Effect of Hydrothermaled Bran on Physicochemical, Rheological and Microstructural Characteristics of Sangak Bread

Journal of Cereal Science 49 (2009) 398–404

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Journal of Cereal Science

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Effect of hydrothermaled bran on physicochemical, rheological and microstructural characteristics of Sangak bread

Laleh Mosharraf, Mahdi Kadivar*, Mohammad Shahedi

Department of Food Science and Technology, College of Agriculture, Isfahan University of Technology, Isfahan 84156-83111, Iran article info abstract

Article history: Increased consumption of whole grain products has been associated with decreased risk of health Received 23 September 2008 problems such as cardiovascular disease, diabetes and obesity. Phytate however, has always been Received in revised form a matter of concern, since it chelates minerals such as iron. Sangak is very popular Iranian flat bread 9 January 2009 invented five hundred years ago, made from 95% extraction flour. The bread is fermented but usually Accepted 24 January 2009 fermentation is not able to remove all phytate from the dough. In this study flours were first debranned; resulting bran was subjected to a hydrothermal process. The hydrothermaled (HT) brans were then Keywords: incorporated in the Sangak flour. In the next step, physicochemical, rheological and microstructural Sangak bread Phytate characteristics of Sangak flour and dough prepared from two Iranian wheat varieties, Tajan and Back Hydrothermaled bran Cross of Roshan were investigated. Results indicated a reduction in phytate up to 55% in the samples. The Minerals resulting dough containing HT bran showed a higher development time and valorimetric value and was more stable than doughs made with normal bran. Dough made with HT bran showed a kind of protein matrix in which proteins and starch granules are oriented in a more non-ordered structure. Ó 2009 Elsevier Ltd. All rights reserved.

1. Introduction bioavailability, phytic acid levels may be decreased by phytase. Fungal phytase can improve nutritional and breadmaking perfor- Flat breads are staple food in Iran, provide most of the calo- mance of whole wheat bread. However, not all the phytates are ries and protein in Iranian diet and have a special importance in hydrolysed (Haros et al., 2001). That could be due to the limited this part of the world. Most flat breads are made from high accessibility of the exogenous enzyme to phytates in the presence extraction or near whole wheat flours, bearing incomplete of unbroken aleurone large particles in bran-enriched wheat flour. fermentation. This produces breads with high fiber and phytate The enzyme substrate contact may thus be hampered by physical content which may complex with bivalent metals such as iron, factors (Sanz Penella et al., 2008) zinc, calcium, and manganese (Davidsson et al., 1995; Lioger In fact, the phytic acid breakdown in the stomach and small et al., 2007; Palacios et al., 2008; Sandberg et al., 1999). Phytic intestine of humans is influenced mainly by dietary phytase, acid or myo-inositol hexakisphosphate is widely distributed in whereas intestinal phytase activity is very low (Eklund-Jonsson nature as it is the major storage form of phosphorus in cereals, et al., 2006; Iqbal et al., 1994). Washing the bran to remove harmful legumes, and oil seeds. It is typically found in the outer (aleu- components, grinding the bran to obtain a smaller particle size, rone) layers of cereal grains. Therefore, products such as whole- pearling of wheat grains or using various heat treatments to inac- meal breads are rich in phytic acid (Harland and Oberleas, 1991; tivate enzymes (Liu et al., 2007) have been successfully used to Reddy et al., 1989). improve the quality of bread supplemented with bran (de Kock The nutritional benefits of fiber to diets have been also et al., 1999; Lai et al., 1989a,b; Nelles et al., 1998). investigated in many studies. Consumption of foods rich in whole Sourdough microflora generally contains a complex mixture of grains and cereal fiber has been shown in epidemiological studies yeasts (mainly Saccharomyces cerevisiae) and hetero and homo- to reduce the risk of chronic diseases such as diabetes, cardio- fermentative lactic acid bacteria (LAB). The latter plays a key role vascular disease and certain cancers (Jacobs and Gallaher, 2004; during fermentation. LAB causes rapid acidification of the raw Larsson et al., 2005; Murtaugh et al., 2003). To improve mineral material through the production of organic acids, mainly lactic acid. Also, their production of acetic acid, ethanol, aroma compounds, bacteriocins, exopolysaccharides, and several enzymes is of * Corresponding author. Tel.: þ98 311 3913382; fax: þ98 311 3912254. importance. In this way, they enhance shelf life and microbial E-mail address: [email protected] (M. Kadivar). safety, improve texture and contribute to the pleasant sensory

