

Literature Cited

Abdi, N., McGIasson, W.B., Holford, P., Williams, M., Mizrahi, Y., 1998.
Responses of climacteric and suppressed-climacteric plums to treatment
with propylene and 1-methylcyclopropene. Postharvest Biol. Technol. 14,
29-39.

Abeles, F.B., Morgan, P.W., Salveit, M.E. Jr., 1992. Ethylene in Plant Biology,
2"‘1 Ed. Academic Press, United States.

Argenta, L.C., Krammes, J.G., Megguer, C.A., Amarante, C.V.T, Mattheis J.,
2003. Ripening and quality of ‘Laetitia’ plums following harvest and cold
storage as affected by inhibition of ethylene action. Pesq. Agropec. Bras.
38, 1139-1148.

Baritelle, A.L, Hyde, G.M., Fellman, J.K., Jatuphong, V., 2001. Using 1-MCP to
inhibit the influence of ripening on impact properties of pear and apple
tissue. Postharvest Biol Techn 23, 153-160.

Beaudry, R., and Watkins, C., 2001. Perishables Handling Quarterty, Issue
No.108 pp.12-16.

Blankenship, S.M., Dole, J.M., 2003. 1-Methylcyclopropene: a review.
Postharvest Biol. Technol. 28, 1-25.

Calvo, G., Sozzi, GO, 2004. Improvement of postharvest storage quality of Red
Clapp’s pears by treatment with 1-methylcyclopropene at low temperature.
J.Hort.Sci. Biotechnol. 79, 930-934

Davies, P. J., 1995. Plant Hormones: Physiology, Biochemistry and Molecular
Biology. Dordrecht: Kluwer.

DeEll, J.R., Murr, D.P., Porteous, M.D., Rupasinghe, H.P.V., 2002. Influence of
temperature and duration of 1-methylcyclopropene treatment on apple
quality. Postharvest Biol. Technol. 24, 349-353.

Dong, L., Lurie, 8., Zhou, H.W., 2002. Effect of 1-methylcyclopropene on
ripening of ‘Canino’ apricots and ‘Royal Zee’ plums. Postharvest Biol.
Technol. 24, 135-145.

18

Fan, X., Blankenship, S.M., Mattheis, JP, 1999. 1-methylcyclopropene inhibits
apple ripening. Journal of the American Society for Horticultural 124(6),
690-695.

Feng X., Apelbaum, A., Sisler, E.C., Goren, R. 2000. Control of ethylene
responses in avocado fruit with 1-methylcyclopropene. Postharvest Biol.
Technol. 20, 143-150.

Ferenczi, A., Song, J., Tiang, M., Vlachonasios, K., Dilley, D., Beaudry, R., 2006.
Volatile ester suppression and recovery following 1-methylcyclopropene
application to apple fruit. J. Amer. Soc. Hort. Sci. 131, 691-701.

Golding J.B., Shearer D., Wyllie S.G. and McGIasson WB 1998. Application of
1-MCP and propylene to identify ethylene-dependent ripening processes
in mature banana fruit. Postharvest Biol. Technol. 14, 87-98.

Golding J.B., Shearer D., Wyllie S.G. and McGIasson WB 1999. Relationships
between respiration, ethylene, and aroma production in ripening banana. J
Agric Food Chem 47, 1646-1651.

Hofman, P.J., Jobin-Décor, M., Meiburg, G.F., Macnish, A.J., Joyce, DC, 2001.
Ripening and quality responses of avocado, custard apple, mango and
papaya fruit to 1-methylcyclopropene. Aust J Exp Agric 41, 567-572.

Huber D., Jeong J. and Ritenour M., 2003. Use of 1-Methylcyclopropene (1-
MCP) on Tomato and Avocado Fruits: Potential for Enhanced Shelf Life
and Quality Retention. Publication HS-914, University of Florida,
http://edis.ifas.ufl.edu (accessed on May 25, 2007).

Jeong, J., Huber, D.J., Sargent, SA, 2002. 1-methylcyclopropene (1-MCP) on
ripening and cell-wall matrix polysaccharides of avocado (Persea
americana) fruit. Postharvest Biol. Technol. 25, 241-256.

Jiang, Y., Joyce, D.C., Macnish, A.J., 1999. Extension of the shelf life of banana
fruit by 1-methylcyclopropene in combination with polyethylene bags.
postharvest Biol. Technol. 16, 187-193.

Kader, AA, 2002. Postharvest Technology of Horticultural Crops. Agriculture
and Natural Resources, Publication 3311. Third Edition. p.39.

19

Mauseth, J. D., 1991. Botany: An Introduction to Plant Biology. Philadelphia:
Saunders. pp. 348-415.

Marriott, J. 1980. Bananas — physiology and biochemistry of storage and ripening
for optimum quality. Crit. Rev. Food. Sci. Nutri. 13, 41-88.

McKeon, T. A., Fernandez-Maculet, J. C. and Yang, S. F., 1995. "Biosynthesis
and metabolism of ethylene". Plant Hormones: Physiology. Biochemistry
and Molecular Biology. Dordrecht: Kluwer. pp. 118-139.

Nanthachai, N., Ratanachinakorn, B., Kosittrakun, M., Beaudry, RM, 2007.
Absorption of 1-MCP by fresh produce. Postharvest Biol. Technol. 43,
291-297.

Pest Management Regulatory Agency, 2004. 1-Methylcyclopropene, Regulatory
note REG 2004-07, PMRA, Health Canada, Ottawa, Ont., p.50,
httpzllwww.pmra-arla.gc.ca/eng|ish/pdf/reg/re92004-07-e.pdf (accessed on
May 25, 2007).

Raven, P. H., Evert, R. F., and Eichhom, S. E., 1992. Biology of Plants. New
York: Worth. pp. 545-572.

Reid M., Celikel F., McKay A., and Hunter D., 2001. Perishables Handling
Quarterly, Issue No.108 pp.7-9.

Salisbury, F. B., and Ross, C. W., 1992. Plant Physiology. Belmont, CA:
Wadsworth. pp. 357-407, 531-548.

Salvador, A., Cuquerella, J., Martinez-Javega, J.M., Monteverde, A., Navarro, P.,
2004. 1-MCP preserves the firmness of stored persimmon ‘Rojo brillante’.
J. Food Sci. 69, S69-S73.

Serek, M., Sisler, E.C., Reid, MS, 1994. Novel gaseous ethylene binding
inhibitor prevents ethylene effects in potted flowering plants. Journal
American Society Hort.Sci. 119, pp.1230-1233.

20

Sisler, EC. and Serek, M., 1997. Inhibition of ethylene responses in plants at
receptor levels: recent developments. Physiologia Plantarum 100, 577-
582.

Simmonds, N.W., Stover, R.H., Harry, R., 1987. Bananas, 3rd edition.
Longmans, London.

Sisler, E.C., Serek, M., Dupille, E. and Goren, R., 1999. Inhibition of ethylene
responses by 1-Methylcyclopropene and 3-Methylcyclopropene. Plant
Growth Regulation 27, 105-111.

Sisler, E.C., Serek, M., Roh, K. and Goren, R. 2001. The effect of chemical
structure on the antagonism by cyclopropenes of ethylene responses in
banana. Plant Growth Regulation 33, 107-110.

Sozzy, G.O, Beaudry, RM, 2007. Current perspectives on the use of 1-
methylcyclopropene in tree fruit crops: an international survey. Stewart
Postharvest Review 2:10.

United States Environmental Protection Agency (US EPA), 2006. Biopesticide
Registration Action Document: 1-Methylcyclopropene (PC Code 224459).
Available at www.epa.gov/pesticides/biopesticides/ingredients/tech_docs/
brad_224459.pdf (accessed on May 25, 2007).

Valero, D., Romero, D.M., Valverde, J.M., Guillen, F., Castillo, S., Serrano, M.,
2004. Could 1-MCP treatment effectiveness in plum be affected by
packaging?. Postharvest Biol. Technol. 34, 295-303

Vallejo, F. and Beaudry, R., 2006. Depletion of 1-MCP by ‘non-target’ materials
from fruit storage facilities. Postharvest Biol. Technol. 40, 177-182.

Watkins, CB, 2002. Ethylene synthesis, mode of action, consequences and
control. In: Fruit quality and its biological basis. Sheffield Academic Press,
180-224.

21

CHAPTER 2

COMPARISON OF DIFFERENT PACKAGING MATERIALS IN CONCERT

WITH 1—MCP IN DELAYING RIPENING OF BANANAS
Abstract

Corrugated board, low and high density polyethylene, and wood based
packaging materials were compared for their effect on efficacy of 1-MCP in
delaying ripening-associated processes such as changes in peel color and
accumulation of CO2 when applied to mature green, non-ripening, non-gassed

banana fruits.

The data confirms that the effect of 1-MCP depends not only on initial 1-
MCP concentrations in the atmosphere surrounding the fruit, but also on the type
of packaging material used (corrugated board box, a Kraft paper pad, wood from

pallets, plastic bins) in concert with the fruit at the time of treatment.

In general, concentrations of 1-MCP around 5-10 nL L" were sufficient to
suppress ripening and the accompanying increase in respiratory activity of the
fruit which resulted in the accumulation of CO2 in response to ethylene for fruit in
treatment chambers in the absence of packaging materials. When corrugated
board was present with the fruit at least 15 nL L" of 1-MCP were needed to
induce a similar magnitude of response. 1-MCP at concentrations of 5 nL L" and
10 nL L" suppressed the loss of green color in fruit packaged in corrugated high
density polyethylene. However, the suppression of chlorophyll loss was marginal

at 10 nL L" and not evident at 5 nL L" on fruit packed in corrugated board.

22

Concentrations of 1-MCP lower than 5 nL L" occasionally induced uneven
ripening and patchy loss of chlorophyll of fruit within the same treatment dose,
whereas concentrations of 20 nL L" were enough to completely block the
response of fruit to ethylene even in the presence of the packaging materials

tested.

In this test, the corrugated board significantly reduced the effectiveness of
low doses of 1-MCP in delaying ripening-associated processes of the fruit in
response to ethylene. The data suggest that current commercial
recommendations should be amended to take into account the effect of sorption

of 1-MCP by packaging materials.

23

2.1 Introduction

Traditionally manipulation of temperature, humidity and atmosphere has
been used to maintain quality and delay over-ripening and senescence of fruits

and vegetables.

During the last decade, the use of compounds that specifically target and
inhibit ethylene responsiveness have emerged as technologies, which can be
used to delay senescence and deterioration of perishable fruits, vegetables,

potted plants, and cut flowers.

Ethylene is produced by all higher plants. It is known to induce ripening-
associated processes such as softening, color change, conversion of starch to
sugars, loss of acidity, etc, in climacteric fruits (Davies, 1995; Mauseth, 1991;
Raven, 1992; Salisbury and Ross, 1992). Production of ethylene varies with the
type of tissue, the plant species, and the stage of development. The mechanism
by which ethylene is produced has been described (McKeon et al., 1995;

Salisbury and Ross, 1992; Abeles et al., 1992).

1-methylcyclopropene (1-MCP) has been shown to specifically, and
typically reversibly, suppress ethylene response and extend the postharvest shelf
life and quality of several ntits and vegetables. In particular, climacteric fruits
such as apple, tomato, and avocado are very responsive to 1-MCP (Huber et al.,

2003)

24

1-MCP works by blocking the ethylene binding site, making it blind to the
presence of ethylene (Serek et al., 1994). It was first utilized by the floral industry

to keep flowers fresher longer (Reid et al., 2001).

1-MCP was discovered more than a decade ago, it is sold for fruit as
SmartFreshTM by AgroFresh, a division of Rohm and Haas (the registrant
company) and is formulated as a cyclodextrin powder that releases the gas

through aqueous dissolution (Blankenship and Dole, 2003).
Definition of the problem

Currently, 1-MCP is used in commercial apple storage, as a complement
to cold storage, for maintaining apple quality. A single exposure to 1-MCP can
inhibit apple fruit sensitivity to ethylene, delay the rise in ethylene production and
thus delay respiration, aroma production, and softening for more than 100-120

days for apples stored at 0°C (32°F) (Beaudry and Watkins, 2001).

In the United States and Canada, the label treatment dosage for apples is
1.0 and 0.6 jJL L", respectively. These dosages are recommended to supply 1-
MCP at a concentration sufficient to saturate the response of the plant material

(Pest Management Regulatory Agency, Health Canada, 2004).

However, saturating levels of 1-MCP (concentrations sufficiently high to
completely block the ethylene receptors, thus inhibiting ethylene response) can
cause excessive delay of ripening in some fruits, and alter ripening-related

developmental processes sufficiently to significantly reduce product quality.

25

Thus, in some instances, it is preferable to obtain short-term or partial responses

by using sub-saturating levels of 1-MCP (Calvo and Sozzi, 2004).

Golding et al. (1998) suggested that climacteric fruits might eventually
make new receptors after 1-MCP treatment, allowing an active, normal, ethylene
climacteric ripening response. This is more likely to occur for application
situations in which the concentration of 1-MCP is not significantly above the
minimal saturating concentration for a plant material, or for applications within the
variable dose response range (Vallejo and Beaudry, 2006). In such
circumstances, losses of 1-MCP during the exposure period might compromise
the effectiveness of the product. Even assuming that the application is in a tight,
sealed storage room (chamber or container) the presence of packaging materials
(i.e. paperboard and/or corrugated paperboard) commonly used for commercial
shipment of fruits, might have the ability to absorb 1-MCP from the storage
environment, thereby reducing the effective concentration available for treatment.
Vallejo and Beaudry (2006) demonstrated that wood and corrugated cardboard

materials, commonly found in apple storage facilities, absorb 1-MCP.

Banana is a climacteric fruit, and as such shows marked physiological
changes during ripening (Simmonds et al., 1987). Ripening is initiated by the
natural evolution of endogenous ethylene as banana fruit reach full maturity.
Commercially, an exogenous source of ethylene is used to induce and trigger
endogenous production of ethylene while ensuring uniform ripening progression

among fruit batches (Marriot, 1980).

26

Exposure to as little as 0.7 nL L" of 1-MCP for 24 hours is required to
protect bananas from the effects of ethylene for about 12 days at 25°C. After 12
days fruit responds to ethylene and resumes normal ripening (Sisler et al., 1998).
Jiang et al. (1999) demonstrated that banana fruit ripening was delayed when

exposed to 0.01 — 1.0 “L L".

Non-published research conducted for a large multinational company
showed that Gran Naine bananas treated with as low as 10 nL L" of 1-MCP
remained green after exposure to ethylene regardless of the ripening cycle used.
Those results supplied the encouragement to do follow up experimentation in a

range of concentrations near that level.

Because of the potential important implications on dosage
recommendations of this phenomenon, a study was proposed to address the
question of how packaging materials might compromise treatment dosages of 1-

MCP for climacteric fruits. Bananas were used as the model system.

Objectives

1- Characterize and describe banana fruit responses to 1-MCP at concentrations
near the minimal effective dosages when applied at the green stage in the
presence of corrugated board, HDPE or wood, followed by treatment with

ethylene.

2- Compare the effects of corrugated board, wood, and HDPE on 1-MCP
sorption by determining the half-maximum effective concentration of applied 1-

MCP.

27

2.2 Materials and Methods
2.2.1 BANANAS INDIVIDUALLY TREATED WITH 1-MCP IN 1.9 L GLASS JARS
Fruit material:

A series of trials were conducted in 2006 at the Postharvest Technology

and Physiology Laboratory in the Plant Sciences Building, MSU.

