The fluorodinitrobenzene (FONB), succinic anhydride (SA), dansyl chloride (DAN), dye-binding lysine (OBL), total lysine (TL), ninhydrin (NIN) and Tetrahymena lysine (TET) methods were compared for their ability to assess available lysine in soyaprotein heated in the absence or presence of glucose, lactose or xylose and in formaldehyde-treated lactalbumin. The reactive lysine methods showed comparable sensitivity to lysine damage in soyaprotein heated in the absence of sugar, the results indicating the presence of acid labile isopeptides and unidentified acid stable derivatives. Results for soyaprotein heated with glucose, lactose or xylose showed that the type of sugar and the extent of heat treatment has a strong influence on the progress of the Maillard reaction. Furthermore since fructoselysine (F-L) and lactulosyl-lysine (L-L) are colourless up to 30% loss of available lysine can occur without any change in product colour. The FONB method is the most sensitive for mildly damaged glucose-soya samples followed by DAN or OBL, SA and TL whereas for mildly damaged lactose-soya samples the order is OBL, FONB, SA, TL and DAN. For severely damaged samples the DAN or SA methods were the most sensitive followed by OBL, FONB and TL. Formylation of lactalbumin occurred more readily at higher formaldehyde concentrations. Exposure time had less effect while pH (5 and 9) had no effect. Methylene derivatives reached maximum levels sooner than the methylol compounds. Lysine and tyrosine but not histidine formed methylene bridges while tyrosine was found to condense with free formaldehyde during acid hydrolysis raising questions as to the interpretation of similar studies reported in the literature. The FONB, OBL and DAN methods were all very sensitive to this type of damage with the NIN and TL methods being less sensitive and the SA method being completely unsuitable. The TET assay is unsuitable for 'early' Maillard damage since at low sample-N levels growth is stimulated by its ability to utilise unavailable F-L and L-L while at higher N-levels growth is inhibited. No single method is most suitable for all types of damage. Furthermore, all except DAN and DBL are either too long, rather complicated, require expensive equipment or involve the use of dangerous chemicals. The DAN method appears promising but the problem of converting arbitrary fluorescence units to lysine values needs to be overcome. The DBL is recommended for routine analysis since it is simple, economical and highly sensitive to all lysine damage provided care is taken to optimise dye-binding for each type of material analysed. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1985.

Thesis (M.S.)--University of Montana, 2007. / Title from title screen. Description based on contents viewed July 24. 2007. Includes bibliographical references (p. 109-114).

Maize (Zea mays L.) is an important cereal world-wide, serving as seed for growers, food for man and livestock as well as an industrial raw material. Unfortunately, it is also a suitable substrate for growth, development and activity of spoilage fungi. Fungal growth is a major problem in cereal grains throughout the world and may lead to poor quality of the products, as well as adverse effects to human and animal health due to mycotoxin production. Maize is usually harvested at high moisture content and then dried to bring down the moisture content to a safe level before storage. Delay in drying to safe moisture levels increases risks of mould growth and mycotoxin production. In rural villages maize is dried using only sun drying and they rely on sacks, thatched silo and drums as their storage facilities. This is insufficient to prevent damage by insects, rain, and rodents, which in turn allows fungi to invade these storage facilities. Maize was sampled in two rural areas of Venda (Limpopo Province) and the percentage moisture content was determined and then screened for total fungal contamination. The samples were also analysed for mycotoxins that have been reported to commonly occur in maize. There was no significant difference in the extent of fungal contamination in Mapate and Folovhodwe villages. Of the fungal species detected, Aspergillus species were the most common with Aspergillus flavus being the most predominant. On analysis by the multi-mycotoxin screen, aflatoxin had the highest incidence amongst mycotoxin, followed by T-2 toxin. However on using the VICAM method of analysis aflatoxins, deoxynivalenol and fumonisin were the most predominant mycotoxins in the samples, while zearalenone toxin was also amongst predominant mycotoxins but with the highest level of 0.1 ppm. Most of the mycotoxin-containing extracts were found to reduce the % cell viability of human lymphocytes, after 24 hours of incubation as determined by the methyl thiazole tetrazolium salt assay. vii In conclusion the co-occurrence of these toxins in maize and maize meal may highlight the problems associated with the intake of numerous toxins that could in turn lead to more adverse health effects such as liver, oesophageal, breast and cervical cancer, male reproductive tract damage and gynacomastasia. There is, therefore, need to disseminate information to these people, using simplified methods such as programs on radio and televisions on mycotoxin hazards and discussion on the issue should also feature regularly on daily newspapers and magazines, about the dangers and management aspects of mycotoxins, and the susceptible produce. / Prof. M. F. Dutton Mr. F. E. van Zyl

