College of Agriculture & Natural Resources (COANRE)

Nutrient Composition of Two Cricket Species (Scapsipedus icipe and Gryllus bimaculatus), and Effect of Extrusion Process Optimization on Nutritional, Functional and Sensory Properties of Maize-Cricket Porridge Flour

2026-05-11T11:01:53Z

Nutrient Composition of Two Cricket Species (Scapsipedus icipe and Gryllus bimaculatus), and Effect of Extrusion Process Optimization on Nutritional, Functional and Sensory Properties of Maize-Cricket Porridge Flour Murugu, Dorothy Kanorio Globally, there is growing interest in integrating cricket flour into plant-based foods to combat nutritional insecurity. However, data on the nutrient profiles of Scapsipedus icipe and Gryllus bimaculatus—the most widely consumed cricket species in Kenya— remains limited. Incorporating crickets into food matrices and using extrusion may impact the nutritional and functional properties of the formulated products. Optimal extrusion parameters for maximizing nutrient yield from various cricket species remain undefined. This study aimed to (i) determine the nutrient and anti-nutrient phytochemical composition of the two cricket species and compare them with published records of key animal and plant sources (ii) develop a nutritionally balanced maize-cricket formulation and evaluate the effect of extrusion on nutrient and functional properties of the formulated product using existing extrusion conditions (iii) determine the sensory attributes of porridges prepared with extruded and non-extruded maize-cricket flour blends and (iv) optimize the extrusion process parameters for attainment of optimal product in extruded maize-cricket porridge flour blends. Standard analytical methods were used to determine the nutrient composition of both cricket species. Maize-cricket blends were formulated using adult cricket powder, maize flour, and sugar. These were optimized using Minitab 20 software to meet the daily protein requirements of children aged 5-12 years. Three formulations containing 10%, 15%, and 20% cricket powder were prepared and processed both by extrusion and non-extrusion methods and samples subjected to nutritional and functional analysis. A semi-trained panel of 46 participants evaluated the sensory attributes of the porridge samples using a 9-point hedonic scale. Response Surface Methodology (RSM) through Box Benhenken design and the extreme vertices model of Mixture Design were employed to optimize extrusion process variables (barrel temperature, screw speed, and feed moisture) and formulation respectively, aiming to produce a porridge with significantly higher nutrient content from blends of S. icipe and G. bimaculatus with standard maize flour. Both cricket species, S. icipe and G. bimaculatus, demonstrated comparable protein content (56.8-56.9%) to animal sources and higher amino acid profiles to plant-based proteins. Their protein digestibility (80-88%) was similar to common plant foods but slightly lower than animal proteins. The cricket species were notably rich in essential minerals like iron, zinc, and potassium, significantly surpassing plant and animal sources. Calcium content was comparable to most sources, except kidney beans and eggs. Both cricket species offered higher levels of riboflavin, thiamine, and folic acid compared to conventional sources. Vitamin A was significantly higher in S. icipe compared to G. bimaculatus. Notable amounts of polyunsaturated fatty acids were found in (S. icipe (24.71%) and G. bimaculatus (19.16%), alongside saturated and monounsaturated fatty acids. Physicochemical properties of oils from both species revealed high similarity across most parameters, including refractive index, specific gravity, peroxide value, and saponification value (P = 0.1047, 0.0774, 0.3581 respectively). However, a highly significant difference was observed in acid values, with S. icipe (2.19 ± 0.36 mg KOH) exhibiting more than double the acidity of G. bimaculatus (1.10 ± 0.01mg KOH; P < 0.001). Additionally, G. bimaculatus demonstrated a slightly higher solidification temperature range (2–7°C) compared to S. icipe (2–5°C). These results suggest that while the primary chemical stability and density of the two lipids are comparable, they differ significantly in their free fatty acid content and thermal xxii behavior. Analysis of anti-nutritional factors in S. icipe and G. bimaculatus revealed significant differences in most phytochemical markers (P < 0.05). G. bimaculatus contained significantly higher levels of phytates (10.33 ± 6.00 mg/100g vs. 3.85 ± 0.44 mg/100g; P = 0.012) and tannins (1.56 ± 1.08 mg/100g), which were not detected in S. icipe (P = 0.003). Conversely, S. icipe exhibited a significantly higher concentration of total polyphenols (65.00 ± 1.79 mg/100g) compared to G. bimaculatus (48.00 ± 4.49 mg/100g; P = 0.021). No significant difference was observed in oxalate concentrations between the two species (P = 0.076). These findings indicate that while G. bimaculatus possesses a more diverse anti-nutritional profile, S. icipe is richer in total polyphenolic content. Extruded porridge flours incorporating cricket powder were significantly more desirable in terms of appearance (P = 0.003), texture (P = 0.001), and mouthfeel (P = 0.028) compared to non-extruded counterparts. Consumer preference was most desirable with the addition of cricket powder at a 10% enrichment level. Taste, texture, and thickness were the most influential sensory attributes with a desirability rate of 21%, 26.6% and 17.2% respectively. The addition of cricket powder at different levels resulted in varying changes in the proximate composition, functional, and pasting properties of the porridge. While some properties like ash, dry matter, and P2 temperature remained unchanged (P = 0.657, P = 0.295, P = 0.851 respectively), protein digestibility increased at the 10% substitution level. Hydration properties improved, and bulk density decreased with increasing cricket powder levels. Extrusion reduced pasting properties, except for P2 temperature (P = 0.851). Optimal extrusion conditions were determined to be a barrel temperature of 120°C, a screw speed of 40 rpm, and a feed moisture content of 12%. Under these conditions, blends with S. icipe achieved a higher protein content (7.7%) with greater reliability (93.8% (d=0.9377)) compared to G. bimaculatus blends (5.8%) with a reliability of 43.5% (0.4347). In conclusion, both cricket species in this study were found to have significant levels of protein, minerals, fat and vitamins. When compared to conventional food sources using the Kenya Food Composition Tables, both species were shown to have either similar or higher values for protein, mineral, vitamins and fat. The extruded corn-cricket porridge evaluated in this study containing 16.52 g/100g of crude protein with an in vitro digestibility of 54.5%, provides 9.00 g of digestible protein per 100 g serving. Based on WHO/FAO (WHO/FAO/UNU, 2007) guidelines, this represents a substantial contribution to the daily requirements of school-going children, meeting approximately 49.1% of the RNI for a 5-year-old and 23.5% for a 12-year-old. Therefore, it is recommended to policy makers as a viable option to be added into the food basket for school meals in Kenya. Ph in Food Science and Nutrition

