College of Science

Permanent URI for this collection


Recent Submissions

Now showing 1 - 5 of 9
  • Item
    Transcriptomics and Immune Profiles of Asymptomatic Filarial-Infected Individuals
    (2015-08) Kwarteng, Alexander
    Filarial infections caused by Wuchereria bancroftiand Brugiaspecies (lymphatic filariasis (LF)) and Onchocerca volvulus(onchocerciasis) affect almost 200 million individuals worldwide and pose major public health challengesinendemic regions. Indeed, the collective DALYs (disability-adjusted life years) for both infections is 3.3 million. Infections with these thread-like nematodes are chronic and although most individuals develop a regulated state, a portion develop severe forms of pathology. Mass drug administration (MDA) programmes on endemic populations focus on reducing prevalencelevels of people with microfilariae (MF), the worm's offspringin the bloodto less than 1%. Although this has been successful in some areas, studies show that MDA will be required for longer than initially conceived. Thus, there is still a requirement for better drugs or vaccines.W. bancrofti-infected individuals without pathology (asymptomatic) can be subdivided into two groupsthat are patent (MF+) or latent (MF-). Patent infections are associated with an immunologically tolerant phenotype state that favours worm survival and in addition does not provoke overt pathology in the host. Latent infections are characterized by the lack of MF in the periphery, despite the presence of adult worms, and their immune profiles show markers of immune-mediated MF control. In O. volvulusinfection however, the majority of individuals havedermal-residing MFand amicrofilaridermic (a-MF) individuals appear to be the consequences of repeated MDA treatment. Interestingly, recent research revealed that O. volvulusendemic areas,with a lowered infection pressure due to MDA,appear to influencebystander responsesto Plasmodium-derived antigens in community members even if they have not regularlyparticipated in the therapy.Pathology that arises in either filarial infection is associated with dampened regulatory T cell responses (Treg) and IL-10 but elevated Th17 responses. Thus, identifying immune determinants that drive these different infection stateshas the potential to guide the development of improvedanti-filarial drugsand vaccines. In this study, microarray and cellular profiling approaches were used to evaluate gene expression patterns and to revealgenetic pathways specific to W. bancroftior O. volvulusinfection. Individuals with latentLFinfections showed an enhanced gene expressionprofile, including genes involved in Actin Nucleation by ARP-WASP Complex, Rac signaling, Cdc42 signaling, RhoGD1 signaling, eosinophil effector functions and CD28 signaling in T helper cellpathways. Interestingly, the Charcot-Leyden crystal/galectin-10(CLC/Gal-10), an immunosuppressive molecule,was among the top commonly expressed genes in both infections and elevated levels were also detected in plasma.Moreover, compared to healthy volunteers, T cells recovered from W. bancrofti-infected individuals secreted higher levels of CLC/Gal-10and were even higher in MF+ individuals: by complementingtheir elevated Treg responses (Foxp3/IL-10). LatentW. bancrofti-infected individualson the other hand had pronounced Th1, Th2 and Th17 responses. With regards to filarial-specificantibody responses, IgG4, IgE and IgA in plasma were associated with MF+, MF-and endemic normals, respectively. Overall, the transcriptome profiling revealed overlappinggenes in both infections: CLC/Gal-10, ribonuclease RNase A family, 2(RNASE2) and ribosomal protein S4, y-linked 1(RPS4Y1). Thus, the study offersinsightinto filarial-specific genes, signaling pathways and ivimmune determinants, which may be central targets towards the development of new anti-filarial interventions.
  • Item
    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.
  • Item
    Optimizing the conditions of ethanol production from cassava and sweet potato
    (Febuary, 2018) Komlaga, Gregory Afra
    Cassava and sweetpotato are root and tuber crops cultivated in Ghana that could serve as industrial raw material for ethanol production. Investigations were conducted to optimize the yield of ethanol from two (2) varieties each of Cassava and Sweetpotato. Response surface methodology was used to model the optimum liquefaction, saccharification and fermentation conditions for ethanol production from the cassava and sweetpotato varieties. Three starch hydrolytic enzymes (Liquozyme SC DS, Spirizyme Fuel, Viscozyme L) and two strains of yeast (Bio-Ferm XR, Baker’s yeast) were used for fermentation. The best liquefaction, saccharification and fermentation times established were 2.1 hours, 4 hours and 57.4 hours at 34oC respectively with Liquozyme SC DS, Spirizyme Fuel/Viscozyme L and Bio-Ferm XR (Lallemand) yeast. The combination of Viscozyme L and Spirizyme Fuel enzymes in a ratio of 1:1 was the best enzyme mix for saccharification for a duration of 4 hours. The yeast to employ for best fermentation was Bio-Ferm XR at temperature of 34oC for 57.4 hours duration. The results also indicated that 10 months matured Sika bankye and 3 months old Apomuden were the best cassava and sweetpotato varieties respectively for ethanol production. The best ethanol yield established from the study was 16.2% v/v from a 50:50 cassava:sweetpotato flour combination. Ethanol production with Sika bankye and Apomuden in a 50:50 ratio with GH¢ 119.00 as cost of fresh roots and tubers, ethanol yield of 15.5% v/v, selling price of GH¢ 4.7 per litre of ethanol and the use of a 10,000 litres per day capacity ethanol distilling plant generates net profit of between 11% and 31% over a period of five years. Ethanol production with cassava and sweetpotato is therefore a profitable venture.
  • Item
    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.  
  • Item
    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.