## 2 Materials and Methods
### GC-MS and GC\(\times\)GC-TOF-MS Analysis of Volatile Arona Compounds
An example of a total ion current GC-MS chromatogram is reported in Figure S1. Standard solutions at six concentration levels were analyzed in the same conditions and calibration curves were constructed. Major volatile compounds were quantified based on peak area of the total ion current, whereas minor compounds were quantified based on peak area of quantifier ions. Internal standard normalization was applied prior to quantification using calibration curves. Method validation parameters were published in our previous study [29]. Semi-quantitative analysis was performed for compounds for which pure chemical standards were not commercially available, assuming equal detector response of compounds of similar chemical structure. For major volatile compounds, odor activity values (OAV) were calculated as quotients of their concentrations and corresponding odor perception thresholds (OPT) from the literature. Similar to the case of GC-MS analysis, prior to analysis by GC\(\times\)GC-TOF-MS, volatile aroma compounds were extracted using HS-SPME according to the methods described in previous studies [22; 30; 31] with slight modifications. A 2.5 mL aliquot of wine was put in a 20 mL glass vial containing 1.5 g of sodium chloride. A volume of 50 \(\upmu\)L of internal standard solution (2-octanol at 1 mg/L) was added. A DVB-CAR-PDMS SPME fiber was preconditioned above the sample for 5 min at 35 \({}^{\circ}\)C and then subjected to the vapors in the headspace for 20 min at the same temperature. Volatile compounds were desorbed in a GC injector at 250 \({}^{\circ}\)C for 3 min in splitless mode and the fiber was reconditioned at 270 \({}^{\circ}\)C for 7 min between each microextraction. Identification and quantification were performed using a GC Agilent 7890N (Agilent Technologies, Palo Alto, CA, USA) coupled to a LECO Pegasus IV time-of-flight mass spectrometer (TOF-MS) (Leco Corporation, St. Joseph, MI, USA) equipped with a Gerstel MPS autosampler (GERSTEL GmbH & Co. KG, Mulheim an der Ruhr, Germany). The carrier gas was helium at a flow rate of 1.2 mL/min. The first dimension GC capillary column was a 30 m \(\times\) 0.25 mm \(\times\) 0.25 \(\upmu\)m film thickness VF-WAXms (Agilent Technologies), whereas the second dimension one was a 1.5 m \(\times\) 0.15 mm \(\times\) 0.15 \(\upmu\)m film thickness Rxi 17 Sil MS (Restek). The first GC oven was initially heated at 40 \({}^{\circ}\)C for 4 min, the temperature was then increased at 6 \({}^{\circ}\)C/min to 250 \({}^{\circ}\)C, and then kept constant for an additional 5 min. The second GC oven was kept at 5 \({}^{\circ}\)Cabove the temperature of the first one throughout the analysis. The modulator was offset by +15 \({}^{\circ}\)C in relation to the secondary GC oven, with modulation time of 7 s with 1.4 s of hot pulse duration, as reported previously [31]. EI mode (70 eV) was used to acquire mass spectra in the 40-350 \(m/z\) range. The ion source temperature was 230 \({}^{\circ}\)C, detector voltage was 1317 V, acquisition rate was 200 spectra/s, and acquisition delay was 120 s. LECO ChromaTOF software version 4.32 (Leco Corporation, St. Joseph, MI, USA) was used for baseline correction, chromatogram deconvolution, and peak alignment. Baseline offset was set to 0.8 and signal-to-noise ratio (S/N) was set at 100. Traditional, not adaptive integration was used. A mix of pure standards of 122 volatile compounds was analyzed under the same GC\(\times\)GC-TOF-MS conditions. Volatile compounds were identified by comparison of their retention times and mass spectra with those of pure standards and with mass spectra from NIST 2.0, Wiley 8, and FFNSC 2 (Chromaleont, Messina, Italy) mass spectral libraries, with a minimum similarity match factor of 750 as a criterion.