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A Modal Approach To Price An Option In Continuous Time
(KNUST, 2018) Osei Antwi
Average value options or Asian options have been priced using geometric and arithmetic averages of the underlying asset. However, these methods do not give accurate results especially in very low volatility regimes. In this study, we develop a new option pricing model based on the modal average of the underlying asset to price options. Using data from the NASDAQ in the United States of America we use the proposed model to price options sold on some stocks listed on the exchanges using software. The results consistently showed that for volatilities less than 3% of the underlying asset, the modal average option pricing model gives a better option price when compared to existing average option pricing models. Moreover, the modal average consistently does better at all levels of volatility when compared to the Black-Scholes model. We further proved analytically that the modal average model indeed does better than the geometric or arithmetic average models especially for low volatility stocks.
An Integrated Approach To Buruli Ulcer Transmission Studies: From Aquatic Environments To Human Infection
(KNUST, 2018-04) Charles Quaye
Buruli ulcer (BU) is a debilitating skin infection usually of impoverished tropical rural populations. BU is caused by Mycobacterium ulcerans (MU), a pathogen described as a non-tuberculous mycobacteria (NTM). The exact mode of transmission of BU is not known and involvement of insect vectors including mosquitoes, animal and small mammal reservoirs and aerosols in transmission and dispersal has been proposed. A holistic approach to studies that involve NTM is proposed especially in transmission and control studies. This study related human MU infections to MU types in identified risk areas and establishing sources of human infections. Water body type preferences of members of the two most implicated insect families in BU transmission, Family Belostomatidae (Hemiptera: Heteroptera) and Family Naucoridae (Hemiptera: Heteroptera) collected from water bodies in Ghana and Cote d’Ivoire were also related to their probability of being involved in transmission of BU. Four BU endemic communities (Bepotenten, Sukuumu, Monia-Gyaman and Wromanso) in the Amansie Central District of the Ashanti Region of Ghana were selected for the study. Two hundred and twenty-four (224) questionnaires administered proportionally to population were used to elicit responses to water use and areas of contact, BU knowledge, animal contact and infection status. Ground truthing of the four communities and the capturing of geographical information allowed the reconciliation of questionnaire water contact points and the subsequent mapping to reveal all surface water contact points. M. ulcerans from environmental sources was detected using 16S rRNA and then IS2404 detections. M. ulcerans genetic material from both human BU cases and identified environmental sources were VNTR (viable number tandem repeats) typed at four loci (VNTR targets: MIRU1, Locus 6, ST1 and Locus 19. Swimming and bathing (p=0.04) in risk environments and the capture of squirrels (p=0.04) were associated with an increased in the risk of acquiring BU in the study communities (OR= 3.28 and OR=5.85 respectively). Rigorous activity in infected water was found to increase the risk of infection laying credence on a direct trauma infection route for M. ulcerans. VNTR typing of MU from human BU disease and environmental samples revealed localized infection with inhabitants mostly being infected from community associated water bodies. Four main VNTR types were detected in human disease MU based on number of copies of four loci: MIRU1, Locus 6, ST1 and Locus 19. These were ‘W’ (1,1,2,1), ‘X’ (1.1.2.2), ‘Y’ (1,2,2,1) and ‘Z’ (1,2,2,2) in the copy number order MIRU1, Locus 6, ST1, Locus 19. The ‘Y’ VNTR type was common to all communities being detected in human as well as environmental samples and is therefore the profile causing the most infections in the study communities. A total of 125 and 321 individual Naucoridae (Hemiptera: Heteroptera) and Belostomatidae (Hemiptera: Heteroptera) respectively were classified to at least genus level. Eight species of the Naucoridae were identified; Ctenopocoris africanus (Leach, 1815), Aneorocoris insolitus (Montandon, 1897), Laccocoris limicola (Stal, 1855), Laccocoris spurcus congoensis (Poisson, 1949), Neomacrocoris bondelaufa (Sites, 2015), Neomacrocoris vuga (Sites, 2015), Naucoris obscuratus (Montandon, 1913) and Neomacrocoris usambaricus (Montandon, 1913). Differences in habitat preference of the Naucoridae were observed. Naucoris spp and Laccocoris spp showed the least preference for lotic water bodies (p<0.05). Four genera of the family Belostomatidae; Abedus, Diplonychus, Lethocerus and Benacus, were identified in collections from 82 water bodies in Ghana and 7 water bodies in Cote d’Ivoire. Abedus spp were the most abundant and most widely distributed. Belostomatidae showed no preference to type of water flow (p=0.2068). The integrated approach of the study offered complementary information, observations and deductions which together enabled verifiable conclusions to be drawn on the transmission of the environmental mycobacterium. The use of few communities facilitated a more concentrated search for risk areas and their link to BU infections in the study communities. A study involving a higher number of communities in a similar geographical range is recommended. In insect transmission studies, individual species competence should be considered and generalizations minimized as species preferences to habitat are important especially in studies involving NTMs.
The anti-termite properties and basic phytochemicals of eight local plants and the chemical characterisation of thevetia peruviana (pers) k. schum in Ghana
(2009) Tagbor, Trinity Ama
There is an increasing interest in the use natural products for termite control because of their environmental safety. Some local plant materials have been mentioned as potential alternatives to synthetic termiticides. The objective of this work was to determine the antitermitic efficacy of locally available plants such as; Thevetia peruviana (pers) K Shum Carapa procera DC, Jatropha curcus L ,Cassia nigricans Vahl, Cymbopogon ginganteus (Hachst) Chiov), Hyptis spicigera Lam., Vetiver zizaniodes Nash (vetiver grass) and Chromolaena odorata (L). Following the identification and collection of the experimental plants and termite samples, a series of field and laboratory experiments were conducted using parts of the plants to determine their antitermite efficacy. Antitermite efficacy was measured as their tolerance to termite damage, repellency and toxicity to termites. This was followed by extraction into petroleum ether, ethanol and water and the analysis of the most efficacious extract by chromatography (thin layer, column and high pressure) and spectrometry (mass spectrometry, nuclear magnetic resonance and infra red) methods to identify the active ingredients in the extract of the most efficacious plant. Resistance to termite destruction was measured by the loss in weight of stakes buried in treated and untreated soil and by visual assessment of extent of destruction. Repellency or attrantancy was determined by counting the number of termites that moved towards or away from filter paper pads treated with extracts of the test material. The results showed that soil treated with pulverised materials from T. peruviana offered the best protection to buried stakes against damage by subterranean termites. Field tests conducted with petroleum ether, ethanol and water extracts of T. peruviana suggested that the ethanol extract of T. peruviana resisted the destructive effects of termites most. In the repellency/attrantancy test, the ethanol extract was found to be an attractant. When the fractionated components of the ethanol extract were tested on brine shrimps, fraction 1 was found to be highly toxic suggesting obvious cytotoxicity. Analysis of fraction 1 by chromatography and spectrometry methods indicated the presence of two components digitoxin and digitoxigenin which were found to be toxic to brine shrimp. Sucrose was also isolated from the crude ethanolic extract of T. peruviana. Thus this work has shown that the potential for the use of anti-termite agents from T. peruviana is promising.
