Synergistic Enhancement of Anthocyanin Stability and Techno-Functionality of Colored Wheat During the Steamed Bread Processing by Selectively Hydrolyzed Soy Protein

To improve the stability of anthocyanins and techno-functionality of purple and blue wheat, the selectively hydrolyzed soy protein (reduced glycinin, RG) and β-conglycinin (7S) were prepared and their enhanced effects were comparatively investigated. The anthocyanins in purple wheat showed higher stability compared to that of the blue wheat during breadmaking. The cyanidin-3-O-glucoside and cyanidin-3-O-rutincoside in purple wheat and delphinidin-3-O-rutinoside and delphinidin-3-O-glucoside in blue wheat were better preserved by RG. Addition of RG and 7S enhanced the quality of steamed bread made from colored and common wheat, with RG exhibited a more prominent effect. RG and 7S suppressed the gelatinization of starch and improved the thermal stability. Both RG and 7S promoted the unfolding process of gluten proteins and facilitated the subsequent crosslinking of glutenins and gliadins by disulfide bonds. Polymerization of α- and γ-gliadin into glutenin were more evidently promoted by RG, which contributed to the improved steamed bread quality.