Table 1 Proximate composition of Sangak ﬂour and bran samples (%, dry basis).a

Flour Bran

Tab H Ta BC H BC BTa BHTa BBC BHBC Moisture (%) 9.00 0.28 8.30 0.27 8.90 0.35 8.10 0.07 6.00 0.16 5.40 0.02 7.00 0.08 5.80 0.13 Protein (%)c 13.19 0.35 a 13.19 0.08 a 10.10 0.22 b 10.01 0.09 b 16.17 0.08 a 15.64 0.52 a 14.30 0.09 b 13.80 0.05 b Ash (%) 1.21 0.19 b 1.27 0.02 b 1.65 0.17 a 1.83 0.20 a 4.68 0.19 c 5.07 0.38 b 5.27 0.82 b 5.78 0.23 a Crude ﬁber (%) 2.20 0.22 a 2.34 0.70 a 2.14 0.33 a 2.25 0.76 a 8.51 0.33 b 9.20 0.15 a 8.06 0.22 c 8.49 0.65 b Fat (%) 3.29 0.15a 2.83 0.11 b 2.40 0.15 c 1.63 0.08 d 5.10 0.22 a 4.33 0.21 b 4.30 0.17 b 3.70 0.11 c

a Values followed by the same letter in the same row are not significantly different (P < 0.05). b Wheat flour with 95% extraction of Tajan (Ta), Tajan containing hydrothermaled bran (H Ta), Back Cross of Roshan (BC) and Back Cross of Roshan containing hydrothermaled bran (H BC), Bran of Tajan (B Ta), hydrothermaled bran of Tajan (BH Ta), Bran of Back Cross of Roshan (B BC) and hydrothermaled bran of Back Cross of Roshan (B HBC). c N 5.7. profile of the end product (Gocmen et al., 2007). The application of 202, and Switzerland). The bran fraction from each wheat cultivar lactic acid bacteria (LAB) in the form of sourdough has been was collected from the last break roll subjected to hydrothermal reported to have positive effects on wheat bread quality and staling treatment and then added to the sample flours. (Clarke et al., 2004). Fermentation of wheat bran with yeast or with yeast and lactic acid bacteria improved loaf volume, crumb structure and shelf life of bread supplemented with 20% wheat bran 2.3. Hydrothermal treatment (Katina et al., 2006; Salmenkallio-Marttila et al., 2001). Incubation of wheat bran at pH 5.2 and at a temperature of 55 C The wheat brans (300 g) were wet-steeped in 2 volumes of for various periods of time can increase the levels of inorganic acetate buffer (pH 4.8) at 55 C for 60 min. The buffer was removed phosphorus and inositol phosphates and a simultaneous decrease and was replaced by new buffer solution. Incubation lasted for 24 h in the level of phytic acid (Larsson and Sandberg, 1992). Due to slow in total. The bran was then dried in an oven at 37 C. hydrolysis of phytate in whole grains during fermentation, hydrothermal processing of whole kernels of barley, wheat and rye at optimal conditions is suggested in order to decrease phytate content of samples (Fredlund et al., 1997; Bergman et al., 1999, 2.4. Proximate analysis of wheat flour 2001). To improve iron absorption, phytate levels should not exceed 0.5 mmol/g. According to Fredlund, phytate content of wheat, rye Moisture, ash, crude fiber, fat and protein were determined and barley was reduced by 46–77% using water and by 84–99% using standard AACC methods (2003). Nitrogen content was using acetate buffer (pH 4.8). measured by the Kjeldahl method. Nitrogen was converted to Sangak which was invented about five hundred ago, is a sour- protein by using a factor of 5.7. dough flat bread, 70–80 cm long, 40–50 cm wide and 3–5 mm thick; its surface is sprinkled with sesame or poppy seeds and is the most popular bread in Iran. Flour of 95%-extraction rate, salt (1.5%), 2.5. Protein fraction sourdough (20%), yeast (0.5%), and water (85%) are mixed to proper consistency and fermented for 2 h. Sangak dough is usually made 2.5.1. Protein extraction from flour with strong protein quality and its paste is more similar The Sangak flour was defatted with chloroform (MacRitchie and to batter rather than the dough of other flat breads. Dough pieces of Gras, 1973). Protein of the defatted flour was extracted using 500 g are flattened on a special paddle, docked with fingers, and conditions similar to the modified Osborne protein fractionation then placed on the floor of a previously heated oven which is (Stevenson and Preston, 1996). covered with small stones that are lubricated from time to time with edible solid lipids. The oven is dome-shaped and heated with Table 2 a natural gas burner and bread is baked for 3–5 min. The bread Phytic acid and Glutathione contenta in Sangak flours, dough and wheat bran weight is about 400 g and due to high moisture content, stales samples. faster than other Iranian breads. Samples Phytic acid content Phytate Glutathione The aims of the present study were to add hydrothermaled (mmol/g dry matter) reductionb(%) content (ml) wheat brans to Sangak dough and then to investigate physico- Tajan bran 6.54 0.05 b 1.40 chemical, rheological and microstructural behavior of Sangak flour HT Tajan bran 3.36 0.06 d 47.8 0.60 and dough prepared with two Iranian wheat varieties. Back Cross of Roshan bran 8.23 0.03 a 1.10 HT Back Cross of Roshan bran 5.71 0.10 c 30.6 0.50 Tajan flour (95%) 1.73 0.11 f 0.90 2. Materials and methods Tajan flour plus HTB 0.74 0.04 h 57.0 0.70 Tajan Sangak dough 1.36 0.08 g – 2.1. Grain material Tajan Sangak dough plus HTB 0.61 0.05 h 55.2 – Back Cross of Roshan 2.16 0.06 e 0.70 flour (95%) The grain samples (Tajan and Back Cross of Roshan) were obtained Back Cross of Roshan 1.15 0.10 g 46.6 0.50 from field trials grown at Isfahan and Golestan Agricultural Research plus HTB Center, in 2006. All chemical reagents were analytical grade. Back Cross of Roshan Sangak 1.74 0.11 f – dough Back Cross of Roshan Sangak 1.10 0.05 g 36.8 – 2.2. Milling dough plus HTB

