Development of whey protein nanoparticles as carriers to deliver soy isoflavones

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Encapsulation is an effective means to improve the stability and bioaccessibility of bioactive ingredients for food or other applications. Soy isoflavones were encapsulated in whey protein nanoparticles, using an emulsification-evaporation method. The physicochemical properties, formation, microstructure of the nanoparticles, stability, antioxidant activity, and bioaccessibility of soy isoflavones were studied. The results showed that the nanoparticles have a small particle size (54.09–59.96 nm), high zeta potential (−35.63 to −31.03 mV) and encapsulation efficiency (91.29%–92.59%) with a mass ratio of soy isoflavones and protein ranging from 1:100 to 1:40. The increased mass ratio of 1:20 resulted in aggregated particles (923.37 nm) and decreased encapsulation efficiency (82.89%). The main driving forces of nanoparticle formation have been proven to be hydrophobic interactions and hydrogen bonding. Transmission electron microscopy micrographs suggested that the nanoparticles have spherical structures. The photochemical stability, antioxidant activity, and bioaccessibility of soy isoflavones were significantly improved by encapsulation. The enhanced effectiveness of polymerized whey protein-based nanoparticles was better than that of whey protein-based nanoparticles. The results demonstrated that isoflavone-whey protein nanoparticles may be an effective nanocarrier to improve the stability, bioactivity, and bioaccessibility of soy isoflavones.