Resistant starch and potential glycaemic index of raw and cooked legumes (lentils, chickpeas and beans)

The amount of resistant starch (RS) in raw and processed legumes, lentils, chickpeas and beans was analysed. In addition, the effect of cooking on the availability of legume starches to enzymes, which may influence the glycaemic response, was studied. Raw legumes were found to have higher RS values (16-21%) than retrograded or cooked ones (4-8%). Cooling increased RS yields, whereas reheating maintained or decreased the value depending on the sample. On the other hand, the kinetics of starch hydrolysis revealed that the rate of digestion was higher for cooked seeds and retrograded flours (15-21% of total starch digested) than for raw flours (5-8% of total starch digested). The estimated glycaemic indices (GIs), i.e. GI(1) from the Hydrolysis Index (HI) and GI(2) from the percentage of hydrolysis within 90 min (H-90), were well correlated with the reported GI values (r = 0.96 and r = 0.95 respectively, P less than or equal to 0.05).