## 4 Materials and Methods
### GC-MS Analysis  
GC-MS analysis was performed using an Agilent 6890N Network gas chromatograph system coupled with a 5973N mass spectrometer (Agilent Technologies, Santa Clara, CA, USA). A DB-5 MS UI column (60 m \(\times\) 0.25 mm i.d., 1.00 \(\upmu\)m film thickness; J&W Scientific, Folsom, CA, USA) was used for chromatographic separation. The SPME injections were performed in splitless mode, and the detector started to operate immediately after each injection. The carrier gas (He) was fluxed at a constant flow of 1 mL/min, with a column head pressure of 15 psi. The initial oven temperature was 40 \({}^{\circ}\)C (held for 5 min), followed by a heating ramp set at 10 \({}^{\circ}\)C/min up to 160 \({}^{\circ}\)C, and then 8 \({}^{\circ}\)C/min, to reach the final temperature of 270 \({}^{\circ}\)C, held for 5 min. The transfer line was heated to 270 \({}^{\circ}\)C.  
The mass spectrometer was operated in electron impact (EI) ionization mode at 70 eV, in full-scan acquisition mode, with a \(m\)/z scanning range from 25 to 300.  
Chromotograms and mass spectra were analyzed using the Enhanced ChemStation software (Agilent Technologies, Santa Clara, CA, USA). Tentative identification of volatile compounds was achieved by matching the mass spectra with the data system library (NIST14 / NIST05 / WILEY275 / NBS75K) and by using some databases accessible via the web, such as the National Institute for Standards and Technology (NIST database [[https://webbook.nist.gov](https://webbook.nist.gov)]([https://webbook.nist.gov](https://webbook.nist.gov)), accessed on 1 September 2021) and the Mass Bank of North America ([[https://mona.fiehnlab.ucdavis.edu](https://mona.fiehnlab.ucdavis.edu)]([https://mona.fiehnlab.ucdavis.edu](https://mona.fiehnlab.ucdavis.edu)), accessed on 1 September 2021).  
A Linear Retention Index (LRI) was used for an additional comparison between our data and those reported in the literature and in the NIST Standard Reference Database, only considering values referring to analyses carried out under the same operative conditions (instrumental specifications and heating ramp).  
The LRIs of compounds were calculated from a series of n-alkanes (C6, C9, C12, C14, C16) subjected to the same analysis procedure as that adopted for the samples.  
The latter proved to be particularly useful for the distinction of E/Z isomers, since these species produce mass spectra that are difficult to differentiate.  
Finally, some analytes were identified by comparing their mass spectra with those of their respective pure standards (when available), analyzed using HS-SPME-GC-MS under the same operating conditions as those used for the samples.  
The volatile compounds such as silane and siloxane derivatives, or Volatile Organic Compounds related to the sorbent fiber, were discarded and are not reported in the GC-MS output tables. The estimation of the amount of each volatile identified in the SPME-GC-MS analysis was expressed as the Total Ion Current (TIC) peak area.  
All the data shown in the tables relate to values obtained from analysis performed at least in triplicate. The reproducibility of the results is expressed as standard deviation in the tables. When absent, the apex \({}^{\mathrm{a}}\) indicates that SD < 0.05.