Food and Packaging Interactions - ACS Publications - American

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Chapter 1

An Overview of Food and Food Packaging Interactions

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Joseph H . Hotchkiss Institute of Food Science, Food Science Department, Cornell University, Stocking Hall, Ithaca, NY 14853-7201 This paper is a b r i e f overview of the symposium that was conducted by the Agricultural and Food Chemistry Division of the American Chemical Society at the Spring, 1987 meeting. Twenty-two papers were presented at the meeting on topics related to the interactions between foods and food packaging. Several papers dealt with specific topics while others were of a review nature. The objective of t h i s introduction is to set the stage for the papers that follow i n t h i s volume.

There have been s i g n i f i c a n t changes i n both food processing and food packaging technologies over the l a s t 5 t o 10 years. These changes have included new ways t o process foods, the use o f new packaging materials, new combinations of standard materials, and new methods of manufacturing containers. While none o f the b a s i c materials (Table 1) used t o package foods has escaped change, more change has occurred i n the area o f p l a s t i c s than any other. F o r example, there has been a large increase i n the use o f p l a s t i c b o t t l e s f o r food packaging (Figure 1). P l a s t i c s which were once perceived as undesirable by food processors and consumers are now o f t e n seen as the best form of packaging a v a i l a b l e . Nearly a l l types of food packaging use p l a s t i c s as p a r t of t h e i r construction. Change has a l s o occurred i n food processing over the l a s t few years. The US Food and Drug Administration's 1981 approval o f hydrogen peroxide t o s t e r i l i z e packages p r i o r t o f i l l i n g was a watershed i n food packaging development. The commercial success of t h i s packaging process demonstrated t h a t the US consumer was ready t o accept packaging innovations i f they provided a u s e f u l b e n e f i t . Soon a f t e r the success of aseptic packaging became apparent, development of new packages such as microwavable containers, r e t o r t a b l e p l a s t i c cans, and s e l e c t i v e / h i g h b a r r i e r f i l m s were under development.

0097-6156/88/0365-0001$06.00/0 © 1988 American Chemical Society

Hotchkiss; Food and Packaging Interactions ACS Symposium Series; American Chemical Society: Washington, DC, 1988.

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FOOD AND P A C K A G I N G INTERACTIONS

TABLE I- Dollar value and market share of materials used to manufacture packaging (data from Rauch, 1986) a

Year

Material

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Paperboard/pulp Metal Plastics Paper Glass Wood Textile

18,842 14,638 9,672 4,432 3,850 1,790 574

Total

53,798

a. b.

1990k

1985

1984 (35) (27) (18) ( 8) ( 7) ( 3) ( i)

19,340 15,052 10,255 4,690 4,100 1,826 570 55,833

(35) (27) (18) ( 8) ( 7) ( 3) ( 1)

24,580 18,600 15,970 5,610 5,225 2,003 622

(34) (26) (22) ( 8) ( 7) ( 3) ( 1)

72,610

m i l l i o n s o f d o l l a r s (percent market share) estimated

Innovations i n food processing have placed new demands on packaging and have accelerated the development o f new packages. For example, the d e s i r e t o thermally process low a c i d foods i n r i g i d p l a s t i c cans has l e d t o the development of multi-layered p l a s t i c materials t h a t maintain t h e i r b a r r i e r s even a f t e r being thermally processed i n steam (1). Because these p l a s t i c containers w i l l most l i k e l y have f l e x i b l e f i l m closures instead of r i g i d double seamed closures, heat s e a l i n g technology has a l s o become o f c r i t i c a l importance. These and other innovations are driven by economic and marketplace forces. Food manufactures have found t h a t packaging can g i v e them a competitive edge i n the marketplace and consumers have shown a w i l l i n g n e s s t o pay more f o r package-product combinations which o f f e r greater convenience and/or higher q u a l i t y . The packaging industry has responded t o food manufactures by developing new packages t h a t promise t o o f f e r e i t h e r reduced packaging costs o r increased sales because o f added package convenience. One of the most discussed examples i s the i n t r o d u c t i o n of high b a r r i e r p l a s t i c b o t t l e s f o r oxygen s e n s i t i v e food products (2). Ketchup i n t h i s container was reported t o capture increased market share during i t s i n i t i a l i n t r o d u c t i o n even though i t s o l d f o r more money. This introductory overview w i l l discuss some examples of the most recent changes i n food processing and packaging technologies and w i l l p o i n t out how these changes have r e s u l t e d i n new problems and opportunities f o r food manufactures. The i n d i v i d u a l papers presented i n t h i s symposium deal i n d e t a i l w i t h the consequences and/or needs created by these changing technologies. Research i n t o the i n t e r a c t i o n s between foods and food packaging has lagged w e l l behind the development of new packages, but as t h i s symposium

Hotchkiss; Food and Packaging Interactions ACS Symposium Series; American Chemical Society: Washington, DC, 1988.

