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Yonas G.A.,Bahir Dar University | Shimelis E.A.,Addis Ababa Institute of Technology | Sisay A.F.,Ethiopian Environment and Forest Research Institute
LWT - Food Science and Technology | Year: 2016

The objective of this work was to evaluate the effect of processing factors on butter yield and mineral concentration of Shea butter (Vitellaria paradoxa) subspecies nilotica extracted using screw expeller. The significant effect of conditioning duration (CD), kernel moisture content (MC) and die temperature (DT) were investigated by a 33 full factorial design combined with response surface methodology. Butter yield, fines particles (foot), Ca and Zn concentration were selected as response variables. The model enabled to identify the optimum operating settings (MC = 6.5 g/100 g w.b and DT = 65.5 °C) for maximize butter yield, under which it predicted 42.05 g/100 g d.w. While considering other response, in allover optimization, CD of 30 min, MC of 9 g/100 g w.b and DT of 65 °C were obtained. © 2015 Elsevier Ltd.


Gezahegn Y.A.,Bahir Dar University | Emire S.A.,Addis Ababa Institute of Technology | Asfaw S.F.,Ethiopian Environment and Forest Research Institute
Food Science and Nutrition | Year: 2016

The quality of Shea butter is highly affected by processing factors. Hence, the aim of this work was to evaluate the effects of conditioning duration (CD), moisture content (MC), and die temperature (DT) of screw expeller on Shea butter quality. A combination of 33 full factorial design and response surface methodology was used for this investigation. Response variables were refractive index, acid value, and peroxide value. The model enabled to identify the optimum operating settings (CD = 28–30 min, MC = 3–5 g/100 g, and DT = 65–70°C) for maximize refractive index and minimum acid value. For minimum peroxide value 0 min CD, 10 g/100 g MC, and 30°C were discovered. In all-over optimization, optimal values of 30 min CD, 9.7 g/100 g MC, and 70°C DT were found. Hence, the processing factors must be at their optimal values to achieve high butter quality and consistence. © 2016 The Authors. Food Science & Nutrition published by Wiley Periodicals, Inc.


Dedefo K.,Arsi University | Derero A.,Ethiopian Environment and Forest Research Institute | Tesfaye Y.,Hawassa University | Muriuki J.,International Center for Research in Agroforestry
Forests Trees and Livelihoods | Year: 2016

Most tree nurseries in Ethiopia overemphasize mass seedling production to the expense of seedling quality. The study aimed at evaluating nursery characteristics and tree seed procurement approaches, and how these influenced seedling quality in eight purposively selected Woredas of Oromia region. A total of 169 respondents from government and non-government organizations, farmer nursery owners and development/extension agents and officers were interviewed. Seed quality was explored through assessing the seed supply sources, the type of seed source and mother tree selection, and the practices in seed physiological quality assessments. Our results revealed that over half (62.5%) of the nurseries were government owned, while 20% were NGO-run nurseries and the remaining 17.5% were owned by farmers. Nine challenges constraining tree seedling production and leading to underperformance were identified, with the two major problems shared by all nursery types being lack of sufficient material and germplasm input and using seeds of low or unknown quality. Informal seed dealers were the main source of seeds (87.6%) for all the nursery types. On the other hand, nursery operator’s own seed collection was from any free-standing trees either planted or retained as these sources were easily accessible. Seeds were, on average, collected from few mother trees, implying a high probability of sourcing seeds of narrow genetic diversity. Analysis of variance revealed statistically significant differences in seedling germination among the different seed procurement approaches within the same seed type. The seeds obtained from formal seed dealers had the highest germination rates in both hard-coated (87.3%) and soft-coated (79.7%) seeds. Our findings suggest that there is need to improve the seed procurement and the seedling supply system through quality assurance of the seeds used in seedling production. © 2016 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group


Iiyama M.,International Center for Research in Agroforestry | Iiyama M.,Japan International Research Center For Agricultural science | Derero A.,Ethiopian Environment and Forest Research Institute | Kelemu K.,Ethiopian Institute of Agricultural Research | And 8 more authors.
Agroforestry Systems | Year: 2016

