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Browsing Food Engineering by Author "Admassu, Shimelis(Professor)"
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Item Byproducts Utilization from Wheat Milling Industries for Development of Value Added Products(Addis Ababa University, 2014-03) Yishak, Yemsrach; Admassu, Shimelis(Professor)The main byproducts of wheat milling industries, wheat germ and bran, have been known as an outstanding sources of protein, dietary fiber, trace minerals, antioxidants, phytochemicals and allied micronutrients. This research was conducted to evaluate utilization of wheat germ (WG) and wheat bran (WB) for the development of value added cookies and tea substitute products; respectively. Supercritical fluid extractor (SFE) was used to extract oil from wheat germ and the defatted wheat germ flour (DWGF) was used as a supplement for wheat flour at 10%, 15% and 20% blending ratios (BR1, BR2 &BR3) and baking temperatures of 150, 180 and 210 oC (T1, T2 &T3).Wheat bran (WB), the other byproduct of wheat milling industries, used to made tea substitute by milling, screening, and heating before utilized as final product. Chemical composition of raw materials, physico-chemical and rheological characteristics of flours were investigated prior to cookies preparation. Proximate analysis for wheat flour (WF)(0.83,11.92,0.52,0.45,9.33) and defatted wheat germ flour (DWGF) (4.72, 12.98,1.01,5.17,28.11); for ash, moisture, fat, fiber and protein were resulted respectively; as a result nutrient dense DWGF used as a substitute for development of cookies . It was found that protein, fiber, ash and minerals (Ca, K, P, and Mg) contents in the blends increased significantly (P<0.05) with an increase in DWGF substitution. The effect of BR2 and T2 on proximate composition resulted with (protein (14.29), fiber (2.84), and ash (1.31)) resulted better together with sensory quality evaluation. Rheological and functional properties of flours, physical properties for cookies and organoleptic properties for both products were analyzed. Total phenolic content (TPC) and antioxidant activity were determined by using Folin-Ciocalteu and DPPH scavenging activity assays respectively. Extraction procedure went out using methanol at three different temperatures (40, 60 and 80)0C. Higher total phenolic content ranged from 1.037 to 3.68mg of gallic acid equivalent (GAE)/gm of dried extract obtained at 60 0C using methanol. While antioxidant activity with lower half maximal inhibitory concentration (IC50) (mg/ml) value of (1.4, 1.75, 2.13) scavenging activity for ascorbic acid, methanol solvent extract of wheat bran and by absolute methanol respectively. Finally, cookies baked at 180oC using blend ratio 15 % resulted better sensory qualification and wheat bran extracted using solvent methanol at 60oC showed potential antioxidant activity and TPC. Keywords: defatted wheat germ, cookies, antioxidant, folin-Ciocalteu assay, DPPH scavenging capacity assayItem Development and Quality Characterization of Whey-Aloe Debrana Based Probiotic Beverages(Addis Ababa University, 2016-10) Semaw, Mohammed; Admassu, Shimelis(Professor)The aim of this research was to develop and characterize whey-Aloe debrana based probiotic beverages. The probiotic beverages were prepared through mixing of whey with Aloe debrana juice, 1% L. Acidophilus probiotic culture, 2% starter cultures of L. Bulgaricus, and S. thermophiles, vanilla and sugar according to the basic formulation for probiotic beverage production. The probiotic beverages were prepared by mixing of whey and Aloe debrana juice containing 70% and 30%, 80% and 20% and 90% and 10% whey and Aloe debrana juice ; respectively. And 100% whey (control). The effect of mixing of Aloe debrana juice (30%, 20% and 10%) and storage days (7 days, 14 days and 21 days) at refrigerated storage and (3 days, 6 days and 9 days) at room storage temperature were evaluated. Physico-chemical properties, microbiological qualities, and sensory quality of probiotic beverages were studied during storage. The decline in pH of the control probiotic beverage was significantly (P<0.05) higher than Aloe based probiotic beverages during refrigerated and room storage temperature; respectively. The control probiotic beverage contained significantly (P<0.05) lower moisture (79.40%) content, higher protein (1.89%) content and fat (0.42%) than Aloe based beverages. Sample containing 20% Aloe juice has scored significantly (P<0.05) higher moisture (82.75%) and protein (1.72) content. Aloe debrana juice scored higher in phytic