**3. Results and discussion**

### **3.1 The main components content**

The results of wheat and soybean flour moisture, starch, protein, ash, lipid, gluten and carbohydrates content are showed in Table 1. Data are presented as means of three determinations with standard deviation. Based on these data, considering the soybean flour portion in mixtures and compared to wheat flour, it is evident the moisture (from 12.8 to 11.6%), the starch (from 76.6 to 56.8%), gluten (23.9 to 16.7%) and carbohydrates content (from 78.8 to 62.8%) decreased, while the protein (from 8.6 to 20.0%), ash (from 0.48 to 2.08%) and lipid (1.2 to 7.2%) content increased with increasing soybean flour portion in mixtures.

Taking into account the protein, carbohydrates and lipid content, based on formula (3) for energetic value determination, it was obtained that the soybean flour increased energetic value in flour mixtures (from 1530 obtained for wheat flour, to 1544, 1554, 1579, 1625, 1674 kJ/100g, when soy flour portion was 3, 5 10, 20 and 30%, respectively) and the maximal increasing of 9.4% was in mixture with soybean flour portion of 30%.

The Main Components Content,

WA

**3.3 Lipid profile** 

Rheology Properties and Lipid Profile of Wheat-Soybean Flour 87

and those values were lower than extensibility of dough with wheat flour only. The ration number, R/Ex, varied depending on soybean flour portion and ranged from 2.76 to 3.42. Based on curve of volume versus ratio number (Djaković, 1980), obtained for round bread, the bread volume was predicted to be in range from 576 to 557 cm3 and it was lower than

Farinograph data

(ml/100g) 53.41.4 53.31.4 53.81.3 53.91.6 61.91.6 64.21.7 DT (min) 10.1 1.30.1 1.30.1 6.50.3 6.80.3 7.30.4 DSt (min) 0.10.1 0.70.2 0.80.2 1.80.4 2.30.5 2.90.5 DSf (BU) 901.6 451.4 501.4 651.7 651.7 661.5 QN 52.81.4 57.71.4 66.71.4 61.71.4 64.21.4 68.81.4 Group B2 B1 B1 B1 B1 B1 Extensograph data E (cm2) 67.81.3 70.51.5 74.21.5 79.01.6 57.11.4 43.41.2 R (EU) 3155.5 3456.0 3506.0 3555.5 3455.5 3055.5 Ex (EU) 1263.0 1253.0 1233.0 1172.5 1012.5 892.0 R/Ex 2.500.2 2.760.3 2.840.4 3.030.4 3.410.4 3.420.4 V (cm3) 58110 57610 57410 56610 55910 55710 Amylograph data T max (oC) 81.20.5 81.50.5 82.00.5 85.00.5 86.50.5 88.80.5 max (AU) 63020 31515 25010 18010 12010 905 Table 2. Rheological properties of wheat flour (WF) and wheat–soy bean flour mixtures

By amylograph data, dough with soybean flour had higher gelatinization temperature (in range 81.5 to 88.8oC) than dough with wheat flour only (81.2oC), and this value was higher when soybean flour portion was higher. Based on Stevenson et al. (2006) results, gelatinization temperature for wheat-soybean flour mixtures value could be lower. They found the gelatinization temperature of soybean starches were lower compared to wheat starch, due to the short amylopectin branch-chains and positive relationship between gelatinization temperature and amylopectin branch-chains. The reason why our gelatinization temperature values were higher maybe a different behaviour of soy starch in combination with wheat starch, which was present in wheat-soybean flour mixtures. The maximal pasta viscosity decreased from 315 to 90 AU when soybean flour portion was increased. The lowest pasta viscosity was when the soybean flour portion was 30% (w/w) and it was seven times lower than maximal pasta viscosity value for wheat flour only. The low peak viscosity of soybean starch could be due to short amylopectin branch-chain which has been correlated in wheat starches (Sasaki & Matsuki, 1998; Shibananuma et al., 1996).

