Introduction

In sub-Saharan Africa, parents are becoming more worried about nutritional deficiency in their young children, since it continues to persist due to dietary pattern1. Vitamin A deficiency (VAD) is the leading cause of preventable blindness, affecting many children and women of reproductive age2. VAD affects 40–60% of African children and 10–20% of pregnant women in low-income countries3. Vitamin A is essential for immune system functions and the survival, growth, and development of children4. Hence, promoting the intake of provitamin A-rich foods is open to a diversity of foods and can be used to enhance the former strategies5. Roots and tubers are generally one of the cheapest and most popular sources of dietary energy in the form of carbohydrates6,7. Orange-fleshed sweet potato (OFSP) is naturally rich in vitamin A, especially β-carotene, and a good source of starch, sugars, and minerals. OFSP is an emerging tuber-based food for the improvement of vitamin A status in the world, particularly in developing countries. It was acknowledged as an excellent source of natural health-promoting compounds, diverse vitamins (A precursors), and minerals that can meet nutrient intake and reduce VAD8. Studies have shown that consumption of OFSP has the potential to curtail VAD which is prevalent in children leading to early blindness and death of a minimum of two hundred and fifty thousand children in Africa9. They serve as a major inexpensive source for improving immunity, preventing blindness in children and women of reproductive age, combating widespread VAD, and reducing degenerative diseases like cancer, cardiovascular disease, cataracts, muscular degeneration, etc10,11,12. Existing studies on the formulation of products have been found to utilize sweet potato in combination with wheat, rice, soybean, cowpea, peanut, cassava, and so on2,7,8,9,13.

The utilization of pulses in the diet has a healthy approach to lessening the risks of several chronic disorders and helping in meeting dietary recommendations14. Commonly used legumes throughout the world are beans, chickpeas, lentils, peas, cowpeas, broad beans, and soybeans15. Cowpea (Vigna ungucuilata) is a primary leguminous food, with about 90% being produced in the West Africa region of the world16. The largest producer of cowpea is Nigeria, which accounts for 61% of production in Africa and 58% worldwide17. Cowpea seeds contain a high protein content (18 to 25%), 1.4–2.7% of fats, and about 6% crude fiber. It also contains about 7.5 mg per 100 g of iron and contains non-essential and essential amino acids, e.g., valine, leucine, phenylalanine, and lysine. The calcium content of cowpeas is higher than that of meat (7%). Besides, it has also been reported as an important source of protein for a large part of the world’s population, especially in countries with the poorest populations and high rates of protein-energy malnutrition17. Cowpea contains water-soluble vitamins (thiamine, riboflavin, and niacin) comparable to the levels found in fish and lean meat18, thus making it extremely valuable to help in alleviation of protein deficiency.

The banana (Musa acuminata), when ripe, is consumed raw as a dessert fruit, which serves as a good source of carbohydrates, minerals such as potassium, and vitamins19. Biernacka et al.20 reported that they contain many important vitamins (A, C, E, K, and B groups), are rich in fiber, and contain many minerals (magnesium, phosphorus, calcium, and potassium). It was also reported to ease constipation due to its fiber content and prevent anemia by stimulating the production of hemoglobin due to its iron content21; about 25% of the total food energy for about 60 million people in Africa comes from bananas and plantains22. Nigeria is one of the largest banana-producing countries in Africa and accounts for about 2.73 million metric tons of bananas per year23. However, during glut season, ripe banana wastes in tonnes due to poor handling and inadequate storage facilities24.

Hence, the production of banana flour from ripe ones would reduce the post-harvest loss of bananas and contribute to the attainment of SDG goal 12, aimed at sustainable responsible consumption and production, thus converting them into useful products. Thus, to combat VAD prevalence and meet the description of being nutritious, acceptable, assessable, and cheap, this study explored the use of orange-flesh sweet potatoes as a source of vitamin A, cowpea, and ripe bananas as sources of protein and iron, respectively, in the production of the flour mix.