Mature green ‘Gran Naine’ bananas were obtained from the Detroit
Terminal Market. The bananas used for these series of experiments were from
Dole’s commercial packs known as 150’s, which consist of 150 single fingers
with the following specifications: length 17.8 to 20.3 cm, and caliper (width) 6 to

6.8 cm; packed in corrugated board cases weighing approximately 22.7 kg.

Fruit was collected every two weeks directly from inbound shipping
containers to prevent contamination with ethylene from the ripening facilities and
brought immediately to the laboratory. Fruit was harvested in farms located in
Costa Rica, with a transit period from the tropics to the market estimated to be

around 12 days.

Fruit was sorted to ensure freedom from visual defects and uniformity of
weight and shape. Hue (H°) was measured (Minolta, CR-300, Japan) upon fruit
arrival to the laboratory and the decrease in H° in response to treatment was

measured.

Packaging materials tested included: HDPE specimens (1.2x11x1.8 cm),
oak wood strips (7.2x11.4x0.5 cm) and corrugated board specimens

(7.5x11.5x0.2 cm). Control fruit was tested in the absence of any packing

28

materials. The oak pieces were from commercial bins stored out-of-doors, and
the HDPE specimens were from plastic bins (Macro Plastics, Fairfield, CA). The
corrugated board was from commercial banana boxes with a combined basis

weight of facings of 94 Lb per 1000 ft2 (Packaging Corporation of America).

1-MCP:

 

1-MCP concentrations tested were 0, 0.5, 1, 2, 3, 4, 5, 10, 15, 20, 30, 40
and 60 nL L". These were obtained from a concentrated source of 1-MCP
(2000 pL L") created by adding 10 mL of distilled water to a 0.47-L glass jar
containing 0.064 g of SmartFreshTM (AgroFresh, Springhouse, PA), which had an
active ingredient concentration of 3.3%. A fresh source of stock gas was

prepared for each run.

The concentration of 1-MCP in the stock preparation was quantified by
gas chromatography (Carle Series 100 AGC) using a 2 m (length) x 2 mm (inner
diameter) stainless steel column packed with 60/80 Chromosorb 0V-103 (Alltech
Associates Inc., Deerfield, IL), and fitted with a flame ionization detector. The
flow rates for the carrier gas (He), H2, and air were approximately 50, 50 and 200

mL min", respectively. The oven temperature was maintained at 140°C.

A 1-butene gas standard was used to determine the concentration of 1-
MCP. To create a 10 (IL L" 1-butene standard, 43 uL of pure 1-butene
(Matheson Gas Products, Chicago, IL), were injected into a 4.3 L specially-made
glass chamber fitted with a Mininert valve (Supelco, Bellefonte, PA). It was
assumed that the response factor for 1-MCP (molecular weight of 54.09 g/mol)

and 1-butene (molecular weight of 51 g/mol) would be similar (Vallejo and

29

Beaudry, 2006). A standard curve for 1-butene was prepared for concentrations
ranging between 1 to 10 uL L", the relationship between 1-MCP and 1-butene

was linear (Appendix A).
Experimental design:

One jar per concentration (C) and material type (M) was used, for a total
of 52 jars per test run. The same experimental setup was repeated every other

week for 20 consecutive weeks (total of 9 runs or replicates).

Upon fruit arrival to the laboratory; one banana finger, along with the
corresponding treatment material, was placed into a 1.9-L glass Mason jar and
closed with a metal lid fitted with rubber septa (Fisher Scientific, Springfield, NJ).
A sufficient volume of the 1-MCP stock gas was added to the jar headspace to
obtain a target 1-MCP gas concentration. A gas tight syringe was used to deliver
the 1-MCP through the rubber septa. After 24 h the jars were vented with fresh
air for 30 min and the HDPE, corrugated fiberboard and wood sticks were

removed from the jars.

The fruit was then exposed to ethylene at an initial concentration of 50 (IL
L" for 24 h at 20°C, by injecting ethylene gas (Matheson Gas Products, Chicago,

IL) into the headspace of the jars, using a gas tight syringe.

The fruit were then removed from the jars and put into corrugated board
boxes lined with HDPE (Muehlstein, Norwalk, CT) under ambient air conditions of
~20°C. The liner, with a thickness of 1.77x10'5 m, had 36 perforations around

the perimeter of the box, each having a diameter of 1.25 cm.

30

Fruit was evaluated daily for peel color. The scoring used for peel color
was determined using a 1-7 commercial color scale (Dole color chart) described
as follows: 1 = all green, 2 = light green, 3 = 50% green / 50% green yellow, 4 =
more yellow than green, 5 = yellow with green tips, 6 = full yellow; and 7 = yellow

flecked with brown.

When the control fruit had reached color stage 5, the peel H° of all
bananas was measured (Minolta, CR-300, Japan). Each measurement was
taken from three different points of the fruit peel (inner whorl, outer whorl and one

side).

To measure the accumulation of C02 in the headspace of the jars, the
banana fingers were placed back in the glass jars and sealed for 6 h prior to C02
sampling. A 100 pL gas sample was withdrawn by syringe and the sample
injected into a C02 analyzer (ADC model 225-MK3, Hoddesdon, England) with

nitrogen as the carrier gas.

To objectively determine the apparent, half-maximum effective
concentration of 1-MCP applied, the relative amount of CO2 formed for each
treatment was fitted with an appropriate equation using commercial curve-fitting

software (Table Curve 20; Jandel Scientific, San Rafael, California).

Statistical significance was determined using analysis of variance and the
software lnfoStat Release 1.0 (Universidad Nacional de Cordoba, Argentina,
2001). Significant differences among treatment means was done using Fisher’s

least significant difference test at P<0.1.

31

2.2.2 BANANAS PACKAGED IN CORRUGATED HDPE VS. CORRUGATED
PAPERBOARD BOXES AND TREATED WITH 1-MCP IN 114 L PLASTIC
BARRELS

After determining the 1-MCP dose responses, an experiment was
designed using an increased sample size and a reduced number of 1-MCP
concentrations. This was primarily a demonstration experiment to test whether
the sorption by fiberboard had the potential to alter 1-MCP effectiveness under
conditions more closely resembling commercial handling and packaging

scenanos.
Treatments:

The treatments were as follows:
T1 - Fruit only, no added packing materials and no 1-MCP,
T2 - Fruit in corrugated fiberboard boxes and treated with 1-MCP at 5 nL L",
T3 - Fruit in corrugated fiberboard boxes and treated with 1-MCP at 10 nL L",
T4 - Fruit in corrugated plastic boxes and treated with 1-MCP at 5 nL L", and
T5 - Fruit in corrugated plastic boxes and treated with 1-MCP at 10 nL L".

Corrugated fiberboard boxes were the commercial “Quad-pack” Mini box
type for Dole bananas with a combined basis weight of facings of 94 Lb per 1000
ft2 (Packaging Corporation of America), taken from inbound shipping containers.
Corrugated high density polyethylene (HDPE) boxes were assembled using a

template of the “Quad-pack” mini box.

32

Fruit in both plastic and fiberboard boxes were packed using a HDPE liner
(Muehlstein lnc., NonNalk, CT) with a thickness of 1.77x10‘5 m to protect bananas
from mechanical injuries. Liners had approximately 36 perforations around its
perimeter, each having a diameter of 1.25 cm. All boxes were filled to a total

weight of 4.54 Kg of banana fruit with an average of 32 fingers per box.

Three boxes of each treatment were placed into different plastic barrels
having a volume of 114-L with lids fitted with rubber septa (Fisher Scientific,
Springfield, NJ) under ambient air conditions of ~20°C. Control fruit consisted of
an equivalent weight of non-boxed fruit placed into plastic barrels. Each box was
considered a replicate of the treatment. The same experimental setup was

repeated two weeks after the first run.

Distilled water was added (3 L) to each barrel (chambers) to generate a
relative humidity of 95% or greater in the airspace of the chambers. The relative
humidity was measured using a moisture analyzer designed to operate with a
dew point sensor (General Eastern, Model 8008). All boxes were placed empty
into the chambers for 24 h prior to treatment with 1-MCP to ensure that they

came to equilibrium with the relative humidity in the chambers.

Additionally, all plastic barrels, used as treatment chambers, were tested
to determine their integrity by injecting a known concentration of 1-MCP in the
headspace to obtain a target gas concentration of around 5 (IL L". Gas
concentration in the headspace of the barrels was measured after 24 h. A slight
declined of around 2% over the 24 h test period occurred suggesting that the

barrels would maintain the desired concentration of 1-MCP.

33

Boxes were placed in a “cross-stacked” pattern. The barrel rims closures
were coated with high vacuum grease (Dow Corning Corp., USA) to ensure
proper gasket sealing. The fruit was then exposed to 1-MCP for 24 h at 20°C,
and a sufficient volume of the 1-MCP stock gas was added to the headspace to
obtain a target 1-MCP gas concentration. A gas tight syringe was used to deliver
the 1-MCP through the rubber septa. A small fan powered with a lantern battery

was placed inside each barrel to allow air flow through the boxes.

A concentrated source of 1-MCP (7,500 pL L") was created by adding 10
mL of distilled water to a 0.47-L glass jar containing 0.32 g of SmartFresh
(AgroFresh, Springhouse, PA), which had an active ingredient concentration of
3.3%. A fresh source of stock gas was prepared for each run. The actual
concentration of 1-MCP in the stock preparation was quantified as previously

descnbed.

After 24 h, the barrels were opened and vented with fresh air for 30 min
following treatment with 1-MCP. Fruit (with added packing materials) was
subsequently exposed to ethylene at a concentration of 100 pL L" for 24 h at
20°C. A single injection of pure ethylene gas (Matheson Gas Products, Chicago,

IL) was delivered to the headspace of the barrels.

All boxes were removed from the barrels at the end of the 24 h exposure
period and kept under ambient conditions at 20°C. Fruit was evaluated daily for
peel color. The scoring used for peel color was determined using a 1-7

commercial color scale (Dole color chart) described as follows: 1 = all green, 2 =

34

light green, 3 = 50% green / 50% green yellow, 4 = more yellow than green, 5 =

yellow with green tips, 6 = full yellow; and 7 = yellow flecked with brown.

When the control fruit reached color stage 5, the hue angle of all fingers
from each treatment (N=96) was measured as previously described. Each
measurement was taken from the center of the outer whorl of the banana finger.
An initial H° was measured upon fruit arrival to the laboratory, and the
subsequent decrease in H° represents a change in peel color from green to

yellow.

For fruit from the second experimental lot, six randomly selected banana
fingers per treatment were placed into 1.9-L glass Mason jars with metal lids
fitted with rubber septa (Fisher Scientific, Springfield, NJ) and held at a constant
temperature of 20°C for 6 h. The accumulation of CO2 was measured on a 100-
uL sample withdrawn using a syringe and analyzed using a C02 analyzer (ADC
model 225-MK3, Hoddesdon, England) with nitrogen as the carrier gas. The
respiration rate was calculated based on the CO2 accumulation rate using the
following relationship: Respiration rate = (C02 % / 100) x (tha. in mL / sample

weight in Kg) x (1 It in hours)

This experiment was repeated once and for each run banana fingers were
sampled from different replicates (boxes). Statistical significance was
determined using analysis of variance and the software lnfoStat Release 1.0
(Universidad Nacional de Cordoba, Argentina, 2001). Significant differences
among treatment means were determined using Fisher’s least significant

difference test at P<0.1.

35

 

2.3 Results and Discussion

2.3.1 BANANA FINGERS INDIVIDUALLY TREATED WITH 1-MCP IN 1.9 L
GLASS JARS

Four days after application with ethylene, control fmit without 1-MCP reached
color stage 5. At that time the accumulation of C02 in the headspace of the jars
was measured, results are summarized in Table 2.1. Treatments within columns
with the same letter are not statistically different at 1% level (FLSD), each value
is the average of 7 determinations on a single fruit samples each time.

Changes in the percent C02 in the jars depended on 1-MCP
dosage concentration and the type of packing material present in the jars. In
general, concentrations of 1-MCP greater than 10 nL L" prevented an increased
(a 50% reduction or more) in the respiratory climacteric of the ntit. When
corrugated board was present, at least 15 nL L" of 1-MCP were needed to
induce a similar magnitude of response. There was no difference between

treatments at 1-MCP concentrations greater than 15 nL L".

36

Table 2.1 Percent (%) CO2 accumulated in 1.9 L glass jars after enclosing

fruit for 6 hr with and without packing materials.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

C02 (%)
1-MCP (ppb) Control Plastic Wood CB
0 3.95 d 4.62 e 4.8 c 4.14 c
0.5 4.12 d 4.31 de 4.63 c 5.01 c
1 4.23 d 4.54 e 3.96 c 4.94 c
2 4.18 d 3.91 cde 3.92 c 4.56 c
3 2.47 c 3.07 bc 2.41 b 4.16 c
4 2.56 c 3.2 bcd 2.66 b 4.07 bc
5 2.47 c 2.56 b 2.65 b 4.3 c
10 1.74 be 1.27 a 2.29 b 3.15 b
15 0.7 ab 0.7 a 0.65 a 1.61 a
20 0.74 ab 0.68 a 0.68 a 0.7 a
30 0.61 a 0.82 a 0.85 a 0.84 a
40 0.86 ab 0.81 a 0.85 a 0.76 a
60 0.8 ab 0.72 a 0.82 a 0.65 a

 

37

 

The data describing the increase in CO2 could be empirically fit by several
of the equations provided by the curve-fitting software. Of these, those equations
having constants that could be used to gather physiologically relevant data such

as maximum effective concentration of 1-MCP were evaluated further.

Of these, the equation providing the best fit for all treatment profiles was:
y=a+0.5b(1+erf((logx-c)/(2"(0.5)d))), where x is the applied concentration of 1-
MCP, erf computes the error function of x, y is the estimated percentage of CO2,

and a, b, c and d are constants.

The value of c was used to obtain an objective estimate of the half-
maximum effective concentration of 1-MCP (050) required to reduce the
respiratory activity of the fruit (050 = 103). The relationship between a, b and d

and curve shape was not evident.

The apparent half-maximum effective concentration of the 1-MCP applied
to the control fruit was 3.83 nL L"; while for plastic and wood the half-maximum
effective concentrations were 4.61 and 3.72 nL L". The half-maximum effective
concentration of 1-MCP was doubled due to the effect of corrugated board on the

effective concentration of 1-MCP applied to the fruit (Table 2.2).

These results are further illustrated in figure 2.1. Each value shown is the
average of 6 determinations on a single fruit samples. Vertical lines represent
standard deviation, and are only shown for control fruit (no packing materials) for

clarity (variation for all other treatments was similar).

38

 

Control
Wood
CB
HDPE

I>0I:lo

Percentage (%) CO2
OI)

 

 

 

 

1-MCP concentration (nL L")

Figure 2.1 Percent (%) CO2 accumulation in 1.9 L glass jars after enclosing

fruit for 6 hr with and without packing materials.

39

Table 2.2 Constants a, b, c, and d and coefficient of determination for fit of
002 data from Gran Naine bananas treated with 1-MCP at concentrations

between 5-60 nL L", with subsequent exposure to ethylene for 24 h at 20°C.

 

Values for constants

 

 

Treatments 3 b c d R2 050

Control 0.706 3.266 0.583 -0.322 0.97 3.83 a
HDPE 0.625 3.462 0.663 -0.354 0.98 4.61 a
Wood 0.647 3.708 0.571 -0.479 0.97 3.72 a
CB 0.789 3.407 1.057 -0.196 0.97 11.40 b

 

Treatments with the same letter (within column showing D50 values) are not
statistically different at 1% level (FLSD).

