Rheological and functional properties of heat moisture treated pearl millet starch

Abstract

Pearl millet (Pennisetum typhoides) starch was subjected to heat moisture treatment (HMT) at different moisture levels i.e., 20 % (HMT-20), 25 % (HMT-25) & 30 % (HMT-30) for 8 h at 110 °C and evaluated for changes in rheological, thermal, functional and morphological properties. Peak, breakdown, cool paste and setback viscosity decreased, while pasting temperature increased after HMT. Shear stability of HMT-30 sample was maximum (stability ratio 0.54). Highest (33.5 Pa) G′ value was observed for native and lowest (14.8 Pa) for HMT-25 sample. Yield and flow point of starch gels also decreased after HMT, indicating softer gels and higher spreadability. HMT increased gelatinization temperature from 62.59 °C for native to 84.05 °C for HMT-30. Resistant starch content increased about three times in HMT-30 sample (7.07 %) as compared to native. Swelling power and solubility decreased after HMT. HMT also induced cavity and some dents on starch granules surface.