Process Engineering
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Browsing Process Engineering by Author "Admassu, Shimelis (Associate Professor )"
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Item Development and Evaluation of Antimicrobial Aloe Based Packaging Films(Addis Ababa University, 2012-11) Asefa, Gashaw; Admassu, Shimelis (Associate Professor )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. Keywords: Aloe extracts, Antimicrobial packaging film, Mechanical properties, Papaya extracts, Pathogenic microorganisms, Physicochemical propertiesItem Production and Characterization of Oat - Wheat Based Food Products(Addis Ababa University, 2012-10) Habtamu, Shewarega; Admassu, Shimelis (Associate Professor )In this study the proximate composition and rheological properties of oat and wheat flour were investigated. The oat flour contained considerable amounts of protein (16.92%), total carbohydrates (64.65%) ash (1.80%), crude fiber (4.92%), moisture (5.61%) and fat (6.10%). The wheat flour also contained protein (13.56%), total carbohydrates (73.51%), ash (0.6%), crude fiber (0.32%), moisture (11.35%) and fat (0.98%). Based on these results, oat flour is nutritious and has a potential for use as composite flour in food formulations. Effects of oat flour supplementation (5%, 10%, and 15% of oat flour) on nutritional properties of the composite bread were investigated. The crude fiber, fat and protein all are increased as the addition of oat flour increased. The farinograph water absorption values of the composite flour (5%, 10%, and 15% of wheat flour) were 58.3%, 59.0% and 64.2% while the dough stability values were 8.5, 5.2 and 3.4 minutes; respectively. The dough development times were also 2.4, 3.0, and 4.3 minutes and that of the farinograph quality number were 99, 65 and 58 Brabender units; respectively. According to the results of wet gluten, falling number, and sedimentation values all decreased with the increase of oat flour supplementation (p<0.05) while color grade and oil absorption increased. The loaf volume of the composite flour bread were 340.6(100% wheat flour), 323.5 (5% oat flour), 298.4(10% oat flour), 250.3 (15% oat flour) and 210.9(100% oat flour). Loaf volume was significantly decreased with increase in level of incorporation of oat flour whereas loaf weight at 5%, 10% and 15% level of oat incorporation was significantly lower as compared to 100% oat supplementation (p<0.05). Results of this research suggested that supplementation of oat flour up to 10% results in bread with acceptable qualities. Oat flakes were prepared from locally grown varieties. The major parameters (specific weight, flake thickness and moisture content) which mostly affect the quality of oat flakes were measured and compared with the control oat flake. Specific weight, flake thickness and moisture content values were 0.53gm/L, 0.51mm and 9.5; respectively. These results are not significantly different to that of the control one. The sensory evaluation results also suggested that the flakes are acceptable. The economic analysis of the composite bread production plant revealed that it is profitable to produce the product. Key words: Composite bread, Farinograph values, Flour supplementation, Oat flake, Wet gluten