Four days after application with ethylene, control fruit without 1-MCP
reached color stage 5. At that time all fingers from each treatment were
measured for their peel Hue angle (H°) using a colorimeter (Minolta, CR-300,

Japan). A decrease in H° represents a change in peel color from green to yellow.

Results from the H° analysis are summarized in Table 2.3. Treatments within
columns with the same letter are not statistically different at 1% level (FLSD).
Color 1 on the commercial scale corresponds to an H° of approximately 120° for
each lot of fruit; color 5 corresponds to an H° of approximately 91°. Each number
represents the average of 6 determinations, for a single fruit sample.

Changes in peel color (hue angle) not only depended on 1-MCP
concentrations, but also on the type of material present with the fruit in the jars
(Table 2.3). In general, it was observed that concentrations of 1-MCP lower than
5 nL L" occasionally induced uneven ripening and patchy loss of chlorophyll of

fruit within the same treatment dose (data not shown). Concentrations of at least

40

10 nL L" of 1-MCP were needed to significantly reduce (a 50% reduction or
more) fruit response to ethylene for control fruit and fruit with plastic or wood.
For fruit with corrugated board, concentrations of at least 15 nL L" of 1-MCP
were needed to suppress fruit response to ethylene, while concentrations of 20
nL L" were enough to completely block the response of fruit to ethylene even in
the presence of the packaging materials tested. In this test, the corrugated board
in the presence of the fruit showed the most significant effect in reducing the 1-

MCP available for delaying peel color change in response to ethylene.

41

Table 2.3

120 at color stage 1, to when control fruit reached color grade 5.

Degree of reduction in the Hue angle (H°) from its initial value of

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A°H

1-MCP (nL L") Fruit Only Fruit + Plastic Fruit + Wood Fruit + CB
0 27.07 e 27.74 (I 26.91 c 27 d
0.5 26.35 e 26.77 cd 27.01 c 26.22 (I
1 23.16 de 26.31 cd 27.18 c 27.14 (I
2 25.51 de 20.19 bcd 22.55 c 26.78 (I
3 22.54 de 18.34 be 22.5 c 26.43 d
4 21.41 cde 21.52 bcd 21.04 c 26.37 d
5 17.71 cd 17.09 b 20.53 c 26.36 d
10 13.33 bc 12.78 ab 12.38 b 19.84 cd
15 9.2 ab 8.19 a 7.89 ab 13.79 bc
20 5.66 ab 6.69 a 6.36 ab 9.79 ab
30 4.13 a 6.09 a 3.78 a 9.48 ab
40 3.51 a 4.87 a 4.62 ab 5.14 a
60 4.01 a 4.65 a 4.35 ab 4.03 a

 

 

 

 

 

42

 

The data describing the decrease in H° could be empirically fit by several
of the equations as described before. The equation providing the best fit for all
treatment profiles was: y=a+0.5b(1+erf((logx-c)/(2"(0.5)d))), where x is the
applied concentration of 1-MCP, erf computes the error function of x, y is the

estimated change in H°, and a, b, c and d are constants.

The value of c was used to obtain an objective estimate of the half-
maximum effective concentration of 1-MCP (D50) required to reduce the change
in peel color (050 = 103). The relationship between a, b and d and curve shape

was not evident.

The apparent half-maximum effective concentration of the 1-MCP applied
to the control fruit was 8.13 nL L"; while for plastic and wood the half-maximum
effective concentrations were 6.25 and 7.46 nL L". The half-maximum effective
concentration of 1-MCP was increased by nearly 50% due to the effect of
corrugated board on the effective concentration of 1-MCP applied to the fruit.
However, results from Fisher’s LSD test suggest that those differences were

minimal and not significant (Table 2.4).

These results are further illustrated in figure 2.2. Each value shown is the
average of 6 determinations on a single fruit samples. Vertical lines represent
standard deviation and are only shown for control fruit (no packing materials) for

clarity (variation for all other treatments was similar).

43

40

 

 

0 Control
35 ‘ III Wood
0 CB
30 ‘ A HDPE
25 -
°I 20 —
15 -
10 -
5 ..
o I l l l l l I

 

 

 

1-MCP concentration (nL L")

Figure 2.2 Reduction in Hue angle from its initial value of approximately 120°H
at color stage 1 of Gran Naine bananas treated with 1-MCP at concentrations

between 5-60 nL L".

44

Table 2.4 Constants a, b, c, and d and coefficient of determination for fit of H°
data from Gran Naine bananas treated with 1-MCP at concentrations between 5-

60 nL L", with subsequent exposure to ethylene for 24 h at 20°C.

 

Values for constants

 

 

Treatments 3 b c d R2 D50
Control 2.874 22.998 0.910 -0.397 0.99 8.13 a
HDPE 2.695 24.943 0.796 -0.605 0.97 6.25 a
Wood 3.395 23.227 0.873 -0.393 0.99 7.46 a
CB 4.491 22.441 1.133 -0.287 0.99 13.58 a

 

Treatments with the same letter (within column showing D50 values) are not
statistically different at 1% level (FLSD).

The inability of Fisher’s LSD test to detect differences between treatment
means for 050 of H° data might be due to the large fruit-to-fruit variability
observed in the response of banana to 1-MCP within each
treatment/concentration combination. This variability reflects commercial reality in
terms of variability of product and suggests that the results must be interpreted
with caution. Considering that fruit was collected at different times over a period
of several weeks, some experimental variability due to naturally occurring

differences between fruit batches was expected.

The physiological stage of the fruit at the moment of harvest, number of
days from harvest to application of ethylene, environmental conditions during

harvesting, temperature fluctuations during transit, handling, and warehousing

45

condition, can all influence/alter the ripening behavior of the fruit, and therefore

affect its sensitivity to both ethylene and 1-MCP.

To reduce biological variability among fruit batches, fruit at the same
harvest age, same farm location, and season of the year could be selected.
Such a protocol could probably be met if the research was done directly in the
tropics. A local alternative at MSU could be to increase the sample size and
reduce the number of treatments by selecting the ones with more promising

results.

After identifying the range of 1-MCP concentrations that yielded sub-
saturating responses, the next step was to pack sample size boxes containing
about 4.5 Kg of fruit and then to select only those 1-MCP concentrations that, if
reduced slightly by non target materials, would yield a marked change in

response.

46

2.3.2 BANANAS PACKAGED IN CORRUGATED HDPE VS. CORRUGATED
FIBERBOARD BOXES AND TREATED WITH 1-MCP IN 114 L PLASTIC

BARRELS

Control fruit exhibited the expected response to ethylene, and undenNent
an extensive change in peel color, reaching color stage 5 (full yellow with green
tips) five days after treatment with ethylene (Figure 2.3). Color progression for
fruit treated with 1-MCP at concentrations of 5 nL L" and 10 nL L" was clearly
influenced by the type of packaging material used during the exposure to 1-MCP:
treatment of fruit in plastic boxes with 1-MCP prevented peel color change at
both concentrations tested, but if the boxes were made of corrugated board, the

suppression of color change by 1-MCP was largely relieved (Figure 2.3).

Fruit in corrugated board boxes exhibited uneven ripening and patchiness
(data not shown). The effect of 1-MCP treatment was greater for fruit treated at a
concentration of 10 nL L" which suggests that corrugated board absorbed

sufficient 1-MCP from the atmosphere to reduce its effects on the fruit.

No significant differences were detected between fruit in plastic boxes
treated with 1-MCP at 5 nL L" and 10 nL L", suggesting that concentrations as
low as 5 nL L" are enough to inhibit peel color changes when fruit is packaged in
HDPE, and that any interaction between polyethylene based materials and 1-

MCP is minimal and not significant.

In Figure 2.3, each value is the average of 96 individual readings taken
per treatment, vertical lines around each value represent the standard deviations.

Treatments with the same letter are not statistically different at 1% level (FLSD).

47

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Lot1 I
30 T1613? ‘ ”T T”— TWT'T— ‘T T 1"” ‘1
I
25 F‘ Tess * _______ + —
F
20 -..-__-J L_.._ 1 _1-.A_—wr-I
EF
<I 15 --—— -—-——-- -—-- -- -~——— ~ «
6.30
10 -——————~~~ -~ —-~— —- -— ~ ~— ~~~3
3.0a 3“
5 -- t ————-—————
0 I I I E l I 4:
Control fruit CB (5 nL/L CB (10 HDPE (5 HDPE (10
(no 1-MCP) 1-MCP) nL/L1- nL/L1- nL/L1-
MCP) MCP) MCP)
Treatments
35
Lot2
30 28.T3a _ _
23.3b 20.6c
25 e LL —~ — — —-W- —
20 -- - - I — . w— —
FF
<1
15 - .
3.1d 3.7d 1
5 “l— - — - “L r —_'”T__'T
0 I I

 

 

 

 

 

 

 

 

 

 

 

 

 

I

Controlntit CB (5 nL/L CB (10 nUL HDPE (5 HDPE (10
(no 1-MCP) 1-MCP) 1-MCP) nL/L1-MCP) nL/L1-MCP)

Treatments

Figure 2.3 Reduction in hue angle (°H) in Gran Naine bananas from an initial
value of approximately 120°H at color stage 1 as a function of 1-MCP treatment

and package composition on 2 lots of fruit.

48

After ripening to color stage 5 following induction by ethylene, control ntit
respiration was approximately 140 mL C02/ kg.h. Treatment with either 5 or 10
nL L" of 1-MCP prevented rise in fruit respiration in the plastic boxes such that
respiration was approximately 18 mL C02/ kg.h, whereas corrugated board fruit
respiration was approximately 130 mL 002/ kg.h (Figure 2.4). The respiration
rates obtained for both yellow and green bananas are consistent with previous

findings (Kader, 2007).

Consistent with previous results on CO2 production by the individual
fingers in the glass jars, changes observed in respiration rates upon application
of ethylene depended not only on 1-MCP dosage concentration but also on the
type of material from which boxes were made (Figure 2.4). In general,
concentrations as low as 5 nL L" of 1-MCP were enough to prevent climacteric
rise activity of fruit packaged in plastic boxes. This confirms that this type of
plastic material does not absorb appreciable amounts of 1-MCP from its

surrounding atmosphere.

However, at these same 1-MCP dosages, corrugated board seemed to
absorb 1-MCP from the atmosphere, and reduced its availability to the fruit

packed in these boxes.

Treatments with the same letter are not statistically different at 1% level
(FLSD). Measurements began when control fruit had reached color stage 5.
Each value is the average of 6 separate jars (N=6 fruits), and vertical lines

represent the standard deviation of each calculated value.

49

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

T 123.91 b

140 ~ —— ~»—«—~-—-- —~ -—-— —---— — v -
E 120 v — —— —— m —- —
U)
i
E 100 ,_ -— - -— — - f -
9
S 80 — - — - _v- -- -
C
O
1:
g 60 — — ~ — —+
O.
8
n: 40 - ~ ~~~~~~

20 _. _ _ __ L_ __4 _ - j_

0 ' I i T T

Control fruit CB (5 nL/L1- CB (10 nL/L HDPE (5 HDPE (10
(no 1-MCP) MCP) 1-MCP) nL/L1-MCP) nL/L1-MCP)
Treatments
Figure 2.4 Respiration rates as 002 production (mL/kg.h) inside 1.9 L glass

jars after enclosing fruit for 6 hr.

Respiratory activity can be extrapolated to the ripening behavior of fruit:

1-MCP retarded ripening, and the plastic material did not interfere with 1-MCP

action on the fruit, while corrugated fiberboard significantly reduced the actively

amount of 1-MCP in the atmosphere surrounding the fruit.

50

 

2.4 Conclusion

The data confirm that part per billion levels of 1-MCP delays ripening-
associated processes such as change in peel color. Respiration rates depend
not only on initial 1-MCP concentrations in the atmosphere surrounding the fruit
but also on factors affecting 1-MCP concentration during treatment like the type
of packaging material present with the fruit at the time of treatment, whether a
corrugated board box, a Kraft paper pad, wood from pallets where fruit boxes are

stacked, etc.

Findings from this study suggest that corrugated board alters the dose
response because it absorbs some of the 1-MCP present, thus reducing the
effectiveness of low doses of 1-MCP. Polyethylene based (HDPE and LDPE)

materials absorb very little 1-MCP.

51

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httpzllwww.pmra-arla.gc.ca/english/pdf/reg/reg2004-07-e.pdf (accessed on
May 25, 2007).

Raven, P. H., Evert, R. F., and Eichhom, S. E., 1992. Biology of Plants. New
York: Worth. pp. 545-572.

Reid M., Celikel F., McKay A., and Hunter D., 2001. Perishables Handling
Quarterly, Issue No.108 pp.7-9.

Salisbury, F. B., and Ross, C. W., 1992. Plant Physiology. Belmont, CA:
Wadsworth. pp. 357-407, 531-548.

Serek, M., Sisler, E.C., Reid, MS, 1994. Novel gaseous ethylene binding
inhibitor prevents ethylene effects in potted flowering plants. Journal
American Society Hort.Sci. 119, pp.1230-1233.

Simmonds, N.W., Stover, R.H., Harry, R., 1987. Bananas, 3rd edition.
Longmans, London.

Sisler, E.C., Serek, M., Roh, K. and Goren, R. 2001. The effect of chemical
structure on the antagonism by cyclopropenes of ethylene responses in
banana, Plant Growth Regulation 33, 107-110.

Vallejo, F. and Beaudry, R., 2006. Depletion of 1-MCP by ‘non-target’ materials
from fruit storage facilities. Postharvest Biol. Technol. 40, 177-182.

53

CHAPTER 3

COMPARISON OF CORRUGATED BOARD, HDPE, AND WOOD RELATIVE
TO THEIR EFFECT ON THE AVAILABLE CONCENTRATION OF 1-MCP
OVER A PERIOD OF TIME OF 24 H AT 21°C AND RELATIVE HUMIDITIES OF
50%, 80% and >95%

Abstract

Corrugated board, high density polyethylene (HDPE), and wood (Gmelina
arboreus) materials were included in a study to determine their effect on the
available concentration of gaseous 1-methylcyclopropene (1-MCP) in an

enclosed chamber.

The materials were evaluated individually in sealed treatment chambers
under conditions of 21°C and relative humidities of 50%, 80%, and >95%. 1-
MCP gas was added to the headspace at concentrations of 10 and 20 UL L".
Gas concentrations were measured every hour during the first 6 hours of the
experiment, then every 3 hours during the following 6 hours and then every 6

hours until a 24 hour treatment period was completed.

The concentration of 1-MCP declined in the presence of the materials
tested, but the rate at which 1-MCP gas was removed from the chamber
headspace differed markedly. The average percentage loss for HDPE and wood
was between 10-12% at all conditions tested, while for corrugated fiberboard it

ranged from 12% to 94%.

The concentration of 1-MCP at any time t seems to follow a decrease

behavior that can be fitted by the exponential model CI = Coe'kt where CI is the

54

concentration of 1-MCP at any time t, Co is the initial concentration of 1-MCP, e is
the base of the natural logarithm, and k is a constant related to the rate at which

1-MCP gas is removed from the chamber headspace.

In the presence of corrugated fiberboard, and as the relative humidity
increased from 50% to 80%, the value of the constant k (related to the rate at
which 1-MCP gas was removed from the chamber headspace) increased up to
10-fold. As humidity increased further to 95%, a slight decrease was observed.
The value of the constant k doubled as the ratio of material was increased from 4
to 8 kg of corrugated fiberboard / m3 air. An increase of initial concentration from
10 to 20 uL L" reduced by half the value of the constant k. This trend was also

observed in the presence of HDPE based materials.

