School of Agriculture and Fisheries Sciences

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    Science and technological development of Omashikwa
    (2009) Bille, Peter G.; ;
    In Namibia, Omashikwa traditional fermented buttermilk made with the root of Omunkunzi (Boscia albitrunca) tree by local farmers is one of the most important rural food products. It provides nutrition, jobs and generates income for food security for the community. As a traditional fermented product, it is unusual as it has a viscous consistency and low syneresis. However, the quality of Omashikwa is inconsistent and is characterized by high acid taste, low pH, rancid flavour, root taste and smell and contains filth. In this research, the production process of Omashikwa, physico-chemical properties of the traditional and laboratory prepared Omashikwa and the role of the root of B. albitrunca tree in Omashikwa, viscosity, syneresis, microbiology and sensory properties were studied and compared in order to improve the quality of Omashikwa for wider community use and for poverty alleviation. Omashikwa was found to have a protein content of about 3.3%, fat 1.6%, moisture 90%, lactose 4.6%, ash 0.7%, total solids 8.7%, lactic acid 0.9% and a pH of 3.3 The quality of traditionally processed Omashikwa (TO) was compared with the laboratory processed Omashikwa (LO), which was made without the root. Traditional fermentation was carried out with raw milk and under rural conditions. After fermentation the milk was agitated vigorously to churn into butter, whereas LO was made with pasteurized (65ºC/30 min) and filtered milk, and cream was scooped off after fermentation instead of churning. LO had a significantly (p < 0.05) higher pH (4.44) compared to traditional Omashikwa (pH 3.25), lower acidity (0.68%) compared to 0.92% of TO. Fat content was higher in LO (2.44% fat) compared to 1.56% fat in TO. LO was free from filth and had higher viscosity (2.98 Pa.s) compared to 2.54 Pa.s and lower syneresis (14.4ml/24 ml) compared to 19.6ml/24ml of TO. It was found that extract from B. albitrunca root showed a low pH of 4.7 and exhibited bacterial inhibition properties on Total Plate Count Agar ring test. The root appear to specifically inhibit Escherichi coli, Staphylococcus aureus and Clostridium species. It also had a high content of soluble carbohydrates (hydrocolloids or gum) (19.4%). Significant difference (p < 0.05) in total aerobic counts was observed in TO of 6.62 log cfu/g compared to 8.62 log cfu/g of LO and lower lactic acid bacterial counts, 6.58 log cfu/g compared to 7.87 log cfu/g of LO. Probably the most affected microorganisms in TO were the non acid formers, as lower pH of TO and inhibitory compounds in Omunkunzi root could have reduced them. Coliforms, yeasts and moulds counts were not significantly different (p<0.05). No pathogenic bacteria were found in either product. The lactic acid bacteria identified belonged to the genera Lactobacillus (Lb.) (Weissella), Leuconostoc (Leuc.), Lactococus (Lact.) and Streptococcus (Str.) Twenty representative strains of LAB isolates were identified to species level; three belonged to the species Lb. delbrueckii subsp. lactis and two belonged to Lb. plantarum and two to Weissella confusa (former Lb. confuses). Three belonged to Str. salivarius thermophilus, three to Leuc. lactis, and two to Leuc. mesenteroides subsp. mesenteroides. Three belonged to Lact. lactis subsp. lactis and two belonged to Lact. lactis subsp. cremoris. Significant differences (p < 0.05) in descriptive and consumer sensory attributes scores were observed between traditional and laboratory Omashikwa. Sensory attributes scores of TO on the levels of syneresis was 3.4 compared to 2.9 for LO, filth 3.0 compared to 1.8 in LO, rancidity scores were 3.4 in TO compared to 1.8 in LO, and bitterness 4.2 in TO compared to 2.5 in LO. Aroma scores were 2.6 for TO and 4.2 for LO, viscosity 2.5 (TO) and 3.8 (LO) and texture 2.7 for TO compared to 4.2 for LO. There was an 80% preference score given to the laboratory Omashikwa by the young consumer panelists. The results of this study indicate justification of using B. albitrunca root in the processing of Omashiwa by the rural community to improve the quality of Omashikwa in terms of flavour, smell and consistency compared to other traditional fermented milk products and in the absence of modern technology. However, application of good manufacturing practices on unit operations, particularly heat treatment of milk prior to fermentation, use of lactic acid starter cultures, maintenance of good hygiene and sanitation including packaging, seem to be the effective methods to improve and sustain the quality and safety of traditional fermented buttermilk (Omashikwa) for a wider market and better price. Namibia Dairies Ltd, just like any other dairies in the region and elsewhere, manufactures buttermilk, a byproduct of butter that is fermented with mesophilic lactic acid cultures and branded as Omashikwa for the purpose of marketing. It has nothing to do with traditional Omashikwa as such; B. albitrunca root is not added and is processed by using modern industrial method. In addition, additives such as preservatives (potassium sorbate), stabilizers (pectin) and sugar are added and packed for distribution. This research project therefore investigated the processing technology, physico-chemical, microbiological, viscosity and sensory quality of traditional Omashikwa. The remedial measures to curb inconsistency and poor quality experienced in Omashikwa processed in Namibia were also investigated and scientific measures were proposed for production of quality Omashikwa for marketing to a wider community. Since laboratory processing method of Omashikwa gave a better quality product compared to traditional method in terms of microbiological quality, sensory attributes, viscosity, filth content, syneresis and general appearance, laboratory processing technique of processing Omashikwa is therefore recommended as an alternative and appropriate processing method for small scale production in the rural set up to improve the quality of Omashikwa.
