Browsing by Author "Mehari, Tetemke (PhD)"

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    Assessment of Heavy Metal Accumulation and associated potential health Risk in Green Leafy Vegetables Grown on Urban Wastewater Irrigated soil in Southern Addis Ababa, Ethiopia (case of Chromium, Lead and Cadmium).
    (Addis Ababa University, 2015-06) Beyene, Yonas; Mehari, Tetemke (PhD)
    A total of 16 Samples of wastewater, vegetable washing water, soil, root, stem, and leaf parts of the vegetables (Ethiopian Kale, Lettuce and Chard) were collected directly from the farm. All the samples were analyzed for the concentration of the three heavy metals lead (Pb), chromium (Cr), and cadmium (Cd). The concentrations of Pb, Cr and Cd in the leaves, stems and roots of Ethiopian Kale, Lettuce and Chard were found to be in mg kg-1 Cadmium (Ethiopian Kale :0.011 }0.0000, 0.007 }0.0002 and 0.011 }0.0003; Lettuce: 0.014 }0.0002, 0.016 }0.0003 and 0.125 }0.0003; Swiss chard: 0.014=0.0000, 0.007 }0.0000and 0.005 =0.0002, Chromium (Ethiopian Kale: 0.124 }0.0117, 0.044 }0.0137 and 0.075=0.0021; Lettuce: 0.193=0.0105, 0.033 }0.0018 and 0.112±0.0074; Swiss chard: 0.103 }0.0088, 0.067=0.0072 and 0.162=0.0000) and Lead (Ethiopian Kale: 0.620 }0.0132, 0.221 }0.0156 and 0.373 =0.0021; Lettuce: 0.019 =0.0187, 0.009 }0.0089 and 0.002 }0.0022; Swiss chard: 0.689 }+0.0093, 1.336 =0.0043 and 0.133 =0.0168) on dry matter basis, respectively. Results showed that, all the samples contain the three heavy metals below safe value limit recommended by FAO/WHO. Accumulation factor has the maximum value in the stem and root parts of Swiss chard (i.e. 0.035 and 0.018 for Pb), respectively. Accumulation factor also has the maximum value in lettuce root and chard leaf parts of the vegetable (i.e. 0.048 and 0.041 for Cr) and 0.250, 0.032 in the lettuce stem and leaf parts for Cd, respectively. The BCF value of Pb is approximately 2- fold in stem than the root. However, all the 3 vegetables samples can be considered excluders of the 3 heavy metals (i.e.BF< 1). PCA (Principal Component Analyses) shows impact of wastewater irrigation and Pb contamination is serious in wastewater-irrigated agricultural soils of the study area. The potential health risk calculated by THQs of all three heavy metals in the three leafy vegetables were less than 1.0 for adults , indicating that the adult residents in the Addis Ababa are not exposed to significant health risks associated with consumption of green leafy vegetables grown around the study area. Keywords ; Wastewater Irrigated soil; Green leafy vegetables; Heavy metals; Bio concentration factor;Target hazard quotient
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    Assessment of Leaching of Pottery Processed Foods A thesis Submitted to the School of Graduate studies of Addis Ababa University in partial fulfillment of the requirement for the Degree of Master of Science in Food Selected Toxic Metals in Some
    (Addis Ababa University, 2015-06) Tadesse, Mahlet; Mehari, Tetemke (PhD); Gashu, Dawd (PhD)
    Raw materials from uninspected sources used for making of cooking utensils could be a potential source for high toxic metal in food prepared in these utensils. Therefore, in the present work, the level of selected metals (Pb, Cd, and Al) in clay pots was determined. The clay pots were obtained from two sites kechene and legeberi the areas are selected because of the raw materials used to make them were brought from suspected places for metal contamination. In addition, leaching of those metals in some foods (bean stew, tomato sauce and coffee) prepared using these materials were investigated. Furthermore, factors that can influence metal leaching like frequent usage of the pots were also studied. Clay pots were crushed while the food and coffee samples were lyophilized and digested in a closed microwave digestion system. The levels of metals were determined using flame atomic absorption spectrophotometer (FAAS). The results showed that level of metals in clay