Yeast dynamics and changes in volatile compounds during the fermentation of the traditional Chinese strong-flavor Daqu

Daqu is the major source of microorganisms, enzymes, flavour compounds, and their precursors in the Chinese liquor production process. In the present study, the yeast community and the volatile compounds of Chinese strong-flavor Daqu during its fermentation were investigated using PCR-DGGE and HS-SPME/GC-MS, respectively. The results indicated that the band number, dominance, diversity and similarity of the 26S rDNA were clearly distinct in the DGGE patterns, due to the significant diversity expressed by the disparate yeast communities in different phases. More than 14 yeast genera, such as Saccharomycopsis fibuligera, Hanseniaspora uvarum, Geotrichum bryndzae, Wickerhamomyces anomalus, Yarrowia Lipolytica, Candida mucifera, Issatchenkia orientalis, Alternaria tenuissima, Kazachstania barnettii, Candida intermedia, Kazachstania barnettii, Pichia occidentalis, Saccharomyces cerevisiae, Pichia kudriavzevii and Saturnispora silvae were observed in the fermentation, among which the dominant strains were Pichia kudriavzevii and Saturnispora silvae. Furthermore, 43 volatile compounds, including 15 esters, 10 acids, 8 alcohols, 4 aldehydes, 2 alkenes, 1 ketone, 1 phenol, 1 furan and 1 pyrrole, were identified. The trajectory plots of the compounds acquired during consecutive stages of incubation revealed that different samples of Daqu correlated with specific groups of volatile compounds. These findings would help to understand the fermentation mechanism of Daqu production.