## 3 Results and Discussion
### Volatile Compounds  
The cooking of meat releases various volatile compounds through different reaction mechanisms. These procedures are primarily due to the Maillard reaction, lipid degradation and oxidation, as well as the interaction among their intermediary compounds ([PERSON], 2017). In our research, a whole of 52 volatile compounds from _Biceps femoris_ muscle were identified in the head space of the cooked samples using the SPME/GC-MS method. Table 3 shows the total compounds of each chemical family and Table 4 displays the individual compounds handed out into five chemical families (aliphatic hydrocarbons, aromatic and alicyclic hydrocarbons, alcohols, aldehydes and \"others\"). According to the diet provided, the families of aliphatic hydrocarbons and aromatic and alicyclic hydrocarbons were significantly (\(P<0.01\)) affected in all the cooking methods. The groups of aldehydes and \"others\" were also affected (\(P<0.05\)) significantly in all culinary treatments, except in the grilled cooking. However, the alcohols group were hardly altered by diet, as only significant (\(P<0.05\)) differences were observed in roasted slices (Table 3). Additionally, the inclusion of chestnut in the pig diet significantly (\(P<0.05\)) affected the levels of 28, 18, 29 and 27 volatile compounds in roasted, grilled, fried and microwaved samples, respectively (Table 4). Regarding the cooking method, significant (\(P<0.001\)) differences were found in all five family groups for both feeds, except for the alcohol group in CH samples (Table 3). More concretely, the heat treatment had a significant (\(P<0.05\)) impact on all volatile compounds quantified, apart from 2,2,4,4-tetramethyl, octane and 2,3-butanediol in CH slices and decane, octane and pentane, 2,3,4-trimethyl- in CF samples (Table 4). For their part, the amount of total volatile compounds was only significantly (\(P<0.05\)) affected by diet in roasted samples. Even so, as we can see in the Figure 2, the CF pigs obtained higher values for total volatile compounds (except for the fried samples). Furthermore, this parameter was significantly (\(P<0.001\)) affected by the cooking method. More concretely, the total volatile compounds were affected in the same way by culinary treatment for both diets (Figure 2). Thus, the maximum value for the quantity of total volatile compounds was found in the grilled slices (1995.78 AU \(\times\) 10\({}^{6}\)/g dry matter for CH versus 2021.63 AU \(\times\) 10\({}^{6}\)/g dry matter for CF) followed by roasted (1825.15 and 1984.17 AU \(\times\) 10\({}^{6}\)/g dry matter for CH and CF, respectively) and microwaved samples (1658.13 AU \(\times\) 10\({}^{6}\)/g dry matter for CH and 1729.28 AU \(\times\) 10\({}^{6}\)/g dry matter for CF). Meanwhile the lowest total volatile compounds was detected in fried treatment (441.58 AU \(\times\) 10\({}^{6}\)/g dry matter for CH and 414.36 AU \(\times\) 10\({}^{6}\)/g dry matter for CF) coinciding with the outcomes obtained by [PERSON] and [PERSON] (2017). In relation to the family of aliphatic hydrocarbons, we have found values between 91.09 and 371.16 AU \(\times\) 10\({}^{6}\)/g dry matter, which represent among 4.0 and 84.1% of the all volatile substances detected (Figure 3). Although the CH samples provided a significantly (\(P<0.001\)) higher content in these compounds for all heat treatments, both diets showed the same trend. Thus, frying was the cooking method with the highest aliphatic hydrocarbon content, followed by microwaved, roasted and grilled. Additionally, after aldehydes, aliphatic hydrocarbons were the second most abundant volatile family (without taking into account the group of \"others\", where five different compounds were arranged). Although there was an exception since in fried CH samples it was observed that the aliphatic hydrocarbons were the main group (Figure 3).