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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

The growth of Salmonella typhimurium, Staphylococcus aureus, and Bacillus cereus in bakery products as related to the food distribution system

Guy, Vicki H. 01 May 1981 (has links)
Current retail food distribution practices, microbial quality of bakery products, and the potential for growth of food borne pathogens (Staphylococcus aureus, Salmonella typhimurium, and Bacillus cereus) were examined using pumpkin pie as a model. The pumpkin pies, as obtained from the retail outlets, showed contamination with food pathogens. The aerobic plate counts reached high numbers (up to 10⁹/g) when stored at 25°C for the specified shelf life as indicated by pull dates. S. aureus was isolated from one sample and B. cereus from two samples of pumpkin pie. Baking conditions were sufficient to destroy IS. aureus and Salmonella typhimurium but not spores of B. cereus. The presence of S. aureus indicated post-processing contamination. When inoculated with S. aureus, Salmonella typhimurium and B. cereus, pumpkin pie supported the growth of all these organisms when stored at 25°C. When stored at severe abuse conditions (35°C), pumpkin pie supported the growth of S. aureus and Salmonella typhimurium but not B. cereus. Refrigeration at 4°C controlled the growth of the pathogens studied. The addition of 0.25% potassium sorbate to the pie filling inhibited the growth of Salmonella typhimurium and B. cereus but not S. aureus at 25°C. The findings of this study indicated a lack of knowledge regarding safe food handling practices among bakers. Current distribution practices indicated that pumpkin pies were often displayed at room temperature from two to five days. If contaminated, the product could become a public health hazard. / Graduation date: 1981

A Comparison of Microbial Contamination in Commercial Intravenous Fluids Packaged in Glass and Flexible Plastic Containers

Guynn, James Bruce 01 January 1973 (has links)
An original study was undertaken in the pharmacy and at the nursing unit simulating conditions of actual use to determine contamination rates for intravenous fluids in glass bottles and flexible plastic bags.

Effect of repeated puncture on the particulate matter contamination of multi-dose vials as assessed by the industrial model B Coulter Counter

Edirimanasinghe, Sylvester Mariadason, January 1968 (has links)
Thesis (M.S.)--University of Wisconsin--Madison, 1968. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Predominance of Bacillus Anthracis in the Biological Population of an Activated Sludge Reactor

Hoyt, Robert Frederick 30 April 2011 (has links)
The effects of heavy metals, endocrine disruptors, and other contaminants on activated sludge and wastewater treatment operations have been studied extensively. However, the potential for infiltration of bacterial species not native to activated sludge has not been extensively examined. This project investigated the effect of the contamination of activated sludge wastewater treatment systems by Bacillus anthracis. From a pure culture of Bacillus megaterium inoculations of two bench-scale, sequencing batch reactors with different solids retention times was studied. Microbial enumeration testing was initially done on the mixed liquor alone, but to further detail the Bacillus path through the reactor, further testing was done to examine the supernatant. The data indicated that little effect would be caused from Bacillus inoculation of activated sludge reactors as population diversity returned to normal within a period of time equal to approximately one quarter of the solids retention time.

On-site system effluent source tracking using geochemical and microbial tracers in a coastal catchment

Geary, Phillip M, University of Western Sydney, College of Science, Technology and Environment, School of Science, Food and Horticulture January 2004 (has links)
The principal aims of this thesis were to examine whether there were hydraulic links between individual on-site wastewater systems in sandy soils at Salt Ash and the Tilgerry Creek estuary near Port Stephens, New South Wales, and whether the chemical and microbiological contaminants from on-site systems could reach surface and groundwaters, and possibly lead to impacts on estuarine oyster growing waters. The research outcomes are contained within the thesis and in four refereed papers presented at conferences, and which have been subsequently published, or are in press. Copies of each of these papers are contained within the thesis Appendices. The presence of faecal contamination from domestic systems in the estuary, and surface drains in particular, has been confirmed by work contained in this thesis. The potential level of risk to human health from the consumption of contaminated oysters is, however, regarded as very low, although an assessment of health risk using established microbial assessment models has not been undertaken / Doctor of Philosophy (PhD)

Laser induced desorption time of flight mass spectrometer analysis of adsorbed surface contaminants on vacuum ultraviolet lithography optic materials

Surpaneni, Yamini. Allen, Susan D. January 2003 (has links)
Thesis (M.S.)--Florida State University, 2003. / Advisor: Dr. Susan Davis Allen, Florida State University, College of Engineering, Dept. of Electrical and Computer Engineering. Title and description from dissertation home page (viewed Apr. 12, 2004). Includes bibliographical references.

Persistance du virus de l'herpès simplex de type 1 sur des surfaces non poreuses et sur des aliments prêts-à-manger

