W[HHWIIUIIHWWWIWIJHNHWHIHHHIWI _|U1_L _‘_\ I COCO—3 llBRARY W \\\\\\\\\\\\\\\l\\\\\\ ”333%” This is to certify that the thesis entitled THE INFLUENCE OF AROMA COMPOUND ABSORPTION ON MECHANICAL AND BARRIER PROPERTIES OF SEALANT FILMS USED IN ASPETIC PACKAGING presented by KAZUHIKO HIROSE has been accepted towards fulfillment of the requirements for M . 5. degree in PACKAGING Dr. Bruce R. Harte. ASSQ£.PrOf. Major professor Date MarCh I6, I987 0-7639 MS U 1': an Waive Action/Equal Opportunity Institution MSU RETURNING MATERIALS: Place in book drop to LjBRAfiJES remove this checkout from __1——. your record. FINES will be charged if book is returned after the date stamped below. 1"” 32553 II ’2'. 1‘3 ‘4 i I . I (I .‘Ff'Lii'J I .9 11’4": -“ ...< 3.; lg. k--~,.d. I THE INFLUENCE OF AROMA COMPOUND ABSORPTION ON MECHANICAL AND BARRIER PROPERTIES OF SEALANT FILMS USED IN ASEPTIC PACKAGING By Kazuhiko Hirose A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE School of Packaging 1987 ABSTRACT THE INFLUENCE OF AROMA COMPOUND ABSORPTION ON MECHANICAL AND BARRIER PROPERTIES OF SEALANT FILMS USED IN ASEPTIC PACKAGING By Kazuhiko Hirose Several workers have reported that d—limonene, a major flavor component in citrus juices, is readily absorbed into polyethylene. In this study, the influence Of aroma compound absorption on mechan- ical properties of polyethylene and ionomer films as a function of d-limonene concentration was investigated. Sample strips of poly- ethylene and ionomer (2.54 cm x 12.7 cm) were immersed in juice until equilibrium was established. The mechanical properties and seal strength of the control (non-immersed) and immersed samples were determined at various concentration levels of absorbant using a Universal Testing Instrument (Instron Corporation, Canton, MA). Oxygen permeability Of the films was also measured. Absorption of d-limonene by the polymers affected (1) modulus of elasticity, (2) tensile strength, (3) percent elongation, (4) seal strength, (5) impact resistance, and (6) oxygen permeability. The polymers varied with respect to the degree of change caused by absorption of flavor component. ACKNOWLEDGMENTS I would like to express sincere thanks and appreciation to: Dr. Bruce Harte, Associate Professor in the School of Packaging and my major advisor, for his kind counsel and assistance throughout the course of this graduate program. Dr. Charles Stine, Professor in the Department of Food Science and Human Nutrition, for his generous donation of laboratory space and time. Dr. Jack Giacin, Professor in the School of Packaging, for being a committee member and donation of his time. Dr. Joseph Miltz, Department of Food Engineering and Biotech- nology in Israel Institute of Technology, for his advice in research work. Kureha Chemical Ind. CO., Ltd., who made this graduate work possible and enriching, for their continued support. I would also like to thank my wife, Mayumi, for her long-time dedication. ii TABLE OF CONTENTS LIST OF TABLES ....................... LIST OF FIGURES ....................... CHAPTER 1. INTRODUCTION ..................... 2. LITERATURE REVIEW ................... 2.1. Aseptic Packaging in the United States ..... 2.2. Shelf Life ................... 2.3. Flavors and Extraction Procedures ........ 2.4. Package Interaction ............... 2.5. Oxygen Barrier ................. 3. MATERIALS AND METHODS ................. 3.1. Introduction .................. 3.1.1 Materials Used in the Study ....... 3.1.2 Quantitative Determination Of d-limonene 3.1.3 Procedure for Determining d-limonene in Orange Juice .............. 3.2. Percent Recovery of d-limonene by Titration 3.3. Method ..................... 3.2.1. Procedure ................ Determination of Extraction Time on d-limonene Recovery from Packaging Material by Titration Method ..................... 3.3.1. Procedure ................ Page vi viii WON-bk 12 12 18 18 18 18 19 20 20 20 20 CHAPTER 3.4. Effect of d-limonene Absorption on Mechanical Properties of Polymer Films ........... 3.4.1. Orange Juice .............. 3.4.1.1. Antioxidant .......... 3.4.1.2. Antimicrobial Agent ...... 3.4.2. Preparation of Samples and Conditions . . 3.4.3. Procedure for Determining Mechanical Properties (Stress-Strain) ....... 3.5. Influence of d-limonene Absorption on Impact Resistance of Polymer Films ........... 3.6. Influence of d-limonene Absorption on Barrier Properties of Polymer Films ........... 4. RESULT AND DISCUSSION ................. 4.1. Recovery of d-limonene ............. 4.2. D-limonene Extraction from Packaging Materials 4.3. Distribution of d-limonene between Juice and Carton Stock .................. 4.4. Effect of Antioxidant and Antimicrobial Agent on Stability of Orange Juice ............ 4.5. Effect of d-limonene Absorption on Mechanical Properties of Polymer Films ........... 4.6. Modulus of Elasticity .............. 4.7. Tensile Strength ................ 4.8. Elongation Percent at Break ........... 4.9. Seal Strength .................. 4.10. Influence of d-limonene Absorption on Impact Resistance of Polymer Films ........... 4.11. Influence of d-limonene Absorption on Barrier Properties of Polymer Films ........... iv Page 21 21 21 22 23 23 23 26 28 28 28 28 37 37 43 43 47 47 59 59 CHAPTER Page 5. CONCLUSION ...................... 61 APPENDICES 1. STANDARDIZATION OF BROMIDE-BROMATE SOLUTION ...... 63 1.1. Standard Solution of Potassium Bromide-Bromate . 63 1.2. Standard Solution of Arsenious Oxide ...... 63 1.3. Standardization of Standard Solution of Potassium Bromide-Bromate ................. 63 2. ONE-WAY ANALYSIS OF VARIANCE ............. 65 3. DETERMINATION OF DART IMPACT FAILURE WEIGHT ...... 72 BIBLIOGRAPHY ........................ 75 Table 10 11 12 13 LIST OF TABLES Aseptic juice and juice drink market in the U.S. in 1985 ......................... The contribution of volatiles to orange juice flavor Transmission rate of aluminum foil (0.00035") and poly- ethylene laminate ................... Permeability of polymers used in aseptic packaging Sealing conditions used to prepare strips for seal strength ....................... Test conditions for determining the mechanical proper- ties (stress-strain) of test films .......... Percent recovery Of d-limonene by bromate titration method using a standard d-limonene solution ...... Effect of extraction time on percent recovery of d-limonene from carton material ............ Percent recovery of d-limonene from package by titra- tion method ...................... Distribution of d-limonene between juice and package material in the aseptically packed orange juice during storage at 24°C, 49 percent RH ............ Distribution of d-limonene between juice and package material in the aseptically packed orange juice during storage at 35°C, 29 percent RH ............ Effect of antioxidant and antimicrobial agent on stability of orange juice ............... Distribution of d-limonene between orange juice and films during storage at 24°C, 49 percent RH ...... vi Page 15 16 24 25 29 3O 31 33 34 38 41 Table Page 14 Change in modulus of elasticity (1 x 103 psi) of films immersed in orange juice during storage at 24°C, 49 percent RH ..................... 44 15 97 percent significant confidence intervals for modulus of elasticity of test films .............. 44 16 Change in tensile strength (1 x 103 psi) of films immersed in orange juice during storage at 24°C, 49 percent RH ..................... 48 17 97 percent significant confidence intervals for tensile strength of test films ................ 49 18 Change in percent elongation at break of films immersed in orange juice during storage at 24°C, 49 percent RH . 51 19 97 percent Significant confidence intervals for percent elongation at break of LDPE films ........... 52 20 Change in seal strength (lb/linear inch of seal) of polymer films immersed in orange juice during storage at 24°C, 49 percent RH ................ 54 21 97 percent significant confidence intervals for seal strength of polymer films immersed in orange juice . . 55 22 Effect of d-limonene absorption on impact resistance of polymer films ..................... 58 23 Effect of d-limonene absorption on oxygen permeability of polymer films ................... 6O 24 ANOVA table for comparing k treatment ......... 66 25 ANOVA table for modulus of elasticity ......... 68 26 ANOVA table for tensile strength ........... 69 27 ANOVA table for elongation percent at break ...... 7O 28 ANOVA table for seal strength ............. 71 29 Impact failure weight of LDPE ............. 