,- . ~ .. . . J ' I J ,v I '1 ‘.,. vn- MCQ~N‘§~VW$Q‘W‘Q‘G‘ ‘ «a. Wm‘w. GRAIN DAMAGE STUDIES IN MODIFIED cmssnow Bavaria Dissertation for the A Degree of M. S. MlCHEGAN STATE UNIVERSETY ADALBERTO DIAZ 1973‘ FLIP $3 ) ABSTRACT GRAIN DAMAGE STUDIES IN MODIFIED CROSSFLOW DRYERS By Adalberto Diaz The effect of the operator on testing the breakage, stress-cracks and germination of shelled corn was analyzed. The dependability of the quality tests when performed by different operators was assessed. The Stein Corn Breakage test, candling (stress- crack test) and the standard germination test as well as test weight were used as quality criteria. Tests of grain damage at six locations along the Michigan State University dryer were performed using seed corn. Corn obtained through trade channels was used for the other tests. The two modified crossflow dryers, the Hart-Carter moving bed model and the Michigan State University station— ary bed type, were investigated. Better uniformity of grain moisture and improved quality after drying are the main differences of these dryers as compared to convention- al crossflow dryers. The effect of the two dryers on corn quality was investigated in particular. Statistical analyses showed the significance of the Operator effect on stress—crack results obtained by the method of candling. No significant difference was ob— served in breakage method, germination test, test weight Adalberto Diaz and moisture content determination. Comparing the Hart-Carter (HC) dryer with the Michigan State University (MSU) dryer with respect to the number of stress-cracks, a significant difference between dryers was observed. Breakage was not significantly different. Checked kernels (seed corn) along the sections of the MSU dryer were affected by the drying treatment. High temperature grain exposed to rapid cooling did not in- crease the number of stress-cracks as expected. Breakage and germination, however, were significantly affected. Approved /////LZJE/»/sé ggmfl/ Major Professor 46A W Department Chairman GRAIN DAMAGE STUDIES IN MODIFIED CROSSFLOW DRYERS By Adalberto Diaz A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Agricultural Engineering 1973 I dedicate this work to my parents, to my wife, Mireya, and my children, Enrique and Barbara. 11 ! .wav an“. . L; 2 (7'! D" 1 «3:3 ACKNOWLEDGMENTS For the guidance and encouragement in this research and throughout my graduate work, I am truly grateful to Dr. Fred W. Bakker-Arkema. Appreciation is also extended to "The Latin American Scholarship Program of American Universities" for Providing financial support for my program at Michigan State University. Thankful acknowledgment is extended to Mr. Ralph Gygax and Mr. Oscar Braunbeck for their assistance in the laboratory and concepts presented in this dissertation. iii LIST OF LIST OF CHAPTER CHAPTER CHAPTER TABLE OF CONTENTS TABLES . . . . . . . FIGURES . . . . . . . . . . I. INTRODUCTION II. REVIEW OF LITERATURE . . Importance of Corn Losses . . . Meaning and Parameters to Evaluate Corn Quality 0 o o o o o o 0 Requirements of Artificial Drying Corn Quality Parameters Considered In Corn Artificially Dried . . . Breakage . . . . . . Stress Cracks . . . . . . . . Germination and Viability Germination Viability . . . . Millability . . . . . . . . III. EXPERIMENTAL PROCEDURES . . . . Corn Grain Quality Parameters and Drying NethOd O O O O O O O O O 0 Methods of Corn Grain Quality Evaluation Used. Corn Samples . . . . . . . . Conditioning of Corn Samples . . The Grain Conditioner . . . iv Page vii WWH .t' 10 12 13 14 15 18 18 18 19 19 20 CHAPTER CHAPTER Breakage Test Procedure . . . . . Stress Crack Test Procedure . . . Germination Test . . . . . . . Test Weight and Moisture Content Determination . . . . Test Weight Moisture Content . . . . . The Dryer . . . . . The Commercial Type . . . . . . Laboratory Type . . . . . . . Drying Conditions . . . . . Humidity and Temperature of the Air Statistical Analysis of the Data . . Comparison of Means . . . . . A Paired-Difference "t" Test . . . . IV. OBJECTIVES . . . . . . . V. RESULTS AND DISCUSSION . . . . Variability of Results in Grain Quality Tests Due to Operator Effect . . . . . Influence of the Operator on Breakage Test Results . . . . . . . . . Influence of the Operator on Germination Test Results . . . . . . . . Influence of Operator on Stress-Crack Test Results . . . . . . . . . Influence of the Operator on Test Weight and Moisture Content Test Results . . . Test Weight . . . . . . . . Moisture Content . . . . . . Page 22 22 2A 25 25 25 27 27 27 32 32 32 32 35 36 37 37 37 38 38 A0 A0 N1 Page Comparison of Corn Quality Parameters Between Hart-Carter and MSU . . . . . A2 Stress Crack Comparison . . . . . . A3 Breakage Comparison . . . . . . . A7 Analysis of Quality Factors for Certified Seed Corn Dried Artificially . . . . . . A8 Moisture Content After Drying . . . . A8 Stress Crack Evaluation . . . . . . 51 Breakage Evaluation . . . . . . . 55 Germination Evaluation . . . . . . 56 CHAPTER VI. CONCLUSIONS . . . . . . . 58 APPENDIX A . 60 APPENDIX B . . 60 APPENDIX C . . . . 61 APPENDIX D . . . . 62 APPENDIX E . . . . . . 63 APPENDIX F . . . . . . 63 APPENDIX G . . . . . . . . 6A APPENDIX H . . . . . . 6A APPENDIX J . . . . . 65 APPENDIX K . . . . 66 APPENDIX L . . . . . . 67 APPENDIX M . . 68 APPENDIX M . . . . . . . . 68 APPENDIX P . . . . . . . . . . . 69 LIST OF REFERENCES . . . . . . . . . 75 vi Table Table Table Table Table Table Table Table Table Table Table Table Table Table 2-3. 2-A. S-A. 5-5. 5-6. LIST OF TABLES Grade and grade requirements for corn Effect of drying method on brittleness of dried corn according to Sinha and Muir (1973) . . . . . . Percentage of checked kernels at various different drying conditions (Thompson, 1967) O O 0 O O O O O O Germination of corn artificially dried at various temperatures . . . . Percentage of moisture content of the Hart Carter samples received . . . Equivalence of pounds per bushel for gram weights . . . . . Operator effect on stress crack results Page 5 10 12 1A 19 26 39 Moisture content result obtained with the Steinlite . . . . . . . . Moisture content results obtained with the Air-Oven . . . . Comparison of average moisture content after drying for H0 and MSU samples . Significant values of'dlfor all compari- sons of the dryers and control . . Results of the stress-crack test for the control, HC and MSU dryers . . Percentage content in the HC and of final grain moisture the middle of the column of MSU dryers . . . . Percent of HC and MSU breakage obtained with the dryers, and Control sample vii Al Al “3 AA “5 as A8 Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table 5-9. 5-10. 5-11. 5-12. C-l. D-l. E-l. J—l. K-l. Duncan's test results for sound kernels . . . . . . Duncan's test results for multiple cracks . . . . . . Duncan's test results for checked kernels . . . . . . . Results of "t" test used to compare Page 52 52 52 means, of single crack for dryer sections and control sample . . . . Duncan's test results for breakage Germination results in seed corn . Duncan's results for germination . Percentage of germination at different 5A 55 56 56 temperatures of drying, initial moistures of grain and relative humidity of drying air according to Watson (1960) . . Percentage of breakage in U.S. No. 2 corn 0 o o ‘ o o o o 0 Percentage of germination in U.S. No. 2 corn 0 O O O O O O O O U.S. No. 2 corn test weight . . . U.S. No. 2 corn stress crack results . "F" significance of different quality tests, using U.S. No. 2 corn . . . "F" significance of stress crack, using U.S. No. 2 corn . . . . . . Values of "t" used to compare stress crack among HC and MSU dryers, and then versus the control . . . . . Value of "t" used to compare breakage between HC and MSU dryers, and control Grain moisture content in each section Percentage of stress crack in seed corn viii 57 6O 6O 61 63 63 6A 6A 65 66 Table Table Table Table Table Table Table Table Table Table P-3o P-A. P-5- P-6. Page "F" test significance for stress cracks in seed corn . . . . . . . 67 "F" test significance for breakage and germination in seed corn . . . . 67 Percentage of breakage for seed corn . 68 Percentage of germination in seed corn. 68 Grain temperature history of drying the 123-MSU sample in the MSU dryer sections 69 Grain temperature history of drying of the 126-MSU sample in the MSU dryer sections . . . . . . . . 70 Grain temperature history of drying of the l27-MSU sample in the MSU dryer sections . . . . . . . . . 71 Grain temperature history of drying of the 123-S sample in the MSU dryer sections72 Grain temperature history of drying of the 126- S sample in the MSU dryer sections . . . . . . . 73 Grain temperature history of drying the 127-S sample in the MSU dryer sections. 7A ix n. n. n “I n. w. r V. I .J L 3 ma U .1 U I I“. an. 33 3c .5 36 30 ED 3.3 a. n1. 1.. . A . no; —.. 7. 