## 3 Results and Discussion
### Thermogravimetric Analysis (TGA)
The first peak (T\({}_{\rm d1}\)), localized in the temperature range of 50-150 \({}^{\circ}\)C, is related to the loss of free and bound water by the sample as a result of sample heating [18]. In the case of gliadins and glutenins samples, the value of this degradation temperature was not shifted after polyphenol addition. This suggests that polyphenols did not interact with water during dough mixing. Similar results concerning this peak were obtained for the gluten network modified by the same polyphenols [10], dietary fiber preparations [19], and fiber polysaccharides [8; 20]. The second peak (T\({}_{\rm d2}\)) is related to the degradation of gluten proteins. In the case of gliadins, this peak is localized at 310 \({}^{\circ}\)C. Interactions between gliadins and the polyphenols induced a shift of this peak to 319 \({}^{\circ}\)C. An increase in the degradation temperature (T\({}_{\rm d2}\)) indicates that the gliadin-polyphenyl complex is more thermally stable than gliadin alone. The temperature T\({}_{\rm d2}\) for glutenins was observed at 301 \({}^{\circ}\)C, and it did not change in the presence of flavonoids/glycos. This indicates that glutenins do not interact with polyphenols. The lower degradation temperature of glutenins compared to gliadins suggests that glutenins are less thermally stable than gliadins. On the other hand, the gluten network, which is a mixture of gliadins and glutenins, is the most thermally stable among these proteins because its degradation temperature is ca. 320 \({}^{\circ}\)C [10]. The present results contradict the assumption of [PERSON] et al. [18] that the thermal properties of the gluten network in dough are connected with glutenins. The present results may also provide an explanation as to why the dough breakdown phenomenon was observed during the mixing process of wheat dough modified by small-sized polyphenols, e.g., phenolic acids [12]. A comparison of changes in the secondary structure of the gluten network between samples taken before dough breakdown and at the end of mixing showed slight differences, probably because phenolic acids interacted with gliadins, not glutenins. Interactions between gliadins and phenolic acids, as changes in the secondary and tertiary structure of gliadins, were also observed by [PERSON] et al. [21]. Additionally, difference TGA thermograms were calculated to describe differences in the thermal behavior of gliadin/glutenin-flavonoid/glycoside complexes in more detail. The difference thermograms are presented in Figures 1 and 2 for gliadins and glutenins, respectively. The TGA thermograms of gliadin samples show two peaks--negative and positive. The negative peak is located at ca. 293 \({}^{\circ}\)C and is probably connected with gliadin degradation. [PERSON] et al. [9] also observed one negative peak for all gluten samples modified by oil pomaces in the difference thermograms that was located at ca. 305 \({}^{\circ}\)C. The positive peak is observed at a different temperature depending on the phenolic compound used and its concentration. In the case of QUE, the positive maxima are observed at 370, 323, and 337 \({}^{\circ}\)C for a 0.05%, 0.1%, and 0.2% QUE concentration, respectively. The peak at 337 \({}^{\circ}\)C can be assigned to the degradation of free QUE, because a similar peak is observed in Figure S2g for free QUE. The peak at 370 \({}^{\circ}\)C can be connected with the gliadin-QUE complex because a shoulder at a similar temperature is observed for higher QUE concentrations. The peak at 322 \({}^{\circ}\)C is also observed for the gliadin-RUTG samples. These observations suggest that QUE can interact with gliadins through OH groups localized at different positions, whereas RUTG forms chemical bonds with the gliadin proteins through precisely defined OH groups due to the presence of the glycosidic part. Similar assumptions to RUTG can be made for HEDG. Thermograms of gliadin-HEDG samples show one peak at 333 \({}^{\circ}\)C, whereas peaks at 342 and 371 \({}^{\circ}\)C were observed for samples modified by HET.