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    Comparison of the rehabilitative effects of mechanical and chemical methods of bush control on degraded highland savanna rangelands in Namibia
    (2010) Kahumba, Absalom; ;
    The study was carried out at Spes Bona 207 farm in Hochfeld district, and Neudamm 63 farm in the Khomas Hochland district,Highland savanna in Namibia. The objective of this study was to investigate the rehabilitative effects of mechanical and chemical methods of bush control of an invasive bush species Acacia mellifera for achieving long term rehabilitation of a degraded highland savanna rangelands in Namibia. At farm Spes Bona, three belt transects (50 x 5m2) were laid in chemical treatments and another three belt transects (50 x 5m2) were laid in mechanical treatments. Moreover, the same method was used in the control experiment. At Neudamm farm, a 200 x 100m2 plot with 495 Acacia mellifera treated stumps were divided into 3 sub-plots for each treatment (mechanical, chemical and control). Each sub-plot was further divided into 3 replicates. In each replicate, stumps were randomly assigned key-tags with sequential numbers from 1-55 per sub-plot, for assessment purpose. At Spes Bona farm, the grass tuft density of species Aristida congesta, Cenchrus ciliaris, Chloris vigata, Eragrostis rigidior, Eragrostis viscosa, Melinis repens and Melinis villosum was significantly higher (P0.05) in chemical and mechanical than in control treatment. Similarly, the total grass density had greater values (P0.05) high in chemical (36.1 ± 9.6a), and mechanical (31.7 ± 9.7a) than in control (25.7±9.0b) treatment. The soil condition did not show significant difference (P0.05) between treatments. Total density of woody plants was significantly greater (P0.05) in the control than chemical and mechanical treatments. At Neudamm farm exmortality of stumps was significantly higher (P0.001) in chemical than in mechanical and control treatments. On the contrary, coppicing of stumps was significantly lower (P0.001) in the chemical method than in the control and mechanical treatments. Tuft greater values outside the canopy than underneath the canopy
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    Assessment of vegetation diversity and rangeland condition in the Highveld communal grazing lands of Swaziland
    (2011) Mapako, Leslie
    Determination of correct stocking rate based on current rangeland condition still remains a big challenge to livestock farmers. Assessment of vegetation diversity and current rangeland condition was carried out in four communal rangelands, namely Siphocosini, Hawane, Motshane and Nkhaba. The rangeland condition assessment method employed in this study was the ecological condition index (ECI) method. Grass species composition and dry matter were estimated using the point-intercept method and the direct harvest method using a metal frame (quadrat) respectively. Vegetation diversity was high. A total of 16 grass species were identified. Of these, 9 species were strong perennials and the remaining 7 were annuals. In addition, 5 species were identified as highly palatable, 6-moderately palatable and 4-less palatable species
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    Assessing the potential of using nylon bags in batch analysis of crude fibre and ether extract of livestock feeds
    (OMICS Group, 2012) Ncube, S.; Mpofu, I.
