Effects of hydrogen peroxide accumulation, lipid peroxidation, and polyphenol oxidation during superficial scald development in ‘Fuji’ apples

Hydrogen peroxide (H2O2) and malondialdehyde (MDA) levels and polyphenol oxidase (PPO) activity were measured in ‘Fuji’ apples with different susceptibilities to the development of superficial scald during storage at 0 and 20°C. Both scald incidence and severity increased gradually in the cold and the symptoms became apparent in the fruits with an early, middle, and late harvest after 12, 15, and 21 weeks storage, respectively. Early harvest fruits had the highest scald incidence and severity as well as H2O2 and MDA contents, while late harvest had the lowest. The H2O2 and MDA levels increased, while PPO activity remained constant during storage at 0°C. All fruits showed a rapid increase in scald incidence and severity after warming, especially at the first 4 days, when H2O2 and MDA levels and PPO activities also increased. The H2O2 and MDA levels in scald-free tissues in late harvest fruits were lower initially but became higher in the scald tissues after warming for 4 days. The PPO activities were equal in both tissues. These results indicated that mature fruits were relatively resistant to scald, and that scald symptom development was highly dependent on the accumulations of H2O2 and MDA during cold storage, but PPO activity was less important.