Modification of Cassava Starch by Esterification and Properties of Cassava Starch Ester Films

Abstract

Cassava starch, a naturally occurring biopolymer, is able to form films which are generally sensitive to moisture. Chemical modification by esterification can enhance the hydrophobicity of starch that depends on the nature of ester group and the degree of substitution (DS). The effects of the ester group chain-length and the DS on the properties of starch ester films were studied. Starch ester slurry containing starch ester 4% and sorbitol 30% w/w of starch as a plasticizer was cast into a film and its mechanical properties were determined. It was found that tensile strength and elongation were in the range of 2-3 kg/mm² and 2-3%, respectively. The water absorptivity and water solubility of the starch ester films were reduced as the ester group chain-length and the DS of starch esters increased. The results indicate that starch esterification can improve the hydrophobicity of starch ester films and this relates directly to the ester group chain-length and the DS of starch esters.