I I I I II] II I I I I I I I I I I II III ] I III II I I II I I An Eyaluaiiszz a: 131: 33135111: Coaiad Pure-Pa: 5m iar the Packaging at Extended Shle-Lfie Milk BERT. EV, TAYLOR Master :32“ Science I 9 59 THESIS {Ii ‘ . ! LIBRARY “I Miclélgan State ’ I U: .iversity ' [I IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII 3 1293 10 45 AN EVALUATION OF THE PLASTIC COATED PU RE-PAK CARTON FOR THE PACKAGING OF EXTENDED SHELF- LIFE MILK BY BERT W. TAYLOR AN ABSTRACT Submitted to the College of Agriculture of Michigan State University of Agriculture and Applied Science in the partial fulfillment of the requirements for the degree of MASTER OF SCIENCE School of Packaging 1969 Approved ABSTRACT The need for a longer shelf-life of pasteurized dairy products has been brought about by the centralizing of milk processing operations and the resulting commitment to longer distribution systems with less frequent deliveries. The adequacy of the existing plastic coated Pure-Pak carton in such a system and modifications of the basic carton structure were investigated. Modifications included (a) the addition of a . 00035 aluminum foil lamination, (b) skiving of the interior raw edge of the carton, and (c) sterilization of the carton with ethylene oxide gas. The ability of the basic carton with or without modification to protect and contain the product were determined by (a) an evaluation of product flavor during extended storage, (b) measurements of carton bulge during a "free standing" period subsequent to casing using two case styles, (c) the effect of extended transport on bulge, and (d) the bacteriological condition of carton blanks prior to use in the dairy. No relationship was found between carton type and the flavor deterioration of whole milk. Pasteurized milk had a higher score at four weeks.' storage than sterilized milk. . The length of time cartons were held in a "free standing" condition was a' very significant variable. In the bulge tests, none of the values obtained exceeded the generally accepted limits of 14/32 inches over the square dimension of the carton. Even so, the length of time in a "free standing" situation was a very significant variable. The difference in bulge between cartons held loosely in metal case and tightly in a corrugated case was real. Bulging with time followed parallel courses for each carton regardless of type of casing. Cartons subjected to vibration and handling during a 500 mile test showed a slightly higher bulge. Bacteriological examination by a swab test of 1050 carton samples showed 28 with counts of from one to six per carton, assuming 52 square centimeters per test. AN EVALUATION OF THE PLASTIC COATED PURE-PAK CARTON FOR THE PACKAGING OF EXTENDED SHELF-LIFE MILK By BERTW. TAYLOR A THESIS Submitted to the College of Agriculture of Michigan State University of Agriculture and Applied Science in the partial fulfillment of the requirements for the degree of MASTER OF SCIENCE School of Packaging 1969 Approved ACKNOW LEDGEMENTS The author wishes to express his sincere thanks to Dr. H. J. Raphael for his valuable direction during the course of this study, and for the constructive criticism offered in the preparation of this manuscript. Gratitude is also expressed to Dr. T. I. Hedrick and Dr. T. H. Harper for their suggestions and encouragement throughout the course of this study. My sincere thanks to Mrs. John Sundheimer for her gracious and invaluable assistance in preparing the finished form of the manuscript. TAB LE OF CONTENTS INTRODUCTION LITERATURE REVIEW EXPERIMENTAL PROCEDURE Whole Milk Flavor Evaluation Test 1% Lactic Acid Static Storage Test 1% Lactic Acid Transportation Test Pour Grasp Firmness Test Microbiological Examination of Finished Cartons RESULTS Whole Milk Flavor Evaluation Test 1% Lactic Acid Storage Test 1% Lactic Acid Transportation Test Pour Grasp Firmness Test Microbiological Examination of Finished Cartons TABLES DISCUSSION SUMMARY AND CONCLUSION LITERATURE CITED APPENDD( page l7 17 19 20 21 21 22 22 24 25 26 27 28 39 44 47 51 INTRODUCTION The keeping quality or "shelf-life" of packaged milk products has always been of prime interest to dairy processors. This "she1f-1ife"is a limiting factor and its influence is felt at all levels of processing and distribution. If milk products could be processed and packaged so as to extend the useable life of the product, efficiencies in the areas of production and distribution could be realized. Also, the consumer would be assured of a more consistent, high quality product. Milk becomes unsaleable due to changes caused by microbiological or physical factors. A processing and packaging system must be devised to control these factors. Two approaches are being suggested to attain this extended "shelf-life". The sterile approach requires the use of ultra high temperature processing, product handling and packaging under sterile conditions in a sterile package with or without refrigerated storage. The "ultra-clean" approach involves the use of existing processing techniques, improved handling and sanitation methods with attention given to the reduction of contamination in the packaging area, an ultra clean system which would reduce bacterial contamination following pasteurization. The product would be held and distributed in a refrigerated system. The Ex-Cell-O Corporation has developed an aseptic packaging system for milk products. It involves the use of a specially designed machine which