Sensory acceptability and nutritional quality of composite bread with added puree from biofortified beans in Malawi

Of late, the global supply of wheat is increasingly becoming lower and lower due to the continuing Russia–Ukraine war, blockages of major seaports as a result of the war and climate change. Importing countries are hardest hit as prices skyrocket. Millions of people relying on bread as staple food are affected in multiple ways. New methods to prepare composite bread that meets sensory and nutritional needs of consumers are needed to help address the problem. This study modified the standard recipe and developed bread with 20%, 30% and 50% of the wheat flour substituted by puree from NUA 45 biofortified beans. Ascorbic acid was added to improve the functionality of the yeast and the quality of the bread. Testers rated the 20% bean puree bread as the most acceptable. The appearance, flavour and taste imparted by the bean puree and lemon juice were the major sensory attributes for acceptance, accounting for over 65.79% of the variance in the principal component analysis. Although the test bread was slightly denser than the traditional one with 100% wheat flour, the bean puree enhanced the nutritional quality with average proximate values of protein found to be 1.66 ± 0.18, fat 7.42 ± 0.36, carbohydrates 57.19 ± 0.27, iron 2.04 ± 0.03 and zinc 2.25 ± 0.02 per 100 g of sample. The study concludes that puree from beans can be used to replace 20%–30% of wheat flour in bread making. The bread can be an option for people interested in variety, heavier meals and nutrition.


| INTRODUCTION
Bread is staple food everywhere in the world.Projections suggest that sub-Saharan Africa (SSA) will be importing 35.4 million tons of wheat by 2050 to make bread and other products.Currently, supplies of wheat and other grains are affected by global economic recession, Russia's invasion of Ukraine and blockages of the Black Sea ports as a result of the war, all of which are constraining shipment of the commodity to importing countries.Climate change is an additional factor.
Wheat productivity has reduced in large growing areas by 5.5% due to climate change (CIMMYT, 2023).It is estimated that production will further decline by 1.9% by mid-century.Net importers and lowincome countries will continue to be disproportionately affected.
The market prices of bread in Malawi, for example, have increased from US$0.21 per loaf in early 2020 to US$1.54 now.Additional and frequent price hikes are anticipated in the months and years to come.
Bread is eaten regularly for breakfast, lunch and dinner.It is prepared in various sizes, textures and tastes to match eating styles of different consumers.Various types of bread form part of the menus in restaurants, banquets and conferences.They have an added advantage of being eaten by people of different cultures, ethnicity and age.
Brown bread is a recommended food for people with diabetes.The rising cost of wheat and bread therefore has negative eating and nutrition implications for millions of people.
Beans are an underutilized crop despite their abundance and nutritional importance in diets (Agyekum et al., 2023).Traditionally, in the majority of African countries, beans are regarded as the poor man's meat because most of the rural people who cannot afford meat get their protein from them.Beans are also daily relish for captive people such as students in boarding schools and inmates in prisons.
Utilization at household level is limited by long cooking times, inadequacies of fuel wood and monotony as the beans are in most cases only eaten as relish after boiling (Mwangwela et al., 2021).The problem is compounded by lack of recipes, processing techniques and knowledge of how to add value and make various products.Currently, bio-fortified beans are largely eaten in the same geographical areas where they are produced because they are unprocessed and bulky to transport to other areas.Nevertheless, there are other ways in which beans can be prepared to increase their value.Fresh and dry beans can be boiled and mashed into puree or transformed into flour for instance.These primary products can be used as ingredients to replace some of the wheat flour in a range of popular and value-added bakery products.
In this way, we can begin to increase variety of breads and commercialize the beans to make them more available to urban consumers who are net buyers of food, which could in turn help increase income and combat widespread protein and micronutrient deficiencies.To date, the vast majority of the studies on bread have tended to focus on orange flesh sweet potatoes (OFSP) rich in β-carotene, which is converted into vitamin A in our bodies (Awuni et al., 2018;Wanjuu et al., 2019).It is widely accepted that OFSP can replace 30%-60% of the wheat flour in bread doughs.Consumers like the sweetness, orange colour and flavour of such breads.Other studies have investigated composite breads from wheat and legumes in general (Kamoto et al., 2018;Makinde & Akinoso, 2014;Ndife et al., 2014), common or soy beans (Bouhlal, Taghouti, Benbrahim, Benali, Visioni and Benba, 2019;Ramírez-Jiménez, Gaytán-Martínez, Morales-Sánchez and Loarca-Piña, 2018;Ukeyima et al., 2019) and cassava (Aryeetey et al., 2019;Chisenga et al., 2020).
There remains a paucity of studies on bread from biofortified bean flour and puree in the scholarly literature.If not developed properly, products with bean flavours and off-colour may be deemed unacceptable by consumers.Conversely, if done well and scaled up, such breads can help address micronutrient deficiencies given that biofortified beans are available and bread is consumed culturally as part of the everyday diet in a number of countries of the world where the problem is largest.The present study aims to assess sensory and nutritional quality of the wheat bread with puree from biofortified beans to increase variety and nutrition in view of the rising cost of wheat.The results will benefit nutrition practitioners, researchers, rural and urban consumers and the bakery sector in their quest to explore ways of making bread a more functional, nutritious and universally consumed food product.

