Effect of lactobacilli and carbon dioxide on the growth of Microbacterium thermosphactum on fresh beef.

Studies with articifially inoculated fresh beef showed that lactobacilli markedlyrestrict the growth of Microbacterium thermosphactum when the beef is vacuum-packaged. High concentrations of carbon dioxide (up to 75%) had little effect on the growthof M. thermosphactum under either aerobic or anaerobic conditions. Tests were madewith samples of lean beef inoculated with pure cultures of lactobacilli and (or) M. thermosphactum and stored unpackaged in air, in air enriched with carbon dioxide, in nitrogen-carbon dioxide mixtures, or vacuum-packaged as in commercial practice. On vacuum-packaged meat, growth of M. thermosphactum was extensive in the absence of lactorbacilli, but was restricted in the presence of lactobacilli. On unpackaged meat (i.e.stored in air) this inhibition did not occur, showing that anaerobic conditions are necessary for it to take place. These results show the import ance of lactobacilli on the storage life of vacuum-packaged fresh beef.