maintains a sterile atmosphere in the carton filling and sealing area. The products so packaged would be subjected to higher than normal processing temperatures to ensure complete destruction of bacteria. In milk products, this higher heat treatment gives a characteristic "cooked” or heated flavor which is different from normally pasteurized milk. Customer reaction to this flavor could be adverse. Ex- Cell-0 has determined that for sterilized products a sterile plastic coated Pure- Pak carton with a foil lamination is needed. This carton, sterilized with ethylene oxide gas would not contribute to the contamination of the product. The foil lamination provides the additional light and gas barrier properties needed for a long storage life (60 days). Storage of the product could be in either a refrigerated or unrefrigerated condition. The cost of the sterilized foil laminated carton is significantly higher than that of the regular plastic coated carton. The price per thousand for a two-color foil laminated carton is $35. 00. The price for a two-color regular plastic coated carton is $15. 58. The Ex-Cell-O Corporation's Aseptic Machine could be used as a component in the "ultra-clean" approach. This study was initiated to determine the adequacy of the existing plastic coated Pure-Pak milk container as a package for the ultra-clean approach, and to determine if modifications were necessary to improve the product protection, strength, or bacteriological qualities of the carton as a component in an ultra-clean processing and packaging system. LITERATURE REVIEW Olsen, et al. (27) noted at least three trends which accent the importance of factors influencing shelf-life; the lengthening of time between processing and distribution, more milk being processed and distributed by centralized plants and distribution over a wider area. Hedrick and Hall (13) stated that high retail delivery costs (approximately one-third of the customer price), besides those of refrigeration, handling, storage, and distribution have stimulated the development of aseptic packaging of milk and cream. Elliker (8) observed that results have further demonstrated that the improved keeping quality attained pays dividends in a longer marketing period, fewer returns, and fewer customer complaints. Overcast (29) wrote that in his opinion today, the most important bacterial problem the industry faces is that of psychrophilic organisms. He stated that we are dealing with these organisms that grow in milk or its products at refrigeration temperature at such a rate as to bring about objectionable changes before its consumption. Given a generation time of six hours at 450 F. and only one of these in a quart of milk, the count increases to one million per ml. after eight days of storage. By and large, these organisms are of soil and water origin; they are destroyed by pasteurization but find their way into the milk through improperly sanitized or contaminated equipment. 5 Psychrophilic organisms are able to grow below 50 C. and do not survive heating at 1450 F. for 30 minutes. Their presence in appreciable numbers in pasteurized products is evidence of post-pasteurization contamination. Pseudomonas, Achrobacter, Flavobacterium, and Alcaligines are psychrophilics according to Thomas (37). A low temperature hold slows down but does not stop psychrophilic growth. 3 Olsen, et al. (27) noted thepmajor factor of keeping quality is metabolic activity of bacterial species which are capable of relatively rapid growth in milk at low temperature, generally in the range of 35-450 F. Taking into consideration lag time and generation time, Harper (11) calculated the expected shelf-life of fluid milk with a contamination level of one per package, based on the observation that over one million psychrOphilic organisms per ml. results in unsalesable fluid milk products. A one-half pint of milk held at 45°, F. would have a shelf-life of 16. 5 days; a quart, 17. 5 days. Randolph, et a1. (31) in a study of the keeping quality of market milk stated that the results of the bacteriological examinations reveal considerable variations in the sanitation programs of the different plants and provide explanations for the differences observed in the keeping quality. The fact that a majority of the samples contained organisms capable of growing at 40 to 45° F. , which is indicative of the presence of psychr0philic organisms resulting from post-pasteurization, suggests 6 that considerably more care is needed to avoid contaminating of the pasteurized product. Irvin (20) stated that during the past few years, there has been a growing interest in the pasteurization of milk and milk products at higher temperatures. The principal economics of higher heat processes are an improvement in shelf-life. This in turn permits handling and distribution practices that result in such important changes in plant operations as concentration of plant facilities, less frequent deliveries, and extension of sales areas. Jordan (22) stated that the most significant change in dairy products subjected to ultra-high temperature (UHT) treatment is the reduction of the viable microorganisms to essentially zero. The extent of destruction of microorganisms necessary to produce a sterilized product determines the intensity of the heat treatment required, which in turn determines the extent of other changes that take place in the products. Pasteurization is defined by the Grade A Pasteurized