Isoflavones Have a Potential Role in Off-Flavour Scavenging, with IFS2 as a Key in Isoflavone Accumulation in Soybean Seeds

Research background. Soybean (Glycine max (L.) Merr) is a nutrient-rich crop containing high protein content as well as various bioactive compounds with health beneficial properties. However, it continues to have limited consumer acceptability as a food crop due to the presence of off-flavour. Owing to the ubiquity of isoflavones in soybean, their inherent antioxidant potential, and inhibitory effect on lipoxygenase activity, their sensorial attribute in mitigating off-flavour is currently being envisaged. Experimental approach. The present study estimated the content and composition of isoflavones in 17 soybean cultivars. The correlation between isoflavone profile and lipid peroxidation was also established where thiobarbituric acid (TBA) number and carbonyl value were used as indices for the off-flavour generation. The cloning, gene expression analysis and in silico analysis of isoflavone synthase (IFS) isoforms were also performed. Results and conclusions. The total isoflavone content in soybean genotypes ranged from (153.53±7.22) µg/g for 'PUSA 40' to (1146.42±43.47) µg/g for 'Bragg.' There was a moderately negative correlation for indices of off-flavour generation with the genistein: daidzein ratio (p<0.1). The relation with total isoflavone content was however found to be insignificant hinting towards complex interactions at play. Higher protein-protein interactions for predicted structure of IFS2 with other biosynthesis enzymes and its comparatively higher expression in the 'Bragg' than IFS1, hinted towards its more substantial role in isoflavone synthesis. Novelty and scientific contribution. The genistein: daidzein ratio was found to be an important factor for controlling off-flavour. IFS2 was identified as a key for generating high isoflavone containing soybean with potentially reduced off-flavour generation.