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Rheological properties of wheat flour dough and pan bread with wheat bran
Journal of Cereal Science 71 (2016) 177e182
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Journal of Cereal Science journal homepage: www.elsevier.com/locate/jcs
Rheological properties of wheat flour dough and pan bread with wheat bran Elis R.F. Boita a, Tatiana Oro b, *, Joseane Bressiani b, Gabriela S. Santetti c, Telma E. Bertolin b, Luiz C. Gutkoski b ~o em Bioexperimentaça ~o, Universidade de Passo Fundo, BR 285, CEP 99052-900, Passo Fundo, RS, Brazil s-Graduaça Programa de Po ~o em Ci^ s-Graduaça Programa de Po encia e Tecnologia de Alimentos, Universidade de Passo Fundo, BR 285, CEP 99052-900, Passo Fundo, RS, Brazil c ~o em Engenharia de Alimentos, Universidade de Passo Fundo, BR 285, CEP 99052-900, Passo Fundo, RS, Brazil Curso de Graduaça a
b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 4 December 2015 Received in revised form 23 July 2016 Accepted 28 August 2016 Available online 30 August 2016
Wheat bran improves the nutritional properties of bread products due to the fiber content and antioxidant compounds, but causes changes in physical-chemical and technological properties. The objective of this study was to investigate the effect of wheat bran reincorporation in the dough properties and subsequent technological properties of breads. The dough and bread making properties were affected by the reincorporation of bran. Parameters such as mixing properties, viscosity, resistance to extension and extensibility demonstrated the influence of bran reincorporation into the gluten network. The presence of the bran also produced breads with lower specific volume, moisture, water activity and more hardness. The bran interactions with the gluten network are the main cause of the effects on dough quality, causing thinning and weakening of the gluten matrix. The flour presented different paste and hydration properties, affecting the rheology of the dough and performance in baking. Samples with 75% and 100% reincorporation were more nutrient-rich, providing enhanced functionality to the body, especially in relation to dietary fiber, but were responsible for more pronounced changes in the technological characteristics of the dough and breads. © 2016 Elsevier Ltd. All rights reserved.
Keywords: Wheat Whole flour Wheat quality Gluten
1. Introduction The whole wheat flour containing more vitamins, minerals, antioxidants and other nutrients compared to that of refined wheat flour, since these compounds are concentrated in the outer layers of the grain (Weaver, 2001). Wheat (Triticum aestivum L.) is one of cereal grain most used worldwide. Despite the health benefits, the presence of components of the parts external grain and germ cause adverse effects on the dough properties of the whole grain based bakery products. These effects are evidenced by reduction of volume, texture modifications, appearance and taste (Pomeranz et al., 1977). Due to this reason, the majority of the consumers prefer products of refined white flour to whole wheat products, because they perceive that the textural properties, the appearance and the lu, taste of whole grain products are less attractive (Boz and Karaog 2013). Bread, one of the most consumed and essential foods of human
* Corresponding author. E-mail address: [email protected] (T. Oro). http://dx.doi.org/10.1016/j.jcs.2016.08.015 0733-5210/© 2016 Elsevier Ltd. All rights reserved.
diet, when enriched with bran improves the nutritional properties and promotes physiological effects by eating habit (Stevenson et al., 2012). However, the effects of the addition of bran in the properties of dough and bread are attributed to the dilution of gluten, which affects the gas retaining capacity of the dough (Wang et al., 2002; mez et al., 2003). Changes in the dough of the water content Go reduce the loaf volume and increase crumb hardness in function of the amount of bran reincorporated on the wheat flour (Curti et al., 2013). According to Wangy (2011), the bran particles can react directly with the structural elements of the gluten network decreasing the dough extensibility and damaging the gas retention. A major problem associated with adding high levels of fibers in foods including confectionary goods is their negative effect on the physical and sensory properties of food products as in flavor, appearance and texture. To solve these problems, the food industry searching for alternatives to resolve or minimize the effects associated with these fractions, as different milling techniques, the use of cellulase enzymes, enzyme inactivation components of the bran, and different heat treatments applied to this fraction of the grain wheat.
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There are several research data on fiber enriched breads, but results might differ and substitution levels used are commonly low. Recently, studies have been conducted in order to show the effect of reducing the size of bran particles in the mass formation and quality of bread, for both whole grain flour, as for refined flour obtained by reincorporation of bran. In function of the benefits of foods rich in fiber and bioactive compounds and considering the availability of bran and consumption of bread by the population, it is relevant to assess its effects on the properties of raw materials and bakery products. This work was carried out to study the effect of reincorporation of bran having particle size reduction in dough and technological properties and shelf-life of breads. 2. Material and methods 2.1. Obtaining the material The batch of 100 kg of wheat (Triticum aestivum L.), purchased from a commercial supplier was subjected to grinding in an industrial mill, obtaining flour fractions and bran with a 75% extraction. The flour was subjected to a new grinding, conducted in a laboratory mill (MA020, Marconi, Brazil), decreasing the average particle diameter from 402 to 369 mm. The bran was reincorporated to the flour in concentrations of zero (100% flour), 25% (93.75% flour and 6.25% bran), 50% (87.5% flour and 12.5% of bran), 75% (81.25% flour and 18.75% bran) and 100% (75% flour and 25% bran). The flours were homogenized with the use of a mixer (HB25, Hyppolyto, Brazil) and stored in cold storage until the time of analysis. 2.2. Analysis of the physicochemical properties of flours The moisture, protein, ash, total fiber, lipids and gluten content were determined according to the official methods of the American Association of Cereal Chemistry (AACC, 2010), 44e15.02, 46e10.01, 08e12.01, 32e10.01, 30e25 and 38e12.02, respectively. The bran particle size distribution was performed by the method 66e20.01 (AACC, 2010). 2.3. Mixing properties The effect of different levels of reincorporation of bran in the dough mixing properties were determined according to method 54e21.02 of the AACC (2010), in a promylograph equipment (T6-E, Koloman Egger, Austria).
