Investigation of the effect of acetylation on the physicochemical properties of grain starches
Use of acetylated starches in the production of composite biodegradable materials is a promising direction, since acetylation increases the water-resistant properties of starches. This article presents the results of studies on the effect of acetylation of wheat A and corn starches with glacial acetic acid on the physicochemical properties of polysaccharides and the study of the potential of using modified starches to obtain a composite mixture of biodegradable films. Comparative studies of the physicochemical properties of polysaccharides and their modifications have illustrated that acetylation leads to a decrease in the proportion of amylose in starch, and also reduces the swelling of starch. It has been revealed that the degree of substitution in starches increases only at the initial stages of the acetylation reaction, which is possibly associated with the rheology of starches common to corn and wheat A during swelling and gelatinization. With a decrease in the amount of acetylating agent, a more uniform course of the reaction is observed, the granules destroyed after absorbing the maximum amount of moisture still have access points for replacement with acetyl groups, the reaction proceeds more slowly, but deeper. Solubility depends more on the reaction time. The optimal technological parameters for obtaining acetylated starches have been determined. For wheat starch A, the following are optimal: the concentration of glacial acetic acid is 1: 6, the reaction time is 40 minutes; for corn starch: concentration of glacial acetic acid 1: 5, reaction time 60 minutes. Samples of acetylated starches obtained under such conditions are convenient for preparing a composite mixture of biodegradable materials.