THEORETICAL STUDY OF PRODUCT - GENERATED ATMOSPHERE PACKAGES FOR FRUIT Thesis for the Degree of M. S. MICHIGAN STATE UNIVERSITY THOMAS JAMES BUSSELL 1976 l(.IHI TTTTTTTTTTTTTTTT “)ITY L'UDAI’IES IIIIIIIIIIIIIIIIIIIIIIIIIIII : 00083 7769 This is to certify that the thesis entitled , flffi/Qfi fid 0/ 5%61/7 a! fiOJQal- genemé/ ”1971029016423 fiM/e4c7’65 #0.,- Fry]? presented by flames Jame; T594556 // 5 been accepted towards fulfillment of the requirements for begee in [M ”1’7 ha Gunilla G. T. Jonson Major professor Date W ‘ I 0-7 639 ‘ OWL {I 7’ > ABSTRACT THEORETICAL STUDY OF PRODUCT-GENERATED ATMOSPHERE PACKAGES FOR FRUIT BY Thomas James Bussell This thesis investigates the possibility of replacing controlled atmosphere storage of fruits with a product-generated atmosphere package. The investiga- tion is comprised of an economic analysis and a computer model. The McIntosh apple is the product. Internal package conditions are generated for three films and temperatures between 3.5°C and 7°C. Results of the economic analysis and computer model support the feasibility of product-generated storage costs for product-generated storage packages are less than either cold storage or controlled atmosphere storage. Apples stored in low density polyethylene had significantly lower respiration rates than cold storage apples. THEORETICAL STUDY OF PRODUCT-GENERATED ATMOSPHERE PACKAGES FOR FRUIT BY Thomas James Bussell A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE School of Packaging 1976 ACKNOWLEDGMENTS I would like to thank Dr. Gunilla Jonson for her patience and understanding with this thesis. Sincere appreciation is also extended to Dr. Wayne Clifford for his assistance in the computer model and to Dick Patterson and Dr. Thomas Pierson for their help. Lastly, I would like to thank my wife, Barb, for all the many ways she helped me. ii TABLE OF CONTENTS Page ACKNOWLEDGMENTS O O O O 0 O O O O O O O O i 1 LIST OF TABLES O O 0 0 O 0 0 O O 0 O O 0 V LIST OF FIGUMS O O O O O O O O O C O O 0 Vi Chapter I 0 INTRODUCTION 0 O O I O O O O O O O O 1 Section 1: Background. . . . . . . . 1 Section 2: Purpose. . . . . . . . . 2 Section 3: Limitations . . . . . . . 2 Fruit and Variety. . . . . . . . . 2 Storage Function . . . . . . . . . 2 Storage Life . . . . . . . . . . 4 II 0 DEFINITIONS 0 O O O O O O O O I O O 5 III. PRODUCT DESCRIPTION . . . . . . . . . 9 Section 1: Ontogeny . 9 Pre-climacteric Minimum Climacteric. . . . Senescence . . . . Section 2: Anaerobiosis . . Section 3: Apple Cultivar--McI Physical Characteristics . Optimum Storage Conditions. to h 0 O C O O O O O i..- w 00:30.... oomooooo Oxygen Effect . . . . . . . . . 17 Carbon Dioxide Effect . . . . . 18 Temperature Effect . . . . . . . 22 IV C STOMGE C O O O O O O O O O O O O 2 5 Cold Storage . . . . . . . . . . . 25 Controlled Atmosphere (CA) Storage. . . . 26 V. THEORY FOR PRODUCT-GENERATED ATMOSPHERE PACKAGE 0 O C C O O O O O 3 2 Section 1: Equilibrium Variables . . . . 33 iii Chapter VI. VII. VIII. Section Section Section Section Section 3 4 5 1 Section 2: Section 3: ECONOMICS Section Section Section Section Section Section BIBLIOGRAPHY . APPENDIX O‘U'luthH CONCLUSION. Oxygen Effect . Carbon Dioxide Effect Temperature Effect Theoretical Equations SIMULATION RESULTS . Films. Thickne SS Pallet-sized Product-generated Atmosphere Package. Building and Equipment . Labor. Management . Storage,Supplies Energy Summary iv and Repairs Page 37 37 40 41 45 45 50 52 59 62 63 64 64 65 68 70 71 80 LIST OF TABLES Table Page 1. Storage Conditions for Some Michigan Apple cultivars O O O O O O O O O O O O 17 2. Respiration Rates for Apples at Several Temperatures . . . . . . . . . . . 24 3. Q10 of Apples for Different Temperature Ranges . . . . . . . . . . . . . 24 4. Summary of Program Simulation . . . . . . 52 5. Storage Economics on a Monthly Basis. . . . 68 6. Storage Economics on a Seasonal Basis . . . 69 LIST OF FIGURES Figure Page 1. Distribution System from Point of Harvest . . 3 2. Ontogeny of Apples as Represented by Respiration Rate. . . . . . . . . . 11 3. Effect of the Partial Pressure of Oxygen on Supsequent Oxygen Uptake and Carbon DiOXide output 0 O O O O O O O O O 15 4. Oxygen Effect on Respiration Rate of McIntosh Apples . . . . . . . . . . 19 5. Carbon Dioxide Effect on Respiration Rate of McIntosh Apples . . . . . . . . . 20 6. Effect of Oxygen on Respiration Quotient . . 23 7. Firmness Losses of McIntosh Apples at 40°F Initial Firmness Aproximately 15 Pounds. . . 29 8. Number of Days McIntosh Remain Marketable After Removal From Storage and Placed in Air at 70°F . . . . . . . . . . 31 9. Unbalanced System . . . . . . . . . . 34 10. Equilibrium Conditions . . . . . . . . 35 11. Oxygen Effect on Respiration Rate of MCIntOSh O O O O O O O I O O O O 38 12. Carbon Dioxide Effect on Respiration Rate of McIntosh . . . . . . . . . . . 39 13. Results of One Mil Cellulose Acetate Simulations . . . . . . . . . . . 46 14. Results of One Mil Low Density Polyethylene Simulations . . . . . . . . . . . 47 15. Results of One Mil Polybutadiene Simulations . 48 vi Figure 16. 17. 18. 19. 20-1. 20-2. 21. 22. 23-1. 23-2 0 23-3 0 23-40 24-10 24-2 0 24-3 0 24-40 25-1. 25-2. 25-3. 26. Low Density Polyethylene, Extended Simulation at 3.5°C . . . Two Mil Low Density Polyethylene . . . . Low Density Polyethylene 1.5 Mil Pallet Bin. Michigan 1976 McIntosh Sales Cold, CA and Combined. . Program Appler Program Appler Functions SOLCOZ and SOL02 . Function RESP. Results of the Acetate . . Results of the Acetate . . Results of the Acetate . . Results of the Acetate . . Results of the Polyethylene Results of the Polyethylene Results of the Polyethylene Results of the Polyethylene Results of the Results of the Results of the Results of the Polyethylene Simulation for Simulation for Simulation for Simulation for Simulation for Simulation for Simulation for Simulation for Simulation for Simulation for Simulation for Simulation for at 7°C . . . vii Cellulose Cellulose Cellulose Cellulose Low Density Low Density Low Density Low Density Polybutadiene. Polybutadiene. Polybutadiene. Low Density Page 51 53 57 60 89 90 91 92 94 95 96 97 98 99 100 101 102 103 104 105 CHAPTER I INTRODUCTION Section 1: Background Packaging fruits and vegetables in transparent plastic bags has become pOpular commercially. These packages provide efficient distribution and attractive display at point of sale.1 This package is utilizing the three basic functions of a package--that is, the package: (1) com- municates to the consumer, (2) provides utility, and (3) provides protection and containment of the product. Extending storage life, which is part of the protection function, is economically important. The major storage life benefit derived from the familiar polyethylene fruit bag is that it hinders water loss and subsequent shriveling of the fruit. Greater gains in extending storage life of fruits are today achieved by modifying the storage atmosphere prior to the packaging and distribution of the poly- ethylene bag. An atmosphere with low concentration of 1R. G. Tomkins, "The Conditions Produced in Film Packages by Fresh Fruits and Vegetables and the Effect of These Conditions on Storage Life," Jrnl. Applied Bacteriology (1962), 25(8):290. 1 oxygen and a high concentration of carbon dioxide retards the fruits' ripening process. This increases the storage life. Section 2: Purpose The objective is to study if it is theoretically possible to achieve and maintain favorable storage conditions within a fruit package and in that way elimi- nate the necessity of controlled atmosphere storage. If this is possible, the package will be analyzed from an economic standpoint. Section 3: Limitations Fruit and Variety The McIntosh apple (Malus pumilu, Mill.) is the particular fruit and variety that this theoretical study focuses on. The McIntosh was chosen on the basis of its commercial importance in Michigan's fruit industry and that it is commonly stored under modified atmospheres. Storage Function The movement of apples from harvest to consumer sales encompasses numerous handlings and environments. The scope of this thesis is limited to the storage func- tion (Figure 1). The emphases of this paper are not concerned with the apples' distribution system, but are concerned with package design and an economic analysis of storage methods. .umm>umm mo ucflom scum Empmmm Gowusnwuumfionn.a whamwm “MAHGBWm rOHadBmOmnga ZOHBUZDM mwgonum REESE ImHo _ _ 8 I _ _ _ _ CHOU _ _ _ _ w Hmamm /\ d0 Hm3ouu UHOU _ _ _ _ _ _ _. I _., _ _ _ _ _ _ Storage Life Storage life is dependent on numerous factors. Some of the factors are: metabolism, moisture loss, physiological disorders, chemical treatments, maturity at harvest dates and rate of cooling.2 Of these factors, controlling the apple’s metabolism is the most critical. The metabolism, or respiration rate, of the apples is affected by the fruits' environment. It is the control of respiration (and, therefore, storage life) that is of concern to this problem. 