## 2 Materials and Methods
### HS-Syme-Ge-Ms  
Sample Preparation and Extraction Conditions  
A previously developed methodology was used to determine the esters in the brandies [17]. Briefly, 25 mL of brandy sample was spiked with 20 \(\mu\)L of an internal standard mix solution of 8 deuterated compounds at 200 mg/L. The peak integration of each ester was normalized using specific deuterated standards, as follows: ethyl isobutyrate, ethyl 2-methylbutyrate, ethyl isovalerate, ethyl propanoate, ethyl butyrate, isoamyl acetate, ethyl valerate, propyl acetate, and isobutyl acetate were normalized with [\({}^{2}\)H\({}_{3}\)]-ethyl butyrate. Ethyl hexanoate, methyl hexanoate, methyl octanoate, isoamyl butanoate,isobutyl hexanoate, ethyl heptanoate, and hexyl acetate were normalized with [\({}^{2}\)H\({}_{11}\)]-ethyl hexanoate. [\({}^{2}\)H\({}_{15}\)]-Ethyl octanoate was used to normalize ethyl octanoate, methyl decanoate. Phenylethyl acetate, ethyl dihydrocinnamate, and ethyl cinnamate were normalized with [\({}^{2}\)H\({}_{5}\)]-ethyl trans-cinnamate; while ethyl dodecanoate, ethyl nonanoate, and ethyl phenylacetate were normalized with [\({}^{2}\)H\({}_{23}\)]-ethyl dodecanoate. Finally, [\({}^{2}\)H\({}_{27}\)]-ethyl myristate, [\({}^{2}\)H\({}_{31}\)]-ethyl palmitate, and [\({}^{2}\)H\({}_{35}\)]-ethyl stearate were used to normalize ethyl myristate, ethyl palmitate, and ethyl stearate, respectively. Then, the spiked samples were diluted in EDTA solution (200 mM and pH adjusted to 7 with NaOH 1 M), since this chemical prevents oxidation of the compounds [18]. Afterwards, the brandy samples were diluted to reach 7.2% \(v/v\) ethanol, and 10 mL of this solution was transferred to a 20 mL SPME vial containing 3.5 g of NaCl, to increase the ionic strength of the analytes and release more volatiles into the headspace [18; 19]. The vials were capped, and the solution was homogenized using a vortex shaker for 30 s and placed in a Combipal autosampler tray (CTC Analytics, Zwingen, Switzerland).  
A 100 \(\upmu\)m PDMS fiber (Supelco, Bellefont, PA, USA), previously conditioned according to the supplier recommendation, was used for extraction of esters via HS-SPME. For the equilibrium step, the vials were incubated at 500 rpm for 2 min at 33 \({}^{\circ}\)C, while the extraction was performed at the same temperature and agitation conditions for 55 min.  
The conditions of the gas chromatograph were as follows: the desorption time and temperature were set at 15 min and 250 \({}^{\circ}\)C, respectively, performed in a Trace GC ultragas chromatograph (Thermo Fisher Scientific S. p.A., Rodano, Milan, Italy). The desorbed volatiles passed to an ISQ Single MS spectrometer (Thermo Fisher Scientific, Austin, TX, USA). The injection was performed in splitless mode, and the column used for volatile separation was a BP21 column of 50m \(\times\) 0.32 mm and 0.25 \(\upmu\)m film thickness (SGE Analytical Science, Milton Keynes, UK). The carrier gas was helium at a constant flow rate of 1.7 mL/min. The oven temperature program was set at 40 \({}^{\circ}\)C for 5 min, raised to 220 \({}^{\circ}\)C at 3 \({}^{\circ}\)C/min, and held for 30 min. The MS operated in electron ionization mode at 70 eV using selected-ion-monitoring (SIM) mode. The transfer line and source temperature of the MS were set at 230 \({}^{\circ}\)C and 200 \({}^{\circ}\)C, respectively. The identification procedure was performed by comparing the retention times and mass spectra with those of the pure standards. All the samples were analyzed in duplicate by repeating the extraction procedure two times for each sample, in order to reduce the contribution of experimental and analytical variability to the final concentration measurements.