Food Bioprocess Technol DOI 10.1007/s11947-007-0037-7
ORIGINAL PAPER
Effect of Rice, Corn and Soy Flour Addition on Characteristics of Bread Produced from Different Wheat Cultivars Dimitrios Sabanis & Constantina Tzia
Received: 19 July 2007 / Accepted: 8 November 2007 # Springer Science + Business Media, LLC 2007
Abstract Preparation and consumption of bread enriched with flours that contain appreciable amounts of protein, lysine, dietary fiber, and minerals will provide a healthy alternative to consumers and also a lowering of bread making cost in countries where wheat is not a major domestic crop. Addition of rice, corn, and soy flour to bread and durum wheat flours at 10, 20, 30, 40, 50% levels was carried out to examine the effects on the baking (specific volume, color, firmness) and sensory characteristics of bread. Dough rheological properties were also studied using Brabender Farinograph and Extensograph. Results of the present study suggest that incorporation of rice, corn, and soy in bread wheat flour up to a level of 10% (flour basis) and in durum wheat flour up to 20% produces bread without any negative effect in quality attributes such as color, hardness, and flavor and reasonable acceptance offering promising nutritious and healthy alternative to consumers. Increasing levels of substitution (30 and 50%) resulted in decreasing dough strength, extensibility, and loaf volume, due to the replacement of gluten by the added protein. Overall acceptability scores of these breads were found to be very low. The durum flour can be substituted with nongluten flours up to 10% more than the bread wheat flour because of its stronger gluten matrix and better dough rheological characteristics.
Keywords Gluten . Durum wheat . Rheological properties . Firmness . Sensory analysis . Bread
Nomenclature BWF DWF RF CF SF BU FWA DDT St. DS Ex R50 A Sp. Vol. L b
bread wheat flour durum wheat flour rice flour corn flour soya flour Brabender units flour water absorption (%) dough development time (min) dough stability (min) dough degree of softening (BU) dough extensibilty (mm) dough resistance to deformation (BU) dough energy (cm2) loaf specific volume (cm3/g) chromatic component (lightness) chromatic component (yellow)
Introduction
D. Sabanis : C. Tzia (*) Laboratory of Food Chemistry and Technology, School of Chemical Engineering, National Technical University of Athens, 5 Iroon Polytechniou St., 15780 Athens, Greece e-mail:
[email protected]
Bread has been regarded for centuries as one of the most popular and staple food products. The wheat cultivars of major commercial importance for milling into flour are the Triticum aestivum (bread wheat) and Triticum turgidum (durum wheat). Durum wheat represents only 8% of the wheat produced worldwide (Bozzini 1988) and is used mainly for the production of pasta products. Apart from being a good source of calories and other nutrients, bread is
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considered to be nutritionally poor, as the cereal proteins are deficient in essential amino acids such as lysine, tryptophan, and threonine (Wrigley and Bietz 1988). Supplementation of wheat with high-protein-content flours improves the nutritional quality of bakery products and satisfies the increasing interest among vegetarians to consume protein-enriched food from plant sources, which are rich in lysine and have great potential in overcoming protein–calorie malnutrition. In many countries where wheat is not a major domestic crop, any effort made to substitute part of the wheat flour by other kinds of available flours will contribute to lowering of cost (Elkhalifa and ElTinay 2002). Rice flour exhibits properties such as the absence of gluten, low levels of sodium, protein, fat and fiber, and high amount of easily digested carbohydrates, which are desirable for certain special diets. It has also bland taste, white color, and hypoallergenic properties (Gujral et al. 2004). Corn ranks as the second most widely produced cereal crop worldwide. Because of the high productivity, corn is by far the most economical cereal to produce. Corn flour contains high levels of many important vitamins and minerals, including potassium, phosphorus, zinc, calcium, iron, thiamine, niacin, vitamin B-6, and folate (Watson 1987). Soybean flours are used in many countries because they are a good resource of vegetable proteins (38–40%), fat (18– 20%), lysine (5–6%), and other biologically active components (isoflavones) that may be effective in reducing the risk of coronary heart diseases and several cancers (Trainer and Holden 1999; Hasler 2002; Murphy et al. 1999). Previous results reported that supplementation of bread wheat flour with rice (Sivaramakrishnan et al. 2004; Gujral et al. 2003; Nishita and Bean 1979), corn (Navickis 1987; Martinez and El-Dahs 1993; Alpaslan and Hayta 2006), and soy flour (Ribotta et al. 2005; Dhingra and Jood 2001; Dervas et al. 1999) results in alteration in rheological and sensory properties of breads. Manufacture of bread with nonwheat flours presents considerable technological difficulty because their proteins lack the ability to form the necessary gluten network for holding the gas produced during the fermentation (Gallagher et al. 2003; Arendt et al. 2002). Durum wheat flour generally has higher protein, gluten, damaged starch, xanthophylls, and total sugar content than bread wheat flour (Toepfer et al. 1972; Troccoli et al. 2000). There is apparently no published research on the physical properties or sensory evaluation of durum wheat flour bread supplemented with other flour because for many years, it was believed that durum wheat flour was inappropriate for bread making due to its weak gluten network (Boyacioglu and D’Appolonia 1994; Feillet 1988; Boggini and Pogna 1989). During the last 15 years, new durum wheat cultivars with stronger gluten properties have been introduced in the United States, Canada, Greece, and Italy. Results of
