## 3 Results and Discussion
### Antioxidant Activity of Yogurts during 21 Days of Storage  
Figure 4a-c show the antioxidant activity of the yogurts stored for 21 days in refrigeration conditions. In general, regardless of the determination method used (FRAP, DPPH, ABTS), the antioxidant status of the EY samples was significantly higher than in the control group. A significant increase in their antioxidant activity was noted during the first two weeks of storage (until day 14). In comparison to day 0, the activity of the EY samples determined using the DPPH and ABTS assays increased by approximately 30%, i.e., from 2.85 to 3.62 mg Trolox/100 mL and from 5.97 A to 7.86 mg Trolox/100 mL, respectively. The iron ion reducing power (FRAP) also increased by 15%, i.e., from 21.57 to 24.32 mg Trolox/100 mL. Similar changes were recorded in the group of the CY samples. In the consecutive week of storage, the antioxidant potential of the yogurts declined. On day 21, the EY samples had a significantly (\(p\leq 0.01\)) lower (by approx. 15%) free radical scavenging capacity (ABTS and DPPH assays) and iron ion chelation capacity (FRAP) compared to day 14. The decrease in the antioxidant activity of the CY samples was higher, i.e., 20%. The \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Yogurt** & **Day of Storage** & \
\begin{tabular}{c} **Water** \\ **Activity** \\ \end{tabular} &
\begin{tabular}{c} **Total Protein** \\ **(\%)** \\ \end{tabular} & **Fat (\%)** & **Dry Matter (\%)** \\ \hline \multirow{4}{*}{CY} & 0 & 0.939 \(\pm\) 0.007 & 3.46 \({}^{\mathrm{b}}\)\(\pm\) 0.19 & 4.27 \(\pm\) 0.17 & 12.33 \({}^{\mathrm{B}}\)\(\pm\) 0.19 \\  & 7 & 0.942 \(\pm\) 0.006 & 3.44 \({}^{\mathrm{ab}}\)\(\pm\) 0.11 & 4.23 \(\pm\) 0.11 & 12.25 \({}^{\mathrm{B}}\)\(\pm\) 0.26 \\  & 14 & 0.954 \(\pm\) 0.011 & 3.38 \({}^{\mathrm{ab}}\)\(\pm\) 0.14 & 4.19 \(\pm\) 0.14 & 12.06 \({}^{\mathrm{AB}}\)\(\pm\) 0.28 \\  & 21 & 0.960 \(\pm\) 0.008 & 3.25 \({}^{\mathrm{a}}\)\(\pm\) 0.16 & 4.16 \(\pm\) 0.15 & 11.58 \({}^{\mathrm{A}}\)\(\pm\) 0.31 \\  & 0 & 0.943 \(\pm\) 0.010 & 3.52 \({}^{\mathrm{b}}\)\(\pm\) 0.13 & 4.30 \(\pm\) 0.09 & 12.38 \({}^{\mathrm{B}}\)\(\pm\) 0.25 \\  & 7 & 0.949 \(\pm\) 0.007 & 3.49 \({}^{\mathrm{ab}}\)\(\pm\) 0.16 & 4.28 \(\pm\) 0.11 & 12.31 \({}^{\mathrm{B}}\)\(\pm\) 0.20 \\  & 14 & 0.955 \(\pm\) 0.009 & 3.42 \({}^{\mathrm{ab}}\)\(\pm\) 0.10 & 4.25 \(\pm\) 0.12 & 12.15 \({}^{\mathrm{B}}\)\(\pm\) 0.29 \\  & 21 & 0.961 \(\pm\) 0.012 & 3.30 \({}^{\mathrm{a}}\)\(\pm\) 0.15 & 4.20 \(\pm\) 0.10 & 11.66 \({}^{\mathrm{A}}\)\(\pm\) 0.17 \\ \hline \hline \end{tabular}  
* CY—control yogurts; EY—experimental yogurts; \({}^{\mathrm{AB}}\)—significant differences at \(p\leq 0.05\); \({}^{\mathrm{A,B}}\)—significant differences at \(p\leq 0.01\).  
\end{table} 
Table 3: Water activity and basic chemical composition of yogurts during 21 days of storage (mean \(\pm\) SD). literature does not provide reports on the use of milk by cows receiving herb-supplemented fodder for yogurt production. In turn, there are many literature reports [55; 56; 57; 58; 59; 60; 61; 62; 63; 64; 65; 66; 67] on the use of various additives as natural sources of antioxidants in the manufacture of yogurts. Enriched yogurts have been shown to have higher antioxidant activity than natural (control) products throughout the storage period. [PERSON] et al. [68] reported a significant effect of the addition of green, white, and black tea on the antioxidant activity (FRAP, DPPH) of yogurts during 21-day refrigerated storage. Additionally, the addition of extracts from red ginseng (_Panax ginseng_) [69] or blackberry flowers (_Rubus unlitigluins_) [70] may increase the antioxidant capacity of yogurts. In the present study, the EY yogurts exhibited higher antioxidant activity than the CY samples during the 21-day storage period.