Theses and Dissertations (Life and Consumer Sciences)

Determination of aflatoxins in peanut (Arachis hypogaea L.) collected from Kinshasa, Democratic Republic of Congo and Pretoria, South Africa : a comparative study

2013-04-27T22:01:10Z

Determination of aflatoxins in peanut (Arachis hypogaea L.) collected from Kinshasa, Democratic Republic of Congo and Pretoria, South Africa : a comparative study Kamika, Ilunga This study assessed the mycological and aflatoxin contamination of peanuts collected from Kinshasa, DRC and Pretoria, South Africa. Forty peanut samples were collected randomly at informal markets in the two cities and analysed for mycoflora and aflatoxins (B1, B2, G1 and G2) using standard methods. The results indicated that 95% and 100% of peanut samples collected from Kinshasa and Pretoria, respectively were contaminated with aflatoxigenic fungi with Kinshasa’s samples being the most contaminated (up to 49, 000 CFU/g). Seventy percent (70 %) of Kinshasa-samples and 35% of Pretoria-samples exceeded the maximum allowable limit of aflatoxin B1 set by JECFA (5 ppb). Statistical evidence showed a significant positive correlation between mycoflora and aflatoxin level for Kinshasa-samples (r = 0.4743, p < 0.005) while Pretoria-samples showed no correlation. The study reveals that high level of contamination in Kinshasa-samples could be due to the tropical nature of the climate and poor storage conditions as compared to Pretoria which is sub-tropical and sanitary regulations are enforced.

A phytochemical and biological investigation of Sutherlandia Frutescens

2013-01-16T08:37:17Z

A phytochemical and biological investigation of Sutherlandia Frutescens Faleschini, Maria Teresa Since ancient times, indigenous plants have been used by traditional healers for treating various ailments. Sutherlandia frutescens is one of the most commonly used medicinal plants of southern Africa. This widely distributed plant has been traditionally used to treat cancer and HIV patients; however scientific validation is still in high demand. This research aimed to phytochemically characterise the various extracts prepared and to determine if any chemotypes were present. Subsequent biological characterisation was carried out to preliminary ascertain whether this medicinal plant could have anti-cancer and/or immunemodulating properties and which compounds might be responsible for these actions. Various traditional and organic extracts were prepared. Extracts, fractions and compounds generated were analysed and chemical profiles obtained. Column chromatographic techniques were used to isolate and purify compounds and structure elucidation was carried out using various analytical techniques. Sulforhodamine B and cytometric bead array assays were performed to determine the biological activities of samples generated.

Prevalence, antimicrobial profiles, molecular serotyping and toxigenicity of "listeria monocytogenes" isolated from food in Gabarone, Botswana

2012-11-01T08:27:42Z

Prevalence, antimicrobial profiles, molecular serotyping and toxigenicity of "listeria monocytogenes" isolated from food in Gabarone, Botswana Morobe, Isaac C. Listeria monocytogenes is known to cause epidemic and sporadic cases of listeriosis. The present study investigated its occurrence, antibiotic sensitivity and serotyping of the organism in foods in various retail outlets in Gaborone, Botswana. Food samples were obtained randomly from selected supermarkets and street vendors from 5 geographical areas in Gaborone from May to September 2007. Listeria monocytogenes was isolated and positively identified by using morphological and biochemical tests. Furthermore, the organism was identified using multiplex PCR. From a total of 1324 food samples tested 57(4.3 %) were positive for Listeria monocytogenes. Out of the 57 isolates, 7 (12.3%), 3 (5.3%), 0 (0.0%), 27 (47.4%) and 20 (35.1%) were isolated from cheese, raw milk, meat (biltong), frozen cabbage and salad (coleslaw). From the 5 geographical areas selected for sampling in this study, Gaborone south recorded the most number 19 (33.3%) of L. monocytogenes isolates while Gaborone west recorded the least, 7 (12.3%). Most of the isolates (49%) belonged to serogroups 4a, 4b and 4c. These isolates were found mostly in cabbage. This was followed by serogroups 4b, 4d and 4e which comprised 30% of the isolates. This is in contrast to most studies that have found serotypes 1/2a and 1/2b to be the most common serotypes in food. That serotype 4b was detected in this study was a significant finding, because this is the number one serotype associated with human listeriosis. REP-PCR was used as a typing tool to characterize the L. monocytogenes strains. The method showed great promise as all of the L. monocytogenes strains were typable using this method, with good correlation between the REP-PCR profiles and the antibiotic resistant profiles. The findings reveal the presence of multi-drug resistant and virulent L. monocytogenes serotype 4b in ready to eat food in Gaborone, Botswana and highlight the need for education and training in food safety programmes.