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The influence of changes in gluten complex structure on technological quality of wheat (Triticum aestivum L.)
Food Research International 40 (2007) 1038–1045 www.elsevier.com/locate/foodres
The influence of changes in gluten complex structure on technological quality of wheat (Triticum aestivum L.) A. Torbica a
a,*
, M. Antov b, J. Mastilovic´ a, D. Knezˇevic´
c
Institute for Food Technology, University of Novi Sad, Novi Sad, Blvd. Cara Lazara 1, Serbia b Faculty of Technology, University of Novi Sad, Novi Sad, Blvd. Cara Lazara 1, Serbia c Faculty of Agriculture Prisˇtina-Lesˇak, University of Prisˇtina, Prisˇtina, Serbia Received 18 April 2007; accepted 9 May 2007
Abstract The influence of changes in glutenin–gliadin complex of grain on technological quality of the wheat variety (Triticum aestivum L.) was studied. It was shown that wheat-bug attack caused differences in electrophoregram pattern of glutenins and gliadins concerning their number, intensities and molecular weights. The environmental influence had detrimental effect on rheological properties of dough. Expected heat-stress effect – the increase of gliadin–glutenin ratio was not detected. The modified method for gluten index was introduced and it was proven as superior to the standard method in predicting technological quality of wheat. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Glutenins; Gliadins; Technological quality; Wheat variety; Gluten index
1. Introduction Gluten can be defined as the rubbery mass that remains when wheat dough is washed to remove starch granules and water-soluble constituents. In practice, the term ‘gluten’ refers to the proteins, because they play a key role in determining the unique baking quality of wheat by conferring water absorption capacity, cohesivity, viscosity and elasticity on dough. Traditionally, gluten proteins have been divided into roughly equal fractions according to their solubility in alcohol–water solutions of gluten (e.g. 60% ethanol): the soluble gliadins and the insoluble glutenins. The glutenin fraction comprises aggregated proteins linked by interchain disulphide bonds; they have varying size ranging from about 500,000 to more than 10 million (Wieser, 2007). When glutenin is treated with reducing agents and analyzed by electrophoresis, two groups of proteins are obtained based on molecular weight: high molecular *
Corresponding author. Tel.: +381 (0) 21 485 3779; fax: +381 (0) 21 6350 20. E-mail address: [email protected] (Aleksandra Torbica). 0963-9969/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodres.2007.05.009
weight glutenin subunits (HMW-GS) and low molecular weight glutenin subunits (LMW-GS) (Wang, Khan, Hareland, & Nygard, 2006). The molecular weight distribution of glutenins has been recognized as one of the main determinants of dough properties and baking performance. Most gliadins are present as monomers; they were initially classified into four groups on the basis of mobility at low pH in gel electrophoresis: a-, b-, c-, x-gliadins in order of their descending mobility (Wieser, 2007). Both glutenins and gliadins are important contributors to the reologhical properties of dough, but their functions are divergent. Hydrated gliadins have little elasticity and are less cohesive than glutenins; they contribute mainly to the viscosity and extensibility of dough system. In contrast, hydrated glutenins are both cohesive and elastic and are responsible for dough strength and elasticity (Wang et al., 2006; Wieser, 2007). Some reports suggest that the overall function of wheat proteins derives mainly from the glutenin, and that gliadin is only as a diluent. Others, however, suggest that gliadin is an important direct contributor to gluten’s properties (Xu, Bietz, & Carriere, 2007).
A. Torbica et al. / Food Research International 40 (2007) 1038–1045
Although the appearance of glutenin and gliadin electrophoregrams with respect to number and band positions depends exclusively on wheat genotype, the intensities of the present bands that refer to protein fractions quantities may reflect also the environmental conditions (Lookhart, Menkovska, & Pomeranz, 1989; Sivri, Ko¨ksel, & Bushuk, 1998). Many factors can produce environmental modifications of grain quality including soil type and fertilizer level (particularly nitrogen, phosphorus and sulphur), climate fluctuations (especially influence of drought and heat-stress during grain filling) and finally the attack of insects and field pests (Altenbach, Kothari, & Lieu, 2002; Daniel & Triboi, 2000; Dupont & Altenbach, 2003; Lookhart et al., 1989). A number of researchers confirmed that some of factors mentioned above affect particularly glutenin–gliadin complex in a way that, e.g. enzyme hydrolysis occurs or rate of gliadins synthesis is higher comparatively to glutenins, what causes change of optimal ratio between glutenins and gliadins 1:1 (Fido, Bekes, Gras, & Tatham, 1997; Goesaert et al., 2005; Pen˜a, 2002; Radovanovic, Cloutier, Brown, Humphreys, & Lukow, 2002). Because of that, the necessity of investigation on essences of changes in glutenin–gliadin complex of wheat, that induces appearance of differences in technological quality, is imposed, and that was the aim of our study. This could be the most objectively investigated by comparing the characteristics of glutenin–gliadin complex of chosen wheat variety grown during the two production years in which it showed high and low technological quality.