2A. VanDoren, "Physiological Studies with McIntosh Apples in Modified Atmosphere Cold Storage,” Proc. Am. Soc. Hort. Sci. (1937), 37:453. CHAPTER II DEFINITIONS Listed below are terms that are frequently used in this paper. Several terms and definitions may only be correct within the context of this paper. Most of the terms are particular to the apple or its storage. Aerobic respiration: Respiration that occurs in an adequate supply of oxygen. This is the typical form of respiration and is referred to as simply "respiration.” Activation energy: A coefficient, particular to the film, that quantifies the effect of temperature on the permeability. Anaerobic respiration: Fermentation--respiration in the absence of oxygen with by-products of ethyl alcohol, carbon dioxide and acetaldehyde. Carbon dioxide scrubbers: Chemicals or processes that remove excess carbon dioxide from controlled atmosphere rooms. Climacteric: Ripening process, evidenced by increasing respiration rate. The high respiration rate supplies energy for the conversion of starch to hexose, the production of ethylene and the distinction of cell wall material.3 Cold Storage: Synonymous with "regular storage"-- warehouse storage units that maintain a low temperature in an air atmoSphere. The temperature is usually near 0°C. Controlled atmosphere (CA) storage: Airtight storage units which control oxygen concentration, carbon dioxide concentration and temperature. Cultivar: Variety. Extinction_point: Minimum oxygen level needed to sustain aerobic respiration. Intercellular spaces: Void spaces between cells within the apple pulp. The oxygen in these spaces pro- vide the immediate supply of oxygen for metabolism. Ontogeny: The life cycle of a single organism. Packing density: Ratio of product volume to package volume. Permeability constant: A measure of grams of Specific gas that pass through one square centimeter of material that is one millimeter thick, in one hour. Product-generated atmosphere package: A sealed, flexible film package that contains a living, reSpiring 3F. Kidd and C. West, "Recent Advances in the Work on Refrigerated Gas--Storage of Fruit," Jrnl. of Pomology (Hort. Sci.) (1936), 14:306. organism (the product), where the respiratory process of the organism produces (generates) concentrations of oxygen and carbon dioxide within the package (atmosphere) that are in different quantities than is found in air. Permeabilityrate: A measure of grams of specific gas that pass through one square centimeter of material one millimeter thick, in one hour, at a temperature other than 0°C. Respiration:- The uptake of oxygen to convert sugar into carbon dioxide, water and energy. The reaction is: 6 02 + C6H1206 -———e» 6H20 + 6CO2 + 673 Real Respiration rate: Measure of oxygen uptake or carbon dioxide output. Typically, carbon dioxide is used, such as: CO2 grams/kilogram apple/hour. Regpiratoryguotient (R.Q.): Volume of carbon dioxide produced divided by volume of oxygen simultane- ously consumed.4 ,Senescence: Post-maturity stage, an aging process. Storage life: Period of time from harvest to 10 percentage wastage.of the fruit. 4W. 0. James, Plant Respiration (1953). p. 82. Temperature coefficient (QIOL: This is the rate of respiration at a given temperature, divided by the respiration rate at 10°C lower. Transmission rate: A measure of grams of a specific gas that pass through a package per period of time. CHAPTER III PRODUCT DESCRIPTION This chapter is divided into three sections. The first section discusses the general ontogeny of apples. It focuses on apples from time of harvest to ultimate degradation. Harvest corresponds to the begin- ning of storage life. The second area discusses anaerobiosis. Anaerobiosis is an important concept to understand if apples are to be stored in modified atmospheres. The final section describes specific character- istics of the McIntosh apple relevant to this analysis. The effect of oxygen, carbon dioxide and temperature on the respiration rate are given special attention. Section 1: Ontogeny An apple is a living, respiring biological system which is constantly undergoing physical, chemical and structural changes as it deve10ps, ripens and dies.5 5A. Jabbari, N. N. Mohserin and W. S. Adams, "Analog Computer Model for Predicting Chemical and Physical PrOperties of Selected Food Materials," Trans- actions, American Soc. Agri. Eng. (1971), 14(2):319. 10 Respiration rate is an ideal parameter for determining the physiological age of the apple. The reSpiration rate has a definite trend through the ontogeny of the apple (Figure 2). Pre-climacterippMinimum The harvest date is at the pre-climacteric minimum (point A in fig. 2). At this stage of ontogeny, the apple is fully developed and the respiration rate is at a minimum. Harvesting at or just prior to the pre- climacteric minimum will provide the greatest storage potential.6 Climacteric The next stage of ontogeny is the climacteric, which is the ripening process. At this point, the apple is converting its energy supply of starch into sugar, oxygen, carbon dioxide, ethylene and heat. This will cause a change in color of the skin and a softening and sweetening of the flesh.7 The climacteric is critical to storage-life. Once the climacteric starts, the ultimate storage-life is 6D. R. Dilley, "Prediction and Verification of Proper Harvest Date for Storage Apples," Mich. St. Hort. Soc. (1965), 95:48. 7F. Kidd and C. West, "Recent Advances in the Work on Refrigerated Gas--Storage of Fruit," p. 306. ll Respiration Rate ;;:;> senescence harvest __ climacteric Growing Season Figure 2.--Ontogeny of Apples as Represented by Respiration Rate. Source: Fidler, J.C.; Wilkenson, B.G.: Edney, K.L.: and Sharples, R.O. (1973), The Biology of Apple and Pear Storage. Headley Brothers, Ltd., London. Page 4. 12 limited. If the climacteric can be delayed or suppressed, the storage-life will be increased.8 A low temperature environment will delay the climacteric. A modified atmosphere can suppress the climacteric to the extent that the respiration rate is not affected.9 At one time, the onset of the climacteric was believed to be initiated by the presence of ethylene. It appeared that the increase in ethylene production by the apple triggered the chemical reactions associated with the climacteric. This has been proven false based on two findings: (1) ethylene production follows the respiratory peak ochIntosh apples by about four days 10 at 20°C, and (2) initial studies were done in air at 20°C, where low temperatures and a modified atmOSphere negate any ethylene effect on the climacteric.11 8F. Gangerth, "Hypobaric Storage of Vegetables," Acta Horticulturae (1974), 1(6):23. 9F. Kidd and C. West, "Recent Advances in the Work on Refrigerated Gas--Storage of Fruit," p. 308; and J. C. Fidler, "Studies of the Physiological-Active Volatile Organic Compounds Produced by Fruit II. The Rate of Production of Carbon Dioxide and of Volatile Organic Compounds by King Edward VII Apples in Gas Storage, and the Effect of Removal of Volatiles from the Atmosphere of the Store on the Incidence of Superficial-Scald," Jrnl. Hort. Sci. (1950), 25(2):104. 10R. M. Smock, "The Influence of One Lot of Apple Fruit on Another," Proc. of the Am. Soc. Hort. Sci. (1942), 40:187. 11J. C. Fidler, B. G. Wilkenson, K. L. Edney and R. O. Sharples, The Biology of Apple and Pear Storage (1973), p. 8. 13 Senescence The final stage of the apple's life is called "senescence." The apple pulp or flesh becomes mealy and loses its flavor. At this point, storage-life and market value are very limited. The respiration rate during senescence is characterized by a downward drift. Section 2: Anaerobiosis Preventing anaerobic respiration is critical to apple quality. The by-products of anaerobic reSpiration are carbon dioxide, ethyl alcohol and acetaldehyde. Ethyl alcohol and acetaldehyde will remain in the apple, which results in an "off" flavor. Quality of apples will be severely affected after approximately one week in anaerobic conditions.12 Oxygen is necessary for the normal respiratory process. Decreasing the available supply of oxygen will have a retarding effect on the rate of respiration. There is, however, a limit to the amount that oxygen can be reduced and still maintain respiration. This lower limit (concentration) for oxygen is referred to as the extinction point. Extinction point is dependent on temperature and apple variety. For the McIntosh apple, 12J. C. Fidler and C. J. North, "The Effect of Periods of Anaerobiosis on the Storage of Apples," J. Hort. §gi. (1971), 45:220: and R. G. Tompkins, "The Conditions Produced in Film Packages by Fresh Fruits and Vegetables and the Effect of These Conditions on Storage Life," p. 304. 14 the extinction point is 2% oxygen at 3.5°C,13 and 3.5% oxygen at 20°C.14 When the oxygen supply falls below the extinction point, respiration is replaced by anaerobic respiration as the oxygen concentration approaches zero (Figure 3).15 Anaerobiosis results in total depletion of oxygen supply within the fruit which will disrupt and accelerate the . 16 . . . . metabolic processes. An increase in carbon dioxide evolution is associated with anaerobic fermentation. Section 3: Apple Cultivar--McIntosh The design of a product-generated package is affected by the characteristics of the product.17 The product traits that must be determined are: (1) physical characteristics, (2) optimum storage conditions, (3) effect of oxygen on respiration rate, (4) effect of 13A. Van Doren, "Physiological Studies with McIntosh Apples in Modified Atmosphere Cold Storage," p. 454. 14V. Jurin and M. Karel, "Studies on Control of Respiration of McIntosh Apples by Packaging Methods," 'Food Technology (1963), 17(6):106. 15H. E. Street and W. Cockburn, Plant Metabolism (1972), p. 90. 16J. C. Fidler and C. J. North, "The Effect of Periods of Anaerobiosis on the Storage of Apples," Jrnl. Hort. Sci. (1971), 46:213. 