Mushroom polyphenol oxidase inactivation kinetics and structural changes during radiofrequency heating

The effects of radiofrequency (RF) heating on the activity, structure, and surface hydrophobicity of mushroom polyphenol oxidase (PPO) were examined and four kinetic models of inactivation (First-order model, Weibull model, Logistic model and Bi-phasic model) were fitted. The results demonstrated that RF heating could effectively inactivate PPO, logistic and Bi-phasic model attained the best fit. The circular dichroism (CD) and fluorescence spectroscopy spectra revealed that RF heating at 65 degrees C for 180 s caused changes in the secondary and tertiary structures of PPO, reducing the alpha-helix content from 38.5% to 30.3% and red-shifting the emission peak wavelength of the maximum fluorescence intensity from 318 nm to 321 nm. RF heating also caused a significant enhancement of the surface hydrophobicity of the PPO (P < 0.05). The color test results showed that RF heating could inhibit the browning of mushrooms (P < 0.05). Thus, RF heating is an effective technique for the inactivation of enzymes and further research should be performed on RF heating applications to inactivate enzymes in the food industry.