Changes of Isoflavone Contents in Soybean Cultivars Pickled in Persimmon Vinegar

Effects of pickling soybeans in acidic solution on soybean isoflavone, and pH and color of immersing solution were investigated. Soybean cultivars, Seoritae and Seomoktae (black beans) and Myeongju-namul (yellow bean), were soaked in persimmon vinegar for 10 days at 20 o C. Isoflavone content increased rapidly during pickling, reaching 51.8 (Seomoktae)-106.8% (Myeongju-namul). Increase of aglycone types, from 6.2-9.3% to 20.9-50.8%, was particularly noted, while glycosidic ones were less affected. Acidity of persimmon vinegar increased from 3.4 to 4.4 up to 4 days of soaking and decreased slowly thereafter. Color ‘L’ and ‘b’ values of persimmon vinegar decreased significantly, whereas 'a' value increased in black beans. All color values of yellow beans were less affected. Key wards: soybeans, pickling, persimmon vinegar, isoflavone