Correlation between Microbial Diversity and Major Volatile Aroma Compounds during Spontaneous Fermentation of Pinot Noir Wine at Industrial Scale

This study aimed to investigate the correlation between microbial community succession and volatile compounds during the spontaneous fermentation of Pinot Noir wine at an industrial scale. Pinot Noir grapes from the production region of Wuwei in the Hexi Corridor were used to produce wine by spontaneous fermentation. High-throughput sequencing was used to monitor the succession of the indigenous microbial community during the fermentation process, and volatile compounds were qualitatively and quantitatively analyzed by headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). Besides, the correlation between core indigenous microorganisms and volatile compounds was investigated using Spearman correlation coefficients. The results showed that the dominant microorganisms were Mycosphaerella, Pichia, Saccharomyces and Tatumella during the fermentation process, Mycosphaerella and Pichia being the dominant fungal genera during the early fermentation period with relative abundances of 44.67% and 18.28%, respectively, whereas the relative abundance of Saccharomyces increased gradually up to 48.42%, which became the dominant fungal genus at the end of the fermentation period. Tatumella was the most dominant bacterial genus during the late fermentation period, as its relative abundance increased gradually up to 44.66% and then remained basically unchanged. In addition, the dominant genera Komagataeibacter, Pantoea and Saccharomyces were positively correlated with the key volatile aroma substances including ethyl butyrate, ethyl caproate and phenylethanol, whose final concentrations were 164.04, 4585.75 and 3694.11 µg/L, respectively, at the end of the fermentation period, imparting floral, fruity and honey-like aromas to the wine. However, the dominant bacterial genera Sphingomonas, Methylobacterium and Mycosphaerella, Aspergillus were negatively correlated with most of the key aroma substances. The results of the present study provide a theoretical basis for improving the quality of wine in the Hexi Corridor.