73 30 Impact failure weight of Surlyn (zinc type) ...... 74 vii Figure 1 2 3 10 11 LIST OF FIGURES D-limonene ...................... Decomposition of limonene hydroperoxide to carvone Decomposition of limonene hydroperoxide to limonene-1, 2-epoxide ....................... D-limonene in juice in glass bottles and carton material stored at 24°C, 49 percent RH ........ D-limonene in juice in glass bottles and carton packs and in carton material stored at 35°C, 29 percent RH Polymer film ..................... Change in d-limonene absorption in films at 24°C, 49 percent RH storage ................. Relationship between d-limonene content and modulus of elasticity for the test films ............. Relationship between d-limonene content and tensile strength for the test films .............. Relationship between d-limonene content and percent elongation at break for the test films ........ Relationship between d-limonene content and seal strength for the test films .............. viii Page 10 11 11 35 36 4O 42 45 50 53 56 CHAPTER 1 INTRODUCTION Aseptic packaging is not a new conception; it has existed for a half century or longer. In actual practice, sterilization of liquid product and package independently of each other in order to avoid thermal damage to sensitive foods has been executed since the 19405. Aseptic packaging of liquid foods was commercial in Western Europe throughout the 19605 and 19705. In the United States (since FDA approval of hydrogen peroxide in 1981, as an approved sterilant for polyethylene contact materials), aseptic packaging has been rapidly accepted by the American fruit juice and drink industry. Because the initial American successes were in high acid foods and especially fruit juice and fruit juice drinks, more technical and commercial development since 1981 has been directed toward these products. According to Marcy in 1981, nearly 85 percent Of all aseptically packaged food in the U.S. were fruit juices or beverages. The appeal of these systems for the food processor was initially based on cost. According to a study comparing the costs of aseptic to conventional fruit juice packaging (Du Pont CO., Ltd., 1983), total system costs for packaging juice products in one-liter aseptic cartons can be 50 percent less than packaging in steel or glass. However, consumers buy because the package is more convenient. Smith (1983) found that 90 percent of all repeat buyers of Ocean Spray Inc. aseptically packaged juices purchased the product at least three times, and that 83 percent of all buyers under the age of twenty-five were repeat purchasers. Aseptic packaging is beginning to have a major impact in the United States because of shelf stability, the elimination of refrigeration, decreased energy costs, convenience, and improved disposability. Aseptic processing of fruit juices has been reported to produce a product of superior flavor and shelf stability when compared to traditional canning. Shelf stability is dependent upon the product and related critical factors, packaging being one. Most aseptically filled juices are packaged into laminated carton packs, such as the Brik Pak or Combibloc, in which the usual sealant layer is poly- ethylene. Some authors have reported that the shelf life of citrus juices in carton packs is shorter than in glass bottles. Several workers have pointed out that d-limonene, a major flavor component in citrus juices, is readily absorbed into polyethylene and thus reduces the sensory quality of citrus juices. Characterization of the compatibility of polymer sealant films with aroma compounds, therefore, would make it possible to select the more suitable packaging material for the flavor sensitive product. The objectives of this study were to investigate: (1) the absorption of d-limonene by carton packs containing aseptically packaged orange juice during storage at 24°C and 35°C; and (2) the influence of d-limonene absorption on mechanical and barrier properties of polyethylene and ionomer films as a function of d-limonene concentration. CHAPTER 2 LITERATURE REVIEW 2.1. Aseptic Packagjng in the United States Roughly fifty U.S. companies have introduced juices and juice drinks in aseptic packages (Sacharow, 1986). Most aseptically filled juices are packed into laminated carton packs such as the Brik Pak or Bloc Pak (Combibloc). Danielsson (1986) reported that Tetra Pak worldwide produced 35 billion packages using 580,000 metric tons of paperboard, 150,000 metric tons of polyethylene, and 30,000 metric tons of aluminum foil in 1985. This amounts to approximately 97 million packages per day. In 1985 1.2 billion packages were sold in the U.S., compared to 31 million in 1981, however, this only touches the surface (about 5 percent) of the total U.S. juice market (Danielsson, 1986). Sacharow (1986) reported that sales of aseptic juice and juice drink now exceed $250 million at retail and are estimated to be $450 million by the year 2,000. The aseptic juice and juice drink market in the U.S. is shown in Table 1. Although such juices and drinks have averaged a 20 percent annual sales gain since 1981, growth is expected to slow in 1986 and average about 6 percent. Con- sumption is still projected to increase to 3.9 billion gallons by the year 2,000. Several juice companies are developing and test Table 1. Aseptic juice and juice drink market in the U.S. in 1985. Company Market Share Coca Cola Foods' Hi-C 22% Shasta's Capri Sun 17%* Delmonte's Hawaiian Punch 11% Ocean Spray 10% Coca Cola's Minute Maid 8% (orange) Other brands 32% *Hot-fill, stand-up pouch (Sacharow, 1986) marketing large size aseptic packages (64-02. to 1-gal. sizes). Most will be designed with a plastic spigot on one side for easy dispensing. According to Rice (1986), the future growth of aseptically packaged products is likely to be less dramatic than that encountered during the initial boom period of 1981-1985. Presently, many food processors are seeking not only new juice drinks but are also inves- tigating the great potential for growth in other markets such as wines, milk products, puddings, gravies, sauces, and soups. 2.2. Shelf Life Potter (1985) studied the stability of citrus flavors in aseptic packages. Aseptically packed orange juices were acceptable for up to 8 months of storage at room temperature. Several workers have reported that shelf life of juices in the brick-style cartons was shorter than in glass packages and was usu- ally not more than 3-4 months at ambient temperatures (Gherardi, 1982; Mannheim and Havkin, 1981). Most aseptically packed juices are packaged into laminated carton packages such as the Brik Pak or Combibloc, in which the food contact material is polyethylene. Durr et al. (1981) investigated the influence of the behaviour of d-limonene and other aroma components on the sensory quality of orange juice during filling and storage. Significant losses of d-limonene, neral, geranial, ortanal, and decanal from orange juice in carton packages were found. However, they concluded that the main quality parameter for shelf life was storage temperature. 0n the other hand, Marshall et al. (1985) reported that d-limonene was absorbed by the packaging material which reduced the organoleptic quality of citrus juices. Mannheim et al. (1985) also reported that the d-limonene content of orange juice in carton packs was reduced by about 25 percent within the first 14 days Of storage at 25°C due to absorption by the polyethylene liner. Sensory evaluation showed a significant difference between juices packed in glass and carton packs stored at ambient temperature after 10 to 12 weeks. Wartenberg (1982) compared the quality of orange juice in different packages, i.e. glass bottles (hot filled) and aseptically filled juices in carton board laminated packages (Polyethylene/Kraft paper/Poly- ethylene/Foil/Surlyn/Polyethylene) with and without headspace during 6 months storage. For the first 5 months storage, juice in glass bottles and carton packages filled without headspace did not Show any difference in the decomposition of ascorbic acid. The loss of ascorbic acid was higher in the carton packages with headspace. During the first 5 months of storage the sensory changes were greater in the glass bottle than in either carton package. There was no difference between the carton package with headspace and that without headspace. As to the color of the juices, no difference could be Observed between the three types of packages. He concluded that It didn't make much sense to try to determine the mini- mum shelf life of orange juice on the basis of the influence of the package only, without including param- eters, such as raw materials and production of the juice and changes in temperature during storage, which are more important for the shelf life and independent of the packages. Granzer (1982) also reported on the quality or orange juice in two carton packages designed to have high barrier against oxygen intrusion. The material composition of the packages was the same as used in Hartenberg's (1982) study. Deterioration of color and loss of ascorbic acid occurred during the first year of storage. These changes were said to be due to the influence of oxygen. This was much more obvious for the orange juice packed in the polyethylene, paper board, aluminum foil packaged filled without headspace than for juice packed in glass bottles. Granzer (1982) estimated that the shelf life of orange juice should be 6.5-9 months in glass bottles and 3-5 months in the aseptic carton package. 