Characterization of recombinant rice quiescin sulfhydryl oxidase and its improvement effect on wheat flour-processing...

In this study, recombinant rice quiescin sulfhydryl oxidase (rQSOX) was expressed and characterized, and its performance in flour-processing quality was further evaluated. The purified rQSOX exhibited the highest sulfhydryl oxidation activity (1.96 IU/mg) using dithiothreitol as a substrate, accompanying the production of H₂O₂. The optimal temperature and pH were 60 °C and pH 8.0 for rQSOX catalyzing oxidation of dithiothreitol. And rQSOX retained 50% of its maximum activity after incubation at 80 °C for 1 h. Moreover, rQSOX supplementation improved the farinograph properties of dough, indicated by the increased dough stability time and decreased degree of softening, and enhanced viscoelastic properties of the dough. Addition of rQSOX (10 IU/g flour) provided remarkable improvement in specific volume (37%) and springiness (17%) of the steamed bread, and significantly reduced the hardness by half, which was attributed to the strengthened gluten network. The results provide an understanding for rQSOX using in flour-processing industry.