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2. Materials and methods 2.1. Material Winter wheat variety which analyzed was created in a breeding centre of Institute of Field and Vegetable Crops, Novi Sad, Serbia. In previous decade this variety showed relatively stable high technological quality. The samples were collected from several locations of province of Vojvodina. Locations were chosen with respect to the high variations of infestation of insect damage attack and heat-stress. Analyzed samples originated from two wheat production years: year 1 was characterized by absence of insect attack and heat-stress, while year 2, in contrary, was characterized by heat-stress and presence of high level of wheat-bug damaged kernels, especially in locations B and C (see Tables 1 and 2). 2.2. Standard methods of evaluation of technological quality of wheat Chosen samples have been tested by all Standard methods for the determination of trading and technological wheat quality: determination of Besatz of wheat (ICC Standard No. 102/1), protein content (NIT analyzer ‘‘Infratec 1241’’), sedimentation according Zeleny (ICC Standard No. 116/1), rheological examinations with farinograph and extensograph (ICC Standard No. 114/1 and ICC Standard No. 115/1), wet gluten content (ICC Standard No. 106/2), gluten index (ICC Standard No. 155)
Table 1 Wheat-bug damaged kernels content and values of indirect and direct gluten quality parameters of wheat samples from the production year 1 Locations
Year 1 A B C D E F G
Wheat-bug damaged kernels (%)
Content of protein (% on dry base)
Zeleny sedimentation value (ml)
Zeleny sedimentation value 6 months after harvest (ml)
Wet gluten content (%)
Dry gluten content (%)
Gluten index (%)
Gluten index at 37 °C (%)
0.60 0.60 0.70 1.10 0.60 1.00 1.10
13.2 11.5 11.8 12.3 12.5 12.3 12.1
47 31 43 40 40 38 41
40 32 36 33 35 29 39
34 31 30 32 30 31 29
12 10 10 9 11 10 10
88.86 91.64 96.61 91.90 89.83 91.59 94.81
65.85 51.08 66.57 46.88 72.81 67.46 73.75
Table 2 Wheat-bug damaged kernels content and values of indirect and direct gluten quality parameters of wheat samples from the production year 2 Locations
Year 2 A B C D E F G
Wheat-bug damaged kernels (%)
Content of protein (% on dry base)
Zeleny sedimentation value (ml)
Zeleny sedimentation value 6 months after harvest (ml)
Wet gluten content (%)
Dry gluten content (%)
Gluten index (%)
Gluten index at 37 °C (%)
3.70 4.40 7.10 2.50 1.30 1.40 1.30
11.7 13.9 16.1 10.3 13.9 12.1 12.2
40 58 60 32 52 38 61
34 38 36 33 38 32 36
37 43 42 30 34 33 36
12 14 13 10 11 11 12
75.68 46.51 52.38 93.33 94.12 96.97 86.11
31.99 0.00 0.00 36.96 53.08 67.52 40.49
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and dry gluten content by apparatus Glutork 2020 from Perten Company by drying of the wet gluten at 150 °C for 4 min (Glutomatic System: AACC/No. 38-12, ICC Standard/No. 137/1, 155 & 158, ISO 7495).
For determination of present proteins bands molecular weights SERVA Unstained SDS–PAGE Protein Marker 6.5–200 kDa Liquid Mix (Serva, Heidelberg, Germany) was used.
2.3. Baking test
2.6. Software analysis
In the method applied for laboratory test baking, dough from 900 g of flour, 2.0% of yeast, 2.0% of salt (based on flour content) and water (whose quantity was determined on the basis of farinographic water absorption and on the degree of softening, and diminished for water content brought in with yeast) was kneaded for 5 min at 85 rpm in the high-speed laboratory dough mixer Diosna. Fermentation was performed in thermostatic box at 30 °C. Fermentation time was determined upon the degree of softening of dough (150 min, or 120 min, or 90 min for dough having degrees of softening of less than 100 FU, 100–150 FU and more than 150 FU, respectively). After fermentation, dough was weighted, divided and formed. Proofing was performed in thermostatic box at 30 °C and relative moisture content of at least 75%. Breads were free baked in the laboratory baking oven 20 min at 220–250 °C with the introduction of steam. Then the breads were cooled under the controlled temperature and moisture conditions and they were sensorically evaluated 24 h after baking through experienced taste panel. General score of sensorical bread characteristics was obtained as an arithmetic mean of ratings of individual evaluators, using scoring system from 1 (unacceptable) to 5 (excellent) for crust color, crumb elasticity and fineness of pores structure.
After gels staining with Coomassie Brilliant Blue R-250 (Sigma–Aldrich, Co.) and destaining with water, the obtained electrophoregrams were scanned. High-resolution digital photographs were analyzed by Gelscan 5.1 software package (BioSciTec GmbH, Frankfurt/Main, Germany). Quantitative determination of glutenin and gliadin total amounts for each analyzed sample was done by SDS– PAGE of samples and known quantities of BSA (Serva, Heidelberg, Germany), as standard, under the same conditions.
2.4. Modified method of evaluation of technological quality of wheat Besides to Standard methods mentioned above, analyses included modified method for gluten index determination. This method demonstrates modification of modified method for gluten index determination (Aja, Pe´rez, & Rosell, 2004). In this work, gluten index modified values were obtained after incubation for 90 min at 37 °C of ball of dough, instead of ball of wet gluten (Aja et al., 2004). 2.5. Electrophoresis of the wheat glutenins and gliadins Glutenins and gliadins extracted from flour samples and reduced with b-mercapto ethanol were separated by sodium dodecyl sulphate polyacrylamide electrophoresis (SDS–PAGE), on the 12% gel (Kasarda, Furlath, & Thrasher, 1986). For examinations was used Maxi Vertical Dual Plate electrophoresis apparatus (Carl Roth GmbH+Co KG, Germany), using constant buffer temperature of 12 °C and current intensity of 30 mA per gel, with the average analysis duration of about 7 h.
3. Results and discussion Values of content of wheat-bug damaged kernels and few gluten quality parameters of examined wheat samples from production years 1 and 2 are presented in Tables 1 and 2. Based on those determined values it is evident that major difference between two production years lies in the increased content of wheat-bug damaged kernels in wheat samples from production year 2 compared with wheat samples from production year 1. Production year 2 was also characterized by the heat-stress lasting several days during grain filling, with temperatures exceeding 30 °C, followed by temperatures in the range 30–39 °C in the first part of harvest (RHMS, 2004). According to many authors (Blumenthal, Barlow, & Wrigley, 1993; Blumenthal et al., 1991; Blumenthal, Bekes, Gras, Barlow, & Wrigley, 1995; Ciaffi, Tozzi, Borghi, Corbellini, & Lafiandra, 1996; Daniel & Triboi, 2000; Dupont & Altenbach, 2003; Hariri, Williams, & El-Haramein, 2000; Peterson, Graybosch, Shelton, & Baenziger, 1998; Sivri et al., 1998) those conditions are usually the reason of inferior quality of glutenins and gliadins, what is not obviously from obtained values of standard gluten quality parameters such as contents of protein, Zeleny sedimentation values immediately after harvest and six months later, wet and dry gluten contents, and gluten index standard values (Tables 1 and 2). This was the reason for modification of method for gluten index determination, aiming to the optimization of temperature–time relationships for action of proteolytic enzymes brought in by the wheat-bugs. In such way rapid (lasting 90 min) method for prediction of technological quality of the examined samples was obtained. Those results were more adequate to the amount of kernels attacked by wheat-bugs and to energy detected on the extensograms than standard gluten index values (Tables 3 and 4). Reduced glutenins of wheat samples from two production years are illustrated in Fig. 1. From the SDS–PAGE it is obvious that there are differences of intensities of HMW glutenin bands in production year 2 for samples
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Table 3 Values of the selected farinograph, extensorgaph and breadmaking quality parameters of the examined wheat variety in the production year 1 Locations
Year 1 A B C D E F G
Water absorption (%) (on 13% water content)
Degree of softening (FU)
Energy on extensogram (cm2)
Resistance to extension at 50 mm extension (EU)
Extensibility (mm)
Ratio of resistance/ extensibility (rs/e)
Yield of volume (ml)
General score for sensory characteristics of bread
62.2 58.5 60.0 61.9 60.9 61.9 61.6
30 60 30 50 60 5 35
93 72 70 59 71 80 95
290 330 240 240 220 330 400
157 133 155 141 161 138 134
1.85 2.48 1.55 1.70 1.37 2.39 2.98
552 578 625 600 561 557 544
3.37 2.63 4.33 3.97 3.63 4.07 3.40
Table 4 Values of the selected farinograph, extensorgaph and breadmaking quality parameters of the examined wheat variety in the production year 2 Locations
Year 2 A B C D E F G a
Water absorption (%) (on 13% water content)
Degree of softening (FU)
Energy on extensogram (cm2)
Resistance to extension at 50 mm extension (EU)
Extensibility (mm)
Ratio of resistance/ extensibility (rs/e)
Yield of volume (ml)
General score for sensory characteristics of bread
61.8 62.7 65.4 59.6 63.7 60.3 64.3
75 180 195 95 35 30 40
14 nda nda 6 74 106 55
65 nda nda 35 210 325 145
167 nda nda 104 177 158 194
0.39 nda nda 0.34 1.19 2.06 0.75
429 – – 418 582 507 580
3.03 – – 3.00 3.90 3.60 4.33
Not detected.
