Gaseous Ozonation of Pigeon Pea, Lima Bean, and Jack Bean Starches: Functional, Thermal, and Molecular Properties

Pigeon pea, lima bean and jack bean starches are oxidized with gaseous ozone (O-3) and their functional, thermal, and molecular properties are determined. Carbonyl content, carboxyl content and the amount of the reacted ozone are positively correlated (p < 0.01). Swelling and solubility profiles of the native starch samples increases upon oxidation. Higher values of peak viscosity, cold paste viscosity, and hot paste lower setback viscosity values and, significantly, similar peak times and pasting temperatures are observed upon ozonation (p < 0.05). Texturally, the oxidized gels are softer and more elastic than the native gels. The range values of gel strengths, among the oxidized starches, are 2.83-5.42 N (pigeon pea), 4.38-4.84 N (lima bean), and 2.98-4.20 N (jack bean). Absorption band peaks at 2925.11 and 2927.14 cm(-1) of CH2 asymmetric stretching, 3200-3400 cm(-1) of OH groups are obtained for the native starches, which were unaltered upon oxidation. Gelatinization temperatures (T-o, T-p, and T-c) of the starches remains unchanged after oxidation, except for T-o, T-p for lima bean and jack bean starches. The gelatinization and retrogradation studies of the oxidized pigeon pea starches exhibits higher endothermic enthalpies than their native starches. The crystals of the starch samples are C-B-type X-ray patterns and the oxidized starches possessed higher crystallite sizes than the native starches. Amylose contents, weight averages, and polydispersity ratios improve upon oxidation whereas an opposite trend is observed in terms of amylopectin content and number averages.