Anti-Wolbachia Treatment of Lymphatic Filariasis and Genetic Analysis of the Pathology of Lymphedema as a Clinical Manifestation of the Disease
(2012) Batsa, Linda
Lymphatic filariasis (LF) caused by Wuchereria bancrofti is a disease of considerable public health and socio-economic burden in the tropics. The recommended drugs (ivermectin and albendazole) for the control of lymphatic filariasis are only microfilaricidal. The regimen of the standard treatment with doxycycline which has proven macrofilaricidal is 200mg/d for 4 weeks. This is considered a long period and dissuades complaince by patients receiving treatment. Therefore reducing the duration or the dosage from the current 200mg/d to 100mg/d would be a better option and will also increase compliance. In search of a more effective drug to complement the existing ones, in an area endemic for bancroftian filariasis in Ghana, 261 adult worm positive men were recruited for a double blind placebo-controlled study in the Ahanta West District of Ghana. Six groups of patients were treated with the gold standard (4 weeks 200mg/d doxycycline), 5 weeks and 4 weeks 100mg/d doxycycline, 3 and 2 weeks combination of 200mg/d doxycycline and 10mg/kg rifampicin and 5 weeks placebo. The effect of the treatment on Wolbachia depletion was assessed at 4 months after treatment; adult worm vitality assessed at pre-treatment, 12, 18 and 24 months, and microfilarial depletion assessed at pre-treatment, 4, 12, 18 and 24 months follow up time points. In accordance with the national mass drug administration programme, all the study participants were given 150mg/kg ivermectin and 400mg albendazole four months after treatment. The treatment drugs were well tolerated with no serious adverse effects in both the treated and the placebo groups. There was significant Wolbachia depletion at 4 months time point in the standard group (p=0.001), 5 weeks 100mg doxycycline (p=0.019), 4 weeks 100mg doxycycline (p=0.03) and 3 weeks combination treatment (p=0.028). However there was no significant Wolbachia depletion in the 2 weeks combination group as well as the placebo group (p>0.05). Microfilarial assessment at 12, 18 and 24 months follow up time points showed a significant depletion in the standard group, 5 weeks and 4 weeks 100mg doxycycline groups as well as the 3 weeks combination of 200mg plus rifampicin group but not in the 2 weeks and placebo groups (p>0.05). The macrofilaricidal activity was significant at 12, 18 and 24 months in the standard and the 5 weeks groups. In the 4 weeks group, it was significant at 18 and 24 months time point and in the 3 weeks group it was significant at 18 months follow up time point, but no significant difference was observed for the 2 weeks and the placebo groups. On the other hand, there is the need to know the genetic markers associated with LF. Such knowledge will be beneficial in terms of diagnosis and possible therapy of various forms of the pathology. For this reason, a cross-sectional study of unrelated Ghanaian volunteers were designed to genotype single nucleotide polymorphisms (SNPs) in 266 lymphedema patients as cases and 691 infected patients without pathology as well as 346 endemic controls. Out of the 147 chosen SNPs that were genotyped, 11 SNPs in eight genes were found to be associated with lymphedema. The associated SNPs were in the vascular endothelial growth factor receptor 3 (VEGFR3), nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor alpha (NFKB- inhibition alpha), carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM-1), tissue inhibitor of metallopeptidase 2 (TIMP) genes, interleukin 10 and two SNPs in insulin like growth factor-1 (IGF-1) and matrix metallopeptidase 2 (MMP-2). A SNP in the interleukin 17 gene revealed a trend but there was significant haplotype association. In conclusion 5 weeks, 4 weeks and 3 weeks combination regimens of doxycycline were effective in treating LF infections, and SNPs in the angiogenic pathway were found to be associated with the pathology of lymphatic filariasis.
The application of starter cultures in the fermentation of pito towards industrial production
(February, 2018) Djameh, Clement Kornu
Pito is a popular traditional sour sorghum beer widely consumed in Ghana and Nigeria. It is brewed mostly by women at an artisanal level but has huge economic potential for industrial production and commercialization. The brewing methods are not standardized and vary according to the ethnic group of the processor or the tribal area where it is brewed. The brewing processes are tedious and uncontrolled resulting in inconsistent product quality. There are two fermentation steps involved in the pito brewing process; an initial spontaneous lactic acid fermentation (souring) by lactic acid bacteria which come with the sorghum grains from the field and from the brewing environment followed by an inoculated alcoholic fermentation. The product is drunk while still fermenting and has a limited shelf life of 2 to 3 days. In this study, the fermentation performance of two commercial lactic acid bacteria, L. delbrueckii and L. amylolyticus and two commercial brewers’ yeast strains of S. cerevisiae, Anchor Brewers’ yeast and Munich Wheat Beer yeast as single strain starter cultures in pito wort were investigated using the Response Surface Methodology. The optimum fermentation conditions for their application in industrial production of pito were determined to be 12 h at 45°C for L. delbrueckii, 19 h at 45°C for L. amylolyticus, 71.6 h at 22.6°C for Munich Wheat Beer Yeast and 71.5 h for Anchor Brewer’s Yeast at 24°C. Both lactic acid bacteria and and yeasts were found capable of achieving the desired end product characteristics of pito. L. delbrueckii and Anchor Sorghum Beer yeast were however selected preferentially on account of the economic advantages of their use over the other two for industrial production. The fermentation profiles of the experimental pito brew fermented with pure single strain starter cultures of L. delbrueckii and Anchor Brewers’ yeast using the derived optimal fermentation conditions was evaluated alongside those of a pito brew fermented using the traditional process. Lactic acid formation, pH change and extract utilization with time were monitored. Both brews followed the general lactic acid and alcoholic fermentation profiles but differences were observed which were on account of the intrinsic specific characteristics and capabilities of the microorganism to utilize the wort substrates and convert them into the fermentation products. Similar levels of sourness as indicated by pH and lactic acid content were achieved in both brews. The starter culture brew had a lower apparent degree of fermentation and lower alcohol level than the traditionally fermented brew. The product quality from the two optimized fermentation processes was also evaluated based on physicochemical analysis, shelf life, volatile fermentation by-products and consumer acceptance sensory evaluation. The pito brewed with the starter cultures compared favourably with pito brewed with the traditional process. Both had physicochemical analytical values within the range established for traditional pito. There was an improvement of shelf life of 2 days in pito brewed with pure single strain starter cultures of L. delbrueckii and Anchor Brewer’s Yeast over traditionally brewed pito. The total level of volatile aroma compounds formed in the pito brewed with the starter cultures was higher (353.13 mg/l) than in the pito brewed with the traditional process (229.04 mg/l). The traditionally brewed pito was characterized by higher levels of ethyl acetate and iso-amylalcohol while the pure single strain culture brew was characterized by higher levels of n-propanol, i-butanol and acetaldehyde. In the consumer acceptance sensory evaluation, there was no significant difference between the two pito products for overall liking and taste liking. There was however a statistical significant difference between them for aroma liking. The fermentation process became predictable and controlled through the application of starter cultures and provided a basis for standardization of the fermentation process towards consistency in product quality and industrial production.