with high (lines 2A–2D) and, according to Serbian Standard JUS E.B1.200, acceptable level (<2%) of wheat-bug damaged kernels (lines 2E–2G). Also, SDS–PAGE shows presence of general differences of LMW glutenin bands intensities between the samples from the same locations from two production years. Comparing the number of bands of reduced glutenins in samples of flours obtained from examined wheat variety from two production years using software package (Fig. 2), it was found that the greatest increases in number of LMW glutenin bands occurred in samples from production year 2 originated from locations A–D, i.e. from the year when heat-stress and insect attack were observed. Reduced gliadins of wheat samples from two production years are illustrated in Fig. 3. From the SDS–PAGE, it is observable that there are differences in number and intensities of gliadins bands in production year 2 for samples with high (lines 2A–2D) and acceptable level (<2%, Serbian Standard JUS E.B1.200) (lines 2E–2G) of wheat-bug damaged kernels. General difference between two production years reflects in the diminished intensity of bands with molecular weights greater than 70 kDa, and the enhanced intensity of bands with molecular weights below 70 kDa in the production year 2 with respect to the production year 1. Comparing the number of reduced gliadins bands in samples of flours obtained from examined wheat variety
from two production years using software package (Fig. 4), it was found, similarly as in the case of glutenins, that the greatest increases in number of bands were in samples from production year 2 originated from locations A– D, i.e. from the year which was characterized by the heat-stress and insect attack. Values of chosen parameters of rheological and breadmaking quality of flours obtained from examined wheat samples from production years 1 and 2 are presented in Tables 3 and 4. With respect to samples from the production year 1, samples from the production year 2 were characterized, in average, by the increased farinograph water absorption of flour and the increased degree of softening of dough. Moreover, the most characteristic appearance was decreased value of energy, up to the limit of the impossibility of detecting of energy on extensogram. This could be explained by the breaking down of the gluten structure which can be caused by the proteolytic enzymes activity as reported in the literature (Hariri et al., 2000; Sivri, Sapirstein, Ko¨ksel, & Bushuk, 1999; Wang et al., 2005). That also stands for SDS–PAGE results showing increased number of bands of glutenins and gliadins of samples from production year 2 originated from locations A–D. Similar findings were obtained for bug damaged wheat varieties in Turkey (Sivri et al., 1998). Values of gluten index determined at 37 °C reached 0 for samples for which it was
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Fig. 1. SDS–PAGE of reduced flour glutenins from samples of the examined wheat variety (S: molecular weight protein standard; 1A–1G: wheat samples from the 1st production year from locations A–G; 2A–2G: wheat samples from the 2nd production year from locations A–G).
Fig. 2. Comparison of number of bands of the reduced glutenins in flour samples obtained in two production year, using software package (1 – first production year; 2 – second production year; A–G: locations where the examined wheat samples were produced).
impossible to detect energy, i.e. flour were declared as being inapplicable for further processing (samples from locations B and C in production year 2; Table 4). In the samples originated from production year 2, the extensograph parameters such as resistance to extension at 50 mm extension, extensibility and ratio of resistance/
extensibility showed the optimum values only in the case of wheat sample from location 2F with the low content of wheat-bug damaged kernels and the highest detected values of energy, gluten index and modified gluten index. Obtained better than expected values of breadmaking quality parameters (yield volume and general score for sensory characteristics of bread) were the consequence of optimization of baking test conditions for each of examined wheat samples. Quantitative relationships of glutenins and gliadins in glutenin–gliadin complex of wheat samples from two production years are illustrated in Figs. 5 and 6. For the production year 1 it could be seen that the percentage of gliadins was more or less uniform for samples 1B–1F, and the samples 1A and 1G have lower ratio gliadins–glutenins (Fig. 5). It was in agreement with lower energy on extensogram for samples 1B–1F. However, it had no detrimental influence on breadmaking quality (Table 3). Observing quantitative relationships between gliadins and glutenins in the glutenin–gliadin complex in samples
A. Torbica et al. / Food Research International 40 (2007) 1038–1045
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Fig. 3. SDS–PAGE of reduced flour gliadins from samples of the examined wheat variety (S: molecular weight protein standard; 1A–1G: wheat samples from the 1st production year from locations A–G; 2A–2G: wheat samples from the 2nd production year from locations A–G).
Fig. 4. Comparison of number of bands of the reduced gliadins in flour samples obtained in two production years, using software package (1 – first production year; 2 – second production year; A–G: locations where the examined wheat samples were produced).
Fig. 5. Quantitative relationships of glutenins and gliadins in glutenin– gliadin complex of the examined wheat variety in the production year 1 (A–G: locations where the examined samples were grown).
of the examined wheat variety in the production year 2 (Fig. 6) it could be seen that the greatest percentages of gliadins were in samples from locations B and C, whose flours showed the worst technological quality (Table 4). With respect to other samples from that year, the lowest percentages of gliadins were in samples from locations F and G, in which number of gliadins bands was not increased comparing then with production year 1 (Fig. 4).
