The physiological responses of 'Delicious' apple slices to 0-30 kPa CO2 at 0-10 kPa O-2 partial pressures at 5 degreesC have been studied. Increasing CO2 partial pressures from 0 to 30 kPa at 0.5, 1 and 10 kPa O-2 reduced respiration rates and ethylene production of the slices. The inhibitory effect of CO2 on respiration rate of slices was best explained by an enzyme kinetics model that combined competitive and uncompetitive types of inhibition. Browning increased during storage and was reduced by CO2 to only a limited extent. CO2 levels of 15-30 kPa resulted in about a 50% reduction in acetaldehyde, ethanol and ethyl acetate concentrations in tissues under both anaerobic and low-O-2 atmospheres compared with slices kept in CO2-free atmospheres. Elevated CO2 might provide a mechanism to reduce accumulation of fermentation products but sensory quality of slices needs be studied before recommending its use. (C) 2001 Elsevier Science B.V. All rights reserved.