Result and discussion

Nutritional composition of the formulated sweet potato, cowpea-banana blends

The nutritional composition of the formulated PCB blends is presented in Tables 1, 2, 3. There was an important significant difference (P < 0.05) in the nutritional composition of the formulated blends. Moisture content value ranged from 2.44 (PCB8) to 3.80% w.b (PCB7). The ash content of the PCB blends varied between 4.04 and 5.14%. It was found to be highest in PCB4, while PCB8 presented the lowest ash value, followed by PCB8. PCB6 showed the lowest fiber content (1.74%), which agrees with the reduction in the proportion of the orange-fleshed sweet potato (OFSP) and banana in the blend, conversely, PCB1 showed the highest fiber content followed by PCB8, PCB3, and PCB4. An increase in fiber as the addition of OFSP flour increases is similar to the observations of Kidane et al.13 and Afework et al.8 during the production of bread and pasta, respectively. Consumption of high-fiber food products has been linked to a reduction in hemorrhoids, diabetes, high blood pressure, and obesity21. Small variations were observed in the fat content of the blends; it ranged from 0.62 to 0.88 percent. The PCB5 blend had the highest fat content, while the PCB4 blend had the lowest fat content. Fat content has been reported to play a crucial role in the shelf-life stability of flour products25. There was a slight variation in the protein content of the formulated blends; it varied between 8.46 and 10.52%. PCB5 presented the highest protein value, which is mainly derived from the increase in cowpea content. The total carbohydrate content of the blends ranged from 77.89% to 81.33%. PCB8 blend had the highest carbohydrate content, closely followed by PCB7 (80.33%), PCB6 (79.90%), and PCB3 (79.58%), though there was no significant difference between them. The higher value of carbohydrates was due to an increase in the proportion of the OFSP inclusion. The energy content of the blends ranged from 1331.36 to 1547.29 kJ/100 g. The range recorded in the study showed that the formulated blends are rich in carbohydrate content, implying that they can be used for the management of protein-energy malnutrition. The average energy required from complementary foods for developing countries (kJ/day) has been estimated at 840 (6–8 months), 1260 (9–11 months), and 1260 (12–23 months)26,27. Bello et al.21 reported that complex carbohydrates instead of sugars should provide more than half of the energy required for children as stipulated by the Food and Nutrition Board (1989). An adequate quantity of carbohydrates can be used to derive energy and spare protein, while the protein in the blends can be used for its primary function, which is building the body and repairing worn-out tissues instead of serving as a source of energy28,29.

Table 1 Proximate composition of the raw materials used for production sweet potato-cowpea-banana blends.
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Table 2 Formulation ratio for the sweet potato-cowpea-banana (PCB) blends.
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Table 3 Nutrient composition of the sweet potato-cowpea-banana (PCB) blends.
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PCB7 blend had the highest calorific value. The beta-carotene content ranged from 0.15 to 0.24 mg/100 g. PCB4 had the highest beta-carotenoid content, while PCB1, PCB2, and PCB6 (0.15) had the lowest value. The carotenoid content of the study is higher than that recorded by Kolawole et al.30 during the production of orange-fleshed sweet potato pasta. This may be due to alterations in the enzymatic oxidation and variations in the retention of carotenoids during processing. OFSP has also been reported as an excellent novel source of β-carotene which is a natural health-promoting compound8. The vitamin A content of the blends varied between 7.55 and 8.35 mg/100 g. The PCB4 blend showed the highest vitamin A value. This is due to an increase in the OFSP proportion. The lycopene content of the blends varied between 78.21 and 92.14 mg/100 g. PCB4 blend had the highest lycopene value.

Color properties of the formulated sweet potato-cowpea-banana (PCB) blends

The color evaluation of the PCB blends is shown in Fig. 1. There was some significance (P < 0.05) in the color parameters for the formulated blends. The lightness value (L) ranged from 42.14 to 67.18. PCB4 blend showed the highest L-value, while PCB2 presented the lowest L-value. This is due to an increase in the OFSP content of the PCB4 blend. The red-green value (a) was highest in the PCB4 blend and lowest in the PCB6 blend. This is also a result of the PCB4 blend having the highest OFSP content. The yellow-blue value (b) ranged from 19.37 to 29.44. PCB4 showed the highest b-value. The huge angle (HA) of the blends showed a small variation (1.33 to 1.47). The maximum HA was recorded for the PCB6 blend, while the lowest HA was shown in PCB3, followed by PCB4. This is expected since the HA reflects the ratio of the b to a value. The chroma value ranged from 13.44 to 24.14. PCB4 had the highest chroma value, while PCB7 showed the lowest, followed by PCB2.

