Browsing by Author "Bekele, Tilahun (Assistant professor)"

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    Effect of Composite Flour Blend of Teff, Sorghum and Maize on Macro Nutritional Quality, Sensory Acceptability and Ph Fermentation Kinetics In Preparation of Injera
    (Addis Ababa University, 2015-06) Legesse, Solomon; Baye, Kaleab (PhD); Bekele, Tilahun (Assistant professor)
    The study attempted to investigate the effect of composite teff flour blend with sorghum and maize through optimization of formulation based on simplex lattice mixture design expert soft ware, on macro-nutritional composition, sensory acceptability and pH fermentation kinetics while looking for opportunities of preparing Injera with an affordable cost from such composites. The study was based on 14 experimental trials including four replication points on the contour triangle plot, three vertex points ([100% teff], [50% teff: 50% sorghum] & [50% teff: 50% maize]) and one point on the center edge (75% teff: 25% maize) which were generated from the soft ware with primarily defined constraint. Proximate and sensory acceptability determinations were carried out on the experimental trials resulting in content of protein (11.27-14.73)%, fat (1.79-3.59)%, crude fiber (5.65-9.57), total carbohydrate (6.97-19.82)%, total energy value (110.36-157.60)Kcal/100g and sensory acceptability scores from liked to extremely liked (color[4-5], taste[3-4], texture[3-4], odor[3-4], appearance[3-4] and over all acceptability[3-4]) based on 5-point hedonic scale which these response results were used for formulation optimization to finally came up with three optimized formulations; (formulation one [F1-control; 100% teff], formulation two [F2; 55.40% teff: 37.20% sorghum: 7.30% maize], formulation three [F3; 50% teff: 30.70% sorghum:19.30% maize], and formulation four [F4; 66.6% teff:19.80% sorghum:13.60% maize]) based on objective criterion. Further determination of proximate, sensory acceptability and pH fermentation kinetics were performed on the three optimized formulations and the control to result in content of (protein [11.34-16]%, fat [1.79-3.01]%, crude fiber [6.00-8.66]%, total carbohydrate [10.33-18.02]% & total energy value [132.39-162.37]Kcal/100g), sensory acceptability scoring from liked to very liked (color[3-4], taste[3-4], texture[3-4], odor[3-4], appearance[3-4] & over all acceptability[3-4]) within three days of preparation of Injera for all the optimized formulations plus the control, and maximum rate of change of pH per hour of (-0.011639 up to -0.040486) within 72 hours of fermentation. Composite teff flour blend with sorghum & maize had brought effect in different manner with regard to macro nutritional composition and sensory acceptability. With regard to pH fermentation kinetics, the fermentation rate of the three optimized formulations (F2,F3 & F4) was faster as compared to the control (F1) that the pH of the optimized formulations reached at a pH value of (3.901-3.906) within (22-26)hrs of fermentation while the control F1 reached at a pH value of 3.903 after 72 hours of fermentation; thus, by limiting the fermentation time of the optimized formulations from 72 hours to one & half days it could be possible to score comparable sensory acceptability responses with that of the control. Therefore, it was found out that F2 is preferable and healthy formulation especially for people whose life style is sedentary and not energy demanding while F3 and F4 are the preferred formulations for people who demand energy in any case. Key words: Formulation optimization;, design expert; pH fermentation kinetics; composite flour blen;, Injera.
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    Study on Aspergillus species and Aflatoxin Levels in Sorghum (sorghum bicolor L.) stored at different period and storage system in Kewet Districts, Northern Shewa, Ethiopia.
