Use of microbial indicators combined with environmental factors coupled with metrology tools for discrimination and classification of Luzhou-flavoured pit muds

Aims Pit mud is essential for the quality and yield of Chinese Luzhou-flavoured liquor. A reliable and fast method based on the use of microbial indicators combined with environmental factors coupled with metrology tools is needed to discriminate and classify different maturity levels of Luzhou-flavoured pit muds. Methods and Results Firmicutes, Bacteroidetes, Actinobacteria, Lactobacillus, Bacillus, Methanosarcina, Methanocorpusculum, Methanoculleus and Clostridium kluyveri were microbial indicators in Luzhou-flavoured pit muds. They were detected by real-time quantitative PCR. Environmental factors investigated included moisture content, pH, total acid and ammonia nitrogen. Principal component analysis (PCA) and partial least square-discriminant analysis were employed to explore the structure of the data and construct discrimination and classification models by reduction in the data dimensionality. Pit muds were distinguished and classified as new, trend to-be aged and aged. Moisture content and pH were significantly negatively correlated with new pit mud, while pH, total acid, amino nitrogen, Firmicutes, Bacteroidetes, Actinobacteria, Methanosarcina, Methanoculleus and C. kluyveri were significantly positively correlated with aged pit mud. Conclusions Microbial indicators combined with environmental factors coupled to metrology tools can reliably and quickly discriminate and classify different maturity levels of Luzhou-flavoured pit muds. Significance and Impact of the Study Modern techniques and metrology tools verified the correctness of the traditional sensory evaluation used in controlling the quality of pit mud, and will contribute to distinguishing different maturity levels of Chinese Luzhou-flavoured pit muds.