International Journal of Nutrition, Pharmacology, Neurological Diseases

: 2020  |  Volume : 10  |  Issue : 3  |  Page : 112--119

Characterization of Whole Wheat Bread Reformulated with Pea and Soy Protein Isolates

Manickavasagan Shivaani 
 Guelph Collegiate Vocational Institute, Guelph, ON, Canada

Correspondence Address:
Manickavasagan Shivaani
Guelph Collegiate Vocational Institute, 155 Paisley St, Guelph, ON, N1H 2P3


Aims: At present, there is an increasing demand for plant-based proteins due to their nutritional values and beneficial effect to the environment. Improving the availability of plant protein enriched foods would be highly beneficial for the consumers to follow a healthy diet. Reformulating a commonly consumed product, such as bread, with plant-based protein will be a convenient option for the people to improve their protein intake. Therefore, the objective of this study was to determine the effect of protein isolate (pea and soy) on color, microscopic structure, sensory properties, and protein content in whole wheat bread. Methods: The experiments were conducted at the University of Guelph, ON, Canada. Seven whole wheat bread samples (control, P20, P30, P40, S20, S30 and S40) were prepared (n = 3 loaves for each treatment). Results: The RGB and L*a*b*values of loaf (crust) and slice (crumb) of the control bread was higher than that of all protein enriched bread samples. The control bread had larger pores than the protein enriched samples. The pores in the pea protein isolate enriched bread were tightly packed while compared to soy protein. There was no difference in most of the sensory attributes between control and S20 breads. In terms of softness, all protein blended breads scored lower than the control. Fifty percentage of the panelists chose S20 as their first choice, whereas only thirty percent selected control as their first choice. The protein content of the bread samples was 8.9, 15.4, 18.1, 20.7, 15.9, 18.6 and 20.9%, for control, P20, P30, P40, S20, S30 and S40, respectively. Conclusion: Soy protein isolate has more opportunities than pea protein isolate to incorporate with whole wheat flour, and produce acceptable bread.

How to cite this article:
Shivaani M. Characterization of Whole Wheat Bread Reformulated with Pea and Soy Protein Isolates.Int J Nutr Pharmacol Neurol Dis 2020;10:112-119

How to cite this URL:
Shivaani M. Characterization of Whole Wheat Bread Reformulated with Pea and Soy Protein Isolates. Int J Nutr Pharmacol Neurol Dis [serial online] 2020 [cited 2020 Sep 22 ];10:112-119
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Protein is an essential macronutrient required for humans on daily basis. The recommended daily protein intake is 1.43, 0.91 and 0.80 gram of protein per kg of body weight for 6 months’ infant, 10 years’ child and adults, respectively.[1],[2],[3] There are several sources available for protein from both plant and animal origin. In general, animal-based food such as red meat, contains saturated fat and cholesterol. Furthermore, processed meat contains food preservatives and taste enhancers such as sodium. In contrast, plant-based protein foods such as cooked lentils contain protein and fiber, and no saturated fat or sodium. The World Health Organization suggests to reduce the intake of saturated fat and sodium to maintain good health.[4] It has been scientifically proven that regular consumption of plant protein foods instead of animal protein foods reduces the risk factors for cardiovascular diseases, diabetes and certain cancers.[2]

The adverse effects to the environment due to the production of protein is much higher for animal sources than plant sources. For example, the greenhouse gas emission from the production of one pound of lamb is thirty times higher than one pound of lentils.[2] Therefore, by considering personal health and the planet’s health, awareness and demand for plant protein have been increasing globally.

Among plant foods, legumes (pulses and soy) contain the highest protein. The consumption of pulses has been demonstrated to ameliorate satiety and metabolism of glucose and lipids because of its high protein and fiber content.

In general, the plant protein isolates (concentrated protein flours; above 80% protein) are being used as meal replacers, energy drinks and ingredients for food preparation.

