Optimisation of the production process of bread fortified with soya protein ısolate and fonio flour blend

Introduction

Food products made from cereals are significant sources of dietary energy that can supply the nutrient needs of people and boost food security. Bread, a widely available product in Nigeria, is obtained from wheat flour. According to Kent and Evers (1994) [13] , wheat flour is the major component of most breads because of the distinctive visco-elastic dough it forms when mixed with water. Nevertheless, non-wheat flours are also being utilized in the production of good quality bread. The major challenge being faced by the bakery industry is the scarcity and or high cost of wheat flour thus the need to investigate other cheaper and more sustainable cereal flours as substitutes (Thompson et al., 2008) [28] . According to Dewettinck et al., (2008) [7] bread can be described as a fermented confectionary produced majorly from a combination of wheat flour, yeast, water and salt through a process involving mixing, kneading, proofing, shaping and baking. Though the consumption of baked products from wheat flour like breads, biscuits, doughnuts and cakes is very popular these days, the low protein content of wheat flour has continued to be a limiting factor in its usage (Young and Pellet, 2001) [29] . Many authors have reported the use of non-wheat flour in the production of bread, (Edema et al., 2005; Shittu et al., 2008; Mesfin and Shimelis, 2013) [9,27,17] . According to Muller and Krawinkel, (2005), Protein Energy Deficiency (PED) poses a significant nutritional problem as a result of undernutrition affecting people in the developing world.

Policies that have been used to solve protein deficiencies include food diversification, fortification of food with indispensable amino acids, supplementation with good quality protein (FAO, 1997) [10] . The fortification of bread and other cereal-based products with legume flours especially in areas where protein utilization is inadequate has long been recognized because of the high protein content of legumes. According to Okoye and Okaka (2009) [20] , legumes can be used to complement other cereals when blended at optimum ratio. Soybean, of the leguminosae family and Papillionnideae subfamily; is a rich source of essential nutrients containing various chemical compounds that have potent bioavailability. According to Kure et al. (1998) [14] , soybean flour has about 35 -45% protein and is considered an excellent source of high-quality plant protein containing all essential amino acids needed for proper growth and maintenance of body. Many authors have reported success with adding soy flour to bakery products towards increasing the daily soy intake in people's diet (Kure et al., 1998; Murphy et al., 1999; Dhingra and Jood, 2002) [14,18] . Fonio is classified among grasses (poaceae) and ranked in the same subfamily as millet. The species can be white (Digitaria exilis) and black (Digitaria iburu) with local names such as acha and iburu respectively. Fonio grains are very tiny with 1000 weighing between 0.5-0.6g (Adoukonou-sagbadja et al., 2007). Polysaccharides are the main constituent (75%) followed by protein (8-10%) and fat (1%). It is also rich in calcium (20%) and phosphorus (25%) (Jideani, 1994) [12] . Delicacies prepared from fonio include porridges, fonio couscous or injera (spongy fermented flat wholegrain bread). Olapade and Oluwole (2013) [21] also reported that fonio flour can be used as a component in multi-composite flour blends like wheat-fonio-cowpea flour. Nigerians face the challenges of deficiency in protein and shortage of calcium in their daily menu. Most of the bread produced are rich in carbohydrate but with less value in protein. It is therefore important to fortify the wheat flour with legumes (like soybeans and fonio flour) in order to produce nutritionally balanced products. Although much work has been done on fortification of bread, the major thrusts of previous research have been on improving the nutritional properties without recourse to how these inclusions affect the end product in different proportions. Soybean (rich in protein) and fonio (rich in both protein and calcium) crops will therefore improve the nutritional contents of bread if added during production. This study will therefore help to bring to light, effects of the different levels of fortification on the overall quality and properties of the end product. Thus, apart from improving the quality and nutritional composition of the bread, data on the effect of the different inclusion levels will be obtained.

Materials and Methods

Materials

The following were used in the study: Wheat flour (Dangote brand), Soybean, Fonio seeds, Sugar (Golden penny), Margarine (Simas brand, Assar-cozinhar industries Indonesia), baking improver (Batta Baker brand), Dry yeast (SKT-Royal instant yeast) and Salt (Dangote brand).

Methods

Preparation of Soybean Flour

For the preparation of the soybean flour, the method of Otegbayo et al., (2018) [23] with slight modification was used. Fig. 1 shows the production of soybean flour.

Soybean

Preparation of Fonio seed Flour

The method of Coda et al., (2010) [6] was used. The fonio seeds were cleaned. The seeds were weighed, milled and sieved with a 250 µm mesh to get the fonio flour. The flour samples were then stored in polyethylene films until needed. The production process is presented in Fig. 2.

