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Effect of wheat germ flour addition on wheat flour, dough and Chinese steamed bread properties
Accepted Manuscript Effect of wheat germ flour addition on wheat flour, dough and Chinese steamed bread properties Ru Sun, Zhengmao Zhang, Xinjuan Hu, Qinhui Xing, Wuyan Zhuo PII:
S0733-5210(15)00064-8
DOI:
10.1016/j.jcs.2015.04.011
Reference:
YJCRS 1975
To appear in:
Journal of Cereal Science
Received Date: 25 June 2014 Revised Date:
19 April 2015
Accepted Date: 26 April 2015
Please cite this article as: Sun, R., Zhang, Z., Hu, X., Xing, Q., Zhuo, W., Effect of wheat germ flour addition on wheat flour, dough and Chinese steamed bread properties, Journal of Cereal Science (2015), doi: 10.1016/j.jcs.2015.04.011. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Effect of wheat germ flour addition on wheat flour, dough and Chinese steamed bread properties
2 3 4 5 6 7 8 9 10
Ru Suna, Zhengmao Zhanga*, Xinjuan Hua, Qinhui Xinga, Wuyan Zhuob a
College of Food Science and Engineering, Northwest A&F University, 28 Xinong Road,
Yangling, Shaanxi 712100, China b
College of Agronomy, Northwest A&F University, 3 Taicheng Road, Yangling, Shaanxi 712100, China
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33 * Corresponding author, Tel.:+8613347411356. Fax: +8602987092486. Postal address: College of Food Science and Engineering, Northwest A&F University, Yangling, Shaanxi 712100, China. E-mail address: [email protected]. 1
ACCEPTED MANUSCRIPT Abstract: Wheat germ flour (WGF) has been developed as a functional food ingredient with high
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nutritional value. In this study, WGF was applied in steamed bread-making in order to improve the
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quality of Chinese steamed bread (CSB). Partial substitution of wheat flour with WGF at levels of
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3%, 6%, 9% and 12% (w/w) was carried out to investigate physicochemical properties of blends
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and their steaming performance. Falling number (FN) values of composite flours ranged from 199
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to 223 s. Viscosity analysis results showed that wheat flour mixed with WGF had higher pasting
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temperature and lower viscosities. Dough rheological properties were also investigated using
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farinograph and extensograph. The addition of WGF diluted the gluten protein in dough and
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formed weak and inextensible dough, which can be studied by scanning electron microscope
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(SEM) analysis. CSB made with WGF had significantly lower volume, specific volume and higher
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spread ratio. The sensory acceptability and physicochemical quality of CSB were improved with
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the application of a low level of WGF (3% and 6%). However, results showed that a high level of
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WGF over 9% is not recommended because of unsatisfactory taste. As a whole, addition of
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appropriate level of WGF in wheat flour could improve the quality of CSB.
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Key words: wheat; wheat germ flour; Chinese steamed bread; quality
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Chemical compounds studied in this article
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phosphate (PubChem CID:24203) ethanol (PubChem CID:702) glutaraldehyde(PubChem
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CID:3485) isoamyl acetate (PubChem CID:31276) water (PubChem CID:962)
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carbon dioxide(PubChem CID:280) sodium chloride (PubChem CID:5234)
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Abbreviations:
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WGF , Wheat germ flour ; CSB , Chinese steamed bread ; wt , weight ; SEM ,scanning electron
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microscope ; RVA , Rapid Visco Analyser ; TV , trough viscosity ; FV , final viscosity ; PV
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peak viscosity ; BV , breakdown viscosity ; SV , setback viscosity ; FN , Falling number .
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1 Introduction
Wheat (Triticum aestivum L.) is one of the most important crops and has been used as a main
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component to produce various food products. Wheat based foods play an important role in the
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food culture of Asian countries since ancient times. Chinese steamed bread (CSB) has 1700 years
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of history and is one of the most popular wheat products in China. With the passage of time,
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various types of CSB have been developed and most typical types are northern-style and
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southern-style steamed breads (Zhu et al., 2001). CSB is mainly constituted by wheat flour, water
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and yeast. Many other food ingredients such as bioactive compounds extracted from barley hull or
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flaxseed hull (Hao et al., 2012), custard cream (Chaiwanichsiri et al., 2011), shiitake stipe, silver
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ear (Tsai et al., 2010), thermostable xylanase (Jiang et al., 2010), lipid (Sun et al., 2010), sodium
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alginates and konjac glucomannan (Sim et al., 2011) have been used for CSB formulation to
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increase CSB diversity, nutritional value and product appeal.
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Wheat germ, accounting for 2-3% of the total weight of wheat kernel, is almost removed
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during milling as it adversely affects the flour processing quality. It has been estimated that the
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world annual discarded wheat germ is up to 25,000,000 tons (Rizzello et al., 2010), which causes
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serious waste. On the other hand, most wheat germ is used for animal feed and other purposes,
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which makes human consumption of wheat germ very limited.
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wheat germ can be separated from the grain with high purity (Srivastava et al., 2007). It is rich in
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bioactive substances such as antioxidants and sterols. The antioxidants mainly include tocopherols,
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tocotrienols, phenolics and carotenoids (Gelmez et al., 2009). Wheat germ also contains some
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unsaturated fatty acids such as oleic, linoleic and α-linoleic acids (Rizzello et al., 2010). Moreover,
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most of the essential amino acids from wheat germ proteins are identified with higher
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During the milling process,
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oil which is applied in the medical and cosmetic industries (Kahlon, 1989). As for human health
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benefits, it is reported that the processed wheat germ can be applied in prevention and treatment of
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cancers (Zalatnai et al., 2001).
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Wheat germ, which is rich in functional food components, and a viable potential wheat base
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ingredient might be used in food. Because of the high nutritional value, some studies considered
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the use of wheat germ for the manufacturing of cereal based food products (Ge et al.,2001). Pasta
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manufactured with semolina blended with 15% of raw and microwaved wheat germ showed
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significant increase of nutritional value (Pınarlı et al.,2004). Replacement of wheat flour with
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defatted wheat germ at levels of 0-25% also increased functional and nutritional properties in
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cookies (Arshad et al.,2007). Compared to breads made with refined flour, the concentration of
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minerals, proteins, fat and dietary fibres was higher in breads supplemented with wheat germ
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(Sidhu et al.,1999).
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To our best knowledge, limited research is available on the physical properties and quality of
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CSB-making with WGF. Studies have reported the improvement of nutritional value of CSB after
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supplementation with WGF; however, the effect of WGF on the functional properties of the flour
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and the organoleptic acceptability of the CSB is rarely reported. Therefore, the objective of the
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current work is to investigate quality and nutritive value of CSB after supplementation of WGF.
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Additionally the extent of this improvement was also part of the investigation.
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2 Materials and methods
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2.1 Sample preparation
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Yangling, Shanxi province, China, was used in this study. The wheat seed sample was first ground
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using a laboratory mill (LSM20, Maosheng milling apparatus, China). The flour contained protein
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(12.0%), ash (0.6%), moisture (12.1%), crude fat (1.3%) and wet gluten (40%). Flour was stored
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at 4 °C in polyethylene bags. Pure 9946 wheat flours or CSB made of pure 9946 wheat flours was
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used as control.
