Selectively hydrolyzed soy protein as an efficient quality improver for steamed bread and its influence on dough components

•The quality of steamed bread was improved by SHSP.•SPI showed a negative effect on the quality of steamed bread.•Competition between soy protein and gluten for water resulted in exposure of starch.•SHSP converted the disordered structure of gluten into an ordered structure. Selectively hydrolyzed soy protein (SHSP) has the potential to improve the quality of steamed bread. To clarify its underlying mechanism, the influence of SHSP on dough properties and components was investigated and compared with that of soy protein isolate (SPI). The results showed that SHSP addition resulted in steamed bread with higher loaf volume, lower hardness, and higher viscoelasticity. In contrast, SPI addition had the opposite effect. Nevertheless, both soy proteins decreased melting enthalpy and increased starch particle exposure due to competition for water. By analyzing molecular weight distribution and the secondary structure, we determined that the GMP content of fermented dough decreased by 10.04% following 1% SPI addition; however, it was enhanced by 7.90% following 1% SHSP addition. Moreover, the content of β-turns decreased with SHSP addition. The present study provides a theoretical basis for the exploitation of soy proteins as a nutritious and technofunctional dough improver.