F». u T rat-«.vtvgx ;.f . ‘x- ; ‘3“"Fi'fi"';‘- ' ‘1: 7 :1“ , ;,\g".‘_~ '9‘.La..w. ARE £977 111111111111 11111 11111 1111111 3 1293 008229 0%ng "'1': Objectives ‘13:ng grain fi ‘33 the ma nautical me C I '3; A \ #: I": R A "Mfg et a Biribe the th filial data dev :3”! , her) the {It 'IE 3: attached t HA1 ‘M The mos 1‘- ""1 5'" U‘) I L3 J ABSTRACT Temperature Effects on . Lysine Availability and Grem Viability in Corn at Constant Moisture and During Drying BY Ralph Allen Gygax The objectives of this study were to define two changes in corn quality as affected by temperature and moisture content and to use reaction kinetics in an attempt to predict the effect of the temperature-moisture histories of two types of corn driers on those quality changes. Success in obtaining both objectives paves the way for using the resulting quality models with existing grain drying models to design corn dryers that do not heat damage corn. The thermal death model for the corn germ is derived through the use of statistical mechanics originally developed by Gumbel (1958) and applied by Rosenberg g£_§l. (1973) and is the first model to date to successfully describe the thermal death of the corn germ. The model is fit to experi- ‘mental data developed through the use of constant-moisture heat treatments; however, the model greatly over—estimates the thermal death of the corn germ when attached to a concurrent-flow drying model or to a fluidized-bed drying model. The most probable cause of this over-estimation is the existance of temperature gradients in the kernel because of the characteristic non- homogeniety of corn kernels and the large air-to-product temperature < c " "-w~‘n 'V v ... .‘vb-cu.&. w . .p‘.,..‘. 7‘ "‘ b-‘I‘i.¢»b€t . ‘- . . ‘ 1 2t 3, 1 - -3 .‘ , , ‘ . o-n. .. L‘ ' . "D‘ ~~£ .. “$5“ 52" .5‘." "‘ «wt. . r: "v: ‘\ '9 m as x “k s .Ner not} gradients which exist in the initial portion of the drying process. The drying models predict only average kernel temperature. The available lysine (AVL) model is a simple consecutive, first-order approximation of the actual reaction mechanisms. The first reaction repre- sents the effect of protein denaturation in making available more lysine for reaction. The second reaction represents the effect of nonenzymatic brown- ing in reducing lysine availability for nutritional use.» The data gave plots characteristic of the model. Heating times less than 20 minutes at 270°F and at moistures less than 16% w.b. increased AVL by as much as 50%. ) Heating at higher temperatures decreased lysine availability while heating ; at lower temperatures slightly increased or did not change the availability of lysine. Significant decreases in AVL were only found when heating was sufficiently severe to cause significant darkening of the corn and when there was an associated "roasted" smell which has been reported in conjunction with other nonenzymatic browning reactions by previous investigators. It was concluded that future work should focus on the detrimental effects of protein denaturation on processing quality. Future work on the nutritive values of corn as affected by high temperature drying should focus on the beneficial effects of protein denaturation. The thermal death model will be useful in predicting the quality of seed stock after drying or after storage under known temperature and moisture conditions. Correlation of any two quality parameters is not recommended because all modes of quality deterior- ation have their own characteristic rate mechanisms. Approved: / . gg’é/[fi/ 4:1 . Major Professor Department Chairman TEMPURATURE EFFECTS ON LYSINE AVAILABILITY AND GERM VIABILITY IN CORN AT CONSTANT MOISTURE AND DURING DRYING By Ralph Allen Gygax A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Agricultural Engineering 1977 DEDICATION This dissertation is dedicated to my parents Roy and Lucille Cygax who lacked college degrees, but not the wiSdom and the vision to guarantee mine. 11 .l‘ “,bL ..:: 5“" uV ' .....: "'1“ c “J a““ . E’ OVA": J;" o '5'.._- . I.a '- I ’Trrej‘ 1‘15"" “ 0" “‘ 3- Tu": ’ . Fl . ““ L Special ”searzh F011 ii: varie t}‘ hide The :5 'iiscons in i‘imzsity. Thanks :21" ‘L n5 Line 5 ACKNOWLEDGMENTS The author sincerely appreciates the assistance of all who have aided in this study. He is especially appreciative of the counsel and encourage- ment provided by his major professor, Dr. Fred W. Bakker-Arkema. Appreciation is also extended to other members of the Guidance Committee, Dr. Martin Hawley (Chemical Engineering), Dr. Dennis Heldman (Food Science and Nutrition) and Dr. Debra Delmer (Biochemistry). The author is especially indebted to Dr. Delmer who gave unselfishly of her time and allowed him the use of laboratory facilities'over an extended period of time. Special appreciation is also extended to the Anderson Agricultural Research Foundation of Maumee, Ohio, for their financial support and to a wide variety of people too numerous to mention from various institutions to include The Pillsbury Company, The University of Minnesota, The University of Wisconsin, and numerous agricultural science departments at Michigan State University. Thanks are extended to my wife, Beverly. Her encouragement and assistance during the years have been invaluable. iii o .1. ."i C _) 0., 2.2 2.3 2.4 re.) fo f“) f“) IQ T1 TABLE OF CONTENTS LIST OF FIGURES . LIST OF TABLES LIST OF SYMBOLS I. II. INTRODUCTION 1.1 Overview of the Corn Industry . 1.2 Objectives of this Investigation SURVEY OF LITERATURE . . . 2.1 2.2 2.3 2.4 Indices of Thermal Damage 2.1.1 Chemical Indices 2.1.2 Physical Indices Seed Viability as a Quality Index 2.2.1 Effect of Heat on Viability . 2.2.2 A Quick Indicator of Viability 2.2.3 Viability as Determined by Germination Germination . . . . . . 2.3.1 The Germination Process 2.3.2 Thermal Death of the Seed 2.3.3 Thermal Death Models 10 ll 11 11 13 14 The Effect of High-Temperature Drying on Corn Quality 14 2.4.1 Process Characteristics 2.4.2 Nutritive Characteristics iv 15 18 .4 I 2.3 39:6 :1“ 3.1 1’"): 393'“ V’ O V. 5 1 I R ‘ 3" T33. 3.3 W 3.5 The Tra 3.5 3.5 :- PROCEDL'RES 1.1 Heat T 1.2 Viabil 1.3 Availa 1.4 Varian .3 Labora III. IV. 2.4.3 Heat Damage to Amino Acids 22 2.5 Determination of Available Lysine 25 THEORY . . . . 29 3.1 Protein Denaturation, the Power Law, and Thermal Death . . . . . . . . 30 3.1.1 Protein Denaturation —- Structural Changes . 31 3.1.2 Protein Denaturation -- An Activation Process . . . . . 32 3.2 Thermal Death of Multicellular Organisms . 38 3.3 The Effect of Drying on Lysine Availability . 44 3.3.1 The Effect of Portein Denaturation 45 3.3.2 The Maillard Reactions . 45 3.3.3 The Reaction System in Corn . 50 3.4 The Complexity of Reaction Systems in Corn as Related to the Maillard Reaction . . 53 3.4.1 The Effect of Water Activity on Reaction Rates . . . . . . . . 54 3.4.2 The Chemical Composition of Corn . . 56 3.4.3 The Non-Homogeneity of Whole Kernal Corn . 60 3.5 The Non-Homogeneity of Corn with Respect to Transport Phenomenona . . . . 60 3.5.1 Moisture Isotherms and Heats of Desorption of the Component Parts of the Corn Kernal . 62 3.5.2 Lumped Parameter Heat Transfer . 64 PROCEDURES . . . | . . 66 4.1 Heat Treatments 66 4.2 Viability Determination 69 4.3 Available Lysine Determination 69 4.4 Variance of Heat Treatments . 71 4.5 Laboratory Scale Concurrent Dryer 73 3.3 11‘ (I) \l ) U‘ 0 UV U! U! 0 PO C fJ PJ '9 r-I 'v‘ Page 4.6 Fluidized Bed Dryer . . . . . . . 75 4.7 The Drying Models . . . . . . . 76 4.8 Parameter Estimation . . . . . . 80 4.9 Numerical Solution of Differential Equations . . 80 V. RESULTS . . . . . . . . . . . 82 5.1 Convective Heat 'rransfer-to TDT Cans . . . . 82 5.2 Effect of Heat and Moisture on Germination . . . 84 5.2.1 Germination Data . . . . . . . 84 5.2.2 Germination Test Variance . . . . . 85 5.2.3 The Effect of Heat Treatment Variance on Germination . . . . . . . . 85 5.2.4 Parameter Values of the Germination Model . . 87 5.2.5 Comparison of Model and Experimental Data . . 91 5.2.6 Moisture and Temperature Effects on Corn Germ Survivorship . . . . . . . 92 5.2.7 The Germination Model as Attached to the Drying Models . . . . . . . 92 5.3 Effect of Heat on Lysine Availability . . . . 98 5.3.1 Available Lysine Data . . . . . . 98 5.3.2 Available Lysine Analysis . . . . .104 5.3.3 Heat Treatment Variance Effect on Available Lysine . . . . . . . . -106 5.3.4 The Available Lysine Model . . . . .106 5.3.5 Comparison of Model and Experimental Data . .112 v1. CONCLUSIONS . . . . . . . . . .113 v11. FUTURE WORK . . . . . . . . . .115 BIBLIOGRAPHY . . . . . . . . . . .117 vi .u ..x xi: 5 Fa 7L p. h f 31C £22.. E ”KG -~. . “‘- Appendix Appendix Appendix Appendix Appendix Appendix Appendix Thermal Effect on Germination . Germination Data Plots . . . Germination Model and Date Plots . Germination Mbde1--Low Temperature . Germination Model--High Temperature Thermal Effects on Available Lysine Available Lysine Model and Data Plots-- Second Reaction only . . . vii . 148 . 154 . 158 . 165 [J L‘- c 3.3 3.5 3.6 ‘1‘4 o p—‘ 5.1 5.2 5.3 5.4 5.5 re Figure 3.1 3.2 3.4 3.5 3.6 5.1 5.2 5.3 5.4 5.5 LIST OF FIGURES Thermal Death of Multicellular Organisms . Scheme of the Non-enzymatic Browning Reactions (Hodge, 1953) Initial Stages of the Browning Mechanism -- Sugar Amine Condensation and Amadori Rearrange— ment (Hodge, 1953) . . . . . Consecutive First Order Reaction Mechanisms for Lysine Availability as Affected by Heat The Effect of Water Activity on Rates of Reaction (Labuza, 1975) . . . Desorption Isotherms of Corn Constituents at 50°C (112°F) (Chung and Pfost, 1967) Concurrent Flow Dryer with Counterflow Cooler . Residence Distribution of Corn in the Concurrent Dryer -- Bed Length of 2 Ft. (.061 m) . Available Lysine as Affected by Heat Treatments at 270°F (132.2°C) for various Times at Various Mbisture Contents . . .. . . . Available Lysine as Affected by Heat Treatments at 280°F (137.8°C) for Various Times at Various Moisture Contents . . . . . . Available Lysine as Affected by Heat Treatments at 290°F (143.30C) for Various Times at Various Moisture Contents . . . . . . Available Lysine as Affected by Heat Treatments at 300°F (148.909) for Various Times at Various Moisture Contents . . . . . . viii 48 52 55 63 74 97 99 100 101 102 5.3 M 3.6 13.1 1.2 1.3 M 1.5 5.6 5.7 B.2 3.3 B.4 B.5 B.6 C.2 C.3 C.4 0.5 Available Lysine and the Standard Deviation of the TNBS Determination as Affected by Temperature and Duration of Heat Treatment at 9 Percent MOisture . . . . First Order Portion of Mbdel . . Germination at 14% w.b. MOisture Content as Affected by Various Temperature-Time Heat Treatments . . . . . Germination at 16% w.b. Moisture Content as Affected by Various Temperature-Time Heat Treatments . . . . . Germination at 17% w.b. MOisture Content as Affected by Various Temperature-Time Heat Treatments . . . . . Germination at 20% w.b. MOisture Content as Affected by Various Temperature-Time Heat Treatments . . . . . Germination at 24% w.b. Moisture Content as Affected by Various Temperature-Time Heat Treatments . . . . . Germination at 28% w.b. MOisture Content as Affected by Various Temperature-Time Heat Treatments . . . . . Comparison of Germination MOdel and Data at 14% w.b. Moisture Content . . . Comparison of Germination MOdel and Data at 16% w.b. Mbisture Content . . . Comparison of Germination Mbdel and Data at 17% w.b. Mbisture Content . . . Comparison of Germination Model and Data at 20% w.b. Mbisture Content . . . Comparison of Germination Model and Data at 24% w.b. Mbisture Content . . . ix Page 105 111 136 137 138 139 140 141 142 143' 144 145 146 [J l J L)! 13.3 6.1 13.2 0.3 13.4 E.2 E.3 E.4 G.l G02 G.3 G.4 Comparison of Germination Model and Data at 28% w.b. Moisture - Germination Model at 14% w.b. Moisture tent for 2 hours - . . . Germination Model at 16% w.b. Moisture tent for 2 hours . . . . Germination Model at 17% w.b. Moisture tent for 2 hours . . . Germination Model at 20% w.b. Moisture tent for 2 hours . . . Germination Model at 24% w.b. Moisture tent for 2 hours . . . . Germination Model at 28% w.b. Moisture tent for 2 hours . . . . Germination Mbdel at 14% w.b. Moisture tent at High Temperatures for 6 minutes Germination Model at 16% w.b. Moisture tent at High Temperatures for 6 minutes Germination MOdel at 17% w.b. Moisture tent at High Temperatures for 6 minutes Germination Model at 20% w.b. Moisture tent at High Temperatures for 6 minutes First Order MOdel Fit to AVL data at 270°F (132.200) . . . First Order Mbdel Fit to AVL data at 280°F (137.7°C) . . . First Order Model Fit to AVL data at 290°F (143.30C) . . . First Order Model Fit to AVL data at 300°C (148.8°C) . . . Con- Con- Con- Con- Con- Con- Con- Con- Con- Con- Page 148 149 150 151 152 153 154 155 156 157 165 166 167 168 (3'! Eu .1, 1 IC LA.) Cc 8} A\ Cr. 01 Table 301 3.2 3.3 3.4. 3.5 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 5.10 LIST OF TABLES Page Basic Constituents of Corn (Motz, 1969) . . 57 Amino Acid Content of Protein Isolated from Maize Seeds (Wolfe and Fowden, 1957) . . . 58 Carbohydrates (Mbtz, 1969) . . . . . 59 Distribution of the Basic Constituents of Yollow Dent Corn Among the Fractions of the Kernel (mtz’ 1969) O O O O 0 O . O I 0 61 Net Heats of Desorption for Different Components of Corn for 4 to 20 Percent Moisture Content (W.B.) at 122°F (31°C) (Chung and Pfost, 1967) *. 65 Calculated Lumped-Parameter Heat Transfer Time Constants of Corn in TDT Cans . . . . 83 Germination Tests —- Mean, Variance and Pooled Variance of Control Samples . . .- . . 86 Variability in Heat Treatment Replication on Viability as Determined by Germination . .. 88 Germination Model . . . . . . . . 89 Concurrent Dryer -- Drying Air Temperature 260°C. 94 Fluidized Bed Dryer -— Drying Air Temperature 87.8°C . . . . . . . . . 94 Death Rate (%/Min.) at 1 Minute of Drying Time . 96 Variability in Heat Treatment Replication on Available Lysine Determinations . . . . 107 Available Lysine Mbdel . . . . . . 109 Comparison of Predicted First-Order Rate Constants of Corn with Published Data of Soybeans . . 110 Cl o rt. A.l F.l Thermal Effect on Germination Thermal Effects on Available Lysine . xii Page 131 158 ”I .J' LIST OF SYMBOLS a lysine molecule temperature dependent death rate constant, hr.-1 convective heat transfer area, 5g. m. a reducing substance, mole per mole proteinaceous nitrogen concentration of the forward transition state Species, mole per mole proteinaceous nitrogen concentration of available lysine, mole per mole proteinaceous nitrogen concentration of reducing substance, mole per mole proteinaceous nitrogen concentration of native protein, mole per mole proteinaceous nitrogen concentration of molecules of protein in which all side-chain hydrogen bonds are broken, mole per mole proteinaceous nitrogen concentration of additional produce, mole per mole proteinaceous nitrogen concentration of Schiff's base, mole per mole proteinaceous nitrogen concentration of water, mole per mole proteinaceous nitrogen average specific heat, Kcal. per kg. specific heat of drying air, Kcal. per Kg. specific heat of water vapor, Kcal. per Kg. specific heat of grain moisture, Kcal. per Kg. xiii Cl and C2 F3(t) f(t) half life viability constants, (% w.b.)‘1 and oC_1, respectively the difference between two measurements, units dependent on measurements degrees of freedom, dimensionless the rate of energy storage within an object, Kcal. per hour probability that the transformation from stage j is accomplished in a time interval of t, dimensionless probability density function for all stages of deterioration, hr.“1 probability density function for the jth stage of deterioration, hr.‘ energy of the system, cal. per mole air flow rate, Kg. per hour product flow rate, Kg. dry matter per hour free energy of the solution phase, cal. per mole partial molar free energy of water, cal. per mole free energy ofia system, cal. per mole free enthalpy of a system, cal. per mole absolute humidity, g. H20 per g. dry air enthalpy of activation, cal. per mole Plank's constant, Joule sec. convective heat transfer coefficient, Kcal. per sq. m. heat of vaporization, Kcal. per Kg. transmission coefficient, dimensionless equilibrium constant for the activated complex, dimensionless the hydrogen bond equilibrium constant, dimensionless Boltzmann's constant, Joule per °K xiv k* kv L 2 O N(t) ni activated complex theory reaction rate, hr."1 half—life viability constant, dimensionless appropriate rate constants, hr.-1 lysine masked by the protein matrix, mole per mole proteinaceous nitrogen moisture, % d.b. unless otherwise specified equilibrium moisture content, % d.b. unless otherwise specified original moisture content, % d.b. unless otherwise specified number of means averaged, dimensionless number of variances pooled, dimensionless initial population the number of moles of water, moles the population as a function of time ' power law Obnstant, dimensionless the number of samples read against one blank to determine the mean the number of moles of j constituents of a solution, moles per liter total number of sample—blank comparisons, dimensionless an addition product, mole per mole proteinaceous nitrogen pressure, Kg. per sq. cm. half viability period, days partition function for stable degrees of freedom, dimensionless partition function for native protein, dimensionless~ partition function for the transition state, dimension- less >0 1“- 2‘11 x12 xrs xzm partition function for unstable degrees of freedom, dimensionless the rate of convective heat transfer to an object, Kcal. per hour gas constant, Joule per mole °K total enthalpy of the system, Kcal. entropy of activation, cal. per mole the variance of each determination, units dependent on measurement pooled estimate of variance, units dependent on measurement temperature, 0C, °K, and 0F time, hr., min. or sec. the number of degrees of freedom associated with each s 2 and s dimensionless i p . velocity of motion along the reaction coordinate, mole per hour water molecule, dimensionless the mean of each determination, units dependent on measurement overall mean, units dependent on measurement the average of the determinations at the ith heat treatment, units dependent on measurement first determination for the ith heat treatment, units dependent on measurement second determination for the 1th heat treatment, units dependent on measurement probabilities that single hydrogen bonds exist, dimensionless probabilities that cooperative hydrogen bonds exist, dimensionless probabilities that double hydrogen bonds exist, dimensionless xvi .Ui £0 reag 60 trans f! (t) f’j energy level of native protein, cal. per mole energy level of the transition state, cal. per mole product temperature, °C, °K, and 0F thermal death rate as a function of time, hr.