Antioxidant Activity, α-Glucosidase and Lipase Inhibitory Activity in Rice Miso with Kidney Bean

Abstract

Rice miso is a traditional Japanese seasoning food which are not only prolonging the consumption term, but also has good sensory characteristics. So thus, rice miso is very popular in Japan. In the present study, in order to improve the potential functionality, we processed rice miso adding with kidney bean (RMKB), red bean (RMRB) and buckwheat (RMBW), respectively. DPPH radical-scavenging activity, melanoidin and polyphenol content, and enzyme inhibitory activity were detected in rice miso products at different fermentation period (0, 3, 6, 24, 36 months), respectively. The results showed the DPPH radical-scavenging activity of each rice miso product was increased with prolonging the fermentation period, and RMKB showed the highest DPPH radical-scavenging activity in different rice miso products at 6, 24, 36 months. Moreover, DPPH radical-scavenging activity, melanoidin and polyphenol content of rice miso with kidney bean (RMKB) were significantly higher than those of rice miso (RM; as control) in methanol fraction purified by Diaion HP-20 column. RMKB-24M showed the highest antioxidant activity which was a better process to produce high antioxidant profiles. Furthermore, the melanoidin content in rice miso products was approximately 6-folds higher than polyphenol content. Comparing with polyphenol, melanoidin was the main antioxidant material in the rice miso products. In addition, RMKB-24M showed stronger α-glucosidase and lipase inhibitions. These results suggest rice miso with kidney bean had useful components, in particular, potential applications for antioxidant, and the treatments of diabetes and anti-obesity.