Evaluating the feasibility of fermentation starter inoculated with Bacillus amyloliquefaciens for improving acetoin and tetramethylpyrazine in Baoning bran vinegar

- Inoculated Daqu was first employed for improving the aroma of vinegar.
- Inoculated Daqu significantly influenced the microbial structure of vinegar Pei.
- Inoculated Daqu distinctly improved the contents of acetoin and tetramethylpyrazine.
- It may provide novel methods to improve the aroma and quality of fermented foods.

Fermentation starters (Daqu) used in present study included traditional herb Daqu (C Daqu), modified Daqu without herbs (M Daqu) and S Daqu fermented by inoculating acetoin and tetramethylpyrazine high-producing bacterium Bacillus amyloliquefaciens into M Daqu. To evaluate the feasibility of S Daqu combined with M Daqu applied for improving contents of acetoin and tetramethylpyrazine in Baoning bran vinegar without remarkably changing the original microbial community and the other volatiles contents compared with C Daqu, vinegar Pei C, M, M1, M2 and S were correspondingly prepared in lab scale using C Daqu, M Daqu, M1 Daqu (S Daqu: M Daqu = 1:9, w/w), M2 Daqu (S Daqu: M Daqu = 5:5) and S Daqu. PCR-DGGE suggested that Bacillus, Lactobacillus, Oceanobacillus, Acetobacter, Pichia, Geotrichum and Trichoderma were dominant microbes. Microbial community of M were similar with M1, while that of the others were similar. Differences in physicochemical properties among samples may be ascribed to different enzymes activities of Daqu and bioactivities of microbial metabolism during fermentation. Moreover, total contents of organic acids in M, M1, M2 and S increased by 33.10%, 25.77%, 4.32% and 7.74% relative to C, respectively. Volatiles and PLS-DA analysis suggested that volatile profiles of M were similar with M1, that of M2 were similar with C, while that of S were significantly different with the others. Both M2 Daqu and S Daqu facilitated the formation of acetoin and tetramethylpyrazine. However, M2 Daqu was more efficient for enhancing acetoin and tetramethylpyrazine contents by 191.84% and 123.17% respectively, without significantly changing the other volatiles contents.