Metabolic Response of ‘Delicious’ Apples to Carbon Dioxide in Anoxic and Low-oxygen Environments

Abstract

Abstract ‘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.