## 3 Results and Discussion
### Volatile Compounds
In spite of its high presence, previous research has determined that this group is not involved in cooked meat's overall aroma [74] because they have high flavour thresholds that minimal contributes to flavour [75]. On the contrary, the group of aromatic and alicyclic hydrocarbons, even showing low concentrations can have a large impact on \begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline  & **Roasted** & **Grilled** & **Fried** & **Microwaved** & **SEM** & **T** & **FxT** \\ \hline \multicolumn{8}{l}{**Aliphatic hydrocarbons**} \\ \hline Chestnut & 256.42 a & 216.93 a & 371.16 c & 300.98 b & 15.932 & *** & ns \\ Commercial feed & 91.09 a & 81.56 a & 185.56 c & 117.23 b & 10.632 & *** & ns \\ SEM & 31.332 & 26.260 & 35.717 & 35.807 & & & \\ F & *** & *** & *** & *** & & & \\ \hline \multicolumn{8}{l}{**Aromatic and alicyclic hydrocarbons**} \\ \hline Chestnut & 12.29 b & 10.87 b & 5.98 a & 4.35 a & 0.895 & *** & *** \\ Commercial feed & 3.47 a & 3.77 a & 10.78 c & 8.18 b & 0.824 & *** & *** \\ SEM & 1.709 & 1.384 & 1.028 & 0.759 & & & \\ F & *** & *** & ** & *** & & & \\ \hline \multicolumn{8}{l}{**Alcohols**} \\ \hline Chestnut & 19.70 & 35.12 & 18.16 & 35.45 & 3.282 & ns & *** \\ Commercial feed & 53.05 b & 50.49 b & 8.51 a & 22.20 a & 5.374 & *** & *** \\ SEM & 7.354 & 4.291 & 4.515 & 3.739 & & & \\ F & ** & ns & ns & ns & & & \\ \hline \multicolumn{8}{l}{**Aldehydes**} \\ \hline Chestnut & 1332.71 c & 1439.59 d & 45.84 a & 1127.46 b & 143.844 & *** & ns \\ Commercial feed & 1554.76 c & 1601.21 c & 206.17 a & 1321.84 b & 147.954 & *** & ns \\ SEM & 45.510 & 44.048 & 32.297 & 51.907 & & & \\ F & ** & ns & *** & * & & & \\ \hline \multicolumn{8}{l}{**Others**} \\ \hline Chestnut & 204.04 b & 293.27 c & 0.44 a & 189.90 b & 28.085 & *** & ** \\ Commercial feed & 281.80 b & 284.61 b & 3.33 a & 259.83 b & 31.391 & *** & ** \\ SEM & 16.486 & 13.688 & 0.550 & 17.218 & & & \\ F & ** & ns & *** & * & & & \\ \hline \multicolumn{8}{l}{**Total volatile compounds**} \\ \hline Chestnut & 1825.15 c & 1995.78 d & 441.58 a & 1658.13 b & 158.561 & *** & ns \\ Commercial feed & 1984.17 c & 2021.63 c & 414.36 a & 1729.28 b & 172.060 & *** & ns \\ SEM & 38.422 & 38.508 & 13.812 & 45.688 & & & \\ F & * & ns & ns & ns & & \\ \hline \multicolumn{8}{l}{SEM: Standard error of the mean. F: significantly different values as influenced by feeding: * (\(P<0.05\)); ** (\(P<0.001\)); *** (\(P<0.001\)); ns: no significant difference. T: significantly different values as influenced by cooking method; * (\(P<0.05\)); ** (\(P<0.01\)); *** (\(P<0.001\)). FX: interaction of feeding and cooking method; * (\(P<0.05\)); ** (\(P<0.01\)); ns: no significant difference. *\({}^{\sim}\) Means within the same row not followed by the same letter differ significantly (influence of cooking method) (\(P<0.05\)).} \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Effects of the inclusion of chestnut in the finishing diet and of cooking methods on volatile compounds grouped by chemical families and on total volatile compounds (expressed as AU \(\times\) 10\({}^{6}\)/g dry matter) of Celta pig _Biceps femoris_ muscle. aroma. This is because this group possesses some aromatic substances, such as pyrazines, that have a low odour threshold [73]. According to the above, low concentrations were obtained for these groups (percentages below 2.6%) in our work (Figure 3). Furthermore, the heat treatment that generated more substances of this type was frying for both diets. This could be due to the high temperature employed in this procedure (180 \({}^{\circ}\)C). Specifically, pyrazine, 3-ethyl-2,5-dimethyl- was detected in the case of fried chestnut samples, which obtained an average value of 5.68 AU \(\times\) 10\({}^{6}\)/g dry matter. This compound could favour the global odour of these samples since pyrazines are related to savvoury, nutty, roasted, and burnt odours [73]. On the other hand, alicyclic hydrocarbons do not contribute significantly to meat flavour because they have a high odour threshold [76].