Abstract:The effects of liquid fermentation of Monascus purpureus on the composition and quantity of Pu-erh tea metabolites were investigated. Significant metabolites in tea，both before and after fermentation，were screened to reveal the impact of liquid fermentation of M. purpureus on Pu-erh tea quality. Changes in tea metabolites following liquid fermentation with inoculated M.purpureum were analyzed using liquid chromatography-mass spectrometry.A multivariate statistical analysis method was employed to identify significantly different metabolites in samples before and after fermentation. In total，991 metabolites were detected from sterilized raw materials and fermentation samples，of which 215 were significantly increased after fermentation.These mainly included xanthine，kaempferol，aminobenzoic acid，quercetin，D-mannitol，cis-11-octadecenoic acid，and others. Another 464 metabolites were significantly downregulated after fermentation，including catechins，epicatechins，coumarin，O-phosphocholine，theaflavin，chlorogenic acid，eugenaldehyde，proanthocyanidins，and others.The composition and quantity of metabolites in tea juice changed significantly after liquid fermentation of M.purpureus compared with sterilized raw materials.The screening and identification of differentially expressed metabolites during fermentation provide reference data for studies on the influence of M.purpureus on tea quality and will inform the development of new Pu-erh tea products through M.purpureus fermentation.