Figure 1
figure 1

Pasting profile of the sweet potato-cowpea-banana (PCB) blends. (a) PCB1; (b) PCB2 (c) PCB3; (d) PCB4; (e) PCB5; (f) PCB6; (g) PCB7; (h) PCB8

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The color intensity (CI) varied between 36 and 53. 36 PCB4 blend presented the lowest CI, while PCB2 had the highest CI. Generally, the objective color evaluation of the blends showed that PCB4 presented significantly (P < 0.05) higher lightness and chroma and the lowest CI and HA. The high lightness values in the study can be attributed to the quantity of OFSP used for the formulation of the blends. OFSP flour has been reported to be high in carotenoid which is rich in β-carotene pigments30.

Functional and pasting properties of the formulated sweet potato-cowpea-banana (PCB) blends

The result of the functional and pasting properties of the blends is represented in Table 4 and Fig. 2. There was a significant difference (P < 0.05) in the functional and pasting properties of the blends. The water absorption capacity (WAC) of the blends ranged from 189.73% to 226.54%. PCB4 blend showed the highest WAC, while PCB6 had the lowest WAC. WAC of flour is usually enhanced by some major chemical composition like protein and carbohydrate. The higher WAC of the PCB4 blend is due to its high starch composition and also depends on the availability of hydrophilic groups that hold water molecules and, on the gel, the forming ability of macromolecules31. Though the low water absorption capacity of the flour blend is desirable for producing a less bulky, thinner gruel with a high caloric density per unit value31,32.

Table 4 Functional and pasting properties of the sweet potato-cowpea-banana (PCB) blends.
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Figure 2
figure 2

Color properties of the sweet potato-cowpea-banana (PCB) blends. Codes: PCB1: 50% OFSP, 30% cowpea, 20% ripe banana flour and 0% sugar; PCB2: 55% OFSP, 30% cowpea, 15% ripe banana flour and 0% sugar; PCB3: 60% OFSP, 30% cowpea, 10% ripe banana flour and 0% sugar; PCB4: 65% OFSP, 30% cowpea, 5% ripe banana flour and 0% sugar, PCB5: 60% OFSP, 40% cowpea, 0% ripe banana flour and 0% sugar; PCB6: 50% OFSP, 30% cowpea, 15% ripe banana flour and 5% sugar; PCB7: 55% OFSP, 30% cowpea, 15% ripe banana flour and 5% sugar; PCB8: 60% OFSP, 30% cowpea, 5% ripe banana flour and 5% sugar.

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The peak viscosity (PV) of the blends ranged from 566.33 to 3221.33 cP. PCB2 blend showed the highest PV, followed by PCB4, while PCB6 presented the lowest PV. This shows that PCB2 and PCB4 had a higher water-binding capacity, quality, and ease of granular disintegration. This increase is due to the higher content of OFSP and bananas due to their higher carbohydrate content and the absence of an additive (sugar). High peak viscosity is responsible for high swelling capacity due to the availability of more starch granules31.