“1 density, Kg./cu. m. the probability of a immediate transformation, dimensionless time constant, hr.-1 xvii same; it is 1'" nec' feeds; am :.;Eyield 139r ‘ Since 1935 raze of 3.52 Vi flat and grits 2:2' for pancal-I used for pan tits are used :es of starch Stabilizers for tisture retent fcads, coating 51” terials sx sdcandies, a1 1'36 increased 1 Warison to 1 iiirease in 1111 11415 is in t1 I. INTRODUCTION 1.1 Overview of the Corn Industry Corn is a major feed crOp for the United States with an average of 93% of annual production being used for animal feeds. Corn is advantageous as a feed grain. It exhibits high digestability; it is a good energy source; it is well—suited as a constituent of nutritionally balanced, nuxed feeds; and it is an economical feed constituent because of its high yield per acre. Since 1955 food consumption of corn increased at an average annual rate of 3.5% with 5% of the 1970 harvest being dry milled into corn meal, flour and grits or wet milled into starch, syrups, and dextrose. Meal is used for pancakes, snacks, mush, cereals, muffins, and corn breads; flour is used for pancakes, baby foods, bakery products, cereals and snacks; and grits are used for breakfast cereal, snack foods and malt beverages. The uses of starch and starch in modified forms include: thickening agents, stabilizers for oil-indwater emulsions, gel-forming agents in confections, moisture retention agents in tappings and cake icings, bonding agents for fOOdB, coating and glazing agents for nut meals and candies, encapsulation 0f materials such as coffee sweeteners, dry dusting of bakery products and candies, and anticaking agents in materials such as powdered sugar. The increased use of corn sweetening agents (which are more economical in comparison to cane sugar) has been largely responsible for the recent increase in the use of corn products in food. The largest use of corn syrups 18 in the confectionery industry. -1- Com oil is cling industrie 32.353115. MC! :13 has caused [am has a v. awefmctional 1 :::;-er:ies, and . a3,licaticns has 15 ietists to a iteration of th idem corn 1 :atinimum aCC t‘ature, foreig given lot of cor fazzcrs considel Levels. One of the that chemical a1 Since the grade 15.119133 quali t wage, there “m. A130, th 1". ...10'1gh factOIS 1631 8 outside 0 ‘1 4% _ 2 _ Corn oil is recovered from the germ, a by-product of the wet-and dry- milling industries. Approximately half of the oil is used in cooking and salad oils. Increased awareness Of the importance of polyunsaturated fatty acids has caused a sharp increase in the use of corn oil in margarines. Corn has a wide variety of industrial uses. Corn starch and flour have functional properties such as viscosity, film formation, adhesive properties, and ability to suspend particles. The growth of industrial applications has resulted both from these prOperties and from the ability of chemists to adapt starch to fit specific industrial requirements through alteration of the starch (Senti and Schaefer, 1972). When corn is traded in the open market, official grades assigned by government inspectors provide the basis for pricing. The grade is based on a minimum acceptable test weight and on maximum acceptable levels of moisture, foreign matter, damaged kernels, and heat damaged kernels. A given lot of corn cannot be graded above the grade for which any Of the factors considered (except moisture content) is at less than acceptable levels. One of the primary short-comings of the present grading system is that chemical and Physical properties are not reflected in the grade. Since the grade is used at the point of initial sale of the product and reflects quality deterioration caused by subsequent handling, drying, and -storage, there is little incentive to the farmer to produce higher quality corn. Also, there is no method by which the purchaser can discriminate through factors other than those included in the official grade unless he deals outside of the normal trade channels. This is not practical at this time. ise °f h: stead“ ' azédfed r8 21:5 in qua: ‘ u .. "WN'RH h ,. .“~uéh M ii sellers . :5: 525590 1e Ream! 197 The neeC catewew 33 rapidity geranve. ' Qtain qualiti 511p mich V This st grain drying Evolved eXp trying-air c study attemp flange of gr The qua grain~drying {era Viabili to decrease 1... value avail 1:70 6 F ~ 260° _ 3 _ Use of high-temperature dryers is the primary cause of differences in the behavior of corn during dry-and wet-milling. This is necessitated by tirequired rapid, mechanized harvest. At the present time, major improve— nents in quality cannot come about through the present grain quality standards or through changes in the standards--which would be rigorously resisted by some sellers. Under present circumstances improvements in quality will be nnst feasible through improved equipment and education of equipment users (Freeman, 1971). 1.2 Objectives of this Investigation The need for studies of corn quality as affected by currently available high-temperature dryers is well-recognized. In spite of the energy situation, the rapidity with which grain must be harvested makes high-temperature drying imperative, especially in the humid, north-central region of the corn belt. Grain quality is greatly dependent on the time—temperature-moisture relation- ship which varies with the specific configuration of each dryer. This study is the first application of process modeling to high-temperature grain drying with respect to grain quality. To date all drying studies have 1Jrvolved exposing corn to drying processes of varying dryer configurations, iirying-air conditions, initial grain moistures and air to grain ratios. This Study attempts to relate grain temperature and grain moisture to the rate of dhange of grain quality. The quality parameters chosen for study are at opposite ends of the Brain-drying temperature spectrum in terms of sensitivity to temperature. Germ viability is most sensitive to small changes in temperature and begins to decrease at approximately 140°F (60°C) (Watson and Hirata, 1962); whereas, lysine availability begins to decrease at relatively high grain temperatures 176°F — 260°F (80°C - 126.600) (Mulhbauer éuui Christ, 1974 and Wall, 1975) :5 is relative ptsite extra: fit that thes: 2112 rates 0' The 01: jec axe changes 1 ii, second, t 13 the tetpera Stunts. 5 5:15 the rese iasign dryers. site-ration of it Considerat 15138 process and is relatively insensitive to temperature increases depending on moisture content. These two quality parameters were chosen because they do represent Opposite extremes in terms of grain drying temperatures and because it was . felt that these are sensitive to temperature and moisture levels only and not to rates of heating and drying. The objectives of this investigation are two-fold: First, to define some changes in corn quality as affected by temperature and moisture content; and, second, to use reaction kinetics in an attempt to predict the effect of the temperature-moisture history on grain quality during any drying treatments. Success in obtaining both objectives will pave the way for using the resulting quality models with existing grain drying models to design dryers. Thus, a design analysis will allow not only for the con- sideration of the economics Of capital investment and energy, but also for the consideration of the economics of quality deterioration caused by the drying process. 2:31 0f r15 aCCE-er 121-13. at r. . 1. ' 1 l:::."501‘JD ke $3....) occr Marcus :g processes litial grair gaeral inde: ling proces successful effect of dr flair method 5131'? incre ‘~" the liter It has :E'A‘erature- 3€éded (Free 5'3 diemica1 “Horatio- 311126, 197: II. SURVEY OF LITERATURE Much of today's corn is artificially dried with excessive heat which, while accelerating the drying process, produces detrimental side effects. Viability, nutritional quality, and millability of the seed are reduced; water-solUble proteins are denatured; browning reactions involving amino acids and carbohydrates produce some nutritional defects; and alteration of the wet-milling characteristics of gluten (a primarily saline—insoluble protein) occurs (Wall, 1964). Numerous investigations have been conducted by exposing corn to dry- ing processes of varying dryer configurations, drying-air conditions, initial grain moistures, and air-to-grain ratios. Attempts to find a general index of thermal damage as related to the behavior of the product duringprocessing and to its nutritive value as food and feed have been luusuccessful. The recommendations of most investigators regarding the €Effect of drying on grain quality have been conservative largely due to their methods of investigation. The result has been that operators have ISlowly increased drying air temperatures far beyond limitations specified in the literature without readily apparent damage to the product. It has been recognized that an investigation which considers the temperature—moisture history of the product during the drying process is needed (Freeman, 1973). If the deterioration of important nutritive and chemical constituents is to be predicted, a knowledge of the rate of deterioration as a function of temperature and moisture must be known (Labuza, 1972). A amber 5.11 a general file affecte: farts-rs, have it change ac. ticlngical sys .:,' nae r mkncm French a1 instigated . listase acti‘ aneiated vi' ii dehydrogel fiastase acti‘ ’19 Measuremer iii the effect “Teratures L .111111, and py _ 6 _ The following literature review presents investigations of the past amd methods which have been applied in food processing, to include: standard indices of thermal damage; seed viability as a quality index; processing characteristics affected by heat and moisture; nutritive de- gradation; and determination of available lysine--the limiting amino acid in whole grain corn. 2.1 Indices of Thermal Damage A number of investigations have been carried out in an attempt to find a general index of thermal damage to corn. Some of the indices, *while affected by heat, are also affected by varietal and cultural factors, have different characteristic sensitivities to heat and moisture, and change according to their own particular stoichiometry. In a biological system such as corn, these stoichiometric relationships are Either unknown or very complex (Labuza, 1972). 2.1.1 Chemical Indices French and Kingsolver'(l964), in search of an index of heat damage, jJrvestigated dehydrogenase activity as determined by tetrazolium salts, diastase activity and esterase activity. Diastase activity is inversely Correlated with drying-air temperature at the 1% level. Esterase activity and dehydrogenase activity are less sensitive to inactivation by heat than diastase activity, but varietal and cultural differences appeared to make the measurement of heat damage inaccurate. MacMasters 2531. (1954) stud- 1Ed the effect of initial moisture contents up to 40% w.b. and drying-air temperatures up to 150°F (65.600) on niacin, pantothenic acid, riboflavin, biotin, and pyridoxine contents of corn. Only pyridoxine content is ""° 1- ans 'L \- H‘s. H ‘nn .4; b‘s-iu Tuite E .‘EHQEratureS tisrure dec is perlanent MST-Ute COn _ 7 _ lowered by drying 40% w.b. corn at drying-air temperatures of 120°F (48.9°C) to 150°F (65.6°C). Varietal and cultural differences produced larger changes in pyridozine content than drying treatments. Glutamic acid decarboxylase activity (GADA) as determined by Linko (1961) was reported to provide a quick, reliable estimate of storage deterioration and protein denaturation caused by high-temperature drying (Bautista and Linko, 1962). The GADA test gives an indication of the enzymatic activity of corn. It involves the measurement of the quantity of carbon dioxide evolved from a mixture of 30g of ground corn and 15ml of a dilute solution of buffered glutamic acid maintained at 86°F (30°C) for 30 minutes. Linko and Sogn (1960) showed that the correlation co- efficient between the log of the "GADA's" and germination is significant at the 5% level. One sample takes 45 minutes for analysis, and ten Samples in series only require 90 minutes (Bautista and Linko, 1962). Mhlhbauer'ggngl. (1976) developed a method of correlating readings on a Hunter model D25D3 MJL colormeter with lysine content as effected by thermal damage. However, the method must be further developed in order to ‘take into account the effects of variations in maturity, frost damage and ulicrobial effects. 2.1.2 Physical Indices Tuite and Foster (1963) reported that corn dried at drying-air temperatures above 140°F (60°C) absorbs less water at relative humidities of 70-80% than corn dried at lower temperatures. The ability to absorb nmisture decreases with increasing drying-air temperatures, and the effect is permanent. Air flow rates, batch versus continuous flow, and initial moisture content do not have a significant effect. 23:23.1 heat :at'rei'ieme :5 iECl‘Jded refers to a ‘ gain use“ m at 1‘9 tit as loss efficiency 1 322853; how :5 kernel d5 {Sell and Hi eiasnern o. If SITESS _ 3 _ Holaday (1964) developed a method of indirectly measuring moisture distribution within the corn kernel by determining the electrical capaci- tance and d.c. resistance of the corn. Capacitance and d.c. resistance were linearly related for corn that had not been heat damaged. A similar plot for heat damaged kernels will produce points not on the linear regression line. This method was reported as being an accurate index of heat damage to grain. Other physical indices which are indicative of heat damage include percent heat damaged kernels, test weight (bulk density), percent stress cracked kernels , and susceptability to breakage. All except the last two are included in the present United States grain standards. Heat damage refers to a discoloration of the kernel due to high temperature. For corn, grain temperatures above 180°F (82.2°C) will cause visible damage; however, drying at kernal temperatures above 140°F (60°C) may result in hidden damage Such.as loss of fermentable carbohydrates or reduced wet- or dry-milling Efficiency .(Liebenow, 1972). Test weight usually increases during the drying [frocess; however, other factors which affect test weight include the degree ‘15 kernel damage, initial and final moisture contents and the grain variety (Hall and Hill, 1972). Stress cracks are fissures or fault lines in the EEndosperm of the corn kernal. Their severity is catagorized as singles-- ‘Nme stress crack--, multiple--two or more parallel stress cracks-—and dhecked--two or more stress cracks which intersect. Even mild drying will Produce singles but as the drying severity increases, the percent of multi- Ples and checks increase (Thompson and Foster, 1963). Unfortunately, stress Cracks are difficult to measure with any degree of precision and, thus, may never be included in the grain standards (Gygax £5 39,, 1974) Friability or susceptibility to breakage is also increased by iii-13' Ra rest-£113“ Of a 2133 5131111] 212310“ in "| 33.21: hand "M: :ester as Corn the treased {T1 aanaclaster :t‘euviabili ifrist gra‘ Evasion of ‘ ae seeds an After i q 7. [‘v "ility Of it the pri ‘1‘ um of appl -9... drying severity. A method for measuring friability through the use of the Stein breakage tester was developed by McGinty (1970). Thompson and Foster (1963) and Ratio (1975) determined that the amount of breakage as measured by the methods of McGinty (1970) is directly related to the severity of drying. Katic (1975) also found that drying in two passes with a moisture reduction of about 4% on the second pass reduced breakage. A storage period should be planned before the second pass in order to allow for stress relaxation in the grain. Stephens and Foster (1976) successfully related the measurement of the susceptability of corn to breakage determined with a Stein breakage tester to the susceptability of corn to breakage in a specific handling system, if gain moisture and temperature are the same in the tester as they are during handling. 2.2 Seed Viability As A Quality Index Corn that is viable does not exhibit decreased processing yields, increased friability or reduced nutritional value (Baird_gt_§1. 1950, and MacMasters 'g£.§1. 1959). The converse is usually but not always true--viability and not processing yield may be low because of freezing of moist grain, mechanical damage inflicted upon the embryo during harvest, invasion of microorganisms in the field or in storage, natural aging of the seeds and other reasons (Freeman, 1973). 2.2.1 Effect of Heat On Viability After investigating the:hfltuious effects of high-temperature on the viability of corn and other seeds, Robbins and Petsch (1932) concluded that the principle factors which decrease viability are the degree and time of application of the heat, the water content of the tissue, and the .3...“ that :iatilitj d r.:'.: iazreasi: titties ani =.::e:;eratur I. ‘ _.". . 3357;..12'83 . u. ’ .. . «it sETIcrc .?.:' ".‘bu . It “as 11' $11133 dea daffisters 3 late 11962) m, 1949) statutes 8130‘ minty 33 Problem sneak S1 Ettause 0f f‘ n :z-dete“ Erata (1952 Severe than 1 at Bishop 1 Several enZY? tetrazolium re - 10 - presence of liquifying or coagulating agents. Watson and Hirata (1962) reported that the drying air temperature which produced a significant drop in viability decreased with increasinginitial moisture of the grain and with increasing drying air humidities and flow rates. Increased drying air humidities and flow rates have the automatic effect of increasing drying air temperatures. Viability was destroyed when corn at 32% w.b. was dried at a drying-air temperature of 140°F (60°C), but 160°F (71.1°C) was the lowest temperature that destroyed the viability of corn at 21% w.b. moisture content. 2.2.2 A Quick Indicator Of Viability It was desirable to develop a quick test for viability, since corn which has dead germ is difficult to process and yields oil of lower quality (MbcMasters 25 a1. 1959). Baird $2.31. (1950), MacMasters 25 31. (1959) and Mbore (1962) suggest the T2 (2, 3, 5'-- triphenyl-tetrazolium chloride) test (Lakon, 1949) as a means of measuring viability. Corn that reaches temp- eratures above 140°F (60°C) during drying shows a definite decrease in viability as determined by the T2 test (MacMasters_gt-al. 1954). Problems have arisen with the use of T2 test. MacMasters_gt_al.