Interactions of grape seed procyanidins with soy protein isolate: Contributing antioxidant and stability properties

The interaction of grape seed procyanidins (GSP) with soy protein isolate (SPI) and the characters of GSP/SPI complex were investigated. The experiment effects were determined using isothermal titration calorimetry (ITC), scanning electronic microscopy (SEM), fluorescence spectroscopy and ultraviolet (UV) spectrophotometry. The results of ITC and SEM suggested that there was a hydrogen bond-dominated interaction between GSP and SPI, and the complex presented as a spherical shape. The results of the fluorescence spectroscopy indicated that the fluorescence quenching effect of GSP on SPI was more obvious as the GSP concentration increased, and the quenching process was mainly static quenching. The results of UV spectrophotometry showed that the GSP/SPI complex can effectively improve the antioxidant properties, thermal stability, light stability, and pH stability of GSP. Thus there appears to be an interaction between GSP and SPI, and the complex improved the physical and chemical properties of GSP.