THE EFFECT of BARRIER PROPERTIES of NON-FOIL RETORT FILMS on SHELF LIFE of OXYGEN SENSITIVE FOODS Mahalaxmi Dharman Clemson University, Mdharma@G.Clemson.Edu

Clemson University TigerPrints

All Theses Theses

8-2011 THE EFFECT OF BARRIER PROPERTIES OF NON-FOIL RETORT FILMS ON SHELF LIFE OF OXYGEN SENSITIVE FOODS Mahalaxmi Dharman Clemson University, [email protected]

Follow this and additional works at: https://tigerprints.clemson.edu/all_theses Part of the Engineering Science and Materials Commons

Recommended Citation Dharman, Mahalaxmi, "THE EFFECT OF BARRIER PROPERTIES OF NON-FOIL RETORT FILMS ON SHELF LIFE OF OXYGEN SENSITIVE FOODS" (2011). All Theses. 1164. https://tigerprints.clemson.edu/all_theses/1164

This Thesis is brought to you for free and open access by the Theses at TigerPrints. It has been accepted for inclusion in All Theses by an authorized administrator of TigerPrints. For more information, please contact [email protected].

THE EFFECT OF BARRIER PROPERTIES OF NON-FOIL RETORT FILMS ON SHELF LIFE OF OXYGEN SENSITIVE FOODS

A Thesis Presented to the Graduate School of Clemson University

In Partial Fulfillment of the Requirements for the Degree Master of Science Packaging Science

by Mahalaxmi Dharman August 2011

Accepted by: Dr. Ronald Thomas, Committee Chair Dr.William Whiteside Dr.Paul Dawson Dr. Anju Rao

ABSTRACT

A simulated food product sensitive to oxygen, which was a mixture of tomato paste, water, and corn oil (2:2:1), was filled into five different barrier coated pouches, a foil barrier and a low barrier pouch. These pouches were thermally processed at 250°F for 30 minutes and stored in darkness under accelerated conditions (45±2°C and

50±2%RH) for up to 180 days.

The simulant was analyzed for lipid oxidation by TBARS and lycopene degradation by colorimetry (L*,a*,b* values and Hue angle). The oxygen permeability

(OP) in all the pouches increased by 5 to 500 fold after retort. TBARS values in all pouches increased throughout storage while the L*, a* and b* values decreased. The samples lost red color and luminosity and became darker. The TBARS and color results correlated well with the OP. Hue angle was significantly different among the pouches except for the low barrier pouch, indicating stability of lycopene in the barrier coated pouches and foil pouch.

The pouches were tested for surface morphology by SEM imaging. Some of the coated low barrier pouches showed a distinct web like cracking, indicating loss of barrier.

All the barrier pouches had minor cracks and fractures on the coated surface after retort, explaining increases in OP and thereby higher lipid oxidation with color degradation.

Shelf life analysis by the linear regression method showed a higher rate of lipid oxidation than loss of color in all the pouches. Shelf life of simulant also coincided well with

TBARS and color data.

DEDICATION

This thesis is dedicated to my parents, teachers and my fiancé. Thank you for all your endless support, inspiration and encouragement throughout this entire journey.

iii

ACKNOWLEDGMENTS

I am grateful to Dr. Ronald Thomas, my advisor and mentor who taught me more than I hoped to learn here at graduate school, without whose support this research work would not have been possible. My success is and will be a reflection of his outstanding abilities as a teacher. Nothing short of this will be adequate to express my gratitude to him. I would also like to thank Dr. Scott Whiteside for the tremendous knowledge and hands on experience I have gained on retort machine and packaging under his guidance. I would like to thank Dr. Anju Rao for being on my committee and providing me with the required raw materials for the project. I would also like to thank Dr. Paul Dawson for being my minor advisor.

I would like to thank Ampac Corporation for providing me with the films. Special thanks to Mr. James Mabry and Ms. Beth Mcgee for all the help with pouch filling on the

Cryovac machine, Mr.Jerry Stoner for help with pouch making and Ralph for the help with the permeation study. I would also like to thank Dr. Young Jae Byun for consistently helping me with ideas for this research. Sincere thanks to Dr. William

Bridges, Dr. Duncan Darby, and Dr. Kay Cooksey for their consultation on many topics in this study. I would like to thank Jeremy Hughes for being a great lab mate and for all the help. Special thanks to Mom, Dad and my Brother for always supporting and believing in me. A very special thanks to my Fiancé for all the patience and for always being there for me. Last, but not the least, a special thanks to Sarah, Amanda, Laura and

Angela for making this journey memorable.

TABLE OF CONTENTS

Page

TITLE PAGE ...... i

ABSTRACT ...... ii

DEDICATION ...... iii

ACKNOWLEDGMENTS ...... iv

TABLE OFCONTENTS ...... v

LIST OF TABLES ...... vii

LIST OF FIGURES ...... viii

CHAPTER

I. INTRODUCTION ...... 1 Literature cited ...... 3

II. LITERATURE REVIEW ...... 4 Food Classification ...... 4 Retort processing ...... 5 Retort packaging ...... 9 Cans...... 10 Glass ...... 10 Rigid plastic containers ...... 11 Pouches ...... 11 Barrier coatings ...... 15 Effect of retort on polymers and coatings ...... 16 Nylon...... 17 EVOH ...... 18 AlOx and SiOx ...... 19 Performance of retorted films with oxygen sensitive foods ...... 20 Oxygen sensitive foods ...... 20 Seafoods ...... 22

Table of Contents (Continued)

Page Curry products ...... 22 Oil ...... 23 Tomato products ...... 25 Literature cited ...... 27

III. MATERIALS & METHODS ...... 35 Film structures ...... 35 Film slitting ...... 36 Pouch making...... 38 Simulant preparation ...... 40 Pouch filling ...... 41 Processing ...... 43 Storage conditions and sampling ...... 44 Color analysis...... 45 TBARS value ...... 46 Oxygen permeability ...... 47 SEM ...... 47 Anti-staining ...... 48 Statistical analysis ...... 48 Literature cited ...... 48

IV. RESULTS AND DISCUSSION ...... 50 Oxygen permeability ...... 50 TBARS value ...... 53 Color analysis...... 56 SEM ...... 65 Anti-staining ...... 66 Relative shelf life prediction ...... 75 Literature cited ...... 82

V. CONCLUSION ...... 87 Literature cited ...... 88

LIST OF TABLES

Table Page

3.1 Recipe for processing ...... 44

4.1 Oxygen permeability (µm gm/[m2-day]) for pouches at 23±2°C and 0±2%RH before and after retort processing ...... 52

4.2 TBARS values (O.D.) over 6 months exposure at 45±2°C and 50±2%RH ...... 55

4.3 L* values over 6 months exposure at 45±2°C and 50±2%RH ...... 61

4.4 a* values over 6 months exposure at 45±2°C and 50±2%RH ...... 62

4.5 b* values over 6 months exposure at 45±2°C and 50±2%RH ...... 63

4.6 Hue angle (Radiance) over 6 months exposure at 45±2°C and 50±2%RH ...... 64

4.7 Linear model equation and estimated shelf-life based on TBARS values at 45±2°C and 50±2%RH ...... 78

4.8 Linear model equation and estimated shelf-life based on L* value at 45±2°C and 50±2%RH ...... 78

4.9 Linear model equation and estimated shelf-life based on a* value at 45±2°C and 50±2%RH ...... 79

vii

LIST OF FIGURES

Figure Page

2.1 Trans-lycopene structure ...... 26

2.2 Reaction pathway of lycopene during processing and storage of tomato powder...... 27

3.1 Un-winding of 26‖ web roll on side 1 of slitting machine ...... 37

3.2 Winding of two 13‖ rolls on side 2 of slitting machine ...... 37

3.3 Two 13‖ webs on pouch making equipment...... 38

3.4 Side view of pouch making machine showing webs coming together, sealing and cooling bars...... 39

3.5 Pouch making equipment with formed pouches on the conveyor table ...... 39

3.6 Small steam jacketed kettle with simulant being emptied ...... 40

3.7 Simulant being stirred in the large kettle ...... 41

3.8 Rotary pouch filling equipment ...... 42

3.9 Volumetric filling of pouch...... 42

3.10 Steam flushing of the filled pouch ...... 43

3.11 Pouches arranged on the crate with the retort machine ...... 44

3.12 L*a*b* color model ...... 45

3.13 Measurement of color value using Minolta colorimeter ...... 46

4.1 Changes in oxygen permeability before and after retort...... 52

4.2 Changes in TBARS values in the different pouches during accelerated storage at 45±2°C and 50±2% RH. Day 0 values are after retort ...... 54

4.3 Changes in L*values in the different pouches during accelerated storage at 45°C and 50±2%RH. Day 0 values are after retort...... 58

viii

List of Figures (Continued)

Figure Page

4.4 Changes in a*values in the different pouches during accelerated storage at 45°C and 50±2%RH. Day 0 values are after retort ...... 59

4.5 Changes in b*values in the different pouches during accelerated storage at 45°C and 50±2%RH. Day 0 values are after retort ...... 59

4.6 Changes in Hue angle (radiance) in the different pouches during accelerated storage at 45°C and 50±2%RH. Day 0 values are after retort .. 60

4.7 SEM images of the outer surface of the film 1-ABC, A is before and B is after retort...... 68

4.8 SEM images of the outer surface of the film 2-HBC, A is before and B is after retort...... 69

4.9 SEM images of the outer surface of the film 3-ABCL, A is before and B is after retort...... 70

4.10 SEM images of the outer surface of the film 4-ABCA, A is before and B is after retort...... 71

4.11 SEM images of the outer surface of the film 5-HBC2, A is before and B is after retort ...... 72

4.12 SEM images of the outer surface of the film 6-PFBC, A is before and B is after retort...... 73

4.13 Microscopic crossectional images(x40) and pictures of the inner layer of film 4-ABCA. A and B are before retort and C and D are after retort .... 74

4.14 Changes in a* values for all films for both before and after retort ...... 75

4.15 Plot of Ln (Optical density) vs. Days for Shelf-life prediction based on TBARS at 45±2°C, 50±2%RH using linear model equation as shown ...... 79

4.16 Plot of Ln (Optical density) vs. Days for Shelf-life prediction based on L*value at 45±2°C, 50±2%RH using linear model equation as shown ...... 80

List of Figures (Continued)

Figure Page

4.17 Plot of Ln (Optical density) vs. Days for Shelf-life prediction based on a* value at 45±2°C, 50±2%RH using linear model equation as shown ...... 80

4.18 Plot of Ln (Optical density) vs. Days for b* value at 45±2°C, 50±2%RH with linear model equation as shown ...... 81

4.19 Plot of Ln (Optical density) vs. Days for hue angle at 45±2°C, 50±2%RH with linear model equation as shown ...... 81

CHAPTER ONE

INTRODUCTION

Consumers around the globe are increasingly looking for convenient, ready- to- eat meals, easy-to-prepare entrees, and shelf stable foods. This demand for instant foods has grown rapidly in recent years. Thermal processing is one way by which shelf-stable foods are produced. Thermal processing of cans is one of the oldest technologies that can ensure commercial sterility and maintain the quality of the product (Williams, T.S.,

2003). With increasing market demand there is more room for creativity and innovation in processing technology and packaging. Retort pouches are a recent innovation and are preferred over cans due to shorter cook time, shelf appeal, and multiple other advantages

(Adams, J.P., & Otwell, W.S., 1982). Allied Development Corporation reported that since 1992 global consumption of pouches each year has exceeded 10 billion pouches and is expected to reach nearly 19 billion by 2011(Allied Development Corporation,

September, 2006). The retort pouch market in the United States is growing at the rate of

13 to 15 percent per year (Gazdziak, S., May 2005). With this growing demand additional innovation is necessary.

Meals Ready to Eat (MRE), military pouches have been in the market since the

1970‘s ( Flexnews, 2007). The primary barrier structure in this pouch is aluminum foil.

Pouches with an aluminum foil layer have ideal barrier properties, but they lack the ability to be microwaved. Aluminum, being opaque, also inhibits the view of the product inside the pouch. Also, it is not possible to co-extrude foil, which increases the number of steps in film making processes (Froio, D., Lucciarini, J., Ratto, J., Thellen, C., &

Culhane, E., 2005). Because of the reasons listed above, non-foil materials are being explored as an alternative to aluminum.

Nylon, ethylene vinyl alcohol (EVOH), polyvinylidene chloride (PVDC), and ethylene vinyl acetate (EVA) are some of the polymers used as barrier layers in non-foil retort pouches. These barrier films provide low permeation to oxygen but can lose their properties when in contact with water. In retort processing water is the main source used to heat and cool the pouch. Co-extruding nylon and EVOH with polypropylene (PP) has helped to maintain the barrier property of these films, but PP does not provide complete moisture barrier. Inorganic metal oxide barrier coatings like AlOx and SiOx and organic coatings are also being used in retort pouches as non-foil barriers. These coatings are deposited on substrates like PET and nylon. Recent studies have shown improvement in barrier property and time-temperature stability for coated films (Felts, J., & Grubb, A.,

1992; Mercea, P., & Bartan, M., 1991) Degradation in barrier property of these films has also been reported due to cracks and pinholes in the coating layer (Chatham, H., 1996;

Erlat, A., Spontak, R., Clarke, R., Robinson, T., Haaland, P., Tropsha, Y., & Vogler, E.,

1999).

It is important to evaluate the performance of barrier films with respect to the oxidation rate of a food product. The oxygen permeability of a film alone cannot be used to predict the shelf life of a food product. The purpose of this study was to determine the shelf life of an oxygen sensitive food product contained in AlOx and organic barrier coated retort pouches compared to a standard foil barrier pouch.

Literature cited

Adams, J. P., & Otwell, W. S. (1982). Suitability of seafoods to retort pouch processing. Paper presented at the Proceedings of the Seventh Annual Tropical and Subtropical Fisheries Technological Conference of the Americas, January 11-14, 1982, New Orleans, Louisiana, 48.

Allied Development Corporation. (September, 2006). Global retort pouch consumption,1992-2011.

Chatham, H. (1996). Oxygen diffusion barrier properties of transparent oxide coatings on polymeric substrates. Surface and Coatings Technology, 78(1-3), 1-9.

Erlat, A., Spontak, R., Clarke, R., Robinson, T., Haaland, P., Tropsha, Y., & Vogler, E. (1999). SiOx gas barrier coatings on polymer substrates: Morphology and gas transport considerations. The Journal of Physical Chemistry B, 103(29), 6047-6055.

Felts, J., & Grubb, A. (1992). Commercial‐scale application of plasma processing for polymeric substrates: From laboratory to production. Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 10(4), 1675-1681.

Flexnews. (2007). Retort pouch – A fast-growing packaging technology in today's consumer world.

Froio, D., Lucciarini, J., Ratto, J., Thellen, C., & Culhane, E. (2005). Developments in high barrier non-foil packaging structures for military rations. Paper presented at the Proceedings of Flexible Packaging Conference,

Gazdziak, S. May (2005), Retort pouches heating up. Retrieved April 02, 2011.

Mercea, P., & Bartan, M. (1991). The permeation of gases through a poly (ethylene terephthalate) membrane deposited with SiO2. Journal of Membrane Science, 59(3), 353-358.

Williams T.S. (2003). Understanding the retort sterilization process – steam air retorts. Retrieved April 04, 2011.

CHAPTER TWO

LITERATURE REVIEW

Food Classification

Microorganisms play an important role in determining the shelf-life of a food product. To reduce the level or growth of microbes, food is processed by 1) increasing the temperature of food by holding at elevated temperature, 2) decreasing the temperature of food by freezing or refrigeration, 3) removing water present in food and thereby reducing the moisture content and water activity, and 4) using barriers in the form of packages to maintain the quality of pre-processed food (Holdsworth, S.D., & Simpson,

R., 2007).

Today, processed or commercial foods are basically classified into refrigerated, shelf-stable, and frozen. The shelf-stable foods are further classified on the basis of water activity (Aw) and pH. These are the two most important criteria that govern the process requirement (Rahman, S., 2007b). Also, both of these factors help in regulating biochemical, chemical and microbiological reactions.