Pageau, Gabrielle 09 June 2023 (has links)
Thèse ou mémoire avec insertion d'articles / Le virus de l'herpès simplex de type 1 (VHS-1) est un virus enveloppé hautement contagieux et répandu dans le monde entier, où 67 % de la population mondiale est infectée. Ce virus cause des maladies incurables bénignes, dont la plus commune est l'herpès labial (ou boutons de fièvre), soit des lésions autour de la bouche. Toutefois, des infections bien plus graves, telles que l'encéphalite, peuvent aussi survenir. Peu d'études ont exploré le VHS-1 dans un contexte agroalimentaire. Bien que le VHS-1 ne soit pas considéré comme un virus d'origine alimentaire, certains travaux ont démontré qu'il pouvait survivre dans l'environnement alimentaire. En plus de persister sur des surfaces couramment rencontrées en industrie alimentaire et sur des aliments fréquemment consommés, la majorité des personnes infectées sont des porteurs asymptomatiques du VHS-1, ce qui contribue grandement à la propagation de celui-ci. D'ailleurs, la main-d'œuvre pratiquant de mauvaises habitudes d'hygiène et le concept de partage entre les individus (partage d'aliments, de boissons, d'ustensiles, etc.) sont des facteurs qui augmentent le risque de transmission du VHS-1. Ce mémoire avait comme objectif d'étudier la persistance du VHS-1 sur des surfaces en contact avec les aliments et sur des aliments prêts-à-manger qui peuvent se partager ; en plus d'évaluer également le potentiel de transfert du VHS-1 d'une surface non poreuse vers un gant. Ce projet de maîtrise a démontré que les surfaces et les aliments pouvaient être des vecteurs potentiels de transmission du VHS-1, puisqu'une récupération du virus infectieux était possible selon les conditions environnementales. En effet, la température, le pH des aliments et potentiellement des composés avec des propriétés antivirales ont affecté la persistance du VHS-1. En conclusion, les résultats de ce mémoire ont pour but de sensibiliser et d'éduquer la population en ce qui a trait aux risques de transmission du VHS-1 entre les personnes. / Herpes simplex virus type 1 (HSV-1) is an enveloped virus that is highly contagious and widespread throughout the world, where 67 % of the world's population is infected. This virus causes mild lifelong diseases, which herpes labialis (or cold sores) is the most common one. However, much more serious infections, such as encephalitis, can also occur. Few studies have explored HSV-1 in an agri-food context. Although HSV-1 is not considered a foodborne virus, some studies have shown that it can survive in the food environment. In addition to persisting on surfaces commonly encountered in the food industry and on frequently consumed foods, most infected people are asymptomatic carriers of HSV-1, which greatly contributes to the spread of this virus. Moreover, the food handlers that have poor hygiene practices and the concept of sharing (sharing food, drinks, utensils, etc.) are factors that may increase HSV-1 transmission. The objective of this thesis was to study the persistence of HSV-1 on surfaces in contact with food and ready-to-eat (RTE) foods that can be shared; and assess the potential for transmission of HSV-1 from a non-porous surface to a glove. This master's project demonstrated that surfaces and food could be potential vectors of HSV-1 since recovery of infectious virus was possible depending on environmental conditions. Indeed, the persistence of HSV-1 was affected by the temperature, the food pH and potentially compounds with antiviral properties. In conclusion, the results of this thesis are intended to raise awareness and educate the population regarding the risks of transmission of HSV-1 between people.

Potential sources of chryseobacterium contamination during poultry processing : a pilot study

De Beer, H., Hugo, C.J. January 2010 (has links)
Published Article / The genus Chryseobacterium is often found in food and is regarded as a food spoilage organism. In this study, the source of the chryseobacteria was uncertain. As an exploratory investigation, the potential source of chryseobacterial contamination was determined. Total bacteria counts and yellow-pigmented colony counts were performed. Chryseobacterium species were present on poultry carcasses at all stages of processing. Total Chryseobacterium counts increased from 5.6 to 11.8 % after the brine injection stage. A significant increase in total Chryseobacterium counts (20.0 and 25.2 %) in the processing waters occurred where cutting up of the carcasses was involved. It is speculated that live chickens are the source of contamination.

Microbial contamination of enteral feeds

Lee, Cheuk-hung, 李卓雄 January 2004 (has links)
published_or_final_version / Ecology and Biodiversity / Doctoral / Doctor of Philosophy

Rapid methods for the determination of post-pasteurization contamination of fluid milk and shelf-life prediction

Isaza, Liliana Urrea 03 June 1986 (has links)
Several methods for estimation of the potential shelf-life of pasteurized fluid milk products were evaluated for their efficacy in this investigation. These methods were evaluated and compared to sensory, biochemical and bacteriological indices through a series of experiments conducted on different brands of commercially pasteurized fluid milk. The methods evaluated included: Standard Plate Count (SPC), Psychrotrophic Bacteria Count (PBC), Modified Psychrotrophic Bacteria Count (MPBC), the Moseley keeping quality test (MKQT), Parmelee tube test (PTT), tetrazolium salt-resazurin test (TRT), modified Parmelee tube test (MPTT), and p-iodonitrotetrazolium violet-phenazine methosulfate test (INT-PMS). Several different conditions of preliminary incubation (PI) were attempted in an effort to accelerate outgrowth of psychrotrophic bacteria and hence obtain sufficient numbers and metabolic activity to reduce the redox potential indicator dye. Correlation coefficients (r) and chi-square (χ²) values were obtained in an attempt to detect significant relationship between the parameters studied and the potential shelf-life of the product. Results suggested that the PTT, TRT and MPTT tests were not reliable predictors of the potential shelf-life of pasteurized milk (r values between -0.445 and 0.734, non-significant P>0.05). The INT-PMS Test at 21°C for 20 minutes following PI at 21°C for 25 hours provided the best estimate of the potential shelf-life of pasteurized whole milk (r= -0.840). This method shows some potential as a method for determining post-pasteurization contamination: it was accurate (92.3%), rapid ( <26 hours), simple, inexpensive (4.54 to 9.64 cents/sample), and sensitive (it was able to detect less than 1 PBC/ml and less than 5.0 x 10¹ total CFU/ml in fresh milk if bacteria were able to reach 1 PBC/ml and 1.0 x 10³ total CFU/ml during PI). However its accuracy could be significantly affected by the intensity of the pasteurization heat treatment given to the milk due to possible denaturation of the whey proteins and release of heat activated reducing substances (-SH groups). / Graduation date: 1987

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