The same was valid for the number of glutenins bands (Fig. 2). This was followed by the best technological quality of these two samples in frames of the analyzed wheat samples in production year 2 (Table 4). Wheat samples from production year 2 despite heatstress before harvest and high daily temperatures during the harvest did not show greater percentage of gliadins comparing with wheat samples from production year 1,
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Fig. 6. Quantitative relationships of glutenins and gliadins in glutenin– gliadin complex of the examined wheat variety in the production year 2 (A–G: locations where the examined samples were grown).
and according to this finding it could be suggested that examined wheat variety shows resistance to heat-stress (Blumenthal et al., 1995; Dupont & Altenbach, 2003). 4. Conclusion In this work, it was shown that the examinated wheat variety showed resistance to the heat-stress, but it did not show resistance to the attack of wheat-bugs. Moreover, the proteolysis of gluten proteins which was probably induced by wheat-bugs attack happened in the glutenin-, as well as in the gliadin fractions of proteins. Results indicate that technological quality should be related to both glutenin- and gliadin fractions of proteins. This study also proved that the modified gluten index method was superior with respect to the standard method in predicting technological quality of wheat. Acknowledgements This work was supported by the Project No 6849, Ministry of Science and Environmental Protection, Republic of Serbia. References Aja, S., Pe´rez, G., & Rosell, C. M. (2004). Wheat damage by Aelia spp. and Erygaster spp.: Effects on gluten and water-soluble compounds released by gluten hydrolysis. Journal of Cereal Science, 39(2), 187–193. Altenbach, S. B., Kothari, K. M., & Lieu, D. (2002). Environmental conditions during wheat grain development alter temporal regulation of major gluten protein genes. Cereal Chemistry, 79(2), 279– 285. Blumenthal, C., Barlow, E. W. R., & Wrigley, C. W. (1993). Growth environment and wheat quality: The effect of heat stress on dough properties and gluten proteins. Journal of Cereal Science, 18(1), 3–21. Blumenthal, C., Bekes, F., Batey, I. L., Wrigley, C. W., Moss, H. J., Mares, D. J., et al. (1991). Interpretation of grain quality results from wheat variety trials with reference to high temperature stress. Australian Journal of Agricultural Research, 42(3), 325–334.
Blumenthal, C., Bekes, F., Gras, P. W., Barlow, E. W. R., & Wrigley, C. W. (1995). Identification of wheat genotypes tolerant to the effects of heat stress on grain quality. Cereal Chemistry, 72(6), 539–544. Ciaffi, M., Tozzi, L., Borghi, B., Corbellini, M., & Lafiandra, D. (1996). Effect of heat shock during grain filling on the gluten protein composition of bread wheat. Journal of Cereal Science, 24(2), 91– 100. Daniel, C., & Triboi, E. (2000). Effects of temperature and nitrogen nutrition on the grain composition of winter wheat: Effects on gliadin content and composition. Journal of Cereal Science, 32(1), 45–56. Dupont, F. M., & Altenbach, S. B. (2003). Molecular and biochemical impacts of environmental factors on wheat grain development and protein synthesis. Journal of Cereal Science, 38(2), 133–146. Fido, R. J., Bekes, F., Gras, P. W., & Tatham, A. S. (1997). Effects of a-, b-, c- and x-gliadins on the dough mixing properties of wheat flour. Journal of Cereal Science, 26(3), 271–277. Glutomatic System: AACC/No. 38-12, ICC/No. 137/1, 155 & 158, ISO 7495. Goesaert, H., Brijs, K., Veraverbeke, W. S., Courtin, C. M., Gebruers, K., & Delcour, J. A. (2005). Wheat flour constituents: How they impact bread quality, and how to impact their functionality. Trends in Food Science & Technology, 16(1–3), 12–30. Hariri, G., Williams, P. C., & El-Haramein, F. J. (2000). Influence of pentatomid insects on the physical dough properties and two-layered flat bread baking quality of Syrian wheat. Journal of Cereal Science, 31(2), 111–118. ICC Standard No. 102/1: Determination of Besatz of wheat. ICC Standard No. 106/2: Working method for the determination of wet gluten in wheat flour. ICC Standard No. 114/1: Method for using the Brabender extensograph. ICC Standard No. 115/1: Method for using the Brabender farinograph. ICC Standard No. 116/1: Determination of the sedimentation value (according to Zeleny) as an approximate measure of baking quality. ICC Standard No. 155: Determination of wet gluten quantity and quality (Gluten Index ac. to Perten) of whole wheat meal and wheat flour (Triticum aestivum). JUS E.B1.200 (1978). The basic quality conditions (in Serbian). Kasarda, D., Furlath, K., & Thrasher, K. (1986). Sodium dodecyl sulfate polyacrylamide gel electrophoresis of wheat grain proteins from selected wheat varieties and FGIS wheat class samples: A survey of samples from the hardness series. Manuscript, Western Regional Research Center, Agricultural Research Service, USDA, Albany, California. Lookhart, G. L., Menkovska, M., & Pomeranz, Y. (1989). Polyacrylamide gel electrophoresis and high-performance liquid chromatography patterns of gliadins from wheat sections and milled and air-classified fractions. Cereal Chemistry, 66(4), 256–262. Pen˜a, R. J. (2002). Wheat for bread and other foods, bread wheat improvement and production. Rome: Food and Agriculture Organization of the United Nations, p. 567. Peterson, C. J., Graybosch, R. A., Shelton, D. R., & Baenziger, P. S. (1998). Baking quality of hard winter wheat: Response of cultivars to environment in the Great Plains. Euphytica, 100(1–3), 157–162. Radovanovic, N., Cloutier, S., Brown, D., Humphreys, D. G., & Lukow, O. M. (2002). Genetic variance for gluten strength contributed by high molecular weight glutenin proteins. Cereal Chemistry, 79(6), 843–849. RHMS (2004): (according to date of Republic Hydrometeorological Service of Serbia from 2004).. Sivri, D., Ko¨ksel, H., & Bushuk, W. (1998). Effects of wheat bug (Eurygaster maura) proteolytic enzymes on electrophoretic properties of gluten proteins. New Zealand. Journal of Crop and Horticultural Science, 26, 117–125. Sivri, D., Sapirstein, H. D., Ko¨ksel, H., & Bushuk, W. (1999). Effects of wheat bug (Eurygaster maura) protease on glutenin proteins. Cereal Chemistry, 76(5), 816–820. Wang, Y. G., Khan, K., Hareland, G., & Nygard, G. (2006). Quantitative glutenin composition from gel electrophoresis of flour mill streams
A. Torbica et al. / Food Research International 40 (2007) 1038–1045 and relationship to breadmaking quality. Cereal Chemistry, 83(3), 293–299. Wang, J., Wieser, H., Pawelzik, E., Weinert, J., Keutgen, A. J., & Wolf, G. A. (2005). Impact of the fungal protease produced by Fusarium culmorum on the protein quality and breadmaking properties of winter wheat. European Food Research & Technology, 220(5–6), 552–559.
