Supercooling and stepwise algorithmic strategies for prolonged freshness and quality preservation in mustard leaf (Brassica juncea) kimchi

Kimchi, a traditional Korean fermented dish, is rich in nutrients and probiotics. Its quality can be compromised by over-fermentation due to temperature fluctuations. Supercooling has been proposed as a method to preserve kimchi, but maintaining this state is challenging. This study used a stepwise cooling system to keep mustard leaf kimchi in a supercooled condition for up to 5 months. Analysis of CO₂ levels, pH, and titratable acidity showed slower fermentation in the supercooled samples compared to refrigerated ones. Notably, the pH of refrigerated samples decreased rapidly to about 4.5 and the titratable acidity increased to about 0.83 % at 5 months of storage. However, there were no significant differences in moisture content and texture between the supercooled and refrigerated samples. Microbial profiles and metabolic compounds revealed that supercooling preservation delayed fermentation by about 3 months. These results suggest that supercooling is an effective method for preserving mustard leaf kimchi, preventing quality degradation during long-term storage.