pot from legeberi were Pb (26.7±0.0 mg/kg), Cd (5.6±0.1 mg/kg) and Al (38.74±0.7 mg/kg) and clay pot from kechene had Pb content (0.6±0.3 mg/kg), Cd (0.3±0.0 mg/kg) and Al (8.92±0.3 mg/kg). In addition, the level of metals leaching in food samples prepared using clay pots from legeberi showed tomato sauce Pb in range (from 9.6±0.0 mg/kg to 13±0.0 mg/kg), Cd (from 0.5±0.0 mg/kg to 1.2±0.0 mg/kg) and Al (from 11.53±0.4 mg/kg to 15.4 ±0.3). The bean stew prepared using clay pots from legeberi had Pb in the range (from1.2±0.0 mg/kg to 3.3±0.0 mg/kg), Cd (from 0.14 ±0.0 mg/kg to 0.38 ±0.0 mg/kg) and Al (from10.8±0.2 mg/kg to 13.5 ±0.3 mg/kg), whereas the coffee samples brewed in coffee pot from legeberi showed Pb in range (from1.6±0.0 mg/kg to 3.9±0.0 mg/kg), Cd (from 0.18 ±0.0 mg/kg to 0.34 ±0.0 mg/kg) and Al (from1.9±0.0 mg/kg to 3.8 ±0.1mg/kg). However, Pb and Cd were not detected in any of the food prepared using clay pot from kechene. The level of Al in food samples prepared in clay pot from kechene was tomato sauce in range (from10.5±0.5 mg/kg to 11.3±0.6 mg/kg), bean stew (from10.1±0.3 mg/kg to 10.4±0.4 mg/kg) and coffee (from1.1±0.0 mg/kg to 2.1 ±0.0 mg/kg). Results of the present investigation indicates that metal (Pb, Cd and Al) content of clay pot from legeberi was significantly higher (p<0.05) than clay pots from kechene. In this manner, food samples prepared using clay pot from legeberi had high level of metals (Pb, Cd and Al) beyond the permissible limit allowed by WHO, for Pb (0.01 mg/kg), Cd (0.003 mg/kg), and Al (1mg/kg) in food. Similar trend was observed for Al content of food prepared using clay pot from kechene. Therefore, metals (Pb, Cd, and Al) leaching due to cooking in legeberi clay pot and Al in clay pot from kechene could be a public health concern. Keywords: leaching; toxic metals;clay pot;;cooking frequenc
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    Determination of Heavy Metals in Canned Dry-Milk and Fish from Supermarkets in Addis Ababa
    (Addis Ababa University, 2013-06-06) Muleta, Kefyalew; Mehari, Tetemke (PhD)
    This study determined the levels of Cd, Cu, Pb, and Zn concentrations and nutritional values in four brands of canned dry-milk and fish in addition. The storage conditions of the supermarkets from where the sample foods collected were discussed. The result indicated that the mean ± SD levels of Cu and Zn in the four brands of milk were lower than the FAO/WHO maximum tolerable limit (FAO/WHO, 1984). The relative highest level of Cd (1.991±0.47mg/g) observed in CM milk brand from Holland was above the maximum tolerable limit 0.2 ppm (FAO/WHO, 1984). In contrast the Cd level was low (0.202±0.309 mg/g) in AM milk branded from Ethiopia. The level of Pb in all milk brands were above the FAO/WHO (1984) limit of lead 1.5 ppm. The mean cadmium content of canned dry-milk significantly (at 0.05) depends on the milk brand. The determined and labeled energy values of all dry-milk brands were significantly (p = 0.05) different. The highest mean ± SD value of Cu (3.004±1.809 mg/g), Cd (3.541±2.467mg/g), Pb (6.574±2.899 mg/g) and Zn (33.897±3.670 mg/g) were observed in CF fish brand canned in sunflower oil imported from Spain; while the lowest Cu level (0.442±0.088 mg/g) of DIF fish brand packed in sunflower oil imported from Thailand, Cd level (0.381±0.274mg/g), Pb level (1.791±0.275) and Zn level (1.918±1.872) were of NF fish brands from Indonesia packed in vegetable oil. Except the CF brand, the determined and labeled energy yield of DIF and NF fish brands were statistically (p=0.05) different. The supermarkets illumination and ventilation condition have significant association (r=0.999) with Cd residue in canned fish only. Therefore, the appropriateness of storage condition of the foods should be kept to the standard. Generally, canned foods should be traced for their heavy metals residue and checked for their nutrient and energy value it yields routinely to make sure the public in getting what is indicated on the label.