2.3. Flavors and Extraction Procedures The oil fraction of Citrus juices has a major impact on aroma and flavor. Much research has been reported pertaining to flavor components in orange juice (Show, 1979; Ahmed et al., 1978; Scheier, 1981; Moshonas and Show, 1984). The contribution of volatiles to orange juice flavor has been summarized by Durr (1981) and is shown in Table 2. Essence Oil and peel oil are usually added to orange juice to provide some flavor. For peel oil there is an upper limit (0.035 per- cent) for frozen concentrated orange juice as established by the USDA (Marshall, 1985); this is much too high from a flavor stand- point. The juice has an undesirable bitter taste at this level. The optimum level of peel oil is considered to be 0.015 percent. Cold pressed peel oil and essence Oil have d-limonene concentrations * Table 2. The contribution of volatiles to orange juice flavor. Contribution to Typical Flavor Contribution to Off-Flavor Important Desirable Precursors Detrimental ethylbutyrate linalool linalool a-terpineol neral limonene limonene carvone geranial a-pinene valencene trans-carveol valencene nootkatone acetaldehyde hexanal octanal trans-2-hexenal nonanal hexanol a-sinensal 4-vinylguaiacol B-sinensal 2,5-dimethyl-4- hydroxy-3-(2H) furanone * Durr, 1981. 10 greater than 90 percent. De-Limonene (Figure 1) content can be determined using the bromate method of Scott et al. (1966). CH 1783C b.p. HC CH Figure I. D-limonene In this procedure, oil is distilled from a small sample of juice mixed with a completely miscible, volatile solvent to insure solubility and dispersion of oil in the flask and to facilitate its rapid volatilization and carryover. The distillate is acidified and titrated with standard bromate solution. In acid solution, the bromate releases bromine which reacts quantitatively with d-limonene through saturation of the double bonds. The end point is established when bromine (in excess) destroys the color Of methyl orange. D-limonene is highly susceptible to oxidative and photo- oxidative degradation. The hydroperoxides from oxidation of d-limonene can decompose very rapidly to yield stable products as Shown in Figure 2 (Farmer and Alvapillai, 1942). Limonene-l, 2-epoxide formation also takes place easily since the hydroperoxides 11 can oxidize the endocylic double bond in limonene as shown in Fig- ure 3 (Anandaraman, 1986). OOH 0 //// + H 0 Limonene Carvone hydroperoxide Figure 2. Decomposition of limonene hydroperoxide to carvone. Q” S? 2“ Limonene Limonene Limone h.Ydr‘operoxide ne Carveol -l. 2-epoxide Figure 3. Decomposition of limonene hydroperoxide to limonene-1, 2-epoxide. Other terpenes in citrus Oils include o, 6 pinene and 8-myrcene. All of these compounds have little flavor impact, but they provide a solvent for the more potent flavorings (Marshall, 1985). 12 2.4. Package Interaction Most of the potent flavorings in citrus juices are highly lipophilic and can potentially interact with the hydrophobic polymers used in aseptic carton packages. The absorption of d-limonene and specific flavorings into the polyethylene lining of the carton board package (Tetra Brik 1,000 ml) was reported by Durr et al. (1981). They reported significant losses of d-limonene, neral, geranial, octanal, and decanal. Shimoda et al. (1984) investigated the absorption of orange juice aroma constituents by two kinds of plastic pouches: Polyethylene etrephthalate (PET)/ aluminum foil (AL)/High density polyethylene (HOPE) and PET/AL/ Polypropylene (CPP). The ratio of amount Of volatiles absorbed (film/juice) was dependent on the kind of compounds and polymer. After 7 days of storage in the pouches, distribution ratios of the volatiles in the PET/AL/HDPE pouch were 1.2-1.7 for terpene hydrocarbons, 0.65 for terpene aldehydes, and 0.19-0.24 for terpene alcohols. While the recoveries of terpene hydrocarbons from the juice in the PET/AL/HDPE pouches decreased continuously for 14 days, recovery from the juice in PET/AL/CPP pouches decreased for 7 days and then began to stabi- lize. Shimoda investigated the effect of pulp content on the dis- tribution of d-limonene between juice and films using orange juices which had pulp content between 0 and 4.4 percent and storing 7 days at 40°C. When the juice with 0 percent pulp was packaged in the PET/AL/HDPE pouch, the recovery of d-limonene from the HDPE was 13 about 95 percent. Recovery decreased linearly as the amount of pulp content increased. The pulp in the juice suppressed the absorption of flavor by the plastic films for the other terpene hydrocarbons as well. He suggested that the film and the pulp compete with each other for the terpene hydrocarbons. Marshall (1985) investigated the absorption of d-limonene by various polymers. He indicated that loss of d-limonene into sealant layers between the juice and Polyvinylidene chloride (PVDC) barriers of various permeabilities (P = 0, 1, 4, and 8 cc oxygen @STP/m2 atm day) was directly related to the thickness of the polyethylene or polypropylene sealant layer rather than the oxygen permeability of the film. Mohney et al. (1986) investigated the solubility and permea- bility of limonene vapor in two cereal package liners. They concluded that it is necessary for the estimation of the storage quality of a packaged fruit-flavored cereal product where quality is related to the retention of volatile aroma constituents within the package headspace. The previous researchers have demonstrated flavor absorp- tion by packaging materials; however, little is known about the influence of aroma compound absorption on the mechanical properties of packaging materials. 2.5. Oxygen Barrier TO provide a barrier to oxygen is one of the critical require- ments of an aseptic package. One mechanism by which oxygen enters the package is transmission or permeation through the package wall. 14 In Table 3 are shown the permeation rates of aluminum foil and alumi- num foil laminated to polyethylene. It should be noted that sub- stantial improvement hi gas barrier properties occurred when poly- ethylene was laminated to the aluminum foil, which is typical of an aseptic package construction. Permeability data for the main polymers used in aseptic packag- ing are shown in Table 4 (Marcy, 1986). Polymers such as polystryrene, polyethylene, and polypropylene do not have good oxygen barrier properties, so they must be used in combination with polymers such as polyvinylidene chloride (PVDC) or ethylene vinylalcohol copolymer (EVOH) to provide both the oxygen and moisture barriers needed for shelf stable foods. The instrument most commonly used to measure oxygen trans- mission is the MoCon (Minneapolis, MN) Oxtran System. For 250 ml carton packages, Mechure (1984) reported that the brick aseptic package using foil as the oxygen barrier had a rate of 0.035 cc 02/ package/24 hr. Bourque (1985) reported that the oxygen permeability Of the brick-type packaging material (flat area) was (30 to 40 cc/m2/24 hr.). However, once the material was scored or in other ways flexed, the oxygen transmission increased remarkably. Transmission over the scored area increased from 30-40 cc to over 1,500 cc/m2/24 hr.; close to a 50 fold increase. Thus the shelf life of an oxygen sen- sitive product would be significantly affected by the oxygen trans- missibility of the packaging material. 15 Table 3. Transmission rate of aluminum foil (0.00035") and poly- ethylene laminate.