Introduction

Sweet potatoes are an essential crop for food security in Sub-Saharan Africa. The root has a three-month growth cycle and is regarded as a climate-smart crop. It grows on marginal terrain, including saline areas, and needs very little water. Orange-fleshed sweet potatoes (OFSPs) are a great source of energy and vitamins, particularly provitamin A carotenoid, which has been demonstrated to be an efficient and long-lasting source of vitamin A in humans¹

Orange-fleshed sweet potato puree is a novel and distinctive ingredient with significant growth potential found in baking items. East African nations are among the major importers of wheat, with African millers spending millions on this purchase ¹. In baked and fried goods, pureed OFSP can take the place of part of the white, wheat flour. OFSP puree can take the place of up to 50% of the wheat flour in bread. which also reduces sugar by 90%, fat by 50%, and artificial coloring by 50%. (egg yellow).  Wheat products have a better texture thanks to the OFSP puree, which makes them simpler to chew and digest. , and the baked bread preserves more than 50% of the β-carotene ².

For a number of years, the International Potato Center (CIP) has been creating and marketing baked goods that substitute OFSP puree for 20–45% wheat flour. These products have been piloted in Ethiopia, Uganda, Ghana, Nigeria, Tanzania, The Gambia, South Africa, and Mozambique. They have also been successfully sold in Kenya, Malawi, Rwanda, and Burkina Faso. The OFSP puree value chain operations have increased the crop’s value and opened up new markets for smallholder sweet potato producers, especially for women and young people.  Increased farm-gate prices for roots may incentivize farmers to utilize more inputs, narrowing the current yield gap and boosting the availability of sweet potatoes in rural regions and nutrient-dense OFSP for urban consumers³.

In developing countries where a lack of vitamin A (VAD)  , especially in young people and expectant mothers, is a serious issue, taking in OFSP is a beneficial choice ⁴. In numerous developing nations, chronic malnutrition is a serious issue since there is a severe dearth of meal high in nutrients.¹

There is a new demand for orange-fleshed sweet potato (OFSP) in Kenya with the emergence of commercially available baked goods using OFSP puree in place of wheat flour due to the extensive reporting on its nutritional content¹. This is promoted under the SUSTAIN (Scaling Up Sweetpotato Through Agriculture and Nutrition) project, where baked goods with OFSP as a primary ingredient were tested and promoted for commercialization. Acceptability of these products depends on sensory properties (appearance, texture, taste, and aroma), functional aspects, and nutritional value ⁵.

It has also been suggested that product diversification increases consumer preference. Although they might embrace value-added products, young people do not like boiled sweet potatoes ⁶. Most African cultures prefer to eat fresh sweet potatoes cooked, steamed, roasted, or fried ⁷ Making OFSP roots into a puree expands how these roots can be consumed, increasing their accessibility in urban areas and lowering food loss and waste. However, the utilization of sweet potatoes among the households in Tot Division is limited to boiling. Despite the documented benefits and interests in growing and consuming OFSP, the smallholder farmers in Tot Division have not embraced it due to limited knowledge. Therefore, it is crucial to introduce simple value-adding technologies and upscale initiatives to educate farmers about the health advantages of cultivating and eating OFSP to boost agricultural value addition and boost the amount of vitamin A in households’ diets.

Materials and Methods

Study Site

This research was done in one of Kenya’s 47 counties, Tot Division, Elgeyo Marakwet County. Its capital and main town is Iten, and it is situated in the region that was once the Rift Valley Province. It shares borders with the counties of Baringo County to the east, Uasin Gishu to the southwest, Trans Nzoia to the northwest, and West Pokot to the north (Figure 1).   For most households, subsistence farming is the primary source of income with sweet potatoes being one of the resilient crops grown

Figure 1: A map of Tot Division in Elgeyo Marakwet County, the study area. Click here to view Figure

Sampling Procedure and Sample Size determination

The survey targeted smallholder farmers residing in the four locations (Murkutwo, Chechan, Ketut, and Endo) in Tot Division where the new varieties of Orange-fleshed sweet potatoes were promoted by the County government and mostly grown by the farmers. About 201 farmers were randomly selected from a list developed with the extension officers from four locations (Murkutwo, Chechan, Ketut, and Endo) in Endo Ward based on Krejcie and Morgan table.

