Graduation date: 1933

Thesis (Msc Food Sc (Food Science))--University of Stellenbosch, 2006. / Consumers demand beef products of consistent and satisfactory tenderness, acceptable meat colour, the necessary nutritional value, as well as being microbiologically safe. However, inconsistency in meat quality, and particularly tenderness, is a problem that has continuously plagued the meat industry Firstly, an investigation was undertaken to determine the muscle variation, particularly in the tenderness of South African beef muscles. Beef muscles were removed from the right-side of beef carcasses and the physical, chemical and sensory characteristics determined 72 h post-mortem. As the beef muscles differed significantly (P≤0.05) in these attributes, the need for increased attention to enhanced processing and meat ageing is accentuated. Therefore, two further investigations were executed, including an enhancement study and a shelf-life study. The enhancement study determined the time effect of a blend of sodium and potassium salts, various phosphates and lactates on the physical quality, chemical composition and sensory quality of South African beef muscles. The corresponding muscles were removed from the left-side of the same beef carcasses and infused 3 d postmortem. The changes in beef quality over 19 d and the initial proximate and mineral composition were determined. The infused beef increased in tenderness, while maintaining an acceptable red colour. The infused muscles had higher moisture and ash contents, and lower lipid and protein contents. The mineral content of the treated muscles increased due to the minerals contained in the infusion blend. For the sensory analysis, beef muscles were stored under vacuum for 24 h (4°C) until the physical data had been collected. Thereafter, the muscles were stored at −18°C until the descriptive sensory analysis could be performed. The infusion of beef muscles successfully enhanced the sensory attributes, resulting in significantly (P≤0.05) more juicy and tender beef. When used in a consumer preference test, the infused samples illustrated a significantly (P≤0.05) higher degree of liking. In the shelf-life study the effect of the blend on the physical attributes, proximate composition and microbial growth of South African beef muscle was determined. One muscle from the left-side of beef carcasses was infused 4 d post-mortem. The purge loss, colour changes and the microbial growth on the muscle steaks over 10 d (overwrap storage) was determined. The infused muscle showed greater colour loss (lower a*, b* and chroma values) during the 10-d period. Physical analysis (purge loss) indicated a significant difference (P≤0.05), with the treated sample losing 2.78% more purge. The infusion extended the microbiological shelf-life of beef by 1 d. Improvement of beef quality and its consistency is essential for the survival of the beef industry. The infusion of beef muscles has the potential to improve the current status of low meat consumption and inconsistent tenderness of fresh beef in South Africa. Despite decreased colour stability in the infused steaks, negatively affecting the purchasing decision of the consumer, the blend could still be applied successfully in the South African meat industry to extend the shelf-life of fresh beef and improve meat quality attributes, providing the consumer with a more acceptable beef product.

Flow injection analysis offers distinct advantages in reproducibility, flexibility, sample throughput and cost performance. Since it was introduced in 1975, there are more than 10 000 publications to date. The present study focuses on the development of process analysers for the determination of nitrogen compounds (namely, nitrate, nitrite and protein), nickel, and phosphate in various combination in samples originating from various fields, such as foodstuffs, water, and fertilisers. Nitrite is potentially unstable; it decomposes with time under acidic medium with an increase in decomposition rate as the concentration of acid increases. Raman spectroscopy was employed as a means of determining the rate of decomposition of nitrite in solutions at various pH values. A simple method for the determination of nitrite in foodstuffs by flow injection analysis (FIA) is described. The foodstuffs containing nitrite are digested in a microwave oven and then treated with 1 moℓ/Q NH4CI solution at pH 9. The simultaneous determination of nitrate and nitrite in foodstuffs and water was also studied. Cadmium (coarse powder) was used to reduce nitrate to nitrite. The effect of pH, length of reductor column, and various types of cadmium reductor on the yield of nitrite are investigated. The flow injection method was developed for the spectrophotometric determination of nickel in cured meat. Dimethylglyoxime (DMG) in acetate buffer at pH 6.4 nickel forms a red complex which is measured at 475 nm. The effects of chemical and physical parameters in flow injection analysis were studied. A new bienzymatic amperometric sensor is proposed for the assay of proteins in milk. The sensor is based on two enzymes, namely, carboxypeptidases A and L-amino acid oxidase. The use of flow injection analysis and Raman spectroscopy for the determination of phosphate in foodstuffs and fertilisers, is also compared in this study. / Thesis (PhD (Chemistry))--University of Pretoria, 2007. / Chemistry / unrestricted