Wheat germ was obtained from a commercial mill (Laoniu milling plant, Yangling, China)
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and was dried in a baking oven at 70
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After roasting, the germ was emptied into a glass jar and cooled to room temperature, and then
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milled with particle size of 100 ± 200 µm. The samples were kept in sealed glass jars at 4 °C.
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for 2 hour in aluminium trays (thickness of 0.5-1.0 cm).
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Mixed flours were prepared by mixing raw wheat flour at different levels of WGF (3, 6, 9 and 12%) to evaluate the physicochemical properties and steaming performance of the mixture.
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2.2 Measurement of α-amylase activity
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The α-amylase activity was measured according to the method of Khalil et al. (1999).
2.3 Pasting properties of starch
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Pasting properties of starches in the wheat flours and the wheat germ flours were measured
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on a Rapid Visco Analyser (NEWPORT, RuA Super 3, USA) (Ragaee et al., 2006).
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2.4 Rheological analysis
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Measurements of water absorption, dough development time, dough stability and softening
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degree were carried out by using a Farinograph (Brabender, Germany). Dough extensibility and
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maximum resistance to extension were determined using an Extensograph (Brabender, 5
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Germany)(Hallén, 2004).
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2.5 Microstructure observation
Microstructure observation was conducted according to Hu et al.(2009) with minor
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modification. Phosphate buffer (PB, 0.1 mol L-1, pH 6.8) and ethanol solvents with ascending
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concentrations of 30%, 50%, 70%, 80%, 90% were used in this part.
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2.6 Preparation of CSB
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The formulation of CSB was as follows: wheat flour or the wheat germ flours (100 g),
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dehydrated yeast (1 g) and water (54 ml) were first prepared. After mixing and kneading into
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dough, the mixture was placed into the fermentation cabinet (38 °C and 85% R.H.) for 1 h. Dough
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was then taken out and sheeted 20 times followed by dividing it into several pieces (60 g per
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piece). The dough piece was rounded and molded manually and proofed for 20 min in the same
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fermentation cabinet. After that, the proofed dough was steamed for 25 min using a steam tray and
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boiling water.
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2.7 Physical properties of CSB
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Volume was measured after steaming 1 h by millet displacement method. The width and height of
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each sample was measured at different locations, and the average values were recorded. Specific
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volume (the volume to the weight, ml/g) and spread ratio (the width to the height, W/H) were
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calculated, respectively.
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2.8 Textural analysis
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Systems, Ltd., UK) equipped with a P36 probe. Steamed bread was sliced horizontally and a
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bottom piece, 24 mm height, was compressed to 50% of its height. The test parameters were as
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follow: pre-test speed 1.0 mm/s, test speed 1.0 mm/s, post-test speed 1.0 mm/s and trigger force 5
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g. From the TPA test profile, textural parameters including hardness, springiness, cohesiveness,
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adhesiveness and resilience were obtained.
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2.9 Sensory evaluation of CSB
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Sensory analysis of bread was carried out according to the method described by Haglund et al.
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(1998) with minor modifications. Elasticity, color, porosity, flavor, sweetness, dryness, taste and
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mouth satisfaction were evaluated using a scale from 0 to 10 points, with 10 being the highest
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score.
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2.10 Statistical analysis
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Data was collected from three duplicated experiments except for Farinograph and
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Extensograph. Statistical analysis of the results was implemented with software SAS 8.1 (Institute
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Inc., USA).
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3 Results and discussion
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3.1 The falling number (FN)
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The FN of mixed flours is presented in Fig.1. The control (0% WGF) showed the highest
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value (230 s) and the 12% WGF showed the lowest falling number (199 s). Results indicated that
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partial substitution of wheat flour by WGF decreased the falling number. The FN value determines
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α-amylase. FN decrease with the increase of substitute level, the lower FN of wheat-WGF
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composite flours as compared to control is due to the higher α-amylase existing in germ (Every et
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al.,2002; Kruger 1981). The production of wheat bread using α-amylase with higher volume and
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good crumb structure was previously reported (Randez-Gil et al., 1995; Pritchard 1992). The
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presence of amylases also increased the level of fermentable and reducing sugars in the flour and
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dough, thereby promoting yeast fermentation (Hamada et al., 2013), which suggested that
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α-amylase activity might improve CSB quality.
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3.2 Pasting properties of mixture
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The effect of WGF on pasting properties of the mixture is shown in Fig. 2. RVA parameters
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have been found to be correlated with oriental flour food quality (Panozzo and McCormick, 1993;
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Sun et al., 2010). The paste viscosity is dependent on the composition of flour and the
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gelatinization of starch. There was a remarkable downtrend of peak viscosity (PV), trough
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viscosity (TV), setback viscosity (SV) and final viscosity (FV) with increase in the addition of
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different levels of WGF. When 12% supplementation addition was done, the PV, TV, SV and FV
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decreased by 25.7, 27.0, 16.5 and 22.3%, respectively, compared to the control. As a whole, the
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value of the above mentioned five indexes was decreased with the increase of WGF addition.
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Among all of the samples, the control had the highest PV, TV, SV, FV and breakdown viscosity
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(BV). There were distinct effects between control and samples that with 6 and 12% addition of
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WGF on peak time, but other addition levels had no remarkable effects on it, which indicated that
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there were other influential factors besides the additive amounts. The results suggested the high
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content of starch in wheat flours compared to substituted flours may contribute, to some extent, to
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also affect pasting viscosity and properties.
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3.3 Rheological properties after addition of WGF
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Rheological properties of wheat flour (control) and those of those substituted with WGF at a 3, 6, 9 or 12% level are shown in Table 1.
The addition of WGF to wheat flour lead to some significant changes in its dough mixing
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behavior as measured by the farinograph. Water absorption of wheat flour used in this study
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(64.5%) remained within ± 0.2% variation, when WGF was incorporated at levels of 3, 6, 9 and
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12%. A correlation between the flour water absorption and increasing levels of WGF can be seen
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in Table 1. Dough water absorption gradually increased from 64.5 to 65.7% with increase of WGF
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level in mixed flour from 3 to 12%. Srivastava et al. (2007) had reported that mixed flour had
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greater water absorption capacities than wheat flour. The addition of WGF to wheat flour is
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expected to increase the protein content of the blends, since WGF contains more proteins than the
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pure wheat flour. The greater water absorptions of mixed flours, therefore, could be an additive
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effect. Rate of hydration, as reflected in dough development time, did not change significantly,
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either. However, addition of WGF had an adverse effect on dough stability, which decreased from
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2.9 min to 1.9 min at 12% level. Following the trend of dough stability, farinograph quality
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number reduced slightly from 51 to 44 at 12% addition level of WGF. A former researcher has
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reported that incorporation of wheat germ had a weakening effect on rheological characteristics of the
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dough (Srivastava et al.2007). Our findings coincide with this previous study. The effect of the
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addition of WGF on the farinographic proprieties of dough were related partly to gluten dilution and
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partly to altered water behaviors caused by components of the added WGF, particularly fats, proteins
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after addition of WGF to pure wheat flour dough (Manuel et al.2012). Stability is related to the quality
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of the protein matrix, which is easily damaged by the incorporation of other ingredients, due to gluten
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dilution and the presence of reducing agents such as glutathione which is available in WGF (Every et
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al. 2006). This was definitely notable at the time of the experiment when handling the different
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dough. The WGF gave weaker dough with increased dough weakening at higher substitution
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levels.
