## 3 Results
As with the commercial yogurts, DPPH values did not significantly differ among fruit types. As in Table 5, to facilitate the interpretation of the results, mean values for phenolic compounds concentration, reduction power and free radicals scavenging capacity were calculated based on the type of fruit added to the yogurt and then compared with those of commercially available fruit yogurts (Table 6). The antioxidant activity of both commercial and diet fruit yogurts is presented as means \(\pm\) standard deviation, with statistically significant differences indicated at \(p\)\(\leq\) 0.05. Among the commercial yogurts, the highest antioxidant activity measured by the ABTS method was observed in bilberry yogurts, while the lowest was in strawberry yogurts. These differences were confirmed in the case of TRC analysis. However, no statistically significant differences were found in DPPH radical scavenging activity or reduction power between the different flavors of commercial yogurts (Table 6). Analyzing the antioxidant activity of diet fruit yogurts, as in the case of commercial yogurts, we can see that the highest total content of phenolic compounds was present in bilberry yogurts (0.98 \(\pm\) 0.15 mg GAE/mL) and the lowest in strawberry yogurts (0.66 \(\pm\) 0.03 mg GAE/mL). Comparable differences were seen in reduction power. As with the commercial yogurts, DPPH values did not significantly differ among fruit types. Notably, the highest values for reduction power and ABTS radical scavenging capacity were recorded in natural yogurts enriched with added cornelian cherry (DD) and bilberry (DB). Overall, this simplified analysis suggests that natural yogurts with the addition of thawed fruit generally exhibit higher antioxidant activity than their commercial counterparts containing the same type of fruit. The simplifications used in Tables 5 and 6 are confirmed by the results presented in Table 7, which shows the results of two-way ANOVA analysis for factorial designs. Fruit type, addition, and fruit type x addition were shown to result in statistically significant (\(p<0.001\)) differences in all four determinants of biological activity (i.e., ABTS, DPPH, RP, and TRC). \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Flavor Variant**} & **ABTS** & **DPPH** & **RP** & **TRC** \\  & **[\% RSA]** & **[\% RSA]** & **[**\% RSA]** & **[mg GAE/mL]** \\ \hline S & 65.12 \(\pm\) 10.12 ** & 59.49 \(\pm\) 20.95  & 0.65 \(\pm\) 0.27  & 1.48 \(\pm\) 0.13  \\ C & 72.22 \(\pm\) 7.92  & 60.95 \(\pm\) 20.04  & 0.63 \(\pm\) 0.28  \\ B & 78.89 \(\pm\) 8.90  & 63.75 \(\pm\) 20.62  & 0.58 \(\pm\) 0.23  \\ DS & 66.08 \(\pm\) 2.51  & 87.68 \(\pm\) 1.10 [ENDFOOTNOTE] & 0.39 \(\pm\) 0.06  & 0.66 \(\pm\) 0.03  \\ DC & 76.14 \(\pm\) 5.57  & 89.55 \(\pm\) 0.82  & 0.58 \(\pm\) 0.14  & 0.70 \(\pm\) 0.06  \\ DB & 92.61 \(\pm\) 3.19  & 84.33 \(\pm\) 4.71 [ENDFOOTNOTE] & 1.64 \(\pm\) 0.86  & 0.98 \(\pm\) 0.15  \\ DD & 90.79 \(\pm\) 5.05  & 88.03 \(\pm\) 1.22 [ENDFOOTNOTE] & 1.05 \(\pm\) 0.42 [ENDFOOTNOTE] & 0.93 \(\pm\) 0.17 [ENDFOOTNOTE] \\ \hline \hline \end{tabular}
\end{table} 
Table 6: The effect of the type of fruit additive on the antioxidant activity of commercial and diet yogurts. \begin{table}
\begin{tabular}{c c} \hline \hline
**Effect** & \(p\) \\ \hline Type of fruit & *** \\ Addition & *** \\ Type of fruit \(\times\) addition & *** \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Basic technological parameters characterizing the tested yoghurts. The addition of fruit to natural yogurts did not significantly affect the number of bacteria of the genus _Streptococcus_ (Table 8). Similar results were observed for the genus _Lactobacillus_ but this only applied to yogurts with the addition of bilberries and cherries. In the case of the addition of cornelian cherry and strawberries, significantly smaller numbers of _Lactobacillus_ bacteria were found when compared to natural yogurt.