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There is growing interest in centralized preparation of retail-ready meat cuts for distribution to widely dispersed retail stores due to the convenience of having high-quality ready-to-go products that are consistently provided to consumers at lower cost. Various centralized packaging techniques are described. Of all packaging techniques, master packaging is the most economical and shows promise for commercial application. Nevertheless, the master-packaging technique must be integrated with strict temperature control in a narrow range just above freezing (- 1.5 +/- 0.5 degrees C), good processing hygiene, and maintenance of a completely anoxic atmosphere in the package headspace throughout the distribution period to maximize storage life. Packaging using the CAPTECH process reduces the residual O2 present in the headspace to 300 ppm. Oxygen scavengers must be incorporated in the package to absorb the residual O2 and preserve the metmyoglobin reducing activity of meat tissues. Integration of all these technologies can provide a storage life of retail-ready meat up to 10 weeks in the master package followed by 3 days of retail display life. This extension of storage life is sufficient for transporting meat to distant markets.

Use of pulsed electric fields (PEFs) for inactivation of microorganisms is one of the more promising nonthermal processing methods. Inactivation of microorganisms exposed to high-voltage PEFs is related to the electromechanical instability of the cell membrane. Electric field strength and treatment time are the two most important factors involved in PEF processing. Encouraging results are reported at the laboratory level, but scaling up to the industrial level escalates the cost of the command charging power supply and of the high-speed electrical switch. In this paper, we critically review the results of earlier experimental studies on PEFs and we suggest the future work that is required in this field. Inactivation tests in viscous foods and in liquid food containing particulates must be conducted. A successful continuous PEF processing system for industrial applications has yet to be designed. The high initial cost of setting up the PEF processing system is the major obstacle confronting those who would encourage the system's industrial application. Innovative developments in high-voltage pulse technology will reduce the cost of pulse generation and will make PEF processing competitive with thermal-processing methods.

Unsliced beef pastrami, reformulated ham and bologna held at 6 degrees C were sliced 21, 17, 12 or 7 days before or at the assigned manufacturer's best before date and vacuum packaged. Packages of sliced meats were held at 6 degrees C for another 7, 12, 17 or 21 days, opened and analyses made for total bacteria, lactic acid bacteria, Enterobacteriaceae and Brochothrix thermosphacta. The maximum storage interval was 42 days; half this period unsliced, the remainder as repacked slices. Numbers of bacteria on pastrami were significantly greater than on ham and bologna (pastrami > ham > bologna) with the lactic acid bacteria dominating in all products. As unsliced meats approached their best before date, insignificant increases were generally noted for numbers of lactic bacteria, Enterobacteriaceae and B. thermosphacta. During subsequent storage of slices under vacuum, numbers of total and lactic bacteria increased exponentially at the same rate while B. thermosphacta growth was significantly slower. Numbers of Enterobacteriaceae remained low and were essentially unchanged during sliced meat storage. Within the context of study storage parameters, shelf-life appeared to be determined by length of time after slicing and repackaging rather than by best before date of the unsliced meat. Packages of sliced meat prepared from wholesale unsliced meats with 21 days left until their best before date or from unsliced meats with 12 days left until the best before date showed similar bacterial levels 21 days later. It was probable that the localization of bacterial growth at the meat surface-packaging film interface of the unsliced meats yielded slices with initially lowered bacterial content when repackaged and sampled from the uppermost slice. When Enterobacteriaceae and B. thermosphacta were absent from unsliced meats, extension of sliced meat package shelf-life beyond the best before date of the parent meat was possible. However, these bacterial groups were not always undetected.

Escherichia coli 157:H7 has evolved as an important foodborne pathogen since its initial description in 1982. Outbreaks of illness associated with E. coli O157:H7 have been reported throughout the northern hemisphere, most frequently in Canada, the United States, Japan, and the United Kingdom. In Canada, infections due to E. coli O157: H7 appear to be more common in the western provinces than in the east, in rural vs. urban environments, and during summer as opposed to winter months. Undercooked ground beef has been implicated as the primary vehicle in E. coli O157:H7 infection, but contaminated fruits, vegetables and water have also been linked to E. coli O157:H7 outbreaks. Epidemiological investigations demonstrate that dairy and beef cattle are primary reservoirs of this organism, carrying it asymptomatically and shedding it intermittently and seasonally in their feces. Surveys in Canada and the United States indicate widespread distribution of E. coli O157:H7 in cattle operations. The prevalence of E. coli O157:H7 in cattle has been increasing in recent reports, likely due to the development of more sensitive methods for the detection of the organism. Escherichia coli O157:H7 has been isolated from feed, water for livestock, manure, soil and flies, all of which represent potential sources of contamination for cattle and their environment. To date, effective methods for controlling E. coli O157:H7 in cattle have not been identified, although dietary manipulation, vaccination and bacteriophage therapy have been reported to have potential as intervention strategies. Effective control of E. coli O157:H7 requires reducing the frequency and intensity of fecal shedding of this pathogen by cattle, in addition to targeting environmental sources of the organism. Key words: Escherichia coli O157:H7, cattle, sources, diet, transmission