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Evaluation of the functionality of five different soybean proteins in yeast-leavened pan breads
Journal of Cereal Science 64 (2015) 63e69
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Evaluation of the functionality of five different soybean proteins in yeast-leavened pan breads lez, Cristina Chuck-Hernandez, Sergio O. Serna-Saldívar* Marco A. Lazo-Ve gico de Monterrey-Campus Monterrey, Av. Eugenio Garza Sada 2501, Monterrey, Centro de Biotecnología- FEMSA, Escuela de Ingeniería y Ciencias, Tecnolo N.L., C.P. 64849, Mexico
a r t i c l e i n f o
a b s t r a c t
Article history: Received 11 December 2014 Received in revised form 12 March 2015 Accepted 1 April 2015 Available online 9 May 2015
Soybean (SB) products are a source of proteins that complement the amino acid profile of cereal-based products and consequently improve human health. Four different SB flours (SBF-1 to SBF-4) and a SB concentrate (SBC) were incorporated into refined wheat flour in order to increase approximately 20e25% the protein content. The composite flours were processed into yeast-leavened pan breads. The SB fortified breads were characterized in terms of dough rheological, baking performance, bread crumb texture and color and sensory properties. The different SB proteins affected differently rheological properties of doughs, bread properties and quality. Addition of the SB proteins increased more than 3% optimum dough water absorption and consequently bread yield but decreased between 7 and 13% bread volume. The fortified breads also had a darker crumb. The best SB protein sources were SBF-3 and SBC which had respectively 75.5 and 52% PDI, 24 and 36% NSI, 4.0 and 8.3 water absorption and 50.3 and 36.9% water solubility indexes. These SB-fortified breads averaged 23% more protein and almost twice as much lysine compared to the control. Therefore, these SB proteins can be utilized to produce yeast-leavened breads with higher protein and upgraded protein quality. © 2015 Elsevier Ltd. All rights reserved.
Keywords: Bread Soybean proteins Functional properties Dough rheological properties
1. Introduction Soybeans (SB) are a rich source of high-quality protein and nutraceuticals. The high protein content plus the high amounts of essential amino acids that are lacking in most cereals make these flours ideally suited to fortify cereal-based foods, with only a slight increase in the production cost (Mashayekh et al., 2008; Novotni et al., 2009). Furthermore, soybeans are rich sources of dietary fiber, flavonoids, isoflavones, soyasaponins, other antioxidant compounds and most B-vitamins that exert positive health benefits especially in terms of prevention of most chronic diseases, osteoporosis and cancer (Mahmoodi et al., 2014). Bread is the main staple in many countries worldwide and is mainly prepared from refined wheat flour. Nutritionally, the wide array of white breads provide energy, proteins, minerals and micronutrients (Shin et al., 2013; Acosta-Estrada et al., 2014), but the nutritional quality of the protein is not adequate due to the low levels of lysine present in wheat flour. The partial replacement of wheat flour by protein rich flours is difficult because they do not
* Corresponding author. Tel.: þ52 81 83284322; fax: þ52 81 83284262. E-mail address: [email protected] (S.O. Serna-Saldívar). http://dx.doi.org/10.1016/j.jcs.2015.04.007 0733-5210/© 2015 Elsevier Ltd. All rights reserved.
contain gluten-forming proteins and therefore are not functional, especially in leavened-bread systems. In an early report, SernaSaldivar et al. (1988) produced SB enriched pan breads with and without sodium stearoyl lactylate and concluded that this dough conditioner improved volume and texture but not to the level of the control bread. Likewise, Shin et al. (2013) manufactured SB-fortified breads and concluded that they had comparatively denser texture and the peculiar beany flavor. However, SB proteins are potentially suited to fortify bread, biscuits and other bakery formulations especially in terms of enhancing protein quality and quantities of relevant nutraceuticals (Serna-Saldivar et al., 1988; Mashayekh et al., 2008; Ivanovski et al., 2012; Yezbick et al., 2013; Mahmoodi et al., 2014). Defatted SB flour used in bread making increases absorption and moisture retention, which enlarges the freshness or textural shelflife of the product. However, if a large amount of SB protein is incorporated into the wheat flour a disruption of the glutenforming proteins occurs. Therefore, the SB protein interferes with the starchegluten matrix negatively affecting volume, crumb scores and overall quality attributes and acceptability of enriched breads (Shin et al., 2013; Mahmoodi et al., 2014). The aim of this research was to assess the effect of addition of four different defatted SB flours or a SB concentrate with
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contrasting functional properties on the rheological dough properties and quality of yeast-leavened pan breads produced by the pup loaf straight or sponge dough processes. Control and SB fortified treatments were compared in terms of chemical composition, amino acids, dough rheological properties, bread texture and sensory attributes. 2. Materials and methods 2.1. Commercial soybean samples Five different commercial SB samples were selected to differ in functional properties especially in terms of urease activity, water absorption (WAI), water solubility (WSI), protein dispensability (PDI) and nitrogen solubility (NSI) indexes. Four were defatted SB flours, Industrial de Alimentos (SBF-1), GAF-120 (SBF-2), ADM (SBF3) and Ragasa (SBF-4) containing approximately 49% protein (N x 6.25 as is basis), whereas the remaining a protein-concentrate (SBC) Provita® containing 67% protein (as is basis). Urease activity (Method Ba 9-58, AOCS, 2011), nitrogen solubility (Method Ba 1165, AOCS, 2011), water absorption and solubility (Cheftel et al., 1989), and protein dispersibility (Method Ba 10b-09, AOCS, 2011) indexes were assayed. Lysine, tryptophan and sulfur containing amino acids (methionine plus cysteine) in wheat flour and the different SB protein sources were determined according to Official Method 982.30 E (a,b,c) of the AOAC (2006). 2.2. Soybean-fortified flours Each of the five different SBF proteins were composited with commercial refined wheat flour (La Perla, Molinos del Fenix, Saltillo, Coahuila, Mexico) in order to increase the protein concentration to about 20e25%. The experimental SB enriched flours were produced by substitution of 6.0% SBF-1; 6.1% SBF-2; 6.3% SBF-3, 6.2% SBF-4 and 4.5% SBC of the refined bread flour. Protein (N 5.7) was determined in the control and experimental composite flour samples using the AACC International (2000) method 46-30. 2.3. Dough rheological properties The dough rheological properties of the control and SB-composite flours were determined with the farinograph (Brabender Instruments, South Hackensack, NJ) and Alveograph (Chopin Instruments, Villeneuve-La-Garenne, France) according to Approved Methods 5421 and 54-30, respectively (AACC International (2000)). 2.4. Straight dough baking The pup loaf straight-dough bread micro-baking method 1010.03 (AACC International, 2000) was utilized. The bakers formulation consisted of 6% refined cane sugar (Avance, Avance Comercial de Monterrey, Monterrey, NL, Mexico), 3% vegetable shortening (Inca, Unilever de Mexico S.A de C.V., Tultitl an, Edo. de Mexico, Mexico), 2% refined iodinated salt (La Fina, Sales del Istmo, Coatzacoalcos, Veracruz, Mexico) and 2% dry yeast (Saccharomyces cerevisiae) (Azteca® Levadura, Iztapalapa, Mexico, D.F., Mexico). Optimum water absorption and mix times were subjectively determined by observing dough properties or gluten development (film formation, gloss and dough stickiness). Bake absorption, mixing time, proof height, loaf height, oven spring, loaf weight, loaf volume, and loaf apparent density were determined. Proof height and loaf height were determined with a proof height meter (National Manufacturing Co., Lincoln, Nebraska). The difference between these values was recorded as oven spring. Loaf volume was
determined by rapeseed displacement (National Manufacturing Co., Lincoln, Nebraska) according to method 10-05.01 of the AACC International (2000). 2.5. Sponge dough baking Sponge dough breads were manufactured in a pilot plant in order to generate loaves for texture and sensory analyses. Sponge doughs were produced by mixing by hand 200 g of refined bread flour, 5 g instant dry yeast and 140 g water. The resulting blend was placed in a plastic container in a fermentation cabinet (National Mfg., Lincoln, NB, USA) set at 28 ± 1 C for 4 h. Resulting sponges were mixed with the remainder of the dry ingredients: 300 g bread flour, 30 g sugar, 20 g shortening, 5 g of dry whole milk (Nestle de Mexico, Mexico, D.F., Mexico), 10 g salt, 1 g lecithin (Proveedores de Ingeniería Alimentaria S.A. de C.V. Monterrey, N.L., Mexico), 1 g Sodium Stearoyl Lactylate (SSL), 1 g calcium propionate and 2.5 g dry yeast instant for one min at low speed in a Hobart mixer equipped with the hook attachment. Then, the rest of the predetermined amount of water was added and blended for one minute at low speed. Next, the velocity was switched to medium until attaining optimum dough development. Film formation, gloss and dough stickiness were subjectively determined to estimate optimum mix times. Resulting doughs were weighed before placing them in a fermentation cabinet set at 28 ± 1 C and 85% relative humidity. After 10 min resting, doughs were punched thru 0.95 cm roll spacing in preparation for molding and panning in 7.5 cm height metal pans that had the following dimensions on the base and top, respectively: 22.5 and 24.5 cm long and 8.5 and 10.5 cm wide. Baking pans were previously greased with vegetable shortening on the bottom and sides. Panned doughs were proofed for 45 min before baking for 25 min in an oven (Electrolux EOG Gas single oven X 601) set at 190 C. Upon 30 min cooling at room temperature, breads were cut into 2 cm thick slices, packaged in sealed polyethylene bags and stored at room temperature for 5 days. 2.6. Crumb texture and color of sponge breads The crumb texture of the slices of bread (2 cm thick) was evaluated with a texture analyzer (model TA.XT plus, Stable Micro systems, United Kingdom) according to the bread firmnesscompression test method 74-10.02 (AACC International (2000)) with a trigger force of 0.048 N. Cohesiveness, hardness, gumminess, chewiness and elasticity were evaluated at the center of the slice. The parameters were calculated from the resulting texture profile analysis curves. Tests were conducted at days 0 (fresh), 1, 2 and 5 days of bread slices kept at room temperature. The crumb color of the control and experimental breads was objectively measured on three slices with a colorimeter (CR 300, Minolta, Japan). Bread-crumb color parameters L*, a*, and b* were the average of three measurements at different parts of the slice. Tests were conducted after 1 day storage at room temperature. 