Milk Ordinance (3) as the process of heating every particle of milk or milk product to at least 1450 F. and holding it continuously at or above this temperature for at least 30 minutes, or to at least 1610 F. , and holding it continuously at or above this temperature for at least 15 seconds in equipment which is properly operated and approved by the health autho rity. Read, et a1. (32) in commenting on pasteurization stated that from a public health standpoint, pasteurization has a single function; to inactivate any viable pathogenic microorganism present in the raw product so that these microorganisms cannot impair the health of the consumer. The Public Health Service has received several requests for milk and milk product pasteurization standards for processes that would involve shorter holding times and higher holding temperatures than are now being used for high-temperature short—time (HTST) pasteurization. These processes are given the general label of ultra- high temperature (UHT) pasteurization. For purposes of identification, UHT pasteurization for milk and milk products can be defined as a group of thermal processes for dairy products that have holding times of 2 seconds or less with holding temperatures of from 190 to 2700 F. The upper limit of 2700 F. was selected because most heating processes for milk and milk products that use holding temperatures above 2700 F. are designed to sterilize rather than pasteurize. Holland (18) indicated that the production of sterilized milk of a satisfactory table and beverage quality has occupied the attention of numerous dairy research workers over many years. The advantages of such a product are obvious. The fact is, however, that no one has yet produced a product that matches the flavor of the high quality pasteurized milk that is available to the American housewife. Flavor is the most important attribute of milk products. Holland (19) observes that many processors no longer hold closely to the pasteurization standards in their heat treatment procedure but are using higher temperatures for longer times. In the case of sterile products, temperatures may approach or even exceed 3000 F. with holding times reduced to a few seconds. In view of these facts it may be timely to take a look at some of the effects of increased heat treatment on the constituents of our product. Johnson (21), Irvin (20) and Herried (17), have all commented on the effects of UHT heat treatment of milk. The cooked or heated flavor is inevitable created in all products during sterilization. The shelf-life of sterile fluid milk. products is limited by cream rising, fat oxidation, settling of solids, chalkiness, gelatin and off-flavors. Gould (19) comments that due to the intricacy of the normal milk system, the heating of milk may be expected to create many new relationships and inter-relationships among the constituents and to form a multitude of compounds not present originally. These chemical compounds in turn are responsible for certain changes which are obvious to the 'consum er; changes such as flavor and color which definitely affect the marketability of the final product. The temperature at which the processed product is held is a factor. O'Sullivan and Keogh (28) observed that the two critical factors limiting the shelf-life of UHT cream are chemical off-flavor development and physical separation. The shelf-life can be markedly extended by low temperature storage of the product. Herried (17) notes that at present there is no substitute for low temperature storage for maintaining 9 and prolonging the palatable shelf-life of sterile fluid milk products. While aseptic packaging has been receiving the publicity, the practical milk plant operators have recognized the need for more efficient pasteurization, improved sanitation and cleaning practices. Equipment manufacturers have modified and improved filling machines that can now handle and fill cartons in a nearly sterile atmosphere. Tests have proven that milk processed under these controlled conditions, given reasonable care in the distribution process will have an extra week or perhaps more of shelf-life, requiring less frequent deliveries to the store and enabling processors to expand marketing areas.(l). Lisiecki (24) stated that storage at low temperature slows the reactions causing unwanted changes in product characteristics and that to date, no substitute for low temperature storage to maintain palatability has been found. No sterilization process completely avoids the problem of cooked and off-flavors in the heated product. Heldman, et al. (16) stated that the shelf-life of many food products, in particular milk and milk products, is directly related to the amount of bacterial contamination which occurs after processing. The importance of post-pasteurization has been emphasized by the increased interest in high-temperature processing and sterilization. Since a part of this contamination is due to contact of the product with airborne microorganisms, methods and equipment must be developed which will prevent airborne 10 contamination, especially during filling and packaging. Hedrick, et a1. (14) took samples, using a Casella vacuum slit sampler, from three areas in a dairy operation. The average bacteria count of 315 samplings in the three areas was 27. 