The loss of 1-MCP in the presence of corrugated board occurred more
readily during the first 9 hours of the treatment period. The mechanism for this
behavior is not yet known, however, transport properties of paper and
paperboard are known to be inherently related to the resistance offered by the
three dimensional structure of paper materials, and are likely affected by
characteristics such as porosity, fiber-void interfacial area (surface area), pore

size distribution, and structural tortuosity.

55

3.1 Introduction

The loss of 1-MCP to non-target materials normally encountered in fruit
storage facilities was first described in the literature by testing the sorptive
capacity of oak, plywood, high density polyethylene (HDPE) and polypropylene
(PP) plastic bin material, corrugated board, urethane insulation and cellulose-

based fire retardant (Vallejo and Beaudry, 2006).

Findings from this study show large differences in absorption of 1-MCP by
the different materials. 0f the bin and box construction materials, those made
from wood or wood fiber adsorbed significant quantities of 1-MCP while plastic
bin material absorbed little to no 1-MCP. Urethane insulation and the fire
retardant did not absorb 1-MCP. lmportantly, wood and corrugated board test

samples dramatically increased depletion of 1-MCP in the test chambers.

Published data on headspace concentrations of 1-MCP in the airspace in
research or commercial treatment chambers is lacking; 1-MCP has been treated
as relatively an inert gas, the assumption being that when the material is added
to an experimental chamber, a small portion of the applied gas is bound to the
ethylene binding sites in the produce and the remainder of the material simply
stays in the airspace of the treatment chamber until it is vented (Sozzi and

Beaudry, 2007).

A series of tests were conducted to evaluate the effect of corrugated
board, wood and HDPE in side-by-slde tests, in a controlled temperature

environment of 20°C and various relative humidities ranging between 50% to

56

saturation (~100%) on concentration of 1-MCP. The objectives of this study are

presented as follows.

Objectives

1- Characterize the effect (if any) of wood, high density polyethylene
(HDPE), and corrugated board on the concentration of 1-MCP during a treatment

period of 24 hours.

2- Evaluate the effect (if any) of the amount of packaging material in the
treatment chamber on the change from initial concentration of 1-MCP during a

treatment period of 24 hours.

3- Determine the effect (if any) of concentration of 1-MCP on the effective
dose available in the treatment chamber in the presence of wood, high density
polyethylene (HDPE), and corrugated board during a treatment period of 24

hours.

4- Compare the effect (if any) of different relative humidities on availability
of 1-MCP when applied in sealed chambers in the presence of wood, high
density polyethylene (HDPE), and corrugated board during a treatment period of

24 hours.

5- Determine how long it takes for packaging materials to absorb 1-MCP.

57

3.2 Materials and Methods

3.2.1 Preliminary characterization of wood, high density polyethylene (HDPE),

and conugated board and their effect on the concentration of 1-MCP.

Packaging materials

A series of experiments were conducted to evaluate the effect of different

materials on the stability of 1-MCP during a treatment period of 24 hours.

Packaging materials tested included: HDPE specimens (1.2x11 cm,
thickness of ~1.77x10'5 m), wood (Gmelina arboreus) cubes (1.5x1.5x1.5 cm)
and corrugated board specimens (7.5x11.5x0.2 cm). Control was an empty jar
tested in the absence of any packing materials. The melina wood pieces were
taken from commercial pallets stored in a ripening facility, the HDPE was taken
from a commercial plastic liner used to pack bananas (Muehlstein lnc., Nowvalk,
CT), the corrugated board was taken from banana boxes having a combined
basis weight of facings of 94 Lb per 1000 ft2 (Packaging Corporation of America).

Materials were conditioned at standard conditions of 20°C, 50% RH for 72
hours to ensure that were in equilibrium. In addition, a condition of 20°C, 80% RH
was included to evaluate the effect of higher RH. To ensure that these conditions
were established and maintained during the experiments, room 125 and one of

the conditioning chambers in room 124 of the Packaging Building were used.

Samples were weighed at the beginning and at the end of the testing
period. The moisture content was determined by drying the corrugated board

and wood samples in an oven at 105 °C for 1 hour, and then cooled in a dry

58

environment and then re-weighed (according to American Society for Testing and
Materials - ASTM 0644). The moisture content of wood and corrugated board

was calculated on a dry weight basis and on a wet weight basis, respectively.

1-MCP

 

The 1-MCP concentration used in these tests was 20 uL L". It was
obtained from a concentrated source of 1-MCP (2000 (IL L") created by adding
10 ml of distilled water to a 0.47 L glass jar containing 0.064 g of SmartFreshTM
(AgroFresh, Springhouse, PA), which had an active ingredient concentration of

3.3%.

The concentration of 1-MCP in the stock preparation was quantified using
gas chromatography (Carle Series 100 AGC) using a 2 m (length) x 2 mm (inner
diameter) column packed with 60/80 Chromosorb OV-103 (Alltech Associates
Inc., Deerfield, IL), and fitted with a flame ionization detector. The flow rates for
the carrier gas (He), H2, and air were approximately 50, 50, and 200 ml min",

respectively. The oven temperature was maintained at 140°C.

A 1-butene gas standard was used to corroborate the concentration of 1-
MCP. To create a 10 uL L" 1-butene standard, 43 uL of pure 1-butene
(Matheson Gas Products, Chicago, IL), was injected into a 4.3 L specially-made

glass chamber fitted with a Mininert valve (Supelco, Bellefonte, PA).

It was assumed that the response factor for 1-MCP (molecular weight of
54.09 g/mol) and 1-butene (molecular weight of 51 g/mol) would be similar. A

standard curve for 1-butene was prepared for a concentrations ranging between

59

1 to 10 pL L", the relationship between 1-MCP and 1-butene was linear
(Appendix A).

Effect of material type on depletion of 1-MQ

The sample materials were placed into 1-L glass Mason jars with metal
lids fitted with rubber septa (Fisher Scientific, Springfield, NJ), 3 jars per
treatment (N=24) were included in the test. The amount of material added to
each chamber headspace was 2 g of HDPE, 6 g of corrugated board and 14 g of

wood.

A sufficient volume of the 1-MCP stock gas was injected into treatment
jars with a headspace volume of 1 L to obtain a target 1-MCP gas concentration
of around 20 uL L". Gas concentrations in the headspace of the treatment jars
were measured after 0, 3, 6, 9, 12, and 24 h. The concentration of 1-MCP in the
airspace of the treatment chambers was measured on a 1000 uL sample

withdrawn by syringe and analyzed using gas chromatography.

Statistical significance was determined using analysis of variance and the
software lnfoStat Release 1.0 (Universidad Nacional de Cordoba, Argentina,
2001). Significant differences among treatment means was done using Fisher’s

Least Significant Difference Test at P<0.1.

6O

3.2.2 Evaluation of the effect of relative humidity, amount of packaging material

in the treatment chamber, and initial concentration on availability of 1-MCP.

After identifying the materials that seemed to have a significant effect on
the availability of 1-MCP, the next step was to increase sample size and

treatment chamber volume. The treatments used are shown in table 3.1.

Table 3.1 Treatments used to test the effects of relative humidity, amount of
packaging material in the treatment chamber, and initial concentration on

availability of 1-MCP.

 

 

 

 

 

Relative Amount of corrugated fiberboard and 1-MCP (initial

Humidity HDPE: kg of material/m3 air space concentration)
50, 80, 95% 4 10 pL L"
50, 80, 95% 8 10 pL L"
50, 80, 95% 4 20 (IL L'1
50, 80, 95% 8 20 (IL L"

 

 

 

 

 

Corrugated board boxes were the commercial “Quad-pack" mini box type
(Dole bananas) with a combined basis weight of facings of 94 Lb per 1000 ft2
(Packaging Corporation of America). Corrugated HDPE boxes were assembled

using a template of the “Quad-pack” mini box type.

The boxes were placed empty in plastic barrels having a volume of 114 L
with lids fitted with rubber septa (Fisher Scientific, Springfield, NJ) and
conditioned for 24 h prior to treatment with 1-MCP. The ratio of mass of

packaging material (kg) per unit volume (m3) of airspace of the treatment

61

chamber was selected to mimic average conditions in commercial forced-air

ripening rooms.

Aqueous salt solutions were prepared with distilled water and chemically
pure salts of magnesium nitrate and sodium chloride were used to generate the
desired relative humidities of 50% and 80%, respectively, in the airspace of the
chambers. The relative humidity was measured using a moisture analyzer

designed to operate with a dew point sensor (General Eastern, Model 8008).

Additionally, all plastic barrels used as treatment chambers were
previously tested for their seal integrity by injecting a known concentration of 1-
MCP in the headspace to obtain a target gas concentration of around 5 uL L".
Gas concentrations in the headspace of the barrels were measured after 24 h.
The headspace levels of 1-MCP declined by ~2% over the 24 h test period

suggesting that the barrels would function as a stable treatment chamber.

A concentrated source of 1-MCP (7,500 (IL L") was created by adding 10
ml of distilled water to a 0.47-l glass jar containing 0.32 g of Smart-Fresh
(AgroFresh, Springhouse, PA), which had an active ingredient concentration of

3.3%. A fresh source of stock gas was prepared for each set of experiments.

A 1-butene gas standard was used to calculate the concentration of 1-
MCP. To create a 10 pL L'1 1-butene standard, 43 uL of pure 1-butene
(Matheson Gas Products, Chicago, IL), was injected into a 4.3-L specially made
glass chamber fitted with a Mininert valve (Supelco, Bellefonte, PA). It was
assumed that the response factor for 1-MCP and 1-butene were similar (Vallejo

and Beaudry, 2006). A standard curve for 1-butene was prepared for

62

concentrations ranging between 1 to 10 uL L", the relationship between 1-MCP

and 1-butene was linear (Appendix A).

The concentration of 1-MCP in the stock preparation was quantified by
gas chromatography (Carle Series 100 AGC) using an oven temperature of
140°C, a 2 m (length) x 2 mm (inner diameter) stainless steel column packed
with 60/80 Chromosorb OV-103 (Alltech Associates Inc., Deerfield, IL), and fitted
with a flame ionization detector. The flow rates for the carrier gas (He), H2, and

air were approximately 50, 50 and 200 ml min", respectively.

Plastic tubing was used to connect the concentrated 1-MCP source
container to a water reservoir. As the gas was removed from the 1-MCP source
container, that same volume was replaced with water from the reservoir, thereby

preventing dilution of the 1-MCP source or the creation of a pressure deficit.

Boxes were placed in a “cross-stacked” pattern. Barrel closure edges
were coated with high vacuum grease (Dow Corning Corp., USA) to ensure
proper gasket sealing. The material was then exposed to 1-MCP for 24 h at
20°C, a sufficient volume of the 1-MCP stock gas was added to the headspace to
obtain a target 1-MCP gas concentration. A gas tight syringe was used to deliver

the 1-MCP through rubber septa.

The concentration of 1-MCP in the airspace of the treatment chambers
was measured on a 1000 pL sample withdrawn by syringe and analyzed using
gas chromatography. Samples were taken every hour during the first 6 hours of
the experiment, then every 3 hours during the following 6 hours, and then every 6

hours until a 24 hour treatment period was completed.

63

3.3 Results 8. Discussion

3.3.1 Preliminary characterization of wood, high density polyethylene (HDPE),

and conugated board and their effect on the concentration of 1-MCP.

Figure 3.1 shows the results for the different materials at conditions of
20°C and 50% RH. In general, the concentration of 1-MCP decreased slightly for
all treatment chambers at a similar rate regardless of the type of material tested.
After 24 hours the initial concentration of 1-MCP had declined by about 11% as
an average for all treatments. Each value is the average of three determinations.

Vertical lines represent standard deviation.

64

 

60~

50*

40+

1-MCP remaining (%)

30
20 .

102

 

 

 

O . I r f I T I I

0 3 6 9 12 15 18 21 24
Time (h)

----<>--- Control ~-III~- Wood -~--A---- HDPE ----o--~ Corrugated board

Figure 3.1 Effects of wood (Gmelina arboreus), HDPE and corrugated board

on 1-MCP concentration at 20°C and 50% RH. Control was a 1-L empty jar.

65

Figure 3.2 shows the results for the concentrations in the glass jars at
conditions of 20°C and 80% RH. Each value is the average of three
determinations. Vertical lines represent standard deviation.

Under these conditions, the difference between corrugated board and the
other materials tested became more evident. After 24 hours, the concentration of
1-MCP had declined slightly for wood and HDPE, and for the control treatment.
For these treatments, the average percentage loss was between 10-12%.

As for the corrugated board, the loss of 1-MCP was estimated to be 10%
within the first 6 h, 27% after 9 h, 33% after 12 hours and 43% at the end of the
24 h exposure period. The apparent reduction of 1-MCP in the presence of
corrugated board occurred within the first 12 hours, and any additional loss
occurred at a much lower rate during the following 12 hours of the exposure

penod.

As expected, change in relative humidity had a significant effect on the
moisture content of corrugated board and melina wood. The moisture content of
corrugated board after 24 h treatment with 1-MCP was 8% when held at 50%
RH, and 11% when held at 80%. For wood, the moisture content was 12% when

held at 50% RH, and 19% when held at 80% RH.

These differences in the moisture content of wood and corrugated board
suggest that the reduction of initial 1-MCP in the headspace of the jars might be
a relative humidity dependent process that is more evident with corrugated board

than it is with wood and HDPE.

66

 

100 c- f
954 i

Nooooco
O'IOO'IO
I———O—III><>

030)
001
ll
1 o, 1 111])"

1-MCP remaining (%)
01
O

 

 

 

O r . . i I I I
0 3 6 9 12 15 18 21 24
Time (h)

--<>--- Control ~--I:I--~ Wood ----A—--~ HDPE -~~o-~ Corrugated board

Figure 3.2 Effects of wood (Gmelina arboreus), HDPE and corrugated board

on 1-MCP concentration at 20°C, 80% RH. Control was a 1-L empty jar.

67

3.3.2 Evaluation of the effect of relative humidity, amount of packaging material
in the treatment chamber, and initial concentration on availability of 1-MCP.

The concentration of 1-MCP in the headspace of the treatment chamber in
the presence of corrugated fiberboard and HDPE boxes at 20°C and 50%, 80%
and 95% RH is shown in Figures 3.3 through 3.5. Each value is the average of
three determinations. Vertical bars represent standard deviation.

In general, it was observed that the effective concentration of 1-MCP was
markedly reduced in the presence of corrugated board, the percentage loss of 1-
MCP over time was greater at higher relative humidities and slightly lower with
increasing initial gas concentrations.

Different relative humidities had a significant effect on the moisture
content of corrugated board. The moisture content of corrugated board at the
end of treatment with 1-MCP was 2.7%, 10.3% and 11.0% when held at 50%,
80%, and 95% RH, respectively. These differences in moisture content suggest
that the reduction of initial 1-MCP in the headspace of the jars is a relative
humidity-dependent process.

Consistent with previous results, there was little interaction between
HDPE and 1-MCP over time. Nonetheless, the relative loss of 1-MCP over time
in the presence of HDPE based materials also increased slightly at higher
relative humidities, the effect of amount of material present or the initial
concentration in the chamber headspace was less evident though. Experimental
error associated with sampling method or injection technique of the sample in the

60 may have caused some differences.

68

A preliminary evaluation of the treatment chambers showed that the
system experienced a loss of 3% over a treatment period of 24 h when the initial
concentration of 1-MCP was 5 pL L" of 1-MCP.

These results suggest that the loss of 1-MCP in the presence of
corrugated HDPE boxes might be explained by interactions of the gas molecule
with the moisture in the airspace and the HDPE material; or might also be an

indication of some molecular instability.