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    Synergetic effects of Mandillo [Crassocephalum macropappum (Sch. Bip. ex. A. Rich.) S. Moore] during Enset fermentation: chemical nature and efficiency
    (Addis Ababa University, 2016-04) Gonfa, Alemu; Megersa, Negussie (PhD); Mehari, Tetemke (PhD); Muleta, Diriba (PhD); Young-Mog, Kim (Professor)
    Enset (Ensete ventricosum (Welw.) Cheesman) is an ornamental plant in Asia, widely distributed in Africa and cultivated only in some regions of Ethiopia. Enset plant withstands prolonged period of drought and known for its high yielding potential. Fermentation of Enset produces a starchy food named Kocho, however, it is not practiced extensively. The principal reasons for low popularity of Enset are its uncommon sensory attributes among non-Enset consuming people, short shelf-life, nutrient losses, long fermentation period and lack of awareness. In Ethiopia, the Shekacho society adds Mandillo (Crassocephalum macropappum (Sch. Bip. ex. A. Rich.) S. Moore) stem during traditional Enset fermentation without knowing its scientific significance to the fermentation processes. Thus, the present study was initiated with the main purposes of investigating the indigenous knowledge of Shekacho society in Enset cultivation, Kocho consumptions, bioactive components of Mandillo parts and to determine its effects in Enset fermentation processes. The study was conducted using standard methods. To evaluate the indigenous knowledge of Shekacho society, analytical data were collected using semi-closed questionnaire, field observations, interviews and discussion with key informants with local annotations review. Enset plant physical structures were assessed. Phytochemical composition of Mandillo was evaluated. Its DNA damage protective and antioxidant activities were analyzed. Antimicrobial activity of Mandillo was tested against standard bacterial and yeast strains. Cytototoxicity of Mandillo was also evaluated. Fermentation process was carried out from 0-90 days. The pH value, titratable acidity, lactic acid and acetic acid contents were measured. Microbial counts were made on their respective agar media. Lactic acid bacteria (LAB) and yeast isolates were identified using morphological, biochemical and molecular techniques. Proximate composition, mineral contents, phytic acid, tannin, water holding capacity, and sensory attributes iii of Kocho were evaluated and the main findings are described as follows. The descriptive analysis of the data and the corresponding results indicated the existence of a high degree of consistency among the respondents with regard to Enset histories, fermentation processes, productivity, shelf-life of Kocho and food preparation. About 115 Enset cultivars were identified. Phytochemical analysis of Mandillo showed the presence of saponins, tannins, anthraquinones, steroids, terpenoids and flavonoids. Total phenolic and flavonoid contents of the aerial part calculated as 101.48 mg GAE (Gallic acid equivalent)/g and 293.25 mg QE (Quercetin equivalent)/g, respectively. Mandillo showed strong 2, 2-diphenyl-1-picryl hydrazyl (DPPH) scavenging potential with IC50 ≤ 50 μg/mL. The stem of Mandillo showed promising protective activity against oxidative DNA damage. The minimum inhibitory concentration of stem against E. coli KCTC 1682 and Candida utilizes KCCM 11355 was ≥ 15.62 μg/mL. The final pH of Kocho fermented with starter culture but no Mandillo (Koki) and with Mandillo (Kom) decreased to 4.49 and 4.10; respectively, which are significantly different and didn’t allow the growth of spoilers in Kom. Titratable acidity, lactic acid and acetic acid contents of Kom increased by 64.34%, 103.90% and 40.04%, respectively when compared to Koki. Koki and Kom samples had LAB counts of 1.16×107 and 2.83×108 CFU/g, respectively, on the day 37. Treatments with Mandillo stem significantly (p < 0.05) lowered counts of aerobic mesophilic bacteria, aerobic spore formers and coliforms. Staphylococci were below detectable level. The 16S rRNA gene sequences analysis and phylogenetic tree reconstruction identified LAB species as Lactobacillus plantarum (69.37%), Leuconostoc mesenteroides (9.91%), Lac. paracasei (9.01%), Lac. brevis (3.60%) and other rare species. Lac. paracasei and Lac. brevis were dominantly found in Kom during the final days of fermentation. An 18S rRNA gene sequences evaluation identified yeast isolates as Candida boidinii (30%), Wickerhamomyces sp. ES22S03 (16%), Pichia fermentans (16%), Williopsis sp. (10%) as dominate species and others minor strains. Kocho composition analysis showed significant (p < 0.05) differences between Koki and Kom in moisture contents (8.34 to 8.80%) and (9.14 to 7.95%), fiber (7.92 to 5.56%) and (6.25 to 3.96%), protein (3.24 to 3.68%) and (3.59 to 3.95), phytic acid (5.83 to 4.11 mg/g) and (4.95 to 4.33 mg/g), water holding capacity (8.55% and 6.37%); respectively. Mineral contents of Koki and Kom also calculated as Ca (9.84 mg/100 g and 10.08 mg/100 g), Fe (2.12 mg/100 g and 2.08 mg/100 g), Zn (1.99 mg/100 g and 1.77 mg/100 g) and Cu (0.12 mg/100 g and 0.16 mg/100 g); respectively. Sensory evaluation revealed overall acceptability values of 73.27% (Koki) and iv 97.20% (Kom). Cytotoxicity evaluation of Mandillo stem against Raw Cells 264.7 showed no toxicity at ≤ 4 μg/mL. From the results of the descriptive analysis of the data and the corresponding results suggested by the respondents, it is understood that Enset is very important for food security and environmental protection. Phytochemical contents and activities of Mandillo revealed consistency with the starter culture role played by the addition of the stem part of the plant. The effect of adding Mandillo during Enset fermentation showed significant differences in all of the measured Kocho quality parameters, food composition, microbial dynamics and diversities and sensory attributes of experimental Kocho product compared to the control sample. In general, improvements of the basic components of Kocho dough are responsible for the enhancement of its shelf-life, safety and sensory attributes of the food as a result of good fermentation processes. In the light of the current finding, extensive investigation are required to qualify Mandillo as food preservative and shelf-life enhancer for its application in food sectors.