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HOTCHKISS

An Overview of Food & Food Packaging Interactions

0-1

1 1975

1970

1 1980

1 1985

YEAR Figure 1. Growth i n the production o f p l a s t i c b o t t l e s f o r foods from 192 χ 1 0 l b s i n 1974 t o 835 χ 1 0 l b s i n 1985 (Data from Rauch, 1986) 6

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Hotchkiss; Food and Packaging Interactions ACS Symposium Series; American Chemical Society: Washington, DC, 1988.

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F O O D AND P A C K A G I N G INTERACTIONS

shows, i s an area of growing research i n t e r e s t . Many foods t h a t were formerly packaged i n nearly i n e r t metal o r g l a s s containers are now being packaged i n l e s s i n e r t p l a s t i c s and foods t h a t were once thought too s e n s i t i v e f o r f l e x i b l e f i l m s are now packaged i n high b a r r i e r f l e x i b l e pouches. I n f a c t , some foods such as " s o f t " cookies o r intermediate moisture foods might not be f e a s i b l e without such packaging. The i n t e r a c t i o n s between foods and packaging must now be considered when changing t o l e s s i n e r t materials, p a r t i c u l a r l y p l a s t i c s .

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Changes i n Food Processing Technology Recently, consumers have shown a w i l l i n g n e s s t o pay more f o r foods t h a t are perceived as fresher, higher q u a l i t y , o r of greater value. Meeting t h i s demand w h i l e maintaining adequate d i s t r i b u t i o n time has necessitated new technologies designed t o extend s h e l f l i f e without s a c r i f i c i n g q u a l i t y . Because of the negative connotations o f food a d d i t i v e s , many s h e l f l i f e extension technologies are based on packaging. One of the most discussed methods t o extend the s h e l f l i f e of r e f r i g e r a t e d , perishable foods i s modified atmosphere packaging (MAP) (3). I n t h i s technology, the gases w i t h i n a package are a l t e r e d t o something other than a i r . This has two consequences. F i r s t , changing the atmosphere changes the balance o f microorganisms. This can r e s u l t i n considerable extension o f s h e l f l i f e f o r those products whose major mode o f d e t e r i o r a t i o n i s mediated through microorganisms. Secondly, the r e s p i r a t i o n r a t e of f r u i t s and vegetables can be reduced by a change i n atmosphere. This can g r e a t l y extend s h e l f l i f e and may r e s u l t i n the brand l a b e l i n g of many products t h a t are now marketed as commodities. In order f o r MAP t o be commercially successful, f i l m manufacturers w i l l have t o develop a wider range of s e l e c t i v e b a r r i e r f i l m s . For example, a f i l m i n which the permeation r a t e of carbon dioxide was as low as t h a t of oxygen would be u s e f u l i n maintaining i n t e r n a l atmospheres. Food manufacturers w i l l have t o c a r e f u l l y determine what mixtures of gases s u c c e s s f u l l y extend the s h e l f l i f e o f t h e i r products The wide spread use of the home microwave oven has a l s o meant s u b s t a n t i a l changes i n food packaging. Several major food processors have converted t h e i r packages from metal t o microwave transparent packaging. Glass and many p l a s t i c s are microwave transparent and new packages made from each m a t e r i a l have been developed. Some packages incorporate a microwave absorbing m a t e r i a l i n order t o a i d i n the t r a n s f e r of heat t o a food. The use of the microwave oven has a l s o meant t h a t higher temperature p l a s t i c s such as c r y s t a l l i z e d polyethylene terephthalate (CPET) have had t o be developed. These containers are not without problems, however. Some containers can t r a n s f e r undesirable odors t o foods during microwave cooking as discussed by Risen and Reineccius i n t h i s volume. Food i r r a d i a t i o n i s c o n t r o v e r s i a l and i t s not c l e a r i f the p u b l i c i s ready t o accept i r r a d i a t e d foods. What i s c l e a r , i s t h a t not enough i s known about the e f f e c t s o f i o n i z i n g r a d i a t i o n on some o f the most u s e f u l packaging materials. As Thayer p o i n t s

Hotchkiss; Food and Packaging Interactions ACS Symposium Series; American Chemical Society: Washington, DC, 1988.

