Browsing by Author "Solomon Abebaw"

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    Urban Vegetable Farmers’ Awareness on the Health Impacts of the Utilization of River Water for Vegetable Production and Environmental Protection Practices in Nefas Silk Lafto Subcity, Addis Ababa
    (Addis Ababa University, 2024-10) Solomon Abebaw; Aseffa Seyoum (PhD)
    The exponential growth of urban population size worldwide created a demand for sustainable solutions to address urban challenges such as food security, environmental pollution, and resource management. Urban river pollution poses significant health risks to vegetable farming. The contamination of rivers with pollutants from various sources negatively affects the quality and safety of vegetables leading to potential health hazards for both farmers and consumers. This particular study investigates the awareness level of urban vegetable farmers in Nefas Silk Lafto sub-city, Addis Ababa, regarding the health impacts of using polluted river water for irrigation and their implementation of environmental protection strategies. The study employed a survey research design. For data collection, structured questionnaires, interviews and field observations were used. In addition, secondary data sources such as books, articles, and legal documents were also reviewed. The data was analyzed using descriptive statistics. The study found critical gaps in urban vegetable farmers' awareness and mitigation of health risks from polluted river water irrigation. While 62% acknowledged the water was polluted, only 13.1% knew the specific risks. Most farmers (86.9%) had not noticed negative impacts on production, and none were employing risk mitigation measures, due to lack of access to alternative water and financial constraints. Though 77.4% knew of relevant regulations, only 60.6% believed there were sufficient government policies to address urban river pollution impacts. Paradoxically, the farmers expressed belief in existing policy guidelines, yet failed to implement sustainable environmental protection strategies. The researcher observed the river was highly polluted, but farmers continued to use it without treatment. The study found a significant knowledge gap among urban vegetable farmers regarding the health risks of using polluted water for irrigation, with the majority lacking awareness of these potential hazards. Farmers did not implement any mitigation measures, despite most not observing negative impacts on crop quality or yields. While many farmers were aware of environmental regulations, they did not effectively adopt sustainable practices due to barriers like limited access to alternative water sources and financial constraints. The recommendations call for improving farmer training and awareness, facilitating stakeholder collaboration, and providing support to enable the adoption of environmentally-friendly irrigation and water management approaches.
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    Valorization of Low-Valued Ray-Finned Fish (Labeobarbus nedgia) Through Enzymatic and Sub-Critical Water Hydrolysis: Green Advanced Processing Technologies to Obtain Protein Hydrolysates for Use as Functional Foods
    (Addis Ababa University, 2025-01) Solomon Abebaw; Shimelis Admassu (Prof.)
    The global demand for sustainable utilization of fish resources, including low-valued and discarded species, has increased due to environmental concerns. Fisheries worldwide face challenges with by-catch, resulting in significant discards of non-commercial species annually. In African contexts like Ethiopia, by-catch management differs, contributing to environmental pollution. While the inefficient resource utilization and environmental impact from discarded fish are significant concerns, another critical issue facing society is the recent global increase in noncommunicable diseases. This growing health crisis underscores the need for foods with health benefits, which can play a crucial role in preventing and managing these conditions. Labeobarbus (LB) spp., non-commercial fish and discarded due to the presence of small bones that are difficult for consumption, possess unused nutritional and functional potential. Therefore, this research aimed to valorize the low-valued LB by employing integrated concept of valorization, advanced processing technologies and green chemistry, thereby reducing waste and enhancing resource efficiency in fisheries management, as well as enabling the production of health beneficial ingredients. In the first finding of this research, the potential of enzymatic hydrolysis for producing protein hydrolysates from LB muscle was studied. Primary, three commercial enzymes, namely Alcalase®, Novozym®, and Protease®, were tested for their potential to hydrolyze the muscle protein of LB at a temperature of 60 oC, pH 8, 10 % (w/v) of substrate loading, and enzyme to LB ratio of 2 % (v/w). The highest hydrolysis degree (DH) was found for protein hydrolysate prepared using Alcalase® (18.4 %) followed by Novozym® (17.2 %) and Protease (15.3 %). Based on this result, Alcalase® and Novozym® were selected to study the effects of enzyme to LB ratio (0 - 3 %, v/w) and hydrolysis temperature (50 – 70 ºC) on free amino acid content, antioxidant capacity and physicochemical characteristics of hydrolysates. The maximum DH (21.8 %) was achieved after hydrolysis of LB for 4 h using Alcalase® at an enzyme-to-LB ratio of 3 % (v/w) and temperature of 60 oC that also corresponded with the highest total free amino acid content (TFAA), antioxidant activity. The kinetic data exhibited a strong fit with the three-parameter Weibull model. The other advanced processing technology investigated as a potential green hydrolysis method for the valorization of LB was subcritical water hydrolysis (SCW) method. Protein hydrolysates were prepared using CO2 and N2 as pressurization agents at different temperatures (140 - 200 °C). The DH and TFAA content of LB muscle protein hydrolysates increased with increasing temperature for both pressurizing agents. Using CO2 as a pressurizing agent at 200 °C resulted in the highest DH (54.5 ± 0.4%) and TFAA content (210 ± 1 mg/gprot). Likewise, the properties of LB skin hydrolysates were significantly influenced by the hydrolysis temperature. The trend of the hydrolysis kinetics of LB skin hydrolysates were similar with the muscle hydrolysates, but the DH of the skin hydrolysates at the final hydrolysis time were significantly lower than the muscle hydrolysates at each hydrolysis temperature studied. The highest DH, 35.7 ± 1.3%, of LB skin hydrolysate was observed at 200 °C. Predominantly, glycine was released in protein hydrolysates from both protein sources (muscle and skin). The antioxidant activity of both muscle and skin hydrolysates, assessed through three different assays, increased with temperature and reached its peak at 200 °C for LB muscle. At the end, four different hydrolysates prepared from the muscle and skin of LB using both hydrolysis technologies at their optimum conditions were subjected to a comparative study on their physicochemical and functional characteristics, as well as antioxidant stability. Accordingly, SCW hydrolysis resulted in significantly higher DH, hydrolysis yield, antioxidant capacity, and free amino acid content than enzymatic hydrolysates. However, enzymatic hydrolysates generally exhibited better functional properties than SCW hydrolysates. Additionally, muscle hydrolysates showed superior physicochemical, antioxidant, and functional properties compared to skin hydrolysates. Furthermore, various food processing conditions, salt, metal ions, and simulated gastrointestinal (GI) digestion significantly impacted the antioxidant stability of the hydrolysates. Generally, enzymatic hydrolysates presented better antioxidant stability than SCW hydrolysates. This research demonstrated the effectiveness of enzymatic and sub-critical water hydrolysis as green and sustainable technologies for valorizing low-valued Labeobarbus fish into high-value protein hydrolysates. These hydrolysates exhibited good physicochemical, functional, and bioactive properties, making them suitable for use as functional food ingredients. SCW hydrolysis, with CO2 as a pressurization agent, exhibited to be a good alternative to the expensive enzymatic methods, producing hydrolysates with higher antioxidant activity, free amino acid profiles, and improved physicochemical qualities. However, additional research is needed to enhance the antioxidant stability of SCW-derived hydrolysates and to explore their applications in functional foods, assessing their performance and stability under real-world conditions