7. m: We“ Wu Wu. W; D: Figure 1. Figure 2. Figure 3. Figure A. Figure 5. Figure 6. Figure 7. Figure 8. Figure 9. LIST OF FIGURES Schematic of conditioner . . Box to evaluate stress-cracks by the candling method . Diagram of the Hart-Carter crossflow dryer . . . . . . . . Diagram of the different stages of the MSU dryer . . . . . . . The MSU dryer . . . . . . Arrangement of the drying set-up . Final grain moisture content along the dryer in 123-8 sample . . . . Final grain moisture content along the dryer in l26-S sample . . . . Final grain moisture content along the dryer in 127-3 sample . . . . Page 21 23 28 29 31 33 A9 A9 50 CHAPTER I INTRODUCTION The diversified uses of corn have motivated extensive research on grain quality. The high initial moisture of shelled corn in the field requires the application of artificial drying to prevent corn deterioration. Depending on air drying temperatures, different degrees of damage to the grain quality will occur. High air drying temperatures impair the grain quality by increasing the stress-cracks and the breakage and by decreasing the germination. Millability is also affected by the lower quality giving lower yields in the dry and wet milling processes. Drying conditions like air temperature, and humidity as well as air flow, will affect corn quality to a different extent depending on the drying method used. Continuous drying methods have been modified in order to achieve the lowest amount of damage using heated air. Energy consumption is also being optimized in continuous dryers taking into account the quality of the grain. Furthermore, processing (milling) of damaged corn requires more energy to produce the same amount of final product. 2 The purposes of this study were: a) To analyze the operator effect on grain quality tests (breakage, stress-crack, germination, test weight and moisture content determination) b) To compare two modified cross flow dryers (The Hart-Carter and the Michigan State University) from the standpoint of grain damage 0) To investigate seed corn damage at different locations along the Michigan State University crossflow dryer. CHAPTER II REVIEW OF LITERATURE Importance of Corn Losses. The world production of corn is used as food for man and domestic animals, and for the manufacture of protein, oil and other materials. Potable alcohol is also manufac- tured from corn. Developing countries, mainly, use their corn production for food without previous industrial processing. It repre- sents the principal source of food for the population. Thus, these countries are affected by losses of corn in quantity and quality caused in different ways with storage being a principal factor. . Officials of the Food and Agriculture Organization (FAO) of the United Nations have estimated that 5% of all har- vested grains are lost before consumption (Christensen and Kaufman, 1968). In 1966, the world production of corn was about 8,500,000,000 bushels and if the 5% loss factor is applied, A25,000,000 bushels were lost. Drying is only considered as an aid to maintain quality of stored grains and seeds. ‘ Losses can occur when heated air causes damage to the grain. Uhrig (1968) defined damaged grain as: "grain that 3 A lacks certain characteristics of quality grain." Meaning and Parameters to Evaluate Corn Quality. To describe the quality of grain, Official Grading Standards (Table 2-1) have been defined. Akiyama (1972) Presented a study of corn damage and its effect on official grading standards. He considered the test weight, moisture content, heat damage, broken corn and foreign material as corn quality factors. ‘ Corn grain quality is a term possessing various mean— ings for different grain users or handlers. To farmers, quality relates to maturity, appearance and test weight. The seedsman may relate quality to germination, uniformity, and good seedling emergence. The miller relates quality as yield of desired product. An exporter may seek test weight and low moisture, foreign matter and total damage as quality factors. Finally, a livestock feeder may look at corn protein quality and total digestible nutrients (Duncan et a1., 1972). Requirements of Artificial Drying. Quality of grain dried with heated air is often lower than that dried naturally (Sinha and Muir, 1973). Due to high moisture content of the corn grain at the time it is harvested, it has to be dried before it can be stored for any length of time. Short harvest seasons and large acreages harvested, require a speed up of the drying U.S. GRADE AND GRADE REQUIREMENTS FOR CORN. Maximum Limits of -— Minimum WEIZEE Bzgkzn Damaged Kernels Grade ,busfizI Moisture foggign T t 1 Heat- ' aterial o a fizflfigig Pounds Percent Percent Percent Percent U.S.No.1 56.0 1A.0 2.0 3.0 0.1 U.S.No.2 5A.0 15.5 3.0 5.0 0.2 U.S.No.3 52.0 17.5 A.0 7.0 0.5 U.S.No.A A9.0 20.0 5.0 10.0 1.0 U.S.No.5 A6.0 23.0 7.0 15.0 3.0 U'S' U.S. Sample grade shall be corn which does Sample grade not meet the requirements for any of the grades from U.S. No. 1 to U.S. No. 5, ‘inclusive; or which contains stones; or which is musty, or sour, or heating; or which has any commercially objectionable foreign odor; or which is otherwise of distinctly low quality. Table 2-1. Grade and grade requirements for corn. to 6 process (Thompson, 1967). Accelerating the drying process results in an increase in drying capacity but it is ob- tained by increasing the drying air temperature, thereby affecting the quality of the dried corn. Storage losses caused by insect damage, mold, and heating due to excess moisture can be practically elim- inated by drying and aeration (Hall,1957). Evidently, modern techniques of harvesting corn have made necessary the use of heated air. Several methods of drying have been evaluated by comparing the influence of heated air and its effect on corn quality. Thompson (1967) evaluated three continuous- flow dryers: the cross-flow, concurrent flow and counter flow dryers. He determined the corn quality after drying from each dryer. He concluded that concurrent flow produces grain of higher quality for marketing than either of the other two methods operating under the same drying conditions. Bakker et a1., (1972) compared grain dried with a concurrent flow dryer and counter flow cooling with grain dried in a crossflow dryer and found that the foreign matter and germination percentages with the concurrent- counter flow dryer design were better than with commercial type dryersr Converse (1972) described a new dryer design called "A Commercial Crossflow—Counterflow Grain Dryer: The Hart-Carter" model. 7 Corn Quality Parameters Considered In Corn Artificially Dried. Generally, those tests used to evaluate corn quality or grain damage have been breakage, stress cracks, germin— ability, discoloration, humidex index and millability. An evaluation of grain damage with respect to breakage, stress cracks, humidex index and millability was made by Thompson (1967), and breakage and germination by Bakker (1972). Thompson and Foster (1963) also studied stress cracks and breakage in artificially dried corn. For measuring one parameter different laboratory procedures may exist. Kamimski (1968) studied the need for standards for evaluation of grain damage and found that the information obtained with some of these different methods showed generally poor correlation between the results. This implies that a breakage test, for instance, must be performed in a specific manner which is adequately defined. The causes of broken kernels, stress cracks, loss of germination, and quality of the corn grain for milling by heated air drying is explained below. Breakage. 'Corn dried artificially becomes brittle and this leads to breakage of the grain during handling (Sinha and Muir, 1973). Keller et a1. (1972), also, mention that field shelling and artificial drying make corn kernels more susceptible to breakage. Sinha and Muir (1973) concluded 8 that it is sometimes difficult to distinguish between damage caused by harvesting and drying. Improperly dried corn tends to become brittle and breaks readily with further loading, unloading or shipping increasing the amount of grain breakage (Kamimski, 1968). Bilanski (1972) studied damage resistance of seed grains and found that corn ker- nels were weakest when impacted on their edge side and strongest when impacted on their flat side. Mechanical strength or resistance to breakage of grains varies with moisture content, variety, temperature, type of load, and orientation of the kernel with respect to the direction of load (McGinty and Kline, 1972). I Thompson and Foster (1963) found that corn dried with heated air (1A0° to 2A0°) was two or three times more susceptible to breakage. The initial moisture content also affected the susceptibility of the grain to break. Corn dried from 30 percent initial moisture was more susceptible to breakage than corn dried from 20 percent. The same results were found by McGinty and Kline (1972), when they compared the Cargill Grain Breakage and the Stein Breakage testers. Susceptibility to breakage increased when drying air temperature and air flow rate increase. When drying air temperature was increased from 1A0°F to 2A0°F, breakage increased from 16.5% to 19.3%, respectively. Breakage was increased from 15.8% to 16.A% with an increase from 32 to 62 cfm per bushel (Thompson and Foster, 1963). 