School of Food Technology, Nutrition and Bioengineering (SFTNB) Collections

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    Evaluating nutrient dynamics, energy utilization, and performance of aquaponics systems for smallholder farmers' sustainability
    (Makerere University, 2025) Ssemuyaba, Henry Beliga
    Aquaponics is promoted as a climate-smart food production system, yet little empirical evidence exists on its resource use efficiency, nutrient dynamics, and productivity under East African conditions, limiting adoption by smallholder farmers. This study, conducted at the Aquaculture Research and Development Centre, Kajjansi, evaluated the effectiveness of aquaponics systems in utilizing resources (nutrient, water, energy). The experiment evaluated the aquaponics systems using one factor – fish type (African catfish (Clarias gariepinus) and Nile tilapia (Oreochromis niloticus)) as nutrient source (treatments) for lettuce (Lactuca sativa) in deep-water culture (for four seasons/growth cycles) and tomatoes (Solanum lycopersicum) in media-filled beds (for one season). Each treatment replicated three times contained fish tanks, filters (mechanical, biological), and plant zones (media-filled bed, deep-water culture) which formed the aquaponics zones. The quality of water from fish tanks was monitored onsite using a seneye device to measure DO, pH, NH₃ and NH₄⁺ while nitrogen (N), phosphorous (P), and potassium (K) nutrients were analyzed in the laboratory at Makerere University. Fish were fed on the same feed, and the quantity was determined using the body weight of fish. The fish’s response was monitored for over 250 days. To determine a system adoptable to a smallholder farmer, photovoltaic (PV) system sizing using PVsyst software was carried out accompanied by a financial evaluation that assessed feasibility of an off-grid solar-powered aquaponics system. Results show that the quality of water from tanks of both African catfish and Nile tilapia remained optimal, though varied significantly in DO, pH, and NH₃ by season and aquaponics zones while NH₄⁺ varied by only season (p ≤ 0.05). Nutrient analysis showed N was significantly different by treatment and zone, P by treatment only, and K by treatment and season (p ≤ 0.05). African catfish systems produced higher N (48.5 mg/L) than Nile tilapia (30.5 mg/L), while Nile tilapia systems yielded greater P (99.3 mg/L) and K (291.2 mg/L) concentrations, indicating species-specific influences on nutrient dynamics in aquaponics. Lettuce yield was significantly different among the four growth cycles, while tomatoes significantly varied across treatments i.e., African catfish and Nile tilapia (p ≤ 0.05). Nile tilapia systems produced better yields than African catfish systems. PV sizing indicated that a 2.4 kWp solar system meets 95% of aquaponics power needs at 70% performance ratio. Furthermore, the financial evaluation showed that the sized system is able to pay back its investment in less than four years with an annual return on investment of ~22%. Therefore, focus should be on Nile tilapia aquaponics for a higher productivity and African catfish aquaponics for diversity.
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    Chemical components of Malakwang (Hibiscus species) leaves and how they are influenced by processing
    (Makerere University, 2026) Ojera, Gertrude Miriam Alal Ato
    Objectives: This study evaluated the nutritional and phytochemical composition and health claims associated with the red and white Malakwang (Hibiscus species) and how these could be affected by different processing methods. Methodology: The study employed laboratory experimental and longitudinal laboratory experimental. The study was done in Kampala, Gulu, and Kitgum Districts. The results are presented as means with standard error of the mean and tested using Scheffe and Student-Newman-Kuels tests for multiple comparisons. Results: The fresh red Malakwang leaves contained higher (p<0.05) quantities of calcium (1753.6 mg), magnesium (1814.4 mg), iron (233.4 mg), vitamin A (RE) (952.7 µg) and vitamin E (22.8 µg) per 100 g when compared to the 1522.2 mg, 1297.9 mg, 179.7 mg, 857.6 µg, and 16.8 µg, for the white respectively. Flavonoids (25.7 %), and alkaloids (5.5%), were higher in the fresh white than the red leaf variety (20.5 % and 2.1 % respectively. The antioxidant percentages of the red (52.7 %) and white (61.3 %) leaf extracts compared favourably with that of ascorbic acid (62.2 %). The biochemical analysis, in Wistar rats fed on the high-fat diet and Malakwang leaf extract, showed a decrease in weight gained up to the fourth week of feeding trial. Acute toxicity calculated based on LD50 values for the white and the red samples were 10,069 and 7224 mg/kg respectively. Cleaning and all cooking procedures led to loss (p<0.05) of crude fat in the white only, B1, B2, B6, B9, and E. by 97-100%.in both red and white. Discarding the cooking liquid lowered (p<0.05) sugar contents to 8.2 and 8.2 mg/100g in the red and white leaf types, respectively. No substantial effect was exhibited in sugar, dietary fibre and protein contents by all drying techniques. All the drying techniques diminished (p<0.05) vitamins C, B1, 2, 6, 9 and tocopherol. Conclusion: Based on the findings, the nutritional composition of the red and white Malakwang leaves were significantly different with respect to crude fat, magnesium, iron, vitamin A (RE) and ascorbic acid. Malakwang leaves can significantly contribute to micronutrient and bioactive components intake in the communities where they are consumed. The phytochemicals compositions were significantly different only in alkaloids and flavonoids. The antioxidant potential of the red and the white leaves were the same and comparable to that of vitamin C. The cooking procedures and the drying techniques were more destructive to vitamin B-complex and E. Cooking for 10 minutes conserved vitamin C better than cooking for 60 minutes. Oven drying at 60ºC retained less moisture. A noticeable potential value of the extracts was demonstrated in regulating low-density lipoprotein cholesterol and urea in the Wistar rats. The two leaf varieties have low toxic levels but the white leaf extract appeared to have a lower toxic level than the red one.
