School of Agriculture and Fisheries Sciences

Permanent URI for this community

http://hdl.handle.net/11070/3308

Browse

Browsing School of Agriculture and Fisheries Sciences by Issue Date

Filter results by year or month
Now showing 1 - 20 of 89
  • No Thumbnail Available
    Item
  • No Thumbnail Available
    Item
  • No Thumbnail Available
    Item
  • No Thumbnail Available
    Item
  • No Thumbnail Available
    Item
    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.
  • Thumbnail Image
    Item
  • No Thumbnail Available
    Item
  • Thumbnail Image
    Item
    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
  • Thumbnail Image
    Item
    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
  • Thumbnail Image
    Item
  • No Thumbnail Available
    Item
  • Thumbnail Image
    Item
  • No Thumbnail Available
    Item
    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
  • No Thumbnail Available
    Item
    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.
  • No Thumbnail Available
    Item
    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.
  • Thumbnail Image
    Item
    A situational analysis of livestock production in liberia: A case study of Nimba, Bong and Montserrado countries
    (2012) Andrews, Leelia R.
    The main objective of the study was to analyze the situation of livestock production in Liberia. The specific objectives were to analyze the population of livestock in Liberia, to establish the factors limiting the production of livestock in Liberia, to analyze Liberia land use system of the livestock production sector and to analyze the economic impact of livestock production in Liberia. The study was a case study which surveyed three counties in Liberia: Nimba, Bong and Montserrado. Nimba and Bong are in the north and Montserrado in the south respectively. Descriptive analysis was conducted through the triangulation involving both qualitative and quantitative research methods and primary data, well- structured questionnaires, key informant interviews, focus group discussions, and meetings with the relevant stakeholders. The study findings revealed that livestock production in Liberia is on the increase. However, livestock production in Liberia is limited by factors such as respondents’ lack agriculture training, insufficient infrastructure, lack of veterinary services, insufficient finances, shortage of commercial feed supplements, inefficient and ineffective implementation of Government policies, lack of market and competition from imported livestock produce. The study established that pasture land is largely communal and is continuously used for livestock production. The study found that there is a little extent of application of pastureland management practices. Most of the farmers produce livestock for immediate consumption and sustainable livelihoods and not for commercial purposes. The study recommended that livestock should be included in the Poverty Reduction Strategy Papers (PRSPs), the public sector should develop and enforce policy and regulatory frameworks for livestock, regulatory capacity of livestock authorities should be strengthened, collective action among smallholders should be strengthened. Moreover, the government should encourage Private or Public-NGO partnerships to deliver livestock services to livestock farmers.
  • No Thumbnail Available
    Item
    Kinetics of thermal degradation of vitamin C in marula fruit (Sclerocarya birrea subsp. caffra) as compared to other selected tropical fruits
    (Elsevier, 2012) Hiwilepo-van Hal, Penny; Bosschaart, Charlotte; Van Twisk, Cherlotte; Verkerk, Ruud; Dekker, Matthijs
    The kinetics of the thermal degradation of vitamin C of marula, mango and guava pulp at different heat treatments at temperature ranging from 80 to 150 C were investigated. For temperatures lower than125 C, the ascorbic acid in marula pulp was about 15 fold more stable to heat than the ascorbic acid in mango and guava pulp. The results showed that a simple first order degradation model could not describe the vitamin C degradation as biphasic behaviour was observed. Therefore the model was transformed in a two-fraction model in which the vitamin C content is divided in relatively stable and instable fractions. Marula had a low kd1,100 C of 7.2 10 3 min 1 compared to kd1,100 C of 1.2 10 1 min for guava and 1.3 10 1 min 1 for mango. Guava had the highest activation energy, Ea of 58 kJ/mol, followed by mango with 39 kJ/mol and then marula with 29 kJ/mol
  • Thumbnail Image
    Item
    Coping with Climate Change Challenges by Feeding Indigenous Chickens under Intensive Systems in Namibia
    (OMICS Group, 2012) Petrus, Ndilokelwa P.; Mpofu, I.; Shikongo-Nambambi, Martha N.
    Floods that have hit Northern Communal Areas (NCAs) of Namibia in recent year pose feeding and other challenges to indigenous chicken. Indigenous chickens constitute a major source of livelihoods among rural farmers. The objective of this study was to determine the potential of intensive feeding of high and low plane of protein nutrition to indigenous chickens as one way of coping with environmental challenges caused by annual floods in the NCAs. Adequacy of protein inclusion in the diet is a viable option for improving the growth of small rural owned chickens. Two hundred and four indigenous chickens were subjected to two levels of plane of nutrition namely high and low plane of protein nutrition. At the low level, the protein was 18% in the 1-8 week age group, 16% in 9-22 week age group and 12% in the 23-36 week age. Feeding at high plane of protein nutrition was as follows; 23% in the 0-8 week age group, 20% in the 9-22 week age group and 16% in the 23-36 week age group. The control group was fed according to the Namibian poultry industry standards. The results showed significant and highest responses between the treatments in weeks 1-8 of age. Between 9-22 weeks, chicken mortality lowest at 5.6% in the high plane of nutrition group compared to 14.4% in the low plane of nutrition. The birds in control group consumed significantly (P<0.05) less feed than those fed with the high and low protein diet. Intensive feeding has a potential of alleviating nutritional stress of indigenous chickens under adverse environmental conditions. Farmers however, have to respond by cropping more intensively for the feed resources to be available.
  • No Thumbnail Available
    Item
    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.
  • Thumbnail Image
    Item