Effect of acetic anhydride on physico-chemical, thermal, retrogradation and pasting properties of rice starches differing in crystallinity.

摘要

Physico-chemical, thermal, retrogradation and pasting properties of acetylated starch (AS) prepared using starch from 2 rice cultivars ('PR-113' and 'IR-64') were studied. Effects of using acetic anhydride at different levels (2-8 g) on the properties of AS were also studied. Acetylation of starches from both the cultivars showed different acetyl (%) and degrees of substitution (DS) under similar conditions. 'IR-64' starch with higher crystallinity and lower amylose content showed lower acetyl (%) and 'DS' than 'PR-113' with lower crystallinity and higher amylose content under similar reaction conditions. 'PR-113' starch showed higher peak- and setback-viscosity, and lower pasting temperature and breakdown viscosity than 'IR-64' starch. AS showed higher amylose content, swelling and solubility than native starches. Swelling and solubility increased with the increase in acetic anhydride level in the reaction medium. 'PR-113' starch showed lower transition temperature and enthalpy of gelatinization than 'IR-64' starch. Acetylation treatment caused a decrease in To, Tp, Tc and Delta Hgel of both the rice starches. After acetylation, the starches began to paste at lower temperature and showed higher viscosities than their corresponding native starches..