A study published in the Journal of Food Science suggests that different salt treatments may cause changes in the bacterial profiles and metabolite profiles of kimchi. The researchers studied the effects of purified salt (PS) and mineral-rich sea salt (MRS), both with different mineral profiles, on kimchi fermentation using a culture-dependent 16S rRNA sequencing technique and mass-based metabolomic analysis.
The researchers found that the different mineral profiles in the fermentation medium caused changes in the bacterial profiles of the two kimchi products. The proportions of Lactobacillus and Leuconostoc, identified as the main kimchi bacteria, were affected by the salt type. The increase in the Leuconostoc proportion of the MRS-kimchi decreased the Lactobacillus/Leuconostoc ratio associated with kimchi quality. The changes of the bacterial profiles caused by the different salt treatments led to a change of the kimchi metabolite profiles associated with sensory and nutritional qualities.
The researchers measured the pH, acid value, and mineral content of the two fermented kimchi products, in addition to their sensory quality. The pH and acid values of the kimchi were significantly changed by fermentation, but neither of the values was affected by the salt treatments. Although there were not any significant differences in the appearance or tastes of the two kimchi products, the flavor and texture of the MRS-kimchi were rated better than those of the PS-kimchi, resulting in an overall significantly higher score of acceptability for the MRS-kimchi.
The researchers also found that the levels of magnesium and manganese, known to be essential minerals for microbial growth and metabolic activities of the lactic acid bacteria, were significantly changed by the salt treatments. The content of magnesium, which is used to improve the texture of foods, was 68% higher in the MRS-kimchi than in the PS-kimchi, whereas the content of manganese in the MRS-kimchi was about half of the day two and week six fermented PS-kimchi samples. Interestingly, the change of manganese amount was directly proportional to the Lactobacillus/Leuconostoc ratio, which was considered to be associated with the quality deterioration of kimchi. Although the relationship between manganese and lactic acid bacteria was not investigated in this study, it was suggested that different bacteria species might have different manganese availability.
They concluded that “although further studies on the relationship between these salt types and kimchi fermentation are needed, these results suggested that the MRS treatment had positively affected the changes of the kimchi mineral contents, bacterial growth, and metabolite profiles, which are linked to kimchi quality.”