Preparation and characterization of cassava starch acetate with high substitution degree

Abstract

In this work, cassava starch (CS) was acetylated by a simple and scalable method to produce a highly hydrophobic polymeric material with potential use in coating and food packaging. The chemical structure, thermal stability and morphological properties of cassava starch acetate (CSA) were determined. Their formation was confirmed using FTIR by the presence of the carbonyl signal around 1749 cm-1. Degrees of substitution (DS) obtained by titration were between 1.9 and 2.9.Thermogravimetric analysis showed an increase in thermal stability with acetylation, the DS=2.9 sample behaving as a homopolymer. SEM micrographs showed the loss of the structure of the starch granule and the appearance of a beehive-shaped new structures.CS and CSA were structurally characterized by NMR. The CS branching percentage obtained by 1H-NMR was 4.76. Using quantitative 13C{1H}-NMR the DS was calculated, confirming the values already obtained and the regioselective substitution pattern was determined, demonstrating that the favorite position of acetylation is that of C6.