## 3 Results and Discussion
### Volatile Compounds
Alcohols are mainly derived from the oxidative decomposition of lipids [73; 75]. These substances are common components of cooked meat and meat products [75]. Nevertheless, they usually have higher odour thresholds and a low impact on the cooked meat flavour [76]. Even so, they occasionally contribute to desirable almond-like, toasted, woody and fatty-floral aroma notes [77; 78]. In our case, alcohols were found in concentrations between 1.1 and 4.1% (Figure 3). Concretely, 1-pentanol was the alcohol that appeared in the highest concentration, being significantly (\(P<0.05\)) higher for CF pigs, except for microwaved samples where this value was not significantly different (Table 4). Despite these differences, cooking also significantly (\(P<0.001\)) affected both diets in a similar way. Like this, 1-pentanol was found to a greater extent in grilled CH samples (26.23 AU \(\times\) 10\({}^{6}\)/g dry matter) and in roasted CF slices (47.65 AU \(\times\) 10\({}^{6}\)/g dry matter). Meanwhile, frying showed the lowest values for the fried CF samples (8.51 AU \(\times\) 10\({}^{6}\)/g dry matter), being even undetectable in CH slices. In addition to standing out for its high concentration compared to other alcohols, 1-pentanol is also important in the aroma of meat, since it has a low odour threshold. So this substance could benefit the global aroma owing to its mild, fruit and bals  
Figure 2: Effects of the inclusion of chestnut in the finishing diet and cooking methods on total volatile compounds of Celta pig _Biceps femoris_ (mean \(\pm\) standard error). Influenced by feeding: * (\(P<0.05\)); ** (\(P<0.01\)); *** (\(P<0.001\)); ns: no significant difference. Different letters within the same feeding regimen (chestnut (\({}^{\mathrm{a,d}}\)) or commercial feed (\({}^{\mathrm{A,C}}\))) indicate significant differences for cooking methods (\(P<0.05\)). On the other hand, aldehydes were the most plentiful chemical family detected in cooked _Biceps femoris_ slices affected by different heat treatments for both diets, with the exception of frying in CH diet, where aliphatic hydrocarbons were predominant (Figure 3). These volatile compounds are mainly generated from the oxidation of the unsaturated fatty acids [59], although they can also be originated through the Strecker degradation [79]. The aldehydes are likely the most important of the lipid-derived  
Figure 3: Volatile families of Celta pig _Biceps femoris_ (expressed as percentages) affected by diet and by cooking method. volatiles due to their low threshold odour, which contributes greatly to the flavour of meat [80]. In the case of cooked pork, aldehydes are mainly responsible for its aroma [80]. In this way, cooked grilled samples showed the highest values of total aldehyde content unlike fried samples (1439.59 vs. 45.84 AU \(\times\) 10\({}^{6}\)/g dry matter for CH and 1601.21 vs. 206.17 AU \(\times\) 10\({}^{6}\)/g dry matter for CF, respectively). In particular within aldehydes, hexanal was the major volatile compound observed in any cooking method according to other works [74, 81], displaying values between 29.50 and 1412.07 AU \(\times\) 10\({}^{6}\)/g dry matter (Table 4). Diet significantly (\(P<\) 0.05) affected hexanal quantity, apart from microwave cooking. Thus, CF seemed to increase the hexanal content in all cooking treatments. Even so, this compound showed the same trend in both diets, obtaining the maximum value for grilled samples, followed by roasted and microwaved muscle. Meanwhile, the lowest values were found for the fried samples. Then again, regarding cooking methods, the treatments used significantly (\(P<\) 0.001) affected the hexanal content as previously indicated. Nevertheless, these aftermaths do not agree with those showed by [PERSON] et al. [9] who determined that frying supplied the higher hexanal content in cooked pork. In the meantime, grilled ions showed the lowest hexanal value in their research.