The trough viscosity (TV) varied between 528 and 2588 cP. PCB2 and PCB4 had the highest TV, while PCB6 showed the lowest TV, followed by PCB8. High TV shows the stability characteristics of the blend during heating and cooling. This is as a result of the increased inclusion of the OFSP (i.e., a carbohydrate source). The breakdown viscosity (BDV) of the blends ranged from 33.33 to 829.67 cP. The least BDV was for the PCB6 blend, while the highest was for the PCB4 blend, followed by PCB3 (771.33 cP) and PCB2 (637.67 cP). The breakdown viscosity is the measure of the degree of paste strength or starch granule fragmentation during heating33. Therefore, the weaning mix with the high breakdown viscosity will have a more stable paste during heating than others with a low breakdown viscosity34. The final viscosity (FV) of the blends varied between 892.33 and 3621.33 cP. PCB2 blend had the highest FV; it was closely followed by PCB4 blend (3060 cP), while PCB6 blend presented the lowest FV. High FV represents a higher ability of the blend to paste during heating, low viscosity connotes thinner gruel which is a desirable quality because the viscosity of weaning or complementary food plays a significant role in its acceptability as well as an infant’s energy intake34. The final viscosity is often regarded as an indicator of the stability of the cooked paste when prepared31; the setback viscosities (SBV) of the blends ranged from 136.33 to 1190 cP. PCB4 showed the highest SBV, while PCB1 presented the lowest SBV. A higher SBV shows the ability of the cooked blend to retrograde during cooling. PCB6 and PCB8 had the lowest SBV values (360.67 and 333.33), which indicate low starch retrogradation and syneresis33. Peak time (PT) varied between 4.67 and 7.17 min. Higher PT was shown for the PCB6 blend, while lower PT was recorded for the PCB8 (4.67 min), PCB5 (4.73 min), and PCB4 (5.6 min). The higher PT reflects that more time is required for complete gelatinization of the starchy blends. The pasting temperature (PAT) ranged from 78.21 to 92.14 °C and the variances in the pasting temperatures of the blends of weaning food show that they all have different gelatinization temperatures. It also suggests the minimum temperature required to cook a given sample, which could also have effects on energy usage35. PCB4 blend showed a lower PAT, while PCB1 blend had a higher PAT, though a lower PAT is still desirable. Generally, the functional and pasting evaluation showed that PCB4 (65 g of OFSP, 30 g of cowpea, and 5 g of ripe banana flour) showed significantly higher water absorption capacity, peak viscosity, trough viscosity, breakdown viscosity, final viscosity, setback viscosity, and lower peak time and pasting temperature. Functional properties of the formulated blends in the study showed reduction in water absorption capacity, and pasting properties which is advantageous as this would assist in the preparation of gruels with low viscosity and high calorie density per unit volume that can be easily swallowed by babies21.

Relationship between color and nutritional properties of the formulated sweet potato-cowpea-banana (PCB) blends

The correlation between the color parameters and some nutritional compositions is represented in Table 5. Beta-carotene showed a strong positive significant (P < 0.05) correlation with vitamin A (0.84**), lycopene (0.56**), L-value (0.65**), a-value (0.68**), b-value (0.58**), and chroma (0.62**), but a negative correlation with HA (− 0.59**) and CI (− 0.61**). This signifies that increase in the proportion of Beta-carotene raw material source will consequently increase the vitamin A, lycopene, L-value, a-value, b-value, chroma and decrease the HA and CI. Vitamin A showed similar positive and negative correlations as beta-carotene. Lycopene had no significant (P > 0.05) correlation with any of the color parameters, indicating that its increase or decrease will not affect the color of the blends. The L-value presented a strong significant correlation with HA (− 0.58**), chroma (0.93**) and CI (− 0.99**). Similar trend was noticed for a and b-value. This study's correlation between colour parameters and some nutritional components, notably lycopene, beta-carotene, and vitamin A, supported earlier researches suggesting that colour has a significant role in drawing children's attention to food while preserving the flour mix's optimal nutritional value8,9,18,20.

Table 5 Relationship between nutritional and colour properties of the potato-cowpea-banana (PCB) blends.
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Relationship between proximate and pasting properties of the formulated sweet potato-cowpea-banana (PCB) blends

The Pearson correlation between proximate and pasting properties is shown in Table 6. The ash content of the blends significantly correlated (P < 0.05) with fiber (− 0.61**), fat (− 0.41*), carbohydrate (− 0.61**), calorific value (− 0.67**), BDV (0.52**), FV (0.45*), SBV (0.67**), and PAT (− 0.52**). This signifies that increasing the raw materials with high ash content will decrease the fiber, fat, carbohydrate, calorific value, and PAT and increase the BDV, FV, and SBV. Fiber content only correlated well with protein (0.61**). Fat content of the blends showed a positive correlation with protein (0.49*) and PT (0.47*), showing that an increase in the raw material with a high fat content will increase the time required for complete gelatinization of the blend. Protein content showed a strong and significant correlation with SBV (− 0.52**) and PAT (0.72**), showing that an increase in protein source will decrease the tendency of the cooked blend to retrograde during cooling and increase the gelatinization temperature. Carbohydrate correlated well with energy content (0.98**), WAC (− 0.44*), BDV (− 0.62**), and SBV (− 0.53**), indicating that an increase in the carbohydrate source will increase the energy content dissipated by the blend, decrease its WAC, and increase the ability of the starch to disintegrate during heating and syneresis. Amongst the pasting parameters there were significant correlation coefficients. In order to improve the health, mineral content, and nutritional values of the developed flour mix as complementary food, it is important to consider the relationship between proximate and pasting properties. Specifically, an increase in protein source will decrease the cooked blend's tendency to retrograde this is agreement with findings of previous researches2,4,9.

