Changes of physiochemical properties and biological activity during the fermentation of Doenjnag with bitter melon (Momordica charantia L.)

Abstract

This study evaluated the changes of physiochemical properties, phytochemical compounds (isoflavones and phenolic acids), and biological activity during the fermentation of Doenjang without and with bitter melon powder (BMP). The pH decreased from 6.41-5.83 to 5.81-5.24, during the fermentation of Doenjang, while the acidity increased from 0.42-0.65% to 1.28-1.48%. The viable cell numbers of Bacillus and Yeast, salinity, and total amino acid contents increased at the end fermentation (60 day). Also, the fermented Doenjang (FD) with 10% BMP showed the highest γ-aminobutyric acid (GABA, 129.87 mg/100 g) contents, among all the Doenjang samples. The FD exhibited significantly higher inhibitory activities than unfermented Doenjang (UFD) on radicals and α-glucosidase. The phytochemical compounds including isoflavone-aglycones and phenolic acids increased, whereas isoflavoneglycosides decreased in the BM following fermentative processing. Moreover, the total phenolic, isoflavone-aglycone, and phenolic acid contents were markedly increased, leading to a general increase in antioxidant and α-glucosidase inhibition activities after fermentation. These results suggest that BMP may be used to prepare a new type of fermented Doenjang with improved antioxidant and antidiabetic activities. ? 2017 The Korean Society of Food Preservation.