http://etd.aau.edu.et:80/dspace/handle/123456789/1580 Search the Channel search http://etd.aau.edu.et:80/dspace/simple-search http://etd.aau.edu.et:80/dspace/handle/123456789/4408 Title: Development and Evaluation of Antimicrobial Aloe Based Packaging Films <br/> <br/>Authors: Gashaw, Asefa <br/> <br/>Abstract: This study was aimed at the development of antimicrobial packaging films, which is one of the most promising active packaging systems, from aloe and papaya leaves extracts with gelatine and glycerol. Three different extracts of papaya leaves were analyzed for their antimicrobial activities. Mechanically obtained papaya leaf extract showed the best result (12.10mm inhibition zone on S.typhi). Based on antimicrobial activity, film forming ability, transparency, and colour; Aloe debrana extract was found to be more appropriate for the development of antimicrobial packaging films than Aloe trichosantha extract. The antimicrobial activity of Aloe debrana extract was increased by the incorporation of papaya leaf extract up to 30%, above which it did not bring significant influence on most test organisms. As a result 70% Aloe debrana extract and 30% papaya leaf extract standard solution was prepared. Various concentrations of gelatine and glycerol were added to the standard solution for packaging films development. Films were evaluated for their antimicrobial activities, physicochemical, and mechanical properties. The antimicrobial activities of aloe based films were tested on E. coli, S. typhi, S.aureus, C. albicans, and F. xylarioides. All films exhibited inhibitory zones on the test microorganisms used in this study. A wide inhibition zone (6.52cm2) was observed on S. typhi growth whereas the least (4.20 cm2) was on C.albicans. Films were soluble in water with highest solubility (90.49%) for P1,1 (film with 1g glycerol and 1g gelatine) and lowest (44.57) for P0,2(film developed by adding only gelatine). Film solubility significantly increased as the concentration of glycerol increased and decreased as the concentration of gelatine increased. Film P0.5,2(with 0.5g glycerol and 2g gelatine) has showed maximum tensile strength (65MPa) where as the lowest (20MPa) was obtained by film P0.5,1(0.5g glycerol and 1g gelatine). Increasing gelatine concentrations significantly increases the tensile strength but glycerol has an opposite effect on the tensile strength. All the films were highly flexible and stretchable. Film P1,2(1g glycerol and 2g gelatine) showed the maximum elongation (180%) and the minimum elongation (89%) was obtained for P0.5,1. This study demonstrated the technological feasibility of developing antimicrobial packaging films from aloe and papaya leaves extracts. http://etd.aau.edu.et:80/dspace/handle/123456789/4406 Title: Effect of adding urea on biogas production potentials of selected fruit wastes in Addis Ababa, Ethiopia <br/> <br/>Authors: Getachew, Dagnew; Gebreeyssus <br/> <br/>Abstract: Fruit wastes are ideal candidates for anaerobic digestion because they contain high levels of easily biodegradable materials. These wastes from the central and biggest fruits, fish & vegetables retail and distribution market in Addis Ababa City, Ethiopia are poorly managed. Again problems such as low biogas/methane yield and process instability are often encountered in anaerobic digestion of these wastes, challenging its reliability and efficiency. This study evaluated the effect of adding urea on biogas (methane) potential of selected fruit wastes following characterization. A laboratory scale experiment on batch anaerobic mesophilic digestion was carried out. Selected and pretreated fruit wastes were fed to digesters using standard procedures. Analytical equipments, simple tools and statistical software were used for data analysis. The ultimate biogas yield from using avocado, banana, and mango fruit wastes as substrate is; 0.48, 0.57, 0.53 l/g VS without adding urea and 0.76, 0.82, 0.82 l/g VS adding urea with a statistically significant difference (p-value; 0.006 for avocado, 0.029 for banana, and 0.007 for mango FW at 95% Confidence Interval respectively). Thus urea addition significantly improved biogas yield. In relation to this, ultimate CH4 yield didn’t show difference in response to the treatment and gave 0.27, 0.33, 0.27 l/g VS without adding urea and 0.44, 0.46, 0.43 l/g VS for avocado, banana, & mango fruit wastes with adding urea where the later yield is above average yield reported for fruits and vegetables wastes. Further, the biogas manure contains nutrients in their useful form and better than the row waste for plant growth signifying the advantages of anaerobic digestion. Prediction of biogas and biogas manure obtainable from the city’s fruit wastes is also made. http://etd.aau.edu.et:80/dspace/handle/123456789/4405 Title: Design and Optimization of Molasses Treatment to Reduce Scale Formation in Ethanol Production (The Case of Metahara