California State University, Northridge

CALIFORNIA STATE UNIVERSITY, NORTHRIDGE

ASCORBIC ACID RETENTION IN GREEN BEANS 11 PACKAGED IN RETORT POUCHES AND IN IviETAL CANS DURING PROCESSING AND STORAGE

A thesis submitted in partial satisfaction of the requirements for the degree of Ivraster of Science in Home Economics

by Wilma Larkin George /

August, 1979 The Thesis of Wilma Larkin George is approved:

Tung-Shan Chen, Ph. D., Chairman

California State University, Northridge

ii Dedication

To my children Teresa and David

iii ACKNOWLEDGENENTS

I vdsh to express my appreciation to the follovdng people: Jay Kern, Kern Foods, Inc., for contributing the metal cans. ., William F. Asp, Reynolds Metals Co., for contributing the retort pouches. Paul Bolton, Carnation Research Laboratory, for use of their heat sealer on the retort pouches, and Dayne Shigematsu for his assistance in using the heat sealer. Dr. Marjory Joseph and Dr. Ann Stasch for making themselves available for my benefit. Dr. Tung-Shan Chen for his guidance and assistance throughout the project. My husband and children for their help and sup- ·port.

iv TABLE OF CONTENTS'

page DEDICATION • • • • • • • • • • • • • • • • • • • • iii ACKNOWLEDGEHENTS • • • • • • • • • • • • • • • • • iv LIST OF TABLES • • • • • • • • • • • • • • • • • • LIST OF FIGURES • • • • • • • • • • • • • • • • • viii ABSTRACT • • • • • • • • • • • • • • • • • • • • • ix CHAPTER

I INTIRODUCTION • • • • • • • • • • • • • • • 1 Objectives of the Study • • • • • • • • 2 Hypotheses • • • • • • • • • • • • • • • 2 Limitations • • • • • • • • • • • • • • 3 II REVIEW OF THE LITERATURE • • • • • • • • • 4 Retort Pouches • • • • • • • • • • • • • 4 Historical • • • • • • • • • • • • • • lj. Advantages and Disadvantages • • • • • 5 Packaging r·1aterial • • • • • • • • • • 7 Processing Procedure • • • • • • • • • 8 Durability • • • • ·• • • • • • • • • • 10 Acceptability •••••••••••• 10 Current Application • • • • • • • • • 11

Canned Cut Green Beans • • • • • • • • • 12 Comparison of Metal Cans \Vi th Pouches • 14 Ascorbic Acid in Green Beans 14 • • • • • • ·,,,"- III HETHODS AND HATERIALS • • • • • • • • • • 18 Green Beans • • • • • • • • • • • • • • 18 Processing Hethods • • • • • • • • • • • 18 Sample Preparation • • • • • • • • • • • 19

v Chapter Page

Ascorbic Acid Determination • • • • • • • 20 Sensory Test • • • • • • • • • • • • • • 20 IV RESULTS AND DISCUSSION • • • • • • • • • • • • 22 Effect of Processing on Ascorbic Acid • • 22 Effect of Storage on Ascorbic Acid • • • • 27 Sensory Evaluations • • • • • • • • • • • 34 V SUMMARY M~D CONCLUSIONS • • • • • • • • • • 38 BIBLIOGRAPHY • • • • • • • • • • • • • • • • • • • 41 APPENDIXES • • • • • • • • • • • • • • • • • • • • 45 A Procedure for Ascorbic Acid Determination 45 B Chemicals and Reagents • • • • • • • • • 48 C Laboratory Equipment • • • • • • • • • • 50 D Sensory Evaluation • • • • • • • • • • • 52

vi·- LIST OF TABLES

Table Page 1. Effect of Processing on Ascorbic Acid Retention of Green Beans • • • • • • • .23 2. Ascorbic Acid Concentrations in Green Beans and Accompanying Liquids • • • • 25 3. ANUYA of Sensory Evaluations on Canned ''">''and Pouched Green Beans • • • • • • • 35

vii LIST OF FIGURES

Figure Page 1. Changes in Ascorbic Acid Content of Green Beans Processed in Neta1 Cans During Storage • • • • ~ • • • • • • • • • • • • 29 2. Changes in Ascorbic Acid Content of Green Beans Processed in Retort Pouches During Storage • • • • • • • • • • • • • • • • • 31 3. Percentage of Retention of Ascorbic Acid During Storage of Green Beans Processed in Metal Cans and Retort Pouches • • • • 33

viii ABSTRACT

ASCORBIC ACID RETENTION IN GREEN BE.Ai"\l"S PACKAGED IN RETORT POUCHES AND IN METAL CANS DURING PROCESSING AND STORAGE by Wilma Larkin George Master of Science in Home Economics August, 1979

The ascorbic acid content of green be~~s pro cessed in retort pouches was compared with that of green beans processed in metal cans. Measurements were taken before and after processing to study the effects of pro cessing on ascorbic acid retention. Measurements were taken also at intervals follo¥dng processing to observe the effects of storage on ascorbic acid retention. Green beans processed in metal cans retained a higher percentage of ascorbic acid during _proc~~~~ng than green bea~s processed in retort pouches. During storage the percentage retention of ascorbic acid was at_so higher for canned green beans than pouched green beans. Sensory evaluations were performed on the canned and pouched green beans. Ratings of color and flavor were

ix very similar. Green beans in retort pouches had a firmer texture than canned green beans. The firmer texture seemed to be preferred by the panelists.

-- X CHAPTER I

INTRODUCTION

The retort pouch may well be a coming form of packaging in supermarkets for domestic consumption. A number of American companies now manufacture retort pouches. Other companies are filling retort pouches on a limited basis. The u. s. Congress' Office of Technology

Assessment (1978) has issued a report entitled "Emergi~g Food Marketing Technologiesfl. One of the points identi fied as needing research attention was new canning methods such as a plastic and aluminum package such as that em ployed in retort pouches. Testing has been done on the package material, seal, durability of package, microbiological penetration, convenience, and to some extent, palatability (Duxbury et al., 1970; Lampi et al., .1976; and Szczeblowski, 1971). But, in the spring of 1979 there had been little in the literature on the nutritive value of food packaged in retort pouches. If this type of package vdll be avail able for consl~ers, it would be most helpful for con sumers to knovv how foods packaged in this vJay compare

1 2

nutritionally with foods packaged by· other processes.

Q.bjecti ve,s of the Stu_dy: The purpose of this project was to provide the consumer ~~th comparative information on nutrient reten tion in products processed in retort pouches and in metal cans. Ascorbic acid was chosen as the nutrient to be mea sured. Green beans were chosen for this project since they are a vegetable consumed in large amounts in this country. A consumer may or may not use a product immedi ately following its purchase. However, it was felt that the product would be used within a few weeks of purchase. In this project ascorbic acid content of green beans was determined at intervals up to twelve weeks following pro cessing. Food must have pleasing flavor, odor, and texture and must also be priced right. Otherwise, no matter how nutritious a fo,od may be, it vlill not be purchased and consumed (Hurt, 1979). A sensory evaluation was made on the acceptability of the products tested.

