A SCALD-LIKE CONTROLLED-ATMOSPHERE STORAGE DISORDER OF EMPIRE APPLES - A CHILLING INJURY-INDUCED BY CO2

Empire apples (Malus domestica Borkh.) were harvested prior to the onset of the ethylene climacteric and stored for six weeks in controlled atmospheres (CA) ranging from 1.3 to 7.3% CO2 and 1.6 to 5.1% O-2 and in air at 1 and 3 degrees C with or without treatment with 1000 mg l(-1) diphenylamine (DPA) scald inhibitor. Fruits were examined for incidence of 'scald-like' disorder upon removal from storage and after two weeks at 20 degrees C. A physiological disorder resembling superficial scald was evident on fruits not treated with DPA upon removal from CA and the severity of symptoms increased only slightly after holding the fruits in air at 20 degrees C. The disorder only occurred on fruit held in CA and was much more prevalent at 1 degrees C as compared to 3 degrees C storage. The disorder predominantly affected the non-red portions of the fruit surface and involved only the hypodermal cells. The fruit surface affected was tan or brown and became wrinkled and sunken as the subtending cells collapsed and dehydrated. The disorder incidence was markedly associated with high CO2 concentration during CA at 1 degrees C and this was exacerbated at 2.0% CO2 with 1.5% O-2 We propose that the mechanism responsible for the Empire fruit 'scald-like' disorder is a free radical-catalyzed oxidation of susceptible amino acid residues in proteins essential for cell function and perhaps other macromolecules, such as membrane lipids containing oxidizable reactive groups.