Assessment of Public Exposure to Naturally Occurring Radioactive Materials from Mining and Mineral Processing Activities of Tarkwa Goldmine in Ghana
(2011-06-14) Faanu, Augustine
Mining has been identified as one of the potential sources of exposure to naturally occurring radioactive materials (NORM). However, mining companies are not being regulated for NORM in Ghana. Whilst the developed countries have identified NORM as potential problems and measures are being taken to address the issues, very little is being done in the developing countries. However, most of the NORM industries such as mining and mineral processing are located in developing countries such as Ghana. Currently, there are over two hundred (200) registered mining companies operating small, medium and large scale mining in Ghana. Tarkwa Goldmine is one of the largest gold mining companies in Ghana and has been in operation for the past 200 years with no data on radioactivity levels. The mine currently undertakes only surface mining and the process produces large volumes of tailings and waste that may contain NORM. Some of the NORM are soluble in water and have the tendency to leach into water bodies and farm lands. These studies have been carried out to determine the exposure of the public to NORM from processing of gold ore at the Tarkwa Goldmine in Ghana. Direct gamma spectrometry and neutron activation analysis (NAA) techniques were used to analyse for U/Th series and K-40 in soil, rock, water, food and particulate (dust) samples from the mining environment. The mean activity concentrations measured for 238U, 232Th and 40K in the soil/rock samples were 15.2 Bq/kg, 26.9 Bq/kg and 157.1 Bq/kg respectively. For the water samples the mean activity concentrations were 0.54 Bq/L, 0.41 Bq/L and 7.76 Bq/L for 226Ra, 232Th and 40K respectively. The mean activity concentrations of 226Ra, 232Th and 40K in the food samples were 0.18, 0.14 and 45.00 Bq/kg respectively. The mean activity concentrations measured in the dust samples were 4.90 and 2.75 µBq/m3 for 238U and 232Th respectively. The total annual effective dose to the public was estimated to be 0.74 mSv. The results in this study compared well with typical world average values. The results indicate an insignificant exposure of the public to technologically enhanced NORMS from the activities of the Goldmine. The radiological hazard due to226Ra, 232Th and 40K were carried out. The radium equivalent activity (Raeq) and the calculated external and internal hazard indices, the absorbed dose rates and the corresponding annual effective dose were estimated in the soil and rock materials that might possibly be used as building materials. The results obtained in this study shows insignificant radiological hazards for the materials considered for use as construction materials for dwellings by the inhabitants in the study area. The results obtained in this study also shows that the background radiation levels are within the natural limits and compared well with similar studies for other countries. The study assessed the concentration of U, Th and K as well as other trace metals, anions and the physical parameters in water and soil samples in the goldmine and its surrounding areas. The mean concentrations of the U, Th and K were 0.020, 0.029 and 1.19 mg/L. The concentration of U, Th and K were variable in soil and rock samples taken from different locations in the study area with mean values varying in a range of 0.2 to 1.8 µg/g, 0.9 to 2.6 µg/g and 7037 to 71360 µg/g respectively. The concentrations of U, Th and K are comparable to world average values of similar studies. The calculated Th/U ratios show that there has not been significant fractionation during weathering of the radioelements with a mean value of 2.5. The concentrations of the other trace metals, anions and the physical parameters are within the WHO guideline levels in drinking water. The mean values of the gross-α and gross-β activity concentrations were 0.012 and 0.137 Bq/L which are also below the WHO recommended guideline values for drinking water.
Bayesian and multilevel approaches to modelling road traffic fatalities
(2017-01-19) Hesse, Christian Akrong
Smeed, in 1949, provided a regression model for estimating road traffic fatalities (RTFs). In this study, a modified form of Smeed’s model is proposed for which it was shown that the multiplicative error term is less than that of Smeed’s original model for most situations. Based on this Modified Smeed’s model, Bayesian and multilevel methods were developed to assess RTF risk across sub populations of a given geographical zone. These methods consider the parameters of the Smeed’s model to be random variables and therefore make it possible to compute variances across space provided there is significant intercept variation of the regression equation across such regions. Using data from Ghana, the robustness of the Bayesian estimates was indicated at low sample sizes with respect to the Normal, Laplace and Cauchy prior distributions. Thus the Bayesian and Multilevel methods performed at least as well as the traditional method of estimating parameters and beyond this were able to assess risk differences through variability of these parameters in space.
Beta-Glucan Content In Tropical Maize Genotypes: Extractability, Structural Analysis, Rheology And Function
(2013-12-16) Sampson, Gilbert Owiah
Beta-glucan is a complex soluble dietary fiber with (1→3),(1→4)-β-D linkages in a repeating unit of cellotriosyl, cellotetraosyl glucose chains interspersed with β-(1→3) linkages, found mainly in the cell walls of cereal endosperm and specifically in oat and barley. Beta-glucan is known to impart some health benefits to consumers including lowering of blood glucose and cholesterol level, as well as prevention of colon cancer. Beta-glucan research has concentrated on oat, barley and wheat. The absence of these cereals in tropical West Africa necessitates an exploration into the use of cereals of tropical origin such as maize to identify their potential of being good sources of β-glucan. The objectives of this study weretoscreen tropical maize genotypes for β-glucan content,and evaluate their structure and functionality in food systems. In the present study, β-glucan contents ofseventeen Ghana maize genotypesviz., ‘Mamaba’, ‘Suwan 1 QPM’, ‘Obatanpa GH’, ‘Omankwa’,‘GH9’, ‘Catete’, ‘Dodzi’, ‘Okomasa’, ‘Aburohemaa’, ‘Abontem’, ‘SotuBaka’, ‘Dorke’, ‘Akposoe’, ‘Abeleehi’, ‘Safita 2’, ‘Ohawu Local’ and ‘Golden Jubilee’ were analyzed using hot water, acid, alkaline and alcohol-enzyme based extraction procedures. Gum content varied by extraction method and genotype. Hot water and alkaline procedures produced low extractability demonstrating gum yield ranging from 0 to 2.29 % and 0 to 22.12 %, respectively. Significantly higher gum yields were produced by the acid and alcohol-based enzyme extraction procedures. The acid treatment produced a mean yield of 45.97 % which was not significantly different from 39.97 % yield obtained by the alcohol-enzyme treatment (P>0.05). With regard to genotype, hybrid maize varieties contained the highest mean gum content of 31.83 % while the landraces contained lowest value of 19.11 %. Genotypes having the highest β-glucan content were 1.4 % for ‘Obatanpa GH’, 1.68 % for ‘Abeleehi’ and 2.56 % for ‘GH 9’. Gum content of kernels had positive correlations with protein and fibre but negative correlation with nitrogen free extract. Minimal levels of impurities in the form of starch, protein and fat were present in the gum isolates. Structural analysis of maize β-glucan by 13CNuclear Magnetic Resonannce produced chemical shifts similar to that of standard oat and barley spectra and characterized by slight displacements as upfield and downfield shifts. The aniline blue fluorescence microscopy revealed that β-1→3 branching in maize β-glucan was less than that in oat and was genotype dependent. ‘Abeleehi β-glucan demonstrated higher β-1→3 branching than ‘Obatanpa GH’ β-glucan. The flow behavior of 10 % maize β-glucan dispersion was pseudoplastic and non-Newtonian just as 5 % oatβ-glucan. High water binding capacity of maize β-glucan up to 232 % makes it a suitable ingredient in food products which should resist syneresis. Maize β-glucan was found to be a good fat replacer, replacing up to 15 % of fat in pie crust without compromising sensory attributes.
