Development and characterization of bread from wheat, banana (Musa spp), and orange-fleshed sweet potato (Ipomoea batatas L.) composite flour

Abstract Malnutrition is a major challenge in Ethiopia. On the other hand, there is high production of banana and orange-fleshed sweet potatoes in the northern part of Ethiopia. However, it is exposed to postharvest loss without value addition to them. This study aimed to characterize bread developed from wheat, banana, and orange-fleshed sweet potato composite flour. The bread was developed with different proportions of wheat, banana, and orange-fleshed sweet potato flour in the ratio of 100:0:0, 90:5:5, 80:10:10, 70:15:15, and 60:20:20, respectively. The value of moisture%, ash%, crude fiber%, crude fat%, and β-carotene µg/100 g was in the range of 7.92–11.23, 1.76–3.66, 1.99–6.43, 1.13–3.20, and 0.13–73.51, respectively, whereas the content of crude protein and carbohydrate and caloric values were in the range of 8.08–11.02%, 67.36–76.27%, and 330.56–359.33 kcal/100 g, respectively. According to the sensory scores, bread composite flour containing (60:20:20) wheat, banana, and orange-fleshed sweet potato was preferred. Based on the result of this finding, it is better to produce bread from wheat, banana, and orange-fleshed sweet potato composite flour than usual wheat flour bread. The results showed that the incorporation of banana and orange-fleshed sweet potato powder can improve the ash and β-carotene content of bread.


PUBLIC INTEREST STATEMENT
Orange-fleshed sweet potato contains vital nutrients, but despite its potential, it is still viewed as a poor man's food.Banana is one of the most widely consumed fruits in the world.The perishable nature of bananas is a major problem for farmers.To overcome such problems, value addition such as bread helps reduce postharvest losses.
Results of this study showed that orangefleshed sweet potato has higher β-carotene and sources of energy, which could help in the reduction of vitamin A deficiency, which helps to prevent night blindness.Banana is also rich in energy and minerals, and its product could be a source of energy and mineral that makes flour a promising raw material for calorie-rich food for children and adults that help solve malnutrition problems.Therefore, the incorporation of banana and orange-fleshed sweet potato flour can improve the nutritional composition and sensory acceptability of bread that help to solve the food malnutrition problem.
wheat, banana, and orange-fleshed sweet potato was preferred.Based on the result of this finding, it is better to produce bread from wheat, banana, and orange-fleshed sweet potato composite flour than usual wheat flour bread.The results showed that the incorporation of banana and orange-fleshed sweet potato powder can improve the ash and β-carotene content of bread.

