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

Abstract

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).