Sustainable Design of High Barrier Films for Modified Atmosphere Packaging of Red Meat

The use of bioplastics in modified atmosphere food packaging has been limited by their poor barrier properties. To investigate the required barrier properties, a mathematical model was developed to predict the effect of permeability on the shelf life of red meat in high oxygen modified atmosphere packaging. Pseudomonas spp. is a gram negative bacteria and is most susceptible to changes in carbon dioxide concentration, hence it is a good indicator of whether the permeability is indirectly decreasing the shelf life by allowing too much carbon dioxide to permeate out. The Pseudomonas spp., carbon dioxide and oxygen dynamics were modelled based on predictive microbiology and gas transfer. These differential equations were solved using MATLAB and the results were successfully validated against two published data sets that varied temperature, headspace concentration and film permeability. From analysis of the resultant model, it was found that to maintain a shelf life of beef steaks within 4% at 5°C, a carbon dioxide permeability of 1.6x10-5 m3 m-2 h-1 was required, much higher than typical permeabilities of packaging films of around 10-8. The results showed that the barrier property requirements for plastic films are often over cautious and use a one-size-fits-all approach, this research, however, indicates a more tailored approach could be taken. Using surface response methodology, the model was simplified to a single equation calculating shelf life predictions as a function of various package design parameters, including permeability. From here, a new bioplastic film will be developed to meet the predicted permeability requirement by adjusting the thickness of the barrier layer. This bioplastic will then be pilot tested against the conventional plastic films to see how the results compare.