## 3 Results and Discussion
### Validation of the Quantification Method for the Volatile Compounds  
The GC-MS method was optimized and validated for this application the validation parameters are shown in Table 3. Acceptable linearities were obtained using a set of calibration curves prepared with six standards diluted using distilled water in the range of concentration shown in Table 2. Additionally, satisfactory reproducibility and repeatability of the method were observed. Furthermore, LOD were between 0.89-1.55 ug Kg\({}^{-1}\), meanwhile for trans-2-decneal was a little bit higher near 20 ug Kg\({}^{-1}\)., these LOD are very similar to a previous work in which multiple HS-SPME was employed. In the present study, the response factor for the four aldehydes quantified was significantly different, the slope of the curve being higher as the length of the chain of the molecule increased. These means that for a quantitative study standard would be necessary for all volatiles. Alternatively, a semiquantitative determination will be done based on the peak are percentage. For the semiquantitative determination, per cent peak area respect to S1 total area was calculated in order to be able to compare among samples. The relative areas are shown in Table 3. Important differences in peak area were observed when comparing the VOC presented in S1 with the cooked _softrios_ (CS). Some compounds detected in the samples were related to tomato and its cooking process. Hexanal is important in the fresh tomato flavour contributing to the green aroma. This aldehyde together with [21] 2-methyl-2-pentanal and benzaldehyde diminished in the cooking process [23]. Others like trans-2-heptenal, 6-methyl-5-hepten-2-one did not change significantly the percentage in all the samples [8; 23]. By contrast, other compounds were not detected in S1 and were quantifiable in the cooked _softrios_. Those compounds were three aldehydes, trans, trans-2,4-decadienal represents (13.6-1.9%) and trans-2-decneal in important proportion (7.5%-5.4%) and octanal in a lower proportion. Unsaturated aldehydes are usually derived from a linoleic acid breakdown pathway [23], which is reasonable after the cooking process [39]. No significant differences were found among all cooked _softrios_ in trans-2-decneal and octanal. Meanwhile trans, trans-2,4-decadienal was significantly different from S5 and S6 to S1-S4 (Table 2). Moreover, octane and 1,2-dimethyl benzene were also detected in the cooked samples probably related to the Maillard reaction [40]. On the other hand, several studies have reported that 2-methyl-2-pentenal, methyl-2-propenyldisulfide, 2,4-dimethylthiophene, di-2-propenyldisulfide, di-2-propenyltrisulfide and 3,4-dihydro-3-vinyl-1,2-dithiin are volatile compounds linked with the presence of garlic and/or onion as ingredients in the tomato sauce [21; 33; 40]. In this sense, di-2-propenyldisulfide, methyl-2-propenyldisulfide, were present in CS1 and CS2 but not in CS5 which contains no garlic. In contrast, alpha-farnesene, 2,4-dimethyl-thiophene, 2-methyl-2-pentenal could be linked with the presence of onion since it was not identified or in lower quantity in CS5 formulated without garlic. Some of these compounds, specially disulfide and trisulfide derivates are known to have antioxidant properties [29]. Regarding the olive oil ingredients, four main volatiles were identified (2,4-heptadienal, 1,2-dimethyl-benzene, benzeneacetaldehyde and 1-octanol) [41]. Additionally, it was observed that the total peak area detected in the raw sample was higher than the area obtained in cooked samples but for CS3 and CS4. This result indicates that during de cooking process part of the VOCs escape to the air [42].