Modified-atmosphere Packaging of Blueberry Fruit: Modeling Respiration and Package Oxygen Partial Pressures as a Function of Temperature

A mathematical model was developed to characterize the interaction of fruit O 2 uptake, steady-state O 2 partial pressures in modified-atmosphere (MA) packages ([O 2 ] pkg ), and film permeability to O 2 (P o 2 ) from previously published data for highbush blueberry (Vaccinium corymbosum L. `Bluecrop') fruit held between 0 and 25C. O 2 uptake in nonlimiting O 2 (R o 2 max,T ) and the [O 2 ] pkg at which O 2 uptake was half-maximal (K ½ T ) were both exponentially related to temperature. The activation energy of 0 2 uptake was less at lower [O 2 ] pkg and temperature. The predicted activation energy for permeation of O 2 through the film ( kJ·mol -1 ) required to maintain close-to-optimum [O 2 ] pkg across the range of temperatures between 0 and 25C was ≈ 60 kJ·mol -1 . Packages in which diffusion was mediated through polypropylene or polyethylene would have values of ≈ 50 and 40 kJ·mol -1 , respectively, and would have correspondingly greater tendencies for [O 2 ] pkg to decrease to excessively low levels with an increase in temperature. Packages that depend on pores for permeation would have an of <5 kJ·mol -1 . Our procedure predicted that, if allowed to attain steady-state conditions, packages with pores and optimized to 2 kPa O 2 at 0C would become anaerobic with as little as a 5C increase in temperature. The results are discussed in relation to the risk of temperature abuse during handling and marketing of MA packaged fruit and strategies to avoid induction of anaerobiosis.