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Extensograph measurements provide useful information about the viscoelastic behavior of
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dough. Data on the effect of added WGF on the extensograph characteristics of wheat flour dough
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samples, throughout 45, 90 and 135 min resting time periods, are presented in Table 1. The
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weakening of dough caused by the addition of WGF to wheat flour is in agreement with earlier
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observations of WGF. Possible reasons for the weakening of dough due to the addition of WGF
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might include an effective decrease in wheat gluten content (dilution effect) by competing for
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water with wheat flour proteins. It is well known that wheat germ proteins alone do not have food
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dough forming properties and that the supplemental proteins disrupt the well-defined
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protein-starch complex in wheat flour bread suggesting a weakening of dough. Cakmakli et al.
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(1995) has reported that addition of wheat germ had a weakening effect on rheological
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characteristics of the dough. This was more evident in the consistent decrease in dough
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extensibility, especially in dough resistance. Samples with higher addition of WGF demonstrated
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lowest dough resistance while the control showed the highest resistance, with a quite steep slope
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down to the much lower values for 12% addition level of WGF.
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3.4 SEM results of the WGF-treated dough
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SEM. The microstructure of all the different dough samples is shown in Fig.3. The appearances of
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dough made from WGF substituted flours exhibited a discontinuous and irregular matrix around
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the starch granules, whereas the control sample (dough made from pure wheat flout) had an
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extensible gluten matrix which covered all starch granules. Thus, the existence of WGF diluted the
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protein and interfered with optimal gluten matrix formation during dough formation. The dilution
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also affected the formation of an elastic network of cross-linked gluten molecules during steaming,
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resulting in easy disruption of the gluten network and lower loaf volume of CSB. In this work, the
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physicochemical properties of dough were affected by adding WGF which might be due to (1) the
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difference in chemical composition of protein in control and WGF; (2) larger particle size of WGF;
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(3) wheat germ contains a certain amount of glutathione, which is an activator of protease that can
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accelerate the decomposition of protein, thus leading to disruption of gluten network; (4) WGF
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contains more lipid, most of which is unsaturated lipid, which can weaken the network of gluten.
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3.5 The effect of WGF on CSB quality
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The effect of the WGF at various levels on the quality of CSB is shown in Table 2. A decrease
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in the volume, specific volume and an increment in spread ratio were observed. Both of these
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effects were expected, as the amount of gluten, which imparts higher volume in steamed bread,
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was decreased as a result of gluten-free WGF in the CSB formulation. Specific volume and spread
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ratio are two important quality parameters of CSB (Su et al., 2005; Zhang et al., 2007). The
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volume of CSB and specific volume decreased by up to 12.5% and 16.1% with addition of 12%
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WGF, respectively. The highest spread ratio rose up to 24.2% when 12% of WGF was added.
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These results were due to the existence of a high amount of dietary fiber in WGF which diluted
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steaming.
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3.6 Texture properties
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Hardness, springiness, cohesiveness, gumminess, chewiness and resilience were textural
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attributes of CSB. These attributes of CSB were determined by TPA. The TPA properties of CSB
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made from mixed flours are shown in Table 3. All of the parameters showed significant difference
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between the WGF CSB and the control. This observation is confirmed by the analysis of variance,
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which indicated that these parameters were significantly influenced (P<0.05) only by addition of
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WGF. The springiness, cohesiveness and resilience was also notable because it decreased with the
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increased level of WGF and vice versa. Hardness is often considered as the index of the total
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textural attributes (Carlo, et al., 2011). After addition of WGF, the value of hardness,
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corresponding to the peak force of the first compression of the product, was higher which
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significantly (P>0.05) differed from the control (1880.959 g), the hardness of CSB increased to
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3335.393 g with 12% supplementation. Resilience indicated the recovery of CSB to its original
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position. The resilience markedly decreased for WGF CSB as the level of substitution increased,
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the lowest value of resilience was found at 12% supplementation (0.466). Values of cohesiveness
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dropped sharply.
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Samples with higher incorporation of WGF influenced consumer’s acceptance of CSB,
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because it results in high crumbling. In the case of chewiness, which is significantly related to
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hardness, highest values were observed for 12% supplementation sample. Similarly to hardness,
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most pronounced reduction of chewiness was caused by the addition of WGF.
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3.7 Sensory evaluation
After steaming (an hour), sensory analysis was carried out. The sensory scores as given by
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the panel have been shown in Table 2. Sensory evaluation of steamed breads implied that, the
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elasticity, color, porosity, flavor, sweetness, dryness, taste and mouth satisfactory of CSB were
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significantly affected by the addition of WGF as compared to the control sample.
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The addition of WGF significantly decreased the elasticity of CSB compared to the control
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sample (pure wheat flour CSB). The elasticity of supplemented WGF CSB was significantly
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decreased at higher levels of supplementation (12%), indicating that the elasticity was mainly
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affected by the addition of WGF. There was a lower pore number and the pore became smaller as
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the substitution level of WGF increased, the score of porosity sharply decreased from 8.0 to 5.5 at
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12% supplementation. These results were probably due to higher water absorption and holding
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capacity of WGF as compared to wheat flour. Moreover, WGF does not contain any gluten, this
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may have partially contributed to higher density in WGF added CSB. The addition of WGF
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improved the flavor and dryness of samples, because WGF has its special flavor and higher water
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absorption than wheat flour. All the samples of WGF CSB scored notably higher in terms of flavor
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and dryness than the control, increasing substitution levels increased the flavor and dryness scores
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of CSB. In the case of WGF CSB, only the taste and flavor score of CSB with 3% WGF differed
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significantly from the control. However, it was observed that CSB made with partial WGF
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substitution (3% or 6%) were more acceptable when it comes to sensory (color, sweetness, taste
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and mouth satisfaction) than other samples, which had moderate color than other samples due to
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the presence of WGF. Conclusively, the substitution of WGF for Pubing 9946 wheat flours
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improved the quality of CSB and the amount of substitution of pure wheat flour was up to 6%.