Aw is the measure of the amount of free moisture present in the product. It ranges from 0-1.0, 0 being completely dry of no active water and 1.0 being pure water. Food can have free and bound moisture. Free water presence helps the growth of microbes

(Ronalds, B., 2011). To stabilize the Aw to 0.85 or below food is either concentrated, freeze dried, dehydrated or subjected to solutes. In these conditions growth of bacteria like Clostridium botulinum and Staphylococcus aureus are inhibited. Mold also ceases to

4 grow in such environments. Water activity of 0.85 or below is considered ideal for shelf- stable food. For food with high Aw i.e. above 0.85 the process requirement is based on pH (FDA, 2010; Rahman, S., 2007b).

According to the Code of Federal Regulation (CFR) Title 21, volume 2, PART

114 ACIDIFIED FOODS, there are various definitions and classifications of food with respect to pH and Aw. Foods with pH 4.6 or below are considered to be Acid foods.

Acidifed foods are low-acid foods with Aw above 0.85, which are modified by adding acids or acidified food to bring the finished equilibrium pH to 4.6 or below. In these foods, microbes are easily destroyed due to the acidic environment and hence they require lower processing times and temperatures. These food are usually hot-filled or pasteurized because mold, spores and yeast have low resistance to heat. However in low- acid foods where pH is above 4.6 and Aw above 0.85, there is more opportunity for the growth of spore forming bacteria like Clostridium botulinum which can produce the deadly botulism toxin in food making it lethal upon consumption (FDA, 2010; Rahman,

S., 2007a). From 1950-96 there were 1087 cases of botulism in the United States.

Clostridium botulinum in low-acid food is a heat resistant microbe and hence is thermal or retort processed at high temperature and pressure for longer time to achieve sufficient bacterial lethality (U.S. Department of Health and Human Services, 1998).

RETORT PROCESSING

Sterilizing food in containers by using heat as a medium is considered old technology. This technology was invented in the early 1800s in France by Nicholas

Appert. The food was preserved in glass jars and bottles. During that time the reason for food spoilage was not really known. Later in 1860 Pasteur discovered the presence of microorganisms (Tucker, G., & Featherstone, S., 2011). Retort processing was previously carried out in metal cookers and containers. With the emerging technology, there has been a major breakthrough in the processing equipment, techniques, and packaging

(Simpson, R., 2008).

The retort process is a steam based process. It utilizes steam as the heating medium applied directly or indirectly to the food container. Steam is considered one of the best heating media (Williams, T.S., 2003). It condenses on the container surface, thereby releasing a high amount of latent heat. It is very important to achieve commercial sterilization during retort processing. Commercial sterility is defined by CFR as The condition achieved by the application of a heat, irradiation, high-pressure, or other process, alone or in combination with other ingredients or treatments, to render the product free of microorganisms capable of growing in the product at nonrefrigerated conditions (over 50 °F or 10 °C) at which the product is intended to be held during distribution and storage. The target microbial destruction levels are usually expressed as

Fo value. Which is the time required at a given temperature to achieve a specific reduction in the microbial population. This value differs from food to food and is based on various physical and biochemical factors like pH, Aw, texture, viscosity, headspace air and also the size of the container (Chambers, J.V., 1993). The temperature and time are then calculated by inserting a thermocouple into the container during processing. The time and temperature data is then used to determine product heating factors and the

6 appropriate thermal process. Sterilization temperatures range from 110-130°C and the cook time is typically above 20 minutes (Richardson, P.S., 2001; Tucker, G., &

Featherstone, S., 2011).

Retort equipment can be mainly classified as batch or continuous. Further, they are classified on the basis of heating medium, container type (i.e. static or rotary), and orientation. Batch retort allows independent control of temperature and pressure. Types of batch retort include saturated steam retort, steam/air retort (static or rotary), full water- immersion retort (static or rotary), cascading water/sprayed water retort (static or rotary) and crateless retort (Williams, T.S., 2003). Continuous retorts allow faster processing throughout than batch retort. Here the food container enters through one end and after processing exits through the other. These are further classified as hydrostatic, hydrolock, reel and spiral retorts generally used in the canning industry (Tucker, G., & Featherstone,

S., 2011).

Irrespective of the style of retort process, the basic principle remains the same.

The retort machine should have an environment where temperature and pressure can be controlled and be consistent with every run, which in turn should reduce the probability of survival of targeted microbes in all the packages at the same time and rate. Also, the process environment should maintain the integrity of the sealed food till the end of the cycle such that the process fluid does not enter through the intact seal, thereby causing contamination (Richardson, P.S., 2001).

Heat transfer in a package containing food depends on the viscosity and movement of food in the pack. A package containing solid food like beans, rice, canned

7 fish and meat have air gaps and also do not have any movement. These foods are heated at a very slow rate and lack uniform distribution of temperature throughout the package.

This takes place due to temperature gradients formed from the geometric center to the wall of the package. This type of heating is conduction heating, and usually such food products are processed in a still retort where there is less agitation (Tucker, G.S., 1991).

Products that are less viscous and free flowing are easy to heat. These food products generally do not require agitation as they have a natural tendency to flow in the direction of convective current, which is formed by the difference in temperature at the wall of the package and the core. This type of heating is called convection heating. During convective heating the products are agitated to facilitate the process of heat transfer which saves on production time. The most common motion used is end-over-end rotation which results in high heat transfer (Parchomchuk, P., 1977). Food products with starch as an ingredient are usually heated partly by conduction and partly by convection this process called broken heating. Ingredients which are thick like starch, gets gelatinized during convection and later it is heated by conduction. Here, the heat transfer in the package is mostly convection first and then conduction (FSIS USDA, 2005; Knap, R.P.,

& Durance, T.D., 1999).

Heat penetration studies are essential before processing different products or packages. The product cannot be heated too long as it may adversely alter the flavor and nutritive quality of the food. It is necessary to get the ideal heating and cooling rate while the populations of microbes are inactivated. As mentioned above, the type of product and profile of package affects the heat penetration. During heat penetration studies the actual

8 package with product is subjected to different time-temperature profiles. The package is fixed with a thermocouple to record the heat at the cold spot which is usually the geometric center of the retort pouch. Once the temperature and pressure data are collected from the retort machine and package, these are used to make time-temperature plots. The data is analyzed to determine the ideal time-temperature and pressure for processing

(Pakola, R.J., 2002). Recently, computer simulation models are being used that determine thermal diffusivity to predict the history of product temperature at any specified location within the package for any set of processing conditions and package profile (Richardson,

P.S., 2001).

RETORT PACKAGING

Packaging plays an essential role in thermal processing. The geometry and the material of the package or container influence the time-temperature profile, production time, food quality and cost. The most critical factor irrespective of material or profile is the seal integrity. The ability of the package to maintain sterility of the product during and after processing is of paramount importance (Holdsworth, S.D., & Simpson, R.,

2007).

Deformation of the container during processing is one of the major problems.

This can be managed by controlling variables like time, temperature and pressure. Apart from this, there are various other factors which can influence container deformation, like headspace volume, gas pressure, property of material with respect to temperature

(stretching or shrinking) and initial gas present in the product (Robertson, G.L., 2006;

Zeuthen, P., & Bøgh-Sørensen, L.,2003).

Cans

Metal cans have played a significant role in the canning industry, the use of which grew tremendously after the American Civil War. The double seaming of cans was patented in 1896, and afterwards products like pineapple and soups were canned

(Robertson, G.L., 2006). Metals mainly have a high mechanical strength and ability to withstand high temperatures. Today, metals like aluminum and tin-free steel have been widely used in canning. The tin-free steel cans are coated with chromium and chromium oxide (Holdsworth, S.D., & Simpson, R., 2007). Cans are also lacquered internally to prevent corrosion of the body. Organic coatings like vinyls and epoxides are also being used to provide corrosion protection (Brody A.L., 1999). There are various processes to manufacture cans like end manufacture, three-piece, and two-piece. These differ in side seams and number of components.

Glass

Nicholas Appert in the 1800‘s first used glass jars and bottles to preserve food by thermal processing. Glass is considered the oldest and cheapest option for packaging.

Glass jars usually have metal lids. During retorting it is essential to have the correct

10 overpressure to avoid lid deformation or opening. Also, it is essential to pre-heat the glass before retorting to prevent breakage by shock (Holdsworth, S.D., & Simpson, R., 2007).

Rigid plastic containers

Plastic cups or trays are currently being used as single portion or snack packs.

They are mainly made of polypropylene (PP) and polyethylene terepthalate (PET). Other barrier materials like polyamide (Nylon), ethylene vinyl alcohol (EVOH) and poly vinyl chloride (PVC) are incorporated to improve barrier properties (Holdsworth, S.D., &

Simpson, R., 2007). The lids on these cups are usually peelable and made of polymer.

Easy-to-pull metal lids are also used. Oxygen scavengers are being added in the form of sachets into the bowls and trays to improve the shelf-life of food (Morvillier, M.R., 2000

). Companies like Del Monte have started using retortable cups for their fresh-fruit products. These cups have an easy peel lid made from barrier materials (Forcinio, H.,

2006). Introduction of microwaveable bowls by the Campbell Soup Company has created a revolution in retort packaging. The main concern for the cups is the seal integrity. The seals of the cups need to be strong enough to withstand high pressure but should be easy to peel open (Hoss, D., 2002).

Pouches

Flexibles in retort packaging have created a stir in the canning industry. This started in 1959 at the U.S. Military Natick Development Center. In 1962, the Continental

11 can company, supplied 40,000 pouches to the U.S military (Stern, M., Hanemann, W., &

Eckhouse, K., 1981). Retort pouches became commercial in Europe and Japan before the

U.S., which was in 1977. The development of the retort pouch has led to replacement of

C-ration in cans by meal ready-to eat (MRE) pouches. Retort pouch materils are usually produced by lamination. The most common materials used to make pouches are PET, PP,

EVOH, nylon and foil .All these materials have good thermal stability and varied barrier properties (Hoss, D., 2002).

William J.R et al.,(1982) performed an economic comparison of canning to retort pouch for fruit and vegetable products with respect to packaging, distribution and processing steps. They concluded that the overall capital cost for a retort pouch packaging system is low compared with an existing or new canning line. Due to the small profile of pouches, a lower freight cost is incurred during transportation. In addition, the processing and packaging system for retort pouches reportedly is less energy intensive compared with canning (Williams, J.R., Steffe, J.F., & Black, J.R., 1982). Article by Li

Pack Corporation Ltd, mentioned that the retort pouch system had a labor reduction over canning (Sacharow, S., 2003). Due to their thin profile, pouches require less time to reach the cook temperature as compared with cans or glass jars (Al-Baali, A.G., & Farid, M.,

2006). The time for processing in a pouch can be reduced as much as 50% .The product in a pouch retains better color and flavor with less nutrient loss(Williams, T.S., 2003). As compared to cans, pouches are environment friendly as they take up less space in a landfill (Hoss, D., 2002; Jun, S., Cox, L.J., & Huang, A., 2006).

The most common type of retort pouch being used is a 3-ply laminate consisting of polyester/aluminum foil/polyolefin. Here the outer (12µm thick) layer polyester has a good printability characteristic. The middle layer foil is considered to be a standard barrier of 7-9µm thickness and the inner layer polyolefin is either cast polypropylene

(CPP), PP, polyethylene (PE) or a co-polymer of the two of 70-100µm thickness used as a sealant. It also provides strength, flexibility and compatibility with food (Robertson,

G.L., 2006). Another common structure used is PET/Oriented PA/Al/CPP. Here, PA

(nylon) is used to increase the durability of the pouch (Selke, S.E.M., 2003). Foils are mainly used in MRE pouches as they have to survive extreme conditions. Ohmic heating is being used in MRE pouches. This has eliminated the use of the chemical hydration reaction of anhydride that was used for heating. Here the pouches contain two foil tabs with electrical contacts that are attached to a heating unit. The electricity through the tabs flows into the product causing the particles to vibrate, and generate heat. The food is heated at 121°C for the required time. Foil pouches also have pull tabs and zip locks which have improved their functionality ( Jun, S., Cox, L.J., & Huang, A., 2006).

Replacing foil as a standard barrier was a significant step in retort packaging.

Non-foil barrier pouches have a major functional utility of being microwaveable over foiled structures (Schirmer, H.G., 1990). The transparency provided by non-foil structures helps in visual inspection of the filled product as compared to opaque foil pouches (Ossian, W.F., 1987). Transparency also helps the consumer to see the product before buying. Foil based multilayer films have to undergo multiple lamination steps, while non-foil multi layer structures have the advantage of being made by different

13 process like co-extrusion or lamination. Technologies like thermal isolation that allows co-extrusion of polymers with different melting points can help reduce processing steps, thereby adding the advantage of cost reduction for manufacturing single step, non-foil structures over multi-step foil structures (Froio, D., 2004). MRE pouches with foil as one of the layers are being used in the battle field. These pouches undergo high impact due to air-drop causing stress induced factures and pinholes in the foil layer. Non-foil pouches can overcome high impacts in such situations thus maintaining physical integrity. Having foil based films in web form limits pouch forming and filling processes. They are difficult to deep draw during horizontal form fill seal (HFFS), and being shallow drawn results in chances of spillage of food into the seal bars while filling (Froio, D., 2004;

Froio, D., Lucciarini, J., Ratto, J., Thellen, C., & Culhane, E., 2005). Product filled in non-foil retort pouches have the advantage of being able to be processed by various techniques like high pressure pasteurization, microwave sterilization and radio frequency sterilization. These techniques have shown improvement in product quality. From a sustainability point of view foil based structures generate more waste as they are non- recyclable. About 14,117 tons of packaging waste per year are generated by the Army,

Air force and Marine Corps by consumption of MRE rations. Non-foil, biodegradable film structures are also being studied as alternatives to reduce environmental impact

(Froio, D., 2004; Operational rations of the department of defense., May 2010).

The common structures used for non-foil pouches are PET/Oriented PA/CPP,

Oriented PA/PVDC/CPP, and Oriented PA/EVOH/CPP. Oriented PA, PVDC and EVOH are susceptible to moisture and hence lose their oxygen barrier property (Mokwena, K.K.,

Tang, J., Dunne, C.P., Yang, T., & Chow, E., 2009). Usually EVOH is coextruded with

PP to improve the barrier. There have been various inventions in non-foil retort films to improve their properties. The Soldier Science Center has conducted studies with biodegradable and recyclable polymer nanocomposites with the intent of using them for

MRE bags. They have successfully developed EVOH and LDPE nanocomposites with improved barrier and mechanical properties. Chaotic blending/smart blending techniques are being developed which allows altering polymer morphologies ( Froio, D., Lucciarini,

J., Ratto, J., Thellen, C., & Culhane, E., 2005). A novel technique to improve the barrier of PVDC is also being developed. PVDC is encapsulated in a second layer of polymer which protects downstream equipment and allows control of temperature, thereby avoiding PVDC degradation. This technique has improved the barrier by 40% ( Froio, D.,

Lucciarini, J., Ratto, J., Thellen, C., & Culhane, E., 2005). An improved version of aromatic polyester liquid crystalline polymer (LCP) has been developed which has 50-

100 times more barrier than PET ( Froio, D., Lucciarini, J., Ratto, J., Thellen, C., &

Culhane, E., 2005).

Barrier coating

Barrier coating technology has developed significantly after the introduction of non-foil retort pouches. It allows deposition of a thin layer onto the polymeric film.

Common barrier coatings are aluminum oxide (AlOx) and silicon oxide (SiOx), and the substrates used are mainly PET or PP. These coatings are deposited by physical vapor deposition or by plasma-enhanced chemical vapor deposition of gaseous organosilane

15 and oxygen onto the substrate. The vapor deposited coatings of AlOx and SiOx have poor resistance to flex and cracks, which affects the barrier property (Bull, M., Steele, R.,

Kelly, M., Olivier, S., & Chapman, B., 2010; Lange, J., & Wyser, Y., 2003). There has also been research done with transparent SiOx coating on polyvinylalcohol (PVOH).

