The rheological properties of dough are determined by the amount and proportion of gliadin and glutenin proteins. Extensibility and resistance to the extension of doughs which can be measured using the extensigraph or alveograph allow good assesment of the baking behavior under realistic conditions. In our study, we compared the extensigraph and alveograph parameters of 87 flour samples. The results showed that the alveograph parameters were different from the extensigraph parameters. The classification of wheat varieties was different, and the order of varieties, as well. The alveograph properties were affected by other factors than the extensigraph properties, except the W value. The two rheological tests did not give similar results, therefor neither test are replaceable.
The aim of storage after harvest is to protect the quality of wheat, because after-ripening occurs in the first 5–6 weeks. During this time it very important to make the optimal storage conditions.
We have carried out storage experiment with wheat samples from Látókép Research Farm of the University of Debrecen. We analyzed the rheological parameters of Lupus and GK Csillag varieties from the crop year 2011/2012. The experiment period was between July and August 2012 (24. 07. 2012., 31. 07. 2012., 21. 08. 2012.).We determined the rheological parameters (water absorption, dough stability time and valorigraph quality number) of Lupus and GK Csillag during short term storage. Our results showed that after-ripening increased the baking quality of Lupus and GK Csillag during storage.
In present paper we have examined the effect of climatic change on the extensigraph characteristics of wheat-flours. The baking quality
of winter wheat is largely determined by cultivar, but it can be influenced by weather conditions during growing period. Flours were from 5
cultivars grown at one location in three cropping years. We have found that the extensigraph properties of dough are affected by the weather
conditions, nevertheless, different cultivars distinctly react to the increase of temperature and decrease of precipitation. In generally, the
higher average day temperature and lower precipitation level is favourable to produce winter wheat flour with better quality
Near-infrared spectroscopy has many advantages that make it a widely used analitical method in the different areas, like agricultural and food industry as well. In wheat quality control rheological characteristics of dough made from wheat flour are as important as physical and chemical properties too. In this work we examined rheological properties of wheat flour samples by alveograph, and spectral data of the same samples were collected by FOSS Infratec 1241 instrument. Modified partial least squares analyses on NIR spectra were developed for two alveograph parameter (P/L és W) to get calibration equations.
In present paper we have examined the effect of mineral fertilization on the extensograph characteristics of wheat-flours. The baking quality of winter wheat is largely determined by cultivar, but it can be influenced by fertilization. Flours were from 4 cultivars grown at six nitrogen fertilizer. The average flour protein content of cultivars was very different (11.8, 13.0, 14.3, and 13.07%, respectively). We have found that the extensograph
properties of dough are affected by mineral fertilization, nevertheless, different cultivars distinctly react to the increase of fertilizer doses. We estimates the correlation between flour protein content and extensograph properties, based on our investigations, it became obvious that the correlation between flour protein content and extensograph parameters is really strong.
The extensograph is widely used in quality control and research laboratories studying wheat flour quality. The most commonly used measurements include Rm, the maximum resistance (maximum height of the curve); R5 the resistance at a constant extension of 5 cm; E, extensibility (total curve length); Rm/E, the ratio of maximum resistance to extension; and A, the area under curve. The extensograph has proved useful in the classification and assessment of flours on the physical dough properties. Another important application is its use in wheat breeding programs. Furthermore, extensograph is an excellent tool to study the effects of a wide range of ingredients on dough properties of wheat flour (like oxidants, enzymes, salt and additives), and it can also be used measure the changes during the frozen storage. In the present study we provide a review of the scientific literature concerning the possible applications of the extensograph.
Wheat is the major cereal component of bread in the world and is grown worldwide. Of the cereals only the bread wheats – and less the triticale – includes storage proteins that play an important role in the performance of gluten. Proteins of gluten complex may be present in two classes:
− low molecular weight (gliadin-) components, and
− high molecular weight (glutenin-) components.
Gliadins shown appreciable heterogenity and can be separated into 40-50 components with gel electrophoresis. The composition of gliadins is employable for the identification the wheat varieties and to investigate the varieties. In the decreasing electrophoretic mobility sequence may be distinguish α-, β-, γ- and ω-gliadins. A glutenin subunits may be include in two classes:
− high molecular weight glutenin subunits (HMW-GS),
− low molecular weight glutenin subunits (LMW-GS).
Wheat varieties can be identified by glutenin and their quality selection is also possible. The gliadin’s polypeptides encoding genes are located on the short arm of chromosomes 1A, 1B and 1D, 6A, 6B and 6D. Genetic coding for HMW subunits is located on the long arms of chromosomes 1A, 1B and 1D, the LMW-GS are also located on chromosomes 1A, 1B and 1D (Glu-3 loci) near the gliadin-coding loci.
Storage proteins affect the rheological properties of gluten by two factors:
1. The quality and quantity of the protein components of the gluten complex,
2. The interactions between the protein fractions.
Wheat, one of the most important cereals, is grown on the largest area in Hungary. During hydration of storage proteins of wheat – gliadin and glutenin – the gluten complex is evolved. The gliadin is responsible for the extensibility of gluten complex as well as the glutenin for the strength of gluten. The structure, composition and rheological properties of gluten proteins influence significantly the baking quality. The gliadin/glutenin ratio and the quality and structure of glutenin fraction play the most important role in evolving gluten complex. Changes in the steps of breadmaking technology also have effect on the quality of product. Several tests proved that the higher glutenin content increases the strength of dough while the higher gliadin content increases the extensibility of dough and decreases maximum resistance to extension. The monomer gliadins play a great part in plasticity of glutenin polymer. The quality of glutenin fraction significantly influences the evolving gluten complex, because of the spiral structure of glutenin which deforms under stress conditions, then the β-spiral structure resumes their original conformation by releasing from stress.
The final quality of product evolves as a result of complex characteristics of wheat proteins, so detailed knowledge on the roles of different protein compounds is the base of the quality oriented product development.
The principle, development and importance of the SDS-PAGE method are presented in this article. The SDS-PAGE method has become one of the basic methods of molecular biological research, because it is widely applicable and its sensitivity is excellent in the separation of wheat storage proteins.
We have shown the application of this method with a concrete example. It was also tested whether, it was possible to obtain a better baking quality product from a large amount of poor quality less valuable wheat by fractioning the flour according to particle sizes after grinding. We studied the rheological properties of flours with different particle size fractions from the original flour. The baking quality of the original flour was B2. The 125-90 and 90-63 μm fractions have significantly better baking quality (B1) than the original flour. The protein contents of these flour fractions were also significantly higher than the protein content of the original flour. We had a question: what has influenced the baking quality: the protein content or other factors? We searched for an explanation on these results in the protein composition of the flour samples. We studied the distribution of glutenin-fractions by SDS-PAGE method and evaluated them. We found with correlation analysis that the amount of LMW-Glutenin D-group (52-60 kDa) is in a strong, negative correlation to the baking quality (r = – 0.855*). Therefore, the baking quality of flour samples was influenced by this glutenin fraction.