# Chemical-Sensory Traits of Fresh Cheese Made by Enzymatic Coagulation of Donkey Milk
## 3 Results and Discussion
For interpreting the gel, the works of [PERSON] et al. (2012) on donkey milk, and of [PERSON] et al. (2019, 2020) on equine caseins in buffered solutions, were considered. By comparing the urea-PAGE patterns of milk and cheese (Figure 3), it was evident that some new bands appeared after 24 h from cheesemaking. In the upper zone of the gel, the intensity of several bands strongly increased in cheese: they should correspond to \(\gamma\)-casein-like fragments deriving from \(\beta\)-caseins. In the central area, five new bands appeared: for those coded \(\mathrm{x}_{1}\) and \(\mathrm{x}_{2}\), no possible correspondence was found in the literature, whereas those coded \(\mathrm{x}_{3}\), \(\mathrm{x}_{4}\) and \(\mathrm{x}_{5}\) laid in the same zone of \(\beta\)-I- and \(\beta\)-II-caseins-like fragments. Finally, the diffuse band positioned in the lower zone (coded \(\mathrm{x}_{6}\) and probably composed of two or three overlapping bands), could correspond to proteose-peptone-like fragments deriving from \(\beta\)-casein, or to fragments with high electrophoretic mobility deriving from \(\alpha\)s1-casein. Considering that the cheese was analysed at 24 h after production, it is likely that these fragments derive from the activity of microbial rennet, which is able to hydrolyse all casein fractions in very short time ([PERSON], 2017). Due to scarce resolution of whey proteins in the urea-PAGE system, SDS-PAGE was used for analysing the whey samples ([PERSON], 2017). The patterns of isoelectric and cheese whey were very similar, except for the total absence of residual casein in the latter (Figure 4). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Compoun.d. ** & & **Donkey** & & **Cow (Control)** \\ \hline \multicolumn{4}{c}{Aldehydes} \\ diacetyl (2,3-butananedione) & n.d. & n.d. & n.d. & \(27.35\pm 2.70\) \\ hexanal & n.d. & n.d. & \(1.04\pm 0.05\) b & \(5.33\pm 0.19\) a  \\ heptanal & n.d. & n.d. & \(0.27\pm 0.07\) b  & \(1.02\pm 0.10\) a  \\ octanal & n.d. & n.d. & \(0.48\pm 0.13\) b  & \(1.77\pm 0.51\) a  \\ nonanal & \(0.02\pm 0.01\) d  & \(0.39\pm 0.08\) c  & \(3.22\pm 1.26\) b  & \(17.97\pm 3.97\) a  \\ decanal & n.d. & n.d. & \(2.05\pm 1.11\) & \(2.54\pm 0.33\) \\
2-methylbutanal & \(0.08\pm 0.01\) & \(8.79\pm 0.37\) & n.d. & n.d. \\
3-methylbutanal & n.d. & \(0.15\pm 0.01\) & n.d. & \(63.66\pm 0.29\) \\
2-ethylhexanal & \(0.09\pm 0.11\) & \(0.71\pm 0.02\) & n.d. & n.d. \\ _Esters_ & & & & \\ ethylacetate & \(0.09\pm 0.01\) b  & \(0.08\pm 0.03\) b  & n.d. & n.d. & \(17.83\pm 5.72\) a  \\ \(1\)-butanol-3-methyl-acetate & n.d. & n.d. & n.d. & \(1.03\pm 0.58\) \\ _Ketones_ & & & & \\ acetone & \(2.84\pm 0.03\) c  & \(0.65\pm 0.01\) d  & \(59.11\pm 9.11\) a  & \(31.55\pm 0.29\) b  \\ \(2\)-butanone & \(0.03\pm 0.01\) d  & \(0.14\pm 0.02\) c  & \(4.21\pm 1.21\) b  & \(13.78\pm 2.85\) a  \\ \(2\)-heptanone & \(0.09\pm 0.02\) d  & \(0.37\pm 0.01\) c  & \(4.81\pm 0.93\) b  & \(16.09\pm 3.74\) a  \\ \(3\)-heptanone & \(0.07\pm 0.01\) & n.d. & n.d. & n.d. \\
2-un.d.ecanone & & & & n.d. \\
3-hydroxy 2-butanone & & & & \\ (acetoin) & \(0.07\pm 0.02\) c  & \(11.93\pm 0.04\) b  & n.d. & \(91.71\pm 23.70\) a  \\ \(6\)-methyl-5-hepten-2-one & \(0.15\pm 0.04\) d  & \(0.38\pm 0.05\) c  & \(0.88\pm 0.29\) b [FOOTNOTE:b]Footnote b: Values in the same row bearing different superscripts (a,b,c,d) are significantly different, \(p<0.05\Table 5 and Figure 5 show the results of the sensory analyses. The restricted list of descriptors and the corresponding reference products that were developed for the experimental and control cheeses are shown in Table 5. For the former, 9 descriptors were selected from a pool of 13 initial attributes, 3 of which regarded texture, 3 aroma, 2 taste and 1 colour. The term \"gamy\" was adopted to indicate the typical animal odour of donkey milk. For the control, the descriptors were mostly different (10 developed). The colour was white in both cases, but with different gradations. The texture was very close to that of fresh Feta cheese for donkey, and to that of Edam cheese for cow.