9 Thompson (1967) presented results of the effect of temperature on quality where breakage (Stein Breakage tester) was A.3 percent more at 200°F than at 300°F. Break- age is related to the number of stress cracks in the kernel. Thompson and Foster (1963) showed this relationship in terms of increase in breakage due to drying; the percentage of checked kernels (6 to 5A%) increased breakage from 8 to 20%. Sinha and Muir (1973) using two-stage dryeration found a slight increase in the number of kernels without stress cracks, but no reduction in breakage. Tests conducted with partial heat drying resulted in an increase of sound kernels and a considerable decrease in the amount of breakage. Besides, the brittleness of the grain after drying can make the grain fall apart at the first impact; this produces a higher percent of breakage (Roberts, 1972). Improper methods of drying can cause more damage to the grain (internally fractured kernels) and Bailey (1968) classified these as using too high a drying temperature, drying too far in one pass, holding corn in heated air too long, drying down too far, or cooling too quickly. Thompson (1967) compared the effect of counterflow and delayed cool- ing and found that a concurrent flow dryer with a counterflow cooler is not an adequate substitute for delayed cooling for reducing the brittleness of dried corn. He, also, concluded that drying speed, expressed in terms of moisture loss in percentage points per hour, increases the brittleness; higher breakage is the result. 10 Sinha and Muir (1973) have presented a table (Table 2-2) of comparison between drying methods with heated air. Partial heat drying gives less breakage and a higher per- centage of sound kernels. However, partial drying has the disadvantage that a long period of drying is required before a safe moisture level is reached. Drying Method égigtflie Sound Kernels Breakage (without stress % cracks) % % Conventional Continuous Flow 25 8.8 11.3 Dryeration 25 60.6 6.7 Two-Stage Dryeration 25 72.0 7.0 Partial Heat Drying 26 80.A A.5 Unheated Air 26 93.8 2.0 Table 2-2. Effect of drying method on brittleness of dried corn according to Sinha and Muir (1973). Stress Cracks. Stress cracks are fissures in the corn endosperm not on the seed coat. Stress cracks have been mentioned before as causing susceptibility to breakage. It also influences germination and millability. Thompson and Foster (1963) found that there is some relationship between stress cracks 11 and germination, and checked kernels almost assures low germination. However, the absence of stress cracks does not assure high viability. The severity of the drying treatment is indicated by the number and type of stress cracks (Thompson and Foster, 1963). Rapid drying or cooling, or both, are responsible for stress cracks (Thompson, 1967). Ross et a1. (1971) studied stress cracking of white corn as affected by over- drying and found that stress cracking was most severe in the grain dried to 10 or 1A percent moisture content, in the drying air temperature range of 130°F to 220°F. Samples dried with air at 100°F had a noticeable drop in stress cracking. Stress cracking decreases with lower final moisture contents and as drying was started at lower initial moisture contents. This phenomenon has not fully been ex- plained; the authors explain that physical and chemical changes occur during overdrying that make the grain more resistant to stress cracking during the cooling period. Sinha and Muir (1973) mentioned the same factors affecting stress cracking such as: rapid drying, increasing of drying temperature, moisture content before and after drying, rapid cooling. Thompson (1967), using the candling method to detect stress cracks, investigated the effect of temperature, initial moisture and airflow rate on quality and obtained the following results: 12 Table 2-3. Percentage of checked kernels at various different drying conditions (Thompson, 1967). Drying Air TEmp. Initial Mbisture Air Flow Rate 23 18 Cont. 200 300 A00 I F I F Cont. LOW’ High Karnels u5.3 39.0 27.8 6.8 36.8 3.2 39.1 6.8 37.8 36.8 I - initial percentage of checked kernels before dry- ing. F 8 final percentage of checked kernels after drying. Corn dried at excessive temperatures develop cracks and fissures in the endosperm that will not yield large grits as is required in the milling industry (Watson, 1960). Checked kernels increase from 20.2 to A0.2% when the drying air termperature is raised from 1A0°Fto 290°F (Thompson and Foster, 1963). They, also, found a 6A.9 percentage of multiple cracks, using candling to detect cracks, in corn dried at 1A0°F. At 290°F, multiple cracks decreased but checked increased. Germination and Viability. Germination and viability are very important corn quality parameters for the dry and wet milling industry. Few results and tests used in determining germination and viability are available. Viability is determined by the l3 2, 3, 5, triphenyl tetrazolium chloride test. Germination. When heated air is employed for drying corn, loss of germinability is directly related to high grain temperatures (above 110°F). Temperatures above 1A0°F decrease germination as mentioned by Watson (1960), Hall (1957) and Christensen et a1. (1969). However, Bakker et a1. (1972) using a con— current flow dryer with counter flow cooling, found that air temperature at 220°F lowered the germination percentage (standard germination test) by less than ten points which is lower than usually obtained in commercial crossflow dryers. Watson (1960) presented germination data of two exper- iments, where germination percentage was adversely affected by drying temperature at high air flow rate, by high rela- tive humidity and by high initial grain moisture; at 32 percent initial moisture, and 120°F air temperature, A0 and 15 percent relative humidities of the drying air, the resulting germination was 39 and 75 percent, respectively. At 21 percent initial moisture, using the same temperature and relative humidities of drying air, germination was 9A and 95 percent, respectively. Under the same experiment when temperature of the air was increased the germination percentage decreased drastically. Another source of loss of germination is the physical 1A damage caused to the grain. As drying stresses increase, single cracks develop into multiple cracks or checks assuring low germination (Thompson and Foster, 1963). Brekke et a1. (1972) published results of the effect of dry— ing air temperature (Table 2-A). Table 2-A. Germination of corn artificially dried at various temperatures. Drying Approx. Dried Corn 1 Air ‘ Mathleenxfl. Brynn; Gennhmwiqn Tbmp. Tbmp. Nbishnxe Thu? 35-90 60 15.8 A8 85 90 90 16.0 7 75 1A0 135 17.A 2.5 23 190 ‘ 180 16.6 1.2 6 Viability. Mayer and Poljakoff-Mayber (1963), Sinha and Muir (1973) and Roberts (1972) consider viability as the ability of seed to germinate. Mayer and Poljakoff—Mayber (1963) have concluded that "even if a seed loses its viability this does not imply that all metabolic processes stop or that all enzymes are in- activated. Only the sum total of processes which lead to germination no longer operates." Positive results of via— bility obtained with the 2, 3, 5, triphenyl tetrazolium 15 chloride method do no indicate a 100 percent of germination (Mayer and PolJakoff-Mayber, 1963). Watson (1960) considers that grain dried at a temper- ature above 150°F shows loss of viability. However, he reports that loss of germination is not a good index of milling damage. Millability. Physical and chemical changes in corn kernels occur when it is dried with heated air. Excessive drying temperatures reduce yields of starch and results in lower oil yields when wet milled; this, also, increases brittleness of corn, reduces the nutritional value and the germination decreases (French et a1., 196A). Drying corn at temperatures above 1A0°F lowers the fermentable carbohydrate content and reduces the efficiency of separation of starch in wet milling (Roberts, 1972). Sinha and Muir (1973) have concluded that corn used in the wet milling process should not be heated above 1A0°F to 1A9°F. Watson (1960) stated that the use of overheated corn results in lower yield of starch and higher protein content in starch, because the protein matrix holding the starch in endosperm cells will not soften in the steeping process and will not release starch during milling. Cracks will cause excessive breakage during dry milling thereby reducing the yield of large grits. Protein content, the viscosity of its 16 aqueous pastes and the color of refined corn syrup are important criteria of starch quality. Preservation of corn viability is another indicator of acceptability for milling. Watson (1960) considers the viability of corn kernels to be destroyed when corn is heated above 1A0°F. Lobanov (196A) says that under modern food technology, the germination capacity of food grain (corn) is extremely important and that so-called dead grain gives products of lower quality because its capacity for fermentation is less than that of grain with a high germination capacity. Reduction in germinability from drying at high temper- atures occurs at about the same temperature that results in the chemical changes that make difficult the separation of starch and protein (Christensen and Kaufman, 1969). Concurrent flow drying test made by Thompson (1967) in 196A showed that the millability score, analyzed by the prime starch milling test, decreased as the temperature increased. Drying air temperature of 200°F, 300°F, and A00°F gave a millability score of 88.8 percent, 73.A percent, and 5A.3 percent, respectively. In 1965, he obtained the same results with an increase of 5 to 10 points in millability scores. Thompson (1967), also, evaluated the effect of the air flow rate on the millability score which decreases at high flow rate. The effect of the depth of the drying column (2 and A feet) did not affect the millability scores. Initial moisture of the grain of 23 and 18 percent decreased 17 millability from 91.7 to 69.A percent and from 89.A to 86.7, respectively. CHAPTER III EXPERIMENTAL PROCEDURES Corn Grain Quality Parameters and Dryinngethod. Breakage, stress crack and germination were chosen as parameters to evaluate grain damage and to determine corn quality, using high-temperature air. Cross-flow drying, one of the methods of continuous drying, was used to dry the grain. Methods of Corn Grain Quality Evaluation Used. Although several methods exist for each test, there has been little work done on comparing criteria for choosing the breakage and stress crack tests. The stress crack detection method of candling offers the possibility of obtaining a correlation between the kind of stress cracks and germination. Besides, the equipment is easy to build in the laboratory, is inexpensive and is precise in determining stress cracks. Thompson and Foster (1963) compared candling and x-rays, and reported that candling was a better method to distinguish cracks. For the breakage test, a Stein Grain Breakage testerl 1 Model CK2, Fred Stein Laboratories, Atchison, Kansas. 