a Values followed by the same letter in the same column are not signiﬁcantly The wheat samples were cleaned and conditioned to 15.5% different (P < 0.05). moisture content, and milled on a small-scale mill (Buhler AG, MLU b Percentage phytate reduction calculated on initial content in untreated samples. 400 L. Mosharraf et al. / Journal of Cereal Science 49 (2009) 398–404

Table 3 2.8. Preparation of Sangak dough Rheological properties (mean SD)a of Sangak ﬂour samples.

Farinogram Sample descriptionb Sangak dough was prepared using 100 g wheat flour, 1.5% salt, characteristics Ta H Ta BC HBC 15% sourdough along with 0.5% yeast which is called Torsh (sour) and an appropriate amount of water. All the ingredients were mixed Water absorption 59.40 0.10 b 59.50 0.20 ab 61.00 0.20 a 61.50 0.30 a (%) thoroughly and the dough was rested at room temperature for 2.0 h. Development time 4.00 0.30 b 8.00 0.50 a 3.00 0.20 d 3.50 0.30 c (min) 2.9. Scanning Electron Microscopy (SEM) Stability (min) 8.00 0.50 b 10.50 0.60 a 1.50 0.20 d 2.20 0.20 c Degree of 20.00 3.20 c 0.00 0.00 d 110.00 10.20 a 90.00 8.50 b Softening (BU Sangak dough and bran pieces were dried by freeze drier. Dried after 10 min) samples were mounted on aluminum stubs and coated with gold. Valorimetric Value 60.00 1.50 b 73.00 2.10 a 46.00 1.15 d 49.00 1.80 c Specimens were observed with scanning electron microscope (BU) (Philips XL13, The Netherlands) operated at 10 KV and a vacuum of a Values followed by the same letter in the same row are not significantly different 2 105 torr. (p < 0.05). b Wheat flour with 95% extraction of Tajan (Ta), Tajan containing hydrothermaled bran (H Ta), Back Cross of Roshan (BC) and Back Cross of Roshan containing 3. Results hydrothermaled bran (H BC). 3.1. Physicochemical characteristics of flours 2.5.2. Glutathione, free sulfhydryl (SHF) and disulfide (S–S) determination The results of the physicochemical tests on Sangak flours and Total reducing substance (glutathione) was determined using corresponding brans are presented in Table 1. Ash, crude fiber standard AACC method 10-01 (2003). A colorimetric method for the and protein content were similar in both Sangak flour samples (with determination of SH and SS groups utilizing Ellman’s reagent was and without hydrothermaled bran). A significant decrease was applied to Sangak flours, gliadin and glutenin extractions (Bever- evidenced in fat content of hydrothermaled samples that could be due idge et al., 1974; Puppo et al., 2005). to the removal of endosperm which is usually adhered to bran particles. On the other hand, treatment of bran with buffer significantly increased crude fiber and ash proportion in the samples. 2.6. Phytate determinations Moreover, activation of enzymes rather than phytase during hydrothermal treatment and their hydrolyzing effects on protein and lipids Phytate determination involved sample extraction with 1.2% has led to a significant release of these two components from fiber, an aqueous HCl containing 10% Na SO and subsequent precipitation 2 4 activity that seems to be higher in the Back Cross of Roshan variety. of the Fe (III)–phytate complex by the addition of ferric chloride hexahydrate (Tangkongchitra et al., 1981). 3.2. Phytate content

2.7. Mixing properties of ﬂour There have been several reports of phytate degradation such as phytate hydrolysis by phytase contributed by the grain (Turk et al., The effect of processed bran on dough rheology during mixing 1996), phytase additives (Haros et al., 2001; Turk and Sandberg, was determined by farinograph (Brabender, Duisburg, Germany), 1992), fermentation of wheat bran (Katina et al., 2006; Sal- according to the AACC Method (2003). Parameters such as water menkallio-Marttila et al., 2001) and hydrothermal processing of absorption, dough development time, stability, degree of softening whole kernels (Bergman et al., 2001). The breads containing the along with valorimetric value were determined. All determinations highest amount of bran contained more phytate than those with were made at least in duplicate, and the average values were lower bran and increasing the amount of bran decreased the phy- adopted. tate degradation. The level of yeast did not have any noticeable

Fig. 1. Farinograms of Tajan ﬂour with (A) and without hydrothermaled bran (B) and Back Cross of Roshan ﬂour with (C) and without hydrothermaled bran (D). L. Mosharraf et al. / Journal of Cereal Science 49 (2009) 398–404 401

Table 4 rheological properties than those of the other variety and was a Sulfhydryls/disulﬁdes content in Sangak ﬂour samples. improved following addition of hydrothermaled bran. Flour Gliadin Glutenin A 50% increase in development time was evidenced after