(l954) and Schenk 25 a1. (1957) found that dead kernels can give positive TZ tests because of fungus activity. MacMasters gg_gl. (1954) reported no correlation (of TZ-determined viability with overall processing results. Watson and Hirata (1962) found that drying conditions which destroy viability are less severe than those which adversely affect wet-milling quality. MacLeod (1950) and Bishop (1957) found germination much more sensitive to heat damage than several enzyme systems, including dehydrogenase which is responsible for the tetrazolium reaction. The T2 test greatly over-estimates germination of grain dried in certain narrow ranges of air temperature and grain moisture. O x) r‘) . w Cerainatio imaéle mist safer-ed viat 5:5 as: be d0? 21:, may gen: E :ase of co rethod Oi fires a five The gen: Ttecretical b tletnlar act Etavior. Ti 3 thermal d. Eve net wit" iiieved in 113‘ ' u. “led to t - 11 _ 2.2.3 Viability As Determined By Germination Germination of a seed is accomplished by simply exposing the seed to favorable moisture and temperature conditions. Seeds which germinate are considered viable; however, all viable seeds will not germinate because some may be dormant and, if exposed to a cyclic temperature—moisture treat-_ ment, may germinate. Fortunately, dormancy is not a predominant factor in the case of corn; thus, the germination test is the simplest, most depend— able method of measuringhviability of corn. Unfortunately, the test re— quires a five to seven day lapse-time before results are obtained (Copeland, 1973). 2.3 Germination The germination process is complex and not clearly understood. Theoretical biologists have not yet developed adequate laws to relate the molecular activities of cells to their' macroscopic growth or death behavior. Thus, it is not surprising that attempts to explain germination or thermal death (the effect of temperature on reduced germination levels) have met with limited success. A moderate amount of success has been achieved in explaining the effect of temperature on the death rate of multicellular organisms (Rosenberg g£_§l. 1973). These methods can be applied to the thermal death rate of the corn germ. 2.3.1 The Germination Process Mayer and Shain (1974) define seed germination as "that series of steps normally occuring prior to the emergence of the radicle from the seedcoat." A germinating seed needs only water and oxygen in order to initiate a broad complexity of metabolic activities which fall into one 3.1.2.3 general ‘ ‘frESP’OYt 0‘ ‘1 rathesis ..' 11 ;. J1 Cf) -. rte‘olic changes :51: of the aCt :tte it"? 599d ‘ eiicljakeff-i‘iaf arization ind azivation of pr ::'rer of growth l'ne proteol :etidoses and a Last, starchy 1 :rteolytic sys 33731. Proteol .. Supplies th 351113113 also Eisination. ”so would no In compar Elatil‘ély ear 11:19 DNA rep] 11.115 Pr0duce 52101}, 30m ( 1811111 Clear 13191013139.“ 0 11351518 to d. 1 “1“?“ and Sh - 12 _ Of three general categories: 1) Breakdown of materials in the seed, 2) Transport of these materials from one portion of the seed to another, and 3) Synthesis of' new materials from the breakdown products. The metabOIic changes which occur in the early stages of germination are the result of the activity of various enzyme systems, which are either present in the dry seed or quickly become active as the seed imbibes water (Mayer and Poljakoff-Mayer, 1963). The complexity of changes which occur during germination include: the activation of proteolytic enzymes, synthesis and activation of proteins and other enzymes, activation or synthesis of a number of growth substances, and changes in membrane permeability. The proteolytic enzyme system of barley includes eight different peptidoses and as many as three proteolytic systems--those in the aleurone layer, starchy endosperm, and the scutellum (Mayer and Shain, 1974). This PrOteolytic system is markedly similar to that of corn (Chen and Varner, 19 73). Proteolysis in the aleurone occurs after the onset of germination but supplies; the necessary nutrients for subsequent growth. The breakdown of lipids also occurs relatively late with respect to the onset of ge‘I-Tnination. These two systems can, therefore, be eliminated, and germin- at1cm would not be blocked. In comparison, synthesis and activation of proteins and enzymes occur ]relatively early in the germination process. RNA systhesis occurs early WI\Ille DNA replication occurs relatively late, possibly because sufficient DNA is produced during seed formation to permit the initiation of germin- Some of the protein activation mechanisms which occur are insuffi- ation. Ciently clear. Present technology limits the determination of the time of development of protein systhesis and protein activation such that it is not possible to determine which of the two processes regulates germination (Mayer and Shain, 1974.) Hormones a sax-e been studi gitterellic ac aleurone layer adiarner, 19 gemination, 1 Present 1 physiological est adequacel knowledge , ch Studies Carried Out that increas faction in \ 120°C) tO 1: viablllty d 1. 01‘ “Eat 1"th 1400 at high te _ 13 _ Hormones and growth promoting substances, particularily gibberellins, have been studied widely. An interesting example is the production of gibberellic acid (GA) in the embryo of corn and its «iiffusion to the aleurone layer to induce hydrolase systhesis to include o(-amlyase (Chen and Varner, 1973). Other growth regulators have been shown to affect germination, but the mechanism by which they do so is not yet clear. Present knowledge of seed germination is rather limited so that the physiological and biochemical changes which occur during germination are not adequately understood (Mayer and Shain, 1974). With this limited knowledge, the specific cause of thermal death cannot be isolated. 2.3.2 Thermal Death of the Seed Studies conducted on the effect.ofheat on seed viability have been carried out from the viewpoint of storage. Ching 35 El- (1959) found that increasing the moisture content-from 5% to 10% causes a greater re- duction in viability than increasing the storage temperature from 68°F (20°C) to 104°F (40°C). Roberts (1960) expressed all known wheat viability data in a simple mathematical relationship: Log p1/2 8 kV - clM - czT where pl/2 = half viability period in days T = temperature, 00 M = moisture, % w.b. kv = constant c1 = constants For wheat kv = 4.22, CI - 0.108, and c2 = 0.050. Temperatures ranged up to 140°F (40°C). No generalized model for thermal death of seeds at high temperatures has been developed. itsenberg :i: as descri 2f dermal dea retried that $158 product T127 further : fations of I Irate limit: eetific math. I!“ ' u ions are the :rganization and reducing r zern. There h, frying is de rations have :ion in the torn will (18 hcorn, is its moisture 1w _ 14 _ 2.3.3 Thermal Death Models Rosenberg £5 21. (1971) presented evidence that protein denatura- tion as described by the activated complex theory equation is the cause of thermal death in unicellular organisms. Rosenberg 35 El. (1973) reported that the thermal death rate of multicellular organisms is described by the product of the activated complex equation and a power law of time. They further speculated that the proteins encountered in the vital functions of multicellular organisms denature most rapidly, and thus, may be rate limiting in the thermal death of multicellular organisms. The Specific mathematical relationships will be developed in Chapter III. 2.4 The Effect of High—Temperature Drying on Corn Quality High temperature drying affects the processing characteristics of corn by changing the water-binding characteristics of the starch. Indica- tions are that this is caused by protein denaturation which changes the organization of the protein molecule mafkedLy,altering its water activity and reducing the ability of sulfurous acid to break the disulfide bond in zein. There has been some controversy over whether or not high temperature drying is detrimental to the nutritive value of corn. More recent investi- gations have concluded that there may be an benefit in starch gelatiniza- tion in the case of the ruminant, and that only very severe heating of corn will decrease its nutritive value. Lysine, the limiting amino acid in corn, is subject to sugar amine condensation at high temperatures and low moisture contents. There is a trend in the use of in vitro (artificial environment) instead of in whn>(animal digestive environment) 24751.5 f0! 333190 site: preliminarj Brekke gt_ El- :5 tigh-tenperatui titternined by I it increasing (1' tithe Brabender teerature up to tinting-air ten Peplinski ar their properties 11Siiisity (measur taternoisture i ‘1 and starch g 231' aut r oclave s 111160); and r Starch wet flea n endosper protein that at” grinding into P1 Screen and is PE nine (Vatson ar starch creating 1.“ Sir . Marlon of s1 -15- analysis for amino acids. Procedures for lysine have been developed so that preliminary testing may be performed using in vitro analysis. 2.4.1 Processing Characteristics Brekke 53 a1. (1972) using a fluidized-bed dryer reported the effect of high-temperature drying on the dry milling quality of corn. Quality as determined by yield and fat content of the prime product mix decreases with increasing drying air temperature. Cold paste viscosity, determined by the Brabender amylograph, was also adversely affected. Drying air temperature up to 104°F (60°C) produced good quality corn. Limitations on drying-air temperatures are different for other drying configurations. Peplinski and Pfeifer (1970) found that steaming of corn grits alters their properties as measured by water-absorption index (WAI) and paste viscosity (measured on a Brabender amylograph viscograph). Increases in temper moisture level, in retention time and in temperature, increases WAI and starch gelatinization. MOisture contents ranged from 15% to 25%; autoclave steam temperature ranged from 212°F (100°C) to 266°F (136.66°); and retention times ranged from 2.5 to 45 minutes. Starch wet milled from badly damaged corn comes mainly from the floury endosperm and has a high protein content because of pieces of protein that adhere to the starch granules. The horny endosperm resists grinding into pieces small enough to pass through the fiber removal screen and is passed into the feed by-product at one—sixth the monetary value (Watson and Sanders, 1961.) Improper drying affects protein and starch creating numerous wet-milling difficulties such as: difficult and incomplete grinding with starch loss to the by-product feeds; poor separation of starch and protein resulting in low starch recovery and poor l .s»: starch' ‘4‘". _' 'iv‘r 356?:L3L U. ”$531 Of the In the we! :J‘ 9 site" the h‘J: :25. Nitroer 2g :geration stint! of sulf! 2; the starch :3 this process 19:21), examin: :Eserred that I Cried that thc mined the 1 Effective is t 51', thus, hre Haulfide bond 1964), They p tins of the ante distinc 131“ 9t al. 1103811 reduc Further study a111011 disulf -l6 - quality starch; difficulty in drying the corn gluten fractions; poor germ separation; low yield of oil; and poor color and high fatty—acid content of the oil (MacMasters 35 21. 1959). In the wet—milling process, shelled corn is steeped in 0.2% sulfurous acid for 40 hours at 115°F to 130°F (46.1 to 54.4°C). The sulfurous acid softens the hull and loosens the protein starch complex for later separa- tions. Nitrogenous material and minerals are dissolved during the steep- ing operation (Seeley, 1958). Cox ggwal. (1944) observed that the action of sulfurous acid is to disintegrate the protein matrix surround- ing the starch granules, thus releasing them. He observed the absence of this process in corn that was heated excessively. Watson and Sanders (1961), examining thin sections of horny endosperm during steeping, Observed that more starch was retained by heat-treated sections and con- cluded that the cause was denaturation of the protein matrix which contained the starch. The reason that the sulfurous acid steep is effective is that sulfurous acid disrupts the disulfide bonds in zein and, thus, breaks the protein network binding the starch (Wall, 1964). Disulfide bonds are covalent bonds between cysteinyl residues (Jones, 1964). They provide permanent constraints and limit possible conform- ations of the protein molecule.' Chemical modification of these bonds can be distinctly different from protein denaturation (Tanford, 1968). Frater et a1. (1960) showed that reducing the number of disulfide bonds in dough reduces the resistance of the dough to mixing and stretching. Further study of the effect of heat on the subsequent action of sulfurous acid on disulfide bonds in protein is necessary. McGuire and Earle (1958) noted that change in protein solubility is also related to decreased wet-milling quality. An investigation of the _ 17 - solubility of zein in water, 0.01N potassium hydroxide, trichloroacetic acid and Duponal-C showed a decreasing trend in solubility with increas- ing drying temperatures from 120°F to 200°F (48.9°C to 93.3°C). Solubility. of protein in water and potassium hydroxide showed the best promise but gave no indication that any drying-air temperature is critical; however, Tanford (1968) observed that the transition from native to denatured states is a "steep" transition which occurs within a narrow range of temperatures. Holaday (1964) reported the influence of initial moisture content on protein denaturation to be marked. Varying drying-air temperature limitations have been reported for corn which is to be wet-milled. Cox 3; a1. (1944) reported difficulty in processing corn dried at 180°F (82.20C) to 200°F (93.3°C). Thompson (1967) reported that a drying-air temperature of 200°F (93.3°C) can be used in a concurrent dryer without affecting wet-milling quality. He observed that most of the decrease in wet-milling quality occured during the initial stage of drying, when both grain temperature and moisture content are high. MacMasters gt_al, (1959) present extensive data show- ing that drying-air temperatures of 180°F (83.2°C) or higher damaged corn for use in starch production. Initial moisture of the corn and drying air relative htmridity were reported as being relatively unimportant. Watson and Hirata (1962) reported the same findings but noted that150°F (71.1°C) . at 40% relative humidity also reduces wet-milling quality. The initial moisture level did not influence milling quality but did affect viability. At 15% relative humidity 200°F (93.3°C) drying-air temperatures could be used. Foster (1965) found that starch yield decreases with increasing drying-air temperature up to 290°F (143.3°C). Various millability tests which give an index of wet-milling quality ‘...m' -Ogfi ..I,.:l.c~b\o v rl’A-Aflfi‘ l" u...:-.—-_ N‘v-tgfi. ~3--¢»..1 ‘ . n..." 1 3sweet we] Heat p‘ HT. *1 (D rals. ‘4." .5“; :«dLEs t he I _ lg - have been developed. Microscopic tests were developed by Cox_g£-§l. (1944), 'Wagoner (1948), Watson and Hirata (1954), and Watson and Sanders (1961). Abbreviated milling tests were developed by Watson £12. _a_l_. (1955) and Freeman and Watson (1969). Freeman (1971), while recognizing the usefulness of microscopic abbreviated tests, suggested that the best test is either a pilot plant test (Anderson, 1967) or a simulated wet-milling process of laboratory scale such as those developed by Lakon (1949), Wolf g£_al. (1954), Watson (1964), and Anderson (1963). All but one test (Freeman and Watson, 1969) require a lapsed time of two days and all require sub- stantial work time. Consequently, none are suited for routine evaluations of samples on a daily basis. Their primary use is to assist in investi— gating production problems of significant magnitude (Freeman, 1971). 2.4.2 Nutritive Characteristics Heat processing affects proteins, carbohydrates, lipids, vitamins and minerals. Denaturation of proteins enhances digestibility by proteases, while reaction of reducing sugars and other compounds with amino acids de— grades the biological value of proteins. Short-term heating of proteins tends to improve the nutritive value of many products, while high-tempera- ture, long-term heating tends to reduce the nutritive value of most products. Carbohydrates, while not of primary concern in food products, have been investigated with respect to the toxic effects of their degradative reaction products (Lang, 1970); however, starch gelatinization has possible beneficial effects in feed corn (Hale, 1973). Fats also have been investigated with respect to their degradation products (Lund, 1973). The water-soluble vitamins are less heat stable than the fat-soluble vitamins and trace minerals (Schoeder, 1971). Feed corn is of importance both as an energy _ 19 _ source and as a protein source. Its protein content averages just under 10% and must be taken into account when it is used as a constituent of mixed feeds, in order that they may be nutritionally balanced in the most economical feed mix and in order to conserve protein sources for food use (Lund, 1973). Investigations of the effects of high-temperature drying on the nutri— tional quality of corn have produced mixed results--some investigators conclude that there were no detrimental effects, while others concluded that, indeed, there were detrimental effects and, also, possible beneficial effects. Heusden and MacMasters (1967) emphasized the importance of invest- igating the effect of grain temperature on quality' rather' than that of drying—air temperature. Chow and Draper (1969), noting frequent outbreaks of vitamin E deficiency in monogastric animals, investigated the effects of high-tempera~ ture drying on vitamin E and fatty acid content. No effect was discernable. Jensen gg‘gl. (1960) reported no effect of drying-air temperature on riboflavin, miacin, or carotene; however, pantothenic acid levels decreased as drying-air temperatures were increased from 140°F (60°C) to 220°F (104.4°C). Lang (1970) listed that heat labile vitamins and heat stable vitamins. Heat labile vitamins include: ascorbic acid, vitamin B2, pantothenic acid, and thiamine; heat stable vitamins include: vitamin A, biotin, choline, cobalamin, vitamin E, folic acids, inositol, vitamin K, (niacin, pyridoxines, and riboflavin. Adams 25.31. (1943) found that kiln drying reduces the fermentable carbohydrate content of corn and attributes this effect to the possible formation of unfermentable dextrine. Hale (1973) presented data which sug- gested that high-temperature gelatinization may improve starch digestion by gymnmt. mg r’ed roas 'w'ted that I! :tres greater t IN energy sourc . 