Sugar Factory Ethanol Plant) <br/> <br/>Authors: Teshale, Firdissa <br/> <br/>Abstract: Fouling in industrial heat exchangers leads to economic penalties. To overcome this problem, either cleaning of heat exchangers or reduction of the scaling is the two possible solutions. But, cleaning of heat transferring unit is an expensive exercise. Therefore, this study has been conducted with the objective to design and optimize molasses treatment plant to reduce scale formation in ethanol production. The study has been conducted in such a way that, first scale samples collected from Metahara sugar factory ethanol plant distillation column and characterized physically and it is hard scale with an average thickness of 2.04cm and gray in color which shows that it is the result of crystallization. In addition to this, it has been characterized chemically to determine its composition and the scale is 63.87% composed of CaO. Then, to assess cause of this scaling, process water and the raw molasses has been characterized for their composition and pH which shows that process water is within a normal hardness and pH range. But, the molasses of Metahara sugar factory is with an average of 2.41% CaO which is abnormally high when compared to world average of 1.5% CaO % molasses. Therefore, the main cause of heat transferring units scaling in the plant is the CaO content of the molasses. To overcome this problem, treating the molasses with H2SO4 and heat is the best technology. Because, the reaction of CaO with H2SO4 at higher temperature give CaSO4 which is insoluble in water and easily separated by sedimentation. Experiments have been conducted with varying influential molasses clarification conditions and 100OC temperature, 4 pH, 50o brix and 2hours retention time have been determined as the optimum clarification process conditions. At these optimum conditions 54.43% of the CaO in the molasses has been removed. At these process conditions, 1.08CaO% molasses has been obtained which is too low when compared with world average of 1.5CaO% molasses. http://etd.aau.edu.et:80/dspace/handle/123456789/4400 Title: Development and Evaluation of Chickpea and Rice Based Dry Fermented Sausages <br/> <br/>Authors: Habtamu, Asmare <br/> <br/>Abstract: This research study was conducted with the aim of development and evaluation of chickpea and rice based dry fermented sausages. The dry fermented sausages were prepared through blending of meat with chickpea and rice flours, sodium chloride, sodium nitrite, garlic, and starter culture according to the basic formulation for sausage production. The effect of fermentation time (24h and 48h), blending of chickpea and rice flours (20% and 30% each), and drying time (7days and 12days) on proximate composition, color, pH and lactic acid values, sausage yields, microbial load, and sensory qualities of the dry fermented sausages were investigated. The ranges for proximate composition of chickpea and rice based dry fermented sausages in (%) were for moisture (25.36 – 30.16 and 24.57 – 31.06), crude protein (29.13 – 31.88 and 20.89 – 27.07), crude fat (17.45 – 23.12 and 15.27 – 19.84), crude fiber (2.68 - 3.38 and 1.62 – 3.48), total ash (6.00 – 7.72 and 5.46 – 7.47), total carbohydrates (11.83 – 16.67 and 20.53 – 27.72) and energy value (338.62 - 385.47 and 321.65 - 380.78kcal/100g); respectively. The mineral components of the dry fermented sausages were significantly (p<0.05) increased as compared to sausage batters. Sodium was the most abundant over other minerals due to the addition of NaCl and NaNO2 salts in sausages processing technology. The processing parameters resulted decrease in pH and rise in lactic acid values which, were more significant (p<0.05) during the 48h fermentation and 7days of drying. The blending level of chickpea and rice flours had effect on color of dry fermented sausages which had revealed higher L* and b* values and lower a* value compared to the control. Higher sausage yields were obtained from the dry fermented sausages processed by blending of chickpea flour and rice flour at 30% blending ratio, 24h fermentation and 7 days drying. Microbiological results showed significant (p<0.05) amount of reduction of undesirable and increment of desirable microbes with in processing parameters. Total lactic acid bacteria were found to be the predominant micro flora of the final products and reached more than 8.5 log cfu/g, however, Enterobacteriaceae were not detected. The sensory quality results indicated that chickpea and rice based dry fermented sausages with 20% blending ratio revealed acceptable range of the hedonic scale. In general, the dry fermented sausages processed by blending of meat with 20% chickpea flour and 20% rice flour, fermented for 48h and dried for 12days gave the promising results. Based on the preliminary techno-economic evaluation, the suggested process technology and product diversification is feasible.