At the commencement of this study, some sensitive overseas markets were rejecting chilled vacuum-packed New Zealand lamb due to higher than expected total viable counts, and counts of Enterobacteriaceae, a family of bacteria used to indicate sanitary condition. Of the many factors that influence the bacterial composition of chilled lamb in the overseas marketplace, the meat producer can only exert significant control over: Hygiene, ensuring the bacterial viable count on the meat prior to packaging is as low as possible, and comprised of as few species as possible that are capable of anaerobic growth at chilled meat temperatures. Maintaining the pH of the meat within acceptable limits, by careful animal selection and minimal pre-slaughter stress. Refrigeration temperatures, through rigorous maintenance of the cold-chain. The type of preservative packaging used, which is often limited by regulation in the marketplace. Initial work established that the bacterial microbiota present on the meat contact surfaces in the butchering facilities at some premises, in particular conveyor belting, was excessive and comprised of species that contributed to the high counts on the meat reported above. As a means of improving the hygiene of this process, this study investigated the hypothesis that some species of bacteria were able to form biofilms on the conveyor belt contact surfaces, becoming reservoirs for cross-contamination. This hypothesis was not been proven by this work; the results showing that biofilms were not present and that adequate hygiene of these surfaces instead depends on the ability to remove all meat-based residues from them at the completion of each day's processing. For premises operating interlocking belts from one manufacturer (Intraloxreg), a clean-in-place system is now available that is able to achieve this. Premises operating conventional disinfectant and water sanitisation of either continuous or interlocking belts must ensure that meat residue is completely removed before disinfection. The majority of New Zealand meat industry premises can now demonstrate that their hygienic processes in this area are under control. The microbiota of conveyor belting in this study was found to consist of bacteria from five taxonomic groups; the Flavobacteriaceae, the Actinomycetales, the Bacillus/Clostridium group, and the alpha and gamma branches of the Proteobacteria. The genera present on belts from premises whose hygiene was found to be in control did not contain species known to cause food-borne disease or spoilage of vacuum packaged meats. The bacterial viable count remains the most effective method available at this time for monitoring conveyor belt hygiene. Attempts to develop a monitoring system based on microscopy of an in-situ sampling device were unsuccessful due to an inability to penetrate the meat residue matrix. Denaturing Gradient Gel Electrophoresis (DGGE) may offer an alternative for rapid investigation of diversity, but further work is required before this can be validated for routine use.
| Identifer | oai:union.ndltd.org:ADTP/238104 |
| Date | January 2007 |
| Creators | Mills, John |
| Publisher | The University of Waikato |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://www.waikato.ac.nz/library/research_commons/rc_about.shtml#copyright |
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