Data collection

Field Survey

The field survey was conducted in April 2023 in the four selected locations in Endo Ward (Mokoro, Chechan, Ketut, and Endo). Depending on whether they engaged in sweet potato farming at least once a year, farmers were purposefully sampled. Interviews were conducted with 201 farmers in total, one for each of the four locations. Data were gathered using structured questionnaires and in-person interviews. Either English or Swahili was used to administer the questionnaire. The study used a variety of closed-ended questions in which respondents could respond “true,” “false,” or “don’t know.”  The questionnaire collected socio-demographic data on gender, educational attainment, occupation, size of the land, and make-up of the family. Three elements made up the questionnaire: demographics, knowledge, and utilization of OFSP products. Ten people from the Chesongoch area participated in a pilot research. The main study did not include the pilot study participants.

Training

Thirty trainers were randomly selected among the 201 sweet potato farmers and trained using the Training of Trainers (ToTs) model to promote value-added OFSP product recipes through practical demonstration and a farmer participation approach. The recipe manuals for the value-added products (mandazi, chapati, and yogurt) were developed and distributed to farmers for their daily use in the households. The evaluation was undertaken using a scoring sheet for the preferred products and reasons to support preferences. 

Preparation of OFSP products

Orange fleshed sweet potato mature roots were procured. The roots were peeled, washed, and cut into approximately 3 cm cubes before boiling and mashing them into a puree for use in different products. For chapatti and Mandazi, a ratio of 1:3 OFSP to wheat flour was used, salt was added to taste and kneading proceeded as normal followed by shallow or deep frying. For yogurt processing, milk was heated just to the boil and then subdivided into four to make the varied four products. The yogurt was prepared with the addition of sugar, 6% of the sugar was added. The sweetened milk was allowed to cool to a temperature of warm on touch before adding a fermenting bacterial culture and OFSP puree followed by incubation for five hours. The control yogurt did not have added OFSP puree.

Sensory evaluation and consumer acceptability

 Twenty panelists (n=20) were randomly selected from a list of 30 training trainers (ToTs) to assess OFSP product samples based on seven sensory attributes; appearance, odor, taste, texture, mouth feel, product separation, and overall acceptability. Panelists were instructed to use a seven-point hedonic scale to record their observations on the sensory sheet (seven and one points showing they like it extremely and dislike it extremely, respectively). Before the samples were assessed, the research assistant gave the participants an explanation of each sensory attribute so they would understand what each of the seven attributes meant. All the panelists were familiar with the products prepared.

Panelists were free to exit the study at any time, and participation was entirely voluntary. Before any data was collected, research assistants who were proficient in Marakwet and Kiswahili were hired and trained. Because the study participants speak Kiswahili and Marakwet as their native tongues, these languages were chosen for the study. To protect participant anonymity, a participant number was provided.

Data Analysis

The data from the sensory evaluation and survey questionnaires were imported into Kobo and transferred to Statistical Package for Social Sciences (SPSS) version 22 for descriptive, inferential, and exploratory factor analysis based on the F test at the 5% level of significance. The data on hedonic scale scores for sensory attributes was subjected to analysis of variance and mean separation was done based on LSD T-test.

Results and Discussion

The respondents’ sociodemographic characteristics

Gender and level of education

The majority of respondents were female (83%) with diverse levels of education background. This agrees with the general observations that sweet potatoes are seen as a “woman’s crop” in terms of the amount of time they require to produce relative to other crops ⁸. This would suggest that women are actively engaged in farming in a region where men have traditionally and culturally been known to participate most. Most of the farmers went to secondary (36.3%) and primary schools (33.8%) with few attending tertiary (20.4%), and adult education levels (4.5%). However, (5.0%) has no formal education (Table 1). Knowledge of nutrition is positively correlated with education level, and those who have higher education levels are more likely to want highly nutritious and quality goods ⁹.  

