Joshua Ombaka Owade

If lettuce is contaminated in the field, Shiga toxin-producing E. coli (STEC) O157:H7 can survive through the distribution chain. Prolonged cold storage during transportation may impact pathogen physiology, affecting subsequent stress survival and virulence. Greenhouse-grown Romaine lettuce, inoculated with three STEC O157:H7 strains, was harvested after 24 h and stored at 2 °C for 5 d following 4 h at harvest temperature (9 °C or 17 °C). Culturable, persister, and viable but non-culturable (VBNC) cells were quantified. Virulence was evaluated using Galleria mellonella and acid tolerance at pH 2.5 and tolerance to 20–25 ppm free chlorine were quantified. Colder harvest temperature (9 °C) before cold storage led to greater transformation of STEC O157:H7 into dormant states and decreased virulence in most cases. Increasing length of cold storage led to decreased virulence and acid tolerance of STEC O157:H7 on lettuce, while having no significant effect on chlorine tolerance. These findings highlight that entry of STEC O157:H7 into dormant states during harvest and transportation at cold temperatures leads to decreased stress tolerance and virulence with increasing cold storage. Changes in STEC O157:H7 physiology on lettuce during cold storage can be integrated into risk assessment tools for producers, which can assist in identifying practices that minimize risk of STEC O157:H7 from consumption of lettuce.

Outbreaks of Enterohemorrhagic Escherichia coli (EHEC), Salmonella enterica, and Listeria monocytogenes linked to fresh produce consumption pose significant food safety concerns. These pathogens can contaminate pre-harvest produce through various routes, including contaminated water. Soil physicochemical properties and flooding can influence pathogen survival in soils. We investigated survival of EHEC, S. enterica, and L. monocytogenes in soil extracts designed to represent soils with stagnant water. We hypothesized pathogen survival would be influenced by soil extract nutrient levels and the presence of native microbes. A chemical analysis revealed higher levels of total nitrogen, phosphorus, and carbon in high-nutrient soil extracts compared to low-nutrient extracts. Pathogen survival was enhanced in high-nutrient, sterile soil extracts, while the presence of native microbes reduced pathogen numbers. A microbiome analysis showed greater diversity in low-nutrient soil extracts, with distinct microbial compositions between extract types. Our findings highlight the importance of soil nutrient composition and microbial dynamics in influencing pathogen behavior. Given key soil parameters, a long short-term memory model (LSTM) effectively predicted pathogen survival. Integrating these factors can aid in developing predictive models for pathogen persistence in agricultural systems. Overall, our study contributes to understanding the complex interplay in agricultural ecosystems, facilitating informed decision-making for crop production and food safety enhancement.

Seasonality in the availability of cowpea leaves has often limited their utilization and thus the promotion of preservation techniques that convert the vegetables into storable and stable forms. The recommendations for the use of highly mechanized techniques in preservation are brought into question due to limited affordability among resource-constrained households that prefer less costly approaches. Therefore, this study used statistical techniques of principal component analysis to comparatively evaluate the trends of physicochemical quality of the two diverse approaches of processing cowpea leaves. The study evaluated dehydrated cowpea leaves of different processing techniques from farmer groups and optimally processed using modern techniques for nutritional composition, phytochemical compounds, and colour changes. Sun drying techniques that excluded blanching had the least content of beta-carotene and ascorbic acid, 2.65 ± 0.95 and 21.80 ± 1.24 mg/100 g dry weight basis (dwb), respectively, accompanied by the most significant ( ) deterioration of colour (7.74 ± 3.49) than techniques that included. Whereas the antinutrients declined, the difference did not significantly differ ( ) based on preservation techniques. With factor analysis determining optimal nutritional quality for cowpea leaves at 8 weeks after emergence, sun drying had the highest loss of beta-carotene and ascorbic acid, 66.7–80.1% and 53.7%–58.3%, respectively ( ), whereas mineral leaching, reduction of antinutrients, and colour changes were more pronounced in dehydration techniques incorporating fermentation as pretreatment. For the traditional preservation techniques, increasing retention of minerals resulted in aggravated losses of beta-carotene and ascorbic acid, whereas in the mechanized techniques, this was not the case. In concluding that the mechanized techniques have a better combination of attenuating losses of micronutrients, the study recommends that in promoting the utilization of traditional preservation techniques, low-cost processes like steam blanching can help improve the nutritional quality of the product.

Cost-effective techniques are usually recommended in the dissemination and adoption of postharvest processing technologies of food products. Due to limited value addition practices for cowpea leaf, the Fruits and Vegetables for All Seasons Project undertook a study to bridge the gap in the seasonal availability of the vegetable in the arid and semi-arid lands (ASALs) of Kenya through the production of cowpea leaf soup mix. However, the adoption of these techniques has an economic perspective that guides decision-making. This study utilized a two-stage linear programming methodology using NutriSurvey and the analytic hierarchy process in a seven-step hierarchy for the production of a cowpea leaf soup mix of an optimal nutrition and sensory quality. The optimal inclusion level of cowpea leaves into the soup mix was 49%. With an R² of 61.36%, consistency, taste, and mouthfeel were the greatest determinants of the acceptability of cowpea leaf soup mixes. The incorporation of blanching in solar drying and sun drying were the least costly options with priority vectors of 0.08 and 0.09 (CR < 0.1) respectively, whereas, in the use of mechanized processing techniques such as oven drying, priority vectors of 0.10–0.19 had higher maximum benefits than the local processing technique of sun-drying that had a priority vector of 0.08 (CR < 0.1). The benefit-cost ratio was maximal without extrusion, with the solar-drying pathway having the highest benefit-cost ratio of 1.5. The study found that resource-intensive pathways yielded maximum benefits in the retention of quality. However, with the exclusion of extrusion, the benefit-cost ratio of the processes improved.