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1.

HOTCHKISS

An Overview of Food & Food Packaging Interactions

out i n t h i s volume, t h i s i s e s p e c i a l l y t r u e f o r multilayered structures. The problems of polymer s c i s s i o n verses c x o s s l i n k i n g , increases i n the l e v e l s o f p o t e n t i a l migrants, and l o s s o f strength o r s e a l i n t e g r i t y have not been f u l l y addressed. While there appear t o be some materials a v a i l a b l e which w i l l perform s a t i s f a c t o r i l y under i r r a d i a t i o n , these materials may not have the desired b a r r i e r properties f o r long term storage of i r r a d i a t e d foods. Aseptic packaging represents a t r u e s y n e r g i s t i c marriage of food processing and packaging technologies. The conventional way t o produce a s h e l f stable food i s t o f i r s t package the food i n a hermetically sealed container followed by batch s t e r i l i z a t i o n (Figure 2). I n aseptic packaging, the package and the food are s t e r i l i z e d separately, u s u a l l y by d i f f e r e n t methods. The food undergoes some type of continuous heating i n a heat exchanger while the package may undergo chemical, thermal, o r r a d i a t i o n treatments. The s t e r i l i z e d food and package are brought together and a s e p t i c a l l y f i l l e d and sealed (Figure 2). Neither the food process nor the package s t e r i l i z a t i o n would be of use alone. I n a s e p t i c packaging, s t e r i l i z a t i o n techniques t h a t would not be s u i t a b l e f o r foods could be used f o r the package; w i t h hydrogen peroxide, f o r example. I t a l s o means t h a t the package need not withstand the same s t e r i l i z a t i o n process as the food. Cheaper, paper-based materials can be used when other materials could be p r o h i b i t i v e l y expensive. The commercial success of the i n i t i a l paperboard based a s e p t i c a l l y packaged j u i c e s and r e l a t e d products has lead t o the development o f second generation aseptic packages. Many o f these packages are made from multi-layered, thermoformed polymer based materials. These containers are u s u a l l y heat sealed w i t h a f l e x i b l e l i d material ( 4 ) . I t i s l i k e l y t h a t there w i l l be an even greater increase a s e p t i c packaging as the technology t o commercially s t e r i l i z e foods containing p a r t i c u l a t e matter becomes a v a i l a b l e . This may mean new forms of packaging. Low a c i d foods i n a s e p t i c packages w i l l present unique problems because the safety of these packages w i l l depend on the r e l i a b i l i t y of the heat seals. More r e l i a b l e and secure heat s e a l i n g polymers t h a t s t i l l can be opened e a s i l y w i l l need t o be developed as w i l l b e t t e r inspection systems and t e s t methods f o r s e a l strength and i n t e g r i t y . The examples given above are only a few o f the changes i n food processing. More changes are on the horizon. Many of these innovations w i l l involve packaging. The d i s t i n c t i o n between food processing and food packaging w i l l become i n c r e a s i n g l y b l u r r e d as the technologies merge. Changes i n Packaging Technology The food industry and the packaging industry are economically c l o s e l y a l l i e d . Nearly 53% of the packaging industry's s a l e s are t o the food industry (5). I n recent years t h i s a l l i a n c e has gone beyond economics t o j o i n t R&D e f f o r t s t o develop improved food packages. The packaging industry i s now i n v e s t i g a t i n g how s p e c i f i c packaging materials i n t e r a c t w i t h foods and the food industry i s becoming more involved i n the d i r e c t development of

Hotchkiss; Food and Packaging Interactions ACS Symposium Series; American Chemical Society: Washington, DC, 1988.

