## 4 Discussion
These compounds possess an olefinic double bond of the cis type or are structurally similar to them [50; 51; 52]. Unlike other disaccharides, trehalose is characteristic for these complexations due to its specific structure, which enables the aromatic rings of compounds to approach the dehydrated, hydrophobic pocket of trehalose, causing the formation of a complex [52]. Alginate/pullulan hydrogels had the highest concentration of individual anthocyanins, followed by alginate/trehalose and alginate/pullulan/trehalose hydrogel beads; however, antioxidant activities evaluated by CUPRAC and FRAP methods were the highest for alginate/pullulan, lower for alginate/pullulan/trehalose, and significantly lower for alginate/trehalose hydrogel beads. In comparison to alginate/pullulan hydrogel beads, alginate/trehalose beads had lower concentrations of neochlorogenic acid and quercetin-3-rutinoside. In alginate/pullulan/trehalose hydrogels, in comparison to the other two above-mentioned samples, chlorogenic acid was present at a higher concentration than neochlorogenic acid, so it probably compensated for the loss of antioxidant activity caused by lower anthocyanin and quercetin-3-rutinoside concentrations. Interestingly, alginate/pullulan/sucrose hydrogel beads also had a higher concentration of chlorogenic acid than neochlorogenic acid, but, due to the fact that this sample had the lowest concentration of anthocyanins, it can be deduced that this was the reason for the lowest antioxidant activities evaluated by the CUPRAC and FRAP methods. Interestingly, alginate/sucrose had the highest antioxidant activity determined by DPPH, followed by alginate/pullulan hydrogel beads, regardless of the fact that alginate/sucrose hydrogel beads had lower concentrations of all phenolics, except neochlorogenic acid, than alginate/pullulan hydrogel beads. One reason could be that neochlorogenic acid had higher antioxidant potential than chlorogenic acid [53]; thus, it contributed to the overall potential. Another reason could be the synergistic effect between phenolic compounds. Synergism or antagonism was also observed in alginate/pullulan/sucrose and alginate/trehalose hydrogel beads, with both having the same antioxidant activity determined by the DPPH assay. This trend was noted regardless of the fact that alginate/trehalose beads contained higher concentrations of anthocyanins than alginate/pullulan/sucrose hydrogel beads, but at the same time, this sample had a higher concentration of neochlorogenic acid than chlorogenic acid, whereas in alginate/pullulan/sucrose beads, the reverse trend was observed. When applying the ABTS assay, the highest antioxidant activity was determined for alginate/pullulan hydrogel beads, followed by alginate/trehalose and alginate/pullulan/trehalose hydrogel beads, i.e., results followed concentrations of individual anthocyanins. The lowest values were determined for alginate/trehalose and alginate/pullulan/sucrose hydrogel beads, again emphasizing the importance of synergistic or antagonistic effects between compounds. The results for antioxidant activity differ among samples, and different trends were achieved for each sample with different methods. One of the most important characteristics of phenolics is their antioxidant activity. It highly depends on their chemical structures, but other factors are also important, such as the ratio between them, the presence of other compounds, and the interactions between these compounds and phenolics. Methods differ from each other based on mechanisms of action. The mechanisms of action of the DPPH and ABTS methods involve reactions between H atom donors and the corresponding free radicals, DPPH and ABTS\({}^{+}\). Even though these mechanisms are similar, the obtained results are different, as, in many other studies, the ABTS method usually generates higher values [54]. Our results for antioxidant activity determined by the ABTS assay were higher than for DPPH results, with the exception of alginate/trehalose and alginate/pullulan/sucrose hydrogel beads.