MODIFIED-ATMOSPHERE PACKAGING OF BLUEBERRY FRUIT - EFFECT OF TEMPERATURE ON PACKAGE O-2 AND CO2

Highbush blueberry (Vaccinium corymbosum L. 'Bluecrop') fruit sealed in low-density polyethylene packages were incubated at 0, 5, 10, 15, 20, or 25C until O2 and CO2 levels in the package reached a steady state. A range of steady-state O2 partial pressures (1 to 18 kPa) was created by placing a range of fruit weights within packages having a constant surface area and film thickness. The steady-state O2 partial pressure in packages containing the same weight of fruit decreased as temperature increased, indicating the respiratory rate rose more rapidly (i.e., had a greater sensitivity to temperature) than O2 transmission through the film. Steady-state O2 and CO2 partial pressures 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 and 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, which implies that blueberry fruit can be stored at lower O2 partial pressures when stored at lower temperatures.