Characterization of physicochemical properties of hypochlorite- and peroxide-oxidized cassava starches

Physicochemical properties of oxidized cassava starch as influenced by different oxidizing agents (sodium hypochlorite and hydrogen peroxide) were investigated. The starch was modified under controlled temperature and pH with 3% oxidants (based on starch) between 30 and 300 min. The results showed that hypochlorite oxidation favored the formation of carboxyl group while carbonyl was the major functional group formed during peroxide oxidation. The molecular sizes determined by HPSEC and the apparent viscosity of starch were decreased to a similar extent by both oxidants; however, the changes observed in peroxide oxidation proceeded with a faster rate. Rheological measurement revealed that peroxide-oxidized starches had a higher tendency for gelation and gave a firmer gel than hypochlorite-oxidized starches. The gelatinization temperatures increased following peroxide oxidation but decreased after hypochlorite oxidation. The gelatinization enthalpy decreased after oxidation by both chemicals. Results from DSC demonstrated that amylopectin retrogradation was not significantly affected by both types of oxidation.