* Foil Foil with LDPE (1 mil) Oxygen Oxygen Pinhole Transmission Transmission Count WVTR Rate WVTR Rate 64 -- 1800 0.0006 0.004 30 0.0004 350 -— 0.004 17 0.0005 550 0.0001 0.004 *Shields, 1984. WVTR = g/lOO sq. in/24 hr. 100°F. 90 percent RH Oxygen transmission rate = cc/lOO sq. in/24 hr. STP 16 Table 4. Permeability of polymers used in aseptic packaging. 02(1) coz(1) 0<2) High density polyethylene 180 580 0.3 Polystyrene 390 1100 6 Low density polyethylene 390 200 1.3 Polypropylene 230 610 0.5 Polyester G 25 133 4 Polyester 10 30 6 Poly vinyl chloride 8 16 1.3 Pan (Barex) 0.8 1.1 5 PVDC (Saran) 0.1 0.3 0.1 Ethylene vinyl alcohol F 0.03 0.08 4 *Marcy, 1986. (1) ASTM 2 cc'mi‘ 100 in /24 h/atm (23°C) (2) ASTM 2 g'mi‘ 100 in /24 h (38°C 90% RH) 17 Further, because orange juice contains lipophilic flavor com- ponents, absorption of these could affect barrier properties of polymers. However, no information in the literature exists on this subject. CHAPTER 3 MATERIALS AND METHODS 3.1. Introduction A major part of the research effort was to determine the absorption of d-limonene from aseptically packed juices by packaging material contacting with the juices. 3.1.1. Materials Used in the Study The materials used in this study included: (a) Orange juice packed in aseptic carton packages. Aseptically packed orange juice in laminated carton packages (polyethylene/ kraft paper/aluminum foil/polyethylene), Brik-style obtained from Squirt Pak Company, Holland, MI. The package contained 8.45 fl oz (250 ml) of juice. (b) A control was maintained by immediately transferring juice from the cartons to brown glass bottles at the plant site. 3.1.2. Quantitative Determination of d-limonene D-limonene concentration was determined by the bromide-bromate titration (Scott and Veldhuis, 1966) method. The reagents are: (a) Standard solution of Potassium Bromide-Bromate (AOAC, 42.018- 42.019, 1965) 18 19 The solution is made by dissolving ca 2.8 g KBrO3 and 12 g KBr (Sigma Chemical CO.) in boiled water and diluting to 1 l with boiled water for 0.099 Normality solution (see Appen- dix 1). TO use, the solution is diluted 1 + 3 with distilled water to give 0.0247 N solution. One ml of 0.0247 N bromate supplies bromine to react with 0.00084 9 of d-limonene (Scott and Veldhuis, 1966). (b) Iso—prOpanOl (Mallinckrodt Inc.) (c) Hydrochloric acid (Mallinckrodt Inc.) Dilute concentrated acid (1 part acid + 2 parts water). (d) Methyl orange indicator (Fisher Sci. Co.) 0.1 percent in water. 3.1.3. Procedure for Determining d-limonene in Orange Juice Measure 25 ml juice (graduate cylinder) into the distillation flask containing several glass beads, and add 25 ml iso-propanol. Distill contents into 150 ml beaker. Completion of distillation (about 3-4 min.) will become apparent by (a) the syrupy consistency of the juice because of concentration effect; (b) condensation of water in the connecting tube; and (c) collection of 30 ml or more distillate. Transfer the contents of the distillation flask into a beaker; add 10 ml dilute HCL and 1 drop of indicator. Titrate with dilute bromate solution while stirring. The major portion of titrant may be added rapidly, but the end point must be approached at about 1 drop/sec. The blank was determined using distilled water instead 20 of orange juice (triplicates). Disappearance Of color indicates the end point. The amount of d-limonene in the juice is obtained from Equation (1). (ml titrant - ml. blank) x 0.00084 9 = d-limonene content (9/25 ml) (1) 3.2. Percent Recovery Of d-limonene by Titration Method 3.2.1. Procedure D-limonene was accurately weighed into a distillation flask (d-limonene, 1 ml = 0.8389 g) and dissolved with 25 ml isopropanol. 25 ml of water was then added. The contents were then distilled using the same procedure as described for orange juice. To deter- mine percent recovery, Equation (2) was used: (ml titrant - ml blank) x 0.00084 x g9?” = percent d-limonene (W/V) (2) (Scott, 1966) 3.3. Determination of Extraction Time on d-limonene Recovery from Packaging Material by Titration mm 3.3.1. Procedure The whole carton (1 x 0.5 cm pieces) is cut up after the juice is removed and rinsed with distilled water. The carton pieces are then placed into a distillation flask. 70 ml isopropanol is added so that the sample is completely immersed. The sample/isopropanol mixture is allowed to sit for approximately 24 hrs. 70 ml of water 21 is then added and the sample is distilled as before. To determine d-limonene concentration, Equation (3) was used: (ml titrant - ml blank) x 0.00084 = d-limonene g/package (1) 3.4. Effect of d-limonene Absorption on Mechanical Properties of Polymer Films 3.4.1. Orange Juice The orange juice used in this study was 100 percent pure orange juice (from concentrate) Obtained from Orchard Grove Company, East Lansing, MI. Antioxidant and antibacterial agents were added to the juice in order to prevent oxidative and microbial Changes during storage of the juice. 3.4.1.1. Antioxidant (a) SUSTANE W (UOP Inc.) Ingredients (wt percent) 1) mono-tertiary-butyl-r-hydroxy anisole (BHA) (10) 2) 2, 6-di-tert-butyl-para-cresol (BHT) (10) ( ( (3) n-propyl-3, 4, 5-trihydroxy benzoate (PG) (6) ( citric acid (6) ( I 5) propylene glycol (8) ) edible oil (28) ) mono and diglycerides of fatty acids (32) 22 (b) SUSTANE 20 A (UOP Inc.) Ingredients (wt percent) (1) tertiary-butyl hydroquinone (TBHQ) (20) (2) citric acid (3) (3) propylene glycol (15) (4) edible oil (30) (5) mono and diglycerides of fatty acids (20) 0.02 percent (w/w) (a) + (b) was added to the juice at the beginning of storage. 3.4.1.2. Antimicrobial Agent (c) Sodium azide (Sigma Chemical Co.) 0.02 percent (w/w) (c) was added to the juice at the beginning of storage. The effect of antioxidant and antimicrobial agent on the quality of orange juice were investigated using the following indicators: (a) pH (ORION Research CO. analog pH meter model 301) (b) Color of the juice (the Hunter Lab Model 0 25 Color Difference Meter) (c) Total counts Total count was determined by aseptically removing a 1 ml sample of the juice from the glass bottle using a pipet and trans- ferring to a petri dish, which was then filled with molten plate count agar (BBL) and gently swirled to mix before hardening. Numbers of colonies after 48 hours of incubation at 35°C were then counted. 23 3.4.2. Preparation of Samples and Conditions Low density polyethylene film (5.1 x 10'2 mm thickness) was obtained from Dow Chemical Co., while Surlyn S-1601 (sodium type; 2 2 mm thick- 5.1 x 10' mm thickness) and S-1652 (zinc type; 7.6 x 10' ness) were obtained from Du Pont Co. The samples were cut to 2.54 cm x 12.7 cm and immersed into juice (7 samples per bottle) which had been filled into amber glass bottles (250 ml) and closed with a screw cap. The ratio of films area in a 250 ml volume of juice (area/volume) was 0.9. Strips of films from polymer were also heat sealed together and immersed into the juice (7 samples per bottle). The samples were sealed using an impulse heat sealer. The conditions are shown in Table 5. 3.4.3. Procedure for Determining Mechanical Properties (Stress-Strain) The stress-strain properties of the samples were determined as a function of absorbant concentration using a Universal Testing Instrument (Instron Corporation, Canton, MA). The procedure used was adopted from ASTM Standards 0 882-83 (1984). Ten specimens were tested to obtain each sample point. Test conditions are shown in Table 6. ' 3.5. Influence of d-limonene Absorption on Impact Resistance of Polymer Films Sample specimens of low density polyethylene (2 mil thickness) and ionomer (zinc type) (3 mil) were immersed into orange juice until equilibrium (d-limonene) was established. The impact resistance of 24 Table 5. Sealing conditions used to prepare strips for seal strength. Material Impulse Time Jaw Pressure Cooling Time (seconds) (psi) (seconds) LDPE 0.6 30 2 Surlyn 0.5 30 2 (3322;) 25 Table 6. Test conditions for determining the mechanical properties (stress-strain) of test films. Cross Head Chart Grip Speed Speed Full Separation Material (in/min) (in/min) Scale (in) LDPE MD 20 20 IO 2 (2 mil) CD 20 20 10 2 (5.1x10"2 mm) Seal strength 20 20 5 2 Surlyn S-160l MD 20 20 10 2 (2 mil) CD 20 20 10 2 (5.1x 10'2 mm) Seal strength 20 20 5 ' 2 Surlyn S-1652 MD 20 20 20 2 (3 mil) CD 20 20 20 2 (7.6x 10"2 mm) Seal strength 20 20 10 2 26 the control (nonimmersed) and the sample films (immersed for 18 days) were measured using the free-fall dart method (ASTM standard 0 1709-85, 1986). Test method A was used with a drop height of 0.66 m for LDPE, and 1.52 m for ionomer. Determination of the