Sorting

Preparation of Soy Protein Isolate (SPI)

The isoelectric precipitation method as described by Petruccelli and Anon, (1995) [24] was used in the preparation of the soy protein isolate. The laboratory work was carried out at STEP B of Federal University of Technology Minna, Niger state. The production process for the soy protein isolate is presented in Fig.

Production of the wheat, soy protein isolate and fonio flour composite bread

The major ingredient (Wheat, SPI and Fonio) gives 52.91% in the formulation while the other ingredients include Water (26.46), Yeast (1.06), Salt (1.06), Granulated sugar (3.18), Margarine (2.12) and baking improver (13.23).

Composite bread baking

The modified straight dough method of Onuegbu et al. (2013) [22] was used in baking the bread. This was carried out at Agricultural and Bioresources Engineering laboratory, FUT, Minna.

Proximate Analysis

The Proximate composition (crude protein, crude fibre, crude fat, ash, moisture content and carbohydrate) of the bread samples was determined based on the method described by the Association of Official Analytical Chemists, A.O.A.C (2012) [4] .

Experimental design

Optimization of the process parameters was carried out using process mixture design. The experimental plan for the mixture consists of three independent parameterswheat flour, fonio flour and soya protein isolate. The experimental plan for the process consists of two independent parameters baking temperature and baking time. The dependent variables are texture, taste, moisture content and colour variables in terms of L*, a* and b* of bread. The independent variables varied using a 2 3 factorial design matrix. The levels of the factorial design are illustrated in Table 1. The experimental layout for the experimental runs is presented in Table 2.

Statistical analysis

The Design Expert Software (version 11) was used to carry out the statistical analysis; this provides test matrices for screening of all the factors in determining the best lines or points of fit, for the purpose of final optimization using a Response Surface Methodology (RSM).

Results

The results of the study are shown in Tables 3,4, 5 and 6 respectively.

Proximate composition of composite bread samples

The result of the proximate analysis of the bread samples is as shown in Table 3.

Optimum condition of composite bread

Table 4 shows the properties of the bread with overall desirability of 0.57. [16] , Ndife et al., (2011) [19] and Otegbayo et al., (2018) [23] ; they all reported an increase in protein content of bread with increase in soya flour. According to Alabi and Anuonye, (2007) and Aly et al., (2012) [2] , legumes having high protein content utilized in composite flour gave an improved quality in the protein content of cereal-based products. The rise in the protein content is expected as a result of the partial replacement of wheat flour with soy protein isolate and fonio flour both of which have high in protein content. The result of the ANOVA (Table 6) showed that the linear and quadratic terms of the model significantly (p< 0.05) influenced the protein content. The mixture of wheat, soy protein isolate and fonio was positive for the protein content, which revealed that increase in the amount of soy protein isolate and fonio led to an increase the amount of protein content of the composite bread. The model F-value of 13.03 implies that the model is significant. The effect of the variables on the protein content are shown in Figures 4 and5.

Fat Content

The fat content ranged from 2.7 to 7.47% with sample 14 having the highest value of 7.47%, while the sample 17 (control) had the lowest value of 2.7% at constant temperature and time of 187.5ºC and 30min respectively (Table 3). There was an increase in the fat content with increase in fonio flour substitution. Ndife et al., (2011) [19] reported an increase in fat content of bread made with composite flour containing soy flour. The result obtained was lower than the one reported by Otegbayo et al., (2018) [23] . Table 7 (ANOVA) shows that the linear and quadratic terms of the model significantly (p< 0.05) influenced the fat content. The mixture of wheat, soy protein isolate and fonio was positive for fat content, which revealed that increase in the quantity of fonio flour led to a rise in the fat content of the composite bread. The model F-value of 5.50 implies that the model is significant. The effect of variables on the fat content are shown in Figures. 6 and7.

Crude fibre

There was a significant decrease (p<0.05) in the crude fibre content as the level of substitution of soy protein isolate increased. Sample 13 had the highest crude fibre content (2.92) with sample 17 (control) having the lowest (1.7). Mesfin and Shimelis, (2013) [17] however reported an increase in fibre content of composite flour comprising of maize and soybean with a comparable increase in the amount of soybean flour. Ndife et al., (2011) [19] also reported a rise in the crude fibre content of composite bread made from whole wheat and soy flour. According to Marer and Martin (2003) [15] , fibre helps in digestion. The effect of variables on the crude fibre content is shown in Figures 8 and9.

