The modification of the starches aims to change the properties of these polymers making them more suitable for specific applications. Therefore, the objective of this study was to modify potato and rice starch using the hydrolysis process with hydrochloric acid (HCl) and the esterification process with citric acid (CA), both acids at different concentrations and reaction time. To verify if the modifications were effective, the physicochemical changes (solubility, swelling power, gel strength and amylose content), thermal, morphological and pasting properties were evaluated. The applied modifications reduced the swelling power, solubility and amylose content of starches. The strength of the gel was reduced with the modifications for the rice starch and increased for the potato starch. Regarding the pasting properties, modified starch RS1 (modified rice starch using 0.1 M HCl) and PS3 (modified potato starch using 2% CA) showed a tendency to reduce retrogradation. Structurally, X-ray evaluation indicated reduced crystallinity. Thermal analyses showed that gelatinization temperatures were increased for all treatments, while gelatinization enthalpies were reduced indicating greater thermal stability of the modified starches. Therefore, modified starches have distinct characteristics that can be used for specific processes that requiring starches with different properties from the conventional ones.
Keywords: Chemical modification; Citric and hydrochloric acid; Crystallinity; Solubility.
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