0, the range was 0 to 155 for 5 cubic feet of air. More specialized air tests whereby a worker was confined to a small container were conducted. The air was sampled after it was drawn through a high efficiency filter and past the worker from head to foot. These data suggest that individuals are a prime contributor of bacteria to air within a building. Air sampling tests have confirmed that floor drains are a source of airborne contamination. A few trials have shown that supplies from dusty storage rooms can increase airborne contamination. Heldman, et al. (15) noted that theoretically, it would be desirable to maintain the airborne population in food packaging areas at zero to prevent any degree of contamination. However, under operating conditions, it is impossible to avoid all contamination due to the presence of workers and the many other factors which contribute to the overall count. On the other hand, methods available for removing microorganisms from air provide a means of limiting the population at least in an isolated area in which the factors contributing to the count can be controlled. The concept of laminar flow was developed to meet the needs for dust-free conditions during assembly of small components or precision instruments. The basic principles involved in a laminar air flow bench 11 or chamber are: (a) remove all particles 0. 3 microns and larger from an air supply by using ultra-high efficiency filters, (b) direct this filtered air through a selected space at a low velocity (usually 50 to 200 ft/min), and (c) prevent mixing of filtered and unfiltered air within the selected Space. Laminar air flow clean rooms are described in Contamination Control Principles (2). A clean room needs: (a) A self-clean-down capability to combat both contamination brought into and generated within the room; (b) Air-flow patterns which carry airborn contamination away from the work and the work area; (c) Reduced personnel restrictions, and ((1) Lower maintenance costs. This laminar flow technique can be adapted to rooms, tunnels, curtained units, hoods, and work stations. Hedrick (12) stated that steady developments taking place in the sterilization and aseptic packaging of liquid milk products in recent years portend the opportunity for dynamic changes in the future. The magnitude of research on packages and aseptic packaging is reason for optimism. Aseptic packaging means the sten' lization‘ of the container, filling and sealing it without contamination of the product. Aseptic packaging systems are still limited primarily to Dole equipment for metal cans and Tetra Pak with cartons of paperboard, foil, and plastic films. Our MSU trial .shows promise using a Pure-Pak type aseptic filler and carton losses during storage have been reduced to less than 1%. Mann (26) noted that the first aseptic Tetra Pak was at the Coop Dairy in Berne, Switzerland. Milk, 15% cream, chocolate milk, and 12 chocolate and vanilla custard are packaged. Mann (25) described the Tetra Pak system. The Tetra Pak Brix Aseptic Machine involves the sterilization of the packaging material in a hot hydrogen peroxide bath and the maintenance of sterility during the subsequent stages by means of pressurized sterile air. The strip of packaging material passes through the hydrogen peroxide at 1760 F. and receives 8 - 9 second treatment. An air blast is employed to remove the chemical adhering to the packaging strip, which is then formed into a tube, filled with product and shaped into rectangular containers. The forming and filling sections of the machine are completely enclosed within a chamber in which an atmosphere of sterile air is maintained above atmospheric pressure. In discussing the packaging needs for sterile milk, Hedrick and Hall (13) observed that the packaging material for sterilized milk had to be specially designed to stand up to handling and prolonged storage. Several combinations have been tried. One that appears satisfactory in preliminary trials consists of 90-lb. paper with a l-mil coating of polyethylene, l-mil aluminum foil, and an inside layer of 2-mil polyethylene. Lisiecki (23) described the Aseptic Pure-Pak as a machine in which operations are carried out in a sterile environment. The Pure-Pak system is designed to prevent the invasion of organisms. The Pure- Pak blank is a five ply laminate. From the inside out, the layers are polyethylene, aluminum foil, polyethylene, paper, and polyethylene. Boxes of blanks are sterilized by the supplier with ethylene oxide gas 13 prior to shipment and remain sterile until opened. During processing, the carton is mechanically handled in a non-sterile environment for a few seconds. It must therefore undergo a minor resterilization treatment to eliminate any casual recontamination which may have occurred. On the Pure- Pak, this secondary treatment is a hydrogen peroxide f0g, which in turn is dried with hot air at approximately 5000 F. Lisiecki (24) found that the standard Pure-Pak carton was not suitable for an aseptic system with a high temperature storage requirement. Yeast, molds, and bacteria caused contamination. A method of carton sterilization using ethylene oxide was tried and found to be very effective. He concluded that the foil-lined container, ethylene oxide treated is the container of choice for the time being. Tests did indicate an extremely low bacterial load on the surface of the carton itself. This was in the range of zero to five organisms per carton. Prucha (30) commented on the development of the paper milk container. The bottling of fluid milk in paper containers is not a