69

 

l

 

 

1!!! II a
o

80 ~ .
g 70 . i
V I?
.3 60
.E
(B
E 50
2
3, 4o
2.
'- 30

20 .

10

0 I I I I I 7

0 3 6 9 12 15 18 21 24
Time (h)

o HDPE-R8-10PPM A HDPE-R8-20PPM o HDPE-R4-10PPM

I:I HDPE-R4-20PPM o CB-R8-10PPM A CB-R8-20PPM

e CB-R4-10PPM I CB-R4-20PPM

Figure 3.3 Effect of amount of HDPE and corrugated board and initial

concentration of 1-MCP on percentage (%) available 1-MCP at 20°C, 50% RH.

70

100

 

 

 

 

. i I 2 i I
90 Q ’ i ! i g g g
I
80- 5 j g It
I!

g 70 . f 1 i
E f I
.E 60 ~ {
c I
i - I
E 50 - I
9 a
95 4o - 1
2. I
t- 30 - i

20 .

10 - 1

O 7 I I I I I IT I
o 3 6 9 12 15 18 21 24
Time (h)

o HDPE-R8-10PPM A HDPE-R8-20PPM o HDPE-R4-10PPM

o HDPE-R4-20PPM o CB-R8-10PPM x CB-R8-20PPM

c CB-R4-10PPM - CB-R4-20PPM

Figure 3.4 Effect of amount of HDPE and corrugated board and initial

concentration of 1-MCP on percentage (%) available 1-MCP at 20°C, 80% RH.

71

I
I
I

100 %

 

 

 

90 - c I o g j g g g g
t . g i §
80 . f t I e a
.. I .
2% 70 _ f O I
OI { ‘ Q
.s 60 ~ I i
.5 L
(U
E 50 -. i
3 I
o.
0 4o - l
2? l
*- 30 ~
20 ~ {
10 ,
0 . I -. I I . I I .
0 2 4 6 8 10 12 14 16 18 20 22 24
Time (h)
o HDPE-R8-10PPM A HDPE-R8-20PPM o HDPE-R4-10PPM
CI HDPE-R4-20PPM e CB-R8-10PPM A CB-R8-20PPM
o CB-R4-10PPM I CB-R4-20PPM

Figure 3.5 Effect of amount of HDPE and corrugated board and initial

concentration of 1-MCP on percentage (%) available 1-MCP at 20°C, 95% RH.

72

Results from Figures 3.3 - 3.5 suggest that:
- The reduction in mass of 1-MCP over time is proportional to mass of 1-
MCP (initial concentration in treatment chamber) and to treatment time.
- Concentration of 1-MCP at any time tseems to follow a declining behavior

that can be fitted by an exponential model (1 ):
ct = cos"1 (1)

where CI is the concentration of 1-MCP at any time t, Co is the initial
concentration of 1-MCP, e is the base of the natural logarithm, and k is a
constant related to the rate at which 1-MCP gas is removed from the chamber

headspace with units given by 1/t.

To remove subjectivity associated with the visual inspection of the plotted
data, some criterion was devised to establish a basis for the fit. Nonlinear
regression techniques are available to directly fit equations to experimental data
directly (Chapra and Canale, 1998). However, a simpler alternative was to use
mathematical calculation to transform expression (1) into a linear form.

Expression (1) was linearized by taking its natural logarithm to yield:

In C(=|n Co-kt (2)
In its transformed state, linear regression was used to fit the model in order to
evaluate the constant coefficient k using the technique of least squares
regression. For a given ratio of mass of packaging material (kg) per unit volume
(m3) of airspace in the treatment chamber, relative humidity, and initial

concentration of 1-MCP; the best fit k values were the ones that minimized the

73

sum of squares of the errors (SSE) between the experimental concentration of 1-
MCP in the treatment chamber and the predicted concentrations using (2).

The best-fit k values are given by (3):

00

SSE = z [In c. — (In co — ktI)]2 (3)
i=1
It can be shown that the partial differential equation of expression (3) with respect

to k can be solved to find the best-fit values using the following expression (4):

co

 

aSSE=0=2Z[tIIn(CI/Co+ktI2] (4)
3k i=1
Solving (4) gives (5):
k=-Zt.ln(Ci/Co) (5)
z 6

Expression (5) gives the experimental k values for a given ratio of mass of
packaging material (kg) per unit volume (m3) of airspace in the treatment
chamber, relative humidity, and initial concentration of 1-MCP. Tables 3.2 & 3.3
provide a summary of the results and also show the sum of squares of the errors
(SSE) between the experimental and predicted concentrations of 1-MCP in the

treatment chamber.

74

Table 3.2 Values of k for the exponential model CI = Coe'kt fit to the

concentration of 1-MCP in the chambers containing HDPE boxes at different
relative humidities (RH), initial concentrations of gas 1-MCP (10 and 20 uL L")
and ratios of packaging material (R = kg/m3).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RH R (kg/m3) 1-MCP (uL L") k (1/h) SSE (IJL L")

4 10 0.004122 0.0020
50 4 20 0.004609 0.0031

8 10 0.009192 0.0147

8 20 0.004935 0.0013

4 10 0.008254 0.0104
80 4 20 0.007393 0.0007

8 10 0.007317 0.0018

8 20 0.006318 0.0044

4 10 0.003537 0.0007
95 4 20 0.002343 0.0004

8 10 0.008218 0.0017

8 20 0.003460 0.001 1

Table 3.3 Values of k for the exponential model CI = Coe'kt fit to the

concentration of 1-MCP in the chambers containing corrugated fiberboard boxes
at different relative humidities (RH), initial concentrations of 1-MCP (10 and 20 uL
L") and ratios of packaging material (R = kg/m3)

 

 

 

 

 

 

 

 

 

 

 

RH R (kg/m3) 1-MCP (uL L" ) k (1/h) SSE (IIL L")
4 10 0.008933 0.0007
50 4 20 0.008833 0.0031
8 10 0.019517 0.0058
8 20 0.008893 0.0008
4 10 0.050360 0.0317
80 4 20 0.024026 0.0018
8 10 0.104053 0.0620
8 20 0.082310 0.0341
4 10 0.038026 0.0000
95 4 20 0.020230 0.0038
8 10 0.093404 0.0076
8 20 0.048189 0.0038

 

 

 

 

 

 

 

 

75

 

These experimental k values were substituted in expression (1) and
the adequacy of the mathematical model for each given ratio of packaging
material (Kg per cubic meter of airspace), relative humidity, and initial
concentration, was tested by plotting the calculated 1-MCP concentration along
with the experimental data collected versus time. Figures 3.6 to 3.17 illustrate
the results obtained. Each value is the average of three determinations. Vertical

lines represent standard deviation.

76

 

.3
O
Lw‘$-I--I—-n

CD

 

 

 

.3 g 2
.J
a 6 II
C
.3
8
II 4~
0
C
O
o
2-.
0 I I f '. I I I
0 3 8 9 12 15 18 21 24

Time (h)

o HDPE exp 0 HDPE calc CI CB exp - CB calc

Figure 3.6 Comparison of experimental and calculated concentration values of
1-MCP in a sealed treatment chamber with a material ratio of 8 kg/m3 and an

initial concentration of 10 uL L" held at 20°C and 50% RH for 24 h.

77

 

NN
ON
1340+—
IBM
G01
IBI'OI
I-B-ll-O-l
lat-01
PEI-01
I-ell
l-OI
+01

_L .3 _s .5 _s
m o N P m m
L 1 1 1 1 1

I'E-I

Concentration (uL L")

«b0?

 

 

0 , I I . . I

0 3 6 9 12 15 18 21 24
Time (h)

 

<> HDPE exp 0 HDPE calc I:I CB exp - CB calc

Figure 3.7 Comparison of experimental and calculated concentration values of
1-MCP in a sealed treatment chamber with a material ratio of 8 kg/m3 and an

initial concentration of 20 uL L" held at 20°C and 50% RH for 24 h.

78

 

 

A A
O N
M—I

 

 

 

PE
0I2323 2 2 § 8
I ,
I7"
Ii 83 II!
3;
8
'5 6
g
C
8
C 4-
o
0
2.
0 I I I I I T
0 3 6 9 12 15 18 21 24

Time (h)

o HDPE exp 0 HDPE calc CI CB exp - CB calc

Figure 3.8 Comparison of experimental and calculated concentration values of

1-MCP in a sealed treatment chamber with a material ratio of 4 kg/m3 and an

initial concentration of 10 (IL L" held at 20°C and 50% RH for 24 h.

79

 

2 2 ..-.-.. _ --.- - - -.... --..._.-......- - - -2
20 i 3 3 1 t I §

§
A
-._|18-
3'14-

Concentration (
_‘L _'L
Ch 0 N
I I

1

 

 

ON-kO)

 

0 3 6 9 12 15 18 21 24
Time (h)

o HDPE exp 4 HDPE calc I:I CB exp . CB calc

Figure 3.9 Comparison of experimental and calculated concentration values of
1-MCP in a sealed treatment chamber with a material ratio of 4 kg/m3 and an

initial concentration of 20 uL L" held at 20°C and 50% RH for 24 h.

80

._x
N

 

 

 

 

f: m I 5
.1 8— 0 Ii
‘3 9,,
O
'8 5 It
*2 II
8 9
E4" I
2, I
1 t
0 I I I I I . 4 .
0 3 8 9 12 15 18 21 24
Time(h)

<> HDPE exp 9 HDPE calc I:I CB exp - CB calc

Figure 3.10 Comparison of experimental and calculated concentration values of
1-MCP in a sealed treatment chamber with a material ratio of 8 kglm3 and an

initial concentration of 10 (IL L" held at 20°C and 80% RH for 24 h.

81

2 2 _._ WWWM .. .. . .. __ - W-, . .-.. ,-,-,-__-,----2 a- ._ ._,- - ._ , 2- WW -m... .W. mums“.-- -_ 2-.-“,

 

 

 

 

18 § if
A lb
.718 -
:.' 11$
314“ El
fi12~ 'im
gm "
.88- t
8 6— Ii
4.. i
2
O ' . l I - 1
o 3 6 9 12 15 18 21 24
Time(h)

<> HDPE exp 0 HDPE calc D CB exp - CB calc

Figure 3.11 Comparison of experimental and calculated concentration values of
1-MCP in a sealed treatment chamber with a material ratio of 8 kg/m3 and an

initial concentration of 20 pL L'1 held at 20°C and 80% RH for 24 h.

82

.3
.b

 

 

 

 

12 §.
A <§§§§§ ’é §
.1110“ m § §
2' M
.8: 8 “a .
E I
E 6 '3 g
8 cu
54 -
0 an
22
O l l T T 1 T i
o 3 6 9 12 15 18 21 24

Time (h)

o HDPE exp o HDPE calc 1:! CB exp - CB calc

Figure 3.12 Comparison of experimental and calculated concentration values of
1-MCP in a sealed chamber treatment chamber with a material ratio of 4 kg/m3

and an initial concentration of 10 uL L'1 held at 20°C and 80% RH for 24 h.

83

 

 

22*
20
18~Q$8$gg .§

A - 8 5
.716 it
" i
314
8124 g
“3 1%
.8104
C
o 6
4
2_
o

 

 

 

T

12 15 18 21 24
Time (h)

o HDPE exp 0 HDPE calc CI CB exp I CB calc

O
09..
C)
(D

Figure 3.13 Comparison of experimental and calculated concentration values of
1-MCP in a sealed treatment chamber with a material ratio of 4 kg/m3 and an

initial concentration of 20 pL L“ held at 20°C and 80% RH for 24 n.

84

 

_|.
A

 

-i
N
;*
H-fl-t
F9101
l-O-I
l-Ol
r01
tel
101

A
O

l—B-l
la

CD
i-B-i
l-E-t
l-E-i

Concentration (uL L‘1)

 

 

 

 

O ' i i r i i . i

O 3 6 9 12 15 18 21 24
Time (h)

<> HDPE exp o HDPE calc Cl CB exp - CB calc

Figure 3.14 Comparison of experimental and calculated concentration values of
1-MCP in a sealed treatment chamber with a material ratio of 8 kg/m3 and an

initial concentration of 10 pL L‘1 held at 20°C and 95% RH for 24 h.

85

 

NN
ON
FOI-I-n
l-C
mm
EhtO-I
1'01
l-Ol
I-e'l
l9
l-Ot
l-GI
afiH———J

 

 

 

18"
lall

r16“
'_|
4314~
5124

10~
g u
8 8*
8 E5
0 6'1

44

2.

o . I T ,

0 3 6 9 12 15 18 21 24

Time (h)
o HDPE exp o HDPE calc l:l CB exp - CB calc

Figure 3.15 Comparison of experimental and calculated concentration values of
1-MCP in a sealed treatment chamber with a material ratio of 8 kg/m3 and an

initial concentration of 20 “L L" held at 20°C and 95% RH for 24 n.

86

 

 

Concentration (pL L“)
O)
l-i-l

 

 

O T I I I l j l

O 3 6 9 12 15 18 21 24
Time (h)

 

o HDPE exp 0 HDPE calc [3 CB exp - CB calc

Figure 3.16 Comparison of experimental and calculated concentration values of
1-MCP in a sealed treatment chamber with a material ratio of 4 kg/m3 and an

initial concentration of 10 uL L'1 held at 20°C and 95% RH for 24 h.

87

 

 

22+ 1
zoéufébfi 2 § § 5

 

 

 

13- a
A BI
'11 16* W
_, W
3144
c W
o 12~
'= 11
E 10~
C
8 61

4a

2.

o r . .

0 3 6 9 12 15 18 21 24
Time(h)

<> HDPE exp 0 HDPE calc [3 CB exp - CB calc

Figure 3.17 Comparison of experimental and calculated concentration values of
1-MCP in a sealed treatment chamber with a material ratio of 4 kg/m3 and an

initial concentration of 20 [L L" held at 20°C and 95% RH for 24 h.

88

 

These results, as plotted in figures 3.6 to 3.17, indicate that the

exponential model Ct = Cne'kt provides an excellent fit to the 1-MCP

concentrations in the chamber headspaces containing the different packaging
materials.

A detailed analysis of the effects of relative humidity, initial concentration
of 1-MCP and amount of corrugated board in the airspace of the treatment
chamber on the experimental k values follows.

The effect of relative humidity on experimental k values is shown in Table
3.3 and illustrated in figure 3.18. It can be observed that as the relative humidity
increased from 50% to 80% the experimental k values differed markedly, up to
10-fold, though a slight decrease was observed at a relative humidity of 95%.

These observations suggest that the relationship between relative
humidity (RH) and the experimental k values is curvilinear (k ~ aRH2 + bRH + c).

The effect of mass of corrugated board relative to air volume (R) on
experimental k values is illustrated in figure 3.19. These results suggest that the
k values are directly proportional to the mass of corrugated board (k ~ R). In
general, the k values doubled as the ratio of corrugated board increased from 4
to 8 kg/ m3.

The effect of initial concentration of 1-MCP on experimental k values is
illustrated in figure 3.20. As observed, an increased in the initial concentration of
1-MCP from 10 to 20 uL L'1 reduced by half the k values, which suggested that
the relationship between initial concentration (Co) of 1-MCP and the experimental

k values is inversely proportional (k ~ 1/Co).

