## 2 Volatile Wood Composition
### _Q. pyrenaica_ Wild
pyrenaica_ wood showed the highest contents [63] at about 5000 \(\upmu\)g/g after toasting at 250-260 \({}^{\circ}\)C and 5979-8332 \(\upmu\)g/g after toasting at 160-170 \({}^{\circ}\)C, while in the traditional ones it was 1161-2153 \(\upmu\)g/g and 2201-4794 \(\upmu\)g/g, respectively. The difference after toasting of this species compared to the traditional ones was mainly due to furfural, 5-HMF and vanillin [63]. [PERSON] et al., 2010 [66] also observed a higher concentration of furanic compounds in _Q. pyrenaica_ woods together with furanecol and _cis_ lactone; however, vanillin concentrations in this study were lower than traditional ones. However, [PERSON] et al., 2003 [64] observed that the concentrations of all compounds in _Q. pyrenaica_ after toasting were between the concentrations of traditional oaks, closer to those of _Q. petraea_ wood. The level of toasting in _Q. pyrenaia_, as in traditional oaks, has a great influence on the concentration of many of the volatiles. This process increases the content by hydrothermolysis and pyrolysis reactions; however, if the temperature increases a lot and is maintained for a long time, the volatile compounds are degraded [40, 64, 66, 70]. [PERSON] et al., 2005 [63] showed that almost all aromas were higher after toasting at 160-170 \({}^{\circ}\)C than after toasting at 250-260 \({}^{\circ}\)C. Similar results were shown by [PERSON] et al., 2010 [66], where it was seen that aromas were formed as the toasting was increased as in traditional woods, but with a very high toasting temperature, they were degraded, especially with heavy toasting. There is much variability among the studies carried out, although, in general, it could be said that the toasted wood of _Q. pyrenaica_ is rich in certain compounds, such as _cis_ lactone, eugenol, 4-VG and furanic compounds. The rest of the compounds are usually present in similar concentrations to traditional woods, as is the case of most volatile phenols, phenolic aldehydes and phenyl ketones (Table 4 and Figure 1). Figure 1 shows that the lactone content in _Q. pyrenaica_ is similar to (Figure 1c) or higher (Figure 1d,e) than _Q. alba_ and always higher than _Q. petraea_. Furthermore, regardless of toasting, a higher content of furanic compounds was observed in the wood of _Q. pyrenaica_ than in the traditional ones (Figure 1). _Quercus faginea Lam_  
Only one work was found on the volatile composition of _Q. faginea_ wood [64], studied both after seasoning and toasting. This wood showed the same compounds and in similar concentrations to the wood of traditional oaks, although butylolactone, hydroxybenzaldehyde and 1H-pyrrole-2-carboxaldehyde were not detected in the seasoned wood, but were detected in the toasted wood. The seasoned wood of _Q. faginea_ showed higher concentrations of some aromas including: volatile phenols, such as guaiacol, 4-EG, phenol, syringol; some phenolic aldehydes, such as 2-(4-hydroxy-3-methoxyphenyl) acetaldehyde, acetovanillone, 1-(4-hydroxy-3-methoxyphenyl)-2-propanone, butylovanillone, 2-(4-hydroxy-3,5-dimethoxyyphenyl) acetaldehyde, acetosyringone, 1-(4-hydroxy-3,5-dimethoxyyphenyl)-2-propanone, propiosyringone, benzaldehyde and the minor ones of 2-furanyl-1-ethanoneome, methyl vanillyl ether, syringaldehyde, coniferaldehyde and sinapaldehyde [64]. Figure 1b shows how this wood after seasoning stands out for its content of furanic compounds (21.3 ug/g). During toasting, at 160-170 \({}^{\circ}\)C for 35 min, the _cis_ and _trans_ lactone contents decreased by about 80% and 40%, respectively, whereas in traditional woods they increased during toasting. Therefore, the toasted wood of _Q. faginea_ is probably a lactone-poor wood among the _Quercus_ woods (Table 4 and Figure 1c). The concentrations of the other volatile compounds studied after toasting were between those found in _Q. petraea_ and _Q.