17R. G. Tomkins, "The Conditions Produced in Film Packages by Fresh Fruits and Vegetables and the Effect of These Conditions on Storage Life," J. Applied Bacteriology (1962), 25(8):305. 15 1.25q s " 'HQ’ 1000'|\ HA: ‘ 3303 \ F1» \ ocm \ >5 ‘ ° N .75_\\ NO \ / 8a) ‘\ 1” .5 \ 58' 21> .50- > .25“ ‘\\ \\~ extinction point I \I j j 1 j .05 .10 .15 .20 .25 .30 Oxygen partial pressure influence of 02 on 02 uptake ________ influence of O2 on CO2 evolution .__ .__ .__ CO2 evolution due to fermentation Figure 3.--Effect of the Partial Pressure of Oxygen on Subsequent Oxygen Uptake and Carbon Dioxide Output. Source: James, W.O. (1953). Plant Respiration. Oxford Claredon Press, England. Page 90. 16 carbon dioxide on respiration rate, and (5) effect of temperature on respiration rate. Physical Characteristics Following is a brief description of the physical characteristics of the McIntosh that are relevant to this study: 1. Density is .814.18 2. 30% - 35% of volume is intercellular spaces.19 3. Approximately 4% of intercellular space is carbon dioxide. 4. Approximately 17% of intercellular space is oxygen. The accumulation of carbon dioxide is almost balinced by the depletion of oxygen. 5. 85% of the weight of the apple is assumed to be water.2 6. 0.5 is the packing density for plastic bags.23 183. A. Stout, D. H. Dewey, and R. F. Mrozek, "Mechanical Orientation of Apples and Related Fruit Characteristics," Agr. Exp. Stn. Mich. St. Univ. Research Bulletin (1971), No. 32, p. I3. 198. P. Burg and E. A. Burg, "Gas Exchange in Fruits," Phypiologia Plantarum (1965), 18:876. 20 Ibid., p. 879. 211bid., p. 878. 22J. C. Fidler, "Studies of the Physiological Active Volatile Organic Compounds Produced by Fruit II,” p. 89. 23R. G. Tomkins, ”The Biological Effects of the Conditions Produced in Sealed Plastic Containers by Pre- packaged Fresh Fruit and Vegetables," Bull. Int. Inst. Refrig, Annexe. (1960), 1:237. 1? Optimum Storage Conditions The optimum storage conditions for McIntosh are a temperature of 3.5°C and an atmosphere of 5 percent carbon dioxide and 3 percent oxygen. This atmosphere can be stated as 5:3. These ideal storage conditions are quite typical among common Michigan apple cultivars (Table 1).24 TABLE l.--Storage Conditions for Some Michigan App1e~ Cultivars. Rates of Respiration C°nd1t1°ns in 1/1,ooo kg day Cultivar ' O T %CO2 %02 CO2 Golden Delicious 3 . 5 5 3 2 0 Delicious 0 5 3 18 Jonathan 3.5 7 13 33 McIntosh 3.5 5 3 35 Oxygen Effect The effects of both oxygen and carbon dioxide partial pressures on the respiration rate of McIntosh 25 apples have been measured by Jurin and Karel. This 24J. C. Fidler and G. Mann, Refrigerated Storage oprpples and Pears--A Practical Guide (1972), p. 34. 25V. Jurin and M. Karel, "Studies on Control of Respiration of McIntosh Apples by Packaging Methods," p. 107. 18 study was conducted at a constant 20°C. The effects of the gases are illustrated in Figures 4 and 5. Jurin and Karel found that the oxygen effect on the rate of respiration was practically linear between the extinction point concentration of .035 and .21. In this span of oxygen concentrations, the respiration was suppressed from 10 cc Oz/Kg-hr to 6 cc Oz/Kg-hr at the extinction point. The respiration rate fell sharply when the oxygen supply was below the extinction point. Carbon Dioxide Effect Increasing the partial pressure of carbon dioxide had a retarding effect on respiration rate (Figure 5). The retarding effect was minor at the lower concentrations. The effect of decreasing the respiration rate by changing the partial pressures of oxygen and carbon 26 When the atmosphere is oxygen dioxide are additive. deficient and carbon dioxide rich, the gases will have a combined retarding effect on the respiration rate. It is not completely understood how the concen— trations of oxygen and carbon dioxide affect metabolism. The probable dictating factor is the quantity of the two 26J. C. Fidler and C. J. North, "The Effect of Conditions of Storage on the Respiration of Apples," Jrnl. Hort. Sci. (1967), 42:203. 19 .noaufimvha Nmoaossoma.©oom. =.mposumz msfimmxomm an moaned smousHoz mo cofiumufimmmm mo Houusou mo mmwpsumg .Ammmav .2 .Hmumx was .> .sflnsn «wousom .mmammd smousHoz mo mumm coaumnflmmmm so Mommmm cmmmxoul.e musmfim whammmum Hafiuumm smmmxo om. ma. 0H. wa. NH. 0H. mo. mo. «0. No. P _ _ b p p P — p P .3 Jq.6x/oo zo eisu °dseg 0H 20 .soauawvha .mmoaosaome poom_.=.mponum2 msflmmxomm an moammd smonsHoz mo cowumswmmwm mo Houusoo mo mmflpsum: AmmmHv .2 .kumm was .> .cflnsn “mondom .mmammm smousHoz mo mumm soaumuammmm so nommmm mpfixowo nonsmouu.m musmwm unammmum Hmwuumm mpflxoflo sonnmu ma. va. NH. 0H. mo. mo. «0. mo. F b p p p P h Iq-bx/oo zoo eqeu °dsea 21 gases that is dissolved in the apple sap.27 The amount of soluble gas in the sap is dependent on physiological age of the apple, temperature and the atmosphere in the intercellular spaces. This atmosphere is dependent on the apple's external atmosphere and current respiration rate.28 When the external atmosphere is altered, the respiration rate may not reach equilibrium for several days. Research in measuring and controlling the solubility of oxygen and carbon dioxide in apple sap has been limited. Most horticulturalists have remained satisfied with quantifying the effects of external conditions on the apple's respiration. This theoretical study is based on their experimental findings. Jurin and Karel also studied the effects of oxygen and carbon dioxide on the respiratory quotient (R.Q.). It was found that at 20°C, the R.Q. was 1.0 and remained at that relationship until the oxygen supply 27J. C. Fidler and C. J. North, "The Effect of Conditions of Storage on the Respiration of Apples V. The Relationship Between Temperature, Rate of Respiration and Composition of Internal Atmosphere of the Fruit," Jrnl. Hort. Sci. (1971), 46:233. 28E. G. Hall, F. E. Huelin, F. M. V. Hackneys, and J. M. Bain, "Gas Exchange in Granny Smith Apples," VIII Congrés International Botanigue (1954), p. 405. 22 fell below the extinction point (Figure 6).29 Carbon dioxide did not effect the R.Q. (respiratory quotient) at any concentration. Temperature Effect Temperature has a great impact on respiration rate. A change of several degrees can have a significant effect on metabolism.3o There is a direct relationship between respira- tion rate and temperature. This relationship is commonly expressed in terms of 910 coefficient. The Qlo for specific varieties, such as McIntosh, could not be obtained. Instead, the average Qlo for apples based on information from Recommended Conditions for Cold Storage of Perishable Produce (Table 2)31 will be substituted for the unknown Qlo for McIntosh. Table 3 has the calculated Qlo for temperature in three ten-degree ranges. The 910 used for McIntosh is 2.77, the average Q10 of the 010's in Table 3. A Q10 of 2.77 means that the respiration rate at 15°C is 2.77 times greater than the respiration rate at 5°C 29V. Jurin and M. Karel, "Studies on Control of ‘Respiration of McIntosh Apples by Packaging Methods," p. 107. 30F. Kidd and C. West, "The Gas Storage of Fruit II. Optimum Temperatures and Atmospheres," Jrnl. of Pomology (Hort. Sci.), (1930), 13:74. 31Recommended Conditions for Cold Storage of ”Perishable Produce, InternationaI Institute of Refrigera- tion (I967T, p. 47. 23 .soauxmvsa rwmoHoanoms.poom. =.mpogums maammxomm an mmamma smousHoz mo cowumuflmmmm mo Houusou co mowpsuma .Ammmav .z .Hmumx can .> .sflHSH "mossom .usmfluoso sowpmnflmmmm so smmmxo mo nommmmll.m musmwm musmmmum Hafiuumm cmmmxo om. ma. 0H. ea. NH. OH. mo. we. we. No. - p p p P p p . p . -o.H ro.¢ 24 (10° less). The 910 corresponds well with the data in the Agriculture Handbook,32 which has an average Q10 of 2.85 in the same temperature range (Table 3). TABLE 2.--Respiration Rates for Apples at Several Temperatures. Temperature 0°C 5°C 10°C 15°C 20°C 273°K 278°K 283°C 288°K 293°K Early Ripening 800— 1280- 3400- 4400- 4800- 1420 2600 5000 7600 10000 Late Ripening 440- 1120- 1680- 2280- 3600- 880 1720 2560 4800 6000 Source: Agriculture Handbook 66, 0.8. Department of Agriculture, Oct. 1968, pg. 8. Heat of Respiration in BTU./ton/day. TABLE 3.--Qlo of Apples for Different Temperature Ranges. QlO Q1o Q10 Sve' 0°-10° 5°-15° 10°-20° 10 Early Ripening 3.78 3.09 1.76 2.77 Late Ripening 3.21 2.49 2.26 32Agriculture Handbook 66, 0.8. Department of Agriculture (October, 1968), p. 8. CHAPTER IV STORAGE The duration of market life is primarily dependent upon physiological changes already accrued during the 33 Different methods of storage suppress storage period. the apple's physiological changes in varying degrees. The duration of maximum storage connotates the effective- ness of different storage methods. In the following discussion, the two main methods of commercial storage will be described and compared. Cold Storage The temperature is held slightly above the temperature that would initiate low temperature breakdown, 34 The temperature is typically a physiological disorder. between -2°C and 1°C. The cold storage temperature for McIntosh is 0°C. This temperature coincides with the lowest respiration 33G. D. Blanpied and D. H. Dewey, "Quality and Condition Changes in McIntosh Apples Stored in Controlled Atmospheres," Quarterly Bulletin of Mich. Agr. Exp. Stn. (1960), 42(4):?78. 34J. C. Fidler and C. J. North, "The Effect of Conditions of Storage on the Respiration of Apples," p. 204. 