## 3 Results and Discussion
### Physicochemical Properties of the Obtained Fermented Whey Beverages
These data are in alignment with previous findings, highlighting the influence of fruit juice addition on beverage quality, as found by [PERSON] et al. [49]--in milk fermentation with _Lactobacillus_ strains, pH reduction was also observed with lactic acid production, increasing the acidity of the final product. According to [PERSON] et al. [41], the addition of acidic fruit juices containing sourspo to whey protein isolate emulsions also decreased the pH values and the degree of acidity. The titratable acidity, expressed in Soxhet-Henkel degrees (\({}^{\circ}\)SH), provides a measure of the total acid content in the beverages. Soxhet-Henkel degrees (\({}^{\circ}\)SH) represent the total titratable acidity, which in whey-based fermented beverages reflects the presence of organic acids formed during fermentation and the release of free fatty acids (FFA) through \begin{table}
\begin{tabular}{c c c} \hline
**Fermented Drink** & **pH \(\pm\) SD** & **Titratable Acidity [\({}^{\circ}\)SH] \(\pm\) SD** \\ \hline SKKr/R & 3.90 g \(\pm\) 0.01 & 116.25 j \(\pm\) 1.25 \\ \hline SSKr/R & 3.98 h \(\pm\) 0.02 & 135.00 \(\pm\) 1.25 \\ \hline SSK/R & 3.84 f \(\pm\) 0.01 & 109.58 i \(\pm\) 0.72 \\ \hline SKK/R & 3.82 e \(\pm\) 0.01 & 127.08 k \(\pm\) 0.72 \\ \hline SSKr/DR & 2.91 a \(\pm\) 0.01 & 79.58 h \(\pm\) 0.72 \\ \hline SSK/DR & 2.98 b \(\pm\) 0.01 & 62.92 e \(\pm\) 0.72 \\ \hline SKKr/DR & 3.09 c \(\pm\) 0.01 & 58.75 d \(\pm\) 1.25 \\ \hline SKK/DR & 2.90 a \(\pm\) 0.01 & 71.67 f \(\pm\) 1.91 \\ \hline SSKr/NP & 4.19 i \(\pm\) 0.01 & 24.65 b \(\pm\) 0.35 \\ \hline SKKr/NP & 3.60 d \(\pm\) 0.00 & 52.63 c \(\pm\) 0.09 \\ \hline SSK/NP & 4.31 j \(\pm\) 0.02 & 21.00 a \(\pm\) 0.00 \\ \hline SKK/NP & 3.61 d \(\pm\) 0.01 & 76.00 g \(\pm\) 0.82 \\ \hline \end{tabular} a-1 Statistical differences in the various columns are indicated by different letters (p \(<\) 0.05). SKKr/R—mpasteurized sour cow whey with sea buckthorn juice; SSK/R—mpasteurized sweet cow whey with sea buckthorn juice; SKK/R—mpasteurized sweet goat whey with sea buckthorn juice; SKK/DR—mpasteurized sour cow whey with rosehip juice; SSK/DR—mpasteurized sweet goat whey with rosehip juice; SSK/DR—mpasteurized sweet goat whey with rosehip juice; SSK/DR—mpasteurized sweet goat whey with rosehip juice; SSK/DR—mpasteurized sweet goat whey with rosehip juice; SSK/NR/NP—mpasteurized sweet cow whey; SSK/NR—mpasteurized sweet goat whey; and SKK/NR—mpasteurized sour whey.  
\end{table} 
Table 4: Results of the pH and \({}^{\circ}\)SH measurements of fermented whey beverages with the addition of various fruit juices. enzymatic activity. Fermentation processes and the selection of starter cultures significantly influence FFA levels. For example, _Lactococcus lactis_ subsp. _lactis_ is known to produce higher levels of FFAs, enhancing the sensory and functional properties of whey-based products [50]. Furthermore, recent research highlights that controlled enzymatic activity, such as the use of walnut lipase, can increase conjugated linoleic acid (CLA) content, offering the potential for optimizing whey beverages [51]. The results indicated a wide range of tittatable acidity values, from 21.00 \({}^{\circ}\)SH in the SSK/NP sample to 135.00 \({}^{\circ}\)SH in the SSKr/R sample. The SKKr/R sample, which used unpasteurized sour cow whey with sea buckthorn juice, exhibited high acidity levels, while the SSK/NP sample, with unpasteurized sweet goat whey without fruit juice, exhibited the lowest acidity levels. According to the Polish norm PN-A-86061:2002 [24], the acidity of fermented milk beverages ranges from 25 \({}^{\circ}\)SH to 45 \({}^{\circ}\)SH. In this study, every drink exceeds this reference except for SSK/NP (21.00 \({}^{\circ}\)SH) and SSKr/NP (24.65 \({}^{\circ}\)SH) (control samples). The reason might be that we used the least favorable environment for the starter culture to grow. The elevated \({}^{\circ}\)SH values are most likely due to the addition of very acidic fruit juices.