Table 6 Correlation between proximate and pasting properties of the sweet potato-cowpea-banana (PCB) blends.
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Acceptability of the formulated sweet potato-cowpea-banana (PCB) blends

Sensory responses to the taste, smell, and texture of foods assist in determining food preferences and eating habits. Color is a strong indicator of whether the developed product will be acceptable. The color of the sweet potato-cowpea banana blends presented to panelists in porridge form ranged from 8.96 to 7.68 as assessed based on a 9-point hedonic scale (Fig. 3), and they were generally acceptable, with the highest average score of 8.96 recorded for PCB8 blends (60:30:5:5 of OFSP, cowpea, ripe banana, and sugar, respectively) and the least (7.68) for PCB1 blends (50:30:20:0 of OFSP, cowpea, ripe banana, and sugar, respectively). Flavor is also a significant element in the acceptance of foods as it’s a combination of the senses of taste, aroma, and mouth feel. There was a significant difference in the flavor of the blends, with PCB8 (8.75) being most preferred, followed by PCB7 (8.57), PCB5 (7.93), PCB3 (7.75), PCB6 (7.71), PCB4 (7.64), PCB1 (7.46), and PCB2 (6.79) in descending order. The panelists rated the appearance (8.88–7.21) in a similar order, except that PCB6 and PCB7 have the same score (7.89); besides that, there is no significant difference between PCB5 (7.39), PCB3 (7.24), and PCB2 (7.21), respectively. There were no significant differences texture and the tastes of all the sweet potato-cowpea-banana (PCB) blends assessed as were all acceptable range with PCB8 most preferred. Overall acceptability of the blend was highly acceptable with the lowest been 6.36 and highest been 7.95. There is no negative report with all sample. Addition of banana and cowpea to OFSP up to 40 and 20% reveal no undesirable descriptions in the developed products. The general observation that PCB8 is more preferred compared to PCB1 agrees with Biernacka et al.20, who reported that overripe banana flour's natural sweetness with little sugar increases the overall acceptability of muffins. Products such as pasta, biscuits, and porridge from OFSP have been reported to be acceptable in terms of color, texture, taste, flavor, and texture8,30.

Figure 3
figure 3

Sensory evaluation of porridge containing sweet potato-cowpea-banana blends (PCB). Codes: PCB1: 50% OFSP, 30% cowpea, 20% ripe banana flour and 0% sugar; PCB2: 55% OFSP, 30% cowpea, 15% ripe banana flour and 0% sugar; PCB3: 60% OFSP, 30% cowpea, 10% ripe banana flour and 0% sugar; PCB4: 65% OFSP, 30% cowpea, 5% ripe banana flour and 0% sugar, PCB5: 60% OFSP, 40% cowpea, 0% ripe banana flour and 0% sugar; PCB6: 50% OFSP, 30% cowpea, 15% ripe banana flour and 5% sugar; PCB7: 55% OFSP, 30% cowpea, 15% ripe banana flour and 5% sugar; PCB8: 60% OFSP, 30% cowpea, 5% ripe banana flour and 5% sugar.

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In conclusion, the nutritional compositions of the formulated blends show that they can be used in the management of protein-energy malnutrition. The formulated blends showed advantages over other blends recorded in the literature as they had good water absorption capacity. PCB4 in particular was noted to be the best in terms of its vitamin A value, functional properties, and pasting properties, as it had higher WAC, PV, TV, BV, FV, and SV. This study is showcasing locally obtained food items for innovative combination of tubers-pulses and banana for production of a nutritionally enriched flour mix with potential of combating vitamin A deficiency (VAD) in the country.

