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 (O2-CO2) and 80% nitrogen-20% carbon dioxide (N2-CO2) atmospheres were compared with respect to the microbial and sensory characteristics of vacuum skin-packaged grain-fed beef steaks stored at -1 and 4 degrees C. In both N2-CO2 and O2-CO2 atmospheres, lactobacilli were predominant over Brochothrix, pseudomonads, enterobacteria and yeasts and moulds. The results of the current investigation showed that the O2-CO2 atmospheres did not yield total viable counts in excess of 10(5) cfu cm-2 on beef steaks after 4 weeks of storage. However, the sensory analysis and thiobarbituric acid (TBA) values (as a measure of oxidative rancidity) of the products were unacceptable at this time. In contrast, the N2-CO2 atmospheres yielded maximum total viable counts of approximately 10(7) cfu cm-2 and the sensory analysis and TBA values of the product were judged to be acceptable after 4 weeks of storage at -1 degree C. These results indicate that sensory effects of the product were influenced to a greater extent by the chemical effects of high concentration of O2 on rancidity than by the high levels of lactobacilli.