Evaluation of microbial contamination levels and biogenic amines content in over-ripened kimchi

Abstract

The purpose of this study was to determine the microbial contamination and the content of biogenic amines (BA) in over-ripened kimchi prepared with different kinds of salted and fermented seafoods during fermentation. The number of bacterial cells in the overall kimchi samples reached a maximum after 3–6 months of fermentation and then gradually decreased thereafter. Yeasts were detected from the overall kimchi samples after 3 months of fermentation, however the amounts of yeast cells were significantly lower than lactic acid bacteria (LAB) cells throughout the fermentation periods. As the fermentation progresses, pH levels and salinity of all kimchi samples gradually decreased, whereas titratable acidity values and amino-type nitrogen and volatile base nitrogen contents sharply increased. There were significant differences (p<0.05) in the microbiological and physicochemical properties observed in freshly-made kimchi and over-ripened kimchi prepared by using different kinds of salted and fermented seafoods. Immediately after preparation, BA-producing LAB were isolated from kimchi samples with salted and fermented seafoods, and the strain numbers of the bacteria in over-ripened kimchi were significantly higher than in freshly-made kimchi. In contrast, the reduction of histamine and putrescine contents in some over-ripened fermented kimchi samples prepared with ‘Kanari-aekjeot’ and ‘Myeolchi-aekjeot’ was observed during the late stage of fermentation, which may be the effect of microorganisms with antibacterial activity against BA-producing bacteria or BA-degrading bacteria.