Hypothesis;. There will be significant differences in color, flavor, texture, and overall acceptability between green beans processed in metal cans and green beans processed in retort pouches.

- 3

Null Hy-oothesis.;_ There will b.e no significant differences in color, flavor, texture, and overall acceptability betv1een green beans processed in metal cans and green beans pro cessed in retort pouches.

. . Limitations of the Study: Retort pouches and metal cans are filled com mercially by machine. In this project pouches and cans were filled by hand. Retort pouches were sealed vdth the equipment of Carnation Company in their laboratory. This-influenced the number of samples in order to keep inconvenience to Carnation personnel to a minimum. Use of Carnatio.n' s qealer on their premises also meant time was lost traveling between their location and the CSUN Food Science laboratory ·where the processing took place. However, it -~~~'!l:_E> n()~ felt that. this amoUI1t of time affected the validity of the results. CHAPTER II

REVIEW OF THE LITERATURE

Retort Pouches Historical Develonment: Work on a retort pouch began about twenty years ago. It has been a joint effort of scientists, engineers, and equipment manufacturers. Two companies which have been active participants for the past twenty years are Reynolds Metals Co. and The Continental Group, Inc. (for merly Continental Can Co.). The military also became interested in this concept. They liked the convenience of a flat shape fitting into pockets of field clothing without restricting physical movements. The softness also eliminated personal injury if a soldier fell on it during combat. 'rhe primary site of military research on the re tort pouch has been the u.s. Army Natick Development Center in Massachusetts (formerly the Quartermaster Food and Con tainer Institute). Reynolds and Continental both worked independently and in conjunction with Natick. In 1978 these three shared the Institute of Food Technologists' Fo.od Technology Industrial Achievement Award for work on

4 the retort pouch (Mermelstein, 1978). Retort pouches have been marketed in Europe since the mid-1960's (Schultz, 1978) and are widely used in Japan (Trauberman, 1974).

Advantages and Disadvantages: Goldfarb (1970) and Mermelstein (1978) list the advantages and disadvantages of the retort pouch.

The advantages listed were: I)_ 1. The profile which is thinner than that of cans or jars requires less time for sterilizing temperatures to reach the center of the food. This should reduce overcooking of food near the surface, resulting in better quality. 2. The pouched product does not require refrigeration or freezing. Pouches have been stored for ten years at room temperature and remained microbiologically sound. Szcze blowski (1971) stated that botulism is no more of a problem with flexible containers than with rigid containers. 3. Pouched food can be eaten without heating or it can be heated quickly by placing the pouch in boiling water for 3-5 minutes. Pans need not get dirty as they would when heating canned foods. Food can even be eaten directly from the pouch. 4. Pouches can be easily and safely opened by tearing across the top'' at a notch or by cutting with scissors, eliminating the need for a can opener and danger of harm from can lids or broken glass. Pouches can be handled

.... 6

immediately after removal from boiling water. 5. Pouches require less energy to manufacture than cans or ·jars. Schulz (1978) reported that a pouch required only about half as much energy to manufacture as a metal can. 6. A pouch weighs less than a can or jar, reducing dis tribution costs. 7. A pouch takes up less storage space than a can or jar.

8. A pouch takes up less disposal space than a c~~ or jar. 9. Pouches lend themselves to portion control which appeals to single people, hospitals, and the elderly. 10. The light weight of pouches, combined \tith shelf sta bil:i.ty ·without refrigeration and ability to \ti thstand rough treatment, makes them especially suitable for military use and recreational camping. Lemaire (1978) reported that Boundary Waters Canoe Area in northern Minnesota has barred all cans, bottles, and other rigid food containers from use in the area. This was one of the first food container regulations in the u.s. Further such regulations could have a profound effect on the demand for pouches. The disadvantages listed were: 1. Pouches require an overwrapper such as a paper carton. 2. There is currently almost no high-speed filling equip ment available. However, a number of companies are working in this area. 3. The retort pouch does not lend itself well to a large quantity in each container. Here, also, work is currently 7

being done.

Packaging Material: In developing a retort pouch the first problem that had to be contended with was that of packaging materials. The packaging material had' to be resistant to the penetration of fat, oil, or other food components; be chemically inert vli th no tendency to impart objecti()nable flavor or odor to foods; have heat sealability over a vdde temperature range; and be capable of being handled on auto matic equipment (Lampi, 1977). Plain and laminated films were available that were heatsealable and had excellent food protection qualities. Early films were tested for permeability to water vapor and oxygen. New films were developed that would ~~thstand steam or water thermoprocessing at 250°F. for 20-40 minutes without destroying the seal or contaminating the food products. Blends of polymers were developed. Since aluminum foil has excellent barrier properties work was done on laminations containing aluminum foil. Research produced successful aluminum foil laminates (Lampi, 1977). The resulting pouch contains three layers. The outer layer of polyester is for strength; the middle layer of aluminum foil serves as a moisture, light, and gas barrier; and the inner layer of polypropylene or polyole fin serves as the heat-seal and food-contact material

·• 8

(Mermelstein, 1978). The retort pouch received FDA and USDA approval in May, 1977. In addition to Reynolds and Continental, American Can Co. also has an FDA-accepted pouch.

Processing Procedure: .. Two types of pouch equipment are used. In one, machines fill preformed pouches. In the other, machines use rollstock pouch material to form the pouches. When the form-fill-seal machine is used the material is unrolled and folded in half. The fold becomes the bottom and is heatsealed, as are the sides. Viith pouches still attached to one .another notches are added at the sides to facili tate opening. Printed information is added at this point. Then pouches are cut apart into individual pouches, held upright by clamps on both sides, and filled (Anonymous, 1978). Machines that use preformed pouches use a pouch- inserting magazine that holds the pouches. The pouches are opened by a mechanical air-jet splitter and a nozzle fills the pouches 01ermelstein, 1976). Preformed pouches may require less initial investment -fer-a company, but form-fill-seal machines are considered cheaper in the long - run as the food company does not pay a manufacturer to form pouches. Excess air is forced out by mechanically squeezing the pouch, flushing i,t OUt VIi th superheated steam, or 9

applying a vacuum. Pouches may be sealed with a hot seal bar or by impulse sealing in which the heat is not continu ous but caused by a momentary electrical impulse. In both methods a major wrinkle or fold of material on the seal surface should be avoided to prevent contamination. How ever, minor irregularities are not considered a hazard. The seal area should not be contaminated by the presence of food or moisture (Lampi et al., 1976; and Lampi, 1977). A "cosmetic" seal is also added ·which goes from the top seal to the edge of the top flaps. This prevents dirt and other contaminants from entering the opening. Sealed pouches are processed in the same manner as metal cans. The processing media could be steam, steam air mixture, or water (Lampi, 1977). Pouches may be pro cessed one load at a time. This is known as the batch method. Another method is the continuous retort where pouches are conveyed through separate sterilizing and cooling tunnels in trays with individual pock_ets. Each pouch must be separately exposed to the heating medium (Pflug et al., 1963). If pouches are processed in water they must be compartmentalized so that water vdll not move them. Pouches are generally placed in racks either vertically or horizontally during processing (Lampi, 1977).

