Characterisation of the physicochemical properties of intact and hydrolysed rice protein ingredients

Abstract The physicochemical properties of rice protein ingredients, including three rice protein concentrates (RPC1, RPC 2 and RPC 3), two rice endosperm protein hydrolysates (RPH 1 and RPH 2) and two rice bran protein hydrolysates (RBPH 1 and RBPH 2), were investigated and compared to those of selected dairy protein ingredients, i.e., skim milk powder (SMP), whey protein isolate (WPI) and whey protein hydrolysate (WPH). RPC samples had low solubility in water (2–35%) in the pH range 2–8, while RPH samples were highly soluble and RBPH samples had intermediate (>60%) solubility. RPHs had the highest foaming capacity, and foams generated using these ingredients displayed the slowest drainage rate and a relatively high stability of foam volume. Increases in viscosity during heating to 95 °C, and on subsequent cooling to 35 °C, of RBPH 1 solution were associated with gelatinisation and retrogradation, respectively, of its starch component. Severe heat treatment (140 °C × 30 min) did not affect the colloidal stability of RPH solutions, but resulted in extensive thickening and particulation of RBPH solutions and coagulation of SMP and WPI solutions. These results demonstrate the excellent physicochemical properties of RPHs and highlights their potential as functional and value-added ingredients in a range of food products.