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4. Conclusions
Incorporation of WGF into wheat flour significantly affected the physicochemical properties
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and steaming performance of the blends. Flour replacement at different levels (from 0 up to 12%)
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by WGF changed the pasting and rheological characteristics of the blends, dough microstructure,
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CSB physical, sensory and textural properties. The trend and the extent of effects of WGF on the
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indexes mentioned above depend on the extent of flour substitution. Addition of WGF to flours
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resulted in a shortening effect for dough machinability. Caution should be paid to addition level of
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WGF because of the adverse increase in solid-like properties of the dough, which may reduce
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expansion during fermentation and steaming. Enrichment with WGF led to lower changes in
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viscoelastic properties of dough than pure wheat flour and had negative effects on physical quality
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and sensory evaluation of CSB. Addition of WGF over 9% is not recommended because of a
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strongly brown color, hard texture and unsatisfactory taste. The present study indicated that CSB
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made with the mixed flour of wheat flour and WGF had acceptable sensory properties and the
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addition level of WGF is up to 6% of flour. Therefore, the addition of WGF could be an effective
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way to produce functional white flour CSB without altering its desirable physical properties.
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Development of such functional foods would be beneficial to improve the nutritional status for the
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consumer. Further studies are needed to evaluate changes in WGF-enriched CSB characteristics
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during storage.
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Acknowledgements
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The authors would like to thank the Shaanxi Province overall pianning science and
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technology project (2011KTZB02-01). We also gratefully acknowledge Dr. Qingbin Guo and Dr.
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Hongju He for making grammatical corrections to this paper.
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Ragaee, S., Abdel-Aal, E. S. M.,2006. Pasting properties of starch and protein in selected cereals and quality of their food products. Food Chem.95,9-18. Randez-Gil,F., Prieto,J. A., Murcia,A., Sanz, P., 1995. Construction of baker's yeast strains that
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secrete Aspergillus oryzae alpha-amylase and their use in bread making. J.cereal Sci.
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21,185-193.. Rizzello,C. G., Nionelli,L., Coda,R., De,Angelis.M., Gobbetti,M., 2010. Effect of sourdough
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25,951-957.
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Su,D.M., Ding,C.H., Li,L.T.,Su,D.H., Zheng,X.Y.,2005.Effect of endoxylanases on dough
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properties and making performance of Chinese steamed bread. Eur. Food Res. Technol.
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220,540-545.
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Tsai,S.Y., Yang,J. H., Tseng,Y. H., Lee,C. E., Mau,J. L., 2010. Quality of silver ear steamed bun. J.Food Process. Pres. 34,649-663.
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Zalatnai, A., Lapis, K., Szende, B., Rásó, E., Telekes, A., Resetár, Á., Hidvégi, M., 2001. Wheat
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germ extract inhibits experimental colon carcinogenesis in F-344 rats. Carcinogenesis
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22,1649-1652.. Zhang,P.P., He,Z.H.,Chen,D.S.,Zhang,Y.,Larroque,O. R.,Xia,X. C., 2007. Contribution of common
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wheat protein fractions to dough properties and quality of northern-style Chinese steamed bread.
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Rheological properties of doughs from composite flours Dough
Farinograph
Dough
Dough
Dough
Flour water
development
stability
quality
weaking
extensibility
resistance
Samples
absortion(%)
(min)
(min)
number
(FU)
(cm)
(BU)
Control
64.5
3.5
2.9
51
92
185
231
3% WGF
64.8
3.3
2.7
49
93
183
146
6% WGF
64.9
3.5
2.3
47
107
184
111
9% WGF
65.3
3
2.1
46
143
183
90
12% WGF
65.7
3.2
1.9
44
150
161
76
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Dough
Used pure 9946 wheat flours as control.
4 5
Table 2
Effect of the WGF at various levels on the quality and sensory evaluation of CSB
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Table 1
Specific Spread Volume volume
Control 160±2
a
3% WGF
155±3
b
6% WGF
148±2
c
9% WGF
145±2
12% WGF
(ml/g)
(W/H)
ity
2.81±
1.61±
7.5±
7.5±
8.0±
6.0±
a
e
a
c
a
e
0.02
140±3e
0.02
0.2
0.1
0.3
0.1
1.75±
7.2±
7.8±
7.4±
6.8±
b
d
b
b
b
d
0.01
0.01
0.2
0.1
0.2
0.2
2.52±
1.81±
7.0±
8.2±
6.9±
7.3±
c
c
bc
a
c
c
0.02
0.01
d
0.02
1.96±
0.1
0.01
b
6.5± 0.1
c
satisfac Total
Color Porosity Flavor -ness -ness Taste
2.57±
2.45± d
Sweet Dry
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ratio Elastic
0.3
7.2±
0.1
6.5±
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Mouth
0.2
d
0.1
d
0.1
7.8± 0.3
b
7.0± 6.8± 7.2±
0.1
bc
0.1
c
0.1
c
7.4± 7.2± 7.5± 0.2
a
0.2
b
0.2
b
7.6± 7.4± 7.8± 0.1
a
0.1
b
0.1
a
6.8± 7.8± 7.1± 0.1
b
0.2
a
0.2
cd
-tion
points
7.8±
57.8±
0.2
c
8.2± 0.1
b
8.5± 0.3
a
7.7± 0.1
cd
1.1c 59.5± 1.4b 60.7± 1.3a 57.4± 1.3c
2.42±
2.00±
5.9±
6.5±
5.5±
8.2±
6.8± 8.0± 6.9±
7.5±
55.3±
0.02e
0.01a
0.1d
0.1e
0.1e
0.3a
0.1c
0.2d
1.3d
0.3a 0.1d
Used CSB made of pure 9946 wheat flours as control.
7
Values followed by same letter in the same column indicated data are not significantly different(P <0.05) by
8
Duncan test.
9
Mean values ± standard deviations for fermentations, analyzed in duplicate.
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Sensory attributes were scored by using a scale 0-10 .
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Table 3 Hardness
g)
Springiness
Cohesiveness (g.s)
Gumminess (g)
Chewiness (g)
Resilience
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Samples
Texture parameters of CSB made of the WGF at various levels
Control
1880.959±112.712e
0.972±0.012a
0.842±0.015a
1581.109±121.098e
1537.763±131.427e
0.518±0.013a
3% WGF
2078.271±130.242d
0.960±0.026b
0.838±0.016b
1740.715±103.125d
1672.043±125.671d
0.499±0.016b
6% WGF
2140.444±151.357c
0.953±0.018c
0.826±0.017c
1763.778±123.435c
1681.490±118.653c
0.488±0.009c
9% WGF
2426.037±125.426
b
d
d
b
b
0.474±0.006d
12% WGF
3335.393±123.564a
2522.183±136.357a
0.466±0.013e
0.929±0.019e
0.817±0.012
0.814±0.014e
1977.559±107.253
2711.436±135.257a
1898.977±113.435
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0.941±0.021
Used CSB made of pure 9946 wheat flours as control.
13
Different superscript letters at each column indicate significant differences (P < 0.05) by Duncan test.
14
Different superscript in the same column indicate that means were significantly different (P < 0.05) by Duncan test.
15
Mean values ± standard deviations for fermentations, analyzed in duplicate.
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ACCEPTED MANUSCRIPT Fig.1. Falling number for all formulations studied. Fig.2. Curves of pasting properties of pure wheat flour mixed with different quantities of wheat germ flour Fig.3. SEM images of dough made from pure wheat flour and its substitutions.
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5 6
Fig. 1.
Falling number for all formulations studied.