Germany) at 30 C until maximum consistency was reached. Initially, 3 min of mixing at slow speed was used for all samples for the purpose of mixing the ingredients flour, enhancer, sugar, salt and water. The yeast and fat were added and the remaining time of the mixture was adjusted according to the development of the dough of each sample using fast speed of 12 min for refined flour; 11 min for the flour with 25% bran reincorporation; 10 min for the flour with 50% bran reincorporation; 9 min for the flour with 75% bran reincorporation; 6 min for the flour with 100% bran reincorporation. The dough was divided in portions of 150 g and fermentation ~o, Brazil), at of was carried out in a chamber (MP20, Multipa 30 ± 1 C and relative humidity of 80%. The baking was performed in a laboratory oven (QA 226, Labor Instruments, Austria) at 220 C for 18 min. The breads cooled at room temperature and after 1 h the analyses were performed. 2.6. Extensional properties of dough Texturometer (TA.XT.plus, Stable Micro Systems, England) equipped with Exponent 32 software using a Kieffer Dough and Gluten Extensibility Rig (A/KIE), probe with pre-test speed of 2.0 mm/s, test of 3.0 mm/s and post-test 10.0 mm/s, a distance of 75.0 mm and strength of 5.0 kg were applied to investigate the extensional properties (extensibility and resistance to extension) of bread dough samples. 2.7. Evaluating the bread quality The breads were evaluated through the specific volume determination at the initial time and through parameters of water activity, moisture content, and firmness at the initial time and along of time of 10 days. The volume was determined by seed displacement in a bread volume measurer according to AACC method 10e05.01 (2010). Moisture of the samples was evaluated according to AACC method 44e15.02 (2010). The firmness of the breads was determined, being carried out in accordance with AACC method 74e09.01 (2010), with the use of a texturometer (TA.XT.plus, Stable Micro Systems, England) equipped with Exponent 32 software. The breads were sliced to 25 mm in thickness, reducing the size of the slices to 25 mm wide x 25 mm long and removal of the crust. An aluminum cylindrical probe P/36R (a radius of 36 mm) was used, pre-test speed of 1.0 mm s1; speed of 1.7 mm s1 test; post-test speed of 10.0 mm s1 and 40% compression strength. 2.8. Statistical analysis
2.4. Paste properties Paste properties were analyzed in accordance with method 76e21.01 of AACC (2010) using a fast speed analyzer (RVA-3D, Newport Scientific, Australia) equipped with Thermocline software for Windows, version 3.1. A sample of approximately 3.5 g flour (corrected to 14% moisture) and 25 ± 0.1 mL of distilled water and Standard 1 temperature profile.
The determinations were performed in triplicate at least. Statistical analysis was performed with use of the Software. The significance of the data was tested by analysis of variance (ANOVA) at 0.05 error probability and in the significant models, the means were compared by Tukey test at 95% confidence interval. 3. Results and discussion
2.5. Baking test
3.1. Bran particle size distribution
To determine the effect of bran reincorporation levels in breadmaking quality, the baking test was used, according to AACC (2010), method 10e10.03, with some modifications, using the flour formulation (100%), hydrogenated vegetable fat (3%), refined salt (1.75%), ascorbic acid (0.01%), sugar (5%), yeast (3%) and water at 4 C, based on water absorption obtained in farinography. The mixing was carried out in a trough (Spiral Mixer SP 12F, Diosna,
Regarding bran particle size distribution (Fig. 1), 86.3% of the sample remained in the opening sieves 250 mm. For the second milling bran, this result was 84.1% of the sample. However, this bran presented better distribution between the three sieves of greater opening (35.4%, 17.8% and 30.9% for the openings 500, 425 and 250 mm, respectively) than initial bran (52%, 13.3% and 21% for the openings of 500, 425 and 250 mm, respectively).
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Fig. 1. Bran particle size distribution.
Brazilian law does not specify limits for the bran particle size, however, it affects the flow of flour and is negatively correlated with the cohesiveness and tensile strength (Kuakpetoon et al., 2011), which may be one of the factors responsible for the improved performance of refined flour during the baking process. In this study, the bran has been subjected to the second milling process, reducing their average size in order to minimize the physical effects it exerts on the rheology of the dough. 3.2. Chemical composition Before determining the effect of different levels of bran reincorporation in the properties of dough and breads, their chemical composition was evaluated (Table 1). In general, the flours with different levels of bran reincorporation had higher values of moisture, proteins, lipids and ashes. Furthermore, these flours presented fiber content as the most important characteristic compared to refined flour, characterizing them as a source of fiber due to the presence of bran, that is removed in the milling process for obtaining refined flour. 3.3. Mixing and gluten properties The presence of bran in samples resulted in significant increase in water absorption compared to refined flour as the percentage of bran reincorporation was increased (Table 1). The amount of water (%) required to obtain optimal consistency in the dough (500 FU) had an increase of up to 9% when 100% of the bran was reincorporated into flour. This behavior is related to the high capacity of
water absorption by the fibers (Ahmed et al., 2013), because the presence of large number of hydroxyl groups in the structure of the fibers allows greater interactions with water through hydrogen bonds (Rosell et al., 2006). The dough development time (DDT) demonstrated that whole grain flours require greater mixing time to achieve maximum consistency when compared to refined wheat flour. This effect is attributed to the interaction which occurs between fibers and gluten which prevents the hydration of the proteins (Rosell et al., 2006) and affects the aggregation and disaggregation of high molecular weight proteins. In this study, the critical limit for mass production appears to be the reincorporation of 50% bran, because from this value decreased the DDT, accompanied by stability and pronounced increase on MTI. The presence of the bran leads to the formation of a weakened gluten network and less stable during extended mixing process due to a number of physical and chemical interactions that interfere directly in the dough stability, because it depends on the number of links between protein molecules present in the gluten and strength of these connections (Indrani and Rao, 2007). A possible explanation is that water absorption as determined by the Farinograph method is the resultant of the complete dough system and appears to be governed by the properties of the gluten network, not only by the properties of fibers. The wet gluten content is a measure of the ability of the gluten protein to aggregate. Maximum reduction of 23.4% was observed in the aggregation of gluten when 100% bran was reincorporated. These results are directly related to the lower stability times observed for samples with bran reincorporation, and can be
Table 1 Approximate chemical composition, mixture properties and paste properties of flours prepared by the reincorporation of wheat bran. Parameters
Treatment (% of bran) 0
25
50
75
100
Moisture (g.100 g-1) Protein (g.100 g-1) Fat (g.100 g-1) Ash (g.100 g-1) Dietary fiber (g.100 g-1) Absorption (%) DDT (min) Stability (min) MTI (FU) Wet gluten (%) Max visc (RVU) Breakdown (RVU) Final visc (RVU) Retrograd (RVU)
12.89a ± 0.00 13.99b ± 0.04 1.16b ± 0.44 0.75d ± 0.02 1.40e ± 0.08
12.72ab ± 0.01 14.07b ± 0.18 1.46b ± 0.14 0.89cd ± 0.08 3.67d ± 0.02
12.61bc ± 0.02 14.31ab ± 0.21 1.69b ± 0.32 1.02c ± 0.01 7.24c ± 0.03
12.41c ± 0.01 14.39ab ± 0.16 2.09ab ± 0.32 1.31b ± 0.02 9.05b ± 0.15
12.50bc ± 0.12 14.39ab ± 0.16 2.39a ± 0.05 1.63a ± 0.02 12.08a ± 0.17
62.1e ± 0.14 1.8c ± 0.00 13.8a ± 0.07 37.0c ± 4.24 28.81a ± 0.97 200,4a ± 3,54 55,95a ± 3,36 242,67a ± 7,07 98,12a ± 0,18
64.0d ± 0.00 2.5c ± 0.21 13.8a ± 0.00 30.5c ± 0.71 27.80b ± 0.15 200,5a ± 3,71 54,21a ± 4,72 236,17a ± 4,72 89,75b ± 0,11
66.9c ± 0.34 9.5a ± 0.42 13.6a ± 0.42 62.5b ± 3.54 24.51c ± 0.57 181,96b ± 1,47 51,87ab ± 1,83 220,08b ± 2,12 90,96b ± 1,00
69.9b ± 0.57 8.2b ± 0.21 12.3b ± 0.57 65.5ab ± 3.54 23.46d ± 0.03 162,87c ± 1,59 46,17bc ± 1,41 201,04c ± 0,88 84,33c ± 0,71
71.2a ± 0.00 7.8b ± 0.00 8.9c ± 0.14 74.5a ± 0.71 22.06e ± 0.06 146,16d ± 0,47 39,37c ± 0,42 184,70d ± 0,18 77,92d ± 1,06
Mean values in the same column followed by different letters are significantly different (p < 0.05). Results expressed as mean of three determinations ± standard deviation. DDT: dough development time. MTI: mixture tolerance index. FU: farinographic units. Max visc: maximum viscosity. Min visc: minimal viscosity at constant temperature. Final visc: final viscosity. Retrograd: retrogradation.
