## 2 Materials and Methods
### Analysis of Volatile Compounds  
The volatile extraction was carried out using solid-phase micro-extraction (SPME) in triplicate. Each sample (3 g) was placed inside a 40 mL amber vial, screw-capped with a PTFE/silicone (Supelco, Bellefonte, PA, USA) septum, in a metallic block thermostat at 35 \({}^{\circ}\)C for 60 min, based on the methodology reported by Flores & Olivares [42]. After this period of time, a DVB/CAR/PDMS (divinylbenzene/carboxen/polydimethylsiloxane) fiber, film thickness 50/30 \(\upmu\)m (Supelco), was placed in the headspace for 120 min at the same temperature. The fiber was conditioned for 60 min at 240 \({}^{\circ}\)C prior to extraction.  
The methodology for quantification of volatile compounds was adapted from Flores & Olivares [42] and carried out on a Gas Chromatography system GC-2010 (Shimadzu Corporation, Kyoto, Japan) equipped with a flame ionization detector (FID). A split-splitless injection port held at 240 \({}^{\circ}\)C was used to thermally desorb the volatile compounds from the SPME fiber onto the front of a DB-624 UI capillary column of 30 m \(\times\) 0.25 mm, i.d., 1.4 \(\upmu\)m film thickness (Agilent J&W, Palo Alto, CA, USA), and nitrogen was used as a carrier gas at a linear velocity of 37 mL/min flow rate. The temperature was 37 \({}^{\circ}\)C, isothermal for 13 min, then raised to 110 \({}^{\circ}\)C at a rate of 3 \({}^{\circ}\)C/min and maintained for 10 min, then raised to 150 at a rate of 3 \({}^{\circ}\)C/min, and then 210 \({}^{\circ}\)C at a rate of 5 \({}^{\circ}\)C/min and held for 10 min. The total run time was 82.67 min. Injector and detector temperatures were both set at 240 \({}^{\circ}\)C. The content of each volatile compound was calculated from the FID area and was multiplied by \(10^{-5}\) for easier data management.  
Volatile compounds were identified with three complementary approaches. These included mass spectrometry using a GC 6890N (Agilent Technologies, Palo Alto, CA, USA) equipped with a mass selective detector 5975N (Agilent Technologies), using the same column and conditions by quantification section. The mass spectra were obtained by electron impact at 70 eV, acquired over the range m/z 40-500, and compared with the database of the NIST MS library (National Institute of Standards and Technology, Gaithersburg, MD, USA). Additionally, the linear retention indices (LRI) for the compounds were obtained by using the series C5-C18 (Supelco) of alkanes in the CG-FID with the same column and conditions, and compared with the LRI available in the references, which used the same column [12; 16; 17; 18; 42; 43; 44]. Finally, some compounds (these are indicated in Table S2, Supplementary Material) were also compared with the retention time of the authentic standards in CG-FID.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Odor** & **Definition** & **Reference Samples** \\ \hline \multirow{2}{*}{Greasy} & Odor associated with the pork & \multirow{2}{*}{5 g of pork back fat} \\  & back fat & \\ \multirow{2}{*}{Fermented} & Odor associated with the lactic acid & \\  & or cheese & \\ \multirow{2}{*}{Garlic} & Odor associated with the & \multirow{2}{*}{5 g of garlic mixture (0.5 g garlic powder/100 g pork meat} \\  & garlic powder & \\ \multirow{2}{*}{Vinegar} & Odor associated with the acetic acid & 25 mL of 0.4\% (\triangledown/\triangledown) acetic acid \\ \multirow{2}{*}{Rancid} & Odor associated with the old oil & 1 soup spoon rancid olive oil \\  & & 5 g of chili mixture (1.5 g \\ \multirow{2}{*}{Chili} & Odor associated with the paprika & paprika + 50 mL water/100 g pork \\  & & meat minced) \\ \multirow{2}{*}{Pork meat} & Odor associated with the minced & \multirow{2}{*}{5 g pork meat minced} \\  & pork meat & \\ \multirow{2}{*}{Pepper} & Odor associated with the pepper & \multirow{2}{*}{5 g of pepper mixture (1 g/100 mL} \\  & powder & \\ \hline \hline \end{tabular}
\end{table}
Table 2: Definition and references used to evaluate the odor intensity.