Effects of salt type on the metabolites and microbial community in kimchi fermentation

Abstract

The taste of kimchi is greatly affected by the salt type used during fermentation. Here, we investigated the effects of salts with different mineral contents on the microbial community and metabolite profiles of fermented kimchi using multivariate statistical analysis. We evaluated different types of salt used to prepare kimchi, namely, solar salt aged for 1 year, solar salt aged for 3 years, dehydrated solar salt, and purified salt. The main microorganisms detected in kimchi were Weissella koreensis, Leuconostoc mesenteroides, and Latilactobacillus sakei. Leuconostoc and Weissella were mainly present in kimchi supplemented with solar salt. However, a high proportion of L. sakei was present in kimchi supplemented with purified salt and dehydrated salt. Additionally, using GC-MS-based metabolite analysis, we revealed that the content of free sugars, organic acids, and amino acids differed in kimchi fermented with different salt types. Therefore, we demonstrated that salt type had a pronounced effect on the resultant microbial community and the type and concentration of metabolites present in fermented kimchi.

Keywords: Kimchi; Lactic acid bacteria; Metabolites; Microbial community; Solar salt.

Figure 1

Changes in the fermentation properties of kimchi samples supplemented with different types of salt during 6 weeks of fermentation. (A) pH, (B) acidity (%), (C) lactic acid bacteria (log CFU/g), (D) total viable bacteria (log CFU/g).

Figure 2

Relative abundance of bacteria at the species level. (A) Principal component analysis (PCA) plot displaying the bacterial communities in each kimchi sample (B) as determined in the SILVA rRNA database. The kimchi samples were collected at 0, 2, 4, and 6 weeks. ‘Other’ indicates genera showing a percentage of reads <0.5% of the total reads in all the kimchi samples in species-level analyses.

Figure 3

Changes in the free sugar contents of kimchi samples supplemented with different types of salt during 6 weeks of fermentation. (A) glucose, (B) fructose, (C) sucrose, (D) maltose, (E) mannitol.

Figure 4

Heatmap showing the metabolite profiles in kimchi samples supplemented with different types of salt during 6 weeks of fermentation. The blue and red colors correspond to negative and positive correlations, respectively. The color intensity is proportional to the correlation coefficient.

Figure 5

Principal component analysis (PCA) score plot derived from metabolite data of kimchi samples supplemented with different types of salt during 6 weeks of fermentation.

Figure 6

Partial least squares-discriminant analysis (PLS-DA) score plot obtained from gas chromatography coupled to mass spectrometry (GC-MS) data of kimchi samples supplemented with different types of salt at the 6 weeks of fermentation.