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explained by the weakening of the gluten network due to the presence of particles of bran. Similar effects were observed by Bae et al. (2014), for farinography of whole grain wheat flour samples. In terms of manufacturing of products, these findings mean low volume, high firmness and short shelf-life. Accordingly, the moderate decrease in the bran particle size does not appear to be an effective alternative to improve the characteristics of the products that have wheat bran in its constitution. 3.4. Paste properties Paste properties can be seen in Table 1, according to parameters that define the behavior of the starch during heating in excess water. The maximum viscosity is a parameter related to the capacity of starch to absorb water and swelling of the starch granules during heating (Oro et al., 2013). When starch is present in large amount, the peak viscosity is high, thus a higher value for the maximum viscosity was observed for refined flour sample, which has no addition of bran and proportionately higher starch content between samples. The absorption of water by the starch granules can be inhibited in the presence of proteins, which helps to give smaller values for the maximum viscosity in flours developed with bran reincorporation (Singh et al., 2011). In the paste properties, the amylose acts partially as a diluent of amylopectin and partially as a swelling inhibitor when complexed to lipids, which justifies the smallest maximum viscosity values of samples elaborated with higher bran content, where lipids derived from grain of wheat germ are present. The breakdown values are associated with high maximum viscosity which, in turn, are related to the stability and degree of swelling of the starch granules during heating (Ragaee and AbdelAal, 2006). This explains why the samples with lower bran concentration present lower break values, because they had lower starch content, proportionally. The reassociation between starch molecules, especially amylose, results in the gel structure formation and viscosity increases reaching a final viscosity which is associated with the starch tendency to retrograde (Ragaee and Abdel-Aal, 2006), which explains why the refined flour sample has the highest value for this parameter. The fibers have the ability to absorb high water content, which makes it less available for retrogradation, as can be observed in this study in the samples with higher reincorporated bran content. The results obtained for the RVA showed the same trend observed in the farinography, wherein 50% appears to be the critical limit of addition of bran with an intermediate particle size. From this value, important features such as breakdown and retrogradation have are more pronounced, which revealed greater difficulty to obtain important characteristics for the quality of products, such as volume and maintenance of softness. However, if the size of the bran particles were smaller, possibly these effects would be more pronounced, considering the larger contact surface of the fibers and interactions with water by hydrogen bonds. This would produce higher viscosity and softness of the products, and in turn, lower shelf-life due to the availability of water for chemical reactions. 3.5. Extensional properties of the dough The resistance to extension, the property of resisting an applied force and the tendency to return to the original shape (elasticity) was significantly (p < 0.05) reduced in flour samples that were reincorporated with bran compared to the values of refined flour (Fig. 2a). A similar trend was observed for extensibility, a parameter that determines the ability of the dough to extend. With the increase in bran reincorporation levels from 25% to 100%, the
resistance to extension of the dough and extensibility gradually decreased, on average, from 44.54 g to 31.07 and 30.00 to 19.67 mm, respectively. The effects observed in the reduction of the properties of resistance to extension and extensibility of the dough is related to gluten network changes due to bran reincorporation (Schimiele et al., 2012). Higher levels of addition of bran in the flour gluten caused more dilution of the matrix, weakening its extensible characteristics which provide impact on the quality attributes of baked goods such as the lower retention of gas and a lower volume of bread. 3.6. Quality characteristics of breads In this study, specific volume was used to evaluate the possible interference of different bran reincorporation levels in the expansion of the breads (data not showed). The results indicated that the volume decreased significantly (p < 0.05) on the reincorporation of bran in the samples, obtaining values between 5.64 and 3.43 mL g1 for refined flour breads and 100% reincorporation, respectively. The degree of bran reincorporation was negatively correlated with specific volume of breads (Fig. 2b). The substitution levels of 75 and 100% affected the bran-protein interactions by a greater degree, implicating directly on the rheological properties of the dough, such as weakening of the gluten network, leading to less expansion of the dough when compared to the control. The bran reincorporated into the flour had a dilution effect on the gluten network, which associated with the negative effects of particle size, significantly reduced the volume of breads. In breads made with whole grain flour (Hung et al., 2007) and refined flour (Oro, 2013), it was found that the dietary fiber of the bran diluted the protein network and affected the formation of the dough gluten matrix. The bran obtained by roller milling presents considerably higher granulometry of the flour. The particles disrupt the formation of alveoli by physical effect, being one of the likely causes of low bread volume. The reduction of the volume of the breads prepared with flour with bran reincorporation can be correlated with rheological characteristics, i.e., the decrease in extensional properties. The correlation between the specific volume and wet gluten content of bread made with bran reincorporation is shown in Fig. 2b and showed a positive correlation with a coefficient of determination of 0.87. This correlation can be explained by the knowledge that to form dough with gas retention properties during the fermentation process, a quality gluten network is required (Noort et al., 2010). In this study, the reincorporation of bran resulted in a significant reduction in the volume of breads, demonstrating that the bran, in addition to reducing the gluten content of the dough also affects aggregation properties. The results showed that breads analyzed were subject to change in moisture content (Fig. 3) during the storage period, in which the breads with 0% and 25% of bran reincorporated showed decrease of moisture content during the period study, while the others (50%, 75% and 100%) showed more pronounced moisture contents throughout the storage time. These results are in agreement with those presented in analysis of farinography, which showed significantly greater water absortion (p < 0.05), as higher bran content reincorporated in the refined flour, proving the strong affinity between water and fibers have and reflected the higher water amount of the relative formulations. Furthermore, as the flour with higher bran content reincorporated had proportionally smaller fraction of the endosperm, to the fibers is attributed the effect predominantly observed on the behavior of the mass, that may have been partially affected by the arabinoxylans of bran fractions (Curti et al., 2015), and known to negatively affect the gluten network (Courtin and
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Fig. 2. Resistance to extension and extensibility of the dough of loaves (a) and correlation between loaf volume and wet gluten content (b) of breads made with reincorporation of different bran levels.