18 19 was used. It was selected on the basis of McGinty's (1970) report which considers this device as simpler in design, easier to operate and presenting a steep breakage-tendency curve that gives good readability, when compared with other breakage test devices. Corn Samples. Three different lots of corn samples were analyzed, U.S. No. 2 corn from a Mason elevator, Hart Carter (HC) samples from Minnesota and certified seed corn (SC). Table 3-1. Percentage of moisture content of the Hart Carter samples received. Moisture . Sample NUmber Content 12l-HC l22—HC l23-HC l2A-HC 125-HC 126-HC 127-HC gndrizg 25.0 25.0 25.0 25.0 23.5 23.5 23.5 1 grieges 20.0 16.0 1A.5 20.0 15.0 15.0 1A.8 Conditioning of Corn Samples. The U.S. No. 2 corn, the Hart Carter and the seed corn samples were conditioned in a conditioner, to reach the equilibrium moisture content (12.5%) at 80°F and 75 percent relative humidity before the tests (breakage, stress-crack and germination) were performed. 1 Corn samples dried in the commercial type. 20 Twelve samples of U.S. No. 2 corn, distributed at random among three operators, were tested. Each operator analyzed at the same time one complete set of tests. The Hart Carter samples (123—HC, l26-HC and l27-HC) were analyzed by one operator. Due to the limited avail— ability of wet corn, only 123-HC, 126-HC and l27-HC could be compared to 123, 126, l27-MSU dried samples. Seed corn samples (123-SC, 126-SC and 127-SC) were re- wetted to 25 percent moisture, and kept for 5 days in a A0°F box before drying. These samples were dried in the MSU dryer. The Grain Conditioner. All dried samples were placed in a conditioner (Figure 1) before performing the tests. The conditioner was set up in such way it provided a moisture content equilibrium of 11 — 12.5 percent. Saturated sodium chloride solution conditioned the air humidity to 75 percent inside of the conditioner and the temperature was controlled by placing the conditioner in a 80°F box. A small fan maintained the air circulation in the conditioner at all times. To dissipate the heat coming from the fan motor an air conditioning was turned on periodically. However, the temperature was not critical since the sodium chloride provides the same equilibrium moisture for a wide range of temperature (32 — 122°F). The samples were taken from the grain conditioner after Grain 1" 1/2" /2ll H :1 .= i i i 3:: AU «‘—— FM ——7 25" , Lg —-- a F. D/ \0 1 H3 "L a \a; Figure 1. Schematic of conditioner. ‘\ ‘. Grain H H «1 |-=r-|l-§r-l /2" 1/2" I] U ran— ._4— m [T "' "“ “l J a U cd——— F =7 a F’ van » \V \xl \ : I :r _—_—‘r+ 4 O " m H m 43>: Hm (UV-c (DB Figure 1. Schematic of conditioner. 972.. 25" #— 13"——+ 22 A or 5 days and the moisture content of the samples was determined. Breakage Test Procedure. Broken and cracked kernels and foreign material were removed from 200 grams conditioned grain. Then a sample of 100 grams was placed in the Stein Corn Breakage tester; when the machine started, the impeller at a speed of 1725 RPM, threw the kernels against the sides of the container for two minutes. The time that the sample remained in the breakage machine was controlled by a timer, insuring all samples to be exposed to the same treatment. Following the two-minute time period, all of the sample was poured into a 12/6A" round hole sieve. The remainder On top of the sieve was weighed and subtracted from 100 grams. The result yielded the percentage of breakage. Stress Crack Test Procedure. The candling device (Figure 2) for determining stress cracks, consists of a rectangular wood box with a 150-watt incandescent bulb in the middle of the box. The top is covered with glass painted a red color everywhere except for a little square where the kernels are placed to be examined. At the same time that the breakage sample was taken, a separate sample of about 75 grams was taken, and the cracked and broken kernels as well as foreign materials were 23 Hole 4L— 12 fl 1 4r- ‘A\\\\‘ Fan '1 l2 \\ Figure 2. Wood box to evaluate stress-cracks by the candling method. 2A removed. Kernels having a chalky appearance had to be taken out of the samples because of the difficulty in looking through them. Then, from the remaining kernels of the cleaned sample, a 50-gram weight was stored in a plastic bag until analysis. Four different categories of kernels were considered: sound kernels, single cracks, multiple cracks and checked kernels. Single crack are those kernels having Just one crack. Multiple cracks are those presenting two or more cracks. Checked kernels have horizontal and vertical cracks given the appearance of a sieve configuration of fissures. Each kernel of the 50-gram sample was examined through the light. The kernel was placed in different positions, in order to detect all cracks through the kernel. Then, sound kernels, single crack, multiple cracks and checked kernels were counted and reduced to percents. The number of corn kernels in 50-gram samples varied from 155 to 180, depending on the kind of grain. Germination Test. Samples of 100 kernels were wrapped up in wax and brown towel paper. The brown towel sheets enclosing the kernels were moistened and wrapped with wax paper to keep the towels moist. Garbage cans placed in a 80°F box kept the samples for the seven-day period recommended by the Association of 25 Official Seed Analysts. A first count and moisture control were made at the fourth day of the test. When the required period of time had elapsed, the germinated seeds were counted and the percent of germination determined. Test Weight and Moisture Content Determination. Test Weight. To obtain the test weight two procedures had to be used. The conventional method used a one-quarter cup. It could be employed if the size of the sample was sufficient to fill up the cup. For small size samples, which was the case of the samples taken from the six sections of the MSU-dryer samples (500 grams or less), a 250-ml. beaker replaced the one-quarter cup. It was filled up with corn and weighed. The weight results were correlated to a previously per- formed linear regression analysis equation, Table 3—2 gives the linear regression analysis results. Moisture Content. Moisture content was determined in the Steinlitel tester. The corn sample of 100 grams is placed into a grain chamber, from where it is dropped into a chamber formed by two plates of a condenser. 1 Fred Stein Laboratories, Atchison, Kansas. 26 Table 3-2. Equivalence of pounds per bushel for gram weights. WEIGHTS lbs/bu grams A7.00 15A.689 A7.25 155.783 A7.50 156.877 “7.75 157.971 A8.00 159.065 A8.25 160.159 A8.50 161.253 A8.75 162.3A7 A9.00 163.AA1 A9.25 16A.535 A9.50 165.629 A9.75 166.72A 50.00 167.818 50.25 168.912 50.50 170.006 50.75 171.100 51.00 172.19A 51.25 173.288 51.50 17A.382 51.75 175.A76 52.00 176.570 52.25 177.66A 52.50 178.758 52.75 179.852 53.00 180.9A6 53.25 182.0A0 53.50 183.13A 53.75 18A.228 5A.00 185.322 5A.25 186.A16 5A.50 187.511 SA.75 188.605 55.00 189.699 55.25 190.793 55.50 191.887 55.75 192.981 56.00 19A.075 27 The dielectric properties of the grain are based on the moisture content. A certain capacitance value corresponds to a certain moisture content. In order to check the results of the Steinlite, the air oven method, using the air-oven (212°F for 72 hours), was used. A sample size of 100 grams was placed on a screen tray inside the oven and weighed after the required time. The Dryer. The Commercial Type. The commercial type is a continuous cross flow dryer which has been modified to improve some characteristics of the conventional cross flow dryer. The modified design gives a better moisture content distribution in the grain. It consists of three sections; the first and the second to dry, and the third to cool the grain (Figure 3). The exhaust air in the first section is exhausted to the atmosphere. The outlet air of the second and third sections is recirculated. This design requires less energy than non-recirculating models. Laboratory Type. A steel dryer consisting of one static section of the commercial type was built in the Agricultural Engineering Department at Michigan State University (MSU dryer). Two drying stages and one cooling stage could be accomplished by switching the one section (Figure A). Heated air is 28 hH< H000 IIIIJ, luv 17 A! HHH omoom sH moommuoom weaosom 10 mass: 11 HH owmpm AlmMI‘L Naomi Anfimv CH H owmpm p50 CH .4 :Hmnw Diagram of the Hart—Carter crossflow dryer. Figure 3. 