impact resistance was made by using the staircase testing technique and cal- culated by using the following equation (0 1709-85). W = No + [AN(A/N - 1/2)] where WF: impact failure weight AW: missile weight increment = 15 N: the total number of failures = 10 A: add the (i) x (ni) WO: missile weight to which an (i) value Of zero is assigned. Where i: integers 0, 1, 2, etc. ni: number Of failures in each missile weight 3.6. Influence of d-limonene Absorption on Barrier Properties of Polymer Films Sample specimens of low density polyethylene and ionomer were immersed into orange juice until equilibrium (d-limonene) was estab- lished. The oxygen permeability of the control (non-immersed) and the sample films immersed (after 35 days) were measured using the Oxtran 100 Oxygen Permeability Tester (Modern Controls Instrument, Rochester, MN). This instrument measures oxygen transmission by an isostatic method. The sensing device (coulometric) detects the amount of oxygen passing from the oxygen Chamber through the film 27 and into the nitrogen Chamber. The oxygen is swept via a carrier gas to the detector. Gas flow rate (both N2 and 02) were maintained at 35 ml/min. Permeability measurements were performed at 100 per- cent RH at 23°C. The oxygen permeability of the films was calculated by multiplying the calibration factor (determined from the standard PET 1 mil) by the mV response observed on the chart recorder. 69.125 cc/mz-day 02 permeability = mV response x 4.13 mV x 20.25 where 69.125: flux of standard PET (1 mil) 4.13: mV of standard PET 20.25: area ratio (4.5)2/(1)2 . . — _ Flux x 1 . 2 Permeablllty constant (P) - -—_ZP—_— (cc-mll/m oday-atm) where 1: film thickness (mil AP: 1 atm CHAPTER 4 RESULT AND DISCUSSION 4.1. Recovery of d-limonene The recovery of d-limonene was determined according to pre- viously described procedures. Using a standard d-limonene solution (Sigma Chemical Co. Ltd.), percent recovery of d-limonene was determined. As shown in Table 7, recovery of d-limonene was 100 i 2 percent. 4.2. D-limonene Extraction from Packaging Materials The time necessary to extract all the d-limonene from the packaging material was determined. The results, shown in Table 8, indicate that an extraction time of 24 hours at 24°C was satisfactory and that one distillation was adequate for recovering d-limonene from the packaging material. The results, Shown in Table 9, suggest that the titration method, with greater than 98 percent recovery of d-limonene from the package, can be used to adequately determine the concentration of d-limonene absorbed by the package. 4.3. Distribution of d-limonene between Juice and Carton Stock Distribution of d-limonene between juice and carton stock in aseptically packed orange juice stored at 24°C, 49 percent RH and 28 29 Table 7. Percent recovery of d-limonene by bromate titration method using a standard d-limonene solution. Concentration Concentration of d-limonene Titrant Recovery Standard ppm (w/v) (ml) ppm (w/v) % Recovery 672 20.60 685 101.9 672 20.35 675 100.5 856 25.70 855 99.9 452 13.60 450 99.6 440 13.05 431 98.0 30 Table 8. Effect of extraction time on percent recovery of d-limonene from carton material. Extraction lst 2nd 3rd % Recovery Time (hr) Distribution Distribution Distribution (A/A + B) x 100 A B C 14.63 1.02 -- 93.5 12.61 0.73 -- 94.5 24 11.65 0.60 -- 95.1 12.07 0.64 -- 95.0 12.32 0.73 -- 94.4 Average 94.5 14.80 1.06 -- 93.3 13.37 0.81 -- 94.3 48 14.04 0.48 -- 96.7 13.08 0.72 -- 94.8 12.19 0.64 -- 95.0 Average 94.8 13.12 0.60 -- 95.6 13.08 0.60 -- 95.6 72 11.19 0.56 -- 95.2 13.67 0.81 —- 94.4 12.40 0.81 -- 93.9 Average 94.9 31 .c.m m mmmcm>m .3, “eats?“ .5 H ep_; madame gape: Amv aeeeeew_-e "emooo.o xea_m ”mm~.o amooo.o x Ammm.o - peeep_p .eve ««m¢.o A mm.mm m.mm «Heo.o mm.mv ofieo.o mmmfi.o Hw¢H.o «.mm Namo.o oo.H¢ memo.o omo~.o ammH.o m.oo~ mumo.o mm.m¢ o~mo.o mfimfi.o mmmH.o N.ooH o~¢o.o oH.me movo.o mNNH.o ommH.o ~.ooH woeo.o om.wu Noeo.o Namfl.o mmq~.o OOH x AQV\AQV on ADV Amv Aoumm & rAmv uczos< AFEV Amv . Aoome acmocma .m m_nm» 32 35°C, 29 percent RH was determined. The results of this study are presented in Tables 10 and 11. The carton contained 2.5 (mg/package) of d-limonene at 0 day. The carton material had already absorbed d-limonene when the experiment was started because filled production samples were Obtained 1 day after production. The results are also presented graphically in Figures 4 and 5, where the amount of d-limonene is plotted as a function of storage time. A rapid loss of d-limonene in the juice, from 25 mg to 19.9 mg at 24°C and 17.8 mg at 35°C was observed within 3 days storage, apparently due to absorption by the polyethylene contacting surface. After 3 days loss of d-limonene in the juice proceeded at a slower rate. These results were similar to those found by Durr et al. (1981) and Marshall et al. (1985). Rapid absorption of d-limonene into the polyethylene occurred during the beginning of storage and then slowed down. After 12 days of storage, absorption reached equilibrium. At equilibrium, the amount at 24°C and 35°C was about 12 mg/package (48 percent of the initial content) and 11 mg/package (46 percent), respectively (Tables 10 and 11). The distribution ratio (package/juice) of d-limonene after equilibrium was established was 0.83 at 24°C and 0.88 at 35°C, respectively. This suggests that both the absorbing rate and amount of d-limonene absorbed by the polyethylene were inde- pendent of storage temperature and not temperature dependent as was the degradation rate. The distribution of d-limonene in the juice and in the carton material was almost identical (Figures 4 and 5). 33 Table 10. Distribution of d-limonene between juice and package material in the aseptically packed orange juice during storage at 24°C, 49 percent RH. Storage Time (days) Sample 0 3 6 11 18 25 Juice in glass bottle 25.0 24.7 24.7 24.0 23.8 23.7 (mg/250 ml) Juice in carton package 25.0 19.9 18.6 17.2 16.9 14.0 (mg/250 ml) Carton package 2.5 7.5 9.9 10.7 11.6 11.6 (mg/pkg) Average of two determinations. 34 Table 11. Distribution of d-limonene between juice and package material in the aseptically packed orange juice during storage at 35°C, 29 percent RH. Storage Time (days) Sample 0 3 6 11 18 25 Juice in glass bottle 25.0 23.4 23.0 22.6 21.1 20.3 (mg/250 ml) Juice hlcarton package 25.0 17.8 16.9 16.5 14.0 12.1 (mg/250 ml) Carton package 2.5 7.6 8.6 9.2 10.1 10.5 (mg/pkg) Average of two determinations. d-limonene (mg) 35 '- C 20 \- 10—- ‘ C) Juice in glass bottle . Juice in carton packs ‘ Carton material 0 _ I I I I LL LL I O 4 8 12 16 20 24 28 Storage time (days) Figure 4. D-limonene in juice in glass bottles and carton packs and in carton material stored at 24°C, 49 percent RH. d-limonene (mg) 36 C O 20 P \O C II 1| \ C 10 AT A L ‘_,..————-—“" C) Juice in glass bottle 1| Juice in carton packs ‘ Carton material 0 _ I I I I I I ‘1 O 4 8 12 16 20 24 28 Storage time (days) Figure 5. D-limonene in juice in glass bottles and carton packs and in carton material stored at 35°C, 29 percent RH. 37 This indicates that the loss of d-limonene from the juice in the carton reflects the increase of d-limonene in the carton material. 4.4. Effect of Antioxidant and Antimicrobial Agent on Stability of Orange Juice To prevent oxidative and microbial degradation of orange juice during storage at 24°C, 49 percent RH (a) mixed antioxidants and (b) an antimicrobial agent was added to the juice at 0.02 percent (w/w) concentration, respectively. As shown in Table 12, there was no bacterial growth or significant change in color (used as an indi- cator of oxidation) during 25 days storage. 83 percent of the ini- tial d-limonene was present after 25 days. Addition of the agents prevented oxidative and microbial changes in the juice. Therefore, both were added to the orange juice prior to conducting all studies with sealant films. 4.5. Effect of d-limonene Absorption on Mechanical Pmerties of Polymer Films To understand the influence of d-limonene absorption on mechan- ical properties of polymer films, strips of the packaging material were immersed in orange juice. The influence of absorption on modulus of elasticity, tensile strength, elongation percent, and seal strength was studied. The effect of d-limonene absorption on mechanical properties of each polymer was statistically evaluated by one way analysis of variance (see ANOVA Table 24, Appendix 2). 