Surface analysis of buna-N-rubber and teflon was performed. Scanning electron microscopy was used to analyze the topography of both materials and x-ray microanalysis identified the elemental chemical composition of the polymers. Teflon was primarily a smooth surface with random irregular spots, while buna-N-rubber had a very rough topography with "caverns" and crevices spread over the surface. The x-ray microanalysis showed that there are no impurities on the surface of teflon; however, calcium, silicone and sulfur were present on the surface of buna-N-rubber. Water contact angle measurements indicated that buna-N-rubber was a more hydrophobic surface than teflon. Qualitative analysis of the attachment of Pseudomonas fragi A TCC 4973, Listeria monocytogenes Scott A and Bacillus cereus ATCC 11778 to buna-N-rubber and teflon was assessed by scanning electron microscopy. These bacteria readily attached to both surfaces. Pseudomonas fragi attached after 2 hours in the presence of this microoorganism and Bacillus cereus and Listeria monocytogenes attached at 12 and 24 hours, respectively. Quantitative analysis of the attachment of Pseudomonas fragi to both surfaces as affected by various milk fat concentrations and temperature, and the availability of nutrients (different dilutions of skim milk, casein, casein and lactose, and whey and lactose) was conducted. Attachment was assessed by impedance microbiology. Milk fat content did not play a significant role in the process of attachment of this organism to either type of surfaces; however, significantly greater numbers attached to buna-N-rubber than to teflon. Overall bacteria attached in higher numbers to both surfaces when grown at 21°C, compared to bacteria grown at 4°C. For buna-N-rubber, bacteria attached in significantly higher numbers when the concentration of nutrients was minimal, while for teflon, the results were, in most cases, opposite to these. / Ph. D.

Variations in ATP content in three ground beef spoilage bacteria, Lactobacillus brevis, Lactobacillus jensenii, and Pseudomonas sp. were investigated using the bioluminescence (luciferin-luciferase) assay. Environmental factors (temperature, atmosphere, pH, aeration, and phase of growth), as well as differences among genera and species, were studied in relation to their effect on cellular ATP. Variations for each of the environmental factors and bacteria were shown statistically to be significantly different at the 0.05 level. The mean ATP/cell for each of the bacteria was 2.71 fg/cell (L. brevis), 2.20 fg/cell (L. jensenii), and 1.36 fg/cell (Pseudomonas sp.). For all three bacteria, ATP/cell was lower and more stable throughout the culture's growth cycle at 3°C or in N₂. In general, ATP/cell increases from a lowest value in lag phase to a highest value in stationary phase. The effect of sonication on ATP/cell was tested for each bacterium at one set of factors. Sonication studies showed that L. brevis cells were clumping, especially in aged cultures. After sonication, ATP/cell remained relatively constant from lag through stationary phase. L. jensenii showed no signs of clumping and ATP/cell increased as the culture aged. Sonication had a lethal effect on the Pseudomonas. Thus the ATP/cell for Pseudomonas increased dramatically as the culture aged. Guidelines concerning temperature, assumed ATP content for major contaminants, and sample handling must be followed in order to use the bioluminescence assay to estimate biomass in foods. / M.S.

The use of the multi-mycotoxin screen based on dialysis to analyze foods and feeds for mycotoxins, is well documented. This study investigated the possibility of incorporating FB I into the screen. Maize meal (25g) was spiked with AFB I , CPA, FB1, ST and ZEA and extraction was done using acetonitrile/4% potassium chloride (90:10 v/v). The recoveriesof the mycotoxins were 77.4, 61.5, 97.4, 79.8 and 98% respectively on analysis by HPLC. Fumonisin B1 could not be completely incorporated into the screen due to its reaction with sodium hydrogen carbonate, which is a component in the method. Thus, FB I was determined in a separate portion of the extract. The high cost of FBI standards which are often of inferior purity necessitated that FB I standards be locally produced in the laboratory using Fusarium moniliforme MRC 826, a good producer of FB 1 . In this study, production of FB I was carried out using a stirred jar fermenter and patty cultures. The yields were 160mg/1 and 6mg/g of FB I for the two methods respectively. Methyl esterification of tricaballylic acid moieties of FB I was done for effective clean-up. This was achieved by derivatizing FBI, with diazomethane. It was found that other functional groups besides the tricaballylic acid moieties of FB I were undesirably methylated as well, which made cleanup by this method difficult as shown by electrospray mass spectrometric analysis. Attempts to de-methylate FBI methyl esters with esterase was not successful. Analysis of human faecal samples was carried out with the view of developing a short term marker for assessing human exposure to FB I . Faeces from rural (20) and urban (23) volunteers were analyzed by high performance liquid chromatography. The results showed that 35% of the rural samples and 9% of the urban volunteers had detectable amounts of FB I ranging from 0.600 to 19.56 mg/kg. There was a significant difference (p = 0.04)between the two population groups. A study was carried out to assess the occurrence of FBI in a rural area of Tugela valley in Kranskop magisterial district of KwaZulu Natal. A questionnaire was administered to gather information on the family health and nutrition. Raw (stored) and processed foods and faeces, were collected for analysis of FB1. A similar control study was carried out in the urban area of Durban Metro. Homes were mapped out using the GIS for easy follow up. Oesphageal cancer (OC) incidence from the local hospital and weather data for the study area were collected from South African Weather Bureau, Johannesburg. The questionnaire results showed that the common diseases were mainly of respiratory origin (24% and 26%) from both rural and urban groups respectively. Food analysis (by HPLC) showed that the number of maize samples with FB I were higher in the rural area (31.9%) in comparison to the urban samples (6.1%). The level ranged from 0.092-22.225 mg/kg in food and 0.513-39 mg/kg in faeces. The mean concentration of FB i in the faeces and maize samples showed a similar significant difference of 0.014 between the two groups. However, these concentrations were much lower than those of high OC area in Transkei (117 mg/kg). There was no detection of FBI in fermented food products. / Thesis (M.Med.Sci.)-University of Natal, Durban, 1998.