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FOOD AND PACKAGING INTERACTIONS

CONVENTIONAL

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ASEPTIC

ASEPTIC

RAW

RAW

CONVENTIONAL

PACKAGE

PRODUCT

PRODUCT

PACKAGE

CONTINUOUS

CONTINUOUS

FILL

STERILIZATION

THERMAL

SEAL

(H 0 ,HEAT)

STERILIZATION

2

2

THERMALLY PROCESS

SHELF STABLE PRODUCT

Figure 2. Comparison o f conventional and a s e p t i c processing systems f o r the production o f s h e l f s t a b l e foods. I n conventional processing the food i s h e r m e t i c a l l y sealed i n the package p r i o r t o processing. I n a s e p t i c processing the food and package are independently œmmercially s t e r i l i z e d p r i o r t o f i l l i n g and s e a l i n g .

Hotchkiss; Food and Packaging Interactions ACS Symposium Series; American Chemical Society: Washington, DC, 1988.

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1.

HOTCHKISS

An Overview of Food & Food Packaging Interactions

packaging. Some food companies have established t h e i r own p i l o t p l a n t s i z e d polymer processing f a c i l i t i e s and nearly a l l major food companies have p r o f e s s i o n a l l y s t a f f e d packaging departments. This cooperation between the two i n d u s t r i e s has accelerated the development o f new packaging technologies. For example, several container companies have developed the technology t o coextrude d i s s i m i l a r p l a s t i c s i n t o sheets o r parisons from which food containers can be formed. This has meant t h a t high b a r r i e r polymers such as ethylenevinyl alcohol (EVOH) o r poly ( v i n y l i d i n e d i c h l o r i d e ) (PVDC) can be incorporated i n t o a r i g i d t r a y o r b o t t l e , even though those materials would not be s u i t a b l e by themselves (6). This technology has r e c e n t l y been used t o package such oxygen s e n s i t i v e foods as ketchup and mayonnaise. Modifications o f the same technology are being used t o manufacture r i g i d p l a s t i c "cans" t h a t can withstand r e t o r t i n g a t 121 C without l o s i n g t h e i r b a r r i e r properties. Several new food products have r e c e n t l y been introduced i n these containers i n c l u d i n g soups, stews, and other entree items (7). The use o f p l a s t i c containers f o r h o t - f i l l e d and r e t o r t e d foods can be expected t o increase (8). The food and packaging i n d u s t r i e s are a l s o combining R&D e f f o r t s t o make use o f the dynamics o f the i n t e r a c t i o n s between food products and packages made from f i l m s . Two areas a r e emerging. F i r s t i s the p r e d i c t i o n o f s h e l f l i f e based on the b a r r i e r properties o f the package and the r a t e and mode o f d e t e r i o r a t i o n o f the food. By modeling these i n t e r a c t i o n s , i t i s p o s s i b l e t o p r e d i c t s h e l f l i f e and t o optimize the package f o r the s h e l f l i f e required by the product. This can r e s u l t i n reduced packaging costs. Several models f o r these i n t e r a c t i o n s are being proposed and improved (See papers by Chao and R i z v i , and Taoukis and Labuza i n t h i s volume f o r a d e t a i l e d d i s c u s s i o n ) . The packaging industry i s a l s o coming c l o s e r t o being able t o engineer desired permeability i n t o f i l m s . This development may mean t h a t r e s p i r i n g produce can be packaged i n bags i n which the i n t e r n a l atmosphere w i l l q u i c k l y come t o equilibrium. By s e l e c t i n g the proper package permeability, an i n t e r n a l atmosphere can be selected which w i l l decrease the r e s p i r a t i o n r a t e o f the produce. This w i l l be s i m i l a r t o the c o n t r o l l e d atmosphere storage o f apples t h a t has been p r a c t i c e d f o r several years. Developments have not been r e s t r i c t e d t o the use o f p l a s t i c s , the g l a s s and metal packaging i n d u s t r i e s have a l s o developed new containers. The glass industry has taken advantage o f the microwave transparency o f glass and has worked w i t h the food industry i n developing new product-package combinations. The g l a s s industry has a l s o improved the way t h a t g l a s s containers are manufactured i n order t o reduce the cost o f g l a s s . The p r i n c i p a l developments have been i n making glass containers l i g h t e r i n weight. Metal can manufacture has s u b s t a n t i a l l y changed over the l a s t few years. Metal cans are no longer manufactured by tin-coated, three-piece, s i d e soldered techniques. A majority o f cans produced i n the US are now made without lead solder o r t i n . Most modern cans are e i t h e r made from two pieces (a body and one end piece) o r are made from three pieces w i t h a welded s i d e seam. As Good points out i n t h i s volume, t h i s has necessitated the development o f improved can i n t e r i o r coatings.