2.7. Sensory analyses In-house consumer panels (pilot consumer panels) consisted of forty untrained panelists, evaluated the sensory features and overall acceptability of control and experimental breads in individual booths after 24 h of baking. Bread evaluation was performed in a sensory evaluation laboratory (ITESM-Campus Monterrey) according to the guidelines described by Watts et al. (1989). Each panelist was simultaneously given six coded samples along with a ballot, and was asked to rate color, texture, flavor, odor, and overall quality on a 5-point hedonic scale, where 1 is like very much and
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5 is dislike very much. In order to obtain an overall evaluation of the samples, a score was assigned to each bread for nutritional, dough properties, baking performance and sensory acceptability parameters. 2.8. Overall evaluation of breads In order to obtain an overall evaluation of the samples, a score was assigned to each bread for nutritional, dough properties, baking performance and sensory acceptability parameters. The control bread scored 1 for each property and considered these values as baseline. The experimental SB-fortified breads were assigned with neutral, positive (better) or negative (worse) values according to variations among means (Tukey tests at p < 0.05). For instance, when the parameter mean was higher or lower than one or two standard deviations compared to the corresponding mean of the control, the individual scores assigned were þ1 and þ2 or 1 and 2, respectively. Final desirability scores were the addition of all individual scores. 2.9. Statistical analysis Each experiment was performed in triplicate in three different weeks and data was reported as means ± standard deviations. Results were subjected to analysis of variance (ANOVA) and differences among means were compared by Tukey tests at p < 0.05. All computations were made by the statistical software JMP (version 11). 3. Results and discussion 3.1. Protein and amino acid composition As planned, the protein content of the different SB-composite flours were higher compared to the control and similar among all the experimental flours. These averaged 14.4% protein (dry weight basis), representing an average increase of 23% compared to the control wheat flour (11.7% protein dry weight basis). More importantly, these SB products contained between 11 and 16 times higher lysine contents (3.45e4.93%) compared to the refined wheat flour (0.31%) (Table 1). Therefore, the addition of approximately 6 and 4.5% of the different SB defatted flours and concentrate respectively increased 1.6 times the lysine content in composite flours and breads (Table 1). The contrasting difference between the refined wheat flour and the SB protein sources especially in terms of lysine makes these proteins ideally suited to upgrade protein quality and nitrogen retention. Earlier studies clearly
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documented that the higher protein and enhanced essential amino acid scores of SB-fortified breads improved protein quality and animal growth (Serna-Saldivar et al., 1988; Mashayekh et al., 2008; Mahmoodi et al., 2014). The limiting essential amino acid in wheat is lysine, which is present in about half the amount required for optimum infant growth. Nutrition studies have clearly indicated that the higher lysine improves the amino acid score, protein efficiency ratio, nitrogen retention evaluated by the biological and net protein utilization values, growth, brain development and memory performance in laboratory animals and humans (Serna-Saldivar et al., 1988; Amaya-Guerra et al., 2006; Khan et al., 2009; Serrem et al., 2011; Mahmoodi et al., 2014). The SBF-1 showed the lowest protein dispersibility (PDI) and water solubility (WSI) indexes. On the other hand, SBF-3 and 4 had about 15 times higher urease activity and 3 times higher PDI compared to SBF-1 or 2. SBF-3 and 4 had high urease activity and PDI values due to the slight heat treatments applied prior to oil extraction and during meal desolventization in a desolventizertoaster or DT. The PDI reported for SBC is similar to the value reported by Wang et al. (2004) for a counterpart produced from acidwashed white flakes. 3.2. Rheological properties of SB-enriched doughs 3.2.1. Farinograms As anticipated, rheological properties of doughs estimated with the farinograph and baking performance were affected by the addition of the different SB protein sources (Tables 2 and 3). Addition of the different SB sources improved the dough water absorption capacity by 3.5 units which represented about 6% more water absorption compared to the wheat flour (Table 2). Compared to the wheat flour, the corrected water absorption was between 2.2 and 4.7% units higher for the different SB-enriched counterparts. Several investigations had documented the effect of increased water absorption in doughs supplemented with different SB flours (Serna-Saldivar et al., 1988; Ribotta et al., 2005). These differences are related to the nature of the soybean proteins which are hydrophilic or with high WAI (Table 1). WAI of the different SB proteins ranged from 4.0 in the high PDI SBF-3 to 5.3 in the lowest PDI SBF-1. Addition of all SB flours prolonged arrival times, the longest times were observed in composite flours containing SBF-2 or SBF-4. Interestingly, these meals had low NSI values (Table 1). Only the composite flour containing 4.5% SBC had similar arrival time compared to the control flour (Table 2). The arrival times were inversely correlated with both nitrogen solubility (NSI) (r ¼ 0.57) and water absorption indexes (WAI) (r ¼ 0.56) (Table 4). In
Table 1 Functional characteristics and main essential amino acids of five different soybean protein sources.a Parameter
Crude Protein % (N 6.25, dry basis)c Amino acid (%, dry weight basis)d Lysine Tryptophan Methionine þ Cysteine Urease activity Nitrogen Solubility (NSI, %) Water Absorption Index (WAI) Water Solubility Index (WSI) Protein Dispersibility Index (PDI) a b c d
Soybean protein sourcesb SBF-1
SBF-2
SBF-3
SBF-4
SBC
53.6 ± 0.2C
54.58±2B
54.58 ± 0.4B
53.6 ± 0.1C
74.9 ± 0.2A
3.45 0.85 1.56 0.10 ± 0.01E 19.7 ± 0.7B 5.3 ± 0.0B 25.7 ± 0.4E 23.2 ± 0.1D
3.5 0.87 1.61 0.15 ± 0.01D 13.4 ± 0.8C 4.8 ± 0.3C 28.4 ± 0.1D 25.3 ± 1.6D
3.54 0.82 1.64 2.25 24.0 4.02 50.3 75.5
3.55 0.76 1.63 2.20 ± 0.03B 25.5 ± 0.7B 4.3 ± 0.1D 47.6 ± 1.8B 66.9 ± 1.5B
4.93 1.09 1.95 0.40 ± 0.01C 36.1 ± 1.5A 8.3 ± 0.1A 36.9 ± 0.2C 52.0 ± 0.5C
± ± ± ± ±
0.01A 0.2B 0.0E 0.2A 1.7A
Averages ± standard deviations, values with the same letter within row are not significantly different at p < 0.05, (n ¼ 3). The experimental SB enriched flours were produced by substitution of 6.0% SBF-1; 6.1% SBF-2; 6.3% SBF-3, 6.2% SBF-4 and 4.5% SBC of the refined bread flour. The refined hard wheat flour contained 11.72% crude protein (N 5.7, dry basis). The wheat flour contained 0.31, 0.18 and 0.50% (dry weight basis) of lysine, tryptophan and methionine þ cysteine, respectively.
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Table 2 Effect of soybean protein addition on the rheological properties of doughs estimated with the farinograph and alveograph.a Parameter
Flour enriched withb
Control Wheat flour
a
c
SBF-2
12.2 ± 0.2
10.1 ± 0.4
Flour fortified protein, % (14% mb) Farinograph Water Absorption (%) Corrected Water Absorption (%) Arrival Time (min) Departure Time (min) Dough Stability (min) Dough Development (min) Mixing Tolerance Index (BU)c Alveograph P (mm H2O) L (mm) P/L G W (104J) b
SBF-1
B
A
SBF-3
12.3 ± 0.7
A
SBF-4
12.4 ± 1
A
SBC
12.3 ± 0.7
A
12.5 ± 0.1A
58.6 58.3 0.9 13.5 12.7 8.0 40
± ± ± ± ± ± ±
0.2C 0.2C 0.1B 0.7A 0.6A 0.2A 0B
63.4 63.04 1.3 11.5 10.2 7.0 50
± ± ± ± ± ± ±
0.3A 0.3A 0.1B 0.4B 0.4B 0.3C 0AB
61.6 60.49 3.9 9.3 5.4 7.0 55
± ± ± ± ± ± ±
0.2B 0.2B 0.5A 0.4C 0.1C 0.4C 7.1A
61.0 60.5 1.25 14.1 12.9 8.0 30
± ± ± ± ± ± ±
0.1B 0.1B 0.1B 0.1A 0.1A 0.2A 0C
63.4 62.98 3.8 11.4 7.7 7.5 40
± ± ± ± ± ± ±
0.1A 0.1A 1.1A 0.1B 1.2C 0.2B 0B
61.8 61.5 0.8 11 10.3 6.5 50
± ± ± ± ± ± ±
0.2B 0.2B 0B 0B 0B 0.4D 0AB
123.5 53.5 2.3 16.3 275
± ± ± ± ±
4.9B 2.1A 0.2C 0.2A 2.8A
172 36 4.9 13 270
± ± ± ± ±
7.1A 0.7B 0.3ABC 0.1B 7.8A
120.5 19 6.6 9.7 101
± ± ± ± ±
4.9B 5.7C 1.7A 1.3C 20.5B
138.5 48 2.9 15.0 278
± ± ± ± ±
4.9B 3.5A 0.3BC 0.6AB 7.1A
134.5 52 2.6 16 288
± ± ± ± ±
0.7B 0A 0C 0.1A 2.1A
183.5 35.5 5.2 13.3 293
± ± ± ± ±
2.1A 0.7B 0.1AB 0B 5.7A
Average ± standard deviations, values with the same letter within row are not significantly different at p < 0.05, (n ¼ 2). The experimental SB enriched flours were produced by substitution of 6.0% SBF-1; 6.1% SBF-2; 6.3% SBF-3, 6.2% SBF-4 and 4.5% SBC of the refined bread flour. Brabender or Farinograph Units.