new idea. In a book by Kenneth Winslow, 1909, "The latest departure in the way of a milk bottle is the single service milk container of pulpwood invented and made by G. W. Maxwell, San Francisco, Calif. " While the milk container was invented some thirty years ago, very little attention was paid to it by the fluid milk industry or by the milk sanitarians. Tracy (38) noted that the early Maxwell containers resembled a drinking glass and were sterilized by dipping in hot paraffin at 2200 F. 14 The first extensive use of a paper milk container was in New York City in 1929. With the recent development of store selling of milk, there has come a demand for an inexpensive single service type of milk container. Prucha (30) studied the papermaking process and its relation to the sanitary aspect of the container. He took 2 inch square samples of paper as they left the hot dryer rollers, placed them in 100 ml. of sterile water and shook well. Plating of these samples gave no colonies on a 1:1 dilution. He also make tests to determine how long bacteria will survive on impregnated strips of paper. Heavily innoculated strips of paraffined paper were examined daily. No living bacteria were found on the strips after the seventh day. When unparaffined strips were innoculated and examined in the same manner, no viable bacteria were present after the sixth day. Appling, et al. (5) in discussing paper food packaging materials noted that a few organisms are introduced in the early phases of paper or paper board manufacture, but practically all are eliminated through the chemical and physical operations necessary in the manufacture of the product. The application of chemicals takes place in the form of strongly acid or alkaline cooking liquors at the digesters, liquors such as chlorine or peroxides at the bleachers and alum at the paper machine. The primary physical factor which reduces microorganisms is heat at the digesters, grinders, drier rolls, and during waxing operations. 15 Casey (7) stated that recent developments in the use of paper containers for milk and other food products where highly sanitary conditions should be maintained have brought the subject of paper mill microbiology to the attention of the health authorities. Tanner (36) felt that (a) paper was devoid of bacteria which had sanitary significance, (b) pathogenic bacteria could not survive the operations used in making paper, (c) the only bacteria present in paper were harmless aerobic spore-forming species widespread in nature, and (d) coliform bacteria were absent in milk containers. Stark (35) noted that paper milk containers have never been incriminated in any outbreak of disease is convincing evidence of their public safety. Sanborn (34) indicated that the influence of calander water is a good example of a source of growth that is controllable. He proposed standards (33) for paper milk containers: (a) use virgin pulp only, (b) use pure process water with (c) suitable protection and wrapping of finished board, (d) mechanical handling during converting, and (e) good plant sanitation. Samples prior to moisture proofing should not have a count exceeding five hundred colonies per gram of disintegrated board. The Guide for Sanitation Standards (4) gives bacterial standards which are now effective under the Grade A Pasteurized Milk Ordinance. Paper stock shall meet the bacterial standard of not more than 250 colonies per gram as determined by the disintegration test. The residual bacterial count of single service containers and closures used 16 for pasteurized milk and milk products shall not exceed one colony per ml. of capacity or not over 50 colonies per eight square inches of a product contact surface in three out of four samples taken at random on a given day. All single service containers shall be free of coliform organisms. Referring to carton structure, Hedrick and Hall (13) stated that the container must be sufficiently durable to provide a long shelf-life without affecting the flavor of the product. Griffin, et al. (10) tested flexible films to determine their ability to provide a barrier to bacterial penetration. They found that there were no signs of penetration by bacteria by any means except through film defects. Whenever bacterial penetration was noted, a pinhole or minute tear was found. There were no signs of diffusion or "grow-through” types of penetration. Bauermann, et al. (6) noted the multiplicity of food packaging materials for today's food products is so great that the selection of a package for a given food entails a great deal of work and testing. Food is packaged for five primary reasons: (a) to protect the product from contamination from microorganisms and filth, (b) to retard or prevent loss or gain of moisture, (c) to shield the product from oxygen and light; (d) to facilitate handling, and (e) to enhance the marketability of the product. 17 EXPERIMENTAL PROCEDURE Two basic carton structures were used. The first was the standard carton now used in the dairy industry. This was a laminated structure with medium density polyethylene coating on either sides of a solid bleached sulphite paperboard. Basis weight of the paperboard was 215 pounds. The interior polyethylene coating was approximately I. 5 mils, the exterior coating 0. 8 mils. The side seam construction was such that a raw edge of paper was exposed on the inside of the carton. The second structure was a foil laminated carton. It was identical to the first but with two additional laminations. Thus from the outside to the inside the laminations were 0. 