PVOH is water soluble and is embedded in between high water barrier materials. This structure has given good barrier to oxygen and water vapor ( Froio, D., Lucciarini, J.,

Ratto, J., Thellen, C., & Culhane, E., 2005). The barrier properties of AlOx have been enhanced by changing the chemical composition to aluminum oxynitride (AlOx Ny) fabricated on a PET substrate by reactive magnetron spluttering. This technique has been reported to greatly improve the barrier to oxygen and water due to the absence of macro- defects ( Froio, D., Lucciarini, J., Ratto, J., Thellen, C., & Culhane, E., 2005). Organic coatings have been developed with the idea to incorporate barrier functionality in the ink or adhesive layer. Polymers like PA, polyurethanes and polyacrylates are being used as binders in ink formulation. For adhesives, polyurethane and polyacrylate are proposed to be used (Lange, J., & Wyser, Y., 2003).

EFFECT OF RETORT ON POLYMERS AND COATINGS

The polymeric materials used for pouches need to maintain good mechanical and barrier properties during processing and throughout storage. The films also need to be flexible enough to transfer pressure onto the food product, so that it does not undergo stress crack or fractures (Galotto, M., Ulloa, P., Guarda, A., Gavara, R., & Miltz, J.,

2009). Seal strength of the pouch should be maintained to achieve good package

16 integrity. Schauwecker, A. et al (2002) reported the effect of high pressure processing

(HPP) at ≥200MPa, ≥90°C for 10min on MRE pouches (PE/Nylon/Al/PP). The structure showed delamination between PP/Al layers and was incompatible for HPP (Hernandez,

R.J., 1994; Schauwecker, A., Balasubramaniam,V., Sadler, G., Pascall, M., & Adhikari,

C., 2002). Only a few barrier polymers in the food industry are known to survive the extreme retort processing conditions. They are Nylon, EVOH, PET, PP, AlOx and SiOx

(Koutchma, T., Song, Y., Setikaite, I., & Juliano, P., 2010).

Nylon

Nylon is considered to have a superior barrier to gases and flavors with good mechanical and thermal property. Nylon 6 has a hydrophilic group present in its polymeric chain and hence tends to absorb moisture easily. The water molecules act as a plasticizer degrading the gas barrier property of the polymer (Hernandez, R.J., 1994).

Water molecules form clusters in the polymer region disrupting its crystalline structure and creating more free space for dissolution of oxygen (Hernandez, R.J.,& Gavara, R.,

1994). Biaxially oriented polymers have been shown to improve barrier properties.

Orientation causes stretching and alignment of the molecular chain which leads to stress- induced crystallization and tortuosity of the permeation path (Zhang, Z., Britt, I.J., &

Tung, M.A., 2001). Biaxially oriented nylon nylon (BON) has an improved barrier over non-oriented nylon (Massey, L.K., 2003).

Halim L et al.,(2009) investigated the effect of pasteurization, HPP and retort processing on the barrier property of Nylon 6 (N6), Nylon6/EVOH and Nylon

6/Nonocomposites (N6/Nano) all coextruded with PP. N6 and N6/Nano showed higher oxygen permeability after retort processing as compared with other processes, while

Nylon 6/EVOH was delaminated after retort (Halim, L., Pascall, M., Lee, J., & Finnigan,

B., 2009). Koutchma T. et al., (2010) studied HP-HT and thermal retort (at 121°C) on oxygen barrier of Nylon/PP; PET/Al/CPP and Nylon/Al/PP. There was an increase in oxygen transmission rate (OTR) for all the pouches by approximately 10-fold over control values. Retort processing was concluded to subject pouches to more abusive conditions as compared with HP-HT process (Koutchma, T., Song, Y., Setikaite, I., &

Juliano, P., 2010).

EVOH

EVOH and EVOH copolymers are both used in retort packaging for their high barrier to oxygen. EVOH copolymer has a hydroxyl group present in its polymer chain. It has a high degree of crystallinity due to a high amount of inter and intra molecular cohesive energy and less free space. Hence, oxygen molecules cannot permeate through the material. But the presence of a hydroxyl group in the material gives it a hydrophilic nature. Water molecules are easily attached to these hydrophilic groups, thereby decreasing the moisture barrier property of EVOH ( López‐Rubio, A., Hernández‐Muñoz,

P., Gimenez, E., Yamamoto, T., Gavara, R., & Lagarón, J. M., 2005). Koros W.J. (1990) reported about ―retort shock‖ on EVOH films causing hydrogen bond interaction with water molecules. Extreme shock has a severe effect on degree of crystallinity, orientation, damage in the amorphous phase hydrogen bond network and formation of crystalline

18 domains. This decreased the barrier to oxygen by 300% even a year after retort (Koros,

W.J., 1990).

López-Rubio. et al.,(2005) investigated the six grades of EVOH based films coextruded in PP for gas barrier properties and morphological alterations after retort processing (120°C /20min). Higher grade EVOH (high copolymer ethylene fraction) showed increasing oxygen permeability as compared with lower grades (low copolymer ethylene fraction).They also proposed a water induced plasticization process

(López‐Rubio, A., Hernández‐Muñoz, P., Gimenez, E., Yamamoto, T., Gavara, R., &

Lagarón, J. M. 2005). Hernandez and Giacin.,(1998) reported a 60 fold increase in oxygen transmission rate for 12µm PET/15µm EVOH/60µm CPP film structure after retort processing (125°C/25min) (Bull, M., Steele, R., Kelly, M., Olivier, S., & Chapman,

B., 2010 ; Hernandez, R., & Giacin, J.,1998).

AlOx and SIOx coating

As previously mentioned, AlOx and SiOx coatings have poor stress crack and flux resistance, leading to decrease in barrier property. There have been very few studies done to determine the effect of retort (121°C/30psi) processing on barrier coatings. Byun

Y. et al., (2010) compared the oxygen barrier of AlOx and SiOx coated films after retort

(121°C/206.84kPa). Permeability for SiOx film increased 10 fold compared to control films, and AlOx permeability increased slightly but still maintained good barrier ( Byun,

Y., Bae, H. J., Cooksey, K., & Whiteside, S., 2010).

Bull M.K et al., (2010) investigated the effect of HP-HT processing on multilayer films for barrier property. Of the 11 films six had barrier coatings (AlOx and SiOx) and the remaining had barrier films like oriented nylon and foil. The barrier coated films post- processing showed tremendous decrease in barrier property. This was associated with the pressurization and depressurization during processing, causing damage to coatings and the films ((Bull, M., Steele, R., Kelly, M., Olivier, S., & Chapman, B.,2010). AlOx coated PET when subjected to HPP showed cracks and pinholes in the films, significantly affecting the mechanical and oxygen barrier property ( Galotto, M., Ulloa, P., Guarda, A.,

Gavara, R., & Miltz, J., 2009).

Chatcham.H, (1996) reviewed and determined that permeation of oxygen through high barrier coatings is mainly through pinholes and micro cracks in the coating layer

(Chatham, H., 1996). Erlat A.G et al.,(1999) also concluded in their study using SiOx gas barrier coating on PET that transportation of oxygen and water vapor through the coating occurs through nanoscale defects in the coating ( Erlat, A., Spontak, R., Clarke, R.,

Robinson, T., Haaland, P., Tropsha, Y., & Vogler, E., 1999).

PERFORMANCE OF RETORTED FILMS WITH OXYGEN SENSITIVE FOODS

Oxygen sensitive foods

Fats, oils and proteins are considered to be highly susceptible to oxidation. On exposure to oxygen the food products lose their physical and chemical characteristics

(Kilcast, D., & Subramaniam, P., 2000a). Change in color of carrots, tomato and meat products takes place because of oxidation of pigments like β-carotene, lycopene and

20 myoglobin, respectively (Mancini, R.A., & Hunt, M.C., 2005; Marković, K., Hruškar,

M., & Vahčić, N., 2007a). Products like virgin olive oil, canola oil, atlantic salmon and potato chips contain fats and oils which upon oxidation become rancid, imparting an off- flavor (Morales, M., Rios, J., & Aparicio, R., 1997; Pangloli, P., Melton, S.L., Collins, J.,

Penfield, M.P., & Saxton, A.M., 2002; Richards, A., Wijesundera, C., & Salisbury, P.,

2005). Change in texture due to oxidation of deboned turkey meat and processed fruits have also been reported (Bolin, H.R., & Huxsoll, C.C.,1989; Smith, D.,1987).

The rate of oxidation is influenced by temperature. In a study conducted to analyze the effect of temperature on oxidation of sunflower oil and rapeseed oil encapsulated in a glassy food matrix, it was determined that at 67°C and 60°C there was a decrease in linoleic acid concentration and an increase in lipid hydroperoxides as compared with low temperature exposure (Crapiste, G.H., Brevedan, M.I., & Carelli,

A.A., 1999; Sink, J., 1973)). Khattab A. H. et al., (1964) studied the effect of time and temperature on ground nut, sesame, butter and cottonseed oil. On heating these oils at

197°C for 3h, there was a distinct increase in peroxide value for all of them. Color loss in tomato juice was accelerated with an increase in temperature and time (Khattab,A.H., El

Tinay, A.H., Khalifa, H.A., & Mirghani,S., 1974). Formation of flavor compounds like alkanals was attributed to thermal degradation of hydroperoxies and peroxy radicals, which were considered to be initial products of fats that were oxidized thermally (Sink,

J.,1973).

Seafoods

Since the introduction of tuna in retort pouches by the Starkist Co, there has been increasing demand to pack various seafoods like salmons, mussel and black clam, etc in retort pouches. Lipid oxidation is considered to be one of the main factors for degradation in fish quality. Fish have high amounts of unsaturated fatty acids which are susceptible to oxidative rancidity, in turn giving off-flavor and color change. Salmon in barrier coated retort pouches showed an increase in TBAR and a*value (color) during storage at

37.7°C.This was influenced by the increase in oxygen permeability into the pouches

(Byun, Y., Bae, H. J., Cooksey, K., & Whiteside, S., 2010). In a study on ready-to-eat mussel meat product, there was an increase in free fatty acid (FFA) and TBA content after retort processing, even though the value was considered to be within the prescribed limit ( Bindu, J., Srinivasa Gopal, T., & Unnikrishnan Nair, T., 2004) .

Curry products

Indian curried products which consist of a mixture of spices and oil with seafood are being retort processed in pouches. Several studies have been conducted to determine the process temperature and shelf-life of these products (Venugopal, K., 2006). Products like ready-to-eat black clam after being vacuum packed and retort processed in pouches showed a gradual increase in TBA and FFA content after 12 months exposure at room temperature. The sensory attributes like flavor, succulence, toughness and fibrosity of the sample was considered acceptable at the end of storage (Bindu, J., Ravishankar, C., &

Srinivasa Gopal, T., 2007). Similarly, for fish curry after retort processing in pouches and

12 month storage, the product was considered acceptable with respect to sensory evaluation ( Gopal, T., Vijayan, P., Balachandran, K., Madhavan, P., & Iyer, T., 2001). In a comparison study of thermal processing of prawn ‗kuruma‘, it was observed that pouches retained better quality than cans (Mohan, C. O., Ravishankar, C. N., Srinivasa

Gopal, T. K., & Bindu, J., 2008).

Oil

Unsaturated fatty acids undergo auto-oxidation by chemical reaction between oxygen and lipid alkyl radical. This reaction consists of three steps : initiation, propogation and termination. Initiation involves formation of free radicals which in the propogation step react with oxygen to form hydroperoxides. Termination is the last step where the reaction ends by the breakdown of hydroperoxides into secondary products like malonaldehyde, alkenes and alkadienals which give off-flavor because of the formation of compounds like nonanal, decenal, 2-heptenal and trans-2-octenal (Chi-Tang, H., & and , Chen,Q., 1994; Choe, E.,& Min, D.B., 2006; Carter, J.S., 2011).

Oxidative stability of oil is affected by several factors such as degree of

1 3 unsaturation of lipids, availability and types of oxygen ( O2, O2), heat, light, radicals, phospholipids, monoglycerides and diglycerides, amino acids, enzymes, chelators, and antioxidants. Linolenic acid is considered to be more sensitive to oxidation as compared with linoleic and oleic acids due to a higher degree of unsaturation ( Allen, J. C.,

Hamilton, R. J., & Berger, K.G., 1994; Chi-Tang, H., & Chen, Q., 1994; Choe,E., &

Min, D.B., 2006; Dawson, P., 2010 ; Kilcast, D., & Subramaniam, P., 2000b). Corn oil

23 and sunflower oil consist of high poly unsaturated fatty acid content with greater amounts of linoleic acid (56% and 78%) as compared to olive oil and coconut oil (10% and 2%), hence they are more susceptible to oxidation (Zamora, A., 2005; Baur, J., & Brown, H.,

1945)

Nobile D.M.A. et al., (2003) studied the influence of packaging (shape and material) on oxidation kinetics of PET and glass bottled virgin olive oil. The rate of oxidation was dependent on the initial partial pressure of oxygen present in the headspace of the bottles and the permeation rate of oxygen through the bottle walls. Bottles with nitrogen flushing and oxygen scavenger in the walls were considered to extend the shelf life of oil (Nobile, D.M.A., Bove, K., Notte, L., & Sacchi, D.,2003). Concentration of oxygen in oil is dependent on the partial pressure of oxygen in the headspace (Andersson,

K., 1998). If the partial pressure is high then the amount of dissolved oxygen in oil also increases, thereby increasing oil oxidation (Min, D.B & Wen, J., 1983).

Dry fermented sausages made with added olive oil and antioxidants packed in a vacuum system showed low oxidation with less volatile compound formation as compared with those packed in aerobic condition (Ansorena, D., & Astiasaran, I., 2004).

Kaya, A.et al., (1993) studied the shelf life of sunflower and olive oil in PET and glass packages. The oxidation rate was determined using peroxide value (PV).The shelf-life of oil in a colored glass container was higher than clear glass while PET showed the lowest oxidative stability(Kaya, A., Tekin, A.R.,& Öner, M.D., 1993).

Tomato products

Tomato (Lycopersicon esculentum) from the family Solanaceae is a red or green colored ripe fruit. About 5-10% of the fruit is made of dry matter, which includes 1% skin and seeds. Approximately 50% of the dry matter is made of reducing sugars like glucose, fructose and low quantities of other sugars like sucrose, galactose and xylose.

The remaining half of the dry matter contains proteins, pectins, cellulose, hemicellulose, organic acids, pigments, lipids, vitamins and minerals (Petro-Turza, M., 1986). More than

80% of tomato that is processed is consumed in the form of tomato juice, paste, puree, catsup, sauce and salsa. Tomatoes can be processed to extract juice either by a hot or cold break method (Thakur, B., Singh, R., & Nelson, P.,1996). Further, based on water content in the juice, puree or paste is formed. Processed tomato consists of different level of soluble solids with paste having 24% or more (Gould, W.A., 1978).

Lycopene present in tomato belongs to the family of carotenoids. These are red, yellow and orange colored pigments. Carotenoids are chemically divided into two classes, i.e. carotenoid species and xanthophylls. Carotenoid species consists of highly unsaturated hydrocarbons like lycopene, α-carotene, β-carotene, γ-carotene, and δ- carotene. They are usually red or orange in color. These species of carotenoid are present in an unsaturated form and hence are considered highly susceptible to oxidation

(Xianquan, S., Shi, J., Kakuda, Y., & Yueming, J., 2005).

Lycopene with chemical formula C40H56 is an acyclic open chain polyene compound consisting of 13 double bonds of which 11 conjugated double bonds are arranged linearly. The presence of double bonds increases the ability to quench singlet

25 oxygen and trap free radicals thereby increasing anti-oxidant activity (Foote C.S., &

Denny, R,W., 1968; Mortensen, A., & Skibsted, L.H., 1997; Stahl, W., & Sies, H.,1996).

Lycopene is present in various geometrical isomers, mainly cis and trans forms. Figure

2.1 shows the trans-lycopene structure. Lycopene in nature occurs in the all-trans configuration. Degradation of lycopene is caused by isomerization and oxidation

(Akanbi, C., & Oludemi, F., 2004; Boskovic, M.A., 1979). During isomerization of the seven bonds, all-trans form is converted into mono and poly-cis forms. This takes place in the presence of heat, oxygen and light. Boskovic M.A (1979) proposed a reaction pathway for degradation of lycopene during processing and storage of tomato powder

(Figure 2.2). All-trans lycopene (ATL) is considered to be the most stable form as its molecules are arranged in a linear array. This imparts a deep red color to the compound.

