Functionalization of pectin by periodate oxidation

High methoxy citrus pectin was oxidized by periodic acid to prepare a dialdehyde functionalized material. The effect of various reaction conditions, viz., reaction time, reaction temperature, pH of the medium, periodic acid concentration and solvent composition on the oxidation process was investigated. With an increase in the reaction time, the aldehyde content increased. However, the intrinsic viscosity of the system decreased indicating that degradation takes place simultaneously with oxidation. The amount of aldehyde generated also increased with an increase in reaction temperature and the concentration of periodic acid. Due to the polyanionic behaviour of pectin, greater aldehyde contents were obtained at lower pH. Keeping all other reaction conditions constant, greater aldehyde contents were obtained in water-ethanol system than in pure aqueous medium. Increase in the ethanol content increased the amount of aldehyde generated. FTIR spectra of oxidized pectin systems show a carbonyl peak at 1734 cm(-1). They further reveal that partial ionisation of-COOH groups takes place leading to a peak at 1614cm(-1). (C) 2013 Elsevier Ltd. All rights reserved.