Superficial scald, carbon dioxide injury, and changes of fermentation products and organic acids in 'Cortland' and 'Law Rome' apples after high carbon dioxide stress treatment

'Cortland' and 'Law Rome' apples [Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf.] were either nontreated or treated with the inhibitor of s uperficial scald development, DPA, and exposed to air or CO2 (40 or 45 kPa) in air at 2 degreesC for up to 12 days. Fruit exposed to air or 45 kPa CO2 were sampled during treatment, and peel and flesh samples taken for fermen tation product and organic acid analyses. After treatment, fruit were air s tored for up to 6 months at 0.5 degreesC for evaluation of disorder inciden ce. 'Cortland' apples were most susceptible to external CO2 injury and 'Law Rome' to internal CO2 injury. DPA treatment markedly reduced incidence of both external and internal injury. Fermentation products increased in peel and flesh of both cultivars with increasing exposure to CO2, but the extent of the increase was cultivar dependant. Acetaldehyde concentrations were a bout 10 times higher in peel and flesh of 'Law Rome' than that of 'Cortland ' apples. Ethanol concentrations in the flesh were similar in both cultivar s, but were about twice as high in 'Cortland' than in 'Law Rome' peels. Nei ther acetaldehyde nor ethanol concentrations were affected consistently by DPA treatment. Succinate concentrations, often regarded as the compound res ponsible for CO2 injury, increased with CO2 treatment, but were not affecte d by DPA application. Citramalate concentrations were reduced by CO2 treatm ent in 'Law Rome' peel, but other acids were not consistently affected by C O2. Results indicate that acetaldehyde, ethanol or succinic acid accumulati on are not directly responsible for CO2 injury in apples. Chemical name use d: diphenylamine (DPA).