Reformulation of commonly consumed carbohydrate-rich foods by partially substituting with plant protein isolate is a novel idea to improve protein intake and reduce carbohydrate consumption. Protein enrichment has been experimented with various food products such as pita bread,[5] white bread,[6] cookies,[7],[8] biscuit,[9] pasta,[10] and gluten-free bread.[11] However, there is no research available on the reformulation of whole wheat bread by partially substituting the whole wheat flour with plant protein. Therefore, the research question of this extended essay was: To what extent can plant protein isolates replace whole wheat flour in bread preparation?

 Materials and Methods

Bread preparation

The bread for all treatments were prepared at the Bakery, University Centre, University of Guelph, ON, Canada. A Chef helped to produce three loaves (n = 3) for each treatment bread: WW (control), P20, P30, P40, S20, S30 and S40. Except the flour (whole wheat flour or blended with protein isolate) and water, the same quantity of other ingredients was used for all treatments. The basic ingredients used for each loaf of the bread are shown in [Table 1].{Table 1}

Protein isolates

Un-flavored and un-sweetened pea protein isolate was purchased from the Canadian Protein (Canadian Protein, ON, Canada), and soy protein isolate was purchased from My Protein (My Protein, Shepherdsville, KY, USA). The composition of protein isolates mentioned on the nutrition label is shown in [Table 2].{Table 2}

Steps used in bread making

Bloom yeast for 15 min.Combine dry ingredients (dry mix).Add bloomed yeast, water, honey and butter and mix for 5 min (at low speed) and 12 min (at high speed).Round up and bulk ferment for 75 min on the bench.De-gas loaf and shape for loaf pan; rest 10 min.Final proof (covered) for 40 min at 27°C and 65% RH.Score loaf and bake at 204°C for 20 min.

Color value assessment

A digital camera (model: Canon EOS 6D, 1024 × 683 pixels, Canon Canada Inc, Brampton, ON) was used to acquire images of bread loaves and slices. The distance between the camera lens and the bread was kept at 30 cm for all samples. The region of interest from the digital images were segmented, and RGB color values were extracted for each image using python open source software. From the R, G, B values, L*a*b* values were calculated using a color converter software (Nix Sensor Limited, Hamilton, ON, Canada).

Microscopic structure analysis

A microscope (model: SMZ 745T, Stereo zoom microscope, Nikon Corporation, Tokyo, Japan) was used to acquire microscopic images of the bread slices.

Sensory evaluation

Ten panelists (six male and four female graduate students at the University of Guelph) volunteered to evaluate the bread samples. The panelists were informed about the ingredients in the bread, however, the samples were coded with random numbers (blind samples) during sensory.

The sensory attributes were measured using a hedonic sensory scale (9–like extremely, 8–like very much, 7–like moderately, 6–like slightly, 5–neither like nor dislike, 4–dislike slightly, 3–dislike moderately, 2–dislike very much, 1–dislike extremely). The choice of the panelists (among seven bread samples) was also collected at the sensory sheet.

Protein content

The Protein analyzer (Model: FP-528 model, Leco Inc., St. Joseph, Michigan, USA) using Dumas combustion method for nitrogen concentration by thermal conductivity was used to measure the protein content of the bread samples. The protein content was calculated as %N × 6.25, and expressed in dry weight basis.[7]

Statistical analysis

All values in each quality category were statistically analyzed using t test (95% confidence interval) through Microsoft excel.

 Results and Discussion

Bread preparation

Protein enriched flour dough warranted additional water to meet the bread dough quality (as determined by the Chef. Vijay Nair, Bakery, University Center, University of Guelph). The average additional water (over control) added for the protein enriched flour was 83%, 90%, 97%, 82%, 95% and 99%, for P20, P30, P40, S20, S30 and S40 treatments, respectively. A similar increased water absorption trend with protein blends was observed in previous studies. Dhingra and Jood found that water absorption capacity increased with increase in the level of soy bean flour substitution for white wheat flour to make bread.[6] Higher water absorption was observed while replacing wheat flour with soy protein blend while making cookies.[7]

