College of Agriculture & Natural Resources (COANRE)

Heavy Metals and Pathogen Content on Soil, Water and Produce in Urban Agriculture of Nairobi City

2026-08-31T13:27:36Z

Heavy Metals and Pathogen Content on Soil, Water and Produce in Urban Agriculture of Nairobi City Njenga, John Ng’ang’a Urban and peri-urban agriculture in Nairobi City County (NCC) is growing as a means of income generation, employment, nutrition and food security. However, environmental health risks outweigh urban agriculture practices in the city, as evident from widespread pollutant sources such as garbage dump site heaps, burst raw sewage pipes, contaminated wetlands, industrial effluent, and motor vehicle exhaust. Consumers are increasingly aware of the importance of buying safe food, and therefore urban agriculture practitioners must be informed on the safety status of their produce in order to adjust to good agricultural practices and take full advantage of the easily accessible consumer food market. The objectives of this research were to assess heavy metal incidence in inputs and food crops for urban farms in eastern zone of Nairobi, determine microbial incidences in food crop produce from farms, determine differences in element uptake by the crops, and to examine influence of environmental quality of the surrounding spaces on crop produce safety. A purposive sampling of farmers who grew any of the three target crops namely arrowroot (Colocasia esculenta L.), kale (Brassica olerasii var.Acephala L.) and tomatoes (Lycopersicon esculentum Mill.) was conducted of which ninety five farmers were identified. To focus on the critical regions of the city and with the guidance of Sub-County Agricultural Officers, three sub-counties of Starehe, Kamukunji and Kasarani, in the Eastern part of Nairobi City County were selected. Farm plots that met the criteria for the three target crops were identified (Starehe 4, Kamukunji 7 and Kasarani 4). From each of the 15 farm plots, samples of tomatoes, arrowroots, kales, water and soil were obtained with three replications per farm, following standard procedures for sample collection. Farmer’s immediate environment (neighbourhoods) were classified according to three pollution levels low, moderate, and high that were classified based on source and type of inputs and the condition of the environment surrounding the farm plot. Contents of cadmium, manganese, zinc and lead were analysed using Atomic Absorption/Flame Emission Spectrophotometer. Microbial analysis on irrigation water and the three produce was done to test for presence of salmonella, shigella and Escherichia coli bacteria. One way ANOVA was applied (i) to examine differences in means of heavy metals between locations and to compare transfer factor (TF) index of the crops and (ii) to examine differences on occurrence of the pathogenic microbes. Elements that were above allowable limits in the crops were Cd, Mn, Pb and Zn in arrowroots; Cd and Mn in kales and Cd, Mn and Pb in tomatoes. Cadmium content was highest in farm plots within Kasarani (2.44±0.86 mk/kg) and was significantly different from other two locations (p<0.05, Tukey HSD test). Between the neighbourhood qualities, heavy metal contents were different but not significant (p>0.05) between classes. The mean TF index for the heavy metals decreased in the order Cd>Pb>Zn>Mn. A transfer factor index of > 1 for cadmium was recorded in arrowroots, kales, and tomatoes. Overall, the highest mean of E.coli bacteria count was recorded in arrowroots at the Kamukunji sub-county (P=0.002). Between neighbourhoods, E.coli was significantly higher in irrigation water and arrowroots in the low-quality neighbourhoods (p<0.05). Kamukunji had the highest occurrence of Salmonella in irrigation water and arrowroots at 40%. There was no significant difference between neighbourhood classes in the prevalence pattern of Salmonella. The sub-county also had the highest prevalence of Shigella in irrigation water, at 20%. The overall mean rate of occurrence of Shigella was highest in irrigation water and in kales, at a rate of 17% in both cases. Compared to the other sub-counties, Kasarani had a much higher prevalence of Shigella in tomatoes with a significant difference in distribution pattern (p=0.001). Based on FAO/WHO standards, the measured heavy metal contents were high enough to cause health risk concerns. Produce from areas designated as of low environmental quality was not necessarily contaminated, as perceived. Urban agriculture producers in Nairobi need technical risk reduction technologies and legislative support to guarantee quality produce and valuable participation in the urban food system framework. It is recommended that future studies diversify crop types and localities and enhance collaboration between stakeholders. MSc in Horticulture

Physicochemical, Nutritional and Functional Properties of Popped Finger Millet (Eleusine coracana) and its Application in Product Development

