ANALYTICAL AND NUTRITIONAL IMPLICATIONS OF LIMITED ENZYMIC AVAILABILITY OF STARCH IN COOKED RED KIDNEY BEANS

Measured with an enzymic method, the starch content of a raw red kidney bean (Phaseolus vulgaris) flour (RBF) was higher than that of a cooked and blended (CBB) and of a cooked, freeze-dried, and milled (CBF) preparation of the seeds. Wet homogenization as well as pepsin pretreatment of CBF increased the starch yield, indicating that starch in the cooked samples is not completely available to enzymic degradation unless cell wall entrapped granules are released by mechanical or enzymatic disruption of the fibrous walls. Solubilization of resistant starch in CBF with 2 N KOH resulted in a further increase in measured starch, which reached the RBF value. Influence of encapsulated and resistant starch fractions on dietary fiber values was also noticed. CBF showed remarkably low values of in vitro amylolysis rate and starch digestibility index in a digestion/dialysis system, features that seemed to depend also on the integrity of cell walls. © 1990, American Chemical Society. All rights reserved.