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This study has evaluated the inactivation of peroxidase (POD) and polyphenoloxidase (PPO) in apple cubes and in apple juice by ultrasonic treatment. Apple cubes and apple juice were subjected to ultrasonic processing by applying power densities ranging from 55 to 3300 W/L. Processing was carried out at temperatures ranging from 23C (ambient) to 60C and processing times ranging from 5 to 20 min, corresponding to the main operating conditions usually applied in ultrasonic treatment. Ultrasound application resulted in partial inactivation of both PPO and POD under specific operating conditions. An increase in enzyme activity was also observed for POD with increasing processing time and for PPO at higher temperatures (60C). [ABSTRACT FROM AUTHOR]