Physicochemical properties of acetylated fractionated potato starches

Physicochemical properties of acetylated fractionated potato starches, prepared using acetic anhydride, were investigated. 1) As levels of acetic anhydride increased, physicochemical properties of acetylated fractionated potato starches changed as follows: (1) Content of acetyl group increased. (2) In distilled water, RVA (Rapid Visco Analyser) characteristics parameters (pasting temperature, peak viscosity and breakdown) and DSC (differential scanning calorimetry) characteristic parameters (onset, peak and conclusion temperatures of gelatinization, and enthalpy change of gelatinization) decreased, but solubility and swelling power increased. (3) Viscoelastic parameters (storage modulus and loss modulus) of starch pastes prepared in distilled water decreased, and their frequency-dependences were observed. Shear stresses of starch pastes at each shear rate decreased, and the extent of thixotropy decreased. (4) Syneresis of 4% starch pastes prepared in 0.1 M NaCl solution decreased. 2) The following differences in physicochemical properties were found among acetylated fractionated potato starches (large, middle and small granules). (1) Acetyl group contents of small granule starches were higher than those of middle and large granule starches. (2) Extent of decrease in RVA peak viscosity measured in distilled water increased with decrease in the starch granule size. Solubility and swelling power in distilled water increased with increase in the starch granule size. (3) In 0.1 M NaCl solution, RVA peak viscosity of starch pastes of small and middle granules increased with the increase in levels of acetic anhydride, and the extent of increase in the viscosity was markedly large for the small granule. (4) Solubility and swelling power in distilled water increased with the increase in the starch granule size. In 0.1 M NaCl solution, with the increase in the starch granule size, solubility increased, but the swelling power decreased. 3) Concerning the effect of 0.1 M NaCl solution on physicochemical properties of acetylated fractionated potato starches, RVA peak viscosity, solubility and swelling power decreased greatly compared with those in distilled water.