Trees on farms are a widespread feature of landscapes across a large part of Ethiopia with an important role in enhancing the resilience of smallholder livelihoods through the provision of ecosystem services. Despite their importance, little is known about what trees are planted or retained from natural regeneration by different types of farmers that results in the pattern of tree cover found in the region. We address this knowledge gap through analysis of household survey data from semi-arid and sub humid areas of Oromia regional state. A set of composite variables that represent distinctive patterns of tree cover on farms were derived from principal component analysis and Pearson correlation analysis. This revealed two major tree adoption strategies: farmer managed natural regeneration (FMNR) of trees to meet subsistence needs as well as contributing to other ecosystem services; and, high value agroforestry (HVAF) involving planted trees used largely to produce fruits, timber and fodder. Regression analysis further identified fine-scale variation in ecological and socio-economic factors that affect which of these two broad strategies are adopted by farmers. Favorable climatic conditions coupled with institutional arrangements to control free grazing were pre-conditions for HVAF, whereas poor biophysical potential and sloping land provided a positive incentive for farmers to adopt FMNR. Farmers with preferences for tree species with multiple utilities and locational flexibility favored FMNR while adoption of HVAF was more asset-driven. Our findings reveal that farmers integrate many native and exotic tree species on their farms to meet their variable farm conditions, needs and asset profiles in stark contrast to most tree promotion efforts that focus on a few, usually exotic, tree species. We recommend that future agroforestry promotion should embrace a diversity of tree species appropriate to matching the fine scale variation in ecological conditions and farmer circumstances encountered in the field. © 2016 The Author(s)


Yilma Z.,Ethiopian Environment and Forest Research Institute | Worku A.,Ethiopian Environment and Forest Research Institute | Worku A.,TU Dresden | Mohammed O.,Ethiopian Environment and Forest Research Institute | And 6 more authors.
Forests Trees and Livelihoods | Year: 2015

Diversity, population structures and regeneration status of gum- and resin- producing woody species, including associated woody species, were assessed in 157 sample plots, each measuring 400 m2 and established along line transects. The data were collected in two selected districts, namely, Sherkole and Guba in Benishangul-Gumuz National Regional State, one of the gum and resin belts in western Ethiopia. Twenty- eight woody species, representing 18 families and 22 genera were recorded, among which six species were sources of commercial gum and resins. The gum- and resin-producing woody species had 1.54 and 0.9 diversity and 0.86 and 0.68 evenness values at Sherkole and Guba districts, respectively. They accounted for 29% and 50% of the density, 53% and 61% of the basal area and 31% and 50% of the Importance Value Index of all the woody species, respectively. The gum- and resin- bearing woody species exhibited three patterns of population structure. The first pattern suggests good reproduction abilities of the species coupled with good recruitment of seedlings and their subsequent continuous growth to replace older individuals over time, indicating stable regeneration. About 57% of the gum- and resin- bearing woody species fall under this category. The other two patterns indicate hampered regeneration status of the woody species. Heavy grazing, conversion to crop land by small- and large-scale farming, resettlement programmes, recurrent fire and climate change were mentioned as major bottlenecks of natural regeneration and recruitment. Policy, extension and research recommendations are discussed. © 2015 Taylor & Francis


Yilma Z.,Ethiopian Environment and Forest Research Institute | Worku A.,Ethiopian Environment and Forest Research Institute | Worku A.,Technology University | Mohammed O.,Ethiopian Environment and Forest Research Institute | And 6 more authors.
Forests Trees and Livelihoods | Year: 2016

Diversity, population structures and regeneration status of gum-and resin-producing woody species, including associated woody species, were assessed in 157 sample plots, each measuring 400 m2 and established along line transects. The data were collected in two selected districts, namely, Sherkole and Guba in Benishangul-Gumuz National Regional State, one of the gum and resin belts in western Ethiopia. Twenty-eight woody species, representing 18 families and 22 genera were recorded, among which six species were sources of commercial gum and resins. The gum-and resin-producing woody species had 1.54 and 0.9 diversity and 0.86 and 0.68 evenness values at Sherkole and Guba districts, respectively. They accounted for 29% and 50% of the density, 53% and 61% of the basal area and 31% and 50% of the Importance Value Index of all the woody species, respectively. The gum-and resin-bearing woody species exhibited three patterns of population structure. The first pattern suggests good reproduction abilities of the species coupled with good recruitment of seedlings and their subsequent continuous growth to replace older individuals over time, indicating stable regeneration. About 57% of the gum-and resin-bearing woody species fall under this category. The other two patterns indicate hampered regeneration status of the woody species. Heavy grazing, conversion to crop land by small-and large-scale farming, resettlement programmes, recurrent fire and climate change were mentioned as major bottlenecks of natural regeneration and recruitment. Policy, extension and research recommendations are discussed. © 2015 Taylor and Francis.

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