## 2 Results and Discussion
\begin{table}
\begin{tabular}{l c c c c c c c c c c c c c c c c c c c c} \hline  & LRI\({}^{1}\) & ID\({}^{2}\) & 60-5v & 60-5a & 60-12v & 60-12a & 80-5v & 80-5a & 80-12v & 80-12a & SEM & P T & P1 & P value & P T \(\times\) 1 & P T \(\times\) vac & P t \(\times\) vac & P T \(\times\) 1 \(\times\) vac & P \(\times\) 1 \(\times\) vac \\ \hline Carbon disulfide & 534 & B & 22 & 10 & 24 & 10 & 16 & 15 & 25 & 23 & 1.81 & ns & ns & * & ns & ns & ns & ns \\ Butanal & 593 & A & 4.61\({}^{\circ}\) & 2.74\({}^{\circ}\) & 5.75\({}^{\circ}\) & 10\({}^{\circ}\) & 8.8\({}^{\circ}\) & 4.19\({}^{\circ}\) & 4.12\({}^{\circ}\) & 0.44 & *** & ** & ** & ** & ns & ns & ns \\ 2-Methyl/filmen & 605 & B & - & 0.35\({}^{\circ}\) & - & 1.56\({}^{\circ}\) & 0.99\({}^{\circ}\) & 1.16\({}^{\circ}\) & 1.84\({}^{\circ}\) & 0.13 & - & ns & ns & - & ** & ** & ** & ** & - \\ 3-Methyl/butanal & 646 & A & 3.01\({}^{\circ}\) & 1.35\({}^{\circ}\) & 3.11\({}^{\circ}\) & 2.98\({}^{\circ}\) & 3.17\({}^{\circ}\) & 2.96\({}^{\circ}\) & 4.86\({}^{\circ}\) & 5.60\({}^{\circ}\) &  
This is no doubt a potential drawback for sous-vide cooked meats at low to moderate temperatures, and in fact, chefs usually heat the meat in an oven or in a grill before serving, to enhance the aroma and color of the surface. **Scheme 1. ** Reaction of 2,4-decadienal with leucine, following [15]. In most VOCs from Maillard reactions and from thiamine degradation, with the exception of 1-(methylthio)-propane, cooking time showed a positive effect on the final levels found, which in the case of 2-methylthiophene was only significant in the samples cooked in the presence of air. On the other hand, the effect of cooking time on the final chromatographic areas of 3-methylbutanal was much more evident in samples cooked at 80 \({}^{\circ}\)C than in those cooked at 60 \({}^{\circ}\)C. These results point out to a positive effect of long cooking times when cooking at moderate to high temperatures on the levels of VOCs originated from amino acids and thiamine, since the involved reactions are favored by the temperature [6], but also seem to be favored by cooking time, since this kind of compounds has been found in long-ripened meat products [17]. In this regard, the Strecker degradation of different amino acids has been shown to strongly depend upon temperature and time [18]. Moreover, higher cooking temperatures and longer cooking times may increase the amount of reactive carbonyls, either from lipids or proteins, which could participate in the initial attack to the amine group of the amino acids [19]. Contrarily, 2-pentylthiophene was higher in samples cooked at 80 \({}^{\circ}\)C for 5 h than in those cooked at 80 \({}^{\circ}\)C for 12 h (Table 1). This could indicate that the formation of this compound is favored by the temperature, but participates in further reactions and thus, long cooking times may cause a depletion of its levels. Contrary to the results described for the rest of VOCs originated from degradation of amino acids and/or thiamine, 2-acetyl-2-thiazoline was only found at detectable levels in samples cooked at 60 \({}^{\circ}\)C, and it was higher in the vacuum-packaged samples than in air-packaged ones (Table 1). This compound has been pointed out as one of the impact flavor compounds in roasted beef [20], which indicates that cooking favors its formation. However, high temperatures might contribute to further reactions to yield other volatile sulfur compounds, leading to its complete degradation in 60 min at 100 \({}^{\circ}\)C [21]. Accordingly, our results suggest that this is not a very stable compound, since moderately high temperatures (80 \({}^{\circ}\)C) for long times led to its degradation. The hexanal/3-methylbutanal ratio has been previously proposed as a way to assess the balance between lipid oxidative reactions and amino acids degradation in meat and meat products [22].