2‘. lever temps: 'rligh dryir eiithrist (l9 :shole keme ‘1: lysine we re marable dec filled by more Iiile equivale inExcess of 3 11% amino acid 7"ng to its \ fEady deficier loss through I "1 3 Protein 5 2‘1”“ of out With a drying temerature r1 iiiil'ltlonally HathaWay (if Mime ear reduct10ns of _ 20 _ the ruminant. Jensen ggigl. (1960) found no effect on the performance of swine fed roasted corn as an energy source; however, Hathaway g§_§l. (1952) reported that mature ear corn dried from 27% to 14% at drying—air tempera- ' tures greater than 140°F (60°C) is of significantly lower energy value as an energy source for rates as compared to the energy value of product dried at lower temperatures. High drying-air temperatures destroy certain amino acids. Mulhbauer and Christ (1974) determined lysine to be the most heat labile amino acid in whole kernel corn as compared to cystine and methionine. Small decreases in lysine were observed at 176°F (80°C) while cystine and methionine showed comparable decreases at temperatures up to 284°F (140°C). Lysine was re- duced by more than one-third in 30 minutes at a temperature of 284°F (140°C) while equivalent reductions in cystine and methionine requinaitemperatures in excess of 320°F (160°C). Liquid ion exchange chromatography was used for the amino acid determinations. Lysine has been found to be most heat labile owing to its very reactive epsilon-amine group (Lang, 1970). Lysine is al- ready deficient in corn protein (Kies and Fox, 1972) so that any additional loss through thermal damage will reduce the overall nutritive value of corn as a protein source. Wall g£_al. (1975) reported a slight decrease in the amount of nutritionally available lysine in product which had been dried with a drying-air temperature of 289.4°F (143°C). The maximum product temperature reached was 219.2°F (104°C) and the method of assessing nutritionally available lysine was the methyl acrylate method. Hathaway g£_§l. (1952) reported that the nutritive value of the protein of mature ear corn dried from a moisture of 27% to 14% at temperatures from 160°F (71.1°C) to 240°F (115.6°C) is adversely affected as evidenced by reductions of 182 to 32% in weight gains of rats. Corn was their source of 0". 1325 rangifi? ... 1:7 ' ..., “l, anc aeasxeé b" a t: m"? (15: :5 rate Of 5 :31. (1961‘ :s'ingair ti axed no di; respectively ': had no e 52:! infrare i 2.7.601: (82 , .etperature om then f F1973b) rep (100°C) as an; - 21 - protein for the eight-week feeding trial. Sullivan gt_al. (1973) compared protein utilization of rats. fed infrared roasted corn. They used roasting times ranging from 30 to 40 seconds to produce product temperatures of 176,. 212, 284, and 320°F (80, 100, 120, 140 and 160°C). Protein utilization, as measured by average-daily-gain, was significantly depressed by corn heated to 320°F (160°C). Jensen (1960) observed no difference in feed efficiency and rate of gain for swine of different ages fed corn dried at drying—air temperatures of 140°F (60°C), 180°F (82.200) and 220°F (104.400). Emerick 1. (1961) found that corn dried from 21 to 10 or 12 percent moisture at _e_t_:_ drying-air temperatures as high as 250°F (121.1°C) and 350°F (176.6°C) caused no difference in weight gains or feed efficiency for checks and rats, respectively. Mild scorching and over-drying occurred at these temperatures but had no effect on weight gains or feed efficiencies. Costa gt al. (1973a) used infrared roasting to produce temperatures of 179.6, 219.2, 260.6 and 287.6°F (82, 140, 127 and 140°C). There was no significant effect of temperature on protein efficiency for growing swine, as measured by average- daily—gain; however, significantly higher gain to feed ratios were experi- enced at 179.60F (82°C) and 287.6°F (142°C). High temperature treatments have other beneficial effects. Johnson .g£.§l. (1958) found higher dry matter digestibility for flaked, steamed, corn then for cracked corn, or steamed, dried and cracked corn. Costa gt al. (1973b) reported that growing swine prefer corn infrared roasted at 212°F (100°C) as compared to corn roasted at 176, 248, 284, and 320°F (80, 120, 140 and 160°C) and corn dried at 176°F (80°C). Jensen 3; 3;. (1960) also reported a similar observation when swine preferred corn dried at 220°F (104.4°C) over that dried at 140°F (60°C) and 180°F (82.20C). Sullivan st 21. (1976) reported increased feed efficiency for ruminants depending on the feed ration. High temperature drying has another potential effect on the nutritive value of \ _ 22 _ corn and other products in that naturally occuring growth inhibitors are deactivated or are destroyed. Wheat, rye, and buckwheat (and to a lesser extent, rice, oats, and maize) contain trypsin inhibitors. Cooking destroys the inhibitors in rice, wheat, and oats but not in other cereals (Bender, 1972). Mannggal. (1967) found that heating peanut meal at 212°F (100°C) for two hours at 20 percent moisture produces 80% reduction in levels of aflatoxin BI and Bz. Neucere gt_al. (1972) reported that moist heat at a temperature of 230°F (110°C) for one hour will destroy trypsin inhibitors and aflatoxin without damage to amino acids. Woodham and Dawson (1968) observed similar results for trypsin inhibitors. 2.4.3 Heat Damage to Amino Acids The view that the nutritive value of vegetable proteins and animal proteins of inferior quality is directly related to the nunber of lysine, epsilon-amine groups has been well-established (Boyne 3; El- 1961; Martinez g£_§l. 1961; Kakade and Liener, 1966; Blom g£_al. 1967 and Boctor g£_al. 1968). Protein in ordinary dent corn is deficient in lysine to the point that lysine is the limiting essential amino acid. Corn is also deficient in methionine and tryptophan but contains an over abundance of glutamic acid and leucine (Mertz gt El- 1964). The importance of lysine in corn stems from the fact that it is the growth limiting amino acid and, also, that it tends to be the most heat labile amino acid in most food systems. Block 35 al. (1946) reported that in certain food systems lysine appears to be the only amino acid which is damaged during heat processing. Exposures of wheat flour, egg, yeast and lactalbumin to temperatures of 392°F (200°C) for 15 to 20 minutes reduced biological values as determined by protein efficiency ration (PER). The addition of lysine restored the initial values. Halevy and Guggenheim (1963) :f the protei :ilized by t Serere SE 31 33? are hour L'Fbeat at 1 53:" 310m! ‘37 be Taduce 373112 is rm fizzle Change “MI (19 erred a com The low :29 - 23 _ found the same result using a mixture of wheat gluten and glucose. Experi- ments by Carpenter gg_§l. (1962) established that damage to amino acids is most severe at 4-14 percent moisture content. Dry materials are relatively A resistant to heat (Miller), 1956), andlxflling in excess water usually has no effect (Bender, 1972). Pomeranz gt §l° (1963) reported that more than half of the protein of wheat, when fed as the sole source of protein cannot be utilized by the animal organism for tissue growth becuase of lack of lysine. Neucere §£.al. (1972) found that dry and wet heat treatments at 248°F (120°C) for one hour have no effect on available lysine (AVL), but that both wet and dry heat at 266°F (130°C) for one hour cause reductions of AVL in peanut meal. Blom g£_al. (1967) reported that the biological availability of lysine may be reduced by heat treatments at 284°to 302°F (140° to 150°C). Available lysine is reduced by severe heating in ground nut cotyledons, but there is little change in the level of available methionine assessed using Streptococcus zymogenes (Anatharaman and Carpenter, 1969). Boyne gt §l° (1961), Carpenter and March (1961), Kakade and Liener (1966), and Boctor and Harper (1968) ob- served a correlation between available lysine content and the biological value of protein. The low natural levels of lysine in corn and the possibility that these levels may be further reduced by high-temperature drying have implications in the efficient utilization of corn as a food or feed protein source. If the hrelease of certain essential amino acids is delayed during digestion, or if certain essential amino acids are lacking and are not present at the site of protein synthesis at the same time, those that cannot be used for protein sythesis are oxidized (Melvick gt 3;. 1946 and Cook g£_§l. 1951). In addition to the need for all amino acids to be present at the same time, energy must also be present, and if not available in sufficient quantity, part of the amino acids will be oxidized and the nutritive value of the protein, lost (Bender, '7— 3:13:58 is subst Ease of start Processing is fellcviflg me Sistazces (in ' :ereeen amino 3 3'? protein - pr :13: by oxidati Friedman, 1972; bmflel syster Serent types 0‘ later 111. The type Sbleed that at “1h autoxidiz to 1300C) , the ilearly eStabj miStWe. and ii‘ége (10:13 1; 3‘: _ 24 _ 1972). Register and Peterson (1958) found that growth is depressed when sucrose is substituted for starch as an energy source. The sustained energy greleasemgf_starch parrellels the slow release of amino acids during digestion. Processing damage to lysine and other amino acids may include any of the following mechanisms: 1) reactions between amino acids and reducing substances (in the case of lysine, the terminal amine groups); 2) reaction between amino acids and carbonyl groups (Bjarnason and Carpenter, 1969); 3) protein - protein interaction (carbon-nitrogen linking); and 4) destruc- tion by oxidation (Lea, 1958, Ellis, 1959; Lea 25 a1. 1960; Finley and Friedman, 1972; Bender, 1972). Hodge (1953) summarized the browning reactions in model systems of carbonyls with amino compounds to include seven dif- ferent types of reactions. These will be described more extensively in Chapter III. The type of damage inflicted depends upon conditions. Lea £5 a1. (1960) showed that at temperatures below 212°F (100°C) lysine was lost by reaction with autoxidizing fat, while at higher temperatures, 239°F to 266°F (115°C to 130°C), the loss is independent of the presence of fat. It has been clearly established that temperature, time of heating, the presence of moisture, and the presence of substances such as reducing agents control the damage done to proteins (Bender, 1972). If the relative humidity of the atmosphere is as high as 70%, or the moisture content is above a certain limit, the Maillard reactions may take place at temperatures as low as 86°F to 104°F (30°C to 40°C). The reducing pentoses and hexoses play a part in these reactions (Blom 35 El- 1967). Evans_g£_§l. (1948) found autoclaving causes two types of inactivation of lysine--one, the reaction of lysine with sucrose and the other, the reaction of lysine with protein to render it un- available to enzymatic digestion in vivo. Hanks g£_§l. (1948) reported the reaction of methionine with sucrose and glucose to form a linkage not F:::'.;:zed by enzy airtime, and hi ease to form ar :étaéthat temper 221511 the avai txtcphan and hi sztrs-se, raffinos i: cavailab 1e (E §T2i‘JCtS can resr Hodge et a1. 3:25 occur larg Ms of amino < .4 u . “6‘ ans A numbe eponyl compoum remit of the Ma: 1953 and Lea, 1‘ tismre determif ii‘H L“ill the kerne 1; “he sucrose a The nutriti _ 25 - hydrolyzed by enzymes in vivo. Evans and Butts (1948) reported cystine, methionine, and histidine inactivation to be caused by a reaction with sucrose to form an enzyme-resistant linkage. Osner and Johnson (1968) sug- ' gested that temperatures above 212°F (100°C) for more than one hour can diminish the availability of lysine, arginine, methionine, cystine, leucine, tryptophan and histidine. Reducing and nonreducing sugars (to include sucrose, raffinose, and trehalose) react with lysine in proteins to render it unavailable (El-Hockinsky and Frampton, 1967). In reaction with reducing sugars, after the formation of a Schiff's base, several further products can result from Browning and Maillard reactions (Hodge £5 31., 1972). Hodge et a1. (1972) reported that the characteristic browned cereal aromas occur largely due to the thermal degradation of the Amandori com— pounds of amino compounds. These compounds result from the Maillard re- actions. A number of investigators have also shown that 002 and volatile carbonyl compounds are produced when cereal products undergo browning as a result of the Maillard reactions (Wiseblatt and Kohn, 1960; Linko £5 a1. 1963 and Lea, 1958). Corn kernels gradually become brown during oven-dry moisture determinations at 217.4°F (103°C). The greatest amount of browning within the kernel takes place in the region surrounding the embryo where most of the sucrose and reducing sugars are located (Motz, 1969), suggesting the possible importance of the Maillard browning reactions. 0n the basis of similarities between products formed during browning in model systems and browning in corn, it appears that the Maillard reactions or very similar reactions occur in corn (Hart, 1972). 2.5 Determination of Available Lysine The nutritive value of food protein not only depends upon essential zit: acid water :ezial 315130 at 941% the avai .2“: has become retained by d 313-. et a1. 19' :ilization (W trzzein efficie 2: information Keith varior it‘s direct me; aired infoma it has become i'te same time When cons P-fintiples mus 53138 Porces: film PIOport zlttlthm Val bialogital Va SW)! and p1 flied only b) Selimting 1 Gran an: Prfitein Sour availdb 19 am _ 26 _ amino acid content but also upon the physiological availability of the es— sential amino acids (Finley and Friedman, 1972). The chemical analysis of protein which is preceded by acid hydrolysis does not yield information con-' cerning the availability of the amino acids to a living organism. Lysine which has become unavailable is set free by hydrolysis and, although it is determined by chemical methods, is not accessible to proteolytic enzymes (Blom et a1. 1967). At the same time, biological values such as net protein utilization (NPU), biological value (BV), and gross protein value (GPV) and protein efficiency ratio (PER) measure only the limiting amino acid and give no information about the other amino acids, unless multiple assays are carried out with various combinations of supplementary amino acids (Bender, 1954). Only direct measurement of the availability of amino acids provides the re- quired information (Bender, 1972). Since direct methods have been applied, it has become clear that in some foods several amino acids may be damaged at the same time (Ford, 1962). When considering the nutritive value of any product, three basic principles must be taken into account: 1) Changes in the nutritive value during porcessing are of little value unless the product comprises a signif- icant proportion of dietary intake; 2) Inadequate assessments of the nutritive value of proteins can lead to false conclusions. Methods such as biological value (BV), gross protein value (GPV), net protein utilization (NPU), and protein efficiency ratio (PER) will reveal changes which are pro- lduced only by the limiting amino acid; and 3) The sulphur amino acids tend to be limiting (Bender, 1972). Grau and Carroll (1958) and Bender (1972) believe that in the future, protein sources will be evaluated on the basis of their proportions of available amino acids. Ideally, these methods should be chemical methods, ::at present, I Elude the vari: salable lysine Costs of as: :ftrinary impor arefere, be be atinn acid need: Wisely define nation. The 73in microorga- rtabolized by LYSine has tic}! 81178 very mica detern ilitrnbemne Elenesulfoni Leiner, (1969) All of th Slicific for 1 Preduct. The finder mild cor. 1%“ Cendit My the E _ tnreact. Ly: mtacted Pox-1 available Ph)’: PE 18 lwere d _ 27 _ but at present, bioassay is the only method available. The few exceptions include the various chemical methods available for the determination of available lysine. Costs of amino acids are dependent upon the protein source and will be of primary importance in the future. Estimates of protein quality must, therefore, be based upon the ability of the protein to supply the necessary amino acid needs of the animal. These needs, in themselves, are not yet precisely defined, because there are no precise standards for their deter- mination. The ruminant is even more complex than the monogastric, because rumen microorganisms utilize ingested food and, in turn, are digested and metabolized by the host (Grau and Carroll, 1958). Lysine has been studied widely and a number of tests for its availability which give very comparable results have been developed. There are three chemical determinations for available lysine content: 1 - fluoro - 2,4 - dinitrobenzene (FDNB), developed by Carpenter (1960); 2, 4, 6 - trinitro- benzenesulfonic acid (TNBS), developed for cereal products by Kakade and Leiner, (1969); and methyl acrylate, developed by Finley and Friedman (1972). All of the above tests modify the lysine epsilon-amine groups and are specific for lysine only. The compounds are first allowed to react with the product. The compounds are allowed to react with the lysyl side chain under mild conditions. These mild conditions are comparable to the physio- logical conditions during digestion (Kotaki and Satake, 1964) and, thus, only the E - amino groups of lysine which are nutritionally available tend to react. Lysyl side chains which are in the chemically or physically protected portions of protein do not react with the compounds and are not available physiologically. Once the reaction has gone to completion, the pH is lowered drastically to stop any further reaction and hydrolysis is minds. The I 37.10:: exchange Several UC :rzteins and 5C :5 available 1y 11;”. carbohydra 22erfere with the sample of e seller the amo 2::ent -- in t "he deteminati with data procu In compari File the FDNB Ethyl acrylate 51110 add anal- :""4119? and m _ 23 _ used to free either the reacted radicals in the case of the TNBS and the FDNB methods or the unreacted radicals in the case of the methyl acrylate methods. The respective radicals are analyzed spectrophotometrically or by ion exchange chromatography (Finley and Friedman, 1972). Several workers have compared the TNBS and FDNB methods with pure proteins and found that they agree quite well with biological determinations of available lysine (Finley and Friedman, 1972); however, in products with high carbohydrate content, colored products formed during hydrolysis tend to interfere with accurate spectrophotometry. Also, sample size (the larger the sample of either pure protein or carbohydrate containing material, the smaller the amount of available lysine detected), filtration, and lactose content -- in the case of milk (Posati g£_al. 1972) -- have an effect on the determination (Blom gt a1. 