## 2 Materials and Methods
### Automated GC-MS-Olfactometry System  
A CTC CombiPal(tm) autosampler with a heated agitator (LEAP Technologies, Inc., Carrboro, NC, USA) was used during the entire experiment. The optimized sampling parameters are described elsewhere [18]. Briefly, a 1 cm 50/30 \(\upmu\)m divinylbenzene (DVB)/carboxen (CAR)/polydimethylsiloxane (PDMS) SPME was used for headspace sampling. Extraction time was 10 min at 50 \({}^{\circ}\)C, after 10 min incubation at 50 \({}^{\circ}\)C. Agitation speed was 500 rpm. The fiber was thermally desorbed in a 260 \({}^{\circ}\)C GC inlet for 2 min before exposure in sample headspace. Analytes were desorbed into the GC inlet for 2 min at 260 \({}^{\circ}\)C.  
The analysis was performed on a 6890N GC/5973 Network mass spectrometer (Agilent Technologies, Santa Clara, CA, USA). The instrument allowed for heartcutting with a Dean's switch, cryogenic focusing, and was equipped with a FID and an olfactometry port. The GC contains two columns connected in series. The first non-polar column was a BPX-5 stationary phase with dimensions \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Dilution Factor** & **Weighting Factor** & \begin{tabular}{c} **Sample** \\ **Volume (mL)** \\ \end{tabular} & \
\begin{tabular}{c} **Model Wine** \\ **Volume (mL)** \\ \end{tabular} &
\begin{tabular}{c} **Total Volume** \\ **(mL)** \\ \end{tabular} \\ \hline
0 & 1.000 & 4.000 & 0.000 & 4 \\
2 & 0.500 & 2.000 & 2.000 & 4 \\
4 & 0.250 & 1.000 & 3.000 & 4 \\
8 & 0.125 & 0.500 & 3.500 & 4 \\
16 & 0.063 & 0.250 & 3.750 & 4 \\
32 & 0.031 & 0.125 & 3.875 & 4 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Dilution and weighting factors of successive wine sample dilutions used in headspace solid phase microextraction gas chromatography-mass spectrometry-olfactometry (HS-SPME GC-MS-O) aroma dilution analysis. 30 m length \(\times\) 0.53 mm ID \(\times\) 0.5 \(\upmu\)m film thickness (SGE, Austin, TX, USA). The second polar column was SOLGEL-Wax stationary phase with dimensions of 30 m length \(\times\) 0.53 mm ID \(\times\) 0.5 \(\upmu\)m film thickness (SGE, Austin, TX, USA). A constant pressure of 5.7 psi was maintained at the midpoint between the first and second column using MultiTrax(tm) V.10.1 (MOCON, Round Rock, TX, USA) system automation and MSD ChemStation(tm) D.02.02.275 data acquisition software (Agilent, Santa Clara, CA, USA). Additional analysis was done using MassHunter Workstation (Agilent, Santa Clara, CA, USA) with NIST11 mass spectral database and BenchTop/PBM with Wiley Registry of mass spectral data, 7 th edition (Palisade Corporation, New York, NY, USA). Flow from the analytical column was directed to the single quadrupole mass selective detector and the olfactometry port in an open-split interface via fixed restrictor tubing. For this research, full heartcut was utilized from 0.05 to 35.00 min. An advantage of using two-dimensional gas chromatography is that separation is based on different and independent physico-chemical interactions (i.e., boiling point on the first column vs. polarity on the second column) for the entire chromatographic run. This serves as a fast screening method for VOCs, and can help select target VOCs for subsequent analysis. Sample flow was first directed through the non-polar column, then immediately to the polar column, therefore known retention indices for either column phase were used for identification. The following instrument parameters were used: injector, 260 \({}^{\circ}\)C; column, 40 \({}^{\circ}\)C initial, 3.0 min hold, 7 \({}^{\circ}\)C/min ramp, 220 \({}^{\circ}\)C final, 11.29 min hold; carrier gas, UHP helium (99.999%) with combination oxygen and moisture in-line gas trap. The mass detector was operated in electron ionization (EI) mode with an ionization energy of 70 eV. The mass detector ion source and quadrupole were held at 230 \({}^{\circ}\)C and 150 \({}^{\circ}\)C, respectively. Full spectrum scans were collected with the mass filter set from \(m/z\) 33 to \(m/z\) 450. The MS was auto-tuned daily before analysis.