Kimchi is a traditional Korean vegetable product that is naturally fermented by various microorganisms present in the raw materials. Among these microorganisms, lactic acid bacteria dominate the fermentation process. Natural fermentation with unsterilized raw materials leads to the growth of various lactic acid bacteria, resulting in variations in the taste and quality of kimchi, which may make it difficult to produce industrial-scale kimchi with consistent quality. The use of starter cultures has been considered as an alternative for the industrial production of standardized kimchi, and recent trends suggest that the demand for starter cultures is on the rise. However, several factors should be carefully considered for the successful application of starter cultures for kimchi fermentation. In this review, we summarize recent studies on kimchi starter cultures, describe practical problems in the application of industrial-scale kimchi production, and discuss the directions for further studies.

Bacterial exopolysaccharides (EPSs) are important alternatives to plant polysaccharides in fermented products and exhibit antioxidant activity, which is particularly desirable for functional foods. This study evaluated the use of spent media wastewater (SMW) derived from kimchi fermentation for the production of an EPS and analyzed the characterization and antioxidant activity of the resulting EPS. The EPS concentration and conversion yields of sequential purification were 7.7–9.0 g/L and 38.6–45.1%, respectively. Fourier transform infrared spectra and NMR spectra indicated that the EPS was a linear glucan with α-(1 → 6) linkages. The EPS also exhibited thermal tolerance to high temperatures. In vitro antioxidant activity analyses indicated the scavenging activity on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, thiobarbituric acid reactance (TBAR), and ferric ion reducing antioxidant power (FRAP) values of 71.6–79.1, 28.2–33.0%, and 0.04–0.05 mM FeCl3, respectively. These results reveal that the EPS extracted from SMW has potential as a thermally tolerant, nontoxic, and natural antioxidant for industrial applications.

Lactococcus lactis subsp. lactis WK11 was introduced as a starter in kimchi fermentation to investigate the role of starter cultures in extending the shelf life of kimchi. Kimchi, with an initial inoculum size of 10 7 CFU/ g as well as control kimchi without the starter culture, were prepared and fermented for 56 days at 8 o C. The addition of L. lactis prolonged the optimal fermentation period (pH 4.2, acidity 0.6-0.8%) up to more than 2 times. The starter culture, L. lactis WK11, persisted throughout the kimchi fermentation, as confirmed by regular monitoring of the L. lactis population by PCR-DGGE. Taken together, our results suggest that L. lactis starter culture may be useful for extending the shelf-life of kimchi without adverse effects of kimchi with a longer shelf life.