89

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0.12 .
‘ 1 1
. ; l 1 1 1
‘ l
' y = -8E-05x2 + 0.013x - 0.435
-«-4 ----- ~~~42é
0.10 ‘ . I ’ I __;-..--_ - __ a. _W . ‘.\W;W_W
‘ l 4 I” ; ‘2‘:
, ' x’ ‘ i .
I . l
0.08 1%” t ,WWW7I - ~ a? e— _ * W W l -. __ -1
l [I l l l I
l,
., ,’ y = 55-0518 + 0.0096x - 0.3222
3 V _____
a 0.06 WW WL- 1< “1W
> / ‘b ’ ‘\4
x. I , , x
l I I \
I '1 ‘_ ’_,._._ ___~ \\
I, I /‘ ..‘ '''' 1' $ "‘~‘\\ }K
0.04 1- _ ,4" ,4’ , . , ’ ’ y = -5l:'-05x2 + 0.0077x - 0.2559 _ WW.
I ,l I I I I K>
I, /’ A ’ I . t
I r ,’
’ y//’ 5 7 :
’l 4’” “Ln—“z """ 5‘ """ 1’ ~~~~~~~~
0.02 (#1, ' "'— 1 - ’éfib-‘Lfn —1— _A_ _ \ s 3
”l, ’ ’ , , » - r l y = -2E-05)8 + 0.003x - 0.0953
I 2 ’ I I ’ i 1
i’ 3 l l 1 l
0.00 . l ' J, ; , l
50 55 50 65 70 75 80 85 9o 95
Relative Humidity
0 R4-10ppm [:1 R4-20ppm A R8-10ppm >K R8-20ppm

Figure 3.18 Effect of relative humidity on experimental k values in a sealed

treatment chamber with a mass of corrugated board to air volume ratio (R) of 4 or

8 kg/m3 and initial concentration of 1-MCP of 10 or 20 uL L'1 applied at 20°C and

50%, 80%, and 95% RH for 24 h. The best fit equation is displayed next to its

corresponding curve.

90

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0.12 ~ [
y=0.0134x-0.0033
0.10 -~-—---—-—__ .’ /'¥ «a
,"l ,,-" y=0.0138x-0.0174
0.08 —*—*— —~ ~ -- —- mi" ' ,K l
x" a ,-" I
<0 , -’ ,. ‘ y=0.0096x-0.0143
g 0.06 * 5 ~ , - - , 7 7» 3; 2 J],— W
x 'l' . ’l’ i
X /' I’II IQ
0.04 '13 ,3!” 1.; ,Wri’ yl= 0.007x-0.0077 .
é ’ ’ y=0.0026x-0.0017
0.02 -- V’ ____________ T
El_if_‘.'_f,'_°..'_‘.'. ..............................................
y = 0.0005x + 0.0048
0.00 +
2 4 6 8 10
R(kg/m3)

— 20 ppm-50%RH
A 20ppm-80%RH
<> 20ppm-95%RH

[:1 1O ppm-50%RH
>K 10ppm-80°/o
O 10ppm-95%RH

Figure 3.19 Effect of amount of mass of corrugated board to air volume ratio (R)

on experimental k values at initial concentrations of 1-MCP of 10 or 20 pL L‘1

applied at 20°C and 50%, 80%, and 95% RH for 24 h; the mass of corrugated

board relative to air volume ratio (R) varied from 4 to 8 kgl. The best fit equation

is displayed next to its corresponding line.

91

 

0.12 7---- on

 

 

 

 

 

 

 

 

 

 

 

 

 

 

.3
y = 05715537398
ox
0.10 wax: --—-;~ To — w a — —— —
"x “a ' !
\\\\ 5 ‘\\\‘
0,03 "\“l:; -7— misfis‘fi w é — v — a
l \\\ ~“~T.“‘
m y: 0.8429 43.9554 \\ i ~~~~~~~
o ‘* ~~~~~~~
3 l \x l “~~<~>
7.006 ; - — —~~~>~l~\ — —— —-
> I I : “~‘l~~“‘
x A“ 10676 ‘ ‘‘‘‘‘‘ '
‘xs y-o.5885x ' l
0.04 E;~\“ 1‘ ‘ “<:‘:‘:::f — l _. _ 7
‘~\‘7‘ ———————— l ~~~~~~~ T ~~~~~~~ l
-o.9105 ““““ *-----—__ fi‘ “““““““ A
__y"0.3094 * _L ‘4 ~~~~~~~~ f- '
0.02 x ~~~~~~~ 1 1.1339 AFT]
~~r __________ y=0.2657 g
<> l l """"""" r ------------- )‘K
_________ .4.--_._..‘____i_~__--____.‘,.__.__-__-_ -__-:::::—.
0 00 l l y = 0.0218x‘0'3% T
10 12 14 16 18 20

o R4-50%RH
o R8-80%RH

Concentration (ppm)

X R8-50%RH
El R4-95%RH

A R4-80%RH
— R8-95%RH

Figure 3.20 Effect of initial concentrations of 1-MCP on experimental k values

when applied in a sealed treatment chamber with a mass of corrugated board to

air volume ratio (R) of 4 or 8 kg/m3 at 20°C and 50%, 80%, and 95% RH for 24 h.

The best fit equation is displayed next to its corresponding line.

92

 

A similar analysis was conducted for HDPE boxes, it can be observed
from Table 3.2 that (a) the effect of R on k is that k is proportional to R, as with
CB, (b) except for R=8 and 00:10, the effect of RH on k is curvilinear, as with
CB, and (c) the effect of Co on k is an inverse one, just like with CB.

Results from the analysis presented above, suggest that the experimental
values for the constant k related to the rate at which 1-MCP gas was removed
from the headspace of the treatment chamber in the presence of both corrugated
board or HDPE depended on the combined effect of relative humidity, initial
concentration of 1-MCP and mass of material in the airspace of the treatment
chamber.

This combined effect can be expressed by equation (6):

k = (RlCo)(aRH2 + bRH + c) (6)
where k is a constant related to the rate at which 1-MCP is removed from the
headspace of the treatment chamber which units are 1/t (t is time in hours), R is
the ratio of mass of corrugated board or HDPE (kg) per unit volume (m3) of
airspace in the treatment chamber, Co is the initial concentration, RH is the
relative humidity, a, b and c are constants that relate relative humidity (RH) and
the experimental k values.

A calculation was performed to estimate k for a given ratio of packaging
material (kg) per cubic meter of airspace of the treatment chamber, relative
humidity and initial concentration of 1-MCP, substituting (6) in (2) gives (7):

In c, = In co — [(R/Co)(aRH2 + bRH + c)ti] (7)

93

 

Identifying the best a, b and c values was done using the technique of
least squares regression. The best fit a, b and c values were the ones that
minimized the sum of squares of the errors (SSE) between the experimental
concentration of 1-MCP in the treatment chamber and the predicted

concentrations using (8).

w

SSE = Z [In Ci - (In Co — (R/Co)(aRH2 + bRH + c)ti)]2 = O (8)
i=1
Microsoft® GW-BASIC® was used to create a program to solve for a, b
and c values. The best-fit values are shown in table 3.4, the sum of squares of
the errors (SSE) between the experimental and predicted concentrations of 1-

MCP in the treatment chamber is included.

Table 3.4 Best-fit for constants a, b and c and sum of squares of the errors
(SSE) for high density polyethylene (HDPE) and corrugated board (CB) for the
different relative humidities, initial concentrations of gas 1-MCP and ratios of

packaging material tested.

 

Material 3 b c SSE

 

HDPE -0.0582 0.0829 -0.0136 0.0000492

 

CB -1.1017 1.7955 -0.5982 0.000183

 

 

 

 

 

 

 

Fitting expression (8) to the data gives the calculated k values. Tables 3.5
and 3.6 summarize the data obtained and also show the sum of squares of the

errors (SSE) between the experimental and predicted concentrations (units are

94

 

pL L") of 1-MCP in the treatment chamber that resulted from using the calculated

k values.

Table 3.5

initial 1-MCP concentrations and ratios (kg/m3) tested.

Calculated vs. Experimental k values for HDPE at the different RH,

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RH Ratio 1-MCP (uL L'1 ) k calc SSE
4 10 0.005306 0.0037
50 4 20 0.002653 0.0075
8 10 0.010612 0.0171
8 20 0.005306 0.0014
4 10 0.006168 0.0229
80 4 20 0.003084 0.0292
8 10 0.012336 0.0273
8 20 0.006168 0.0046
4 10 0.005027 0.0033
95 4 20 0.002513 0.0005
8 10 0.010053 0.0060
8 20 0.005027 0.0040

 

Table 3.6 Calculated vs. Experimental k values for corrugated board at the

different RH, initial 1-MCP concentrations and ratios (kg/m3) tested.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RH Ratio 1-MCP (pL L") k calc SSE
4 10 0.009645 0.0058
50 4 20 0.004822 0.0012
8 10 0.019289 0.0013
8 20 0.009645 0.0080
4 10 0.053245 0.0300
80 4 20 0.026622 0.0714
8 10 0.106489 0.0490
8 20 0.053245 0.0043
4 10 0.045300 0.0039
95 4 20 0.022650 0.0137
8 10 0.090600 0.0648
8 20 0.045300 0.0111

 

95

 

 

 

These results confirm that the exponential model Ct = Coe'kt is an

excellent fit to the decreasing concentration of 1-MCP observed over time. The
SSE values observed from Tables 3.5 and 3.6 suggest that there was good
agreement between experimental and calculated concentrations of 1-MCP in the
treatment chamber, which suggests that expression (6) provides a good
estimator for the constant k values. Deviations between the experimental and
calculated results were probably more due to experimental error than model
error.

Calculated k values were substituted into expression (1) and the adequacy
of the mathematical model for each given ratio of mass of corrugated board or
HDPE (kg) per unit volume (m3) of airspace in the treatment chamber, relative
humidity and initial concentration, was tested by plotting the calculated 1-MCP
concentration along with the experimental data collected versus time. Figures in
Appendix C illustrate the results obtained.

As observed in figures 3.6 to 3.17, the loss of 1-MCP in the presence of
corrugated board occurred more readily during the first 9 hours of the treatment
period. The mechanism by which 1-MCP decreased in the presence of
corrugated board is not yet known. It is possible, that 1-MCP is absorbed by
glucose-based compounds in the plant cell walls. The a-1,4 glycosidic structure
of cellulosic microfibrils has a cavity roughly similar in size to the cyclodextrin
used in the SmartFresh® formulation (Carpita and McCann, 2000; cited by Vallejo

and Beaudry, 2004).

96

 

Understanding diffusion is important in paperrnaking and end uses of
paper and board. Presently, there is no general analytical model that can
accurately predict the transport properties of fibrous composite structures such
as paper and paperboard (Ramaswamy and Ramarao, 2004). Initially an attempt
was made to model diffusion of 1-MCP through paperboard based on one-
dimensional diffusion theory (please see Appendix B). This model failed to
explain the actual behavior of MCP in the presence of corrugated board.

Paper and paper board are complex three dimensional layered structures
of interconnected pores and cellulose fibers. Therefore, it is reasonable to
expect that 1-MCP might penetrate into the bulk material and interact with it.

In terms of fundamental mechanisms, transport properties of paper are
inherently related to the resistance offered by the three dimensional structure
(Ramaswamy and Ramarao, 2004). Porosity (ratio of void volume to total
volume), for instance, is known to effect permeation of ethylene oxide, a gas
commonly use to sterilize medical devices packaged in paper pouches (T wede
and Selke, 2004).

There might be several reasons to the decrease of 1-MCP concentration
over time at different relative humidities, one of the reasons could be the effect of
RH on changes in the structure of paper. Cellulose fibers are hygroscopic in
nature, swelling of cellulose fibers in paperboard during moisture uptake might
alter the fiber diameter.

There is not generally accepted explanation for the swelling behavior of

fibers in paperboard. It has been suggested that the moisture content of paper

97

and paperboard is highly influenced by capillary condensation (Parker et al.,
2006). Capillary condensation in the fiber walls is not significant at RH lower than
80%, but at RH conditions higher than 80% moisture is directly adsorbed by the
mechanism of capillary condensation (Parker et al., 2006).

Interestingly, it has been reported that fibers are almost impermeable at
relative humidities below 58%, but at higher relative humidities pores as well as
fibers will behave as permeable media (Nilsson, 1993).

It follows, therefore, that as the RH increases (>80%) the fiber swelling will
result in an increase of fiber diameter, while at the same time the pore space is
opened up. This indicates that the molecules of 1-MCP gas diffusing through the
paperboard might encounter a more open structure, easier to penetrate, and
interact with it (Ramaswamy and Ramarao, 2004).

Furthermore, paper fibers have been traditionally treated as hollow
cylindrical objects, but in reality their internal structure is very complex with many
micro-fibrils, then the probability of interactions occurring inside the fibers cannot
be ignored.

In addition to the structure parameters (porosity, fiber-void interfacial area,
and pore size) discussed above, tortuosity is also important. Tortuosity is
defined as the ratio of the actual length of the capillary to the straight line (or the
shortest length) length of the capillary. In porous materials such as paper and
paperboard, the inter-fiber capillaries can be expected to be highly tortuous
(Ramaswamy and Ramarao, 2004). It has been suggested that it is also

possible that shallow pores between almost parallel fiat fiber surfaces act as

98

 

traps inside which the gas molecules have to bounce for a long time before
escaping with a qualitative effect similar to that of sorption (Hellén et al., 2002).

The effect of tortuosity might be more evident at low concentrations of 1-
MCP than at high concentrations as fewer molecules are available in the
headspace of the treatment chamber to be trapped in these tortuous channels
through the sheet, causing the initial concentration to decrease faster. Similarly
this might explain why at higher ratios of corrugated board the initial
concentration of 1-MCP is reduced more readily.

Although the method presented in this research is based on some
assumption, idealization, and limitations, it provides a protocol of practical

significance if applied carefully.

99

3.4 Conclusions

The concentration of 1-MCP declined in the presence of the materials
tested, and the rate and amount of 1-MCP gas removed from the chamber was
dependent on the type of material. The average percentage loss for HDPE and
wood was between 10-12% at all conditions tested, while for corrugated
fiberboard it ranged from 12% to 94%.

The reduction in mass of 1-MCP over time seems to follow a behavior that

can be fitted by the exponential model C. = Coe'kt. The rate at which 1-MCP gas

was removed from the headspace of the treatment chamber is proportional to the
initial mass of 1-MCP in the treatment chamber and to treatment time. It is also
apparently proportional to the mass of material in the headspace of the treatment
chamber, and is proportional to the mass of moisture (RH) present in the
treatment chamber.

The mechanism to explain loss of 1-MCP in the presence of
corrugated board is not yet known, however, transport properties of paper and
paperboard are known to be inherently related to the resistance offered by the
three dimensional structure of paper materials, and are likely affected by
characteristics such as porosity, fiber-void interfacial area (surface area), pore

size distribution, and structural tortuosity.

100

 

Literature cited

Chapra, S., Canale, RP, 1998. Numerical methods for engineers, 3'd edition.
McGraw-Hill, Inc. USA.

Hellén, E.K.O., Alava, M.J., Ketoja, J.A., and Niskanen, K.J., 2002. Diffusion
through Fibre Networks. Journal of Pulp and Paper Science, Vol.28, No.2, 55
—62.

Nilsson, L., Wilhelmsson, B., and Stenstrom, S., 1993. The Diffusion of Water
Vapor through Pulp and Paper. Drying Technology 11(6): 1205-1225.

Parker, M.E., Bronlund, J.E., and Mawson, A.J., 2006. Moisture sorption
isotherms for paper and paperboard in food chain conditions. Packaging
Technology Science 19: 1 93-209.

Ramaswamy, S., and Ramarao, B.V., 2004. 3-D Characterization of the
Structure of Paper and Paperboard and Their Application to Optimize Drying
and Water Removal Processes and End-Use Applications. US. Department
of Energy, DOE Project DE-FCO7—00ID13873 (available on-line).