acid (467.68) mg/100gm, tannin (130.10) mg/100gm and polyphenol 330ppm followed by sample contain1ing 30% Aloe juice. Microbiological results showed that all probiotic beverages were within the limit range for acceptable condition for consumers according to FAO. Sensory quality evaluation results showed that the sample containing 30% Aloe juice scored higher in overall acceptability (4.15) at the initial day of storage. Sample containing 30% Aloe juice scored the highest in overall acceptability throughout the refrigerated and room storage temperature. In general, the probiotic beverages processed by mixing of whey with 30%, 20% and 10% Aloe debrana juice and stored for 21 days and 9 days at refrigerated and room storage temperature; respectively gave promising results. Thus, it is possible to manufacture probiotic beverages by incorporating Aloe debrana juice and food ingredients with whey. Keywords: Aloe debrana juice, Bioactive compound, Probiotic beverages, Toxicity test, Aloe debrana Whey beveragesItem Development of Ready to Eat Protein Enriched Extruded Product(Addis Ababa University, 2013-06) Taye, Abayneh; Admassu, Shimelis(Professor)The study was conducted with the aim of producing protein enriched extruded product that can be used as a protein supplement by combining legumes, cereal and oil seeds. Accordingly, maize, defatted soy flour and chickpea were selected based on their nutritional value, availability in the local market and affordability. By Applying mixture experimental design, formulation containing 589 g/kg corn, 291 g/kg defatted soy flour, and 120 g/kg of chickpea flour was selected as the best source of protein. The effects of extrusion parameters on the specific length, bulk density, and expansion ratio, functional properties (water solubility index, water absorption index and water holding capacity) were done, after extruding the blend with moisture content (17and 20%) barrel temperature (120, 130, and 140 0C), and screw speed (150,200 and 250 rpm). Sensory characteristics of extruded products (texture, color and overall acceptability) were also studied to evaluate the suitability of the product as extruded snack. Using the blend ratio obtained from the design, an extrudate containing 21.34% protein, 2.81 % of fat and 65.06% of carbohydrate was found to be the protein enriched product. The specific length, expansion ratio and bulk density were found highly affected by barrel temperature and moisture content. As the barrel temperature increased from 1200C to 1400C and the feed moisture content kept at 17 %, extrudates with high expansion ratio (146%) and lower bulk density (9%) were found. An increment in barrel temperature from 120 0C to 140 0C was the only parameter that significantly affects (P<0.05) the specific length of the extrudates by increasing from 1.81 to 2.74. Screw speed effect was only seen on the extrusion dependent variables through decreasing torque, die pressure and SME from 24.75 to 12.42, 19.5 to 11.12 and 302.28 to 173.73, respectively. The functional properties ,water solubility index, water absorption index and water holding capacity of the extrudates (4.59, 21.84 and 3.165) were found higher than that of the formulated flour (2.48, 13.49 and 1.59); respectively due to starch gelatinization. Results on the antinutrents studies showed reduction of 20% in phytate and 28% in tannin. The sensory evaluation result showed that extrudate produced with Moisture content of 17%, temperature of 140 0C and screw speed of 200rpm was perceived as the most accepted product. Accordingly a process technology for the production of the snack is suggested. Key words: Chickpea flour, Defatted soy flour, Extrusion, Flake, Maize flour, Mixture DesignItem Effect of Processing an Phytochemicals and Nutrients Composition of Fenugreek (Trigonella Foenum-Graecum L.), and Development of Value Added Products(Addis Ababa University, 2012-10) G/Silassie, Birhane; Admassu, Shimelis(Professor)The primary purpose of this research was to study the effects of germination, fermentation, autoclaving, extraction and their combinations on the phytochemicals and nutrients composition of fenugreek seed varieties (Challa, Ada’a and Wello). The chemical compositions, physico-chemical and functional properties, mineral bioavailability, and phytate and non phytate phosphorus contents of fenugreek seeds were investigated. Furthermore, during polar solvent extraction process, the influences of rinsing stages, solvent type, and proportion of solvent to water on the rate of extraction were also examined. The average