. . Pouches then go to a dryer and are packed in·cartons. Lampi (1977) reported that the reliability of the pouch has been established. Accepting a figure of 0.1% 10

failure for metal cans, he regards the retort pouch to be at least as durable and safe as the metal can.

Durabili t,J..:. Pouches were submitted to rigorous treatment by the military to test the dur~bility of the pouch and the seal. Metal cans and flexible pouches of similar size, containing similar products, were subjected to a series of rough-handling tests which included drop tests and vibrator tests. Pouches vdthstood the rough handling at least as well as the cans (Burke and Schulz, 1972; and Schulz, 1978). Shipping durability is also an important factor. Goldfarb (1971) reported that pouches in cartons have been shipped successfully by both rail and truck on pallets. Lampi (1977) also reported that tests showed that pouches traveled well by all means of transportation, including tracked vehicles across country, trucks on secondary roads, and air drops.

Acceptability: Schulz (1978) reported that when more than 600 soldiers were given a free choice of rations in conven- tional cans or retort pouches, 88% chose the foods in retort pouches. All subjects had previously eaten both types of rations so novelty of the package was not con sidered a significant factor. In December, 1978, the 11

military began replacing C-rations with retort pouches.

Current Application: There is wide versatility in the types of foods available for pouches. Foods packaged in pouches include meats, vegetables, sauces and/or gravies, soups, fruits, and bakery items. Since the flat shape of the pouch allows for a shorter process time it is possible to pouch rela tively delicate items. Not suitable for pouching are foods with sharp, protuding objects such as bones or shells -===-= (Lampi, 1977). Semi-rigid retortable containers have been de veloped (Schulz, 1978). The sizes range from single serving to half-size steam table trays. Retortable pans shaped to occupy half a food service steam table opening are less than ~1 inches deep and hold 106 oz. or the equiv alent of a No. 10 can. The reduced cross section allows use of shorter processing times, resulting in better fla- vors. European food processors are now examing a retortable thin-gage aluminum tray coated on both sides vii th ~-~------~ polypropylene designed for single portions. A Swedish company offers a rigid retortable container that saves 20% space compared with cylindrical cans (Anonymous, 1979). Currently the equipment for retort pouches has slow line speeds. A few companies offer 60 units/minute. On.e of these, Rexham Corporation's Bartelt Hachinery 12

Division, is committed to producing a 250 pouch/minute machine within the next tvro years. FHC Corporation's Packaging Hachine Division has on the market a machine they say will handle 440 pouches/minute. This machine can also handle pouches up to 25 in. x 30 in. (Anonymous, 1978) • . .

Canned Cut Green Beans Vegetables provide a number of micro/macronutri ents in the diet, but are chiefly regarded as sources of vitamins A and c. The consumption of fresh vegetables has declined while that of canned and frozen vegetables has shown an increase. In 1940 the percentage consumptions per person were: fresh vegetables, 78%; canned, 21%; and frozen, 1%. In 1975 they were: fresh, 64%; canned, 24%; and frozen, 10%. Total overall vegetable consumption per p'erson also increased (Hurt, 1979). The 1976 per capita consumption of green beans was 6 lb. canned, 1.5 lb. fresh, and 1.1 lb. frozen (Goddard and Hatthews, 1979). In 1977 over 50 million cases of green beans were canned in the United States (Judge and Sons, 1978). Procedures for processing green beans in commer cial canneries are largely automatic. Beans are washed and graded according to size. Smaller sizes are left whole. Larger sizes are cut crosswise by machines into lengths of 1-1± inches. The one inch length is more common for canning and the 1± inch more common for freezing (Cruess, 1958). Cut beans are screened to remove fine fragments and short pieces (Luh and Woodroof, 1975). Beans are blanched, usually in hot water (170- 1900F.) for lt-2 minutes (Cruess, 1958; Lopez, 1969; and ------~-.,..,._.---~ -~~·u-''~-.~-- ~ ·~~-~-H-oo~~-,..--~"' Luh and Woodroof, 1975). The purposes of blanching are to destroy enzymes, to obtain the desired appearance and flavor of the product, to facilitate proper fill of the container, and to eliminate air and other gases, thus reducing internal can pressure during processing (Cameron et al., 1949; and Harris and Karmas, 1975). These investigators also reported that short time-high temperature blanching is superior to long time-low temperature blanching for green beans. Mundt and McCarty (1960) reported that the variety of bean seems to be the most influential factor in determining blanching time. Cans are filled mechanically. Hot water and dry salt or brine is usually added. Beans are heated in a steam exhaust bcx and cans are sealed. Processing time depends upon the size of the can, initial temperature, and processing temperature (Cruess, 1958). A common size can for cut green beans is one designated 303 x 406 (3 3/16 in. x §/1,9_1P:,!J. Davis, Cockrell, and Wiese (1979) reported that a higher tin coating weight (#50/25) tinplate resulted in significantly less pitting than lower weight (#25) tinplate in canned g~een beans. 14

Comparison of Hetal Cans With Pouche~ Heidelbaugh and Karel (1970) found that metal cans and aluminum laminate pouches were equally effective in preserving the ascorbic acid of cranberries and junior baby food vegetables and bacon dinners. Jimenez et al. (1976) reported that beef stew retained twice as much ascorbic acid in retort pouches ,, than in metal cans soon after processing. The 2,6-dichloroindophenol method of AOAC was used to determine the ascorbic acid in this project (Ang, 1979). These inves tigators also found that a taste panel, during a period of one year, consistently preferred beef stew packaged in retort pouches to that packaged in metal cans.

Ascorbic Acid in Green Beans Ascorbic acid is one of the most readily destroyed vitamins. If ascorbic acid is well retained it is unlikely that there has been any serious loss of other nutrients (Bender, 1966; and Hurt, 1979). In cooking fresh vegetables the greatest losses of ascorbic acid are due to leaching into the processing water. The amount of water used in cooking fre~h vegetables greatly affects ascorbic acid loss, with vegetables covered with water showing much higher losses than vegetables one-quarter covered with water (Bender, 1966). Blanching vegetables to stop enzymatic action -- before canning or freezing causes some loss of ascorbic acid into the blanching water (Bender, 1966). Steam

