The microbial diversity and flavour metabolism of Chinese strong flavour Baijiu: a review

Abstract

Strong flavour Baijiu is widely consumed in China and is produced by the fermentation of grains using microbial starters. However, a comprehensive understanding of the diversity and metabolic characteristics of microbial communities involved in the solid-state fermentation of Baijiu is important for determining the relationship between microbial composition, flavour metabolism and understanding Baijiu fermentation conditions. Although studies have examined the metabolic pathways and impact of major processes on flavour compounds in strong flavour Baijiu, aspects of the fermentation process remain unexplored. In this review, methods are discussed for the optimisation of microbial diversity in strong flavour Baijiu and associated effects on the flavour of Baijiu. Recent studies are reviewed on starters (Daqu), fermented grains (Jiupei), and pit mud together with the effects of microbial composition on the quality of strong flavour Baijiu. The challenges of Baijiu research and production are discussed, including the role of the microbial diversity of Daqu and Jiupei in the flavour composition of strong flavour Baijiu. This review contributes to the current understanding of processing strong flavour Baijiu and serves as a reference for screening flavour related microorganisms, which is valuable for improving the quality of strong flavour Baijiu.

Airborne microbes in five important regions of Chinese traditional distilled liquor (Baijiu) brewing: regional and seasonal variations

“…During the saccharification process, especially in Daqu, a variety of extracellular enzymes (e.g., amylase, glucoamylase, protease, cellulose, and lipase) hydrolyze the macromolecules in cereals to form fermentable sugars ( Wang, 2022 ). These extracellular enzymes could be secreted by the species identified in this study, such as the bacteria of Bacillus, Enterobacter, Lactobacillus, Staphylococcus, Thermoactinomyces, and Weissella and the fungi of Aspergillus, Cladosporium, Mucor, Penicillium, and Rhizopus ( Figure 3 ; Table 1 ; Xu et al, 2017 ; Zou et al, 2018 ; Wang, 2022 ; Cheng et al, 2023 ). Yeast species in the fermentation process can be divided into two groups, which are responsible for ethanol production and flavor compound formation, respectively ( Wang, 2022 ).…”

“…Table 1 summarizes the major functional microbes of strong-flavor Baijiu brewing according to previous studies ( Zou et al, 2018 ; Cheng et al, 2023 ). Among these microbes, 41 genera were rich in at least one of the ten sample groups.…”

“… a The genera of this table are collected from Zou et al (2018) , Tu et al (2022) , and Cheng et al (2023) . b The genera in blue were rich in the atmosphere in at least one group (relative abundance > 0.1%; Supplementary Tables S4, S6 ).…”

“… a The genera of this table are collected from Zou et al (2018) , Tu et al (2022) , and Cheng et al (2023) . …”

“…The species detected in this study and related to ethanol production included but were not limited to S accharomycopsis, Saccharomyces, and Wicherhamomyces ( Wang et al, 2019 ; Figure 3 ; Table 1 ). Esters are the main aromatic components, and lactic acids are one of their precursors ( Cheng et al, 2023 and references therein). Lactic acid is mainly generated from carbohydrates by LAB (e.g., Lactobacillus, Streptococcus, Lactococcus, Leuconostoc, and Weissella in this study).…”