29 wcwaooo I1 moprm II wcfizho .7 owoom share fill! oMMpm ccooom omoom omens poo use oso m “M has Hooo m .nTIIII. eH ass pom a Anvllll eH has pom Diagram of the different stages of the MSU Figure A. dryer. 30 blown first at one side (A) of the grain layer for a time period equal to the residence time of the grain within the first stage. The heated air is then blown through the other side (B) of the grain layer for a time equal to the residence time of the second stage. Second stage is very important, since in that phase non-uniformity of moisture content of the dried grain is avoided. In the conventional cross flow type, one side of the grain column is exposed to heated air. With the Hart-Carter modification, both sides are exposed to heated air. Cooled air is then blown through the same B side for a time period equal to the residence time in the third (cooling) section of the continuous flow dryer. The MSU dryer is shown in Figure 5. It has six sections of 2 inches each, giving a column width of corn of one foot. It also has two more inches in the upper part to compensate for up to 30 percent shrinkage. The upper part is removable to facilitate filling and emptying of the dryer. The grain temperatures through the MSU dryer can be continuously monitored by copper-constant— an thermocouples placed in each section. Relative humidity can be monitored by hygro-sensors. \ \ ,‘ . ,\ , > . \~ . \ \ \ \ \. \ e \ \ x .\ 2 N in? 1'15. All"! 1"} s. l t S ry bed MSU dryer. 5. The stationa Figure 32 Drying,Conditions. Humidity and Temperature of the Air. In order to condition the humidity of the air, an Aminco-Airel unit was used. An electric heater was used to raise the air temperature up to 2A0°F. Air flow was 2 measured continuously by a laminar flow meter . The arrangement of these parts and of the dryer is given in Figure 6. Statistical Analysis of the Data. The limited availability of grain constrained the possibility of an a-priori statistical design. Thus, posteriori statistical tests were carried out. A one-way analysis of variance was used to analyze the influence of the operators in corn quality tests. The same statistical test was carried out for analyzing the seed corn results. Comparison of Means. If the "F" value calculated was non-significant, a t—test comparing two sample means was applied. The "t" test equation is: l lunerican Instrument Company, Silver Spring, Maryland. 2 flflie Meriam Instrument Company, Cleveland, Ohio. 33 Awake mcampmoELmQB Honpcoo soaoaesm / / .Hmv DwEOCMZ :1 Logo: \ sofim meHqu Lopmom assasoooam pouoz Lad oocfiea Arrangement of the drying set-up. Figure 6. 3A _ _ 1 t = 2 2 1/2 Zyl + 2512 n (n - 1) Y1 = mean of sample one Y2 = mean of sample two Eyi = sums of squares n = number of replicates The hypothesis that ul — u2 = 0 was tested. If the "F" value was significant, a Duncan's Multiple Range Test was used to compare means. In the representation of the Duncan's test results a line links all means with non-significance difference. The means that are not linked by a line are significant different among them. Significant studentized ranges (rp) for the five per- cent level were used in all tests. This value (rp) mul- tiplied by the standard error of the mean (sy) gives what Duncan has termed the "shortest significant ranges" (Rp). Then the difference between means is compared against the range Rp for the number of means (p) being compared. As given by Duncan2 two statements resume the test, first "each difference is significant if it exceeds the l Mendenhall, w. (1971). Cited by Le Clerg (1970). 35 corresponding shortest significant range, otherwise, it is not significant." Second is the exception rule "that no difference between two means can be declared significant if the two means concerned are both contained in a subset of the means which has a non-significant range." A Paired-Difference "t" Test. When comparing the HC (Hart-Carter) versus the MSU (Michigan State University) dryer and both against the control dryer, a paired difference "t" test was made. A pooled estimate of the common variance value of "t", for testing the hypothesis of u1 = u2, was compared with the tabulated "t" value in order to accept or reject the hypothesis. CHAPTER IV OBJECTIVES A brief statement of the objectives of this study is given below: 1. Analyze and become acquainted with the existence of variability in corn quality tests. 2. Compare the Hart-Carter and the MSU dryers with respect to using high air temperature of drying. 3. Evaluate certified seed corn as affected by the MSU dryer. 36 CHAPTER V RESULTS AND DISCUSSION Variabilitygof Results in Grain Qualiterests Due to Operator Effect. Operators A, B, and C analyzed four U.S. No. 2 corn samples. The moisture content of the samples varied from 11 to 13 percent after four days in the grain conditioner. Each test included the evaluation of the three basic quality parameters breakage, germination and stress crack plus complementary analysis of moisture content and test weight. All operators carried out the tests under the same ambient conditions. A one-way analysis of variance for a completely randomized design of equal sample size was performed. Influence of the Operator on Breakage Test Results. The breakage test results are given in Appendix A. The "F" test (Appendix E) indicated non-significant operator effect (0C=:25%). That means the operator is not an impor- tant source of variability when testing breakage with the Stein Corn Breakage tester. Even though the test is exposed to personal errors when cleaning and choosing the samples, the results show that 37 38 sample preparation has little influence on the outcome of the test. The breakage test itself was not expected to be sig- nificantly affected by the operator since the machine tester is self-controlled in the functioning of its mechanisms and timer. The applied breakage method is very dependable. It can be performed by different operators and still give the same results, if the moisture content and temperature of the sample are maintained constants at the test time. Influence of the Operator on Germination Test Results. The results of the germination tests (Appendix B) showed a non-significant operator effect (OC= 50%) as indicated by the "F" statistics (Appendix E). Low germination percentages were due to the condition of U.S. No. 2 corn coming from the 1972 harvest, which was unusual and a lot of damaged grain was present. The germination test method used was a simple one. The use of garbage cans did not need an exact control of relative humidity and temperature. The 80°F box maintained the desired temperature. Relative humidity was kept uniform by placing a cover on the can. Influence of Operator on Stress-Crack Test Results. Inconsistency in the pattern to separate sound kernels, single cracks, double stress cracks, and checked kernels 39 was found among operators. Pictures of single and double cracks and checked kernels served as a guide for the Operators to classify the kernels. An analysis of variance of the results of the stress crack tests (Appendix F) shows the following results: there is a significant operator effect on the results of the stress crack test. The levels of significance for each type of stress crack are listed in Table 5-1. The data is given in Appendix D. Table 5—1. Operator effect on stress crack test results. Level of Significance Type of Stress Crack Of Operator Effect Sound Kernels .5 % Single Cracks .1 % Multiple Cracks .1 % Checked Kernels .5 % The significant difference for sound kernels can have two explanations: one due to the variance in the kernel itself or second due to the operator. The latter case is only explained when the operator does not examine the kernels in different positions. The stress crack configuration is variable. This makes it very difficult to standardize the test and cancel the operator effect. A0 The technique allows the operator to develop his own criteria of classification when performing the test. Often, it is not clear how to classify a given kernel. It is recommended that a few samples be analyzed before performing the actual test samples in order to be— come acquainted with the grain and be consistent. Influence of the Operator on Test Weight and Moisture Content Test Results. Test Weight. This test is important from the point of View of U.S. corn standard classification. It also determines the mois- ture content correction by test weight (lb/bu) when using the Steinlite meter. One pound deviation from the actual test weight may change the moisture content reading as much as 0.25%. Two factors may account for the difference between operators when measuring test weight: a) the operator read— ing of the weight, and b) variability of moisture content among samples. The "F" test (Appendix