------~-···------~· blanching results in better retention of ascorbic acid than water blanching (Fennema, 1977; and Harris and Kar mas, 1975). Apart from thi~ loss into the blanching water ascorbic acid keeps very well in frozen foods. It is also very stable when protected from air as when in metal cans (Bender, 1966). Ho·w·ever, in general, canning resu.,cts in greater vitamin losses than freezing of fruits and vegetables (Lund, 1979). Watt and Merrill (1963) in Agriculture Handbook No. 8 list the ascorbic acid content of fresh green beans as 19 mg/100 g. Noble and Gordon (1956) found the average ascorbic acid content of raw beans to be 16.5 mg/100 g using a modified Horell indophenol photometric method of analysis. In a later experiment Noble (1967) found the average ascorbic acid content of raw green beans to be only 13.8 mg/100 g using the same method. Fennema (1977) reported a 20-25% loss of ascorbic acid during blanching of green beans. Harrison (1975) reported a range of 76-91% ascorbic acid retention after blanching green beans. After canning, Cameron et al. (1949) found the average ascorbic acid retention in green beans to be 55%, with the range being 40-75%. Fennema (1977) reported that the average loss of ascorbic acid after canning in ten ·- 16

vegetables, including green beans, was 51%. Lund (1979) found a higher loss of. ascorbic acid in green beans after canning. He reported a 78.9% loss of ascorbic acid in canned green beans. Agriculture Handbook No. 8 (1963)

lists 4 mg/100 g ascorbic acid in ca~ned green beans and, thus, a loss of 80% during processing. The AOAC (1975) Official Hethod for determining ascorbic acid is the 2,6-dichloroindophenol method. This· method determines the amount of L-ascorbic acid. The vitamin is extracted and then titrated in the presence of an acid, usually metaphosphoric acid, to maintain proper

acidity. Ascorbic acid reduc~s the dye 2,6-dichloroindo phenol to a colorless solution. At the end point of titration excess unreduced dye is rose pink in acid solution. This was the method of determination used in this project • .Ascorbic acid may al.so be determined by micro- flurormetric method. Using Norit charcoal the ascorbic F ---~~~----"·--'~·~- acid is oxidized to dehydroascorbic acid which is reacted with a-phenylenediamine to produce fluorophor. Fluores- cence intensity is proportional to ascorbic acid concentration (AOAC, 1975) • .Another procedure uses paper chromatography. Ascorbic acid is extracted from the paper vrith water con taining oxalic acid. It is then titrated with 0.001 N 2,6-dichloroindophenol. Photometric assay of ascorbic acid is also used. l'?

Ascorbic acid is converted by diazotized 2-nitroaniline to oxalic acid 2-nitrophenylhydrazide. An excess of sodium hydrazide solution added forms a reddish-violet sodium salt. The solution is measured photometrically at its absorption maximum. Photometric assay of vitamin C may also be used ·with 2, 4-dini trophenylhydrazine' (Joslyn, 1970).

In determining ~scorbic acid Noble (1967) .. reported that reduced and total ascorbic acid were not significant ly different in green beans. Heidelbaugh and Karel (1970) stated that titration against 2,6-dichloroindophenol, if done rapidly and in acid solution, can give results that agree vdth the biological estimation of ascorbic acid content of foods. In the presence of oxygen and a suitable catalyst ascorbic acid is oxidized to dehydroascorbic acid. Dehy droascorbic acid has approximately 75-80% of the vitamin activity of ascorbic acid. Below pH 4 dehydroascorbic acid is fairly stable. Above pH 4 it undergoes an irre versible rearrangement to a biologically inactive material (Joslyn, 1970). CHAPI'ER III

METHODS AND MATERIALS

Green Beans: Fresh green beans of the Kentucky Wonder variety were purchased from Northern Produce Co., Los Angeles. The green beans were washed, the ends snipped, and the beans cut into uniform pieces between 1 and lt inches long. They were then blanched at 180°F. for two minutes and cooled rapidly in cold water.

ProcessinR Methods: Metal cans, obtained through Kern Foods, Inc., City of Industry, were 303 x 406 in size, 50/25 tinplate, and vrlth enamel inside and plain outside. Cans were washed; each can was filled vrl th 225 g of blanched green beans and then 2% brine at 200°F. The cans were exhausted

--~~~~~~-__.-.·~----~·>">~a-·~~ ~-,-.~ .. ,_,. --·~··~--~·~-·>c.o-~0 _,..,_,.. ~.-· .. -..--~··---·~·--.---'A<~~-...~.,.., r "-' ~ -, ~ ~< -r•r• in hot water for 2-3 minutes to obtain an internal temperature of 120°F. Cans vrere then sealed with a Dixie automatic can sealer and processed in an All-American pressure cooker at 240°F. (10 ,p.s.i.) for 25 minutes (Luh and Wood- roof, 1975). Retort pouches, measuring 5t" x 7", were obtained

18 19

through Reynolds Metals Co., Los Angeles. They were manually opened and f~lled vdth 175 g of blanched green beans per pouch. Each pouch had 75 ml of 2% brine at 75°F. added. The pouches were sealed with a Sentinel heat sealer at Carnation Research Laboratory. They were processed in the CSUN Food Science lab at 240°F •. (l0 p.s. i.) for 12 minutes in an All-American pressure cooker. Allowing for the differences in weight, this was an ap proximate reduction in processing time of 30% for the pouches, as suggested by Continental Flexible Packaging (1979). Pouches and cans were both cooled in running cold water follovdng processing. They were stored at room temperature in boxes.

Samnle Prenaration: The ascorbic acid content of fresh green beans was determined before and after blanching. The ascorbic acid content of the blanching water was also. assayed. The ascorbic acid content of stored green beans was determined daily during the first week following pro cessing; three times during week 2; tvdce during week 3; once during weeks 4,5, and 6; once during week 8; once during week 10; and once during week 12. The contents of two retort pouches or two metal cans were combined and poured into a vdre mesh sieve. The green beans were drained for tvm minutes to determine the drained vTeight. 20

Moisture determinations were made in triplicate on samples of green beans weighing approximately 2 g each. The samples were dried in an electric drying oven for one hour, then placed in a desiccator to cool, and weighed. This procedure was repeated until the samples showed no further loss in weight. The loss in weight was calculated as moisture content.

Ascorbic Acid Determination: The ascorbic acid content of green beans and brine was determined by the 2,6-dichloroindophenol visual titration method (AOAC, 1975) as shown in Appendix A. This is a method for determining L-ascorbic acid. At some points the precipitate of the bean extract from this procedure was also assayed for ascorbic acid content. This was done by adding metaphosphoric acid-acetic acid solution to the precipitate and titrating three 10 ml aliquots of this slurry.

SensorY, rre.st:

A sensory eva~uation of.canned and pouched green beans was made during the first week of the project and again in the 11th week. The testing method was a prefer ence/acceptance test which used a hedonic scale (Larmond, 1977). Panelists were junior, senior, or graduate stu dents enrolled in nutrition or food processing courses. The sensory evaluations attempted to follow the guidelines ------·------~. ·~~-- ~-- ~~· --······ ~-··- . ._.. .,. ·-- . ~ ,.,,""' ,.,, ' ''"''' ."' " '"''·"'''"''"'""''''''"'''"''''"" 21

suggested by Larmond (1977): 1. Testing was done in late morning or mid-afternoon.

2. ~ne room was quiet 1v.ith no conversation and uniform light. 3. White disposable plates and stainless steel utensils were used. 4. Green beans were served between 60-66°c. Before serving, unopened pouches were in boiling water for 5 minutes. \,.~'"v-•---~·-• .--~.-, "~·--~··~~~,-~.--.----- ._, __ ,. •• • •• "o '";~ "-•• •• '"•''"•"'"~A"• ->.,•• -<·•---~-· -=o.A,,-,_"...>" '-•••••·"~•--•, • ••~~.'»•< o-•,>-' •'""• -~·-"·' •••'>

C~~ed green beans were poured into a pan and also boiled for 5 minutes. 5. Approximately 2 ounces of each sample were presented. 6. Beans were coded with three random numbers. 7. Water and saltine crackers were provided to separate the tastes of the samples. Panelists ·were asked to evaluate green beans as to color, flavor, texture, and overall acceptability. A rating scale of 1 to 5 ·was used a.s suggested by Cloninger and Baldwin (1976), vdth 1 being the most desirable and 5 being the least desirable. The questionnaire used is sho1vn in Appendix D. Results were analyzed by analysis of variance as suggested by Larmond (1977) and Prell (1976) at 0.05 level of significance.