The lipid profile of wheat flour and soybean flour obtained by HPLC analysis and based on these results the lipid profile of wheat-soybean flour mixtures, is presented in Table 3. The content of components was determined by measuring the peak area at 1.76 min for free fatty acids, peak area at 2.15 min for methyl esters, peaks area in the range of 3.44-4.58 min for

Wheat flour 3% 5% 10% 20% 30%

bread volume obtained from wheat flour only which was 581 cm3.


Table 1. The main components content in wheat and soybean flour and their mixtures

#### **3.2 Rheology properties**

Farinograph, extensograph and amylograph data of flours and flour mixtures with different portions of soybean flour are given in Table 2. The results showed the farinograph data depended on the soybean flour portion in mixtures. The water absorption increased from 53.4 to 64.2% with increasing soybean flour portion in mixtures. It is well known, that the main dough component in wheat flour responsible for water absorption is gluten. The soy flour is without gluten but had even more than 5 times higher protein content than wheat flour (46.7 to 8.6 g/100g). The higher absorption ability could be due to soy protein components, such as globulins, which interacted with gluten protein in the composite dough (Maforimbo et al., 2008). The same effect of soy flour on water absorption value was reported by Ribotta et al., 2005, when heat-treated full-fat flour, enzyme-active defatted flour and soy protein isolates were used for wheat flour substitution in portion from 3 to 12% and enzyme-active full-fat flour in portion from 5 to 12%. The differences in dough development time and dough stability among flour mixtures with different soybean flour portions, ranged from 1.3 to 7.3 min and 0.7 to 2.9 min, respectively and both values for mixtures were higher than for wheat flour where value for dough development time was 1 min and for dough stability was 0.1 min. The effect of delaying dough development time and dough stability by addition the mostly of investigated soy flours was obtained in Ribotta et al. (2005) experiments, too.

Degree of dough softening was increased with increasing soybean flour portion in mixtures, from 45 to 66 BU and all values were lower than value for wheat flour, i.e. than 90 BU. The same effect of soybean flour on this farinographic characteristic was obtained by Ribotta et al. (2005), for all investigated samples, except for soy protein isolate Samsory 90 HI and portion of 5, 10 and 12%, when dough softening value was higher. According to appropriate triangle area on farinograph curves, the quality number, known as Honkocy number could be in the range from 0 to100, and quality groups are A1 (area of 0-1.4 cm2), A2 (area of 1.5-5.5 cm2), B1 (area of 5.6-12.1 cm2), B2 (area of 12.2-17.9 cm2), C1 (area of 18.0-27.4 cm2) and C2 (area of 27.5-50.0 cm2) (Djaković, 1980). The soybean flour addition in all investigated portions had positive influence on quality number and quality group which was B1 instead B2, which was for wheat flour.

Data obtained on extensograph, showed that dough with soybean flour portion of 20 and 30% had lower values for energy and dough resistance in comparison to dough made of wheat flour only. The extensibility of dough with soybean flour ranged from 125 to 89 EU

(g/100g) Moisture Starch Protein Ash Lipid Gluten Carbo-

flour 12.80.6 76.61.2 8.60.34 0.480.04 1.20.05 23.90.4 78.82.2

flour 8.70.6 10.70.6 46.70.6 5.800.6 21.20.6 - 25.40.6 3% 12.7 74.6 9.7 0.64 1.8 23.2 77.2 5% 12.6 73.3 10.5 0.75 2.2 22.7 76.1 10% 12.4 69.9 12.4 1.01 3.2 21.5 73.5 20% 11.9 63.4 16.2 1.54 5.2 19.1 68.1 30% 11.6 56.8 20.0 2.08 7.2 16.7 62.8

Table 1. The main components content in wheat and soybean flour and their mixtures