Fig. 3. Moisture content of breads made with different bran reincorporation levels, followed over 10 days.
Delcour, 2002), instead of be resultant of by complex dough system governed by the properties of the gluten network, as described by Noort et al. (2010). In addition, evaluating the flour paste behavior, is not possible impute the moisture of bread over time to the starch ability to absorb water, because the flour with lower bran content were those that absorb less water and which showed less retrogradation in RVA. The values of peak viscosity, breakdown, and final viscosity are strongly associated with crystalline structure in starch granules and starch swelling properties (Crosbie, 1991). Becker et al (2001), reported that the smaller the particle size of flour, the lower the RVA viscosity values. Thus, results clearly showed that reduction of bran particle size did not cause changes in starch characteristics. The bread enriched with bran showed higher water content but also higher hardness, suggesting that the moisture content is not the only factor influencing the hardness and was possibly not important enough to counteract the negative action that bran fractions may have had on texture (Fig. 4). Chen et al. (2011) found that the smaller bran particle size resulted in significantly greater hardness. Textural parameters are correlated with the RVA pasting properties, and decreased maximum viscosity can result in harder texture of bread because of less swelling power of starch granule. It was expected that samples with higher fiber contents were those presented earlier aging of starch, by having naturally higher levels of lipids which difficult the absorption of water by the granule. Regarding the water activity the breads produced showed a significant decrease (p < 0.05) throughout the storage period (Fig. 5), following the results obtained for decrease of specific volume, of moisture and firmness increase of breads and reflected in the decreased quality of produced breads. Noort et al. (2010) studied the effect of reduced particle size in the interactions between the bran and gluten proteins, it has proposed that a
Fig. 4. Firmness of breads made with different bran reincorporation levels, followed 10 days.
Fig. 5. Water activity of breads made with different bran reincorporation levels, followed over 10 days.
combination of chemical and physical mechanisms may be related and have pronounced effect. The major interactions with gluten proteins are also attributed to the increase in the amount of phytochemicals reactive compounds that are released during the grinding process due to cell rupture of the outer layers, in particular of the aleurone layer. Thus, the decrease in size of the bran particles was not effective enough to mitigate the undesirable effects of fiber bread. 4. Conclusions The physicochemical characteristics of wheat flour with different levels of bran reincorporation were investigated and their
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performance in the dough and technological properties of breads evaluated. The flour with bran reincorporation had different paste and hydration properties, affecting the rheology of the dough and performance in baking, which was perceived by the evaluation of the specific volume, color and firmness of the elaborated breads. When the influence of bran in the loaves was evaluated, samples with 75% and 100% reincorporation proved to be the richest in nutrients, providing better functionality to the body, especially regarding the dietary fiber, however, they brought about more pronounced changes in the technological characteristics on the dough and breads. Acknowledgements To the National Council for Scientific and Technological Development (CNPq), for the financial support and scolarships and to the Higher Education Personnel Improvement Coordination (CAPES) for the scolarship. Appendix A. Supplementary data Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.jcs.2016.08.015. References AACC, 2010. Official Methods of Analysis. AACC Interntional, St Paul, MN. Ahmed, J.A., Almusallam, A., Al-Hooti, S.N., 2013. Isolation and characterization of insoluble fiber (Phoenix dactylifera L.). LWT Food Sci. Technol. 50, 414e419. Bae, W., Lee, B., Hou, G.G., Lee, S., 2014. Physicochemical characterization of wholegrain wheat flour in a frozen dough system for bake off technology. J. Cereal Sci. 60, 520e525. Becker, A., Hill, S.E., Mitchell, J.R., 2001. Milling e a further parameter affecting the rapid visco analyser (RVA) profile. Cereal Chem. 78, 166e172. lu, M.M., 2013. Improving the quality of whole wheat bread by using Boz, H., Karaog various plant origin materials. Czech J. Food Sci. 31, 457e466. Chen, J.S., Fei, M.J., Shi, C.L., Tian, J.C., Sun, C.L., Zhang, H., et al., 2011. Effect of particle size and addition level of wheat bran on quality of dry white Chinese noodles. J. Cereal Sci. 53, 217e224. Courtin, C.M., Delcour, J.A., 2002. Arabinoxylans and endoxylanases in wheat flour bread-making. J. Cereal Sci. 35, 225e243.
