Component Changes in Antioxidant Activity and Isoflavones (β-glucoside & aglycone) Contents of Small Black Bean According to Different Cooking Methods

Purpose: In this study, small black beans (Rhynchosia nulubilis) that were produced in the Jungsun province of South Korea were selected for use in various cooking recipes because they are known to contain higher isoflavones and excellent antioxidant effects, as compared to any other domestic soybeans. Methods: Physicochemical and antioxidant characteristics of small black beans were analyzed with uncooked beans and four other cooking methods of pan broiling, boiling, steaming, and pressure cooking. Results: Contents of ${\beta}$-glucosides (daidzin, glycitin, and genistin) and aglycone (daidzein, glycitein, and genistein) in small black beans were significantly different depending on the cooking methods (p<0.001). The results of the experiment indicated that the amount of total polyphenol in pressure cooked beans was highest, showing a value of 7.16 mg/g (p<0.001). Most contents of isoflavones (${\beta}$-glucoside, aglycone) in uncooked beans appeared to increase after cooking. In particular, the amount of glycitein was highest in pan broiled beans ($9.63{\mu}g/g$). The total isoflavone content differed among the different cooking methods, ranging from highest to lowest in the following order : pan broiled beans ($759.49{\mu}g/g$), pressure cooked beans ($725.12{\mu}g/g$), boiled beans ($591.05{\mu}g/g$), steamed beans ($511.61{\mu}g/g$), and uncooked beans ($180.80{\mu}g/g$) (p<0.001). Conclusion: Especially, the amount of isoflavones increased significantly in pan broiled beans and pressure cooked beans, suggestive of optimized cooking methods for increasing nutritional and functional contents in cooked food.

조리방법을 달리한 쥐눈이콩의 항산화력 및 이소플라본 배당체·비배당체 함량 비교