International Journal of Agriculture and Food Science https://www.agriculturaljournals.com

Moisture Content

The moisture content ranged between 22.5% and 33.2% (Table 3), with sample 17 (control) having the highest value, while sample 11 had the lowest value. The values obtained for moisture content of composite bread in this study were compared with the values of 12.94% reported by Gbadamosi and Oladeji, (2013) [11] for cassava; 11.08% reported for taro by Amandikwa, (2012) [3] and the value of 4.40% obtained for water yam by Saputri and Joni Kusnadi, (2013) [25] . The results showed that at higher amounts of soy protein isolate and low amounts of fonio flour, the moisture content was lower, while at lower level of protein isolate and higher level of fonio, the moisture content was higher; this shows that the higher level of fonio substitution has significant effect on the moisture content of composite bread produced. According to Bugusu et al. (2001) [5] , the moisture content and water activity of a product majorly dictates the shelf life of the foods.

The fitted linear moisture content model with p<0.05 was significant as indicated in Table 8. The model F-value implies that the model was significant (p<0.05), the table also shows that model terms are significant. This reveals that the goodness of the model for moisture content based on the mixture design makes the model for predicting moisture content as a response valid. Adequate precision quantifies the signal to noise ratio. The effect of variables on the moisture content is shown in Figure 10.

Ash content

The ash content in the samples were between 1.5 and 3.9% (Table 3), with the control having the lowest value and sample 8 having the highest value. A rise in soy protein isolate substitution greatly increased the ash content of the product. Otegbayo et al., (2018) [23] reported a similar trend. The model's linear and quadratic terms of the ash content are significant as shown in Table 9 (ANOVA). The effect of variables on the ash content are shown in Figures 11 and12.

Carbohydrate content

The carbohydrate content ranged between 42.04% and 55.32 (Table 3), with sample 8 having the highest value; while sample 14 had the lowest value. There was a decrease in the carbohydrate content as the amount of soy flour increased. This result agrees with the findings of Sanful and Darko, (2010) [26] and Aly et al., (2012) [2] , who reported a decrease in the carbohydrate content of composite flour obtained by substituting wheat flour with soy flour or chickpea flour at different levels. Table 10 (ANOVA) shows that the linear mixture of soy protein isolate had a significant (p<0.05) influence on the carbohydrate content. The 3D effect of variables on the carbohydrate content are shown in Figures 13 and14.

Conclusion

In this study, composite bread samples were produced with the aid of mixture design. The response surface methodology (RSM) was particularly effective in determining the effect of three independent variables; Wheat (A), Soy protein isolate (B) and Fonio (C) at constant temperature and time of 187.5 o C and 30min respectively on the proximate properties of composite bread. ANOVA indicated that the linear, quadratic and interactive effects of wheat (A), soy protein isolate (B) and fonio (C) significantly (p<0.05) affected all the composite bread properties evaluated. The emperical models fitted to the experimental data showed that the model was significant with the following: 13.03 (protein), 5.50 (fat content), 3.52 (crude fibre), 49.62 (moisture content), 6.13 (ash content) and 17.31% (carbohydrate). The bread with optimal quality indexes with overall desirability index of 0.568 was obtained from 39.42% wheat, 6.28% SPI and 13.76% Fonio.

The properties of this optimal bread were: protein 17.25%, fat 8.83%, crude fibre 2.81%, moisture content 28.47%, ash content 2.80%, carbohydrate 41.35% and acceptability 3.56 respectively.