25 26 rate attainable without midifying the atmospheric condi- tions. The maximum cold storage life for McIntosh is two to four months.35 Cooling is rapid in cold storage. The temperature of the fruit is cooled from 20°C to 3°—4°C within five days. It is essential to establish storage conditions within a week.36 Cold storage aids in suppressing respiration, aging due to ripening, water loss and spoilage due to bacteria, fungi and yeast.37 If the temperature is 2° or 3° above the optimum temperature, there is an increased danger of increased decay and unnecessary ripening.38 Controlled Atmosphere (CA) Storage The atmospheric concentration of oxygen and carbon dioxide of CA storage will hinder the respiration of the organism. CA is used extensively for apples to extend storage life and marketability.39 35Agriculture Handbook 66, p. 23. 36J. C. Fidler, et al., The Biology of Apple and Pear Storage, p. 33. 37Agriculture Handbook 66, p. 2. 381bid., p. 2. 39F. Veiraju and M. Karel, "Control of Atmosphere Inside a Fruit Container," Modern Pkg. (1967), 40(2):168: and A. Van Doren, "Physiological Studies with McIntosh Apples in Modified Atmosphere Cold Storage," p. 453. 27 Controlled atmosphere storage facilities consist of airtight store rooms that control oxygen concentration and carbon dioxide, as well as temperature. Apples are pre-cooled before being sealed in the storage rooms. The ideal atmospheric conditions are either achieved by artificial means or by letting the apples' respiratory process generate ideal conditions. The effect of these partial pressure changes is to decrease the respiration rate. Product-generated and artificially-generated atmospheres give identical storage results.40 It may require two to three weeks to attain CA conditions.41 The desired conditions are maintained by venting with cooled air and using carbon dioxide scrubbers. The oxygen concentration is kept slightly above the extinction point to reduce the possibility of incurring anaerobic conditions. The temperature main- tained in CA storage is generally several degrees higher than found in cold storage. The change in gas concentra- tion elevates the temperature at which low temperature breakdown starts to appear.42 40Fidler, et a1., The Biology of Apple and Pear Storage, p. 33. 41Agriculture Handbook 66, p. 17. 42G. D. Blanpied and D. H. Dewey, "Quality and Condition Changes in McIntosh Apples Stored in Controlled Atmospheres," p. 774. 28 CA offers several advantages over cold storage. They are: 1. Carbon dioxide retards not only respiration, but also the germination and growth of fungi.43 2. Brown core, storage scald and mealy break- down is retarded. 4 3. Firmness is better maintained. 4. Ripening is significantly slowed down.45 5. Shelf-life after removal from storage is greatly lengthened. 6. Storage life is extended to 6-8 months.46 7. Climacteric is suppressed. The retention of flesh firmness during CA storage is apparent from the results shown in Figure 7. The storage temperature was 3.5°C. Cold storage is associated with the greatest loss of flesh firmness, while all of the various modified atmospheres indicate some degree of maintaining firmness. The atmosphere 5:2 preserved the most firmness. 43F. Kidd and C. West, "The Gas Storage of Fruit II. Optimum Temperatures and Atmospheres," p. 77. 44G. D. Blanpied and D. H. Dewey, "Quality and Condition Changes in McIntosh Apples Stores in Controlled Atmospheres," p. 778. 45F. Kidd and C. West, "Recent Advances in the Work on Refrigerated Gas—Storage of Fruit," p. 303. 46Agriculture Handbook 66, p. 23. 29 8‘ Air Pressure Firmness Lost in Lbs. .5 U1 H C 5.: .__: H O N 3d 2. .2 l. 4443 S bans. {4.5:}: QUOTMGMQMSJ go zonmz‘nzn Figure 7.—-Firmness losses of McIntosh apples at 40°F. Initial firmness approximately 15 pounds. Source: Van Doren, A. (1937) "Physiological Studies with McIntosh Apples in Modified Atmosphere Cold Storage." Proc. Am. Soc. Hort. Sci. 37:455. 30 The atmosphere of 5:2 is sometimes used in lieu of 5:3 for McIntosh. However, this is not the general cormnercial practice. The risks of anaerobiosis offset the possible gains gotten at 5:2 rather than at 5:3. Extending the market life after removal from ' storage (Figure 8) is almost as important commercially as extending the storage period. Extending the storage period only to have the quality to maintain for several weeks would hardly justify the added costs of CA storage. Fortunately, this is not the case with CA stored McIntosh apples. Modifying the atmosphere consistently preserves apple quality47 and marketing life in compari- son to cold storage. 47T. Murata and T. Minamide, "Studies on Organic Acid Metabolism and Ethylene Production During Controlled Atmosphere Storage of Apples (Mallus pumila Miller, cv. Rolls)," Plant and Cell Physiology (1970), ll(3):857 Days Marketable so, 60‘ 40- 20- 31 Jan r i U T Feb Mar Apr May June Figure 8.—-Number of days McIntosh remain marketable after Source: removal from storage and placed in air at 70°F. Van Doren, A. (1937). "Physiological Studies with McIntosh Apples in Modified Atmosphere Cold Storage." Proc. Am. Soc. Hort. Sci. 37:456. CHAPTER V THEORY FOR PRODUCT-GENERATED ATMOSPHERE PACKAGE The hypothesis of this thesis is that it is possible to design a flexible package system that will provide longer storage life for fruits and vegetables (specifically, apples) than is possible with cold storage. If an atmosphere within a package is oxygen deficient and/or carbon dioxide rich, the metabolism will be suppressed. Metabolism is inversely related to storage life. The intensity of metabolism is evidenced by the respiration rate. The rate of respiration is altered by changing temperature and partial pressure in the apples' environment. Metabolism can be depressed in a number of ways: decreasing oxygen concentration, increasing carbon dioxide concentration, decreasing temperature, or any combination of the three.48 This chapter is divided into five sections. The first section will present the variables that effect 48F. Kidd and C. West, "The Gas Storage of Fruit II. Optimum Temperatures and AtmoSpheres," p. 67. 32 33 equilibrium concentrations. The next three sections quantify three of the variables: oxygen effect, carbon dioxide effect and temperature effect. The other vari- ables are quantified in the Appendix. The final section depicts these variables in two theoretical equations. A computer simulation based on the two equations is presented in the Appendix. Equilibrium conditions may not be achieved. Respiration has a minimum rate that corresponds with the extinction point in oxygen. If the net transmission rate for oxygen is less than the respiration rate when the partial pressure of oxygen is at the extinction point, the partial pressure will continue to decrease. Reducing the oxygen partial pressure below the extinction point will cause anaerobic respiration. Fermentation increases the respiration rate (Figure 9). This will cause a greater imbalance in the system because the oxygen supply is further depleted. Equilibrium will not be attained. Section 1: Equilibrium Variables The equilibrium is approached by two actions, a declining respiration rate and an increasing net trans- 49 mission rate (Figure 10). The barrier qualities and a 49R. G. Tompkins, "Film Packaging of Fresh Fruit and Vegetables--the Influence of Permeability," The Inst. ‘of Packaging Conference Guide, 1962, p. 66. 34 Grams of O2 Internal Partial Pressure of Oxygen Respiration Rate ----- Transmission Rate E.P., Extinction Point Figure 9.--Unba1anced System. Grams of O2 35 ) Equilibrium Internal Partial Pressure of Oxygen Respiration Rate Transmission Rate Figure lO.--Equilibrium Conditions. 36 respiring organism will provide a dynamic environment system that will continue to evolve until equilibrium conditions are reached. Equilibrium conditions are reached when the respiration rate is equal to the package's transmission rate of oxygen and carbon dioxide.50 The transmission rate and respiration rate are dependent upon a number of variables. The variables affecting transmission rate are: l. permeability constant 2. film thickness 3. temperature 4. package surface area 5. activation energy for the film 6. concentration of oxygen 7. concentration of carbon dioxide 8. head space in the package. The variables affecting respiration rate are: 1. apple variety 2. concentration of oxygen 3. concentration of carbon dioxide 4. temperature 5. respiratory quotient 6 . total apple weight. Ibid. 37 The interaction of these variables will determine the eventual atmosphere within a product-generated atmosphere package.51 Section 2: Oxygen Effect Respiration rate is a function based on the effect of oxygen, carbon dioxide and temperature and can be written as RR(P ,P ,T). The effect of oxygen is O2 CO2 based on Figure 4. This figures is simplified into a straight line (Figure 11). The oxygen effect can be written as: 6*+ (22.2 - partial pressure of 02) (1) based on line points (6.0, 0.03) and (10.0, 0.21). Section 3: Carbon Dioxide Effect The depressing effect of carbon dioxide is based on Figure 5. The results are represented by two connect- ing straight lines (Figure 12). The carbon dioxide effect for line AB can therefore be written as: 1.0 - 2.25 - CO2 partial pressure (2) based on points (1.0, 0.0) and (0.82, 0.08). 51R. G. Tomkins, "The Conditions Produced in Film Packages by Fresh Fruits and Vegetables and the Effect of these Conditions on Storage Life," p. 293. 38 (10,.21) (6,.03) Resp. Rate 02_gm/kg-hr T T V I r T r I .02 .04 .06 .08.10 .12 .14 .16 .18 .20 .22 02 partial pressure Figure ll.--Oxygen Effect on Respiration Rate of McIntosh. 