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Assessment of freshness and quality of meat and fish is a major activity of both food regulatory agencies and the food industry. Various methods are used for measuring fish and meat quality, each with its particular advantages and limitations. However, methods based on monitoring the products of proteolysis have received relatively little attention. The objective of the present study was to identify specific protein and peptide products of proteolysis as indicators of freshness and quality during chilled storage of fresh fish and meat. / Samples of meat and fish were subjected to chilled storage; at intervals of 0, 2, 4, 8, 12 and 16 days, samples were subjected to protein and peptide extraction, and separation of individual sarcoplasmic and myofibrillar proteins by SDS and native electrophoresis. These extracted proteins along with acid soluble nitrogen (ASN) were separated by RP-HPLC, fractions were collected and identified by electrospray ionization mass spectrometry (ESI-MS). / RP-HPLC separated at least thirty fractions from the ASN extract of fresh fish. ESI-MS revealed the presence of at least twenty-five polypeptides with molecular weights (MW) ranging from 2 to 32 kDa. The relative area % of the polypeptides with MW 32.8 kDa and 42.8 kDa decreased during the storage while polypeptides of MW of 10.9 kDa and 16.7 kDa increased during storage. Changes in polypeptides of MW 12, 34.2 and 42.8 kDa was also observed. The sarcoplasmic protein extracted from ground and whole meat contained at least 12 polypeptides with MW ranging from 11 to 42 kDa. The relative area % of polypeptide of MW of 35.7 kDa decreased during storage. The results suggest that changes in proteins and polypeptides of MW 10.9, 12, 16.7, 32.8, 34.2 and 42.88 kDa in fish and 35.7 kDa in meat could serve as indicators of spoilage.

Previous results indicated that lactic acid bacteria (LAB) and Bacillus spores were the predominant spoilage microorganisms in minimally processed products after 35 days storage at 15$ sp circ$C. Furthermore, most packages were swollen due to carbon dioxide production by the LAB. The fact that spores survived mild heat treatment is of concern since it implies that other more pathogenic spores, e.g. Clostridium botulinum would also survive and may pose a public health problem in products stored at 15$ sp circ$C. As such, the influence of combination treatments (viz., mild heat processing treatment, pH, water activity, storage temperature, lactic acid bacteria) were evaluated through challenge studies with selected strains of C. botulinum type A, B, and E spores. The shelf life and safety of the products following a 13D process at 75$ sp circ$C, could be extended to $ ge$42 days by a combination of pH $ le$ 5.0 and storage at 5$ sp circ$C. Other combination treatments were also effective in controlling growth of, and toxin formation in the products by C. botulinum. For instance, botulinum toxin was not detected until day 35 in inoculated spaghetti and meat sauce products (pH 5.25 and a$ sb{w}$ 0.992) with type A and B spores and stored at 15$ sp circ$C. Shelf life extension and inhibition of toxin production was also possible through reductions in a$ sb{w}$ levels achieved by addition of 1-3% salt (w/w) to the products. Water activity levels of $ le$0.983 prevented botulinum toxin production in the minimally processed spaghetti and meat sauce product for $ ge$42 days during storage at 15$ sp circ$C. / Similar trends were observed in sous-vide rice and salmon products. Furthermore, when sodium lactate was used as the humectant to lower the a$ sb{w}$ of this product, toxin production was also delayed, but not to the same extent as achieved with NaCl. When two strains of bacteriocin-producing lactic acid bacteria were co-inoculated separately in the sous-vide rice and salmon products that had been challenged with C. botulinum type E spores, toxin formation was only slightly delayed in products with added NaCl (1%), while toxin formation was neither delayed nor prevented in similarly lactic acid bacteria-treated samples with no added NaCl. Furthermore, in most of the products in which botulinum toxin was detected, spoilage preceded toxigenesis, however, in some samples stored at 5$ sp circ$C toxigenesis preceded spoilage. Addition of $ alpha$-2-macroglobulin at a level of 2.7 ppm did not delay or prevent toxin formation in the product. Microwave heating of products at half-power or full power (800 Watts) for 5 to 10 min proved effective in inactivating all of the pre-formed toxin in toxic samples. (Abstract shortened by UMI.)

Dissertation (PhD)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1999. / Typescript. Vita. Includes bibliographical references (leaves 216-235). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1999. / Typescript. Vita. Includes bibliographical references (leaves 216-235). Also available on the Internet.

Thesis (Ph.D.) - University of St Andrews, June 2009.

Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2016. / Microbial spoilage has been reported in various food products and this has led to increased food, fruit and beverage losses, thereby threatening economic growth, food safety and security. Furthermore, statistics have shown that more than 30% of agricultural produce in developing countries, mostly in Africa, is lost owing to microbial spoilage. Beverages, food and fruits are predominant contributors to the South African export market. In recent years, contamination of these products resulting in spoilage has been a problem, although partial spoilage control has been achieved using chemical preservatives such as dimethyl dicarbonate, sodium benzoate, potassium sorbate, and sulphur dioxide (SO2). However, prolonged exposure to these chemical preservatives can cause human health problems such as skin and/or eyesight damage, muscle and stomach pain, cardiovascular disease and the impairment of brain function. To mitigate such health concerns, biologically benign alternatives are deemed suitable, providing the rationale for this study.

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