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Item Microbiological quality, safety, mycotoxins and heavy metals levels in underprized Kalahari truffle, Termitomyces schimperi and Ganoderma mushroom species(University of Namibia, 2020) Hainghumbi, Tukuna AlveIn many African countries, edible mushrooms are used as a source of food and income. In Namibia, Ganoderma mushrooms are barely utilised. Kalahari truffles and Termitomyces schimperi are the common harvested for domestic consumption and/or selling in the informal markets. Though truffles in western markets fetch very high prices, the cost of truffles in Namibia is barely reported. The microbial quality, safety and heavy metal level in the edible Namibian mushrooms is not known. This study investigated the cost of truffles at a select informal market in north-central Namibia and assessed the effect of washing and drying of truffles on the microbial quality, safety, mycotoxin and heavy metal levels. The microbial quality, safety, mycotoxin and heavy metal levels were also determined in the Ganoderma and Termitomyces schimperi mushrooms collected from the wild. Microbial analyses were carried out using culture techniques. Mycotoxin analysis was carried out using ELISA kits. Heavy metal analysis was done using the ICP-OES. The price of Kalahari truffle ranged from N$ 29 to N$ 71 per kg. Truffles in Namibia are underpriced than in developed nations and has no objective price consistent with a unit mass. Generally, all mushrooms samples had total aerobic counts that are mostly within the acceptable total aerobic count limit of <5.7 log cfu/g. No yeast and Salmonella detected in Ganoderma samples. The levels of fumonisin B1 (17.4 to 142.1 µg/kg) in truffles irrespective of washing were within the permissible limits (200-300 µg/kg). The levels of all the analysed mycotoxins in Termitomyces schimperi were above the permissible limits. Nickel and mercury were not detected in truffles or Termitomyces schimperi. There is a need for appropriate processing to take place before consumption of majority of the studied mushrooms.Item Identification and cultivation of Ganoderma mushroom species in Namibia and the physicochemical properties, phenolics composition and in vitro antioxidant activity of their infusions(University of Namibia, 2020) Hamwenye, Karlin KundeingeGanoderma is a fungus that grows in natural habitants from different parts of the world. It is a prized mushroom in developed nations especially in Asian countries due to its health promoting properties such as anticancer, antibacterial, anti-inflammatory, antioxidant, anti-diabetic. These health promoting effects are attributed to bioactive compounds such as the phenolics. However, in developing countries such as Namibia, Ganoderma is still an untapped and barely identified resource. The objectives of this study was to identify and cultivate wild Ganoderma species harvested from different host trees in Namibia and to determine their physicochemical properties (moisture, ash, water absorption and water solubility indices). The phenolics composition (total phenolics (TP), total flavonoids (TF), condensed tannins (CT)) and in vitro antioxidant activity (AA) of hot water infusions of the wild and cultivated mushrooms were also determined. Folin-Ciocalteu, Aluminium Chloride, Vanillin-HCl, DPPH assay methods were used to determine TP, TF, CT and AA, respectively. Ganoderma species were identified using DNA based on the sequences in the GenBank with 98-100% similarity. Two new Ganoderma species: Ganoderma enigmaticum and Ganoderma wiireonse were identified for the first time in Namibia. Wild species had 6.12- 11.70% moisture, 1.91- 5.32% ash, 11.55- 24.40 (g of absorbed water/g of dry sample) water absorption index, 3.60- 24.10% water solubility index, 18.37- 44.78 (mg GAE/g of sample) TP, 0.09- 1.67 (mg QE/g of sample) TF, 2.97- 6.37 (mg CAE/g of sample) CT and 40.8- 49.3% AA. Cultivated species had 9.64- 13.45% moisture, 2.34- 6.20% ash, 13.55- 28.30 water absorption index, 6.40- 25.35% water solubility index, 36.70- 52.73 (mg GAE/g of sample) TP, 0.41- 0.86 (mg QE/g of sample) TF, 11.38- 15.29 (mg CAE/g of sample) CT and 53.6- 63.7% AA. Infusions prepared from cultivated Ganoderma species had higher levels of TP, CT and AA than those prepared from wild Ganoderma species suggesting that they can be potential nutraceuticals and source of healthful antioxidants. Further studies should be done on in vitro and in vivo medicinal effects of Ganoderma species in Namibia.Item Nutritional composition and in vitro starch digestibility of crackers from pearl millet and wheat composted with mushrooms(University of Namibia, 2020) Uukule, Erick N.Type 2 diabetes is a global problem that can be controlled by a diet that consists of carbohydrates with substantial amounts of slowly digestible starch amongst others. Pearl millet (Pennisetum glaucum (L) R. Br.) is an underutilised cereal crop that in recent times, raised interest due to its health benefits. The low starch hydrolysis rate of pearl millet is particularly of interest in type 2 diabetes modulation. To contribute to the value-addition and food diversification using pearl millet, this project investigated the nutritional content and starch digestibility of composite flours and crackers made of pearl millet-wheat, truffle (Kalaharituber pfeilii) and Oyster mushroom (Pleurotus ostreatus) composite flours and crackers. Equal amounts of fermented whole pearl millet grain and bread wheat flour were mixed. Of this mixture, 5%, 10% and 15% were substituted with Oyster mushroom and Kalahari truffle powders. The moisture, fat, protein, ash and minerals contents, water absorption (WAI) and water solubility (WSI) indices, total starch and starch digestibility of the flour formulations and the resultant crackers were determined. The consumer acceptance of the composite crackers was also assessed. The ash content, WSI and WAI were higher in the mushroom flours than in the cereals