Physiology and control of apple scald

The effect of controlled atmosphere (CA) storage, and antioxidant treatment on polyphenoloxidase (EC 1. 1418.1:PPO), peroxidase (EC11.11.1.7:POD), and superoxide dismutase (EC 1.15.1.1:S0D) activities and superficial scald and soft scald development in 'Virginiagold','Stayman', and 'Rome' apples (Malus domestica Borkh.) was investigated. 'Virginiagold' apples treated postharvest with an aqueous solution of diphenylamine (DPA) + 1,2, dihydro -6- ethoxy -2,2,4-trimethylquinoline (ethoxyquin) and stored in CA exhibited lower soft scald incidence and higher firmness than comparable fruits stored at O°C in air storage. Fruit firmness and titratable acids (TA) decreased continuously, while ethylene increased in storage. Titratable acids and firmness were positively correlated, while TA and ethylene and firmness and ethylene were negatively correlated. 'Stayman' and 'Rome' apples analyzed during storage showed increase in levels of λ±-famesene and its oxidation products conjugated trienes. During storage fruits showed an increase in the activities of polyphenoloxidase (PPO), peroxidase (POD), and superoxide dismutase (SOD), which reached a maximum when scald symptoms in 'Stayman' were observed. Our results indicate that 'Stayman' apples exhibited scald and 'Rome' did not, because 'Stayman' apples had a ten fold higher PPO activity than 'Rome.'