Effect of dielectric barrier discharge (DBD) plasma on the activity and structural changes of horseradish peroxidase

As an emerging nonthermal technology, cold plasma has been used to inactivate endogenous enzymes that are responsible for enzymatic browning reaction of fruits and vegetables. This study aimed to investigate the inactivation effect of dielectric barrier discharge (DBD) plasma on horseradish peroxidase (HRP), a typical plant peroxidase. The results showed that DBD plasma caused inactivation of HRP in a time-and discharge power-dependent manner. The HRP activity decreased by 32.5, 50.6, 65.5, and 75.4%, respectively, after 2, 4, 6, and 8 min of exposure to DBD plasma at 57.6 W. The efficacy of DBD plasma for HRP inactivation was enhanced on increasing the discharge power from 6.0 to 57.6 W. Intrinsic fluorescence spectra showed that DBD plasma induced obvious structural changes in HRP. DBD plasma also caused fragmentation and carbonylation of HRP as well as the oxidative degradation of heme, which might be due to the reactive species in plasma. After DBD plasma exposure at 43.0 W for 8 min, there was approximately an 8.4-fold increase in surface hydrophobicity of HRP. After exposure to DBD plasma, the aggregation of HRP was observed by using atomic force microscopy analysis. In conclusion, DBD plasma causes structural changes and chemical modification of HRP, which may be responsible for the loss of enzymatic activity. These data contribute to the application of cold plasma in the control of enzymatic browning of food products during processing and storage.