1960). If these are standardized, concurrence with data procured by more established methods can be observed. In comparing the three methods, the TNBS analysis requires two hours, while the FDNB analysis requires 16 hours (Kakade and Liener, 1969). The methyl acrylate method requires about an intermediate amount of time and an amino acid analyzer, but is well-suited for high-carbohydrate content products (Finley and Friedman, 1972). The TNBS method requires that blanks and samples be run in triplicate (Posati_g£_§l. 1972). 72?}:ng in the Tar? cozplex l ration kins" 1:; nutritiw faith of micr The obje iiiitive nuts”? 5 J-‘elop data i3131a: Pact III. THEORY The mechanisms of chemical reactions in biological systems such as whole kernel corn are complex. It has been the practice of individuals working in the applied areas of food and feed processing to approximate the very complex reactions which occur during thermal processing by simple reaction kinetics. First order reaction kinetics have been used in describ- ing nutritive degradation during heat processing or in describing thermal death of microorganisms during commercial food sterilization. The objective in assuming a simplistic model is to reduce the pro— hibitive number of experiments and associated costs required in order to develop data which will discriminate between a potentially large number of complex reaction systems. The results of a simplistic investigation yield insight into the complexity of a more thorough investigation and will give information which may be of as much use, practically, as that obtained from a more comprehensive investigation (Labuza, 1972). The general approach taken during this investigation has been, first, to search the range of variables for areas where there are reactions occurring; then, to cover those areas with a limited number of experiments; and finally, to use the limited data as quantitative evidence in order to demonstrate that the particular process behaves according to one of a few simplistic reaction mechanisms. Although the limited amount of data will not produce conclusive evidence for one reaction mechanism, the results will provide a general index for process design and a basis from which to make a defini- tive statement on the feasibility of conducting more thorough investigations. _ 29 _ ..\ .Ih- . ... .p-- a... r- -0." .II' o . -.—.~- -9 .‘ ‘ I. v- v :1; s.“ . ~~bs ‘ ~~ ‘ -« *‘b-gL'S .. I,“ *5 "\-..L’. g end D at M. u It] .- ‘ sc.a .‘ P. ,4 t]: 9 7;. _ 30 _ Two chemical attributes of corn were studied—~thermal death, as measured by germination (AOSA, 1965) and available lysine, as measured by the TNBS method (Kakade and Liener, 1969). Work in the area of bio— physics and statistical mechanics has produced models for the thermal death rate of multicellular organisms which can be applied to the corn germ (Rosenberg gt a1. 1973 and Skurnick, 1974). Hart (1972) has implicated the Maillard reactions, reactions between amino acids and re— ducing sugars, as producing decreased lysine availability. Although there is strong quantitative evidence, conclusive proof of either mechanism has not been produced. 3.1 The Thermal Death, Protein Denaturation and The Power Law There are three possible general mechanisms of thermal death: 1) There may be an increased rate of loss of heat sensitive structural and functional units such as cells, enzymes, and nucleo proteins; 2) The rate of utilization or destruction of some limiting non—replaceable metabolite, catalyst, or co-factor is increased by normal pathways at higher temperatures; and, 3) There may be an increasing rate of accumulation of some deleterious factor at the higher temperatures. The activation energies for the re— actions involved in substrate utilization or in formation of metabolic by products are small, whereas the activation energies for protein or nucleo- protein denaturative processes and processes involving important biological constituents as described in mechanisms of the first type are markedly higher (Strehler, 1961). . . u L‘ . " ~nal p ..- '1 A“ f 5“... . F “a“ 3:161 O - ‘l u-"' a ' . :ratttk’aLlC“ ' ' vac ::-:nrnt~_1 ~ the unfoldinfi IEdCthE’ gI’O enzymatic pf Proteir held togeths hands are r and are the EicalJmol.) and disul f: ital/n01.) hy _ 31 _ 3.1.1 Protein Denaturation (Structural Changes) Tanford (1968) defined protein denaturation as "a major change from the original native structure without alteration of amino acid sequence." Disruption of bonds (hydrogen and disulfide linkages) responsible for the secondary, tertiary, and quaternary structures of protein occurs during denaturation; the compact configuration of polypeptide chain unfolds into flexible chains showing random modes of coiling. During denaturation, some reactive groups of —NH -COOH, —OH and —SH are liberated; enzyme 2: inactivation may result from this type of denaturation. In the case of food proteins, denaturation increases susceptibility to proteolysis, and the unfolding of the coiled peptide chains brings to the surface many reactive groups (including amino acids) which were formerly masked from enzymatic proteolysis (Lang, 1970). Proteins are made up of more than 20 different amino acid residues held together by a variety of chemical bonds and other forces. Covalent bonds are responsible for the skeletal structure of the protein molecule and are the shortest bonds exhibiting the highest energies (30 - 100 Kcal./mol.). Covalent bonds form intraresidue linkages, peptide bonds, and disulfide bonds between.CYSt€1ne residues. Ionic bonds (10 — 20 Kcal/mol.) are the strongest polar bonds but are far less energetic than covalent bonds. Ionic bonds aneformed between the acidic and basic polar sidechains of lysine, arginine, aspartic acid, and glutamic acid residues; they can also be formed from interaction with the free terminal amine and carboxyl groups at the ends of polypeptide chains. The hydrogen bond (a polar bond) is the next strongest bond with an energy level of 2-10 Kcal/mole. The presence of the o(- helix in proteins is a result of polar bonding caused by hydrogen between_amide and carbonyl groups of peptides three residues apart. 4 a. u‘ 4 .v“ arr be 6‘ -— at. .s.. e "V- ? v ‘ P a D.» 5.. a. » A .H V. c . .a... u . I... .. N. _ 32 _ Van der Waals forces of mutual induction of dipole movements in electrically apolar groups and of repulsion between apolar groups in close proximity are less energetic, but equally important bonding forces. Also present is coulomb repulsion between charged groups of like sign (Jones, 1964). 3.1.2 Protein Denaturation (An Activation Process) Denaturation is accompanied by a change in free energy which results from the destruction of secondary bonding. Changes in the secondary structure alter the vibrational frequencies of bonded groups by increas- ing their vibrational freedom and alter the vibrational frequencies in the structural backbone through extra freedom resulting from unfolding. Major increases in free energy occur with changes in secondary bonding -— this is especially true of hydrogen bonding (Joly, 1965). The kinetics of protein denaturation can be developed in terms of activated complex theory. Gibbs' function defines the free energy for systems in which the state can be specified by temperature, pressure and variables of composition. Let G = H - TS (3.1) where G = energy of the system H = enthalpy of the system T = temperature, absolute S == entropy of the system The entropy is interpreted as an indication of the randomness of the protein molecule. With greater randomness there is increased entropy. When a protein molecule goes from a folded to an unfolded structure I. FF- 1. s... g: ",“ u ., ,- V'w 9 I ‘l 5 r n I‘D J rt» ' ”f I 41 F4- Ill -33- (denaturation), the change in terms of free energy is given by A G = Hun (3.2) _ H — T S + T S f fold unf unf fOld fold at COHStant temperature A G=AH- TAS (3.3) where AG AH 43 (Moore, 1972). free energy of the system enthalpy of activation entropy of activation There are three fundamental assumptions in activated complex theory: 1) The reacting molecules must traverse certain states of potential energy higher than the average levels of either reactant or product; 2) Molecules at the high potential energy levels are in statistical equilibrium.with the reactants; and 3) The rate of reaction is proportional to the con— centration of molecules at the high potential energy state (Glasstone gt El- 1941). It is possible to define a reaction coordinate along which movement corresponds to the transformation from reactant through transition state (activated complex) to product. Native protein may be imagined as an assembly of helical peptide fragments held in a rigid configuration by disulfide bonds and side chain hydrogen bonds. When these bonds are broken, the protein molecule is considered to be in an activated state. In the activated state the protein molecule is unstable, and one of the bond vibrations or a special combination of vibrations will lead to decay of the activated state into denaturedruntein, In other words, one of the vibrational degrees of freedom in the activated complex has a potential energy maximum rather than a minimum and is thus unstable. The partition function for this .n.“ ._; v"_ ,5 ov-O‘ 1 p- p. — w lies- .n‘ .-_ .:_r€ “L Q Lv ._‘ . V‘s .. ”7M _ 34 _ unstable degree of freedom, Qu’ multiplied by the velocity of motion along * the reaction coordinate, V , is equal to KkT/h. V‘k on where h T KkT/h (3.4) = partition function velocity of motion along the reaction coordinate = transmission coefficient = Boltzman's constant = Plank's constant = temperature, degrees absolute (Glasstone_g£.al. 1941) The reaction rate, k*, is given by k* where C* C* where K CN In terms of C9: where Qtrans e. trans 6° reag concentration of the forward—moving transition state species K CN (3.6) equilibrium constant for reaction concentration of native protein partition functions = Qtrans * exp (" Egtrans " €cavreag) * CN QN kT (3.7) partition function for the transition state partition function for native protein energy level of the transition state energy level of native protein '..o\f*" 7;...A-h- , _; V~v ,__ ... -.- ~;-a- ..C:'u-—~ u . u -; '5. st. “ . -. - 1., b ‘.‘ - u. :- .. ‘3 'n. u . ~x-r _ 35 _ Factoring the partition function for the transition state into two terms ~- one for the unstable degrees of freedom and one for other degrees of freedom = * 3.8 Qtrans Qu * Q ( ) where Qu = partion function for unstable degrees of freedom Q* = partion function for other degrees of freedom The reaction rate then can be simplified * _ _ k* = v* Qu Q exp Eb trans £0 reag) CN (3.9) Q kT reag — K kT . Q* exp — Bo trans - £0 reaé) CN (3.10) Qreag kT Defining the equilibrium constant * x - E - E K* = Q e P ( o trans o reag) (3.11) Q kT reag it follows to define quantitiesAG, AH, and A S which are the free energy, enthalpy, and entrOpy of activation. They are defined as the usual standard partial molar quantities of reaction. A G* = RT In K* (3.12) Am = RT2 3 1n 1(* (3.13) 48* = - 9 CRT. ‘p (3.14) where —2rfir_ p p = pressure The rate constant is then k* = .I(_1->m:¢ FZuLQUO 00.09,. PERCENT SURVIVORS _ 40 _ 00-031 00°05! 00 09 00 or SHOAIAHDS 1N33803d TIME Figure 3.1 Thermal Death of Multicellular Organisms _ 41 _ Z I — the initial population 2 A r? V II the population as a function of time (73> I temperature dependent rate-constant (defined by Eq. 3.29) n a power law constant Statistics of extremes show that under rather general circumstances order statistics for the first event can take on only one of three possible (asymptotic) forms one of these being the power law (Gumbel, 1958). An abstract representation of a multicellular organism may be a chain consist- ing of a very large number of links. The chain is assumed to break (the organism parishes) when the first link breaks, regardless of which link breaks frist. If the failure of a link is described by a sequential process, the transformation of a link from one state to another is equivalent to deterioration. Assuming that the link must go through o(units of deteriora- tion and that the time spent in each stage of deterioration is independent of the time spent in other stages, let the time spent in each stage of deter- ioration be described by some probability density function fj(t). Then, the cummulative distribution function, Fj(t), gives the probability that the transformation from the j to the 3 +11 state takes place in a time interval of length t. Assuming the probability of completion of a transformation from one stage to another is independent of the time spent in that stage, the failure mechanism is composed of stages which, individually show no aging characteristics (independent of time). Expressed mathematically 1 d F (t) 3,0 (3.32) 1 - F3(t) dt 3 j j(t) - probability that in the transformation from stage j is accomplished in a time interval of t. where F ’01 = the probability of an immediate transformation From1which it follows by integration that Fj(t) - 1 - e ""1C (3.33) _ 42 _ and differentiating f (c) - e" 3': (3.34) j 3 where f (t) 8 corresponding probability density function for each stage 3 of deterioration The time for the failure of a link, T¢(, is the sum of the time spent in all stages of deterioration. ex Tqa Z cj (3.35) 3 = 1 The distribution in time for the link failures and, thus, the death rate of the population can be found by Laplace transforms. Since -t .. S 2 ---e 3t ) (3.36) “ E(e"3Ta¢) =n(e'sztj)=8(e'3t1 . e i=1 with the "tj's" mutually independent it follows that the set '{h sti? is also mutually independent. Then E (e_ST") -- E (e‘scl ) - E (e'StZ) E (e‘SW ) (3.37) Since .9 E (e-stj ) =/e-St fj(t)dt a 1 {gm} (3.38) where fj(t) = the probability density for completion Letting f(t) be the probability density function for the completion of all stages of deterioration, combining Equations 3.37 and 3.38 gives {£13m} =j'fl'1o({£j(c)3 -R {ring-TX (3.39) which only applies if the time spent in each stage is identically distributed. Thus, Equation 3.34 becomes 133(8) =pe7’t (3.40) -43.. for 9 j “r { 1,633 to -st -/Ot ‘dgf-e Ice dt (lo/90+ s) (3.41) «({w} Taking the inverse transform gives the distribution in terms of T“ the time (PH/0+ s) (3.42) of thermal death for each organism. “‘1 -/°t l f(t) =,o (’01:) e / («x- 1) . (3.43) The probability that a link fails by time t is given by integrating the probability density function so that F(t) if“ f(u) du (3.44) O which becomes F(t) = l (0‘ . t ) (3.45) ———(u_ 1)! b” ,0 a function of the incomplete gamma function defined as [at -x “-1 ‘yfl «x t) :/I- e x dx yo 0 This differs from F (°(), the gamma function, since the upper limit is not infinity. If/at.is small, the incomplete gamma function can be expanded as M (0‘) F(t) = 3.7:... 2 P got)“ + S (3.46) («x-1): s-o («+s+1) 2 fl“ (3.47) O( _ 44 _ It is apparent that F(o) =0 and that F(€)>O for each € )0. Similarly ,Qén‘, F (Z;Dt) cg (ft) " o —"_ = T (3 48) F931;) ° for2r>10 Thus by Gnedenko's criterion (Gnedenko, 1943), there are constants an and bn such that F(ant + bn) belongs to a domain of attraction of the limited distribtuion Hfik(k) (t). Thus, the decline of a cohort as described by the kinetics of chain breakage is described by the power law (Skurnick, 1974). Two other forms may be derived for/9t large and/at of intermediate size. However, the case for/0t small gives the simplest analytical function and has met with the most success in being fit to experimental data (Rosenberg _e_§ g_1_. 1973). 3.3 The Effect of Drying On Lysine Availability The reactions taking place during high-temperature drying which have a direct effect upon the nutritional availability of lysine in corn.are denaturation and nonenzymatic browning. Protein denaturation functions to unfold the protein molecule and to bring amino acids (including lysine) which were previously buried in the protein matrix to the surface. The nonenzymatic browning reaction has the reverse effect and involves the reaction of the lysyl residues with reducing sugars to include glucose and fructose. Only a small percentage of other amino acids to include arginine, histidine, tyrosine, and methionine are involved (Lea and‘Hannan 1950 a,b). Kinetic modeling of these two reactions involves assuming that the rate at which lysine becomes available is preportional to the rate of protein denaturation and that the nonenzymatic browning system can be represented by a simple kinetic rate equation. - 45 - 3.3.1 The Effect of Protein Denaturation Protein denaturation unfolds the coiled polypeptide chains bringing to the surface many amino acids which were formerly masked from enzymatic proteolysis during digestion. The effect of denaturation in increasing lysine availability can be described by a first order reaction. Assuming that the rate at which lysine is made available is proportional to the rate of protein denaturation, the rate is given by -—-—-= le dt L where CA.” concentration of available lysine C = concentration of lysine masked from proteolysis by the protein matrix time ('1 ll k1 = first-order rate constant This form follows directly from equation 3-16- 3.3.2 The Maillard Reactions Hodge (1953) outlined an extensive system of reactions which are thought to be responsible for the degradation of protein in food systems (See Figure 3.2). Hart (1972) concluded that this system of reactions or a very similar reaction system is activated in corn during high temperature drying. The associated stoichiometry is very complex, and one would expect that, with changing temperature and the consequent shifts in equilibrium constants, the predominating reaction mechanisms will change. Reaction paths 1 and 2 (Figure 3.2) dominate at low temperatures. Schiff's _ 46 - (A) ALDOSE + AMINO ___._, N-SUESTITUIED + H o SUGAR COMPOUND *— cLYcOSYLAM'INE 2 , J _ r71 1' (B) AMADORI REfiRRANGEMENT 1—AMINO— l-DEOXY- 2-KETOSE (1,2-ENOL FORM) (1) (C) (2) (C) (3) (D) -3 H20 ; -2 320 + o4-AMINO ACID scam BASE I f 1 OF EMF OR FREDUCTONESJ STRECKER DEGRADATION FURFURAL y (E) -AMINO COMP'D + H20 +211 FISSION m PRODUCTS 3 (ACETOL, + HM]? OR DEHYDRO PYRUVALDEHYDE , FURFURAL REDUCTONES DIACETYL, ETC) ~ 3 I (F) ' (F) l ' l ' + AMINO (F) WITH OR (F) + AMINO (F) + AMINO OOMPOUND WITHOUT COMP'D COMP'D AMINO COMP' D I ALDOLS AND N-FREE POLYMERS * (G) (G) ' ALDIMINES ALDIMINEs A [ALDIMINEfl , ~ + AMINO ICOMP'D 0R , * ~ KETIMINES (c) I (a) 1 (a) MELANOIDINS .