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.

Milk is an important nutritious component of our diet consumed by most humans on a daily basis. Microbiological spoilage affects its safe use and consumption, its organoleptic properties and is a major part of its quality control process. European Union legislation and the Hazard Analysis and the Critical Control Point (HACCP) system in the dairy industry are therefore in place to maintain both the safety and the quality of milk production in the dairy industry. A main limitation of currently used methods of milk spoilage detection in the dairy industry is the time-consuming and sometimes laborious turnover of results. Attenuated total reflectance (ATR) and high throughput (HT) Fourier transform infrared (FTIR) spectroscopy metabolic fingerprinting techniques were investigated for their speed and accuracy in the enumeration of viable bacteria in fresh pasteurized cows' milk. Data analysis was performed using principal component-discriminant function analysis (PC-DFA) and partial least squares (PLS) multivariate statistical techniques. Accurate viable microbial loads were rapidly obtained after minimal sample preparation, especially when FTIR was combined with PLS, making it a promising technique for routine use by the dairy industry. FTIR and Raman spectroscopies in combination with multivariate techniques were also explored as rapid detection and enumeration techniques of S. aureus, a common milk pathogen, and Lactococcus lactis subsp cremoris, a common lactic acid bacterium (LAB) and potential antagonist of S. aureus, in ultra-heat treatment milk. In addition, the potential growth interaction between the two organisms was investigated. FTIR spectroscopy in combination with PLS and kernel PLS (KPLS) appeared to have the greatest potential with good discrimination and enumeration attributes for the two bacterial species even when in co-culture without previous separation. Furthermore, it was shown that the metabolic effect of L. cremoris predominates when in co-culture with S. aureus in milk but with minimal converse growth interaction between the two microorganisms and therefore potential implications in the manufacture of dairy products using LAB. The widespread and high consumption of milk make it a target for potential financial gain through adulteration with cheaper products reducing quality, breaking labeling and patent laws and potentially leading to dire health consequences. The time consuming and laborious nature of currently used analytical techniques in milk authentication enabled the study of FTIR spectroscopy and matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-ToF-MS) as rapid analytical techniques in quantification of milk adulteration, using binary and tertiary fresh whole cows', goats' and sheep's milk mixture samples. Chemometric data analysis was performed using PLS and KPLS multivariate analyses. Overall, results indicated that both techniques have excellent enumeration and detection attributes for use in milk adulteration with good prospects for potential use in the dairy industry.

Surface-enhanced Raman spectroscopy (SERS) is an emerging and sensitive technique in food analysis providing advantages of rapid detection, simple sample preparation and on-site detection capability over GC and LC methods. Most SERS applications focus on detecting trace amount of analyte in liquid as an alternative approach to HPLC. Herein, we invented an innovative SERS-active needle which is composed with an injection needle and a gold-nanoparticles coated fiber inside the injection needle. The gold nanoparticles-coated fiber was fabricated by reducing gold (III) on a chemically etched stainless wire. The SERS needle can be used to insert into the headspace and liquid sample for simultaneous multiphase sample detection, or a soft tissue like a tomato fruit to detect the analyte inside of the tissue with minimum invasion. Using this needle, we can detect as low as 5 ppb of fonofos in the headspace of water and apple juice samples, compared with the dip method, which cannot detect lower than 10 ppb in water and 50 ppb in apple juice. The SERS needle was also applied in real time pesticide translocation study to monitor internalized thiabendazole in tomato fruit after root uptake. The SERS needle detected thiabendazole inside tomato fruits 30 days after the pesticide exposure in a hydroponic planting environment. Moreover, realizing the advantage of detecting volatile components in the headspace of food sample, we applied the SERS needle in a ground beef spoilage study to detect the spoilage biomarkers in the headspace of the raw beef. As a result, the SERS needle detected volatile spoilage compounds produced by bacteria Lactobacillus. Overall, this invention opens a new field of SERS strategy for broad analytical applications.

No description available.

No description available.

No description available.

No description available.