7 8 9 10 11
3%WGF 6%WGF 9%WGF 12%WGF
Temperature ( )
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Viscosity(RVU)
Control
Temperature curve
Time(min)
Fig.2. Curves of pasting properties of pure wheat flour mixed with different quantities of wheat germ flour.
Used pure 9946 wheat flours as control.
1
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Control
3%WGF
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6%WGF
9%WGF
12%WGF
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► WGF affected properties and steaming performance of the blends. ► CSB made with ≦ 6% WGF had acceptable sensory properties. ►WGF can be used for making CSB. ► WGF can improve nutritious quality of CSB.
S0733-5210(15)00064-8
DOI:
10.1016/j.jcs.2015.04.011
Reference:
YJCRS 1975
To appear in:
Journal of Cereal Science
Received Date: 25 June 2014 Revised Date:
19 April 2015
Accepted Date: 26 April 2015
Please cite this article as: Sun, R., Zhang, Z., Hu, X., Xing, Q., Zhuo, W., Effect of wheat germ flour addition on wheat flour, dough and Chinese steamed bread properties, Journal of Cereal Science (2015), doi: 10.1016/j.jcs.2015.04.011. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Effect of wheat germ flour addition on wheat flour, dough and Chinese steamed bread properties
2 3 4 5 6 7 8 9 10
Ru Suna, Zhengmao Zhanga*, Xinjuan Hua, Qinhui Xinga, Wuyan Zhuob a
College of Food Science and Engineering, Northwest A&F University, 28 Xinong Road,
Yangling, Shaanxi 712100, China b
College of Agronomy, Northwest A&F University, 3 Taicheng Road, Yangling, Shaanxi 712100, China
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33 * Corresponding author, Tel.:+8613347411356. Fax: +8602987092486. Postal address: College of Food Science and Engineering, Northwest A&F University, Yangling, Shaanxi 712100, China. E-mail address: [email protected]. 1
ACCEPTED MANUSCRIPT Abstract: Wheat germ flour (WGF) has been developed as a functional food ingredient with high
35
nutritional value. In this study, WGF was applied in steamed bread-making in order to improve the
36
quality of Chinese steamed bread (CSB). Partial substitution of wheat flour with WGF at levels of
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3%, 6%, 9% and 12% (w/w) was carried out to investigate physicochemical properties of blends
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and their steaming performance. Falling number (FN) values of composite flours ranged from 199
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to 223 s. Viscosity analysis results showed that wheat flour mixed with WGF had higher pasting
40
temperature and lower viscosities. Dough rheological properties were also investigated using
41
farinograph and extensograph. The addition of WGF diluted the gluten protein in dough and
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formed weak and inextensible dough, which can be studied by scanning electron microscope
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(SEM) analysis. CSB made with WGF had significantly lower volume, specific volume and higher
44
spread ratio. The sensory acceptability and physicochemical quality of CSB were improved with
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the application of a low level of WGF (3% and 6%). However, results showed that a high level of
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WGF over 9% is not recommended because of unsatisfactory taste. As a whole, addition of
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appropriate level of WGF in wheat flour could improve the quality of CSB.
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Key words: wheat; wheat germ flour; Chinese steamed bread; quality
49
Chemical compounds studied in this article
50
phosphate (PubChem CID:24203) ethanol (PubChem CID:702) glutaraldehyde(PubChem
51
CID:3485) isoamyl acetate (PubChem CID:31276) water (PubChem CID:962)
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carbon dioxide(PubChem CID:280) sodium chloride (PubChem CID:5234)
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Abbreviations:
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WGF , Wheat germ flour ; CSB , Chinese steamed bread ; wt , weight ; SEM ,scanning electron
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microscope ; RVA , Rapid Visco Analyser ; TV , trough viscosity ; FV , final viscosity ; PV
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peak viscosity ; BV , breakdown viscosity ; SV , setback viscosity ; FN , Falling number .
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1 Introduction
Wheat (Triticum aestivum L.) is one of the most important crops and has been used as a main
59
component to produce various food products. Wheat based foods play an important role in the
60
food culture of Asian countries since ancient times. Chinese steamed bread (CSB) has 1700 years
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of history and is one of the most popular wheat products in China. With the passage of time,
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various types of CSB have been developed and most typical types are northern-style and
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southern-style steamed breads (Zhu et al., 2001). CSB is mainly constituted by wheat flour, water
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and yeast. Many other food ingredients such as bioactive compounds extracted from barley hull or
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flaxseed hull (Hao et al., 2012), custard cream (Chaiwanichsiri et al., 2011), shiitake stipe, silver
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ear (Tsai et al., 2010), thermostable xylanase (Jiang et al., 2010), lipid (Sun et al., 2010), sodium
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alginates and konjac glucomannan (Sim et al., 2011) have been used for CSB formulation to
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increase CSB diversity, nutritional value and product appeal.
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Wheat germ, accounting for 2-3% of the total weight of wheat kernel, is almost removed
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during milling as it adversely affects the flour processing quality. It has been estimated that the
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world annual discarded wheat germ is up to 25,000,000 tons (Rizzello et al., 2010), which causes
72
serious waste. On the other hand, most wheat germ is used for animal feed and other purposes,
73
which makes human consumption of wheat germ very limited.
74
wheat germ can be separated from the grain with high purity (Srivastava et al., 2007). It is rich in
75
bioactive substances such as antioxidants and sterols. The antioxidants mainly include tocopherols,
76
tocotrienols, phenolics and carotenoids (Gelmez et al., 2009). Wheat germ also contains some
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unsaturated fatty acids such as oleic, linoleic and α-linoleic acids (Rizzello et al., 2010). Moreover,
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most of the essential amino acids from wheat germ proteins are identified with higher
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During the milling process,
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80
oil which is applied in the medical and cosmetic industries (Kahlon, 1989). As for human health
81
benefits, it is reported that the processed wheat germ can be applied in prevention and treatment of
82
cancers (Zalatnai et al., 2001).
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Wheat germ, which is rich in functional food components, and a viable potential wheat base
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ingredient might be used in food. Because of the high nutritional value, some studies considered
85
the use of wheat germ for the manufacturing of cereal based food products (Ge et al.,2001). Pasta
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manufactured with semolina blended with 15% of raw and microwaved wheat germ showed
87
significant increase of nutritional value (Pınarlı et al.,2004). Replacement of wheat flour with
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defatted wheat germ at levels of 0-25% also increased functional and nutritional properties in
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cookies (Arshad et al.,2007). Compared to breads made with refined flour, the concentration of
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minerals, proteins, fat and dietary fibres was higher in breads supplemented with wheat germ
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(Sidhu et al.,1999).
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To our best knowledge, limited research is available on the physical properties and quality of
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CSB-making with WGF. Studies have reported the improvement of nutritional value of CSB after
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supplementation with WGF; however, the effect of WGF on the functional properties of the flour
95
and the organoleptic acceptability of the CSB is rarely reported. Therefore, the objective of the
96
current work is to investigate quality and nutritive value of CSB after supplementation of WGF.
97
Additionally the extent of this improvement was also part of the investigation.
