45G-22 |
Structural characteristics of b-conglycinin in soybeans as affected by storage |
D. H. J. HOU, Cereal and Food Sciences, North Dakota State University, 9480 Utica Ave., Suite #611, Rancho Cucamonga, CA 91730 and S. K. C. Chang, Dept. of Cereal Science, North Dakota State Univ., IACC 322, Fargo, 58105-5728. Soybeans after harvest are stored in various environmental circumstances before they are processed. Storage conditions influence bean quality and protein functionality. A comprehensive study of the structural characteristics of soy proteins is needed for the understanding of the relationships between structure and functionalities. The structural changes of glycinins have been reported. However, the changes in b-conglycinins as affected by storage have not been reported. The objective was to investigate how various storage conditions influenced the structural characteristics of b-conglycinins. Soybeans were stored under four conditions, 84% RH 30 ° C, 57% RH 20 ° C, cold (4 ° C), and uncontrolled ambient-temperature condition. The storage period for soybeans under 84% RH was 9 months and that for the other conditions was 18 months. b-Conglycinin was isolated and purified from hexane-defatted soy flour by solvent fractionation and column chromatography. The protein molecular mass, amino acid composition, secondary structures, glycoprotein content, sulfhydryl and disulfide contents, and surface hydrophobicity were determined. The molecular weight of b-conglycinin remained in the range of 199~212 kDa after storage for all conditions. In the adverse conditions (84% RH and 30 ° C), the structural characteristics of the b-conglycinin changed significantly in some structural characteristics. The total free sulfhydryl content increased significantly. The content of intramolecular disulfide bonds increased from 2 to 3 for the 8-month samples. Surface hydrophobicity decreased significantly after 8 months. a-helix content slightly increased, but the b-sheet content decreased. Glycosylation did not increase significantly during storage under the adverse conditions. For the other selected conditions, there were no significant structural changes of b-conglycinin when compared to the control. It can be concluded that the b-conglycinin molecules changed during storage under adverse conditions. Storage for up to 18 months under mild conditions would not change proteins' molecular structures.
Session 45G, Fruit & Vegetable Products: Vegetables (Fresh)
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