39 (1.00, 0.0) 1 1.00 4.) 3 9o 3: ' (.82, .08) m m 080‘ G. :3 .70. 5.. B 0 .60. m 8 050.. (U a: 5 ~40 ‘ (.40,.13) '13 .30. (U H '5'. .20. U) 33 010‘ fir T— .02 .04 .06 .08 .10 .12 .14 .16 .18 .20 CO2 partial pressure Figure 12.--Carbon Dioxide Effect on ReSpiration Rate of McIntosh. 40 The second line represents the effect of carbon dioxide of a partial pressure at or above 0.08. The equation for line BC based on points (0.82, 0.08) and (0.40, 0.13) is: .82 - 6.6 - (CO2 partial pressure)- 0.08 (3) The values generated from equations (2) and (3) are in the form of percentages. The product of equations (2) or (3) with equation (1) reflect the additive effect of carbon dioxide and oxygen on the respiration rate. Section 4: Temperature Effect The temperature effect is based on a 910 of 2.77. The following statement is made to quantify the temperature effect on respiration rate: x 1 1 e [-8181 ° (:17 - 79-3)] (4) RR if fifizgéifi = 2.77 (5) 283°K RR 0 then §§3§2_§. = 0.36 (6) 293°K x AH 1 l O.36=e -R—-° (fig-553)] (7) 41 AH _ 1n 0.36 if " 1 _ *1 (8) 283 293 AH _ _ if - 8470 This is the temperature effect between 10°C and 20°C. The temperature effect between 0°C and 10°C is: The average The _ x AH . 1 1 AH _ _ 7? — 7892 of the two %? is -8181. Section 5: Theoretical Equations definitions of symbols used in this discussion are: A dpco2 flap 02 dt surface area of package in square centimeters. derivative of partial pressure of carbon dioxide. derivative of partial pressure of oxygen. derivative of time external partial pressure of carbon dioxide. internal partial pressure of carbon dioxide. IpCO IT) RR(P I O2 2 32 44 = permeability constant for 42 carbon dioxide at temperature T°K, where "K" is degrees absolute. atmospheric pressure. external partial pressure of oxygen. internal partial pressure of oxygen. permeability constant for oxygen at T°K. gas constant respiration rate in grams of carbon dioxide per kilogram product per hour as a function of the partial pressure of oxygen and carbon dioxide and the temperature. solubility of carbon dioxide in apple sap in grams carbon dioxide per kilogram apple sap as a function of temperature. solubility of oxygen in apple sap in grams oxygen per kilogram apple sap as a function of temperature. standard temperature, O°K. weight of apples in kilograms. film thickness in centimeters. combined void volume of gas in cubic centimeters of package head Space and intercellular spaces in the apples. molecular weight of oxygen. molecular weight of carbon dioxide. 43 The initial supply of oxygen and carbon dioxide within the package can be represented as: u N a< (initial 02 supply) 502(T) - WA + 7§_7—_' (10) .3; .5 8< (initial CO2 supply) SCOZ(T)° WA + if—7'—' (11) The supply includes gas that is in apple sap, inter- cellular spaces and package headspace or void. The transmission rate of oxygen is represented as: 32 - P . ~ ‘0 e i P - -———. ' ° (P - P ) (12’ 02(T) R To 02 02 XI» Carbon dioxide transmission rate is represented as: 44'PO. g ..______. C02 ('1‘) R To (13) “ID e i (p “P ) CO2 C°2 Combining the respiration function (equations (1) and (2)), initial gas supplies (equations (10) and (11)), and the representations for transmission rates (equations (12) and (13)) can be simplified into two theoretical equations. The equation for oxygen is: dP . 32-v,, O2 32 Po A i [s -w + , , = [f5 -—,—-—-(p°-p )1- 02(T) A R T dt 02 (T) R To x 02 O2 44 The second equation, which represents carbon dioxide evolution within the package, is: dP CO 44°F 44", 2 ~ (3 A [S 'W + -—1—4 “———*'= H’ ' *—7—-”'-'(P "P )1 + C02 (T) A R T dt CD2 (T) R To x (D2 CO2 [RR“T5‘QIEJT)°“AJ (15) Equations (14) and (15) provide the basis for the computer model. The computer model is presented and described in the‘appendix. CHAPTER VI SIMULATION RESULTS In this chapter the results from the simulation of the three films are presented. This is in Section 1. The following two sections discuss the effect of film thickness and pallet-sized product-generated atmosphere packages, respectively. Section 1: Films The respiration rate and package atmosphere are affected by the film used. Respiration rate at equi- librium is directly related to the permeability con- stants. Figures 13, 14 and 15 denote the downward trend of respiration at the different temperatures over a thirty day period for the three films. The two hori- zontal lines in each figure represent the respiration rates of cold storage and CA storage. The cold storage respiration rate corresponds with .0025 grams COz/Kg x hr. The CA respiration rate is the lower of the two lines and represents a rate of .0020 grams COz/Kg x hr. 45 46 .0050. \ 7°C \ 60c 3 m .0040. x_ R 5° s ‘-——_ 8 v N o 4 U a; 3.5° u “-—___ 5‘2 A .00301 n m a: Cold Resp. Rate CA Resp. Rate 00020 "‘ ——————————————————————————— 5 10 15 20 25 30 Days ~ -4 502 = 2.44 x 10 P 3 co2 = 1.47 x 10' Figure 13.--Results of One Mil Cellulose Acetate Simulations. 47 .0050. .J H 5 .0040. m .2 E H m N d O U a? t; m 7°C 3 . m 6 c 5°c 3.5° CA Resp. Rate .0020~ ____________________________ 5 10 15 20 25 30 Days R = 1.75 x 10"5 ~02 _5 Pcoz = 8.8 x 10 Figure 14.--Results of One Mil Low Density Polyethylene Simulations. 48 ' .0050 . .0040q .0030 " Resp. Rate, CO2 gram/kg-hr Cold Resp. Rate .00204 _______________ g *3.5°c 8 10 13° 30 25 30 Days * anaerobic conditions, simulation terminated R = 8.57 x 10'° ~oZ _5 P a 2.97 x 10 co2 Figure 15.--Results of One Mil Polybutadiene Simulations. 49 These two respiration rate values were calculated from the FUNCTION RESP of the model in the appendix. The environmental values of cold storage and CA storage were substituted into the model. The cold and CA respiration rates are important in the analysis of the data. These two respiration rates are reference points in analyzing the effectiveness of the packages. The package would be effective in extend- ing storage life if the respiration rate is below the respiration rate of cold storage. The respiration rate is an index of storage potential. Cellulose acetate (Figure 13) is not an effective package. It is not effective because the final respira- tion rate at the lowest temperature, 3.5°C, is .0032. This rate is greater than the cold storage respiration rate (.0025). The storage life provided by this package would be less than the storage life attained through cold storage conditions. The low density polyethylene (Figure 14) provided a package option that will extend storage life. In an ambient temperature of 3.5°C, an effective respiration is achieved. The respiration rate is .0022. Within seven days, the respiration was below .0025. The respiration rate was still falling after thirty days, indicating that equilibrium conditions had not been reached. 50 The oxygen concentration at the end of the simulation was .0491. This partial pressure was almost .02 above the extinction point. In order to state with confidence that this package would extend storage life, an additional simulation was made. The duration of the simulation is 210 days, or 7 months. The results of this simulation are presented in Figure 16. The equilibrium conditions are: 4.716% oxygen, 3.289% carbon dioxide, and a respiration rate of .00220 grams carbon dioxide/Kg x hr. It can now be stated that the low density polyethylene package at 3.5°C is effective. The barrier prOperties of polybutadiene are too restrictive (Figure 15). Anaerobic conditions are established at all temperatures. Less than 3% oxygen was reached within 11 to 15 days. Table 4 is a summary of the simulations. The values represent the conditions at the 30th day of the simulation, unless anaerobic conditions develop. In event of anaerobiosis, the values are taken from the day that anaerobic fermentation initiated. Section 2: Thickness Changing the thickness will alter the equilibrium of the package. Increasing the thickness is similar to using a less permeable material. 51 .Uom.m um cofiumasswm pmpamuxm .mcmamsummaom mafimsmp 30A:I.mH shaman omH mNH mama owa mp 1.omoc. .mmoo. .omoo. mmoo. Jq.6x/m5zoa eqeu °dseu 52 TABLE 4.--Summary of Program Simulation. . Temp. Final Final Final Film °C ppO2 ppCO2 RR Cellulose Acetate 3.5 .1906 .0035 .003249 5.0 .1882 .0038 .003790 6.0 .1865 .0040 .004196 7.0 .1848 .0043 .004641 Low Density P.E. 3.5 .0491 .0331 .002207 5.0 .0417 .0347 .002528 6.0 .0369 .0358 .002766 7.0 .0322 .0369 .003023 Polybutadiene 3.5 .0281* .0874 .001738 5.0 .0244* .0928 .001928 6.0 .0278* .0964 .002094 7.0 .0259* .0998 .002240 * Anaerobic Condition. The thickness of the low density polyethylene in Section 1 was increased from one mil to two mils. The results of the 2 mil simulation was anaerobic conditions at all temperatures (Figure 17). Anaerobic conditions were reached in 10-15 days. The outcome for 2 mils is similar to the results of the least permeable material in Section 1, ploybutadiene. Section 3: Pallet-sized Product- generated'Atmopphere Package The commercial impact of product-generated atmosphere packages is significant. The model is based on a five-pound retail package. The impact would be 53 .0050 .0040. o 0030 ‘ Resp. Rate COzgm/kg°hr Days *anaerobic conditions, simulation terminated. Figure l7.--Two Mil Low Density Polyethylene. 54 maximized if the concept of product-generated atmosphere packages could be applied to storage containers. Most of Michigan apple growers store apples in pallet bins instead of the retail package.52 The apples are placed in pallet bins at time of harvest. The base of the bin is a standard pallet size (40 inches x 48 inches) and is 32 inches in height. The weight capacity is 1100 - 1200 pounds. Once at the warehouse, the bin and apples are drenched with a fungicide and water solution. The bins are then moved to storage and rapidly cooled. The apples are then retail-packaged and shipped, according to sales demand. 