Insight on the interaction between soybean protein isolate and ionic/non-ionic polysaccharides: Structural analysis, oil-water interface properties investigation and double emulsion formation

In this study, hydroxypropyl methylcellulose (HPMC) and xanthan gum (XG) were utilized to enhance the interfacial activity of soybean protein isolate (SPI) by forming complexes with SPI, respectively. Meanwhile, SPI-HPMC and SPI-XG were used to construct a double emulsion to investigate the effects of the interaction of ionic/nonionic polysaccharides with SPI on the performances of the double emulsion. The results of multispectral analyses showed that both HPMC and XG induced structural changes in SPI, thereby exposing a large number of hydrophobic groups. Moreover, molecular simulation results showed high stability of the complexes formed by SPI with HPMC and XG. The results of molecular simulations showed that the complexes formed by SPI with HPMC and XG were highly stable. Furthermore, the ability of SPI to reduce interfacial tension at the oil-water interface and its emulsifying ability was enhanced by the formation of complexes with polysaccharides, which also improved the physicochemical properties of the double emulsion stabilized by the SPI-polysaccharide complex. When the phase ratio (W1/O:W2) was 4:6 and the polysaccharide addition was 0.4%, the double emulsion showed the smallest particle size, the highest encapsulation efficiency and the best stability. Th in vitro digestion models demonstrated that the SPI-XG double emulsion could effectively protect the encapsulated bioactives during the digestion process and increase their bioaccessibility to 70.86%. In summary, this study was beneficial in corroborating the ability of ionic/non-ionic polysaccharides in improving the interfacial properties of SPI and improving the performance of the double emulsion.