# Electronic Nose Analysis to Detect Milk Obtained from Pasture-Raised Goats
## 3 Results and Discussion
### Sensory Analysis of Milk  
A sensory analysis on raw bulk milk of each milking period was carried out to verify the olfactory properties that characterised the two types of milk and which allowed their discrimination. The results of the sensory evaluation of milk samples are shown in Figure 2.  
The \"grassy\" and \"sweet aromatic\" descriptors showed a higher level in P milk in almost all periods (from 1 to 5). The first descriptor obtained the highest intensity score in P4 while the second in P3. The other descriptors were more variable between the periods. Considering a bulk milk, the P sample showed a significant sensory difference for \"grassy\" and \"sweet aromatic\" odour descriptors with an increase of 1.4 and 1, respectively. Previously it was reported that milk from pasture-fed goats had a higher intensity of herbaceous odour [35], compared to milk from goats fed in confinement with hay and concentrate. [PERSON] et al. [36] also reported a higher intensity value of \"grass\" and \"plant\" attributes for milk of cows fed with fresh forage than those fed with hay- or silage \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c} \hline \hline
**To** & **From** & **P1** & **P2** & **P3** & **P4** & **P5** & **S1** & **S2** & **S3** & **S4** & **S5** & **Total** & \
\begin{tabular}{c} **Correct** \\ **Response (\%)** \\ \end{tabular} &
\begin{tabular}{c} **Correct Response** \\ **P vs. S (\%)** \\ \end{tabular} \\ \hline P1 & 9 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 & 9 & 100\% & 100\% \\ P2 & 0 & 7 & 1 & 0 & 0 & 1 & 0 & 0 & 9 & 78\% & 89\% \\ P3 & 0 & 0 & 7 & 0 & 0 & 2 & 0 & 0 & 0 & 9 & 78\% & 78\% \\ P4 & 0 & 0 & 0 & 6 & 0 & 0 & 0 & 2 & 1 & 9 & 67\% & 67\% \\ P5 & 0 & 0 & 0 & 7 & 0 & 0 & 0 & 2 & 9 & 78\% & 78\% \\
**S1** & 0 & 0 & 0 & 0 & 9 & 0 & 0 & 0 & 0 & 9 & 100\% & 100\% \\ S2 & 0 & 0 & 0 & 0 & 0 & 5 & 4 & 0 & 0 & 9 & 56\% & 100\% \\ S3 & 0 & 0 & 0 & 0 & 0 & 0 & 1 & 8 & 0 & 0 & 9 & 89\% & 100\% \\ S4 & 0 & 0 & 0 & 1 & 0 & 0 & 0 & 0 & 8 & 0 & 9 & 89\% & 89\% \\ S5 & 0 & 0 & 0 & 0 & 2 & 0 & 0 & 0 & 1 & 6 & 9 & 67\% & 78\% \\ \hline Total & 9 & 7 & 8 & 7 & 9 & 9 & 9 & 12 & 11 & 9 & 90 & **80\%** & **88\%** \\ \hline \hline \end{tabular}  
* P: Pasture milk (green); S: Stall milk (red). Numbers from 1 to 5 indicate the milking period (April 2021 to June 2021; see Table 1 for further details). The last two columns of the table represent, respectively, the % of correct responses recorded for the samples of each milking period and for the overall samples (P vs. S, considering only the animal diet).  
\end{table} 
Table 3: Confusion matrix of the Pasture and Stall goat’s milk samples. -based feeding system. On average, the \"Feed/malty/silage\" descriptor was perceived to be more intense in milk S (+0.6), although the difference was not statistically significant because its level increased only in S2 and S3. Although the chemical composition, and hence the odorous compounds of the milk, undergo changes during lactation [34], one cause of the different perceived intensity of the odour descriptors in the S milk samples of the different periods could be attributed to the diet of stall-fed goats which, in addition to the hay (which had a constant chemical composition during the investigated period), provided for the use of fresh clover that had a variable composition during the three months of the study. Generally, sensory differences related to the odour of preserved feed in milk appear to be greater when comparing a grazing diet versus a diet based on silages [37; 38]. Some volatile compounds may impart a malty odour in milk that resembles that of preserved fodder [39]. [PERSON] et al. [40] reported a higher intensity for the \"cream\" odour attribute in milk from pasture cows compared to those fed with hay. In their study, the \"cream\" attribute was more related to the pasteurisation of milk than the animal diet. In fact, in our study, the difference for the \"Cream\" attribute was not statistically significant as the effect of the animal diet on raw milk samples was evaluated.