Call number: LD2668 .T4 1979 S23 / Master of Science

In order to gain a better understanding of the mechanism of As(V) tolerance in rice, a number of hydroponic tolerance tests have been done on the interaction of As(V) with phosphate (PO₄^3-), reduced glutathione (GSH) and O₂ supply.  The PO₄^3—As(V) interaction test revealed that increasing PO₄^3- concentration reduces the toxicity of As(V).  Low PO₄^3- (0.05 mM) showed no protection against As(V) induced root inhibition, but higher PO₄^3- (0.5 and 5 mM) showed marked protection, suggesting PO₄^3- derived tolerance is not due to reduced PO₄^3- transport that has been postulated in other grass species.  The glutathione (GSH)-As(V) interaction test revealed a strong effect of GSH, increasing tolerance in rice.  The O₂ supply test also revealed a significant effect with enhanced tolerance in rice.  Therefore it can be suggested that PO₄^3-, GSH and air bubbling supply all reduces As(V) toxicity in rice by increasing tolerance.  The protection against As(V) provided by GSH and PO₄^3- were not the same for two rice varieties, Azucena (As sensitive) and Bala (As tolerant).  However these tolerance tests cannot explain why Azucena and Bala differ in susceptibility to As(V).  Three green house pot experiments revealed that As(V) treatment reduces growth in dose dependent way.  Total As concentration in the shoots and grain increases with the increasing concentration of the As(V) treatments.  Surprisingly, application of PO₄^3- does not alter As(V) toxicity.  Anaerobic (lowland) soil shows higher shoot As concentration but uptake is lower.  Rice genotypes show significant variation in their plant growth, total shoot As concentration and total As uptake which reveal that tolerant genotypes contain higher shoot As. Results of the hydroponics and pot experiments suggested that tolerance of rice is not derived from competition with As(V) at the PO₄^3- transporters, but rather reflects another, as yet unknown, mechanism.

This is the first study to compare total arsenic (As) and other trace elements in the agricultural soils and grain of Eastern, Western and Southern Libya, North Africa and the Middle East (NA &amp; MIDEA). Soil pot experiments and field experiments were conducted to determine the levels of As within wheat grains in Libya. In the soil pot experiments, wheat genotypes were planted in similar soils and yet differences in grain As concentration were found among the cultivars. The highest As accumulation was found in <i>T. durum; </i>however, in the field data the highest levels were found in <i>T. aestrivum.</i> The levels of As and other trace elements found in agricultural soils from the Eastern Western and Southern regions of Libya are examined. Mean As concentrations in the clay mineral agricultural soils of the Eastern Region were nearly 4.8 and 4.1 times higher than in the southern and western regions, respectively. It is possible that the parent material of that region contains elevated levels of As, which are then exhibited in the overlying soil. Differences in the levels of As and other trace elements found in the irrigated agricultural soil of Southern Libya were compared with non-irrigated soil from the same region.  Concentrations of P, Zn and As in soil were higher in irrigated compared to non-irrigated soils, while the concentration of Cd is nearly the same in all soil samples. A market basket investigation was conducted to determine the total levels of As and Se in rice purchased from supermarkets. The average level of As in rice from NA &amp; MIDEA is 0.22 mg/kg, comparable with average levels in Australia.