(BROWN NITROGENOUS POLYMERS AND COPOLYMERS)I (1) ACID CONDITIONS (2) BASIC CONDITIONS (3) HIGH TEMPERATURE Figure 3.2 Scheme of Nonenzymatic Browning Reactions (Labuza, 1975 and Hodge, 1953) -47- base of HMF or furfural is produced under acidic conditions, and reductones are produced under basic conditions. Reaction path 3 (Figure 3.2) is dominant at high product temperatures. In spite of the associated, complex stoichio- metry good success has been achieved in the use of simple rate equations to describe nonenzymatic browning (Labuza, 1975). Two factors contribute strOng— 1y to this success. First, reactions B, C, D, E, F, and G can follow reaction A spontaneously, especially at low moisture levels (Hodge, 1953). And, second, the first two transformation, reactions A and B (See.Figure 3.3), occur in series, and there is a possibility that one of the forward re- actions is rate limiting. Thus, it is conceivable that after an initial reaction time the reactant concentrations, before the rate-limiting step, I will be proportional to the reactant of interest (the preceding reactions are at or close to equilibrium). The product concentrations after the rate limiting reaction will be small (highly reactive product) in compari- son to the reactant concentration and the reaction will become pseudo? first or second order. The reactants involved in the reactions A and B, (Figure 3.3) begin- ing with the Schiff's base are reported as being very unstable (Hodge, 1953). If the concentration to Schiff's base is assumed to be very small, the rate limiting step is then one of the first two reversible reactions. Stoichiometrically the reaction is k1 k3 _.s.. (3-50) C + A P -45' S + W k2 kl. where C II a reducing substance A = a lysine molecule _ 48 - AmmmH.mmvomv usoamwsmuumou snowman can sowummcmpsoo mafismlumwsm II Emwamnuma wsac3oun OSu mo mowmum amauwsH ”m.m madman mmoumxINIkxovaHIoaHsmIH wmusuwumnsmlz AEMOM oumxv Aauou.aoamv Oman m.wmwnom msfisma>moohaw mo soaumu vmusuwumnsmIz N 11 N l mo mo more mo 5 8wa a _ _ a _ Amonusmv solouuumv 90-015 ofllw one A mono. ntT mououm +m+ Asalesman:- _ = . _ N5 5 mo o_|II|| u I m _ _ W = . mzm mzm +mzm I. mzm Hzmzmuz’ u available lysine C a reducing substance such as a carbohydrate R = a reaction product k1 & k2 = the associated constants If reaction 3.55 is used, the associated rate equations for the three components are ch __ .. Kl CL (3.60) dt ch :17;— k1 cL k2 CR (3.61) The associated initial conditions are L L0 CA a CA0 (3.63) . C (3.62) Solution of Eg. (3.60) gives . -k I; CA CA0 l (3.64) and solution of Eg. (3.61) gives -k t -k t -k t - e e _ . cA CLO k1( 1 + 2 ) CAOe 2 (3 65) k2 -k1_ kl .k2 The family of curves of Figure 3.4 illustrates the model for available lysine for various kllkz ratios. _ 52 _ om.m .ummm an emuumuma mm suaaanmaam>< mswmxa uom mamficmnumz coauummm HovMOIumuHm o>wu90mmsoo q.m muswwm mz-px-fi-x oo.4 oo.¢ : owum ov.~ om.“ om.o so. It F — mz-h w> mz-w>4 w4m¢JH¢>¢ hzmummm Of'O I 08-0 ENISAW HTQUWIUAU lNBUUHd 03'! OO-IfD OST'I -53- If k, (see Equation 3.59) is sensitive to a temperature change at a different temperature than k2 (see also Equation 3.57) or, more precisely, if the activation temperature is different for the two reactions, one will be more dominant depending on the temperature of the reactants. Also, if the activations energies are grossly different even though the activation temperatures are the same, different temperatures will produce different k2/k1 ratios and thus different plots according to Figure 3.4. One expects protein denaturation to occur at a relatively low temperature of approxi- mately 140°F (60°C) having a relatively high activation energy of 80-120 k cal/mole (Labuza, 1972) and nonenzymatic browning to occur at relatively higher temperatures of approximately 220°F (104.40C) (Wall et_gl,, 1975) and relatively low activation energies of approximately 25-50 k cal/mole. Thus, with protein denaturation occuring (Labuza, 1972) at a relatively low temperature and being very sensitive to small temperature changes as compared to nonenzymatic browning, the regain above 140OF (60°C) and below 220°F (104.4°C) will produce plots characteristics of kZ/kl = 0.0 ( k1 ¥ 0) and kZ/k1 - 0.1. Regions above 220°F (104.400) will produce plots characteristic of kZ/k]_= 0.8, 1.0 and 6.4. 3.4 The Complexity of Reaction Systems in Corn as Related to the Maillard Reaction Food systems as related to the chemistry of degradative reactions during drying are complex and corn is no exception. Not only is the nonenzymatic browning system complex with many pathways to the end products, melanoids, but there are a number of reaction systems and physical mechanisms which can have a profound effect upon not only the reaction rate, but also the availability of reactants for the reaction system. - 54 _ Water activity controls the reaction rate of many reactions, including the Maillard reaction (Labuza, 1975). The composition of the product before drying determines the total amount of each reactant present; and other reactions to include protein denaturation, sucrose carmeliza— tion, and rancidity reactions will furnish more reactants -- both free amino acids and reducing substances (Labuza, 1974 b, c). 3.4.1 The Effect of Water Activity on Reaction Rates The water activity of a food is defined as the ratio of the water vapor pressure of the food to the vapor pressure of pure water. It is an index of the relative chemical activity of the water contained in the food. The chemical potential Uw, of water in food is controlled by temperature, pressure, and composition of the solution phase and is equal to its partial molar free energy 6% defined as follows uw 3 GW ( Gs/ Nw ) (3.66) T, P, nj where G I free energy of the solution phase the number of moles in water :2 T 8 temperature '6 II pressure nj number of moles of other constituents of the solution (Bone, 1969). The effect of water activity on the nonenzymatic browning reaction is one which is directly related to the involvement of water in the re- action mechanisms. Figure 3.5 shows the general effect of water activity, - 55 - Mbisture Content o.H Annma .musnmqv cowuomom mo mmumm so >ufi>auo¢ nouns mo uommwm one m.m ouswwm mufi>wuu< scum: ado w.o 5.0 o.o m.o «.0 m.o ~.o H.o q . 1 d a q d u u I a Relative Reaction Rate -56... Aw, on many reactions, including the nonenzymatic browning reaction. The Aw of .3 corresponds to the monOlayer level of concentration of water in the product. It is at this point that reactants are able to begin to move or diffuse in solution, contact, and react, and it is at this level that the reaction rate will start to increase from a very low rate. The reaction rate will peak at Aw .65 to .70 and, then, begin to decline (Labuza, 1974 a, 1975). In corn this Aw corresponds to a moisture con- tent of less than 14% wb, depending on temperature. 3.4.2 The Chemical Composition of Corn The chemical composition of corn will not only determine the rates of reaction during high-temperature drying, but also the end point to which the reaction will go (i.e. whether all of the reactants will react). The basic constituents of corn are shown in Table 3.1. Those of primary interest are protein and sugars which may become involved in the Maillard reaction. Table 3.2 shows the amino acid composition of corn protein. There is an average of approximately 3.7 x 10"5 gram moles lysine/grams corn. The carbohydrates of immediate importance are the reducing sugars glucose and fructose (See Table 3.3). There is an average of 1.56 x 10"5 gram mole fructose/ gram corn and an average of 1.41 x 10'5 gram moles glucose/gram corn. So there is approximately enough reducing sugar to react with the lysine. However, there are two other complicating factors in the reaction system -- first, at temperatures above approximately 250°F (121.1°C) a carmelization reaction will cause sucrose to hydrolyze to glucose and fructose and other products, thus, providing as much as an average of -57.. Moisture, Z w.b. 16.2 Starch, Z 71.5 Protein, Z 9.91 Fat, Z 4.78 Ash (oxide), Z 1.42 Fiber (crude), Z 2.66 Sugar, total, Z 2.58 Total carotenoids, mg/kg 30.0 Table 3.1 Basic Constituents of Corn (Motz, 1969) _ 58 _ Amino Acid Range Average Alanine 5.3 - 7.5 6.6 Arginine 8.5 -14.7 11.7 Aspartic Acid 3.2 - 5.5 4.0 Cyst(e)ine 1.8 - 3.0 2.4 Glutamic Acid 7.5 - 9.5 8.5 Glycine 2.7 - 4.7 3.8 Histidine 4.8 - 7.8 6.2 Isoleucine * 2.9 - 4.9 4.0 Lysine * 4.2 - 7.5 5.4 Leucine * 6.8 -ll.0 9.3 Methionine * 2.6 - 3.3 3.0 Phenylalanine * 3.5 - 5.6 4.3 Proline 3.3 - 5.0 4.5 Serine 3.2 - 4.1 3.6 Threonine * 2.1 -10.8 6.5 TryptOphan * 0.72- 1.05 0.83 Tyrosine 2.0 - 3.2 2.5 Valine * 2.9 - 6.2 4.4 Amide 4.7 - 8.6 ... * essential amino acids Table 3.2 Amino Acid Content of Protein Isolated from Maize Seeds (Wolfe and Fowden, 1957). - 59 _ Starch, Z Amylopectin, Z total Amylose, Z total Sugar, Z Raffinose, Z Sucrose, Z Glucose, Z Fructose, Z Table 3.3 Carbohydrate Content of Corn (Motz, 1969). 8.18 x 10‘5 gram moles/gram corn of each reducing sugar to react with lysine; and second, cysteine tends to react preferentially with reducing substances to in effect protect lysine from destruction (Labuza, 1974 b). This would provide up to 2.3 x 10"5 gram moles/grams corn of amine substances to be reduced. These two reactions have not been studied in corn and were not considered in the stoichiometry of the previous section. Also, there are no acceptably accurate methods to measure the percent of cysteine and cystine in the product. Cysteine is a strongly reactive sulfur amino acid; whereas, cystine (approximately two cysteine residues) is not reactive (Simpson, 1975). 3.4.3 The Nonhomogeneity of Whole Kernel Corn Another complicating factor, which potentially is a rate controlling mechanism, is the fact that the concentration of protein and sugars varies from portion to portion of the corn kernel. There is an abundance of protein in the endosperm and an abundance of sugars in the embryo (see Table 3.4). This can have two possible effects. First there may be an overabundance of one reactant in either or both of the locations, causing the reaction of lysine with reducing substances to go to completion in the germ or embryo and leaving some lysine in the available state in the endosperm. Second, there is the possibility that diffusion can be rate controlling. 3.5 The Nonhomogeneity of Corn with Respect to Transport Phenomena. Corn is nonhomogeneous physically as well as chemically. The basic _ 61 - DISTRIBUTION OF THE BASIC CONSTITUENTS OF YELLOW DENT AMONG THE FRACTIONS OF THE KERNEL EndOSperm Embryo Pericarp Tip Cap (Z) (Z) (Z) (Z) Proportion of the part to the whole kernel 82 11.6 5.5 0.8 Protein 73.1 23.9 2.2 0.8 Oil 15.0 83.2 1.2 0.6 Sugar 28.2 70.0 1.1 0.7 Starch 98.0 1.3 0.6 0.1 Ash 18.2 78.5 2.5 0.8 Table 3.4 Distribution of the Basic Constituents of Yellow Dent Corn Among the Fractions of the Kernel (Motz, 1969). - 62 _ components of corn which are physically different are starch, gluten, hull and germ. These components have different heat and moisture diffusi- vities and different adsorption and desorption isotherms. Thus, heat and mass transport become VEIY' complex. Even if the water vapor concen— tration within the kernel are uniform the moisture contents of different portions of the kernel would not be. Different portions of the kernel display different moisture isotherms. The germ has the lowest moisture content for a given Aw' Fortunately, under most heating and drying condi- tions significant temperature gradients only last for the first three to four mdnutes (Pabis and Henderson, 1962). Thus, lumped parameter systems are used to describe the temperature and moisture history of grain in current grain drying models (Bakker-Arkema gt a1. 1974). 3.5.1 Mbisture Isotherms and Heats of Desorption of the Component Parts of the Corn Kernel. There is a marked difference in the moisture isotherms of the component parts of corn. Since drying occurs largely on the desorption isotherms (Figure 3.6) it will be used in order to illustrate this point. The corn germ is the dryest portion of the kernel for any relative humidity. In addition, the germ is located at the tip cap of the kernel which is a very vapor permeable area. On the other hand starchy areas which are the wettest portions of the kernel at a given relative humidity, are well protected by the relatively vapor impermeable pericarp (Kumar, 1973). Thus, with the dryest portions of the kernel in a realtively unprotected area and the wettest portion of the kernel in a protected area, one would expect the possibility of a grain air space moisture gradient and a product moisture gradient. An investigation to ascertain the possible Moisture (Z w.b.) - 63 - 30 Starch lO 0 l I I l I l l J l 0 50 Relative Humidity (Z) Figure 3.6 Desorption Isotherms of Corn Constituents at 50°C (122°F) (Chung and Pfost, 1967). 100 _ 64 - magnitude of these moisture gradients is needed before more grain quality simulation is performed because most rate constants in the degradation mechanisms of food systems are sensitive to moisture differences (Labuza, 1974 b). 3.5.2 Lumped Parameter Heat Transfer The possibility of the existance of temperature gradients is more difficult to ascertain because of differences in net heats of desorption (Figure 3.7), the effect of which are confused with the effects of isotherm and permeability nonhomogeneity of corn. If all portions of the seed dry at the same rate, even though the isotherms and the grain air space humidities vary, the germ would most certainly be at the lowest tempera- ture. However, with the complexity of permeability and diffusivity non- homogeneity, only in-depth investigations to include simulation of internal heat and mass transfer will give indications of the possibility that temperature gradients do exist and of the drying conditions that tend to produce them. Pabis and Henderson (1962) have reported temperature gradients only during the first three to four minutes of drying. Thus, until further investigations are conducted, lump-para- meter heat and mass transfer gives the most accurate indication of grain temperature. All existing grain drying models assume no grain temperature gradients (Bakker-Arkema gt_al, 1974). - 6S _ Table 3.5 Net Heats of Desorption for Different Components of Corn for 4 to 20 Percent Moisture Content (w.b.) at 122°F (31°C) (Chung and Pfost, 1967). Component Net Heat of Desorption (Kcal./Kg. H20) Whole Kernel 593-838 Starch 647-866 Hull 598-750 Gluten 592—739 Germ 589-679 IV. PROCEDURES Laboratory investigations were conducted in an effort to define the effect of various temperature histories at different moisture contents on two chemical attributes of the product and to explore the difficulties which might be encountered in applying this knowledge to predict the effect of a drying treatment by a laboratory or field dryer. Constant moisture heat treatments were given through the use of thermal-death-time (TDT) cans and either a hot water bath or a stream retort as a constant temperature heat source. The two chemical attributes studied were viability as measured by germination (AOSA, 1970) and available lysine as measured by the 2, 4, 6-trinitrobenzenesulfonic acid (TNBS) method (Kakade and Liener, 1969). Parameter estimation of proposed kinematic models was performed through the use of a generalized curve fitting program. A laboratory-scale concurrent dryer with counter- flow cooler was used in conjunction with a drying model and the pro- posed kinematic models in an attempt to predict the effect of a drying treatment on the product. And a thin-layer drying model with attached kinematic models was used to model a fluidized bed dryer described by Brekke ggflal. (1972). 4.1 Heat Treatments Heat treatments of corn at constant moisture content and for various temperature-time combinations were accomplished through the use _ 66 - _ 67 _ of thermal-death-time (TDT) cans. Moisture contents of approximately 14, l6, 17, 20, 24, and 28 percent wet basis were used with temperatures ranging from 130°F (51°C) to 212°F (100°C) and for time periods up to 2 hours in studies of the effect of heat and moisture on viability as measured by germination. Moisture contents of approximately 9, 14, 16, 17 and 20 percent wet basis were used with temperatures ranging from 220°F (lO4.4°C) to 300°F (148.80C) and for times of 10 minutes up to 60 minutes in the available lysine studies. Single cross Garno corn from the 1973 harvest was picked and crib- stored approximately three months, then, shelled and stored at 40°F (4.4°C). The moisture content was 20% w.b. and, thus, the 24% and 28% samples were obtained through the controlled total moisture procedure of rewetting (Kumar, 1973) and stored for more than one month at 40°F (4.4°C) sealed in TDT cans before receiving the respective heat treatments. The 14%, 16%, 17% samples were dried at approximately 80°F and at the equilibrium humidity of a saturated sodium chloride solution. The 9% sample was dried at ambient room conditions. The 20% sample was neither rewetted nor dryed._ All samples were sealed in TDT cans and stored at 40°F (4.4°C) before receiving the respective heat treatment. A cepper-constantan thermocouple was placed through the dented portion of the kernel into the germ of one kernel in 1/3 of the TDT cans . in order to record temperature histories. Temperature histories were recorded on paper tape at time intervals of 10 seconds. The recorded data were used to estimate the temperature history of the product, especially during heating and cooling. Temperature gradients were ignored during the heating and cooling phases of the heat treatment, and a lumped-system transient heat transfer parameter was estimated I _ 68 _ from the data (see section 3.5.1). The only energy terms considered in a lumped-system are convective heat transfer from ambient (the water bath or the retort) and the energy stored in the object (TDT can and corn). The energy balance can then be written as qc g ES (4.1) where qc = the rate of convective heat transfer to the object E8 = the rate of energy storage within the object The appropriate energy transfers can be written as 0c = hca (Too - T) (4.2) E . Vc QT (4.3) 3 PC dt where h = convective heat transfer coefficient a - convective heat transfer area Tho- ambient temperature T - average object temperature c 8 average object specific heat lac = average object density t = time Substituting Equations (4.12) and (4.13) into (4.11) gives .g%_ +1 3a (T - Too) = 0 (4.4) 20cc Upon solution with the initial condition T = Ti at t = O, the solution becomes -h/ t T - T -= (Ti - Too) e ( 63,3 VC) (4.5) The lumped heat transfer parameter is ha/olhh It is termed a lumped c :arazeter beta :3: be estimaI The ef f e assured thro "rag doll" me if Official S all seeds in as being Viab “‘58 used for The mean at Various ti hethOdS as ( t0 the CompuI Section 4. 