# Possibility of Using Fermented Curly Kale Juice to Manufacture Feta-Type Cheese
## 3 Results and Discussion
### Milk Clotting Ability of Fermented Curly Kale Juice
The dry matter content of the obtained cheese at the start of ripening was \(58.31\pm 0.96\) and decreased to \(55.28\pm 0.32\) throughout ripening. The decrease in the dry matter may have been a consequence of migration of various compounds from the cheese matrix to the brine. This involves breaking the peptide bonds and extended proteolysis [34]. An opposite tendency was reported for the salt content, which increased dramatically as the cheese was ripening (Table 2). In line with our findings, [PERSON] et al. [35] and [PERSON] et al. [36] also demonstrated a similar increasing trend in the salt content during ripening of Feta (4.5% of fw after 60 days) and Siahmazi cheese (up to 6.49% of fw after 120 days). This salt level is probably related to the fact that when cheese is placed in brine, a dynamic process of diffusion of NaCl molecules occurs in the face of the osmotic pressure difference between the brine and cheese. Similarly, an increase in the fat content in the Feta-type cheese was also observed after the ripening process (from \(49.60\pm 0.48\) to \(52.44\pm 0.33\) of dw). Similarly, [PERSON] et al. [37] also reported an increase in the fat content after 50 days of maturation of white cow cheese, which was probably due to the high salt content and the loss of water from the cheese matrix. The most difficult task in the functional cheese production is survival of bacteria during the long ripening period. Therefore, \(10^{6}\) CFU per milliliter or gram is the most widely accepted minimum concentration of probiotic bacteria in food [38]. After the first manufacture day, the level of LAB was found to be \(7.25\pm 0.24\) log CFU/g, which significantly increased (\(7.8\pm 0.15\) log CFU/g) after the ripening period. Similarly, other researchers [39; 40] reported a population of lactobacilli species after ripening of approx. 8 log. On the other hand, in this same study [39], the authors reported reduction in the lactobacilli numbers after 30 days of ripening, which may be due to the development of adverse conditions of their growth. \begin{table}
\begin{tabular}{c c c} \hline \hline  & \multicolumn{2}{c}{**Analyzed Manufacture Stage**} \\ \cline{2-3}  & **Cheese before Ripening** & **Cheese after Ripening** \\ \hline _Physico-chemical composition_ & & \\ pH & \(6.73\pm 0.01\)b & \(5.3\pm 0.05\)a  \\ Dry matter (\%) & \(58.31\pm 0.96\)b & \(55.28\pm 0.32\)a  \\ Lactose (\% of dw) & \(2.41\pm 0.11\)b & \(0.00\pm 0.00\)a  \\ Protein (\% of dw) & \(25.69\pm 0.33\)b & \(19.61\pm 0.97\)a  \\ Salt (\%of dw) & \(0.67\pm 0.08\)a  & \(4.98\pm 0.72\)b  \\ Fat (\% of dw) & \(49.60\pm 0.48\)a  & \(52.44\pm 0.33\)b  \\ _Microbiological analysis_ & & \\ Log (CFU/g) & \(7.25\pm 0.24\)a  & \(7.8\pm 0.15\)b  \\ _Color parameter_ & & \\ \(L^{*}\) & \(88.55\pm 0.35\)a  & \(89.42\pm 0.27\)b  \\ _a_* & \(-1.89\pm 0.04\)a  & \(-1.77\pm 0.02\)b  \\ _b_* & \(17.27\pm 0.48\)b  & \(15.03\pm 0.19\)a  \\ _c_* & \(17.37\pm 0.48\)b  & \(15.14\pm 0.18\)a  \\ _b_* & \(95.90\pm 0.13\)a  \\ _Textural properties_ & Hardness (N) & \(6.01\pm 0.31\)b  & \(4.50\pm 0.01\)a  \\ Fracturability & \(7.89\pm 1.26\)b  & \(5.75\pm 0.29\)a  \\ Springiness & \(0.81\pm 0.01\)a  & \(0.87\pm 0.04\)b [FOOTNOTE:a]Footnote a: The results are given as mean values \(\pm\) standard deviation. The uppercase letters (a,b) in the same row express significant differences (\(p<0.05\)) between the cheese samples for the measured parameter. fw—freshColor is one of the most important features defining the quality of edibles. Changes in color parameters during ripening are caused by different factors such as acidification, dehydration and oxidation processes. In our study of the instrumental color parameters, lightness (L*) increased in a statistically significant way (\(p<0.05\)) throughout the ripening process and a similar trend was observed for redness (a*). The negative value obtained for the parameter a* demonstrated that green was prevalent for both cheeses with a final value of \(-1.77\pm 0.02\).