A simple pretreatment with low O2 to alleviate superficial scald in Granny Smith apples

Sealing Granny Smith apples in a low-O2 atmosphere for 7 days at 20 °C (LO2-20C) prior to cold storage reduced superficial scald development after 6 and 8 months at 0 °C plus 10 days at 20 °C. This LO2-20C treatment reduced the O2 levels that induce endogenous production of significant amounts of CO2, acetaldehyde and ethanol, and thereby reduced ethylene production in cold storage, which in turn reduced scald development. Treatment with ethanol vapour (20 mL L−1) for 1 day at 20 °C plus 6 days at 1 °C or with low O2 for 1 day at 20 °C plus 6 days at 1 °C (LO2-1C) did not reduce scald effectively. 1-Methylcyclopropene (1-MCP) treatment at 0.5 µL L−1 was the most efficient at reducing scald development. In all treatments, superficial scald development proceeded from the distal blossom end towards the proximal stem end of fruits. After 6 months of cold storage at 0 °C, peel browning and membrane leakage, measured as electrical conductivity in situ, were greater at the blossom end than at the stem end of control, ethanol- and LO2-1C-pretreated fruits. In LO2-20C- and 1-MCP-pretreated fruits, colour indices (hue angle, lightness and chroma) and electrolyte leakage were similar at both the stem and blossom ends and were associated with less scald development after 6 months at 0 °C. The reduction in scald development was also associated with lower peroxidase and polyphenol oxidase activities in the peel of LO2-20C- and 1-MCP-pretreated fruits. A simple treatment at 20 °C (LO2-20C) prior to regular cold storage could also be suitable for organically grown apples that cannot be treated with diphenylamine or 1-MCP. Copyright © 2007 Society of Chemical Industry