The typical color images of the bread loaves and slices are shown in [Figure 1] and [Figure 2]. Surface cracks were observed in 30% and 40% samples. More cracks were seen in pea protein blended bread samples than in soy protein blended bread samples. The volume of expansion of protein blended bread loaves were lower than that of control (visual observation). Des-Marchais et al.[12]stated that addition of pea protein isolate with refined wheat flour reduced the loaf specific volume compared to the control.{Figure 1}{Figure 2}

The control bread slices had larger pores than the protein blended breads [Figure 2]. Bread samples blended with soy protein had relatively larger pores than pea protein breads. The central core of S30 and S40 samples were moist. These treatments might require more baking time. Pea protein blended bread slices were dense and tightly packed. Since the pore sizes play a vital role in consumer’s acceptability in terms of appearance and texture, it should be critically evaluated and optimized while developing white bread with protein isolates.

While evaluating four legume flours (chickpea flour, carob germ flour, pea isolate, soy flour) on baking characteristics of gluten-free bread, carob germ flour bread had a more compact microstructure than chickpea flour and soy flour.[11]

Color values

The RGB values of loaves and slices are given in [Table 3]. The R, G and B values of the control loaf were higher than that of the protein enriched samples. There was no difference in the B values among the protein enriched loaves. A similar trend was also observed for slices.{Table 3}

For food product experiments L*, a* and b* (L* = lightness scale (100 = pure white, 0 = black); a* = red; b* = yellow[7] values have been used to mention the color profiles.

Both loaf and slice of the control bread were brighter (higher L* values) than their protein enriched counterpart [Table 4]. There was no difference in a* values among protein enriched slices. The a*and b* values of protein enriched loaves were higher at lower protein concentrations.{Table 4}

In a similar study with white bread, the L*a*b* values of the crust were 49, 15 and 29 for the control, and 37, 15 and 18 for 10% pea protein isolate substitute.[12] Phongthai et al. reported that while adding 6% soy concentrate, the L*a*b* values of pasta were 70.4, −0.62, and 7.6 respectively. Whereas soy concentrate was increased to 9%, the L*a*b* values changed to 77.1, 0.21 and 9.2, respectively.[10]

The color values of the bread might not have significant effect in consumer acceptability as toppings or spread are used most of the time along with bread. However, darker breads are sometimes associated with burnt foods and create a pre-biased dislike.

Microscopic structure

[Figure 3] shows the microscopic images of the control and protein blended bread slices. Like the trend seen in RGB color images, the control slices had larger pores than protein blended slices. Soy protein breads, especially, S20 and S30, had uniform small pores. In general, pea protein breads had irregular pores, and the particles were tightly packed.{Figure 3}

Sensory properties

The mean hedonic scores for various sensory qualities reported by the sensory panelists are shown in [Table 5].{Table 5}

Crust color

The scores for crust color of various bread samples ranged from 5.3 to 7.6. There was no difference between control and S20. There was also no difference in the crust color between the remaining bread samples.

In a similar study, while assessing the crust color of legume flour based gluten-free bread using the hedonic scale, it was 6.9 and 6.8 for pea isolate and soy flour products, respectively.[11] Dhingra and Jood[13] reported that the crust color of soy flour blended (20%) white flour bread scored only 5.6.

Crumb color

There were no differences in the crumb color scores of control, S20 and P20 (7.1 to 7.9). However, at higher protein levels, the crumb color scored significantly lower than the control.

In a previous study, the crumb color of the legume flour-based gluten-free bread was 6.6 and 6.8 for pea isolate and soy flour, respectively.[11]

Crumb texture

There was no difference between the crumb texture of control and S20 bread samples. All pea protein blended breads scored lower than control, and there was no difference between the various levels.


The softness of the control bread had the highest score (8). The protein addition in the breads reduced the acceptability of their softness, and resulted in significantly lower scores than control. There was no difference amongst the softness of the protein blended breads.