Materials and methods

Materials

Freshly harvested OFSP (Ipomoea batatas) and bunches of ripe sweet bananas (Musa acuminate) were transported to the food processing laboratory in sacks and Ife brown variety cowpea (Vigna unguiculata) were procured from a local vendor in Omu-Aran, Nigeria. Table 1 shows the proximate analysis of the raw materials used for production of sweet potato-cowpea-banana blends.

Production of sweet potato-cowpea-banana blends

Sorted cowpea seeds were weighed (5 kg) and soaked in 10 L of potable water for 6 h. The soaked seeds were drained, manually dehulled, and washed under running water. Four (4) kg of cleaned dehulled cowpea was steamed in 2 L of boiling water for 15 min, allowed to cool and dried in a hot air oven for 12 h at 60 °C, and kept for further processing. Washed and peeled OFSP tubers were diced (3 mm) and dried on stainless steel trays at 60 °C for 12 h2. The modified method of (36) was used for the preparation of dried banana chips. Ripe bananas were peeled, sliced into thin sheets (2 mm) using a slicer; 0.5% (v/w) of fresh lime juice were added to reduce browning of the chips during drying and dried at 600C for 24 h. Eight (8) different formulations of the sweet potato-cowpea-banana (PCB) blends were carried out as shown in Table 2 and properly labeled samples were packaged and sealed in 100 g sachets in triplicates for further analysis. All methods were carried out in accordance with relevant guidelines and regulations. In addition, all experimental protocols were approved by Landmark University ethical committee (LUAC/FSN/SCI/0001).

Acceptability assessment of sweet potato-cowpea-banana blends

Eight sweet potato-cowpea-banana blends flour samples were prepared into porrigde. The porrigde samples were prepared Blended sweet potato, cowpea, and banana Reconstituted porridge was made by mixing 50 g of flour with 250 mL of portable water, then adding boiling water and stirring constantly until gelatinization took place. and 50 ml randomly served in a labelled cups to 60 members of a panel conversant (nursing mothers) with commercial complementary food in coded plates, for evaluation using a 9 point structured Hedonic scale with 9 synonymous to like extremely and 1 dislike extremely. The colour, appearance, aroma, smoothness, and overall acceptability were assessed and scored. Inclusion criteria requires the recruited panelist must be a nursing mother or mothers with toddlers within the ages 6 months to 5 year. The participation is voluntary coupled with willingness to participate, availability and freedom from food allergies. Panelist must be familiar with the raw materials used for production and the final product. Those who participated in sensory tests are willing to use product as potential consumers based on their acceptability. While those who did not meet the inclusion criteria were excluded as well as those subjects who have prior technical knowledge of products or projects were not allowed to participate in sensory testing31.

Colour analysis of sweet potato-cowpea-banana (PCB) blends

Using a bench-top spectrophotometer Colorflex-EZ (A60-1014–593, Hunter Associates, Reston, VA, USA); colour of sweet potato-cowpea-banana (PCB) blends were measured in terms of lightness (L*) and color values (+ a: red; -a: green; + b: yellow; -b: blue) as described by36.

$${\text{Hue angle }}\left( {{\text{H}}*} \right) \, = {\text{ arctan }}\left( {{\text{b}}*/{\text{a}}*} \right)$$
$${\text{Chroma}}, \, \left( {{\text{C}}*} \right) \, = \sqrt {{\text{a}}^{2} + {\text{b}}^{2} }$$
$${\text{Hue}}\;{\text{angle}} = \tan^{ - 1} \left( {{\text{b}}/{\text{a}}} \right)$$
$${\text{Total}}\,{\text{color}}\,{\text{difference}}\left( {\Delta {\text{E}}*} \right) \, = \sqrt {\left( {\Delta {\text{L}}*} \right)^{2} + \left( {\Delta {\text{a}}*} \right)^{2} \left( {\Delta {\text{b}}*} \right)^{2} }$$

Differences of L*, a* and b* were used to calculate the changes in different color attributes of samples.

$$\Delta {\text{L}}* \, = L* \, - \, L$$
$$\Delta a* = a* - a$$
$$\Delta b* = b* - b$$

where L, a, b is color component values of control. The following values were used to determine if the total color difference was visually obvious36.

