An in silico analysis, purification and partial kinetic characterisation of a serine protease from Gelidium pristoides
- Authors: Ntsata, Zolani
- Date: 2020
- Subjects: Gelidium Proteolytic enzymes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/12076 , vital:39149
- Description: The aim of this study was to characterize the protease enzyme (s) from red algae. An in silico analysis of red algae genomes was used to identify gene coding for protease. Protease sequences identified from these genomes were examined for conserved domains, active site and structures. The domain search revealed that the identified sequences were from the five classes of protease enzymes. For function inference, the red algae sequences were aligned to identify the catalytic sites, and the tertiary structures were predicted using homology modelling. An in silico analysis provides an indication of the class and potential functions of the enzymes. However, it cannot predict whether the gene is constitutively expressed in the red algae or under which conditions it may be induced, and it cannot determine the kinetic efficiency of an enzyme against various substrate, or the optimum conditions for the protein activity. Attempts to clone and recombinantly express selected red algae proteases, proved unsuccessful, as the available genomes where from red algae species found mainly in Asia, and the designed primers, therefore, did not amplify a corresponding PCR product from the red algae harvested in South Africa. Crude extracts of red algae collected from Kenton-on-Sea, along the East Coast of South Africa, were screened for protease activity using Benzoyl-Arginine-pNitroAnilide (BApNA) as substrate. The proteases detected in the crude extract were purified using ammonium sulphate precipitation and HiPrep DEAE FF 16/10; CM FF 16/10, and HiPrep Q FF 16/10 columns for ion-exchange chromatography. The HiPrep Q FF 16/10 column yielded active protein, which revealed two bands of 11kDa and 17kDa on SDS-PAGE. It was assumed that these bands represented two subunits of the purified protease. Kinetic characterisation of the purified protease revealed a pH optimum of 9, using BApNA as substrate, a temperature optimum at 60ºC, and sensitivity to temperature when stored above 4ºC. The protease activity was inhibited by Ferric chloride (32%), induced by calcium chloride (156%), no inhibition by magnesium chloride (97%) and slight inhibition by potassium chloride (77%) and manganese chloride (70%). Phenylmethylsulfonyl fluoride (PMSF), a serine protease inhibitor, almost totally inhibited the protease activity, indicating that the protease from red algae was most likely a serine protease. The Km and kcat values were 1.96 µM, and 0.364 s -1 , respectively using BApNA as the substrate. This study revealed that the red algae genome contains numerous genes that encode for proteases from almost all the classes of proteases. A serine protease from the red algae Gelidium pristoides was partially purified and kinetically characterised, confirming that red algae found along the Eastern Coast of South Africa contain genes that express active proteases that may be of medical or industrial interest. Further studies, however, are required to recombinantly express, purify and characterise the numerous proteases encoded by the genes identified in the in silico analysis of this study.
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Analysis of maximum power point tracking data for obtaining photovoltaic parameters
- Authors: Chitura, Anesu Godfrey
- Date: 2020
- Subjects: Photovoltaic power system
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/18576 , vital:42610
- Description: As a standard, photovoltaic (PV) modules are rated by the use of standard test conditions (STC). Such details entail current and voltage (I-V) measurements for modules under an irradiance of 1000 W/m2 an air mass ration of 1.5 global spectrum and 25˚C cell temperature. Outdoor weather conditions continuously vary with time and from one location to the other. This further offset the expected operational power outputs as outdoor conditions are generally characterized by high cell temperatures. The technology one uses will also complicate the power output prediction since different module technologies respond to these outdoor conditions differently. I-V tracers are able to measure the full I-V curve of the module thus can give the operational PV parameters at any given time. However, these tracers are sold at exorbitant prices and they require skilled personnel in order to operate them. Most if not all tracers require isolation of the module under test thereby disrupting the power production function of the module._________________________________________________________________________________________________________________________________________ In this study a method to obtain photovoltaic (PV) parameters using the maximum power point tracking (MPPT) data is presented and tested under natural outdoor conditions. The method features a customized data acquisition system (DAS) designed for the measurement and storage of meteorological and MPPT data. The DAS is capable of extracting parameters from any combination of modules with an open circuit voltage 〖(V〗_oc) less than or equal to 120 Volts and a short circuit current 〖(I〗_sc) of 100 Amps. The system used is capable of extracting MPPT data using a reliable, improved storage and a programmable data logger. In order to match the sampling operational speeds of internal charge controller switches a computer interfaced Peripheral Component Interconnect (PCI) card was also used. Data collection and characterization of the MPPT data was done in such a way that the power generation process remained uninterrupted throughout the whole process. The regression nonlinear least squares method was used to fit MPPT crests and obtain the knee part of the I-V curve. This was then extrapolated to obtain the full I-V curve, which then produces the operational PV parameters. The resultant parameters from the characterization process were logged and accessible at any time. The end result was a method that can be incorporated within a charge controller for quick, hands-free PV parameter extraction, using only the MPPT scanned data.
