Abstract: The effects of soymilk fermented with single and mixed (1:1:1) cultures of three strains of lactic acid bacteria (LAB) isolated from sourdough from Fuchun Teahouse in Yangzhou City on the fermentation characteristics of dough and the quality of steamed bun were investigated. The results showed that the acidity and viable bacterial count of soymilk fermented with the mixed culture were 85.06 °T and 9.66 (lg(CFU/mL)), respectively, which were higher than those of the single culture fermented samples. Meanwhile, compared with the control group, the addition of fermented soymilk significantly increased the organic acid content and viable bacterial count of dough. The lactic acid content and viable bacterial count of dough supplemented with Lactobacillus pentosus 203 fermented soymilk were the highest, which were 18.57 mg/g and 8.94 (lg(CFU/g)), respectively. Dough added with Lactobacillus fermentum 202 fermented soymilk had the highest acetic acid content (3.81 mg/g). Compared with control steamed buns, the specific volume, elasticity and height to diameter ratio of four steamed buns supplemented with fermented soymilk were significantly increased, while the hardness and chewiness were significantly decreased. Steamed buns added with mixed-culture fermented soymilk had the highest overall acceptability. A total of 48 volatile flavor substances were detected in the five groups of steamed buns. Among them, the relative contents and types of flavor substances in the mixed culture group were the highest, which were 71.62% and 47, respectively. After being stored at 4 ℃ for 4 days, the moisture loss rate and retrogradation enthalpy of steamed buns added with fermented soymilk were significantly lower than those of the control group; the highest moisture content of 38.53% and the lowest retrogradation enthalpy of 1.00 J/g were found in the mixed culture group. In conclusion, adding fermented soymilk can effectively improve the quality and flavor and delay the aging of steamed buns, this effect being most pronounced with the incorporation of mixed-culture fermented soymilk.

Key words: fermented soymilk; dough; fermentation characteristics; steamed bun quality