- ...,,. CHAPTER IV

i RESULTS AND DISCUSSION

Effect of Processing.on Ascorbic Acid in Green Beans The ascorbic acid content of raw green beans, blanched beans, and canned and pouched beans immediately after processing was determined. The extracts of the green bean solids were titrated with 2,6-dichloroindophenol, ac cording to the AOAC method. In addition, the precipitate from the bean extract was made into a slurry by the addi tion of metaphosphoric acid-acetic acid solution. This slurry was titrated as before to see if there might be more ascorbic acid that was not in the extract. The results are ..------~-~------···------presented in Table 1. As shown in Table 1, the ascorbic acid content of the extract plus precipitate of raw beans measured 18.48 mg/ 100 g on a fresh basis. This compares quite favorably with the 19 mg/100 g value reported in Agriculture Handbook No. 8 (Watt and I1errill, 1963). This is slightly higher than the 16.5 mg/100 g value reported by Noble and Gordon (1956), the 13.8 mg/100 g value reported by Noble (1967), and the 14.8 mg/100 g value reported by Elkins (1979).

22 2.3

TABLE 1

EFFECT OF PROCESSING ON ASCORBIC ACID OF GREEN BEANS

Ascorbic Acid Content1 Mean

Fresh Basis Moisture Retention (mg/100 g) free Basis (%) (mg/100 g)

EXTRACT ONLY Raw Green Beans 15.56 112.67 100 Blanched 9.43 68.28 60,.60 Canned* 3.48 25.20 22.37 Pouched* 3.18 23.03 20.44

EXTRACT PLUS PRECIPITATE Raw Green Beans 18.48 133.82 100 Blanched 12.76 92.40 69.05 Canned* 5.05 37.29 27.87 Pouched* 4.55 32.95 24.62

1 Average values of triplicates * Values determined immediately after processing 24

The ascorbic acid measurement of 15.56 mg/100 g determined from the extract alone .fell within the range of these last investigators. When measuring the ascorbic acid of green beans during processing, a slurry of green beans and metaphos phoric acid-acetic acid solution without centrifugation was also titrated vdth standard solution of 2,6-dichloroind? phenol. This procedure gave a result of 27 mg/100 g for ascorbic acid in raw green beans. Since this figure is higher than those reported in the literature it was felt that these data were not as reliable and the pro~edure was, therefore, not used. The 30-40% loss of ascorbic acid during blanching of green beans was higher than the 20-25% average loss report ed by Fennema (1977) and 9-24% loss reported by Morrison (1975) during blanching. Fennema (1977) and Harris and Karmas (1975) pointed out that steam blanching retains more ascorbic acid than water blanching. The green beans in this project were water blanched which may account for the higher losses. Table 2 shows the extent the ascorbic acid v1as leached in the blanching water. The blanched green beans retained 60.6% of the ascorbic acid of the fresh green beans. The 0.40 mg/100 g concentration of ascorbic acid in the blanching water represented a 33.6% loss of the fresh green bean ascorbic acid concentration due to leaching. 25

TABLE 2

ASCORBIC ACID CONCENTRATIONS IN GREEN BEANS AND ACCOMPAWIING LIQUIDS

Ascorbic Acid Content+ Fresh Basis (mg/100 g)

Rav1 Green Beans 15.56 Blanched Beans 9.43 Blanching Water 0.40 Canned Beans* 3.48 Brine from Canned Beans* 2.65 Pouched Beans* 3.18 Brine from Pouched Beans* 0.83

+ Determined by AOAC metnod * Values determined immediately after processing

- 26 ..

It must be assumed that the remaining 5.8% of the ascorbic acid was destroyed by heat during blanching. The blanched beans lost further ascorbic acid during processing. As shown in Table 2, the canned green beans had higher concentrations of,ascorbic acid in both beans and brin~. Approximately 25% of the ascorbic acid in the blanched beans was leached into the brine of the canned green beans. This meant·that approximately 36% of'che ascorbic acid entering the can was unaccounted for. It must be assumed that this amount was lost due to heating. By contrast, only about 3% of the ascorbic acid of the blanched beans was found in the brine of the pouched green beans. This meant that approximately 60% of the ascorbic acid entering the pouch was unaccounted for or assumed to be lost due to heating. The values of 22.37% and 27.85% retention of ascor bic acid in canned green beans shovm in Table 1 are lower than the 55% average ascorbic acid retention after canning reported by Cameron et al., (1949) and 51% average reten tion reported by Fennema (1977). However, they agree \tith the 21.1% ascorbic acid retention reported by Lund (1979), the 20% retention reported in the Agriculture Handbook No. 8 (Watt and Herrill, 1963), and the 27% reported by Elkins (1979). The canned green beans showed a slightly higher retention of ascorbic acid during processing than did the - 27

pouched green beans. These results do not agree vrith the work done by Jimenez et al. (1976) who reported that besf stew processed in retort pouches retained twice as much ascorbic acid as beef stew in metal cans soon after processing. This is also not what one would expect from the literature about the advantages of the pouch. Since the pouches are processed for shorter times than the cans, a better quality product would be expected to result, both in terms of palatability and nutrient retention. The shorter processing time for pouches is indi- cated by both the flatter shape of the pouch and the materials of which the pouch is m~de. However, since pouches are relatively new on the u. s. market it was difficult to find established times for processing. It may be that the pouched green beans in this project were overprocessed, even though the actual processing time was 30% shorter than that of the canned green beans, as recommended by Continental Flexible Packaging (1979). It would appear that more research is needed to establish optimum processing times for retort pouches.