Biting Patterns of Mosquitoes, the dynamics of Malaria Transmission and Existence of the Knockdown Resistance (kdr) Gene in parts of the Central Forest Belt of Ghana
(2010-8-24) Abonuusum, Ayimbire
Malaria is presumed to be holoendemic in the forest belt of Ghana, through no comprehensive transmission studies have been conducted...
Carbohydrate composition and amylase activity of sweetpotato (Ipomoea Batatas) root
(AUGUST, 2016 ) Mensah, Eric Owusu
Selection of sweetpotato clone(s) for production and utilisation depends on its quality attributes especially sugars, dry matter, starch content and amylase activity. The levels of these attributes are however influenced by factors such as the diversified production environments, cooking treatments, and genotypic compositions. The aim of the study is to determine the range of variation and factors of significant influence on concentrations of these attributes during growth and processing of sweetpotatoes. Development of an efficient and accurate technique for rapid assessment of these quality attributes was also relevant to the study. In order to achieve the overall aim, two main approaches were adopted; varying the levels of identified factors that alter the concentration of the attributes, and using near-infrared reflectance spectroscopy technique to develop a prediction model for their assessment. Sugars (sucrose, glucose, fructose and maltose), starch, dry matter content, amylase activity and sweetness were evaluated at harvest, during heating and after cooking. Adaptive Main Effects and Multiplicative Interaction (AMMI) model was employed to ascertain the magnitude of interactions between the factors tested. It was established that concentrations of the quality attributes were significantly affected by all the factors examined. Genotype contributed the highest variability during the growth stage while cooking treatment produced the highest effect during processing. Effect of interaction was more pronounced on amylase activity compared to sugars, dry matter and starch content. Sucrose was the predominant sugar in the raw form while levels of maltose increased substantially during cooking. High precision calibration was also developed for evaluating sugars and starch content in cooked sweetpotato roots. Sweetpotato varieties in Ghana have a wide range of quality attributes, making it a versatile crop for many food applications. Nonetheless recommendation for specific application should consider choice of production environment and processing conditions, which have significant impact on the final quality of the processed product.
Characterization of water yam (Dioscorea Alata) for existing and potential food products
(2009-08-05) Baah, Faustina Dufie
The yam species, Dioscorea alata has an advantage for sustainable cultivation due to its comparatively good agronomic characteristics. This research was aimed at identifying the major chemical and physical characteristics of D. alata tubers that affect food and industrial processing qualities. Tubers from 20 varieties of D. alata were compared to a reference variety, D. rotundata. The tubers were processed into flour for the determination of quality characteristics. Pounded yam, boiled yam and amala products were also prepared for sensory assessment against the reference. The influences of tuber maturity and length of storage on the quality characteristics were also evaluated, as well as the tuber tissue microstructure. On the average, most of the characteristics evaluated were relatively higher in D. alata varieties as compared to D. rotundata: moisture (72.2%), sugar (5.7%), protein (6.0%) and total dietary fibre (6.9%) contents; higher water binding capacity (163.3%), solubility (11.0%), and amylose (29.4%); breakdown (198.7 RVU), peak time (6.3 min) and pasting temperature (84.2 oC). However, dry matter (27.8%) and starch contents (68.4%), peak, setback, and final viscosities (215.7, 57.3 and 256.0 RVU respectively) were comparatively lower. D. alata varieties equally had appreciable contents of minerals. Based on the physicochemical and chemical properties, D. alata could be processed to flour for use in bakery products and diet formulations. The measured physicochemical properties in conjunction with pasting properties of the D. alata varieties suggest the presence of strong bonding forces within their starch granules. The relatively higher pasting temperatures required, and the lower pasting viscosities make D. alata suitable for producing weaning foods and other products that require low viscosity. Pasting properties of D. alata revealed relatively higher thermal and mechanical stability which will make it a good ingredient for processed foods, especially those that require thermal sterilization. The sensory analyses showed that D. alata varieties have comparative advantage over D. rotundata for amala production. However, specific promising varieties (TDa 98-159, TDa 291, TDa 297 and TDa 93-36) would need further genetic improvement to render them suitable for boiled yam and pounded yam dishes. Microstructural studies of the cooked cells in majority of the D. alata varieties (71%) showed incomplete disruption of the cells and consequently reducing exudation of starch contents. This feature partly accounts for less suitability of D. alata for sticky and doughy yam products in production areas. Moisture content of D. alata tubers decreased significantly from 5 to 9 months after planting (MAP) (74.53 to 71.76%) and throughout the 5 months storage period (71.76 to 68.06%) as a result of dehydration. Sugar and starch contents increased from the 5MAP to 9MAP (4.54 to 4.70%; 65.92% to 72.01% respectively), however, starch content decreased at the end of 5 months storage period (72.01 to 66.55%) with concomitant increase in sugar content (4.70-6.83%). The observations are due to photosynthetic materials accumulation during growth period and breakdown of starch to sugars as a result of respiration during storage. Amylose content generally decreased with the storage period but swelling power increased (6.26-9.02%). Pasting viscosities increased throughout the growth period to the end of storage. The increases in dry matter and sugar contents, swelling power and pasting viscosities of stored D. alata tubers would have significant improvement in their organoleptic and textural properties. Contribution to Science From this study, the following have been established and therefore add onto the scientific knowledge on D. alata yam species: 1. D. alata varieties had higher total dietary fibre than what is reported for brown rice (5%) (Best, 2005) with a few varieties having comparable values to whole wheat flour. The specific varieties with high TDF will be useful in diet formulation because of its health benefits 2. D. alata flour (elubo) is very good for amala product. This product should be promoted in Ghana due to the high flour storability and ease of preparation. 3. Significant mineral variations were observed among D. alata varieties which suggest the potential for improvement through breeding programmes.
Combining Data Envelopment Analysis with Machine Learning Algorithms for Predictions
(KNUST, 2020-09) Appiahene, Peter
Comparative to other methods, DEA is an improved method to organize and analyze data. However, it is very difficult to use only DEA to predict the efficiency and performance of other or new Decision Making Units (DMU). The main objective of this study is to build a high accuracy machine learning predictive models for predicting the efficiencies of banks by combining DEA with Machine Learning algorithm. The study built four Machine Learning Models namely; DEA-DT, DEA-RF, DEA-NN and DEA-LR to predict the efficiencies of banks. The study used 33% of the total bank branches in Ghana, largely in the nine regions. A two-stage DEA was used to determine the efficiencies of all bank branches and these banks were grouped based on a proposed algorithm, Bank Classification Algorithm (BC Algorithm). In building the predictive models, 70% of the banks dataset were used to train and validate the models. The developed models were used to predict the efficiencies of the other 30% banks. A 10-fold Cross-Validation was applied to check the performance of all predicting models on each case dataset. All experiments were executed within a simulation environment and conducted in R studio using R programming language. Standardized Machine Learning evaluation metrics were used to compare the models. The results suggested a very good performance of all the machine learning models proposed by the study. However, a comparison among them clearly indicated a much better performance by the DEA-RF for predicting banks’ efficiency in collecting deposit and DEA-DT for predicting banks’ efficiency in investing deposits. This study has demonstrated that combing two models improve the performance, predictions and classification accuracies suggested by previous studies. In conclusion, the study proposed the usage of the proposed BC Algorithm for classifying banks based on their efficiencies in deposit stage and investment stage.
