Starch Content and α-Amylolysis Rate in Precooked Legume Flours

Dried lentils (Lens culinaris) and beans (Phaseolus vulgaris, black, brown, white, and red) were boiled until soft, freeze-dried, and milled. This procedure yielded precooked flours (PCF), rich in intact cells filled with starch granules. Starch content in the various bean PCFs was underestimated by enzymic assays. Potentially available starch in PCFs was evaluated after complete release of starch by mechanical disruption of cell wall structures. Total starch content, measured after solubilization in 2 N KOH, was higher than the potentially available starch, indicating that all PCFs contained important quantities of resistant starch, i.e., retrograded amylose (3–9%, dwb). Limited enzymic availability of starch in PCFs was also demonstrated by their low -amylolysis rate. Pepsin preincubation and additional heat treatment increased the rate and extent of in vitro enzymic hydrolysis. Considerable differences in susceptibility to a-amylase attack were observed between the various legume flours