Soy proteins as vehicles for enhanced bioaccessibility and cholesterol-lowering activity of phytosterols

BACKGROUND The formulation of phytosterol (PS)-enriched functional foods has attracted increasing interest in the recent years, owing to its potential health effects. However, the poor solubility and bioavailability greatly limit PS application in this regard. This study investigated whether soy protein isolate (SPI) could effectively perform as a nanocarrier for improving the water solubility, bioaccessibility, and cholesterol-lowering activity of PSs. RESULTS In this work, we fabricated SPI-PS nanocomplexes, which not only can enhance the stability and bioaccessibility of PS, but also improve the cholesterol-lowering ability of SPI. This improvement was mainly due to the formation of protein-active substance complexes, through hydrophobic interactions. The complexation with PSs resulted in formation of nanosized particles with greater sizes, lower zeta-potential, and higher surface hydrophobicity. The encapsulation efficiency, loading amount, and solubility of PS were closely related to the applied PS concentration in the mixed dispersions, and the maximal PS solubility in the aqueous phase reached about 1.63 mg mL(-1) at the highest PS concentration (2.0 mg mL(-1)). The PS molecules in the nanocomplexes were mainly present in the amorphous form. The enhanced in vitro cholesterol-lowering activity of PS nanocomplexes relative to free PS seemed to be closely related to its higher bioaccessibility. CONCLUSION The findings are of relevance for the development of food-grade PS ingredients suitable for the formulations of PS-enriched functional foods. (c) 2022 Society of Chemical Industry.