Consumption Patterns, Protein Quality and Hazards of “NULs” Utilization
(NOVEMBER, 2017) Ofosu, Isaac Williams
Many people consume large quantities of plant-based products, including neglected and underutilized legumes (NULs), because of their availability or affordability. This makes NULs a critical food security resource. However, NULs are known to contain toxins such as lectins (glycoproteins) which persistently resist heat inactivation, making them a potentially serious health hazard. In order to promote their continuous and sustainable utilization, consumption profile, safety and nutritional quality by way of essential amino acids need to be investigated. Furthermore, suitable ways of attenuating the possible risks of lectins in NULs need to be investigated. A survey was carried out aimed at finding the processing and consumption patterns of five selected NULs; Vigna subterranea, Cajanus cajan, Mucuna pruriens, Phaseolus lunatus and Canavalia ensiformis focusing on consumer characteristics such as: age, house hold numbers, educational levels, marital status and occupation. Also considered were, the familiarity of NULs, perception of hazards and the risks, in terms of exposure assessment and exposure frequency of dishes consumed per body weight of consumers. Time-heat inactivation of the lectins in NULs flours, as well as their NULs’ model dishes were studied, from which risk was evaluated, using the hazard-based approach. Five different NULs protein extracts were profiled to ascertain the essential amino acids, and the quality evaluated by matching them against the standard FAO/WHO dietary indispensable amino acids for three age groups; infants, children and adults. −Radiated starches prepared using radiation doses from 3 to 42 kGy were composited at 10% composition with defatted NULs flours, with respect to quantities of native starches present in NULs. The composites were agitated in an extruder which operated within intrinsic temperature ranging from 2 to 12 oC. Residual lectins from the extrudates were quantified by ELISA analysis. The statistical analysis of the collected survey data involved the use of Palisade @Risk software to fit each measured parameter to the most adequate probabilistic distribution, based on its Akaike information criterion. Subsequently, the central tendency characteristics of the measured parameters, together with their variations, uncertainties and distribution functions were recorded. In the survey of the consumption of NULs, it was observed that, majority of the respondents who were over 40 years (67.6%) were familiar (59.4%) with NULs and consumed NULs dishes. The most popular dishes were prepared from Vigna subterranea (15.9%) and Phaseolus lunatus (14.95%). The majority of consumers (66%), perceived the presence of hazards in NULs, citing pesticide residues (58.7%), but no intrinsic hazards as threat. However, a few (16.6%) considered the interaction between pesticide residues and food additives as dangerous. Majority (66.1%) regarded NULs dishes as safe, while at the same time complained of stomach discomfort (97.2%) after consumption. In spite of these observations, they would still recommend their use to others. Through the ELISA analysis, significantly high quantities of lectins still remained in Vigna subterranea flours even after cooking for 1 h. Risk analysis of the modelled foods revealed that the hazard quotient (HQ) of all the NULs dishes were above 1, meaning consumers are at risk of systemic toxicity. Assessment of essential amino acids revealed that, out of the five NULs studied, Vigna subterranea had adequate quantities of histidine (26.2 mg/g) that met the dietary requirements of all the three age groups. However, the levels of isoleucine (35.9 mg/g) and the aromatic amino acids phenylalanine and tyrosine (94 mg/g) were adequate for only children and adults. In the case of Phaseolus lunatus, lysine (53.6 mg/g) and threonine (44 mg/g) were relatively high. However, this could only meet the adults’ requirement. In spite of these contributions of amino acids, protein quality of Vigna subterranea and Phaseolus lunatus proteins, based on digested indispensable amino acid scores (DIAAS) presented a different outlook. Thus, the DIAAS of Vigna subterranea (3.6) and Phaseolus lunatus (2.5), show low quality, relative to international standards. In the studies involving the attenuation of lectins in NULs, Mamdani type fuzzy logic inference system was used to model the two input variables of the NULs flour treatment to predict the optimal lectin inactivation at 100% accuracy. While lectins from Canavalia ensiformis recorded 83% inactivation, lectins from Vigna subterranea rather potentiated up to 44%. Thus, -radiated starches incorporation into NULs flours during low temperature extrusion treatment, inactivated NULs lectins at varying degrees and these were adequately predicted by the model.
Dehydration Characteristics, Quality Evaluation And Consumer Assessment Of Solar Dried Tomato.