Crosbie, G.B., 1991. The relationship between starch swelling properties, paste viscosity and boiled noodle quality in wheat flour. J. Cereal Sci. 13, 145e150. Curti, E., Carini, E., Bonacini, G., Tribuzio, G., Vittadini, E., 2013. Effect of the addition of bran fractions on bread properties. J. Cereal Sci. 57, 325e332. Curti, E., Carini, E.G., Tribuzio, G., Vittadini, E., 2015. Effect of bran on bread staling: physico-chemical characterization and molecular mobility. J. Cereal Sci. 65, 25e30. mez, M., Ronda, F., Blanco, C.A., Caballero, P.A., Apesteguía, A., 2003. Effect of Go dietary fibre on dough rheology. Eur. Food Res. Technol. 51e56. Hung, P.V., Maeda, T., Morita, N., 2007. Dough and bread qualities of flours with whole waxy wheat flour substitution. Food Res. Int. 40, 273e279. Indrani, D., Rao, G.V., 2007. Rheological characteristics of wheat flour dough as influenced by ingredients of Parotta. J. Food Eng. 17, 105e110. Kuakpetoon, D., Flores, R.A., Milliken, G.A., 2011. Dry mixing of wheat flours: effect of particle properties and blending ratio. LWT 34, 183e193. Noort, M.W.J., Haaster, D.V., Hemery, Y.Y., Hamer, R.J., 2010. The effect of particle size of wheat bran fractions on bread quality e evidence for fibre-protein interactions. J. Cereal Sci. 52, 59e54. Oro, T., Limberger, V.M., Miranda, M.V., Richards, N.S.P.S., Gutkoski, L.C., Francisco, A., 2013. Pasting properties of whole and refined wheat flour blends used for bread production. Cienc. Rural. 43, 754e760. Oro, T., 2013. Adaptation of Methods for Whole Wheat Flour Technological Quality Assessment (PhD thesis). Federal University of Santa Catarina, Brazil. from. https://repositorio.ufsc.br/bitstream/handle/123456789/107225/319262.pdf? sequence¼1 [3 July 2015]. Pomeranz, Y., Shogren, M.D., Finney, K.F., Bechtel, D.B., 1977. Fiber in breadmaking e effects on functional properties. Cereal Chem. 54 (25e41), 1977. Ragaee, S., Abdel-Aal, E., 2006. Pasting properties of starch and protein in selected cereals and quality of their food products. Food Chem. 95, 9e18. Rosell, C.M., Santos, E., Collar, C., 2006. Mixing properties of fibre enriched wheat bread doughs: a response surface methodology study. Eur. Food Res. Technol. 223, 333e340. Schimiele, M., Jaekel, L.Z., Patricio, S.M.C., Steel, C.J., Chang, Y.K., 2012. Rheological properties of wheat flour and quality characteristics of pan bread as modified by partial additions of wheat bran or whole grain wheat flour. Int. J. Food Sci. Technol. 47, 2141e2150. Singh, S., Singh, Nn, Mac Ritchie, F., 2011. Relationship of polymeric proteins with pasting, gel dynamic- and dough empirical-rheology in different Indian wheat varieties. Food Hydrocoll. 25, 19e24. Stevenson, L., Phillios, F., O'Sullivan, K., Waltin, J., 2012. Wheat bran: its composition and benefits to health, a European perspective. Int. J. Food Sci. Nutr. 63, 1001e1013. Wang, J., Rossel, C.M., Barber, C.B., 2002. Effect of the addition of different fibres on wheat dough performance and bread quality. Food Chem. 79, 221e226. Wangy, Li M.Q., 2011. Effects of ultra-fine grinding on the properties of wheat bran. Mod. Food Sci. Technol. 27, 271e274. Weaver, G.L., 2001. A miller's perspective on the impact of health claims. Nutr. Today 36, 115e118.
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Rheological properties of wheat flour dough and pan bread with wheat bran Elis R.F. Boita a, Tatiana Oro b, *, Joseane Bressiani b, Gabriela S. Santetti c, Telma E. Bertolin b, Luiz C. Gutkoski b ~o em Bioexperimentaça ~o, Universidade de Passo Fundo, BR 285, CEP 99052-900, Passo Fundo, RS, Brazil s-Graduaça Programa de Po ~o em Ci^ s-Graduaça Programa de Po encia e Tecnologia de Alimentos, Universidade de Passo Fundo, BR 285, CEP 99052-900, Passo Fundo, RS, Brazil c ~o em Engenharia de Alimentos, Universidade de Passo Fundo, BR 285, CEP 99052-900, Passo Fundo, RS, Brazil Curso de Graduaça a
b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 4 December 2015 Received in revised form 23 July 2016 Accepted 28 August 2016 Available online 30 August 2016
Wheat bran improves the nutritional properties of bread products due to the fiber content and antioxidant compounds, but causes changes in physical-chemical and technological properties. The objective of this study was to investigate the effect of wheat bran reincorporation in the dough properties and subsequent technological properties of breads. The dough and bread making properties were affected by the reincorporation of bran. Parameters such as mixing properties, viscosity, resistance to extension and extensibility demonstrated the influence of bran reincorporation into the gluten network. The presence of the bran also produced breads with lower specific volume, moisture, water activity and more hardness. The bran interactions with the gluten network are the main cause of the effects on dough quality, causing thinning and weakening of the gluten matrix. The flour presented different paste and hydration properties, affecting the rheology of the dough and performance in baking. Samples with 75% and 100% reincorporation were more nutrient-rich, providing enhanced functionality to the body, especially in relation to dietary fiber, but were responsible for more pronounced changes in the technological characteristics of the dough and breads. © 2016 Elsevier Ltd. All rights reserved.
Keywords: Wheat Whole flour Wheat quality Gluten
1. Introduction The whole wheat flour containing more vitamins, minerals, antioxidants and other nutrients compared to that of refined wheat flour, since these compounds are concentrated in the outer layers of the grain (Weaver, 2001). Wheat (Triticum aestivum L.) is one of cereal grain most used worldwide. Despite the health benefits, the presence of components of the parts external grain and germ cause adverse effects on the dough properties of the whole grain based bakery products. These effects are evidenced by reduction of volume, texture modifications, appearance and taste (Pomeranz et al., 1977). Due to this reason, the majority of the consumers prefer products of refined white flour to whole wheat products, because they perceive that the textural properties, the appearance and the lu, taste of whole grain products are less attractive (Boz and Karaog 2013). Bread, one of the most consumed and essential foods of human
* Corresponding author. E-mail address: [email protected] (T. Oro). http://dx.doi.org/10.1016/j.jcs.2016.08.015 0733-5210/© 2016 Elsevier Ltd. All rights reserved.
diet, when enriched with bran improves the nutritional properties and promotes physiological effects by eating habit (Stevenson et al., 2012). However, the effects of the addition of bran in the properties of dough and bread are attributed to the dilution of gluten, which affects the gas retaining capacity of the dough (Wang et al., 2002; mez et al., 2003). Changes in the dough of the water content Go reduce the loaf volume and increase crumb hardness in function of the amount of bran reincorporated on the wheat flour (Curti et al., 2013). According to Wangy (2011), the bran particles can react directly with the structural elements of the gluten network decreasing the dough extensibility and damaging the gas retention. A major problem associated with adding high levels of fibers in foods including confectionary goods is their negative effect on the physical and sensory properties of food products as in flavor, appearance and texture. To solve these problems, the food industry searching for alternatives to resolve or minimize the effects associated with these fractions, as different milling techniques, the use of cellulase enzymes, enzyme inactivation components of the bran, and different heat treatments applied to this fraction of the grain wheat.
