Occurrence of astringent oligomeric proanthocyanidins in legume seeds.

The distribution of oligomeric proanthocyanidins in legume seeds was investigated in connection with organoleptic astringency.The seeds contained various kinds of oligomers (dimers~hexamers).The total oligomer contents were at least 0.040% in azuki beans, 0.017% in black soybeans, 0.005% in mung beans and a trace amount in regular soybeans.Each aliquot of aqueous solution of partially purified proanthocyanidin oligomers tasted astringent even at a concentration of 0.001 % (w/v).The possible contribution of oligomeric proanthocyanidins and polymeric proanthocyanidins to the astringent off-taste of legume seeds is discussed.