Farinograph, extensograph and amylograph data of flours and flour mixtures with different portions of soybean flour are given in Table 2. The results showed the farinograph data depended on the soybean flour portion in mixtures. The water absorption increased from 53.4 to 64.2% with increasing soybean flour portion in mixtures. It is well known, that the main dough component in wheat flour responsible for water absorption is gluten. The soy flour is without gluten but had even more than 5 times higher protein content than wheat flour (46.7 to 8.6 g/100g). The higher absorption ability could be due to soy protein components, such as globulins, which interacted with gluten protein in the composite dough (Maforimbo et al., 2008). The same effect of soy flour on water absorption value was reported by Ribotta et al., 2005, when heat-treated full-fat flour, enzyme-active defatted flour and soy protein isolates were used for wheat flour substitution in portion from 3 to 12% and enzyme-active full-fat flour in portion from 5 to 12%. The differences in dough development time and dough stability among flour mixtures with different soybean flour portions, ranged from 1.3 to 7.3 min and 0.7 to 2.9 min, respectively and both values for mixtures were higher than for wheat flour where value for dough development time was 1 min and for dough stability was 0.1 min. The effect of delaying dough development time and dough stability by addition the mostly of investigated soy flours was obtained in

Degree of dough softening was increased with increasing soybean flour portion in mixtures, from 45 to 66 BU and all values were lower than value for wheat flour, i.e. than 90 BU. The same effect of soybean flour on this farinographic characteristic was obtained by Ribotta et al. (2005), for all investigated samples, except for soy protein isolate Samsory 90 HI and portion of 5, 10 and 12%, when dough softening value was higher. According to appropriate triangle area on farinograph curves, the quality number, known as Honkocy number could be in the range from 0 to100, and quality groups are A1 (area of 0-1.4 cm2), A2 (area of 1.5-5.5 cm2), B1 (area of 5.6-12.1 cm2), B2 (area of 12.2-17.9 cm2), C1 (area of 18.0-27.4 cm2) and C2 (area of 27.5-50.0 cm2) (Djaković, 1980). The soybean flour addition in all investigated portions had positive influence on quality number and quality group which was B1 instead

Data obtained on extensograph, showed that dough with soybean flour portion of 20 and 30% had lower values for energy and dough resistance in comparison to dough made of wheat flour only. The extensibility of dough with soybean flour ranged from 125 to 89 EU

hydrates

Content

Wheat

Soybean

**3.2 Rheology properties** 

Ribotta et al. (2005) experiments, too.

B2, which was for wheat flour.

and those values were lower than extensibility of dough with wheat flour only. The ration number, R/Ex, varied depending on soybean flour portion and ranged from 2.76 to 3.42. Based on curve of volume versus ratio number (Djaković, 1980), obtained for round bread, the bread volume was predicted to be in range from 576 to 557 cm3 and it was lower than bread volume obtained from wheat flour only which was 581 cm3.


Table 2. Rheological properties of wheat flour (WF) and wheat–soy bean flour mixtures

By amylograph data, dough with soybean flour had higher gelatinization temperature (in range 81.5 to 88.8oC) than dough with wheat flour only (81.2oC), and this value was higher when soybean flour portion was higher. Based on Stevenson et al. (2006) results, gelatinization temperature for wheat-soybean flour mixtures value could be lower. They found the gelatinization temperature of soybean starches were lower compared to wheat starch, due to the short amylopectin branch-chains and positive relationship between gelatinization temperature and amylopectin branch-chains. The reason why our gelatinization temperature values were higher maybe a different behaviour of soy starch in combination with wheat starch, which was present in wheat-soybean flour mixtures. The maximal pasta viscosity decreased from 315 to 90 AU when soybean flour portion was increased. The lowest pasta viscosity was when the soybean flour portion was 30% (w/w) and it was seven times lower than maximal pasta viscosity value for wheat flour only. The low peak viscosity of soybean starch could be due to short amylopectin branch-chain which has been correlated in wheat starches (Sasaki & Matsuki, 1998; Shibananuma et al., 1996).