SHb SHþS–Sc SH SHþS–S SH SHþS–S hydrothermal treating of Tajan and 14.3% of Back Cross of Roshan. Tajan flour was more stable than Back Cross of Roshan and its Tajan flour (95% 0.69 a 8.29 a 1.72 b 6.31 c 0.75 b 13.38 a extraction) stability significantly increased in dough containing hydro- Tajan flour containing 0.85 a 8.14 ab 2.08 a 5.83 d 1.97 a 9.78 b thermaled bran. Addition of bran into flour decreased dough HT bran development time at lower addition levels, but a slight increase was Back Cross of Roshan 0.84 a 8.12 ab 1.11 d 10.98 a 0.20 c 13.54 a evidenced at higher levels in 20% bran. (Martinez-Anay and Devesa, flour (95% extraction) Back Cross of Roshan 0.85 a 7.96 b 1.51 c 9.20 b 0.77 b 9.41 c 2000). The treatment decreased degree of softening from 110 to 90 flour containing HT BU in Back Cross of Roshan and 20 to 0 BU in Tajan (Fig. 1). bran hydrothermaled bran Improvement of rheological properties may be due to elimination a Values followed by the same letter in the same column are not significantly of reducing agents such as glutathione, which is evidenced by different (P < 0.05). lower reducing agent content of bran after hydrothermal treatment b Free sulfhydryls (SH) mmol/g of dry flour. (Table 2). On the other hand, rheological properties of both flours c Total thiol groups (SH þ S–S) mmol/g of dry flour. were affected and improved by the treatment. In Iran, because there is an unpredictable and large variation in the rheological effect on the amount of phytate remaining in the breads (Kadan and properties of domestic flours, the treatment might be considered to Phillippy, 2007). Hydrothermal treatment in acetate buffer be promising. In this study brans after hydrothermal treatment improved the hydrolysis of phytate (Table 2). The results showed were ground to fine particles and then added to flours. Therefore, that there are significant differences in phytate content between doughs containing fine hydrothermaled brans showed better the two varieties. After hydrothermal treatment, the phytate rheological properties than others that contained normal brans. It content decreased up to 57% in Sangak flour and up to 55% in its was shown that hydration of bran before addition to the dough doughs. In terms of corresponding brans, although initial phytate increased loaf volume and improved bread quality in wheat bread content of Back Cross of Roshan (8.23) was significantly higher than containing 12% bran, mostly due to improved hydration of flour that of Tajan, more phytate was removed from Tajan (ca. 50%) than components, lipoxygenase activation, and a washing out of free Back Cross of Roshan which was just 30%. This variation could be reduced glutathione. (Nelles et al., 1998). Physicochemical or related to the lower element content of Tajan which appears in its enzymatic modifications of wheat bran may enhance the functional lower ash content. The inverse relationship between phytate properties of bran (Rasco et al., 1991). On the other hand, baking degradation and bran level may be explained by the presence of quality of bran is influenced by its particle size (Moss, 1989; O¨ zboy phytase inhibitors such as high level of minerals and phytate, which and Ko¨ksel, 1997). Bran supplementation, which has both have been shown to inhibit many of phytases when present at mechanical and chemical effects on the structure of the dough, is millimolar concentration (Konietzny and Greiner, 2002). more detrimental to loaf volume than would be expected from According to the results and due to the high proportion of bran simple dilution of gluten protein (Gan et al., 1992; Lai et al., 1989b). in Tajan and Back Cross Sangak