Viscometric characteristics and physicochemical properties of acid-modified cocoyam starch

Abstract

Cocoyam (Colocasia spp.) tuber, which has high starch yield, was subjected to acid modification. Effects were evaluated relative to the pasting, structural, physicochemical, and morphological properties. Native cocoyam starch (NCS) was treated with hydrochloric acid to produce acid-modified cocoyam starch (AMCS). Pasting properties were examined using a Rapid Visco Analyzer (RVA), while water and oil absorption capacities, swelling power, and gelatinization features were evaluated using standard methods. Morphological and structural alterations were analyzed. Acid treatment significantly higher peak, final, trough, and setback viscosities, signifying greater paste stability at high temperature, higher swelling capacity, and greater retrogradation tendency. AMCS also displayed higher gel-forming ability at lower concentrations, higher swelling power, and increased water and oil absorption capacities relative to NCS. Scanning electron microscopic images showed surface erosion and granule disruption after acid modification, while FT-IR spectra affirmed that modification occurred primarily via depolymerization without the introduction of new functional groups. X-ray diffraction analysis revealed retention of crystalline polymorphism with improved relative crystallinity after acid hydrolysis. In all, the acid treatment effectively altered the granular and molecular structure of cocoyam starch, enhancing its functional properties and demonstrating its suitability for food and industrial applications requiring strong gels, stable pastes, and enhanced hydration characteristics.