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2 Materials and methods
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2.1 Sample preparation
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Yangling, Shanxi province, China, was used in this study. The wheat seed sample was first ground
102
using a laboratory mill (LSM20, Maosheng milling apparatus, China). The flour contained protein
103
(12.0%), ash (0.6%), moisture (12.1%), crude fat (1.3%) and wet gluten (40%). Flour was stored
104
at 4 °C in polyethylene bags. Pure 9946 wheat flours or CSB made of pure 9946 wheat flours was
105
used as control.
Wheat germ was obtained from a commercial mill (Laoniu milling plant, Yangling, China)
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and was dried in a baking oven at 70
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After roasting, the germ was emptied into a glass jar and cooled to room temperature, and then
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milled with particle size of 100 ± 200 µm. The samples were kept in sealed glass jars at 4 °C.
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for 2 hour in aluminium trays (thickness of 0.5-1.0 cm).
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Mixed flours were prepared by mixing raw wheat flour at different levels of WGF (3, 6, 9 and 12%) to evaluate the physicochemical properties and steaming performance of the mixture.
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2.2 Measurement of α-amylase activity
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The α-amylase activity was measured according to the method of Khalil et al. (1999).
2.3 Pasting properties of starch
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Pasting properties of starches in the wheat flours and the wheat germ flours were measured
116
on a Rapid Visco Analyser (NEWPORT, RuA Super 3, USA) (Ragaee et al., 2006).
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2.4 Rheological analysis
118
Measurements of water absorption, dough development time, dough stability and softening
119
degree were carried out by using a Farinograph (Brabender, Germany). Dough extensibility and
120
maximum resistance to extension were determined using an Extensograph (Brabender, 5
ACCEPTED MANUSCRIPT 121
Germany)(Hallén, 2004).
122
2.5 Microstructure observation
Microstructure observation was conducted according to Hu et al.(2009) with minor
124
modification. Phosphate buffer (PB, 0.1 mol L-1, pH 6.8) and ethanol solvents with ascending
125
concentrations of 30%, 50%, 70%, 80%, 90% were used in this part.
126
2.6 Preparation of CSB
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The formulation of CSB was as follows: wheat flour or the wheat germ flours (100 g),
128
dehydrated yeast (1 g) and water (54 ml) were first prepared. After mixing and kneading into
129
dough, the mixture was placed into the fermentation cabinet (38 °C and 85% R.H.) for 1 h. Dough
130
was then taken out and sheeted 20 times followed by dividing it into several pieces (60 g per
131
piece). The dough piece was rounded and molded manually and proofed for 20 min in the same
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fermentation cabinet. After that, the proofed dough was steamed for 25 min using a steam tray and
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boiling water.
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2.7 Physical properties of CSB
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Volume was measured after steaming 1 h by millet displacement method. The width and height of
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each sample was measured at different locations, and the average values were recorded. Specific
138
volume (the volume to the weight, ml/g) and spread ratio (the width to the height, W/H) were
139
calculated, respectively.
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2.8 Textural analysis
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142
Systems, Ltd., UK) equipped with a P36 probe. Steamed bread was sliced horizontally and a
143
bottom piece, 24 mm height, was compressed to 50% of its height. The test parameters were as
144
follow: pre-test speed 1.0 mm/s, test speed 1.0 mm/s, post-test speed 1.0 mm/s and trigger force 5
145
g. From the TPA test profile, textural parameters including hardness, springiness, cohesiveness,
146
adhesiveness and resilience were obtained.
147
2.9 Sensory evaluation of CSB
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Sensory analysis of bread was carried out according to the method described by Haglund et al.
149
(1998) with minor modifications. Elasticity, color, porosity, flavor, sweetness, dryness, taste and
150
mouth satisfaction were evaluated using a scale from 0 to 10 points, with 10 being the highest
151
score.
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2.10 Statistical analysis
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Data was collected from three duplicated experiments except for Farinograph and
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Extensograph. Statistical analysis of the results was implemented with software SAS 8.1 (Institute
155
Inc., USA).
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3 Results and discussion
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3.1 The falling number (FN)
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The FN of mixed flours is presented in Fig.1. The control (0% WGF) showed the highest
159
value (230 s) and the 12% WGF showed the lowest falling number (199 s). Results indicated that
160
partial substitution of wheat flour by WGF decreased the falling number. The FN value determines
7
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162
α-amylase. FN decrease with the increase of substitute level, the lower FN of wheat-WGF
163
composite flours as compared to control is due to the higher α-amylase existing in germ (Every et
164
al.,2002; Kruger 1981). The production of wheat bread using α-amylase with higher volume and
165
good crumb structure was previously reported (Randez-Gil et al., 1995; Pritchard 1992). The
166
presence of amylases also increased the level of fermentable and reducing sugars in the flour and
167
dough, thereby promoting yeast fermentation (Hamada et al., 2013), which suggested that
168
α-amylase activity might improve CSB quality.
169
3.2 Pasting properties of mixture
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The effect of WGF on pasting properties of the mixture is shown in Fig. 2. RVA parameters
171
have been found to be correlated with oriental flour food quality (Panozzo and McCormick, 1993;
172
Sun et al., 2010). The paste viscosity is dependent on the composition of flour and the
173
gelatinization of starch. There was a remarkable downtrend of peak viscosity (PV), trough
174
viscosity (TV), setback viscosity (SV) and final viscosity (FV) with increase in the addition of
175
different levels of WGF. When 12% supplementation addition was done, the PV, TV, SV and FV
176
decreased by 25.7, 27.0, 16.5 and 22.3%, respectively, compared to the control. As a whole, the
177
value of the above mentioned five indexes was decreased with the increase of WGF addition.
178
Among all of the samples, the control had the highest PV, TV, SV, FV and breakdown viscosity
179
(BV). There were distinct effects between control and samples that with 6 and 12% addition of
180
WGF on peak time, but other addition levels had no remarkable effects on it, which indicated that
181
there were other influential factors besides the additive amounts. The results suggested the high
182
content of starch in wheat flours compared to substituted flours may contribute, to some extent, to
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184
also affect pasting viscosity and properties.
185
3.3 Rheological properties after addition of WGF
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Rheological properties of wheat flour (control) and those of those substituted with WGF at a 3, 6, 9 or 12% level are shown in Table 1.