0 This system is advantageous to immediate retail packaging on three counts. This first advantage is that an employment level can be regulated. Immediate retail packaging means that all the packaging efforts are concentrated during the harvest season. The labor force already fluctuates on a seasonal basis. Immediately packaging the apples would amplify the fluctuations in employment. Harmonizing packaging with sales demand would have stabilizing effects on the growers' workforce. 52Unpublished apple storage information, March 1976, Richard Patterson, School of Packaging, Michigan State University, East Lansing, Michigan. 55 A second advantage is that a bottleneck in the packaging operation can be avoided. In order to package the fruit as it is harvested, the operation would need an enormous capacity. The investment to accommodate a high capacity, short-duration packaging operation may be prohibitive for most growers. By the grower packaging as the demands require, a more moderate size operation can fulfill the packaging needs. The final advantage is that better quality fruit will reach the retail market. It is inevitable that handling operations, such as sorting and packaging, bruise some of the fruit. Bruises are not visible immediately and lead to deterioration. If the fruit is packaged and then stored for several months, the bruises incurred from the packaging operation will initiate deterioration. By the time the fruit reaches the market, the bruised apples from the packaging operation will be inferior in quality. Storing in pallet bins minimizes the handling prior to storage. This in turn will eliminate much of the rotting. Whatever damaged fruit there is at the time of packaging can be sorted out during the pre-packaging operation. This type of operation would enable greater numbers of high-quality fruit to reach the retail market. 56 A simulation was conducted with the pallet bin as the product-generated atmosphere package. The pallet bin would be more practical than a five-pound package in current storage operations. Only low density polyethylene film was in the simulations. The change in package size to 40" x 48" x 32" necessitates changes in the package's parameters. These changes are: 1. Weight is based on 1200 pounds. This is 545,454 grams. 2. Package void space is 685,542 cm3. 3. Film area is 61,111 cmz. 4. Film thickness is 1.5 mil.53 Low density polyethylene was not successful in producing a beneficial atmosphere (Figure 18). The extinction point for oxygen was reached within 7 to 10 days, depending on the temperature. The carbon dioxide accumulations are in excess of 12 percent at all four temperatures. This accounts for the extremely low respiration rates in the simula- tions. Such high partial pressures are not used in conjunction with low oxygen partial pressures. The physiological disorder, carbon dioxide injury, is a problem at the higher carbon dioxide concentrations. 53D. H. Dewey, H. J. Raphael and J. W. Goff, "Polyethylene Covers for Apples Stored in Bushel Crates on Pallets," Quarterl Bulletin, Mich. Agri. Exp. Stn., (1959), 42(1): . .0050 .0040 .0030 Resp. Rate CO2 gm/kg-hr .0010 .0020. 1 q 57 Cold Resp. Rate CA Resp. Rate Days 25 30 Figure 18.--Low Density Polyethylene 1.5 mil Pallet Bin. 58 In summary of this chapter, it is possible to produce a beneficial atmosphere within a package. Each package variable has a significant effect on the equilibrium and must be consolidated into the package system. CHAPTER VII ECONOMICS In order to analyze the various storage costs of cold storage, CA storage and product-generated atmo- spheres storage packages on a monthly basis, it is necessary to determine the maximum storage life of each type of storage. Based on Figure 19, the cold storage of McIntosh is depleted after approximately four months and the last CA storage apples are predicted to be sold after about seven months. The monthly storage costs are based on four months and seven months, respectively, for cold storage and CA storage. The results in Chapter VI indicated that the Optimum product-generated atmosphere package was one mil low-density polyethylene at 3.5°C. Based on the theoretical respiration rate (Figure 14) the maximum storage life from this package is assumed to be six months. Implementation of the product-generated atmosphere package would affect five cost areas of storage: building and equipment, labor, management, storage supplies/repairs, and energy. 59 60 .HQd HMS .nmm can newsman n.oooa ca nmamm Combined Cold CA Figure l9.--Michigan 1976 McIntosh Sales Cold, CA and Combined. 61 Packaging material costs are not effected. The current retail package and the product-generated atmosphere package both utilize one mil low density polyethylene. Therefore, packaging material costs have not been included in this cost analysis. The average size cold storage warehouse in Michigan accommodates 72,000 bushels of apples and the average capacity for CA storage warehouses is 80,000 bushels.54 The cost analysis is based on the average size cold and CA storage warehouses. ,All cost figures are based on unpublished work by Brown and Pierson.SS The costs in this work are expressed in a per storage season basis. To reduce the costs to costs per month, the cold storage seasonal costs were divided by four and the CA storage costs were divided by seven. The description of the various cost areas is based on work done by Mathia56 unless otherwise referenced. 54Unpublished apple packing cost information, December, 1975. N Brown, County Building, Grand Haven, Michigan andtr.Pierson, Dept. of Agri. Econ., MSU, East Lansing, Michigan, pp. 7-10. 551bid., pp. 9-10. 566. A. Mathia, "Cost of Storing North Carolina Apples," Economics Information Report No. 5, N.C. State University (1967), pp. 8-19. 62 Section 1: Building and Equipment Building and equipment costs command the total investment costs. The difference in investment costs between cold and CA storage is significant. Buildings and equipment have an expected life of 25 years.57 The storage process for cold storage is a simple procedure that requires only the monitoring and control of temperature. Building and equipment costs are $13.00 per square foot. Interest and depreciation amounts to $.l36/bushe1/year. Interest and depreciation accrue throughout the year, even though the buildings may be empty much of the time. The income from the storage season must be used to meet interest and depreciation expenses. Therefore, the yearly interest and depreciation expense must be offset by profits from the storage. season. This expense will amount to $.0340/bushel/month. CA storage and equipment is more sophisticated than that found in cold storage. It is necessary that the structure has airtight storage rooms and equipment to measure and maintain the gas components, as well as the storage temperature. The building and equipment costs are based on a cost of $21.00 per square foot. Interest and depreciation amounts to $.29l/bushel/year (storage season). This will be a monthly expense of $.0416. 57Ibid., p. 9. 63 Product-generated storage packages would utilize cold storage facilities. Building and equipment costs are the same for storage packages as for cold storage. The cost for the storage season is $.136/bushe1/6 months, or $.0227/bushel/month. Section 2: 'Labor Labor costs are essentially the same in cold storage and CA storage. Both storage methods require placing fruit into storage,58 removing fruit from storage and daily monitoring storage conditions and appraising fruit quality. The average wage is essentially the same in either storage method. The average hourly wage for labor in cold storage is $3.35/hr and for CA it is $3.39/hr. Labor time per bushel is nine seconds for cold storage (4-mongh storage period) and eighteen seconds for CA storage (7—month storage period). Labor costs for cold storage is $.01/bushel/4 months, or $.0025/bushel/month. The seasonal labor cost of CA storage is $.018/bushe1/7 months. The monthly cost is the same as cold storage, $.0025/bushe1/month. 58J. C. Thompson, “Apple Storage Costs in New York State," Agricultural Experimental Station, Res. 87 (1962), p. 23. 64 This monthly labor cost, $.0025, is used for product-generated atmosphere packages. The seasonal cost would be $.015/bushe1/6 months. Section 3: Management The hourly costs for management for both storage methods is $6.69/hr. The time spent per bushel in cold storage (4 months) was three seconds or $.006/bushel/4 months, or $.0015/bushel/month. Management costs for CA storage (seven months) was somewhat higher. Management was costed at 8 seconds per bushel. This is $.016/ bushel/7 months, or $.0023/bushel/month. 1 It is not clear what the difference between $.0015 and 5.0023 is attributed to. It is assumed here that the management costs for the product-generated storage package will be the higher of the two, or $.0023/ bushel/month. This would be a seasonal cost of $.138/ bushel/6 months. Section 4: Storage'Spppiies and Repairs Other than supplying refrigerant, few supplies and repairs are needed for cold storage. However, CA storage requires the purchase of carbon dioxide scrubbers, such as caustic soda, which is a significant expense. Additional expenses, although minor, would be caulking compound and charcoal. 