Skin Permeability to Oxygen in Apples Stored in Controlled Atmosphere

Abstract

The skin permeability to O2-diffusion and the mass transfer equilibrium constant for ‘Super Golden Delicious’ spur and ‘Red Stark’ (Malus domestica Borkh.) have been studied using a kinetic approach. A direct proportionality between the O2-exchange initial rate and the environmental PO2 is shown by a linear regression line passing near the origin of the axes. This confirms the suitability of the adopted mass-transfer equations and allows the calculation of the two involved constants: the equilibrium mass-transfer constant and the kinetic constant, which represents a suitable measure of permeability of the apple skin. As apple-skin permeability to O2 increases with fruit ripening, to reach a maximum near the commercial harvesting time, this parameter could be used as a ripening index.