Microbial ecology of fresh pork stored under modified atmosphere at -1, 4.4 and 10 degrees C

The prevalent bacteria on fresh pork packaged in modified atmosphere with elevated CO2 were determined by selection of representative colonies from the greatest dilution of meat samples. The pork samples were stored in two packaging films of different oxygen permeability at three storage temperatures. Strains were classified and those identified as lactic acid bacteria were screened for production of inhibitory substances. The types of bacteria isolated from samples stored in the two packaging films were similar. Storage temperature influenced the type of bacteria that dominated the microbial population. At 10 degrees C the prevalent microflora consisted of aeromonads, Enterobacteriaceae and lactic acid bacteria but at 4.4 and -1 degrees C, aeromonads, Brochothrix thermosphacta and lactic acid bacteria dominated. Listeriae were detected as part of the prevalent microflora on samples stored at -1 degree C, but not on samples stored at 4.4 or 10 degrees C. Species of lactic acid bacteria dominating the microflora were influenced by growth medium. The majority of isolates taken from Plate Count agar were carnobacteria whereas those from Lactobacilli MRS agar were homofermentative lactic acid bacteria. Of the 538 lactic acid bacteria isolates screened for production of inhibitory substances, 162 strains showed deferred inhibition toward a range of lactic acid bacteria and nonlactic acid bacteria indicator strains.