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Wieser, H. (2007). Chemistry of gluten proteins. Food Microbiology, 24(2), 115–119. Xu, J., Bietz, J. A., & Carriere, C. J. (2007). Viscoelastic properties of wheat gliadin and glutenin suspensions. Food Chemistry, 101(3), 1025–1030.
The influence of changes in gluten complex structure on technological quality of wheat (Triticum aestivum L.) A. Torbica a
a,*
, M. Antov b, J. Mastilovic´ a, D. Knezˇevic´
c
Institute for Food Technology, University of Novi Sad, Novi Sad, Blvd. Cara Lazara 1, Serbia b Faculty of Technology, University of Novi Sad, Novi Sad, Blvd. Cara Lazara 1, Serbia c Faculty of Agriculture Prisˇtina-Lesˇak, University of Prisˇtina, Prisˇtina, Serbia Received 18 April 2007; accepted 9 May 2007
Abstract The influence of changes in glutenin–gliadin complex of grain on technological quality of the wheat variety (Triticum aestivum L.) was studied. It was shown that wheat-bug attack caused differences in electrophoregram pattern of glutenins and gliadins concerning their number, intensities and molecular weights. The environmental influence had detrimental effect on rheological properties of dough. Expected heat-stress effect – the increase of gliadin–glutenin ratio was not detected. The modified method for gluten index was introduced and it was proven as superior to the standard method in predicting technological quality of wheat. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Glutenins; Gliadins; Technological quality; Wheat variety; Gluten index
1. Introduction Gluten can be defined as the rubbery mass that remains when wheat dough is washed to remove starch granules and water-soluble constituents. In practice, the term ‘gluten’ refers to the proteins, because they play a key role in determining the unique baking quality of wheat by conferring water absorption capacity, cohesivity, viscosity and elasticity on dough. Traditionally, gluten proteins have been divided into roughly equal fractions according to their solubility in alcohol–water solutions of gluten (e.g. 60% ethanol): the soluble gliadins and the insoluble glutenins. The glutenin fraction comprises aggregated proteins linked by interchain disulphide bonds; they have varying size ranging from about 500,000 to more than 10 million (Wieser, 2007). When glutenin is treated with reducing agents and analyzed by electrophoresis, two groups of proteins are obtained based on molecular weight: high molecular *
Corresponding author. Tel.: +381 (0) 21 485 3779; fax: +381 (0) 21 6350 20. E-mail address: [email protected] (Aleksandra Torbica). 0963-9969/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodres.2007.05.009
weight glutenin subunits (HMW-GS) and low molecular weight glutenin subunits (LMW-GS) (Wang, Khan, Hareland, & Nygard, 2006). The molecular weight distribution of glutenins has been recognized as one of the main determinants of dough properties and baking performance. Most gliadins are present as monomers; they were initially classified into four groups on the basis of mobility at low pH in gel electrophoresis: a-, b-, c-, x-gliadins in order of their descending mobility (Wieser, 2007). Both glutenins and gliadins are important contributors to the reologhical properties of dough, but their functions are divergent. Hydrated gliadins have little elasticity and are less cohesive than glutenins; they contribute mainly to the viscosity and extensibility of dough system. In contrast, hydrated glutenins are both cohesive and elastic and are responsible for dough strength and elasticity (Wang et al., 2006; Wieser, 2007). Some reports suggest that the overall function of wheat proteins derives mainly from the glutenin, and that gliadin is only as a diluent. Others, however, suggest that gliadin is an important direct contributor to gluten’s properties (Xu, Bietz, & Carriere, 2007).
A. Torbica et al. / Food Research International 40 (2007) 1038–1045
Although the appearance of glutenin and gliadin electrophoregrams with respect to number and band positions depends exclusively on wheat genotype, the intensities of the present bands that refer to protein fractions quantities may reflect also the environmental conditions (Lookhart, Menkovska, & Pomeranz, 1989; Sivri, Ko¨ksel, & Bushuk, 1998). Many factors can produce environmental modifications of grain quality including soil type and fertilizer level (particularly nitrogen, phosphorus and sulphur), climate fluctuations (especially influence of drought and heat-stress during grain filling) and finally the attack of insects and field pests (Altenbach, Kothari, & Lieu, 2002; Daniel & Triboi, 2000; Dupont & Altenbach, 2003; Lookhart et al., 1989). A number of researchers confirmed that some of factors mentioned above affect particularly glutenin–gliadin complex in a way that, e.g. enzyme hydrolysis occurs or rate of gliadins synthesis is higher comparatively to glutenins, what causes change of optimal ratio between glutenins and gliadins 1:1 (Fido, Bekes, Gras, & Tatham, 1997; Goesaert et al., 2005; Pen˜a, 2002; Radovanovic, Cloutier, Brown, Humphreys, & Lukow, 2002). Because of that, the necessity of investigation on essences of changes in glutenin–gliadin complex of wheat, that induces appearance of differences in technological quality, is imposed, and that was the aim of our study. This could be the most objectively investigated by comparing the characteristics of glutenin–gliadin complex of chosen wheat variety grown during the two production years in which it showed high and low technological quality.
