Changes in Nutritional Composition and Physicochemical Properties of Mustard Leaf (Brassica juncea) Kimchi during Fermentation

Nutritional and physicochemical changes of mustard leaf kimchi were examined during fermentation periods up to 3 months. As the fermentation processed, pH decreased, and titratable acidity gradually increased. The crude ash and protein contents increased during fermentation, but crude lipid content was significantly reduced from 5.97 to 5.07%. Crude fiber and carbohydrate showed no distinct changes. Dietary fiber contents were slowly changed between control and 1 month fermentation sample, and were maintained thereafter. The major free sugars of mustard leaf kimchi were fructose and glucose, and the amount of them were significantly decreased at the end of fermentation stage. Lactic acid showed a dramatic increase and reached its maximum at 3 months. All kimchi contained 20 amino acids; in particular, glutamic acid was the highest in mustard leaf kimchi. Amino acid contents fluctuated during fermentation. Except for calcium and selenium, the content of other ingredients (Fe, K, Mg, Na, and Zn) increased with prolonged fermentation time. Fermentation promotes a significant increasing in the content of linoleic acid and DHA. The highest antioxidant vitamins (β-carotene, tocopherol) contents were determined at mustard leaf kimchi fermented for 2 months. The results will provide fundamental data for proposing an appropriate fermentation periods to promote quality of kimchi