On cooking, heating and drying processes, ATL undergoes thermal isomerization and is converted to mono or poly-cis forms. Cis form twists the molecule making it energy-rich and unstable. Cis-form is less red in color compared to ATL. During storage this cis-form is reisomerized to ATL or autoxidized followed by depletion. In the later stage ATL undergoes autoxidation forming degradation products which are small molecules imparting discoloration and hay like off-flavors (Boskovic, M.A., 1979; Marković, K.,

Hruškar, M., & Vahčić, N., 2007b).

Figure 2.1. Trans-lycopene structure

Figure 2.2. Reaction pathway of lycopene during processing and storage of tomato powder (Boskovic, M.A., 1979)

Literature cited

Akanbi, C., & Oludemi, F. (2004). Effect of processing and packaging on the lycopene content of tomato products. International Journal of Food Properties, 7(1), 139-152.

Al-Baali, A. G., & Farid, M. M., (2006). Sterilization of food in retort pouches Springer Verlag.

Allen, J. C., Hamilton, R. J., & Berger. K.G. (1994). Rancidity in foods. In (pp. 68) Aspen Publishers.

Andersson, K. (1998). Influence of oxygen concentration on lipid oxidation in food during storage. Chalmers University of Technology.

Ansorena, D., & Astiasaran, I. (2004). Effect of storage and packaging on fatty acid composition and oxidation in dry fermented sausages made with added olive oil and antioxidants. Meat Science, 67(2), 237-244.

Baur J., & Brown, J. (1945). The fatty acids of corn oil. Journal of the American Chemical Society, 67(11), 1899-1900.

Bindu, J., Ravishankar, C., & Srinivasa Gopal, T. (2007). Shelf life evaluation of a ready- to-eat black clam (villorita cyprinoides) product in indigenous retort pouches. Journal of Food Engineering, 78(3), 995-1000.

Bindu, J., Srinivasa Gopal, T., & Unnikrishnan Nair, T. (2004). Ready‐to‐eat mussel meat processed in retort pouches for the retail and export market. Packaging Technology and Science, 17(3), 113-117.

Boskovic, M. A. (1979). Fate of lycopene in dehydrated tomato products: carotenoid isomerization in food system. Journal of Food Science, 44(1), 84-86. doi:10.1111/j.1365-2621.1979.tb10011.x

Bolin, H. R., & Huxsoll, C. C. (1989). Storage stability of minimally processed fruit. Journal of Food Processing and Preservation, 13(4), 281-292. doi:10.1111/j.1745- 4549.1989.tb00107.x

Brody A.L. (1999). Packaging of foods. (pp. 1611)

Bull, M., Steele, R., Kelly, M., Olivier, S., & Chapman, B. (2010). Packaging under pressure: Effects of high pressure, high temperature processing on the barrier properties of commonly available packaging materials. Innovative Food Science & Emerging Technologies, 11(4), 533-537.

Byun, Y., Bae, H. J., Cooksey, K., & Whiteside, S. (2010). Comparison of the quality and storage stability of salmon packaged in various retort pouches. LWT-Food Science and Technology, 43(3), 551-555.

Carter.S.J (2011). Lipids: Fats, oils, waxes, etc..Retrieved 04/17, 2011, from http://biology.clc.uc.edu/courses/bio104/lipids.htm

Chambers J.V., N. P. E. (1993). Principles of aseptic processing and packaging Food Processors Institute (Washington, DC).

Chatham, H. (1996). Oxygen diffusion barrier properties of transparent oxide coatings on polymeric substrates. Surface and Coatings Technology, 78(1-3), 1-9.

Chi-Tang, H. and , Chen.Q (1994). Lipids in food flavors-an overview. In (pp. 2-14) ACS Publications.

Choe, E., & Min, D. B. (2006). Mechanisms and factors for edible oil oxidation. Comprehensive Reviews in Food Science and Food Safety, 5(4), 169-186.

Code of Federal Regulation (CFR) Title 21, Volume 2, PART 114ACIDIFIED FOODS (2010).

Crapiste, G. H., Brevedan, M. I. V., & Carelli, A. A. (1999). Oxidation of sunflower oil during storage. Journal of the American Oil Chemists' Society, 76(12), 1437-1443.

Dawson.P., (2010) Mechanisms of lipid oxidation ,Clemson university,FD SC 810

Nobile, D.M., Bove, S., La Notte, E., & Sacchi, R. (2003). Influence of packaging geometry and material properties on the oxidation kinetic of bottled virgin olive oil. Journal of Food Engineering, 57(2), 189-197.

Forcinio.H. (2006). Shelfstable packing.Packaging Machinery technology.

Foote, C. S., & Denny, R. W. (1968). Chemistry of singlet oxygen .7. quenching by beta- carotene. Journal of the American Chemical Society, 90(22), 6233-&.

Froio, D. (2004). Nanocomposites research for combat ration packaging.

Galotto, M., Ulloa, P., Guarda, A., Gavara, R., & Miltz, J. (2009). Effect of High‐Pressure food processing on the physical properties of synthetic and biopolymer films. Journal of Food Science, 74(6), E304-E311.

Gopal, T., Vijayan, P., Balachandran, K., Madhavan, P., & Iyer, T. (2001). Traditional kerala style fish curry in indigenous retort pouch. Food Control, 12(8), 523-527.

Gould, W. A. (1978). Quality evaluation of processed tomato juice. Journal of Agricultural and Food Chemistry, 26(5), 1006-1011.

Halim, L., Pascall, M., Lee, J., & Finnigan, B. (2009). Effect of pasteurization, High‐Pressure processing, and retorting on the barrier properties of nylon 6, nylon 6/Ethylene vinyl alcohol, and nylon 6/Nanocomposites films. Journal of Food Science, 74(1), N9-N15.

Hernandez, R. J. (1994). Effect of water vapor on the transport properties of oxygen through polyamide packaging materials. Journal of Food Engineering, 22(1-4), 495- 507.

Hernandez, R., & Giacin, J. (1998). Factors affecting permeation, sorption, and migration processes in package-product systems. Food Storage Stability, , 269–330.

Hernandez, R. J. (1994). Effect of water vapor on the transport properties of oxygen through polyamide packaging materials. Journal of Food Engineering, 22(1-4), 495- 507. doi:DOI: 10.1016/0260-8774(94)90050-7

Hernandez, R. J., & Gavara, R. (1994). Sorption and transport of water in nylon-6 films. Journal of Polymer Science Part B: Polymer Physics, 32(14), 2367-2374. doi:10.1002/polb.1994.090321407

Holdsworth, S. D., & Simpson, R. (2007). Thermal processing of packaged foods Springer Verlag.

Hoss.D. (2002), Hand book on Flexible packaging., 19-25.

Jun, S., Cox, L. J., & Huang, A. (2006). Using the flexible retort pouch to add value to agricultural products.

Kaya, A., Tekin, A. R., & Öner, M. D. (1993). Oxidative stability of sunflower and olive oils: Comparison between a modified active oxygen method and long term storage. Lebensmittel-Wissenschaft Und-Technologie, 26(5), 464-468. doi:DOI: 10.1006/fstl.1993.1091

Khattab, A. H., El Tinay, A. H., Khalifa, H. A., & Mirghani, S. (1974). Stability of peroxidised oils and fat to high temperature heating. Journal of the Science of Food and Agriculture, 25(6), 689-696. doi:10.1002/jsfa.2740250610

Kilcast, D., & Subramaniam, P. (2000a). The stability and shelf-life of food. (pp.47-255) CRC.

Kilcast, D., & Subramaniam, P. (2000b). The stability and shelf-life of food. (pp. 279- 306) CRC.

Knap, R. P., & Durance, T. D. (1999). Thermal processing of suspended food particles in cans with end-over-end agitation. Food Research International, 31(9), 635-643. doi:DOI: 10.1016/S0963-9969(99)00037-X

Koros, W. J. (1990). Barrier polymers and structures: Overview. Paper presented at the ACS Symposium Series, , 423 1-21.

Koutchma, T., Song, Y., Setikaite, I., Juliano, P., Barbosa-Cánovas, G. V., Dunne, C. P., & Patazca, E. (2010). Packaging evaluation for high-pressure high-temperature sterilization of shelf-stable foods. Journal of Food Process Engineering, 33(6), 1097- 1114. doi:10.1111/j.1745-4530.2008.00328.x

Lange, J., & Wyser, Y. (2003). Recent innovations in barrier technologies for plastic packaging a review. Packaging Technology and Science, 16(4), 149-158. doi:10.1002/pts.621

López‐Rubio, A., Hernández‐Muñoz, P., Gimenez, E., Yamamoto, T., Gavara, R., & Lagarón, J. M. (2005). Gas barrier changes and morphological alterations induced by retorting in ethylene vinyl alcohol–based food packaging structures. Journal of Applied Polymer Science, 96(6), 2192-2202.

Mancini, R. A., & Hunt, M. C. (2005). Current research in meat color. Meat Science, 71(1), 100-121. doi:DOI: 10.1016/j.meatsci.2005.03.003

Morvillier M.R.,Oxygen scavengers in barrier plastic cups ensure the freshness of long shelf life pates, ciba.

Marković, K., Hruškar, M., & Vahčić, N. (2007a). Stability of lycopene in tomato purée during storage. Acta Alimentaria, 36(1), 89-98.

Marković, K., Hruškar, M., & Vahčić, N. (2007b). Stability of lycopene in tomato purée during storage. Acta Alimentaria, 36(1), 89-98.

Massey, L. K. (2003). Permeability properties of plastics and elastomers: A guide to packaging and barrier materials .

Min. D. B., & Wen, J. (1983). Effects of dissolved free oxygen on the volatile compounds of oil. Journal of Food Science, 48(5), 1429-1430. doi:10.1111/j.1365- 2621.1983.tb03508.x

Mohan, C. O., Ravishankar, C. N., Srinivasa Gopal, T. K., & Bindu, J. (2008). Thermal processing of prawn ‗kuruma‘in retortable pouches and aluminium cans. International Journal of Food Science & Technology, 43(2), 200-207.

Mokwena, K. K., Tang, J., Dunne, C. P., Yang, T., & Chow, E. (2009). Oxygen transmission of multilayer EVOH films after microwave sterilization. Journal of Food Engineering, 92(3), 291-296.

Morales, M., Rios, J., & Aparicio, R. (1997). Changes in the volatile composition of virgin olive oil during oxidation: Flavors and off-flavors. Journal of Agricultural and Food Chemistry, 45(7), 2666-2673.

Mortensen, A., & Skibsted, L. H. (1997). Importance of carotenoid structure in radical- scavenging reactions. Journal of Agricultural and Food Chemistry, 45(8), 2970-2977.

Operational rations of the department of defense. (May 2010). Natick PM 30-25, (8th edition)

Ossian, W. F. (1987). Multiple layer films containing oriented layers of nylon and ethylene vinyl alcohol copolymer ,Google Patents.

Pakola, R. J. (2002). Heat penetration studies of stewed tomatoes in 6, 8, and 17 quart household pressure retorts. Paper presented at the 2002 Annual Meeting and Food Expo-Anaheim, California,

Pangloli, P., Melton, S. L., Collins, J. L., Penfield, M. P., & Saxton, A. M. (2002). Flavor and storage stability of potato chips fried in cottonseed and sunflower oils and palm Olein/Sunflower oil blends. Journal of Food Science, 67(1)

Parchomchuk, P. (1977). A simplified method for agitation processing of canned foods. Journal of Food Science, 42(1), 265-268. doi:10.1111/j.1365-2621.1977.tb01267.x

Petro-Turza, M. (1986). Flavor of tomato and tomato products. Food Reviews International, 2(3), 309-351.

Rahman, S. (2007a). Handbook of food preservation, CRC.

Rahman, S. (2007b). Handbook of food preservation, CRC.

Richards, A., Wijesundera, C., & Salisbury, P. (2005). Evaluation of oxidative stability of canola oils by headspace analysis. Journal of the American Oil Chemists' Society, 82(12), 869-874.

Richardson, P. S. (2001). Thermal technologies in food processing Taylor & Francis US.

Robertson, G. L. (2006). Food packaging: Principles and practice CRC press.

Ronalds.B.,Water activity in food. Retrieved 04 April, 2011 from wateractivity.com.

Schauwecker, A., Balasubramaniam, V., Sadler, G., Pascall, M., & Adhikari, C. (2002). Influence of high‐pressure processing on selected polymeric materials and on the migration of a pressure‐transmitting fluid. Packaging Technology and Science, 15(5), 255-262.

Schirmer, H. G. (1990). Oxygen- barrier retort pouch Google Patents.

Selke, S. E. M. (2003). Plastics in packaging.

Simpson, R. (2008). Engineering aspects of thermal food processing CRC.

Sink, J. (1973). Lipid-soluble components of meat flavors/odors and their biochemical origin. Journal of the American Oil Chemists' Society, 50(11), 470-474.

Smith, D. (1987). Functional and biochemical changes in deboned turkey due to frozen storage and lipid oxidation. Journal of Food Science, 52(1), 22-27.

Stahl, W., & Sies, H. (1996). Lycopene: A biologically important carotenoid for humans? Archives of Biochemistry and Biophysics, 336(1), 1-9.

Sacharow. S., (2003), Book : Is the retort pouch really ready to replace the metal can?

Stern, M., Hanemann, W., & Eckhouse, K. (1981). Energy and Process Substitution in the Frozen-Food Industry: Geothermal Energy and the Retortable Pouch

Williams. S.T. (2003). Understanding the retort sterilization process – steam air retorts. Retrieved April 04, 2011, from

Thakur, B., Singh, R., & Nelson, P. (1996). Quality attributes of processed tomato products: A review. Food Reviews International, 12(3), 375-401.

Tucker, G., & Featherstone, S. (2011). Essentials of thermal processing ,Wiley Online Library.

Tucker, G. S. (1991). Modelling of heat transfer into plastics food containers. Packaging (Boston, Mass.), 62, 19.

U.S. Department of Health and Human Services. (1998). Botulism in united states 1899- 1996.

Venugopal, V. (2006). Seafood processing: Adding value through quick freezing, retortable packaging, and cook-chilling CRC.

Williams, J. R., steffe, J. F., & Black, J. R. (1982). Economic comparison of canning and retort pouch systems. Journal of Food Science, 47(1), 284-290. doi:10.1111/j.1365- 2621.1982.tb11080.x

Xianquan, S., Shi, J., Kakuda, Y., & Yueming, J. (2005). Stability of lycopene during food processing and storage. Journal of Medicinal Food, 8(4), 413-422.

Zamora A. (2005). Fats, oils, fatty acids, triglycerides. Retrieved 04/17, 2011, from http://www.scientificpsychic.com/fitness/fattyacids1.html

Zeuthen, P., & Bøgh-Sørensen, L. (2003). Food preservation techniques. In (pp. 155) CRC press.

