Changes of physical properties of wheat gluten an starch as a function of removing some attending substances
1998
Nierle, W. | Kersting, H.-J. | Burmann, I.
Gluten and starch, the main components of a dough were extracted with different solvents and conditions, without heat or mechanical denaturation. By removing substances, especially lipids and lipoproteins, physical properties of gluten and starch are altered. Solubility, water absorption capacity and rheological properties of ethanol extracted gluten were changed as a function of different conditions of extraction. Extracting the lipids of starch alterations of the kernel starchsurface properties can be observed by TEM. Most changes of physical properties become evident above all when starches are gelatinized by heating. But this behaviour is not important for binding starch and gluten during dough kneading. Intensive extraction of lipid substances from gluten leads to an enhanced waterbinding capacity, but at the same time the ability to form a homogenous wet gluten structure is diminished. Rheological studies in ethanol-water slurries point to variations in viscosity behaviour. For physical and microscopical studies doughs of gluten-starch mixtures were prepared from gluten, differently extracted starches and water soluble substances. Freshly prepared flour extract was added to dry mixtures (82 % starch, 18% gluten) and the dough system was characterized in a mixograph and in a rotation viscosimeter. Doughs prepared with same amounts of extract showed differences in kneading and viscosity properties. In general, the extraction of lipids from gluten influenced dough properties in a higher degree than extraction of starch. More intensive extraction of gluten causes disturbance of dough structure. A certain restoration of viscoelastic properties of dough is attainable by adding more water soluble substances.
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