Reaction process and characteristic changes in soybean oil bodies during the formation of volatile flavour compounds in soymilk

Abstract

Oil bodies (OBs) are lipid-storing organelles of soybean seeds and the source of substrates for the enzymatic oxidation reaction of soymilk flavour formation. However, the triacylglycerols (TAGs) in the OBs are surrounded by a membrane composed of phospholipids embedded with integral oleosins to prevent them from being hydrolyzed by lipase. Therefore, the specific reaction process of the OBs in the soymilk flavour formation process becomes complicated and is not well understood. In this study, the optimal substrate, OBs, were extracted by sucrose and washed with water at pH 11.0. The oxidation products (i.e., lipid hydroperoxides, and volatile flavour compounds) of the reaction systems, with OBs as substrate, showed that phospholipase A2 (PLA2) can directly hydrolyze external phospholipids (PLs) of OBs, and pancreatic lipase can hydrolyze the internal TAGs of OBs only after oleosins or PLs are hydrolyzed. Phospholipase D (PLD) cannot hydrolyze PLs of OBs. These findings are of great significance for understanding the mechanism of flavour formation in soymilk and further improving the flavour of soymilk.