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Design of a Traffic Surveillance Application using iFogSim
- Authors: Sinqandu, Mluleki
- Date: 2020
- Subjects: Cloud computing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/18676 , vital:42705
- Description: __iFogSim is a toolkit to model, simulate and evaluate networks of Fog computing, Edge computing and Internet of Things (IoT). This framework provides the capabilities of analysing and evaluating the performance of applications and resource management policies in Fog/IoT environments, based on which designers can model and test their applications. This thesis proposes a novel application model of a traffic surveillance vehicular network application through smart cameras using iFogSim, where the scenario of multiple vehicles tracking is considered. The effectiveness of the proposed application model is assessed and validated by simulations using a modified application model inherited from a case study of intelligent surveillance through distributed camera networks introduced. Simulations are conducted using the iFogSim tool and performance evaluation is done. The comparison between one vehicle and multiple vehicle tracking is done and the results demonstrate that the multiple vehicle application model achieves a better performance in terms of average latency and data transfer rate
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Determinants of adaptation to climate variability:A case study of crop farming households in Tyhume Valley communities Eastern Cape,South Africa.
- Authors: Mtintsilana, Olona
- Date: 2020
- Subjects: Climatic changes Sustainable agriculture Climatic changes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/18789 , vital:42733
- Description: Climate variability affects rural households and agricultural productivity, yet it is just one of many stresses that vulnerable rural households have to cope with. Climate variability is not as noticeable as weather variability, because it happens over seasons and years. It is the manner in which climate fluctuates above or below a long-term average value. Without measures at local and national level to adapt to climate variability, risk of food insecurity will continue to increase at household level. The objective of the study was to determine factors affecting adaptation to climate variability. Purposive sampling was used to identify households who participated because of un-availability of sampling frame. Information was elicited from the selected households with the aid of a semi-structured questionnaire. The study utilised a cross-sectional survey of 205 farming households in Tyhume Valley communities. Data gathered was subjected to descriptive statistics, Cross tabulations and Binary logit model. The results indicate that rural households from Tyhume Valley communities practiced coping adaptation through use of the following adaptation strategies; crop rotation, planted drought resistant crops, changed planting dates and used indigenous strategies such as using ash to kill mule (intuku). Most of the households used irrigation as the coping strategy to adapt to climate variability. However, heatwave, high winds, employment status, cell phones, age and gender of the rural households’ heads have effects on households’ adaptation to climate variability in Tyhume Valley. In view of the research findings, a large number of farming households are old and are females, there is a need for development of labour saving technologies and extension services to increase the likelihood of adaptation of climate variability by vulnerable farmers such as women and elderly farmers.The study also recommends that there must be a development of infrastructure for farmers as they are negatively affect by high winds due to low infrastructural development.The study also shows that farming households who have access to cellphones are more likely to adapt to climate variability, therefore the study recommends that communication of farming households must be improved.Adapting to climate variability is an increasingly important issue in agriculture and one that is likely to persist for many years.
