Effect of simultaneous treatment combining ultrasonication and pH-shifting on SPI in the formation of nanoparticles and encapsulating resveratrol

Plant protein-based nano-delivery systems have rencently drawn increasing attention, and several physical and chemical methods for improving the functional properties of plant proteins have been reported. In this work, we applied ultrasonication and pH-shifting combined treatment on soy protein isolates (SPI) and investigated the structure changes of SPI and its effects on the formation of SPI- sodium alginate (Alg) electrostatic complex and SPI-resveratrol nanocomplex. It was found that the combined ultrasonication/pH-shifting treatment resulted in a smaller particle size and larger surface hydrophobicity, which were 114.6 +/- 1.2 nm and 12741 +/- 456, respectively. During the formation of the complex with Alg, compared with pH-shifting or ultrasonication treatment, the combined ultrasonication/pH-shifting treatment expanded stable region, where the particle size was smaller and the binding constant with sodium alginate was higher. Moreover, the encapsulation efficiency of resveratml in SPI increased to 91.4 +/- 4.3% after the combined ultrasonication/pH-shifting treatment. Thus, simultaneous treatment combining ultrasonication and pH-shifting was significantly more effective than ultrasonication alone and was thought as an effective method for protein modification.