    The objective of this study was to determine the potential of laboratory batch analysis and optimum number of bags to be used. Katambora, veld hay and maize stover were analyzed for Crude Fibre (CF) and Ether Extract (EE) using the proximate analysis procedure but with samples bagged in nylon bags of pore size 60 micron. A completely randomized block design was used with Treatment 1 as the control, Treatment 2 with 1 bagged sample, Treatment 3 with 2 bagged samples, Treatment 4 with 3 bagged samples and Treatment 5 with 4 bagged samples. Results showed that there is a potential to use nylon bags in CF and EE analysis on katambora, veld hay and maize stover. There was an interaction between block and treatment. EE analysis on Katambora showed no significant difference among all treatments but for maize stover and veld hay, treatment 4 and 5 were significantly different from all the other treatments. In CF analysis trial, treatment 2 and 3 did not differ significantly from the control, while treatment 4 and 5 were significantly different from the control for all the diets. It was concluded that there is a potential to do batch analysis with optimum number varying between forage type and component of analysis. The proposed batch analysis is more sensitive with EE than with CF analysis.
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    The role, isolation and identification of Vibrio species on the quality and safety of seafood
    (Academic Journals, 2012) Shikongo-Nambambi, Martha N.; Petrus, Ndilokelwa P.; Schneider, Martin B.
    Seafoods in their natural environments are associated with a variety of microorganisms. Fish shelf life reduction results from microbial metabolism, mainly by Gram negative bacteria that produce chemical compounds responsible for bad odour, texture and taste. Shelflife is estimated by performing total viable bacterial counts at ambient and refrigeration temperatures. The type and number of bacteria present on seafood depends on the microbial composition of the surrounding waters, on the intrinsic factors, extrinsic factors, processing, and implicit factors and on the microbial interactions within the fish itself. Although, sea food safety assessment is preferably determined by detecting indicator organisms; such as Enterobacteriaceae and coliforms, none of these groups fulfil all requirements that guarantee food safety necessitating direct detecting of relevant pathogens. Vibrio species are part of the bacteria genera associated with seafoods borne diseases. Prompt and accurate detection and identification methods of pathogens are imperative to determine the product compliance with seafood microbiological criteria. Although cultural methods have long been used in detecting human pathogens including Vibrio species in fish, these methods are time consuming and sometimes inaccurate. Also some pathogens have the propensity to change into the Viable but non culturable (VBNC) state in unfavourable environments. The use of molecular methods is hampered by drawbacks, such as inter species 16S rRNA sequence similarity and that some strains carry multiple copies of the 16S rRNA gene. A combination of classical, numerical taxonomy and Multi locus sequence analysis (MLSA) methods are promising to give absolute resolution between closely related Vibrio species.
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    Impact of lifestock on vegetation and soil nutrients around water points in Highland Savanna rangelands, Namibia
    (2012) Mbango, Oscar
    Artificial watering points can have significant ecological effects in typically arid and semi-arid rangelands where permanent natural surface water is scarce or absent for provision of livestock farming in dry lands Namibia. The impact of livestock grazing on the vegetation and soil status was studied along a grazing gradient from watering points in the Neudamm high land savannah area, in both large and small livestock management system during wet season. Eight artificial points were selected for the study. A 600 m transect was laid out perpendicular to the direction of the grazing gradient from watering points, more or less into the middle of each of the livestock grazing camps. On each transect of each grazing gradient seven 20 x 20 m sample plots were laid out at interval distances of 0 m, 25 m, 50 m, 100 m, 200 m, 400 m and 600 m from water points and at each sampling distance on the transect a nested design of 1 m2, 5 m2 and 20 m2 plots were used for sampling grasses, shrubs and trees resulting in a total of 56 plots in the experimental unit plots. All shrubs and trees were identified, counted and recorded. Density was presented for individual shrubs and trees per 25 m2, 400 m2 to a hectare and grass percentage cover in 1 m2, respectively. Plant species diversity was calculated for each plot using the Shannon-Wienner diversity index. The results indicated significantly (P 0.05) lower plant densities, species diversity, richness and evenness with close proximity to water points, than further away from the water points. Significant differences (P 0.05) were observed for soil particle size analysis, pH, ECw, OC, CEC, P, K, Mg, Ca, Na and K contents along the gradient from water points. Thus, this study concluded there are differences along grazing gradient possibly due to livestock impact of trampling and grazing on vegetation and soil nutrients. This negatively influences vegetation composition, structure, richness and diversity around water points. However, no significant difference (P 0.05) in the quantized impacts of grazing and trampling were observed on soil nutrients and vegetation properties by livestock in different grazing management systems i.e. large-cattle and small stock-sheep camps
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    An assessment of the role of research and extension services for small-scale crop farmers in North-Central Namibia
    (2012) Thomas, Benisiu
    The aim of this study was to assess agricultural research and extension services that are aimed at improving rural household livelihoods in the changing environment in the north-Central Regions of Namibia. The study reviewed various secondary sources or publications and unpublished sources comprising technical reports, books, review papers and maps, all of which were deemed useful based on the role of agricultural research and extension services in north-Central Namibia. The presentations of the results were illustrated by examples from the area of crop production including seed multiplication, animal draught power and crop improvement schemes. The study found sufficient evidence that some research-extension strategies being employed are moderately successful. The main challenge, however, remains to strengthen national farming research or extension systems with an appropriate institutional and coordinating structure, focusing on decentralised participatory and adaptive research and on farm trials.
