Abstract
The microbiota involved in Korean soy paste (doenjang) fermentation are the key factors determining its quality aspects. In this study, doenjang was prepared by adding three different herbs (Peppermint, Korean mint, and Coriander), and their effect on the microbiota composition was evaluated by 16S rRNA metagenomic analyses. The β-diversity statistics indicated clear distinctions in the doenjang microbiota after the addition of herbs. A microbial composition analysis revealed that Tetragenococcus was among the dominant genera in the four doenjang groups, with a relatively higher abundance in the Korean mint group. In the Peppermint and Korean mint doenjang groups, the levels of undesirable microbes, such as opportunistic pathogens belonging to the genera Sphingobacterium and Pantoea, were significantly reduced. Additionally, other desirable microbes that are known to exhibit beneficial properties and produce bioactive compounds, such as Saccharopolyspora and Buttiauxella, were present at significantly higher levels. Significant negative correlations between members of the Bacillaceae and Halomonadaceae, Lactobacillaceae and Tissierellaceae, and the Lacobacillaceae and Erwiniaceae families were observed, indicating possible antagonistic relationships. Taken together, our results demonstrated that the incorporation of herbs, particularly Peppermint and Korean mint, during doenjang fermentation resulted in significant shifts in the microbial composition and could be utilized for beneficial effect on its fermentation.
Highlights
Fermentation has been practiced for thousands of years for the preservation and storage of food materials [1]
The microbiota involved in doenjang fermentation are the key factors that determine the end-product’s quality and safety aspects [13]
It is important to study the microbial composition of doenjang, and to endeavor to provide fermentation conditions aimed at enhancing desirable microbes
Summary
Fermentation has been practiced for thousands of years for the preservation and storage of food materials [1]. Fermented foods are important sources of nutrition and have improved flavors; they are known for their potential health promoting and disease preventing properties, which contribute to their current worldwide popularity [2]. Doenjang is a traditional Korean fermented soy paste that has been consumed for thousands of years as a protein source and a basic seasoning ingredient. Doenjang production is a two-stage process that is initiated by preparing meju, a dry fermented, moldy cooked soybean block, using naturally occurring bacteria and fungi. The second stage is performed by soaking the meju in salty water in porcelain containers under sunlight for several weeks to produce a solid portion that is called soybean paste (doenjang) and a liquid portion called soy sauce (gangjang). The doenjang is mashed and further fermented before consumption through a few weeks to several years [3]
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