Hotchkiss; Food and Packaging Interactions ACS Symposium Series; American Chemical Society: Washington, DC, 1988.

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F O O D AND P A C K A G I N G INTERACTIONS

Food and Food Packaging Interactions

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Changes i n food packaging have meant t h a t the ways foods i n t e r a c t w i t h packaging have l i k e w i s e changed. Interactions between foods and packaging can be c l a s s i f i e d i n t o four types: Migration or the Transfer of Components of the Package t o the Food During Storage o r Preparation. Migration can have both q u a l i t y and t o x i c o l o g i c a l s i g n i f i c a n c e . Very often, the components t h a t migrate from p l a s t i c s are odor a c t i v e and can adversely a f f e c t the f l a v o r of foods. This i s e s p e c i a l l y a problem when foods are heated i n p l a s t i c containers, as i n a microwave oven (See Risen and R e i n i c c i u s i n t h i s volume). Migration may a l s o r e s u l t i n the t r a n s f e r of p o t e n t i a l l y t o x i c substances t o foods. There has been considerable research i n t h i s area i n recent years, yet a l l the concerns have not been f u l l y addressed (9). For example, there i s s t i l l concern about the t r a n s f e r of v i n y l c h l o r i d e monomer (VCM) to foods packaged i n p o l y v i n y l c h l o r i d e (PVC). Migration o f p o t e n t i a l l y t o x i c components becomes a regulatory concern and a t l e a s t two papers (Breder, and H o l l i f i e l d and Fazio) i n t h i s symposium address the issues surrounding r e g u l a t i o n of migrants. The t h e o r e t i c a l aspects of migration are addressed by Chang and Smith i n t h i s volume. In recent years, migration has been used t o t r a n s f e r desired a d d i t i v e s t o foods. At l e a s t one can manufacturer has developed a system i n which metal ions t h a t w i l l help s t a b i l i z e the green c o l o r o f c h l o r o p h y l l are incorporated i n t o the can i n t e r i o r coating. The d e s i r e t o have antioxidants migrate from packaging to foods during storage i s a l s o addressed i n t h i s volume (see Harte e t a l ) . Permeation of the Food Container t o Fixed Gases and Water Vapor. U n l i k e g l a s s o r metal containers, f i x e d gases and water vapor can permeate packages made from p l a s t i c s o r t h i n f o i l s . While a l l p l a s t i c s are permeable t o some degree, permeation rates vary over three orders of magnitude (10). Considerable work has been undertaken i n the area of p r e d i c t i n g the e f f e c t s o f package permeation on the s h e l f l i f e of i n d i v i d u a l products. This work i s of considerable economic importance as the s h i f t t o p l a s t i c packaging continues. In nearly a l l cases, higher b a r r i e r f i l m s are much more expensive. The i d e a l s i t u a t i o n i s t o package products i n materials which w i l l protect foods only f o r the maximum s h e l f l i f e desired o r found i n the marketplace. P r o t e c t i n g foods f o r longer periods than necessary i s a form o f over-packaging (See Taoukis and Labuza i n t h i s volume f o r a discussion). The objective of modeling s h e l f l i f e work i s t o understand how s p e c i f i c b a r r i e r s influence the q u a l i t y of i n d i v i d u a l foods. There are a t l e a s t three ways t o approach t h i s problem. First i s t o package the food i n several containers and t o determine the s h e l f l i f e of each under a c t u a l d i s t r i b u t i o n conditions. While the data from such a t e s t i s good, t h i s i s not a p r a c t i c a l s o l u t i o n because of the time necessary t o conduct the t e s t on foods t h a t may have a s h e l f l i f e of several months. The second method i s t o place the packages i n storage under elevated temperature and

Hotchkiss; Food and Packaging Interactions ACS Symposium Series; American Chemical Society: Washington, DC, 1988.

1.