dough, fermentation was able to Bran particles cause physical disruption of the foam structure of the remove just about 20% of phytate (1.73 vs. 1.36 and 2.16 vs. 1.74 dough. Fine grinding and presoaking of wheat bran had a beneficial respectively) whereas phytate content in Tajan Sangak dough effect on loaf volume (Lai et al., 1989a,b). containing hydrothermaled bran decreased by 55% compared to its counterpart containing normal bran. It should be noted that the 3.4. Glutathione, free sulfhydryl (SHF) and disulfide (S–S) analyses phytate content reduced up to 65% (from 1.73 to 0.61) in Tajan Sangak dough containing hydrothermaled bran and 49% (from 2.15 There was a strong correlation between glutathione (GSH)/ to1.10) in Back Cross of Roshan Sangak dough containing hydro- oxidized glutathione (GSSG) and ash content in millstream flours, thermaled bran in comparison to their flours. Therefore, hydro- which indicated that much of those components was likely to have thermal treatment in Sangak dough as shown in the present study been derived from contamination by bran, aleurone, and germ and seems to be an effective treatment to decrease phytate while the suggestion that there are higher total glutathione (GSH plus showing positive effects on rheological properties of the dough. GSSG) levels in higher extraction grade flour (Every et al., 2006). In this study there was no significant difference in the SH content of the 3.3. Rheological parameters two flours (Table 4). These values were in the same range as those obtained by Puppo et al. (2005) for wheat flour. Hydrothermaled Supplementation of bread formulations with fiber-rich mate- bran treatment significantly increased SH content in all samples; rials may cause problems with dough handling properties and however, significant decrease in total thiol groups present in just bread quality (O¨ zboy and Ko¨ksel, 1997). However, flat breads have gliadin and glutenin samples were evidenced (Table 4). The flours a better chance of incorporation of high levels of dietary fiber containing hydrothermaled bran showed significantly higher SH without causing drastic deterioration in quality (Basman and Kok- content indicating glutathione could break some S–S bonds just sel, 1999; Qarooni et al., 1992). before complete elimination. The volume and quality of bread made In this study the farinograms showed significant differences with a variety of straight-run flours have no relation to the levels of between Sangak flour samples with and without treated brans endogenous GSH/GSSG in the flour. But higher levels of GSH (Table 3). Sangak flour samples with treated bran showed higher (400 nmol/g of flour) reduced the baking quality (Every et al., 2006). valorimetric value, longer development time, being more stable The results of Jarraud and Kobrehel (2000) suggest that free and showing a lower degree of softening (p < 0.05). Addition of sulfhydryl groups, formed through reduction by the NADP/thio- bran of each variety increased the water absorption of flours redoxin system and a glutathione system, are essential in forming slightly. Although high water absorption is important from the gluten aggregates. The thioredoxin protein and other low molecular economical point of view and avoiding staling, hydrothermal weight disulfide reducing proteins in dough may produce optimal treatment did not significantly increase water absorption in the two dough and bread properties (Every et al., 2006; Jarraud and varieties. Results indicated that Tajan dough showed better Kobrehel, 2000). Both structure and rheological properties of 402 L. Mosharraf et al. / Journal of Cereal Science 49 (2009) 398–404

