Effect of composition on the structure and digestibility of starch in Idli batter

Abstract

This study investigates the effects of varying the proportion of parboiled rice, raw rice, mixed rice, and black gram on idli batter structure and starch digestibility. A total of six different batters (batters 1 to 6) were prepared by varying the composition of raw material. Batter 1 (Parboiled Rice: Black gram dal: Baking soda), Batter 2 (Parboiled Rice: Black gram dal: Yeast), Batter 3 (Parboiled Rice: Raw Rice: Mixed Rice: Black gram dal), Batter 4 (Raw Rice: Mixed Rice: Black gram dal), Batter 5 (Raw rice: Yeast) and Batter 6 (Parboiled Rice: Black gram dal). In comparison to the other five batters, batter 6 (parboiled rice (3): Black gram dal (1)) exhibited superior texture, sensory, enzyme activity, and better digestibility. Structure changes in starch for batter 6 were noticeable until day five and complete degradation was observed after day seven, whereas in other batters, the structure degraded from 3rd day of storage. Batter 6 exhibited the highest protein content (0.6 mg/g to 0.3 mg/g) and lowest reducing sugar content (4.51 mg/g to 6.66 mg/g) from day 1 to day 7 of the storage period. The difference in amylose content from day 1 to day 7 (27.80% to 26.75%) was low compared to others. The starch digestibility index of batter 6 was 40.35% on day 1 and 68.96% on day 7 which was comparatively less compared to other prepared batters. As a result, the proportion of dal and parboiled rice used in batter preparation significantly influences its storage, digestibility, and enzyme activity. Thus, studying the method and proportion of idli preparation helps us understand how the batter is stored, digested, and modified, thereby improving our understanding of Indian cuisine.