Introduction
Ethiopia's high rates of malnutrition are a serious obstacle to the country's economic and social progress.Poverty and a family's limited purchasing capacity are two major causes of malnutrition among children and workers (Nigusse et al., 2019).In Ethiopia, vitamin A deficiency and proteinenergy imbalance are major issues.
Bread is made from dough made of flour and water and is typically baked.It is one of the most popular foods throughout the world (Onoja et al., 2011).In Africa, particularly in Ethiopia, lack of macro and micronutrients has a major impact on people's health.Because the cost of imported wheat is prohibitive for developing nations since bread is essential for daily snacks, bread production is highly dependent on wheat; therefore, it is essential to use locally available resources in addition to wheat (Nwanya & Okonkwo, 2018).The need for nutrient-dense products is rising today.Similarly, to this, interest in underutilized crops has grown to boost global food and nutrition security (Zula et al., 2020).
The primary purpose of the composite flour is to produce baked products from locally available resources, mainly in a country that was unable to meet its own wheat requirements.Utilizing a variety of flours, inexpensive local raw materials, and composite flour technology creates highquality food items (Nwanya & Okonkwo, 2018).
Wheat is a major source of carbohydrates and vegetal protein (13%) in human foods.It has high value of carbohydrates and protein compared to other major cereals, but it is relatively low in vitamin A and mineral content (Kim et al., 2019).Wheat is a source of numerous minerals and dietary fiber when consumed whole.Functional proteins contain glutenin and gliadin, which are found in wheat and used for structure formation of bread.Wheat-based bread is frequently consumed.However, the expensive price of imported wheat and wheat's restricted nutritional profile cause people to consider other raw materials with better nutritional profiles to supplement wheat for bread production (Zula et al., 2020).
Orange-fleshed sweet potato (Ipomoea batatas L.) has an advantage over most vegetables in that it is a staple diet.It is one of the vital root vegetables full of dietary fibers and bioactive substances like carotenes, as well as considerable amounts of several other functional elements with key health-promoting effects (Neela & Fanta, 2019).Due to the orange-fleshed sweet potato and its products' growing popularity as a significant source of naturally occurring antioxidants with anticancer properties, consumption of these foods is rapidly rising.Orange-fleshed sweet potatoes include free fructose, glucose, and sucrose (Nigusse et al., 2019).
It is the greatest tuber source of provitamin A and an excellent source of antioxidant compounds.The provitamin A precursors, sometimes referred to as provitamin A, are present in plantbased meals like tubers, fruits, and vegetables.As a result of diversity and environmental factors, β-carotene levels fluctuate.It generally ranged between 10 and 26,000 μg/100 g (Vimala et al., 2011).
Banana (Musa spp.) is an important staple crop for millions of people in developing countries.Its carbohydrate ranges from 22% to 32% of the fruit's weight and is a great source of energy.It contains plenty of minerals, including calcium (8 mg/100 g), potassium (385 mg/100 g), magnesium (30 mg/100 g), and phosphorus (22 mg/100 g), as well as vitamins A (68 µg/100 g), B6 (470 µg/100 g), and C (11.7 mg/100 g) (Ashokkumar et al., 2018).Because banana fruit is perishable, post-harvest loss is a major concern.Value addition is important to lower post-harvest losses of this crop; hence, it is preferable to use in the form of other products like bread to solve this issue.There have been reports of banana flour being made from unripe flour.Some researchers have reported making banana flour from unripe fruit (Adeniji & Adeniji, 2015).
Generally, orange-fleshed sweet potatoes are inexpensive in Ethiopia and have higher levels of β-carotenes, which are critical for preventing vitamin A deficiency or night blindness.On the other hand, banana fruit can offer a substantial amount of minerals and is also inexpensively available locally.Protein can be found in wheat.In the contemporary world, composite flour products are superior to single-flour products.Different raw materials combined can offer their benefits in terms of nutrition and organoleptic.Therefore, the aim of this study was to develop and characterize bread made from wheat, banana, and orange-fleshed sweet potato composite flour.Furthermore, the study evaluates the properties of the developed bread in terms of sensory evaluation, proximate, and β-carotene composition.

Raw materials
All necessary raw materials including wheat flour, banana, orange-fleshed sweet potato (OFSP) tubers, salt, oil, sugar, and yeast were collected and obtained from a market of Bahir Dar and were transported to Bahir Dar Institute of Technology.All necessary equipment's such as mixers, blenders, kneaders, bowls, knives, digital scales, graduated cylinders, boilers, baking pans, ovens, Soxhlet, Kjeldahl, and ovens were sourced from the Food Engineering laboratory.All other chemicals used were from analytical chemistry laboratories.

Preparation of OFSP powder
Matured and fresh orange-fleshed sweet potato tubers were selected and cleaned with water.Cleaned FSPs were peeled using a knife.Peeled OFSPs were sliced.The peeled sample was blanched at a temperature of 65°C for 10 min in a water bath.The purpose of blanching is to maintain flavor, color, and texture by controlling enzymatic activity.The blanching also removes some dirt and microorganisms on the surface.The blanched slices were dried in an oven at 50°C for 24 h.The samples were milled into flour using a laboratory mill (Model R 23, robot @ couple).The flour was sieved using a 500 µm sieve.The powder was packed properly using a polyethylene bag and stored in a cold place.

