AN EXTERNAL ADDITION OF SOY PROTEIN ISOLATE HYDROLYSATE TO SOURDOUGH AS A NEW STRATEGY TO IMPROVE THE QUALITY OF CHINESE STEAMED BREAD

Soy protein isolate (SPI) was hydrolyzed and then its hydrolysate (Hyd-SPI) was supplemented to dough. The dough fermented by a starter consisting of Lactobacillus paralimentarius 412 and Anqi's yeast was applied to manufacture Chinese steamed bread. Addition of 1% Hyd-SPI to dough is found to significantly improve the farinograph and extensograph values. Moreover, 1% Hyd-SPI stimulates the growth and metabolism of the starter culture better compared with the control and thus improves the sourdough fermentation. The sourdough supplemented with 1% Hyd-SPI observed by scanning electron microscopy contains starch granules that are largely hydrolyzed. Additionally, the sourdough has more free amino acids than the control. A total of 45 volatile compounds are recognized in the Chinese steamed breads containing 1% Hyd-SPI. This is the first report that SPI hydrolysate is used to improve the quality of Chinese steamed bread products.