Effect of ozonation on selected properties of starches

Corn starch-water, potato starch-water and rice starch-water mixtures were prepared in the ratio of 1:9 (dry sample to water) and ozonated at a concentration of 4.2 mg dissolved ozone L-1 water for 60 min. A wheat starch-water mixture was also ozonated for 15, 30 and 60 min. Onset, peak and conclusion temperatures of wheat, corn and potato starches increased while the corresponding gelatinization enthalpies were reduced after ozonation, except the wheat starch. Ozone has more distinct effect on the birefringences of corn and potato starch samples under polarized light microscopy. Changes in the granule shape under SEM are visually distinct for ozonated corn and potato starches. Ozonation changed starch pasting charactersistics causing a significant reduction in peak, trough, breakdown and final viscosities of all starch samples. A significant reduction was observed in values of pasting parameters of wheat starch with increasing ozonation time. Shear-thinning behaviour was observed for the control and all ozonated wheat starch samples. Longer ozonation time resulted in more gelatinized starch molecules. Significant increases in brightness and whiteness for ozonated wheat, corn and potato starch samples were observed. The ozonation process caused significant decrease in pH and in both total bacteria and mold/yeast counts for all wheat, corn, potato and rice starch samples studied.Key words: Ozone, starch, gelatinization, morphology, rheology, color