Ultrasonic modification of purple taro starch (Colocasia esculenta B. Tini): structural, psychochemical and thermal properties

Abstract

Purple taro tubers (Colocasia esculenta B. Tini) were used in extraction of starch by aqueous methodology. After isolation, the starch was characterised and subjected to physical modification by ultrasound technique, using different amplitudes (40, 50 and 60%). Starch characterisation was performed by thermal analysis, pasting properties, X-ray powder diffractometry and high-resolution scanning electron microscopy. The root presented high carbohydrate content and low protein and lipid content. The apparent amylose content obtained from native starch was 26.45%. From thermal analysis, three major mass loss events were observed for all samples, and due the modification, an increase in thermal stability was achieved. There was a decrease in transition temperatures during the gelatinisation process after sonicated samples. The degree of relative crystallinity was lower for modified starches. An increase in peak and final viscosities was observed for physically modified samples, accompanied by a decrease in pasting temperature. The size of the granules showed a slight decrease, and agglomerations were not observed in this studied amplitude range.