| Study area
Sensory acceptance sessions and laboratory analysis of the samples were conducted at Lilongwe University of Agriculture and Natural Resources (LUANAR) in Malawi.

| Formulations for the wheat-bean puree bread
The study developed different formulations of bread with 50%:50%, 70%:30% and 80%:20% wheat to bean puree ratios.No bread is made from wheat and bean for commercial use currently in Malawi and the majority of the countries, which necessitated the trials.Test bread samples developed were becoming denser in texture and colour as the amount of bean puree increased in the recipe.Breadmaking qualities are largely dependent on wheat gluten, consisting of two major proteins, gliadins and glutenins, which are responsible for the strength and elasticity of the dough (Biesiekierski, 2017).Gluten is formed when water is mixed with the wheat flour.Adding water to the dry wheat flour causes gliadin and glutenin to become flexible and begin to stick to each other.When this happens, they form gluten-a very stretchy and elastic substance (Biesiekierski, 2017).
The stretchiness and elasticity of gluten, and its ability to trap small pockets of air, make it useful in bread making.Gluten is almost absent in the beans.

| Procedure for developing the bread
The study followed a standard recipe by Kamoto, Kasapila and Manani (2018), with minor modifications.These researchers used amaranth and not bean puree in their bread.Ingredients used in this study were wheat flour (three portions), puree from biofortified beans (20%, 30% and 50% of the wheat flour), liquid (one portion scalded milk to facilitate growth of the yeast), white baker's yeast (6 g), sugar (10% of the flour), salt (2 g, too much salt produces a heavy bread due to excessive inhibition of yeast) and a spoonful of fat (32 g).The straight dough method was used to prepare the bread.This involved blending all the ingredients for 5 min in a mixer into a dense and pliable dough.From Figure 1b, effects of not adding lemon were seen to be cracks on the bread crumbs, uneven shapes (e.g., the sample in the middle), increased crust thickness and reduced loaf volume when compared with the samples with same formulations containing ascorbic acid (Figure 1a).The sample with 50% bean puree also had the brownness concentrated on the centre of the bread (e.g., the third sample at the bottom in Figure 1b), denoting poorly leavened doughs as the amount of bean puree increased.
F I G U R E 1 (a) Test bread made with 20%, 30% and 50% bean puree and 25% lemon juice.(b) Test bread samples made with 20%, 30% and 50% bean puree and no lemon juice.

| Modifications to the recipe
The main objective of the study is more on finding solutions to the scarcity and increasing prices of wheat flour than to come up with new methods for bread making.However, the study made minor modifications to the method by Kamoto et al. (2018) by including ascorbic acid (Table 1) to improve the functionality of yeast and quality of the composite bread.Yeast is a leavening and oxidizing agent.It adds strength to the dough, gives rise to it and creates a more open and airy texture in the bread.Yeasts are generally acidophilic organisms and, as such, grow better under acidic conditions.No commercial bread uses ascorbic acid currently because wheat flour on its own results in the bread with desired qualities.

| Nutrient analysis
Bread samples were analysed to proximate the amounts of protein, fat, carbohydrates, iron and zinc based on the ingredients and recipes used.The Chemistry Laboratory at Lilongwe University of Agriculture and Natural Resources (LUANAR) conducted the analysis using the AOAC official procedures.Each sample was analysed in three replicates to increase efficiency of the results.All chemicals were analytical grade.

| Descriptive analysis of the test bread
Descriptive analysis was done according to the procedure by Lawless and Heymann (2010).Twelve testers (six females and six males), familiar with bread, assessed and described sensory attributes.The bread with 20% puree and ascorbic acid was used for sensory evaluation because it had qualities that resembled the traditional bread that testers are already used to.The descriptors used are presented in Table 1.