2026-08-06T08:15:49Z

Physicochemical, Nutritional and Functional Properties of Popped Finger Millet (Eleusine coracana) and its Application in Product Development Koros, Clarice Jepchirchir Finger millet (Eleusine coracana) is a highly nutritious grain with significant health benefits; however, its traditional processing methods have not been fully optimized for modern applications to enhance commercialization. This study evaluated the physicochemical, nutritional, and functional properties of popped finger millet and its application in cereal bar development. Finger millet grains were sourced from Jamhuri Market in Thika Town. The grains were sorted, cleaned, and dried, with an initial moisture content of 10.01%. The moisture content was subsequently adjusted to 15%, 18%, and 21% (in triplicates) and popped at chamber pressures of 120, 140, and 160 psi. The popped grains were analyzed for selected physicochemical, nutritional, functional, and microstructural properties. Grains popped at 21% moisture content and 160 psi were used to formulate five cereal bar variants with varying concentrations of guar gum and honey, which were then subjected to sensory, physicochemical, and microbiological analyses. Results indicated that increasing moisture content and pressure significantly (p≤0.05) enhanced popping yield and expansion ratio while reducing bulk density. The interaction between pressure and moisture content also had a significant (p≤0.05) effect on these parameters. Increasing moisture content from 15% to 21% significantly (p≤0.05) increased lightness and total color difference, while redness and browning index decreased significantly with increasing moisture content and pressure. Crude fat and moisture content of the popped grains decreased significantly (p≤0.05) with increasing pressure and moisture, whereas crude protein content increased significantly with pressure. Mineral analysis showed significant (p≤0.05) increases in zinc and iron content with increasing pressure and moisture levels. Total phenolic content also increased significantly, while phytates and tannins decreased significantly (p≤0.05), indicating improved nutritional quality. Functional properties were significantly influenced by processing conditions, with water absorption capacity, swelling power, and viscosities increasing, while bulk density decreased when popping pressure and moisture content were raised. Particle size distribution was also significantly affected by pressure, moisture, and their interaction. For the developed cereal bars, color attributes (lightness, redness, yellowness, and hue angle) varied significantly (p≤0.05), with increased lightness and yellowness observed at higher honey levels (10%–50%). Water activity ranged from 0.391 to 0.776 and decreased with increasing honey concentration, remaining within safe microbial limits. Bulk density and texture decreased significantly (p≤0.05) with increasing honey levels, improving handling and packaging characteristics. Proximate composition showed moisture content ranging from 3.47% to 11.35%, crude fiber from 2.31% to 2.70%, crude protein from 7.17% to 8.39%, and carbohydrates from 70.02% to 78.24%, all significantly influenced by formulation. Microbial analysis of the developed cereal bars revealed total viable counts ranging from 2.2007 to 2.7253 log CFU/g, within acceptable limits for ready-to-eat foods. No coliforms were detected, indicating satisfactory hygienic practices. Staphylococcus aureus was detected in two cereal bars, although no immediate health risk was indicated, while yeast and mold counts remained within acceptable limits. Sensory evaluation showed significant differences (p≤0.05) in appearance, flavor, taste, texture, and overall acceptability. Samples B1 and B5 were the most preferred, with overall acceptability scores above 7.0. Honey and guar gum significantly influenced sensory attributes,  xiv with higher honey levels enhancing flavor and consumer acceptance. In conclusion, popping pressure and moisture content significantly affect the nutritional, functional, and physicochemical properties of finger millet and demonstrates strong potential for value addition. The developed cereal bars exhibited acceptable sensory and microbial quality, supporting their potential as nutritious snack products. These findings highlight the role of popped finger millet in enhancing food and nutrition security and promoting the utilization of this underutilized indigenous crop. MSc in Food Science and Technology

Farmers’ Perceptions, Occurrence and Transmission of Moroccan Watermelon Mosaic Virus Infecting Cucurbits in Selected Counties in Kenya

