Effects of vacuum, modified atmospheres and storage temperature on the microbial flora of packaged beef

The flora growing on beef stored in vacuum and 100% CO2 at 2 or 6 degrees C (experiment 1) and in vacuum and different mixtures of CO2 and N-2 at -1 or 2 degrees C (experiment 2) was determined in two separate experiments. Both a high concentration of CO2 and a low storage temperature inhibited bacterial growth, especially of the spoilage bacteria pseudomonads and Brochothrix thermosphacta. No packaging conditions gave growth of coliforms. High numbers (log(10) 5-6) of lactic acid bacteria after storage in vacuum or gas packs, inhibited growth of pseudomonads and B. thermosphacta during subsequent storage under retail conditions. Samples of the lactic acid bacteria obtained in experiment 2 were identified by genus-specific rRNA probes. Leuconostocs dominated in vacuum and CO2 packs at both temperatures, whereas carnobacteria dominated in N-2 at -1 degrees C. (C) 1996 Academic Press Limited