Characteristics and Concentrations of α‐Amylase Inhibitor in Phaseolus vulgaris Biotypes

Abstract

AbstractFlours from six legume species (lentil, lima bean, field pea, chickpea, fababean, mung bean) were devoid of α‐amylase inhibitory activity but five biotypes of Phaseolus vulgaris showed activities of 27 to 40 units/mg protein. Air classification of the pin milled flours yielded fine fractions which contained 37% (black bean) to 61% (navy bean) protein and 38 to 66 units of inhibitor activity/mg protein, respectively. The coarse starch fractions were proportionately depleted in protein content and inhibitor activity. The partially purified amylase inhibitor from navy bean was active towards porcine pancreatic α amylase. The optimum pH for inhibition was 5.6 ‐ 5.7, with the inhibitor being most stable at pH 6.9 after 4 h incubation at 37°C. The inhibition was faster at 37°C than at 25°C. Although retaining most of its inhibitory power between 37°C–60°C, the navy bean inhibitor showed a complete loss of activity after 20min at 90°C.