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 O₂ uptake, steady-state O₂ partial pressures in modified-atmosphere (MA) packages ([O₂]_pkg), and film permeability to O₂ (Po₂) from previously published data for highbush blueberry (Vaccinium corymbosum L. `Bluecrop') fruit held between 0 and 25C. O₂ uptake in nonlimiting O₂ (Ro₂^max,T) and the [O₂]_pkg at which O₂ uptake was half-maximal (K_½^T) were both exponentially related to temperature. The activation energy of 0₂ uptake was less at lower [O₂]_pkg and temperature. The predicted activation energy for permeation of O₂ through the film (\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \(\mathrm{E}_{\mathrm{a}}^{\mathrm{P_{\mathrm{o}_{2}}}}\) kJ·mol^-1) required to maintain close-to-optimum [O₂]_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 \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \(\mathrm{E}_{\mathrm{a}}^{\mathrm{P_{\mathrm{o}_{2}}}}\) of ≈ 50 and 40 kJ·mol^-1, respectively, and would have correspondingly greater tendencies for [O₂]_pkg to decrease to excessively low levels with an increase in temperature. Packages that depend on pores for permeation would have an \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \(\mathrm{E}_{\mathrm{a}}^{\mathrm{P_{\mathrm{o}_{2}}}}\) of <5 kJ·mol^-1. Our procedure predicted that, if allowed to attain steady-state conditions, packages with pores and optimized to 2 kPa O₂ 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.