8 mils polyethylene, paperboard, 0. 8 polyethylene, . 00035 zero temper oil free aluminum foil, and l. 5 mils polyethylene. Variations of the two basic cartons were considered. First, by a process of skiving and rolling, the raw edge on the inside side seam of the carton was eliminated. Second, cartons were sterilized using ethylene oxide gas. Whole Milk Flavor Evaluation Test In three separate trials, sterilized and pasteurized milk was packaged in Pure-Pak style milk containers using the Ex-Cell-O NLL machine at Michigan State University. Six variations of the basic Pure-Pak design were used. They were: 1. Regular plastic coated carton. 18 2. Regular plastic coated carton with skived and rolled inner seam. 3. Regular plastic coated carton sterilized with ethylene oxide gas. 4. Foil laminated plastic coated carton. 5. Foil laminated plastic coated carton with skived and rolled inner seam. 6. Foil laminated plastic coated carton sterilized with ethylene oxide gas. These six variations are types which are presently in use. Types other than the regular plastic coated carton are for special products such‘as syrups, dry, or sterile products. Whole milk from the Michigan State University dairy herd was used. The milk to be sterilized was processed through a Cherry-Burrell Unitherm at a temperature of 2980 F. The holding time was 8 sec. Following sterilization the milk was homogenized, cooled to 600 F. , piped directly to the Ex-Cell-O NLL aseptic filler where the filling was accomplished. The processing equipment used was cleaned, sanitized with a 200 ppm chlorine solution, then steamed at 10 psi for two hours. The only piece of equipment which did not receive the steaming treatment was the pasteurizing vat. 19 The pasteurized milk.“ as processed at 1500 F. for 30 minutes, homogenized at 2000 psi, cooled to 500 F. in a plate heat exchanger, and then moved to the sterile surge tank. From the sterile. surge tank, the product flowed by gravity to the Ex-Cell—O aseptic filler where the filling was aCComplished. Immediately after filling, the cartons were placed in metal cases, 24 quarts to a case. They were then transported to Ohio State University where they were stored in the University Dairy cooler at 420 F. A flavor evaluation was made by members of the Department of Dairy Technology staff at one week intervals using organoleptic methods. The scoring ranges used and flavor defects noted were those recommended by The American Dairy Science Association and are in common use in the dairy industry. This evaluation was continued until the milk became unsaleable. 1% Lactic Acid Static Storage Test A standard test for the laboratory testing of carton integrity involves the use of a 1% solution of lactic acid in water. This simulates the action of hard-to-hold products such as orange juice. Carton deterioration or leaks may be noted and bulge measurements made. Pure-Pak cartons which had been previously bottom formed were filled'by hand with a 1% lactic acid solution of water, then top sealed using a hand operated bench top sealing unit. Four variations of the 20 basic Pure—Pak design were used. They were: 1. Regular plastic coated carton 2. Regular plastic coated carton with a skived and rolled inner seam 3. Foil laminated plastic coated carton 4. Foil laminated plastic coated carton with a skived and rolled inner seam The cartons were then placed in two types of cases. ' One was a standard wire case holding l6 quarts. The other was an RSC corrugated case, 275 pound test, C flute, holding 12 quarts. Cartons in both style cases were held at 420 F. for one week. At the end of one week the cartons were removed from the cases and placed in a free standing unsupported condition. Measurements were made from front to back and side to side at point of maximum bulge with a pair of calipers. These measurements were made at 0, 3, 5, 7, 10, 14, and 17 days. 1% Lactic Acid Transportation Test Using the same filling and sealing procedures and carton variations as in the static storage test, the filled cartons were packed in RSC corrugated cases, 275 pound test, C flute. Cartons in these cases were held for one week at 420 F. They were removed from the cooler, placed on a truck, and subjected to a 510 mile round trip. This was from Cleveland, Ohio to Flint, Michigan and return. During the trip the cartons were subjected to vibration and handling similar to that experienced in a dairy distribution system. The cartons in the cases were 21 returned to the cooler and held for an additional five weeks. At the end of this time, the cartons were removed from the cases and placed in a free standing unsupported condition. Measurements were made as in the static storage test at intervals of 0, 3, 5, 7, 10, 14, and 17 days. Pour Grasp Firmness Test At the end of the 17 days holding period, the four basic carton variations were emptied by opening the pitcher pour spout but leaving the remainder of the gable unopened. The "pour grasp" firmness of each variation was tested. In this test, the carton is placed in a standing position with one side touching a rail. By moving a switch, a plunger is activated which moves out to contact the carton on the opposite side from the rail, thus simulating the thumb and finger grip normally used when holding a milk container. A gauge indicates the pressure in pounds necessary to break the vertical dimension of the carton. Microbiological Examination of Finished Plastic Coated Milk Containers Full cases of cartons were selected at random from the production line just prior to warehousing. All twelve corner edges of the shipping container were taped prior to shipment for evaluation. Samples were taken over a six-month period. Microbiological counts were made by the swab test. In this test, a sterile cotton swab contacts a known area of the carton to be examined. The swab is placed in sterile water, shaken and aliquots plated in nutrient agar. Incubation is at 90 or 980 F. for 48 hours. 