Effect of Rice (<i>Oryza sativa</i> L.) Added to Meju (Korean Soybean Koji) Dough on Variation of Nutritional Ingredients and Bacterial Community Diversity in Doenjang (Korean Soybean Paste)

Abstract

In this study, effect of rice added to meju dough was evaluated based on the variation of nutritional ingredients and bacterial community diversity in finished doenjang. The ratio of rice added to meju dough (cooked and crushed soybean before fermentation) was 0, 0.2, and 0.4 based on dry weight. Free amino acids, minerals, polyphenol, and total phenolic compounds relatively decreased by addition of rice. However, 2,2-diphenyl-1-picrylhydrazyl free radical (DPPH) scavenging and ferric ion reduction activity was not influenced. Organic acids, which are fermentation metabolites, significantly increased in proportion to percentage balance of rice. Seven and four volatile compounds (VCs) were detected in doenjang prepared without and with rice, respectively, and contents of VCs were significantly lower in the rice-supplemented doenjang. Bacterial community diversity was significantly increased by addition of rice to meju dough. Rice alters chemical composition, fermentation products, and bacterial diversity, but does not downgrade the nature of doenjang.

Total phenolic content, antioxidant, tyrosinase and α-glucosidase inhibitory activities of water soluble extracts of noble starter culture Doenjang, a Korean fermented soybean sauce variety

“…Similar findings were observed for reducing power capacity of Stryphnodendron adstringens leaf extracts (dos Santos Filho, Ferreira, & Paiva Gouvea, 2011). Jeon and Park (2012) also confirmed significant antioxidant activities in Doenjang samples and reported that antioxidants in Doenjang may function as protective agents against deterioration of quality due to oxidation reactions. Lower absorbance values indicate lower reducing power ability, whereas higher values indicate higher ability.…”