Table 3 Effect of soybean protein addition on the dough mixing and baking properties of pup loaves produced with the straight dough micro-baking procedure.a Treatment
Flour enriched withb
Control Wheat flour
Water Absorption (%) Dough Mixing Time (min) Oven Springc (cm) Bread Weight (g) Bread Volume (cm3) App. Bread Densityd (g/cm3) a b c d
63.7 3.9 2.3 145 899.2 0.16
± ± ± ± ± ±
0.5D 0.13BC 0.38A 0.7BC 20A 0.1C
SBF-1 65.2 4.1 1.5 146.7 783.5 0.19
SBF-2 ± ± ± ± ± ±
0.3C 0.1AB 0.2B 1.8ABC 34C 0.1AB
66 4.0 1.5 149.4 775.8 0.19
SBF-3 ± ± ± ± ± ±
0.8B 0.0AB 0.39B 1.7AB 33C 0.1A
64.7 4.4 1.5 144.5 809 0.18
SBF-4 ± ± ± ± ± ±
0.5C 0.34A 0.44B 2.6C 27BC 0.0B
65.3 4.4 1.6 151.1 818.3 0.18
SBC ± ± ± ± ± ±
0.3BC 0.46A 0.61B 5.3A 9.3BC 0.0AB
67.3 4.1 1.7 146.6 828.3 0.18
± ± ± ± ± ±
0.3A 0.34AB 0.28B 2.1ABC 20B 0.0B
Averages ± standard deviations, values with the same letter within row are not significantly different at p < 0.05, (n ¼ 6). Temperature of fermentation 31.2 ± 0.8 C. The experimental SB enriched flours were produced by substitution of 6.0% SBF-1; 6.1% SBF-2; 6.3% SBF-3, 6.2% SBF-4 and 4.5% SBC of the refined bread flour. Oven spring ¼ bread height e proof height. Apparent Bread Density.
contrast, the departure time was positively correlated with both WSI (r ¼ 0.73) and PDI (r ¼ 0.72). These data indicated that the quantity of soluble proteins and PDI increased departure time. According to Maforimbo et al. (2008), the poor dough and baking qualities of composite wheat-soybean formulations could be explained by the fact that wheat proteins favor hydrophobic
Table 4 Correlation between soybean quality parameters and rheological properties, and micro-baking test estimated with different SBFs. Parameters Farinograph Water Absorption (%) Arrival Time (min) Departure Time (min) Dough Stability (min) Dough Development (min) Mixing Tolerance Index (BU)2 Alveograph P (mm H2O) L (mm) P/L G W (104J) Baking properties Water Absorption (%) Dough Mixing Time (min) Oven Spring (cm) Bread Volume (cm3)
%NS
WAI
WSI
PDI
0.05 ¡0.57 0.30 0.49 0.26 0.22
0.12 ¡0.55 0.28 0.13 ¡0.83 0.48
0.33 0.06 0.73 0.49 0.73 ¡0.91
0.27 0.12 0.72 0.51 0.63 ¡0.88
0.67 0.47 0.33 0.52 0.76
0.79 0.29 0.45 0.22 0.22
0.26 0.79 ¡0.84 0.77 0.49
0.14 0.82 ¡0.85 0.81 0.59
0.53 0.26 0.89 0.93
0.90 ¡0.52 0.76 0.41
0.34 0.91 0.16 0.67
0.24 0.89 0.30 0.77
The bolded data had significant Pearson correlations (p < 0.05).
interactions whereas SB proteins had more affinity for water or are hydrophilic. Dough development times were similar (p > 0.05) for the control and SBF-3 composite dough and lowest for the SBC dough (Table 2). The dough development times were positively correlated with WSI (r ¼ 0.73) and PDI (r ¼ 0.63), and showed a high negative correlation with WAI (r ¼ 0.83). The soluble proteins related to PDI affected the time to achieve maximum consistency likely due to the gel-forming ability of these macromolecules. Dough stability times in all SB-enriched flours, except for the one containing SBF-3, were lower compared to the control. The farinograph dough stabilities were around 20% less for composite flours with SBF-1 and SBC, 40% less for the SBF-4, and 57% less for SBF-2. Ribotta et al. (2005) observed that both dough development and stability times decreased in doughs prepared with mixtures of wheat flour with SB (active or heat-treated). In conclusion, the highest PDI (Table 1) SBF-3 was the protein source that impacted the most of all farinograph parameters. The two best performing SB sources (SBC and SBF-3) had farinograph dough development and stability times of 6.5e8 and 10.3e12.9 min, respectively. The correlation between farinograph dough stability time and PDI (r ¼ 0.51) was moderate whereas correlations between mixing tolerance index and PDI (r ¼ 0.91) and WSI (r ¼ 0.88) were negative. The mixing tolerance indexes in all experimental doughs showed varying tolerances in relation to the control. The flour containing SBF-2 with a low PDI yielded the weakest dough. This particular dough had 37.5% reduced strength followed by counterparts containing SBF-1 or SBC which were approximately 25%
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weaker. Interestingly, the composite flour with SBF-4 had similar strength compared to the control whereas the flour with SBF-3 increased its strength by 25%. These values analyzed jointly with the dough stability indicated that the flour enriched with SBF-2 was unstable and less suitable for baking (MTI > 50 BU and dough stability time of only 5.4 min). On the other hand, SBF-3 had the best farinograph dough rheological properties (MTI < 30 BU and dough stability time of 12.9 min) for bread making. 3.2.2. Alveograms Alveograms also demonstrated that the different SB proteins affected differently the properties of doughs. In terms of alveograms (Table 2), composite flours containing SBC or SBF-1 had a higher maximum alveograph over pressure compared to the wheat flour whereas the composite flour containing SBF-2 showed the lowest P value. The highest extensibility dough values were observed in the control and high-PDI SBF-3 and 4 composite flours. This indicates that the low heat-treated flours favored extensibility to a level similar to the control wheat flour. These notorious differences in P and L values affected the P/L ratios that are known to be closely related to flour functionality. The composite flours that had similar values to wheat flour were the composite flours containing SBF-3 and 4. As expected and due to the addition of glutenfree SB proteins, the index of swelling (G), that gives an indication of the work to extend the dough, was significantly lower for all composite flours except for the system containing SBF-4. The best performing composite flours produced with SBC or SBF-3 had G values between 13.3 and 15 and W values between 293 and 278 *104 J (Table 2). Therefore, these doughs were suitable for yeastleavened bakery purposes (W values ranging from 200 to 300 *104 J). These G and W values were similar to the control dough. Addition of the SBF-2 to wheat flour negatively influenced most of the alveograph parameters. This particular composite flour had the lowest G and W values. In fact, this flour with a W value of only 101 104 J was in the range suited for pastries (60e120 W). The alveograph W values showed a moderate positive correlation with NSI (r ¼ 0.52) and PDI (r ¼ 0.60). The PDI has been proposed as a quality parameter to appraise heat treatment processes applied to legume flours during their production in the oil crushing industries. Soybean flours having PDI values higher than 50 were the most recommended for bread making (Table 1). 3.3. Baking properties of soybean enriched pup loaves The SBF-3 and SBC with adequate alveograph W values and farinograph parameters produced the best straight dough breads in terms of bread volume, height and apparent density (Table 3). The optimum dough water absorptions assayed in the straight microbaking procedure of all composite flours were significantly higher compared to the control (p < 0.001). As similar as observed in farinograms (Table 2), the SB-enriched doughs absorbed on average 3.2% more water compared to the control (Table 3). Among the different SB composite flours, the SBC absorbed the highest (67.3%) water, despite it being the source added with the least amount (only 4.5%). Similar results were previously reported by SernaSaldivar et al. (1988). Soybean proteins are rich in hydrophilic and binding protein moieties which increase water absorption. As a result, the SB fortified yeast-leavened breads usually contain more moisture and retain longer their crumb softness (Serna-Saldivar et al., 1988; Sathe, 2012). On the other hand, a high positive correlation was observed between dough water absorption and WAI and a moderate positive correlation with NSI (Table 4). Thus, the composite flour containing SBC with the highest WAI (8.34) showed the highest flour water
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absorption. Interestingly, the SBC had approximately 50% more WAI compared to the SBF defatted flours tested herein (Table 1). Optimum dough mixing times estimated during the microbaking tests were also affected by the addition of the different SB proteins with values fluctuating from 4.0 to 4.4 min. Doughs produced with SBF-3 and 4 (higher PDI) required longer dough mixing schedules (4.4 min) compared to the control (3.9 min). Doughs with SBF-1, SBF-2, or SBC had intermediate dough mixing requirements. Dough mixing times were highly correlated with WSI (r ¼ 0.91) and PDI (r ¼ 0.90). It is well known that high PDI and WSI soybean flours contain high amounts of water soluble-proteins and resulting doughs commonly require higher mixing times due to their lower dough integration and the thickening effect. On the other hand, doughs manufactured with SB with low NSI (<20%) values had evident problems with integration and yielded sticky doughs. This was especially observed with the composite flour containing SBF-2 (Table 1). Interestingly, the SBF-3 or SBC did not present major integration and textural problems during the dough mixing stage. These two SB proteins had high PDI (>52) and NSI (>24%) values (Table 1). Thus, a correct balance between NSI and PDI are crucial for the selection of the most appropriate SB proteins in order to generate appealing and good quality yeast-leavened breads. Low NSI values indicate that the protein is denatured to a higher extent which leads to water insolubilization and the formation of protein aggregates (Ribotta et al., 2005). Thus, longer dough mixing times might be due to inefficient dough integration, especially during the first minutes of kneading. Moreover, a moderate inverse correlation (r ¼ 0.52) between WAI and optimum dough mixing time was attributed to the high hydration capacity of the SBF proteins. It is well-known that SB has high concentrations of hydrosoluble proteins (65e75%) compared to cereals (25%) (Serna-Saldivar, 2010). Both oven spring and bread volume were negatively affected by the different SB sources (p < 0.0001) (Table 3). Flours containing SBC, SBF-4 or SBF-3 yielded breads with volumes higher than 800 cm3; however, only the flour containing SBC exceeded the 820 cm3 considered as optimal. The gluten strength and dilution explain the lower oven-spring values observed in all experimental breads The oven spring had a positive correlation with WAI (r ¼ 0.76) and with NSI (0.89) (Table 4). Dough viscosity has a water-release effect necessary for starch gelatinization during baking (Shin et al., 2013) and expedited yeast proliferation with a consequent better gas generation and retention that positively affected bread volume. Therefore, higher flour water absorptions generally yield better bread volumes. However, the slightly lower bread volume observed in SB enriched breads is mainly attributed to the addition of a non-gluten forming protein and the loss of gluten interaction. It is also known that incorporation of single-cell protein can disrupt the elastic gluten structure, allowing losses of gas during proofing and baking (Fleming and Sosulski, 1978). Ribotta et al. (2005) showed that different SB flours and proteins produced a gluten film which was more permeable to the CO2 generated by yeast. Fleming and Sosulski (1978) showed that the loss of gas during baking may be through small pores in the viscoelastic gluten film protein observed by scanning electronmicroscopy in breads supplemented with SB protein concentrate. Soybean enriched doughs produced from denatured and partially denatured proteins yielded weaker gluten films compared to counterparts produced from less denatured sources. These observations are in accordance to Ribotta et al. (2005). 3.4. Sensory analyses and overall evaluation of breads Sensory evaluation results revealed that panelists did not perceive significant differences in color, odor, flavor, texture and overall acceptance of all breads with scores ranging from 1.5 to 1.8
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Fig. 1. A. Effect of soybean protein addition on the sensory properties of pan breads using a 5-point hedonic scale (1 ¼ like very much and 5 ¼ dislike very much) and B. Texture parameters of slices of fortified breads throughout five days storage at room temperature. Values with the same letter within cluster are not significantly different at p < 0.05.