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Household and business recycling programs as green strategies for waste management in East London, South Africa
- Authors: Fotoyi, Tenjiwe
- Date: 2020
- Subjects: Refuse and refuse disposal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/18687 , vital:42706
- Description: Municipalities in South Africa generate enormous waste which is disposed of in a few landfill sites which, in turn, have a limited life span. Household recycling is one important mechanism that can be used to reduce the amount of waste that reaches overfilled landfill sites. The city of East London is running out of land to dispose waste, and their landfill sites, in particular, are filing up fast. Most of the waste generated, is recyclable, however recycling in the city remains fragmented, and is moving very slowly. This is because of the lack of a co-ordinated approach between the BCMM and the local communities, across the many suburbs of East London. Considering that urban areas have limited space, effective and efficient use of current landfills is of strategic importance. This research therefore will examine ways of improving recycling in East London, addressing challenges facing current recycling. Data for this study was collected from the random administration of 100 questionnaires on different categories of respondents in the study area. The study revealed that by the introduction of the “Hand-on-waste” programme, the waste management personnel have taken the first step towards household waste recycling. However, the level of awareness and knowledge of the public on domestic recycling was quite poor, if residents are given the necessary encouragement, motivation and recycling infrastructure waste minimisation would be achieved
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Identification of differentially expressed proteins involved in wheat (Triticum aestivum) resistance against Russian Wheat Aphid (Diuraphis noxia) SA2 using SWATH-MS analysis
- Authors: Ntlokwana, Sitha Emmanuel
- Date: 2020
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/18872 , vital:42888
- Description: Wheat (Triticum aestivum) is the second most-consumed cereal crop in the world, second only to maize. In South Africa it is mainly produced in three provinces; the Free State, Western Cape, and the Northen Cape. The average total land area used for wheat cultivation in these three Provinces, is 533 000 hectares, with a resultant annual production of between 1.3 to 2 million tons. The total wheat requirement in South Africa is currently 2.7 million tons according to the production of wheat guidelines published by the Department of Agriculture, Forestry and Fisheries, which is higher than the total annual production. One of the primary reasons that contribute to the lower production levels is insect and pest infestation, in particular, the Russian wheat aphid (Diurophis noxis), which can result in crop loss of up to sixty percent. Russian wheat aphids (RWA) are invasive insects that feed on the phloem of the plant through their specialised thin stylet-like mouthparts and release toxic agents contained in their saliva during feeding, which disrupt cellular functions inside the host plant. This damage leads to symptoms like; chlorosis, necrosis, wilting, stunting and curling of leaves, also known as leaf rolling. This study aimed to identify differentially expressed proteins in resistant and susceptible wheat (Triticum aestivum) cultivars during Russian wheat aphid Biotype South African 2 (RWA-SA2) infestation, in order to identify proteins involved in the wheat resistant mechanism against RWA-SA2. Two wheat cultivars SST398 (resistant to RWA-SA2) and SST356 (susceptible to RWA-SA2) were used, and a total number of 126 plants were planted and divided according to four different harvest times (Control day 0; day 5; day 7 and day 12). The wheat plants were infested with approximately 10 aphids per plant at the three-leaf stage, and placed within an insect cage inside a growth chamber (Conviron, Winnipeg, Canada) set at 24ºC, light intensity of 352 µmol.m-2.sec-1, ambient CO2 levels (410 ppm) and humidity of 60% with a 16h/8h day/night cycle. Wheat leaves were harvested at various time frames, and total protein extraction was performed. The protein samples were reduced with 10 mM dithiothreitol (DTT) and alkylated with 30 mM iodoacetamide (IAA). Sample clean-up and on-bead trypsin digest were performed on megReSyn Hilic columns, over four hours. The resultant peptides were vacuum dried and resuspended in 2% acetonitrile (ACN) before submitting them to LC-MS/MS (SWATH) for analysis. A total number of 611 proteins were differentially expressed, of which 19 were identified to be involved in the resistance response of wheat, and an additional 20 involved in biotic stress responses. This study showed that reactive oxidative species (ROS) such as hydrogen peroxide and hydroxyl radicals (OH-) play a significant role in the early stages of wheat resistance against RWA-SA2 infestation. They are involved in cell wall strengthening, activation of defence genes, involvement of phytohormone signals such as salicylic and jasmonic acid, which also mediates the systemic defences such as, systemic acquired resistance (SAR), leading to the expression of pathogen-related proteins such as (thaumatin-like proteins, oxalate oxidase, defensin, chitinase, and thionins). Although up-regulation of photosynthesis proteins such as (chlorophyll a/b binding protein, photosystem I and II, rubisco and divinyl chlorophyllide a, and 8 vinyl-reductase) were seen on both infested cultivars (susceptible and resistance), higher numbers of these classes of proteins were identified in the resistance cultivar, suggesting that they also play a critical role in resistance. In conclusion, the SWATH analysis used in this study was able to identify numerous proteins involved in the wheat resistance mechanism against RWA-SA2, most of which have not yet been reported to be involved in either biotic stress or RWA-SA2 resistance responses. Future studies are required to biochemically confirm the involvement of these enzymes and proteins the specific metabolic pathways where they are found, in the wheat resistance mechanism against Russian wheat aphid Biotype 2
