## 2 Results and Discussion
### Phenolics, Antioxidant Activity and Color of Citrus Fiber/Blackberry Gels
  
\begin{tabular}{l c c c c c} \hline \hline
**Samples** & **TPC** & **PAC** & **DPPH** & **ABTS** & **FRAP** & **CUPRAC** \\ \hline \multicolumn{7}{c}{After preparation} \\ \hline
10\%\_S & 4.652 \(\pm\) 0.005 \({}^{\text{c}}\) & 120.33 \(\pm\) 0.98 \({}^{\text{d}}\) & 197.92 \(\pm\) 1.23 \({}^{\text{d}}\) & 1.054 \(\pm\) 0.038 \({}^{\text{d}}\) & 245.71 \(\pm\) 2.94 \({}^{\text{c}}\) & 148.76 \(\pm\) 0.98 \({}^{\text{d}}\) \\ \hline
20\%\_S & 4.937 \(\pm\) 0.056 \({}^{\text{b}}\) & 129.78 \(\pm\) 0.45 \({}^{\text{c}}\) & 233.91 \(\pm\) 1.47 \({}^{\text{a}}\) & 1.114 \(\pm\) 0.067 \({}^{\text{d}}\) & 253.70 \(\pm\) 0.41 \({}^{\text{b}}\) & 153.71 \(\pm\) 1.21 \({}^{\text{a}}\) \\ \hline
10\%\_T & 4.946 \(\pm\) 0.045 \({}^{\text{b}}\) & 140.46 \(\pm\) 1.11 \({}^{\text{b}}\) & 204.13 \(\pm\) 1.21 \({}^{\text{c}}\) & 1.478 \(\pm\) 0.044 \({}^{\text{b}}\) & 292.29 \(\pm\) 1.10 \({}^{\text{a}}\) & 170.16 \(\pm\) 1.05 \({}^{\text{b}}\) \\ \hline
20\%\_T & 5.233 \(\pm\) 0.044 \({}^{\text{a}}\) & 156.85 \(\pm\) 1.34 \({}^{\text{a}}\) & 216.55 \(\pm\) 1.57 \({}^{\text{b}}\) & 1.526 \(\pm\) 0.099 \({}^{\text{b}}\) & 291.05 \(\pm\) 0.96 \({}^{\text{a}}\) & 170.61 \(\pm\) 1.11 \({}^{\text{b}}\) \\ \hline \multicolumn{7}{c}{After storage} \\ \hline
10\%\_S & 4.133 \(\pm\) 0.044 \({}^{\text{f}}\) & 88.45 \(\pm\) 0 do not have OH groups on the B-ring and aromatic acids that have only one OH group in their structure will not react with DPPH, whereas this is not the case with ABTS [35; 36]. Food is a complex matrix in which various interactions between individual ingredients occur that can lead to increased or decreased antioxidant activity. In general, oxidation of phenolics leads to a reduced antioxidant activity, which can be assumed to have occurred with gels during storage (if the ABTS assay was omitted). Furthermore, some studies suggested that partially oxidized phenolics may show higher antioxidant activity than non-oxidized ones [37; 38; 39; 40; 41]. It can be concluded that the application of different methods for determining antioxidant activity led to different results due to the differences in the selectivity of methods and mechanisms of their action. Color parameters of citrus fiber/blackberry gels after preparation and after storage are presented in Table 7. Taking into account the gels after preparation, the highest value of L* belonged to gels with 10% of sucrose (35.79), and the lowest to gels with 20% of trehalose (32.32). After storage, the L* value increased for all samples, and the highest value was again found in gels with 10% of sucrose (39.02), while the lowest value was found in gels with 20% of sucrose (35.96). The highest a* value in the samples after preparation had a gel with 10% of trehalose (13.50), and the lowest gel with 20% of sucrose (12.14). The value of a* after storage was lower in all gels, which indicated a decrease in the intensity of the red color of samples after storage. In the gels after storage, the highest a* value was found for a gel with 20% trehalose (7.76), and the lowest value for a gel with 20% sucrose (6.72). Low positive values of the b* parameter indicated the presence of a small amount of yellow in the samples after preparation. The results showed that gels with 20% sucrose had the lowest b* value (3.92), and gels with 10% trehalose had the highest (4.33). After storage, there was an increase in b* value in all samples, and the highest b* value was found for a gel with 10% sucrose. The lowest change in b* value was observed for a gel with 20% sucrose. Color changes (\(\Delta\)E) of samples after storage versus samples after the preparation were calculated using the L*, a* and b* values. The largest color change was observed for a gel with 10% sucrose (7.39). The value of *h of samples after preparation ranged from 17.29 to 18.46. It was observed that the *h value increased drastically after storage. Gels with 10% sucrose had the highest *h value both before (18.46) and after storage (45.93).