Effect of succinylation on the physicochemical, rheological, thermal and retrogradation properties of red and white sorghum starches

Starches isolated from red and white sorghum were modified with succinylation. After modification proximate composition, moisture content, ash, protein and fat were reduced in percentage. Increase in swelling power was observed and did not show any significant change in solubility. Swelling and solubility were pH dependent with higher values obtained at pH 12 in both native and modified starches. At pH 4 both succinylated red and white starches had lower solubility. Rapid visco-analyser (RVA) revealed increased in peak viscosity of the succinylated starches and reduction in setback and breakdown values. There was no significant change in the pasting temperature. Gelatinization enthalpy reduced from 1.275 and 1.953 J/g in RNS (red native starch) and WNS (white native starch) respectively to 1.105 and 1.178 J/g in SUCR (succinylated red starch) and SUCW (succinylated white). Endothermic transition temperatures (To, Tp and Tc) reduced and the retrogradation enthalpy increases with the storage time of gelatinized starches. Therefore retrogradation tendency was reduced by succinylation.