| Acceptability test used in the study
A total of 245 consumers rated their acceptability of the bread.The hedonic rating scale used ranged from 1 like a lot to 5 dislike a lot.
Testing sessions took place, from 10.00-12.00 and 14.00-16.00hours when testers were not full or hungry, between June and July 2023.Each tester participated in a single session and tasted the bread once.People often eat bread with beverages like tea and soft drinks.The study used hot tea as a carrier.It was very suitable also because it is winter during this time in Malawi.

| Statistical analysis
Data were entered and analysed in SPSS (version 20).Sensory data were subjected to analysis of variance (ANOVA) followed by Tukey's least significant difference (LSD) test to compare treatment means, with differences considered significant at 95% level (P ≤ .05).Correlation coefficient were determined to establish relationship among variables.Principal component analysis (PCA) was performed to determine main factors in the acceptance of such bread.

| Description of the test bread samples
Table 2 presents details on bean puree, puree-water ratios and ascorbic acid used in the samples of test bread.The table also provides information about weight, height, length and width of the bread.Samples with 50% bean puree were more brown and denser than the other formulations.Ascorbic acid in lemon juice improved the ability of the dough to retain gas and rise faster (evidenced by increased oven spring and expansion), and this resulted in bread with finer cells.It also helped to yield bread with greater loaf volume, reduced crust thickness and softer crumbs when compared with the other formulations.The juice additionally incorporated flavour and vitamin C to the bread.Freshness contributed to the general acceptability also, given that bread is a hot food.

| Descriptive and consumer tests
Of the 245 participants, 143 male and 102 female, involved in the consumer test, 232 (136 male and 96 female, e.g., 95%) liked the bread for the same reasons as cited by the panel for descriptive test (Figure 3).There was no tester who entirely disliked the bread a lot.Nevertheless, the study observed sex differences (P < .05) in the preference of the bread.Male consumers were more likely to show Bread width (cm) 9.5 cm 9.5 cm 9.5 cm 9.5 cm 10 cm 9.5 F I G U R E 2 A biplot from principal component analysis (PCA) showing two major sensory considerations for the acceptance of the test bread.These considerations, based on individual attributes scattered in the rotated space of the biplot, largely relate to taste (top right plot) and appearance (top left plot).They contributed 65.79% of the total variance when the extraction method was performed in PCA.Ivanovski et al., 2012;Kure et al., 2021;Malavi et al., 2022;Otegbayo et al., 2018;Ukeyima et al., 2019).These breads are an option for people interested in variety, heavier meals and nutrition.At home, the wheat-bean bread studied can be improved by adjusting ingredients in the recipe to suit texture needs, while at the same time maintaining sensory and nutritional quality.Various types of improvers can help optimize quality at the commercial level, which together with promotional activities could help increase demand.

| Nutritional quality
This study has shown that puree from beans can be used to replace 20%-30% of wheat flour in bread making.The overall cost to the bakers is estimated to be 12%-20% lower.Commercially prepared white bread on the market in Malawi has iron content of 1.19 mg/100 g and zinc at 0.99 mg/100 g on average.The nutritional information for bread varies by brand and type, as do the number of Results from the consumer study by testers 19-52 years of age.
T A B L E 3 Results for proximate analysis of the wheat bean bread per 100 g of the sample.calories.The mounts of iron and zinc in the test bread (20% bean puree with ascorbic acid), in grams per 100 g of sample, was 2.04 ± 0.03 and 2.25 ± 0.02, respectively.NUA 45 bean puree contributed to the higher amounts observed.
Iron, zinc and protein deficiencies are of major public health concern in Malawi and other developing countries.High rates of deficiencies mean that the current diets are lacking and need to be diversified and varied.The test bread can help address the problem.
Available studies have presented mixed results on the amounts of iron and zinc in biofortified beans.Hoppler et al. (2014) found iron of 53.3 ± 1.4 mg/100 g in NUA 45 beans.Carvalho et al. (2012) reported iron and zinc to be around 7.4 mg/100 g and 3.2 mg/100 g after cooking the beans respectively.A study by Beebe (2020) in Rwanda found 5.5 mg/100 g and 1.7 mg/g zinc in raw beans.These differences are due to variations in climatic conditions and soils.NUA beans, like any other biofortified crops, are not loaded with the nutrients in advance.They are bred to absorb them from the soil on their own.
Bean puree also contributed to macronutrients.Protein (1.66 ± 0.18), fat (7.42 ± 0.36) and carbohydrate (57.19 ± 0.27) were all high per 100 g of bread sample (Table 3).Two and four slices, which children and adults eat, mean doubling or quadruplicating these figures.A standard whole wheat bread is relatively high in protein, fat and carbohydrates already.One bread sample taken at random from the market, for instance, showed to have 0.8 g protein, 1.7 g fat and 48.9 g carbohydrates per 100 g of portion.However, in a population with low intake of these nutrients from other sources and where bread is a staple food, the enrichment is of great economic and nutritional importance.