Sozzy, G.O, Beaudry, RM, 2007. Current perspectives on the use of 1-
methylcyclopropene in tree fruit crops: an international survey. Stewart
Postharvest Review 2:1 0.

Twede, D. and Selke, S., 2005. Cartons, crates and corrugated board: Handbook

of paper and wood packaging technology, pp.107-108. Destech Pub.,
Lancaster, PA. ISBN No. 1-932078-42-8.

Vallejo, F. and Beaudry, R., 2006. Depletion of 1-MCP by “non-target” materials
from fruit storage facilities. Postharvest Biol. Technol. 40, 177 — 182.

101

 

APPENDICES

102

 

APPENDIX A
1-MCP CALIBRATION CURVE

A 1-butene gas standard was used to determine the concentration of 1-
MCP. To create a 10 uL L" 1-butene standard, 43 uL of pure 1-butene
(Matheson Gas Products, Chicago, IL), were injected into a 4.3 L specially-made
glass chamber fitted with a Mininert valve (Supelco, Bellefonte, PA). It was
assumed that the response factor for 1-MCP (molecular weight of 54.09 g/mol)
and 1-butene (molecular weight of 51 g/mol) would be similar (Vallejo and
Beaudry, 2006). A standard curve for 1-butene was prepared for concentrations
ranging between 1 to 10 uL L'1 and it is shown in figure A1. The solid line
represents the regression line fitted using experimental data (dots).

As observed, the equation that adequately describes the relationship between 1-
MCP and 1-butene is linear in the range of 1 to 10 pL L".

y = 1.0134x - 0.0045
R2 = 0.9915

 

1.1000
1.0000 -
0.9000 1
0.8000

0.7000
0.6000

0.5000 ----

Target levels

 

 

0.4000

 

 

0.3000

 

 

 

0.2000 ~

0.1000 —

 

 

 

 

0.0000 ‘ v Y 7 I T ' 1 r
0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1
Actual levels

Figure A1. 1-MCP calibration curve prepared using 1-butene: correlation

between target and actual levels of 1-MCP.

103

 

APPENDIX B

MODEL TO DESCRIBE PERMEABILITY OF 1-METHYLCYCLOPROPENE
THROUGH PAPERBOARD

Diffusion theory basis used for this model

In many packaging applications, the permeability of a polymer membrane
can be described by the following expression:

P=DS a)

where P is the permeability coefficient, D is the Fickian diffusion coefficient, and
S is the Henry's Law solubility coefficient. The permeability coefficient (P) is the
steady-state transport rate of permeant molecules through a polymer membrane
of unit area per unit of thickness and driving force, while the diffusion coefficient
(D) represents how fast the permeant molecules move through the polymer bulk
phase, and the solubility coefficient (S) is a measure of the mass of permeant
molecules sorbed by a unit of polymer mass per unit of partial pressure (Barr,
Giacin and Hernandez, 2000).

The simplest solutions for diffusion-controlled behavior usually correspond
to assuming a semi-infinite medium with a motionless flat interface, initial uniform
concentration, without reactions, and transport controlled by diffusion (Frade,
1997)

For situations in which Fick’s law with a constant diffusion coefficient
applies, the unidirectional flux through a membrane is given in equation (2).

@9= 0 a2_c_ (2)
a 8%

where C is the concentration of the diffusing penetrant, x is the direction in which
the diffusion takes place, and tthe time (Crank, 1975).

Henry's law describes the solubility of a compound present in a gas phase
that is in contact with a solid phase; it states that the concentration of a solute
gas in the solid phase is directly proportional to the concentration (or partial
pressure) of that compound in the contacting gas phase.

For situations in which Henry’s law is obeyed the sorption expression
through a membrane is given in equations (3).

01 = $91 (3)

where c) is the concentration of the gas in the solid phase, S the solubility
coefficient of the substance at equilibrium, and pi the partial pressure of the gas
in the contacting gas phase (Selke, Culter, and Hernandez, 2004).

104

 

Materials and Methods

A concentrated source of 1-MCP gas was created by adding 25 mL of
distilled water to a 0.47-L glass jar containing 0.32 g of Smart-Fresh (AgroFresh,
Springhouse, PA), with an active ingredient concentration of 3.3%.

A gas standard of 1-butene was used to calculate the concentration of 1-
MCP in the headspace of the stock jar. To create a 10 (IL L" 1-butene standard,
43 (IL of pure 1-butene was injected into a 4.3-L specially made glass chamber
fitted with a Mininert valve. It was assumed that the response factor for 1-MCP
and 1-butene were similar.

The concentration of 1-butene and 1-MCP in the stock preparation was
quantified by gas chromatography (Carle Series 100 AGC) with an oven
temperature of 140°C on a 2 m (length) x 2 mm (inner diameter) column packed
with 60/80 Chromosorb OV-103 (Alltech Associates Inc., Deerfield, IL) fitted with
a FID. The flow rates for the carrier gas (He), H2, and air were approximately 50,
50, and 200 mL min", respectively. The actual concentration of 1-MCP in the
stock gas was calculated.

Then a volume of 1-MCP gas from the stock gas was injected into an
empty glass jars (with a headspace volume of 1,000 mL) sufficient to obtain a
target gas concentration of 500 )JL L".

The jar was fitted with a rubber septum by drilling a hole on one of the side
walls. Kraft paper samples with a thickness of 17 mil (0.04318 cm) and a
diameter of 2.2 cm were cut and previously conditioned at 20°C, 90% RH for 24
h. The jar mouth was covered with the conditioned paperboard; the paper lid
was tight against the mouth edges using a threaded metal ring.

The jar, which will be referred to as Chamber 1, was put inside a larger
chamber - Chamber 2 (a high density polyethylene bucket with clamp closures
on the top) with a headspace volume of 20 L at 20°C, 95% RH. The relative
humidity was achieved by pouring 25 mL of water in chamber 2. This second
chamber was fitted with a rubber septum on the top and tight sealed.

The concentration of 1-MCP in the headspace of Chamber 2 was
monitored by gas chromatography, gas samples were taking at intervals of 60 s
for the first 5 min and right afterwards time intervals were increased from 1 min to
5 minutes until equilibrium was reached; this happened 135 minutes after
injecting concentrated 1-MCP in chamber 1.

The figure below illustrates the setup of the experiment:

105

 

 

 

mamber 2\
\ /

 

m

Chamber 1

C)

Figure B1. Setup of an experiment to determine the solubility of 1-MCP
through paperboard.

 

 

 

 

 

106

 

 

Results:
Results are summarized in tables B1 & 82.

Table B1. Concentration of 1-MCP (g/cc) in Chamber 2 after diffusing through a
paperboard membrane — Replicate 1.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Time (m) Time (s) [1 -MCP] in [IL L" [1 -MCP] in g/cc

0 0 0 0.00E+00

1 60 2.9 6.99E-09

2 120 3.5 8.43E-09
3 180 3.5 8.43E-09
4 240 4.05 9.76E-09

5 300 4.65 1.12E-08
7.5 450 5.1 1.23E-08
10 600 5.95 1 .43E-08
15 900 6.25 1.51 E-08
20 1200 7.1 1.71 E-08
25 1500 7.9 1 .90E—08
30 1800 8.45 2.04E-08
40 2400 9.18 2.21 E-08
50 3000 10.1 1 2.44E-08
60 3600 10.23 2.46E-08
70 4200 10.58 2.55E-08
80 4800 1 1.05 2.66E-08
90 5400 1 1 .5 2.77E-08
100 6000 12.2 2.94E-08
1 10 6600 12.55 3.02E-08
120 7200 12.56 3.03E-08
130 7800 12.56 3.03E-08
140 8400 12.56 3.03E-08

 

 

 

 

107

 

Table B2. Concentration of 1-MCP (g/cc) in Chamber 2 after diffusing through a
paperboard membrane - Replicate 2.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Time (m) Time (s) [1-MCP] in )JL L" [1-MCP] in g/cc

0 0 0 0.005+00

1 60 0.43 1.045-09
2 120 1.51 3.64E-09

3 180 2.36 5.69E-09

4 240 2.79 6.72E-09

6 360 4.3 1.04E-08
9 540 6.07 1.46E-08
12 720 7.63 1.84508
15 900 9.25 2.23E-08
18 1080 10.65 2.57E-08
21 1260 11.83 2.85E-08
24 1440 12.74 3.07E-08
27 1620 13.87 3.34E-08
30 1800 14.62 3.52E-08
33 1980 14.95 3.605-08
39 2340 16.02 8.865-08
42 2520 16.29 3.92E-08
45 2700 16.34 3.94E-08
48 2880 16.98 4.095-08
51 3060 17.2 4.14E-08
54 3240 17.2 4.14E-08
57 3420 17.63 4.255-08
60 3600 17.63 4.25E-08
70 4200 18.92 4.56E-08
80 4800 18.92 4.565-08
95 5700 18.92 4.565-08
110 6600 19.14 4.61E-08
125 7500 18.92 4.56E-08
140 8400 19.14 4.61E-08

 

 

 

 

108

 

 

 

As observed in Table A2, steady state was reached 1 h and 10 min after
injection with 1-MCP. The concentration of 1-MCP in the headspace of chamber
2 was monitored for an additional 18 h to verify an airtight seal in chamber 2:

- after 1 h and 30 min the concentration of 1-MCP remained constant (this
is no change from steady state),

- after 6 hours the concentration of 1-MCP declined slightly by 1%,

- after 18 hours the concentration of 1-MCP in the headspace of chamber 2
declined by 5%.

These results suggest that during the first 7 h of the experiment (70 min of
non-steady state plus 6 h after reaching steady state) losses of 1-MCP gas from
the headspace of Chamber 2 were not significant.

However, the 5% loss of 1-MCP detected during the last measurement (18
h after reaching steady state) might be due to either minor leaks in the system or
to reaction of the 1-MCP molecules with the paperboard, which could have
trapped (physically or chemically bound) some of them.

Several methods have been described for measuring the mass transfer
characteristics of polymer films, including a gravimetric technique and an
isostatic permeation procedure (Barr, Giacin and Hernandez, 2000).

From the data collected we attempted to calculate the diffusion and
solubility coefficients. The calculated results obtained in the course of this work
are summarized below.

For constant diffusivity, the mass balance for 1-MCP in the paperboard
reduces to expression (2).

Only in the simplest cases of sorption or desorption from a plane sheet
with constant surface concentration, is it possible to derive formal mathematical
solutions for the diffusion coefficient of this kind. Finite difference methods must
be used to obtain numerical solutions (Crank, 1952) for general cases.

Expressions 2 and 3 presented above must be defined quantitatively
before the numerical work can proceed. For more quantitative information, we
resorted to calculation.

The initial conditions of our experiment are
At t = 0: C1 = Co; C2 = 0, C(x,0) = 0 (3)
where Co is the initial concentration of 1-MCP in chamber 1.
Figure B2 below illustrates the variables involved.

109

 

 

 

Chamber2\
C /

02(t)

C ,t Kraft paper
k.) 5...... 1:
C10)
Chamber1
/b‘\
“\¥ /

 

 

 

 

 

Figure B2. Variable in the experiment to determine the solubility of 1-MCP
through paperboard.

The boundary conditions of our experiment are

 

 

At x = 0: C(0,t) = k C1(t) (4)

At x = ID: ac = V1 & (5)
8x DAk at

Atx=w: _a;=-V2 as; (6)
8x DAk at

where is w the thickness of the material specimen (0.0004318 m), V1 is the
volume in chamber 1 (0.001 m3), V2 is the volume in chamber 2 (0.02 m3), A is
the area of the membrane (0.00038 m2), and k is related to the solubility of 1-
MCP in the paper.

Equation (5) comes from a mass balance for 1-MCP in the headspace of
chamber 1. The rate at which 1-MCP enters the surface x=0 of the paperboard
is given by Fick’s law: -DA (aC/ax). The rate at which 1-MCP is removed from the
headspace is given by — d(C1V1)ldt.

110

 

Equating these two rates and using d_C_1 = 1 it; from (4) gives (5).
dt k at

A similar argument yields (6).
To relate the constant k to solubility, we know from the ideal gas law that:
Pi = fl (7)
V

where

pi = partial pressure of 1-MCP (Pa) in chamber 2
n = number of moles of 1-MCP
R = molar gas constant (8.314 m3 Pa mole" K")
T = temperature (293K for our experiment)
V = volume (in liters)
n can also be expressed as: n= 9! (8)
M
where
c = concentration of 1-MCP in chamber 2
V = volume (liters)
M = molecular weight (54.09 g/mole)
By substituting in expression (7), we get:
pi = IiT_C_= 45,040 C
V
Substituting in expression (4) the concentration of 1-MCP in the paper is:
Cpaper = 45,040 Cheadspace S (9)

Since the product of 45,040 and the solubility coefficient S is a constant value,
equation (9) can be expressed as

Cpaper = k Cheadspace (10)
where k = 45,040S.

111

Prediction of the mmeabilig coefficient

It can be shown that the partial differential equation given by expression
(2) can be solved by the separation of variables method (Arfken, 1985); that
equation and both boundary conditions of our experiment are satisfied by the
following expression‘:

°° 2
. ' 2
C(k,t)= go + z g.[cos(8, x / w) - R1 8, sin(j3l x / w)]e' 5' D“ w (11)
i=1
where the eigenvalues Bi satisfy
2
[Bi-_1__]tanl31 =[_.1_ +_..1_]Bi (12)
R1R2 R1 R2
with
R1: V1 and R2: V2 (13)
kAw kAw

There are an infinite number of eigenvalues satisfying

(i-1)1T < Bi < (i - V2)" (14)

Since the functions cos((3i x / w) — R1 131 sin(Bi x / w) are not orthogonal on (0,w),
the only way to determine the g’s is by collocation.

Microsoft® GW-BASIC® was used to create a program to solve for the
eigenvalues and the 9’s by collocation. The program is shown below.

 

‘ lntemal communication from Dr.Gary Burgess, Professor at the School of Packaging, MSU;
January 31, 2007.

