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Kimchi cabbage, the key ingredient in kimchi, is cultivated year-round to meet high production demands. This study aimed to examine the effects of seasonal harvesting (spring, summer, fall, and winter) on the microbial and metabolic profiles of kimchi during 30 days of fermentation. Lactic acid bacteria distribution is notably influenced by seasonal variations, with Latilactobacillus dominant in fall-harvested kimchi group and Weissella prevailing in spring, summer, and winter. The microbial communities of spring and fall group exhibited similar profiles before fermentation, whereas the microbial communities and metabolic profiles of spring and summer group were similar after 30 days of fermentation. Seasonal disparities in metabolite concentrations, including glutamic acid, serine, and cytosine, persist throughout fermentation. This study provides a comprehensive understanding of the substantial impact of seasonal harvesting of kimchi cabbage on the microbial and metabolic characteristics of kimchi, providing valuable insights into producing kimchi with diverse qualities., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Capsaicinoids in red pepper powder are known to show anti-bacterial effects; however, their effects during kimchi fermentation are not known. This study aimed to investigate the effects of various concentrations of capsaicinoids on kimchi fermentation. Five sets of kimchi samples were prepared using 0 mg/kg (control), 98.34 ± 5.34 mg/kg (mild), 243.47 ± 3.71 mg/kg (medium), 428.63 ± 30.78 mg/kg (hot), and 1,320.49 ± 28.27 mg/kg (extreme) capsaicinoid. The characteristics of each kimchi sample, including pH, acidity, organic acid, sugars, sugar alcohol, capsaicinoid content, and microbial community were periodically investigated during fermentation. Kimchi with red pepper powder shows significantly higher acidity than control kimchi, whereas pH values were the same. Organic acid in kimchi with red pepper powder was higher than in control kimchi, probably caused by higher lactic acid bacteria (LAB) counts in kimchi samples with red pepper powder. Our results show that addition of red pepper powder decreased Leuconostoc spp. counts in the bacterial community. In particular, Lactobacillus sakei and Leuconostoc gelidum counts increased and decreased, respectively, with increasing capsaicinoid content of red pepper powder added to kimchi. Overall, the results of this study indicate that physicochemical properties and LAB such as L. sakei and L. gelidum are influenced by capsaicinoid content. However, further studies are necessary to investigate the effects of the percentage of red pepper powder in kimchi on fermentation to provide practical guidelines for producing standardized kimchi.

Glucosinolates (GLS) have been reported to have significant anti-oxidative, antimicrobial, and anti-cancer activities. The current study was aimed to develop an analytical method for glucosinolate quantitation in eight Brassica species from Gwangju, Republic of Korea. For this purpose the UHPLC-Q-Orbitrap-MS technique was used and validated for optimal extraction conditions, detection and quantitation limits, linearity, precision, and accuracy. According to the results of GLS profiling, the total GLS concentration decreased in the order of cabbage > broccoli > cauliflower > mustard > kimchi cabbage > young radish ∼ kale. All Brassica species contained glucoerucin (GER) and glucobrassicin (GBR) as major GLS with the high levels in cabbage (5.913 μM/g) and broccoli (1.723 μM/g), respectively. The contents of minor GLS were species-dependent, and could therefore be used for Brassica species classification., (Copyright © 2018. Published by Elsevier Ltd.)

To investigate the effects of red pepper powder on kimchi fermentation, Baechu (Chinese cabbage) and Mu (radish) kimchi, with and without red pepper powder, were prepared and their characteristics, including pH, colony-forming units (CFU), microbial communities, and metabolites, were periodically monitored for 40days. Measurements of pH and CFU showed that the lag phases of kimchi fermentation were clearly extended by the addition of red pepper powder. Microbial community analysis using a barcoded pyrosequencing analysis showed that the bacterial diversities in kimchi with red pepper powder decreased more slowly than kimchi without red pepper powder as kimchi fermentation progressed. The kimchi microbial communities were represented mainly by the genera Leuconostoc and Lactobacillus in all kimchi, and the abundance of Weissella was negligible in kimchi without red pepper powder. However, interestingly, kimchi with red pepper powder contained much higher proportions of Weissella than kimchi without red pepper powder, while the proportions of Leuconostoc and Lactobacillus were evidently lower in kimchi with red pepper powder compared to kimchi without red pepper powder. Metabolite analysis using a (1)H NMR technique also showed that the fermentation of kimchi with red pepper powder progressed a little more slowly than that of kimchi without red pepper powder. Principle component analysis using microbial communities and metabolites supported the finding that the addition of red pepper powder into kimchi resulted in the slowing of the kimchi fermentation process, especially during the early fermentation period and influenced the microbial succession and metabolite production during the kimchi fermentation processes., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Kimchi fermentation usually relies upon the growth of naturally-occurring various heterofermentative lactic acid bacteria (LAB). This sometimes makes it difficult to produce kimchi with uniform quality. The use of Leuconostoc mesenteroides as a starter has been considered to produce commercial fermented kimchi with uniform and good quality in Korea. In this study, a combination of a barcoded pyrosequencing strategy and a (1)H NMR technique was used to investigate the effects of Leu. mesenteroides strain B1 as a starter culture for kimchi fermentation. Baechu (Chinese cabbage) and Chonggak (radish) kimchi with and without Leu. mesenteroides inoculation were prepared, respectively and their characteristics that included pH, cell number, bacterial community, and metabolites were monitored periodically for 40 days. Barcoded pyrosequencing analysis showed that the numbers of bacterial operational taxonomic units (OTU) in starter kimchi decreased more quickly than that in non-starter kimchi. Members of the genera Leuconostoc, Lactobacillus, and Weissella were dominant LAB regardless of the kimchi type or starter inoculation. Among the three genera, Leuconostoc was the most abundant, followed by Lactobacillus and Weissella. The use of Leu. mesenteroides as a starter increased the Leuconostoc proportions and decreased the Lactobacillus proportions in both type of kimchi during kimchi fermentation. However, interestingly, the use of the kimchi starter more highly maintained the Weissella proportions of starter kimchi compared to that in the non-starter kimchi until fermentation was complete. Metabolite analysis using the (1)H NMR technique showed that both Baechu and Chonggak kimchi with the starter culture began to consume free sugars earlier and produced a little greater amounts of lactic and acetic acids and mannitol. Metabolite analysis demonstrated that kimchi fermentation using Leu. mesenteroides as a starter was completed earlier with more production of kimchi metabolites compared to that not using a starter, which coincided with the decreases in pH and the increases in bacterial cell number. The PCA strategy using all kimchi components including carbohydrates, amino acids, organic acids, and others also showed that starter kimchi fermented faster with more organic acid and mannitol production. In conclusion, the combination of the barcoded pyrosequencing strategy and the (1)H NMR technique was used to effectively monitor microbial succession and metabolite production and allowed for a greater understanding of the relationships between the microbial community and metabolite production in kimchi fermentation., (Copyright © 2011 Elsevier B.V. All rights reserved.)