## 3 Results and Discussion
### Yoghurt Total Phenolic Content and Antioxidant Profile  
Highly significant differences (\(p<0.001\)) were found in yoghurt total phenolic content between the treatments (Table 8). In general, the total phenolic content of orange peels is affected by the treatment applied for extraction [78]. Yoghurt produced from milk from ewes on the POP treatment had a significantly lower phenolic content than yoghurt from the Control and the UOP treatment. This finding indicates that enzymatic hydrolysis of the orange peels (POP treatment) affected the content of phenolic compounds. On the other hand, the lack of difference between yoghurt from the Control and the UOP treatment shows that replacement of concentrates with orange peels did not negatively affect the total phenolic content of the feed, although differences in the content of individual phenolic compounds might have existed due to the inclusion of the orange peel ingredient. However, there were no significant differences (\(p>0.05\)) in the total antioxidant capacity (ABTS), free radical scavenging activity (DPPH), and the ferric reducing power activity (FRAP) between the treatments (Table 8), showing that the inclusion of orange peels in the diets of lactating ewes did not result in differences in the antioxidant capacity of the produced yoghurt in relation to samples from ewes on the conventional diet. The antioxidant properties of the samples were assessed using two different types of methods. The Folin-Ciocalteu and the FRAP tests are based on the transfer of one electron, whereas the ABTS and DPPH tests are based on the transfer of both a hydrogen atom and an electron. Furthermore, the Folin-Ciocalteu and the FRAP tests measure hydrophilic antioxidants, while the ABTS test can measure both hydrophilic, and lipophilic antioxidants, and the DPPH hydrophilic antioxidants [79]. Additionally, [PERSON] et al. [80] reported that a thorough understanding of the antioxidant properties of dairy products requires the use of multiple analytical methods, since different components, such as caseins and lipids, have a different sensitivity to different methods. The lack of standardisation among different methods for assessing the antioxidant properties of milk and dairy products was also highlighted by [PERSON] et al. [81] in their recent review. Therefore, the different mechanisms employed by each assay are related to the variations in the expression of the antioxidant activity between the different methods and within samples of the same treatment. It should be noted that the suitability of each assay for determining the antioxidant capacity of dairy products needs further investigation. The antioxidant capacity of dairy products depends on components such as sulphur amino acids, whey proteins (particularly \(\beta\)-lactoglobulin), vitamins A, E, and C, carotenoids, zinc, selenium, enzyme systems, superoxide dismutase, catalase, glutathione peroxidase, milk oligosaccharides, and peptides that are produced during fermentation. Furthermore, \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Index**} & \multicolumn{4}{c}{**Treatment**} \\ \cline{2-6}  & **Control** & **UOP** & **POP** & **SEM** & **Significance** \\  & **(n = 4)** & **(n = 4)** & & & \\ \hline TPC \({}^{1}\) (mg GAE/g) & 0.038 b & 0.035 b & 0.026 a & 0.012 & *** \\ ABTS \({}^{2}\) (\(\mu\)M TE/g) & 102.433 & 96.433 & 97.767 & 1.599 & NS \\ DPPH \({}^{3}\) (\(\mu\)M TE/g) & 23.492 & 20.506 & 22.436 & 0.661 & NS \\ FRAP \({}^{4}\) (\(\mu\)M TE/g) & 66.260 & 84.027 & 71.460 & 6.283 & NS \\ \hline \hline \end{tabular}  
* UOP = unprocessed orange peel; POP = processed orange peel; 1 = total phenolic content (TPC); 2 = total antioxidant capacity; 3 = free radical scavenging activity; 4 = ferric reducing antioxidant power; *** = \(p<0.001\); NS = non-significant; superscripts a, b differ at \(p<0.05\).  
\end{table} 
Table 8: Yoghurt total phenolic content and antioxidant profile.