Contamination of meat with microorganisms during slaughter is inevitable. Hygiene management systems (HMSs) such as the Hygiene Assessment System (HAS) and Hazard Analysis Critical Control Point (HACCP) are used to prevent the contamination of beef with both spoilage and pathogenic microorganisms during slaughter. This study compared the effect of the HAS alone and a combination of HAS + HACCP on the microbiological quality of beef and investigated the survival of Escherichia coli O157:H7 co-cultured with different levels of Pseudomonas fluorescens and Lactobacillus plantarum on fresh beef. HAS alone and HAS combined with HACCP systems were each represented by two abattoirs. Sponge swab samples were collected from chilled beef carcasses for indicator organisms: Aerobic Plate Counts (APC), Enterobacteriaceae, Pseudomonas spp., and lactic acid bacteria. Swabs were also collected for pathogenic bacteria: E. coli O157:H7, Staphylococcus aureus and Salmonella spp. There was no significant difference between the microbiological quality of beef carcasses processed in the abattoirs with the HAS and that of beef carcasses processed in abattoirs with combined HAS + HACCP. E. coli O157:H7 was isolated from carcasses processed in an abattoir with the combined HAS + HACCP system. Moreover, although overall S. aureus counts at all abattoirs were comparable, a higher incidence (47% of carcasses) was obtained from an abattoir with combined HAS + HACCP. Salmonella spp. was not detected during the study. The microbiological quality of beef at HAS abattoirs is not significantly different to that of beef processed at HAS + HACCP abattoirs. The combined HAS + HACCP did not prevent contamination of beef carcasses with E. coli O157:H7 and S. aureus. Effective implementation of HAS can reduce contamination of beef with spoilage and pathogenic microorganisms. The effect of different levels of P. fluorescens (102 and 106 log10 cfu/ml) and L. plantarum (102 and 104 log10 cfu/ml) on the survival of E. coli O157:H7 on beef loins was investigated. Sterile beef loins inoculated with E. coli O157:H7 and P. fluorescens were aerobically stored for 7 days at 4°C, while those inoculated with E. coli O157:H7 and L. plantarum were vacuum-packaged and stored for 8 weeks at 4°C. APC, E. coli O157:H7 and either P. fluorescens or L. plantarum counts were determined at different storage intervals. For the aerobically packaged beef loins, E. coli O157:H7 was detected throughout the 7-day storage period regardless of the P. fluorescens level in the inoculum. For the vacuum packaged beef loins, similar inoculum levels of E. coli O157:H7 and L. plantarum allowed E. coli O157:H7 to survive until week 5 of storage, while a higher inoculum level of L. plantarum inhibited E. coli O157:H7 from week 3. Once fresh beef has been contaminated with E. coli O157:H7 the level of P. fluorescens in the background flora does not inhibit its survival and growth. However, under vacuum storage, the application of L. plantarum as a biopreservative inhibits the survival of E. coli O157:H7 on beef. Comprehensive strengthening of preventive strategies is required to eliminate contamination of beef carcasses with E. coli O157:H7. Bacterial contamination of carcasses during slaughter is inevitable. Effective implementation of HAS at abattoirs produces beef carcasses of microbiological quality comparable to that produced through the use of combined HAS and HACCP. While the level of P. fluorescens on beef does not inhibit the survival of E. coli O157:H7 on aerobically stored beef, the combination of L. plantarum, and low storage temperature inhibits the survival of this pathogen on beef under vacuum storage. / Thesis (PhD)--University of Pretoria, 2011. / Food Science / unrestricted

The influence on eating quality of beef of cooking method, sires, mineral (Fe, Mg, Zn, Na, K, and P), lipid, and nitrogen content was determined by objective measurements, sensory evaluations, cooking losses, and chemical analysis. Two adjacent arm and two adjacent rib roasts from 18 Herford animals were used. The arm and rib (sixth to eighth ribs) roasts were deboned, cut in half, and randomly assigned to the conventional or electronic ovens for dry roasting to the medium-rare stage (145 F, 147 F). Roasts of the ninth to twelfth ribs were dry-roasted in a meat research oven at 325 F to an internal temperature of 155 F. The Warner-Bratzler shear test determined tenderness to be greater in conventional roasts, Press fluid amounts were similar for both ovens. Cooking losses were greatest in the electronic oven. The taste panel judged conventional roasts to have better flavor and to be more tender and juicy. Laboratory analysis of minerals indicated specific ones influenced the tenderness of beef, Lipid content was found to be significantly correlated with juiciness, tenderness, shear force, and percentage drip. The findings showed nitrogen to affect juiciness inversely and the cooking losses positively. High correlations for roasts containing the ninth to twelfth ribs were indicated for flavor, tenderness, and shear force; also tenderness was judged by the taste panel with shear force, and press fluid with cooking loss.

Internal and external factors affect the quality of meat, however ageing affects final product. Main objective of this work was to determine the effects of ageing on selected physical factors (pH, colour, water holding capacity and texture shear force) which affect meat quality from consumer and further meat processing perspective. Measuring of those factors was performed in periodical time sequences (one day post-mortem and 14 days of ageing) and factors of raw and heat-modified meat were measured. There were two hundred and fifty-eight samples from Czech pied cattle used in research. Musculus longissimus lumborum et thoracis (sirloin) was analyzed. Statistically high shear force difference (P=0.001) was identified at heat-modified and aged samples (decrease from 22.574 kg to 14.885 kg). Decrease of shear force during ageing of raw meat samples was observed at normal pH (pH < 5.8) beef ? from 6.403 kg to 5.982 kg. Correlations between pH and water holding capacity was found at samples which undergone ageing (r = 0.879 ***) and also at one day post-mortem samples (r = 0.872 ***). Middle correlation was observed between colour and pH at all colour parameters ? L* (r = -0.479 ***), a* (r = -0.478 ***) and b* (r = -0.581 ***). Water holding capacity and pH have influence on shear force of raw beef and also heat-modified beef; this was confirmed by correlation analysis. Lightness (L*) and water holding capacity affect heat-modified samples texture which was confirmed with multi-regression linear analysis (R2 = 0.565). As shown above the influence of meat ageing on quality parameters is high and properly aged meat from young bulls has better texture values. If the aged beef will be sold regularly it could be expected that consumer demand will increase especially due to remove the inconsistency of the quality of beef.