mean value on dry weight basis of fenugreek’s moisture content was 7.5%, crude protein 29.3%, crude fat 7.9%, crude, fiber 7%, total ash 3% and total carbohydrates 45.2%. The major mineral constituents of fenugreek seeds were K (10351.7 mg/kg), P (5651.3 mg/kg), Mg (1257.3 mg/kg) and Na (121.5 mg/kg), Ca (553.7 mg/kg), Fe (81.3 mg/kg) and Zn (43.4 mg/kg). Saponins, phytates and tannins concentrations ranged from 4581.3 to 6320.8, 76.11to 111.08 and 235.24 to 269.13mg/100g; respectively. Water and oil absorption capacities were 7.5, 10.2 & 7.2 g/g of water and 1.04, 1.12 & 2.3g/g of oil absorption capacity for Challa, Ada’a and Wello; respectively. Crude protein, fat, fiber, mineral bioavailability and non phytate phosphorus compositions were improved during processing methods. Significant reduction of phytochemicals was achieved by employing conventional, heat and chemical processing methods. Germination reduced phytates, tannins, and saponins by 47.9 – 66.4%, 33.7 – 56.8%, & 46.3 – 69.9%, fermentation 68.7 – 100%, 40.7 – 87.9% & 67.8 – 81.0%, autoclaving 32.5 – 36.4%, 66.4 – 74.7%, & 88.6 – 94.6% and extraction 6.7 – 7%, 100%, & 100%; respectively. Extraction was less effective in reducing phytates as compared to other processing methods due to insolubility of phytates in alcohol (ethanol &methanol). The combination of germination and fermentation resulted in a significant and successive reduction in phytates, tannins and saponins levels. However, complete removal of all phytochemicals was achieved by the combination of fermentation followed by extraction process. During extraction, as the proportion of water increases the percolation rate decreases due to water binding property of fenugreek. Methanol extraction was faster and powerful than ethanol extraction. The extraction process also removed the astringent smell and bitterness of fenugreek. Thus, debitterized fenugreek powder was produced. In addition, to preserve the health benefits and to maintain dose of fenugreek required for different age groups, sex and health conditions, fenugreek capsules were also produced. Key words: Chemical composition, extraction rate, Fenugreek, phytochemical, processing methods, solventItem Effect of Processing on Qualtiy Characteristics of Pearl Millet (Pennisetum Glaucum) Based Value Added Products(Addis Ababa University, 2013-06) Legesse, Eyoel; Admassu, Shimelis(Professor)The effect of processing on characteristics of pearl millet (Pennisetum glaucum) was investigated. The proximate and mineral compositions, physicochemical and functional properties and reduction of antinutrients concentration were determined. In addition, the sensory quality of pearl millet value added products were studied. The value of moisture content of raw, roasted, fermented, blanched and autoclaved pearl millet flours were 8.82, 7.58, 11.55, 10.04 and 7.77%, crude protein 11.72, 12.02, 20.79, 11.26, and 12.25% and total ash 2.75, 3.11, 2.57, 3.08, and 2.69%; respectively. Micronutrient concentration of the seeds showed large variation. Phosphorus was the most abundant (290.04 mg/100g) mineral whereas Ca was low (2.66mg/100g). The ranges for tannins and phytate were 0.80 to 3.66mg/100g and 167 to 294mg/100g, respectively. Significant difference (p<0.05) were observed between treated pearl millet flours in their proximate and antinutritional composition. Roasting process was least effective in reducing phytate and tannins as compared with other processing methods due to the less antinutrient loss expected by roast in cereals. A slight significance was observed during autoclave on elimination of phytate as compared to conventional processing methods. In contrast, fermentation (72h) and blanching (110 o Keywords: Antinutritional factors, Least gelation concentration, Liquefaction, Pearl millet flour, Staple food, Wheat flour C) was found to be the relatively best method for reducing the phytate and tannins content (0.83 and 0.80mg/100g for tannin and 167.14 and 208.17mg/100g for phytate), respectively. The sensory evaluation of thin porridge and bread products was generally acceptable by panelists. The thin porridge prepared from 75% of unfermented and 25% of fermented pearl millet flour was more preferred in sensory attribute investigation, while the thin porridge prepared from 100% fermented and blanched pearl millet flour was least preferred. With respect to, the acceptability of control and 5% substituted of fermented pearl millet flour breads were highly acceptable by the panelists and prominently for 5% blanched pearl millet flour bread. Meanwhile, loaf