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    Identifying learning styles and technology acceptance of agriculture students: an effort to improve educational effectiveness
    (Association for International Agricultural and Extension Education, 2012) Murphrey, T.P.; Kalundu, S.K.; Jones, W.A.
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    Identification of putative vibrio species isolated from processed marine fish using Thiosulphate-Citrate-Bile-Sucrose (TCBS), Agar
    (School Domain International, 2012) Shikongo-Nambambi, Martha N.; Chimwamurombe, Percy M.; Venter, Stephanus N.
    Aims: To identify putative Vibrio isolates obtained from processed hake, pilchards and horse mackerel using Thiosulphate-Citrate-Bile-Sucrose (TCBS) agar.Place and Duration of Study: Sampling during April – June 2005 in Walvis Bay Namibia. Further analyses performed at the Department of Microbiology and Plant Pathology, University of Pretoria, South Africa between 2005 and 2007. Methodology: The 247 putative Vibrio isolates obtained from Thiosulphate-Citrate-Bile- Sucrose (TCBS) agar were initially grouped according to their Gram, oxidase and oxidation-fermentation reactions. Thereafter PCR was used to screen the isolates for genes specific to human pathogenic Vibrio species such as Vibrio cholerae, Vibrio parahaemolyticus and Vibrio vulnificus. This was followed by sequencing the 16S rRNAgene for isolates of interest and drawing Neighbour Joining phylogenetic trees based on the data. All atypical isolates were further characterised by a combination of selected phenotypic tests and the V. alginolyticus specific collagenase gene PCR. Results: Of the 247 isolates obtained from TCBS, four were Gram positive. Many of the Gram negative isolates belonged to the family Enterobacteriaceae and others were members of the Pseudomonadaceae. Of the 91 isolates identified as belonging to the Vibrionaceae and related families, Vibrio alginolyticus was the dominant Vibrio species. None of the bacteria isolated from the processed fish belonged to the human pathogenic Vibrio species. Conclusion: This study again demonstrated that TCBS agar is not selective for the isolation of Vibrio species and that a wide range of bacteria could be isolated on this medium when analysing marine fish. The identity of putative Vibrio isolates obtained from this medium should therefore be confirmed employing a number of phenotypic and genetic techniques to accurately identify the atypical isolates.
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    Control of bacterial contamination during marine fish processing
    (Macrothink Institute, 2012) Shikongo-Nambambi, Martha N.; Shoolongela, Abrahams S.; Schneider, Martin B.
    Fish is a vital source of nutrients to humans due to its proteinaceous nature, high content of unsaturated fatty acids and low contents of carbohydrates. In their natural environments fish are exposed to a myriad of microorganisms some of which compromise the shelf life of the product and/or safety in humans. Most fish factories located along coasts find it economical to use processed sea water during processing. Processed sea water however can be a source of microbial contamination to fish. Fish factories are also vulnerable to biofilm formation on surfaces and within water distribution pipes. Biofilms result from bacterial attachment and growth in aqueous environments that render bacteria resistant to sanitising agents. This article reviews the conditions permissible to bacterial contamination in marine fish factories. The role of water in bacterial contamination and survival has been highlighted. Bacterial pathogens commonly associated with fish factories and their survival strategies have also been discussed. The use of selected sanitizing agents and UV irradiation in marine fish processing have been explored. The fundamental antimicrobial mechanisms of chlorine, ozone and H2O2 is the generation of toxic metabolic intermediates that damage microbial structural and functional components, causing metabolic paralysis and cell death. UV radiation damages DNA hindering gene expression processes. Controlling bacteria biofilm has been well experimented in fresh water systems, but knowledge about disinfection of marine waters is still lacking. The review concludes that in order to optimise the microbiological quality of marine fish, suitable disinfectants effective in sea water need to be authenticated.