3) _ 69 _ parameter because in parameter estimation only the value of the fraction can be estimated from temperature time data (Myers, 1971). 4.2 Viability Determination The effect of heat at different moisture levels on viability was measured through germination tests. Germination was determined by the "rag doll" method in adherence to the requirements of the Association of Official Seed Analysts (1970). However, in determining viability, all seeds in which the radicle had emerged from the seedcoat were counted as being viable. Vigor was not evaluated. Only 50 kernel samples were used for viability studies. The mean and pooled variance of germination tests of control samples at various times during the storage period were calculated by statistical methods as described by Himmelblau (1970) and discussed in reference to the computation of the variance of the available lysine test (see Section 4.3). 4.3 Available Lysine Determination Available lysine as affected by heat at different moisture levels was determined by the procedure of Kakade and Liener (1969). However, some minor modifications were incorporated into the procedure for reason as will be stated later. Approximately a 30 gram sample (the contents of one TDT can) was ground in a Thomas mill to pass through a 20 mesh screen. The sample was mixed thoroughly and a 50 mg aliquot placed in a pyrex, 125 ml, screw-ton, erleneyer flask. To it was added 5 m1 of 4% NaHCO3, pH 8.5. jg suspensil at 104°F (40 prepared wat at 10401 (40 added. The explosions o for 1 hour. of distilled twice with 3 acid which 1' Peptides and carried thro “'15 added to PIOCEdure (11 Sample Size This alterat aCcuracy and In aCcc were run in 346m“ The calculated 1 Adkade and I _ 7o _ The suspension was then placed in a constant temperature shaking bath at 104°F (40°C) for 10 minutes prior to the addition of 5 ml of a freshly prepared water solution of 12 TNBS. The reaction was allowed to proceed at 104°F (40°C) for 2 hours at which time 15 ml of concentrated HCl were added. The screw tape of the flask were then loosened slightly to prevent explosions or implosions and their contents autoclaved at 246°F (120°C) for 1 hour. After the hydrolyzate cooled to room temperature, 25 m1 of distilled water was added. The contents of each flask were extracted twice with approximately 50 m1 ethyl ether in order to remove picric acid which results from the reaction, TNP-N-terminal amino acids or peptides and picric acid which result from the reaction. Blanks were carried through the same procedure except that the concentrated HCl was added to the solution before the addition of the TNBS reagent. The procedure differs from that of Kakade and Liener (1969) in that the sample size and all reagents were 5 fold those used in their procedure. This alteration was necessary in order to improve sample measurement accuracy and to obtain a more homogeneous, representative sample. In accordance with Posati st 31. (1972) both blanks and samples were run in triplicate. All samples were read against all blanks at 346 mu. The amount of E-TNP-lysine (or the lysine equivalent) was calculated from the extension factor of 1.46 E + 04 M-1 cm-l given by . Kakade and Liener (1969). The mean and variance of each determination was computed by first computing the mean and variance of all three samples read against each blank, and, then by computing the weighted average of the means and a pooled estimate of variance (Himmelblau, 1970).. The overall mean was computed as ”I stare >wuum u M mxh qumomNm.o .quumsou m.MuomHm u a Mo mHoB\.Hmu .hoopuom sowum>wuum u m Mo\H mmlmmowm.H .uomumoou m.osmaNH0M u M mace Mo\Hmu 5mm.a .usmumooo mow Hmmum>fiso u M unowofiwmmou scammfismomuu u M mm co+moooomq. II 0.0 ¢0+Mmow., oo+MmoonH. HH+Mmm~. NH+MmmomoH. MM MN mo+mommmqo. II oomocq.a II mo+mwmnowa. II NH+mewomH. mm om mo+MNNmnmo. mom. oomamm.a mo+MnoH. oo+mqooama. HH+anm. NH+Mmmmme. MM «N qo+mmwomma. II enqmm.a II wo+meommma. II 0H+m~mmmmm. am mm eo+momoqo~. NNH. oooqco.~ «0+MHNM. oo+MmH¢HoN. mo+MwNm. 0H+Mommmqe. MM on ¢o+mmoqqmm. II OummHN.H II oo+maomqma. II oa+moooccm. am am co+mwm~aaq. mmq. omeoNH.H mo+M~om. oo+momcoea. oa+mooa. OH+MNNH<¢N. MM RH ¢o+mammwm¢. com. ouamqn. mo+maam. mo+mmmnoma. 0H+Mmqu. oa+mhmwoam. am NH qo+muqmeoq. mwo. oowomm. mo+Mo¢m. oo+m~qmoma. OH+MmoN. oa+mmoNH-. MM ca co+Mmom~mm. II ommamo.a II oo+mooaowa. II ¢o+Mmmwoqm. mm mm qo+mmo~cuw. mun. noamco. mo+Mmm<. oo+quoomH. mo+mmmm. m0+Mm~comc. MM «a a wonumz up woumovm coaumw>mn a GOHuMH>ma M. oowuma>mo IMI.« M Asa mamsvfimoM mo Bow vumvsmum vumvsmum vumstum. .umwoz Mo .muaumuooaoa u Mo smaoa\.amu m.¢o I M o~m\M n m a N .oowumsflsuou muoon .mfiwu AH«M\MIvoxm * AM\mvnxo a MHM.« M n < up QU¥U* 3.33....» reg... x wzuh Ahzmumwm. zmou uucme La 4.1! 00'03! 00'091 - 98 _ Complete death at 170°F (76.70C) and 24% average moisture content occurs in less than 20 seconds in the case of the fluidized bed dryer and almost instantaneously 230°F (110°C) and 19% average moisture con- tent in the case cfthe concurrent dryer. These rates are not extraordinarily high according to people associated with the grain industry and biochemists familiar with the thermal death of seed germ. 5.3 Effect of Heat on Lysine Availability The available lysine data at 270°F (132.200) gives a plot character- istic of the consecutive first-order reaction mechanism (see Figure 3.4); however, data plotted at higher temperatures does not exhibit the initial increase in AVL attributed to protein denaturation. It is possible that the sampling rate is too low to detect increased lysine availability caused by protein denaturation at higher temperatures since the reaction is very temperature-sensitive. Significant decreases in AVL were only found when heating was severe enough to cause marked darkening of the kernels and when there was an associated "roasted" smell which has been reported in conjunction with other non—enzymatic browning reactions by previous investigators. The temperatures at which this occurred were beyond those of convective-air corn dryers. 5.3.1 Available Lysine Data The available lysine data (Figures 5.2-5.5 and AppendixID , although scattered for long heat-treatment times, does exhibit the characteristics of the consecutive first-order reaction mechanism (see -99.. .mucmucoo musumHoz msowum> um moEHH m30Hcm> new AoomdmC MOONN um mquEummuM. umom Mn. wmuummmae mm 9593 machine/.1» m.m ouowwm U A ...U H.2sz mzHH I. oo.oe oo.oe oo.om oo.oe oo.om oo.o~ oo.os oo.pUnI _ _ p e e e e “U J was 0-II 3 .l IA r09 . .Umm > .3 ... 1. 1N} 00 ...I-l .LL-——————“V .9mm 0 HI 955:... 535.. 8 ON 2.322. :85: 2 . f. 9.322. 235: 3 . Z 9558: 535.. a t x msz .I w> nu m omw kc msz>4 mom¢4H¢>¢ ZE'O — um - .musmocoo opoumHoz mSOHuc> um moEHH msowuc> cow Aoow.NmMV moomm um mucmEumouH umom Mo couummm< mm mcflmmq mHomHHm>< m.m muowwm H.2qu mzHH 85m. 86% Doom. 85w 8.3m 85m 85m 1 D O _C) ) I VO'O ENISAW EWQUWIUAU V to o I ZI'O can 888 mum Lama coca Clio-0N axes 01 H (N WON/WON) 02-0 M 0mm Hm wsz>4 mom¢4H¢>¢ 82'0 .mucmuooo mpoumHoz magnum; um mmEE. m30Hum> you Bonds: soomm no oncogene: stem .3 Boone: no 2:93 oHonHHoEe so enema U A H. A . 2:... H m: M H I oo.o> oo.om oo.om oo.o¢ oo.om oo.o~ 00.0” oo.o_mw r F _ P P p F 08 ..u_l 13 a .l IA ti :09 ‘4 001 N L3 N _ I00 m r_./. .1 on 0 HI 5:22. 535.. 3 m 0N 5:22. :95: 8 . I Map—2e: 2.35.. 3 x 2 5:22. 235.. a ... .8 x ME: 3 m ... omN E szw: mommdgm 18'0 .mucmucou monumHoz mSOHum> um moEHH w30Hpm> new Aoom.quV mooom um muomfiummuy ummm Mp omuomwm< mm mowmka manmawm>< m.m ouswwh H.2Mzu szH oo.oe oo.om oo.om oo.oe oo.om oo.o~ oo.os oo.pu F p p L p p o TIHAH no 00 3 An--_--“.LA‘- a 11mm” I 80'0 01 i (N WON/WON) 3NISA1 318 I 91'0 - 102 - 22. e 5.. 8 o 0 as ea mzH» w> m can Hm msz>4 mom¢4H¢>¢ ZS'O - 103 - Equation 3.31 and Figure 3.3). At 270°F (132.200) the percent initial increase in available lysine (AVL) is highest at 9% w.b. moisture content and decreases with increasing moisture content and time for the 10 and 20 minute heat treatments. This contrasts with the data reported by Mfihlbauer and Christ (1974) in that they were not able to detect the initial increase in available lysine. In using it“: exchange liquid chromatographyIflwy measured the total concentration of lysine-m-that which was masked by the protein matrix and that which was nutritionally available (see.equation 3.59). Whereas, the TNBS method tends to detect only the amount of lysine which is nutritionally available. Thus, the TNBS data is indicative of the effect of high temperature_ drying on the nutritional value of corn. Moisture content does not markedly affECt the browning reaction in corn so thatwdata at. higher temperatures and longer heat- ing times compare well with the findings of Mfihlbauer and Christ (1974) At higher temperatures, either the rate of decrease in AVL masks the effect of protein denaturation in increasing AVL or, more likely, the frequency at which data was developed during the process is not high enough to detect the initial, short-duration increase in AVL. The physical limitations of the method of investigation prevented the gather- ing of data at high sampling rates, especially during the first 10 minutes of the process. It took approximately 3 minutes for the product to reach processing temperature, leaving, at most, a 7-minute time interval for gathering data. Each data point was obtained by heating the product to temperature for a desired time, cooling the product at the end of the processing time in order to stop the process and, finally, performing a 3-hour procedure in order to analyze for AVL. Although the processing time was precisely controlled, the large number of chemical analyses -1o4- required and the time required for heat treatment and chemical analysis prohibited high sampling rates at each processing temperature. As can be seen from the data as plotted in Figures 5.2 - 5.5, the time-temperature treatment at which there is a significant decrease in AVL is beyond that normally experienced by corn during drying. Corn seldom reaches temperatures above 200°F (93.3°C) for more than one hour and very seldom experiences temperatures as high as 260°F (126.6°C). Furthermore, only samples which showed physical evidence of severe heat damage (browning) and exhibited a strong, roasted-nut odor were found to contain less available lysine than the control samples. Thus, the feasibility of a more intensive investigation is very questionable when considering browning reactions that may occur during the drying process. 5.3.2 Available Lysine Analysis The standard deviation of single determinations are of the same order of magnitude as the concentration reading and increase as temper- ature and heating time increase (see Figure 5.6 and appendix F.1). This makes multiple determinations on each sample mandatory which is in con- currence with the recommendation of Posati 23.31. (1972). This is a major disadvantage of the TNBS method; however, with only 3 blanks and 3 samples precision was increased adequately in order to obtain proper resolution to the first half-life reduction in‘AVL. Any parameter estimation performed using results from the test must take into consideration the relationship between the standard deviation of the TNBS method and the concentration determination. It is interesting in comparing the analysis of the control samples that as moisture content decreases, the amount of AVL per mole of nitrogen - 105 - STD DEVIATION CONCENTRATION — — —- —- 126.7 Figure 5.6 131.1 135.0 140.0 144.4 148. Temperature (°C) Available lysine and the Standard Deviation of a single TNBS Determination as Affected by Temperature and Duration of Heat Treatment at 9% Moisture. Time (min.) - 106 - detected also decreases. This is in concurrence with observations of Posati st 31. (1972). As sample size increases, the amount of AVL detected by the TNBS method decreases. Thus, since there is more dry matter and, therefore, more proteinaceous material as moisture content decreases ( the effective sample size is larger) it is expected that the amount of AVL detected will decreaSe. It is also interesting to note that the levels and the decrease in AVL reported by Wall e£_al. (1975) in corn dried at'a maximum product temperature of 219.2°F (104°C) are almost identical to those of the control samples at high and low moisture. Wall e£_§l. (1975) may be observing the same effect of de- creased moisture content causing decreaSed AVL even though he used the methyl acrylate method. This is not unlikely since the reaction Innufitions for the methyl acrylate method and the TNBS method are comparable. 5.3.3 Heat Treatment Variance Effect on Available Lysine Variance reduction by pairing of replicated tests was used to estimate the variance of heat treatments through its effect on avail- able lysine reduction. The estimated standard deviation produced by heat treatment (see table 5.8) is of the same order of magnitude as that of the control-sample determination. 5.3.4 The Available Lysine Model As mentioned previously, it was not practical to develop the data necessary for the estimation of parameters in the first of the two con- - 107 - Table 5.8 Variability In Heat Treatment Replication on Available Lysine Determinations. . Moisture Temperature Time AVL (mol/mol N) 0C (Min.) 9 137.8 30 .01374 .01270 14 121.1 60 .01716 .01664 14 126.7 60 .02205 .01279 .004763 14 137.8 60 .01308 .004195 14 137.8 30 .01349 .01190 17 137.8 60 .005196 .007437 Pooled variance = .3393E-5 Standard Deviation = .5825E-3 Degrees of freedom = 7 - 108 — secutive first-order reaction mechanisms of the available lysine model. .Parameter values for the second reaction (sugar-amine condensation) are given in Table 5.9. The rate constant is not markedly sensitive to temperature change except when the temperature is increased from 290°F to 300°F (143.300 to 160°C). This may be evidence that the reaction system shifts markedly or, more likely, that another reaction (possibly the direct destruction of lysine) is activated at these extreme temperatures. Using the Arrhenius relationship for the data taken at 9% moisture shows that the AVL reaction is relatively insensitive to temperature changes in comparison to germination. The activation energy is only 18,000 cal. for AVL as compared to 130,000-200,000 cal. in the case of viability. Also, the reaction is relatively slow at normal drying product temperatures and is of little consequence unless product temperatures are reached which would produce visible, severe heat damage to the kernels. Table 5.H)compares some calculated rates with rates published for soybeans. The rates predicted by the first order portion of the AVL model for corn are much higher, quite possibly, because of published data for soybeans was only fit to a simple first order model and did not) take the effects of protein denaturation into account; however, since the reported rates are from soybeans, no definitive conclusions can be drawn. A plot of model "B" (see Table 5.9) based only on the 9% moisture data is presented in Figure 5.7. In.contrast to the germination model there is very little variation in reaction rate with variation in temp- 'erature. Also, the reaction is relatively slow as compared to the germination model and takes place at much higher temperatures which, oowumEHumm HoumEmuma How nwws oou mousmwum> II ousumHoz Nom.cfi.qa uom 109 - mo-mweoowo. n oonoeom nHoeeHoom no son .oHHe u ooeooeeon nonsense e.~sowH u m mN u soooons no monsoon HH+mon. u eosooe>oe enooeoem oH+mmmoom. u on Mano ououmwoz.No pom M .oosoH u eoenoeeoe oeooeoem e.~HowH u m e n sooooee mo nonemoa NH+mmeH. u eosooeeoa,eeoeeoem oH+mHo~oeH. u om < NN Ho-mwmeoom. o~.e Hmo.ms ¢.H~e o.wes ows.eH.eH.o o ON mo-mmmoomm. owN. esmm.s m.ose m.mes ouo.es.eH.o m cm 8.323%. mHN. mmmmH we: win 036H$H£ s cm HOImmoeNow. No.H omoe.e N.moe ~.~m~ omo.os.es.o m H mo-mHH~ewH. cos. once.s H.omm H.o~H omo.oH.eH.o N e eo-moewwem. mom. mmoem. H.emm H.HNH omo.os.ee.o H Eovmmuh omumoom GOHuMH>on nus M 00 as N .02 mo newsman mamsvfimmM mo 83m oumpcmum HM mumumumoEoH ououmwoz umoa Ham\m-vexo t oM u M e u no 0 ye M 4 m4m¢4H¢>¢ No on oanse oHeoHHn>< nos Hoeoz noose sense H.m onemee 3:: m2: om.N o¢.N oo.N om.~ ow.“ om.o 0¢.o oo.pu p — p p . P F M .U nunn nouu I 1: a um .I. 8 rflnl m.wes OOH a mww: m.mei omm . nu w.Hmi owm .. IA H.Nmi oHN no H.omi com a Ii 3. slo -.oN mCOHmHme/oou 1.3 muoummmmEmH .1 0] nw nu t can m 1| t can a nun: n one + x. n: i see c t. n ecu a. n:// nw m2: 0 1I w> 3 Mn 02'0 1-013" - 112 - as mentioned previously, are above the product temperatures normally encountered in high-temperature drying. 