(KNUST, 2018-11-29) Mavis Owureku Asare
Tomato (Lycopersicon esculentum) is an important vegetable used in cooking most local foods in Ghana. At the peak season of harvesting, high loses are incurred because of the absence of facilities to process fresh tomato and extend the shelf life. Solar drying has been proven to be a more efficient and low cost method of enhancing quality and adding value to tomato and other vegetables. However, there are concerns on the usage, functionality and sensory appeal of the dried products by consumers. In this study a natural mixed mode solar dryer suitable for drying tomato was adapted and used to investigate the dehydration characteristics, quality and consumer acceptability of the dried products. An initial baseline survey was conducted using semi structured questionnaires administered to 395 randomly selected respondents in the Accra Metropolis. Information was obtained on the demographics, consumption pattern, knowledge and acceptance of tomato processing technologies and assessment of quality attributes of tomato. The efficiency of a passive solar dryer was evaluated and used in the processing of fresh tomato to powder. The processing involved the pre-treatment of 6mm slices of fresh roma tomato by dipping in (a) 1% potassium metabisulphite solution (b) 1 % ascorbic acid solution (1:1) for 10 minutes respectively. Untreated tomato slices served as control. Samples were then dried in the passives and in the open sun, with the open sun drying serving as control. The moisture content, moisture ratio and dehydration rate of solar dried tomato was assessed. The quality of dried tomato was assessed for their physicochemical, nutritional and microbiological characteristics. Physicochemical analysis involved determination of pH, total titratable acidity, dry matter, ash, tristimulus colour, total soluble solids, water activity and moisture. Nutritional quality was assessed for lycopene, beta-carotene, total carotenoid acids using high performance liquid chromatography (HPLC) procedures. Flowability, smoothness and compressibility (or packing porosity), particle size and shape distribution of the tomato powder was determined using a Morphologi G3-ID. Scanning electron microscopy of pre-treated solar and sundried tomato samples were imaged with an FEI Quanta 3D FEG scanning electron microscope. Quantitative Descriptive Analysis (QDA) was carried out to compare the sensory descriptive profiles of solar dried tomato powder with existing products on the market using a trained descriptive panel of nine (9). Home Use Test (HUT) was conducted using a trained panel to assess the acceptability of solar dried tomato powder in local foods. The results showed that, most consumers (74%) preferred tomato powder that was conveniently packaged to retain the characteristic intense taste and the flavour. The first day dryer efficiency of 24.2 % facilitated the drying process of tomato (final moisture content of 12-14%). The ash content was slightly higher in the sun-dried tomato (9.3 -10.14 %) compared with the solar dried tomato (9.4 - 9.68 %), an indication of potential contamination with extraneous materials from the environment. Water activity for solar dried tomato powder were significantly lower (0.35 - 0.38) than sundried tomato powder (0.53 - 0.57) and water activity lower than 0.6 is considered microbiologically safe for storage. Lower tristimulus colour L* values (37.81 - 40.31) observed for sun-dried tomato samples indicated that these samples were darker in colour than the solar dried samples with L* values (50.35 - 46.44). Aerobic mesophile counts were lower in solar dried (3.90 CFU/g) tomato pre-treated with potassium metabisulphite compared with sun-dried samples (4.85 CFU/g). Sulphur dioxide content (740.8 ppm) of solar dried tomato pre-treated with potassium metabisulphite was lower than the maximum legal limit (2000 ppm) recommended in fruits and vegetables, indicating its safety for human consumption. A strong, negative correlation between sulphur dioxide 740.9 ppm concentration and microbial load was observed for solar dried tomato. QDA results indicated a strong tomato aroma intensity (scored 127 out of 150) for solar dried tomato powder with the market samples having an extremely low intensity score of 0.7 out of 150 for tomato. Sensory profiling of the two products differed extremely in aroma, appearance and texture. Sensory characteristics of reconstituted solar dried tomato powder was similar to that of fresh tomato and tomato paste (two products commonly used in cooking). It had a very coarse appearance and texture (as predicted by the particle size distribution and shape profile and parameters of convexity and circularity) and a strong boiled/cooked aroma compared to tomato paste which had a higher intensity of red colour, metallic and stewed tomato concentrate aroma and flavour. Most of the participants used tomato powder to prepare local dishes such as “jollof “rice, tomato stew and light soup because of the good swelling characteristics of the product. The mixed mode solar dryer developed in this study was efficient in processing tomato powder which appealed to consumers and had varied uses in food production. The dryer has the potential of enhancing post-harvest loses, extending the shelf life of tomato and creating an alternative processing method which is simple and convenient.
Dehydration Characteristics, Quality Evaluation and Consumer Assessment of Solar Dried Tomato
(November, 2018) Owureku-Asare, Mavis
Tomato (Lycopersicon esculentum) is an important vegetable used in cooking most local foods in Ghana. At the peak season of harvesting, high loses are incurred because of the absence of facilities to store, process and extend the shelf life of fresh tomatoes. Solar drying has been proven to be a more efficient and low cost method of enhancing quality and adding value to tomato and other vegetables. However, there are concerns on the usage, functionality and sensory appeal of the dried products by consumers due to the methods of drying. In this study a natural mixed mode solar dryer suitable for drying tomato was adapted and used to investigate the dehydration characteristics, quality and consumer acceptability of the dried products. An initial baseline survey was conducted using semi structured questionnaires administered to 395 randomly selected respondents in the Accra Metropolis. Information was obtained on the demographics, consumption pattern, knowledge and acceptance of tomato processing technologies and assessment of quality attributes of tomato. The efficiency of a passive solar dryer was evaluated and used in the processing of fresh tomato to powder. The processing involved the pre-treatment of 6mm slices of fresh roma variety of tomato by dipping in (a) 1% potassium metabisulphite solution and (b) 1 % ascorbic acid solution (1:1) for 10 minutes. Untreated tomato slices served as control. Samples were then dried in the passive solar dryer and in the open sun, with the open sun drying serving as control. The moisture content, moisture ratio and dehydration rate of solar dried tomato was assessed. The quality of dried tomato was also assessed for their physicochemical, nutritional and microbiological characteristics. Physicochemical analysis involved the determination of pH, total titratable acidity, dry matter, ash, tristimulus colour, total soluble solids, water activity and moisture. Nutritional quality was assessed for lycopene, beta-carotene, total carotenoid acids using high performance liquid chromatography (HPLC). Flowability, smoothness and compressibility (or packing porosity), particle size and shape distribution of the tomato powder was determined using a Morphologi G3-ID. Scanning electron microscopy of pre-treated solar and sundried tomato samples were imaged with an FEI Quanta 3D FEG scanning electron microscope. Quantitative Descriptive Analysis (QDA) was carried out to compare the sensory descriptive profiles of solar dried tomato powder with existing products on the market using a trained descriptive panel of nine (9). Home Use Test (HUT) was conducted using a trained panel to assess the acceptability of solar dried tomato powder in local foods. The results showed that, most consumers (74%) preferred tomato powder that was conveniently packaged to retain the characteristic intense taste and the flavour. The 24 hr dryer efficiency of 24.2 % facilitated the drying process of tomato (final moisture content of 12-14%). The ash content was slightly higher in the sundried tomato (9.3 -10.14 %) compared with the solar dried tomato (9.4 - 9.68 %), an indication of potential contamination with extraneous materials from the environment. Water activity for solar dried tomato powder were significantly lower (0.35 - 0.38) than the sundried tomato powder (0.53 - 0.57). Generally, water activity lower than 0.6 is considered microbiologically safe for storage. Lower tristimulus colour L* values (37.81 - 40.31) observed for sundried tomato samples indicated that these samples were darker in colour than the solar dried samples with L* values (50.35 - 46.44). Aerobic mesophile counts were lower in solar dried tomato pre-treated with potassium metabisulphite (3.90 CFU/g) compared with sundried samples (4.85 CFU/g). Sulphur dioxide content of solar dried tomato pre-treated with potassium metabisulphite (740.8 metabisulphite (3.90 CFU/g) compared with sundried samples (4.85 CFU/g). Sulphur dioxide content of solar dried tomato pre-treated with potassium metabisulphite (740.8 ppm) was lower than the maximum legal limit (2000 ppm) recommended in fruits and vegetables. This indicates its safety for human consumption. A strong, negative correlation between sulphur dioxide concentration and microbial load was observed for solar dried tomato. QDA results indicated a strong tomato aroma intensity (scored 127 out of 150) for solar dried tomato powder, with the market samples having an extremely low intensity score of 0.7 out of 150 for tomato. Sensory profiling of the two products differed extremely in aroma, appearance and texture. Sensory characteristics of the reconstituted solar dried tomato powder was similar to that of fresh tomato and tomato paste (two products commonly used in cooking). It had a very coarse appearance and texture (as predicted by the particle size distribution and shape profile and parameters of convexity and circularity) and a strong boiled/cooked aroma compared to tomato paste which had a higher intensity of red colour, metallic and stewed tomato concentrate aroma and flavour. Most of the participants used tomato powder to prepare local dishes such as “jollof “rice, tomato stew and light soup because of the good swelling characteristics of the product. The mixed mode solar dryer developed in this study was efficient in processing tomato powder which appealed to consumers and had varied uses in food production. The dryer thus has the potential of enhancing post-harvest loses, extending the shelf life of tomato and creating an alternative processing method which is simple and convenient.
