Abstract: In order to study the effect of fermentation with a mixed starter culture of lactic acid bacteria on the quality of multigrain dough and steamed bread, yellow pea flour, naked oat flour, gluten flour and oat β-glucan (OBG) were mixed together to prepare dough and steamed bread with a direct vat set (DVS) mixed starter?culture of lactic acid bacteria. The acidifying capacity of lactic acid bacteria in dough was investigated, and the contents of OBG, resistant starch (RS) and free amino acids and the microstructure of dough were analyzed. Also, the quality and nutritional characteristics of steamed multigrain bread and steamed wheat bread before and after fermentation were compared. The results showed that lactic acid bacteria had strong acidifying capacity in fermented multigrain dough, and the contents of lactic acid and acetic acid were 24.85 and 8.98 mg/mL, respectively, after 24 hours of fermentation. Compared with unfermented multigrain dough, the OBG content in lactic acid bacteria fermented multigrain dough decreased by 32.56%, the RS content increased by 32.88%, the total amount of free amino acids increased by 1.46 times, the amino acid composition pattern was better, proteins and cellulose were partially degraded, and the gluten network was more compact and continuous. In terms of nutrition, the dietary fiber content of steamed multigrain bread was higher than 6% both before and after lactic acid bacteria fermentation, and the protein content was 40.35% and 38.38% in steamed unfermented and fermented multigrain bread, respectively, indicating that steamed multigrain bread is rich in dietary fiber and protein. Its dietary fiber and protein contents were higher than those of steamed wheat bread. Lactic acid bacteria fermented multigrain steamed bread had higher in vitro protein digestibility and specific volume, and the overall sensory score of steamed lactic acid bacteria fermented multigrain bread was significantly higher than that of steamed unfermented multigrain bread, and the overall acceptability was higher.

Key words: direct vat set starter culture; lactic acid bacteria; multigrain dough; microstructure; nutritional evaluation