5.3.5 Comparison of Model and Experimental Data A comparison of the first order portion of the AVL models 3.6 with the experimental data is found in appendix C. For the most part, the firstorder model was successful in describing the data; however, at 300°F (148.80C) the data does not fit the first-order model. This suggests, as mentioned before, that the dominant mechanism may have shifted. - 113 - VI. CONCLUSIONS This investigation was the first attempt to use TDT cans to give a known temperature-moisture heat treatment to corn and to develop corn quality models. While this method was useful, some limitations were encountered. The TDT heat treatment may be more severe than a drying treatment at the same average product temperature and moisture. The dif- ference between these constant moisture heat treatments and drying treat- ments must be accounted for in order to use the TDT method of investigation to develop certain models which predict grain quality deterioration. The existence of temperature gradients is the most likely cause. The survivorship model was successfully fit to the germination data. Since the survivorship model is markedly different than other chemical modes of deterioration and its range of temperature and moisture sensitivity is different than other quality indicators, germination is a questionable index of grain quality; however, there is a potential for the use of the model by seed scientists in predicting the effect of age, moisture, and temperature on seed viability and vigor during storage and drying. The simple first or second order reaction models commonly used in food systems are not adequate for describing the effect of heat and moisture on lysine availability in whole corn. The effect of protein denaturation on increasing lysine availability will be of most interest with respect to the drying process. Sugar-amine condensation (The Maillard reaction) occurs in a temperature range outside of the - 114 - temperature range normally experienced by the product in high-temperature corn drying. This indicates that drying temperature lindtations are not necessary to preserve the nutritional quality of corn protein. Corn must be severely heat damaged before nutritional quality is effected. The disulfide bridge in protein is directly related to the physio- chemical behavior of corn flour obtained by dry-milling. The disulfide bond is also key to the release of starch by the wet-milling process. Heat denatures the usually compact configuration of polypeptide chains into greatly entangled flexible chains showing random modes of coiling. The end result in the case of the dry milling process is that character- istics attributed to the normal "slippage" of the disulfide bond such as cold paste viscosity are greatly reduced. This is due to the disorganized nature of the polypeptide chains even though the disulfide bonds are left in tact. In the case of wet-milling, denaturation reduces the solubility of the protein, thus, greatly inhibiting the ability of the $02 steeping process to disrupt the disulfide bonds. A study of the effect of heat on the physiochemical properties of corn protein would be useful with regard to the dry-milling process while a study of the effect of heat on the ability of an S02 steep to break the disulfide bond would be useful in evaluating the wet-milling quality of corn. - 115 - VII. FUTURE WORK This work has been extensive but not intensive in nature in that it dealt with a large number of aspects of the problem of predicting corn quality after drying. The investigation covered the measure- ment of two quality attributes, the construction of one model for the effect of heat and moisture on germination, and a more thorough under- standing of the effect of heat and moisture on the nutritive value of corn as measured by one chemical attribute. Areas were covered which need a more intensive investigation if grain quality deterioration is to be predicted apriori in the design of any grain drying systems. They range from an investigation of a more complicated drying model, which includes a multi-thin layer model, to more direct methods of determining the nutritional and processing quality of corn. Most importantly, a search for an index of thermal damage should concentrate on criteria which are directly related to the monetary value of the product as feed, food or raw product for wet or dry- milling, or as a nonfriable product in shipment. Any efforts to use one attribute for any combination of the above will not be successful because all chemical and physical properties deteriorate according to their own characteristic mechanisms and because the rates of deteriora- tion are affected in different characteristic regions of temperature and moisture. This is very evident when comparing germination and available lysine. The former has a relatively low range of temperature sensitivity and a high range of moisture sensitivity as compared to the latter. - 116 - 0f almost equal importance is the need for slightly more complex drying models. Although drying models give an adequate description of average product temperature and moisture during drying, there is a need for a study of moisture and temperature distributions within specific portions of the kernel (germ, floury endosperm, and horny endosperm) in order to accurately describe the effect of different drying treatments on physiochemical properties. The value of the germination percentage of corn as a quality indicator is very limited with the exception of the seed industry. The value of using the survivorship model in predicting seed quality to include viability and vigor as effected by drying and storage should be investigated. A more thorough investigation of the effects of heat on protein denaturation as related to the effect of the SO2 steep used in the wet milling process is needed. The feasibility of chemically determining the extent of disulfide bonding after steeping should be investigated. A similar investigation of the role of disulfide bonding and protein denaturation on the quality of corn for dry-milling should also be conducted. BIBLIOGRAPHY - 117 - BIBLIOGRAPHY Adams, S. L., W. H. Stark and P. Kolachov, 1943. Reduction of fermentable carbohydrates content of corn by kiln drying. Cereal Chemistry 20:260-266. Anderson, R. A., 1963. Wet-milling properties of grains: Bench-scale study. Cereal Science Today 8: 190-195, 221. Anderson, R. A., 1967. A pilot plant for wet-milling. Cereal Science Today 2: 78-80. Anderson, R. A., 1972. Commercial concurrent flow heating- counterflow cooling grain dryer-Anderson model. ASAE Paper: 72-846. Anantharaman, K. and K. J. Carpenter, 1969. 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APPENDICES APPENDIX A Thermal Effects on Germination Table A.1 Thermal Effect on Germination - 131 - Meisture Treat Content Temperature Time Germination No. %‘wb OF 00 min. % 1 14 150 65.6 110 32 ‘2 14 150 65.6 100 78 3 14 150 65.6 90 50 4 14 150 65.6 80 72 5 14 150 65.6 70 66 6 14 150 65.6 60 70 7 14 160 71.1 '30 6 8 14 160 71.1 25 26 9 14 160 71.1 20 50 10 14 160 71.1 15 74 11 14 160 . 71.1 10 88 12 14 165 73.9 12 34 13 14 165 73.9 10 7O l4 14 165 73.9 9 82 15 14 165 . 73.9 6 86 16 14 165 73.9 4 94 17 14 170 76.7 9 6 18 14 170 76.7 8 38 19 14 170 76.7 7 40 -20 14 170 76.7 6 76 21 14 170 76.7 5 92 22 14 170 76.7 4 98 23 14 180 82.2 6 2 24 14 180 82.2 5 46 25 14 180 82.2 4 46 26 16 150 65.6 80 38 27 16 150 65.6 70 5 28 16 150 65.6 60 44 29 16 150 65.6 50 25 30 16 150 65.6 40 72 31 16 150 65.6 30 84 32 16 160 71.1 20 10 33 16 160 71.1 15 36 34 16 160 71.1 10 68 - 132 - Treble A.1 (cont.) Thermal Effect on Germination Moisture firest Content Temperature Time Germination no. % wb °F 00 min. % 35 16 165 73.9 9 2 36 16 165 73.9 8 40 37 16 165 73.9 7 52 38 16 165 73.9 6 40 39 16 165 73.9 5 74 40 16 170 76.7 8 2 41 16 170 76.7 7 4 42 16 170 76.7 6 32 43 16 170 76.7 5 54 44 16 170 76.7 4 86 45 16 180 82.2 4 50 46 17 150 65.6 60 32 47 17 150 65.6 50 40 48 17 150 65.6 40 42 49 17 150 65.6 30 7O 50 17 150 65.6 20 84 51 17 150 65.6 10 96 52 17 151 66.1 60 10 53 17 151 66.1 50 30 54 17 151 66.1 40 46 55 17 151 66.1 30 74 56 17 151 66.1 20 82 57 17 151 66.1 10 94 58 17 160 71.1 25 8 59 17 160 71.1 20 6 60 17 160 71.1 20 4 61 17 160 71.1 15 42 62 17 160 71.1 15 50 63 17 160 ‘ 71.1 10 88 64 17 160 71.1 10 72 65 17 160 71.1 5 92 66 17 165 73.9 8 22 67 17 165 73.9 7 42 68 17 165 73.9 6 66 69 17 165 73.9 5 88 7O 17 165 73.9 4 92 -133- Table A.1 (cont.) Thermal Effect on Germination Moisture Test Content Temperature Time Germination No. —— —— — —— % wb 0F 03 min % 71 17 170 76.7 7 12 72 17 170 76.7 6 20 73 17 170 76.7 5 64 74 17 170 76.7 5 60 75 17 170 76.7 4 88 76 17 180 82.2 414 14 77 17 130 32,2 4 26 78 17 180 82.2 4 26 79 17 186 85.6 4 14 80 20 140 60.0 130 32 8 1 20 140 60.0 120 30 82 20 140 60.0 110 42 83 20 140 60.0 100 44 84 20 140 60.0 90 48 85 20 140 60.0 80 72 86 20 140 60.0 80 64 87 20 140 60.0 70 78 88 20 140 60.0 60 78 89 20 140 60.0 50 78 90 20 140 60.0 40 88 91 20 140 60.0 30 90 92 20 154 67.8 20 2 93 20 154 67.8 15 6 94 20 154 57,3 12 76 95 20 154 67.8 10 88 96 20 154 67.8 8 84 97 20 154 67.8 7 9o 98 20 154 67.8 6 94 99 20 154 67.8 5 94 100 20 162 ‘ 72.2 8 6 101 20 162 72.2 7 16 102 20 162 72.2 7 4 103 20 162 72.2 6 44 104 20 162 72.2 5 84 105 20 162 72.2 4 90 106 20 152 72,2 3 100 “-1 ‘1') - 134 - frable A.1 (cont.) Thermal Effect on Germination Moisture Tkast Content Temperature Time Germination No. —- —- -— % wb 0F 0C min. % 107 20 171 77.2 6 6 108 20 171. 77.2 6 8 109 20 171 77.2 5 48 1 10 20 171 77.2 5 12 1 1 1 20 171 77.2 4‘»: 14 112 20 171 77.2 4 76 1 13 20 171 77.2 4 8o 1 14 20 171 77.2 3‘»; 92 1 15 20 171 77.2 3 9o 1 16 20 180 82.2 311 20 1 17 20 180 82.2 3 68 1 18 24 130 54.4 90 82 1 19 24 130 54.4 80 72 120 24 130 54.4 70 94 12 1 24 130 54.4 60 9o 122 24 130 54.4 so 82 123 24 130 54.4 40 88 124 24 140 60.0 60 2 125 24 140 60.0 50 4 126 24 140 60.0 40 16 127 24 140 60.0 30 46 128 . 24 140 60.0 20 70 129 24 140 60.0 15 86 130 24 150 65.6 9 12 131 24 150 65.6 8 22 132 24 150 65.6 7 46 133 24 150 65.6 6 8o 134 24 150 65.6 5 9o 135 24 150 65.6 5 94 136 24 150 65.6 4 9o 137 24 160 ‘ 71.1 5 6 138 24 160 71.1 4 74 139 24 170 76.7 4 2 14o 24 170 76.7 3 58 - 135 - Table A.1 (cont.) Thermal Effect on Germination Moisture Test Content Temperature Time Germination No. -- -——- -—- -——- % wb 0F 0C min. % 141 28 131 55.0 110 42 142 28 131 55.0 ' 100 80 143 28 131 55.0 90 80 144 28 131 55.0 80 64 145 28 131 55.0 70 82 146 28 131 55.0 60 82 147 28 135 57.2 80 26 148 28 135 57.2 70 76 149 28 135 57.2 60 52 150 28 135 57.2 50 50 151 28 135 57.2 40 72 152 28 135 57.2 30 60 153 28 141 60.6 50 6 154 28 141 60.6 40 16 155 28 141 60.6 30 10 156 28 141 60.6 20 38 157 28 141 60.6 10 36 158 28 146 63.3 20 4 159 28 146 63.3 15 10 160 28 146 63.3 10 34 161 ~ 28 ‘ 146 63.3 5 78 162 28 150 65.6 9 6 163 28 150 65.6 8 16 164 28 150 65.6 7 46 165 28 150 65.6 6 52 166 28 150 65.6 5 36 167 28 150 65.6 4 86 APPENDIX B Germination Data Plots 136 - .muooEummuH ummm mEHHImuoumumeamH mSOHum> mo omuommw< mm usmusoo mucumHoz .n.m Nqa um cOHumoHsuoo H.m muswwm n.2H2. wzuh Do DD.DJM DD.DM~ oo.omw oo.mm .mr oo.£¢ DD.QN OD. 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N N u ...III III! 45.5.: 4 455.: e ...:zufi a ...:sz x ..Ezufi u msz m> .ucmudoo musumfloz .p.3 NQH 0.0 ouswflm mmDPwHoz Hzmommm 00 Pm onhcszmmo (f3 ownr (lNEOUBd) NOIlUNIHHBO 00' I T 00'08 UU'OZI I 00'091 .ucoucoo musumaoz .n.3 Nqa um muma 0cm Hmvoz cowumcwaumw mo comfiumqaoo N.0 munwfim H 0 mth o.om .ooqovfl -oo.o~ go. I‘ n.z o 8.2: 8.8: 8.9: 8.8 r\.LT\*r;T,u (F) T 00' I 00'09 00'08 N.Nm omfi “.0“ and .w ¢.m~ mofi u a. 0.: oS . v onmm cm 00 mo mGOHme>COU musumumaEmH » 45.65550 N “.2: Swuwowt x Jawzunwangu a u a», owns... o 4:52:39 x L: a $39: 9 ..Ezusfium .. 2: $-28... ..Ezufifi u ._ 2: 020p m> mmDHwHoz pzmumwm ¢H Hm ongmszmmo (lNBJUBdJ NOIlUNINHBO OO'OZI 00'091 144 - .udmucoo munumwoz .n.3 NRA um mumn 0cm H0002 coaumcwshmu mo somfiummaou 0.0 muswwm 3.2:: m2: 00.0¢0 00.000 00.000 00.00 00.00 00.0w punu l . . - . . . ..IO 3 NH N I N 0.3 S: U ~00 S: uMl “.0“ 0.0 . 11 of ms mm 0.05 000 0.00 Hmfi 1: ...... om. u. U ..H r8 mawwmumkaom .OAMJu mudumummsmh m3 MN . .. fig . an m 88.8.... > .... 5.: c ._ as a £8: N .5»sz e L 2: u... amt 8.... x .... 5.: a ._ 92 Z a 882... o .55? x ._ a: 0 BEBE... o 455.: u .. 2: .0 m: H h o w> 002000: Hzmummm : E 2030202000 - UO'OQ! .uamuzoo mMSumfloz .n.3 NON um mama 0cm Hmvoz coaumaHEpmo mo comfiumaaoo “.22.: mzz. 00.00: 00.0N0 00.000 00.00 00.00 00.0w. _x .N .UN ~.Nw owfi N.NN HRH H _ ~12 NS u m 0.3 .2 n 9B em. _ 00 mo mSOHmhm>GOU muaumquSmB » 05355.5 m .8. awwuwomt x 42355.6 5 h. E a o o .... 43553.5 x L «2 auho_au¢. .. achzu=~¢u0xu . cm. 0238.: 0 4522298. u g a: w> mmDHwHoz Hzmummm 0N Hm onhcszmwo «.0 musmfim boga [f3 UNINHE‘J 00' r i o' I 00- N0 00.0¢~ 00 0.05 000 H.0n 000 _ 0.m0 omfi ”w 0.00 000 L .....m om _ 00 mo mfioamuw>coo musumquEmH mm» a 0.0 ms; mm_ on; .0NH OGKN) ..J C p. 5 LKILLII- $88 don-unu- n.z o .ucouaoo muaumaoz .n.3 qu um mama 0am Haves cOHumcHEhww mo comfiumgaoo H 040 mmDHmHoz Hzmumwm ¢N kc onpcthmmo m .0 muswwm .Efio¢- d3 UNINHBO 00' I own» N011 I oowm (1N3383d) r OD'OZI 00'091 APPENDIX D Germination Model-«Low Temperature 00.0+~ 00.0N~ o.mo omH 0.00 oqfi _ 0.00 flea ./ «.mm mmH m o ..m 6. _ 00 mo mcowmum>co0 muzumuwQEMH 8.— BE » ...: «we. 3: ...: .— 2... x ...: mm» 9... « ...: us. At 00.00~ .ucmuaoo mudumfioz .n.3 Nwm um mama cam ammoz coaumawsumo mo somwummeoo 0.0 0960 ..2020 0:00 095. 00.00 1].]. I c ‘ LEE-ILL 33:98 untidy-Iv- mmapwHoz pzmummm 0N Hm zo~p¢z~zmm0 3° UNINHEO 00 'i ownt J N011 I owns (1N3383d I OO'DZI 00'091 .mudom N pom ucmucou mHSumHoz q» .93 NS .2. Enos 832258 Nd 8:30 OQw 9Tm m.mm mofi. 0.00 000 m.mo mmH _ 0.m0 OmH w mwm mm. .I 00 mo _ mcowmum>cou musumquEmH mmapwHoz Fzmommm 00 #0 H010 020p 00.0 00.0 00.0 0v.0 5i; 1, _n a. . Maw» .33 + as: 4 note :00 w> wmo>0>msw Hzmummm 00. .11., 1 00' l 00'0? 00‘08 SHOAIABHS lNEJHBd OU'OZI 00'091 .musom N How ucmucoo wusumwoz .0.3 NNH um Hmvoz cowumcflEpwo 00mm 0.00 000 m.00 mmfi _ o.mm omfi O 0&0 m3 ”D 0.bm. omw. _ 00 mo mcowwum>coo muaumumaEmH mmDHwHoz pzmommm 00 #0 w m a Saw: HmIH mzHH ill: ,Lfil a» an rm 6: d 00' oo-o't SHUAIAHHS 1N3383 I 00'08 mmmmm 00000 vvumu Giulio-0"" 0Q+XO I OO‘OZI 03 ;> 0>H>mnw Hzmommm 0: 00‘091 .9300 N pow ucmucoo musumfioz 5.3 Now um H0002 coaumcflcfiwu «.0 mudwfim 3:: m: H ._. 00 .N 0¢ .N 00 N .0010 WN rad 00 r0 0¢ .0 00 JUM Mug 3 3 N l .. .7 IDS . n mug ©.m© omfi A w.N® qu 1A1 _ ._.Ho Nqfi n. 0.8 oi 5.0% 1. fl? mm. a. a - . _ 00 mo : n n n .. . m mcowmumiuoo .. ... u u a .VI. mpnumummfiwa a...“ a. .. :2 u 4% uma— a mu MZHH 0 w> mkawHoz ._.zuummm ON ._.¢ mmD>H>mzw ._.zmumwm u 00‘091 \‘f\DN©O .musom N pom uGMucoo mHSumHoz .L.B qu um H0002 coaumcwaumo m.0 munwwm 00.0 r. .00 000 .00 000 .mm mmfi .mm N00 .0. E. 00 mo chHmum>coo muSumMMQEmH mmzbmHoz Hzmummm 0N H0 ”010 msz 07% 00. N 00.0 00.0 00._0 0.3.0 00. 00d . .- - . .. , ~03 nuud 3 3 N I. INS mun Duo A M. 3 80 a .. [DUO : .4 .08 0 “mm ... t :5 ... rZ $0 .0 ..u 0:: m w> wmo>0>mzm 0200000 . .9250 N How ucquOU 9:593: 5.3 NmN um 1:52 coauwawnfimo 0.0 wuawwm ET: 0:: 00HN 07% 00.0 00.0 ow; 00.0 0¢.0 00.00:0 .llll‘ . 4]. . loo-.4.“ DUO 3 3 N I. rms 0.m0 omfi .0“ 0.00 mi Duo 0.00 03 A «Km m2 1.. «WWW Om ... .J a. ... .... n ... WW mmsmgmpmammm .. - W9 ...: o 0...: a 0mm. 9 W 0:: w> 0 0000.000: ._.zmummm 0w .5 0003350 ._.zmumum r APPENDIX E Germination Mode 1--Hi gh Temperat ure .wmuncflz 0 now mmuSumuwQEmH 3000 um unmucoo musumfloz .n.3 Nqa um Hmvoz coaumcHEumw .HAm muzwwm [f3 H~:i0 wraHp ¢H.mw «duo 00.0 . 00.0 00.0 e0.0 No.0 00. N.N0 000. «.mn mNH . n.0m ORA “m 0.05 000 I y ..w» 000 _ 8 mo 9 n n a a a - mGOHmuw>coo : muSumumaEmH ._oog .. ..wp— v. u op. .+ I max: c ._oa. .u 000 Ujhd >>F— mePwHoz Hzmummm v0 Hm 000>H>mzw Hzmummm oo-or oo- SHDAIAHHS 1N3383d 00'08 OO'OZI' 00'091 «0.0 N.Nw 000 «.00 mma 0.00 000 0.0m 000 H ..K QB 00 mo mcowmum>coo musumquEmH 0000000: .mmusdfiz 0 now mmusumumaawe 2000 um uamucoo musumfloz .0.3 Noa um Hmvoz dowumawaumu ”~00. ureHH N~.o ofi.o mo.o no.0 . .o.o LL00; 00000 00000 “0"!!!“ 04+XO mw> #200000 00 pm 000>H>000 #200000 N .m 9303 N0.. 0 00. Hr .mmusaflz 0 you mmusumumasme 5000 um uamuCOU muSumfioz .n.3 Nma um H0002 coaumcfieumu m.m mudwflm .Huo «duo 00.0 N.N0 000. 0.00 mnfi _ n.0m 000 ”w 0.0n 000 n n l H.Hm. OWN _ 00 mo mcowmum>cou muSumumaEmH :0 ... .. no: ... J6 $0 ... .o .. manpwsz Hzmummm 5 #0 0003550 ._.zmummm r HONQN .mmudcfiz 0 How mmuDumuwQEmH swam um ucmucoo munumaoz NON um Hmvoz cowumcflEhmw .030 005000 A H010 020p 3._0 N700 00.0 00.0 00.0 0.0.0 N0..0 . .00.pud .mm 000 3 .mm 0N0 .05 000 .mm 000 .K CE 00 mo mdoamuw>co0 muSumquEmH “.02 m “mm + ..u a“ m .0 2% m waspwHoz 0200000 ON 00 000>H>000 #200000 - APPENDIX F Thermal Effects on Available Lysine tlI.{0J>n‘ 14> nJJU~4~L -WELQE~ ~ «1 qu‘f... 160 - .wcfivmmu mawcww mo cowumfi>mw wumwGMum *« .Am.q coauumm mmmv mwcwvmmu mHaHuHDB mo wwmum>< « o No-m~mmm. Ho-mouoa. OH m.mmfi owm ¢H mm q No-mH¢mo. No-moom¢. om m.~mfi omN «H mm o No-mohha. Ho-moeflfi. om w.NmH 0mm «H Hm o No-mHH¢~. Ho-moqmfi. om m.hmfi owm «H om o No-mmmhm. No-m¢NHH. oq w.~m~ owN «a me o No-mmwo~. No-mmqflm. om w.~m~ 0mm ea we 0 No-memqm. No-mmmfie. oo m.~m~ owm «H Ne o No-mmmmq. Ho-mmoma. co m.NmH omN «a me o No-mwmqm. Ho-ma~om. oH ~.~mH ohm ea me o No-mo~ofi. Ho-mommN. ON «.mmfi cum «H «q o No-mflmmq. Ho-mmwmfi. om «.mmH cum qfi me m No-mommm. No-mmm~m. oe N.~m~ cum «H Ne o ~o-momo¢. Ho-mmowa. om N.~mH ohm «H He 0 Ho-mmmofi. Ho-m~o0H.- co «.mmH cum «a oe o No-m~¢Hm. Ho-mom~H. om N.¢N~ com ea ¢m e Ho-m¢m~m. No-mmohq. om N.©~H com efi mm q Ho-mmmHH. Ho-mmomw. om ~.o- com efi mm o ~o-mom~w. Ho-mm-H. co N.QNH com ea on 2 macs z mHoa o g>< mmfioe a>< mmHoe .afia 00 no as e .02 sovmmpm «*a0wumw>mn «coauwuuamuaoo maHH wpsuwumasma ucmucou umma mo mmmpwmo unavamum wusumwoz mcwqu mHAmHHm>< co muuwmwm HmEuOSH A.uaouV H.m mHan - )t))44] 4354114 \.JIDJJ 4.H Dianne 164 - .mafinmmu mawawm mo cowumfi>mv vumvamum «¥ .Am.¢.:0Huumm mmwv mwcwvmmu mamwuasa mo mmmum>< « o No-mwmo~. Ho-mmmmfl. 0H m.wefi oom om mHH o ~o-m~o-. No-m~m¢¢. ON m.wq~ com ON “HH 0 No-mfiomm. Ho-mmH¢H. om m.wq~ com on OHH o No-M¢Hofi. Ho-mHHoH. oe m.me~ com om mHH o No-mwomm. Ho-momHH. om m.mq~ com om ¢HH o ~o-mom¢m. No-m~oH~. ow a.qu _oom ON mHH o No-mmmom. Ho-mnmmfl. 0H m.mq~ com om NHH o mo-mflm~w. Ho-maqofi. oq m.mq~ O¢~ ON HHH o ~o-mo-~. No-moooo. om m.mq~ omm ON oHH o ~0-mo-~. mo-mHHmH.- ow m.mefi oaN om aoH z macs z macs . o g>< mmfios q>< mmfioa sea uo no as e .02 aowmmum «ecowuww>mn «cofiumuucmuaoo mEHH musumquEmH ucwucoo ume mo mmmuwm vumvcmum musumwoz I '1 mcwmku mammawm>< co wuuwmmm HMEum£H A.uc00v H.m mHAMH 162 - .wcavmmu mawcfim mo coaumfl>mv vumvamum *« .Am.¢ defiuomm mmmv mwaflvmmu maawuasa mo mwmum>< « o No-momfim. Ho-mommfi. om n.0NH cow 5H Hm o Neumamem. acanHoH. om H.HNH omm NH om o NouMmmmm. Henmwwmm. a Houucou NH mm o NOnmNoqN. Neumommq. om m.mq~ com 0H mm o NOumonH. Neumowom. om m.mq~ com me mm o NOanmom. Neummwom. oq m.mq~ oom «H mm o Noumamoa. NanmmHHN. om m.wq~ com 0H mm o Neummomw. menmqomq. om m.m¢~ oom 0H qm o Noumowmm. Heumwowa. 0H m.mq~ omN ma mm o Noummmwo. Ho-mo~qH. om m.mq~ omm 0H mm q Nonmmmmq. Holmomoa. oq m.mq~ omN 0H Hm o Neum~¢wa. Neumuqmn. om m.mq~ 0mm 0H om o menmmmqq. menuanm. om m.m¢~ omm 0H mm o NeummmoH. acumomoa. oH m.mmH 0mm 0H mu m Nonmoawm. acumHHnH. om w.mm~ owm oH mm o Nouqumm. H01m¢NMH. om w.mmH owm ma on o Noumm¢mm. Hoummoafl. oe m.mmfi owm 0H mm m monmwaoa. «cummowe. om w.an owm 0H «m o Ho-mm~HH. ~o-mmhmm.- om m.nmfi omN 0H mm Z me08 Z mQHOE A>< mmHoe A>< mmfioe .:H8 00 mo 23 N .02 Bovmmum **coHumw>mQ «cowumuucmocoo oEHH musumquBMH uamucou ummH mo mmmpmwa wumwGMum , musumaoz mawmzq manmawm>< co muowmmm HmeuwnH A.ucoov H.m mHnma APPENDIX G Available Lysine Model and Data Plots --Second Reaction Only RVRILRBLE LYSINE RT 270 F TIME 165 — 9030 9030 9030 zo-u (N WON/WON] BNISAW BWQUWIUAU 00 C) D (132.20C). First order model fit to AVL data at 270°F Figure 6.1 ] 66 — D D. r? L o o C.’ $ erg p. a: C) Lu 9 ._D Eafi u: (,0>o—c >- v— —I 0 Lu 9": a‘ " *3: 3 2 H H E 3m 0: ’8: F- D D. -D N i D C? "S D D . c 3;: x . . D' 0 03'0 Z 0 ’0’0 90'0- (N WON/WON) 3 ISA-I BWBUWIUAU (137.800). Figure C.2 First order model fit to AVL data at 280°F -167- .8093: moomN um 3% .5. 3 “E 335 $30 $5 Md 3&2 72:: ME: 00.0.0 00.0.0 00.0.0 00.0% 00.0.0 00.0_N 00.0% 00.0. e ..uuu a mA ”U m ..ng 0.]. L3 1 IA S '01 9.3 a. x .J c N calm“. m am a II/ $me “ saw 0 “I .._ 03 E MESS 523E; -om e LU DO. D¢u F .Aoom.quV mooom um mums g>< ou “Hm Hmuos “mayo umuflm q.u muswam “.2020 mth 00.0m0 00.0mu 00.00 00.00 a. I x” .lu BE n ._.. .9. 63 w 2:22. t. ._ 8 awmmm as? was mm“ m“ mzmh w> m oom Hm msz>J MJm¢4H¢>¢ XflEl 00.0w P m 0 00. "‘Tfijlljullllllllll“