(p ¼ 0.09), 1.8-2.2 (p ¼ 0.54), 1.8-2.1 (p ¼ 0.32), 1.8-2.1 (p ¼ 0.64) and 1.7-2.1 (p ¼ 0.26) (Fig. 1A), respectively. Although rated equally, panelists documented changes in crumb colorations in the SBenriched breads. These breads had a darker cream coloration compared to the light cream color of the control or SBC enriched crumbs. As expected, among the different SB enriched breads the one manufactured with SBC had the lightest crumb color. All SB enriched breads also had darker crust colors compared to the control. These color changes have been previously documented in other investigations (Mashayekh et al., 2008; Ivanovski et al., 2012; Yezbick et al., 2013). Thermal non-enzymatic caramelization and Maillard reactions occurring between reducing sugars and amino acids are the main ones responsible for the observed darker crust colorations (Ivanovski et al., 2012). Thus, the observed changes in
the crust are related to the non-protein fraction of the different SBF proteins associated with the NSI. Objective crumb bread lightness L* and a* values were not significantly different among breads, whereas b* values were similar among breads manufactured with SB having high and low PDI. Also, bread crust lightness (L*) values were different in all breads whereas a* values were similar (Supplementary Fig. 1). On the other hand, bread cohesiveness, hardness and chewiness, evaluated by the texture analyzer showed no significant differences after one-day storage (Fig. 1B). Elasticity was the most stable parameter during the 5 day storage. Values did not significantly differ among breads. Moreover, chewiness and hardness showed significant differences (p ¼ 0.007 and 0.001, respectively) after the second day of storage. Cohesiveness was the other textural
M.A. Lazo-Velez et al. / Journal of Cereal Science 64 (2015) 63e69 Table 5 Overall scores of soybean-fortified breads compared to wheat bread estimated by nutritional attributes, dough properties, baking, crumb texture and organoleptic tests. Parameters
Control
Flour enriched witha
Wheat flour SBF-1 SBF-2 SBF-3 SBF-4 SBC Nutritional Protein content Amino acid composition Dough machinability Alveograph P Mixing tolerance index Baking performance Water absorption Dough mixing time Bread volume App. bread density Acceptability Overall acceptability Texture after 5 days storageb Desirability value
1 1
þ1 þ1
þ1 þ1
þ1 þ1
þ1 þ1
þ1 þ1
1 1
þ1 0.5
1 1
þ1 þ1
þ1 0
þ1 0.5
1 1 1 1
þ1 1 2 1.5
þ2 1 2 2
þ1 1.5 1.5 1
þ1.5 1.5 1.5 1.5
þ3 1 1 1
1 1 1
0 0.5 ¡1.5
0 1 ¡4
0 1.5 ¡0.5
0 1 ¡1
0 1 þ1.5
a
The experimental SB enriched flours were produced by substitution of 6.0% SBF1; 6.1% SBF-2; 6.3% SBF-3, 6.2% SBF-4 and 4.5% SBC of the refined bread flour. b Average of cohesivity, hardness and chewiness.
parameter in which all sample values were very close. The control and SBC enriched breads showed the higher and lower values respectively (Fig. 1B). Ivanovski et al. (2012) showed that SB flour or protein isolates that substituted wheat flour 20 or 12%, respectively, also influenced both bread flavor and texture. SB enriched breads had a significantly stronger flavor characterized as beany. Mahmoodi et al. (2014) described that, appearance, flavor and taste in breads containing 3, 7 or 12% defatted SB decreased with higher substitution levels. These authors concluded that the best formulations were attained between 3 and 7% substitution. Finally, overall evaluations of the best performing flours were made (Table 5). Scores for white bread compared to the different SB sources were obtained according to the improvement in protein quality, changes in rheological properties, features of breads and organoleptic tests. The best scores were for SBC followed by the SBF-3 whereas the worst treatment was the composite flour containing SBF-2 mainly because its addition worsened rheological properties, lowered bread volume and increased apparent density of bread.
4. Conclusions In conclusion, the SBC and SBF-3 blended with refined wheat flour produced the best enriched breads in terms of organoleptic perception, texture, and bread properties. These SB proteins yielded slightly higher amounts of bread due to their higher dough water absorption. The SB enriched breads had improved protein concentration and amounts of the limiting amino acid lysine and consequently a better protein quality as has been documented by other investigations. The SB-enriched breads had comparable sensory acceptability values and texture throughout 5 days storage compared to the control wheat bread. Additionally, correlation between functional soybean properties, baking properties of pup loaves, and rheological properties of SB composite flours (farinograms and alveograms) evidenced that the functional characteristic of the SB flours especially in terms of PDI and NSI should be taken into consideration for the production of fortified yeast-leavened breads.
69
Acknowledgments The authors would like to acknowledge USSEC for providing the array of soybean samples and sponsoring this research. In addition, authors acknowledge the continuous support of the Consejo xico, Secretaría Nacional de Ciencia y Tecnología (CONACyT), Me n Nacional de Estudios Superiores, Ciencia, Tecnología e Innovacio (SENESCyT), Ecuador and the Nutrigenomic Research Chair of Tec gico de Monterrey for providing research and support funds for nolo the senior author. Appendix A. Supplementary data Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.jcs.2015.04.007. References AACC International, 2000. Approved Methods of the American Association of Cereal Chemists. Methods 10e10.03, 10-05.01, 46-13.01, 54-21.02, 54-30.02 and 7410.02, tenth ed. The Association, St. Paul, MN. AOAC, 2006. Official Methods of Analysis. Official Method 945.30 and 982.30 E(a,b,c), chp. 45.3.05, acid hydrolysis, 23rd ed. Association of Official Analytical Chemists, Gaithersburg, MD. AOCS, 2011. Official Methods and Recommended Practices of the American Oil Chemists' Society. Methods Ba10be09, Ba 9-58 and Ba 11-65, Sixth ed. American Oil Chemists' Society, Champaign, IL. USA. lez, M.A., Nava-Valdeza, Y., Gutie rrez-Uribe, J.A., SernaAcosta-Estrada, B., Lazo-Ve Saldívar, S.O., 2014. Improvement of dietary fiber, ferulic acid and calcium contents in pan bread enriched with nejayote solids from white maize (Zea mays). J. Cereal Sci. 60 (1), 264e269. Amaya-Guerra, C., Serna-Saldivar, S.O., Alanis-Guzman, M.G., 2006. Soybean fortification and enrichment of regular and quality protein maize tortillas affects brain development and maze performance of rats. Br. J. Nutr. 96, 161e168. Cheftel, J.C., Cuq, J.L., Lorient, D., 1989. Propiedades Funcionales de las Proteínas. Chapter 4. In: Proteínas Alimentarias. Acribia. Spain, pp. 49e57. Fleming, S.E., Sosulski, F.W., 1978. Microscopic evaluation of bread fortified whit concentrated plant proteins. Cereal Chem. 55 (3), 373e382. Ivanovski, B., Seetharaman, K., Duizer, L.M., 2012. Development of soy-based bread with acceptable sensory properties. J. Food Sci. 77, 71e76. Khan, M.I., Anjum, F.M., Zahoor, T., Sarwar, M., Wahab, S., 2009. Nutritional characterization of wheat-soy unleavened flat bread by rat bioassay. Sarhad J. Agric. 25 (1), 73e80. Maforimbo, E., Skurray, G., Uthayakumaran, S., Wrigley, C., 2008. Incorporation of soy proteins into the wheategluten matrix during dough mixing. J. Cereal Sci. 47, 380e385. Mahmoodi, M.R., Mashayekh, M., Entezari, M.H., 2014. Fortification of wheat bread with 3e7% defatted soy flour improves formulation, organoleptic characteristics, and rat growth rate. Int. J. Prev. Med. 5, 37e45. Mashayekh, M., Mahmoodi, M.R., Entezari, M.H., 2008. Effect of fortification of defatted soy flour on sensory and rheological properties of wheat bread. Int. J. Food Sci. Technol. 43, 1693e1698. Novotni, D., Curic, D., Gabric, D., Cukelj, N., Curko, N., 2009. Production of high protein bread using extruded corn and soybean flour blend. Italian J. Food Sci. 21, 123e134. n, A.E., An ~o n, M., 2005. Effect of soybean addition on Ribotta, P.D., Arnulphi, S.A., Leo the rheological properties and bread making quality of wheat flour. J. Sci. Food Agric. 85 (11), 1889e1896. Shate, S.K., 2012. Protein solubility and functionality. In: Hettiarachchy, N., Sato, K., Marshall, M., Kannan, A. (Eds.), Food Proteins and Peptides Chemistry, Functionality, Interactions and Commercialization. Taylor & Francis Group, Boca Raton, FL, pp. 95e124. Serna-Saldivar, S.O., 2010. Cereal Grains: Properties, Processing and Nutritional Attributes. CRC Press (Taylor & Francis Group), Boca Raton, FL, USA. Serna-Saldivar, S.O., Lopez-Ahumada, G., Ortega-Ramirez, R., Abril-Dominguez, J.R., 1988. Effect of sodium-stearoyl-2-lactylate on the rheological and baking properties of bread fortified with defatted soybean and sesame meal. J. Food Sci. 53, 211e214. Serrem, C.A., de Kock, H.L., Taylor, J.R.N., 2011. Nutritional quality, sensory quality and consumer acceptability of sorghum and bread wheat biscuits fortified with defatted soy flour. Int. J. Food Sci. Technol. 46, 74e83. Shin, D., Kim, W., Kim, Y., 2013. Physicochemical and sensory properties of soy bread made with germinated, steamed, and roasted soy flour. Food Chem.141, 517e523. Wang, H., Johnson, L.A., Wang, T., 2004. Preparation of soy protein concentrate and isolate from extruded-expelled soybean meals. J. Am. Oil Chem. Soc. 81 (7), 713e717. Watts, B.M., Ylimaki, G.L., Jeffery, L.E., 1989. Basic Sensory Methods for Food Evaluation. IDRC, Ottawa, Canda. Yezbick, G., Ahn-Jarvis, J., Schwartz, S.J., Vodovotz, Y., 2013. Physicochemical characterization and sensory analysis of yeast-leavened and sourdough soy breads. J. Food Sci. 78, 1487e1494.
