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

Thesis (M. Tech.(Environmental Health)) - Central University of Technology, Free State, 2005 / As the concentration of dust has been shown to be proportional to seasonal change in the Free State Province of South Africa, one might expect the prevalence of associated microorganisms to follow the same pattern. The presence of dust is also associated with an aerosolised microbial population that gets blown into almost any unsealed environment including food storage facilities at schools. In addition, facility design and storage practices at these schools are under-developed and could subsequently lead to the contamination of stored food by dust, insects and rainwater. The foods in question include fortified biscuits that are intended for malnourished, and in several cases immunocompromised, children who are susceptible to opportunistic pathogens. Therefore this study aimed to determine the impact of facility design on the level and distribution of viable airborne microorganisms (fungi and bacteria) in the storage rooms and the outdoor environment at both rural (higher dust exposure) and urban schools. Besides the pathogenicity of these organisms, their ability to degrade the sugars (major fortifying agent) in the mentioned biscuits was also established. The results showed the presence of Escherichia coli, which signifies faecal contamination and could be attributed to the lack of toilet facilities in the schools, especially in rural areas. Although Staphylococcus sp. is normally related to poor personal hygiene practices, these organisms were also isolated from the air of the storerooms and school premises. The presence of moulds and airborne microorganisms was attributed to unfavourable environmental conditions as well as crowding in the classrooms. The microbial contamination originally present on the fortified biscuits or originating from the air further caused deterioration in the quality of the food. The fungi present in the air (identified species) cause respiratory problems when inhaled by children as they are opportunistic pathogens. It is further evident that a change of season corresponded to a general change in bioaerosol composition, such as the increased presence of dust during the winter months. It was further concluded that schools situated in different environments (urban/rural) should have storerooms that address the various environmental factors influencing bioaerosols. This would impact not only directly on the health of children in terms of their exposure to possible allergens, but also indirectly through the food that they consume as part of the feeding programme.

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In this work, an automated statistical approach for the condition monitoring of a fluid power system based on a process sensor network is presented. In a multistep process, raw sensor data are processed by feature extraction, selection and dimensional reduction and finally mapped to discriminant functions which allow the detection and quantification of fault conditions. Experimentally obtained training data are used to evaluate the impact of temperature and different aeration levels of the hydraulic fluid on the detection of pump leakage and a degraded directional valve switching behavior. Furthermore, a robust detection of the loading state of the installed filter element and an estimation of the particle contamination level is proposed based on the same analysis concept.

Several lactic acid bacteria (LAB) of the Lactococcus, Lactobacillus, Leuconostoc and Pediococcus genera were screened for inhibition of food-borne pathogens and spoilage microorganisms in raw milk and dairy products. Listeria monocytogenes was killed by Lactococcus lactis subsp. lactis and Pediococcus pentosaceus due to their production of bacteriocin-type inhibitors. Staphylococcus aureus was not able to grow in raw milk at temperatures below 5°C even without LAB being present. Gram negative Salmonella enteritidis. Salmonella typhimurium and Escherichia coli, along with spoilage bacteria of the genus Pseudomonas were dramatically inhibited by a Lactobacillus species, designated AS-1, in raw and pasteurized milk as well as in cottage cheese. However, other LAB were not able to inhibit these organisms. Lactobacillus AS-1, did not produce hydrogen peroxide but carbon dioxide was produced. The AS-1 strain was a gram positive coccobacillus, catalase and oxidase negative and produced DL-lactic acid. It deaminated arginine and grew over a temperature range of 5°C to 45°C. It was also able to ferment glucose, galactose, fructose and lactose in addition to 17 other carbohydrates. High numbers (107 CFU/ml) of AS-1 were required to obtain complete inhibition of gram negative bacteria. A selective medium (ASLM) for Listeria monocytogenes was developed to follow the fate of this particular pathogen in association with LAB in raw milk; other selective media were not able to inhibit the growth of background flora of raw milk. ASLM was superior to four other media in allowing only the growth of the target pathogen. For the Lactococcus genus, a selective and differential agar medium (Alsan) was formulated to selectively allow growth of Lactococcus spp. and to differentiate between Lactococcus lactis subsp. lactis and the biovariety diacetylactis, based on citrate utilization. / Graduation date: 1993

1p. / Most of the "bad food" reported illnesses are due to bacterial contamination. Nearly all of these cases can be linked to improper food handling, both in our homes and in restaurants. This article briefly discusses the causes of food contamination and how to handle food safely.

Six lactating Holstein cows received ammonia-treated or untreated aflatoxin-contaminated whole cottonseed (AFWC) or pure AFB₁ with their regular ration. Treatments were: AFWC (5,010 ppb AFB₁), 4 kg/day; the same AFWC treated with 1.5% anhydrous ammonia and 10% water; pure AFB₁ (2.2 mg twice daily) given in capsules; same amount AFB₁ treated with 50% NH₄OH for 26 days at 29°C; same amount ammoniated AFB₁ acidified to final pH of 5.0; same treatment as first except concentration of AFB₁ was 5,511 ppb. Levels of aflatoxin M₁ (AFM₁) in milk were monitored before, during, and after each treatment, and conversion and feed-through ratios were calculated. Feed consumption and milk production were also measured. Mutagenicity of acetone extracts of spray-dried milk was determined using Salmonella/microsomal assay. Ammoniation of AFWC did not reduce concentration of AFB₁ to below FDA action level; however, when the seed was fed, the concentration of AFM₁ in milk was less than FDA action level (0.5 μg/L). Ammoniation of AFB₁ was very effective in reducing levels of AFM₁ in milk of treated cows to less than the FDA action level. The average AFB₁/AFM₁ conversion ratios for the steady-state period of AFM₁ excretion in milk while giving AFWC and AFB₁ was 1.06% and 1.18%, respectively. Ammoniation of AFWC reduced the average AFB₁/AFM₁ ratio to 0.20% during the constant-state period of AFM(,1) excretion in milk. The ration containing AFWC (5,010 or 5,511 ppb AFB₁) caused a highly significant decrease in total milk production and feed consumption; ammoniated AFB₁ decreased total milk production significantly. Complete disappearance of AFM₁ from milk after discontinuing Treatments 1-6 was 120, 48, 95, 72, 96, and 120 h, respectively. Under these laboratory conditions, significance of the results of the Ames test was questionable.

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