Occupation, land size, and household size

The main occupation of most of the respondents was mixed farming with 44.3% growing crops and 24.9% keeping livestock. This can be a sign of a change in the county of Elgeyo Marakwet communities’ economic and/or social priorities from pastoralism to crop farming. The average farm size was 1.78±1.402 ha with an average of 0.30 ± 0.441ha occupied by OFSP (Table 1). Farm size has a big impact on what farmers decide to do with crop diversification and new agronomic technologies. Large farms allow farmers to reduce the risk of loss due to resource scarcity and climate change, as well as to vary their livestock and crop options. According to the survey findings, the majority of households in the Tot division were medium-sized with a range of 4-8 individuals and an average size of 7. The average household size is greater than 3.9 which is the average household size as reported in the most recent national census of population and housing. ⁸. This demonstrates the high demand for food in the households.

Table 1: Sociodemographic characteristics of the surveyed participants (n=201)

* Percentage of sample calculated using total sample (n = 201).

Knowledge of sweet potato production and nutritional content

The farmers were aware that Sweet potatoes are easier to grow than other crops (80.1%) and are well suited to tough climates (82.6 percent). This is consistent with reported information by ¹. The farmers are also aware of the advantages OFSP has for health due to the high levels of beta-carotene (61.7%) and how it helps prevent deficiencies in young people, expectant mothers, and the aged (54.2%). This is in agreement with a report that, in developing countries where lack of vitamin A, especially in young people, is a serious issue, consuming OFSP is a beneficial choice¹⁰ .The farmers also acknowledge the relevance of sweet potato production to household food security (79.1%) as reported by ¹, supplementing animal feed (86.1%), employment (52.7%), and enhancing soil fertility since it is a cover crop (84.1%) Table 2.

Table 2: Percentage of participants’ responses to knowledge on sweet potato production and nutritional content

Methods of utilization of sweet potatoes

The most common mode of utilization of sweet potatoes by households in Tot Division is through boiling (70%) while a few people make snacks (30%) (Figure 2). Most studies highlight that OFSP is turned into flour, which is then used to make unique food items including chips, cereal, biscuits, bread, porridge and drinks.  like chapati¹¹. However, this is contrary to the study findings and this may be attributed to inadequate knowledge and skills in value addition techniques. Through provision of effective and efficient extension training on the utilization of modern processing techniques to increase agricultural value addition, OFSP farmers should feel more empowered.  Therefore, the promotion of recipes of diverse value-added products like mandazi, chapati, and yogurt enriched with OFSP may raise the amount of vitamin A that is consumed in food in the households as suggested by ¹².

Figure 2: Methods of sweet potato utilization by most households in the Tot division. Click here to view Figure

Sensory evaluation and consumer acceptability

Typically, consumers were asked to rate how much they enjoyed a product to determine the level of customer acceptability ¹³.  Even if a product has been shown to provide health benefits, consumers may not accept it if it is not appealing to them or if their expectations are not met by its sensory qualities¹⁴. A seven (7) point hedonic scale scores were used in the evaluation and data was presented based on attribute scores ranging from 1 to 7.

Chapati

There was a significant variation (P<0.05) in color, texture, and oiliness between chapati made with OFSP puree and wheat (Table 3). Chapati made from OFSP puree was mostly preferred (6.38±0.97)than that made with wheat (5.38±1.88). Chapatis are mostly made from wheat products that rely on imports to prepare. In this preparation, wheat had been replaced by OFSP up to 30%, and yet the products were more acceptable. OFSP was locally grown and is more nutritious since it has vitamin A which is lacking in wheat, and it also has additional antioxidants that are beneficial to human health¹⁵. Besides, OFSP are climate-smart crops that should be promoted for both local and international markets¹.

Table 3: Hedonic scale scores for sensory attributes of chapati made with OFSP puree compared to wheat (n=20)

Scores on the hedonic scale that are followed in a column by a different letter (a or b) show a significant difference (p < 0.05).

Mandazi

Mandazi made with OFSP puree were the most preferred (6.3±1.41) compared to the regular wheat Mandazi (5.7±0.66) as reflected in the overall acceptability scores (Table 4). There were significant differences (P<0.01) in color, flavor, and texture with Mandazi made with OFSP puree ranking highest at 6±0.97, 5.5±1.2, and 5.9±0.85 for the parameters respectively. In terms of oiliness, there was no significant difference (P>0.05) between wheat Mandazi and those prepared with OFSP.