38 Table 12. Effect of antioxidant and antimicrobial agent on stability of orange juice. Storage Days Component 0 14 25 pH 3 62 3.61 3 55 Color * L 48.7 i 0.2 47.4 i 0.1 46.2 1 0.1 a* -2.6 s 0.2 -3.1 a 0.2 -3.0 s 0.1 6* 22.1 s 0.1 21.1 s 0.1 20.6 s 0.1 ** Colony counts < 50 < 50 < 50 (n/250 ml) Amount of 11.0 10.0 9.1 d-limonene (mg/250 ml) Stored at 24°C, 49 percent RH * Means and standard deviations of five determinations. * * Five determinations Other results are average of two determinations. 39 Three polymers were used in this study which included Low Density Polyethylene, Surlyn (S-1601), and Surlyn (S-1652) (see Figure 6). The ionomers (S-1601 and S-1652) differ from polyethylene in that they contain low levels of covalently bound carboxy groups and ionically bound metal ions. Surlyn (S-1601) is a sodium type and Surlyn (S-1652) is a zinc type. The absorption of d-limonene in orange juice by the films during storage at 24°C, 49 percent RH is shown in Table 13. The absorption of d-limonene into each polymer film as a function of storage time is also presented in Figure 7. Within 3 days storage, all the polymer's films had rapidly absorbed d-limonene. After 3 days, the rate of absorption in LDPE and Surlyn (sodium type) slowed while that of Surlyn (zinc type) reached saturation. To reach satura— tion Surlyn (zinc type) and LDPE were immersed in the juice 12 days and 18 days, respectively; the amounts of d-limonene absorbed at equilibrium were 6.4 mg/IOO cmz, by Surlyn (sodium type), 5.3 mg/lOO cm2 by LDPE, and 3.3 mg/IOO cm2 by Surlyn (zinc type). Thus the metal ion in Surlyn affected the absorption characteristics of the film, the reason probably being that under acid conditions the sodium ion is lost from the film structure into the juice in a substitution type reaction (Du Pont Co., 1986). The results showed that the carboxy and zinc groups in the Surlyn films alter the lipophilic Character of the polymer, but did not exclude flavor absorption. 40 - + [CH2 - CH2]n [(CH2 - CH2)X(CHZCCH3COO M )an LDPE Ionomer (Low density polyethylene) (Ethylene methacrylic acid copolymer - partial metal salt) Figure 6. Polymer film. 41 Table 13. Distribution of d-limonene between orange juice and films during storage at 24°C, 49 percent RH. Content of d-limonene (mg) Storage Time (days) Juice LDPE Juice S-1601 Juice S-1652 O 46.3 0 46.3 0 35.5 0 3 36.1 6.8 29.3 10.8 26.6 7.0 6 33.9 8.3 26.6 12.0 23.4 7.3 12 28.5 10.2 23.5 14.7 23.2 7.4 18 26.6 11.8 22.5 14.7 22.4 7.5 27 26.5 11.9 22.3 14.5 21.6 7.5 The values are represented as mg/250 ml in juice and mg/225.8 cm2 in films. The results are means of triplicates. S-1601: Surlyn sodium type S-1652: Surlyn zinc type 42 A LDPE Q S-1601 O S-1652 2) d-llmonene (mg/100 cm 0‘ T .\ ’\ r \ R40, 0 O O 2 b 0 I I I I I I I I I 0 6 12 18 24 Storage time (days) Figure 7. Change in d-limonene absorption in films at 24°C, 49 per- cent RH storage. 43 4.6. Modulus of Elasticity Modulus of elasticity can be calculated by drawing a tangent to the initial linear portion of the strain-stress curve and dividing the stress (from any point on that line) by the corresponding strain. The value of modulus of elasticity of the films as a function of storage time was measured (Table 14). The relationship between the relative percent of modulus of elasticity for the films and amount of d-limonene absorbed is shown in Figure 8. The results of statistical analysis (ANOVA Table 24, Appendix 2 and Table 15) showed that d-limonene absorption significantly affected modulus of elasticity in LDPE and Surlyn (sodium type (a = 1 percent). After 3 days storage both materials had significantly lower (a==3 per- cent) values in comparison with initial values (Table 14). Further, decreases were noted with increasing absorption of d-limonene in LDPE and Surlyn (sodium type). Retention of modulus of elasticity by LDPE was larger than that by Surlyn (sodium type). The absorption of d-limonene decreased the stiffness of these two films. For the Surlyn film (zinc type), modulus of elasticity in both (MD) and (CD) was not affected significantly by absorption of d-limonene (Fratio = 0.92: not significant among the means during storage; see ANOVA Table 24, Appendix 2). 4.7. Tensile Strength Tensile strength can be calculated by dividing the maximum load by the original cross-sectional area of the specimen. 44 Aoofi x o<\xmuw—mg ”mwmmgpcmcms :owuumgwu mmocu "no cowpomc_u mcwgumz ”oz Amgau u:_~v capgzm Aqup Ezwuomv capgam "Nmoflum ”Hoofllm mm_qsmm :mu eo memos mew mu_=mmg asp Am.mmv Am.mav Ao.mmv Am.mmv Am.emv AOOHV Anus mm.o oo.oH ma.o oo.oH N~.o mm.m mm.o oo.oH mm.o mm.m mm.o Ne.ofi Nmefi-m Am.mmv Am.mmv Am.mmv Aoofiv AOOHV AOOHV Aazv NH.o oo.o~ mm.o 05.5 NH.o oo.oH N~.o No.oH NN.o No.oH -.o No.0H Nme~-m Am.eev A~.eev Am.mev A~.oev Ae.eev Aoofiv Aggy Ne.o mm.m em.o N~.e me.o Hw.m an.o oe.m me.o we.m Nfi.o mm.m Hoefi-m Am.mmv Aa.oev Am.eev Am.mev AN.ONV Aoofiv Aozv om.o mo.m om.o NH.m mm.o o~.m ee.o em.m Ne.o mm.m NH.o mm.m Hoefi-m Ae.emv Ae.emv Am.mwv Am.mmv Am.emv Aoofiv Aouv NN.o eH.m HN.o mH.m NN.o Hm.m Hm.o mm.m mm.o Ne.m mm.o mm.oH was; Ae.mwv Ao.omv AH.amv AH.mmv he.eav Acofiv Anzv eH.o me.m eN.o mm.m om.o m~.w N~.o m~.m NN.o mN.m mN.o Hm.m ”and NN< wH< ~H< eq ma ca e_ea .e.m m .e.m m .e.m m .e.m m .e.m m .e.m m AN mH NA 0 m o Amxmuv mark mmweoam .zm ucmocma me .uaem um mmmcoum mcwgzu wows” mmcmmgo cw ummgmsew map?» Co A_ma oH x Hv apwuwpmmpm eo mapsuos cw mmcmsu .¢H o_nmp m 45 § 100 X 0 do 2: _ 4th 3; 80 § I = 2 _ U 60 r- ED 5 (U '33 LDPE (MD) ‘ LDPE (CD) “a 40 e. .e S-1601 (MD) I S-1601 (CD) fg S-1652 (MD) . S-1652 (CD) 4.: 2 20 .. é’ 0 41 II I I J .L 0 1 2 3 4 5 6 Amount of d-limonene absorbed (mg/100 cmz) Figure 8. Relationship between d-limonene content and modulus of elasticity for the test films. 46 Table 15. 97 percent significant confidence intervals for modulus of elasticity of test films. Material LDPE S-1601 Mean Difference (MD) (CD) (MD) (CD) ** ** ** ** A0-A3 0.53:0.36 1.38:0.62 2.48:0.86 2.18:0.86 ** ** ** ** A0-A6 1.06:0.36 1.60:0.62 2.66:0.86 2.79:0.86 ** *9: ** ** A0-A12 1.06:0.36 1.60:0.62 2.82:0.86 2.58:0.86 ** ** *1: ** A0-A18 0.98:0.36 1.66:0.62 3.35:0.86 2.17:0.86 ** ** ** *1: A0-A27 1.02:0.36 1.69:0.62 3.47:0.86 0.81:0.86 * A3-A6 0.53:0.36 * 0.22:0.62 0.12:0.86 0.08:0.86 *9: A3-A12 0.53:0.36 0.16:0.62 0.28:0.86 -0.13:0.86 *9: A3-A18 0.45:0.36 0.28:0.62 0.81:0.86 -0.54:0.86 ** *9: A3-A27 0.49:0.36 0.31:0.62 0.96:0.86 0.10:0.86 A6-A12 0:0.36 -0.06:0.62 0.16:0.86 -0.21:0.86 A6-A18 -0.08:0.36 0.06:0.62 0.69:0.86 -0.62:0.86 A6-A27 -0.04:0.36 0.09:0.62 0.81:0.86 0.02:0.86 A12-A18 -0.08:0.36 0.12:0.62 0.13:0.86 -0.41:0.86 A12-A27 -0.04:0.36 0.15:0.62 0.65:0.86 0.23:0.86 A18-A27 0.04:0.36 0.03:0.62 0.12:0.86 0.64:0.86 A0 = mean value in initial A3 = mean value after 3 days A6 = mean value after 6 days A12 = mean value after 12 days A18 = mean value after 18 days A27 = mean value after 27 days **Significant difference (a = 3 percent) 47 Although the mean values for LDPE (M0) did decrease due to absorption (0 = 1 percent), the degree of influence was less than that for Surlyn (zinc type), as shown in Tables 16 and 17 and Fig- ure 9. There were no significant differences in both (CD) of LDPE (F = 2.0) and Surlyn (zinc type) (F = 0.28) (ANOVA Table 24, ratio Appendix 2). However, the tensile strength of Surlyn (sodium type) ratio decreased 53 percent to 63 percent of the original value which was similar to that found for modulus of elasticity (59 percent to 66 percent). 4.8. Elongation Percent at Break Percentage elongation at break can be calculated by dividing the length of the sample at the moment of rupture by the initial length of the Specimen and multiplying by 100. The results (Tables 18 and 19 and Figure 10) show that elonga- tion percent of LDPE (MD) increased due to absorption (0 = 1 percent). The absorbant probably acted as a plasticizer to allow the chains to slide past one another. Elongation of LDPE (CD) showed a tendency to decrease, though the values were not significant Since they varied substantially (F = 1.2). The absorption of d-limonene did not sig- nificantly affect elongation for either of the Surlyn films (ANOVA Table 24, Appendix 2). 4.9. Seal Strength Change in seal strength due to absorption for each film is shown in Tables 20 and 21 and Figure 11. The seal strength of Surlyn 48 AooH x o<\xwumpmc um_mm;acmcmm Amaxu ucw~v capgam ”Nmofilm co_pomgwu mmocu "mu Amaxu Eswuomv capszm "Hoofilm :owuomg_u mcwcumz ”oz mmpasmm cm“ mo memos men mppammg mgh AH.wmv AN.va Am.emv Am.emv Ao.emv Aoofiv Anus Hm.o NH.m mm.o ¢~.m mm.o m~.m m~.o mH.m N~.o oH.m mH.o mm.m mmofium A~.emv Am.~wv A~.wmv Am.