E) indicates, however, the operator effect on test weight result is non-significant (°‘= 10%). Thus, the two mentioned factors did not affect the test and it can be reliable even when done by different op— erators. It should be remembered that the moisture content of each sample was brought to equilibrium in the conditioner before testing. Moisture Content. The Steinlite and air-oven methods, as expected, had no significant differences at the five percent level (Appendix E). Test results are given in Tables 5-2 and 5-3. Table 5-2. Moisture content result obtained with the A1 Steinlite. Moisture Content (z) Sample Operator No. A B C A, 10, 1 11.26 11.75 11.63 12, 6, 8 11.65 11.36 11.65 5, 7, 2 11.00 11.59 11.A6 3, ll, 9 10.97 11.26 11.AA Table 5-3. Moisture content results obtained with the Air-Oven. Moisture Content (Oven Dry %) Sample Operator No. A B C A, 10, 1 12.0 13.0 12.0 12, 6, 9 13.0 12.0 13.0 5, 7, 2 12.5 12.5 12.5 3, ll, 9 12.0 13.0 12.5 A2 Steinlite and air oven methods of moisture content determination were not affected by the operator. Compagison of Corn Quality Parameters Between Hart-Carter and MSU. Air temperatures of 200°F and air humidity of 0.021 (lbs of water per lbs of dry air) were the drying conditions of the HC and MSU dryers. The temperature and humidity of the air during cooling were 67°F and 0.005 (lbs of water per lbs of dry air) respectively. Control samples dried at 80°F and 75% relative humidity in the conditioner were compared with those dried with the Hart-Carter (HC) and MSU dryers. Control samples were designated as 123-C, l26-C and 127-C. To test breakage, stress-cracks and germination, samples had to be placed in the conditioner in order to decrease the moisture content to that recommended for the breakage test. The samples reached a moisture content of about 12.5 percent after four days. Samples l23-MSU and 127—MSU, dried with the MSU dryer, gave a higher average moisture content after drying than the 123-HC and 127-HC samples, dried with the HC dryer (Table 5-A). The initial moisture content was the same in both cases. Temperature history showing the grain temperature "3 Table 5—A. Comparison of average moisture content after drying for H0 and MSU samples. Moisture Samples Fhrfl.Awuege 123-HC 123-MSU l27—HC l27-MSU Dkfishne Oxnent % 1A.5 17.A lA.8 17.1 versus time for different sections of the MSU dryer are given in Appendix P. Only breakage and stress-cracks results were compared using a paired "t" test, since the germination data was meaningless. The percent of germination was very low, from 0 to 3 percent, because the samples were kept at 10°F for a period of five months. Hall (1957) reported that corn with moisture content between 25 and 30 percent, decreased germ- ination to 7 percent when kept at 8°F for 2A hours. Ob- viously, only very low germination could be expected after 5 months of storage at 10°F. Stress Crack Comparison. The number of stress cracks were found to be signifi- cantly different between samples dried in H0 and MSU dryers (Table 5-5). Sound kernels, single crack, multiple cracks and checked kernels had a significant difference at 2, 1, l and less than 0.1 percent level, respectively. AA Table 5-5. Significant values OfCKLfOP all comparisons of the dryers and control. Sauce Comparison Sound Single Double Checked HC Dryer vs. MSU 2 l l 1< .001 HC Dryer vs. CONTROL < .001 5 <.001 < .001 MSU Dryer vs. CONTROL <-.001 <1.001 1 5 Detailed information about the paired "t" test is given in Appendix G. The data is given in Table 5-6. The amount of damage in the HC dryer was higher than in the MSU dryer. The 123-MSU and 127-MSU samples, with higher moisture content after drying, presented fewer single crack, multiple cracks and checked kernels; consequently, the amount of sound kernels increased. Samples dried with the HC and MSU dryer had the same residence time, but 123- and l27-MSU presented higher moisture content after drying (lower rate of drying). This could have affected the formation of stress-cracks and give a better quality of the grain. Maximum grain temperatures, in the inlet hot side (MSU dryer), varied from 18A to 200°F. However, grain tempera— tures along the drying column were always lower. In the HC dryer, grain in the middle of the column reached temperatures ‘that were 30°F lower than the highest temperatures. That A5 Table 5-6. Results of the stress-crack test for the control, HC and MSU dryers. Control Samples Sample No. 123-C 126-C l27—C Source % % % Sound 90.0 90.36 85.A8 Single 5.8 3.61 3.76 Multiple 2.6 A.82 8.06 Checked 1.6 1.21 2.70 HC DRYER Sample No. 123-HC 126-HC 127-HC Source % % 1 Sound 18.23 33.87 28.33 Single 16.57 12.36 15.00 Multiple A9.l7 A0.86 39.AA Checked 16.03 12.91 17.23 MSU DRYER Sample NO. l23-MSU 126-MSU 127-MSU Source % % % Sound A7.90 A2.05 52.87 Single 12.57 11.36 12.6A Multiple 23.95 37.50 27.59 Checked 15.58 9.09 6.90 A6 temperature.difference ranged between 50 and 70°F for the MSU dryer. The samples dried at a lower average temperature in the MSU dryer showed significantly lower values of stress— crack (Table 5-6). The lower temperatures of the MSU samples at the initial cooling stage also contributed to the lower values of stress-cracks obtained with the MSU dryer. Individually monitored moisture contents of the MSU samples showed that the grain in the middle of the column had from 3 to 5 percent higher moisture content than in the HC samples (Table 5-7). Table 5—7. Percentage of final grain moisture content in the middle of the column of the HC and MSU dryers. Samples 123 126 127 HC MSU HC MSU HC MSU 16 20.9 15 18.5 17 20.6 15 20.A 1A.5 18.5 15 18.7 The lower moisture content reduction (higher final moisture content) obtained in the MSU dryer may also have had some influence on the lower number of stress cracks. HC and MSU samples were also compared against the control sample. The significant differences (Table 5—5) A7 obtained between HC versus Control, and MSU versus Control, lead to the conclusion that the drying process significantly increased stress cracks. For the HC dryer versus the Control, sound and checked kernels and multiple cracks had a significant difference at UC<0.001 percent level, and single crack at 5 percent level. For MSU dryer and Control, sound kernels and single crack had a significant difference at oc.<0.001 percent level, multiple cracks at 1 percent and checked kernels at 5 per- cent level. Breakage Comparison The amount of breakage for samples dried in RC and MSU dryers was not significantly different (0C= 90%). Moisture content and number of stress cracks have been reported as factors causing breakage.. Relating the grain moisture content difference of the HC and MSU samples (15 versus 17%), after drying, with the moisture content-break— age curve published by Thompson and Foster (1963), breakage would be increased to less than one percent. In the case of stress—cracks, it could increase the susceptibility to breakage. Both HC and MSU samples were significantly different from the Control sample (0C= 2%). The Control sample had breakage as much as 2 or 3 times less than that of the HC and MSU samples (Table 5-8). A8 Results of breakage are given in Table 5-8 and "t" test results in Appendix H. Table 5-8. Percent of breakage Obtained with the HC and MSU dryers, and Control sample. Breakage (Z) _ Sample No . Treatments 1’ qumol HCIkyer NBUIXyer ; 123 6.1 11.0 1A.A ! 126 7.2 15.0 21.8 127 5.5 18.0 10.u I Analysis of Qualitnyactors for Certified Seed Corn Dried Artificially, Influence of the grain temperature and moisture content gradients on grain damage, along the dryer column, could not be measured because no samples were available for the intermediate stages of the HC dryer. The MSU dryer permitted the analysis of quality factors in each section (the dryer had six sections sepa— rated by a metallic screen) under the same conditions used as with the HC dryer. Moisture Content After Drying. Average moisture content varied from 17 to 19 percent in all samples (123-S, 126-3 and 127-S). The distributions A9 22- 20- MC(%) 16‘ 1A.. 12- 10+ 8 . . . I A . I II III IV V VI Sections C(— Figure 7. Final grain moisture content along the dryer in 123-S sample. 2A- 22‘ 20. MC(%) 184 16- 1A‘ I I _l I 12 , $ 5 a u I II III IV V 'VI Sections Figure 8. Final grain moisture content along the dryer in 126-S sample. 50 2A- 22— 20* MC 18‘ (z) 16.. 1AA up ‘ 12 . ‘ : e I II III IV' V VI Sections d d IFigure 9. Final grain moisture content along the dryer in 127-S sample. 