‘Delicious’ apples (Malus domestica Borkh.) were transferred from commercial controlled atmosphere (CA) storage after 7 months into a factorial series of CO2 (0%, 3%, 6%, and 12%) and O2 (0.0%, 0.5%, and 1.0%) concentration mixtures at 0.5°C for up to 14 weeks. Fruit tolerance to specific atmospheres that yielded anaerobic products was determined. Tissue ethanol levels ranged from about 2700 to 5800 µl·liter–1 in apples stored in 12:0 (CO2:O2) and 0:0 atmospheres, respectively, indicating CO2 inhibition of ethanol accumulation in the absence of O2. Less than 360 µl ethanol/liter was produced in the 0.5% and 1.0% O2 treatments, No CO2 inhibition of ethanol or acetaldehyde production occurred in the 0.5% and 1.0% O2 treatments. Tissue acetaldehyde concentrations ranged from 6 to 14 µl·liter–1 in fruit held in 0.0% O2 and 3 to 9 µl·liter–1 in fruit held in 0.5% O2. No visible injury developed from the high CO2 and low O2 concentrations used in any of the storage treatments. After a week in air at 20°, following 0.0% O2 storage, the fruit tissue ethanol content decreased while the acetaldehyde content increased.
‘Delicious’ apples (Malus domestica Borkh.) harvested on two dates and stored in controlled atmospheres (CA) from 0.0% to 1.5% O2 were analyzed biweekly during a 14-week storage period for tissue ethanol and other quality parameters. After 14 weeks, ‘Delicious’ fruit stored in 0.0% O2 was significantly firmer, lower in soluble solids, and had 10 times more ethanol than fruit stored in 0.5% to 1.5% O2. Upon return to ambient air for 7 days following low-O2 storage, up to 50% of the ethanol accumulated was lost. The first external symptoms of low-O2 injury appeared after 8 weeks in 0.0% O2 followed by a week in air. Symptoms were associated with ethanol contents >2500 μg·liter−1. Fruit harvested 7 Oct. produced more ethanol than fruit harvested 23 Sept. (i.e., greater concentration and faster rate). There were no differences in firmness, soluble solids, and titratable acidity due to harvest date.