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Deciphering the role of traditional flipping crafts in medium-temperature Daqu fermentation: Microbial succession and metabolic phenotypes

Summary

This research explains how traditional flipping techniques during Daqu (a fermentation starter for Chinese Baijiu liquor) improve its quality. By comparing fermented Daqu that was flipped versus unflipped, scientists discovered that flipping creates better conditions for beneficial microorganisms to thrive, leading to more desirable flavors and higher enzyme activity. The findings suggest that flipping works by managing temperature and moisture, creating a simpler but more stable community of beneficial bacteria and fungi that work together to enhance the fermentation process.

Background

Medium-temperature Daqu (MTD) serves as a saccharification and fermentation starter for Baijiu production. Traditional flipping operations during fermentation are crucial for maintaining uniform fermentation conditions, but their mechanistic role remains unclear. This study aims to elucidate how flipping crafts influence microbial community succession and metabolic outputs.

Objective

To systematically compare flipping Daqu (FD) with non-flipping Daqu (NFD) to understand the mechanisms underlying microbial succession dynamics, metabolic phenotypes, and environmental drivers that govern traditional MTD fermentation.

Results

FD exhibited significantly higher enzyme activities, volatile ketone content, and lower temperatures compared to NFD. Bacterial and fungal communities showed divergent succession patterns after day 6 flipping, with FD dominated by non-thermophilic species and NFD by thermophilic genera. FD’s microbial network was simpler yet more stable. Forty differential metabolites were identified between crafts, with temperature identified as the primary driver of microbial assembly.

Conclusion

Flipping operations enhance microbial functionality and metabolic diversity by modulating environmental conditions, particularly temperature and moisture. The simplified yet stable microbial network in FD, driven primarily by temperature, provides a theoretical basis for optimizing MTD production and transitioning to intelligent fermentation systems.
  • Published in:Current Research in Food Science,
  • Study Type:Experimental Study,
  • Source: PMC12059395; PMID: 40343192; doi: 10.1016/j.crfs.2025.101063
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