Objective: To compare the knowledge of mothers on food contamination in the home between the towns of Peru and Costa Rica. Methods: It was conducted in a rural area of Peru (San Pablo and Huascar) in San Juan de Lurigancho in Lima, and Costa Rica (San Vicente of Three Rivers). The questions were part of a scale that was validated on an expert opinion. It was developed to measure three components or domains.After validation,the instrument was applied in Costa Rica with a group of mothers or caregivers with children under five. The application was developed in Peru in a population with similar characteristics. Results:The sample consisted of 50 caregivers in Costa Rica and 194 in Peru. There is no significant difference in the domains of contamination utensils at home (p=O.750>0.05) and knowledge of child illness (p=0.060>0.05). Knowledge of agents of contamination was highly significant (p=0.000<0.01). In general there is enough evidence to say that knowledge of food contamination in the home are different in mothers of Peru and Costa Rica, (p=0.013 <0.05). Conclusions: No significant differences on pollution and disease. There is highly significant difference in knowledge about pollutants. Overall knowledge of food contamination in the home were higher in mothers or caretakers of Peru.The scale can contribute to the planning of interventions in the aspect of pollution in the home. / michellelozadau@gmail.com / Objetivo:Compararelconocimiento de las madres sabre Ia contaminaci6n de los alimentos en elhagar entre las poblaciones de Peru y Costa Rica. Metodos:Se llev6 a cabo en una zona rural de Peru (San Pablo y Huascar) en San Juan de Lurigancho en Lima,yen Costa Rica (San Vicente de Tres rfos).Las preguntas formaron parte de una escala que fue validada bajo un juicio de expertos. Se elabor6 para medir tres componentes o dominies. Despues de Ia validaci6n, el instrumento fue aplicado en Costa Rica a un grupo de madres o cuidadoras con nifios menores a cinco anos. La aplicaci6n en Peru fue desarrollada en una poblaci6n con caracteristicas similares. Resultados: La muestra fue de 50 cuidadoras en Costa Rica y 194 en Peru. No existe diferencia significativa en los dominies sabre contaminaci6n por utensilios en el hagar (p=O,750>0,05) y por conocimiento sabre enfermedades del n1no (p=0,060 >0,05). El conocimiento sQbre agentes de contaminaci6n result6 ser altamente significative (p=0,000<0,01). En generalexiste evidencias suficientes para afirmar que el conocimiento de contaminaci6n de los alimentos en el hagar son diferentes en las madres del Peru y Costa Rica, (p=0,013<0,05). Conclusiones: No existen diferencias significativas sabre contaminaci6n y enfermedades. Existe diferencia altamente significativa en el conocimiento sabre agentes contaminantes.En general el conocimiento de contaminaci6n de los alimentos en elhogarfueron mas altas en las madres o cuidadoras del Peru. La escala puede contribuir a Ia planificaci6n de las intervenciones en elaspecto de contaminaci6n en elhagar.

No presente trabalho foram realizadas análises de enterobactérias e Salmonella em cecos e papos de frangos de corte criados sem reaproveitamento de cama e com baixa densidade, submetidos a períodos de jejum de 3, 6, 9, 12, 15 e 18 horas; também foram feitas análises das mesmas bactérias, incluindo esporos de Bacillus subtilis e bactérias ácido lácticas em papos e cecos de frangos de corte alimentados com probióticos (bactérias lácticas, Bokashi e esporos de B. subtilis) e antibiótico (bacitracina de zinco) nas rações. Não houve diferença significativa entre as populações de enterobactérias nos períodos de jejum analisados, e não foram isoladas cepas de Salmonella nos diferentes tratamentos. Houve diminuição significativa na população de enterobactérias nos cecos em relação ao grupo controle quando os frangos foram alimentados com bactérias ácido lácticas nas rações. Com Bokashi e antibiótico nas rações, a população de enterobactérias nos cecos foi maior que no grupo controle. Nos papos, não houve diferença significativa entre as populações de enterobactérias para os diferentes tratamentos, mas o tratamento com Bokashi foi o que obteve menor população das enterobactérias nesse habitat. As contagens de bactérias ácido lácticas e esporos de B. subtilis dos cecos e papos analisados não sofreram alteração significativa devido aos diferentes aditivos presentes nas rações, quando comparadas ao grupo controle. Novamente não foram isoladas cepas de Salmonella nos cecos e papos dos frangos analisados. A ausência de Salmonella pode ter explicação no modo de criação dos frangos, com baixa densidade (12 aves/m2) e sem reaproveitamento de cama, pois foi um resultado encontrado nas duas fases do trabalho. A diminuição de enterobactérias nos cecos por parte das bactérias ácido lácticas administradas na ração pode ter sido devido à exclusão competitiva, apesar da população dessas bactérias não ter aumentado significativamente neste habitat. O tratamento com administração de Bokashi obteve menor contagem de enterobactérias no papo possivelmente devido ao fato de ser um produto fermentado, com pH baixo, que poderia agir prontamente no papo. A administração de esporos de B. subtilis não surtiu efeito nas populações das bactérias analisadas nos cecos e papos dos frangos de corte. / This study analyzed the population of enterobacteria and Salmonella in the crop and caeca of broiler chickens submitted to 3, 6, 9, 12, 15 and 18 hours of feed withdrawal, and raised without reutilization of the litter, in low density. The same bacteria were analyzed, plus Bacillus subtilis spores and lactic acid bacteria, in the crop and caeca of broiler chickens fed rations with probiotics (lactic acid bacteria, Bokashi and B. subtilis spores) and antibiotic (zinc bacitracin). There were no significant differences between enterobacteria populations on the analyzed withdrawal periods, and Salmonella and antibiotic (zinc bacitracin). There were no significant differences between enterobacteria populations on the analyzed withdrawal periods, and B. subtilis spores populations from the caeca and crops of analyzed broiler chickens did not differ from the control group when the different additives were fed through the ration. Again there were no Salmonella isolates in the analyzed crop and caeca. The absence of Salmonella may have an explanation on the way that chickens were raised, with low density (12 birds/m2) and no litter reutilization, because this result was found on the two phases of the study. The lower caeca enterobacteria population found when the broilers were fed lactic acid bacteria may have been due to competitive exclusion, even though the lactic acid bacteria counting did not increase significantly in this habitat. Treatment with Bokashi administration had lower counting of enterobactérias in the crop, possibly due to the fact that Bokashi is a fermented product, with low pH, that could act readily in the crop. The administration of B. subtilis spores did not have any effect on the populations of the analyzed bacteria, in the crop and caeca of broiler chickens.