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Influence of Tamarix species on soil physicochemical properties and mapping its distribution and density using GIS in Western Cape, South Africa
- Authors: Mlahlwa, Asiphe
- Date: 2020
- Subjects: Tamarisks
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/18588 , vital:42611
- Description: Tamarix ramosissima invasion is unarguably one of the worst ecological disasters in South Africa and is classified under category 1b by the National Environmental Management: Biodiversity Act 2014 (NEM: BA). The exotic Tamarix species was introduced in South Africa during the early 1900s as an ornamental or phytoremediating plant. This study was conducted to assess Tamarix distribution and evaluate its impact on soil physicochemical properties in two sites at Leeu River and Olifant River in Western Cape, South Africa. Samples were collected from Leeu River (which consists both the exotic and native Tamarix species) and Olifant River (only exotic Tamarix species). Three transects were laid from the water point outwards, with exotic Tamarix invading the river bank (first transect), the control on the open land (second transect) and the native Tamarix at the far end of the study site (third transect) in Leeu River. In Olifant, transects were laid according to the degree of invasion, low Tamarix density transect was referred to as T1, the medium as T2 and the high density as T3. Soil samples from each transect were taken from three points, at three soil depths (0-10, 10-20 and 20-30 cm) during winter and summer. Soil physiochemical properties such as soil pH, electro-conductivity (EC), total nitrogen (TN), total carbon (TC), soil organic carbon (SOC), sodium (Na+ ), potassium (K+ ), Calcium (Ca2+), Magnesium (Mg2+), bulk density, soil texture and sodium adsorption ratio (SAR) were determined. Soil chemicals properties including EC, Na+ , SAR, K+ and Mg2+ were found significantly higher under the native and the exotic Tamarix species when compared to Tamarix free soils. In general, salinity of surface soils (0–10 cm) was greater than those in the deeper soils with 5.05 mS/cm and 4.73 mS/cm observed under exotic and native Tamarix species, respectively. High levels of EC, K+ , Ca2+, Na+ , SAR, TN, TC and SOC were observed under T3, followed by T2 with the lowest being recorded in T1 at 0-10 cm. Unlike the soil EC, the effect of Tamarix density on soil pH at 0-10 cm soil profile was not significant. Alterations of soil physicochemical properties were more pronounced under the high Tamarix density as compared to the low invasion. Increased in distance from the river was related to a higher density of the invasive species and also topography had a major role in the change of species density. An increase in Tamarix density, results in high leaf litter which in turn results in salinity and soil nutrient at 0-10 cm. Soil salinity was dramatically increased under Tamarix species. Tamarix species are capable of altering the soil properties making it conducive for their growth.
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Spatio-temporal variation of the land surface parameters in Temperature, in King Williams Town, Eastern Cape Province, South Africa
- Authors: Willie, Yanga Adrian
- Date: 2020
- Subjects: Environmental sciences
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/12106 , vital:39152
- Description: The world is currently experiencing unprecedented urban growth. The influx of people into urban areas from rural areas is motivated by both economic and social factors such as increased employment opportunities. The latter is a result of, in part, industrialization, and the perceived higher standard of living that is often associated with access to better infrastructure. Surface Heat Island (SHI) is a phenomenon whereby urban areas experience higher surface temperatures than the surrounding rural areas. The presence of the SHI in urban areas has a negative impact not only on city dwellers, but also on the environment and the economy. The development of SHI is often associated with patterns of land use and land cover in urban areas. Numerous methods exist that can be used to study SHI’s. Literature suggests that Land Surface Temperature (LST), derived from satellite imagery, is a proven method that produces reliable results. The aim of this study was to evaluate the SHI in King Williams Town by studying the relationship between land surface temperatures, land cover and land cover indices. The derived indices are the Normalized Difference Vegetation Index (NDVI) and Normalized Difference Built up Index (NDBI). These indices were selected because they are representative of the land cover scheme used in the research study. This study was conducted in the King Williams town area between the years 1995 and 2018 the land surface temperature was derived from Landsat ETM + high thermal band data. The findings from this study provide an idea on the correlation between satellite derived land surface temperature and the land modification which occurred during the urbanization of King Williams Town during a 23 year period between1995 and 2018. The built up land category was the most influential in the development of high land surface temperature levels , vegetation had an opposite effect as a series of data sets illustrated that vegetated areas had a iv cooling effect on the surface. Water bodies in the study area had an insignificant effect on the Surface temperature levels while the grass lands weren’t as cooling as the vegetation but provided a cooling environment in the study area .The spatial distribution of areas of high surface temperature (hot spots) was discovered to be concentrated in the urban areas of the study area which is in the northwest region of the study area and correlates to the land cover and land cover indices associated with built up and artificial surfaces. The cooler areas or patches of land with lower values of land surface temperature were distributed on the outskirts of the study area away from the CBD and residential areas. This was the case because of the high concentration of vegetation and thicker grass lands in those regions.
