## 3 Results and Discussion
\begin{table}
\begin{tabular}{l c c c c} \hline \multicolumn{5}{c}{**(a) _Castanea s._**} & \multicolumn{5}{c}{**(b) _Castanea s. HT_**} \\ \hline
**Compound** & **GC-MS** & **SPME** & **Compound** & **GC-MS** & **SPME** \\ \hline
1H-Benzocycloheptene,2,4a,5,6,7,8,9,9a- & & & & \\ octahydro-3,5,5-trimethyl-9-methylene-, & & 2.40 & 10-Methylnonadecane & 1.36 & \\ (4 aS-cis) & & & & \\ \hline
1H-Inden-1-one, & & & & \\
2,3-dihydro-3,3,5,6-tetramethyl & & & & \\ hexahydro-3,5,5,9-tetramethyl & & & & \\ \hline
1H-Indole-2,3-dione,1-(tert- & & & \\ butyldimethylsilyl)-6-[(tert- & & & \\ butyldimethylsilyl)])-6-[(tert- & 1.61 & & 1H-Inden-1-one,2,3-dihydro- & \\   butyldimethylsilyl)])oxy]-3-(O-ethyloxime) & & & & \\ \hline
2,5-Cyclohexadiene-1,4-dione,2,6-bis(1,1- & & & \\ dimethylethyl) & & 0.16 & 1H-Indole, 2,3-dihydro-4-methyl & 0.67 \\ \hline
2-Ethylhexyl salicylate & & 0.08 & 1H-Pyrazole,4,5-dihydro-5,5- & \\  & & dimethyl-4-isopropylidene & & \\ \hline
2-Furancarboxylic acid & 0.36 & & 2,6-Bis(1,1-dimethylethyl)-4-(1- & \\  & & oxopropyl)phenol & & \\ \hline
2-Nonenal, (E) & & 0.19 & 2-Benzoxazolamine,N-(1,1- & \\  & & dimylethyl) & & \\ \hline
3,5-Dimethoxy-4-hydroxycinnamaldehyde & 2.14 & 2-Furancarboxaldehyde, 5-methyl & 1.51 \\ \hline
3-Allyl-6-methoxyphenylol & 0.13 & 2-Nonenal, (E) & 0.42 \\ \hline
3-Furancarboxylic acid, methyl ester & 0.10 & 6,7-Dimethoxyquinoxaline & 1.16 \\ \hline
4-((1E)-3-Hydroxy-1-properyl)-2- & & 4.73 & Acetic acid & 1.75 \\   methoxyphenol & & & \\ \hline
4-Hydroxy-2-methoxycinnamaldehyde & 1.84 & Acetic acid, 2-phenylethyl ester & 2.14 \\ \hline
4-Metchoxy-4\({}^{\prime}\),5\({}^{\prime}\)-methylenedioxybiphenyl-2- & & 3.20 & Acetic acid, octyl ester & 0.73 \\ \hline
5-Hydrooxymethylfurfurral & 3.60 & & \
\begin{tabular}{c} alpha-Amino-3\({}^{\prime}\)-hydroxy-4\({}^{\prime}\)- \\ methoxyacetophenone \\ \end{tabular} & 0.90 & \\ \hline Acetic acid & & 8.16 & Benzaldehyde & 0.15 \\ \hline alpha-Amino-3\({}^{\prime}\)-hydroxy-4\({}^{\prime}\)- & & & \\ \hline methoxyacetophenone & 0.28 & &
\begin{tabular}{c} Benzene, \\ 1-methyl-3-(1-methylethyl) \\ \end{tabular} & 0.10 \\ \hline Apocynin & 0.21 & Creosol & & 0.50 \\ \hline Ar-tumore & & 0.48 & Decanal & 0.21 \\ \hline Benzaldehyde & & 0.10 & Eicosane & 2.82 & \\ \hline Benzaldehyde,2-hydroxy-,(2,4-dinitrophenyl) & 3.71 & & Ethanone, 1-(2-hydroxyethylphenyl) & 0.34 \\ \hline Benzene, (3-methyl-2-butenyl) & & 0.19 & Eugenol & 2.73 \\ \hline Benzene, 1-(1-buten-3-yl)-4-pentyl & & 0.76 & Furfurral & 10.53 \\ \hline Benzene, 1,4-dimethyl-2,5-bis(1-methylethyl) & & 0.44 & Hexacosane/Heneicosane & 1.89 & \\ \hline Benzene, 2-(2-butenyl)-1,3,5-trimethyl & & 0.74 & Hexadecane/Heptadecane & 2.12 & \\ \hline Benzofuran, 2,3-dihydro-2-methyl & & 0.11 & Indan, 1,1,6,7-tetramethyl & 0.21 \\ \hline Benzoic acid, 4-hydroxy-3,5-dimethoxy & 6.32 & Isochroman & 0.16 \\ \hline \end{tabular}
\end{table} 
Table 2: Compounds found in GC-MS and SPME analysis of (**a**) _Castanea s._ and (**b**) _Castanea s._ heat-treated (HT) wood water extractives. Autoclave extraction resulted in a large number of compounds in the thermo-modified chestnut and beech, with a greater amount of alkyl compounds only found in modified wood of both wood species. Derivatives of fatty acids have been extracted from both modified wood species, in particular, octadecanoic acid. This is a saturated fatty acid obtained from hydrolysis or the degradation of fatty acids during the heat process. Octadecanoic acid is used in the production of candles, soaps, plastics, oil pastels, and cosmetics [39]. As can be seen from Tables 1 and 2, sweet chestnut and beech showed a different response to thermal treatment, although both were processed at a temperature of 170 \({}^{\circ}\)C. At temperatures of 150-200 \({}^{\circ}\)C, the degradation rate during thermal modification was four times higher for hemicellulose than for cellulose and lignin, and VOCs, formed due to heating of wood, were trapped in the process and promote the degradation rate [37].