∆E* < 1 = color differences are not obvious for the human eye.

1 < ∆E* < 3 = color differences are not appreciative by the human eye.

Sweet potato-cowpea-banana (PCB) blends proximate composition determination

Sweet potato-cowpea-banana (PCB) blends proximate composition was determined using the procedure of AOAC, (2019) for crude fat, protein, fiber, ash, and moisture contents. Total carbohydrate was calculated by difference and calorific value were calculated and documented in kJ/100 g.

β-Carotene and lycopene estimation in sweet potato-cowpea-banana blends

Beta-carotene and Lycopene of sweet potato-cowpea-banana (PCB) blends were determined using dried methanolic extract Olaniran et al.37. 100 mg of extract was mixed with 10 ml of an acetone-hexane mixture (4:6) for 1 min and filtered. The absorbance was recorded at three different wavelengths 453, 505, and 663 nm respectively, and calculated using the formula:

$${\text{Beta}} - {\text{Carotene }}\left( {{\text{mg}}/{1}00{\text{ml}}} \right) \, = \, 0.{\text{216 X A663 }}{-} \, 0.{3}0{\text{4 X A5}}0{5 } + \, 0.{\text{452 X A453}}$$
$${\text{Lycopene }}\left( {{\text{mg}}/{1}00{\text{ml}}} \right) \, = - 0.0{\text{458 X nA663 }} + \, 0.{\text{372X A5}}0{5 } - \, 0.0{8}0{\text{6 X A453}}$$

where A = absorbance.

Sweet potato-cowpea-banana (PCB) blends Vitamin A quantification

One (1) gram of sweet potato-cowpea-banana (PCB) blends samples were homogenized and saponified with 5 ml of 12% alcoholic potassium hydroxide in a water bath for 30 min at 60 °C. The saponified extract was transferred into a separating funnel and thoroughly mixed with 15 ml of petroleum ether. The lower aqueous layer was transferred to a new separating funnel followed by a collection of the upper petroleum ether layer containing the carotenoids. Extraction was repeatedly done till the aqueous layer became colorless. Anhydrous sodium sulphate was added to the petroleum ether extract to remove excess moisture. The absorbance of the yellow color was read in a spectrophotometer at 460 nm using petroleum ether as blank. The quantity of Vitamin A (beta-carotene equivalent) was calculated as 1 IU Vitamin A = 0.6 μg β-carotene, 1 IU Vitamin A = 0.3 μg vitamin A38.

Pasting properties of sweet potato-cowpea-banana blends

Pasting properties were determined using Rapid Visco Analyzer (RVA). Three (3) grams of sweet potato-cowpea-banana (PCB) blends were weighed into a test canister and distilled water (5 ml) added. The paddle placed in the canister and the slurry was vigorously jogged using a blade as the analysis proceeds and terminated automatically. The heated slurry from 50 to 95 °C was allowed to cool to 50 °C by the thorough continuous stirring of the content using a plastic paddle within 12 min rotating the can at 160 rpm. Peak viscosity, setback viscosity, final viscosity, pasting temperature, pasting time, trough, and breakdown value were estimated39.

Water absorption capacity of sweet potato-cowpea-banana-blends

Water absorption capacity (WAC) of the sweet potato-cowpea-banana (PCB) blends sample was determined by weighing 0.5 g of the sample dissolved in 10 ml of distilled water in centrifuge tubes and vortexed for 30 s. The dispersions were allowed to stand at room temperature for 30 min, centrifuged at 3000 rpm for 25 min. Fitration of resultant supernatant through filter paper (Whatman No 1) was carried out and volume recovered was correctly measured. Calculation of differences between initial volumes of distilled water added to the sample and the volume obtained after filtration was recorded. The results were reported as mL of water absorbed per gram of sample (ml/g)31.

Statistical analysis

Analyses of the samples were conducted in triplicates. Analysis of variance (ANOVA) and Duncan's multiple range tests (P < 0.05) were conducted using IBM SPSS Statistics 22.

Informed consent

Informed consent was obtained from all participants for this study.