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Synthesis and characterization of MXS (M = Mo & V) and carbon supported MXS nanocomposites as Pt-free counter electrodes for electrode for DSSC application
- Authors: Bede, Asanda
- Date: 2020
- Subjects: Voltammetry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/18599 , vital:42612
- Description: It has been reported that the morphology, crystalline phase composition and electrochemical properties of counter electrode materials such MxS (Mo, V) and carbon supported MxS (Mo, V) composite nanomaterials was of considerable importance because it governs the efficiency of many photon assisted chemical and physical reactions in dye sensitized solar cells (DSSCs). The efficiency of DSSCs with composite counter electrode materials is reliant on the stability of the photochemistry reactions which can be optimized by appropriate doping levels of the composite materials. Moreover, the microstructure such as surface area, distribution of the MxS (Mo, V) and carbon supported MxS (Mo, V) composite nanomaterials, and the stability of the electrostatic bonds between the MxS (Mo, V) with the carbon support also play a significant role in the performance of the DSSCs. This work evaluates the effect of different mole ratios of the MxS (Mo, V) and carbon supported MxS (Mo, V) composite nanomaterials on the morphological, structural and electrochemical properties of the composite materials. MoS2 nanoflakes nanostructures have been synthesized by hydrothermal technique using sodium orthovanadate (Na2MoO4) as precursor. In this work Carbon supported MoS2 NFs have been prepared by physically/chemically mixing different mole ratios of MoS2 NFs with multi-walled carbon nanotubes (MWCNTs) and polyvinylidene in N-methyl-2-pyrrolidinone. The morphological, structural and electrochemical properties of the composite counter electrode materials have been investigated using SEM, XRD FTIR, TEM, RS and CV. SEM analysis has revealed the presence of large MoS2 nanoflakes (NFs) as synthesized. SEM analysis has also revealed significant change in the surface morphology of carbon supported MoS2 composite nanostructures with the change in the mole ratio of the MoS2 NFs and carbon support multi-walled carbon nanotubes. Structural analysis through HRTEM analysis revealed a d-spacing of 0.65 nm with a corresponding (002) lattice plane belonging to a trigonal crystalline phase of MoS2. Also, HRTEM analysis has revealed d-spacing of 0.291 nm corresponding to 002 plane of MWCNTs. Raman spectroscopy has revealed Characteristic Raman vibration frequencies and symmetries at 264.6 cm-1(Eg), 354.2 cm-1 (Ag ) belonging trigonal phase of MoS2 (1T-MoS2). FTIR analysis has revealed a narrow peak at 457.6 cm-1 due Mo-S vibration bond. This observation confirms the success of synthesis of MoS2 nanostructures. Cyclic voltammetry (CV), charge-discharge (CD) and electrochemical impedance spectroscopy (EIS) measurements have revealed that the ratio 6:3:1 have shown to be optimum ratio due to its large reduction rate compared to pristine MoS2 NFs and other carbon supported MoS2 NFs. Calculated Rreduction for the carbon supported MoS2 NFs is the order 3:6:1>1:8:1>6:3:1>8:1:1 indicating the trend of ratio 3:6:1 appeared to have higher reduction rate than the rest of the material and it had far less ΔEpp than the rest of other ratios. All CV curves for both pristine MoS2 NFs and carbon supported MoS2 NFs confirmed a distinct Faradic characteristic. The VS2 nanosheets (NSs) and carbon supported VS2 NSs were also effectively synthesized via hydrothermal method. The SEM micrographs for VS2 NSs and carbon supported VS2 NSs samples reveals level increased. Furthermore, SEM-EDX analysis have confirmed the presence of V and S as well as C and O on carbon supported VS2 nanocomposites, and it clearly shown a gradually blending as the ratios increases. The structural studies through XRD analysis have revealed peaks at 2θ angles of 15.4◦, 28.2◦, 34.2◦, 36.2◦, 43.3◦,48.3◦, 54.4◦, 57.7◦ and 66.2◦ which correspond to the lattice planes (001), (002), (100), (011), (102), (003), (110), (103) and (201) belonging to hexagonal VS2 (H-VS2) crystalline phase as per JCPDS card 36-1139. The HRTEM have revealed that the VS2 NSs have an edge to edge length of ~ 0.294 – 1.248 µm. Also, HRTEM micrographs of VS2 NSs have revealed interplanar d spacing of 0.571 nm belonging to the (001) lattice plane of hexagonal VS2 (H-VS2) structure. FTIR analysis have shown a peak at 558 cm-1 attributed to V-S which is evident that sulfur has bonded with the metal (V) and is in agreement with EDS. CV, CD and EIS measurements have shown that the ratio 1:8:1 is more superior to VS2 NSs and other carbon supported VS2 NSs. Based on Rreduction for the carbon supported nanosheets VS2 nanosheets are ordered as 1:8:1>3:6:1>6:3:1>8:1:1. Carbon supported VS2 NSs of the mole ratio 1:8:1 showed a small resistance of 0.32 Ω. This is further evidence that the carbon supported VS2 NSs of the mole ratio 1:8:1 in addition to revealing excellent catalytic behaviour is also more chemically stable and has good conductivity properties._________
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The effect of muscle type and freezing on the evolution of physico-chemical properties during processing of South African biltong and its final textural properties
- Authors: Ngwendu, Nwabisa
- Date: 2020
- Subjects: Biltong Meat -- Quality -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/12128 , vital:39154
- Description: The study investigated the effect of muscle type and freezing on evaluation of mass transfer during processing physico-chemical of South African biltong and its textural properties. In the first experimental phase of this study, mass transfers, physico-chemical and textural properties (hardness, cohesiveness, springiness, and chewiness) of commercially produced biltong from biceps femoris (BF) and semitendinosus (ST) (n=9) were measured. Biltong was dried at 30oC and 40% relative humidity until it had lost 50% of its initial weight. The initial moisture content, water activity (Aw) of BF muscles (74.3% and 0.992) were significantly lower compared those of ST muscles (75.4% and 0.994%). The fat content of BF (2.3%) muscles was higher (P<0.05) than in ST muscles (1.7%). The salt, weight and water gain for the BF muscle were 2.3%, -2.6% and -7.0% respectively and were significantly higher than those of ST muscles which were 2.1, -0.4 and -4.0, respectively. After drying, the moisture content, Aw, and pH were lower in BF (42.2, 0.886 and 5.29) than those of ST muscles (45.1, 0.911 and 5.42). The salt content was higher (P<0.05) in BF muscle than in ST. Among textural properties, hardness was significantly higher in biltong from the BF (233.0N), while the springiness was significantly lower compared to the ST muscle (178.2N). Therefore, it was concluded that the use of different muscles results in variation of biltong physicochemical characteristics. The second experiment investigated the effect of freezing and muscle type on mass transfers, lipid oxidation, physico-chemical and textural properties of biltong. In this experiment, the iii ST muscles were replaced with semimembranosus (SM) muscles. A total of 12 beef muscles were used, with six BF and six SM muscles frozen in a blast freezer at -40 oC till they reached -20oC; then they were transferred to -20oC for 14 days. The thawing loss for the BF and ST muscles was 1.3 and 2.4% respectively, but there were no significant (P>0.05) differences. The protein and salt content were significantly higher in frozen-thawed (24.3 and 0.13%) muscles than in fresh muscle (20.2 and 0.08%); whereas the fat content and pH were lower (P<0.05) in frozen-thawed (5.36) compared to fresh muscles (5.51). Between muscles, the moisture, salt content, and pH were higher in BF muscles than in SM muscles (73.2, 0.12% and 5.49). Aw was affected by the interaction between freezing and muscle type, with frozenthawed SM having lower Aw (0.990). During salting, salt, weight and water gain did not show any differences (P<0.05). There were no major significant differences after