No description available.

Thesis (Ph.D.)--Touro University International, 2007. / Adviser: Marc Strassburg. Includes bibliographical references.

M.Tech. (Biomedical Technology) / Malawi is located in the south eastern Africa. It is a landlocked country covering an area of 118,484 Square Kilometres (45,747Sq.Miles) of which 20.6% is water. It is bordered with Zambia to the north-west, Tanzania to the north and Mozambique surrounding it on the south, east and west (refer map of Malawi on page 2). Malawi is one of the sub-Sahara heavily populated countries, having a population of about 13 million people of which about 80% live in the rural areas relying on small scale farming. The country is divided into three regions, south, centre and north and these regions are further divided into districts. The southern region has most districts and is the most heavily populated. Malawi’s economy heavily depends on agriculture. Cash crops such as tobacco, tea and sugar canes are grown by commercial farmers while smallholder farmers grow a variety of crops such as tobacco, coffee, beans, fava beans, cotton, rice, sorghum, soybeans, groundnuts, cassava, potatoes, wheat, millet, peas, bananas, citrus fruits, sugar canes, vegetables and maize which is the main staple food. Malawi has a subtropical climate with the rainy season starting from mid October up to April and the dry season is from May to October. During the dry season it is hot and humid in most parts of the country especially along the lake and the lower Shire valley, while the rest of the country can be cold at night with temperatures between 5ºC and 14ºC. The southern region has the highest annual rainfall and is humid most part of the year. This is where many tea plantations are and the climate allows growth of almost all types of crops and fruits. Most Malawians consume home grown unprocessed food commodities. There are only commodities are imported, mainly from South Africa. Malawi is self reliant on maize but when drought strikes, Malawi is forced to import from neighbouring countries or from South Africa and other countries as was the case in 2004 and 2005

M. Tech. / Fusarium species are common contaminants of maize and are also capable of producing mycotoxins, in particular the fumonisin. These are implicated in animal and human mycotoxins fumonisin B1 (FB1) for example, has been associated in the aetiology of oesophageal cancer in South Africa and other parts of the world, i.e., China and Iran. Because maize is the staple diet of the South African rural population, this study was designed with the aim of monitoring Fusarium spp. and FB1 in the food of rural people of Venda, Limpopo province of South Africa, during the course of processing maize into porridge which gave a means of estimating dietary exposure to this mycotoxin. Measurement of fumonisin in the excreta of these people allowed a determine of the extent to which FB1 the body is actually exposed to the mycotoxin.Fumonisin B1 has been identified as a major fungal contaminant on maize, especially in the home grown crops intended for human consumption. Thus the rural population of Limpopo Province is at high risk from FB1 exposure and it is therefore of importance to assess this exposure by the analysis of suitable samples.It can be seen that levels of FB1 in maize from Venda are quite high, as several of these samples had exceeded levels above 1750 μg/kg as recommended as maximum tolerance levels by theEuropean Commission. It is equally seen that a much higher proportion of this mycotoxin was destroyed by processing maize to porridge. And because porridge and other maize-based products are usually consumed on a daily basis, the low levels found in the present study must not be under-estimated, as such levels may accumulate over time and cause more severe chronic effects in humans. When setting daily tolerable levels of FB1 in foods in South Africa, it is imperative to take into account the food habits, especially those within the rural communities

Several countries have enacted regulations on tolerance limits for common mycotoxins because of the hazardous nature and widespread occurrence of these fungal secondary metabolites in agricultural commodities. Screening of agricultural commodities destined for animal consumption for the presence of mycotoxins is now becoming a prerequisite in several countries as a means of minimizing ingestion of these toxins. Silage samples were analyzed for pH, % dry matter (DM) content, and the presence of total fungi, yeasts and the types of lactic acid bacteria present. The samples were also analyzed for mycotoxins that have been reported to commonly occur in silage. The pH of the samples was found to be acidic ranging from pH 3.4 to 4.7, with few samples having pH values above 6. There was a significant difference in the % DM content amongst the sampling regions. There was no significant difference in the extent of fungal contamination amongst the different regions. Aspergillus fumigatus was the predominant species from all the samples. Most of the yeast species were isolated from the Bergville region. The yeast species isolated from all samples were Trichosporon, Cryptococcus and Candida species, which are all regarded as nonlactate fermenters. Lactobacillus plantarum and Lactobacillus buchneri were the only two lactic acid producers isolated from the samples. Aflatoxins, citrinin and patulin were the most predominant toxins in the samples. Ochratoxin A and deoxynivalenol was not detected in all samples using thin layer chromatography, while the latter two toxins were only detected in two samples using VICAM fluorometry. The level of fumonisins that was found in the forage crops used for silage production was fairly low with the highest level being 9.36 ppb. Most of the mycotoxin extracts were found to reduce the % cell viability of human lymphocytes after 18 hours of incubation as determined by the MTT assay. / Professor Mike Dutton Mr. F. E. Van Zyl

