**The Main Components Content, Rheology Properties and Lipid Profile of Wheat-Soybean Flour**

Nada Nikolić and Miodrag Lazić *University of Niš, Faculty of Technology, Leskovac Serbia* 

#### **1. Introduction**

80 Recent Trends for Enhancing the Diversity and Quality of Soybean Products

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Soybean (*Glycine max* (L.) Merr.) is a species of legume, native to a Eastern Asia and an important global crop, today. Soybean is rich in high quality proteins, contains essential amino acids, similar to those found in meat, minerals such as Fe, Zn, Cu, Mn, Ca and Mg as well as phytic acid. The bulk of seed soybean proteins contains albumins and globulins as major components, but there are minor, undesirable components such as inhibitors of trypsyn and chymotrypsin, and sugar-binding lecitins. The inhibitors and lecitins are generally inactivated by heat treatment. A new immunochemical methods can be used for quantitative detection of soybean proteins and production of healthful foods (Brandon & Friedman, 2002). The soybean lipid contains a significant amount of unsaturated acids: linolenic acid, known as omega-3 acid, linoleic, -linolenic and arachidonic acid, known as omega-6, and oleic acids known as omega-9 acid and are very important in human nutrition (Liu, 1997). The soybean lipid also contains saturated acids: palmitic and stearic acid (Bressani, 1972; Olguin et al., 2003; Bond et al., 2005), as well as tocopherols (Ortega-Garcia et.al., 2004, Yoshida et al., 2006). These soybean components make the products with soybean have higher nutritional value.

#### **1.1 Soybean in bread making industry**

In the bread making industry, the soybean is used with the aim to increase the bread protein value and decrease carbohydrate value. In ordinary white bread protein content ranges from 8 to 9% and by including soybean, the protein content can be made up to 16% (Ribotta et al. 2010) and at the same time, the dough and bread are richer with lipoxygenase enzymes preparation which can make the dough physical properties better. The fact is that bread made with soybean costs less and it is especially important in countries where wheat is not a major domestic crop. Bread and products with higher protein content and lower carbohydrate content are more suitable for use in some diets than bread and products formulations currently used (Mohamed et al., 2006). As the main protein component in white bread is gluten, a component which causes celiac disease, the usage of soy is useful for decreasing the gluten content in bread. A portion of 0.3 to 5% of soybean flour portion is usually added (Auerman, 1979), but rational addition for increasing bread protein value is 20-30% of soybean flour. Besides whole soybean flour, different soybean products can also

The Main Components Content,

properties were found.

**2. Experimental 2.1 Soybean seed** 

**2.2 Chemicals** 

additives.

**2.4 Flour analyses** 

Chemicals, Germany).

Rheology Properties and Lipid Profile of Wheat-Soybean Flour 83

wheat flour with other changed these properties. Ribotta et al. 2005, presented data about effect of soybean addition on farinographic properties such as water absorption (WA), dough development time (DT), dough stability (Dst) and dough degree of softening (DSf). The present work has been undertaken with the objective to investigate the effect of whole soybean seed flour (»full-fat soy flour«) portion of 3 to 30% on dough farinographic, but extensographic and amylographic properties, too. Based on the composition of wheat and soybean flour lipids, the aim is to obtain lipid composition in wheat-soybean flour mixtures, and compare it to wheat flour only, with an emphasis on content of total saturated fatty acids (TS), total monounsaturated fatty acids (TMUS), total polyunsaturated fatty acids (TPUS) and total unsaturated fatty acids (TU). In order to value wheat-soybean flour mixtures, they were classified into groups by using statistical analysis and Euclidean distances and the correlations between content of some lipid components and rheological

The whole soybean seeds (*Glycine max* L.) cultivars ZP Lana, grown in Serbia in summer of 2006 were used. The seeds were purchased in local store "Green Apple" (Leskovac, Serbia) and milled. The particle size was determined by method of insemination via riddles with gaps size from 0.315 to 3.15 mm. The overall particle size was determined using equations:

Chemicals used for oil extraction were high quality chemicals (Centrohem, Serbia) and for HPLC and GC analysis they were analytical grade (Riedel-de Haën, Honeywell Specialty

The wheat flour, Kikinda Mill, Serbia (WF) was bought from the local market. The soybean flour (SF) as »full-fat soy flour« was obtained by soybean seeds milling (IKA Model M120), to an overall particle size ( *dsr* ) of 0.4 mm. Quantities of 291, 285, 270, 240 and 210 g of wheat flour and 9, 15, 30, 60 and 90 g of soybean flour, respectively, were used to make flour mixture with 3, 5, 10, 20 and 30 % (w/w) soybean flour portion, without adding

Flour protein content was determined by the Kjeldahl method (Nx5.95). The moisture content was determined by Scaltec SMO 01 (Scaltec instruments, Germany) instruments: flour (5 g) was put into the disk plate analyzer, dried at 110oC to a constant weight, and the

where *<sup>i</sup> d* is weight of fraction with appropriate particle size in %, and

where *i*<sup>1</sup> *d* is bottom riddle gap size and *i*<sup>1</sup> *d* is upper riddle gap size.

