Electrolytic oxidation of gelatinised tapioca starch: Effect of sodium chloride content on structural and physicochemical properties

Abstract

This is the first study on electrolytic oxidation of tapioca starch in the gelatinised state. Tapioca starch was first gelatinised and then oxidised in an electrolytic tank with NaCl as the electrolyte. The structural and physicochemical properties of the native and the oxidised starches were characterised by FTIR, XRD, molecular mass distribution, degree of oxidation, and thermal gravimetry. FTIR spectra and degree of oxidation analyses showed that 2 - 3% NaCl concentration in the electrolytic tank resulted in the highest content of carbonyl and carboxyl groups in the oxidised starch. The depolymerisation of starch increased with the concentration of NaCl. As a result of these structural changes, the thermal stability of starch samples decreased with the increase of NaCl concentration. The present work demonstrated a fast, simple, and benign process of oxidising starch that can be used in industrial production.