Characterization of Soy Protein Isolate/Flammulina Velutipes Polysaccharide Hydrogel and Its Immunostimulatory Effects on RAW264.7 cells

Soy protein isolate (SPI) is a nutritional commercial product, while the poor solubility and gelling restricts its applications for functional foods. To surmount the challenge presented by this poor solubility, the gelling polysaccharide shows potential in ameliorating SPI. In this study, SPI/Flammulina velutipes polysaccharide (FVP) hydrogels were prepared under four mixing ratios (32:1, 20:1,15:1 and 10:1, w/w) at both pH6.5 and pH3.5, respectively. The stability of hydrogels and its immunostimulatory impact on RAW264.7 cells were assessed. Initial results revealed that water holding capacity increased when increasing the mixing ratios, likely to be the results of enhanced electrostatic interaction between SPI and FVP. The addition of FVP contributed to the improved swelling ratio and lowered the degradation ratio. Such structure feature was shown to be favorable for hydrogels to culture cells. More importantly, SPI/FVP hydrogels demonstrated no cytotoxic effect on cell metabolic activity. The culture of SPI/FVP hydrogels enhanced the immunostimulatory capacity in RAW264.7 cells by increasing phagocytosis and inducing the production of pro-inflammatory cytokines. The performances of the hydrogels made at pH3.5 were superior to those prepared at pH6.5. Our results suggested SPI/FVP hydrogels may provide application potential for the development of functional foods.