Metabolite profiling of Cheonggukjang, a fermented soybean paste, during fermentation by gas chromatography-mass spectrometry and principal component analysis
Metabolite profiling by applying principal component analysis (PCA) to a GC–MS data set was performed to assess changes in a select number of pre-defined metabolites during the fermentation of Cheonggukjang. A total of 20 amino acids, 12 organic acids, and nine fatty acids were found as targeted metabolites in Cheonggukjang. As fermentation proceeded, the levels of most amino acids decreased during the early stage of fermentation, but increased in the later part of fermentation. On the other hand, amounts of fatty acids increased throughout the fermentation process, while those of most organic acids, except for tartaric acid, decreased. A PCA score plot illustrated good separation of the Cheonggukjang samples according to fermentation period by combining principal component 1 (PC 1) (36.8%) with PC 2 (30.3%). Tryptophan, citric acid, Î²-alanine, itaconic acid, 2-hydroxyglutaric acid, Î³-aminobutyric acid, leucine, malic acid, and tartaric acid were the major components that differentiated the various samples.