Effects of rice bran stabilization procedures and proteases on rice bran protein hydrolysates

Rice bran stabilization is typically performed after rice milling to improve storage performance. In the present study, we investigated the effect of extrusion (EX) and superheated steam (SS) on the physicochemical and functional characteristics of rice bran protein hydrolysates (RBPHs) obtained with acid, alkaline, and neutral proteases (AP, ALP, and NP). The deactivation parameters were optimized as EX (140 °C, water content: 25%) and SS (130 °C, 5 min). After stabilization, the enzymatic hydrolysis of proteins was inhibited. The untreated RBPHs obtained with ALP exhibited the highest degree of hydrolysis (15.93%), while RBPH-EX-NP presented the lowest (10.75%). EX reduced the solubility of RBPHs, while SS improved the solubility at pH 2–4. Both stabilizations increased the β-sheet and β-turn contents of RBPHs while reducing the α-helix and random coil contents. The antioxidant activity of RBPHs decreased, while their emulsifying activity and ferrous chelating ability increased. This study could contribute to insight into the effects of industrial stabilization on RBPHs.