Correlation Analysis among Physicochemical Parameters, Flavor Compounds and Microbial Community during Fourth Round of Heap Fermentation of Jiang-Flavor Baijiu

The composition and change of the microbial community during the fourth round of heap fermentation of Jiang-flavor baijiu were explored using traditional culture-dependent approaches and high-throughput sequencing, and flavor compounds from fermented grains were analyzed by gas chromatography. The correlation among physicochemical parameters, flavor compounds and the microbial community was also analyzed. The results showed that the dominant bacteria were Bacillus amyloliquefaciens, B. licheniformis, uncultured Kroppenstedtia sp., K. eburnea, Sphingobium yanoikuyae and Lactobacillus sp., and the dominant fungi were Pichia kudriavzevii, Kazachstania humilis, Thermomyces languginosus, Byssochlamys spectabilis, Zygosaccharomyces parabilii and Aspergillus sp. The microbial community had a complex relationship with physicochemical parameters and flavor compounds. The water content was positively correlated with yeasts like P. kudriavzevii, negatively correlated with filamentous fungi such as T. lanuginosus, B. spectabilis and A. costiformis, while the starch and reducing sugar contents were positively correlated with Bacillus sp., and negatively correlated with P. kudriavzevii. Meanwhile, yeasts were positively correlated with alcohols such as propanol, isobutanol, isoamyl alcohol and β-phenylethanol (P < 0.01), while filamentous fungi and bacteria were positively correlated with acids and esters, such as acetic acid, propionic acid, isobutyric acid, ethyl lactate, ethyl oleate and butyl caproate (P < 0.01). This study may provide a theoretical basis for further clarifying the mechanism of heap fermentation of Jiang-flavor baijiu.