M.Tech. / Please refer to full text to view abstract

M.Tech. (Biomedical Technology) / A study was conducted to determine the extent of fungi and mycotoxins contamination of Rwandan selected food commodities. A total of one-hundred food samples including maize, rice, cassava, beans and peanuts were collected from all five provinces of Rwanda and analysed. Mycological data obtained revealed a high level of contamination of common toxigenic fungi belonging mainly to the Aspergillus, Penicillium and Fusarium genera. Accordingly, Aspergillus flavus was the most prevalent fungal contaminant in maize (90%), while A. carbonarius was mainly concentrated in peanuts at an incidence rate of 70%. Aspergillus fumigatus was mostly found in cassava (85%) in combination with Penicillium decumbens at the rate of 70%, meanwhile P. citrinum was found at an incidence rate of 80% in rice. The genus Fusarium was dominantly present with F. verticillioides and F. graminearum found in all analysed commodities. A toxigenicity study was also conducted to evaluate the capacity of these fungi recovered to produce their respective mycotoxins. Certain species such as A. flavus and A. parasiticus isolated from these commodities produced the aflatoxins (AFs). Other Aspergillus spp. such as A. carbonarius produced ochratoxin A (OTA) and F. verticillioides and F. graminearum also showed their capacity in producing different mycotoxins viz: zearalenone (ZEA), fumonisins (FBs) and deoxynivalenol (DON). The analysis of mycotoxins in these commodities was performed following thin layer chromatography (TLC) and high performance liquid chromatography (HPLC). Data obtained revealed that peanuts and maize were the most contaminated with mycotoxins at incidence rates of 85 and 80%, respectively, and at the highest contamination levels. The highest AF-contaminated commodity was maize from Western province (range: 1.3-3219.6 μg/kg; mean: 829.3 μg/kg) followed by peanut from the same region whose mean level found was 401.5 μg/kg (range: 3.2–1755.8 μg/kg). Ochratoxin A was also found in peanuts with a mean concentration of 302.6 μg/kg, while DON was found at the highest level of 419.6 μg/kg in a rice from Kigali-city. Maize was the main substrate for FBs (mean: 134 μg/kg; max: 4591 μg/kg). Zearalenone was also recovered from samples but at a low incidence rate of 40% with the highest level of 5.2 μg/kg recorded. It was also observed that 65% of samples analysed were contaminated with more than one mycotoxin.

Magister Scientiae - MSc / Listeria monocytogenes is a Gram-positive bacterium responsible for listeriosis, a food-borne disease, which may result in severe illness and possible death. The importance of L. monocytogenes as a food-borne pathogen has been recognized since the 1980's when a correlation between the cunsumption of contaminated foodstuffs and human listeriosis outbreaks was observed. Listeriosis occurs with the ingestion of contaminated foods. The aim of this study involved developing DNA based methods to aid the food industry for the fast detection of L. monocytogenes in food products. Therefore assays were developed in such a way that they will have potential applications in the food idustry. / South Africa

No description available.

Submitted in fulfillment of the requirements for the Degree of Master of Technology: Biological Sciences at Technikon Natal, 2000. / Spice oils are known to exhibit antifungal activity and therefore have the potential to control mycotoxin production. There is a need in the food industry to find measures to control mycotoxins that are frequently associated with grains that form the staple diet of the majority of the population in South Africa. Clove, cinnamon, oregano, tumeric, eucalyptus, neem, aniseed, mace and nutmeg oils were tested to determine their inhibitory potential against growth of Aspergillus parasiticus and Fusarium moniliforme using the agar overlay technique. Varying concentrations of the spice oils, ranging from 0.1 ppm to 2.0 ppm, were incorporated into broth cultures of A. parasiticus and maize patty cultures ofF. moniliforme. Levels of production of aflatoxins and fumonisin were determined using standard thin layer chromatography and highpressure liquid chromatography methods. In addition, the active component of the spice oils were isolated, characterised and tested. The inhibitory potential of these compounds for field use was tested by incorporating clove oil, whole cloves and ground cloves in samp / M