22 RESU LTS Whole Milk Flavor Evaluation Test The results of the whole milk flavor test are summarized in Tables 1 - 4. If post-pasteurization contamination can be eliminated by sterilization of equipment and the use of an aseptic filler and the product moved in a refrigerated system then the ability of the carton to protect and contain the product for a longer period is of importance. This test was to determine the relative ability of various carton structures to protect and contain the product. If no psychrophilic organisms were present, the shelf-life should be extended. The foil laminated carton, sterilized with ethylene oxide gas was used as a control. This carton should not contribute any organisms to the product and give the best barrier protection. The skived and rolled edge used on both regular and foil cartons should prevent moisture penetration of the side seam, thereby contributing to the strength and bacteriological integrity of the carton. It was anticipated that chemical and/0r enzymatic changes would be the limiting factor of shelf-life. The sterilized product was included as a control. Table 1 gives the initial flavor scores. In all cases, the pasteurized samples scored higher than the sterilized. The pasteurized milk was criticized as having a "feed" flavor. This is a common defect of pasteurized milk and is due to a carry-over of feeds such as silage into the milk. The sterilized milk was scored "astringent. " 23 There was a variation in initial flavor scores and bacteria counts from trial to trial. The sterilized milk samples were not sterile. Tables 2, 3, and 4 give the flavor scores for all carton structures. Flavor scores of the pasteurized milk were above those of sterilized product. The average scores in each trial of pasteurized milk for all types of cartons were 39. 05, 37. 93, and 38. 57 after one week of storage. Sterilized samples scored 38. 36, 37. 47, and 37. 73. The average for all pasteurized samples was 38. 52. The average for all sterilized samples was 37. 85. For the third week, pasteurized ave rages were 38. 49, 36. 66, and 38. 88. Sterilized samples had average scores of 37. 58, 37. 05, and 34. 27. The average third week pasteurized flavor score was 38.14, that of the sterilized samples was 36. 36. At the fourth week, however, the average sterilized score was higher than the pasteurized being 36. 53 and 35. 23. At four weeks all types of regular pasteurized carton scores averaged 35. 85. All foil pasteurized carton scores averaged 34. 58. For sterile milk at four weeks, regular cartons of all types scored 36. 67, foil cartons 36. 39. For pasteurized milk no one style carton gave a considerably higher score. At four weeks, the sterile foil carton had the highest score in Table 2, the skived regular in Table 3, and the sterile regular carton in Table 3. Neither did any particular style carton give a consistently lower score. 24 By the end of the fifth .week bacterial counts in the milk from all packages exceeded 300, OOO/ml. Off-flavors noted were bitter, yeasty, fruity, and astringent. 1% Lactic Acid Static Storage Test In the 1% lactic acid static storage test, the bulge characteristics of four carton variations were studied in relation to casing tightness. A comparison was made between a metal case and a corrugated case. The metal case used was a standard wire Pure-Pak case holding l6 quarts. The interior dimensions were 12. 25 inches x 12. 25 inches which gives a case space per carton of 3. 06 inches. This is O. 31 inches over the square dimension of the carton. The corrugated case used had an interior measurement of 11. 75 inches x 8. 54 inches. This gives a case space per carton of 2. 90 inches and is 0.15 inches over the square dimension of the carton. Thus, the corrugated case held the cartons in a more confined condition, 0.16 inches. Results of this study are shown in Tables 5, 6, and 7. In the industry, carton bulge values are generally given in 1/32 inches over the square dimension of the carton. Thus a value of 5. 0 in the tables would indicate a 5/32 inch bulge over the nominal side carton dimension of 2—3/4 inches. In Table 5, the regular cartons, both plain seam and skived have a value of 7. 0, the foil cartons a value of 6. 0. By the seventh day, the regular cartons have increased in size to 8. 6 and 8. 3 respectively and at seventeen days, 10. 8 and 10. 6. The foil cartons at seven days have 25 values of 8. .3 and 8.1, at seventeen days, 10. 4 and 10. O. For the first week in a free standing condition, the foil cartons, regular and skived increased in sire. more than the regular cartons. The regular cartons had a seven day increase of l. 6 and l. 5, the foil cartons 2. 3 and 2.1. At seventeen days there was less than 1. 