Fig. 2. Scanning Electron Microscopy (SEM) of Sangak dough prepared from two wheat varieties: Tajan Sangak dough (A), Tajan Sangak dough contains hydrothermaled bran (B) Back Cross of Roshan Sangak dough (C) Back Cross of Roshan Sangak dough containing hydrothermaled bran (D), Tajan bran before (E) and after (F) hydrothermal treatment along with Back Cross of Roshan bran before (G) and after (H) same treatment. L. Mosharraf et al. / Journal of Cereal Science 49 (2009) 398–404 403 dough are closely related to the content of free sulfhydryls of dough assumed to play an important role in starch and gluten rigidity and the formation of disulfide bonds during mixing (Anderson and (Chinachoti and Vodovotz, 2001; Katina et al., 2006). Ng, 2000). Mixing decreases free sulfhydryls and increases the It is, noteworthy, that during bran treatment, brans were sub- release of gliadin proteins of dough until it reached the develop- jected to water for a long period of time (24 h). This allows textural ment stage, but overmixing cleaves some of the disulfide bonds, modification of bran particles before bran is added to the dough. and consequently increase free sulfhydryls (Puppo et al., 2005). The The hydrolysis of cell wall material can also affect the microstruc- free sulfhydryl content and sulfhydryl–disulfide interchange of ture of dough. The positive effect of this change has been proposed wheat flours may be an important determinant of the rheological to be due to increased levels of soluble pentosans and fructosans in properties and the action of chemical improvers in wheat flour the dough (Martinez-Anay and Devesa, 2000; Salmenkallio-Mart- doughs. The flours containing hydrothermaled bran showed higher tila et al., 2001). SH content indicating glutathione could break some of the S–S In the dough containing untreated bran, the starch and protein bonds just before its complete elimination. Flours containing appeared more in large separate areas than in the dough in which hydrothermal bran had more disulfide bonds, that showed better bran has been treated. The protein matrix was clearly separated rheological properties after mixing. Releasing of gliadin protein from the large starch granules (Fig. 2), indicating that adhesion which had higher SH content than glutenin and decrease of SH between gluten and starch had been reduced. Differences in starch bonds during mixing continued until the development stage of granule structure and the degree of adhesion between the gluten dough (Puppo et al., 2005). Flours of both varieties containing and starch are all dependent on water content of the dough and hydrothermal brans showed longer development times and distribution of water between the various dough components produced more stable dough with a lower degree of softening (Salmenkallio-Marttila et al., 2001). The swelling of the starch (Fig. 1, A and B) compared to the samples prepared without HT bran granules and the degree of adhesion between gluten and starch (Fig. 1, C and D) granules were more in the doughs made with hydrothermaled brans probably due to lower reducing components in the dough.

