Browsing by Author "Mekonnen, Fiseha"

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    Production of Gluten-Free Beer from Pearl Millet Cultivar
    (Addis Ababa University, 2014-03) Mekonnen, Fiseha; Sheferaw, Gezachew (Professor)
    Pearl millet starch has featured in many foods recipes and industrial applications. However its use as a raw material in brewing has not received much attention. This work therefore sought to establish the suitability of pearl millet starch as a raw material substitute for barley in production of gluten-free beer. Two type of beer were produced, one with caramel and another without caramel. It is produced mainly from pearl millet grain (Pennisetum typhoideum) and the process of brewing involves malting, mashing, fermentation and packaging. Chemical analyses were carried out on both drinks, which not gave a significant (p≤0.05) difference. Pearl millet beer had a total acidity of 0.562±0.03, fixed acidity of 0.203±0.001, Volatile acidity 0.360±0.02, PH 3.92, specific gravity 1.042±0.003, total dissolved solids 1.12×105ppm, total suspended solids 1.65×105ppm, ethanol content of 4.45±0.03% respectively .The gelatinization temperature of pearl millet starch samples were determined and results ranged between 80 and 85°C. Other key parameters evaluated were wort perfect primaries, gravities and pH, attenuation limits, colour, and bitterness, Head retention (HR) and carbon dioxide (CO2) content of finished product were also determined. Results showed that the present gravities (PG), pH, bitterness (BU) and colour (EBC) obtained for the pearl millet starch wort samples ranged from, 65.64- 68.36°P, 5.39 – 6.09 PH, 24.25 – 25.65BU and 4.25 – 5.65 EBC respectively. In addition to the above parameters, two additional parameters, original gravities (OG) and alcohol by volume (abv) were measured for the pearl millet starch green beer with the following results, (OG) 58.24. – 60.78°P, (pH) 4.2 – 4.4, (BU) 20.5 – 19.6 BU, (abv) 4.45.6 – 4.56%. Results for head retention and carbon dioxide for finished products were, (HR) 77 – 83sec, (CO2) 3.08 – 3.43g/l. Sensory evaluation showed that the 25% pearl millet starch substituted sample was the most preferred based on estery flavor, tingly mouth feel, colour and bitterness. The microbial count for pearl millet beer had no growth of E.coli, streptococcus and staphylococcus but aspergillus was present from the 4th day and heaviest on the 8th day. While the drink which was made of barely with the same processing method had growth of staphylococcus and aspergillus which was seen from the 2nd day and heaviest on the 4th day but E.coli and streptococcus was absent. From the results, the drink which was made of pearl millet could keep for a longer period of time than the barely beer. Thus, the grain nature could extend the shelf-life of pearl millet beer longer than the barely beer at normal circumstance brewed. Keywords: pearl millet, bitterness, colour, attenuation limit, Fermentation time, Head retention.
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    Project Portfolio Selection Model Development Using Project Portfolio Management (Ppm) Approach With Special Reference to Djenna Endowment
    (Addis Ababa University, 2007-07) Mekonnen, Fiseha; Chandra, Subhash (PhD)
    The general objective of the thesis is to develop a model that assists companies’ for the selection and management of an optimal project portfolio that maximizes the benefits using project portfolio management (PPM) approach. In this thesis two models are developed. The first model is a general Project Portfolio Management (PPM) model that describes the whole process and steps of PPM. In this model the PPM process is divided in to six steps. The relationships between the steps, the processes and activities of each step are discussed in detail. The second model developed in this thesis is the portfolio selection step of the PPM process. In the portfolio selection model project evaluation criteria and sub-criteria are identified, and projects that are screened in the individual project evaluation step are arranged in Analytical Hierarchy Process (AHP) structure to prioritize and give relative weights of each component against to the next higher level components. At the most lower level the candidate projects for portfolio selection are arranged. These projects are going to be prioritized and scored in accordance with their contribution to the total sub-criteria, which are placed on the next higher level in the structure. The score or weights of the projects are used as a coefficient of the optimization problem. A zero-one integer linear programming is proposed to find the solution of the optimization problem. The developed model is tested and validated by considering one local multi-project owner corporate office. The corporate office vision, mission, objectives, criteria, sub-criteria, ongoing and candidate projects are considered and the objective function of the corporate office is formulated with an inclusion of the Endowment constraints and interdependence of projects. Then considering three probable demand scenarios and using a zero-one integer linear programming two portfolios of projects are generated. The portfolios’ risk and objective function values are calculated thereafter. The selection of one out of the two portfolios by taking into account the trade-offs of the risk and objective function value is left unto management for their decision.