The Physicochemical Characteristics and Antioxidant Properties of Commercial Nurungji Products in Korea

Purpose: Nurungji is a traditional Korean food made by yellowish scorched rice. After getting gelatinization of rice, a thin crust of scorched rice will usually be left in the bottom of the traditional cooking pot. In this study, physicochemical characteristics and antioxidant properties of five commercial nurungji products (CNP1, CNP2, CNP3, CNP4, and CNP5) were evaluated. Methods: Physicochemical properties of the five commercial nurungji products were evaluated with AOAC method. The antioxidant activities were assessed using the 1,1-diphenyl-2-picryl hydrazyl (DPPH), 2,2-azinobis-(3-ethyl-benozothia zoline-6-sulfonic acid)(ABTS), ferric reducing antioxidant power (FRAP), and reducing power assays. Results: Water content was the highest in CNP3, followed by CNP1, CNP2, CNP5, and CNP4. Crude ash content of all nurungji was less than 1%. In Hunter color parameter, the significantly highest a value (redness) and b value (yellowness) were measured in the CNP4 product, meanwhile the lowest in CNP3 (p<0.05). The nurungji products of CNP4 and CNP5 had the significantly higher content in total polyphenols and total flavonoids, compared to those of other products. CNP3 and CNP2 had the lowest in total polyphenols and total flavonoids, respectively. CNP4 and CNP5 products showed the significantly higher values in antioxidant activities, whereas CNP3 had the lowest activity. Conclusion: The high value of antioxidant activities in CNP4 and CNP5 might have been affected primarily by the total polyphenols with increasing browning color during the heat treatment.