Divergence regularization method for solving ill-posed Helmholtz equation
(June, 2016 ) Barnes, Benedict
In this work, we introduce Divergence Regularization Method (DRM) for regularizing the Cauchy problem of the Helmholtz equation where the boundary deflection is not equal to zero in Hilbert space H. The DRM incorporates a positive integer scaler which homogenizes inhomogeneous boundary deflection in Cauchy problem of the Helmholtz equation to ensure the existence and uniqueness of solution for the equation. The DRM employs its regualarization term (1 + 2m)em to restore the stability of the regularized Helmholtz equation, and guarantees the uniqueness of solution of Helmholtz equation when it is imposed by Neumann boundary conditions in the upper half-plane. The DRM gives better stability approximation when compared with other methods of regularization for solving Cauchy problem of the Helmholtz equation where the boundary deflection is zero. In the process, we introduce AdaptiveWavelet Spectral Finite Difference (AWSFD) method to obtain the approximated solutions of the regularized Helmholtz equation with regularized Cauchy boundary conditions, regularized Neumann boundary conditions in the upper half-plane, and finally with regularized both Dirichlet and Cauchy boundary conditions where the boundary deflection is equal to zero. The AWSFD method captures the boundary points to obtain approximated solution of Helmholtz equation. This method reduces the Helmholtz equation in two dimensions to one dimension which is then solve spectrally using a suitable wavelet basis. The solutions by AWSFD method confirms the analytic solutions of regularized Helmholtz equation by DRM. The norm of relative error between the analytic solution by DRM and the approximated solution by AWSFD method is minimal. Moreover, we introduce interpolation scheme in the AWSFD method to obtain the approximated solutions of the regularized Helmholtz equation with above boundary conditions.
Diversity in Anopheles gambiae s.s and Wuchereria bancrofti, and the Distribution of Lymphatic Filariasis in Ghana
(2010) Dziedzom, Komi de Souza
Lymphatic Filariasis (LF) is a disease transmitted by the filarial worm Wuchereria bancrofti. It is a disease of public health importance, and has been earmarked for elimination by the year 2020 through Mass Drug Administration (MDA) programs. In Ghana, the distribution of LF reveals a pattern of endemicity separated by a continuous area of non-endemicity. As such, this study hypothesized that genetic differences – probably not revealed by current identification methods, within LF vectors and parasite populations, may be responsible for the observed distribution pattern. The main aim of this project was therefore to explain the current observed distribution of LF based on the diversity in the Anopheles gambiae s.s and Wuchereria bancrofti in Ghana. Mosquito samples were collected from 14 sites across Ghana, divided into 4 ecological zones, and falling into endemic and non-endemic areas. W. bancrofti samples were picked from dissected mosquitoes -using dissecting pins, collected from previous studies in Ghana. The samples were morphologically and molecularly identified using routine methods. Using the PCR, the Cytochrome C Oxidase subunit 1 (COI) from W. bancrofti and An. gambiae s.s was amplified, sequenced and analyzed. To better understand the effects of environmental factors on the diversity in the An. gambiae s.s, the spatial distribution of the An. gambiae M and S molecular forms and associated environmental factors were examined, and their relationship with disease prevalence was determined. A total of 10274 mosquitoes were collected, out of which 6150 (59.9%) were morphologically identified as An. gambiae s.l; 1494 (24.3%) of the An. gambiae s.l were further classified into sibling species. The S form of An. gambiae s.s predominated in the middle belt, while the M form predominated in the northern and coastal Savannah belts. Bivariate correlation analysis between the M and S forms indicated that their prevalences were negatively correlated (-0.763). Spatial analyses carried out, indicated a positive spatial clustering for both the An. gambiae M (MI =0.19, Z score=4.2, P< 0.01) and An. gambiae S (MI =0.19, Z score=4.2, P< 0.01) forms. Multiple regression analyses of all data (n=70 sites), indicated that temperature was an important variable for both forms, explaining for An. gambiae M, 28% (R2=0.28, F=25.8, P<0.001) and for An. gambiae S, 36% (R2=0.36, F=37.9, P<0.001) of the variance in the model. An. gambiae M was significantly correlated with LF, and 2.5 to 3 times more prevalent in the high LF zone than low to medium LF zones. Phylogenetic analyses of An. gambiae s.s revealed the samples to be grouped according to endemicity and ecological zones. The equality of evolutionary rate between the consensus sequences from the endemic and non-endemic areas, revealed a χ2 test statistic of 3.71 (P = 0.054), rejecting the null hypothesis of equal rates between lineages. Seven and 15 W. bancrofti specimens from Gomoa District (in the South) and Bongo District (in the North) respectively were sequenced. There was a significant difference in the evolutionary rate between the consensus sequences of W. bancrofti from the North and the South, with a χ2 test statistic of 7.44 (P = 0.00637). The results of this study indicate that environmental factors, especially temperature, play an important role in the distribution of LF and its vectors in Ghana. The observed genetic differences in An. gambiae s.s and W. bancrofti populations in Ghana may affect the vector-parasite interactions in various areas, and may explain the observed distribution of LF in the country.
Diversity within yeast involved in spontaneous fermentation of pito
(2007-11-11) Glover, Richard Lander Kwame
A survey was conducted in ten (10) “Dagarti pito” production sites located in nine towns within eight administrative regions of Ghana to investigate diversity within yeast varieties involved in the spontaneous fermentation of Dagarti pito. Samples of dry yeast were obtained from commercial Dagarti pito producers from Tamale and Nyankpala (Northern Region); Ayigya- Kumasi and Monaco-Kumasi (Ashanti Region); Accra (Greater- Accra Region); Cape Coast (Central Region); Takoradi (Western Region); Sunyani (Brong Ahafo Region); Ho (Volta Region) and Suhum (Eastern Region). For purposes of comparison, dry yeast was also sampled from three dolo production sites in Ouagadougou, Burkina Faso. Yeast populations ranged between 106 and 108 cfu g-1. Twenty-five yeast isolates from each site were characterized phenotypically by colony and cell morphology as well as carbohydrate assimilation profiling, using the API ID 32 C Kit (Biomerieux SA, Marcy L’Etoile, France). Ninety-nine percent (247) of the isolates showed colony and cell morphologies typical of S. cerevisiae. Of these, 72 % (179) had fifty-three carbohydrate assimilation profiles similar to S. cerevisiae (according to Vaughan-Martini and Martini, 1998) and were subsequently identified as such while 28 % (68) which had four carbohydrate assimilation profiles atypical of S. cerevisiae or any other member of the sensu stricto complex could not be identified in API galleries. Two isolates (1%) which had colony and cell morphologies atypical of S. cerevisiae, and a broad-spectrum assimilation profile, were identified as Candida kefyr. Genotyping of five randomly selected isolates from each site was carried out using the Polymerase Chain Reaction (PCR) to amplify the region spanning the two intergenic transcribed spacers (ITS) and the 5.8S ribosomal gene (ITS1-5.8S rDNA-ITS2), followed by restriction analysis (ITS-PCR+RFLP) of the product, as well as Pulsed Field Gel Electrophoresis (PFGE). The genetic analyses indicated that all of them belonged to S. cerevisiae, notwithstanding the phenotypic differences. The mitochondrial cytochrome-c oxidase II gene (COX 2) of four isolates representing the four chromosome profile groupings that emerged after PFGE, were then sequenced to confirm their close relatedness to S. cerevisiae, particularly type strain CBS1171. Two isolates randomly selected from each of the ten production sites, (one with a broad carbohydrate assimilation spectrum and the other with a narrow carbohydrate assimilation spectrum) and assessed for technological properties showed different patterns of growth and flocculation without much change in pH during fermentation, and most of them produced pito having sensory attributes which compared favorably with commercially produced pito. Pito produced with each of ten out of the twenty yeast strains from Ghana used for the earlier investigations and three from Burkina Faso was analyzed by headspace, for its aroma constituents. All ten Ghanaian isolates could form aromatic compounds representing the alcohols, esters, and ketones which are among reported typical flavor compounds of conventional beer. This study has demonstrated diversity within S. cerevisiae strains involved in fermentation of pito wort. These strains possess desirable technological properties, including sufficient growth during fermentation and efficient hydrolysis of sugars for biomass enhancement. They also demonstrated fermentation activities, particularly, ethanol production, formation of aroma compounds and metabolites, which impart appropriate sensory attributes to pito.
