MICROBIOLOGICAL CHANGES AND SHELF-LIFE OF MAP, IRRADIATED FRESH PORK

The effects of irradiation dose (0, 0·5 and 1·0 kGy), packaging atmospheres (0, 10 and 20% O2, balance N2) and storage temperature (5, 15 and 25°C) on the survival and growth of microbiological populations and on the shelf life of fresh pork were studied using factorial design experiments. An irradiation dose of 1 kGy reduced both psychrotrophic and mesophilic bacterial counts by two log cycles and inactivated most of the Enterobacteriaceae while lactic acid bacteria were largely unaffected. For products stored at 25°C, the numbers of micro-organisms were unacceptably high after 2 days for non-irradiated samples and after 10 days for those irradiated at 1 kGy, irrespective of packaging atmosphere. Product packaged with 10% O2 and 90% N2 and irradiated at 0·5 kGy had a shelf life of 6 days at 15°C. However, shelf life could be extended to 21 days when product was packaged in 0% O2, irradiated at 1·0 kGy and stored at 5 °C. While the presence of O2 in the package headspace enhanced the antimicrobial effects of low dose irradiation, it adversely affected the organoleptic qualities of pork. © 1992 Academic Press Limited.