Background: As much as local communities have employed traditional techniques of preservation to enhance availability and utilization of cowpea leaves, the efficiency of these techniques in achieving food security need to be established. The current study sought to document trends and constraints of utilization of preserved cowpea leaves in the arid and semi-arid lands (ASALs) in order to overcome of seasonal availability of the vegetable. Method: A mixed method convergent design that included household survey of randomly sampled cowpea producing households and focus group discussion and key informant interviews with stakeholders in the ASAL areas of Kitui and Taita Taveta Counties of Kenya was conducted. Results: The study found that the utilization of preserved forms of cowpea leaves in the in-season was by 58% of the respondents. Three quarters (73.6%) of the households could not get the vegetables from their own sources during scarcity, whereas 25% did not consume the vegetables at all at such times. The preserved forms of the vegetables was utilized among 24.0% of the households, with significantly (p < 0.05) higher utilization in less arid areas. Households that were involved in commercialization of cowpea leaves and sale of the preserved forms in the open air market had significantly higher likelihood (p < 0.001, OR = 2.47 and p < 0.001, OR = 2.3, respectively) of utilization of the vegetables during scarcity. Emerging themes from the qualitative survey showed that weaknesses in the policy environment, stakeholder interest, marketing and accessibility to proper equipment were the deterrents of traditional preservation of the vegetable. Conclusion: In conclusion, the preserved forms of cowpea leaves promoted availability of the vegetable especially in the dry seasons. In as much as there is limited practising of preservation of the vegetables, its availability is enhanced through dehydration and other value-addition techniques among a significant number of the households.

In as much as spontaneous fermentation of cowpea leaves enhances product diversification, the process is rather slow with poor product quality. Limited work has been undertaken to provide input toward standardization of the process and enhancing of product quality. The current study sought to evaluate the in‐process fermentative bacteria profile changes due to the effect of optimization of fermentation process of cowpea leaves. Lactic acid bacteria (LAB) isolates from spontaneous and optimized fermentation were characterized using biochemical tests, whereby optimization was done using the Response Surface Methodology model of the central composite design in the Design Expert Software. The RSM models accounted for 89% and 60% variability in the response variables of pH and titratable acidity, respectively (p < .001). Increasing the sugar concentration and period of fermentation significantly (p < .05) increased the titratable acidity, while reducing the pH. The optimal fermentation parameters were established as sugar and salt concentrations of 5% and 2%, respectively, 16 days of fermentation, pH of 3.8 and titratable acidity of 1.22% with a desirability of 0.859. Of the 13 identified LAB isolates, Lactobacillus brevis and Lactococcus lactis dominated the onset stage of spontaneous fermentation whereas only Lactobacillus brevis dominated the onset stage of optimized fermentation. Additionally, the final stage with the dominant isolates of L. plantarum was longer in the spontaneous fermentation process than in the optimized process. Evidently, optimizing the fermentation process resulted in increasing dominance by heterofermenters in the production of soured cowpea leaves, with the yielded product having enhanced acidity.

Prevalent risks in meat value-chains of sub-Saharan African (SSA) countries are increasingly attributed to microbial rather than chemical hazards. Resource constraints and lack of capacity has limited the utilization of risk assessment tools in the instituting of food controls to mitigate the risks. The review sought to bring to light the focus of risk assessment studies in SSA while generating evidence of feasible options to further the contribution of this component in risk mitigation. The informal street vending sector emerges as a priority in the meat value chain with a vendor population that are unwilling to abandon it. Campylobacter and Staphylococcus aureus are prevalent risks that have bedeviled this sector. However, limited risk assessment studies with capacity to inform proper food controls for the sector have been done. Evidence in place indicate that the incorporation of qualitative aspects in quantitative approaches serve as less-costly and effective ways of generating risk estimates. Limitations of capacity and gaps in epidemiological data are also circumvented. Considering that the street-vending sector is robust and its dynamics of operation are not fully in the picture of policy actors; incorporation of a participatory approach that combines qualitative and quantitative aspects of risk assessment is highly recommended.

Cowpea (Vigna unguiculata) leaves are nutritious indigenous vegetables that are produced and consumed among local communities in Kenya. However, seasonal production limits their utilization. The study investigated the changing trends in the consumption and utilization of cowpea leaves among cowpea producing households in arid and semi-arid land (ASAL) areas. A cross-sectional survey of randomly selected households producing and consuming cowpea leaves was carried out in Eastern and Coastal ASALs of Kenya to determine the trends and constraints in the production and utilization of the vegetable, thus evaluating its efficiency as a food security crop. The average household production in a season was found to be 3.03 ± 0.9 of 90 kg bags. Lesser severity of the constraints, poor soils, drought, lack of access to seeds and massive spoilage with an odds ratio of 0.4, 0.9, 2.0 and 2.3, respectively, significantly (p < 0.05) predicted the production quantities among households, R ² = 0.21. The study also found that the reliance on own production among households for sourcing the leaves in-season and off-season was 97.5% and 24.9%, respectively. The households consumed the leaves in boiled (87.5%), sundried (27.5%) or blanched (13.6%) forms. Households in the coastal ASALs significantly (p < 0.05) consumed more of dried forms (odds ratio: 3.3) but less of boiled ones (odds ratio: 0.1) than those in the Eastern parts. Households that had more members or a female deciding the food to be bought had significantly (p < 0.05) higher frequency of consumption of cowpea leaves. Marketing challenges, lack of access to inputs and inadequate postharvest technologies for preservation of the vegetables constrained the production and utilization of cowpea leaves. In order to promote the availability and utilization of cowpea leaves both in and out of season, accessibility of good quality seeds and postharvest management are necessary.