Enhancing bioavailability of soy protein isolate (SPI) nanoparticles through limited enzymatic hydrolysis: Modulating structural properties for improved digestion and absorption

The bioavailability of nanoparticles during the digestive process is intricately linked to their structural integrity and interactions with bile salts. In this study, enzymatically hydrolyzed protein nanoparticles encapsulating β-carotene (BC) were prepared using three proteases with different cleavage specificity. In vitro digestion and cellular uptake models are employed to investigate the structural changes of BC during the digestion process and their bioavailability. It was found that Flavorzyme exhibited lower hydrolysis degree as compared to Neutrase and Alcalase, selectively hydrolyzing the 7S subunit of SPI while retaining a higher content of acidic peptides within the 11S subunit, resulting in higher surface hydrophobicity. Therefore, partially hydrolyzed protein nanoparticles (SPIH@NPs) prepared with Flavorzyme (SPIH–F@NP) demonstrated the strongest resistance to digestion. Compared to SPI nanoparticles, the release rate of β-carotene in SPIH-F@NP was reduced from 25.99% to 13.13%, leading to a higher retention of β-carotene in the aqueous phase and a 2.66-fold increase in its bioaccessibility. Moreover, SPIH-F@NP demonstrated the highest affinity for bile salts, resulting in a 1.48-fold improvement in the absorption efficiency of β-carotene compared to SPI nanoparticles. These findings establish a theoretical basis for further enhancing the application potential of protein-based nanoparticles in terms of bioavailability.