Physical and nutritional properties of Chinese Steamed Bun (mantou) made with fermented soy milk

The incorporation of fermented soy milk as an ingredient in Chinese steamed bun (CSB) was investigated to improve nutritional properties and flavour. Soy milk, fermented with lactic acid bacteria (LAB) isolated from sourdough, was used at a level of 40% to prepare CSB. According to the rheological and microstructural analyses, the addition of fermented soy milk effectively improved the internal structure of the dough. CSB containing fermented soy milk had better texture properties. The protein content of CSB increased from 7.17% to 8.83%, and the fat content increased from 0.75% to 1.22%. The total phenolic compounds (TPCs) increased by 35.79%, the total flavonoids compounds (TFCs) increased by 100.08%, and the scavenging rate against DPPH increased by 8.01%. The antinutritional compounds (e.g., condensed tannins, phytic acid, total saponins) were significantly reduced by 43.35%, 21.28% and 52.18%, respectively. The in vitro protein digestibility (IVPD) increased by 10.69%, and the total free amino acids (TFAAs) concentration increased from 65.16 mg/g to 73.25 mg/g. In addition, the glucose content of CSB decreased by 13.61%, and fermented soy milk significantly increased the flavour compounds. The results confirmed that fermented soy milk could be a promising supplement for potential industrial applications.