Zhang, Z., Britt, I. J., & Tung, M. A. (2001). Permeation of oxygen and water vapor through EVOH films as influenced by relative humidity. Journal of Applied Polymer Science, 82(8), 1866-1872. doi:10.1002/app.2030

CHAPTER THREE

MATERIALS & METHODS

Film structures

The film structures used in this study were supplied by Ampac Flexibles (St.Louis

Park,MN) and were as follows:

1) 0.5µm AlOx/12µm PET/0.5µm AlOx // 15µm BON // 70µm CPP

2) 0.5µm HYBRID/12µm PET/0.5µm HYBRID // 15µm BON // 70µm CPP

3) 0.5µm AlOx/12µm PET/0.5µm AlOx // 15µm BON // 70µm CPP Linear Tear

4) 0.5µm AlOx/12µm PET/0.5µm AlOx // 15µm BON // 110µm white anti-stain

5) 0.5µm HYBRID/15µm BON/0.5 µm HYBRID // 70µm CPP

6) 12µm PET // 9µm Foil // 15µm BON // 80µm CPP

7) 80µm CPP

Abbreviations:

AlOx-Aluminum Oxide

PET-Polyethylene terepthalate

CPP- Cast Poly propylene

BON-Biaxially oriented Nylon

Films 1- 6 were laminated structures except film 4 which had a co-extruded layer

(company proprietary material). Films 1-5 had barrier coatings of AlOx and HYBRID

(company proprietary material) which is an organic coating. Films 1-4 had coatings on

PET substrate, while film 5 had a coating of HYBRID on BON. Film 4 had an anti-stain property; the white antistain (company proprietary material) was a three layer coextruded material. Film 6 was considered a control containing a standard foil barrier, and film 7-C was a single layer CPP added as a known low barrier control. The films for experimental purpose were marked as follows:

1) ABC

2) HBC

3) ABCL

4) ABCA

5) HBC2

6) PFBC

7) CPP

Film slitting

Films 1-6 for the pouches were received in web form from Ampac Flexibles

(St.Louis Park, MN). The roll stock was 5,128 ft in length and 26 inches in width. The width of the film roll was too long for making single pouches. Hence, for convenience, the film roll was slit to 13‖ width. The slitting machine used was from John Dusenbery company (Clifton, NJ) model no 53779.The roll was unwound onto another core while the film was being slit into two halves. Figure 3.1 shows the 26‖ web being unwound on

36 side 1 of the slitting machine, while figure 3.2 is the view of side 2. Here the unwound

26‖ film is being slit in to two 13‖widths and rewound onto a new core.

Figure 3.1. Un-winding of 26‖ web roll on side 1 of slitting machine.

Figure 3.2. Winding of two 13‖ rolls on side 2 of slitting machine.

Pouch Making

The pouches were made with the two 13‖ rolls as shown in figure 3.3. The pouch forming machine used was from Shanghai Gaoqin (Shanghai, China) Model no.FDS-

600S2.The machine had the capability to make 3-side sealed pouches. Figure 3.4 shows the two webs coming together and passing through the sealing and cooling bar. The pouches were sealed at 140°C except pouch 6 which had to be sealed at 145°C.The pouches were tested for seal strength as per ASTMF 88. The seal strength of all the pouches complied with the required industrial standard for premade retort pouches, which is above 26lbf for companies like Sealed Air Corporation. The pouch dimension was 255 x 180mm which included 5mm bottom and side seals. About 150 pouches of each variant were made. Figure 3.5 shows the pouch making equipment with formed pouches on the conveyor table.

Figure 3.3 Two 13‖ webs on pouch making equipment.

Figure 3.4. Side view of pouch making machine showing webs coming together, sealing and cooling bars.

Figure 3.5. Pouch making equipment with formed pouches on the conveyor table.

Simulant preparation

The oxygen sensitive simulant used for this study was formulated with tomato paste, water and corn oil. Bulk tomato paste (approx 400lbs) was provided by the

Campbell Soup Company, Maxton, NC. The tomato paste was divided into 25 lb containers and frozen until the beginning of the study. The simulant was made with the ratio of 2:2:1 of tomato paste: water: corn oil. About 585 lbs of simulant was prepared for this study. This was done in seven batches using a small steam jacketed kettle (132 liter capacity) as shown in Figure 3.6. The simulant was slightly warmed and mixed using a homogenizer to make sure an emulsion was formed. The small batches were eventually transferred into a kettle (1000 liter capacity) which had an in-built stirrer for continuous agitation (Figure 3.7). The large kettle was attached to the pouch filling equipment.

Figure 3.6. Small steam jacketed kettle with simulant being emptied.

Figure 3.7. Simulant being stirred in the large kettle.

Pouch filling

The pouches were filled using a rotary pouch filling system from Cryovac- Sealed

Air corporation (Duncan, SC) model 8084A (Figure 3.8).The machine was equipped with a servo driven pumping system which pumped the simulant from the kettle through the volumetric filler into the pouch (Figure 3.9). The size of the pouch was finalized on the basis of the minimum length of the pouch holder on the filler. The pouches were filled with 440g of paste, which was the minimum fill weight. The equipment had a steam flushing system (Figure 3.10) which helped remove the headspace oxygen from the filled packs. Sealing for the filled pouches was set to 135°C. After sealing the filled pouches were dropped onto the conveyor belt. About 600 pouches (100 of each variant) were filled for the study. Pouch 7 (CPP) was filled by hand and sealed using a Toyo Jidoki Co. model PMS heat sealer at 125°C.

Figure 3.8. Rotary pouch filling equipment.

Figure 3.9. Volumetric filling of pouch.

Figure 3.10. Steam flushing of the filled pouch.

Processing

The retort equipment used was a pilot-scale rotary, single cage, water spray in static mode. The machine was a Surdry, model APR-95 rotary pilot retort (Stock

America, Raleigh, NC).The pouches were loaded on crates and arranged as shown in

Figure 3.11. As the pH of the simulant was below 4.6 (i.e. 4.3) it was not necessary to conduct a heat penetration study. The processing recipe is described in Table 3.1.Cooking temperature was 250°F at 30psi for 45 minutes.

Table 3.1: Recipe for retort processing

#1 #2 #3 #4 #5 #6 #7 #8 #9

Steps Fill Come Come Hold Hold iMicro iMicro iCool Drain

up up (cook) cool cool

Temperature(°F) N/A 200 250 250 250 200 85 85 N/A

Pressure (psi) N/A 15 30 30 30 20 15 5 0

Time(minute) 2 7 8 1 45 6 8 30 2.30

Figure 3.11 Pouches arranged on the crate with the retort machine.

Storage conditions and sampling

The retorted pouches were stored in an environmental chamber at 45±2°C with

50±2 % RH for a period of 6 months. The chamber was set up without light to avoid photo oxidation. The sampling days were 0,7,21,35,49,79,110,140,180. Three pouches of each variant were removed from the storage on the sampling days for analysis as

44 described below. Samples were also taken before retort processing for TBARS and color analysis.

Color analysis

The change in color during storage was measured using a Konica Minolta Chroma

Meter model CR-400.The colorimeter was calibrated before every test using a reference tile, CR A-43. The samples were measured using the CIELAB color space system, which is an improvement of CIE system (López Camelo & Gómez, 2004). Indicated by L*a*b* here, L* is for luminance (towards 100-white and 0-black), a* indicates red saturation index (positive a* is red and negative a*is green) and b* is yellow saturation index

(positive b* is yellow and negative b* is blue) as indicated in Figure 3.12 (Heuvelink,

2005). The pouches were manually shaken before testing to make sure there was no separation of oil from the mixture. Duplicate samples from each pouch were transferred into a rectangular glass cell housed in a black box to avoid external light interference.

Mean values were calculated from 6 measurements for each variant. Hue angle was also calculated using the formula [tan-1(b*/a*)]. Figure 3.13 illustrates the sample measurement for color value.

Figure 3.12. L*a*b* color model

Figure 3.13 Measurement of color value using a Minolta colorimeter

Thiobarbituric acid reactive substance (TBARS)

TBARS is one of the most widely used method for measuring lipid oxidation in products containing oil. The assay used in this study was a modified technique used by other researchers ( Byun, Y., Bae, H. J., Cooksey, K., & Whiteside, S., 2010; Gomes, H.

A., Silva, E. N., Nascimento, M. R. L., & Fukuma, H. T., 2003; Pikul, J., Leszczynski,

D.E., & Kummerow, F.A., 1983; Sepe, H.A., 2005). Duplicate samples from each pouch were used for analysis. Since the paste was difficult to filter, it was diluted with distilled water. The manually mixed samples were measured to 1g in a falcon tube and 10mL of distilled water was added for dilution. About 1ml of sample was then transferred to a

15mL falcon tube and to this 10mL of trichloroacetic acid (TCA, 100 g/L) and 0.1mL of butylated hydroxyanisole (BHA, 10 g/L) was added. The mixture was vortexed for 2

46 minutes using a Fisher brand touch mixer model 12-810 (Japan). The sample was then centrifuged at 25000 rpm for 20 minutes. The supernatant was drawn into a syringe and filtered through a syringe filter of 0.45µm. 1ml of this clear filtrate was transferred into a glass tube with 1ml of 2-thiobarbituric acid (TBA, 3g/L).The test tube was incubated at

97°C for 20 minutes in a water bath and then cooled to room temperature. The absorbance was measured at 531nm using a model UV-2101 PC Spectrophotometer. The value was expressed in terms of optical density (OD).

Oxygen Permeability (OP)

The oxygen transmission rate (OTR) was measured as per ASTM D 3985 standard, using an OX-TRAN 2/20 (Mocon, Inc., Minneapolis, MN, USA). The films were tested in duplicate for each variant before and after retort processing. The test conditions were 23 ± 1 °C and 0% RH. The film samples were cleaned with paper towel to remove the residual product before testing. Permeability to oxygen (gm μm /m2 day) was calculated by multiplying film thickness by the OTR (gm [m2-day]) value.

Scanning electron microscopy (SEM)

SEM analysis was performed to determine surface morphology of the films before and after retort using a SEM 3400 model S-3400N (Hitachi High technologies America,

Inc, USA). The films were cut into 1 x 0.5 in samples and glued with the help of carbon conductive tape on a metal disc which was mounted onto the microscope specimen chamber. The samples were analyzed using backscattered electron mode by maintaining

50Pa pressure. Acceleration voltage was set at 20.0Kv for a working distance of 9-10mm.

Images were taken at 270x and 900x magnification.

Anti-staining

Film 4-ABCA had an anti-staining property and hence this test was included in this research. The measurements were taken in triplicates both before and after retort for all the films. The films after retort were wiped clean with dry paper towel and measured for color (a*- value, which corresponds to the redness) using a Konica Minolta Chroma meter, model CR-400. Also, a cross-sectional view for only 4-ABCA film at 40x magnification was observed, with a Nikon OPTIPHOT (Nikon, Tokyo, Japan) to determine if the paste had affected the anti-stain layer.

Statistical Analysis

All readings (TBARS, L*,a*,b* value, Hue angle and OP) were subjected to analysis of variance (ANOVA) using SAS 9.2 to determine if there was a significant difference (p >

0.05) between treatment means using proc GLM. Specific differences among pouches and/or date means were determined using Fisher‘s least significant difference test with the LSMEAN and pdiff options from PROC GLM.

Literature cited

Gomes, H. A., Silva, E. N., Nascimento, M. R. L., & Fukuma, H. T. (2003). Evaluation of the 2-thiobarbituric acid method for the measurement of lipid oxidation in mechanically deboned gamma irradiated chicken meat. Food Chemistry, 80(3), 433- 437.

Heuvelink, E. (2005). Tomatoes CABI publishing.

López Camelo, A. F., & Gómez, P. A. (2004). Comparison of color indexes for tomato ripening. Horticultura Brasileira, 22(3), 534-537.

Pikul, J., Leszczynski, D. E., & Kummerow, F. A. (1983). Elimination of sample autoxidation by butylated hydroxytoluene additions before thiobarbituric acid assay for malonaldehyde in fat from chicken meat. Journal of Agricultural and Food Chemistry, 31(6), 1338-1342.

Sepe, H. A., Faustman, C., Lee, S., Tang, J., Suman, S. P., & Venkitanarayanan, K. S. (2005). Effects of reducing agents on premature browning in ground beef. Food Chemistry, 93(4), 571-576. doi:DOI: 10.1016/j.foodchem.2004.04.045

CHAPTER FOUR

RESULTS AND DISCUSSION

Oxygen Permeability

Diffusion and solubility of gas through a polymer is considered to be the most important mechanism that controls gas permeability apart from flow through pinholes

(Barker, C., Kochem, K.H., Revell, K., Kelly, R., & Badyal, J., 1995; Benmalek, M.,&

Dunlop, H., 1995a). Macro pores formed during deposition of barrier coatings have been reported which allow permeation of oxygen (Henry,B.M., 2001). For barrier coatings flow of gas through micro-cracks, micro-channels, nano-scale defects and pinholes are dominant compared to diffusion of permeants ( Chatham, H., 2001; Henry, B.M., &

Earlat, A.G., 2001).

Table 4.1 and Figure 4.1 show the oxygen permeability (OP) (µm gm/[m2-day]) at

23°C and 0%RH for pouches before and after retort processing. The OP for 1-ABC and

3-ABCL was the same before retort as they had similar barrier structures. 2-HBC had the lowest OP. 5-HBC2 was similar to 2-HBC with respect to barrier coating. It had a 2-layer structure with high OP compared to other barrier structures. 7C, as expected, had the maximum OP. 4-ABCA and 6-PFBC showed intermediate barrier before retort. Films were also subjected to various stresses during film slitting, pouch making and the filling process. This can be one of the reasons for variation in permeability before retort.

Barker C.P et al., (1995) reported stretching of film leads to tensile fracture, which further leads to buckling and delamination on surface coatings of AlOx/PET and

50 induces loss of gas barrier (Barker, C.P., 1995). Retort pouches during processing tend to bulge causing stress that induces cracking in the coating layer (Hughes, A., 2000; Barker

C.P., 1995). This is reflected in the OP results for this study. The barrier after retort was significantly different and OP increased for all the pouches. Cracking and peeling has been reported for coatings above 150nm (Benmalek, M., & Dunlop, H., 1995b). The coatings on the pouches in this study were 150nm each on both sides of a PET layer. This thickness is adequate for minor flaking, especially when subjected to thermal stress. 1-

ABC, 2-HBC and 3-ABCL showed similar barrier when subjected to retort. The barrier decreased by approximately 7 fold in 1-ABC and 3-ABCL. For 2-HBC it declined by approximately 10 fold, and this may be because of the difference in coating material. 5-

HBC2 showed the highest OP even after retort in comparison to other barrier coatings.

This may be due to less thickness of film, making it more flimsy and prone to stress induced cracks in the coating, especially during processing. Bull M. et al., (2010) also reported a decrease in barrier for AlOx and SiOx coated films after HPHT processing

(Bull, M., Steele, R., Kelly, M., Olivier, S., & Chapman, B., 2010). 4-ABCA showed the lowest OP and better barrier than the foil film, 6-PFBC. 4-ABCA had an anti-stain layer which might have also contributed to the barrier property when compared with other films.

Henery B.M.et al.,(2001) reported permeability of water vapor through an AlOx layer to be greater than a PET substrate at high temperature and related this to chemical interaction between water and AlOx (Henry, B.M., & Earlat, A.G., 2001). The permeability of oxygen through the semi crystalline nylon is dependent on the water

51 content in the nylon layer (Hernandez, R.J., 1994). It is possible that water permeation through the cracks in barrier coating can degrade the barrier property of BON present in all the films during retort processing.

Oxygen Permeability @ 23±2°C, 0±2%RH 500 450 400

350

day]) day]) - 300 250 Before 200 After 150

OP ( µm( gm/[m² OP 100 50 0 1-ABC 2-HBC 3-ABCL 4-ABCA 5-HBC2 6-PFBC

Figure 4.1. Changes in oxygen permeability before and after retort.

Table 4.1. Oxygen permeability (µm gm/[m2-day]) for pouches at 23±2°C and 0±2%RH before and after retort processing OP(µm gm/[m²- day]) Before retort After retort 1-ABC 31.2±14.7 a3 198.3±27.9 b3 2-HBC 19.9±4.7 a1 202.2±11.3 b3 3-ABCL 34.3±14.8 a3 202.9±22.1 b3 4-ABCA 22.7±0.1 a2 27.4±1.3 b1 5-HBC2 64.5±17.3 a4 484.3±11.9 b4 6-PFBC 25.9±6.5 a2 40.5±10.3 b2 7-C 1431.7±13.8a5 1583.9±68.6b5 Means ± standard deviation. Different letters (a and b) within a row are significantly different (p<0.05). Different numbers (1 through 5) within the column are significantly different(p<0.05).n=2

TBARS Value (Lipid Oxidation)

TBARS detects the secondary products of lipid oxidation like malondialdehyde

(MDA). The color intensity of TBA pigment in this study was expressed in terms of optical density (OD), corresponding to the MDA formed in the deterioration reaction

(Tarladgis, B.G., Watts, B.M., Younathan, M.T., & Dugan, L.,1960; Tarladgis, B.G.,

Pearson, A., & Jun, L., 1964). Before the retort process, the TBARS value of the product in all the pouches was the same (Table 4.2). There was no significant change in TBARS values in pouch 1-ABC, 3-ABCL, 4-ABCA and 6-PFBC after retort and also the values were not significantly different for these pouches, indicating there was no lipid oxidation during retort. However, there was an increase in TBARS value for 2-HBC, 5-HBC2 and

7-C after retort. The rate of lipid oxidation is dependent on the concentration of oxygen in the pack (McClements, D., & Decker, E., 2000). The head space oxygen concentration in all the pouches measured during a preliminary study was in the range of 3-8 %. It is also possible that oxygen might have permeated into the pouch during processing. This is supported by the large increase (2.5 fold) in TBARS value after retort in the low barrier

7-C film. Also, there may be oxygen present in the dissolved form in the food simulant.