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Evaluation of the functionality of five different soybean proteins in yeast-leavened pan breads lez, Cristina Chuck-Hernandez, Sergio O. Serna-Saldívar* Marco A. Lazo-Ve gico de Monterrey-Campus Monterrey, Av. Eugenio Garza Sada 2501, Monterrey, Centro de Biotecnología- FEMSA, Escuela de Ingeniería y Ciencias, Tecnolo N.L., C.P. 64849, Mexico
a r t i c l e i n f o
a b s t r a c t
Article history: Received 11 December 2014 Received in revised form 12 March 2015 Accepted 1 April 2015 Available online 9 May 2015
Soybean (SB) products are a source of proteins that complement the amino acid profile of cereal-based products and consequently improve human health. Four different SB flours (SBF-1 to SBF-4) and a SB concentrate (SBC) were incorporated into refined wheat flour in order to increase approximately 20e25% the protein content. The composite flours were processed into yeast-leavened pan breads. The SB fortified breads were characterized in terms of dough rheological, baking performance, bread crumb texture and color and sensory properties. The different SB proteins affected differently rheological properties of doughs, bread properties and quality. Addition of the SB proteins increased more than 3% optimum dough water absorption and consequently bread yield but decreased between 7 and 13% bread volume. The fortified breads also had a darker crumb. The best SB protein sources were SBF-3 and SBC which had respectively 75.5 and 52% PDI, 24 and 36% NSI, 4.0 and 8.3 water absorption and 50.3 and 36.9% water solubility indexes. These SB-fortified breads averaged 23% more protein and almost twice as much lysine compared to the control. Therefore, these SB proteins can be utilized to produce yeast-leavened breads with higher protein and upgraded protein quality. © 2015 Elsevier Ltd. All rights reserved.
Keywords: Bread Soybean proteins Functional properties Dough rheological properties
1. Introduction Soybeans (SB) are a rich source of high-quality protein and nutraceuticals. The high protein content plus the high amounts of essential amino acids that are lacking in most cereals make these flours ideally suited to fortify cereal-based foods, with only a slight increase in the production cost (Mashayekh et al., 2008; Novotni et al., 2009). Furthermore, soybeans are rich sources of dietary fiber, flavonoids, isoflavones, soyasaponins, other antioxidant compounds and most B-vitamins that exert positive health benefits especially in terms of prevention of most chronic diseases, osteoporosis and cancer (Mahmoodi et al., 2014). Bread is the main staple in many countries worldwide and is mainly prepared from refined wheat flour. Nutritionally, the wide array of white breads provide energy, proteins, minerals and micronutrients (Shin et al., 2013; Acosta-Estrada et al., 2014), but the nutritional quality of the protein is not adequate due to the low levels of lysine present in wheat flour. The partial replacement of wheat flour by protein rich flours is difficult because they do not
* Corresponding author. Tel.: þ52 81 83284322; fax: þ52 81 83284262. E-mail address: [email protected] (S.O. Serna-Saldívar). http://dx.doi.org/10.1016/j.jcs.2015.04.007 0733-5210/© 2015 Elsevier Ltd. All rights reserved.
contain gluten-forming proteins and therefore are not functional, especially in leavened-bread systems. In an early report, SernaSaldivar et al. (1988) produced SB enriched pan breads with and without sodium stearoyl lactylate and concluded that this dough conditioner improved volume and texture but not to the level of the control bread. Likewise, Shin et al. (2013) manufactured SB-fortified breads and concluded that they had comparatively denser texture and the peculiar beany flavor. However, SB proteins are potentially suited to fortify bread, biscuits and other bakery formulations especially in terms of enhancing protein quality and quantities of relevant nutraceuticals (Serna-Saldivar et al., 1988; Mashayekh et al., 2008; Ivanovski et al., 2012; Yezbick et al., 2013; Mahmoodi et al., 2014). Defatted SB flour used in bread making increases absorption and moisture retention, which enlarges the freshness or textural shelflife of the product. However, if a large amount of SB protein is incorporated into the wheat flour a disruption of the glutenforming proteins occurs. Therefore, the SB protein interferes with the starchegluten matrix negatively affecting volume, crumb scores and overall quality attributes and acceptability of enriched breads (Shin et al., 2013; Mahmoodi et al., 2014). The aim of this research was to assess the effect of addition of four different defatted SB flours or a SB concentrate with
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contrasting functional properties on the rheological dough properties and quality of yeast-leavened pan breads produced by the pup loaf straight or sponge dough processes. Control and SB fortified treatments were compared in terms of chemical composition, amino acids, dough rheological properties, bread texture and sensory attributes. 2. Materials and methods 2.1. Commercial soybean samples Five different commercial SB samples were selected to differ in functional properties especially in terms of urease activity, water absorption (WAI), water solubility (WSI), protein dispensability (PDI) and nitrogen solubility (NSI) indexes. Four were defatted SB flours, Industrial de Alimentos (SBF-1), GAF-120 (SBF-2), ADM (SBF3) and Ragasa (SBF-4) containing approximately 49% protein (N x 6.25 as is basis), whereas the remaining a protein-concentrate (SBC) Provita® containing 67% protein (as is basis). Urease activity (Method Ba 9-58, AOCS, 2011), nitrogen solubility (Method Ba 1165, AOCS, 2011), water absorption and solubility (Cheftel et al., 1989), and protein dispersibility (Method Ba 10b-09, AOCS, 2011) indexes were assayed. Lysine, tryptophan and sulfur containing amino acids (methionine plus cysteine) in wheat flour and the different SB protein sources were determined according to Official Method 982.30 E (a,b,c) of the AOAC (2006). 2.2. Soybean-fortified flours Each of the five different SBF proteins were composited with commercial refined wheat flour (La Perla, Molinos del Fenix, Saltillo, Coahuila, Mexico) in order to increase the protein concentration to about 20e25%. The experimental SB enriched flours were produced by substitution of 6.0% SBF-1; 6.1% SBF-2; 6.3% SBF-3, 6.2% SBF-4 and 4.5% SBC of the refined bread flour. Protein (N 5.7) was determined in the control and experimental composite flour samples using the AACC International (2000) method 46-30. 2.3. Dough rheological properties The dough rheological properties of the control and SB-composite flours were determined with the farinograph (Brabender Instruments, South Hackensack, NJ) and Alveograph (Chopin Instruments, Villeneuve-La-Garenne, France) according to Approved Methods 5421 and 54-30, respectively (AACC International (2000)). 2.4. Straight dough baking The pup loaf straight-dough bread micro-baking method 1010.03 (AACC International, 2000) was utilized. The bakers formulation consisted of 6% refined cane sugar (Avance, Avance Comercial de Monterrey, Monterrey, NL, Mexico), 3% vegetable shortening (Inca, Unilever de Mexico S.A de C.V., Tultitl an, Edo. de Mexico, Mexico), 2% refined iodinated salt (La Fina, Sales del Istmo, Coatzacoalcos, Veracruz, Mexico) and 2% dry yeast (Saccharomyces cerevisiae) (Azteca® Levadura, Iztapalapa, Mexico, D.F., Mexico). Optimum water absorption and mix times were subjectively determined by observing dough properties or gluten development (film formation, gloss and dough stickiness). Bake absorption, mixing time, proof height, loaf height, oven spring, loaf weight, loaf volume, and loaf apparent density were determined. Proof height and loaf height were determined with a proof height meter (National Manufacturing Co., Lincoln, Nebraska). The difference between these values was recorded as oven spring. Loaf volume was
determined by rapeseed displacement (National Manufacturing Co., Lincoln, Nebraska) according to method 10-05.01 of the AACC International (2000). 2.5. Sponge dough baking Sponge dough breads were manufactured in a pilot plant in order to generate loaves for texture and sensory analyses. Sponge doughs were produced by mixing by hand 200 g of refined bread flour, 5 g instant dry yeast and 140 g water. The resulting blend was placed in a plastic container in a fermentation cabinet (National Mfg., Lincoln, NB, USA) set at 28 ± 1 C for 4 h. Resulting sponges were mixed with the remainder of the dry ingredients: 300 g bread flour, 30 g sugar, 20 g shortening, 5 g of dry whole milk (Nestle de Mexico, Mexico, D.F., Mexico), 10 g salt, 1 g lecithin (Proveedores de Ingeniería Alimentaria S.A. de C.V. Monterrey, N.L., Mexico), 1 g Sodium Stearoyl Lactylate (SSL), 1 g calcium propionate and 2.5 g dry yeast instant for one min at low speed in a Hobart mixer equipped with the hook attachment. Then, the rest of the predetermined amount of water was added and blended for one minute at low speed. Next, the velocity was switched to medium until attaining optimum dough development. Film formation, gloss and dough stickiness were subjectively determined to estimate optimum mix times. Resulting doughs were weighed before placing them in a fermentation cabinet set at 28 ± 1 C and 85% relative humidity. After 10 min resting, doughs were punched thru 0.95 cm roll spacing in preparation for molding and panning in 7.5 cm height metal pans that had the following dimensions on the base and top, respectively: 22.5 and 24.5 cm long and 8.5 and 10.5 cm wide. Baking pans were previously greased with vegetable shortening on the bottom and sides. Panned doughs were proofed for 45 min before baking for 25 min in an oven (Electrolux EOG Gas single oven X 601) set at 190 C. Upon 30 min cooling at room temperature, breads were cut into 2 cm thick slices, packaged in sealed polyethylene bags and stored at room temperature for 5 days. 2.6. Crumb texture and color of sponge breads The crumb texture of the slices of bread (2 cm thick) was evaluated with a texture analyzer (model TA.XT plus, Stable Micro systems, United Kingdom) according to the bread firmnesscompression test method 74-10.02 (AACC International (2000)) with a trigger force of 0.048 N. Cohesiveness, hardness, gumminess, chewiness and elasticity were evaluated at the center of the slice. The parameters were calculated from the resulting texture profile analysis curves. Tests were conducted at days 0 (fresh), 1, 2 and 5 days of bread slices kept at room temperature. The crumb color of the control and experimental breads was objectively measured on three slices with a colorimeter (CR 300, Minolta, Japan). Bread-crumb color parameters L*, a*, and b* were the average of three measurements at different parts of the slice. Tests were conducted after 1 day storage at room temperature. 