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    Yield, Pesticide Residues and Bioactive Compounds in Flowers of Ugandan-Grown Arabica and Robusta Coffee
    (Makerere University, 2025) Ajiambo, Diana Rose
    Coffee flowers are byproducts of coffee cultivation that are gaining interest due to their various potential applications. However, little information existed on their safety and composition of bioactive compounds. This study evaluated the coffee flower yield per plant and pesticide application practices of coffee farmers (n=100) in Bulambuli (Arabica coffee) and Luwero (Robusta coffee) districts, Uganda. A cross sectional survey employing questionnaires was used to collect information from respondents. Samples of coffee flowers were then picked from selected farmers for laboratory analysis. Analysis for pesticide residues and bioactive compounds was done by a Gas Chromatography Mass Spectrometry (GCMS) and data were analysed using SPSS. It also studied pesticide residues in fresh Arabica and Robusta coffee flowers. Bioactive compounds were studied in fresh, air-dried and oven-dried Arabica and Robusta coffee flowers. The average coffee flower yield per tree was 350g. Pesticide application mainly targeted the entire coffee plant. The use of synthetic pesticides was more in Arabica coffee. Residues from the pesticides used were mevinphos, phorate, fonofos, parathion-methyl, parathion, triazophos, anthraquinone, allethrin-1, 2, resmethrin-1, phenothrin-1, deltamethrin-1, and piperonyl butoxide. Pesticide residue levels in the flowers varied significantly (p<0.05) with maturity stage, and coffee variety. Robusta coffee flowers had the highest level of anthraquinone (301.7±86.7μg/L) while Arabica coffee flowers had the highest level of mevinphos (137.4±56.5μg/L). Overall, Arabica coffee flowers of 6-10 years old retained more pesticide residues. The level of bioactive compounds varied significantly (p<0.05) with maturity stage, drying method, and coffee variety. The predominant bioactive compounds in Robusta coffee flowers were caffeine (689.3±104.1mg/100g), squalene (93.7±21.1mg/100g), and pentadecanoic acid (41.8±33.5mg/100g). In Arabica flowers, they were caffeine (346.1±150.0mg/100g), and n- hexadecanoic acid (142.4±34.3mg/100g). Retention of bioactive compounds was in the order; fresh, air-dried and oven-dried coffee flowers. Most coffee plants had a flower yield of 1 to 500g per plant in both Arabica and Robusta coffee plants. Bioactive compounds were higher in oven- dried Robusta and air-dried Arabica coffee flowers with maturity affecting their levels. Generally, pesticide usage was rampant indicating the need to educate coffee farmers on correct pesticide application.
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    Test title2 8th Jan 2026
    ( 2026) Mwesigwa, Test2
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    Efficacy of hibiscus sabdariffa (malakwang) leaves in increasing milk production in lactating albino rats
    (Makerere University, 2025) Ayo, Margaret
    Hibiscus sabdariffa (Malakwang) is a leafy vegetable that is rich in nutrients and has been used traditionally in the Luo communities in Northern Uganda to increase breast milk production. Despite the widespread use as a galactagogue, there is no scientific evidence confirming its lactogenic effects, hence the need for scientific investigation. This study investigated the lactogenic properties of Hibiscus sabdariffa leaves. Focus group discussions were used to collect data on the indigenous knowledge and the utilization of Hibiscus sabdariffa as a lactogenic. The data was thematically analyzed using an inductive approach, allowing themes to arise from the participants discussion. Preliminary phytochemical screening of the hydro ethanolic–methanolic extract of dried Malakwang leaves was conducted using standard biochemical tests to identify compounds linked to lactation. A randomized controlled trial method was used to assess the effect of Malakwang leaves on milk production in lactating albino rats. Majority of the participants (99%) reported that after using Malakwang, they observed an increase in breast milk production, however its potential side effects, when consumed by people with ulcers and its scarcity during the dry seasons were of concern. Preliminary photochemical screening revealed alkaloids, saponins, flavonoids and tannins in the Malakwang leaves. Flavonoids and tannins were relatively abundant in Hibiscus sabdariffa leaves. The total milk yield in groups treated with the Malakwang leaf extract was significantly high at doses of 250 mg/kg and 500 mg/kg compared to the group treated with metoclopramide and distilled water (p>0.005) with the 500mg/kg dose showing a greater effect. The pups of dams that received the Malakwang leaf extract exhibited significant weight gain compared to the control groups. Malakwang leaf extract did not significantly impact prolactin. Malakwang leaves revealed lactogenic activity by increasing milk yield, weight gain of pups and presence of lactogenic phytochemicals though the effect on prolactin was insignificant.