qualities expressed in such a way loaf volume range between (451- 134ml), and specific volume range between (4.1- 1.2ml/g) were significantly decreased (p<0.05) at higher substitution level of pearl millet flours. Based on the preliminary techno-economic evaluation, the suggested process technology and product diversification is feasible.Item Optimization of Process Variables to Develop Teff-Amaranth Based Extrudates(Addis Ababa University, 2014-06) Berhe, Aregay; Admassu, Shimelis(Professor)Response Surface Methodology was adopted to study the effect of barrel temperature (A), screw speed (B), feed moisture content (C) and blend ratio (D) to optimize the proximate composition, physical properties(expansion ratio, bulk density and specific length), functional properties(WAI and WSI) and sensory quality attributes during extrusion process to develop teff-amaranth based extrudates using twin screw co-rotating extruder. Kuncho and red teff grains with voucher numbers DZ-C1-387 and DZ-01-99, respectively and three amaranth varieties (white, pale-white and black amaranth) were studied for proximate composition, mineral content, phytochemical content and functional properties. The moisture contents for DZ-C1-387 and DZ-01-99 were11.12 and 12.27%, respectively. The proximate compositions of DZ-C1-387 were 12.46(protein), 2.82(fat), 2.82(ash), 2.45(crude fiber) and 68.64% (total CHO), respectively, and the proximate composition of DZ-01-99 were 10.19, 2.42, 2.42, 2.51and 70.12% for crude protein, crude fat, ash, crude fiber and total CHO respectively. The energy value of DZ-C1- 387(349.78kcal/100g) was significantly (p<0.05) higher than the energy value of DZ-01-99 (343.02kcal/100g). Among the three amaranth varieties, moisture (10.24), protein (17.85), fat (7.00), ash (2.70), crude fiber (6.86) and total CHO (55.35%), respectively were the proximate compositions for white amaranth. The proximate compositions of pale-white amaranth were11.50, 14.15, 6.30, 5.40, 2.20 and 60.45% for moisture, crude protein, crude fat, crude fiber, ash, total CHO, respectively. The moisture, crude protein, crude fat, crude fiber, ash and total CHO content of the black amaranth were 10.89, 15.30, 6.50, 5.75, 2.40 and 59.16%, respectively. The energy value of white amaranth (354.80kcal/100g) was significantly (p<0.05) higher than the energy values of pale white amaranth (351.10kcal/100g) and black amaranth (351.34kcal/100g), respectively. On the basis of extruded product quality, the extrusion process variables were feed moisture (12, 18, and 24%), teff - amaranth blend ratio (90:10, 85:15 and 80:20%), barrel temperature (110, 130 and 150°C) and screw speed (120, 140 and 160 rpm) through a die of opening about 9.00mm. The extruded products were evaluated for their chemical composition, mineral content, physical properties, functional properties and sensory quality attributes. The optimum extrudate which was obtained at 1300c (barrel temperature), 140rpm (screw speed), 15% (feed moisture content) and 15% amaranth in the feed had 13.70% protein, 3.53% fat, 2.98% fiber, 2.66% ash and 70.27% total CHO and 19.52, 170.47, 5.08, 386.54, 176.98mg/100gm for Fe, Ca, Zn, P and Mg and 33.72% phytates and complete reduction of tannins was observed in this study. The maximum expansion ratio (3.0789), maximum WAI (8.728g/g) and minimum bulk density (0.1614g/cm3) values of the extrudates were observed at 130 0C, 140 rpm, 15% feed moisture content and 85:15 blend ratio. The the maximum specific length(3.6193cm/g) was obtained at 150 0C, 160 rpm, 15% feed moisture content and 80:20 blend ratio and the maximum WSI (22.217%) was obtained at 150 0C,120 rpm, 15 feed moisture content and 80:20 blend ratio. In this study, promising results were obtained for teff- amaranth based extrudate development and process optimization studies. Keywords: Teff, Amaranth, Extrusion, Extrudates, Optimization, Response Surface MethodologyItem Process Parameters Optimization and Development of Extruded Teff Based Snacks(Addis Ababa University, 2015-03) Wondimu, Asnakech; Admassu, Shimelis(Professor)Protein-energy malnutrition has been identified as one of the problems in East Africa. Attempts have been made to combat this nutritional problem by developing nutritious foods of high protein and energy value from cereal-legume combinations. This study aimed to develop nutritious and sensorial acceptable teff based expanded product using twin screw extruder through optimization of extrusion process variables. Experimental design with barrel temperature (120,140,160°C), feed moisture