51 of moisture content are shown in Figures 7, 8 and 9. The moisture content distribution of each test is given in Appendix J. The grain exposed to hot air (Section I) in the first stage of drying had the lowest moisture content. Section VI exposed to hot air in the second stage had the second lowest moisture content. The middle sections presented moisture contents only 2 percent below the initial mois- ture (25%). All samples were conditioned to 12 percent of moisture content before the quality tests were performed. The effect of drying on grain quality was determined by means of a one-way AOV. In tests where drying effect on grain quality was significant, a Duncan's test was used to compare the treatments. If the drying effect was non- significant, only comparison between treatments that were considered likely to be different before actually collect- ing the data (priori test), were compared using a "t" test. Stress Crack Evaluation. Twenty-two stress-crack analyses were carried out. IEach section of the dryer represented a treatment in the one-way AOV. The one—way analysis of variance shows that the per- <3entage of sound kernels, multiple cracks and checked kernels was significantly affected (00:- 5%) by the drying lxrocess (Appendix L). Single crack was not significantly 52 affected (0¢= 5%) by drying (Appendix L). The data is given in Appendix K. Since there was a significant effect of drying on sound kernels, the means of the multiple crack and checked kernels were compared with the Duncan's test. Duncan's test results, for significant "F" test, are given in Tables 5-9, 5-10 and 5-11. Table 5—9. Duncan's test results for sound kernels. Treatments VI V I II III IV S-C IMeans 10.15 10.23 15.39 15.87 18.0 18.A5 26.65 Ramflts Table 5-10. Duncan's test results for multiple cracks. Treatments S—C I II III IV ‘V VI .Means A6.72 60.58 60.87 61.8A 62.98 68.06 70.6A Remflts Table 5-11. Duncan's test results for checked kernels. Treatments IV “V II III S-C VI I Means 1.86 2.13 2.50 2.51 2.66 3.17 6.87 Ramflts 53 The percentage of sound kernels in Sections III and IV was not significantly different from that of the control sample (Table 5-9). The lower moisture content reduction obtained in this sections as well as the lower drying temperatures explain the result. The multiple cracks percentage was not significantly different among sections, but all sections were significant- ly different from the control sample (Table 5—10). The percentage of checked kernels was significantly higher in Section I (Table 5-11). The rate of temperature increase was considerably higher for Section I, since it was exposed to the inlet drying air (200°F) directly from room temperature. Also, the moisture content reduction in Section I was higher than in any other section. This partially explains the higher percentage of checked kernels. The temperature history of the grain during drying (Appendix P) showed a variation from 100°F in Sections II and IV to 200°F in Sections I and VI. Moisture content of the grain was higher for the central sections (III and IV) of the dryer. Sections where the grain temperature reached 200°F were expected to have more damaged grain than those where the grain reached only 100°F. The data shows differences between sections, but they were not large enough to be detected by statistical analysis. The grain moisture content after drying did not affect the stress-crack number in the sections either. 5A Corn in Sections III and IV had the highest moisture content after drying. In the first stage of drying, moisture picked up in Sections I and II is carried through Sections III, IV, V and VI. In the second stage, moisture from Sections V and VI is carried through Sections IV, III, II and I. Heated water vapor might have condensed in the middle sections, where corn had a lower temperature. This might explain the high moisture content of Sections III and IV. Well known is that grain cooled rapidly increases in the number of stress-cracks. Section VI in all samples was exposed to this condition but stress-cracks were not sig- nificantly increased. As the effect of drying on the number of single cracks was not significant, means were compared with the "t" test. The "t" test results (Table 5—12), comparing means, gave a significant difference (°<= 5%) on single crack of the control against Sections I, III, IV and V. The effect of drying on single crack for sections 11, VI and the control was not significant (“1= 5%). Table 5-12. Results of "t" test used to compare means, of single crack for dryer sections and control sample. 'Treatments I II III IV' 'V VI Control 6.39* 2.50 6.56* 3.Al* 3.A3* 1.8A 55 Breakage Evaluation. Breakage was significantly affected (d3= 5%) by drying (Appendix M). Thus, Duncan's test was used to compare means. Duncan's test results (Table 5-13) show that break— age in Section I was significantly different (°C= 5%) from breakage in Sections III, IV, V, II, VI and the control G‘#= 5%) as shown by Duncan's test (Table 5-13). The data is given in Appendix A. Table 5-13. Duncan's test results for breakage. Treatments S-C III IV V' II VI I Means 12.63 12.8 l3.A3 16.66 17.26 19.56 28.1 Ramflts Susceptibility to breakage depends on the number of stress-cracks and level of moisture content. The severe conditions to which Section I was exposed could be related to the high breakage in that section. Residence time of hot air of drying was longer for Section I (30 minutes). The grain in that section reached the max- imum drying temperature and lowest moisture content. Grain temperature in Section VI was the same as in Section I, but moisture content was higher. Section VI had shorter residence time (19 minutes) than Section I. Section VI had the second highest percentage of breakage. 56 Germination Evaluation. Germination was significantly affected 0X?= 5%) by drying (Appendix N). The data is given in Table 5—lA. The Duncan's test results (Table 5-15), to compare means, show that all section means were significantly different (°<= 5%) from control. Table 5—1A. Germination results in seed corn. Samfle ffieahmnms "0' Control I II III IV v VI 123-S A0 0 O l8 l2 2 0 126-S 32 0 0 l7 5 2 0 127—S 36 0 0 12 25 3 0 Tflfle 545. EMncan's results for germination. Treatments I VI II v IV III S-C Means 0 0 1.66 2.33 1A.0 15.66 36 Results -------------------- The grain temperature in Sections I, VI, II and V reached values that varied between 160°F and 200°F. Watson (1960) studied the effect of drying conditions on germ- ination in an experimental bacth dryer and found that 57 temperatures of 160°F or above reduced germination to 0%. Watson used two initial grain moisture contents (32 and 21%) and two relative humidities of drying air (A0 and 15%) (Table 5-16). Table 5-16. Percentage of germination at different temp- eratures of drying, initial moistures of grain and relative humidity of drying air accOrding to Watson (1960). Air 32% 21% Initial Mbisture Initial Mbisture Isnperature °F Relative Humidity of Drying Air A0% 15% A0% 15% 160° 0 0 0 0 180° 0 0 0 0 200° 0 0 The seed control sample had a 99% germination before rewetting. The rewetted grain maintained in a AO°F box for 5 to 7 days decreased germination to an average of 36 per- cent. Hall (1957) mentioned the same relation of germin- ation reduction when grain is rewetted. CHAPTER VI CONCLUSIONS Breakage and germination, test weight and moisture content determinations can be performed by different operators. Stress—crack determinations by candling can only be performed by one operator. Adequate training before performing final tests is necessary. The number of stress-cracks were significantly in- creased by the HC and MSU dryers compared to the control. The number of stress—cracks were significantly different in the HC and MSU dryers. Breakage percentage was not significantly affected by the HC and MSU dryers. The number of checked kernels at the different locations in the drying column was a function of the temperature and moisture content of the grain reached during drying. Increased grain breakage was observed in Section I (MSU dryer) exposed to the highest temperature for a long period of time. The percentage of breakage in Section I was significantly different from the 58 59 amount sections and the control. Germination was also significantly different in Section I as com- pared with Sections III and IV and the control. The percentage of broken kernels in the sections was the same probably because the number of stress- cracks was not significantly different among sections. Sections I and VI exposed to 200°F air temperature gave 0 percent of germination. APPENDICES 60 APPENDIX A Table A-1. Percentage of breakage in U.S. NO. 2 corn. Breakage (%) Sample No. Operator A B C A, 10, 1 I3 12 16 12, 6, 8 13 12 12.3 5, 7, 2 11.5 11 12.2 3, 11, 9 12.A 10 12.3 APPENDIX B Table B—1. Percentage of germination in U.S. No.2 corn. Germination (%) Sample No. Operator A B C A, 10, 1 15 ll ll 12, 6, 8 9 '10 13 5, 7. 2 23 9 l2 3, ll, 9 12 13 1A 61 APPENDIX C Table C-l. U.S. No. 2 corn test weight. Test Weight (lbs/bu) Sample No. Operator A B C A, 10, 1 56.0 5A.0 5A.0 l2, 6, 8 55.0 5A.5 53.5 5. 7. 2 55.0 5A.o 5A.5 3, 113 9 51400 51405 5305 62 APPENDIX D Table D-l. U.S. NO. 2 corn stress crack results. Sound Kernels (%) Sample NO. Operator A A B c A, 10, l 23.39 32.00 3l.A 12, 6, 8 17.75 3A.6o 20.13 5, 7, 2 18.75 36.00 17.7A 3, 11, 9 20.12 33.00 16.67 Single Crack (%) A, 10, 1 17.5A 30.00 30.0 12, 6, 8 18.3A 26.00 30.52 5, 7, 2 18.19 23.00 30.65 3, ll, 9 l3.A1 23.00 30.36 Multiple Cracks (%) A, 10, l 35.68 23.00 20.6 12, 6, 8 33.73 23.00 25.32 5, 7, 2 39.20 26.00 20.16 3, ll, 9 37.20 21.00 2A.AO Checked Crack (%) A, 10, 1 23.39 15.00 18.00 12, 6, 8 30.18 17.00 2A.o3 5, 7, 2 23.66 15.00 31.A5 3, ll, 9 29.27 23.00 28.57 63 APPENDIX E Table E-l. "F" significance of different quality tests, using U.S. No. 2 corn. Fs Percent F source Calculated Level ( ) (2’9) Breakage 2.37 0.25 1.62 Germination 1.18 0.50 0.7A9 Test weight A.02 0.10 3.01 Mbisture Content 2.26 0.05 A.26 Mbisture Content* .30 0.05 A.26 * Oven dry. APPENDIX F Table F-l. "F" significance of stress crack, using U.S. No. 2 corn. Type of Fs Percent F(2 9) Stress Crack Calculated Level ( ) ’ Sound Kernels 12.A8 0.005 13.6 Single Crack 3A.00 0.001 22.9 Multiple Crack AA.A0 0.001 22.9 Checked Kernels A.88 0.05 A.26 6A APPENDIX G Values of "t" used to compare stress crack among HC and MSU dryers, and then versus the control. Type of HC Dryer HCIhyer MSU Dryer Stress Crack Vs.MSU Dryer Vs. Control Control Sound 3-75* 12.77*** 11,76*%& Single 6.21“ 330* 9.51%" Multiple 8.53** 11.11*** 5.6A** Checked 10.60*** 9.96*** 3.28* 13(A) UL025) APHDEEXII Table H91. 