**2.3 Wheat and soybean flour and flour mixtures** 

*sr <sup>i</sup> <sup>i</sup>* <sup>100</sup> / *<sup>d</sup> <sup>d</sup>* / *<sup>d</sup>* (1)

*di* (*di*<sup>1</sup> *di*1)/ 2 (2)

be used: defatted soy flour (Mashayekh et al., 2008), physically modified soy flour (Maforimbo et al., 2008), soy flour and durum wheat flour mixture (Sabanis & Tzia, 2009), commercial soy protein isolate (Roccia et al., 2009), diffrerent kinds of soy protein powder (Qian et al., 2006) and part of soy seeds such as a hulls (Anjum et a., 2006). Based on these investigations results, different bread formulations are defined, and soy is used in portion up to 20%. When soy flour in wheat flour was to a level of 10% and in durum wheat flour up to 20%, the produced bread was without any negative effects in quality attributes such as colour, hardness and flavour, promising nutritious and healthy alternative to consumers (Sabanis & Tzia, 2009). By investigating the effect of defatted soy flour on sensory and rheological properties of wheat bread, Mashayekh et al. 2008, concluded that adding 3 and 7% defatted soy flour gives as good a loaf of bread as the 100% wheat bread and acceptable consumer attribute with rheological and sensory characteristics. Adding small quantity of soy protein powder of 3% to wheat flour did not change the sensory properties of bread and a large quantity of soy flour adding, exceeding 7%, can lead to stickiness and leguminous flavour (Roccia et al., 2009). The results of investigation (Anjum et al., 2006) of soy hulls usage showed the content of 4.5% soy hulls combined with wheat flour is acceptable and suitable level by the consumers.

#### **1.2 Wheat-soybean bread manufacturing**

The manufacture of bread from flour without gluten represents considerable technological difficulties (Jong et al., 1968; Schober et al., 2003) because gluten is the most important structure forming protein for making bread (Gujural et al., 2003; Moore et al,*.* 2004) and by using appropriate soy-wheat flour mixture these difficulties can be avoided. When soy was added to wheat, the soy globulins interact with wheat gluten proteins forming aggregates of high molecular weight. As reduction-reoxidation treatment facilitated the interaction of glutenin subunits and soy proteins (11S subunits), interaction probably occurs through the oxidation of SH groups (Maforimbo, 2008). Investigations of the changes in glutenin macro polymer content, protein composition and free sulfhydryl content showed that active soy flour decreased glutenin macro polymer content due to gluten depolymerization and glutenin macro polymer content increased by inactive soy flour because soy proteins became insoluble and precipitated together. Soy proteins were associated to wheat protein through physical interaction and covalent and non-covalent bonds during mixing and resting and these interactions produced large and medium-size polymers. This increased solubility of insoluble gluten proteins, producing a weakening of the gluten network (Perez et al., 2008) and decreasing availability of water to build up in gluten network (Roccia et all. 2009). Physicochemical status of soy protein in the product had a great influence on how wheat-soy proteins will interact (Perez et al., 2008). Incorporation of soy proteins changes the rheolocical and bread properties. The investigations showed that adding soy protein powder depresses loaf volume, gives poor crumb characteristics and decreases acceptability by consumers (Qian et al., 2006.) Ribotta et al. 2010. tested different additive combinations for improved bread quality obtained from soy-wheat flour in ratio of 90:10 w/w and found that the combination with transglutaminase showed a major improving effect on dough rheological properties and crumb uniformity.

#### **1.3 Aims of investigations**

Dough rheological properties have great relevance in predicting the mixing behaviour, sheeting and baking performance (Dobraszczyk & Morgenstain, 2003) and supplementation wheat flour with other changed these properties. Ribotta et al. 2005, presented data about effect of soybean addition on farinographic properties such as water absorption (WA), dough development time (DT), dough stability (Dst) and dough degree of softening (DSf). The present work has been undertaken with the objective to investigate the effect of whole soybean seed flour (»full-fat soy flour«) portion of 3 to 30% on dough farinographic, but extensographic and amylographic properties, too. Based on the composition of wheat and soybean flour lipids, the aim is to obtain lipid composition in wheat-soybean flour mixtures, and compare it to wheat flour only, with an emphasis on content of total saturated fatty acids (TS), total monounsaturated fatty acids (TMUS), total polyunsaturated fatty acids (TPUS) and total unsaturated fatty acids (TU). In order to value wheat-soybean flour mixtures, they were classified into groups by using statistical analysis and Euclidean distances and the correlations between content of some lipid components and rheological properties were found.
