Metabolomic profiling of Cheonggukjang during fermentation by ¹H NMR spectrometry and principal components analysis

Metabolomic analysis of extracts of Cheonggukjang was carried out using ¹H nuclear magnetic resonance (NMR) spectrometry and principal components analysis (PCA). The major peaks in the ¹H NMR spectra of the 50% methanol fraction were assigned to isoleucine/leucine, lactate, alanine, acetic acid, citric acid, choline, fructose, sucrose, tyrosine, phenylalanine and formic acid. The first two principle components (PC1 and PC2) of the ¹H NMR spectra of the aqueous fraction allowed discrimination of Cheonggukjang extracts of samples obtained after different periods of fermentation. These two principal components cumulatively accounted for 98.5% of the total variation of all variables. The major peaks within the ¹H NMR spectra that contributed to discrimination of different samples were assigned to isoleucine/leucine, lactate, acetic acid, citric acid, choline, fructose, glucose and sucrose. This metabolomic analysis of samples of Cheonggukjang extract demonstrates that NMR and PCA can be used to obtain standard trajectory plots and related information for Cheonggukjang and other fermented foods.