Subcritical water (SCW) hydrolysis is an alternative to traditional methods of protein hydrolysis that uses water as a reaction medium. In this study, the effect of SCW treatment on heat-induced conformational changes in wheat gluten and its relation to enzymatic susceptibility were investigated. The degree of deamidation increased rapidly from 12.5 to 47.4% with increase in the temperature range of 160-220 °C. Protein solubility increased in a similar pattern with degree of deamidation and almost all protein was solubilized after treatment with SCW at 200 °C. SCW treatment in a particular time-temperature combination results in a significant decrease in enzymatic susceptibility. After SCW treatment at 220 °C for 20 min, enzymatic susceptibility of gluten protein was exceedingly decreased to nearly complete loss. Because of excess degradation and deamidation and small molecular size (less than 6500 Da) many hydrolysis sites disappear and are difficult to access by protease.
Keywords: Enzyme hydrolysis; Enzyme susceptibility; Hydrothermal process; Subcritical water; Wheat gluten.