2026-07-30T06:51:15Z

Farmers’ Perceptions, Occurrence and Transmission of Moroccan Watermelon Mosaic Virus Infecting Cucurbits in Selected Counties in Kenya Wutue, Abenigo Sieh Cucurbits are important food crops worldwide due to their nutritional benefits and also contribution to the national economies. In Kenya, cucurbits are mainly produced by small scale farmers for their leaves, immature and mature fruits and seeds. However, the production in the country is constrained by viral disease infections including Moroccan watermelon mosaic virus (MWMV), a potyvirus in the family potyviridae. The virus is transmitted by several species of aphids in a non-persistent manner and also by mechanical means.The cucurbit crops can be infected by the virus at every stage of growth, with early infection resulting in total yield loss if no management measures are taken.The virus was recently reported in Kenya in two counties infecting pumpkin (Cucurbita pepo L). Since the virus is known to infect several cucurbit species, determination of farmers perceptions, and distribution of MWMV in the major cucurbits growing counties in the country as well as transmission to different host species are important in the development of effective management strategies. A survey was conducted in the year 2024, covering a total of 229 cucurbit fields in seven sub-counties within three counties namely; Machakos County (Matungulu and Kangundo sub-counties) Kirinyaga County (Kirinyaga East, Kirinyaga West, and Mwea East sub-counties) and Embu County (Embu West and Mbeere North sub-counties). To understand farmers’ knowledge, perception and management strategies of the MWMVdisease, a total of 229 farmers’were randomly identified in seven sub-counties and a semi-structured questionnaire was administered through face to face interviews.The disease severity in the farmers’ fields was determined using a scale of 0 to 4. To determine the disease incidence, ten (10) plants per field were visually inspected for symptoms that are associated with MWMV disease. Moroccan watermelon mosaic virus distribution was determined by testing samples collected from the field using polymerase chain reaction (PCR)-based approach. To determine the influence of host plant species on aphid’s transmission efficiency of the virus, a greenhouse trial was carried out at the Jomo Kenyatta University of Agriculture and Technology (JKUAT). Aphids (Myzus persicae) were obtained from the University farm and maintained on common beans (Phaseolus vulgaris) plants established in the pots and placed in cages in an insect freee screenhouse. Two infected and natural host plants; pumpkin and papaya were used as source of MWMV inoculum for subsequent aphid transmissions. The experiment was laid out in a completely randomized design (CRD) with three treatments replicated (3) times. To transmit the virus, aphids were straved for one hour before feeding on the infected plants for 30 seconds to acquire the virus, The viruliferous aphids were then transferred to the healthy plants and allowed to feed for 40 seconds before spraying them with an insecticide. The plants were observed for MWMV disease symptoms development daily after transmission for a period of six weeks. Data for farmers perceptions were subjected to analysis of variance at p < 0.05 using (SPSS) and correlation analysis was done to determine the relationship between knowledge, perception and management of MWMV. Incidence and severity data was analysed through descriptive statistics, percentages and mean values using (SPSS). Influence of host plant efficiency data was analysed by determining the virus presence based on the amplification of the right size of fragment as observed in the agarose gel electrophoresis. The findings indicate that the farmers were aware of MWMV disease symptoms presence in their farms ranging from deformation, dark green blisters, and mosaic. Majority of the respondents 49.5% perceived the symptoms to be caused by weather changes, while 16.1% associated the symptoms with pest infestation while 11.1% did not know the cause of the symptoms in their farms. As a management measure, majority of the famers 85.5% used chemical control.The highest disease severity of 3.8 was recoded in Matungulu sub-county in Machakos county and the lowest 1.6 in Embu West sub-county in Embu county. Kangundo and Kirinyaga East sub-counties recorded the highest disease incidence of 100% while Kirinyaga West reported the lowest disease incidence of 62.5%. The number of positive samples was 12,8,4,and 3obtained from Matungulu, Embu West, Mwea East, and Mbeere North subcounties respectively. All the samples tested positive were from pumpkin crop species. Moroccan watermelon mosaic virus aphid transmission occurred from pumpkin to watermelon, Zucchini, and butter nut and not in papaya. Conversely, the virus was transmitted by aphids from papaya to zucchini crop species and not in the other cucurbit species. Although the virus was earlier reported in two counties, the presence of the virus to these counties under current study indicates that the virus is present in other counties and could probably spread to other parts of the country leading to damage cucurbit crops. Further, pumpkin crop species could be playing an important role in the epidemiology of the disease. Limited knowledge and management of MWMVsuggest farmers’ training is necessary for improved disease diagnostics and management. Futher, a detailed survey across the country is recommended to determine the extent of the virus spread. MSc in Plant Health Science and Management

Farmers’ Perceptions, Occurrence and Transmission of Moroccan Watermelon Mosaic Virus Infecting Cucurbits in Selected Counties in Kenya

2026-07-22T07:34:10Z