Effect of intense pulsed light on polyphenol oxidase activity and structure properties

To explore the inhibitory effect and related inactivation mechanism of intense pulsed light (IPL) on the endogenous enzyme activity in fruits and vegetables, the effect of IPL treatment on the activity of polyphenol oxidase (PPO) was investigated by spectrophotometry, and the structure properties of PPO under different IPL treatment was also analyzed by ANS fluorescent probe, intrinsic fluorescence spectroscopy, gel electrophoresis and circular dichroism (CD) spectra. The results showed that PPO activity decreased with the increase of single pulsed energy, pulse times and the reduction of pulse distance. After IPL treatment, the optimal emission wavelength of PPO was red-shifted, and the surface hydrophobicity, the content of free sulfhydryl and β-structure were increased, while the intrinsic fluorescence intensity and the content of α-helix were decreased. Meanwhile, the electrophoresis pattern showed that oxidative degradation of PPO protein occurred. The above results indicated IPL treatment could change the secondary and tertiary structure of PPO, promote protein oxidative degeneration, and decrease the enzyme activity. This study provides a theoretical basis for the study of IPL technology in inhibiting endogenous enzyme activity and reveals related inactivation mechanisms. (authors)