Ozonation of cornstarch at pH 13 was performed using a semi-batch reactor to analyse the influence of a continuous ozone-oxygen gas flow (40 NL/h) at different ozone concentrations (0-42.30 g/Nm3) and temperatures (20-60ºC). A pseudofirst-order kinetic model was proposed to elucidate the reaction mechanisms associated with ozone at high pH conditions. The radical concentration remains constant and proportional to the ozone continuous dose, being a non-limiting factor independent of temperature (activation energy 14.2-14.5 KJ/mol). The oxidation kinetic of starch was studied monitoring the Chemical Oxygen Demand, finding a reduction in ozone concentration when both temperature and time increased (activation energy 8.1 KJ/mol). Therefore, the model proposed for the starch ozonation at high alkaline solutions provides a better understanding of the oxidation processes of common product additives such as starch, also making it possible to determine the environmental impact of such solutions by Chemical Oxygen Demand measurement.