Journal of Cereal Science 49 (2009) 398–404 Contents lists available at ScienceDirect Journal of Cereal Science journal homepage: www.elsevier.com/locate/jcs 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 0733-5210/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.jcs.2009.01.006 L. Mosharraf et al. / Journal of Cereal Science 49 (2009) 398–404 399 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 Æ 0.28 8.30 Æ 0.27 8.90 Æ 0.35 8.10 Æ 0.07 6.00 Æ 0.16 5.40 Æ 0.02 7.00 Æ 0.08 5.80 Æ 0.13 Protein (%)c 13.19 Æ 0.35 a 13.19 Æ 0.08 a 10.10 Æ 0.22 b 10.01 Æ 0.09 b 16.17 Æ 0.08 a 15.64 Æ 0.52 a 14.30 Æ 0.09 b 13.80 Æ 0.05 b Ash (%) 1.21 Æ 0.19 b 1.27 Æ 0.02 b 1.65 Æ 0.17 a 1.83 Æ 0.20 a 4.68 Æ 0.19 c 5.07 Æ 0.38 b 5.27 Æ 0.82 b 5.78 Æ 0.23 a Crude fiber (%) 2.20 Æ 0.22 a 2.34 Æ 0.70 a 2.14 Æ 0.33 a 2.25 Æ 0.76 a 8.51 Æ 0.33 b 9.20 Æ 0.15 a 8.06 Æ 0.22 c 8.49 Æ 0.65 b Fat (%) 3.29 Æ 0.15a 2.83 Æ 0.11 b 2.40 Æ 0.15 c 1.63 Æ 0.08 d 5.10 Æ 0.22 a 4.33 Æ 0.21 b 4.30 Æ 0.17 b 3.70 Æ 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 hydro- thermaled 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 Â 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 struc- ture 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, hydro- thermal 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).