Skin Permeance and Internal Gas Composition in `Hass' Avocado (Persea americana Mill.) Fruits

Abstract

The gas skin permeance and the internal atmosphere composition of `Hass' avocado (Persea americana Mill.) fruits were evaluated during the ripening period by using surface chambers. Plant material was harvested at physiological maturity at Uruapan, Michoacan, Mexico, in November of 2001. Storage was conducted under natural atmosphere at 20°C and 81% RH; the physiological stages were expressed in terms of ethylene internal partial pressures and pulp firmness. The climacteric onset occurred at 18.2 N and the peak was reached at 5.0 N. The interñal partial pressure decreased consistently for O2 while for CO2 increased. This result suggested that the resistance to gas exchange imposed by skin caused that O2 taken up was not enough to supply fruit requirements and also that CO2 was produced faster than the rate at which it was given off to ambient. It was found that skin permeance to O2 and CO2 could vary during ripening period and that avocado skin was more permeable to O2 than to CO2 with a 1.7:1 ratio. Surface chambers were useful to determine internal concentrations and gas skin permeance, but care must be taken to select the best sampling procedure to allow getting accurate values of these parameters.