Antimicrobial activities of green tea extract on the retardation of kimchi fermentation

Kimchi fermentation is complex process which really depends on the composition of microfloa under the optimum ripening environment such as salt concentration, acidity, pH and temperature conditions. Most kinds of bacteria belonging to Lactobacillus group have been identified in kimchi, which continuously produce lactic acids after ripening and cause the change of kimchi tasty and physical texture. Green tea extract as a natural preservative was investigated on the antimicrobial activity and the change of pH, in terms of retardation of kimch fermentation. Minimal Inhibitory Concentration (MIC), paper disc assay, bacterial growth, and pH change were tested against four microorgasnisms, Leuconostoc mesenteroides, Lactobacillus sake, Lactobacillus plantarum, and Weissella koreensis. 2 mg/mL of green tea extract completely inhibited the growth of test organisms after 5-7 hours. Furthermore, it showed the maximized clear zone (24-34 mm) was observed at the 2mg/disc concentration. pH change resulted in a slow downward drift for fermentation period. Moreover, green tea extract showed long-term buffer effects for over 35 days (5 weeks) at 4°C.