## 4 Discussion
### Physic-Chemical Composition  
The higher syneresis of both buffalo and sheep curd from kiwi extract was responsible for the higher dry matter of these cheeses compared to those obtained by calf rennet (Table 2). Thus, the higher content of lipids and ashes in BM-K and in SM-K are due to a \"concentration\" effect. However, the cheese protein content was not affected by the type of coagulant used. This could be due to the higher proteolysis of cheeses obtained with kiwi extract, which produces small peptide fragments (5b), which, in turn, are soluble in whey, thus offsetting the wider syneresis of these kinds of cheeses.  
The level of carbohydrates was expected to be lower in cheeses from kiwifruit, as these lose whey to a higher extent. In reality the level was higher than expected, perhaps because kiwi extract provided some sugars.  
The mineral composition was in line with [PERSON] et al. [34] (Table 2). In spite of the wider syneresis of cheeses from kiwi and their solubility in water, except for sodium, none of the coagulants affected the mineral content of the cheese. Again, these minerals came to some extent from the kiwifruit extract. The fact that calcium was affected by the cheesemaking procedure is difficult to explain, as it is present in milk in three different forms: ionic, soluble as calcium phosphate and colloidal in apatite bridges within casein micelle.  
The kind of coagulant affected the sodium content of the cheeses. In fact, cheeses produced by kiwifruit extract showed the lowest sodium amount. Calf rennet is rich in sodium chloride and sodium  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & \multirow{2}{*}{**Kiwi**} & \multicolumn{6}{c}{**Buffalo**} & \multicolumn{6}{c}{**Sheep**} \\ \cline{3-10}  & & \(\mathbf{BM_{C}}\) & \(\mathbf{BM_{K}}\) & SEM & \(\mathbf{S}\) & \(\mathbf{SM_{C}}\) & \(\mathbf{SM_{K}}\) & SEM & \(\mathbf{S}\) \\ \hline
**Others** & & & & & & & & & \\
2-ethyl-hexyl tert-butyl ether & - & 1.44 & 1.92 & 0.28 & ns & 1.28 & 0.96 & 0.21 & ns \\ Dimethyl disulfide & - & 0.57 & 0.95 & 0.24 & ns & - & - & - & - \\
2 ethyl hexyl chloroformate & - & 2.95 & 6.15 & 2.80 & ns & 2.81 & 3.61 & 0.83 & ns \\ a-ethyl-furan & 8.12 & - & - & - & - & 0.42 & 0.33 & 0.09 & ns \\ m-d-tert-butyl-benzene & - & 0.26 & 0.45 & 0.09 & ns & 0.71 & 0.60 & 0.15 & ns \\ Ethykneanol & 4.83 & - & - & - & - & - & - & - & - \\
1-cyclopropyl pentane & 2.33 & 0.23 & 0.22 & 0.04 & ns & 0.39 & 0.33 & 0.05 & ns \\
1-hexyl-2-methylcyclopropane & 1.78 & 0.42 & 0.44 & 0.10 & ns & 0.40 & 0.23 & 0.03 & ns \\ Ethyl benzene carboxylate & 3.88 & - & - & - & - & - & - & - \\ _Total_ & _20.94_ & _5.85_ & _10.11_ & _2.48_ & _ns_ & _6.01_ & _6.06_ & _1.13_ & _ns_ \\ \hline
**Total VOCs** & 893.34 & 117.85 & 129.34 & 15.61 & ns & 130.88 & 143.55 & 11.91 & ns \\ \hline BMC, buffalo– calf rennet cheese; BMK, buffalo–kiwifruit cheese; SMC, sheep–calf rennet cheese; SMK, sheep–kiwifruit cheese; SEM, standard error medium; S, significance; ns, not significant; ne, not estimable. *: 0.01 \(<P<\) 0.05; **: 0.01 \(<P<\) 0.001; **: \(>\) 0.001; & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 4: _Cont._benzoate, which are added as a preservative, thus partially explaining the different amount of sodium in the cheeses.  
The different proteolytic activity of the two kinds of coagulant may explain the differences in colour of the cheese. In fact, both the lower lightness and the higher yellow index, might be related to the occurrence of proteolysis, which, in turn, is related to cheese browning [35]. Is worth noting that the colour differences between two coagulants were detectable only using instruments, as the total colour differences (\(\Delta\)E) were much lower than 3, which is the discrimination threshold for the human eye [19].