Soymilk is consumed as such or used in the preparation of tofu, fermented soymilk, and soy yogurt, among others. In this study, hemicellulase-assisted extraction (HAE) and ultrasound-assisted extraction (UAE) were used during soymilk manufacturing. The activity of endogenous β-glicosidases was increased 1.3 and 1.5-fold in soymilk produced upon HAE and UAE, respectively. Likewise, the concentration of isoflavones in the aglycone form increased 1.7 and 2.4 times in samples subjected to HAE and UAE, respectively. UAE, but not HAE, rendered an equimolar conversion from conjugated isoflavones to their respective aglycones. In addition, HAE and UAE showed higher antiradical activity towards ABTS radical cation and peroxyl radical, compared to those of the control. The aglycone isoflavones/conjugated isoflavones (aISO/cISO) ratio correlated with the antiradical activity, thus suggesting that the soybean industry may use this new quality index to indicate the antioxidant potential of products. Food formulations containing soymilk with high aISO/cISO ratio may translate to higher oxidative stability of the final product. Likewise, the higher absorption of aglycone isoflavones compared to that of their conjugated counterparts is well recognized. Therefore, high aISO/cISO ratio of soymilk and/or its products may provide a better antioxidant protection under physiological conditions.

Isoflavones, which exist in their conjugated or aglycone forms, are well recognized for their potential health benefits. However, isoflavones as aglycone have been regarded as the most bioactive form. In the present study, the profile of isoflavones and their scavenging activity as affected by germination were investigated in several soybean fractions, namely cotyledons, epicotyls, radicles, and hypocotyls. Only aglycones were detected in the radicles from 144 h until 168 h of germination, which makes this component a potential feedstock for studies aiming at isolation, especially of daidzein, which was present in higher concentrations. In terms of total yield and contribution to the total weight of the germinated soybeans, the cotyledons are the best source of aglycones, which was achieved at 144 h of germination. The higher scavenging activity of high-aglycone components from germinated soybeans supports the use of germination to obtain functional foods and/or ingredients with potentially superior bioactivities.