salting. There were lower TBARS and pH in frozen-thawed (1.5mgMDA/kg and 5.15) muscles than in fresh muscles (3.3mgMDA/kg and 5.19) as well as in SM muscles (1.8mgMDA/kg and 5.16) than in BF muscles (3.0mgMDA/kg and 5.19). The moisture was significantly lower in frozen-thawed SM (68.1%) than in fresh SM, BF and frozen-thawed BF (69.3,70.5 and 71.7%) after salting. On the final product, the interaction between muscle type and freezing affected the moisture content, TBARS, chewiness and the springiness of biltong, with the biltong from fresh SM (39.8%) having significantly lower moisture content compared frozenthawed BF and ST muscles as well fresh BF muscles (42.8% in average). The TBARS were higher in biltong from fresh BF muscles (5.1mgMDA/kg) compared to other muscles. Furthermore, the chewiness and springiness were higher (P<0.05) in biltong produced from SM frozen-thawed muscles (327.7N and 1.5). The WBSF was higher in biltong from the BF muscles (108.8N) than in the biltong from SM (80.1) but it was not affected by the freezing effect (P>0.05). Freezing did not show any major differences in biltong. iv The third experiment was conducted to determine the effect of freezing African buffalo carcasses on weight loss during salting, physico-chemical and textural properties of biltong. Five muscles (ST, SM, BF, LTL, and RF) were randomly selected from 30 carcasses (15 frozen-thawed and 15 fresh), cut along the grain, traditionally salted and dried at 26oC till they lost 45-50% of their initial weight. The salting weight loss was higher in frozen-thawed muscles (-1.45%) than in fresh muscles (-0.89%). The freezing treatment affected the physico-chemical properties of the biltong. The biltong produced from frozen-thawed muscles showed significantly higher protein and ash (47.6 and 7.6%) compared to fresh (43.9 and 7.1); whereas the moisture, fat, pH and Aw were lower (43.7, 2.1, 0.870 and 5.30, respectively) compared to those of biltong from fresh muscles (45.5%, 2.9%, 0.890 and 5.38). The moisture, pH and fat content were further affected by muscle type. The interactive effect was observed in salt content, with RF frozen-thawed showing higher salt content (8.2%) compared to all other muscles. The hardness and WBSF were significantly higher (P<0.05) in biltong frozen-thawed (204.1N and 135.0N) than in fresh muscles (146.2N and 113.1N). Moreover, the chewiness and springiness were affected (P<0.05) by muscle type, with RF muscle having higher springiness 0.89 and chewiness 171.1N than all the other muscles. Therefore, it can be concluded that freezing buffalo carcasses significantly influenced the quality characteristics of biltong. The fourth experiment studied the effect of drying methods on physico-chemical properties of traditional biltong produced from African buffalo muscles. The BF and SM muscles were randomly selected from 15 fresh carcasses, cut into strips, salted and divided into two batches per muscle. The first batch of each muscle type was dried in the ambient-air drier at 22oC average and the second batch in the cabinet drier at 26 oC till 45-50% weight loss. No differences (P>0.05) were observed in salting weight loss between the drying method and muscle type. The protein content was significantly higher in SM (46%) muscles compared to v BF (43%) but there was no effect (P>0.05) caused by the drying method. The interactions between the muscle type and drying method affected the fat content, with biltong from airdried BF muscles having significant lower (2.1%) fat content. There were no significant differences in other physico-chemical properties of biltong, with moisture content, salt, ash content, Aw and pH being 45.0%, 5.13%, 44.8%, 7.3%, 2.7%, 0.885 and 5.61 on average, respectively. Overall, the findings of the study show that freezing does have a significant effect on the final quality of biltong. However, it can be concluded that a significant effect on the physico-chemical properties of biltong depends on the changes of mass transfers during salting and drying.
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