Effect of atmospheric pressure changes on gas transmission through microperforated packages of respiring products

The objective of this work was to quantify the effect of atmospheric pressure changes on gas transmission through microperforations, in order to understand the role of fluctuations in the atmospheric pressure on the headspace composition of microperforated modified atmosphere packages. A 3D numerical model that considers the spatial-time and pressure dependence of the gas composition was adapted to simulate the gas exchange through microperforations at different fixed pressures and at variable pressure due to atmospheric pressure fluctuations (such as those caused by atmospheric tides or by the development of high and low-pressure systems) or to changes in altitude during land or air transport. The model results were successfully verified with experimental data recorded in an experimental system built to measure the CO₂ exchange through microperforations affected by pressure changes due to weather conditions (the root mean squared error of the CO₂ composition was 0.01%). The results reveal the importance of contemplating the convective flow generated by a change in pressure outside the package. In the simulated routes, the difference in CO₂ concentration between considering the pressure-driven flow and neglecting it is one order of magnitude in a 10-h land transport through a medium mountain route, for a 1250 mL container with a single microperforation of 7420.6 μm² area and initial CO₂ concentrations on both sides of the hole of 0.05% and 20.95%. The air transport simulations showed that it is not enough to consider the difference in altitude between the cities of origin and destination, but rather all the pressure fluctuations along the route must be included in the model.