Effect of Fermentation Conditions on Functional Quality of Napa Cabbage Kimchi

This study investigated the effects of storage temperature on the functional quality of kimchi during short- and long-term fermentation. Pretreated napa cabbage (NC) quality was analyzed, and kimchi was prepared using pretreated NC and stored at either 4 °C or 15 °C until reaching optimal and excessive fermentation stages. Fermented kimchi samples were analyzed for pH, lactic acid bacteria (LAB) counts, total polyphenol content (TPC), DPPH and ABTS radical scavenging activities, and glucosinolates and their breakdown products. Fermentation at 15 °C progressed rapidly, reaching the optimal pH range (4.0-4.5) within 3 days, and resulted in significantly higher LAB counts and TPC compared to samples stored at 4 °C (p < 0.05). In contrast, prolonged storage at 4 °C led to a decrease in both TPC, radical scavenging activities, and LAB counts during the excessive fermentation stage. Glucosinolates were progressively degraded overtime; however, their breakdown product, ascorbigen, increased under short-term fermentation at 15 °C than during prolonged storage at 4 °C. These results suggest that short-term fermentation at 15 °C is more effective than long-term fermentation at 4 °C in enhancing the functional quality of kimchi by promoting LAB growth and preserving bioactive compounds.