~mv Ae.mmv Aoofiv Agzv om.o mo.m mH.o oH.m NH.o mH.m m~.o wo.m Hm.o NH.m N~.o mm.m Nmofium Am.mev Am.eev Aw.~ev Ae.oev Am.mev Aoofiv Aouv mm.o co.m um.o mm.m om.o No.m mm.o mm.m mH.o vo.m om.o NH.¢ floofirm A~.mmv Am.~mv Am.5mv Aa.flev Ae.emv Aoofiv Aozv am.o NN.N em.o mH.~ mm.o mm.m Hm.o mm.m mm.o mm.m o¢.o NH.¢ Hoofium Am.mmv Ao.mmv Ae.emv Am.umv Am.mmv Aoofiv Aouv mo.o mo.H No.o mm.H oo.o om.H no.o mm.H eo.o No.~ oo.o mo.~ weep Am.emv RH.~mv AH.NmV AN.eav Am.emv Aooflv Aozv mH.o mm.m o~.o em.m NH.o eo.m wo.o mo.m mo.o -.N mo.o mm.m was; mm< mH< ~H< o< m< o< sped .c.m m .u.m m .c.m m .u.m m .u.m m .u.m m RN ma NH 0 m o Amxmuv meek mmmgoum .Im peeeeea me .uoaw pa mmmgoum mcwcau muwaw mmcmco cw comgwsaw ms_w$ eo fiwma oH x Hy guacmgpm m_wmcmp cw mucosa .oH mpnmh m 49 Table 17. 97 percent significant confidence intervals for tensile strength of test films. Materials Mean LDPE S-1601 S-1652 Difference (MD) (MD) (CD) (MD) ** ** ** A0-A3 0.06:0.14 1.82:0.48 1.53:0.42 0.41:0.29 ** ** ** *1: A0-A6 0 1510.14 1.59:0.48 1.65:0.42 0.45:0.29 ** ** ** ** A0-A12 0.14:0.14 1.78:0.48 1.55:0.42 0.40:0.29 ** ** ** ** AO-A18 0.14:0.14 1.99:0.48 1.49:0.42 0.43:0.29 ** ** ** *1: A0-A27 0.20:0.14 1.95:0.48 1.53:0.42 0.47:0.29 A3-A6 0.09:0.14 -0.23:0.48 0.12:0.42 0.04:0.29 A3-A12 0.08:0.14 -0.04:0.48 -0.02:0.42 -0.01:0.29 A3-A18 0.08:0.14 0.17:0.48 -0.04:0.42 0.02:0.29 A3-A27 0.14:0.14 0.13:0.48 0:0.42 0.06:0.29 A6-A12 -0.01:0.14 0.19:0.48 -0.14:O.42 -0.05:0.29 A6-A18 -0.01:0.14 0.40:0.48 -O.16:0.42 -0.02:0.29 A6-A27 0.05:0.14 0.36:0.48 -O.12:0.42 0.02:0.29 A12-A18 010.14 0.21:0.48 -0.06:0.42 0.03:0.29 A12-A27 0.06:0.14 0.17:0.48 -0.02:0.42 0.07:0.29 A18-A27 0.06:0.14 -0.04:0.48 0.04:0.42 0.04:0.29 **Significant difference (a = 3 percent) 50 E; o 100 - ... . —_5._ x 5% A a 8 Q8 8 V 80 .- .C .1.) 2’ O) V’ 60 - D 0 E C13 (.0 C .8 .5 40 _ A LDPE (MD) . LDPE (CD) °\° D S-1601 (MD) I S-1601 (CO) Q) E o S-1652 (MD) 0 S-1652 (CD) .3 20 .. 6'2 0 J J J J L l J 0 1 2 3 4 5 6 7 Amount of d-limonene absorbed (mg/100 cmz) Figure 9. Relationship between d-limonene content and tensile strength for the test films. AooH x o<\x_um_mg conpomg_u mmogu ”no "mnmwzucwcma Amaze u=n~v cxpgsm "mmofilm ”Hoofilm mmegsmm cm» eo memos mew mp_=mmg mg» Amgxu Sancomv cxpgsm conuomgeu onesumz ”oz 51 Ao.n0nv An.noHv An.eonv An.n3nv An.noHv AooHv Annv o.nn nnn m.nn enn e.on nnn o.en onn ~.nn enn n.en nne mnen-n Ae.nnv An.nnv An.nnv Ae.nnv An.nnv Ronny Anzv n.nn nun n.on own H.en nnn e.nn nnn H.nn nnn n.en onn nnnn-n An.nnv An.nnv Ae.nnv an.nnv An.env Anonv Anus n.ne nne n.nn ene n.en nne o.e~ one e.on one e.on nee nonn-n An.nnv An.nnv An.nnv An.nnv An.nnv AooHV Ange n.ne nne e.ne nne e.nn fine e.ne nee H.nn nne H.nn fine Hoen-n An.nnv An.nnv An.nnv An.nnv Ao.nnv AooHv Anew nen one HHS mnn nHH nne onn nen onn nnn n.nn one page An.nnHv Ae.nnHv An.nnnv An.onHv An.nnHv Roenv Anzv n.nn nnn n.nn onn n.en enn n.nn nnn H.nn nen e.on new page nne nne nHe ne ne oe e__a .e.n m .e.n m .e.n m .e.n m .e.n m .e.n m KN nn NH n n o Amxmuv ms_h mmmgoem .zm neeeeea ne .uoen en mmmeopm m:_czc monsw mmcngo cw nomemese ms_ee mo xmmen an :o_wmmcopm acmucma cw mmcccu .me m_nmn 52 Table 19. 97 percent significant confidence intervals for percent elongation at break of LDPE films. Mean Difference LDPE (MD) ** A0 - 43 -79 i 36 ** A0 - A6 -55 i 36 *1: A0 - A12 -47 i 36 *1: A0 - A18 -63 i 36 ** A0 - A27 -58 t 36 A3 - A6 24 i 36 A3 - A12 32 1 36 A3 - A18 16 i 36 A3 - A27 21 i 36 A6 - A12 8 i 36 A6 - A18 -8 i 36 A6 - A27 -3 i 36 A12 - A18 -16 i 36 A12 - A27 -11 s 36 A18 - A27 5 i 36 **Significant difference (a = 3 percent) 120 100 53 ’5 S X 0 U \ 8 S 80 .5 E’ Al O '6 60C q. 0 T A LDPE (MD) A LOPE (C0) 0) .3 40 l- .5 C) S-1601 (MD) I S-1601 (CD) E2 0 S-1652 (MD) 0 S-1652 (CD) 20.. 0 I I 11 0 2 4 6 Amount of d-limonene absorbed (mg/100 cmz) Figure 10. Relationship between d-limonene content and percent elon- gation at break for the test films. 54 AooH x o<\xnam_mg nm_mm;ucmgma connomgeu mcncomz no: Amaau o=n~v =»_L=m "Nmonum noun» Eznuomv :xpgam "Hoonlm .mw_asnm cm» eo came one mupammc one An.nnv An.nnv An.env Ao.env An.nnv AOOHV Anzv en.o nn.e nn.o en.e nn.o nn.e en.o nn.e nn.o en.e nn.o nn.e nnnn-n An.nnv An.nnv Ae.onv Ae.env An.nnv AooHv Aozv nn.o ne.n nn.o nn.n nn.o on.n nn.o en.n nH.o nn.n HH.o nn.n nonn-n AN.NnV An.nnv Ao.nnv An.nnv An.oonv AOOnV Aozv nn.o en.n Hm.o Hn.n nn.o en.n on.o nn.n en.o nn.n Hn.o nn.n mane nne nne mne we ne oe .entenez .e.n m .e.n m .e.n m .e.n m .e.n m .e.n m en nn NH e n o Amxmuv weep mmmcoum .zm ucmugmq me .UOeN um mmmgoum mangau muesn mmcngo an ummemaen ween; cmsneog no Aemmm eo socn Lumen—\n_v sumcmeum Fawn an «mango .om mennn 55 Table 21. 97 percent Significant confidence intervals for seal strength of polymer films immersed in orange juice. Material Mean Difference LDPE (MD) S—1601 (MD) A0 - A3 -0.01 s 0.58 -0 77 s 0.26** A0 - A6 0.49 e 0.58 0.94 e 0.26** A0 - A12 0.46 s 0.58 1.08 s 0.26** A0 - A18 0.51 e 0.58 0.83 s 0.26** A0 - A27 0.68 s 0.58** 0.89 a 0.26** A3 - A6 0.50 s 0.58 0.17 s 0.26 A3 - A12 0.47 e 0.58 0.31 s 0.26** A3 - A18 0.52 a 0.58 0.06 e 0.26 A3 - A27 0.69 e 0.58** 0.12 e 0.26 A6 - A12 0.03 e 0.58 0.14 e 0.26 A6 - A18 0.02 e 0.58 -0.11 a 0.26 A6 - A27 0.19 e 0.58 -0.05 e 0.26 A12 - A18 0.05 s 0.58 -0.25 e 0.26 A12 - A27 0.22 t 0.58 -0.19 s 0.26 A18 - A27 0.17 e 0.58 0.06 s 0.26 **Significant difference (a = 3 percent) 56 100 80 Relative % of seal strength (f/fo x 100) 60 r. 45 LDPE (MD) 40 - I:I S-1601 (M0) 0 S-1652 (MD) 20 _. 0 I l J I l I I 0 1 2 3 4 5 6 7 Amount of d-limonene absorbed (mg/100 cm2) Figure 11. Relationship between d-limonene content and seal strength for the test films. 57 (sodium type) decreased due to absorption. A reduction of 24 percent in the seal strength was found after maximum absorption occurred (a = 1 percent), which was lower than that determined for LDPE. 0n the contrary, significant decrease was not observed with Surlyn (zinc type) regardless of absorption (F = 1.75: ANOVA Table 24, Appendix 2). 4.10. Influence of d-limonene Absorption on Impact Resistance of Polymer Films The data for impact resistance of LDPE and Surlyn (zinc type) are Shown in Appendix 3. The impact failure weight of LDPE and Surlyn (zinc type) (non-immersed) were 69 g and 217.5 g, respectively (see Table 22). After d-limonene was absorbed by the films, the impact resistance of LDPE decreased to 60 g (13 percent reduction). The impact resistance of Surlyn (zinc type) increased to 244.5 g (12.4 percent increase). The failures were different; upon contact with the LDPE film, the dart caused a slit to open; by contrast, it made a circular hole in the Surlyn film. This difference is probably due to the difference in the structure of the polymer chains. The decrease in impact resistance of LDPE after d-limonene absorption was probably due to d-limonene weakening or causing loss of bonds holding the polymer molecules together. The absorption of d-limonene may have resulted in the buildup of environmentally induced stresses in the polymer matrix. On the other hand, the increase in impact resis- tance of Surlyn (zinc type) might be due to increased cross-linking resulting in increased film toughness. 58 Table 22. Effect of d-limonene absorption on impact resistance of polymer films.* Amount of d-limonene Impact Thickness absorbed*** failure weight*** Material (mil) (mg/100 cmz) (g) 0 69 LDPE 2 4.2 60 (13% decrease) 0 217.5 Surlyn 3 3.8 244.5 (12.4% increase) * Impact resistance was measured differently for the films. The results from film to film should not be compared. ** Average of three determinations. * ** See Appendix 3. 59 The absorption of d-limonene by the test polymers generally affected the following mechanical properties, depending on polymer type: (a) Modulus of elasticity (stiffness) (b) Tensile strength (c) Percent elongation (d) Seal strength (e) Impact resistance 4.11. Influence of d-limonene Absorption on Barrier Properties of Polymer Films As shown in Table 23, the oxygen permeability constants for LDPE, Surlyn (sodium type), and Surlyn (zinc type) (non-immersed) were 3.5 x 103, 4.4 x 103 , and 4.6 x 103 (cc-mil/mZ-day-l atm), reSpectively. After d-limonene was absorbed by the films, the material was more permeable. This is probably due to an increase in size of the "holes," "pores, and other voids between polymer strands which allowed more 02 to permeate through. It is known that plasticizers tend to increase the permeability of all gases due to the increased mobility of polymer chains (Karel, 1975). Mohney et al. (1986) and Baner (1986) found that absorption of organic flavor constituents increased permeability of polyolefine films. The absorption of d-limonene into LDPE increased the plas- ticity as is apparent from the results shown. The oxygen permeability of LDPE due to absorption of d-limonene increased 4.4 fold (see Table 23). 