65 Repairs are also more costly for CA storage than cold storage. Before each season, the storage rooms are inspected, renovated and repaired to maintain air- tightness. During the storage period there is a continual effort to prevent gas leaks and maintain the equipment used in monitoring the storage atmosphere.59 Therefore, the costs in this category are $.055/ bushel/7 months of CA and $.Oll/bushel/4 months for cold storage. The month costs per bushel for CA and cold storage are $.0079 and $.0028, respectively. Product-generated atmosphere packages would utilize the same facilities as cold storage. Monthly costs for storage supplies and repairs should not be affected ($.0028/bushel/month). Since the storage season lasts six months or 50 percent longer, seasonal supply and repair costs will reflect the extra use. The seasonal cold storage cost for supplies and repairs will be increased 50 percent to represent these costs for product-generated atmosphere packages. The seasonal cost per bushel is $.0165. Section 5: Energy Energy is the main component of operating costs. Energy used to operate refrigeration and CA equipment 59Ibid., pp. 28-29. 66 is the primary energy expense. Energy requirements for lights and miscellaneous items are insignificant. On a month to month basis, energy expenses are erratic. The first month of storage has the greatest energy requirement because of the need to rapidly cool the apples. The following months also fluctuate because of changes in seasonal temperatures. In this analysis, the energy costs are a per-month average for the storage season. The energy expenses for cold storage is $.06/ bushel/4 months, or $.015/bushel/month, and, for CA storage, is $.13/bushe1/month, or $.0186. CA storage maintains a temperature of 3.5°C for McIntosh as Opposed to +.5°C in cold storage. The energy required for refrigeration during the first four months of CA storage would be less than the energy needed for four months of cold storage. However, this lower energy- requirement is offset by the power needed to refrigerate during the succeeding months, which will be warmer, and the operation of carbon dioxide scrubbers and other CA equipment. The optimum temperature of the atmosphere for a product-generated storage package is 3.5°C. To achieve this temperature inside the package, a lower storage temperature will be needed. It has been shown that at the same storage temperature, crates with polyethylene 67 liners have an internal temperature that is 1°C greater than unlined crates. These were unsealed liners.60 When air flow is restricted, a lower temperature is necessary to maintain the temperature of the air around the apple. If a sealed package were used, it is conceivable that the storage temperature needed to establish a 3.5°C internal temperature may be close to the cold storage temperature of 0-1°C. When comparing the energy expense of product- generated storage packages to CA storage, the added refrigeration cost for the storage packages is partially offset by several factors. Refrigeration for the product-generated storage packages does not include the seventh month, May, which is the warmest storage month. Also, the storage packages would not utilize a carbon dioxide scrubber or most of the other CA equipment, all of which require energy to operate. From this discussion, it is assumed that the energy requirements for CA and product-generated storage packages are approximately the same, $.0186/bushel/month. The seasonal energy costs would be $.1116/bushel/6 months. 60D. H. Dewey, H. J. Raphael, and J. W. Goff, "Polyethylene Covers for Apples Stored in Bushel Crates on Pallets," p. 206. 68 Section 6: Summapy The storage costs for the three methods are summarized below. Costs are presented on a monthly and a seasonal basis. Table 5 summarizes costs of storage methods on a monthly basis. Product-generated storage packages have the smallest monthly cost per bushel, even though manage- ment and energy costs are greater than cold storage. CA costs are almost 28 cents greater than product- generated atmosphere packages on a monthly basis. TABLE 5.--Storage Economics on a Monthly Basis. Dollars/Bushel/Month Cold C.A. (Prgdgct- generated) Building & Equipment .0340 .0416 .0227 Labor .0025 .0025 .0025 Management .0015 .0023 .0023 Supplies & Repairs .0028 .0079 .0028 Energy .0150 .0186 .0186 TOTAL $.0558 $.0729 $.0489 Table 6 summarizes the seasonal costs of the storage methods. The total costs show that product- generated storage packages will provide a storage period 69 that is two months longer than cold storage for a cost of $.07/bushel. The additional month provided by CA storage would almost cost an extra $.22/bushe1. TABLE 6.--Storage Economics on a Seasonal Basis. Dollars/Bushel Cold C.A. (Prgdfict- generated) Building & Equipment .1360 .2910 .1360 Labor .0100 .0180 .0150 Management .0060 .0160 .0138 Supplies & Repairs .0110 .0550 .0165 Energy .0600 .1300 .1116 TOTAL $.2230 $.5100 $.2929 CHAPTER VIII CONCLUSION The product-generated atmosphere is a unique concept from a packaging perspective. Presently, packaging is used to protect or maintain the internal conditions of the package. Producing conditions that extend storage life would be a new function for the package. Product-generated atmosphere package is not a proven method in the storage of fruits and vegetables. The results of this study do indicate that product- generated atmosphere package is a feasible storage method. It is feasible not only in terms of storage, but also in terms of economics. Further work is recommended to establish product-generated atmosphere packages as a viable storage method. 70 B IBL I OGRAPHY 71 BIBLIOGRAPHY Allen, F. W. (1937). 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"The Relationship Between the Rate of Respiration of an Apple Fruit and its Content of Protein. II. The Value of the Relation Immediately after Picking and at the Respiration- Climateric for Several Varieties of Apples." J. Hort. Sci. 29(4):98-103. Hulme, A. C. (1954). "Studies on the Maturity of Apples. Respiration Progress Curves for Cox's Orange Pippin Apples for a Number of Successive Seasons." J. Hort. Sci. 29(4):l42-l49. Jabbari, A.; Mohaenin, N. N.; and Adams, W. S. (1971). "Analog Computer Model for Predicting Chemical and Physical Properties of Selected Food Materials. Transactions, American Soc. Agri. Eng. 14(2): 319-325. James, W. O. (1953). Plant Respiration. Oxford Claredon Press, England. James, W. O. (1973). An Introduction to Plant Physiology. Oxford University Press, England. Jurin, V. and Karel, M. (1963). "Studies on Control of Respiration of McIntosh Apples by Packaging Methods." Food Technology 17(6):104-08. 76 Karel, M. and Go, J. (1964). "Control of Respiratory Gases." Modern Packaging 37(6):123. Kidd, F. and West, C. (1930). "The Gas Storage of Fruit. II. Optimum Temperatures and Atmospheres." J. of Pomology (Hort. Sci.) 13:67-77. Kidd, F. and West, C. (1936). "Gas Storage of Fruit. VI. Cox's Orange Pippin Apples." J. of Pomology (Hort. Sci.) 14:276-94. Kidd, F. and West, C. (1936). "Recent Advances in the Work on Refrigerated Gas-Storage of Fruit." J. of Pomology (Hort. Sci.) 14:299-316. Kidd, F.: West, C.; Griffith, D. G.; and Potter, N. A. (1950). "The Degradation of Starch in Apples Removed from the Tree at Different Stages of Development." J. Hort. Sci. 25:289-296. Levitt, J. (1974). Introduction to Plant Phygiology. C.V. Mosby Company, Saint Louis, Mo. Looney, N. E. (1971). "Interaction of Ethylene, Auxin and Succinic Acid -2,2-Dimethy1hydrazide in Apple Fruit Ripening Control." J. Amer. Soc. Hort. Sci. 96(3):350-353. Lougheed, E. C.; Franklin, E. W.; Miller, S. R.: and Procter, J. A. (1973). "Firmness of McIntosh Apples as Effected by Alar and Ethylene Removal from the Storage Atmosphere." Can. J. Plant Sgi. 53:317-22. Mathias, G. A. (1967). "Cost of Storing North Carolina Apples." Economics Information Report No. 5. N.C. State Univ., December, 41 pp. McLean, D. C.: Dedolph, R. R.; Dilley, D. R.: and Dewey, D. H. (1969). "Effects of Cyclic Anaerobiosis of Pome Fruits." J. Amer. Soc. Hort. Sci. 94:221-23. Meherink, M. and Porritt, S. W. (1972). "Effects of Waxing on Respiration, Ethylene Production and Other Physical and Chemical Changes in Selected Apple Cultivars." Can. J. Plant Sci. 52:257-59. 77 Meherink, M. and Porritt, S. W. (1973). "Effects of Picking Dates, Delayed Storage, Storage Temperatures and Storage Atmosphere on the Quality of Starking Delicious Apples." Can. J. Plant. Sci. 53:593-95. Meherink, M.: Fisher, D. V.: and Lapins, K. O. (1973). "Some Morphological and Physiological Features of Several Red Delicious Apple Sports." Can. J. Plant Sci. 53:335-39. Michigan Apple Committee, Report 1—13, Jan. 23, 1976 through April 16, 1976. Michigan Apple Council, Newsletter No. 9-17, Nov. 6, 1975 through March 3, 1976. Murata, T. and Minamide, T. (1970). "Studies on Organic Acid Metabolism and Ethylene Production During Controlled Atmosphere Storage of Apples (Mallus pumila Miller, cv. Rolls). Plant and Cell Physiologyfll(3):857-63. Pekmezci, M. (1970). Interrelations Between the Carbon Dioxide and Oxygen Concentrations of the Cell Sap and of the Internal and External Atmospheres in Fruit of Different Pome Fruit Varieties. Diss. rhein, Friedrich Wilhelms, Univ. Bonn, pp. 92. Porritt, S. W. and Meheriak, M. (1973). "Influence of Storage Humidity and Temperature on Breakdown in Spartan Apples." Can. J. Plant Sci. 53:597-99. Potter, N. A. and Griffiths, D. G. (1947). "Effects of Temperature and Gas Mixture on the Production of Volatile Substances by Apples During Storage." J. Hort. Sci. 23:171-77. Price, C. A. (1970). Molecular Approaches to Plant Physiology. McGraw-Hill Book Company, New York. Rasmussen, M. P. (1961). "The Effects of Plastic Timers on the Storage Behavior of Apples." Int. Inst. of Refrig. 