At higher temperatures the rate of oxidation is greater (Gordon, M.H., 2004). This could be one of the reasons why 2-HBC, 5-HBC2 and 7-C, having high OP, showed increase in

TBARS values after processing. The values on day 180 for all the pouches were significantly different from initial retort values. This verifies lipid oxidation taking place in all the pouches during storage.

6-PFBC and 3-ABCA did not show changes in TBARS value from day 49 to 180

(Figure 4.2) 1-ABC and 2-HBC also showed a similar trend after day 79 until day 180.

On day 35 pouch 1-ABC, 2-HBC, 3-ABCL,4-ABCA and 6-PFBC showed similar

TBARS values while 5-HBC2 and 7-C had higher values of 0.062±0.005 and

0.088±0.018, respectively. Day 110 showed the highest TBARS value of 0.103±0.012 for

7-C, which was a low barrier control film. The TBARS value was the lowest for the foil laminate, 6-PFBC and similar to 4-ABCA. Other pouches showed intermediate increases.

After 6 months exposure 6-PFBC and 4-ABCA showed the lowest and similar TBARS values compared with 1-ABC, 2-HBC and 3-ABCL, which had the same intermediate values, while 5-HBC2 had the highest value of 0.089±0.020 . TBARS results coincided well with the after retort oxygen permeability value.

TBARS value(Optical density)

0.100

1-ABC 0.080 2-HBC

0.060 3-ABCL 4-ABCA

0.040 5-HBC2 Opticaldensity 6-PFBC 0.020 7-C

0.000 0 20 40 60 80 100 120 140 160 180 Days

Figure 4.2. Changes in TBARS values in the different pouches during accelerated storage at 45±2°C and 50±2% RH. Day 0 values are after retort.

Table 4.2.TBARS values (O.D.) over 6 months exposure at 45±2°C and 50±2%RH

TBARS (OD) Before retort After retort Day 7 Day 21 Day 35 1-ABC 0.017±0.009 a1 0.022±0.005 a1 0.028±0.006 b12 0.046±0.010 c23 0.052±0.012 c1 2-HBC 0.017±0.009 a1 0.029±0.004 b2 0.031±0.003 b23 0.047±0.007 c23 0.058±0.014 d1 3-ABCL 0.017±0.009 a1 0.020±0.003 a1 0.025±0.004 a12 0.038±0.012 b123 0.055±0.009 c1 4-ABCA 0.017±0.009 a1 0.020±0.007 a1 0.022±0.004 a1 0.034±0.003 b12 0.045±0.014 c1 5-HBC2 0.017±0.009 a1 0.032±0.004 b2 0.036±0.008 bc3 0.049±0.019 cd3 0.062±0.005 d2 6-PFBC 0.017±0.009 a1 0.018±0.004 a1 0.024±0.003 a12 0.032±0.005 b1 0.049±0.010 c1 7-C 0.018±0.004 a1 0.046±0.009 b3 0.054±0.011 b4 0.067±0.012 c4 0.088±0.018 d3

TBARS (OD) Day 49 Day 79 Day 110 Day 140 Day 180 1-ABC 0.055±0.013 c3 0.068±0.009 d23 0.069±0.004 d23 0.073±0.004 d34 0.076±0.006 d2 2-HBC 0.061±0.014 de34 0.070±0.007 ef23 0.074±0.009 f3 0.075±0.009 f34 0.078±0.005 f23 3-ABCL 0.056±0.009 c23 0.063±0.007 cd23 0.068±0.003 de23 0.069±0.003 de23 0.074±0.004 e2 4-ABCA 0.052±0.004 cd12 0.059±0.016 de12 0.063±0.011 e1 0.062±0.007 de12 0.059±0.004 de1 5-HBC2 0.063±0.021 de4 0.075±0.012 ef3 0.076±0.003 ef3 0.080±0.010 g4 0.089±0.020 g3 6-PFBC 0.051±0.008 cd1 0.055±0.015 cd1 0.060±0.003 cd1 0.059±0.007 cd1 0.058±0.010 d1 7-C 0.091±0.011 de4 0.095±0.009 de4 0.103±0.012 f4 Means ± standard deviation. Different letters (a through g) within the rows are significantly different (p<0.05). Different numbers (1 through 4) within the columns are significantly different (p<0.05). n=6

Color analysis

Color is considered a measure for total quality in tomato and tomato based products. The degradation of color pigments (lycopene) in tomato is mainly due to thermal isomerization and autoxidation (Boskovic, M.A., 1979; Cole, E.R., & Kapur,

N.S., 1957). The L*, a* and b* values decreased in all the pouches after retort processing

(Figures 4.3, 4.4 and 4.5). For barrier coated films L* value decreased by approximately

2 units (Table 4.3), a* by 6 units (Table 4.4) and b* by 2 units (Table 4.5) after retort.

Lycopene in tomato undergoes thermal isomerization at temperatures in the range of 100-

120°C (Shi, J., Dai, Y., Kakuda, Y., Mittal, G., & Xue, S.J., 2008). This causes conversion of all-trans lycopene to mono-cis and poly-cis forms leading to loss of red color. Further, the mono-cis form during storage is re-isomerized to all-trans in the absence of oxygen. Mono, poly-cis and all-trans in the presence of oxygen undergo oxidative degradation causing complete loss of red color(Ax, K., Mayer‐Miebach, E.,

Link,B., Schuchmann, H., & Schubert, H., 2003; Lovric, T., Sablek, Z., & Boskovic, M.,

1970). The degradation of lycopene during storage is mainly due to oxidation (Shi, J., &

Maguer, M.L., 2000). In 7-C this mechanism was clearly seen as it had the highest OP after retort. Here, L*, a* and b* values changed tremendously due to the presence of oxygen resulting in oxidation of lycopene isomers. During storage this value declined continuously until the red color was lost completely. The a* value for 7-C on day 49 decreased from 24.7±0.8 to 3.3±0.1 (Table 4.4). The same was observed for L* and b* values. The L*, a* and b* values after retort and at the end of storage were significantly different for all the pouches. 4-ABCA and 6-PFBC showed the highest and similar L*, a*

56 and b* values after 180 days, indicating good barrier to oxygen. These color values correlate well with the TBARS values and OP (after retort) for these films. 5-HBC2 showed the lowest L*, a* and b* values on day 180 with the highest TBARS value and

OP (after retort) when compared with the other barrier films, indicating high oxidation taking place in this pouch. While 1-ABC and 2-HBC showed no significant difference with intermediate L*, a* and b* values, 3-ABCL had L* and a* values similar to 1-ABC and 2-HBC but the b* value was slightly higher than that for 5-HBC2. The intermediate performance of 1-ABC, 2-HBC and 3-ABCL shows similarity with OP (after retort) results for these pouches. In a study for double concentrated tomato paste heated at 70-

90°C for 90 min, L*value was reported to decrease rapidly in an initial stage involving degradation of thermally unstable pigment and also resulted in formation of dark compounds and decrease in luminosity. The a* value was dependent on the red color of lycopene and decreased with an increase in time and temperature. The same was observed for the b*value. Non-enzymatic browning (Maillard) (Min,S., & Zhang, Q.,

2003; Porretta, S.,1991) due to the presence of reducing sugars and amino acids in tomato paste can be one of the reasons for change in color observed in 6-PFBC foil laminate, but it is not the only factor contributing to color change since color values continued to decline. In the 7-C pouch color change was likely due to oxygen permeation into the film during storage, proving barrier to be a significant factor.

Hue angle expressed in radiance was measured using the formula (tan-1 (b*/a*).

For double concentrated tomato paste the hue angle has been observed to increase with temperature and time (Barreiro, J., Milano, M., & Sandoval, A., 1997; Noble, A.C.,1975).

In this study the hue angle increased significantly after retort and during storage for all the pouches (Figure 4.6 and Table 4.6). Wiese K.L. et al., (1994) reported loss of red color in tomato juice with significant increase in hue angle (Wiese, K.L., & Dalmasso,

J.P., 1994). On day 180 the radiance was not significantly different for 1-ABC, 2-HBC,

4-ABCL and 6-PFBC indicating the rate of change to be the same in these pouches, while for 3-ABCL and 5-HBC2 the radiance values were similar and highest among the barrier pouches, showing more loss of red color. Radiance was highest for 7-C indicating high oxidative degradation.

L* value

32 1-ABC 30 2-HBC 3-ABCL 28 L*value 4-ABCA 26 5-HBC2

24 6-PFBC 7-C 22 0 20 40 60 80 100 120 140 160 180 Days

Figure 4.3. Changes in L*values in the different pouches during accelerated storage at 45°C and 50±2%RH. Day 0 values are after retort.

a* value 25

20 1-ABC

15 2-HBC 3-ABCL

a*value 10 4-ABCA 5-HBC2 5 6-PFBC 7-C 0 0 20 40 60 80 100 120 140 160 180

Days Figure 4.4. Changes in a*values in the different pouches during accelerated storage at 45°C and 50±2%RH. Day 0 values are after retort.

b*value 20

16 1-ABC 2-HBC 14 3-ABCL 12 b* value b* 4-ABCA

10 5-HBC2 6-PFBC 8 7-C 6 -20 30 80 130 180 Days Figure 4.5. Changes in b* values in the different pouches during accelerated storage at 45°C and 50±2%RH. Day 0 values are after retort.

Hue Angle (Radiance) 1.2

1.1 1-ABC 1

(b*/a*)] 2-HBC

1 - 0.9 3-ABCL 4-ABCA 0.8

5-HBC2 Radiance[Tan 0.7 6-PFBC 7-C 0.6 0 20 40 60 80 100 120 140 160 180 Days

Figure 4.6. Changes in Hue angle (radiance) in the different pouches during accelerated storage at 45°C and 50±2%RH. Day 0 values are after retort.

Table 4.3. L* values over 6 months exposure at 45±2°C and 50±2%RH

L*value Before retort After retort Day 7 Day 21 Day 35 1-ABC 32.9±0.7 a2 30.9±0.4 b1 30.4±0.4 bc23 30.0±0.1 c3 29.8±0.4 c12 2-HBC 32.9±0.7 a2 30.7±0.6 b12 30.7±0.3 b12 30.4±0.3 b12 29.7±0.2 c23 3-ABCL 32.9±0.7 a2 30.7±0.6 b12 30.5±0.5 bc2 30.1±0.4 cd23 29.5±0.4 d3 4-ABCA 32.9±0.7 a2 30.9±0.3 b1 30.8±0.3 b12 30.6±0.2 b1 30.0±0.1 c12 5-HBC2 32.9±0.7 a2 30.1±0.3 b23 30.0±0.1 b3 29.5±0.2 b4 28.6±0.1 c4 6-PFBC 32.9±0.7 a2 30.9±0.2 b1 30.9±0.3 b1 30.7±0.1 bc1 30.3±0.1 c1 7-C 34.4±0.1 a1 29.6±0.1 b3 26.7±0.1 c4 25.6±0.2 d5 24.6±0.2 e5

L*value Day 49 Day 79 Day 110 Day 140 Day 180 1-ABC 28.5±0.2 d1 27.6±0.1 e3 25.9±0.2 f4 25.7±0.2 f3 25.1±0.4 g2 2-HBC 28.5±0.2 d1 28.1±0.1 d2 26.5±0.1 e3 26.1±0.3 e2 25.3±0.1 f2 3-ABCL 28.5±0.4 e1 27.7±0.2 f3 26.7±0.3 g23 26.1±0.2 g2 25.1±0.1 h2 4-ABCA 28.7±0.1 d1 28.5±0.5 d1 26.9±0.1 e2 26.3±0.1 f2 25.9±0.3 f1 5-HBC2 27.3±0.5 d2 26.9±0.2 d4 25.2±0.4 e5 25.2±0.3 e4 24.0±0.1 f3 6-PFBC 28.8±0.2 d1 28.5±0.1 d1 27.5±0.2 e1 26.9±0.1 f1 25.9±0.4 g1 7-C 23.3±0.1 f3 Means ± standard deviation. Different letters (a through g) within the rows are significantly different (p<0.05). Different numbers (1 through 5) within the columns are significantly different (p<0.05). n=6

Table 4.4. a* values over 6 months exposure at 45±2°C and 50±2%RH

a*value Before retort After retort Day 7 Day 21 Day 35 1-ABC 24.5±0.2 a1 18.6±0.1 b2 18.1±0.1 c2 17.4±0.2 d2 16.4±0.2 e2 2-HBC 24.5±0.2 a1 18.5±0.1 b2 17.9±0.1 c2 17.3±0.2 d23 16.3±0.1 e2 3-ABCL 24.5±0.2 a1 18.5±0.2 b2 18.1±0.1 b2 17.1±0.2 c3 16.4±0.4 d2 4-ABCA 24.5±0.2 a1 18.9±0.1 b1 18.7±0.1 b1 17.8±0.2 c1 16.8±0.1 d1 5-HBC2 24.5±0.2 a1 17.7±0.3 b3 17.1±0.1 c5 16.1±0.2 d4 15.9±0.1 d3 6-PFBC 24.5±0.2 a1 18.9±0.1 b1 18.8±0.1 b1 17.9±0.0 c1 16.9±0.1 d1 7-C 24.7±0.8 a1 14.3±0.2 b4 10.9±0.1 c4 8.6±0.1 d5 6.5±0.1 e4

a*value Day 49 Day 79 Day 110 Day 140 Day 180 1-ABC 15.0±0.1 f2 14.0±0.2 g2 12.7±0.1 h4 12.5±0.1 h2 10.9±0.2 i2 2-HBC 15.0±0.1 f2 14.2±0.1 g2 13.1±0.2 h3 11.6±0.3 i4 10.9±0.2 j2 3-ABCL 14.9±0.1 e2 13.8±0.6 f2 12.9±0.2 g34 11.9±0.1 h3 9.3±0.7 i2 4-ABCA 15.3±0.5 e12 14.7±0.1 f1 13.3±0.2 g2 12.3±0.1 h23 11.7±0.1 i1 5-HBC2 14.2±0.4 e3 13.0±0.2 f3 11.30±0.2 g5 10.0±0.4 h5 7.9±0.6 i4 6-PFBC 15.6±0.5 e1 14.9±0.1 f1 14.0±0.0 g1 13.3±0.2 h1 11.9±0.1 i1 7-C 3.3±0.1 f4 Means ± standard deviation. Different letters (a through i) within the rows are significantly different (p<0.05). Different numbers (1 through 5) within the columns are significantly different (p<0.05). n=6

