The identification and quantification of HS volatile compounds was performed using an Agilent HP 7890 series II GC (HewlettePackard, Palo Alto, CA) with an HP 5975C mass selective detector
(HewlettePackard) equipped with Gerstel MPS2 multipurpose sampler (Gerstel, Germany). Extraction of HS volatile compounds was performed using SPME as indicated above. The compounds extracted by the fibre were desorbed in the injection port of the GCeMS for 5 min at 240 C with purge valve off (splitless). The analysis of volatile compounds in the GCeMS was performed as described Olivares et al. (2011). The compounds were identified by comparison with mass spectra from the library database (Nist’05), kovats retention index (Kovats, 1965) and by comparison
with authentic standards. The quantification of volatile compounds was done in SCAN mode using either total or extracted ion chromatogram (TIC or EIC) on an arbitrary scale. The results
were expressed as abundance units (AU) 106.