The addition of WGF to wheat flour lead to some significant changes in its dough mixing
189
behavior as measured by the farinograph. Water absorption of wheat flour used in this study
190
(64.5%) remained within ± 0.2% variation, when WGF was incorporated at levels of 3, 6, 9 and
191
12%. A correlation between the flour water absorption and increasing levels of WGF can be seen
192
in Table 1. Dough water absorption gradually increased from 64.5 to 65.7% with increase of WGF
193
level in mixed flour from 3 to 12%. Srivastava et al. (2007) had reported that mixed flour had
194
greater water absorption capacities than wheat flour. The addition of WGF to wheat flour is
195
expected to increase the protein content of the blends, since WGF contains more proteins than the
196
pure wheat flour. The greater water absorptions of mixed flours, therefore, could be an additive
197
effect. Rate of hydration, as reflected in dough development time, did not change significantly,
198
either. However, addition of WGF had an adverse effect on dough stability, which decreased from
199
2.9 min to 1.9 min at 12% level. Following the trend of dough stability, farinograph quality
200
number reduced slightly from 51 to 44 at 12% addition level of WGF. A former researcher has
201
reported that incorporation of wheat germ had a weakening effect on rheological characteristics of the
202
dough (Srivastava et al.2007). Our findings coincide with this previous study. The effect of the
203
addition of WGF on the farinographic proprieties of dough were related partly to gluten dilution and
204
partly to altered water behaviors caused by components of the added WGF, particularly fats, proteins
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ACCEPTED MANUSCRIPT and carbohydrates (the major components of WGF). The literature showed reduction in dough stability
206
after addition of WGF to pure wheat flour dough (Manuel et al.2012). Stability is related to the quality
207
of the protein matrix, which is easily damaged by the incorporation of other ingredients, due to gluten
208
dilution and the presence of reducing agents such as glutathione which is available in WGF (Every et
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al. 2006). This was definitely notable at the time of the experiment when handling the different
210
dough. The WGF gave weaker dough with increased dough weakening at higher substitution
211
levels.
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Extensograph measurements provide useful information about the viscoelastic behavior of
213
dough. Data on the effect of added WGF on the extensograph characteristics of wheat flour dough
214
samples, throughout 45, 90 and 135 min resting time periods, are presented in Table 1. The
215
weakening of dough caused by the addition of WGF to wheat flour is in agreement with earlier
216
observations of WGF. Possible reasons for the weakening of dough due to the addition of WGF
217
might include an effective decrease in wheat gluten content (dilution effect) by competing for
218
water with wheat flour proteins. It is well known that wheat germ proteins alone do not have food
219
dough forming properties and that the supplemental proteins disrupt the well-defined
220
protein-starch complex in wheat flour bread suggesting a weakening of dough. Cakmakli et al.
221
(1995) has reported that addition of wheat germ had a weakening effect on rheological
222
characteristics of the dough. This was more evident in the consistent decrease in dough
223
extensibility, especially in dough resistance. Samples with higher addition of WGF demonstrated
224
lowest dough resistance while the control showed the highest resistance, with a quite steep slope
225
down to the much lower values for 12% addition level of WGF.
226
3.4 SEM results of the WGF-treated dough
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ACCEPTED MANUSCRIPT The microstructures of dough with and without WGF supplementation were investigated by
228
SEM. The microstructure of all the different dough samples is shown in Fig.3. The appearances of
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dough made from WGF substituted flours exhibited a discontinuous and irregular matrix around
230
the starch granules, whereas the control sample (dough made from pure wheat flout) had an
231
extensible gluten matrix which covered all starch granules. Thus, the existence of WGF diluted the
232
protein and interfered with optimal gluten matrix formation during dough formation. The dilution
233
also affected the formation of an elastic network of cross-linked gluten molecules during steaming,
234
resulting in easy disruption of the gluten network and lower loaf volume of CSB. In this work, the
235
physicochemical properties of dough were affected by adding WGF which might be due to (1) the
236
difference in chemical composition of protein in control and WGF; (2) larger particle size of WGF;
237
(3) wheat germ contains a certain amount of glutathione, which is an activator of protease that can
238
accelerate the decomposition of protein, thus leading to disruption of gluten network; (4) WGF
239
contains more lipid, most of which is unsaturated lipid, which can weaken the network of gluten.
240
3.5 The effect of WGF on CSB quality
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The effect of the WGF at various levels on the quality of CSB is shown in Table 2. A decrease
242
in the volume, specific volume and an increment in spread ratio were observed. Both of these
243
effects were expected, as the amount of gluten, which imparts higher volume in steamed bread,
244
was decreased as a result of gluten-free WGF in the CSB formulation. Specific volume and spread
245
ratio are two important quality parameters of CSB (Su et al., 2005; Zhang et al., 2007). The
246
volume of CSB and specific volume decreased by up to 12.5% and 16.1% with addition of 12%
247
WGF, respectively. The highest spread ratio rose up to 24.2% when 12% of WGF was added.
248
These results were due to the existence of a high amount of dietary fiber in WGF which diluted
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250
steaming.
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3.6 Texture properties
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Hardness, springiness, cohesiveness, gumminess, chewiness and resilience were textural
253
attributes of CSB. These attributes of CSB were determined by TPA. The TPA properties of CSB
254
made from mixed flours are shown in Table 3. All of the parameters showed significant difference
255
between the WGF CSB and the control. This observation is confirmed by the analysis of variance,
256
which indicated that these parameters were significantly influenced (P<0.05) only by addition of
257
WGF. The springiness, cohesiveness and resilience was also notable because it decreased with the
258
increased level of WGF and vice versa. Hardness is often considered as the index of the total
259
textural attributes (Carlo, et al., 2011). After addition of WGF, the value of hardness,
260
corresponding to the peak force of the first compression of the product, was higher which
261
significantly (P>0.05) differed from the control (1880.959 g), the hardness of CSB increased to
262
3335.393 g with 12% supplementation. Resilience indicated the recovery of CSB to its original
263
position. The resilience markedly decreased for WGF CSB as the level of substitution increased,
264
the lowest value of resilience was found at 12% supplementation (0.466). Values of cohesiveness
265
dropped sharply.
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Samples with higher incorporation of WGF influenced consumer’s acceptance of CSB,
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because it results in high crumbling. In the case of chewiness, which is significantly related to
268
hardness, highest values were observed for 12% supplementation sample. Similarly to hardness,
269
most pronounced reduction of chewiness was caused by the addition of WGF.
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3.7 Sensory evaluation
After steaming (an hour), sensory analysis was carried out. The sensory scores as given by
272
the panel have been shown in Table 2. Sensory evaluation of steamed breads implied that, the
273
elasticity, color, porosity, flavor, sweetness, dryness, taste and mouth satisfactory of CSB were
274
significantly affected by the addition of WGF as compared to the control sample.
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The addition of WGF significantly decreased the elasticity of CSB compared to the control
276
sample (pure wheat flour CSB). The elasticity of supplemented WGF CSB was significantly
277
decreased at higher levels of supplementation (12%), indicating that the elasticity was mainly
278
affected by the addition of WGF. There was a lower pore number and the pore became smaller as
279
the substitution level of WGF increased, the score of porosity sharply decreased from 8.0 to 5.5 at
280
12% supplementation. These results were probably due to higher water absorption and holding
281
capacity of WGF as compared to wheat flour. Moreover, WGF does not contain any gluten, this
282
may have partially contributed to higher density in WGF added CSB. The addition of WGF
283
improved the flavor and dryness of samples, because WGF has its special flavor and higher water
284
absorption than wheat flour. All the samples of WGF CSB scored notably higher in terms of flavor
285
and dryness than the control, increasing substitution levels increased the flavor and dryness scores
286
of CSB. In the case of WGF CSB, only the taste and flavor score of CSB with 3% WGF differed
287
significantly from the control. However, it was observed that CSB made with partial WGF
288
substitution (3% or 6%) were more acceptable when it comes to sensory (color, sweetness, taste
289
and mouth satisfaction) than other samples, which had moderate color than other samples due to
290
the presence of WGF. Conclusively, the substitution of WGF for Pubing 9946 wheat flours
291
improved the quality of CSB and the amount of substitution of pure wheat flour was up to 6%.