Dynamics of price stabilization with buffer stock: an application of cobweb model using delay differential equation: (the case of maize supply in Ghana)
(July 28, 2016) Anokye, Martin
This study is intended to use mathematical models for controlling fluctuations in the price of maize by employing a nonlinear continuous time delay diff erential equation derived from linear demand and nonlinear supply functions of price. These models are formulated from parameters estimated from real economic data of maize price demand and production in the Ashanti Region of Ghana through the use of regression methods. The data is obtained from the Ministry of Food and Agriculture, Statistical Directorate Kumasi-Ghana, pertaining to years from 1994 to 2013. The results of the study are connected to the assertion that commodity price is dependent on planting time, storage time, relaxation time and total production time. It is proven that if all these individual time segments are combined as one for supply delay to make up total storage time, which is the delay for the bu er, then price oscillations would be drastically reduced. Also the study is an improvement on the work done by earlier researchers, whose discrete time models are limiting cases of the delay bu er stock model used in this study. The effi ciency of a bu er system is proven to be dependent on delay variation suitable enough to be used by bu er stock operators. It is noted that, the more the bu er stock delay and supply delay are reduced in connection with the type of price scheme operated in the bu er stock scheme, the more stable the price becomes and the eff ects of bu er stock are felt more by stakeholders. The results of the analysis provide an average stable price of maize as GHC 30.49 compared to the actual average price of GHC 30.27. The equilibrium price in turn provides the average equilibrium weight of 2931.6 and 8217.6 metric tons for demand and supply respectively. The average excess supply that constitutes the stocks in the bu er is also given as 5286 metric tons and they are kept in stock for the next market period (i.e planting period). When at another period (i.e during harvesting period) demand exceeds supply then the appropriate diff erence is released from the bu er to the market in order to keep price in equilibrium. The standard deviation is also reduced to 0.1602 compared to the original 29.48 before the application of bu er stock scheme. Thus, before the application of bu er stock scheme, price oscillated between two price points and could not converge. This affi rms the fact that bu er stock acts as a reserve against short- term shortages and dampens excessive fluctuations. Inferences are drawn from this study that researchers should rather use continuous time nonlinear delay models as they reflect the realities prevailing in most real-life economic problems. While continuous time delay di fferential bu er stocks models or equations could be applied in managing unstable market price of maize irrespective of the type of the supply function it is integrated with, being it linear or nonlinear, the discrete time bu er stock models instead work well with linear supply functions.
Effects of Drying on Quality and Drying Characteristics of Aerial Yam (Dioscorea Bulbifera)
(JUNE, 2017 ) Sanful, Rita Elsie
The preference for Dioscorea rotunda and other yams to the aerial yam, by consumers has led to its underutilisation and post-harvest losses. The quality attributes of the aerial yam processed into flour using various processing techniques (boiling, steaming, solar and oven drying) were determined. Drying characteristics of the aerial yam bulbis slabs were determined and fitted to twelve different drying models. Flour yields for the boiled flours were high (32.5%, 31.25%) for solar and oven drying methods. Protein content was high in steamed flour and low in boiled flour for solar drying and high in the fresh flours for the oven drying method. All the processed flours were significantly high in fat content which ranged from 0.96 to 1.40%. Oven dried flours were also high in ash content (0.24-0.51). Results suggested that aerial yam was a good source of calcium, iron, sodium and potassium. Oven drying did not significantly change P, K and Na contents relative to the other methods. The values of water binding capacity were different between boiled solar dried flour (303%) and all oven dried flours (241.05% -235.11%). Solubility was high in the solar dried flours with a range of 15.98% -22.01%. No significant differences occurred between drying methods for swelling power. For the drying methods, solar dried flours had the highest pH values of 5.90-7.25. Although the drying methods and pre-treatment showed no significant differences in the breakdown, final and setback viscosities of the aerial yam flours, pre-treatment of boiling and steaming and the two drying methods resulted in low peak and holding strength viscosities. The aerial yam flour, however, required higher temperature and time to cook with the exception of the boiled solar dried yam flour. Low final viscosity values of 0.50-46.00 BU indicated the inability of the aerial yam flour to form a firm gel after cooking and cooling making it appropriate for infant baby food formulation. Oven dried flours had lower pasting properties in all the pre-treated flour except for the breakdown and setback viscosities. Solar drying, boiling and steaming methods showed slight decreases in the amylose content of the yam flour while oven drying showed slight increases in the amylose content. Oven dried flours showed increases in yellowness whiles solar dried flours exhibited increased redness indicating a high potential for enzymatic browning. High temperatures resulted in shorter drying times, which increased with increasing thickness. Boiling decreased the rate of moisture movement which resulted in increased drying time. Midilli et al., 2002; Verma et al., (Dadali et al., 2007); Diffusion Approach, (Yaldiz and Ertekin, 2001), Wang and Singh, (Demir et al., 2007); Parabolic (Sharma and Prasad, 2001) and Simplified Ficks Diffusion (Babalis et al., 2004) models best described the thin-layer drying characteristics of aerial yam slabs. The effective moisture diffusivity values of aerial yam, varied between 1.401 ×10-10 m2/s to 6.720 x 10-10 m2/s for the fresh samples and 7.223 x 10-11 m2/s and 2.306 x 10-10 m2/s for the boiled samples over the temperature range of 50–70°C. Moisture diffusivity increased with increasing temperature. From the result aerial yam could be utilised in the food industry for baby food formulation and the above selected drying models will facilitate the design and manufacture of a suitable dryer for the aerial yam in the food industry.

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