2.7. Sensory analyses In-house consumer panels (pilot consumer panels) consisted of forty untrained panelists, evaluated the sensory features and overall acceptability of control and experimental breads in individual booths after 24 h of baking. Bread evaluation was performed in a sensory evaluation laboratory (ITESM-Campus Monterrey) according to the guidelines described by Watts et al. (1989). Each panelist was simultaneously given six coded samples along with a ballot, and was asked to rate color, texture, flavor, odor, and overall quality on a 5-point hedonic scale, where 1 is like very much and
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5 is dislike very much. In order to obtain an overall evaluation of the samples, a score was assigned to each bread for nutritional, dough properties, baking performance and sensory acceptability parameters. 2.8. Overall evaluation of breads In order to obtain an overall evaluation of the samples, a score was assigned to each bread for nutritional, dough properties, baking performance and sensory acceptability parameters. The control bread scored 1 for each property and considered these values as baseline. The experimental SB-fortified breads were assigned with neutral, positive (better) or negative (worse) values according to variations among means (Tukey tests at p < 0.05). For instance, when the parameter mean was higher or lower than one or two standard deviations compared to the corresponding mean of the control, the individual scores assigned were þ1 and þ2 or 1 and 2, respectively. Final desirability scores were the addition of all individual scores. 2.9. Statistical analysis Each experiment was performed in triplicate in three different weeks and data was reported as means ± standard deviations. Results were subjected to analysis of variance (ANOVA) and differences among means were compared by Tukey tests at p < 0.05. All computations were made by the statistical software JMP (version 11). 3. Results and discussion 3.1. Protein and amino acid composition As planned, the protein content of the different SB-composite flours were higher compared to the control and similar among all the experimental flours. These averaged 14.4% protein (dry weight basis), representing an average increase of 23% compared to the control wheat flour (11.7% protein dry weight basis). More importantly, these SB products contained between 11 and 16 times higher lysine contents (3.45e4.93%) compared to the refined wheat flour (0.31%) (Table 1). Therefore, the addition of approximately 6 and 4.5% of the different SB defatted flours and concentrate respectively increased 1.6 times the lysine content in composite flours and breads (Table 1). The contrasting difference between the refined wheat flour and the SB protein sources especially in terms of lysine makes these proteins ideally suited to upgrade protein quality and nitrogen retention. Earlier studies clearly
65
documented that the higher protein and enhanced essential amino acid scores of SB-fortified breads improved protein quality and animal growth (Serna-Saldivar et al., 1988; Mashayekh et al., 2008; Mahmoodi et al., 2014). The limiting essential amino acid in wheat is lysine, which is present in about half the amount required for optimum infant growth. Nutrition studies have clearly indicated that the higher lysine improves the amino acid score, protein efficiency ratio, nitrogen retention evaluated by the biological and net protein utilization values, growth, brain development and memory performance in laboratory animals and humans (Serna-Saldivar et al., 1988; Amaya-Guerra et al., 2006; Khan et al., 2009; Serrem et al., 2011; Mahmoodi et al., 2014). The SBF-1 showed the lowest protein dispersibility (PDI) and water solubility (WSI) indexes. On the other hand, SBF-3 and 4 had about 15 times higher urease activity and 3 times higher PDI compared to SBF-1 or 2. SBF-3 and 4 had high urease activity and PDI values due to the slight heat treatments applied prior to oil extraction and during meal desolventization in a desolventizertoaster or DT. The PDI reported for SBC is similar to the value reported by Wang et al. (2004) for a counterpart produced from acidwashed white flakes. 3.2. Rheological properties of SB-enriched doughs 3.2.1. Farinograms As anticipated, rheological properties of doughs estimated with the farinograph and baking performance were affected by the addition of the different SB protein sources (Tables 2 and 3). Addition of the different SB sources improved the dough water absorption capacity by 3.5 units which represented about 6% more water absorption compared to the wheat flour (Table 2). Compared to the wheat flour, the corrected water absorption was between 2.2 and 4.7% units higher for the different SB-enriched counterparts. Several investigations had documented the effect of increased water absorption in doughs supplemented with different SB flours (Serna-Saldivar et al., 1988; Ribotta et al., 2005). These differences are related to the nature of the soybean proteins which are hydrophilic or with high WAI (Table 1). WAI of the different SB proteins ranged from 4.0 in the high PDI SBF-3 to 5.3 in the lowest PDI SBF-1. Addition of all SB flours prolonged arrival times, the longest times were observed in composite flours containing SBF-2 or SBF-4. Interestingly, these meals had low NSI values (Table 1). Only the composite flour containing 4.5% SBC had similar arrival time compared to the control flour (Table 2). The arrival times were inversely correlated with both nitrogen solubility (NSI) (r ¼ 0.57) and water absorption indexes (WAI) (r ¼ 0.56) (Table 4). In
Table 1 Functional characteristics and main essential amino acids of five different soybean protein sources.a Parameter
Crude Protein % (N 6.25, dry basis)c Amino acid (%, dry weight basis)d Lysine Tryptophan Methionine þ Cysteine Urease activity Nitrogen Solubility (NSI, %) Water Absorption Index (WAI) Water Solubility Index (WSI) Protein Dispersibility Index (PDI) a b c d
Soybean protein sourcesb SBF-1
SBF-2
SBF-3
SBF-4
SBC
53.6 ± 0.2C
54.58±2B
54.58 ± 0.4B
53.6 ± 0.1C
74.9 ± 0.2A
3.45 0.85 1.56 0.10 ± 0.01E 19.7 ± 0.7B 5.3 ± 0.0B 25.7 ± 0.4E 23.2 ± 0.1D
3.5 0.87 1.61 0.15 ± 0.01D 13.4 ± 0.8C 4.8 ± 0.3C 28.4 ± 0.1D 25.3 ± 1.6D
3.54 0.82 1.64 2.25 24.0 4.02 50.3 75.5
3.55 0.76 1.63 2.20 ± 0.03B 25.5 ± 0.7B 4.3 ± 0.1D 47.6 ± 1.8B 66.9 ± 1.5B
4.93 1.09 1.95 0.40 ± 0.01C 36.1 ± 1.5A 8.3 ± 0.1A 36.9 ± 0.2C 52.0 ± 0.5C
± ± ± ± ±
0.01A 0.2B 0.0E 0.2A 1.7A
Averages ± standard deviations, values with the same letter within row are not significantly different at p < 0.05, (n ¼ 3). The experimental SB enriched flours were produced by substitution of 6.0% SBF-1; 6.1% SBF-2; 6.3% SBF-3, 6.2% SBF-4 and 4.5% SBC of the refined bread flour. The refined hard wheat flour contained 11.72% crude protein (N 5.7, dry basis). The wheat flour contained 0.31, 0.18 and 0.50% (dry weight basis) of lysine, tryptophan and methionine þ cysteine, respectively.
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Table 2 Effect of soybean protein addition on the rheological properties of doughs estimated with the farinograph and alveograph.a Parameter
Flour enriched withb
Control Wheat flour
a
c
SBF-2
12.2 ± 0.2
10.1 ± 0.4
Flour fortified protein, % (14% mb) Farinograph Water Absorption (%) Corrected Water Absorption (%) Arrival Time (min) Departure Time (min) Dough Stability (min) Dough Development (min) Mixing Tolerance Index (BU)c Alveograph P (mm H2O) L (mm) P/L G W (104J) b
SBF-1
B
A
SBF-3
12.3 ± 0.7
A
SBF-4
12.4 ± 1
A
SBC
12.3 ± 0.7
A
12.5 ± 0.1A
58.6 58.3 0.9 13.5 12.7 8.0 40
± ± ± ± ± ± ±
0.2C 0.2C 0.1B 0.7A 0.6A 0.2A 0B
63.4 63.04 1.3 11.5 10.2 7.0 50
± ± ± ± ± ± ±
0.3A 0.3A 0.1B 0.4B 0.4B 0.3C 0AB
61.6 60.49 3.9 9.3 5.4 7.0 55
± ± ± ± ± ± ±
0.2B 0.2B 0.5A 0.4C 0.1C 0.4C 7.1A
61.0 60.5 1.25 14.1 12.9 8.0 30
± ± ± ± ± ± ±
0.1B 0.1B 0.1B 0.1A 0.1A 0.2A 0C
63.4 62.98 3.8 11.4 7.7 7.5 40
± ± ± ± ± ± ±
0.1A 0.1A 1.1A 0.1B 1.2C 0.2B 0B
61.8 61.5 0.8 11 10.3 6.5 50
± ± ± ± ± ± ±
0.2B 0.2B 0B 0B 0B 0.4D 0AB
123.5 53.5 2.3 16.3 275
± ± ± ± ±
4.9B 2.1A 0.2C 0.2A 2.8A
172 36 4.9 13 270
± ± ± ± ±
7.1A 0.7B 0.3ABC 0.1B 7.8A
120.5 19 6.6 9.7 101
± ± ± ± ±
4.9B 5.7C 1.7A 1.3C 20.5B
138.5 48 2.9 15.0 278
± ± ± ± ±
4.9B 3.5A 0.3BC 0.6AB 7.1A
134.5 52 2.6 16 288
± ± ± ± ±
0.7B 0A 0C 0.1A 2.1A
183.5 35.5 5.2 13.3 293
± ± ± ± ±
2.1A 0.7B 0.1AB 0B 5.7A
Average ± standard deviations, values with the same letter within row are not significantly different at p < 0.05, (n ¼ 2). The experimental SB enriched flours were produced by substitution of 6.0% SBF-1; 6.1% SBF-2; 6.3% SBF-3, 6.2% SBF-4 and 4.5% SBC of the refined bread flour. Brabender or Farinograph Units.
