Kimchi, a popular traditional Korean fermented food, is produced by fermenting vegetables with various spices and salt. Salt plays an important role in the preparation of kimchi and affects its taste and flavor. This study aimed to investigate the effects of salinity on kimchi fermentation. The salinities of five sets of kimchi samples were adjusted to 1.4%, 1.7%, 2.0%, 2.2%, and 2.5%. The characteristics of each kimchi sample, including its pH, acidity, free sugar content, free amino acid content, organic acid content, and microbial community composition, were evaluated during kimchi fermentation. The low-salinity kimchi sample showed a rapid decline in the pH at the beginning of the fermentation process, a relatively high abundance of Leuconostoc mesenteroides, and high mannitol production. In the late fermentation period, Latilactobacillus sakei had a higher abundance in the kimchi sample with high salinity than in other samples. In the initial stage of fermentation, the metabolite composition did not differ based on salinity, whereas the composition was considerably altered from the third week of fermentation. The findings showed variations in the characteristics and standardized manufacturing processes of kimchi at various salt concentrations. Therefore, salinity significantly affected the types and concentrations of fermentation metabolites in kimchi.

White colony-forming yeast (WCFY), also referred to as film forming yeast or spoilage yeast, that appear on the surface of kimchi can deteriorate the sensory properties of kimchi, such as odor and texture. Thus, the aim of this study was to develop a method to inhibit the formation of the white colony in kimchi. First, alterations in kimchi manufacturing and storage conditions, including temperatures, pH, salinity, and anaerobic condition, were investigated to determine if they could inhibit the growth of WCFY (i.e., Kazachstania servazzii, Candida sake, Debaryomyces hansenii, Pichia kudriavzevii, and Hanseniaspora uvarum). Thereafter, the anti yeast activity of freeze-dried garlic powder (FGP) and cinnamon ethanol extract (CEE) was evaluated against WCFY using the agar-well diffusion assay. Following the direct application of FGP and CEE to the surface of the kimchi, the inhibitory effects on white colony were determined. The results showed that WCFY can grow under various manufacturing and storage conditions of kimchi. Regarding the growth inhibitory effect on WCFY, FGP exhibited anti yeast activity against four WCFYs. It did not show anti yeast activity against K. servazzii. However, CEE showed anti yeast activity against K. servazzii. In particular, the mixture of 10% FGP and 1.75% CEE, which was manufactured considering the influence of sensory properties in kimchi, exhibited anti yeast activity against all WCFY. Furthermore, the application of the FGP and CEE mixture supplemented with 0.02% xanthan gum to kimchi to enhance adhesion to the kimchi surface, led to a delay in the formation of a white colony on the surface of the kimchi by an average of 17 d at 10 °C compared to the control group. Collectively, the use of a FGP, CEE, and xanthan gum mixture could be an effective method for the inhibition of white colony formation on the surface of kimchi, extending its shelf life.

Recently, kimchi has been recognized as a healthy food worldwide, prompting increased interest in its health benefits and quality characteristics. Although commercial kimchi is manufactured in various countries, little is known about quality differences between the kimchi from different countries. To clarify differences in quality characteristics, minerals, free sugars, organic acids, free amino acids, and volatile compounds, commercial kimchi manufactured in Korea, China, and the United States were investigated. The composition of the microbial community and antioxidant activity were compared. Mineral and free sugar contents were high in Korean commercial kimchi, while the organic acid content was relatively low. The free amino acid content was markedly higher in Korean kimchi than that in kimchi manufactured in China and the United States. In addition, the volatile compound content differed between the kimchi produced in different countries. Considering the microbial communities, Leuconostoc and Weissella were more abundant in commercial kimchi from Korea than that from China or the United States. Commercial kimchi in Korea showed the highest antioxidant activity. These results support the high quality and antioxidant activity of commercial kimchi manufactured in Korea, emphasizing its importance in the global kimchi industry.

Jeotgal containing abundant free amino acids plays an important role in the unique savory taste (umami) and flavor in kimchi. However, it is also responsible for the unpleasant fishy smell and high salt content of kimchi. Therefore, the present study aimed to identify alternative jeotgal sources and investigate the fermentation properties of jeotgal alternatives added to kimchi. The tomato hot-water extract (TH2) and dry-aged beef hot-water extract (DBH) were selected as jeotgal alternatives for kimchi preparation based on their glutamic acid contents. Characteristics of kimchi with TH2 alone (JA1) and TH2 and DBH in combination (1:1, JA2) were compared with kimchi prepared using commercially available anchovy fish sauce (CON). The pH of JA1 and JA2 was slightly decreased during fermentation, whereas the salinity was significantly lower than CON (p < 0.05). Notably, the most effective factor of the savory taste of kimchi, glutamic acid contents of JA1 and JA2 were significantly higher than that of CON (p < 0.05). In conclusion, JA1 showed slower fermentation with lower salinity and higher glutamic acid content than CON. Overall, this study showed that JA1 derived from TH2 could improve the taste and quality of kimchi by increasing glutamic acid content and decreasing the unpleasant flavor.