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The object of this investigation was to ripen and dry soybeans in such a way as to prevent the formation of bad taste and odor in the oil. Field run soybeans were treated in specially constructed gas-tight silos through which mixtures of air, carbon dioxide, and ethylene in varying concentrations were recirculated for the purpose of maturing and stabilizing the beans and to prevent peroxidases action, the latter being credited with imparting the offensive odor and taste to the oil and meal obtained by processing the bean. Nine silos were run simultaneously with nine different mixes of gases varying between 90 to 35% ethylene and 10 to 65% carbon dioxide and air. Whole beans were treated for 24 and 48 hours at 24, 37, and 50°C., rolled flat in a roll mill and expressed at 45-60°C. in a Carver hydraulic press at 10,000 lb. per sq. inch. From each sample of beans pressed was taken two samples of oil. One sample was left exposed to the air while the other one was sealed by means of a cap. From the taste and odor tests it was found that whole beans treated with ethylene at 24°C. Gave the best oil, being only slightly better than the oil from the whole beans treated at 37°C. Soybeans, when treated with ethylene and carbon dioxide, absorb varying amounts of the gases, depending on the gas concentration and the water removed. The drying rate of the soybeans by air was considerably less than the drying rate when ethylene and carbon dioxide were used. / Master of Science

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Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 95-107). Also available via the Internet.

Five soymilk quality-related characteristics were investigated as affected by different grinding, heating, extraction methods and varieties. The five characteristics are (1) protein and solid recovery, (2) trypsin inhibitor activity, (3) antioxidant compounds and antioxidant capacity, (4) soy odor, and (5) isoflavone content and profile. The two varieties were Prosoy and black soybeans. The results show that significant differences existed among the three grinding methods (ambient grinding, cold grinding, and hot grinding). Ambient grinding gave the best protein and solid recoveries. Hot grinding showed the best results for the other four parameters. Cold grinding gave the poorest performance, with the exception of the odor profile. The three heating methods (traditional stove cooking, one-phase UHT, two-phase UHT) also resulted in significant differences in the chemical compounds and properties of the soymilk. In many cases, the effects of heating methods were closely related to grinding methods and varieties. Our results clearly demonstrated that a UHT processor equipped with a vacuum chamber was a very efficient way to reduce or eliminate some undesirable soy odors, especially in conjunction with hot grinding. Our results also demonstrated that many complex reactions occurred during thermal treatment. Because of different seed characteristics, the two different varieties behaved differently during processing. For both varieties, extraction with okara washing water from last batch (Method #2) gave the highest solid and protein recoveries.

Soy protein concentrate (SPC) was autoclaved at 121°C and 15 p.s.i for 0, 10, 30 min., 2 and 4 hr. The solubility of the control, 10 and 30 min. autoclaved samples was quite low (about 12%) as compared with the 2 and 4 hr. samples (about 27%) in potassium phosphate buffer (pH 7.6, 0.5 ionic strength). When urea and beta-mercaptoethanol were added in increasing concentration to the buffer, the solubility of control, 10 and 30 min. samples increased dramatically up to 60%; while the solubility of 2 and 4 hr. autoclaved samples changed very little remaining at 25 to 40% throughout. Digestibility of SPC samples was determined by three in vitro methods, all including treatment of SPC with selected proteases, followed by measurement of (1) TCA soluble N production (2) breakdown products via SDS-PAGE and (3) pH drop resulting from enzyme action. In vivo apparent digestibility was determined in a rat feeding study. The digestibility of SPC samples were found to be significantly affected by length of autoclaving. The digestibility of control was higher than autoclaved samples as determined by both in vivo and in vivo assays. The digestibility of 10 and 30 min. autoclaved SPC samples was significantly higher than 2 and 4 hr. autoclaved samples in in vivo assays. While, apparent in vivo digestibility of 10, 30 min. and 2 hr. autoclaved samples was significantly higher than the 4 hr. sample. Correlation coefficients of in vivo digestibility as determined by the TCA soluble N measurement, SDS-PAGE and pH drop method with in vivo apparent digestibility were 0.96, 0.92 and 0.95, respectively. There was no actual destruction of amino acids except cysteine; 10, 30 min., 2 and 4 hr. SPC samples contained 6, 20, 27 and 39% less cysteine respectively than the SPC control. The chemical score of SPC samples indicated that cysteine became the first limiting amino acid in the 2 hr. sample. PERs of the 2 and 4 hr. autoclaved SPC samples were significantly less than control, 10 and 30 min. autoclaved samples. While C-PERs of control, 10 min. samples were higher than 30 min., 2 and 4 hr. samples. Decreased PER values of autoclaved SPC samples were likely due to i) decreased protein digestibility and rate of enzymatic hydrolysis, ii) destruction of essential amino acids, and iii) decreased food intake. / Ph. D.

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