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There are several research data on fiber enriched breads, but results might differ and substitution levels used are commonly low. Recently, studies have been conducted in order to show the effect of reducing the size of bran particles in the mass formation and quality of bread, for both whole grain flour, as for refined flour obtained by reincorporation of bran. In function of the benefits of foods rich in fiber and bioactive compounds and considering the availability of bran and consumption of bread by the population, it is relevant to assess its effects on the properties of raw materials and bakery products. This work was carried out to study the effect of reincorporation of bran having particle size reduction in dough and technological properties and shelf-life of breads. 2. Material and methods 2.1. Obtaining the material The batch of 100 kg of wheat (Triticum aestivum L.), purchased from a commercial supplier was subjected to grinding in an industrial mill, obtaining flour fractions and bran with a 75% extraction. The flour was subjected to a new grinding, conducted in a laboratory mill (MA020, Marconi, Brazil), decreasing the average particle diameter from 402 to 369 mm. The bran was reincorporated to the flour in concentrations of zero (100% flour), 25% (93.75% flour and 6.25% bran), 50% (87.5% flour and 12.5% of bran), 75% (81.25% flour and 18.75% bran) and 100% (75% flour and 25% bran). The flours were homogenized with the use of a mixer (HB25, Hyppolyto, Brazil) and stored in cold storage until the time of analysis. 2.2. Analysis of the physicochemical properties of flours The moisture, protein, ash, total fiber, lipids and gluten content were determined according to the official methods of the American Association of Cereal Chemistry (AACC, 2010), 44e15.02, 46e10.01, 08e12.01, 32e10.01, 30e25 and 38e12.02, respectively. The bran particle size distribution was performed by the method 66e20.01 (AACC, 2010). 2.3. Mixing properties The effect of different levels of reincorporation of bran in the dough mixing properties were determined according to method 54e21.02 of the AACC (2010), in a promylograph equipment (T6-E, Koloman Egger, Austria).
Germany) at 30 C until maximum consistency was reached. Initially, 3 min of mixing at slow speed was used for all samples for the purpose of mixing the ingredients flour, enhancer, sugar, salt and water. The yeast and fat were added and the remaining time of the mixture was adjusted according to the development of the dough of each sample using fast speed of 12 min for refined flour; 11 min for the flour with 25% bran reincorporation; 10 min for the flour with 50% bran reincorporation; 9 min for the flour with 75% bran reincorporation; 6 min for the flour with 100% bran reincorporation. The dough was divided in portions of 150 g and fermentation ~o, Brazil), at of was carried out in a chamber (MP20, Multipa 30 ± 1 C and relative humidity of 80%. The baking was performed in a laboratory oven (QA 226, Labor Instruments, Austria) at 220 C for 18 min. The breads cooled at room temperature and after 1 h the analyses were performed. 2.6. Extensional properties of dough Texturometer (TA.XT.plus, Stable Micro Systems, England) equipped with Exponent 32 software using a Kieffer Dough and Gluten Extensibility Rig (A/KIE), probe with pre-test speed of 2.0 mm/s, test of 3.0 mm/s and post-test 10.0 mm/s, a distance of 75.0 mm and strength of 5.0 kg were applied to investigate the extensional properties (extensibility and resistance to extension) of bread dough samples. 2.7. Evaluating the bread quality The breads were evaluated through the specific volume determination at the initial time and through parameters of water activity, moisture content, and firmness at the initial time and along of time of 10 days. The volume was determined by seed displacement in a bread volume measurer according to AACC method 10e05.01 (2010). Moisture of the samples was evaluated according to AACC method 44e15.02 (2010). The firmness of the breads was determined, being carried out in accordance with AACC method 74e09.01 (2010), with the use of a texturometer (TA.XT.plus, Stable Micro Systems, England) equipped with Exponent 32 software. The breads were sliced to 25 mm in thickness, reducing the size of the slices to 25 mm wide x 25 mm long and removal of the crust. An aluminum cylindrical probe P/36R (a radius of 36 mm) was used, pre-test speed of 1.0 mm s1; speed of 1.7 mm s1 test; post-test speed of 10.0 mm s1 and 40% compression strength. 2.8. Statistical analysis
2.4. Paste properties Paste properties were analyzed in accordance with method 76e21.01 of AACC (2010) using a fast speed analyzer (RVA-3D, Newport Scientific, Australia) equipped with Thermocline software for Windows, version 3.1. A sample of approximately 3.5 g flour (corrected to 14% moisture) and 25 ± 0.1 mL of distilled water and Standard 1 temperature profile.
The determinations were performed in triplicate at least. Statistical analysis was performed with use of the Software. The significance of the data was tested by analysis of variance (ANOVA) at 0.05 error probability and in the significant models, the means were compared by Tukey test at 95% confidence interval. 3. Results and discussion
2.5. Baking test
3.1. Bran particle size distribution
To determine the effect of bran reincorporation levels in breadmaking quality, the baking test was used, according to AACC (2010), method 10e10.03, with some modifications, using the flour formulation (100%), hydrogenated vegetable fat (3%), refined salt (1.75%), ascorbic acid (0.01%), sugar (5%), yeast (3%) and water at 4 C, based on water absorption obtained in farinography. The mixing was carried out in a trough (Spiral Mixer SP 12F, Diosna,
Regarding bran particle size distribution (Fig. 1), 86.3% of the sample remained in the opening sieves 250 mm. For the second milling bran, this result was 84.1% of the sample. However, this bran presented better distribution between the three sieves of greater opening (35.4%, 17.8% and 30.9% for the openings 500, 425 and 250 mm, respectively) than initial bran (52%, 13.3% and 21% for the openings of 500, 425 and 250 mm, respectively).
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Fig. 1. Bran particle size distribution.
