Selected odor compounds in soymilk as affected by chemical composition and lipoxygenases in five soybean materials.

Protein, fat content, and beany odor affect consumers' choice of soy foods. Our objective was to characterize protein, lipid, and lipoxygenase activities and fatty acid compositions in food soybeans and to determine how chemical composition and enzyme activities related to the generation of beany odor components, including hexanal, hexanol, trans-2-nonenal, 1-octen-3-ol, and trans-2,trans-4-decadienal in soymilk. Protein, lipid, and fatty acid compositions and lipoxygenase activities of five soybean materials, including Proto, IA2032, IA 2064, IA3017, and L-Star varieties, were analyzed. Soymilk was prepared by a traditional method involving soaking, grinding, and cooking processes. Selected odor compounds in raw and cooked soymilk were analyzed by solid-phase microextraction and gas chromatography. Results showed that soybeans differed in crude protein and lipid content, lipoxygenase activities, and fatty acid compositions. L-Star had the highest and Proto the lowest lipid content among the five soybean cultivars. Protein content, lipoxygenases, and linoleic acid were positively correlated with beany odor content in soymilk made from the selected soybean materials. After boiling for 20 min, the soymilk made from L-Star and IA2032 retained the lowest odor profiles among the soymilk products made from the five selected materials.