Apple polyphenoloxidase inactivation during heating in the presence of ascorbic acid and chlorogenic acid

► During apple processing, ascorbic acid (AA) is added to prevent polyphenol oxidation catalysed by polyphenoloxidase (PPO). ► Evolution of PPO activity was studied during heating model systems in the presence of chlorogenic acid (CG) and/or AA. ► After 2 h of heating at pH 3.8, PPO was still active, keeping 61 and 4% residual activity at 45 and 60 °C. ► The combined treatment of heating and AA was more effective in reducing PPO activity than during heating PPO with CG and AA. ► Losses of CG and AA observed during heating mainly resulted from oxidation reactions.