Changes in fatty acid composition and lipid profile during koji fermentation and their relationships with soy sauce flavour

Evolution of lipids during koji fermentation and the effect of lipase supplementation on the sensory properties of soy sauce were investigated. Results showed that total lipids of the koji samples were in the range of 16–21%. The extracted lipid of initial koji consisted mainly of triacylglycerols (TAGs, >98%), followed by phospholipids (PLs), diglycerides (DAGs), monoacylglycerols (MAGs) and free fatty acids (FFAs). As the fermentation proceeded, peroxide value of the lipids decreased while carbonyl value increased (p < 0.05). Linoleic acid was utilised fastest according to the fatty acid composition of total lipids, and preferential degradation of PLs to liberate FFAs was also observed. Moreover, phospholipase supplementation had significant influence on the sensory characteristics of soy sauce, especially enhanced (p < 0.05) scores for the umami and kokumi taste attributes. All these results indicated that the control of PLs utilisation during fermentation was a potential method to improve soy sauce’s characteristic taste.