| CONCLUSION
The study faced limitations typical of sensory studies, for example, the inability to control positive bias in reporting acceptability of new products.Testers recruited, like consumers in the general population, are used to the traditional bread made from wheat only.The extent to which they can bake or buy and consume composite bread of wheat and bean puree in real-life situations remains unknown.Further innovations, research and commercialization efforts are needed to increase uptake.Regarding product development, the study has shown that ascorbic acid in lemon juice has the potential to increase quality of the wheat-bean bread by enhancing acidic conditions under which yeast functions.The benefits are many for researchers, bakers and consumers.However, given that it is not currently one of the best practices to add ascorbic acid to the ingredients as wheat flour on its own gives bread with desired qualities, there is need for more research to understand how best to do it.Suitable amounts, stages, acidity levels and temperatures required need to be investigated.Oxidising, antioxidant and shelf life properties of the bread after the addition of ascorbic and other food acids should also be researched into to standardise recipes for making such bread.The nutrient profile of the bread will differ within and across countries because biofortifed bean varieties vary in the way they load up nutrients due to disparities in weather and soil conditions.
Researchers from the Pan-African Bean Research Alliance (PABRA) under the Alliance of Bioversity and International Center for Tropical Agriculture (CIAT) and the Department of Agricultural Research Services (DARS) have released various biofortified beans to address micronutrient deficiencies in Malawi.These varieties include Chitedze BN 8 (NUA 45), Chitedze BN9 (NUA 59) and Chitedze BN 12 (NUA 35).Chitedze BN 8 (NUA 45) and Chitedze BN 9 (NUA 59) were released in 2009 and Chitedze BN 12 (NUA 35) in 2017.The present study used the NUA 45 variety.
Kneading was then done to help mix the ingredients and develop gluten.Kneading continued until blisters showed on the dough when folded over.As the yeast fermented, the dough rose and doubled in size following production of carbon dioxide by the yeast.The risen dough was punched down, left to rise a second time, shaped and proofed for 40 min.The proofing allowed the shaped dough to undergo further fermentation and final rising while in the pan to increase its volume and quality.Yeasts are very sensitive to temperature extremes.Optimal fermentation temperatures of between 25 C to 38 C were used during all the stages of fermentation.The dough was baked at 230 C for 20-25 min, for example, when a pleasing brown colour developed.The bread was removed from the oven and allowed to cool in readiness for sensory evaluation and nutrient analysis.Figure 1a,b shows samples of the bread.

Figure 2
Figure2shows a biplot from PCA for the descriptive test conducted by 12 panellists aged 22-38 years.The panellists described the 20% bean puree bread with ascorbic acid used in the sensory evaluation as a medium brown, denser and flavourful bread, with a unique taste and flavour that made it pleasantly different from the traditional white bread available on the market.NUA 45 beans are brown in colour, and this was depicted in the bread.The volume and quality were good also due to appropriate amounts of sugar, milk and shortening added.
T A B L E 1 Descriptive test attributes for the test bread.i.e. smaller, more even cells and bubbles) acceptability of the test bread than their female counterparts in particular those in the age groups of 21-32 years.The difference can be attributed to sensory preferences and eating styles of young women who tend to be selective in their food choices.Denser textures were due to a reduction in the amount and functionality of gluten, particularly in samples without ascorbic acid.Studies that have substituted wheat flour with other ingredients have reported similar results(Bibiana et al., 2014;Chikpah et al., 2021;    T A B L E 2 Composition, weight, length, height and width of the bread samples. N stands for the number of replicates; **Values expressed as average means ± standard deviation of the three replicates.Within a column, values with the same superscript are not significantly different at 95% level of significance (Tukey test).CHO means carbohydrates.***Values for wheat flour are from the nutritional information panel on one of the packages taken from the local market in the country. *