Food Chemical Studies on Soybean Proteins

Part V. On the insoluble protein components of defatted soybean heated by steaming

Abstract

To discuss about the behavior of protein components effected by steaming of defatted meal, the amounts of extractable nitrogen in water (W), 0.076M tris-citrate buffer (pH 8.6) (B), B contaning 0.1M 2-mercaptoethanol (BM), and BM containing 8M urea (BUM), respectively, were detrmined over a wide range of steaming time (100°C, RH 100%), and the extracted protein components were analyzed by starch gel electrophoresis. The amount of extractable nitrogen decreased progressively with the increase of steaming time, and the extraction rate was high in order of BUM, BM, B, and W at each steaming condition examined. The insolubilization of proteins in the meal by steaming was more pronounced in the order of D, A, and C components. By increasing the concentration of urea and guanidine, the amount of extractable nitrogen in the meal steamed for 90min. was increased, and the increase in extracted protein components was detected in order of bands 1 to 4, 7 to 9, 5 to 6, and 10. From these results, the insolubilization of soybean proteins in the steamheated meal was discussed.