Characteristics of Cheonggukjang produced by the rotative fermentation method

Culture-dependent and -independent analyses of bacterial compositions and its contributions to formation of γ-aminobutyric acid and poly-γ-glutamic acid in Cheonggukjang

This study was performed to unveil bacterial compositions and their contributions to the formation of γ-aminobutyric acid (GABA) and poly-γ-glutamic acid (γ-PGA) in Cheonggukjang. To predict possible key factors contributing to the content of the bioactive compounds in Cheonggukjang, commercial products were analyzed for various parameters. The content of GABA and γ-PGA showed a negative (R2 = 0.61 - 0.73) and positive correlation (R2 = 0.53 - 0.96) with antioxidative activity. Consistently, GABA content showed a moderate negative correlation with γ-PGA content (R2 = 0.58). Among the physicochemical and microbial parameters, only salinity showed a moderate negative correlation with γ-PGA content (R2 = 0.75), which might be due to the inhibition of bacterial growth. It was also suggested that multiple factors (including bacterial species) were involved in the formation of GABA and γ-PGA in Cheonggukjang. To reveal dominant bacterial species and further presume their contributions to the bioactive compound formation in Cheonggukjang, both culture-independent (metagenomic) and -dependent (culturomic) methods were used. Culture-independent method showed that Bacillus piscis was dominant (23.37 - 94.89 %), followed by B. hisashii (0.00 - 62.45 %) and B. coagulans (0.00 - 13.82 %). Considering the quantitative speciation data on the bioactive compound content in Cheonggukjang (and bacterial production capability) together, it was further elucidated that B. piscis contributed primarily to the bioactive compound formation. Unlike this, culture-dependent analysis revealed that B. licheniformis and B. subtilis were dominant (30.0 - 47.6 and 17.5 - 39.5 %, respectively). Based on the quantitative speciation data on the bacterial production capability of GABA and γ-PGA, B. subtilis was the primarily contributing bacterial species to the bioactive compound formation. Consequently, it was observed that the bacterial compositions and their contributions to the bioactive compound formation determined by the two methods differed considerably, i.e., B. piscis and B. subtilis were identified to be prominent bacterial contributors, respectively, depending on the method used.

Biogenic amine reduction by food additives in Cheonggukjang, a Korean fermented soybean paste, fermented with tyramine-producing heterogeneous bacterial species

This study was conducted to mitigate the food safety risks related to biogenic amine (BA) by reducing the BA content in Cheonggukjang using applicable food additives. In in-vitro experiments, of the additives tested, tartaric acid (TA), potassium sorbate (PS), and sodium benzoate (SB) considerably inhibited tyramine production of strains of Bacillus spp. and Enterococcus faecium while less affecting their growth. In addition to these three additives, two additives, glycine (GL) and nicotinic acid (NA), reported to have significant inhibitory effects in previous studies, were applied to the Cheonggukjang fermentation with prolific tyramine-producing strains of B. subtilis and E. faecium. The content of tyramine in the Cheonggukjang samples treated with TA, PS, SB, GL, and NA was significantly reduced by 27.5%, 50.7%, 51.4%, 76.1%, and 100.0%, respectively, compared to the control sample. Additionally, the content of polyamines (putrescine, cadaverine, spermidine, and spermine) in the GL-treated sample was reduced by 42.6%-62.4%. The mode of action could be attributed to inhibiting the bacterial decarboxylase activity and/or growth. Consequently, excluding NA that interfered with Cheonggukjang fermentation, GL was the most outstanding additive with an inhibitory effect on tyramine formation in food, followed by SB and PS, all of which showed a more than 50% reduction. Therefore, the use of appropriate additives could be one of the promising strategies to avoid the food safety issues implicated in BAs in Cheonggukjang.

Protective Effects of Fermented Soybeans (Cheonggukjang) on Dextran Sodium Sulfate (DSS)-Induced Colitis in a Mouse Model

Inflammatory bowel disease (IBD) is a chronic inflammatory disease, and the incidence of IBD is increasing every year owing to changes in dietary structure. Although the exact pathogenesis of IBD is still unclear, recent evidence suggests that gut dysbiosis is closely associated with IBD pathogenesis. Cheonggukjang is a traditional Korean fermented soybean paste produced using traditional and industrial methods, and contains probiotics, which affect the gut microbiota composition. However, the protective effect of Cheonggukjang against IBD is unknown. In this study, we investigated the bacterial community structure of traditional and commercial Cheonggukjang samples, as well as the protective effect of Cheonggukjang on a dextran sulfate sodium (DSS)-induced colitis mouse model. Traditional and commercial Cheonggukjang were found to contain various type of useful probiotics in their bacterial community structure. Cheonggukjang reduced the progression of DSS-induced symptoms, such as body weight loss, colonic shortening, disease activity index, and histological changes. Further, Cheonggukjang improved the intestinal epithelial barrier integrity on DSS-induced colitis mice. In addition, Cheonggukjang suppressed the expression of proinflammatory cytokines and inflammatory mediators through the inactivation of NF-κB and MAPK signaling pathways. These results indicate that Cheonggukjang exerts protective effects against DSS-induced colitis, suggesting its possible application as a functional food for improving inflammatory diseases.

Toxicological evaluation of lotus, ginkgo, and garlic tailored fermented Korean soybean paste (Doenjang) for biogenic amines, aflatoxins, and microbial hazards

The present study aimed to develop a consortium of nutritive fermented food products, supplemented with phytochemicals, with reduced toxicological contents. We developed new flavored Doenjang products (protein rich) fermented with lotus, ginkgo, and garlic plant extract-based Meju (termed as EMD) as the starter culture and by using traditional Meju (termed as TMD), where these plant extracts were added later during the fermentation process. Fermented Doenjang samples were analyzed for reduced levels of biogenic amines (BAs), aflatoxins, and microbial hazards, (including Bacillus cereus) as well as for their nutritive contents and antioxidant potential, after varying periods of fermentation (0, 3, 6, 9 and 12 months). All Doenjang samples prepared using plant extracts and their mixtures (1% and 10%) showed desired reduction in B. cereus counts, BAs, aflatoxins, and other foodborne pathogens as well as showed potent antioxidant abilities, including phenolic/flavonoid contents. Based on the higher efficiency in reducing various toxicants, Ginkgo biloba leaf extract added TMD samples were selected for the development of Doenjang products as an innovative approach, with great potential to improve the quality and safety of soybean fermented products in the Korean market, offering enhanced health benefits and reduced risks of toxicity.

Occurrence and reduction of biogenic amines in traditional Asian fermented soybean foods: A review

Biogenic amines are harmful substances generated during the fermentation process. Regulations on biogenic amine content in fermented foods are currently insufficient in comparison to the popularity of fermented food consumption in Asian countries. The current review evaluated the biogenic amine content of fermented soybean-based Asian foods to determine whether the food products are safe for consumption. Though the reported ranges of biogenic amine content in fermented soybean foods varied widely, most products contained biogenic amine concentrations at potentially hazardous levels. To ensure the safety of fermented soybean food products, further efforts are required in the improvement of the food manufacturing process, as well as the establishment of regulations on managing biogenic amine content.