112

 

 

10 I*********** experimental data **************

20 ND=20 : DIM TIME(ND),CONC(ND) 'time vs conc (sec vs kg/m"3)

30 FOR l=1 TO ND : READ TIME(I),CONC(I) : NEXT I

40 DATA (insert data here)

80 W=.0004318 : A=.004536 'thickness (m) & area (m"2)

90 V1 =.001 : CO=.0007612 'Ieft vol (m"3) & initial concentration (kg/m"3)
100 V2=.02 'right volume (m"3)

110 CF=45040! 'Henry's Law conversion factor

120 D=.0000004 : S=.000006 'diffusion coeff (m"2/sec) & solubility (kg/m"3-Pa)
130 CO=CONC(ND)*(V1+V2+CF*S*A*W)/V1 'corrected 60

131 'PRINT CO : STOP

140 0************* eigenvalues ****************

150 R1=V1/(CF*S*A*W) : R2=V2/(CF*S*A*W)

160 NEV=10 : DIM BETA(NEV)

170 FOR l=1 TO NEV : BETA(I)=(I-1)*3.141592654#+.0001

180 DB=.1 : FOR M=1 TO 6

190 Y=(BETA(I)"2-1/(R1*R2))*TAN(BETA(I))(1/R1+1/R2)*BETA(I)

200 IF Y<O THEN BETA(I)=BETA(I)+DB : GOTO 190

210 BETA(I)=BETA(I)-DB : DB=DB/10 : NEXT M

220 'PRINT "beta"l;"=";BETA(i);" error in y="Y

230 NEXT l

240 !************ co'location **************

250 N=NEV+1 : DIM C(N,N+1),G(N)

260 FOR l=1 TO N : C(l,1)=1 :C(I,N+1)=0 : NEXTI

270 FOR J=1 TO N+1 : C(1,J)=1 : NEXT J

280 FOR l=2 TO N : FOR J=2 TO N

290 C(l,J)=COS(BETA(J-1)*(I-1)/NEV)-R1*BETA(J-1)*SlN(BETA(J-1)*(I-1)/NEV)
300 NEXT J : NEXTI

310 FOR l=1 TO N 'solve system of equations

320 PVT=I : FOR K=|+1 TO N : IF ABS(C(K,I))>ABS(C(PVT,I)) THEN PVT=K :
NEXT K

330 FOR J=I TO N+1 : CHG=C(I,J) : C(l,J)=C(PVT,J) : C(PVT,J)=CHG : NEXT J
340 FOR K=1 TO N : IF K=I THEN 360

350 FOR J=l+1 TO N+1 : C(K,J)=C(K,J)-C(K,l)*C(I,J)/C(I,I) : NEXT J
360 NEXT K: NEXTI

370 FOR K=1 TO N : G(K)=C(K,N+1)/C(K,K) : NEXT K

380 'FOR K=1 TO N : PRINT K,G(K) : NEXT K : STOP

390 I************** solution ******************

400 PRINT "time c2-exact c2-exp"

410 FOR l=1 TO ND

420 C2=G(1) : FOR J=1 TO NEV

430 Z=EXP(-BETA(J)"2*D*T|ME(I)/W"2)

440 C2=CZ+G(J+1 )*(COS(BETA(J))—R1*BETA(J)*S|N(BETA(J)))*Z

450 NEXT J : 02=CZ*CO : PRINT TIME(I),02,CONC(I)

460 NEXT I

470 LIST 120 Ok

 

113

 

Identifying the best pair of values for D and S was done using the
technique of least squares regression. The best fit values of D and S were the
ones that minimized the sum of squares of the errors (SSE) between the
experimental concentration of 1-MCP in chamber 2 and the predicted
concentrations using (11).

Tables B3 and B4 show the results of a search for D and S.

Table B3. Best values of D and S within different ranges, using experimental
data from Replicate 1.

Range of D & S Best D Best S SSE P

FOR D=.000001 TO .000002
STEP .0000001

FOR S=.0000015 TO
.000008 STEP .0000005

FOR D=.000001 TO .000002
STEP .0000001

FOR S=.0000085 TO
.000015 STEP .0000005

FOR D=.0000015 TO
.0000035 STEP .0000005

FOR S=.0000015 TO
.000008 STEP .0000005

FOR D=.0000025 TO
.0000035 STEP .0000001

FOR S=.0000015 TO
.000008 STEP .0000005

 

 

2.000E-06 7.500E-06 2.442228 1.500E-11

 

2.000E-06 9.000E-06 2.184647 1.800E-11

 

3.500E-06 5.500E-06 2.179936 1.925E-11

 

2.800E-06 6.500E-06 2.170954 1.820E-11

 

 

 

 

 

 

 

114

 

 

Table B4. Best values of D and S within different ranges, using experimental
data from Replicate 2.

Range of D & S Best D Best S SSE P

FOR D=.000001 TO .000002
STEP .0000001

FOR S=.0000015 TO
.000008 STEP .0000005

FOR D=.000001 TO .000002
STEP .0000001

FOR S=.0000085 TO
.000015 STEP .0000005

FOR D=.0000015 TO
.0000035 STEP .0000005

FOR S=.0000015 TO
.000008 STEP .0000005

FOR D=.0000025 TO
.0000035 STEP .0000001

FOR S=.0000055 TO
.0000075 STEP .0000001

 

 

2.000E-06 7.500E-06 1.539987 1.500E-11

 

1.400E-06 1.300E-05 0.106572 1.820E-11

 

3.000E-06 6.000E-06 0.108755 1.800E-11

 

2.600E-06 7.000E-06 0.103756 1.820E-11

 

 

 

 

 

 

 

The units of S were kg m'3 Pa". The units of D were m2 s". Finally, the
units of P were kg m m”2 s'1 Pa".

As observed in Tables 3 8 4, the best values for D and 8 during the first
test were 2.8x10'6 and 6.5x10'6, respectively. The best values for D and S
during the second test were 2.6x10’6 and 7.0x10'6, respectively.

The permeability coefficient was calculated from expression (1). The
obtained value was 1.82x10'11 kg m rn'2 3’1 Pa‘1 for both tests.

Model validation

After identifying the best values for D and S, the next step was to validate
the model using different concentrations of 1-MCP and relative humidities.
Materials and methods were identical to the ones presented above;
concentrations tested were 100, 200 and 500 uL L", at relative humidities of 10
and 95%.

A glass system device was designed to reduce experimental error and is
shown in figure B3 below.

115

 

 

 

 

 

 

 

 

 

 

 

Valve \
v\ [C j
0“ Valve
101
/"
Chamber 2
(V=3.9L) Paperboard \
membrane \
Chamber 1
C E 050-249 E

Figure B3. Glass system designed to validate the model to describe permeability
of 1-MCP through paperboard.

 

The concentration of 1-MCP in the headspace of Chamber 2 was monitored by
gas chromatography, gas samples were taking at intervals of 120 s for the first 5
min, and then to 3 minutes until equilibrium was reached. Figure B4 illustrates

results.

116

 

60505 ----- kw

50505 - - ~~

40505»-

3.0505 - no - __ .m _____________ ,

 

Concentration (kg/r1?)

ZOE-05 . om — UDUD-~ — —-_ -2. -_ .

1.05.0545 xx--. -4 . 8

 

O¢0E+OO I I I I 7 1

O 15 30 45 60 75 90 105 120 135 150
Time(m)

<> 95%RH—500 ppm Cl 95%RH-200 ppm A 95%RH-100 ppm X 10%RH-100 ppm

Figure B4. Concentration of 1-MCP on chamber 2 after diffusing through a

paperboard membrane at different relative humidities and concentrations of 1-
MCP

Following the procedure developed for our model, we estimated the
solubility (S), diffusion (D) and permeability (P) coefficients at the different
conditions tested (Table B3). The units of S were kg m"3 Pa". The units of D
were in2 s". Finally, the units of P were kg m m'2 3'1 Pa".

117

 

 

Table B5. Predicted values of coefficients S, D and P for 1-MCP through

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

paperboard.
Treatment Replicate Best D Best S SSE P = DS
1 2.50E-07 3.70E-04 0.383665 9.25E-1 1
2 5.50E-07 1 .51E-04 0.17968 8.31 E-11
95%RH-500 uL L" 3 4.50E-07 1.81 E-04 0.353451 8.14E-11
Avg 4.17E-07 2.34E-04 8.57E-11
Std.Dev. 1.53E-07 1.19E-04 5.97E-12
1 2.50E-07 3.60E-04 0.138213 9.00E-11
2 3.50E-07 2.59E-04 2.19E-02 9.06E-1 1
95%RH-200 |JL L" 3 1.50E-07 4.96E-04 5.51 E-02 7.44E-11
Avg 2.50E-07 3.72E-04 8.50E-1 1
Std.Dev. 1.00E-07 1 .19E-04 9.20E-12
1 3.50E-07 2.63E-04 2.89E-02 9.20E-1 1
2 5.50E-07 1.68E-04 3.39E-02 9.24E-1 1
95%RH-100 uL L" 3 5.50E-07 1.56E-04 8.34E-03 8.58E-11
Avg 4.83E-07 1.96E-04 8.91 E11
Std.Dev. 1 .15E-07 5.86E-05 4.67E-12
1 5.50E-07 1.65E-04 1.74E-02 9.07E-1 1
2 1.50E-07 5.33E-04 3.78E-02 8.00E-1 1
10%RH-100 pL L" 3 6.50E-07 1.64E-04 2.64E-02 1.07E-10
Avg 4.50E-07 2.87E-04 8.54E-1 1
Std.Dev. 2.65E-07 2.13E-04 7.64E-12

 

 

 

 

 

 

 

118

 

 

 

Discussion

Results from our model showed almost identical estimated values for the
P coefficient regardless of the relative humidity or initial concentration, similar
results were obtained for the values of D and S.

When comparing these results with the actual behavior of 1-MCP
concentration observed in experiments conducted simultaneously with
corrugated fiberboard boxes (made from the same Kraft paper used for our
modeling experiments) in large treatment chambers we were able to determine
that the proposed model was not adequate to explain the experimental results
obtained from this later system.

The inhomogeneous structure of paper and board complicates the
diffusion analysis. The average diffusion constant of a relatively thick sheet can
be quite different from the diffusion constant of a thin sheet or a thin layer of a
thick sheet (Hellen et al. 2002).

Furthermore, it has been reported that when sorption is significant, steady-
state measurements of the diffusion constant combined with one-dimensional
diffusion theory are not enough to predict the dynamic evolution of diffusion flux
(Hellen et al. 2002).

A pore space diffusion model has been developed to simulate
simultaneous diffusion in heterogeneous porous materials such as paper
containing cellulose fibers and void spaces. A stochastic dynamic approach
along with random walk simulation has been used to model simultaneous
diffusion in the 3D matrix of cellulose fibers and pores. This model is suitable for
simulating simultaneous diffusion in porous materials under a variety of
conditions including low relative humidity where diffusion occurs predominantly
through one medium (i.e. pore space) and high humidity where both mediums
(i.e. fiber and pore spaces) are highly conductive (Ramaswamy and Ramarao,
2004)

Even though the existence of such models is recognized, their use is
complex and calculations are time consuming. As an alternative, we decided to
try an approach that would mimic commercial conditions, which is discussed in
Chapter 3.

119

Literature Cited

Arfken, G. "Separation of Variables" and "Separation of Variables—Ordinary
Differential Equations." §2.6 and §8.3 in Mathematical Methods for Physicists,
3rd ed. Orlando, FL: Academic Press. pp. 111-117 and 448-451, 1985.

Barr, C.D., Giacin, J., Hernandez, R.J.; A determination of solubility coefficient
values determined by gravimetric and isostatic permeability techniques.
Packag. Techn. Sci. 2000; 13: 157-167.

Crank, J.; A theoretical investigation of the influence of molecular relaxation and
internal stress on diffusion of polymers. Journal of Polymer Science, Vol. XI,
No.2, 1952, pp. 151-158.

Crank, J.; The Mathematics of Diffusion. Clarendon Press, Oxford, 1975.

Frade, J.R.; Diffusion in materials with variable temperature - Par l: One-
dimensional problems. Journal of Materials Sciences, Vol.32, 1997, pp. 3549-
3556.

Hellén, E.K.O., Alava, M.J., Ketoja, J.A., and Niskanen, K.J., 2002. Diffusion
through Fibre Networks. Journal of Pulp and Paper Science, Vol.28, No.2, 55
—62.

Ramaswamy, S., and Ramarao, B.V., 2004. 3-D Characterization of the
Structure of Paper and Paperboard and Their Application to Optimize Drying
and Water Removal Processes and End-Use Applications. US. Department
of Energy, DOE Project DE-FCO7-00lD13873 (available on-line).

Selke, S., Culter, J., Hernandez, R., 2004. Plastics Packaging: Properties,
Processing, Applications and Regulations, 2nd Ed. Hanser Pub., Munich.

120

 

 

APPENDIX C

COMPARISON OF EXPERIMENTAL AND ESTIMATED CONCENTRATION OF
1-MCP USING THE CALCULATED k VALUES

 

 

 

E
6 n
8 _ g 8 8 5 g 8
5 9 <>
J" a
'__| 0
_l
1 —<
2’ 6 it
.Q
E
5 4 «
O
C
O
o
2 .
0 I If I I I I l
0 3 6 9 12 15 18 21 24
Time (h)

o HDPE exp . HDPE calc 0 CB exp - CB calc

Figure C1. Comparison of experimental and estimated concentration of 1-MCP
using the calculated k values (R = 8 kg/m3, Co = 10 uL L", 50%RH at 20°C).

121

22

20
18

12
10

Concentration (uL L")

161
14*

(SN-#030)

 

 

90
E0
E0
[IO
(10
I30

0’
0

 

 

I T T I

3 6 9 12 15 18 21 24
Time (h)

o HDPE exp . HDPE calc Cl CB exp - CB calc

Figure CZ. Comparison of experimental and estimated concentration of 1-MCP
using the calculated k values (R = 8 kg/ m3, Co = 20 uL L", 50%RH at 20°C).

122

 

 

 

Concentration (uL L")
O)

 

 

 

0 3 6 9 12 15 18 21 24
Time (h)
o HDPE exp . HDPE calc 1:] CB exp - CB calc

Figure CB. Comparison of experimental and estimated concentration of 1-MCP
using the calculated k values (R = 4 kg/ m3, Co = 10 uL L", 50%RH at 20°C).

123

N
N

 

 

 

 

 

 

190666 9 o
20“ 6 <> 0 6
18m9500 - .
Cl C] '
,:~16 '3
'_l
314
gm-
810
C
§8
O
O 64
4
2,,
0 T I I I I I I
0 3 6 9 12 15 18 21 24
Time(h)

<> HDPE exp 0 HDPE calc Cl CB exp - CB calc

Figure C4. Comparison of experimental and estimated concentration of 1-MCP
using the calculated k values (R = 4 kg/ m3, Co = 20 uL L", 50%RH at 20°C).

124

12

 

 

 

 

10
8999990 9
4: l:l ’ o 0
3'8“ ‘5 ’ i.
E El
.9 6 5
10 B
*2
8
5 4 '-
0
El
22
1“
0— I r . . I
0 3 6 9 12 15 18 21 24
Time(h)

<> HDPE exp o HDPE calc 1:] CB exp I CB calc

Figure CS. Comparison of experimental and estimated concentration of 1-MCP
using the calculated k values (R = 8 kg/ m3, Co = 10 uL L", 80%RH at 20°C).

125

22

 

 

 

 

0
20 55555 -. 5
18 . 6 2)
A16-D'_
:1 ”0'
314— C1..
312 ”U .-
1a
g10 .
E El
8 8
g I
O 6" D L11
4.
22
O I I I I I I I
0 3 6 9 12 15 18 21 24
Time(h)

<> HDPE exp 0 HDPE calc 1:! CB exp - CB calc

Figure C6. Comparison of experimental and estimated concentration of 1-MCP
using the calculated k values (R = 8 kg/ m3, Co = 20 uL L", 80%RH at 20°C).

126

 

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Time (h)
0 HDPE exp 0 HDPE calc [3 CB exp - CB calc

Figure C7. Comparison of experimental and estimated concentration of 1-MCP
using the calculated k values (R = 4 kg/ m3, Co = 10 uL L", 80%RH at 20°C).

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Figure C8. Comparison of experimental and estimated concentration of 1-MCP
using the calculated k values (R = 4 kg/ m3, Co = 20 pL L", 80%RH at 20°C).

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Figure 09. Comparison of experimental and estimated concentration of 1-MCP
using the calculated k values (R = 8 kg/ m3, Co = 10 pL L", 95%RH at 20°C).

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Figure C10. Comparison of experimental and estimated concentration of 1-MCP
using the calculated k values (R = 8 kg/ m3, Co = 20 uL L", 95%RH at 20°C).

130

 

 

 

 

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Figure C11. Comparison of experimental and estimated concentration of 1-MCP
using the calculated k values (R = 4 kg/ m3, Co = 10 uL L", 95%RH at 20°C).

131

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Figure C12. Comparison of experimental and estimated concentration of 1-MCP
using the calculated k values (R = 4 kg/ m3, Co = 20 pL L", 95%RH at 20°C).

132

 

 

   

 

  

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