Physicochemical and Surface Properties of Rice Albumin for its Application as a Functional Food Material

Abstract

The thermal and acid stability of Oryza sativa rice albumin (RA), which suppresses postprandial hyperglycaemia, was evaluated for its use in foods. RA showed high thermal stability, with a peak temperature (T_p) of 100.8 °C by differential scanning calorimetry measurement. However, its T_p shifted to 52.0 °C with the addition of dithiothreitol, suggesting that the heat resistance of RA is attributed to its rigid structure supported by intermolecular disulphide bonds. The α-amylase inhibitory activity of RA was retained even after heating to 100 °C, although it gradually decreased with longer heating times or increasing concentrations of RA. RA showed high nitrogen solubility and surface properties, such as emulsifying and foaming properties, even under acidic conditions, as opposed to other common food proteins (i.e., casein, soy protein isolate, and dried egg white). These findings suggest that RA can be used as an additive in various foods.