## 2 Materials and Methods
### GC-MS Analysis  
Volatile organic compounds (VOCs) were analyzed by HS-SPEM-GC-MS as described by [PERSON] et al. [30], with modifications. A total of 5 mL cherry wine, containing 2 g NaCl and 20 \(\upmu\)L 2-octanol (internal standard, 413 \(\upmu\)g/mL) was placed in a 15 mL headspace vial, and equilibrated for 30 min at 40 \({}^{\circ}\)C under an agitation speed of 500 r/min ( PC-420D, Corning, NY, USA). Before extraction, the SPME fiber (50/30 \(\upmu\)m DVB/CAR/PDMS, SPME, Bellefonte, PA, USA) was conditioned at 250 \({}^{\circ}\)C for 40 min by being inserted into the injection port of GC-MS. Then, it was injected into the headspace vial for 30 min (40 \({}^{\circ}\)C) and inserted into the injection port immediately to desorb for 8 min at 250 \({}^{\circ}\)C under a splitless mode. An 8860-gas chromatograph (GC) coupled to a 5977-mass selective detector (MS) (Agilent, Santa Clara, CA, USA) was employed for separation and detection analyses. The DB-225 ms column (30 m \(\times\) 0.25 mm \(\times\) 0.25 \(\upmu\)m, Agilent, USA) was used to perform the chromatographic separations. The oven temperature program is listed in Table 3. Helium was used as the column carrier gas with a constant flow rate of 1 mL/min. The transfer line, ion trap and quadrupole temperature were 280 \({}^{\circ}\)C, 230 \({}^{\circ}\)C and 150 \({}^{\circ}\)C. The MS parameters included electron impact ionization with electron energy of 70 eV at 1 s/scan, full scan mode and a mass range of m/z 50-550. A blank run was carried out to ensure no carryover of analytes from previous injections before sampling. The VOCs were identified by comparing their mass spectral data with the NIST 1.1 mass spectral database. The relative concentration of VOCs was calculated according to the following equation:  
\[Concentration\left(\frac{\mu g}{L}\right)=\frac{\mathit{Peak\ of\ compound}}{\mathit{ Peak\ of\ internal\ standard}}\times\mathit{concentration\ of\ internal\ standard} \tag{2}\]  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sensor** & **Responsive Substance** & **Performance Description** & **Threshold Value** \\ \hline W1C & Aromatics & Sensitive to aromatic compounds & 10 ppm \\ \hline W5S & Broad range & Sensitive to nitrogen oxides & NO\({}_{2}\), 1 ppm \\ \hline W3C & Aromatic & Sensitive to ammonia, & Benzene, 10 ppm \\ \hline W6S & Hydrogen & Sensitive to hydride & H\({}_{2}\), 100 ppb \\ \hline W5C & Arom–aliph & Sensitive to short-chain alkanes, & \\  & & aromatic compounds & Propane, 1 ppb \\ \hline W1S & Broad–aliph & Sensitive to short-chain alkanes, & \\  & & aromatic compounds & CH\({}_{3}\), 100 ppm \\ \hline W1W & Sulfur–organic & Sensitive to sulfides, pyrazine and & \\  & & many terpenes & H\({}_{2}\)S, 1 ppm \\ \hline W2S & Broad–alcohol & Sensitive to alcohols, aldehydes & \\  & & and ketones & CO, 100 ppm \\ \hline W2W & Sulfur–chlor & Sensitive to aromatics, sulfur and & \\  & & chlorine containing organics & H\({}_{2}\)S, 1 ppm \\ \hline W3S & Methane–aliph & Sensitive to methane and alkanes & CH\({}_{3}\), 100 ppm \\ \hline \hline \end{tabular}
\end{table}
Table 2: The sensors and their main properties in the PEN3 electronic nose.