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2. Materials and methods 2.1. Material Winter wheat variety which analyzed was created in a breeding centre of Institute of Field and Vegetable Crops, Novi Sad, Serbia. In previous decade this variety showed relatively stable high technological quality. The samples were collected from several locations of province of Vojvodina. Locations were chosen with respect to the high variations of infestation of insect damage attack and heat-stress. Analyzed samples originated from two wheat production years: year 1 was characterized by absence of insect attack and heat-stress, while year 2, in contrary, was characterized by heat-stress and presence of high level of wheat-bug damaged kernels, especially in locations B and C (see Tables 1 and 2). 2.2. Standard methods of evaluation of technological quality of wheat Chosen samples have been tested by all Standard methods for the determination of trading and technological wheat quality: determination of Besatz of wheat (ICC Standard No. 102/1), protein content (NIT analyzer ‘‘Infratec 1241’’), sedimentation according Zeleny (ICC Standard No. 116/1), rheological examinations with farinograph and extensograph (ICC Standard No. 114/1 and ICC Standard No. 115/1), wet gluten content (ICC Standard No. 106/2), gluten index (ICC Standard No. 155)
Table 1 Wheat-bug damaged kernels content and values of indirect and direct gluten quality parameters of wheat samples from the production year 1 Locations
Year 1 A B C D E F G
Wheat-bug damaged kernels (%)
Content of protein (% on dry base)
Zeleny sedimentation value (ml)
Zeleny sedimentation value 6 months after harvest (ml)
Wet gluten content (%)
Dry gluten content (%)
Gluten index (%)
Gluten index at 37 °C (%)
0.60 0.60 0.70 1.10 0.60 1.00 1.10
13.2 11.5 11.8 12.3 12.5 12.3 12.1
47 31 43 40 40 38 41
40 32 36 33 35 29 39
34 31 30 32 30 31 29
12 10 10 9 11 10 10
88.86 91.64 96.61 91.90 89.83 91.59 94.81
65.85 51.08 66.57 46.88 72.81 67.46 73.75
Table 2 Wheat-bug damaged kernels content and values of indirect and direct gluten quality parameters of wheat samples from the production year 2 Locations
Year 2 A B C D E F G
Wheat-bug damaged kernels (%)
Content of protein (% on dry base)
Zeleny sedimentation value (ml)
Zeleny sedimentation value 6 months after harvest (ml)
Wet gluten content (%)
Dry gluten content (%)
Gluten index (%)
Gluten index at 37 °C (%)
3.70 4.40 7.10 2.50 1.30 1.40 1.30
11.7 13.9 16.1 10.3 13.9 12.1 12.2
40 58 60 32 52 38 61
34 38 36 33 38 32 36
37 43 42 30 34 33 36
12 14 13 10 11 11 12
75.68 46.51 52.38 93.33 94.12 96.97 86.11
31.99 0.00 0.00 36.96 53.08 67.52 40.49
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and dry gluten content by apparatus Glutork 2020 from Perten Company by drying of the wet gluten at 150 °C for 4 min (Glutomatic System: AACC/No. 38-12, ICC Standard/No. 137/1, 155 & 158, ISO 7495).
For determination of present proteins bands molecular weights SERVA Unstained SDS–PAGE Protein Marker 6.5–200 kDa Liquid Mix (Serva, Heidelberg, Germany) was used.
2.3. Baking test
2.6. Software analysis
In the method applied for laboratory test baking, dough from 900 g of flour, 2.0% of yeast, 2.0% of salt (based on flour content) and water (whose quantity was determined on the basis of farinographic water absorption and on the degree of softening, and diminished for water content brought in with yeast) was kneaded for 5 min at 85 rpm in the high-speed laboratory dough mixer Diosna. Fermentation was performed in thermostatic box at 30 °C. Fermentation time was determined upon the degree of softening of dough (150 min, or 120 min, or 90 min for dough having degrees of softening of less than 100 FU, 100–150 FU and more than 150 FU, respectively). After fermentation, dough was weighted, divided and formed. Proofing was performed in thermostatic box at 30 °C and relative moisture content of at least 75%. Breads were free baked in the laboratory baking oven 20 min at 220–250 °C with the introduction of steam. Then the breads were cooled under the controlled temperature and moisture conditions and they were sensorically evaluated 24 h after baking through experienced taste panel. General score of sensorical bread characteristics was obtained as an arithmetic mean of ratings of individual evaluators, using scoring system from 1 (unacceptable) to 5 (excellent) for crust color, crumb elasticity and fineness of pores structure.
After gels staining with Coomassie Brilliant Blue R-250 (Sigma–Aldrich, Co.) and destaining with water, the obtained electrophoregrams were scanned. High-resolution digital photographs were analyzed by Gelscan 5.1 software package (BioSciTec GmbH, Frankfurt/Main, Germany). Quantitative determination of glutenin and gliadin total amounts for each analyzed sample was done by SDS– PAGE of samples and known quantities of BSA (Serva, Heidelberg, Germany), as standard, under the same conditions.
2.4. Modified method of evaluation of technological quality of wheat Besides to Standard methods mentioned above, analyses included modified method for gluten index determination. This method demonstrates modification of modified method for gluten index determination (Aja, Pe´rez, & Rosell, 2004). In this work, gluten index modified values were obtained after incubation for 90 min at 37 °C of ball of dough, instead of ball of wet gluten (Aja et al., 2004). 2.5. Electrophoresis of the wheat glutenins and gliadins Glutenins and gliadins extracted from flour samples and reduced with b-mercapto ethanol were separated by sodium dodecyl sulphate polyacrylamide electrophoresis (SDS–PAGE), on the 12% gel (Kasarda, Furlath, & Thrasher, 1986). For examinations was used Maxi Vertical Dual Plate electrophoresis apparatus (Carl Roth GmbH+Co KG, Germany), using constant buffer temperature of 12 °C and current intensity of 30 mA per gel, with the average analysis duration of about 7 h.
