Peptide hydrolysis and isoflavones enhance selenium bioavailability in soybean protein systems

Plant-derived selenium (Se) proteins represent a promising strategy for delivering bioavailable selenium while retaining the nutritional functionality of soybean proteins. In this study, the in vivo metabolic kinetics and bioavailability of different Se-enriched soybean protein systems, including Se-enriched protein (SePro), its hydrolysate peptide hydrolysates (SePep), and their mixtures with isoflavones (daidzein, SePep+Da; genistein, SePep+Ge), were systematically investigated. Compared with L-selenomethionine (L-SeMet), which exhibited a rapid peak blood Se concentration at 10 min, SePro showed a delayed absorption profile with a peak at 20 min and a relative bioavailability of 94%. Enzymatic hydrolysis further enhanced Se utilization, with SePep reaching its peak blood Se concentration earlier than SePro and increasing relative bioavailability by 18.6%. Incorporation of daidzein and genistein further increased the relative bioavailability by 23.9% and 9.4%, respectively, accompanied by higher C_max and greater overall Se exposure than SePep. These results demonstrate that peptide hydrolysis and isoflavone interactions synergistically regulate Se release and absorption kinetics, highlighting a novel strategy for designing protein-based Se delivery systems with enhanced bioavailability and functional performance.