Table 3 Effect of soybean protein addition on the dough mixing and baking properties of pup loaves produced with the straight dough micro-baking procedure.a Treatment
Flour enriched withb
Control Wheat flour
Water Absorption (%) Dough Mixing Time (min) Oven Springc (cm) Bread Weight (g) Bread Volume (cm3) App. Bread Densityd (g/cm3) a b c d
63.7 3.9 2.3 145 899.2 0.16
± ± ± ± ± ±
0.5D 0.13BC 0.38A 0.7BC 20A 0.1C
SBF-1 65.2 4.1 1.5 146.7 783.5 0.19
SBF-2 ± ± ± ± ± ±
0.3C 0.1AB 0.2B 1.8ABC 34C 0.1AB
66 4.0 1.5 149.4 775.8 0.19
SBF-3 ± ± ± ± ± ±
0.8B 0.0AB 0.39B 1.7AB 33C 0.1A
64.7 4.4 1.5 144.5 809 0.18
SBF-4 ± ± ± ± ± ±
0.5C 0.34A 0.44B 2.6C 27BC 0.0B
65.3 4.4 1.6 151.1 818.3 0.18
SBC ± ± ± ± ± ±
0.3BC 0.46A 0.61B 5.3A 9.3BC 0.0AB
67.3 4.1 1.7 146.6 828.3 0.18
± ± ± ± ± ±
0.3A 0.34AB 0.28B 2.1ABC 20B 0.0B
Averages ± standard deviations, values with the same letter within row are not significantly different at p < 0.05, (n ¼ 6). Temperature of fermentation 31.2 ± 0.8 C. The experimental SB enriched flours were produced by substitution of 6.0% SBF-1; 6.1% SBF-2; 6.3% SBF-3, 6.2% SBF-4 and 4.5% SBC of the refined bread flour. Oven spring ¼ bread height e proof height. Apparent Bread Density.
contrast, the departure time was positively correlated with both WSI (r ¼ 0.73) and PDI (r ¼ 0.72). These data indicated that the quantity of soluble proteins and PDI increased departure time. According to Maforimbo et al. (2008), the poor dough and baking qualities of composite wheat-soybean formulations could be explained by the fact that wheat proteins favor hydrophobic
Table 4 Correlation between soybean quality parameters and rheological properties, and micro-baking test estimated with different SBFs. Parameters Farinograph Water Absorption (%) Arrival Time (min) Departure Time (min) Dough Stability (min) Dough Development (min) Mixing Tolerance Index (BU)2 Alveograph P (mm H2O) L (mm) P/L G W (104J) Baking properties Water Absorption (%) Dough Mixing Time (min) Oven Spring (cm) Bread Volume (cm3)
%NS
WAI
WSI
PDI
0.05 ¡0.57 0.30 0.49 0.26 0.22
0.12 ¡0.55 0.28 0.13 ¡0.83 0.48
0.33 0.06 0.73 0.49 0.73 ¡0.91
0.27 0.12 0.72 0.51 0.63 ¡0.88
0.67 0.47 0.33 0.52 0.76
0.79 0.29 0.45 0.22 0.22
0.26 0.79 ¡0.84 0.77 0.49
0.14 0.82 ¡0.85 0.81 0.59
0.53 0.26 0.89 0.93
0.90 ¡0.52 0.76 0.41
0.34 0.91 0.16 0.67
0.24 0.89 0.30 0.77
The bolded data had significant Pearson correlations (p < 0.05).
interactions whereas SB proteins had more affinity for water or are hydrophilic. Dough development times were similar (p > 0.05) for the control and SBF-3 composite dough and lowest for the SBC dough (Table 2). The dough development times were positively correlated with WSI (r ¼ 0.73) and PDI (r ¼ 0.63), and showed a high negative correlation with WAI (r ¼ 0.83). The soluble proteins related to PDI affected the time to achieve maximum consistency likely due to the gel-forming ability of these macromolecules. Dough stability times in all SB-enriched flours, except for the one containing SBF-3, were lower compared to the control. The farinograph dough stabilities were around 20% less for composite flours with SBF-1 and SBC, 40% less for the SBF-4, and 57% less for SBF-2. Ribotta et al. (2005) observed that both dough development and stability times decreased in doughs prepared with mixtures of wheat flour with SB (active or heat-treated). In conclusion, the highest PDI (Table 1) SBF-3 was the protein source that impacted the most of all farinograph parameters. The two best performing SB sources (SBC and SBF-3) had farinograph dough development and stability times of 6.5e8 and 10.3e12.9 min, respectively. The correlation between farinograph dough stability time and PDI (r ¼ 0.51) was moderate whereas correlations between mixing tolerance index and PDI (r ¼ 0.91) and WSI (r ¼ 0.88) were negative. The mixing tolerance indexes in all experimental doughs showed varying tolerances in relation to the control. The flour containing SBF-2 with a low PDI yielded the weakest dough. This particular dough had 37.5% reduced strength followed by counterparts containing SBF-1 or SBC which were approximately 25%
M.A. Lazo-Velez et al. / Journal of Cereal Science 64 (2015) 63e69
weaker. Interestingly, the composite flour with SBF-4 had similar strength compared to the control whereas the flour with SBF-3 increased its strength by 25%. These values analyzed jointly with the dough stability indicated that the flour enriched with SBF-2 was unstable and less suitable for baking (MTI > 50 BU and dough stability time of only 5.4 min). On the other hand, SBF-3 had the best farinograph dough rheological properties (MTI < 30 BU and dough stability time of 12.9 min) for bread making. 3.2.2. Alveograms Alveograms also demonstrated that the different SB proteins affected differently the properties of doughs. In terms of alveograms (Table 2), composite flours containing SBC or SBF-1 had a higher maximum alveograph over pressure compared to the wheat flour whereas the composite flour containing SBF-2 showed the lowest P value. The highest extensibility dough values were observed in the control and high-PDI SBF-3 and 4 composite flours. This indicates that the low heat-treated flours favored extensibility to a level similar to the control wheat flour. These notorious differences in P and L values affected the P/L ratios that are known to be closely related to flour functionality. The composite flours that had similar values to wheat flour were the composite flours containing SBF-3 and 4. As expected and due to the addition of glutenfree SB proteins, the index of swelling (G), that gives an indication of the work to extend the dough, was significantly lower for all composite flours except for the system containing SBF-4. The best performing composite flours produced with SBC or SBF-3 had G values between 13.3 and 15 and W values between 293 and 278 *104 J (Table 2). Therefore, these doughs were suitable for yeastleavened bakery purposes (W values ranging from 200 to 300 *104 J). These G and W values were similar to the control dough. Addition of the SBF-2 to wheat flour negatively influenced most of the alveograph parameters. This particular composite flour had the lowest G and W values. In fact, this flour with a W value of only 101 104 J was in the range suited for pastries (60e120 W). The alveograph W values showed a moderate positive correlation with NSI (r ¼ 0.52) and PDI (r ¼ 0.60). The PDI has been proposed as a quality parameter to appraise heat treatment processes applied to legume flours during their production in the oil crushing industries. Soybean flours having PDI values higher than 50 were the most recommended for bread making (Table 1). 3.3. Baking properties of soybean enriched pup loaves The SBF-3 and SBC with adequate alveograph W values and farinograph parameters produced the best straight dough breads in terms of bread volume, height and apparent density (Table 3). The optimum dough water absorptions assayed in the straight microbaking procedure of all composite flours were significantly higher compared to the control (p < 0.001). As similar as observed in farinograms (Table 2), the SB-enriched doughs absorbed on average 3.2% more water compared to the control (Table 3). Among the different SB composite flours, the SBC absorbed the highest (67.3%) water, despite it being the source added with the least amount (only 4.5%). Similar results were previously reported by SernaSaldivar et al. (1988). Soybean proteins are rich in hydrophilic and binding protein moieties which increase water absorption. As a result, the SB fortified yeast-leavened breads usually contain more moisture and retain longer their crumb softness (Serna-Saldivar et al., 1988; Sathe, 2012). On the other hand, a high positive correlation was observed between dough water absorption and WAI and a moderate positive correlation with NSI (Table 4). Thus, the composite flour containing SBC with the highest WAI (8.34) showed the highest flour water
67
absorption. Interestingly, the SBC had approximately 50% more WAI compared to the SBF defatted flours tested herein (Table 1). Optimum dough mixing times estimated during the microbaking tests were also affected by the addition of the different SB proteins with values fluctuating from 4.0 to 4.4 min. Doughs produced with SBF-3 and 4 (higher PDI) required longer dough mixing schedules (4.4 min) compared to the control (3.9 min). Doughs with SBF-1, SBF-2, or SBC had intermediate dough mixing requirements. Dough mixing times were highly correlated with WSI (r ¼ 0.91) and PDI (r ¼ 0.90). It is well known that high PDI and WSI soybean flours contain high amounts of water soluble-proteins and resulting doughs commonly require higher mixing times due to their lower dough integration and the thickening effect. On the other hand, doughs manufactured with SB with low NSI (<20%) values had evident problems with integration and yielded sticky doughs. This was especially observed with the composite flour containing SBF-2 (Table 1). Interestingly, the SBF-3 or SBC did not present major integration and textural problems during the dough mixing stage. These two SB proteins had high PDI (>52) and NSI (>24%) values (Table 1). Thus, a correct balance between NSI and PDI are crucial for the selection of the most appropriate SB proteins in order to generate appealing and good quality yeast-leavened breads. Low NSI values indicate that the protein is denatured to a higher extent which leads to water insolubilization and the formation of protein aggregates (Ribotta et al., 2005). Thus, longer dough mixing times might be due to inefficient dough integration, especially during the first minutes of kneading. Moreover, a moderate inverse correlation (r ¼ 0.52) between WAI and optimum dough mixing time was attributed to the high hydration capacity of the SBF proteins. It is well-known that SB has high concentrations of hydrosoluble proteins (65e75%) compared to cereals (25%) (Serna-Saldivar, 2010). Both oven spring and bread volume were negatively affected by the different SB sources (p < 0.0001) (Table 3). Flours containing SBC, SBF-4 or SBF-3 yielded breads with volumes higher than 800 cm3; however, only the flour containing SBC exceeded the 820 cm3 considered as optimal. The gluten strength and dilution explain the lower oven-spring values observed in all experimental breads The oven spring had a positive correlation with WAI (r ¼ 0.76) and with NSI (0.89) (Table 4). Dough viscosity has a water-release effect necessary for starch gelatinization during baking (Shin et al., 2013) and expedited yeast proliferation with a consequent better gas generation and retention that positively affected bread volume. Therefore, higher flour water absorptions generally yield better bread volumes. However, the slightly lower bread volume observed in SB enriched breads is mainly attributed to the addition of a non-gluten forming protein and the loss of gluten interaction. It is also known that incorporation of single-cell protein can disrupt the elastic gluten structure, allowing losses of gas during proofing and baking (Fleming and Sosulski, 1978). Ribotta et al. (2005) showed that different SB flours and proteins produced a gluten film which was more permeable to the CO2 generated by yeast. Fleming and Sosulski (1978) showed that the loss of gas during baking may be through small pores in the viscoelastic gluten film protein observed by scanning electronmicroscopy in breads supplemented with SB protein concentrate. Soybean enriched doughs produced from denatured and partially denatured proteins yielded weaker gluten films compared to counterparts produced from less denatured sources. These observations are in accordance to Ribotta et al. (2005). 3.4. Sensory analyses and overall evaluation of breads Sensory evaluation results revealed that panelists did not perceive significant differences in color, odor, flavor, texture and overall acceptance of all breads with scores ranging from 1.5 to 1.8
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Fig. 1. A. Effect of soybean protein addition on the sensory properties of pan breads using a 5-point hedonic scale (1 ¼ like very much and 5 ¼ dislike very much) and B. Texture parameters of slices of fortified breads throughout five days storage at room temperature. Values with the same letter within cluster are not significantly different at p < 0.05.
