Effect of various processing methods on the in vitro starch digestibility and resistant starch content of Indian pulses

The effect of different processing treatments on the in vitro starch digestion rate and resistant starch (RS) formation in two little-known Indian legumes (moth bean and horse gram) as compared with a pulse widely consumed in Asian countries (black gram) was studied. Samples were cooked until edible without previous treatment, after overnight soaking in water or in a 0.02% sodium bicarbonate solution, and after sprouting. Cooked samples were analyzed for their RS content immediately after cooking or after storing for 24 h at 4 degrees C. The in vitro starch digestion rate was also measured in the freshly cooked (FC) legumes, and the hydrolysis index (HI) and glycemic index (GI) were calculated. RS in processed samples varied between 2.7 and 7.9 g kg(-1) of dry matter, the highest values corresponding to the stored legumes. Sprouting and direct cooking resulted in the lowest RS content in FC and stored legumes, respectively. Soaking significantly improved in vitro starch digestibility in the little-known pulses but not in black gram; Sprouting yielded the highest III and GI.