Effect of acetylation on structural and functional properties of starches from cassava (Manihot esculenta Crantz) and yam (Dioscorea alata cv. Diamante 22)

Abstract

Acetylation is a chemical modification by esterification which causes in the starch granules changes in the structure and consequently in its functional characteristics. In this study to evaluate the effect of the modification, native cassava starch (NCS) and yam (NYS) were used with acetic anhydride at different reaction times (10 to 240 min). Significant differences were found in the degree of substitution (DS) in relation to the reaction time and the species into study (p <0.05). Through Analysis by Fourier transform infrared, the modification was proved where a signal to 1087 cm−1 corresponding to stretching C-O bond of acetyl groups was found. Diffraction patterns exhibited after the modification were very similar to the native, wherein the native cassava starch presents type A pattern and native yam starch type B pattern. The micrographs showed minor lacerations from the modification in the surface of the granules. The functional properties such as water absorption, solubility and swelling power increased when the degree of substitution increased. The introduction of acetyl groups in the starch structure, caused a decrease in gelatinization temperature, greater stability and tendency to retrogradation.