Comparison of quality characteristics of nurungji according to shaking and ultrasonic treatment

The purpose of this study was to determine physicochemical and antioxidant properties of nurungji between sonication and shaking treatments. The nurungji was prepared by heat-treating 10g of cooked rice at 215℃ for 6 min. The nurungji was treated with sonication and shaking at 60℃ up to 5 hrs, respectively. Water content of control nurungji was significantly lower than those of nurungji treated by sonication and shaking. There was a significant difference in pH change between sonication and shaking treatments. The reducing sugar content of nurungji decreased rapidly until 1 hr. It, then continuously decreased as treatment time increased. L*, a*, and b* values were the highest in the control. They decreased untill 1 hour after treatment. After that, there was no significant change in either sonication or shaking treatment group. The browning intensity was significantly higher in the shaking treatment than in the sonication treatment. Total polyphenol contents were significantly decreased until 3 hours after treatment in both sonication and shaking groups. Antioxidant activities, such as DPPH radical scavenging activity, ABTS radical scavenging activity, Ferric Reducing Antioxidant Power, and reducing power showed similar trends.