References

1. Adoukonou-Sagbadja H, Schubert V, Dansi A, Jovtchev G, Meister A, Pistrick K, et al. Nutritional and sensory attributes of soy-supplemented cereal meals. Nigerian Food Journal. 2007;25(1):100-110.
2. Aly MS, Alaa El-Din S, Salah HB, Essam IA. Effect of partial substitution of wheat flour with either defatted soybean or chickpea flours at different ratios on rheological and physical properties of dough, and quality characteristics of biscuits. Journal of Applied Sciences Research. 2012;8(12):5806-5817.
3. Amandikwa C. Proximate and functional properties of open air, solar and oven dried cocoyam flour. International Journal of Agriculture and Food Science https://www.agriculturaljournals.com International of Agricultural and rural development. 2012;15(2):988-994.
4. AOAC. Official Methods of Analysis. Association of Official Analytical Chemists. 19 th ed. U.S.A: Gaithersburg, 2012.
5. Bugusu BA, Campanella O, Hamaker BR. Improvement of sorghum wheat composite dough rheological properties and bread making quality through zein addition. Cereal. Chem. 2001;78(1):31-35.
6. Coda R, Di Cagno R, Edema MO, Nionelli L, Gobbetti M. Exploitation of Acha (Digitariaexilis) and Iburu (Digitariaiburua) flours: Chemical characterization and their use for sourdough fermentation. Food Microbiol. 2010;27:1043-1050.
7. Dewettinck K, Bockstaele FV, Kuhne B, Van WD, Courtens T, Gellynck X. Nutritional value of bread: Influence of processing, food interaction and consumer perception. Rev. J. Cereal Sci. 2008;48:243-257.
8. Dhingra S, Jood S. Organoleptic and nutrition evaluation of wheat breads supplemented with soyabean and barley flours. Food Chemistry. 2002;77:479-488.
9. Edema MO, Sanni LO, Sanni AI. Evaluation of maizesoybean flour blends for sour maize bread production in Nigeria. African Journal of Biotechnology. 2005;4:911918.
10. FAO. Agriculture Food and Nutrition for Africa -A Resource Book for Teachers of Agriculture. Food and Agriculture Organization: Rome, 1997.
11. Gbadamosi SO, Oladeji BS. Comparative studies of the functional and physic-chemical of isolated cassava, cocoyam and bread fruit starches. International Food Research Journal. 2013;20(5):2273-2277.
12. Jideani IA, Owusu RK, Muller HG. The effect of cooking on proteins from acha (Digitaira exilis) and durum wheat, J Sci. Food Agric. 1994;65:465-476.
13. Kent NL, Evers AD. Technology of Cereals: An introduction for students of Food Science and Agriculture, 4th Ed. Elsevier Science: Oxford. 1994, p 78-190.
14. Kure OA, Bahago EJ, Daniel EA. Studies on the proximate composition and effect of flour particle size of acceptability of biscuits produced from blends of soyabeans and plantain flours. Namoda Technology Scope Journal. 1998;3(2):17-22.
15. Marer E, Martin A. Fiber feast lowers cancer risk, health (Time inc. Health). 2003;17(7):58.
16. Mashayekh M, Mahmoodi MR, Enterazzi MH. (): Effect of fortification of defatted soy flour on sensory and rheological properties of wheat bread. International Journal of Food Science and Technology. 2008;43:1693-1698.
17. Mesfin W, Shimelis A. Effect of soybean/ cassava flour blend on the proximate composition of Ethiopian traditional bread prepared from quality protein maize. African Journal of Food, Agriculture, Nutrition and Development. 2013;13(4):7985-8003.
18. Murphy PA, Song T, Buseman G, Barua K, Beecher GR, Trainer D. Isoflavones in retail and institutional soy foods. Journal of Agriculture and Food Chemistry. 1999;47:2697-2704.
19. Ndife J, Abdulraheem LO, Zakari UM. Evaluation of the nutritional and sensory quality of functional breads produced from whole wheat and soya bean flour blends. African Journal of Food Science. 2011;5(8):466-472.
20. Okoye JI, Okaka JC. Production and evaluation of protein quality of bread from wheat cowpea flour blends. Cont. J. Food Sci. Technnol. 2009, 1-7.
21. Olapade AA, Oluwole OB. Bread Making Potential of Composite Flour of Wheat-Acha (Digitariaexilis staph) Enriched with Cowpea (Vignaunguiculata L. walp) Flour. Nigeria food journal. 2013;13(1):6-12. www.nifst.org
22. Onuegbu NC, Ihediohanma NC, Odunze OF, Ojukwu M. Efficiency of wheat: maize composite flour as affected by baking method in bread and cake Production. Sky Journal of Food Science. 2013;2(8):005-013.
23. Otegbayo BO, Adebiyi OM, Bolaji OA, Olunlade BA. Effect of soy enrichment on the bread quality. International food research journal. 2018;25(3):11201125.
24. Petruccelli S, Anon MC. Thermal aggregation of soy protein isolates. J. Agric. Food Chem. 1995;43(12):3035-3041.
25. Saputri E, Joni Kusnadi. Effect of blanching on properties of water yam (Discoreaalata) flour. Advance Journal of Food Science and Technology. 2013;5(10):1342-1350.
26. Sanful RE, Darko S. Utilization of soybean flour in the production of bread. Pakistan Journal of Nutrition. 2010;9(8):815-818.
27. Shittu TA, Dixon A, Awonorin SO, Sanni LO, MaziyaDixon B. Bread from composite cassava-wheat flour II: Effect of cassava genotype and nitrogen fertilizer on bread quality. Food Research International. 2008;41:569-578.
28. Thompson JL, Manore MM, Vaughan AV. The Science of Nutrition. Pearson Education Publishing: San Francisco, CA. 2008, p 220-259.
29. Young VR, Pellet PL. Wheat proteins in relation to protein requirements and availability of amino acids. Am. J Clin. Nutr. 2001;41:1077-1090.