Physicochemical characteristics and isoflavones content during manufacture of short-time fermented soybean product (cheonggukjang).

Changes in physicochemical properties, isoflavone composition, antioxidant activities, and microbial count of cheonggukjang during the manufacturing process were investigated. During fermentation, isoflavone glucosides are converted to isoflavone aglycones. After fermentation, the increased isoflavone aglycone content was determined. The total phenolic and total flavonoid content, as well as antioxidant activities, significantly increased in cheonggukjang at fermentation process. In proximate composition, fermented soybeans had the highest crude protein content. A gradual increase in the browning index and pH values was observed from the primary processing procedure to fermentation. The total bacterial count increased with each manufacturing step, except for the steamed step. The traditional processing methods for cheonggukjang from raw soybean induced several changes in chemical composition. In addition, the change of isoflavone glucosides to isoflavone aglycones during fermentation could enhance their bioavailability and antioxidant properties.