1961:309-14. Recommended Conditions for Cold Storage of Perishable Produce (1967). International Institute of Refrigeration 117, Boulevard Malesherbes, 75, Paris, France. 78 Smith, W. H. (1954). "The Structure of the Mature Apple Fruit in Relation to Gaseous Exchange." VIII. Congres International de Botanique, 405-407. Smock, R. M. (1942). "The Influence of One Lot of Apple Fruit on Another." Proc. of the Am. Soc. Hort. Sci. 40:187-92. Street, H. E. and Cockburn, W. (1972). Plant Metabolism, 2nd ed., Pergamon Press, Oxford, Great Britain. Stout, B. A.; Dewey, D. H. and Mrozik, R. F. (1971). "Mechanical Orientation of Apples and Related Fruit Characteristics." Agr. Exp. Stn. Mich. St. Univ., Research Bulletin No. 32. Thompson, J. C. (1962). "Apple Storage Costs in New York." Agricultural Experimental Station Res. ‘gl, Cornell UniVersity, 56 pp. Tomkins, R. G. (1960). "The Biological Effects of the Conditions Produced in Sealed Plastic Containers by Prepackaged Fresh Fruit and Vegetables." Bull. Int. Inst. Refrig. Annexe 1961, 1:233-41. Tomkins, R. G. (1961). "The Changes in the Concentration of Carbon Dioxide and Oxygen Produced Within Sealed Plastic Packages by Fruits and Vegetables." Int. Inst. Refrig. Annexe 1961, 1:315-23. Tomkins, R. G. (1962). "The Conditions Produced in Film Packages by Fresh Fruits and Vegetables and the Effect of these Conditions on Storage Life." J. Applied Bacteriology 25(8):290-307. Tomkins, R. G. (1962). "Film Packaging of Fresh Fruit and Vegetables--the Influence of Permeability.“ The Inst. of Packaging Conference Guide - 1962, pp. 64-69 Troyan, A. V.: Mel'nichuk, L. 1.; and Kedesh, S. S. (1972). "Determining the Intercellular Volume in Succulent Fruit." Pishshevaga Tekhnologiya, No. 3, 183-84. Van Doren, A. (1937). "Physiological Studies with McIntosh Apples in Modified Atmosphere Cold Storage." Proc. Am. Soc. Hort. Sci. 37:453-58. 79 Veeraja, P. and Karel, M. (1967). "Control of Atmosphere Inside a Fruit Container.” Modern Packaging 40(2):168—l75. Walls, L. P. (1942). "The Nature of Volatile Products from Apples." J. Hort. Sci. 20(8):59-67. Woolrich, W. R. and Hallowell, E. R. (1970). Cold and Freezer Storage Manual, Avi Publishing Company, Inc., Westport, Connecticut. Unpublished apple packing cost information, Dec. 1975, Brown, N., County Building, Grand Rapids, Mich., and Pierson, J., Dept. of Agri. Econ., MSU, East Lansing, Mich. APPENDIX 80 APPENDIX Section 1: Assumptions The assumptions made in the computer simulation are listed below: 1. 2. Apple metabolism adjusts instantaneously to any change in the atmosphere. Solubility of oxygen and carbon dioxide in apple sap at a given temperature is equivalent to water solubility constants. . Temperature effect on metabolism is additive to the oxygen-carbon dioxide effect. Temperature does not affect the R.Q. No physiological disorders in the package. Internal package humidity and apple transpiration are not factors. 81 82 Section 2: Values for Program Parameters This section quantifies the parameters of equations (1) and (2), with the exception of "RR(p ,p ,T)." The 02 CO2 computer program symbols are in parentheses. Three films were used in the simulation. They were chosen On a basis of relative permeability rates. 1.CblldkEEmkxfiBte 3 . . a. {so (PEROZZ)=2.44x10-4 cm xstandgrd taup. &garess x cm thickness 2 an )thouritaumemene b. activation energy for oxygen (EPOQ) = 4200 kcal/mole -3 cm31xoo ho nod Quthfluwmu CNN Ob ma mwoccm Ccaaadwocubzu 2n «(9 map mwnaauzmomnmmtwdammbuuma w UGNIOCQ ucumzu Udofiantfid Ncu 02¢ No to ”scuhcabzwwmmwlN mu 0 on No. .8111111111...11.11.111.1..1.1..1..111..11111111..11..11..1..11...1 1 881118118811 - . - 81mm.1111111.“.111111111111“swamps 1 .. In rb¢\ (do 0 0 0&041 an N can > 1&1 m a 81.1111111111111111111111111111111 . .. . ..111.1. 1111111111111 11111111111111.1111 8. 8111811111111... ......1111...1..1.111111118111818111.111.11.881. 04h hd mbzmhm200. whudna¢mzdwa wad Nooawa 02¢ mmwwuz~vu C o no 8.111.111P111111.111.1.1..111.1111111.1111111 cub oulmb hd Nou 62¢ NO to muubuduoadom u!» udcamwwMNWJWMNWMN Nmmm o .n a damn .. 8.8.. 8.811.111.181111111811811111 1 .awzmmm.a awn” so. , no a on. u acosuuww wasnmwmuuwcwhucn JCIWbem uamxo m zwoumwoo «sane mxon: can mumuuax u».mz u: a :axunaww* mum 21.1muflwn=m¢¢¢..mmam .o a-£=\ Q>U2Uo b:- xndmu >W: ufluwunWHMMGmwwumutmmmoxwmfi n-Nhtuueunnofl amuse: “zen nu hawtmuouuuummwummu u an .m>¢o on do mcaox .Ns mu lambcdalum no “wmwmumoucun u 1 .. owouxouo c h a ) mu NO 8 :4 u 1111.1.111.11.1111.1111111111.1 1.1111.11111.1.11.11.11 1 nhzchmzou runauncuta w>~bomawwa u!» Had NNoodwa 98¢ NNOdwn u .8. 8 .. .88111111111111 111.11111 11..1.11 1 8 oflaut 2w Dummwanxw wmw2¥o~zh an In 88.8.... .8. 8. .. 8...... 8. 81.811181 18.118111 1 .. . 888.811.118112.1.1.1.11 1 .. . . .. . .11..1.1.111...11.1..1.11111.....1.111.11..1..1 1 11111....1 11 .. .111 1.8.1.1111 no... INNon 8-11.81.1111 .. «mnmmemmmmm .n \..k.s.o..uo.m.n\uuhm»~mu«a awe-hathao.h9h2m aw tutuonwuwuwm u a mac; mnoosouNo osxsc\m- odtomoo tut unhao ns\ns uwdccc 4¢¢QOCQ 90 .Hmammd Emumoumnn.mlo~ musmfim can accouuno-oodboucueh1880k a.” u83h cuttu 2 a b Jaca¢u ¢ 81 mzo bbuaomwmuuWQ w and .111..11M.11.11111 111111..11.1M1111..11111111. . 1. m m o o z *hmozwu wmdthmoxb< c2! ht“ Nut bcd towbcxunmuw exuutdxu mbdaatum 02¢ eNu uozwduuma Oh 80‘“ 6004 Oh w:8~*soo W 44H: tcuaoa& Hz» mane: aNs bczb mama u urn» md «80 MC 0 Odd 8.11.. ..11.111111111111 111 abuhcaaxuw fluctuzumb 44H: hzmzubdhw math 0 xdthuwtub mud .Oowh¢lnr¢wh o o o hmuxu ”Sanhuozoo 0Ho08u¢210oxan.axuh¢nwnu ch ”scubnozoo u~oa¢w«mmumm ”awn“ aNu ob co acowoo xummz omzouhu o $3ISO»ANNMWZWW n man» 0 no 111 1..1..1111.11111111.1. 11. 1111 11.1.1.1.111111 .. calcubdchzwuzou N00 and No acxcubzu aux u:* mac Nmuaumzc Nma a o . b uoo.~o a\ .0NO:&INO¢ ~4u981~oaxqa~8mmmu~ot aUwatuwt Nou math: auducxw Noo- mzcuu Suda“CMOMOMNWM8ummoW acne w n. 888... 88.8.. ...111.11.11.111.1...1..1.11.11..1.111.1.1.11 1 h s oat. a! N a .N manna .8:0D¥\Nou tCUUv whtu Icahcdnammi us» mu 8 u .0 coo-u\¢30¢m I 8 nuzuh.ohaNooa Noses» «add .Nd Nada mnoacodN. onsho\mo oucomoo gnu «Inna ns\ns «watt. IClWO¢t 9C1 « Uu-auoaaom us» mup¢4a¢¢upz~ .p.mo mm soupuzwu w .~.~oaom zonpozau a ma.o¢.«~. osssaxm. .«:.a.o 2pm an».o nssns uoaou soupuaan a an... a. gum . ‘muaa zaaumw o 23.3.: .«mwmnmfiu.unuummmu.umowfiw 3 o umma.-m.m«_.x. «unfiu.»a.w~u~ «oasb u s~.u«...usou....wmm...o-~...o:nn..\xa . 4». . swam w: mamas»... mam» “Wanna“... w a” ~oo go ppuau wm 2¢a¢ zmamuuzno .».~auaom zoupuzau « mnoac.«~c cuss-\m. eu:omoo 2pm dlbto ns\n~ ”0040” leuholau 532 .mmmm Gowuocdmll.mm wusmwm zaammm and mu .c..~un. cued .« mud.p¢zuou n tuna ~oua no; u: am an pzuya QWECCQ Oh XOMON b‘ OWmWhmw>WM? :WW WuWheuH 0 uauxuuo zona‘o o. ux¢ua= xuupuo «new:xmmxmun.dua buoauwno w .~ ...no~\.uu.uw*a*uammmam «um mwu .:« °.n~ zuwpwzau uuu mu 0 I m I 5.“... fimwmum- :5 .: .amom...«.m~.n.... .. 3... umnmw?flu&umwzmmuowomouummouommfimufiwum?w=mamuu .__.mafi m xx udoquu., >o um*n«wwm mwu mm umwmum “wuxwmg fimnuumwxm w n .mu:..¢u¢zuh pzu.¢z¢ m2» oz. mo.uu.u u p u Sn: 0 mauxona zoo¢.u ax. zua.xo no muaammmua 4¢~.¢¢a us» :0 can a a: o cox-ou mc¢ao a u.¢¢ zoub¢¢uawu¢ uz» wuu»~a¢ua.q.zo.pu2=u aux. o .w 2“» » uou; ~o¢.amuu :nnbuzqu a Uudt mac-couwo o~\se\mo eusomo: :hu duhno n~\n~ umufl leukozau 93 Section 4: Data from Simulations and Proof of Program This section presents the data from the simula- tion. Values are printed out for the following: 1. 10. 11. 12. l3. 14. 15. 16. 17. Material name Bag area Headspace volume Weight of apples External partial pressure of oxygen External partial pressure of carbon dioxide Oxygen permeability Carbon dioxide permeability Mils thickness Temperature, degrees Celcius Temperature, degrees absolute Solubility constant of oxygen Solubility constant of carbon dioxide Time, in days Internal oxygen concentration Internal carbon dioxide concentration Respiration Rate. Figure 23, 24 and 25 show the results of the simulations for cellulose acetate, low density polyethylene and polybutadiene, respectively. Figure 26 verifies the program by reducing the time increment from four hours to two hours. at 7°C. This simulation is for low density polyethylene BAG HAYFRIAL IS CELLULOSF ACETIYE 1628.1 SGUAQE CENTIHEFEQS 3A5 ARtA IS 1. Z. NYIWEYERS CE C V O CUB 3696.0 OF APPLES IN GPANS IS VOLUME I§ WEIGH' 2273.0 3. .21C OXYGEN IS 0F I983" DYOXIDE EtYERNAL PARIIAL PRESSURE IS E‘YERNAL PQRYIAL HE T ‘0. 13 oGC 5. HILS Y-CFLSIUS Y-ABSOLUTE SCL‘CZ SCL°602 C02 PEQWEAHXLIYV EA‘YLIVY 02 "6R4 .0553 .9915 276.5 3.5 1.: g - .16596.€251E- I? #22?- .2‘91?5 RESPIRQTION DATE \.‘ OYYG V ’NTRAYYOH . CONC YIN“ 94 ““0 ”MN :MMNNNNNNNNNN BJNNBINMINNNNN :8 wasmmmmm mmmmmmu‘mm mmmmmw muumnm .Dw mow-c ormcrmnrcmncrrccmoo.“concoc- DOU‘JQJJQJ’le-YJJJJJJ 313.931.? 3.943.? NN NtvNNNNNNNNNNNNNNN NNNNNWNNNNN 06": ”Min"? 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O . ndNMJm on (Rho-«Im- .vuut‘vsr Roam” ”cure”: .ua—umnfiruun«anUNGQMVNnflUM Figure 23-l.-Resu1ts of the Simulation for Cellulose Acetate. SOL-02 SOL°COZ T-ABSOLUYE Y°CELSIUS NIL? CO? 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