Electrophoretic separation revealed several PPO isoforms but only in chilled fruits that developed IB symptoms. Many POD isoforms were detected in both chilled and nonchilled fruits of the four varieties. The specific colorations for PPO (with pyrocatechol as substrate) and for POD (with guaiacol and H2O2 as substrates) allowed us to distinguish a main area for PPO isoforms (0.74 < Rf < 0.80) and a main area for POD isoforms (0.45 < Rf < 0.61) (Figure 3).