## 2 Materials and Methods
### Analysis
#### 2.4.6 GC \(\times\) GC/TOF-MS Analysis of Volatile Compounds  
Prior to GC \(\times\) GC/TOF-MS analysis, volatile compounds were extracted by HS-SPME following the method described in previous studies ([PERSON], 2018; Bellefonte, PA, USA), with minor modifications. A 2.5 mL aliquot of wine was placed in a 20 mL vial containing 1.5 g of sodium chloride. An internal standard solution (2-octanol) was added (50 \(\upmu\)L). A DVB-CAR-PDMS fibre was conditioned above the sample for 5 min at 35 \({}^{\circ}\)C and then exposed to the headspace for 20 min at the same temperature. Desorption of the volatiles occurred in a GC injector at 250 \({}^{\circ}\)C for 3 min in splitless mode. The fibre was reconditioned at 270 \({}^{\circ}\)C for 7 min between extractions. For identification and quantification, an Agilent 7890N GC (Agilent Technologies, Palo Alto, CA, USA) was coupled to a LECO Pegasus IV TOF-MS (Leco Corporation, St. Joseph, MI, USA) 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 column was a 30 m \(\times\) 0.25 mm \(\times\) 0.25 \(\upmu\)m VF-WAXms (Agilent Technologies), and the second-dimension column was a 1.5 m \(\times\) 0.15 mm \(\times\) 0.15 \(\upmu\)m Rai 17 Sil MS (Restek). The first oven was programmed to start at 40 \({}^{\circ}\)C for 4 min, followed by a ramp of 6 \({}^{\circ}\)C/min to 250 \({}^{\circ}\)C, held for 5 min. The second oven was kept at temperatures 5 \({}^{\circ}\)C higher than the first one throughout the analysis. Modulation occurred with a 7 s cycle time, including a 1.4 s hot pulse, with the modulator offset by +15 \({}^{\circ}\)C from the secondary oven, as detailed in a previous report [14]. Mass spectra were acquired in EI mode (70 eV) over the 40-350 \(m/z\) range. The ion source was set at 230 \({}^{\circ}\)C, with a detector voltage of 1317 V, an acquisition rate of 200 spectra/s, and an acquisition delay of 120 s. LECO ChromaTOF software (v4.32) was used for deconvolution, peak alignment, and baseline correction, with a signal-to-noise ratio of 100 and baseline offset at 0.8. Integration was performed manually. A standard mix of 122 volatile compounds was analysed under the same conditions. Identification was based on comparison of retention times and mass spectra with pure standards, and mass spectra libraries (NIST 2.0, Wiley 8, FFNSC 2) with a match factor of at least 750. Additional confirmation was achieved by comparing linear retention indices (calculated from C10 to C30 n-alkanes) with literature values for similar GC columns. Compound concentrations (\(\upmu\)g/L) were calculated relative to the internal standard 2-octanol, assuming equal detector response.  
During the HS-SPME GC\(\times\)GC-TOF-MS analysis, a quality control (QC) sample was created by combining equal amounts of all wine samples and analysed periodically among other samples. Principal component analysis (PCA) showed that the QC samples were tightly clustered and distinctly separated from the wine samples, suggesting good method repeatability. The relative standard deviations of the internal standard concentration 2-octanol in the QC samples were 9.2% in 2021 and 7.0% in 2022, which are considered satisfactory for this analytical method.