Metabolomic insights into premature yeast flocculation: identification of galangin as a key positive factor

Abstract Objectives: Premature yeast flocculation (PYF) poses a significant threat to beer quality and economic efficiency in the brewing industry. While previous research has focused primarily on genomic and proteomic aspects, the metabolic mechanisms underlying PYF remain poorly understood. This study aimed to elucidate the metabolic differences associated with varying degrees of PYF through a metabolomics-based approach. Materials and Methods: Metabolomic profiling was conducted on unfermented wort (WORT) and samples obtained from the 3-d European Brewery Convention (EBC) fermentation test, which exhibited different PYF severities. Differential metabolites were identified and compared between groups. Correlation analysis was performed to assess the association between metabolite levels and fermentation duration. Additionally, reverse addition experiments were conducted to evaluate the role of specific metabolites in promoting PYF. Results: A total of 46 differential metabolites, including arginine, daidzein, and galangin, were identified in the EBC group, whereas 30 differential metabolites such as daidzein, galangin, and tenuazonic acid were found in the WORT group, with 13 metabolites shared between both groups. In the PYF36 group, correlation analysis revealed that galangin and daidzein levels were positively associated with fermentation duration. Reverse addition experiments demonstrated that galangin significantly promoted PYF, as indicated by increased wort clarity, identifying it as a positive regulatory factor. Conclusions: This study provides the first comprehensive insight into the metabolic alterations associated with PYF. The identification of galangin as a key promoter of PYF offers a novel target for controlling this phenomenon, potentially enhancing beer production efficiency and quality in the brewing industry.