Physicochemical, Functional Properties, and In Vitro Digestibility Studies of Starch from Rice Cultivars Grown in Indian Temperate Region

Four rice cultivars (SR-4, K-39, Mushq Budij, and Pigmented) grown in Kashmir were selected for starch extraction and characterization. Rice starches were observed for physicochemical, functional properties, and in vitro digestibility studies for estimation of their glycemic indices. Compositional analysis revealed that moisture, crude fat, ash, and protein contents of rice starches varied significantly (p <= 0.05) from 7.96 to 11.33, 0.15-0.31, 0.23-0.27, and 0.29-0.36 g per 100 g. Pigmented starch revealed high amylose content (25.40 g per 100g) that contribute for high solubility index (0.01-0.08 g per g) and low peak viscosity (3.31 Pa s). Scanning electron microscopy of all the starches revealed polyhedral granule shape. An X-ray diffractogram showed the starches to possess A-type pattern with prominent peaks at 15.27, 17.63, and 23.29 degrees. Gelatinization enthalpy of starches varied significantly (p <= 0.05) from 8.30 to 11.15 J g(-1). K-39 starch with least amylose content (21.08 g per 100 g) had high peak (92.01 degrees C) and conclusion (107.95 degrees C) temperatures, indicating more thermal stability. Pigmented starch displayed high resistant starch content (12.61 g per 100 g). Starches displayed high predicted glycemic index scores (82.10-84.80), indicating their non-utility for diabetic populations.