Sungryul Yu

Antioxidant Activity of Korean Traditional Soy Sauce Fermented in Korean Earthenware, Onggi, from Different Regions

The purpose of this study was to compare color, protease, and antioxidant activities of Korean traditional soy sauce fermented for 120 days in Onggis obtained from five regions-Gangjin, Jeju, Ulsan, Yeoju, and Yesan in Korea. The brown color of soy sauce was increased during the fermentation period and was the highest in soy sauce fermented in Yesan. The values of total phenol contents, protease activity, and ferric reducing antioxidant power (FRAP) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity activities were also increased during the fermenta- tion period of soy sauce. Soy sauce fermented in Gangjin Onggi showed the highest protease activity, total phenol contents, DPPH radical scavenging activity, and FRAP ability. The partial least squares regression analysis indicated that the regional Onggis affect the quality of soy sauce with in terms of color, protease activity, and antioxidant activity.

Antioxidant Activity of Korean Traditional Soy Sauce

The purpose of this study was to investigate the antioxidant activity of Korean traditional soy sauce and its relationship with physicochemical properties. Seventeen samples of soy sauce prepared by using a Korean traditional method were obtained from six provinces of Korea. The most powerful antioxidant activity of soy sauce was ranging from 8.96 to 63.39% for 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, from 0.12 to 2.41 AE mg/mL for ferric reducing antioxidant power (FRAP) value, and from 8.42 to 115.69 TE mg/mL for oxygen radical absorbance capacity (ORAC). Protease activity and total polyphenol contents were highly correlated with antioxidant activities such as DPPH radical scavenging activity and FRAP value (R=0.97). The contents of amino nitrogen were also correlated with DPPH radical scavenging activity (R=0.92), FRAP (R=0.93), and ORAC values (R=0.80). Based on these results, antioxidant activities were highly influenced by protease activity, contents of total polyphenols, and amino nitrogen.