Transformation profiles of the isoflavones in germinated soybean based on UPLC-DAD quantification and LC-QTOF-MS/MS confirmation

Germinated soybean is one kind of food and a medicine. In the actual process of producing a large amount of naturally germinated soybean, it is difficult to strictly control the germination process conditions. However, sprout length may be more suitable as the terminal judgment indicator for naturally germinated soybean. An UPLC-DAD method was developed and validated to explore the transformation profiles of soybean isoflavones in germinated yellow or black soybean with different sprout lengths. Moreover, an LC - QTOF-MS/MS method was used to avoid false positive results. The contents of daidzein, glycitein, and genistein almost reached their corresponding maximum values when the sprout length ranged from 1.0 cm to 1.5 cm (P < 0.05). Therefore, yellow soybean is suggested to be the processing raw material with higher contents of those isoflavones, and the optimal sprout length for germinated soybean may be in the range of 1.0-1.5 cm.