Profiling of fermentative metabolites in kimchi: Volatile and non-volatile organic acids

Gas chromatograph/mass spectrometry (GC/MS) analysis was carried out to determine both the volatile and nonvolatile organic acids in kimchi during 60 days of fermentation at 10°C. Principal component analysis (PCA) was applied to differentiate the pre-defined organic acids and lactic acid bacteria (LAB) during fermentation. Acetic acid was observed as dominant, which was vigorously produced until the middle of fermentation. Lactic acid was the major non-volatile organic acid in the kimchi and was produced throughout fermentation. In contrast, malic acid content decreased sharply at the initial stage of fermentation. Colony forming units of LAB in the kimchi, such as Leuconostoc, Lactobacilli, Pediococci, and Streptococci, were measured on selective media. Populations of Leuconostoc and Lactobacilli increased exponentially over 7 days of fermentation, indicating acetic acid and lactic acid were mainly produced by Leuconostoc and Lactobacilli. PCA demonstrated that acetic acid, propionic acid, lactic acid, butanoic acid, malic acid, Leuconostoc, and Lactobacilli were major components that differentiated the kimchi according to fermentation time.