Azuki bean sizes and ama-natto preparation

Ama-natto is the Japanese name for cooked and sweetened whole beans. Studie s were conducted to examine the effect of soaking four sizes of azuki beans (Vigna angularis) for 10, 14 or 18 h, and cooking the soaked beans for 16, 20 or 25 min to prepare ama-natto. Studies also examined the effect of coo king four sizes of azuki beans for 40, 45, 50, or 55 min to prepare ama-nat to. Small azuki beans soaked for 10 h were softer, and exhibited larger qua ntities of water imbibition and solids leached into the soaking solution th an the large beans. When the soaking time was increased to 14 or 18 h, the differences in bean hardness and water imbibition among the four sizes of a zuki beans were largely reduced. When raw azuki beans were cooked for 40 mi n, the hardness of cooked beans and ama-natto decreased with the decrease i n bean size. The differences in hardness among the four sizes of cooked bea ns and ama-natto decreased when the cooking time of raw beans was increased from 40 to 55 min. Compared to the raw beans, the soaked beans required le ss cooking time to reduce differences in hardness among the four sizes of c ooked beans and ama-natto. (C) 1999 Canadian Institute of Food Science and Technology. Published by Elsevier Science Ltd. All rights reserved.