Development of Oxygen Concentration Gradients in Flesh Tissues of Bulky Plant Organs

Abstract

Steady-state oxygen diffusion in flesh of apples (Malus domestics Borkh. cvs . Braeburn and Cox's Orange Pippin), Asian pears (Pyrus serotina Rehder. cvs . Hosui and Kosui), and nectarines [Prunus persica (L.) Batsch. cvs . Red Gold and Sunglo] was studied using a nondestructive method at 20C. Fruit flesh was found to exert a significant resistance to O 2 diffusion resulting in measurable O 2 gradients between tissues immediately beneath the skin and those at the fruit center for all these fruits. The magnitude of these O 2 gradients varied between crops and cultivars and depended on the respiration rate and on effective O 2 diffusivity in fruit flesh (D e ). Values of D c varied with the cultivar and were broadly consistent with intercellular space volume. The range of D e values obtained suggested that 0 2 diffusion in fruit flesh takes place in a combination of series and parallel modes in the intercellular space and fluid/solid matrix of the flesh. The results imply that O 2 diffusivity in flesh tissues must be taken into consideration in the determination of critical external O 2 level in controlled/modified atmosphere (CA/MA) storage.