Abstract:
The rapid and accurate identification of microorganisms is essential to providing important information for downstream decision making in the food industry. Current methods used to detect and identify bacterial species tend to be slow and/or expensive. The aim of this thesis is to investigate the use of a near real time all-fibre fluorometer to detect fluorescently stained bacterial samples as a novel detection system for microbial contamination on meat. To reach this aim, a series of experiments were conducted in this thesis to test the hypothesis that the optrode, a novel fibre-optic based system, is capable of detecting bacterial species using fluorescent emissions from the SYTO 9 and Propidium iodide (PI) fluorescent stains, and using these emissions for identification purposes. Pure bacterial cultures of six species of interest to the meat industry were stained using SYTO 9, and their emission spectrum was collected using the optrode. Bacterial endospores are also potential contaminants during meat processing and are capable of changing into a variety of viability states; germination into vegetative bacterial cells, heat activation allowing for more rapid germination, remaining as dormant endospores, and death. These viability states were induced and detected using both SYTO 9 and PI to determine if the emission spectrum changes depending on the viability state, which can be used to identify the state of endospores during cold storage of meat products. A meat swab sampling model was then created to allow a laboratory scale meat contamination to be used to determine the capabilities of the optrode when detecting bacterial species on meat products. The work in this thesis has shown that the optrode is capable of detecting bacterial vegetative cells and bacterial endospores using SYTO 9 fluorescent emission, in both laboratory conditions and those mimicking the conditions found in the meat industry. However, the specificity of the SYTO 9 emission spectrum is not sensitive enough to distinguish between different microbial species, and the limit of detection for the optrode is not low enough for accurate detection of low bacterial concentrations seen on contaminated meat products.