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

2026-05-04T06:54:48Z

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. xiii 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

Farmers’ Perceptions, Distribution and Molecular Characterization of Groundnut Rosette Disease in Western Kenya

2026-03-26T11:39:36Z

Farmers’ Perceptions, Distribution and Molecular Characterization of Groundnut Rosette Disease in Western Kenya Were, Eric Osewo Groundnut rosette disease (GRD) is the most important viral disease of groundnuts in sub-Saharan Africa. In Kenya, GRD attack especially before flowering results in 100% loss in pod yield. Surveys were conducted between 2015 and 2017 to determine farmers’ knowledge and perceptions of GRD and its management as well as its distribution in five major groundnut growing Counties of western Kenya. In addition, the molecular diversity of the viruses causing GRD was determined. A structured questionnaire was used to assess GRD incidence and severity as well as farmers’ knowledge and management of GRD. Reverse transcription (RT)-polymerase chain reaction (PCR) was used for the detection of groundnut rosette assistor virus (GRAV), groundnut rosette virus (GRV) and satellite RNA (SatRNA), the causal agents of GRD in symptomatic and asymptomatic samples collected during the survey. The amplified RT-PCR products from the isolates of GRAV, GRV and Sat-RNA from infected groundnut plants were sequenced using the Sanger sequencing method. The sequences were edited, aligned and compared with other published sequences from GenBank using a Basic Local Alignment Search Tool (BLAST) and phylogenetic analysis. A total of 76 purposively selected farmers with groundnut fields were interviewed, and results indicated that pests and diseases are the main production constraints as indicated by 77% of the farmers. Awareness of GRD varied significantly (P < 0.001) among the farmers across the five counties as well as their knowledge on causes and management of GRD (P < 0.001The study findings revealed that 18.4% of groundnuts farmers in western Kenya had some knowledge about GRD. For the management of GRD, more than forty percent (43.58%) of respondents removed infected plants from the fields, 12.34% sprayed plants showing disease symptoms with chemical insecticides, 12.58% carried out crop rotations in their fields while 27.76% did not apply any management strategy on the diseased plants. It was also observed that GRD was prevalent in all the fields surveyed in the five Counties. The highest (35.7%) mean disease incidence was in Busia County while the lowest (23.1%) incidence was in Siaya. The most conspicuous symptoms observed in all the fields inspected were yellow/chlorotic and green rosette. The highest (3.1) mean disease severity was observed in farmers’ fields in Busia County, while the lowest (2.8) was observed in Siaya. Both GRAV and GRV were detected in all symptomatic and asymptomatic samples of groundnut leaves collected from the surveyed region. There was high degree of nucleotide identity among the Kenyan GRAV isolates from the five Counties in western Kenya. In conclusion, groundnut farmers in the sampled regions have limited awareness, knowledge and management of GRD. It is therefore important to build capacity of the farmers on detection, identification of the disease and its management. GRD is widely distributed in all groundnut fields in western Kenya and hence the need to use certified seeds. The disease is caused by presence of GRAV and GRV. It’s therefore important for plant breeders to develop groundnut varieties that are resistance to both GRAV and GRV with farmers’ preferred traits and high yielding. Researchers to perform Next Generation Sequencing to identify other unknown viruses infecting groundnuts in western Kenya MSc in Plant Health Science and Management

