Physicochemical properties of soy protein prepared by enzyme-assisted countercurrent extraction

Synchronous improvements of both nutritional properties and the flavour of protein by optimising preparation processes are highly challenging. The prehydrolysis of soy meals by cocktail enzyme (beta-glucosidase, phytase and acid protease) treatment and subsequent countercurrent extraction were designed based on similar hydrolysis conditions. The composition, flavour volatiles and physicochemical properties of soy proteins were investigated. Compared to alkaline extraction and acid precipitation, enzyme-assisted countercurrent extraction significantly increased protein yield and carbohydrate content, accompanied by a decrease in protein purity. This protein exhibited larger molecular weight distribution, less flavour volatiles, higher thermal stability and surface hydrophobicity, as evidenced by higher denaturation temperature (T-d) and enthalpy change (Delta H) of protein. The conversion of isoflavone glycosides to aglycone and the partial degradation of phytic acid were observed for enzyme-prepared soy proteins. These results suggest a feasible protocol for producing a nutrient-improved soy protein with excellent flavour and thermal stability.