Effect of pectin on the inactivation of mango polyphenol oxidase treated by high-intensity ultrasound

This study evaluated the activity and structural changes of mango polyphenol oxidase (PPO) after ultrasound (US) treatment at 21.3 W/cm 2 for 9 min, with varying concentrations of apple pectin (AP). The results showed that after US treatment, the PPO solution alone had a residual activity (RA) of 50.0%, and PPO exhibited changes in its secondary and tertiary structures. However, the addition of pectin increased RA of PPO and the RA reached 92.66% at 20 g/L AP, which was not significantly different from the untreated group (p > 0.05). Additionally, the introduction of pectin significantly reduced its structures changes. The exogenous fluorescence intensity of PPO solution added with 10 g/L AP treated with US did not differ significantly compared to the untreated sample. Thus, when the process of US inactivates PPO, pectin binds to PPO and exerts a protective effect, improving its stability. • AP can interact with both the surface and internal hydrophobic structure of PPO. • The activity of PPO decreased and its structure changed after US treatment. • AP increases PPO activity after US treatment. • AP reduces the changes in the structures of PPO after US treatment. • Pectin binds with PPO and provides a protective effect on it during US treatment.