3. Results and discussion Values of content of wheat-bug damaged kernels and few gluten quality parameters of examined wheat samples from production years 1 and 2 are presented in Tables 1 and 2. Based on those determined values it is evident that major difference between two production years lies in the increased content of wheat-bug damaged kernels in wheat samples from production year 2 compared with wheat samples from production year 1. Production year 2 was also characterized by the heat-stress lasting several days during grain filling, with temperatures exceeding 30 °C, followed by temperatures in the range 30–39 °C in the first part of harvest (RHMS, 2004). According to many authors (Blumenthal, Barlow, & Wrigley, 1993; Blumenthal et al., 1991; Blumenthal, Bekes, Gras, Barlow, & Wrigley, 1995; Ciaffi, Tozzi, Borghi, Corbellini, & Lafiandra, 1996; Daniel & Triboi, 2000; Dupont & Altenbach, 2003; Hariri, Williams, & El-Haramein, 2000; Peterson, Graybosch, Shelton, & Baenziger, 1998; Sivri et al., 1998) those conditions are usually the reason of inferior quality of glutenins and gliadins, what is not obviously from obtained values of standard gluten quality parameters such as contents of protein, Zeleny sedimentation values immediately after harvest and six months later, wet and dry gluten contents, and gluten index standard values (Tables 1 and 2). This was the reason for modification of method for gluten index determination, aiming to the optimization of temperature–time relationships for action of proteolytic enzymes brought in by the wheat-bugs. In such way rapid (lasting 90 min) method for prediction of technological quality of the examined samples was obtained. Those results were more adequate to the amount of kernels attacked by wheat-bugs and to energy detected on the extensograms than standard gluten index values (Tables 3 and 4). Reduced glutenins of wheat samples from two production years are illustrated in Fig. 1. From the SDS–PAGE it is obvious that there are differences of intensities of HMW glutenin bands in production year 2 for samples
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Table 3 Values of the selected farinograph, extensorgaph and breadmaking quality parameters of the examined wheat variety in the production year 1 Locations
Year 1 A B C D E F G
Water absorption (%) (on 13% water content)
Degree of softening (FU)
Energy on extensogram (cm2)
Resistance to extension at 50 mm extension (EU)
Extensibility (mm)
Ratio of resistance/ extensibility (rs/e)
Yield of volume (ml)
General score for sensory characteristics of bread
62.2 58.5 60.0 61.9 60.9 61.9 61.6
30 60 30 50 60 5 35
93 72 70 59 71 80 95
290 330 240 240 220 330 400
157 133 155 141 161 138 134
1.85 2.48 1.55 1.70 1.37 2.39 2.98
552 578 625 600 561 557 544
3.37 2.63 4.33 3.97 3.63 4.07 3.40
Table 4 Values of the selected farinograph, extensorgaph and breadmaking quality parameters of the examined wheat variety in the production year 2 Locations
Year 2 A B C D E F G a
Water absorption (%) (on 13% water content)
Degree of softening (FU)
Energy on extensogram (cm2)
Resistance to extension at 50 mm extension (EU)
Extensibility (mm)
Ratio of resistance/ extensibility (rs/e)
Yield of volume (ml)
General score for sensory characteristics of bread
61.8 62.7 65.4 59.6 63.7 60.3 64.3
75 180 195 95 35 30 40
14 nda nda 6 74 106 55
65 nda nda 35 210 325 145
167 nda nda 104 177 158 194
0.39 nda nda 0.34 1.19 2.06 0.75
429 – – 418 582 507 580
3.03 – – 3.00 3.90 3.60 4.33
Not detected.
with high (lines 2A–2D) and, according to Serbian Standard JUS E.B1.200, acceptable level (<2%) of wheat-bug damaged kernels (lines 2E–2G). Also, SDS–PAGE shows presence of general differences of LMW glutenin bands intensities between the samples from the same locations from two production years. Comparing the number of bands of reduced glutenins in samples of flours obtained from examined wheat variety from two production years using software package (Fig. 2), it was found that the greatest increases in number of LMW glutenin bands occurred in samples from production year 2 originated from locations A–D, i.e. from the year when heat-stress and insect attack were observed. Reduced gliadins of wheat samples from two production years are illustrated in Fig. 3. From the SDS–PAGE, it is observable that there are differences in number and intensities of gliadins bands in production year 2 for samples with high (lines 2A–2D) and acceptable level (<2%, Serbian Standard JUS E.B1.200) (lines 2E–2G) of wheat-bug damaged kernels. General difference between two production years reflects in the diminished intensity of bands with molecular weights greater than 70 kDa, and the enhanced intensity of bands with molecular weights below 70 kDa in the production year 2 with respect to the production year 1. Comparing the number of reduced gliadins bands in samples of flours obtained from examined wheat variety
from two production years using software package (Fig. 4), it was found, similarly as in the case of glutenins, that the greatest increases in number of bands were in samples from production year 2 originated from locations A– D, i.e. from the year which was characterized by the heat-stress and insect attack. Values of chosen parameters of rheological and breadmaking quality of flours obtained from examined wheat samples from production years 1 and 2 are presented in Tables 3 and 4. With respect to samples from the production year 1, samples from the production year 2 were characterized, in average, by the increased farinograph water absorption of flour and the increased degree of softening of dough. Moreover, the most characteristic appearance was decreased value of energy, up to the limit of the impossibility of detecting of energy on extensogram. This could be explained by the breaking down of the gluten structure which can be caused by the proteolytic enzymes activity as reported in the literature (Hariri et al., 2000; Sivri, Sapirstein, Ko¨ksel, & Bushuk, 1999; Wang et al., 2005). That also stands for SDS–PAGE results showing increased number of bands of glutenins and gliadins of samples from production year 2 originated from locations A–D. Similar findings were obtained for bug damaged wheat varieties in Turkey (Sivri et al., 1998). Values of gluten index determined at 37 °C reached 0 for samples for which it was
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Fig. 1. SDS–PAGE of reduced flour glutenins from samples of the examined wheat variety (S: molecular weight protein standard; 1A–1G: wheat samples from the 1st production year from locations A–G; 2A–2G: wheat samples from the 2nd production year from locations A–G).
Fig. 2. Comparison of number of bands of the reduced glutenins in flour samples obtained in two production year, using software package (1 – first production year; 2 – second production year; A–G: locations where the examined wheat samples were produced).
impossible to detect energy, i.e. flour were declared as being inapplicable for further processing (samples from locations B and C in production year 2; Table 4). In the samples originated from production year 2, the extensograph parameters such as resistance to extension at 50 mm extension, extensibility and ratio of resistance/
extensibility showed the optimum values only in the case of wheat sample from location 2F with the low content of wheat-bug damaged kernels and the highest detected values of energy, gluten index and modified gluten index. Obtained better than expected values of breadmaking quality parameters (yield volume and general score for sensory characteristics of bread) were the consequence of optimization of baking test conditions for each of examined wheat samples. Quantitative relationships of glutenins and gliadins in glutenin–gliadin complex of wheat samples from two production years are illustrated in Figs. 5 and 6. For the production year 1 it could be seen that the percentage of gliadins was more or less uniform for samples 1B–1F, and the samples 1A and 1G have lower ratio gliadins–glutenins (Fig. 5). It was in agreement with lower energy on extensogram for samples 1B–1F. However, it had no detrimental influence on breadmaking quality (Table 3). Observing quantitative relationships between gliadins and glutenins in the glutenin–gliadin complex in samples
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Fig. 3. SDS–PAGE of reduced flour gliadins from samples of the examined wheat variety (S: molecular weight protein standard; 1A–1G: wheat samples from the 1st production year from locations A–G; 2A–2G: wheat samples from the 2nd production year from locations A–G).
Fig. 4. Comparison of number of bands of the reduced gliadins in flour samples obtained in two production years, using software package (1 – first production year; 2 – second production year; A–G: locations where the examined wheat samples were produced).