research with these cultivars challenge the long-established belief that durum wheat is suitable for high-quality pasta production but not for bread making (Sabanis and Yupsanis 2000; Palumbo et al. 2000; Pasqualone et al. 2004). In Greece, durum accounts for 80% of the wheat produced. This is attributed to climate conditions and as well as to the fact that EU does not support financially the cultivation of bread wheat. Durum wheat with good baking quality is a desirable goal because such cultivars would have alternative markets in years of high production, by being used as bread wheat. The purpose of using both types of wheat flour is that these are the most predominant in the Greek food market and that due to their compositional divergence they may exhibit different breadmaking potential. The objectives of this work were (1) to compare bread and durum wheat flour in terms of bread making and to indicate that Greek durum wheat flour is capable of producing an extensive viscoelastic matrix during baking and (2) to investigate how the rheological, baking, and textural properties change as bread, and durum wheat flour are partially replaced with rice, corn, and soy flour to develop nutritionally rich bread.
Materials and Methods Raw Materials Two types of commercially milled wheat flour, bread wheat flour (BWF) with 72% extraction ratio and durum wheat flour (DWF) with 80% extraction ratio, were purchased from P. Dakos Flourmill (Attika, Greece). Medium grain rice flour (RF) was obtained from Agrino S.A (Agrinio, Greece), corn flour (CF) was obtained from Chalkidiki Mills S.A. (Chalkidiki, Greece), and full fat soy flour (SF) was obtained from Viotrek S.A (Athens, Greece). According to the manufacturer, this flour had a fat content of 18% (dry basis). All other ingredients such as dried yeast, sugar, salt, and olive oil were purchased from the local market. Proximate Composition Nitrogen content was determined by using the Kjeldahl method and was multiplied by a factor of 5.7 to determine protein content in wheat and corn flour and 6.25 to determine protein content in soy expressed on a dry weight basis. Moisture content was determined on the basis of weight loss of a sample dried by infrared radiation to constant weight (Moisture Analyzer 30, Sartorius AG, Goettingen, Germany) and expressed on wet basis. The infrared drying is a thermo gravimetric method for the determination of moisture content. Gluten content was
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determined by manual washing according to the official method (ICC no 106/2 1984) and expressed on wet basis. Ash content was estimated according to official method (ICC no 104/1 1990) and expressed on dry basis. Dough Rheological Properties The dough rheological properties were examined with the Brabender Farinograph, mixer type S300H (Brabender, Duisburg, Germany) according to the constant flour weight procedure (ICC no 115/1 1992). The results were expressed as: flour water absorption (FWA) which is the amount of water that the flour can absorb until the dough consistency reaches 500 Brabender Units (BU), dough development time (DDT) which is the time required for the curve to reach its maximum height (i.e., 500 BU), dough stability (St.) which is the time needed before the dough consistency starts to decline from 500 BU line and the degree of softening (DS) which is defined as the difference (in BU) between the line of the consistency and the medium line of the torque curve, 12 min after weakening begins. This provides information about the dough’s stability. After the Farinograph measurement, the dough was cut into two parts of 150 g each, rolled into a ball, shaped into a cylinder and clamped into the holder of the Brabender Extensograph (model 8600, Brabender, Duisburg, Germany). After a 45-min rest, the dough was stretched in the Extensograph using a hook in the middle of the cylinder until ruptured. The same procedure was repeated for another twice after 90 and 135 min (data not shown), following the official procedure (ICC no 114/1 1992). The results were expressed as: Dough extensibility (Ex), which is the distance travelled by the recorder paper (expressed in mm) from the moment in which the hook touches the test piece until rupture and is a measure of dough elasticity, dough resistance to constant deformation after 50 mm stretching (R50) and energy (A) required breaking the strength of the dough which is a measure of the flour quality. A is the area under the curve and was evaluated by means of a planimeter (expressed in cm2). The results for R50 are given in BU with a precision of 5 BU.