The small dinoflagellate Azadinium spinosum produces azaspiracid (AZA) toxins which can contaminate filter feeding shellfish to dangerous levels. Toxin-contaminated shellfish flesh, when consumed by humans, can cause acute intense illness and chronic health issues. Shellfish biotoxins are monitored in Scottish shellfish by Food Standards Scotland (FSS), and the concurrent monitoring of harmful phytoplankton in the water column acts as an important early warning system of future shellfish toxin contaminations. Since A. spinosum is very small (12-16 μm long) it is difficult to identify using a light microscope, therefore molecular techniques have been developed to detect species-specific environmental DNA from phytoplankton samples. In this thesis the application and verification of quantitative real time polymerase chain reaction (qPCR) is discussed in detail and documents its first use in Scottish waters to survey A. spinosum abundance and seasonality. The limit of detection of the method was found to be 2000 ±5600 cells L-1, however it is unclear whether this is adequate for regulatory monitoring because it is not yet understood how cell density in the water column relates to AZA shellfish toxicity. The qPCR probe and primer sequences were also found to be too specific to detect all strains of the A. spinosum species, as new strains have been isolated since their development. This is a significant hindrance to the application of the tool for monitoring which will need to be addressed in the future through the isolation of local A. spinosum strains. Over a year long sampling period, A. spinosum was detected only twice (maximum cell density of 2545 ±5600 cells L-1, August 2014) off the Shetland Islands. The seasonality of the species in Scottish waters could not be assessed with so little data, however other observed harmful species of importance to shellfish regulatory monitoring are discussed; of particular note an unusual bloom of Dinophysis acuta as its association with a temperature front at the mouth of Loch Fyne. This thesis critiques the use of this qPCR technique for A. spinosum detection at high-throughput. The issues which have been highlighted do not prevent its future use by FSS, but highlight specific areas of development which need addressed before national monitoring can occur.

Extended shelf-life cook-chill meals can pose a potential risk of botulism if they are subjected to a temperature abuse. Spores of group II non-proteolytic Clostridium botulinum can survive the mild heat treatment typically given to these products and can grow at refrigeration temperatures. To circumvent this safety issue, existing preservation methods can either affect the sensory properties of these foods or damage their image. Therefore, additional natural preservation hurdles are needed. Thus, the aim of this study was to develop a novel bio-preservation method based on the principle of antibiosis between protective cultures (PCs) and C. botulinum. Consequently, the objectives were to select effective anti-botulinal cultures and study their inhibition pattern in microbiological media and foods, identify the conditions for effective inhibition and the nature of the antibiosis. This research demonstrates for the first time that the bacteriocinogenic protective cultures inoculated at high levels had an anti-botulinal effect in a range of commercial cook-chill products, which supported active growth of non-proteolytic C. botulinum. The protocol for commercial application of the protective cultures was developed. / Doctor of Philosophy (PhD)