Microwave Assisted Synthesis and Characterization of Acetate Derivative Cassava Starch

Abstract

The aims of this study were to observe the possibility of application of microwave heating in the acetylation of cassava starch and to study the physicochemical properties of the starch acetate obtained. The acetylation was carried out by mixing native cassava starch with chloroacetic acid and sodium hydroxide of a certain weight ratio in a sealed container. The mixture was then sprayed with ethanol and heated using microwave power. The degree of substitution (DS), reaction efficiency (RE) and some physical properties of the acetylated starches were then analyzed. It was found that microwave assisted acetylation of cassava starch using chloroacetic acid can be done in a very short reaction time. The highest DS and RE obtained were 0.045 and 0.051%, respectively. Acetylation of cassava starch reduced gel hardness during storage. Acetylation also inhibits the retrogradation of starch gel. Cassava starch acetylation changed starch molecular motion, resulting in a decrease in the glass transition temperature. Amylopectin retrogradation was not significantly reduced, indicating that the degrees of modification of the starches in this study were too low to cause enough steric hindrance to prevent retrogradation. The modifications were done on native starch granules; they took place preferentially on the amylose fraction, not the amylopectin fraction, thus leaving amylopectin retrogradation was mostly unaffected. It can be concluded that microwave heating can be applied in the acetylation of cassava starch to obtain significant changes of the properties of starch.