Cooked pork chops (pumped with salffpolyphosphate brine or untreated) and cured hams were inoculated with Listeria monocytogenes and Salmonella typhimurium. The samples were irradiated at low (0.75 to 0.90 kGy) or medium doses (1.8 to 2.0 kGy), and each dose was delivered at either a low (2.5 M/min conveyor speed) or high (5.4 M/min) dose rate. Low-dose irradiation reduced L. monocytogenes by more than 2 log and S. typhimurium by 1 to 3 log. Pathogen populations and total plate counts (TPC) were reduced to undetectable levels by medium doses. No meat quality attributes were affected, and no dose rate effect was observed. Nitrite reduced (P < 0.05) both pathogens and TPC during 7°C storage in ham, especially when combined with low-dose irradiation.

Beef steaks and ground beef were inoculated with Listeria monocytogenes, Yersinia enterocolitica, or Escherichia coli 0157:H7. Samples were packaged in air or under vacuum and irradiated at low (0.60 to 0.80 kGy) or medium (1.5 to 2.0 kGy) doses, with each dose delivered at either a low (2.8 M/min conveyor speed) or high (6.9 M/min) dose rate. Medium-dose irradiation accompanied by 7°C storage resulted in no Y. enterocolitica or E. coli 0157:H7 survivors being detected. There was no effect on survival of the pathogens by dose rate or storage atmosphere. No difference (P>O.OS) was observed in meat pH or color, but TBA values increased after 7 days storage.

Pork carcasses were sprayed with 1.5% acetic, citric, or lactic acid. Loins were vacuum packed and stored at 0-2"C, chops were cut periodically from loins and stored at 2-4"C. Acetic and citric acids decreased (PcO.05) aerobic plate counts (APC) and total coliforms in loins for 14 days. Species of Salmonella, Yersinia, and Campylobacter were found on 0, 6, and 5% of samples. Lisreria spp were detected on 69% of loins and on 33% of chops. The sanitizing treatments were of relatively limited effectiveness for long term storage. No pH, TBA or sensory quality differences were observed.

Microbiological, chemical, physical and sensory attributes of beef rib eye steaks packaged in air, vacuum or combinations of %Oa-%COa (lo-20,20-20,10-40,20-40), were examined during storage at 2" -4" C. Modified atmosphere (MAs) changes over time were measured. Oxygen concentration decreased while CO* increased during storage, for all MAs. Vacuum was superior to MAs in delaying bacterial growth other than that of Enterobacteriaceae, in protecting beef color and lipids against oxidation and in maintaining sensory attributes in steaks. MAs were superior to packaging in air for all parameters tested, and to vacuum only in that Enterobucteriuceae were strongly inhibited, purge losses decreased by 50% and cooking yields increased. High-CO* MAs (40%) did not impair beef color, but COa promoted lipid oxidation. Volatile basic nitrogen (VBN) did not indicate beef freshness.

This study was undertaken to develop a modified atmosphere package to control microbial growth in ready-to-eat (RTE) products stored at ambient temperature. Ethanol and/or limonene associated with modified atmosphere (CO 2 : O 2 : N 2 = 30% : 5% : 65%) was used to inhibit the growth of total air-borne microorganisms and Escherichia coli in RTE products stored at 25°C. The results indicated that 0.05% ethanol vapour in the headspace was effective to inhibit the growth of airborne microorganisms and E. coli at 25°C for 72 h in a model study, and the effectiveness was related to ethanol content. Both 73 ppm limonene and 0.05% ethanol vapour enhanced the bacteriostatic effect of modified atmosphere in RTE sushi roll products, and no off-flavour was detected using this formulated gas; however, no significant inhibitory effect was observed for RTE cold noodle products. This study concludes that combinations of carbon dioxide, ethanol or limonene vapours are effective to inhibit microbial growth in RTE food at ambient temperature, and the outcome may be due to the hurdle effect.