composite flours. Contrary, mushroom containing flours had the lowest starch content of all the flours. For crackers, ash content, WAI and WSI were directly proportional to the levels of mushroom incorporation. In terms of consumer acceptance, 5% oyster mushroom and 5% Kalahari truffle incorporated crackers scored the highest on the 9 point hedonic scale. Starch digestibility of mushroom incorporated flours and crackers were lower than those of cereal composite products. The higher the mushroom incorporation level, the slower the glucose release rate, showing that mushroom incorporation may be beneficial to people with type 2 diabetes.Item Investigation of the Pathogenicity of Vobrio Alginolyticus strains isolated from processed hake and seawater in Namibia and validation of hydrogen peroxide (H2O2) for the disinfection of seawater(2015) Shetunyenga, DionisiusIn Namibia seawater is employed by marine fish factories during processing. Previous studies indicated that chlorine and Ultra Violet (UV) light are ineffective in keeping seawater free from bacteria throughout the distribution system. However, laboratory studies showed that hydrogen peroxide eliminates both sessile and attached bacteria from seawater. Secondly it is not known whether Vibrio alginolyticus bacteria isolated from the Namibian marine waters and from hake fish whose detection results into rejection of export products are pathogenic or not. This study was aimed at validating the ability of hydrogen peroxide (H2O2) to eliminate V. alginolyticus in seawater and to detect Vibrio species associated virulence factors in V. alginolyticus strains isolated from seawater and from hake fish products. Seawater used by factory B was dosed with 0.05% H2O2 and allowed to pass through pipes to collection points after which Vibrio counts in water and in fish products were determined. Secondly, V. alginolyticus strains isolated from seawater and hake fish and identified using 16S rRNA and rpoB genes were screened for toxR, tlh and tdh genes using PCR. V. parahaemolyticus LMG 2850 and V. alginolyticus Bcc892 were used as positive and negative controls respectively. High bacterial counts were detected from seawater treated with chlorine alone. Vibrio alginolyticus was detected in the fish processing factories were seawater was used and on fish products. Vibrio species were eliminated from seawater distribution system by 0.05% H2O2. Only one (1.9 %) out of 54 strains, tested tlh positive, but all the strains tested were toxR and tdh negative. This study, confirmed that these strains do not contain specific virulence genes known in other Vibrio species. Furthermore, this study confirmed that H2O2 is an effective disinfectant of seawater.Item Antimicrobial activity profiles of traditional fermented milk starter culture from north-eastern Namibia(2014) Heita, LusiaThe aim of this study was to identify and examine the antimicrobial properties of Lactic Acid Bacteria (LAB) isolated from fermented milk collected from Ohangwena, Omusati, Oshana, Oshikoto, Zambezi and Kavango regions. Traditional fermented milk in Namibia are produced by spontaneous fermentation using traditional utensils. In this study, thirty homesteads from six regions that produce and process fermented milk were selected and interviewed using semi- structured questionnaires. Omashikwa and Mashini ghakushika have similar processing method whereby fermentation is achieved by accumulation of milk; mean while Mabisi is produced by allowing the milk to ferment naturally. The pH decreased logarithmically, nonlinearly over the fermentation period from 6.5 ± 0002 from first day of fermentation to 3.92±0.001 over 4 days.There was no significant difference (p<0.05) in the pH values between the three types of fermented milk preparations. Cell free supernatants (CFS) of 180 LAB isolated from traditional fermented milk were evaluated for antimicrobial activities against selected food borne pathogens; Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923, Candida albicans ATCC 14053, Bacillus cereus ATTC 10876 Geotrichum klebahnii (IKST F. Lab. isolate) Escherichia coli ATCC 25922 using the well diffusion method. Twenty LAB isolates that shown the highest inhibitory effects were selected for biochemical identification using API 50 CHL were identified as; Lactobacillus plantarum (53%), Lactobacillus rhamnosus (29%), Pediococcus pentosaceus (6 %), Lactobacillus paracasei ssp. paracasei (6%) and Lactococcus lactic ssp. lactis (6%), of which Pediococus pentosaceus showed the most inhibitory effect on all the indicator strains and they have potential to produce bacteriocin Pediocin and the most inhibited indicator strain belonged to yeast Candida famata. In addition to antimicrobial activities, the major organic acids in all three types of milk were found to be lactic acid 0.265±0.056 mg/L. However, the levels of volatile organic compounds in the naturally fermented samples varied from one sample to another but, butyric, acetic and propionic acid were found in trace amounts. Some of the volatile flavor compounds found in Omashikwa, Mabisi and Mashini ghakushika were acetic acid, 2,3 Butanediol and Lactic acid. Further genetic confirmation of species was carried out using the 16S rDNA sequences. The research outcome addressed the establishment of the newly identified starter cultures and contributes positively to the advancement of national LAB’s profiling. The study is also the first attempt that indicates probiotic potential and exceptional preservation properties of LAB from traditional fermented milk produced in North- Eastern Namibia.Item Molecular, environmental and nutritional evaluation of bambara groundnut (Vigna subterranea(L) Verdc.) for food production in Namibia(2010) Mukakalisa, Celine; ; ;Abstract provided by authorItem The maintenance of sweet potato planting materials in Namibia(1998) Rusch, Bianca RoswithaItem The study on Bifidobacterium strains with resistances acid and bile salts(2003) Shigwedha Nditange