Dough/Bread Preparation The ingredients were placed in a 7 speed spiral mixer (Model KM 400, Kenwood, UK) and mixed for 2 min at 90 rpm and for 8 min at 180 rpm. Low speed is required for homogeneous ingredient dispersion and flour hydration (brief duration), whereas more extensive mixing required for optimum dough development. As soon as the dough was formed, it was placed in a baking pan and fermented at an incubation chamber (Bekso EB 1N, Bekso, Brussels, Belgium) set at 35°C and 80% relative humidity for 35 min. Then the dough was remixed for 1 min at 90 rpm and was separated in samples of 80 g, which are round shaped by hands, placed in aluminum baking pans (measuring 70 by 40 mm) and placed for refermentation for another 35 min. Baking for each sample was conducted in a laboratory oven with air circulation (Thermawatt TG103, Thermawatt, Peristeri, Greece) at the temperature of 220°C for 30 min. The loaves were removed from the pans and cooled at room temperature. Baking, sensory and firmness characteristics were tested 1 h after the loaves were removed from the oven (time 0). Then the loaves were placed in polyethylene bags until tested for firmness. Baking Characteristics Breads were weighed (g) and then their volume (cm3) was determined by rapeseed displacement (Hallen et al. 2004). Specific volume (cm3/g) was calculated by dividing volume by weight. Crust and crumb color of baked samples were measured using a Minolta CR200 tristimulus chromatometer (Minolta Company, Osaka, Japan). The chromatometer was calibrated by using a white reference plate which is the standard of reflectiveness. Readings were displayed as L and b color parameters according to the CIELAB system of color measurement. L gives a measure of the lightness of the product from 100 for perfect white to 0 for black, and b value indicates yellowness for positive and blueness for negative values (Hutchings 1994). While testing the various bread properties, the room temperature was 25°C and the relative humidity 60%. The average value of two replicates was reported. In the case of bread analysis, the replicates were from the same baking process but from different bread pieces.
Dough Formulation
Textural Properties
The control baking formula (based on flour weight) consisted of wheat flour 500 g (100%), compressed yeast 10 g (2% flour basis), salt 10 g (2% flour basis), olive oil 15 g (3% flour basis), sucrose 20 g (4% flour basis), and the amount of water required for the dough to reach 500 BU of consistency in the Farinograph. In the trials, bread and durum wheat flours were substituted by rice, corn, and soy flours at levels of 10, 20, 30, and 50% of flour weight.
Crumb firmness evaluated by the Texture Analyzer (TA-XTi2 Stable Microsystems, Surrey, UK). The samples were sliced in the middle using a double blade knife (fabricated in house) of 1-cm thickness. A two-cycle crumb compression test was performed using the Sris P/75 aluminum platen probe (test speed 3 mm/s, penetration distance 15 mm). The peak force of compression was reported as firmness (N) in accordance with the AACC method 74–09 (AACC 1995). An indication of
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the staling rate of bread samples was taken by determining crumb firmness 2 days after bread making.
Table 2 Particle size distribution of the different flours used (BWF, bread wheat flour; DWF, durum wheat flour; RF, rice flour; CF, corn flour; SF, soy flour)
Sensory Evaluation
Particle size
BWF (%)
d
