MAP OF BLUEBERRY FRUIT: EFFECT OF TEMPERATURE AND CO2 ON PACKAGE O2 AND THE RQ BREAKPOINT

Abstract

The respiratory behavior of blueberry (Vaccinium corymbosum L. `Bluecrop') fruit was determined under a variety of conditions using a modified-atmosphere packaging (MAP) approach. In each case, O2 and CO2 partial pressure gradients across the film were used to calculate rates of O2 uptake, CO2 production and the respiratory quotient (RQ). The effects of temperature and O2 partial pressure on O2 uptake, CO2 production and the RQ were characterized. The steady state O2 partial pressure at which the fruit began to exhibit anaerobic CO2 production (the RQ breakpoint) increased with increasing temperature from approximately 2 kPa O2 at 0C to 4.5 kPa O2 at 25C. It was determined that the energy of activation of O2 permeability for a film needed to be approximately 60 kPa to maintain O2 levels at or above the RQ breakpoint across this temperature range. RQ was also dependent on CO2 levels. As CO2 partial pressure increased, the RQ breakpoint increased. The lower O2 limit was estimated to be 6, 7, 11 and 23 kPa O2 for 5, 20, 40 and 60 kPa CO2, respectively, at 15C.