Effects of acetic acid bacteria in starter culture on the properties of sourdough and steamed bread

Sourdough starters for making traditional steamed bread are rich in microbes. Studies have shown that, in addition to yeast and lactic acid bacteria (LAB), acetic acid bacteria (AAB) are other functional species in sourdough, but the influences of AAB on the properties of sourdough and steamed bread were rarely reported. This study aimed to assess the effects of a selected strain of acetic acid bacterium on the properties of sourdough and steamed bread. Sourdoughs and steamed breads were prepared from five different starter cultures, marked as CK (control, with no starters), Y (only yeast), YL (yeast+LAB), YA (yeast+AAB) and YLA (yeast+LAB+AAB), and their properties were determined. The results of sourdough properties showed that the YLA sourdough had the highest total titratable acid of 14.6 mL and the lowest pH of 3.87 compared with the other groups after fermentation to 8 h; and the YLA sourdough had the greatest elasticity and viscosity. The results of quality properties of steam bread revealed that the L* value (88.40 ± 0.09) of the YA steamed bread was significantly higher than those of the YLA and YL steamed breads; the YLA steamed bread had the highest specific volume and the highest sensory score 89.6 ± 3.31 in comparison to those of the other groups; the hardness and chewiness of YLA and YA steamed breads were significantly lower than those of the other groups. Volatile compounds in the steamed breads were also determined by SPME-GC–MS. A total of 42 flavor substances were detected, including 3 kinds of alcohols, 8 kinds of aldehydes, 7 kinds of ketones, 2 kinds of acids, 15 kinds of esters, 1 furan, and 6 kinds of other types of compounds, mainly alkanes and esters, followed by alcohols and aldehydes. The YLA steamed bread was richer in esters, aldehydes, and acids than those from the other treatment groups. By contrast, alkanes and aldehydes were dominant in the Y and YL steamed breads. Therefore, the flavor and quality of the steamed bread made from the YLA sourdough could be improved obviously. These results could provide references for the application of AAB in dough fermentation and the improvement of new kinds of starters.