(p ¼ 0.09), 1.8-2.2 (p ¼ 0.54), 1.8-2.1 (p ¼ 0.32), 1.8-2.1 (p ¼ 0.64) and 1.7-2.1 (p ¼ 0.26) (Fig. 1A), respectively. Although rated equally, panelists documented changes in crumb colorations in the SBenriched breads. These breads had a darker cream coloration compared to the light cream color of the control or SBC enriched crumbs. As expected, among the different SB enriched breads the one manufactured with SBC had the lightest crumb color. All SB enriched breads also had darker crust colors compared to the control. These color changes have been previously documented in other investigations (Mashayekh et al., 2008; Ivanovski et al., 2012; Yezbick et al., 2013). Thermal non-enzymatic caramelization and Maillard reactions occurring between reducing sugars and amino acids are the main ones responsible for the observed darker crust colorations (Ivanovski et al., 2012). Thus, the observed changes in
the crust are related to the non-protein fraction of the different SBF proteins associated with the NSI. Objective crumb bread lightness L* and a* values were not significantly different among breads, whereas b* values were similar among breads manufactured with SB having high and low PDI. Also, bread crust lightness (L*) values were different in all breads whereas a* values were similar (Supplementary Fig. 1). On the other hand, bread cohesiveness, hardness and chewiness, evaluated by the texture analyzer showed no significant differences after one-day storage (Fig. 1B). Elasticity was the most stable parameter during the 5 day storage. Values did not significantly differ among breads. Moreover, chewiness and hardness showed significant differences (p ¼ 0.007 and 0.001, respectively) after the second day of storage. Cohesiveness was the other textural
M.A. Lazo-Velez et al. / Journal of Cereal Science 64 (2015) 63e69 Table 5 Overall scores of soybean-fortified breads compared to wheat bread estimated by nutritional attributes, dough properties, baking, crumb texture and organoleptic tests. Parameters
Control
Flour enriched witha
Wheat flour SBF-1 SBF-2 SBF-3 SBF-4 SBC Nutritional Protein content Amino acid composition Dough machinability Alveograph P Mixing tolerance index Baking performance Water absorption Dough mixing time Bread volume App. bread density Acceptability Overall acceptability Texture after 5 days storageb Desirability value
1 1
þ1 þ1
þ1 þ1
þ1 þ1
þ1 þ1
þ1 þ1
1 1
þ1 0.5
1 1
þ1 þ1
þ1 0
þ1 0.5
1 1 1 1
þ1 1 2 1.5
þ2 1 2 2
þ1 1.5 1.5 1
þ1.5 1.5 1.5 1.5
þ3 1 1 1
1 1 1
0 0.5 ¡1.5
0 1 ¡4
0 1.5 ¡0.5
0 1 ¡1
0 1 þ1.5
a
The experimental SB enriched flours were produced by substitution of 6.0% SBF1; 6.1% SBF-2; 6.3% SBF-3, 6.2% SBF-4 and 4.5% SBC of the refined bread flour. b Average of cohesivity, hardness and chewiness.
parameter in which all sample values were very close. The control and SBC enriched breads showed the higher and lower values respectively (Fig. 1B). Ivanovski et al. (2012) showed that SB flour or protein isolates that substituted wheat flour 20 or 12%, respectively, also influenced both bread flavor and texture. SB enriched breads had a significantly stronger flavor characterized as beany. Mahmoodi et al. (2014) described that, appearance, flavor and taste in breads containing 3, 7 or 12% defatted SB decreased with higher substitution levels. These authors concluded that the best formulations were attained between 3 and 7% substitution. Finally, overall evaluations of the best performing flours were made (Table 5). Scores for white bread compared to the different SB sources were obtained according to the improvement in protein quality, changes in rheological properties, features of breads and organoleptic tests. The best scores were for SBC followed by the SBF-3 whereas the worst treatment was the composite flour containing SBF-2 mainly because its addition worsened rheological properties, lowered bread volume and increased apparent density of bread.
4. Conclusions In conclusion, the SBC and SBF-3 blended with refined wheat flour produced the best enriched breads in terms of organoleptic perception, texture, and bread properties. These SB proteins yielded slightly higher amounts of bread due to their higher dough water absorption. The SB enriched breads had improved protein concentration and amounts of the limiting amino acid lysine and consequently a better protein quality as has been documented by other investigations. The SB-enriched breads had comparable sensory acceptability values and texture throughout 5 days storage compared to the control wheat bread. Additionally, correlation between functional soybean properties, baking properties of pup loaves, and rheological properties of SB composite flours (farinograms and alveograms) evidenced that the functional characteristic of the SB flours especially in terms of PDI and NSI should be taken into consideration for the production of fortified yeast-leavened breads.
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Acknowledgments The authors would like to acknowledge USSEC for providing the array of soybean samples and sponsoring this research. In addition, authors acknowledge the continuous support of the Consejo xico, Secretaría Nacional de Ciencia y Tecnología (CONACyT), Me n Nacional de Estudios Superiores, Ciencia, Tecnología e Innovacio (SENESCyT), Ecuador and the Nutrigenomic Research Chair of Tec gico de Monterrey for providing research and support funds for nolo the senior author. Appendix A. Supplementary data Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.jcs.2015.04.007. References AACC International, 2000. Approved Methods of the American Association of Cereal Chemists. Methods 10e10.03, 10-05.01, 46-13.01, 54-21.02, 54-30.02 and 7410.02, tenth ed. The Association, St. Paul, MN. AOAC, 2006. Official Methods of Analysis. Official Method 945.30 and 982.30 E(a,b,c), chp. 45.3.05, acid hydrolysis, 23rd ed. Association of Official Analytical Chemists, Gaithersburg, MD. AOCS, 2011. Official Methods and Recommended Practices of the American Oil Chemists' Society. Methods Ba10be09, Ba 9-58 and Ba 11-65, Sixth ed. American Oil Chemists' Society, Champaign, IL. USA. lez, M.A., Nava-Valdeza, Y., Gutie rrez-Uribe, J.A., SernaAcosta-Estrada, B., Lazo-Ve Saldívar, S.O., 2014. Improvement of dietary fiber, ferulic acid and calcium contents in pan bread enriched with nejayote solids from white maize (Zea mays). J. Cereal Sci. 60 (1), 264e269. Amaya-Guerra, C., Serna-Saldivar, S.O., Alanis-Guzman, M.G., 2006. Soybean fortification and enrichment of regular and quality protein maize tortillas affects brain development and maze performance of rats. Br. J. Nutr. 96, 161e168. Cheftel, J.C., Cuq, J.L., Lorient, D., 1989. Propiedades Funcionales de las Proteínas. Chapter 4. In: Proteínas Alimentarias. Acribia. Spain, pp. 49e57. Fleming, S.E., Sosulski, F.W., 1978. Microscopic evaluation of bread fortified whit concentrated plant proteins. Cereal Chem. 55 (3), 373e382. Ivanovski, B., Seetharaman, K., Duizer, L.M., 2012. Development of soy-based bread with acceptable sensory properties. J. Food Sci. 77, 71e76. Khan, M.I., Anjum, F.M., Zahoor, T., Sarwar, M., Wahab, S., 2009. Nutritional characterization of wheat-soy unleavened flat bread by rat bioassay. Sarhad J. Agric. 25 (1), 73e80. Maforimbo, E., Skurray, G., Uthayakumaran, S., Wrigley, C., 2008. Incorporation of soy proteins into the wheategluten matrix during dough mixing. J. Cereal Sci. 47, 380e385. Mahmoodi, M.R., Mashayekh, M., Entezari, M.H., 2014. Fortification of wheat bread with 3e7% defatted soy flour improves formulation, organoleptic characteristics, and rat growth rate. Int. J. Prev. Med. 5, 37e45. Mashayekh, M., Mahmoodi, M.R., Entezari, M.H., 2008. Effect of fortification of defatted soy flour on sensory and rheological properties of wheat bread. Int. J. Food Sci. Technol. 43, 1693e1698. Novotni, D., Curic, D., Gabric, D., Cukelj, N., Curko, N., 2009. Production of high protein bread using extruded corn and soybean flour blend. Italian J. Food Sci. 21, 123e134. n, A.E., An ~o n, M., 2005. Effect of soybean addition on Ribotta, P.D., Arnulphi, S.A., Leo the rheological properties and bread making quality of wheat flour. J. Sci. Food Agric. 85 (11), 1889e1896. Shate, S.K., 2012. Protein solubility and functionality. In: Hettiarachchy, N., Sato, K., Marshall, M., Kannan, A. (Eds.), Food Proteins and Peptides Chemistry, Functionality, Interactions and Commercialization. Taylor & Francis Group, Boca Raton, FL, pp. 95e124. Serna-Saldivar, S.O., 2010. Cereal Grains: Properties, Processing and Nutritional Attributes. CRC Press (Taylor & Francis Group), Boca Raton, FL, USA. Serna-Saldivar, S.O., Lopez-Ahumada, G., Ortega-Ramirez, R., Abril-Dominguez, J.R., 1988. Effect of sodium-stearoyl-2-lactylate on the rheological and baking properties of bread fortified with defatted soybean and sesame meal. J. Food Sci. 53, 211e214. Serrem, C.A., de Kock, H.L., Taylor, J.R.N., 2011. Nutritional quality, sensory quality and consumer acceptability of sorghum and bread wheat biscuits fortified with defatted soy flour. Int. J. Food Sci. Technol. 46, 74e83. Shin, D., Kim, W., Kim, Y., 2013. Physicochemical and sensory properties of soy bread made with germinated, steamed, and roasted soy flour. Food Chem.141, 517e523. Wang, H., Johnson, L.A., Wang, T., 2004. Preparation of soy protein concentrate and isolate from extruded-expelled soybean meals. J. Am. Oil Chem. Soc. 81 (7), 713e717. Watts, B.M., Ylimaki, G.L., Jeffery, L.E., 1989. Basic Sensory Methods for Food Evaluation. IDRC, Ottawa, Canda. Yezbick, G., Ahn-Jarvis, J., Schwartz, S.J., Vodovotz, Y., 2013. Physicochemical characterization and sensory analysis of yeast-leavened and sourdough soy breads. J. Food Sci. 78, 1487e1494.