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. 2024 Mar 15;13(6):899.
doi: 10.3390/foods13060899.

Study on the Fermented Grain Characteristics and Volatile Flavor Substances during the Tuqu Fermentation of Hunan Light-Flavor Baijiu

Jie Xu  1   2 , Ting Zhang  1   2 , Huitai Chen  3 , Yijie Dai  4 , Zongjun Li  4 , Jia He  1   2 , Rongfang Ju  1   2 , Aixiang Hou  1   2
Affiliations

Study on the Fermented Grain Characteristics and Volatile Flavor Substances during the Tuqu Fermentation of Hunan Light-Flavor Baijiu

Jie Xu et al. Foods. .

Abstract

The present study employed Hunan local Tuqu for fermentation and investigated the physicochemical properties, microbial community composition, and volatile flavor compounds of the fermented grains, as well as the correlation between the physicochemical indicators and the microbial community. The findings reveal that the activities of α-amylase and glucoamylase were highest during the initial stages of the fermentation process. The acid protease activity increased to 30.6 U/g on the second day and then decreased. Cellulose and lipase activities both showed an increasing trend. The moisture content increased sharply to 73.41% and then remained relatively stable. The acidity was highest on the eighth day. Fifty genera of bacteria and twenty-two genera of fungi were detected. Lactobacillus was dominant among bacteria, and Saccharomyces was dominant among fungi. A correlation analysis showed that there were positive correlations between moisture, acidity, cellulose, lipase activities and Lactobacillus, and there were positive correlations between moisture content, acidity, cellulase activity, acidic protease activity and Saccharomyces. A total of 46 volatile flavor compounds were detected, of which 6 alcohols and 14 esters constituted the major portion, and 9 key flavor compounds with an ROAV > 1 were identified throughout the fermentation process. Isoamyl acetate had the highest ROAV and made the greatest contribution to the flavor.

Keywords: bacteria; fermented grains; fungi; light-flavor Baijiu; volatile flavor substances.

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Conflict of interest statement

Author Huitai Chen was employed by Hunan Guoyuan Liquor Co., Ltd. Huitai Chen has contributed toward project administration. The objectivity and authenticity of the experimental results and discussion were not affected by the company. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Sampling sites of the fermented grain samples.
Figure 2
Figure 2
The brewing process of Hunan light-flavor Baijiu.
Figure 3
Figure 3
Variation of moisture and acidity with fermentation days during the Toqu fermentation of Hunan light-flavor Baijiu ((A): moisture; (B): acidity).
Figure 4
Figure 4
Alpha diversity analysis of bacteria in the Tuqu fermentation process of Hunan light-flavor Baijiu. * is a marker indicating significance.
Figure 5
Figure 5
Community structure distribution of bacteria based on genus level during the Tuqu fermentation of Hunan light-flavor Baijiu.
Figure 6
Figure 6
Heat map of the genus-based level of bacteria in the Tuqu fermentation process of Hunan light-flavor Baijiu.
Figure 7
Figure 7
Alpha diversity analysis of fungi in the Tuqu fermentation process of Hunan light-flavor Baijiu.
Figure 8
Figure 8
Community structure distribution of Fungi based on genus level during the Tuqu fermentation of Hunan light-flavor Baijiu.
Figure 9
Figure 9
Heat map of the genus-based level of Fungi in the Tuqu fermentation process of Hunan light-flavor Baijiu.
Figure 10
Figure 10
Heat map of correlation between bacterial microorganisms and physicochemical indicators based on genus level.
Figure 11
Figure 11
Heat map of correlation between fungi microorganisms and physicochemical indicators based on genus level.
Figure 12
Figure 12
Numbers and percentages of volatile compounds identified in the Tuqu fermentation process of Hunan light-flavor Baijiu: (A) numbers of different types of volatile compounds in different steps; (B) the percentages of different volatile compounds in the Tuqu fermentation process of Hunan light-flavor Baijiu; (C) the changes in the content of alcohols and esters of Hunan Tuqu light-flavor Baijiu.
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