Isoflavones have a potential role in off-flavour scavenging, with isoflavone synthase 2 (IFS2) as a key player in determining isoflavone accumulation in soybean seeds

Abstract Soybean (Glycine max (L.) Merr) is a nutrient-rich crop with limited consumer acceptability because of the presence of off-flavour. Owing to the ubiquity of isoflavones in soybean, their inherent antioxidant potential, and their inhibitory effect on lipoxygenase activity, their sensorial attribute in mitigating off-flavour is currently being envisaged. We estimated the content and composition of isoflavones in 17 soybean cultivars and established the correlation between isoflavone profile and lipid peroxidation, which was measured in terms of thiobarbituric acid (TBA) number and carbonyl value. The results showed a significant negative correlation of these parameters with the total isoflavone content and genistein: daidzein ratio. In addition, expression analysis of a key gene involved in isoflavone biosynthesis, i.e., isoflavone synthase (IFS1 and IFS2), in contrasting soybean genotypes during seed development revealed a higher expression of both isoforms in Bragg (high isoflavone) compared to PUSA 40 (low isoflavone) at different stages of seed development accompanied by more isoflavone accumulation. The cloning and in silico analysis of IFS isoforms revealed a more significant interaction with other biosynthesis enzymes by IFS2, indicating its more substantial role in isoflavone synthesis. IFS2 overexpression can thus be a valuable target to increase isoflavone biosynthesis, thereby scavenging off-flavour.