Research on Fungal Diversity and Flavor Characteristics during Alcoholic Fermentation of 'Chardonnay' Dry White Wine in Wuwei, Gansu

In order to explore the diversity of fungal communities during the alcoholic fermentation of 'Chardonnay' dry white wine in Wuwei, Gansu, and its effect on flavor characteristics, high-throughput sequencing technology was used to analyze the succession of fungal communities during the alcoholic fermentation of 'Chardonnay' wine in Liangzhou (HC) and Minqin (XC) sub-regions of Wuwei. At the same time, conventional physicochemical tests and headspace solid phase microextraction-gas chromatography-mass spectrometry were used to analyze the physicochemical indexes and volatile aroma compounds of wine samples. Redundancy analysis and the Spearman correlation coefficient were used to explore the correlation between fungal communities and physicochemical indexes and aroma components. The results showed that the fungal community composition and abundance of 'Chardonnay' wine in the two sub-regions of Wuwei were significantly different at different stages of alcohol fermentation. The dominant fungal genera in the early stage of XC fermentation were mainly Pichia (63.23%), Hanseniaspora (17.28%), Starmerella (12.66%), Cladosporium (1.51%), and Aspergillus (3.22%); while the dominant fungal genera in the early stage of HC fermentation were Pichia (68.63%), Saccharomyces (3.46%), Hanseniaspora (4.69%), Penicillium (17.25%), Cladosporium (2.53%), and Alternaria (1.01%). As the fermentation progressed, the proportion of Saccharomyces increased significantly in the middle stage of XC fermentation. At the end of fermentation, the Saccharomyces flora tended to be stable, with Pichia (23.16%), Saccharomyces (36.19%), and Starmerella (38.11%) dominating the XC wine sample, and Pichia (73.89%) and Saccharomyces (16.85%) dominating in the HC wine sample. The results of redundancy analysis showed that Saccharomyces was significantly positively correlated with total acid, alcohol content, volatile acid and lactic acid, and played a key role in the late fermentation period. While Pichia was significantly positively correlated with YAN, pH, malic acid and total sugar, and played a major role in the early fermentation period. In addition, correlation analysis showed that Saccharomyces was extremely significantly positively correlated with acetic acid and citronellol, while Pichia was the opposite. Hanseniaspora was extremely significantly positively correlated with isoamyl acetate and phenylethyl acetate, while Starmerella was extremely significantly negatively correlated with ester substances (ethyl hexanoate and ethyl octanoate). Filamentous fungi Penicillium, Cladosporium, Alternaria, Erysiphe and Aureobasidium were positively correlated with most ester substances, and were also positively correlated with linalool and decanal. It can be seen that there are a large number of core fungal groups in 'Chardonnay' dry white wine produced in Wuwei, and there is a significant correlation between each fungal genus and flavor substances. The results of this study provide data reference for the use of local microorganisms to regulate wine quality.