Physico-chemical, thermal and rheological properties of starches isolated from newly released rice cultivars grown in Indian temperate climates

Starches isolated from three newly released rice cultivars were tested for different physico-chemical, thermal and rheological properties. The starch granule had either polygonal or irregular shapes with small particle size mainly falling in the range of 1-10 μm. SR-1 had more polygonal shapes than SKUAST-5 and SKUAST-27. SR-1 starch also showed significantly high (p ≤ 0.05) amount of amylose (28.6 g/100 g starch) which possibly was responsible for high swelling power (25.9 g/100 g starch), solubility (26.4 g/100 g starch) and syneresis (35.2 g/100 g starch). Thermal properties (To; Tp; Tc) and enthalpy of gelatinization (ΔHgel) also exhibited significant (p ≤ 0.05) differences thereby affecting the stability of crystalline structures among the rice starches. SKUAST-5 starch showed the lowest value for To (58.5 °C) but exhibited highest value of ΔHgel (18.5 J/g). SR-1 starch exhibited slightly higher degree of retrogradation (83.1 g/100 g starch) than SKUAST-5 (80.2 g/100 g starch) and SKUAST-27 (79.6 g/100 g starch). The flow behavior indicated differences in shear thinning behavior and hysteresis area. All samples showed high structural recovery indicating their suitable use in high shear processing. SKUAST-27 exhibited high value (42.4 g/100 g starch) of rapidly digestible starch (RDS) than SR-1 (39.8 g/100 g starch) and SKUAST-5 (39.4 g/100 g starch).

► Rice cultivars grown in temperate climates were tested for starch quality. ► Physico-chemical, flow behavior & thermal properties were determined to predict the starch applications. ► Digestibility studies indicated high glycemic index of rice starches. ► We report high digestibility and recovery of starches under pressure processing.