The objectives of this study were to determine the dissolved CO2 and O2 concentrations in the purge of vacuumpackaged
pork chops over a 60 day storage period, and to elucidate the relationship of dissolved CO2 and O2 to the
microbial populations and shelf life. As the populations of spoilage bacteria increased, the dissolved CO2 increased
and the dissolved O2 decreased in the purge. Lactic acid bacteria dominated the spoilage microflora, followed by
Enterobacteriaceae and Brochothrix thermosphacta. The surface pHdecreased to 5.4 due to carbonic acid and lactic
acid production before rising to 5.7 due to ammonia production. A mathematical model was developed which
estimated microbial populations based on dissolved CO2 concentrations. Scanning electron microscope images
were also taken of the packaging film to observe the biofilm development. The SEM images revealed a twolayer
biofilm on the packaging film that was the result of the tri-phase growth environment.