HOTCHKISS

An Overview of Food & Food Packaging Interactions

Downloaded by CORNELL UNIV on September 26, 2016 | http://pubs.acs.org Publication Date: March 9, 1988 | doi: 10.1021/bk-1988-0365.ch001

r e l a t i v e humidity conditions. This t e s t i s commonly conducted a t 100 F and 90% r e l a t i v e humidity. This method decreases the time necessary f o r the t e s t but problems occur when t r y i n g t o r e l a t e the accelerated conditions t o a c t u a l use conditions. The t h i r d method i s t o combine the b a r r i e r p r o p e r t i e s of the package w i t h the s t a b i l i t y of the food i n an appropriate mathematical model. This technique allows the s h e l f l i f e t o be predicted given any type of b a r r i e r and storage conditions. Several models have been proposed and several are reviewed by Chao and R i z v i i n t h i s volume. Sorption and/or Permeation by Organic Vapors. Continuous polymer f i l m s are permeable t o organic vapors i n a s i m i l a r manner t o f i x e d gases (10). Transfer of organic vapors across polymeric food packaging could have two adverse consequences. F i r s t , packaged foods t h a t are exposed t o undesirable v o l a t i l e odors during storage or shipment might pickup the odor. The c l a s s i c a l case occurs when d i e s e l odors or the aroma of laundry soaps are absorbed by foods because of improper storage o r shipping. The second type of problem can occur when the d e s i r a b l e aroma compounds associated w i t h a p a r t i c u l a r food are diminished by being sorbed i n t o or permeated through the package. This l a t t e r problem has only r e c e n t l y became an area of research i n t e r e s t . Several papers i n t h i s volume deal d i r e c t l y w i t h t h i s area. While the data are not complete, a couple of generalizations can be made. F i r s t i s t h a t some p l a s t i c s can sorb or t r a n s f e r s u f f i c i e n t aroma compound t o be detected by human senses. The second g e n e r a l i z a t i o n i s t h a t j u s t as d i f f e r e n t polymers vary g r e a t l y i n t h e i r permeation rates f o r f i x e d gases, they a l s o vary over orders of magnitude i n t h e i r permeation r a t e s f o r organic vapors. This means t h a t foods t h a t are s e n s i t i v e t o changes i n t h e i r aromatic f l a v o r can be protected by switching t o higher aroma b a r r i e r f i l m s . Several papers i n t h i s symposium deal w i t h t h i s problem. The Forth I n t e r a c t i o n Between Foods and Food Packaging Results From the Transparency of Many Food Packages t o Light. L i g h t , p a r t i c u l a r l y i n the shorter wave lengths, can c a t a l y z e adverse reactions such as o x i d a t i o n i n foods. This may lead t o d i s c o l o r a t i o n , l o s s of n u t r i e n t s , o r the development of o f f odors. Conclusions The a c c e l e r a t i o n i n the switch from nearly i n e r t packaging t o more i n t e r a c t i v e s y n t h e t i c polymers has brought f o r t h a new i n t e r e s t i n the i n t e r a c t i o n between foods and food packaging. I n the l a s t few years research i n t h i s area has begun t o gain momentum. The major problems i n studying these i n t e r a c t i o n s are the l a c k of standard methodology, agreed upon models, and data concerning the a c t u a l changes i n food q u a l i t y .

Hotchkiss; Food and Packaging Interactions ACS Symposium Series; American Chemical Society: Washington, DC, 1988.

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FOOD AND PACKAGING INTERACTIONS

Literature Cited

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Haggin, J . Chem. Eng. News. 1984, 62(8), 21. Dembowski, R.J. Food and Drug Packaging 1983, 47(10), 17. S i l l i k e r , J.H.; Wolfe, S.K. Food Technol. 1980, 34(3), 59. Dilberakis, S. Food and Drug Packaging 1987, 51(5), 22. Rauch, J.A. The Rauch Guide to the Packaging Industry; Rauch Associates, Inc: Bridgewater, NJ, 1986; p 1. 6. Anon. Packaging 1984, 29(12), 70. 7. Anon. Packaging Digest 1987a, 24(3), 42. 8. Anon. Food and Drug Packaging 1987b, 51(6), 45. 9. Crosby, N.T. Food Packaging Materials: Aspects of Analysis and Migration of Contaminants; Applied Science Publishers Ltd: Essex, England, 1981;p190. 10. Yasuda, H.; Stannett, V. In Polymer Handbook; J . Brandrup and E.H. Immergut, Eds; John Wiley & Sons: New York, New York, 1975; p 111-229. RECEIVED September 24, 1987

Hotchkiss; Food and Packaging Interactions ACS Symposium Series; American Chemical Society: Washington, DC, 1988.