Effect of Storage on Ascorbic Acid in Green Beans Ne.asurements of ascorbic acid in both green beans and brine were taken over a period of twelve weeks to determine the effect of storage on green beans processed in metal cans and retort pouches. The ascorbic acid 28

concentrations of green beans during storage were deter mined only from the extracts as described by the AOAC method. The changes in ascorbic acid content during storage of canned green beans are presented in Figure 1. The concentrations of ascorbic acid in the solids of canned green beans ranged from 3.48 mg/100 g at the begin ning of the storage period to 1.12 mg/100 g at the end of the storage period. Ascorbic acid content in the solids decreased rapidly in the first three days after processing. The loss of ascorbic acid in green beans slowed dovm during the first three weeks of storage. After that time the con centrations of ascorbic acid in beans remained at about the same level throughout the storage period. The concentrations of ascorbic acid in brine of the canned beans ranged from 2.65 mg/100 g to 0.39 mg/ 100 g. At some points the concentrations of ascorbic acid in brine exceeded those of solids. The ascorbic acid con tent of the brine of the canned green beans was relatively high during the first week of storage. After that time the ascorbic acid levels decreased gradually until the fifth week of storage vvhen the levels remained about the same. The ascorbic acid measurements of the canned green beans and brine were combined to obtain the total concentrations of ascorbic acid in green beans processed l . I 6 ~!>

e Beans I + Brine 5 t ~ Total Concentration

4 II -bO \ 0 0 r-1 ...... Yj· bO 3 ..._.,s +i ..

'd ·rlu· ' i''~- ;N. c:r: 2 l .t•' ·~ u 1 •rl ,.0 H .JI ... 0 .,. lito 1/ u I UJ c:r: 1 t

1 l I I I --i·-· ~----~----~~ I Week 1 2 3 4 5 6 I 12 Figure 1. Changes in Ascorbic Acid Content of Green Beans Processed in Metal Cans During Storage

N '-.0 30

in metal cans during storage. The total concentrations ranged from 6.13 mg/100 g to 1.51 mg/100 g. The ascorbic acid content decreased rapidly in the first three days of storage. There was a general dovmward trend until the fifth week of storage. Ascorbic acid concentrations re mained about the same after that time until the end of the storage period. Marchesini et al. (1975) also reported a marked decrease in ascorbic acid in canned green beans during the first two days of storage. The changes in ascorbic acid content during storage of green beans processed in retort pouches are presented in Figure 2. The ascorbic acid content of bean solids ranged from 3.18 mg/100 g to 0.52 mg/100 g. The decrease was very pronounced during the first week of storage. After the first week, ascorbic acid concentra tions showed only slight variations for the remainder of the storage period. Brine measurements of ascorbic acid in the pouched green beans ranged from 0.83 mg/100 g to 0.11 mg/ 100 g. Here, also, most of this decrease occurred during the first week of storage. Total concentrations of ascorbic acid, obtained by combining those of pouched green beans and brine, ranged from 4.01 mg/100 g to 0.63 mg/100 g. As with the green beans and brine, the total concentrations of green beans • Beans + Brine 5 • Total Concentration

4 ,-.. bO 0 0 .--! 'bD 3 ...._,.s '0 ·rl . () ~ • 2 () •rl ..0 H 0 () U} ~ 1 ~ . ~ +- l. : + t + ~. I t J t . : ~~::~~~~·==~,~~~- i 12 Week ~ 2 3 ~ 5 6

Figure 2. Changes in Ascorbic Acid Content of Green Beans Processed in Retort Pouches During Storage

\)J !-• 32

processed in retort pouches showed marked losses during the first week. Ascorbic acid concentrations remained quite similar from the end of the first week to the conclusion of.the storage period. Figure 3 shows the percentage of total ascorbic acid retention during storage of canned and pouch.ed green beans based on the amount of ascorbic acid in fresh green beans. The ascorbic acid retention in canned green beans ranged from 39% to 10%. This decrease is considerably more than the 6% storage loss of ascorbic acid reported by Elkins (1979) in canned green beans stored over a peri od of 12 months. The ascorbic acid retention in pouched green beans ranged from 26% to 4% based on the amount in fresh green beans. This represented a loss of 85% of ascorbic

~cid of pouched green beans compared vdth a loss of 74% for canned green beans during 12 weeks of storage. The percentage of ascorbic acid retention in pouched green beans dropped markedly during the first week. In canned green beans a decrease continued until the fifth week vdth levels remaining .fairly even thereafter. At no time did pouched green beans show higher concentrations of ascorbic aci~ than canned green beans. This is not in keeping with the work of Jimenez et al. (1976) who found a higher ascorbic acid retention in pouched beef stew than in canned beef stew. They re- • Canned green beans 501 + Pouched green beans

I 40, s:: 0 ·r-1 ~s:: Q) ~ Q) p:j 30 I '"d ·r-1 () <:t: () 20 l ..a·r-1 H 0 I () {!) <:t: .. * 10 r I ""+ 4 "'" i ' t/ + I ~ . I 1----t---- Week 1 2 3 4 5 6 12 ,.

Figure 3. Percentage of Retention of Ascorbic Acid During Storage of Green Beans Processed in Metal Cans and Retort Pouches

\.,)'! '•.)'! 34

ported a rather slow rate of ascorbic acid destruction in pouches during 12 months of storage. These findings are also not in agreement with those of Heidelbaugh and Karel (1970) who found cans and pouches equally effective in re taining ascorbic acid in cranberries and baby food dinners.

Sensory Evaluations Samples of canned and pouched green beans were evaluated by a taste panel during the first week of the project and again near the end of the project. Color, flavor, texture, and overall acceptability were scored by panelists on a scale of 1 to 5 with 1 being the most de sirable. The mean ratings are presented in Table 3. Statistically, there were no significant differ ences in color or flavor between the canned and pouched green beans in the first test. However, the F value as determined by analysis of variance showed a significant difference in texture (p

-~~OF SENSORY EVALUATIONS ON CANNED AND POUCHED GREEN BEA.W"S -, /' ·•• •._~."""'""'-'"'''o"',f

Vveek 1 Week 11 Can Pouch F Value Can Pouch F Value

Color 2.2L~ 2.33 0.2 1.92 2.42 3.66 • Flavor 2.52 2.38 0.1 2.67 2.16 1.32 Texture 2.86 1.95 17.37** 2.58 1.92 1.69 Overall Acceptance 2.62 2.14 5.53* 2.58 2.08 1.58

I I -J<·p<.: 0.05 I- **P-< o.o1

·-·..

"''\Jl 36

become puffed. This enabled the green beans in the pouches to be cooked in an atmosphere of steam rather than boiling brine. Both cans and pouches were cooled in cold water after processing. The center of the pouch could cool fast er than the center of the can because of the flatter shape.

This faster cooling may also have contributed to firme~ texture. In the same testing the F value showed a signi ficant difference in overall acceptability (p< 0.05).

The pouched green beans were judged to be more ~cceptable. It would appear that the preference for the texture of the pouched green beans affected this result. In the later sensory evaluation there was, again, no significant difference in color or flavor between the canned and pouched green bean:s. It was noticed, however, that color in the canned green beans was slightly prefer red to the color of pouched green beans in both tests, and ratings for color in the canned beans improved in the second test. The flavor of the· pouched green beans received slightly better ratings in both tests. In the later test several panelists commented afterward that the canned green beans tasted saltier than the pouched green beans. Brine concentrations in both were identical. However, there was a larger proportion of brine in the cans than 37

in the pouches since enough brine was added to fill the

cans. Panelists seeme~ to prefer the less salty taste. Vlliile panelists still showed a preference for the texture of the pouched green beans in the later test, the difference was not significant. It may be assumed that in storage for 11 weeks the green beans in the pouches lost some of the firmness that the panelists seemed to prefer in the first evaluation. Overall acceptability in the second evaluation also showed no significant difference as would be expected si.nce color, flavor, and texture all showed no significant differences between the canned, and pouched green beans. Panelists showed a slight preference for the pouched green beans •