'Value of "t" used to compare breakage between HC and MSU dryers, and control. Comparison "t" Value HC Dryer and MSU Dryer .22 HC Dryer and Control A.03 MSU Dryer and Control 2.78 65 APPENDIX J Table J-l. Grain moisture content in each section. Moisture Content (%) Section Sample No. 123-S 126-S 127-S I 11.97 12.09 1A.Al II 17.0A 17.50 18.65 III 19.63 22.50 23.7A IV 20.51 19.52 21.98 V 18.01 16.35 18.A8 VI 17.20 15.65 l6.A1 ”mt. 1-117; 53“] 66 APPENDIX K Table K-l. Percentage of stress crack in seed corn. Sound Kernels (%) Sample Treatments No. Control I II III IV V VI 123—S 28.75 13.12 lA.81 1A.38 11.88 7.10 7.6A 126-S 26.66 23.A6 17.79 25.16 22.22 lA.8A 1A.01 127—S 2A.5A 9.61 15.03 1A.A6 21.25 8.75 8.80 Single Crack (%) 123-S 22.50 16.88 lA.8l 18.12 20.62 13.55 15.92 126-S 2A.2A J 18.52 21.A7 18.86 17.90 17.A2 2A.20 127-S 25.15 16.03 19.61 18.87 15.00 20.00 15.72 Multiple Cracks (%) 123-S A5.63 65.62 67.78 63.75 66.25 76.13 73.89 126-S A6.06 A6.91 58.28 55.3A 57.A1 65.81 58.60 127-S A8.A7 69.23 63.A0 63.52 61.88 70.00 71.70 Checked Kernels (%) 123-S ,3.12 A.38 3.10 3.75 1.25 3.22 2.55 126-S 3.0A 11.11 2.A6 .6A 2.A7 1.93 3.19 A 127-S 1.8A 5.13 1.96 3.15 1.87 1.25 3.78 67 APPENDIX L Table L-1. "F" test significance for stress cracks in seed corn. Type of F3 F Stress Crack (Calculated) (6,19) (.05) Sound H.20* 2.85 Single 2.06 2.85 Multiple H.01* 2.85 Checked 3.25* 2.85 Table L-2. "F" test significance for breakage and germination in seed corn. Source FS F(6,114) (.05) (Calculated) Breakage H.60* 2.85 Germination 26.68* ' 2.85 68 APPENDIX M Table M-l. Percentage of breakage for seed corn. Breakage Smmfle fiteahmfims No. Control I II III IV 'V 'VI 123—S 12.6 28.9 18.8 1H.7 19.9 15.6 17.5 126-S 12.3 37.4 19.3 11.1 15.3 20." 23.0 127-S 13.0 18.0 13.7 12.6 10.1 19.0 18.2 APPENDIX N Table N-l. Percentage of germination in seed corn. Germination Smmfle Cheahmxms No. Control I II III IV 'V VI 123-S N0 0 0 18 12 2 0 126—3 32 0 0 l7 5 2 0 127-S 36 0 5 12 25 3 0 69 APPENDIX P Table P-l. Grain temperature history of drying the 123-MSU sample in the MSU dryer sections. Time Dryer Sections mmn. I II III IV V VI 0 59 65 60 60 67 55 First 5 198 101 96 96 87 73 Stage 10 189 126 98 98 95 98 of 15 197 196 109 109 95 97 Drying 20 200 156 115 115 95 98 25 200 166 136 136 96 98 30 200 170 120 120 96 108 35 130 110 100 100 98 157 Second 90 109 102 108 108 108 198 Stage 95 109 107 130 130 129 200 of Drying 50 116 119 133 133 118 199 Cooling 55 119 119 107 107 88 76 Stage 60 9O 89 78 78 76 71 65 75 78 72 72 79 71 70 72 79 72 72 79 71 70 Table P—2. Grain temperature history of drying of the 126—MSU sample in the MSU dryer sections. Time Dryer Sections nfln. I II III IV V VI 0 96 92 96 96 9O 36 First 5 106 88 88 88 81 66 Stage f 10 121 93 93 93 89 93 o 15 128 98 99 99 87 99 Drying 20 135 102 100 100 89 99 25 192 110 119 119 89 95 30 196 119 129 129 91 95 Second 35 120 108 96 96 92 150 Stage 90 110 102 102 102 99 185 of Drying 95 103 100 120 120 107 189 50 100 102 132 132 120 189 55 99 102 128 128 119 136 Cooling 60 98 100 122 122 110 90 Stage 65 95 97 106 106 97 75 70 99 93 99 99 88 73 75 90 90 82 82 80 73 71 Table P-3. Grain temperature history of drying of the 127-MSU sample in the MSU dryer sections. Time Dryer Sections min I II III IV V v1 0 62 65 99 99 39 39 FirSt 5 100 70 79 79 98 39 Stage 10 192 86 91 91 9o 79 °f 15 170 92 99 99 99 91 Dnying 20 183 96 95 95 95 93 25 188 100 95 95 95 99 ’ 30 197 109 101 101 96 99 Second 35 159 103 95 95 93 110 3:888 90 113 99 93 93 92 152 O 95 100 95 93 93 105 175 Danna 5o 99 99 100 100 128 189 Cooling 55 102 103 102 102 132 170 Stage 60 9“ 99 97 97 139 100 65 90 86 97 97 112 77 70 89 83 90 9O 88 79 72 Table P-9. Grain temperature history of drying of the 123-S sample in the MSU dryer sections. Time Dryer Sections min I II III IV V' VI 0 50 50 50 50 39 38 FirSt 5 192 101 77 77 8o 68 Stage 10 185 103 82 82 102 109 Of 15 198 109 86 86 103 105 20 200 127 91 91 103 106 Ikwing 25 200 150 92 92 109 106 30 200 159 99 99 109 106 Second 35 152 113 95 95 103 126 Stage 90 118 107 97 97 109 176 Of 95 112 107 95 95 127 199 ‘Dnying 50 112 109 96 96 157 200 55 109 109 92 92 126 99 Cooling 60 101 97 78 78 85 85 same 65 88 82 73 73 75 76 70 77 75 71 71 79 76 73 Table P-5. Grain temperature history of drying of the 126-S sample in the MSU dryer sections. fflne _ Dryer Sections min I II III IV 'v ‘VI 0 90 57 98 98 99 92 “I St 5 105 93 9o 90 67 50 Stage 10 199 98 100 100 95 99 of 15 173 100 101 101 102 102 20 198 112 103 103 101 107 Dmflng 25 199 138 100 100 102 107 30 200 156 107 107 99 102 Second 35 119 100 99 99 109 160 Stage 90 109 95 100 100 136 200 of Drying 95 103 97 112 112 157 200 50 107 100 116 116 157 188 55 109 108 110 110 135 165 CodUng 60 96 109 100 100 129 199 SW99 65 91 100 99 99 116 129 70 85 93 90 90 110 119 75 80 88 86 86 109 99 79 Table P-6. Grain temperature history of drying the 127—S sample in the MSU dryer sections. ings Dryer Sections mhl I II III IV v VI 1 0 88 69 50 50 96 60 “1'5“ 5 109 93 56 56 83 62 35mg 10 139 99 90 9o 99 93 °f 15 150 95 95 95 93 96 Drying 20 169 109 96 96 93 96 25 168 125 95 95 99 96 30 179 139 96 96 99 96 Second 35 132 101 96 96 100 110 Sumfi 1“) 105 96 96 96 96 160 °f 95 102 96 97 97 105 189 Drying 50 102 100 98 98 120 198 55 109 98 99 99 112 172 H “mg 60 100 92 83 83 109 128 Mime 65 91 83 79 79 109 106 70 85 77 72 72 90 8o LI ST OF REFERENCES LIST OF REFERENCES Akiyama, H. (1972) Corn Damage and Its Effects on Official Grading Standards. Grain Damage Symposium, Ohio State University, April 5-7, 1972. Bailey, J. (1968) Problems in Marketing Damaged Grain and Corn. Proceedings of A Symposium on Grain Damage, Iowa State University, April 17-18, 1968. Bakker-Arkema, F. w., L. E. Lerew, W. G. Bickert and R. J. Anderson (1972) Better Quality Grain Through the Use of a Concurrent Flow Dryer With Counterflow Cooling. Grain Damage Symposium, Ohio State University, April 5-7, 1972. Bilanski, W. K. (1966) Damage Resistance of Seed Grains. Trans. ASAE 9 (3) 360. Brekke, O. L., E. L. Griffin, Jr. and G. C. Shove (1972) Dry Milling of Corn Artificially Dried at Various Temperatures. ASAE Paper No. 72—820. Christensen, C. M. and H. H. Kaufmann (1969) Grain Storage. University of Minnesota, Minneapolis. Converse, J. O. (1972) A Commercial Crossflow-Counterflow Grain Dryer: The HC. ASAE Paper No. 72-828. Duncan, E. R., D. G. Woolley, V. M. Jennings, and G. L. Kline (1972) Varietal Variability and Corn Grain Quality. Grain Damage Symposium, Ohio State University, April 5-7, 1972. French, R. C. and C. H. Kingsolver (1969) The Effect of Excessive Heat During Artificial Drying of Corn Reducing Sugar Content and Diastatic Activity. Cereal Chemistry, Vol. 91, pages 97-57, 1969. Hall, C. W. (1957) Drying Farm Crops. Edwards Brothers Inc., Ann Arbor, Michigan. Kamimski, T. (1968) Need for Standards for Evaluation of Grain Damage. Proceedings of A Symposium in Grain Damage, Iowa State University, April 17-18, 1968. 75 76 Keller, D. L., H. H. Converse, T. O. Hodges and D. S. Chung (1972) Corn Kernel Damage Due to High Velocity Impact. Trans. ASAE 15(2) 330. Lobanov, V. Ya. (1969) Quality Determination of Seeds. Translated by Zvi Shafiro, published pursuant to an agreement with the U.S.D.A. and the National Science Foundation, Washington, D. C. Mayer, A. M. and A. PolJakoff—Mayber (1963) The Germination of Seeds. Pergamon Press Inc., Long Island, New York. McGinty, R. J. and G. L. Kline (1972) Development and Results of a Standard Grain Breakage Test, Grain Damage Symposium, Ohio State University, April 5—7, 1972. Roberts, E. H. (1972) Viability of Seeds. Chapman and Hall Ltd., London. Roberts, H. J. (1972) Corn Damage and Its Effects on Dry Milling. Grain Damage Symposium, Ohio State University, April 5-7, 1972. Ross, I. J. and G. M. White (1972) Discoloration and Stress ' Cracking of White Corn As Affected by Overdrying. Trans. ASAE 15(2) 327. Thompson, R. A. and G. H. Foster (1963) Stress Cracks and Breakage in Artificially Dried Corn. Marketing Research Bulletin No. 631, Transportation and Facilities Research Division, Agricultural Market— ing Service, U.S.D.A., October. Thompson, T. L. (1967) Predicted Performance and Optimal Designs of Convection Grain Dryers. .PhD Thesis, Purdue University, 1967. - Sinha, R. N. and w. E. Muir (1973) Grain Storage: Part of a System. The AVI Publishing Company, Inc., Westport, Connecticut. Uhrig, J. W. (1968) Economic Losses of Damaged Grain. Proceedings of A Symposium on Grain Damage, Iowa State University, April 17-18, 1968. Watson, B. K. (1960) Storing and Drying Corn for the Milling Industries. 'Proceedings of Fifteenth Annual Hybrid gorn Industry Research Conference, Part III, pages 2-92. - MICHI AN I 91 M1 1 TAT 293 Will) 0 3 0 E R 7 Ii 1 ITY 1 LI 11 m 7 ARIES