    (2015-06) Tassew, Geremew; Bekele, Tilahun (Assistant professor); Zewedu, Ashagrie(Assistant professor)
    Sorghum serves as staple food for over 100 million people in Sub-Saharan African countries. It is the most important nutritional security crop and ranks third among major cereal crops in terms of area and production next to teff and maize in Ethiopia. However, sorghum is susceptible to contamination by fungal species mainly Aspergillui flavus and Aspergillui parasiticus species producing mycotoxins, aflatoxins that have hepatotoxic and carcinogenic effects on humans and animal. Study was conducted to assess Aspergillus species and aflatoxin levels in sorghum (sorghum bicolor L.) stored at different period and storage system. Thirty Samples were analyzed for aflatoxins contamination using HPLC with fluorescent detection and Aspergillus species were isolated and identified using culture media. About 56.7%, 16.7%, and 23.3% of the sorghum samples were found to be contaminated with Aspergillus flavus, Aspergillus niger and Aspergillus parasiticus, respectively. Total aflatoxin and AFB1 contamination occurred in sorghum with a maximum concentration range of 11.44 to 344.26μg/kg and 3.95 to 153.72μg/kg, respectively. The levels of Aflatoxins detected in sorghum were within the range of 1.17 to 91.82μg/kg for AFB2, 3.22 to 52.02μg/kg for AFG2 and 9.87 to 139.64μg/kg for AFG1. Sorghum stored for ≥ 2 years had high level of the aflatoxin B1 (52.19 μg/kg) followed by sorghum stored for < 12 months (38.24 μg/kg). Although storage period had resulted in no significant difference in AFB2, AFG1, and AFG2 concentrations, AFB1 varied significantly (P<0.05). On the other hand, the concentration of aflatoxins in all sorghum samples surpassed the maximum level set by the European commission, 10μg/kg for total aflatoxin and 5μg/kg for aflatoxin B1.Therefore, this situation clearly demands wider national or international programs for the control of aflatoxin contamination in sorghum. In conclusion, creating unfavorable conditions for fungal growth with storage system and use of proper storage methods may help in minimizing aflatoxin contamination. Keywords: Sorghum; Aflatoxin; Aspergillus spp., Storage
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    Study on Level of Aflatoxin in Dairy Cattle Feeds and Assess Knowledge, Attitued And Practice of Feed Producers, Dairy Farmers and Feed Treaders Around Addis Ababa, Ethiopia.
    (Addis Ababa University, 2017-01) Fikere, Mulugeta; Getu, Emana (Professor); Bekele, Tilahun (Assistant professor)
    Aflatoxins are naturally occurring toxic metabolites of Aspergillus flavus and Aspergillus parasiticus fungi. The aim of this study was to assess the level of aflatoxins G2, G1, B2 and B1 in dairy cattle feed around Addis Ababa. For this purpose twelve nug cake, twelve wheat bran and six atela samples were randomly collected from Debrezeyt, Sululta and Debrebrhan for aflatoxin analysis by using high performance liquid chromatography with Immunoaffinity column clean up. The result indicated that, from the total 12 samples 7(58.3 %) of nug cake were contaminated with all aflatoxins for G2 from 16.396 to 83.173 ng/g , for G1: from 128.235 to 981.122ng/g, for B2: from 18.089 to 944.271ng/g , for B1: from 149 to 887ng/g and total aflatoxin from 450 to 2320.53ng/g. The mean level of aflatoxin G2, G1, B2, B1 and total aflatoxin level in nug cake samples were 34.58ng/g, 334.15ng/g, 223.89ng/g, 347.9ng/g and 691.08ng/g respectively. In 3( 25 % ) of wheat bran samples only G1,B2 and B1were detected with the range of G1: from 0 to 24.229ng/gm for B2: from 0 to 22.435ng/g , for B1: from 0 to 35.318 ng/g and total aflatoxin from 0 to 61.947ng/g . The mean level of aflatoxin G1, B2, B1 and total aflatoxin level in wheat bran were 18.768ng/g, 18.52ng/g, 21.55ng/g and 59.0572ng/g respectively. Level of aflatoxin in atela samples about 3(50%) of the samples were investigated below the limit of quantification and one sample was below the limit of detection while, in two samples were not detected. The mean level of aflatoxin G2, G1, B2, B1 and total aflatoxin in nug cake were exceeded the maximum limit set by food and agriculture organization(FAO)/world health organization (WHO) 20μg/kg and European Union (EU) 5μg/kg for dairy cattle feed. In wheat bran only B1and total aflatoxins were exceed the limit of food and drug authority and food and agriculture organization(FAO)/world health organization(WHO)20μg/kg and the level of G2, G1, B2, B1 were exceed the limit of European Union(EU) 5μg/kg. Aflatoxin contamination in all atela samples were below the limit. The result of knowledge, attitude and practice assessment in this study revealed that, awareness of mold growth and formation of mycotoxin is very low among dairy farmers and feed traders. From the experiment it can be concluded that nug cake feed was highly contaminated with all aflatoxins and wheat bran was less contaminated. Implying that feeding atela to dairy cattle is the safest, while nug cake is the most dangerous in terms aflatoxin contamination. Key words: Aflatoxin G2; G1; B2,;B1;Total aflatoxin, Diary feeds; Immunoaffinity cleanup.