. - CHAPTER V

Sill~1.ARY .AND CONCLUSIONS

Fresh green beans were processed in metal cru1s and retort pouches to compare the effects of processing and storage on ascorbic acid concentrations •

.Ascorbic acid measurements were ~ade on raw green beans, blanched beans, and green beans in cans and pouches immediately after processing. Contrary to Tihat was ex pected from the literature, the pouched green beans showed a higher percentage of ascorbic acid loss than canned green beans immediately after processing. The brine in the pouches also showed lower concentrations of ascorbic acid than the brine in cans immediately follovdng processing. The pouched green beans appeared to have lost more ascorbic acid due to heat destruction during processing than the canned green beans. Measurements of ascorbic acid of the canned and pouched green beans and th~ir brine were taken at regular intervals during storage. ~~!'~·'·-~ aJ,~~~.!--~Q§_.JtQJ.iC.he_d, __ b§.0tl_q., made a poorer shovdng. .Ascorbic acid concentrations vJere "•''•·~·---~····-'-••-,."~~<""">-~'-"' ••'"'u~,· •·~-·'•'···-··C .higher in canned green beans and their brine throughout

38 39

the 12 week storage period. Sensory evaluations were done to compare the acceptability of the two methods of processing. A sensory evaluation was done during the first week of processing and again near the end of the storage time. The null hypothesis stated that there would be no significant differences in color, flavor, texture, or overall acceptability between green beans processed in metal cans and green beans processed in retort pouches.

Pe~elists found no significant differences in color or flavor in either test. Therefore, the null hypothesis was accepted for both of these items. Panelists found the biggest difference in tex ture. In the first test the hypothesis that there would be a significant difference in texture was accepted. Largely on this basis of texture panelists found the pouched green beans in the first test to have significantly h:i.gher overall acceptability and the hypothesis that there would be a significant difference between the two methods of processing also was accepted for overall acceptability. However, in the second sensory evaluation there was no significant difference in texture or overall accept ability, so the null hypothesis was accepted for texture and overal.l acceptability in the second test. Since retort pouches are relatively new to the market in this country, processing times are still being ·- 40

established. The green beans in pouches in this project may have been processe~ longer than was necessary. Perhaps the general rule of a 30% reduction of processing time for pou.ches compared to cans with equal quanti ties can be re duced further. What seems more likely is that it is too general a rule and each food product should have its ovm processing time established. Suggestions for future work would be to study nutrient retention in products processed in retort pouches for varying lengths of time. Vlith the establishment of processing times for various pouched products it would be very useful to have informatioiJ. on nutrient retention in these products. BIBLIOGRAPHY

Ang, Catharina. 1979. Letter from Dr. Ang, u.s. Dept. of Agriculture, Agriculture Research, Athens, Ga. April.24. Anonymous. 1978. New packages, new products seen in iook at food service future. The National Provisioner Hay 6:30-37. Anonymous. 1979. The retortables are ready. Hodern Plastics 56(1):81.

AOAC. 1975. Official Hethods .2.f Analysi~. 12th ed. Association of Official Analytical Chemists, Washing ton, D. c. Bender, A. E. 1966. Nutritional effects of food process ing. J. Food Technol. 1:261-289. Burke, P. T. and Gerald L. Schultz. 1972. The compara tive performance of flexible packages and metal cans. Tecru1ical Report 73-62-GP. u. s. Army Natick Labora tories, Natick, Ha. August. Cameron, E. J., R. Vl. Pilcher, and L. E. Cliforn. 1949. Nutrient retention during canned food production. Am. J. Public Health 39(6):756-763. Cloninger, 1'1. R. and Ruth E. Baldwin. 1976. Analysis of sensory rating scales. J. Food Sci. 41:1225-1228. Continental Flexible Packaging. 1979. Personal correspon dence from Allan Corning, Hanager-Customer Technical Service. Feb. 23.

Cruess, w. H. 1958. Commercial Fruit ~ VeRetable £!£ ducts •. 4th ed. New York: HcGraw-Hill. DaYis, D. R., c. w. Cockrell, and K. F. \'Iiese. 1979. Pit ting in canned green beans; effect of cultural prac tices, tin coating, vacuum, corrosion accelerators and storage conditions. J. Food Sci. 44:241-245.

41 Thlxbury, D. D., P. F. Sams, w. F. Howeler, J. H. Gee, and w. N. ~tiller. 1970. Reliability of flexible pack aging for thermoprocessed foods under production conditions. Technical Report 72-77-GP. u. s. Army Natick Laboratories, Natick, Ha. July. Elkins, E. R. 1979. Nutrient content of raw and canned green beans, peaches and sweet potatoes. Food Tech nol. 33(2):66-70. Fennema, o. 1977. Loss of vitamins in fresh and· frozen foods. Food Technol. 31(12):32-36. Goddard, Mary s. and Ruth H. Matthews. 1979. Current knowledge of nutritive values of vegetables. Food Technol. 33(2):71-73. Goldfarb, P. L. 1970. Pouch for low-acid foods. Part I. Modern Packaging 43(12):70-76. Goldfarb, P. L. 1971. Pouch for low-acid foods. Part II. Modern Packaging 44(1): 70-76. Harris, Robert s. and Endel Karmas. 1975. Nutritional Evaluation Q! EQQg Processing. 2nd ed. Westport, Conn.: Avi Publ. Co., lnc. Heidelbaugh, N. D. and l-1. Karel. 1970. Changes in pouched heat-processed foods. Modern Packaging 43(11):80- 88. Hurt, H. David. 1979. Effect of canning on the nutritive value of vegetables. Food Technol. 33(2):62-65. Jimenez, M. A., G. L. Cox, R. c. Griffin, Jr., and E. H. Kane. 1976. Quality and nutritiona~ value of beef stew in the Flex-Can and tin plate can. Unpublished Reynolds Metals Company Report, Project Pl-P30-P3D. November 16. Joslyn, M. A. 1970. Hethods in Food Analysis. 2nd ed. New York: Academic PresS: ---- Judge, Edward E. and Sons, Inc. 1978. The Almanac Qi ih£ ~anning, Freezing, Preserving Industries. Westminster, Hd. Lampi, Rauno A. 1977. Flexible packaging for thermo processed foods. Advances in Food Research edited by C. O. Chichester, E. H. r·1ra.k."""'alid G. F. Stewart. 23:305-428. 43

Lampi, Rauno A., Gerald L. Schulz, Tedio Cervarini and Peter T. Burke. 1976. Performance and integrity of retort pouch seals. Food Technol. 30:38-48. Larmond, Elizabeth. 1977. Laboratory methods for sensory evaluation of food. Publication 1637. Canada Dept. of Agriculture.

