Impact of precooling strategies on microbial dynamics during cabbage kimchi fermentation.

Previous studies have focused on improving the shelf life of kimchi, whereas the optimal pre-processing temperatures for kimchi cabbage have rarely been investigated. We analyzed the impact of precooling and lowtemperature storage on kimchi fermentation and microbial dynamics, considering variations in precooling temperatures, storage conditions, and manufacturing methods. Kimchi raw materials (salted cabbage and seasoning) were subjected to different precooling temperatures for varying durations. For precooling, they were stored at 0 and 5◦C for 24 h, while those maintained at 20◦C served as non-precooled treatments. Subsequently, kimchi was manufactured from the raw materials and the product was then stored at 0 and 10◦C for 0, 7, 14, and 28 days. The pH and acidity values of precooled samples subsequently stored at 10◦C changed rapidly, while those of samples stored at 0◦C showed negligible changes. The total lactic acid bacterial count remained < 5 log₁₀ CFU/g and gradually increased in precooled samples when stored at 0◦C for 7 days. Leuconostoc and Lactobacillus growth was identified in the early phases of fermentation, lasting up to 14 days in precooled samples, whereas Weissella growth gradually increased at 0◦C, becoming the dominant strain. Kimchi pungency, characterized by yeasty and sourness flavors, was significantly reduced when both salted cabbage and kimchi seasoning were precooled at 0◦C. These findings indicate that precooling raw materials at 0◦C and storing kimchi at 0◦C delayed kimchi fermentation and enhanced its quality.