3.5. SEM analysis of dough 4. Discussion

The knowledge of structure–function relationships of the raw From the overall results, it could be concluded that incorpora- materials and products is valuable in order to achieve the quality tion of hydrothermaled bran, modifies rheological properties of required for successful products. Scanning electron microscopy Sangak dough. Moreover, the treatment broke a considerable part (SEM) investigations have shown e.g. that the different rheological of the phytate in Sangak flour and therefore seems to be a suitable properties and gas retention of wheat can be explained by micro- treatment to upgrade Sangak bread (which is very popular in the structural differences (Aranyi and Hawrylewicz, 1969). Porosity, the country) in terms of its nutritional quality. It also removed/washed extent of starch gelatinization and protein structure contributes to out thiol groups that basically have a detrimental effect on dough the appearance and texture of cereal products (Prabhasankar et al., rheological characteristics. Following addition of hydrothermaled 2003). SEM was found to be a valuable tool for understanding bran to the bread, while most quality attributes were improved, no molecular interactions between starch and protein molecules change was shown in its fiber content. In terms of flat breads during the baking process of flat breads. SEM provides an appro- including Sangak, one of the major drawback and concerns has priate means for characterising the physical properties and textural been always their phytate content; however, incorporation of attributes of food ingredients in a formulated product (Belsie et al., hydrothermaled bran may encourage both bakers and consumers 1993). The advantages that make the scanning electron microscope to process these kinds of breads. an extremely useful tool for examination of the flour–dough tran- sition include its very large depth of focus and the possibility of obtaining three-dimensional images of sample surfaces at rela- Acknowledgments tively low magnifications with minimal preparation (Aranyi and Hawrylewicz, 1969). The authors are thankful to Isfahan Agricultural Research Center Sangak dough structure analyzed by SEM is shown in Fig. 2 (A– for financial support of this project. Technical assistance of Mr. B. D) indicating differences in the structure of both doughs (with and Bahrami is greatly appreciated. without hydrothermaled brans). In dough containing non-hydrothermaled bran, proteins have formed a laminar protein matrix, Appendix A. Supplementary data which is probably due to the presence of a completely hydrated system (Campos et al., 1997). The dough showed protein films that Supplementary data associated with this article can be found, in have covered starch granules providing an amorphous structure, the online version, at doi: 10.1016/j.jcs.2009.01.006. a structure which did not appear in non-hydrothermaled samples. The microstructure of bran is shown in Fig. 2 (E–H). Preston and References Kilborn (1984) suggested that fully developed dough has a well- organized, web like (laminar) gluten protein structure, suggesting Anderson, A.K., Ng, P.K.W., 2000. Changes in disulfide and sulfhydryl contents and a strong and a firm dough structure. Results of SEM tests, however, electrophoretic patterns of extruded wheat flour proteins. Cereal Chemistry 77, indicated that dough containing hydrothermaled bran seems to 354–359. Aranyi, C., Hawrylewicz, E.J., 1969. Application of scanning electron microscopy to portray a stiffer dough structure than non-hydrothermaled bran cereal specimens. Cereal Science Today 14, 230–233. dough. Water content of dough affects the properties of its different Basman, A., Koksel, H., 1999. Properties and composition of Turkish flat bread chemical components. Hydrothermal treatment affects the (Bazlama) supplemented with barley flour and wheat bran. Cereal Chemistry 76, 506–511. swelling and gelatinization of the starch component of bran. Water Belsie, P.R., Rasco, B.A., Siffring, K., Bruinsma, B., 1993. Baking properties and is more abundant in the swollen amorphous regions of starch, microstructure of yeast-raised breads containing wheat bran, carageenan facilitating local polymer chain mobility (plasticization) and blends or laminated. Food Structure 12, 489–496. Bergman, E.L., Fredlund, K., Reinikainen, P., Sandberg, A.S., 1999. Hydrothermal subsequent crystallization and retrogradation. Water distribution processing of barley (cv. Blenheim): optimisation of phytate degradation and within regions in gluten, amorphous and crystalline starch is increase of free myo-inositol. Journal of Cereal Science 29, 261–272. 404 L. Mosharraf et al. / Journal of Cereal Science 49 (2009) 398–404

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