The chewiness score was between 5.3 and 7.4 for the bread samples. There was no difference between the control, P20, S20 and S30. Other samples scored lower than the control. A similar score was obtained while evaluating the chewiness of the legume flour-based gluten-free bread (pea isolate bread = 5.4 and soy flour bread= 6.0).[11]


There was no difference in moistness between the control, P20, P30 and S20. Other samples scored lower than the control.


There was no difference in taste between 30% and 40% protein blended breads, however they scored lower than the control. There was no difference between the taste of control and S20 bread samples.

While evaluating protein bended white bread, Dhingra and Jood[13] reported that the taste of 20% soy flour substituted bread scored only 3.6. The taste of the legume flour-based gluten-free bread scored 5.3 and 6.5 for pea isolate and soy flour, respectively.[11]

Desired aroma

There was no difference between the desired aroma of the control and S20 bread samples. All other bread samples had lower desired aroma compared to the control.

Overall acceptably

There was no difference between the overall acceptability of control and S20 bread samples. All other bread samples scored a lower overall acceptability (no difference between them) compared to the control. There was no consistent trend in overall acceptability of the protein enriched food products.In a study with pita bread, Borsuk et al.[5] reported that the sensory qualities of bread substituted with 25% coarse pinto bean or navy bean flour were better than the wheat control. Dhingra and Jood[6] mentioned that the substitution of 15% barley flour, 10% full fat soy flour, or 10% defatted soy flour into bread did not affect the sensory quality. However, a higher percentage than previously mentioned did affect the sensory quality of the bread.

In some products, protein enrichment did not affect the sensory qualities. For instance, while soy bean and cassava flour blends were used to make biscuits, soy bean flour at all levels did not affect color, texture, flavor, taste, and overall acceptability of the biscuits.[9] Whereas, substituting wheat flour with pea flour (5% and 10%) to make bread and cookies, it was found that the sensory qualities were not affected only up to 5% substitution compared to the control.[8]

Panelists’ choice

None of the panelists selected P20, P40, S30 and S40 bread samples as their first choice [Figure 4]. One panelist did not respond to this question. Five panelists reported S20 as their first choice, whereas only 3 mentioned control as their first choice. One panelist selected P30 as their preferred choice. As S20 bread was the preferred choice for more panelists, soy protein isolates could be blended in bread and other bakery products to improve protein consumption with enhanced taste.{Figure 4}

Protein content

The protein content of the bread samples is shown in [Figure 5]. The control bread had the lowest protein content (8.9%). The protein content increased with addition of protein isolates. The protein content of the protein blended breads was 15.4%, 18.1%, 20.7%, 15.9%, 18.6% and 20.9% for P20, P30, P40, S20, S30 and S40, respectively. Since bread is consumed for breakfast in several countries, high protein breads would be beneficial for those looking for increasing protein consumption.{Figure 5}


The particles in the pea protein bread were tightly packed with an overall reduced pore size. This property reflected in a lower preference of pea protein bread on many sensory attributes. The addition of 20% soy protein isolate did not affect most of the sensory qualities. In fact, more than half of the panelists chose S20 as their first choice, even over control. Soy protein isolate has the potential to blend up to 20% with improved acceptability. Further research is warranted for pea protein isolate and higher level soy protein isolate to improve the pores by selecting additional ingredients or optimizing the baking condition to improve their acceptability.

Overall, protein enriched whole wheat bread can be made available in Canada or elsewhere to improve plant protein consumption especially among children. While consuming more plant-based food than animal food, there would be a significant improvement in the health profile of people.


The author is grateful to Ms. Turner, Extended Essay advisor for her continuous motivation and support throughout this project. Also, I would like to thank Chef Vijay Nair, Annie, and Rose, University Centre Bakery, University of Guelph for their help in making the bread, Rathnapriya and Sindhu for slicing and microscopic imaging, Hillary Rooyakkers for digital imaging, Tamizhselvan for image segmentation and color extraction, Sonu Sharma for protein content measurement and all sensory panelists.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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