Banana flour preparation
The ripened banana was cleaned with water to remove impurities.The fruits were peeled and cut with the aid of a knife into uniform sizes.Bananas underwent hot water treatment (95°C for 5 min) to control microbial growth and undesirable reactions.It was dried at 60°C for 24 h using an oven.A sample of dried banana fruit was ground and sieved through a 700 µm sieve.Finally, the banana powder was packed in a polyethylene plastic bag.

Formulations of composite flour and recipes
The formulation of blended flour was formed depending on some major factors of bread characteristics.The amount was standardized in the laboratory by conducting many preliminary experiments as well as in consultation with documented literature.Bread is mainly produced from hard wheat, which is one of the major raw materials, and the flour provides more elastic and texture.Three different flours such as wheat, OFSP, and banana flour were mixed in different ratios: (100, 0, 0), (90, 5, 5), (80, 10, 10), (70,15,15), and (60, 20, 20)%, respectively.

Development of wheat, OFSP, and banana composite flour bread
All necessary baking instruments and procedures were checked before the experiment started.The flours of wheat, OFSP, and banana were blended in different ratios: (100, 0, 0), (90, 5, 5), (80, 10, 10), (70,15,15), and (60, 20, 20)%, respectively.Other ingredients were added based on standard formulas.The ingredients include 28 g/100 g of cooking oil, 1.12 g)/100 g of baking powder, 5 g/100 g of sugar, 1 g/100 g of salt, and 48 mL of water.The flour was mixed and dough was developed by hand.It takes a total of 20 min to mix.The resulting dough was manually stretched into a 5-mmthick film.It was cut into 48-mm-diameter pieces before being placed on a lightly oiled baking sheet.The bread was baked in an oven at 200°C for 12 min (Saric et al., 2014).

Moisture content
Moisture content of flour and bread was carried out using AOAC (2005) method.Two grams of sample of flour was placed in a crucible.The sample was dried at 103°C for 24 h in the oven.A desiccator was used to cool the crucible, and its contents and its weight were recorded.Then, moisture content of the sample was determined using the following formula: Where: W-Mass of dish, W1-mass of dish plus sample before drying, and W2-mass of dish plus sample after dry

Ash content
The ash content was measured using AOAC (2005) method.Five grams of sample was measured into a crucible, and the samples were burned at 550°C using muffle furnace until light grey was observed and a constant weight was produced.Samples were cooled in a desiccator to prevent moisture absorption.The samples were then weighed to determine the ash concentration.Ash content is determined as follows: Where: w-Weight of crucible, w1-Weight of crucible and sample, and w2-Weight of crucible and sample after drying.

Determination of protein
The protein content of the sample was measured using micro-Kjeldahl method (AOAC, 2005).Two grams of wheat sample were added to the digestion flask.One gram of catalyst (copper sulphate and sodium sulphate) in a ratio of 1:10 was added.Then, 5 ml of concentrated sulfuric acid was added to the digestion flask.The flask was placed on a fume hood digestion block and heated until the frothing stopped, becoming clear and slightly blue-green.The mixture was cold and diluted with 30 mL of distilled water followed by the addition of 30 mL of 40% NaOH.A distillation apparatus was installed.Boric acid was used for liberation of ammonia and then treated with 0.01 M hydrochloric acid until green color changed to purple.Nitrogen content was determined using the following formula: Where: V-Volume of HCl, N-Normality of HCl about 0.01 N, and molecular weight of nitrogen ( 14) Protein (%) = F × %N Note: Conversion factor is 6.25 (F)

Determination of crude fat
The fat content of flour and bread was determined by Soxhlet extraction method (AOAC, 2005).About 2 g of the sample was measured, and the mass of the flat bottom flask was taken with the extractor mounted on it.The thimble that held the sample was far away from the extractor.Extraction process was performed at boiling point 40-60°C and the solvent was removed after 3 h of extraction.Then, evaporate in an oven and dry the remainder in the flask at 70°C.The fat was dried in the oven for 30 min and cooled in a desiccator.The flask was remeasured, and the fat percentage was calculated as follows:

Determination of crude fiber
The fiber content was determined using AOAC (2005) method.A 5 g flour and bread sample was measured and placed into a 500 ml Erlenmeyer flask.Then, 100 ml of TCA digestion reagent was added.After the boiling began, it was refluxed for 40 min.Then, it was cooled slightly and filtered with a 15.0 cm number 4 Whitman filter paper.The residue was washed using hot water and transferred to a porcelain dish.The samples were dried at 105°C overnight.After drying, it was transferred to a desiccator, and the weight was set to W1.Then, it was fired in a muffle furnace at 500°C for 6 h, allowed to cool, and reweighed as W2.
Note: weigh of Crucible after drying (W1) and weight of crucible after ash (W2)

Determination of carbohydrate
The total carbohydrate content (%) of the samples was calculated by taking the difference of 100 and the sum of percentages of moisture, crude protein, crude fat, crude fiber, and ash.

Determination of caloric (energy) value
The total energy was determined by calculating from fat, protein, and carbohydrate, and content using Atwater's conversion factor.Protein is 4, fat is 9, and carbohydrate is 4, expressed in calories.Calorie (energy) Value = 4*CHO + 4*Protein + 9*Fat

Determination of β-carotene content
β-Carotene content was determined using the method of Bibiana et al. (2014).A 5 g sample was weighed into a 250 mL separatory funnel.Then, 2 mL of NaCl solution was added and shaken forcefully, 10 mL of ethanol and 20 mL of hexane were followed.The mixture was shaken carefully for 5 min.It was stood for 30 min before draining the bottom layer.Finally, the absorbance was measured using a spectrophotometer at a wavelength of 460 nm, and the carotenoid content was obtained from the following formula: Where: ∑-Molar extinction coefficient (15 × 10 −4 ), specific extinction efficiency (∑ × molar mass of β-carotene), 536.88 g/mol-Molar mass of β-carotene, and 1 cm-path length of the cell.

Statistical analysis
The analysis was subjected to ANOVA (analysis of variance) and least significant difference (P < 0.05) was used to determine significant differences between means.Statistical analysis was performed using SAS software.

Proximate composition of wheat, banana, and OFSP flours
The composition (moisture, ash, crude fat, crude fiber, crude protein, β-carotene, carbohydrate, and energy values) of wheat, banana, and OFSP flour is shown in Table 1.The three flours' proximate compositions (moisture, protein, ash, fiber, and carbohydrates) vary significantly.The ash (5.5%) and fiber (11.7%)contents of banana flour are slightly higher than those of wheat flour (0.80 & 2.41%) and OFSP powder (4.02 & 10.67%), respectively.In comparison to OFSP (63.29%, 304.14 kcal/100 g, and 6.76%) and banana powder (60.46%, 288.52 kcal/100 g, and 9.90%), wheat flour had the highest levels (69.24%, 344.41 kcal/100 g, and 12.70%) of carbohydrate, energy value, and protein content, respectively.In the current study, wheat has a greater protein content (12.70%) than in the study by Calderón de la Barca et al. (2022), which had a protein level of (11.6%).Compared to wheat and banana powder, orange fleshed sweet potato (OFSP) powder exhibited a greater β-carotene content.Banana flour appears to be superior to wheat flour in ash (minerals) and dietary fiber.Additionally, it seems that OFSP powder raises the levels of βcarotene, carbohydrates, and energy values.