Brazilian law does not specify limits for the bran particle size, however, it affects the flow of flour and is negatively correlated with the cohesiveness and tensile strength (Kuakpetoon et al., 2011), which may be one of the factors responsible for the improved performance of refined flour during the baking process. In this study, the bran has been subjected to the second milling process, reducing their average size in order to minimize the physical effects it exerts on the rheology of the dough. 3.2. Chemical composition Before determining the effect of different levels of bran reincorporation in the properties of dough and breads, their chemical composition was evaluated (Table 1). In general, the flours with different levels of bran reincorporation had higher values of moisture, proteins, lipids and ashes. Furthermore, these flours presented fiber content as the most important characteristic compared to refined flour, characterizing them as a source of fiber due to the presence of bran, that is removed in the milling process for obtaining refined flour. 3.3. Mixing and gluten properties The presence of bran in samples resulted in significant increase in water absorption compared to refined flour as the percentage of bran reincorporation was increased (Table 1). The amount of water (%) required to obtain optimal consistency in the dough (500 FU) had an increase of up to 9% when 100% of the bran was reincorporated into flour. This behavior is related to the high capacity of
water absorption by the fibers (Ahmed et al., 2013), because the presence of large number of hydroxyl groups in the structure of the fibers allows greater interactions with water through hydrogen bonds (Rosell et al., 2006). The dough development time (DDT) demonstrated that whole grain flours require greater mixing time to achieve maximum consistency when compared to refined wheat flour. This effect is attributed to the interaction which occurs between fibers and gluten which prevents the hydration of the proteins (Rosell et al., 2006) and affects the aggregation and disaggregation of high molecular weight proteins. In this study, the critical limit for mass production appears to be the reincorporation of 50% bran, because from this value decreased the DDT, accompanied by stability and pronounced increase on MTI. The presence of the bran leads to the formation of a weakened gluten network and less stable during extended mixing process due to a number of physical and chemical interactions that interfere directly in the dough stability, because it depends on the number of links between protein molecules present in the gluten and strength of these connections (Indrani and Rao, 2007). A possible explanation is that water absorption as determined by the Farinograph method is the resultant of the complete dough system and appears to be governed by the properties of the gluten network, not only by the properties of fibers. The wet gluten content is a measure of the ability of the gluten protein to aggregate. Maximum reduction of 23.4% was observed in the aggregation of gluten when 100% bran was reincorporated. These results are directly related to the lower stability times observed for samples with bran reincorporation, and can be
Table 1 Approximate chemical composition, mixture properties and paste properties of flours prepared by the reincorporation of wheat bran. Parameters
Treatment (% of bran) 0
25
50
75
100
Moisture (g.100 g-1) Protein (g.100 g-1) Fat (g.100 g-1) Ash (g.100 g-1) Dietary fiber (g.100 g-1) Absorption (%) DDT (min) Stability (min) MTI (FU) Wet gluten (%) Max visc (RVU) Breakdown (RVU) Final visc (RVU) Retrograd (RVU)
12.89a ± 0.00 13.99b ± 0.04 1.16b ± 0.44 0.75d ± 0.02 1.40e ± 0.08
12.72ab ± 0.01 14.07b ± 0.18 1.46b ± 0.14 0.89cd ± 0.08 3.67d ± 0.02
12.61bc ± 0.02 14.31ab ± 0.21 1.69b ± 0.32 1.02c ± 0.01 7.24c ± 0.03
12.41c ± 0.01 14.39ab ± 0.16 2.09ab ± 0.32 1.31b ± 0.02 9.05b ± 0.15
12.50bc ± 0.12 14.39ab ± 0.16 2.39a ± 0.05 1.63a ± 0.02 12.08a ± 0.17
62.1e ± 0.14 1.8c ± 0.00 13.8a ± 0.07 37.0c ± 4.24 28.81a ± 0.97 200,4a ± 3,54 55,95a ± 3,36 242,67a ± 7,07 98,12a ± 0,18
64.0d ± 0.00 2.5c ± 0.21 13.8a ± 0.00 30.5c ± 0.71 27.80b ± 0.15 200,5a ± 3,71 54,21a ± 4,72 236,17a ± 4,72 89,75b ± 0,11
66.9c ± 0.34 9.5a ± 0.42 13.6a ± 0.42 62.5b ± 3.54 24.51c ± 0.57 181,96b ± 1,47 51,87ab ± 1,83 220,08b ± 2,12 90,96b ± 1,00
69.9b ± 0.57 8.2b ± 0.21 12.3b ± 0.57 65.5ab ± 3.54 23.46d ± 0.03 162,87c ± 1,59 46,17bc ± 1,41 201,04c ± 0,88 84,33c ± 0,71
71.2a ± 0.00 7.8b ± 0.00 8.9c ± 0.14 74.5a ± 0.71 22.06e ± 0.06 146,16d ± 0,47 39,37c ± 0,42 184,70d ± 0,18 77,92d ± 1,06
Mean values in the same column followed by different letters are significantly different (p < 0.05). Results expressed as mean of three determinations ± standard deviation. DDT: dough development time. MTI: mixture tolerance index. FU: farinographic units. Max visc: maximum viscosity. Min visc: minimal viscosity at constant temperature. Final visc: final viscosity. Retrograd: retrogradation.
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explained by the weakening of the gluten network due to the presence of particles of bran. Similar effects were observed by Bae et al. (2014), for farinography of whole grain wheat flour samples. In terms of manufacturing of products, these findings mean low volume, high firmness and short shelf-life. Accordingly, the moderate decrease in the bran particle size does not appear to be an effective alternative to improve the characteristics of the products that have wheat bran in its constitution. 3.4. Paste properties Paste properties can be seen in Table 1, according to parameters that define the behavior of the starch during heating in excess water. The maximum viscosity is a parameter related to the capacity of starch to absorb water and swelling of the starch granules during heating (Oro et al., 2013). When starch is present in large amount, the peak viscosity is high, thus a higher value for the maximum viscosity was observed for refined flour sample, which has no addition of bran and proportionately higher starch content between samples. The absorption of water by the starch granules can be inhibited in the presence of proteins, which helps to give smaller values for the maximum viscosity in flours developed with bran reincorporation (Singh et al., 2011). In the paste properties, the amylose acts partially as a diluent of amylopectin and partially as a swelling inhibitor when complexed to lipids, which justifies the smallest maximum viscosity values of samples elaborated with higher bran content, where lipids derived from grain of wheat germ are present. The breakdown values are associated with high maximum viscosity which, in turn, are related to the stability and degree of swelling of the starch granules during heating (Ragaee and AbdelAal, 2006). This explains why the samples with lower bran concentration present lower break values, because they had lower starch content, proportionally. The reassociation between starch molecules, especially amylose, results in the gel structure formation and viscosity increases reaching a final viscosity which is associated with the starch tendency to retrograde (Ragaee and Abdel-Aal, 2006), which explains why the refined flour sample has the highest value for this parameter. The fibers have the ability to absorb high water content, which makes it less available for retrogradation, as can be observed in this study in the samples with higher reincorporated bran content. The results obtained for the RVA showed the same trend observed in the farinography, wherein 50% appears to be the critical limit of addition of bran with an intermediate particle size. From this value, important features such as breakdown and retrogradation have are more pronounced, which revealed greater difficulty to obtain important characteristics for the quality of products, such as volume and maintenance of softness. However, if the size of the bran particles were smaller, possibly these effects would be more pronounced, considering the larger contact surface of the fibers and interactions with water by hydrogen bonds. This would produce higher viscosity and softness of the products, and in turn, lower shelf-life due to the availability of water for chemical reactions. 3.5. Extensional properties of the dough The resistance to extension, the property of resisting an applied force and the tendency to return to the original shape (elasticity) was significantly (p < 0.05) reduced in flour samples that were reincorporated with bran compared to the values of refined flour (Fig. 2a). A similar trend was observed for extensibility, a parameter that determines the ability of the dough to extend. With the increase in bran reincorporation levels from 25% to 100%, the