Table 4.5. b* values over 6 months exposure at 45±2°C and 50±2%RH

b*value Before retort After retort Day 7 Day 21 Day 35 1-ABC 18.4±0.1 a2 15.2±0.1 d4 16.9±0.0 b4 16.9±0.5 b45 16.6±0.2 b3 2-HBC 18.4±0.1 a2 15.5±0.1 ef3 16.7±0.1 cd5 17.8±0.1 ab12 17.3±1.2 bc123 3-ABCL 18.4±0.1 a2 16.0±0.1 d2 17.2±0.1 b3 17.2±0.0 b34 17.1±0.3 b123 4-ABCA 18.4±0.1 a2 16.3±0.0 d1 17.4±0.0 bc2 17.5±0.4 b23 17.5±0.1 b12 5-HBC2 18.4±0.1 a2 15.9±0.1 c2 16.4±0.1 b6 16.7±0.1 b5 16.7±0.1 b23 6-PFBC 18.4±0.1 a2 16.4±0.1 e1 17.7±0.1 b1 17.9±0.1 b1 17.7±0.1 b1 7-C 18.7±0.1 a1 14.5±0.1 b5 10.1±0.0 c7 8.5±0.0 d6 7.5±0.1 e4

b*value Day 49 Day 79 Day 110 Day 140 Day 180 1-ABC 16.8±0.6 b23 16.2±0.3 c2 15.4±0.4 d3 14.5±0.4 e3 13.3±0.3 f2 2-HBC 16.7±0.8 cd23 16.2±0.2 de2 15.3±0.3 f3 14.1±0.3 g3 13.1±0.5 h2 3-ABCL 16.9±0.7 b123 16.4±0.4 c2 15.6±0.3 e23 14.3±0.2 f3 12.3±0.4 g3 4-ABCA 17.2±0.4 bc12 17.0±0.3 c1 16.1±0.4 d2 15.4±0.2 e2 14.5±0.3 f1 5-HBC2 16.5±0.3 b3 15.2±0.3 d3 13.2±0.5 e4 12.8±1.2 e4 10.8±0.5 f4 6-PFBC 17.5±0.3 c1 16.9±0.4 d1 16.9±0.1 d1 16.2±0.4 f1 14.6±0.1 g1 7-C 6.8±0.1 f4 Means ± standard deviation. Different letters (a through g) within the rows are significantly different (p<0.05). Different numbers (1 through 7) within the columns are significantly different (p<0.05). n=6

Table 4.6. Hue angle (Radiance) over 6 months exposure at 45±2°C and 50±2%RH

tan-1 (b*/a*) Before retort After retort Day 7 Day 21 Day 35 1-ABC 0.644±0.004 g1 0.686±0.007 f4 0.754±0.004 e34 0.771±0.016 e3 0.792±0.009 d2 2-HBC 0.644±0.004 g1 0.697±0.005 f4 0.747±0.005 e4 0.801±0.003 d1 0.814±0.039 dc2 3-ABCL 0.644±0.004 g1 0.714±0.007 f3 0.762±0.002 e12 0.787±0.005 d2 0.805±0.016 d2 4-ABCA 0.644±0.004 g1 0.710±0.003 f3 0.749±0.004 f4 0.777±0.011 e23 0.808±0.004 e2 5-HBC2 0.644±0.004 g1 0.731±0.009 f2 0.766±0.004 e1 0.802±0.002 d1 0.812±0.004 d2 6-PFBC 0.644±0.004 g1 0.713±0.005 f3 0.757±0.004 e23 0.784±0.003 d2 0.809±0.004 c2 7-C 0.648±0.017 f1 0.794±0.007 e1 0.748±0.004 d4 0.776±0.006 c23 0.853±0.012 b1

tan-1 (b*/a*) Day 49 Day 79 Day 110 Day 140 Day 180 1-ABC 0.842±0.016 c23 0.857±0.012 c12 0.879±0.008 ab1 0.860±0.014 bc2 0.883±0.016 a2 2-HBC 0.837±0.026 bc3 0.852±0.005 ab12 0.865±0.005 ab2 0.881±0.018 a12 0.875±0.009 a2 3-ABCL 0.847±0.020 c23 0.870±0.015 b1 0.878±0.005 b1 0.876±0.006 b12 0.925±0.019 a1 4-ABCA 0.844±0.012 d23 0.858±0.015 c12 0.880±0.006 b1 0.897±0.004 a1 0.890±0.008 a2 5-HBC2 0.858±0.007 c2 0.861±0.011 c12 0.862±0.016 c2 0.902±0.052 b1 0.933±0.049 a1 6-PFBC 0.845±0.021 b23 0.847±0.010 b2 0.878±0.003 a1 0.883±0.004 a12 0.884±0.002 a2 7-C 1.121±0.007 a1 Means ± standard deviation. Different letters (a through f) within the rows are significantly different (p<0.05). Different numbers (1 through 4) within the columns are significantly different (p<0.05). n=6

Scanning Electron Microscopy (SEM)

SEM has been used by many researchers for analyzing surface morphology and defects in polymeric film surfaces(Caner, C., Hernandez, R., Pascall, M., & Riemer, J.,

2003; Gotz, J., & Weisser, H., 2002; López-Rubio, A., 2003). Figures 4.7-4.12 are images of before and after retort films. All the films before retort (Figures 4.7A - 4.12A) were clear without any pinholes or cracks on the surface, but after retort about 10-200µm thick cracks and pinholes were observed.1-ABC and 3-ABCL (Figures 4.7B and 4.9B) showed similarity in cracks as the surface coatings were the same for both. Also, OP after retort was similar for these films. 4-ABCA (Figure 4.10B) showed cracks or stress induced fractures after retort but the results for OP, TBARS and color showed superior barrier. This may be due to the presence of the anti- stain layer which had a co-extruded oxygen barrier material that acts as an additional barrier. Also the total thickness of the film was higher compared to the other films. 2-HBC (Figure 4.8B) and 5-HBC2 (Figure

4.11B) had a similar barrier coating but the images after retort were very different. 2-

HBC showed pinholes and macro scale defects on the surface, justifying the 10 fold increase in OP after retort. 5-HBC2 showed web like cracking on the surface. Figure

4.11C illustrates the magnification (x900) of image 4.11B.The cracks are very prominent in this image. Hence, the performance of 5-HBC2 declined in all tests. Similar images

(web like cracking) to figure 26C have been observed for PET-AlOx film after high pressure processing with a fatty acid simulant. After HPP treatment PPSiOx also showed cracking due to less flexibility of the barrier layer (Galott, M., 2008; Galotto,M., Ulloa,

P., Guarda, A., Gavara, R., & Miltz, J., 2009). 5-HBC2 was a flimsy film with a 2 layer

65 structure and even though the surface coating is the same as 2-HBC, during retort the film might have undergone stress induced cracking. 6-PFBC (Figure 4.12B) also showed minor cracks after processing. All the coated films had barrier coating on top and bottom of the PET layer. SEM only showed the image of the coating on the surface, hence it can be said that even though the coating on surface is cracked, the coating layer below PET may be intact or less damaged, thus maintaining barrier.

Anti-Staining

Anti- staining was one of the mechanical properties of 4-ABCA. All the pouches were tested on the inner surface for a* value (Figure 4.14). Before retort all films showed a negative a* value but after retort the values increased for all the films. All the films were stained except 3-ABCL which showed less staining comparatively. This may be due to linear polypropylene which is oriented. Orientation increases crystallinity and decreases permeability (Breil, J., 2009; Hernandez, R.J., Selke, S.E.M., & Culter, J.D.,

2000; Miller K., & Krochta, J., 1997; Sha, H.,& Harrison, I.R., 1992). The wettability of the surface could also determine the adsorption of simulant.

The cross-sectional view of 4-ABCA (Figure 4.13A and C) was viewed by microscopy (x40 magnification). The image before retort was clear and after retort the inner layer of CPP absorbed tomato paste but the anti-stain layer was clear. Figures 4.13

B and D show the inner surface of the film before and after processing. The white 4-

ABCA film was transformed to reddish yellow due to adsorption of oil and tomato paste onto the surface. Dobias. J., (2002) studied the migration of water, olive oil and other

66 solvents into PP and PE films during high pressure processing. There was 8-9% migration (scalping) of olive oil and 0% migration (scalping) of water into the PP films.

During absorption or the scalping process the food molecules are absorbed into the holes, which is the free volume present in the amorphous region of the polymer. This affects the diffusion rate of the permeants. Flavor compounds compete with oxygen for the same hole or site, thereby reducing solubility of oxygen in the polymer. Also, simulant or flavor compounds can be absorbed into the polymer and swell the polymer structure increasing permeability (Hernandez-Muñoz, P., Catala, R., & Gavara, R., 1999; Stern, S.,

& Trohalaki, S., 1990). Polymers like PP, LDPE and HDPE during sorption of flavor compounds like limonene and rapeseed oil lost barrier, but PET and APET did now show any change in permeability(Johansson, F., & Leufvén, A., 1994; Sadler, G.D., &

Braddock, R.J., 1990; Willige, V.R., Linssen, J., Meinders, M., Van Der Stege, H., &

Voragen, A., 2002). Water sorption in polymers tends to decrease the solubility of non- polar substances and increase solubility of polar substances (Aucejo, S., Pozo, M.J., &

Gavara, R., 1998). Formation of bio-films due to adsorption and scalping of the simulant

(lycopene, water and oil) onto and into the polymer film respectively is also possible.

This food simulant may have plugged the holes in the polymer matrix and blocked the flow of permeants, thereby increasing the barrier.

4.7 A)

4.7 B)

Figure 4.7. SEM images of the outer surface of the film 1-ABC, A is before and B is after retort.

4.8 A)

4.8 B)

Figure 4.8. SEM images of the outer surface of the film 2-HBC, A is before and B is after retort.

4.9 A)

4.9 B)

Figure 4.9. SEM images of the outer surface of the film 3-ABCL, A is before and B is after retort.

4.10 A)

4.10 B)

Figure 4.10. SEM images of the outer surface of the film 4-ABCA, A is before and B is after retort.

4.11 A)

4.11 B) 4.11 C)

Figure 4.11. SEM images of the outer surface of the film 5-HBC2, A is before and B is after retort and C is magnification x900 of after retort image.

4.12 A)

4.12 B)

Figure 4.12. SEM images of the outer surface of the film 6-PFBC, A is before and B is after retort.

4.13A) 4.13 B)

4.13C) 4.13D)

Figure 4.13. Microscopic crossectional images(x40) and pictures of the inner layer of film 4-ABCA. A and B are before retort and C and D are after retort.

a*-value (Anti-staining)

14.0

9.0

a* value a* 4.0 Before After -1.0

-6.0 1-ABC 2-HBC 3-ABCL 4-ABCA 5-HBC2 6-PFBC Days

Figure 4.14. Changes in a* values for all films for both before and after retort.

Relative shelf-life prediction

Relative shelf-life in this study was predicted for accelerated conditions (45±2°C at

50±2%RH). The simulant used in this study was a complex mixture of corn oil with 10% vitamin E and lycopene, which also had anti-oxidant properties. It is difficult to measure the kinetics of lipid oxidation in an oil-in-water emulsion (McClements, D., & Decker,

E., 2000). Oxidation of corn oil and lycopene in the pouches started during processing. At high temperature the rate of oxidation for oil is high and has a linear correlation

(Gómez‐Alonso, S., Mancebo‐Campos, V., Salvador, D.M., & Fregapane, G., 2004).

Lycopene undergoes thermal isomerization at high temperature and oxidation of lycopene in oil also depends on factors like anti oxidant and ascorbic acid content (Ax, K., 2003;

Smith,J.S., & Hui, Y.H., 2004). Hence, it is difficult to calculate the kinetics of

75 degradation due to oxidation. The relative shelf-life was calculated from the values after retort and during storage . A relative comparison was necessary within the pouches with respect to lipid oxidation and lycopene degradation to evaluate the performance of the different pouches.

Relative shelf-life was calculated using an extrapolation method used by previous researchers (Lee, S.Y., & Krochta, J., 2002; Sedaghat, N., 2010). Shelf-life prediction curves were drawn by plotting natural log of (OD, L* and a* value) versus time in days.

Multiple linear regression was carried out on the plotted points. OD, L* and a* values

(Figure 4.15,4.16 and 4.17) showed a good correlation coefficient (r2) which was >0.88, the linear model equation derived was used to determine shelf life at accelerated condition. While, for b* value and hue angle (4.18 and 4.19) the r2 value was <0.80 which was not a good fit and hence was not used to determine shelf-life. End of shelf-life value for OD was considered to be the ln(OD) value on day 49 (week 7) for 6-PFBC pouch.

This was based on previous research which showed shelf-life of sunflower oil stored in a glass bottle containing 1/3 headspace oxyen exposed at 40°C to be 9.04 to 10.45 weeks

(Makhoul, H., 2006). For the color of tomato with respect to L* and a* value the end of shelf-life was considerd as ln(L* and a* value) on day 79 (week 11.2) for 6-PFBC pouch.

Eckerle Jean. R. et al., (1984) determined the shelf-life of canned tomato paste exposed at

45°C to be 10-15 weeks. This was based on instrumental methods like serum color and hunter lab value, with trained profile panel evaluation. In this study 6-PFBC being the standard foil barrier was assumed to perform similar to glass bottle and metal can.

6-PFBC showed a 47 days shelf life with respect to OD, which was the maximum days.

This was expected as it had the foil barrier. 4-ABCA had a 44 days shelf-life. The shelf- life for 5-HBC2 was 29 days, higher than 2-HBC with 32 days. The rate of change of

TBARS was assumed to be similar between 1-ABC and 3-ABCL giving 37 and 38 days shel-life respectively. Hence, It can be said that the performance of 5-HBC2 is also intermediate like 1-ABC, 2-HBC and 3-ABCL. 7-C, which had the lowest barrier showed the least shelf life of 2 days. For L* and a* values (Figures 4.16, 4.17 and Tables 4.8 and

4.9) linear regression was best fit with r2 value >0.88. The rate of color change for L* value was assumed to be similar for 4-ABCA and 6-PFBC with 72 and 74 days of shelf life, respectively. 1-ABC, 2-HBC and 3-ABCL showed 56, 60 and 55 days respectively.

This indicated color change with respect to lightness was similar in these pouches. For 5-

HBC2 the shelf-life was 37 days with the highest reaction rate compared with the other barrier pouches. The rate of reaction for a* value for 5-HBC2 was also high with least shef-life of 43 days. This indicated loss in red color for 5-HBC2 would be at a faster rate compared to that in other barrier pouches. 1-ABC, 2-HBC and 3-ABCL showed 59, 61 and 57 days respectively. 4-ABCA had a good shelf life of 72 days in comparison with

78 days for 6-PFBC. 7-C with the highest degradation of lycopene and having high OP showed -1 days shelf-life indicating end of shelf-life during the processing step. The shelf-life data correlated well with the OP result.

Lycopene is considered to be more stable in corn oil as preferential oxidation inhibits oxidation of lycopene. Anti-oxidants like tocopherols oxidize first (Boon, C.S., 2008).

Lycopene being lipophilic is soluble in oil. Oil coats the lycopene and protects it against

77 oxidation by blocking its ability to react with oxygen molecule (Chen,J., Shi, J., Xue,S.J.,

& Ma, Y., 2009). This was observed in comparison of shelf-life with respect to lipid oxidation and color change. Oxidation of lipids takes place at a higher rate hence the shelf-life in all the pouches were lower in comparison with rate of color change, e.g. end of shelf-life with respect to lipid oxidation is 29 days for the low performance barrier film

5-HBC2, while for L* and a* values the shelf-life is 37 and 43days, respectively.