Effect of blending ratio on proximate composition of bread
The entire composition (ash, moisture, fat, fiber, protein, carbohydrate, β-carotene, and energy value) of bread was determined, as shown in Table 2.The amount of banana flour and OFSP powder increases the bread's moisture, β-carotene, ash, fiber, and fat contents.Since banana fruit or flour is high in mineral and fiber content, the ash and fiber levels have increased (Christiana, 2019).Since hydrophilic molecules form banana flour, the moisture content rises as the proportion of banana and OFSP flour increases.The dried banana flour was found to be thermoplastic and highly hygroscopic.This is supported by Saric et al. (2014); bread made from wheat, defatted soybeans, and banana flour.The authors reasoned that the increased moisture content may be due to the increased number of hydrophilic molecules found in the banana flour.The fiber content of bread increases due to OFSP and banana flour rich in fiber because most tuber plants have high fiber content.
The β-carotene content of composite flour bread increased with the increase in OFSP flour because OFSP is rich in carotenoids than wheat and banana flour.It rises from 0.13 to 73.51 mg/ 100 g as the OFSP proportion rises from 5% to 20% in the blending matrix.This value is high in comparison to 0.14-0.45mg/100 g reported by Christiana (2019).
However, as the percentage of OFSP and banana flour in the blending matrix increased from 5% to 20%, the values of protein, carbohydrate, and energy value reduced.The reduction of wheat flour from 90% to 60% in the blending matrix may be the cause of the decreasing of protein content and energy values.With increasing amounts of OFSP and banana flour in the composition, the bread's carbohydrate content decreased as its moisture, ash, fat, and fiber contents increased.
The amount of OFSP and banana flour increases, while that of wheat flour decreases, and as a result, the protein, carbohydrate, and calorie content decreased.With the reduction in wheat flour proportion and increase in banana and OFSP powder proportion, the value of protein, carbohydrate, and energy levels has been reduced.The reduction in carbohydrate content of  bread may be as a result of increases in moisture, ash, fat, and fiber content when the proportion of OFSP powder and banana flour in the formulation was increased, resulting in a decrease in carbohydrate content that is a measured difference.
Carbohydrates are the main source of energy in bread, and the energy value of bread generally has a direct relationship with carbohydrate content.Reducing wheat flour (protein source), increasing OFSP and banana flour can be reasons for the decreasing of protein content.Therefore, OFSP should be added to increase the carotene content.Wheat contains very few vitamin A precursors (Christiana, 2019).OFSP, in contrast, is a rich source of provitamin A, which is the most active form of carotenoids, that has been used for fortification.Nutrient-rich bread can be used to solve the problem of malnutrition.

Effect of blending ratio on sensory properties of bread
The quality of bread can be evaluated by sensory properties.This can be indicated in Table 3.The sensory properties of bread include taste, flavor, color, texture, and overall acceptability.The taste, flavor, and texture of all blended samples are significantly different from the control sample.Adding banana and OFSP flour modifies bread taste suitability score.This is probably due to OFSP powder containing sweet compounds.
The increase in banana flour and OFSP powder contributes in improvement in flavor of the bread.The color and overall acceptability of bread were not significantly different compared to the 100% flour bread (control) (p < 0.05).Texture scores for all breads were not significantly affected (p < 0.05), except for control bread.All samples were insignificantly different from the control in terms of overall acceptability.The sensory properties of flavor, taste, and overall acceptability scores of the bread are enhanced by the addition of both banana and OFSP flour to 20% in the blending matrix in comparison with the control bread.The color of bread enhanced as banana and OFSP flour was added.The improvement of color acceptability in composite flour bread may be the result of attractive color of OFSP.

Conclusion
The higher sensory acceptability of bread can be made by replacing banana and OFSP powder from 10% to 40% of the wheat in the recipe than wheat-based bread.Bread produced from wheat, banana, and OFSP powders has a better proximate composition (fat, fiber, ash (mineral), and βcarotene) than the control wheat-based bread.Based on the current research, bread formulated from wheat, banana, and orange sweet potatoes powder can be promising in terms of nutritional value and acceptability.Developing a more nutritious and sensorially acceptable bread by substituting wheat with locally accessible and low-cost ingredients (banana and OFSP) benefits highyielding native plant species, enables a better supply of nutrient-rich commodities, and expands the overall use of domestic agriculture production.

Table 3 . Sensory properties of the composite bread
Note: Data were means ± SD, n = 3. Mean values not followed with the same letter in a column are significantly different from each other (P < 0.05).