The inhibitory effect of UV-A LED treatment on PPO activity was con-
firmed using non-reducing SDS-PAGE electrophoresis and zymographic
analysis in order respectively to isolate enzymatic isoforms and visualize
the appearance of colored bands in the gel lanes as indicator of
enzyme activity (Fig.3). The UV-A LED irradiation at the best experimental
conditions fixed previously was carried out at room temperature
for 30 min on a model solution of TYR and on Golden Delicious apple
slices subjected to subsequent PPO extraction. The zymograms of TYR
(Fig.3A) and apple PPO (Fig.3B) showed only one enzymatic isoform
whose activity decreased after irradiation reducing significantly the
color intensity of corresponding band (UV) in comparison to the untreated
control (C).