Table 4.7. Linear model equation and estimated shelf-life based on TBARS at 45±2°C and 50±2%RH Pouches Model equation Approximate days 1-ABC y = 0.0190x - 3.6928 37 2-HBC y = 0.0168x - 3.5215 32 3-ABCL y = 0.0225x - 3.8416 38 4-ABCA y = 0.0204x - 3.8813 44 5-HBC2 y = 0.0145x - 3.4109 29 6-PFBC y = 0.0219x - 3.9332 47 7-C y = 0.0108x - 3.0251 2 Here, y= -2.98249 i.e. Ln (OD) on day 49 for 6-PFBC

Table 4.8. Linear model equation and estimated shelf-life based on L* value at 45±2°C and 50±2%RH Pouches Linear model equation Approximate days 1-ABC y = -0.0014x + 3.4282 56 2-HBC y = -0.0013x + 3.4285 60 3-ABCL y = -0.0014x + 3.4268 55 4-ABCA y = -0.0012x + 3.4363 72 5-HBC2 y = -0.0016x + 3.4095 37 6-PFBC y = -0.0012x + 3.4395 74 7-C y = -0.0043x + 3.3508 5 Here, y= 3.349787 i.e. Ln (L* value) on day 79 for 6-PFBC

Table 4.9. Linear model equation and estimated shelf-life based on a* value at 45±2°C and 50±2%RH Pouches Linear model equation Approximate days 1-ABC y = -0.0037x + 2.9224 59 2-HBC y = -0.0035x + 2.9142 61 3-ABCL y = -0.0038x + 2.9180 57 4-ABCA y = -0.0035x + 2.9425 69 5-HBC2 y = -0.0039x + 2.8717 43 6-PFBC y = -0.0034x + 2.9473 78 7-C y= -0.0275x + 2.6691 -1 Here, y= 2.700578 i.e. Ln (a* value) on day 79 for 6-PFBC

TBARS (Oxidation kinetics) 0 y = 0.0190x - 3.6928 0 10 20 30 40 50 -0.5 1-ABC R² = 0.8757 y = 0.0168x - 3.5215 -1 2-HBC R² = 0.9242 -1.5 y = 0.0225x - 3.8416 3-ABCL R² = 0.9297 -2 y = 0.0204x - 3.8813 4-ABCA R² = 0.9669

-(OD) Ln 2.5 y = 0.0145x - 3.4109 -3 5-HBC2 R² = 0.9556 -3.5 y = 0.0219x - 3.9332 6-PFBC R² = 0.941 -4 y = 0.0108x - 3.0251 7-C -4.5 R² = 0.9185 Days

Figure 4.15. Plot of Ln (OD) vs. Days for Shelf-life prediction based on TBARS at 45±2°C, 50±2%RH using linear model equation as shown.

3.5 L* value (Oxidation kinetics) 3.45 y = -0.0014x + 3.4282 R² = 0.9807 3.4 1-ABC 3.35 y = -0.0013x + 3.4285 2-HBC R² = 0.8953 3.3 y = -0.0014x + 3.4268 3.25 R² = 0.9789 3-ABCL 3.2 y = -0.0012x + 3.4363 Ln(L* value) Ln(L* 3.15 4-ABCA R² = 0.8828 3.1 y = -0.0016x + 3.4095 5-HBC2 R² = 0.9296 3.05 y = -0.0012x + 3.4395 3 6-PFBC R² = 0.8845 2.95 y = -0.0043x + 3.3508 0 20 40 60 80 7-C R² = 0.9107 Days

Figure 4.16. Plot of Ln (L* value) vs. Days for Shelf-life prediction based on L* value at 45±2°C, 50±2%RH using linear model equation as shown.

3.5 a* value (Oxidation kinetics)

y = -0.0037x + 2.9224 3 1-ABC R² = 0.9798 y = -0.0035x + 2.9142 2.5 2-HBC R² = 0.9742 y = -0.0038x + 2.9180 2 3-ABCL R² = 0.9865 y = -0.0035x + 2.9425 1.5 4-ABCA

Ln (a* value) (a* Ln R² = 0.9537 y = -0.0039x + 2.8717 1 5-HBC2 R² = 0.9773 y = -0.0034x + 2.9473 0.5 6-PFBC R² = 0.9594

0 7-C y = -0.0275x + 2.6691 0 20 40 60 80 R² = 0.9536 Days

Figure 4.17. Plot of Ln (a* value) vs. Days for Shelf-life prediction based on a* value at 45±2°C, 50±2%RH using linear model equation as shown.

b* value (Oxidation kinetcs) 3.5 y = 0.0002x + 2.7923 1-ABC R² = 0.027 3 y = 0.0001x + 2.8106 2-HBC R² = 0.0062 2.5 y = -7E-050x + 2.8239 3-ABCL R² = 0.0046 2 y = 0.0002x + 2.8352 4-ABCA R² = 0.0456 1.5

Ln(b* value) Ln(b* y = -0.0007x + 2.8079 5-HBC2 1 R² = 0.2618 6-PFBC y = -7E-050x + 2.8565 0.5 R² = 0.0034 7-C y = -0.0139x + 2.5214 0 R² = 0.8089 0 20 40 60 80 Days

Figure 4.18. Plot of Ln (b* value) vs. Days at 45±2°C, 50±2%RH with linear model equation.

HUE Angle (Oxidation kinetics) 0.3 y = 0.0025x - 0.3273 1-ABC 0.2 R² = 0.8422 y = 0.0023x - 0.3103 0.1 2-HBC R² = 0.7879 y = 0.0023x - 0.3024 0 3-ABCL R² = 0.8033 0 20 40 60 80 -0.1 4-ABCA y = 0.0023x - 0.3115 R² = 0.7943

-(radiance)Ln 0.2 5-HBC2 y = 0.0020x - 0.2827 R² = 0.8527 -0.3 6-PFBC y = 0.0021x - 0.3008 -0.4 R² = 0.8369 7-C y = 0.0069x - 0.3177 -0.5 R² = 0.7145 Days

Figure 4.19. Plot of Ln (Hue angle) vs. Days at 45±2°C, 50±2%RH with linear model equation.

Literature cited

Aucejo, S., Pozo, M. J., & Gavara, R. (1998). Effect of water presence on the sorption of organic compounds in ethylene–vinyl alcohol copolymers. Journal of Applied Polymer Science, 70(4), 711-716.

Ax, K., Mayer‐Miebach, E., Link, B., Schuchmann, H., & Schubert, H. (2003). Stability of lycopene in Oil‐in‐Water emulsions. Engineering in Life Sciences, 3(4), 199-201.

Barker, C., Kochem, K. H., Revell, K., Kelly, R., & Badyal, J. (1995). Atomic force microscopy and permeability study of stretching-induced gas barrier loss of AlOx layers. Thin Solid Films, 259(1), 46-52.

Barreiro, J., Milano, M., & Sandoval, A. (1997). Kinetics of colour change of double concentrated tomato paste during thermal treatment. Journal of Food Engineering, 33(3-4), 359-371.

Benmalek, M., & Dunlop, H. (1995a). Inorganic coatings on polymers. Surface and Coatings Technology, 76, 821-826.

Benmalek, M., & Dunlop, H. (1995b). Inorganic coatings on polymers. Surface and Coatings Technology, 76, 821-826.

Boskovic, M. A. (1979). Fate of lycopene in dehydrated tomato products: carotenoid isomerization in food system. Journal of Food Science, 44(1), 84-86. doi:10.1111/j.1365-2621.1979.tb10011.x

Boon, C. S., Xu, Z., Yue, X., McClements, D. J., Weiss, J., & Decker, E. A. (2008). Factors affecting lycopene oxidation in oil-in-water emulsions. Journal of Agricultural and Food Chemistry, 56(4), 1408-1414.

Breil, J. (2009). Oriented film technology. In (pp. 119-135)

Caner, C., Hernandez, R., Pascall, M., & Riemer, J. (2003). The use of mechanical analyses, scanning electron microscopy and ultrasonic imaging to study the effects of high‐pressure processing on multilayer films. Journal of the Science of Food and Agriculture, 83(11), 1095-1103.

Chatham, H. (1996). Oxygen diffusion barrier properties of transparent oxide coatings on polymeric substrates. Surface and Coatings Technology, 78(1-3), 1-9.

Chen, J., Shi, J., Xue, S. J., & Ma, Y. (2009). Comparison of lycopene stability in water- and oil-based food model systems under thermal-and light-irradiation treatments. LWT-Food Science and Technology, 42(3), 740-747.

Cole, E. R., & Kapur, N. S. (1957). The stability of lycopene. II.?oxidation during heating of tomato pulps. Journal of the Science of Food and Agriculture, 8(6), 366- 368. doi:10.1002/jsfa.2740080611

Eckerle, J.R., Harvey C.D., & Che T.G (1984). Life cycleof canned tomato paste: Correlation between sensory and instrumental testing methods. Journal of food science, 49, 1188-1193.

Galotto, M., Ulloa, P., Hernandez, D., Fernández‐Martín, F., Gavara, R., & Guarda, A. (2008). Mechanical and thermal behaviour of flexible food packaging polymeric films materials under high pressure/temperature treatments. Packaging Technology and Science, 21(5), 297-308.

Gómez‐Alonso, S., Mancebo‐Campos, V., Desamparados Salvador, M., & Fregapane, G. (2004). Oxidation kinetics in olive oil triacylglycerols under accelerated shelf‐life testing (25–75° C). European Journal of Lipid Science and Technology, 106(6), 369- 375.

Gordon M.H. (2004). Factors affecting lipid oxidation. In Understanding and measuring shelflife of food (pp. 128-131) Woodhead Publishing.

Gotz, J., & Weisser, H. (2002). Permeation of aroma compounds through plastic films under high pressure: In-situ measuring method. Innovative Food Science & Emerging Technologies, 3(1), 25-31.

Henry, B. M., Erlat, A. G., McGuigan, A., Grovenor, C. R. M., Briggs, G. A. D., Tsukahara, Y., Niijima, T. (2001). Characterization of transparent aluminium oxide and indium tin oxide layers on polymer substrates. Thin Solid Films, 382(1-2), 194- 201. doi:DOI: 10.1016/S0040-6090(00)01769-7

Hernandez, R. J. (1994). Effect of water vapor on the transport properties of oxygen through polyamide packaging materials. Journal of Food Engineering, 22(1-4), 495- 507.

Hernandez, R. J., Selke, S. E. M., & Culter, J. D. (2000). Plastics packaging Hanser.

Hernandez-Muñoz, P., Catala, R., & Gavara, R. (1999). Effect of sorbed oil on food aroma loss through packaging materials. Journal of Agricultural and Food Chemistry, 47(10), 4370-4374.

Hughes, A. (2000). Canned food safety CRC.

Johansson, F., & Leufvén, A. (1994). Influence of sorbed vegetable oil and relative humidity on the oxygen transmission rate through various polymer packaging films. Packaging Technology and Science, 7(6), 275-281. doi:10.1002/pts.2770070604

Lee, S. Y., & Krochta, J. (2002). Accelerated shelf life testing of whey-protein-coated peanuts analyzed by static headspace gas chromatography. Journal of Agricultural and Food Chemistry, 50(7), 2022-2028.

López-Rubio, A., Lagaron, J. M., Giménez, E., Cava, D., Hernandez-Muñoz, P., Yamamoto, T., & Gavara, R. (2003). Morphological alterations induced by temperature and humidity in ethylene-vinyl alcohol copolymers. Macromolecules, 36(25), 9467-9476.

Lovric, T., Sablek, Z., & Boskovic, M. (1970). Cis-trans isomerisation of lycopene and colour stability of foam?mat dried tomato powder during storage. Journal of the Science of Food and Agriculture, 21(12), 641-647. doi:10.1002/jsfa.2740211210

Makhoul, H., Ghaddar Tarek., Toufeill.I., (2006). Identification of some rancidity measures at the end of the shelf life of sunflower oil. Eur.J.Lipid Sci.Technol, 106,143-148.

McClements, D., & Decker, E. (2000). Lipid oxidation in Oil‐in‐Water emulsions: Impact of molecular environment on chemical reactions in heterogeneous food systems. Journal of Food Science, 65(8), 1270-1282.

Miller, K., & Krochta, J. (1997). Oxygen and aroma barrier properties of edible films: A review. Trends in Food Science & Technology, 8(7), 228-237.

Min, S., & Zhang, Q. (2003). Effects of Commercial‐scale pulsed electric field processing on flavor and color of tomato juice. Journal of Food Science, 68(5), 1600- 1606.

Noble, A. C. (1975). Investigation of the color changes in heat concentrated tomato pulp. Journal of Agricultural and Food Chemistry, 23(1), 48-49.

Porretta, S. (1991). Nonenzymatic browning of tomato products. Food Chemistry, 40(3), 323-335.

Robertson, G. L. (2006). Food packaging: Principles and practice CRC press.

Sadler, G. D., & Braddock, R. J. (1990). Oxygen permeability of low density polyethylene as a function of limonene absorption: An approach to modeling flavor ?scalping? Journal of Food Science, 55(2), 587-588. doi:10.1111/j.1365- 2621.1990.tb06826.x

Sedaghat, N. (2010). Pistachio nuts shelf life based on sensory evaluation. American- Eurasian Journal of Agricultural & Environmental Sci,

Sha, H., & Harrison, I. R. (1992). CO2 permeability and amorphous fractional free- volume in uniaxially drawn HDPE. Journal of Polymer Science Part B: Polymer Physics, 30(8), 915-922. doi:10.1002/polb.1992.090300814

Shi, J., Dai, Y., Kakuda, Y., Mittal, G., & Xue, S. J. (2008). Effect of heating and exposure to light on the stability of lycopene in tomato puree. Food Control, 19(5), 514-520.

Shi, J., & Maguer, M. L. (2000). Lycopene in tomatoes: Chemical and physical properties affected by food processing. Critical Reviews in Food Science and Nutrition, 40(1), 1-42.

Smith, J. S., & Hui, Y. H. (2004). Food processing: Principles and applications Wiley- Blackwell.

Stern, S., & Trohalaki, S. (1990). Fundamentals of gas diffusion in rubbery and glassy polymers. Barrier Polymers and Structures, , 22-59.

Tarladgis, B. G., Pearson, A., & Jun, L. (1964). Chemistry of the 2‐thiobarbituric acid test for determination of oxidative rancidity in foods. II.—formation of the tba‐malonaldehyde complex without acid‐heat treatment. Journal of the Science of Food and Agriculture, 15(9), 602-607.

Tarladgis, B. G., Watts, B. M., Younathan, M. T., & Dugan, L. (1960). A distillation method for the quantitative determination of malonaldehyde in rancid foods. Journal of the American Oil Chemists' Society, 37(1), 44-48.

Van Willige, R., Linssen, J., Meinders, M., Van der Stege, H., & Voragen, A. (2002). Influence of flavour absorption on oxygen permeation through LDPE, PP, PC and PET plastics food packaging. Food Additives & Contaminants: Part A, 19(3), 303

Wiese, K. L., & Dalmasso, J. P. (1994). Relationships of color, viscosity, organic acid profiles and ascorbic acid content to addition of organic acids and salt in tomato juice. Journal of Food Quality, 17(4), 273-284.

CHAPTER FIVE

CONCLUSION

Based on the results using TBARS, 4-ABCA showed the best performance with respect to lipid oxidation, lycopene degradation and OP. It was one of the best alternatives to replace 6-PFBC foil barrier, especially for high fat content products. While 1-ABC, 2-

HBC and 3-ABCL showed an intermediate performance for all the tests with no significant difference among them except for Hue angle, the performance of these pouches were not significantly different to 4-ABCA and 6-PFBC. These films are a good option if a product containing lycopene like tomato sauce or paste is to be packed. The rate of lipid oxidation was assumed to be higher than color degradation of lycopene pigment because of the coating formed by oil on lycopene, thus interfering with lycopene oxidation. Lycopene undergoes degradation by thermal isomerization and oxidation, hence a high amount of color change was observed before and after processing. The barrier coating on 5-HBC2 was seen to be greatly affected by retort and hence it had high

TBAR and low color values with high OP after retort. This film still performed well compared to 7-C because of the dual barrier coating. It was observed that nano-scale defects and cracks in the coatings decreased the barrier property of the films. However, if the coating was below PET layer it may have been less prone to damage. Film thickness was seen to greatly affect the deteriration of barrier coating. 4-ABCA showed the least cracks and pinholes on SEM as compared to other barrier films.Also, the cracks and pinholes on the coating did not recover during storage. Permeability can also be affected

87 by the scalping of biological compounds into the polymer film. These compounds can block or swell the free volume space in the polymer thereby reducing or increasing the oxygen permeability. This phenomenon mainly occurs during retort processing. Oil and lycopene undergo oxidation at higher rate in presence of light ( Kaya, A., Tekin, A. R., &

Öner, M. D., 1993; Lee, M., & Chen, B., 2002). 4-ABCA being opaque and having equivalent barrier to foil would be a good option when the product is to be stored on a retailer shelf.

Literature cited

Kaya, A., Tekin, A. R., & Öner, M. D. (1993). Oxidative stability of sunflower and olive oils: Comparison between a modified active oxygen method and long term storage. Lebensmittel- Wissenschaft Und-Technologie, 26(5), 464-468. doi:DOI: 10.1006/fstl.1993.1091

Lee, M., & Chen, B. (2002). Stability of lycopene during heating and illumination in a model system. Food Chemistry, 78(4), 425-432.