Fig. 5. Quantitative relationships of glutenins and gliadins in glutenin– gliadin complex of the examined wheat variety in the production year 1 (A–G: locations where the examined samples were grown).
of the examined wheat variety in the production year 2 (Fig. 6) it could be seen that the greatest percentages of gliadins were in samples from locations B and C, whose flours showed the worst technological quality (Table 4). With respect to other samples from that year, the lowest percentages of gliadins were in samples from locations F and G, in which number of gliadins bands was not increased comparing then with production year 1 (Fig. 4).
The same was valid for the number of glutenins bands (Fig. 2). This was followed by the best technological quality of these two samples in frames of the analyzed wheat samples in production year 2 (Table 4). Wheat samples from production year 2 despite heatstress before harvest and high daily temperatures during the harvest did not show greater percentage of gliadins comparing with wheat samples from production year 1,
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Fig. 6. Quantitative relationships of glutenins and gliadins in glutenin– gliadin complex of the examined wheat variety in the production year 2 (A–G: locations where the examined samples were grown).
and according to this finding it could be suggested that examined wheat variety shows resistance to heat-stress (Blumenthal et al., 1995; Dupont & Altenbach, 2003). 4. Conclusion In this work, it was shown that the examinated wheat variety showed resistance to the heat-stress, but it did not show resistance to the attack of wheat-bugs. Moreover, the proteolysis of gluten proteins which was probably induced by wheat-bugs attack happened in the glutenin-, as well as in the gliadin fractions of proteins. Results indicate that technological quality should be related to both glutenin- and gliadin fractions of proteins. This study also proved that the modified gluten index method was superior with respect to the standard method in predicting technological quality of wheat. Acknowledgements This work was supported by the Project No 6849, Ministry of Science and Environmental Protection, Republic of Serbia. References Aja, S., Pe´rez, G., & Rosell, C. M. (2004). Wheat damage by Aelia spp. and Erygaster spp.: Effects on gluten and water-soluble compounds released by gluten hydrolysis. Journal of Cereal Science, 39(2), 187–193. Altenbach, S. B., Kothari, K. M., & Lieu, D. (2002). Environmental conditions during wheat grain development alter temporal regulation of major gluten protein genes. Cereal Chemistry, 79(2), 279– 285. Blumenthal, C., Barlow, E. W. R., & Wrigley, C. W. (1993). Growth environment and wheat quality: The effect of heat stress on dough properties and gluten proteins. Journal of Cereal Science, 18(1), 3–21. Blumenthal, C., Bekes, F., Batey, I. L., Wrigley, C. W., Moss, H. J., Mares, D. J., et al. (1991). Interpretation of grain quality results from wheat variety trials with reference to high temperature stress. Australian Journal of Agricultural Research, 42(3), 325–334.
Blumenthal, C., Bekes, F., Gras, P. W., Barlow, E. W. R., & Wrigley, C. W. (1995). Identification of wheat genotypes tolerant to the effects of heat stress on grain quality. Cereal Chemistry, 72(6), 539–544. Ciaffi, M., Tozzi, L., Borghi, B., Corbellini, M., & Lafiandra, D. (1996). Effect of heat shock during grain filling on the gluten protein composition of bread wheat. Journal of Cereal Science, 24(2), 91– 100. Daniel, C., & Triboi, E. (2000). Effects of temperature and nitrogen nutrition on the grain composition of winter wheat: Effects on gliadin content and composition. Journal of Cereal Science, 32(1), 45–56. Dupont, F. M., & Altenbach, S. B. (2003). Molecular and biochemical impacts of environmental factors on wheat grain development and protein synthesis. Journal of Cereal Science, 38(2), 133–146. Fido, R. J., Bekes, F., Gras, P. W., & Tatham, A. S. (1997). Effects of a-, b-, c- and x-gliadins on the dough mixing properties of wheat flour. Journal of Cereal Science, 26(3), 271–277. Glutomatic System: AACC/No. 38-12, ICC/No. 137/1, 155 & 158, ISO 7495. Goesaert, H., Brijs, K., Veraverbeke, W. S., Courtin, C. M., Gebruers, K., & Delcour, J. A. (2005). Wheat flour constituents: How they impact bread quality, and how to impact their functionality. Trends in Food Science & Technology, 16(1–3), 12–30. Hariri, G., Williams, P. C., & El-Haramein, F. J. (2000). Influence of pentatomid insects on the physical dough properties and two-layered flat bread baking quality of Syrian wheat. Journal of Cereal Science, 31(2), 111–118. ICC Standard No. 102/1: Determination of Besatz of wheat. ICC Standard No. 106/2: Working method for the determination of wet gluten in wheat flour. ICC Standard No. 114/1: Method for using the Brabender extensograph. ICC Standard No. 115/1: Method for using the Brabender farinograph. ICC Standard No. 116/1: Determination of the sedimentation value (according to Zeleny) as an approximate measure of baking quality. ICC Standard No. 155: Determination of wet gluten quantity and quality (Gluten Index ac. to Perten) of whole wheat meal and wheat flour (Triticum aestivum). JUS E.B1.200 (1978). The basic quality conditions (in Serbian). Kasarda, D., Furlath, K., & Thrasher, K. (1986). Sodium dodecyl sulfate polyacrylamide gel electrophoresis of wheat grain proteins from selected wheat varieties and FGIS wheat class samples: A survey of samples from the hardness series. Manuscript, Western Regional Research Center, Agricultural Research Service, USDA, Albany, California. Lookhart, G. L., Menkovska, M., & Pomeranz, Y. (1989). Polyacrylamide gel electrophoresis and high-performance liquid chromatography patterns of gliadins from wheat sections and milled and air-classified fractions. Cereal Chemistry, 66(4), 256–262. Pen˜a, R. J. (2002). Wheat for bread and other foods, bread wheat improvement and production. Rome: Food and Agriculture Organization of the United Nations, p. 567. Peterson, C. J., Graybosch, R. A., Shelton, D. R., & Baenziger, P. S. (1998). Baking quality of hard winter wheat: Response of cultivars to environment in the Great Plains. Euphytica, 100(1–3), 157–162. Radovanovic, N., Cloutier, S., Brown, D., Humphreys, D. G., & Lukow, O. M. (2002). Genetic variance for gluten strength contributed by high molecular weight glutenin proteins. Cereal Chemistry, 79(6), 843–849. RHMS (2004): (according to date of Republic Hydrometeorological Service of Serbia from 2004).
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