Management of Root Knot Nematode, Meloidogyne incognita Using Tithonia diversifolia and Tagetes minuta Through a Slow-Release Technique in Tomato

2026-02-24T09:34:15Z

Management of Root Knot Nematode, Meloidogyne incognita Using Tithonia diversifolia and Tagetes minuta Through a Slow-Release Technique in Tomato Macharia, Rachael Muthoni Tomato (Solanum lycopersicum) is an economically important crop in Africa produced largely by small-scale farmers. The root-knot nematode (RKN), Meloidogyne incognita (Kofoid and White) Chitwood, causes serious constraints in tomato production. Synthetic nematicides have been used in the management of RKN, however, they have adverse effects on users and the environment. Botanical pesticides are a safer alternative since they contain compounds that act as hatching inhibitors, repellents and nematoxicants. These compounds are constituted in leaves, seeds, flowers and roots and are applied through aqeous extracts, essential oils, powder or pellets derived from various plant parts. The use of plant extracts has been effective, however, more than two applications are done for effective RKN management. This study investigated the use of a filter bag as a slow release technique, to ensure the continuous release of the nematotoxic compounds to enhance the management of M. incognita and minimize the number of applications done. Powder and pellet of Mexican sunflower, Tithonia diversifolia Hemsl. and Mexican marigold, Tagetes minuta L. incorporated in a filter bag made of non-woven interfacing fusible fabric, were used in the management of M. incognita in tomato production. The experiment was laid out in a completely randomized design with a Pre-plant and Post-plant application of ammendments. Tomato seedlings were inoculated with about 1500 freshly hatched second-stage juveniles of M. incognita in both trials. Data collected on the nematode population dynamics, changes in tomato fruit qualities, and yield and root phenols and soil chemical properties. Data was subjected to analysis of variance and means separated using the Tukey Studentized Range Test (P = 0.05). Results of this study showed that pellet and powder from respective plant parts significantly (P = ˂0.001) reduced nematode populations relative to the untreated control but compared favorably to the positive control. The filter bag technique significantly improved the management of M. incognita. Pre-plant application of pellets incorporated in the filter bag resulted in plants that had lower egg mass and gall index and soils with lower juvenile populations. The fruit qualities were significantly improved where higher total soluble solids (4.37), total titratable acidity (0.83) and Vitamin C (18.33) content was recorded. The root phenols, N, P, K and organic carbon levels were higher in soils amended with ammendments incorporated in the filter bag. There was however no significant difference between ammendments in the filter bag and those without. The filter bag technique proved to be better in the pre-plant application relative to the post-plant application. These findings indicate that the filter bag technique averts the need for re-application which could help reduce the operation costs. MSc in Plant Health Science and Management