Depth-depended quality comparison of light-flavor fermented grains from two fermentation rounds

To improve the utilization of raw materials, the fermentation of light-flavor Baijiu (LFB) will usually take two rounds of fermentation to the same batch of raw materials. The microorganisms involved in the fermented grains (FG) from these two fermentation rounds are the key to the quality formation of light-flavor style. Using Illumina MiSeq high-throughput sequencing and electronic-senses, it was found that the microbiota and flavor of FG for light-flavor Baijiu were mainly affected by fermentation rounds rather than depths, while the physicochemical factors were just the opposite. Starch was the most influential physiochemical factor on the microbiota. FG from the first fermentation round (FFRFG) had a higher fungal diversity, while FG from the second fermentation round (SFRFG) had a higher microbial richness and bacterial diversity. Monascus and the function of metabolism were significantly enriched in FFRFG; while Nocardia, Saccharomyces, Aspergillus and the functions of information storage and processing as well as cellular processes and signaling were significantly enriched in SFRFG. The flavor characteristics of FFRFG were mainly sourness as well as rich in sulfur organic compounds and broad range compounds, while that of SFRFG was mainly saltiness, umami, and bitterness, as well as rich in aromatic compounds. The findings could contribute to a comprehensive understanding of the role of FG in LFB fermentation from the perspective of rounds and depths.