32 inches variation in all types of regular and foil. The foil cartons while showing slightly lower values, had greater increases from zero to seventeen days. Table 6 gives the values obtained using the corrugated case. The regular cartons had initial Values of 5. 0, the foil cartons 4. 0. At seven days the regular cartons had values of 8. l and 8. 3, the foil cartons 7. 3 andi7. 5. The seven day increases were 3.1, 3. 3, 3. 3, and 3. 5. At seventeen days, the regular cartons measured 10. 4 and 10. O, the foil cartons 9. 8 and 9. 4. There was 1/32 inches difference between the regular carton with raw edge and the foil carton with skived edge. Increases in bulge ranged from 5. 0 to 5. 8. Initial values were higher with the more loosely cased cartons. As shown in Table 7 however, the more tightly cased cartons had a greater increase in bulge at both seven and seventeen days. Final dimensions of all cartons tested varied from O. 4 to 0. 6. 1% Lactic Acid Transportation Test In the trans port study, the initial free standing values ranged from 7. 6 for the regular carton to 6. 6 for the skived foil carton. The increase in bulge from zero days to three days was significant, being 26 l. 7 to l. 9. The skived foil hail the greatest increase. At seventeen days the regular carton hat. a. value of ll. 9, an increase of 4. 3; regular skived was 11. 3, an increase of 4. 6. The foil cartons were slightly lower; the foil carton measured 11. 5, an increase of 5.1; the foil skived, 11.1, an increase of 4. 5. There was less than 1/32 inches differences in the final measurements. The transportation test showed final values slightly higher than in the other cased tests. Greater increase in bulge was obtained in the first three days with the transporta- tion test than with either cased study. Pour Grasp Firmness Test Results of the pour grasp firmness test are shown in Table 9. Cartons stored in corrugated cases had a slightly better pour grasp firmness than did their like cartons stored in wire cases. Cartons with skived seams were slightly better in pour grasp firmness than their like cartons with a regular seam. Foil lined cartons had a significantly better pour grasp firmness than their respective regular cartons. Values for regular cartons ranged from 5. 8 to 6. 3 pounds while foil cartons were 8. 9 to 9. 3 pounds. The six week storage cartons had a slightly lower pour grasp firmness than the other cartons tested. Microbiological Examination of Finished Cartons Results of the microbiological examination are summarized in Table 10. In all, 1050 samples were examined. Of these, 28 showed bacteria counts ranging from one to six per carton assuming 52 square centimeter 3 per test. 27 Five cartons had a count of one, two a count of three, eleven a count of four, and ten a count of Six. This gives a total count of 115 colonies in 1050 samples or a count of 0.11 per sample. TABLES 28 Trial 29 "TABLE 1 Initial Standard Plate Counts and Flavor Scores of Whole Milk Flavor Test Pasteurized Milk Sterilized Milk Initial SPC Initial Flavor Initial SPC Initial Flavor 300-600/ml. 38. 0 - 39. O lOO-400/ml. 37. O - 38. 5 3,000/m1. 37. 5 - 39. 0 , lOO-300/ml. 37.0 - 38.0 800—17, OOO/ml. 38. O - 39. 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Carton measurement is 2-3/4 inches. 34 TABLE 6‘ 1% Lactic acid Static Bulge Test Cartons Held in Corrugated Case for One Week After Filling Then Out of Case to a Free Standing Position- Room Temperature Days Free Standing 0 3 5 7 10 l4 l7 Carton Style Regular 5.0 6. 6 7.8 8.1 9.5 10.0 10.4 Regular-Skived 5.0 6. 5 7 0 8 3 9.0 9.5 10.0 Foil 4. 0 5. 3 6. 5 7. 3 8. 6 9. 0 9. 8 Foil-Skived 4. 0 5. 0 6. 3 7. 5 8. 0 8. 6 9. 4 Quantities shown are averages of six cartons for each carton type. Measurements given in 1/32 inches over square dimension of carton. Carton measurement is 2-3/4 inches. TABLE 7 1% Lactic Acid Static Bulge Test 35 Comparison of Metal and Corrugated Cased Cartons Bulge Increase Over Initial Free Standing Value Carton Style 7 Days Metal Corrugated Regular 1. 4 3.1 Regular-Skived l. 3 3. 3 Foil 2. 3 3. 3 . Foil-Skived 2. 1 3. 5 17 Day 8 Metal Corrugated 3.8 5.4 3.6 5.0 4.4 5.8 4.0 5.4 Quantities shown are averages of six cartons per each carton type. Measurements given in 1/32 inches over square dimension of carton. Carton measurement is 2- 3/4 inches. 36 TAB LE 8 1% Lactic Acid Transportation Bulge Test Days Free Standing at Room Temperature 0 3 5 7 ' 10 14 17 Carton Style Regular 7.6 9.3 10.8 11.0 11.9 Regular—Skived 7. 3 9. 0 10. 4 10. 9 11. 7 Foil 6.4 8.7 9.3 9.7 10.0 10.7 11.5 Foil Skived 6. 6 8. 5 9. 5 10. 3 11.1 Quantities shown are averages of fifteen cartons of each carton type. Measurements given in 1/32 inches over square dimension of carton. Carton measurement is 2-3/4 inches. 37 'TABLE 9 Pour Grasp Firmness Test Corrugated Cas e Metal Case Corrugated Case Six Weeks Storage One Week Storage One Week Storage Transport 500 mi. 17 Days "Free" 17 Days ”Free" 17 Days ”Free" Carton Style Regular 5. 8 . 6. 3 5. 2 Regular-Skived 5. 9 6. 2 5. 6 Foil 9. l 9. 3 8. 4 Foil-Skived 8. 9 9. 3 8. 7 Firmness in Pounds Quantities shown are averages of six cartons for each carton type. 38 33653ch mumsqm you 3 menu”: 6.335 w you mmficofloo cm .820 “oz so 583de mo .1: sea >co~oo eco mo pumpcmum co newsman 32 o 2 o 2 N o m 30; 4 swam Nm 0 m w. m N H ummH pumpcmum 53H mom EdoU fimwuouomm «63on 9.33 60532 823683ch 923200 mcfipmooxm mecca Go 93sz E *umbfidz ponEdZ bmumvfi mama‘s mcouumU poumoU 333nm posmflcmrm .«o coEmEmem Anoflmofiowuouomm o~ MA m