Starch Gelatinization and Microstructure of Azuki An Granules Prepared From Whole, Abraded, or Ground Beans

An, the Japanese equivalent of bean paste, is conventionally prepared by mashing whole cooked beans and removing the seed coats. An granules processed from raw azuki beans with 1 sec of abrasion, 2 sec of abrasion or a grinding treatment prior to cooking were compared to an granules processed from raw whole beans. The effects on the microstructure of an granules of increasing the cooking time from 30 to 45 min for beans pretreated with 1 sec of abrasion, or from 85 to 120 min for whole beans were also examined. Freeze dried an granules processed from beans abraded for 1 or 2 sec, or whole beans, were intact. Freeze dried an granules processed from ground beans exhibited ruptured cell walls. Freeze dried an granules also exhibited damaged cell walls when the cooking times during the an process were increased. The starch gelatinization enthalpies determined by differential scanning calorimetry for an processed from whole beans, from beans pretreated by abrasion or grinding, or with the increased cooking times were 45–54% of the starch gelatinization enthalpy determined for raw azuki bean cotyledon flours.