STEAM-COOKING AND DRY HEATING PRODUCE RESISTANT STARCH IN LEGUMES

Starch was isolated from either raw or steam-heated black, red, and li ma beans. Isolates from steam-heated legumes were rich in indigestible (resistant) starch (19-31%, dmb), a fact not observed when raw seeds were used. Similarly, resistant starch measured directly in convention ally and high-pressure steamed beans was 3-5 times higher than in the raw pulses, suggesting retrogradation as the major mechanism behind th e reduction in digestibility. Thus, steam-heating comes forth as an ef fective way to produce resistant starch in legumes. Prolonged steaming as well as short dry pressure heating decreased the enzymatically ass essed total starch content of whole beans by 2-3% (dmb), indicating th at these treatments may induce formation of other types of indigestibl e starch.