resistance to extension of the dough and extensibility gradually decreased, on average, from 44.54 g to 31.07 and 30.00 to 19.67 mm, respectively. The effects observed in the reduction of the properties of resistance to extension and extensibility of the dough is related to gluten network changes due to bran reincorporation (Schimiele et al., 2012). Higher levels of addition of bran in the flour gluten caused more dilution of the matrix, weakening its extensible characteristics which provide impact on the quality attributes of baked goods such as the lower retention of gas and a lower volume of bread. 3.6. Quality characteristics of breads In this study, specific volume was used to evaluate the possible interference of different bran reincorporation levels in the expansion of the breads (data not showed). The results indicated that the volume decreased significantly (p < 0.05) on the reincorporation of bran in the samples, obtaining values between 5.64 and 3.43 mL g1 for refined flour breads and 100% reincorporation, respectively. The degree of bran reincorporation was negatively correlated with specific volume of breads (Fig. 2b). The substitution levels of 75 and 100% affected the bran-protein interactions by a greater degree, implicating directly on the rheological properties of the dough, such as weakening of the gluten network, leading to less expansion of the dough when compared to the control. The bran reincorporated into the flour had a dilution effect on the gluten network, which associated with the negative effects of particle size, significantly reduced the volume of breads. In breads made with whole grain flour (Hung et al., 2007) and refined flour (Oro, 2013), it was found that the dietary fiber of the bran diluted the protein network and affected the formation of the dough gluten matrix. The bran obtained by roller milling presents considerably higher granulometry of the flour. The particles disrupt the formation of alveoli by physical effect, being one of the likely causes of low bread volume. The reduction of the volume of the breads prepared with flour with bran reincorporation can be correlated with rheological characteristics, i.e., the decrease in extensional properties. The correlation between the specific volume and wet gluten content of bread made with bran reincorporation is shown in Fig. 2b and showed a positive correlation with a coefficient of determination of 0.87. This correlation can be explained by the knowledge that to form dough with gas retention properties during the fermentation process, a quality gluten network is required (Noort et al., 2010). In this study, the reincorporation of bran resulted in a significant reduction in the volume of breads, demonstrating that the bran, in addition to reducing the gluten content of the dough also affects aggregation properties. The results showed that breads analyzed were subject to change in moisture content (Fig. 3) during the storage period, in which the breads with 0% and 25% of bran reincorporated showed decrease of moisture content during the period study, while the others (50%, 75% and 100%) showed more pronounced moisture contents throughout the storage time. These results are in agreement with those presented in analysis of farinography, which showed significantly greater water absortion (p < 0.05), as higher bran content reincorporated in the refined flour, proving the strong affinity between water and fibers have and reflected the higher water amount of the relative formulations. Furthermore, as the flour with higher bran content reincorporated had proportionally smaller fraction of the endosperm, to the fibers is attributed the effect predominantly observed on the behavior of the mass, that may have been partially affected by the arabinoxylans of bran fractions (Curti et al., 2015), and known to negatively affect the gluten network (Courtin and
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Fig. 2. Resistance to extension and extensibility of the dough of loaves (a) and correlation between loaf volume and wet gluten content (b) of breads made with reincorporation of different bran levels.
Fig. 3. Moisture content of breads made with different bran reincorporation levels, followed over 10 days.
Delcour, 2002), instead of be resultant of by complex dough system governed by the properties of the gluten network, as described by Noort et al. (2010). In addition, evaluating the flour paste behavior, is not possible impute the moisture of bread over time to the starch ability to absorb water, because the flour with lower bran content were those that absorb less water and which showed less retrogradation in RVA. The values of peak viscosity, breakdown, and final viscosity are strongly associated with crystalline structure in starch granules and starch swelling properties (Crosbie, 1991). Becker et al (2001), reported that the smaller the particle size of flour, the lower the RVA viscosity values. Thus, results clearly showed that reduction of bran particle size did not cause changes in starch characteristics. The bread enriched with bran showed higher water content but also higher hardness, suggesting that the moisture content is not the only factor influencing the hardness and was possibly not important enough to counteract the negative action that bran fractions may have had on texture (Fig. 4). Chen et al. (2011) found that the smaller bran particle size resulted in significantly greater hardness. Textural parameters are correlated with the RVA pasting properties, and decreased maximum viscosity can result in harder texture of bread because of less swelling power of starch granule. It was expected that samples with higher fiber contents were those presented earlier aging of starch, by having naturally higher levels of lipids which difficult the absorption of water by the granule. Regarding the water activity the breads produced showed a significant decrease (p < 0.05) throughout the storage period (Fig. 5), following the results obtained for decrease of specific volume, of moisture and firmness increase of breads and reflected in the decreased quality of produced breads. Noort et al. (2010) studied the effect of reduced particle size in the interactions between the bran and gluten proteins, it has proposed that a
Fig. 4. Firmness of breads made with different bran reincorporation levels, followed 10 days.
Fig. 5. Water activity of breads made with different bran reincorporation levels, followed over 10 days.
combination of chemical and physical mechanisms may be related and have pronounced effect. The major interactions with gluten proteins are also attributed to the increase in the amount of phytochemicals reactive compounds that are released during the grinding process due to cell rupture of the outer layers, in particular of the aleurone layer. Thus, the decrease in size of the bran particles was not effective enough to mitigate the undesirable effects of fiber bread. 4. Conclusions The physicochemical characteristics of wheat flour with different levels of bran reincorporation were investigated and their
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performance in the dough and technological properties of breads evaluated. The flour with bran reincorporation had different paste and hydration properties, affecting the rheology of the dough and performance in baking, which was perceived by the evaluation of the specific volume, color and firmness of the elaborated breads. When the influence of bran in the loaves was evaluated, samples with 75% and 100% reincorporation proved to be the richest in nutrients, providing better functionality to the body, especially regarding the dietary fiber, however, they brought about more pronounced changes in the technological characteristics on the dough and breads. Acknowledgements To the National Council for Scientific and Technological Development (CNPq), for the financial support and scolarships and to the Higher Education Personnel Improvement Coordination (CAPES) for the scolarship. Appendix A. Supplementary data Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.jcs.2016.08.015. References AACC, 2010. Official Methods of Analysis. AACC Interntional, St Paul, MN. Ahmed, J.A., Almusallam, A., Al-Hooti, S.N., 2013. Isolation and characterization of insoluble fiber (Phoenix dactylifera L.). LWT Food Sci. Technol. 50, 414e419. Bae, W., Lee, B., Hou, G.G., Lee, S., 2014. Physicochemical characterization of wholegrain wheat flour in a frozen dough system for bake off technology. J. Cereal Sci. 60, 520e525. Becker, A., Hill, S.E., Mitchell, J.R., 2001. Milling e a further parameter affecting the rapid visco analyser (RVA) profile. Cereal Chem. 78, 166e172. lu, M.M., 2013. Improving the quality of whole wheat bread by using Boz, H., Karaog various plant origin materials. Czech J. Food Sci. 31, 457e466. Chen, J.S., Fei, M.J., Shi, C.L., Tian, J.C., Sun, C.L., Zhang, H., et al., 2011. Effect of particle size and addition level of wheat bran on quality of dry white Chinese noodles. J. Cereal Sci. 53, 217e224. Courtin, C.M., Delcour, J.A., 2002. Arabinoxylans and endoxylanases in wheat flour bread-making. J. Cereal Sci. 35, 225e243.
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