THE COMPARATIVE EFFECTS OF NITROGEN AND OXYGEN ON THE MICROFLORA OF BEEF STEAKS IN CARBON DIOXIDE-CONTAINING MODIFIED ATMOSPHERE VACUUM SKIN-PACKAGING (MA-VSP) SYSTEMS

The effects of 80% oxygen-20% carbon dioxide (O-2-CO2) and 80% nitroge n-20% carbon dioxide (N-2-CO2) atmospheres were compared with respect to the microbial and sensory characteristics of vacuum skin-packaged g rain-fed beef steaks stored at - 1 and 4 degrees C. In both N-2-CO2 an d O-2-CO2 atmospheres, lactobacilli were predominant over Brochothrix, pseudomonads, enterobacteria and yeasts and moulds. The results of th e current investigation showed that the O-2-CO2 atmospheres did not yi eld total viable counts in excess of 10(5) cfu cm(-2) on beef steaks a fter 4 weeks of storage. However, the sensory analysis and thiobarbitu ric acid (TBA) values las a measure of oxidative rancidity) of the pro ducts were unacceptable at this time. In contrast, the N-2-CO2 atmosph eres yielded maximum total viable counts of approximately 10(7) cfu cm (-2) and the sensory analysis and TEA values of the product were judge d to be acceptable after 4 weeks Of Storage at - 1 degrees C. These re sults indicate that sensory effects of the product were influenced to a greater extent by the chemical effects of high concentration of O-2 on rancidity than by the high levels of lactobacilli.