Effect of aqueous ozonation on the pasting, flow and gelatinization properties of wheat starch

Wheat starch-water suspensions were exposed to ozone gas for 15, 30, and 60 min at 5 degrees C at a concentration of 0.00042 g dissolved ozone/100 g. Pasting properties were determined by using a Rapid Visco Analyzer (RVA) while a Bohlin rheometer was used to obtain flow behaviour (n) and consistency (K) indices. An enzymatic method using glucoamylase was applied to calculate percent starch gelatinization. Pasting temperature (P-T) of ozonated starch samples decreased significantly (P < 0.05) as compared to that of native starch. Cooking stability starch samples increased upon ozonation indicated by lower breakdown viscosity (B-V) values. The retrogradation tendency of wheat starch samples was reduced after ozonation which was indicated by lower setback viscosities (S-V). Native and ozonated starch samples exhibited a shear-thinning behaviour with values of flow behaviour indices (n) between 0.57 and 0.76. The greater n values obtained for ozonated starch samples as compared to native starch showed that ozonation increased the shear-thinning behaviour of wheat starch. Percent gelatinization for all ozonated starch samples were significantly higher than the control starch samples (P < 0.05), probably due to, weakened hydrogen bonding between the starch molecules and partial depolymerization of starch molecules by ozonation. (C) 2014 Elsevier Ltd. All rights reserved.