Respiratory rate and quality changes in fresh-cut pears as affected by superatmospheric oxygen.

Changes in the respiration rate of fresh-cut "Flor de Invierno" pears stored under superatmospheric oxygen concentrations were studied and compared to those observed under traditional modified atmosphere packaging conditions. Changes in package headspace O(2) and CO(2) concentrations throughout storage were curve-fitted to nonlinear equations, calculating respiration rates by combining the derivatives of the equations and the gas permeations throughout storage. Moreover, relationships between respiratory activity and quality parameters of fresh-cut Flor de Invierno pears dipped into an antioxidant solution (0.75% N-acetylcysteine and 0.75% glutathione) were assessed. CO(2) production of fresh-cut Flor de Invierno pears stored under 70 kPa O(2) atmospheres was successfully estimated with the proposed mathematical procedure. This method also proved to describe well CO(2) production rates of fresh-cut pears stored under initial 2.5 kPa O(2)+ 7 kPa CO(2) or 21 kPa O(2). In addition, a modification of Michaelis-Menten enzyme kinetics was adequate to describe the changes in estimated CO(2) production due to fermentative processes occurring under low oxygen concentrations. Superatmospheric O(2) concentrations seem to promote oxidative processes, which result into a dramatical modification of some quality attributes of fresh-cut pears.