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Item 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.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.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.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, MatthijsThe 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/molItem Compositional and bacteriological quality of heat treated milk marketed in Namibia(African Scholarly Science Communication Trusts, 2012) Bille, Peter G.; Kaposao, S.Production of fresh farm milk in Namibia is low due to the arid climate that prevails in the country, low pasture availability and a high milk demand. This scenario has forced Namibia to import dairy products to meet its needs from neighbouring South Africa, South America and Europe. Namibia imports different brands of fresh full cream milk including Parmalat, Clover, Super milk to add on to its own brands such as Namdairies, UNAM milk and others from private and commercial farms in bulk or in plastic sachets and bottles. Generally, milk quality is determined by its safety, shelf life and nutrition. The presence of different brands of milk makes it difficult for milk consumers in Namibia to choose the brand they would prefer including assessing their value for money. The aim of the project was to determine the quality of full cream milk brands marketed in Namibia by assessing their proximate composition, titratable acidity, pH, protein stability, total plate count and Coliform bacteria as indicator bacteria for the presence of pathogens, using standard dairy procedures and AOAC methods. The results of the study indicated that all imported brands of pasteurised full cream milk in Namibia were not significantly different from each other and were safe and stable, and nutritionally of good quality. They were practically the same in composition and bacteriological quality. Butterfat ranged from 3.4 to 3.7%, density from 1.029 to 1.032g/cm3, total solids from 12.3 to 13.0%, solids-not-fat from 8.6 to 9.7%, moisture content from 87.10 to 87.70%, acidity as lactic acid from 0.15 to 0.17% and pH from 6.4 to 6.7. The total plate count (TPC) ranged from 0 to 40 cfu/cm3 and there were no Coliform bacteria found in all the brands. The local products were not statistically different in composition from imported brands, with fat ranging from 3.3 to 3.7%, density from 1.029-1.032g/cm3, TS from 12.3-12.9% and SNF from 8.6-9.4% though they were not standardized but heat treated. The total aerobic counts and Coliforms were the same as those of imported milk brands. The statistical analysis showed that there were no significant differences at p<0.05 among the brands and between the brands of the imported and local milk in Namibia as they were all within the South African Standard Specifications. All the brands were, however, regarded as good, stable and safe for consumption.