Lemaire, William H. 1978. The retortable pouch--~here we stand now. Food Engineering 50(8):61-64. Lopez, Anthony. 1969. ! Complete Course in Canning. 9th ed. 'rhe Canning rrrade, Baltimore, Hd. Luh, B. s. and J. G. Woodroof. 1975. Commercial Vege table Processing. Westport, Conn.: Avi Publ. Co., Inc. Lund, Daryl B. 1979. Effect of commercial processing on nutrients. Food Technol. 33(2):28-34. Harchesini, A., G. Harjorino, F. Montuori, and D. Cagna. 1975. Changes in the ascorbic and dehydroascorbic acid contents of fresh and canned beans. J. Food Sci. 40:665-668. Mermelstein, Neil H. 1976. An overview of the retort pouch in the u. s. Food Technol. 33(2):28-37. Mermelstein, Neil H. 1978. Retort pouch earns 1978 IFT Food Technology Industrial Achievement award. Food Technol. 32(6):22-33. Morrison, Mary H. 1975. The vitamin C content of quick frozen green beans. J. Food Technol. 10:19-28. Mundt, J. o. and I. E. McCarty. 1960. Factors affecting the blanching of green beans. Food Technol. 14(6): 309-311.

Noble, Isabel. 1967. Ascorb~c acid and color of vege tables. J. Am. Dietet. A. 50:304-307. Noble, Isabel and Joan Gordon. 1956. Ascorbic acid and color retention in green beans cooked by different methods. J. Am. Dietet. A. 32:119-122. Office of Technology Assessment. 1978. Emerging Food ~arketing Technologies. Congress of the u. s:; Washington, D. c. 44

Pflug, I. J., J. H. Bock, and F. E. Long. 1963. Sterili zation of food in flexible packages. Food Technol. 17(9):87-92. Prell, Patricia A. 1976. Preparation of reports and manu scripts which include sensory evaluation data. Food Technol. 30(11):40-48. Schulz, Gerald L. 1978. Trends in food packaging for foodservice. J. Food Protection 41:464-467. Szczeblovrski, Joseph w. 1971. An assessment of the flexi ble packaging system for heat-processed foods. Technical Report 71-57-GP. u. s. Army Natick Labo ratories, Natick, 11a. April. Trauberman, Leonard. 1974. 1975--year of the retort pouch? Food Engineering 46(12):69-72. Watt, Bernice K. and Annabel L. Nerrill. 1963. Agri culture Handbook No. 8. Composition of Foods, Rav1, Processed, Prepared. u. s. Dept. of ·Agri culture, Washington, D. _c. APPENDIX A

PROCEDURE FOR ASCORBIC ACID DETERHINATION

The procedure used for the ascorbic acid analysis was as follows: 1. A sample of 100 g green beans was blended with 50 ml metaphosphoric acid-acetic acid solution for three minutes in a Waring blender. 2. .The slurry was centrifuged for 30 minutes at 12,000 r.p.m. at 40 c. in a Beckman centrifuge. 3. The supernatant was decanted and the volume measured. 4. Three 20 ml aliquots of the supernatant were titrated with a standard solution of 2,6-dichloroindophenol to a light but distinct pink color which persisted for more than 5 seconds. 5. Similarly, three blanks of 20 ml metaphosphoric acid- acetic acid solution were titrated. 6. Three samples of 2 ml ascorbic acid standard solution in 5 ml metaphosphoric acid-acetic acid solution were ti trated vdth a standard solution of 2,6-dichloroindophenol to a light but distinct pink color which persisted for more than 5 seconds. 7. Similarly, three blanks of 7 ml metaphosphoric acid-

45 46

acetic acid solution were titrated. 8. Three 15 ml samples of brine \tith equal amounts of metaphosphoric acid-acetic acid solution were titrated with a standard solution of 2,6-dichloroindophenol to a light but distinct pink color which persisted for more than 5 seconds. 9. Similarly, three blanks of 15 ml metaphosphoric acid- acetic acid solution were titrated. A preliminary test for appreciable amounts of basic substance was made by testing a drop of sample with a drop of thymol blue indicator (HCB). A red color in dicated pH below 1.2. Ten ml 0.05% aqueous solution of methylene blue (MCB) were added to a 10 ml sample and mixed. Disappear- ance of the blue color in 10 seconds would indicate the presence of interfering substances of ferrous Fe or cu- ,__...~...... ~--·----.,.-·__,__....,. prous Cu. Color did not disappear. Five drops of 0.05% aqueous solution of indigo carmine (MCB) were added to a 10 ml sample to which 10 ml

HCl (1~3) had been added. Disappearance of color in 5-10 seconds would indicate the presence of interfering substance stannous Sn. Color did not disappear. Ascorbic acid content was calculated using the formula mg ascorbic acid/g = (X-B) x (F/E) x (V/Y) X = average ml for sample titration 47

B = average ml for sample .blank titration F = mg ascorbic acid equivalent to 1.0 ml indophenol standard solution E = number of grams assayed v = volume initial assay solution y = volume sample aliquot titrated

{\.

- APPENDIX B

CHEMICALS AND REAGENTS

.. The solutions used for ascorbic acid determinations were as follows: Metaphosnhoric acid-acetic acid solution

Fifteen grams HP03 pellets (Matheson Coleman and Bell) were dissolved in 40 ml acetic acid and 200 ml distilled water. This was diluted to 500 ml, filtered through fluted filter paper, and stored in the refrigerator. The solution was never used when it was more than 7 days old. Indophenol standard solution Fifty mg 2,6-dichloroindophenol sodium salt (HCB) were dissolved in 50 ml distilled water to which 42 mg soldium bicarbonate (MCB) had been added. After dye dis solved this was diluted to 200 ml \tith water and filtered through fluted filter paper. The solution was stored in the refrigerator in an amber bottle. The solution was never used v;hen it was more than 7 days old. Ascorbic acid standard solution Fifty mg ascorbic acid 01CB) that was stored in a desiccator away from sunlight were dissolved in and

48 1.!..0•./

then diluted to 50 ml vdth metaphosphoric acid-acetic acid solution. This was prepared immediately before use. Thymol blue pH indicator One-tenth gram thymol blue (MCB) was added to 10.75 ml 0.02 N NaOH and diluted to 250 ml vdth distilled ' water.

{ ~ -

- APPENDIX C

LABORATORY EQUIPMENT

Large kettle Cheesecloth rack ,, I' Thermometer Scales Metal cans Can sealer - Dixie Automatic Can Sealer Model 23-500, Dixie Canner Co., Athens, Ga. Retort pouches Pouch sealer (at Carnation) - Sentinal Heat Sealer Model 12-12, ASC Packaging Industries, Montclair, N. J. Pressure cookers - All-American Pressure Cooker No. 94lt and No. 1925X, Wisconsin Aluminum Foundry Co., Inc., Hanitowoc, Wis. Timer Aluminum dishes vnth lids Drying oven Desiccator Waring blender Centrifuge - Beckman Hodel ·J-21 B Centrifuge, JA20 Rotor Whatman fluted filter paper, grade No. 2V Refrigerator

·-50 Miscellaneous laboratory glassware Titration equipment - Metrohm Herisau Multi-Burette E485

. . APPENDIX D

SENSORY EVALUATION

Please rate the two samples of green beans using the follovnng scale: 1 - very desirable 2 - somewhat desirable 3 - neither desirable nor undesirable 4 - some·what undesirable 5 - very undesirable

Sample#__ _ Sample#___ _ Color____ _ Color----- Flavor----- Flavor----- Texture----- Texture----- Overall acceptability______Overall acceptability______

Thank you for your participation.