content (14, 17, 20%) and blend ratio BR1 (70T:20M:10L), BR2 (60T:25M:15L) and BR3 (50T:30M:20L) as independent variables which were three factors at three levels produced 20 different runs. The experimental study was performed using response surface methodology face centred central composite design to investigate the effect of independent variables such as barrel temperature, feed moisture content and blend ratio on products functional properties (water absorption index and water solubility index),physical properties (expansion ratio, specific length),textural property (hardness) and sensory quality. Proximate composition, mineral content, anti-nutritional content and functional properties values for raw materials, blended flour were evaluated and the blended flour was extruded then extrudate proximate composition, mineral and anti-nutritional content, physical, textural, functional properties and sensory quality evaluation were investigated. The maximum expansion ratio (4.85mm/mm), maximum water absorption index (7.80 g/g),minimum bulk density(0.108 g/cm3) and minimum hardness (13.49N) values of the extrudates were observed at 1400C, 14% feed moisture content and 60T:25M:15L blend ratio. Sensory quality evaluation of extrudate produced at 140ºC barrel temperature, 14% feed moisture content and 60T:25M:15L blend ratios with added vanilla powder were significantly (P<0.05) better in colour (8.33 ± 21), flavour (8.35 ±0.76), crispiness (8.33±0.64) and overall acceptability (8.56 ± 0.79).The model developed could be used for designing of extrusion conditions for getting extrudates with desirable physical characteristics. Keywords: Blend ratio, Extrusion process, Extrudates, Process optimization, Response Surface Methodology, Teff, Twin screw extruderItem Product Development and Quality Characterization of Pulse-based Extruded Ready to Eat Snacks(Addis Ababa University, 2017-06) Alemayehu, Haylemikael; Admassu, Shimelis(Professor)This study was aimed to enhance the value of pulse based food products and estimate its suitability for manufacturing of extruded snack products. Response surface methodology (RSM) was implemented to study the effect of extrusion process parameter and to optimize proximate and mineral composition, phytochemicals, physical properties (expansion ratio, bulk density and specific length), functional properties (WHC, WAI and WSI), microbial load and sensory quality attributes during extrusion process. Chickpea (Desi), Haricot Bean (Nasir), Maize (Melkassa 2) and Finger Millet (Taddesse) varieties were studied for proximate composition, phytochemical content, physical properties and functional properties. By applying mixture experimental design D-optimal software formulation containing 41.1g/100g Chickpea flour,16.0g/100g Haricot Beans flour, 31.9g/100g Maize flour and 10.9g/100 of Finger Millet flour was selected as the greatest source of energy (400.561kcal) and protein (18.09g/10g). The extrusion process variables were barrel temperature (120, 140 and 160°C) and screw speed (200, 270 and 340 rpm) feed moisture (15, 16.5 and 18%) through a die diameter of 6mm. The optimum extrudate which was obtained at 120oC (barrel temperature), 340rpm (screw speed) and 15% (feed moisture content) had 16.24% protein, 6.49 % fat, 2.66 % fiber, 2.51% ash and 74.01 % total CHO and 3.38, 2.22, 15.53, 90.47mg/100g for Fe, Zn, Ca, and Mg and 38.05 % phytate and 56.34% reduction of tannins was observed in this study. The maximum water absorption index (6.017g/g) and minimum load at break (16 N) values of the extrudates from texture analyzer (LLOYD level-05) were observed at 120oC, 340 rpm screw speed and 15% feed moisture content. Sensory quality evaluation of extrudate produced at 120oC, 340 rpm screw speed and 15% feed moisture content were significantly (P<0.05) better in color (8.22 ± 0.667), appearance (8.22± 0.441) crispiness (8.44 ± 0.527) flavour (8.33± 0.50), and overall acceptability (8.33 ± 0.50). The increment in mass flow rate from 19.84g/sec to 33.82g/sec was observed due to increase in screw speed from 200 to 340 rpm. Microbiological result showed that Coliform and E. coli were not detected at all in all extrudate. The total plate count and yeast and mold count analysis was found in the safe limit according to FAO and WHO. In conclusion 120oC barrel temperature, 340 rpm screw speed and 15% moisture content have been found to be ideal operating variables for pulse-based extrudate development. Key words: - Haricot beans, finger millets, Maize, response surface methodology, mixture design, ready to eat snacks.