Table 4: Hedonic scale scores for sensory attributes of Mandazi made with OFSP puree compared to wheat (n=20)

Scores on the hedonic scale that are followed in a column by a different letter (a or b) show a significant difference (p < 0.05)

Yogurt

There was no significant variation (P>0.05) in separation (syneresis) for the four products with yogurt made with sugar and strawberry having the highest rating (5.56±1.333) and the natural yogurt with the lowest rating (4.56±1.33; Table 5). Yogurt that had sugar and strawberry, ranked highest in all other parameters; color (6.3±0.675), flavor (5.8±1.229), mouthfeel (6.3±0.823), smoothness/lumpiness (6.3±0.823) and overall acceptability (6.5±0.707). There was a distinct difference (P<0.05) in color and mouthfeel for the four products. The use of OFSP in yogurt serves four main purposes: first, it thickens the product and hence prevents the use of expensive or artificial thickeners, secondly, it gives a desired flavor and prevents the use of artificial and non-nutritive flavorings, thirdly, it imparts sweetening and reduces the need for the addition of sugars and lastly, OFSP adds to the yogurt drink pro-vitamin A carotenoid (beta carotene). Adoption and use of the OFSP, therefore, gives a great advantage to yogurt consumers and hence the need to promote its use by fronting the health benefits of the OFSP yogurt.

Table 5: Hedonic scale scores for sensory attributes of yogurt made with OFSP puree compared to natural (n=20)

Scores on the hedonic scale that are followed in a column by a different letter (a or b) show a significant difference (p < 0.05)

Conclusion

The farmers in Elgeyo Marakwet are aware that Compared to other crops, sweet potatoes are easier to grow and more suited to difficult climates. They are also aware of the advantages OFSP has for health and are ready to adopt the crop. Orange fleshed sweet potato puree can be used to produce acceptable and nutritious Chapati, Mandazi, and yogurt as part of diversification from the current practice of boiling the roots. The county government of Elgeyo Marakwet should take the lead in upscaling initiatives to educate farmers about the health advantages of cultivating and eating OFSP through effective and efficient extension training.

Acknowledgments

The authors thank FSNET-Africa for the fellowship and the technical assistance from Elgeyo Marakwet County government, agricultural extension officers, village elders, and chiefs. We also appreciate the farmers from Tot division’s Endo ward who participated in the survey. 

Funding Sources

The research was funded by the Food Systems Research Network for Africa (FSNet-Africa). FSNet-Africa is funded by the Global Challenges Research Fund (GCRF) as a Research Excellence project under the partnership between UK Research and Innovation (UKRI) and the African Research Universities Alliance (ARUA). FSNet-Africa is a flagship project in the ARUA Centre of Excellence in Sustainable Food Systems (ARUA-SFS), which is hosted by the University of Pretoria (South Africa) in collaboration with the University of Nairobi (Grant number: ES/T015128/1).

Conflicts of Interest

The authors declare no conflict of interest

Author Contributions

Conceptualization, J.C., H.G., T.N. and M.K.; methodology, J.C., G.A; H.G. and T.N.; software, J.C and G.A.; validation, J.C; G.A; H.G., T.N. and M.K. formal analysis, J.C and G.A.; investigation, J.C.; resources, J.C.; data curation, J.C. and H.G.; writing—original draft preparation, J.C., G.A; H.G., T.N. and M.K.; writing—review and editing, J.C; G.A; H.G. and T.N.; visualization, J.C. and H.G.; supervision, J.C. project administration, J.C.; funding acquisition, J.C. All authors have read and agreed to the published version of the manuscript.

Data Availability Statement

The manuscript incorporates all datasets collected in this study. The corresponding author can provide any extra data from this study upon request.

Ethics Statement

The KNH-UoN Ethics and Research Committee granted ethical approval (P717/09/2022) https://erc.uonbi.ac.ke/index.php/, accessed on 29 November 2022 while the National Council of Science, Technology and Innovations (NACOSTI-Kenya), a regulatory agency, provided the study permit (NACOSTI/P/23/22730).

Informed Consent Statement

Each research participant provided their free and informed consent before beginning the study. Throughout the study, the values of secrecy and respect were upheld. Community standards related to data collection were adhered to when collecting data. Only relevant information was collected from the community members and the participants were given information on the objective of the research and access to the findings.

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