## 5 Materials and Methods
### Metabolomics Analyses  
Both VOC and non-VOC detection was performed on an Agilent 7890B (Santa Clara, CA, USA) gas chromatograph equipped with a Pegasus HT time-of-flight (TOF) mass spectrometer (Leco Corporation, St. Joseph, MI, USA). \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Type of Distillate** & **Abbreviation** & **Place of Origin** & **Raw Material** \\ \hline \multirow{5}{*}{Chinese baijius} & Soy sauce aroma type liquor & C1 & Guizhou, China & Sorghum, wheat \\  & Soy sauce aroma type liquor & C2 & Guizhou, China & Sorghum, wheat \\  & Strong aroma type liquor & C3 & Sichuan, China & Sorghum, wheat, corn \\  & Strong aroma type liquor & C4 & Anhui, China & Sorghum, wheat, corn \\  & Light aroma type liquor & C5 & Shanyi, China & Sorghum, barley, pea \\  & Light aroma type liquor & C6 & Beijing, China & Sorghum, barley, pea \\ \hline \multirow{5}{*}{Western liquors} & Whisky & W1 & Kentucky, America & Barley malt, corn, caramel \\  & Whisky & W2 & Speyside, Scotland & Barley malt, caramel \\  & Whisky & W3 & Ireland & Barley malt, corn, caramel \\  & Whisky & W4 & Scotland & Barley malt, corn, caramel \\  & Whisky & W5 & Scotland & Barley malt, caramel \\  & Brandy & B1 & France & Grape, caramel \\  & Brandy & B2 & France & Grape, caramel \\  & Brandy & B3 & France & Grape, caramel \\  & Brandy & B4 & France & Grape, caramel \\  & Brandy & B5 & France & Grape, caramel \\  & Rum & R1 & Puerto Rico & Sugar cane, caramel \\  & Rum & R2 & U.S. & Sugar cane, caramel \\  & Rum & R3 & France & Sugar cane, caramel \\  & Rum & R4 & Cuba & Sugar cane, caramel \\  & Vodka & V1 & Britain & Wheat, barley malt \\  & Vodka & V2 & Sweden & Wheat \\  & Vodka & V3 & France & Wheat \\  & Vodka & V4 & Poland & Wheat, potato \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Distilled liquors used in this studyFor the detection of VOCs, samples were analyzed on a DB-FFAP column (60 m \(\times\) 0.25 mm i.d., 0.25 \(\upmu\)m film thickness, Agilent JandW Scientific, Folsom, CA, USA). The detector and injector temperature was 250 \({}^{\circ}\)C. The oven temperature was held at 45 \({}^{\circ}\)C for 3 min, and then raised to 150 \({}^{\circ}\)C at a rate of 4 \({}^{\circ}\)C per min, and held for 2 min, then raised to 200 \({}^{\circ}\)C at a rate of 6 \({}^{\circ}\)C per min, then raised to 230 \({}^{\circ}\)C in 10 min, and held for a final 15 min. The column carrier gas was helium at a constant flow rate of 1 mL/min. Splitless injection mode was used. The temperature of the ion source was 230 \({}^{\circ}\)C, and the electron impact mass spectra were recorded at 70 eV ionization energy. The GC-MS analysis was carried out in the scanning mode (SCAN) in the 35-400 \(\upmu\)m mass range, and the acquisition rate was 100 spectrum/s in the TOFMS setting. For the detection of non-VOCs, each 1-\(\upmu\)L aliquot of the derivatized solution was injected in split mode (split ratio 1:10). Separation was achieved on a DB-5 ms capillary column (30 m \(\times\) 250 \(\upmu\)m i.d., 0.25 \(\upmu\)m film thickness, Agilent JandW Scientific, Folsom, CA, USA). Helium was used as the carrier gas at a constant flow rate of 1.0 mL/min. The temperatures of injection, transfer interface, and ion source were set to 250, 250, and 230 \({}^{\circ}\)C, respectively. The GC temperature programming was set to 2 min of isothermal heating at 50 \({}^{\circ}\)C, followed by 6 \({}^{\circ}\)C/min oven temperature ramps to 230 \({}^{\circ}\)C, and a final 15 min maintenance at 230 \({}^{\circ}\)C. MS measurements were recorded with electron impact ionization (70 eV) in full-scan mode (\(m\)/2 30-600), and the acquisition rate was 20 spectrum/second in the TOFMS setting. To ensure the stability of the system over the different sequences and provide confidence in our data, we completed the following. Before testing, a tuning solution was used to ensure the stability of the fragment ion. During testing, we ensured the stability of chromatography and column by monitoring the retention index of n-alkane or fatty acid methyl ester.