6O .pcmpmcoo nuep_nnmsgma ”a .csc mumo_Pa=u we mmmgm>m mew muezmmg use moH x om.n mod x me.m o.m Amaxu oce~llcx_g:mv moH x Hm.e moH x em.H o m Nmmfium eoH x mo.H moH x He.m «.0 Amaxp asnuomllcxegzmv moH x oe.e mod x om.m o m Hoofium eoH x mm.H moH x mn.n m.e mo~ x mm.m moH x on.H o m wasp Aeum.xmu.ms\_ee.oov Aamu.ms\uuv Amsu ooH\mEV Apnsv —mngmamz x: umacoma< mmmcxowgn m _d mcmcoseelu no uczos< .ms_ne cmsxpoq eo xpnenammsgma :mmxxo co coepqgomnm mcmcosepuu mo Homewm .mm meson CHAPTER 6 CONCLUSION Distribution of d-limonene between juice and carton stock in aseptically packed orange juice during storage at 24°C, 49 percent RH and 35°C, 29 percent RH was determined by the titration method. A rapid loss of d-limonene was shown within 3 days storage in the juice. After 3 days storage loss of d-limonene in the juice occurred at a slower rate, apparently due to absorption by the polyethylene contacting surface. The distribution of d-limonene between the juice in the carton and in the carton material was almost identical. All of the polymer test films rapidly absorbed d-limonene within 3 days storage, then the rate of absorption slowed down and reached equilibrium. The influence of d-limonene absorption on mechanical and barrier properties of LDPE, Surlyn (sodium type), and Surlyn (zinc type) films as a function of d-limonene concentration was investigated. The results indicated that the absorption of d-limonene by polymers generally affected the (a) modulus of elasticity, (b) ten- sile strength, (c) percent elongation, (d) seal strength, (e) impact resistance, and (f) oxygen permeability though depending on polymer type. 61 62 Consequently, Surlyn (zinc type) would be better than LDPE as a contact layer for orange juice in regard to d-limonene. Alteration of the polymer, however, may only change which compounds are absorbed. Investigation of absorption phenomena is very important and clarifi- cation of the thermodynamic properties of the absorbant would aid in designing packaging for flavored, liquid products. APPENDICES APPENDIX 1 STANDARDIZATION 0F BROMIDE-BROMATE SOLUTION 1.1. Standard Solution of Potassium Bromide-Bromate (AOAC, 1965) Dissolve about 2.8 g KBrO3 and 12 g KBr in boiled water and dilute to 1 liter with boiled water for about 0.1 Normality solution. 1.2. Standard Solution of Arsenious Oxide (JAOAC, 1981) Weight the A5203 accurately by difference from small-stoppered weighing bottle (use about 4.95 g per 1 liter for 0.1 Normality solu- tion). Dissolve in normal NaOH solution about the same quantity of normal H2504. Cool and transfer mixture quantitatively to volumetric flask and make to volume. (Solution must be neutral to litmus, not alkaline.) A5203 + 212 + H20 + A5204 . g A5203 x 4000 N°rmallty ‘ (ml final volume) x 197.84 1.3. Standardization of Standard Solution of Potassium Bromide-Bromate (JAOAC, 1948) Measure 40 ml of standard A5203 solution from buret into 300 ml erlenmeyer. Add 10 ml HCl and 3 drops of methyl orange. Titrate with (KBR - KBr03) solution until 1 drop causes color of methyl 63 64 orange to fade completely. Swirl solution constantly and add last ml drOpwise, swirling between drops. A5203(ml) x A5203(N) Normality = Bromide - Bromate (ml) APPENDIX 2 ONE-WAY ANALYSIS OF VARIANCE The purpose of this analysis was to determine significant absorption effects on mechanical properties of each polymer film. The data were analyzed by the following analysis of variance (ANOVA Table, Bhattacharyya, 1977). Population model for comparing k treatments .. = + . + .. ° = ... ., ' = , ..., Y1J p 8J eIJ, l 1, , nJ j 1 k where 0 = overall mean k 8j = the jth treatment effect, 2: Bj = 0 i=1 and eij are all independently distributed as N(0, a), Reject Ho: 81 = 32 = ... e 8k = 0 if Treatment SS/k - 1) Residual SS/(n - k > Fa(k - 1, n - k) where k " =Z.=1”i J 65 66 a 3 e - e N Na - . .3 MW 2:: 3. .ee 3. Tn .n 3. - e N T... 7., 7n v_ - -.n .n - .2 - mnn - mnz 3. e N NA m 3 ”W- mnn LE: 3. .ee 3. Tn H..- e. u Hm: H n 0. N3 .. amvm: Nu hmm 3553: mm x 9.25m :82 £6 mmgmzcm mo 5% musaom .ucmspmmcp x mcegmasoo com mean» <>oz< .em m—am» 67 and Fa(k - 1, n - k) is the upper a point of the F distribution with d.f. = (k - 1, n - k). Multiple-t Confidence Intervals A set of 100 (1 - a)% simultaneous confidence intervals for m number of pairwise differences (“j - “j') is given by - - 1 1 (.Yj‘YJIIita/st $4.7]? where s = ‘V MSU, m = the number of confidence statements, and ta/Zm = the number a/2m point of t with d.f. = n - k. Using this procedure, the probability of all the m statements being correct is at least (1 - a). tm/2m for 97 percent simultaneous confidence intervals t0.03/2 x 15 = t0.001 tabulated value of t with d.f. = 54 is 3.248. 68 .Hpcmugma H n 8V umucoaaam mH mocmngHHu acmu_HH=mHm a .mm.m x m=Hm> d vm>gmmno mg» cmgzex .mm.m uucmogma H n oH.o em m¢.w m mm.~ Ne.o m wo.~ an owpmcd m: .w.u mm mogaom Anny nnnH-n mm.o em mo.mH m H.em mm.HH m No.mm a» «a. ceased m: .w.u mm mugaom Houv HonH-n mH.o em om.m m o.mm mN.¢ m mm.Hm an «* opumgm m2 .m.u mm mucaom Houv wasp e n8 Hen.nv u .e.e see: a to eenns cane—seen men meo.o em mm.m w mm.o oeo.o m mm.o ah onumgd m2 .w.u mm mucaom Hazv nnnn-n mm.o ¢m mm.mH m m.m¢ mo.oH m mm.om mp «r oHHnem m: .H.u mm mogaom Hazv HonH-n $0.0 em mm.m m m.om mw.H m m~.m ah me oHmem m2 .e.c mm muezom Aozv maoH .AHHoHpmmHm Ho msHanoE sow mHnmp <>oz< .mm mHamH 69 no.o en on.n o nn.o no.o n oH.o on ooooeo n: .o.o no ooeoon Hooo nnoH-n eoo.o em oo.e o nn.oe no.e n nH.oN on «a. ooooeo n: .e.o on ooeoon Hooo HooH-n eoo.o en oH.o o o.n noo.o n eo.o on oneneo n: .o.o no ooeoon Hooo mooo eo.o en oH.~ o oo.n on.o o oo.H on is onoeeo n: .e.o nn ooeoon Hozo nnoH-n HH.o en oo.o o on.nn on.n n on.nn on «on oneneo n2 .o.o nn ooeoon Hozv HooH-n ooo.o eo Hn.o o on.n oo.o n n~.o on «a. onoeeo n: .e.o on eoeoon Hozo woos .cpmcmgum mHHmcmH Low mHnmp <>oz< .om mpawh 7O ono en nnnen o nn.n oonH o onoo on ooooeo nz .o.o nn ooeoon Hooo nooH-n nooH en ooooo o eo.o Non o oHoN on oeooeo n: .o.o nn ooeoon Hooo HooH-n noonH en neooen o Hn.n ooonn o oneooH on oneneo n: .o.o nn ooeoon Hooo oooo no en noon o on.n ooH n oeo on onoeeo n: .o.o nn ooeoon Hozo nooH-n nnnn eo onooo o on.H oan o oeooH on «k onoeeo n: .o.o nn ooeoon Hozo HooH-n ono en annn o i..oe.: oonn o oooon on ovumgm m: .$.fi mm wULzom Hozo oooo .xomca um acmucma conuomcon com mHnmu <>oz< .NN mHno» 71 Table 28. ANOVA table for seal strength. LDPE (MD) Source SS d.f. MS Fratio *1): TR 4.18 5 0.84 5.25 E 8.41 54 0.16 S-1601 (MD) Source SS d.f. MS Fratio ** TR 7.41 5 1.48 51.0 E 1.58 54 0.029 S-1652 (MD) Source SS d.f. MS Fratio TR 0.35 5 0.07 1.75 E 2.11 54 0.04 APPENDIX 3 DETERMINATION OF DART IMPACT FAILURE WEIGHT The determination of dart impact failure weight of LDPE and Surlyn (zinc type) is shown in Tables 29 and 30. 72 73 Table 29. Impact failure weight of LDPE. Missile wt (9) ni i i x ni Control 90 x 1 1 1 75 x x x x x x x x x 9 0 O 60 0 o o 0 0 0 o 0 N = 10 A = 1 ”HM w0=75 AN=15 Immersed 90 x 1 3 3 75 x x x x x 4 2 8 60 o o o o x x x x 4 1 4 45 x 0 0 o o 1 O 0 30 O N = 10 A = 15 NF = 29.191 Wo = 45 AW = 15 0: non-failure x: failure Method A (dropping height: 0.66 m) 74 Table 30. Impact failure weight of Surlyn (zinc type). Missile wt (9) ni i i x ni Control 255 x 1 3 3 240 o x x 2 2 4 225 x x o x o 3 1 3 210 x o x x o o x o 4 0 0 195 0 o o o N = 10 A = 1 WF=M w0=75 AW=15 Immersed 270 x x 2 3 6 255 o x x x x x 5 2 10 240 0 o o x x o 2 1 2 225 o x o 1 0 0 210 o N = 10 A = 18 WF = 244.5 (9) W = 225 AH = 15 o: non-failure x: failure Method A (dropping height: 1.52 m) BIBLIOGRAPHY BIBLIOGRAPHY Ahmed, P.E., Dougherty, R.H., and Shaw, P.E. 1978. Journal of Agriculture and Food Chemistry 26:187. Anandaraman, S., and Reineccius, G.A. 1986. Food Technology 40(11): 88. AOAC. 1965. Association of Official Agricultural Chemists 42.018- 42.019. ASTM. 1984. American Society for Testing and Materials Selected ASTM Standards on Packaging 0 882-83z49-58. ASTM. 1986. American Society for Testing and Materials 01709-85: 86-95. Baner, A.L. 1986. "Diffusion and Solubility of Toluene in Polymer Films. 13th Annual IAPRI Symposium, Oslo, Norway, 26-68 May. Benson, S.W. 1960. The Foundation of Chemical Kinetics. 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