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4. Conclusions
Incorporation of WGF into wheat flour significantly affected the physicochemical properties
294
and steaming performance of the blends. Flour replacement at different levels (from 0 up to 12%)
295
by WGF changed the pasting and rheological characteristics of the blends, dough microstructure,
296
CSB physical, sensory and textural properties. The trend and the extent of effects of WGF on the
297
indexes mentioned above depend on the extent of flour substitution. Addition of WGF to flours
298
resulted in a shortening effect for dough machinability. Caution should be paid to addition level of
299
WGF because of the adverse increase in solid-like properties of the dough, which may reduce
300
expansion during fermentation and steaming. Enrichment with WGF led to lower changes in
301
viscoelastic properties of dough than pure wheat flour and had negative effects on physical quality
302
and sensory evaluation of CSB. Addition of WGF over 9% is not recommended because of a
303
strongly brown color, hard texture and unsatisfactory taste. The present study indicated that CSB
304
made with the mixed flour of wheat flour and WGF had acceptable sensory properties and the
305
addition level of WGF is up to 6% of flour. Therefore, the addition of WGF could be an effective
306
way to produce functional white flour CSB without altering its desirable physical properties.
307
Development of such functional foods would be beneficial to improve the nutritional status for the
308
consumer. Further studies are needed to evaluate changes in WGF-enriched CSB characteristics
309
during storage.
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Acknowledgements
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The authors would like to thank the Shaanxi Province overall pianning science and
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technology project (2011KTZB02-01). We also gratefully acknowledge Dr. Qingbin Guo and Dr.
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Hongju He for making grammatical corrections to this paper.
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Rheological properties of doughs from composite flours Dough
Farinograph
Dough
Dough
Dough
Flour water
development
stability
quality
weaking
extensibility
resistance
Samples
absortion(%)
(min)
(min)
number
(FU)
(cm)
(BU)
Control
64.5
3.5
2.9
51
92
185
231
3% WGF
64.8
3.3
2.7
49
93
183
146
6% WGF
64.9
3.5
2.3
47
107
184
111
9% WGF
65.3
3
2.1
46
143
183
90
12% WGF
65.7
3.2
1.9
44
150
161
76
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Dough
Used pure 9946 wheat flours as control.
4 5
Table 2
Effect of the WGF at various levels on the quality and sensory evaluation of CSB
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Table 1
Specific Spread Volume volume
Control 160±2
a
3% WGF
155±3
b
6% WGF
148±2
c
9% WGF
145±2
12% WGF
(ml/g)
(W/H)
ity
2.81±
1.61±
7.5±
7.5±
8.0±
6.0±
a
e
a
c
a
e
0.02
140±3e
0.02
0.2
0.1
0.3
0.1
1.75±
7.2±
7.8±
7.4±
6.8±
b
d
b
b
b
d
0.01
0.01
0.2
0.1
0.2
0.2
2.52±
1.81±
7.0±
8.2±
6.9±
7.3±
c
c
bc
a
c
c
0.02
0.01
d
0.02
1.96±
0.1
0.01
b
6.5± 0.1
c
satisfac Total
Color Porosity Flavor -ness -ness Taste
2.57±
2.45± d
Sweet Dry
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Samples (cm )
ratio Elastic
0.3
7.2±
0.1
6.5±
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Mouth
0.2
d
0.1
d
0.1
7.8± 0.3
b
7.0± 6.8± 7.2±
0.1
bc
0.1
c
0.1
c
7.4± 7.2± 7.5± 0.2
a
0.2
b
0.2
b
7.6± 7.4± 7.8± 0.1
a
0.1
b
0.1
a
6.8± 7.8± 7.1± 0.1
b
0.2
a
0.2
cd
-tion
points
7.8±
57.8±
0.2
c
8.2± 0.1
b
8.5± 0.3
a
7.7± 0.1
cd
1.1c 59.5± 1.4b 60.7± 1.3a 57.4± 1.3c
2.42±
2.00±
5.9±
6.5±
5.5±
8.2±
6.8± 8.0± 6.9±
7.5±
55.3±
0.02e
0.01a
0.1d
0.1e
0.1e
0.3a
0.1c
0.2d
1.3d
0.3a 0.1d
Used CSB made of pure 9946 wheat flours as control.
7
Values followed by same letter in the same column indicated data are not significantly different(P <0.05) by
8
Duncan test.
9
Mean values ± standard deviations for fermentations, analyzed in duplicate.
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Sensory attributes were scored by using a scale 0-10 .
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Table 3 Hardness
g)
Springiness
Cohesiveness (g.s)
Gumminess (g)
Chewiness (g)
Resilience
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Samples
Texture parameters of CSB made of the WGF at various levels
Control
1880.959±112.712e
0.972±0.012a
0.842±0.015a
1581.109±121.098e
1537.763±131.427e
0.518±0.013a
3% WGF
2078.271±130.242d
0.960±0.026b
0.838±0.016b
1740.715±103.125d
1672.043±125.671d
0.499±0.016b
6% WGF
2140.444±151.357c
0.953±0.018c
0.826±0.017c
1763.778±123.435c
1681.490±118.653c
0.488±0.009c
9% WGF
2426.037±125.426
b
d
d
b
b
0.474±0.006d
12% WGF
3335.393±123.564a
2522.183±136.357a
0.466±0.013e
0.929±0.019e
0.817±0.012
0.814±0.014e
1977.559±107.253
2711.436±135.257a
1898.977±113.435
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0.941±0.021
Used CSB made of pure 9946 wheat flours as control.
13
Different superscript letters at each column indicate significant differences (P < 0.05) by Duncan test.
14
Different superscript in the same column indicate that means were significantly different (P < 0.05) by Duncan test.
15
Mean values ± standard deviations for fermentations, analyzed in duplicate.
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ACCEPTED MANUSCRIPT Fig.1. Falling number for all formulations studied. Fig.2. Curves of pasting properties of pure wheat flour mixed with different quantities of wheat germ flour Fig.3. SEM images of dough made from pure wheat flour and its substitutions.
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5 6
Fig. 1.
Falling number for all formulations studied.
7 8 9 10 11
3%WGF 6%WGF 9%WGF 12%WGF
Temperature ( )
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Viscosity(RVU)
Control
Temperature curve
Time(min)
Fig.2. Curves of pasting properties of pure wheat flour mixed with different quantities of wheat germ flour.
Used pure 9946 wheat flours as control.
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Control
3%WGF
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12 13
6%WGF
9%WGF
12%WGF
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Fig.3. SEM images of dough made from pure wheat flour and its substitutions.
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► WGF affected properties and steaming performance of the blends. ► CSB made with ≦ 6% WGF had acceptable sensory properties. ►WGF can be used for making CSB. ► WGF can improve nutritious quality of CSB.