D.Tech. (Biomedical Technology) / To determine the quality of human food commodities commonly consumed in Cameroon, various districts in the western highland (Bamenda and Kumbo) and tropical rain forest (Douala and Yaounde) regions were sampled. Two mycological investigations were conducted to evaluate the incidences of mycotoxigenic fungi (95 samples) and mycotoxins (82 samples). Serial dilution of ground samples was employed to isolate fungi, subculture on various culture media and fungal species were identified morphologically followed by molecular phylogenetic approach. In general, data obtained indicate samples from various geographical regions showed no consistent variation with regard to the type of fungal species. The mycobiota of food materials were characterized by a diversity of fungal species with the predominance of Aspergillus (125 isolates) followed by Penicillium (94 isolates) and Fusarium (52 isolates). The less predominant genera include Rhizopus (14 isolates) and the Alternaria (9 isolates). Aspergillus flavus and A. parasiticus occurred in 53 and 44% of the samples, respectively, with higher frequencies in maize than peanuts or beans and absent in rice, pumpkin seed and cassava products. Aspergillus fumigatus was detected in 20% of samples and A. niger in 18% of the samples. Aspergillus isolated less frequently included A. carbonarius A. awamori, A. oryzae and A. tamarii, A. pseudotamarii, A. ochraceus, A. ostianus, A. avenaceum, A. oryzae and A. variabile. Consistent results were observed for A. tamarii, A. pseudotamarii, A. ochraceus and A. ostianus with respect to substrate specificity. While A. tamarii, A. pseudotamarii and A. ochraceus were isolated only from peanuts, A. ostianus strains occurred only in bean samples. Penicillium contamination was dominated by P. polonicum and P. crustosum with incidence rates of 43 and 41%, respectively, with highest contamination levels registered in samples from Yaounde. Penicillium citrinum, P. purpurogenum, P. islandicum, P. aurantiogriseum, P. expansum were also inconsistently isolated from food samples. There was a relatively low incidence of Penicillium spp. in pumpkin seed and fermented cassava product samples.

No description available.

No description available.

Thesis (PhD.(Animal Science) North-West University, Mafikeng Campus, 2012

<p>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.</p>

The aim of the present work was to investigate aflatoxin levels in various food commodities and to study its production by Aspergillus parasiticus in culture to find out the possible ways to control it. Of 40 food samples collected from Abha region, Saudi Arabia, only 25% were contaminated with aflatoxins. Oil-rich commodities had the highly contaminated commodities by fungi and aflatoxins while spices were free from afatoxins. The optimal pH for the growth of A. parasiticus and its productivity of aflatoxin B, was found at 6.0, while the best incubation conditions were found at 30°C for 10 days. D-glucose was the best carbon source for fungal growth, as well as aflatoxin production. Corn steep liquor, yeast extract and peptone were the best nitrogen sources for both fungal growth and toxin production. (NH4)2HPO4 (1.55 gL-1) and NaNO2 (1.6 gL-1) reduced fungal growth and toxin production with 37.7% and 85%, respectively. Of ten amino acids tested, asparagine was the best for aflatoxin B, production. Zn2+ and Co2+ supported significantly both fungal growth, as well as aflatoxin B, production at the different tested concentrations. Zn2+ was effective when added to A. parasiticus growth medium at the first two days of the culture age. The other tested metal ions gave variable effects depending on the type of ion and its concentration. Water activity (a ) was an important factor controlling the growth of A. parasiticus and toxin production. The minimum aW for the fungal growth was 0.8 on both coffee beans and rice grains, while aW, of 0.70 caused complete inhibition for the growth and aflatoxin B, production. H202 is a potent inhibitor for growth of A. parasiticus and its productivity of toxins. Incubation with NaHCO3 and C6H5000Na converted aflatoxin B, to a water-soluble form which returned to aflatoxin B, by acid treatment. Black pepper, ciliated heath, cuminum and curcuma were the most inhibitory spices on toxin production. Glutathione, quinine, EDTA, sodium azide, indole acetic acid, 2,4-dichlorophenoxy acetic acid, phenol and catechol were inhibitory for both growth, as well as, aflatoxin B, production. Stearic acid supported the fungal growth and decreased the productivity of AFBI gradually. Lauric acid is the most suppressive fatty acid for both fungal growth and aflatoxin production, but oleic acid was the most potent supporter. Vitamin A supported the growth but inhibited aflatoxin B, production. Vitamins C and D2 were also repressive particularly for aflatoxin production. The present study included determining the activities of some enzymes in relation to aflatoxin production in A. parasiticus culture during 20 days. Glycolytic enzymes and pyruvate-generating enzymes seems to be linked with aflatoxin B, production. Also, pentose-phosphate pathway enzymes may provide NADPH for aflatoxin B, synthesis. The decreased activities of TCA cycle enzymes particularly from 4th day of growth up to 10th day were correlated with the increase of aflatoxin B, production. All the tested enzymes as well as aflatoxin B, production were inhibited by either catechol or phenol.

<p>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.</p>