## 3 Results and Discussion
### Differential Scanning Calorimetry (DSC)
Hence, it can be claimed that only QUE interacts with gliadins through hydrogen bonds because the addition of this polyphenol causes an increase in the decomposition temperature of the gliadin-QUE samples. A similar assumption was presented by [PERSON] et al. [16], who also observed a shift in the decomposition temperature toward higher temperatures after the addition of hydrochloric and citric acids to gliadin. The authors claimed that modified gliadins contained more chemical bonds than native gliadins and hence formed a more compact structure. The thermal parameters and DSC thermograms of glutenins are presented in Table 2 and Figure S5 in the Supplementary Material, respectively. The addition of flavonoids and glycosides does not affect the decomposition temperature and transition enthalpy for the modified glutenin samples. A lack of changes in the thermal parameters does not mean that the studied polyphenols do not interact with glutenin polypeptide chains. They can interact, but these changes are probably very small. The DSC technique has too low a sensitivity to show these changes, and glutenins form a complex matrix. In previous studies, we observed that unenriched gluten (gliadins and glutenins) had a lower decomposition temperature (283 \({}^{\circ}\)C) than the gliadins and glutenins extracted from it. Additionally, the gluten decomposition process was endothermic, and the enthalpy of this process was 12 J/g (similarly to glutenins extracted from the gluten network) [10]. However, the decomposition temperature of gliadins was higher (308 \({}^{\circ}\)C) compared to gluten and glutenins extracted from it. This indicates the greater thermal stability of the extracted gliadins. Differences in thermal stability between gluten, gliadins, and glutenins extracted from it may result from the ability of each of these objects to form disulfide bonds. The bonds formed between two SH groups (disulfide bridges) are covalent bonds that are difficult to break. Gliadins, due to the small number of cysteine residues in their structure, form significantly fewer SS bonds, and they are mainly intramolecular bonds. Most \(\alpha\)- and \(\gamma\)-gliadins contain six and eight cysteine residues, respectively, and form three or four homologous intrachain SS bonds [27]. Glutenins have more cysteine in their amino acid sequence, which makes them capable of forming many disulfide bonds both intra- and intermolecularly [28]. [PERSON] [29] claims that disulfide bonds increased the resistance of proteins to thermal denaturation. However, temperatures above 55 \({}^{\circ}\)C break these bonds. [PERSON] et al. [30] observed in their research that temperature is one of the factors that reduces the strength of gluten. As a result of temperature increase, disulfide bonds are split and rearranged. The presence of the intrachain disulfide bonds in gliadins may increase the folding of the amino acid chain [31]. Therefore, these bonds may be less accessible, and the temperature needed to break the bonds and decompose gliadins is slightly higher, even though they have fewer SH residues and can form fewer disulfide bonds than glutenins. According to [PERSON] et al. [32], interchain bonds formed by glutenin chains are easier to break than intrachain bonds in gliadins. [PERSON] et al. [33] claims that glutenins are more sensitive to temperature than gliadins. As a result of temperatures above 60 \({}^{\circ}\)C, glutenin undergoes thermal denaturation, and inaccessible SH groups are exposed. At high temperatures, gliadins are capable of forming intermolecular SS bonds. Enriching these proteins with flavonoids and glycosides can lead to the formation of hydrogen bonds between gluten proteins and polyphenols, which are much weaker than disulfide bonds. The authors of Ref. [10] observed the formation of hydrogen bonds between quercetin and tyrosine present in the amino acid sequence of gluten proteins. At the same time, [PERSON] & [PERSON] [34] claimed that polyphenols, thanks to their antioxidant properties, can reduce disulfide bridges.