Spme fiber

We used the HS-SPME method to collect volatiles. Static headspace sample extraction was achieved by exposing a 65-μm polydimethylsiloxane/divinylbenzene (PDMS/DVB) SPME fiber (SUPELCO, Bellefonte, PA, USA) to the headspace for 10 min at 60°C. Following the extraction, the fiber assembly was transferred to the GC injection port for desorption at 250°C for 5 min, with the split valve closed for 2 min.

Chemicals including standards were purchased from Sigma (St. Louis, MO, USA). A 50/30 µm divinylbenzene/Carboxen on polydimethylsiloxane on a StableFlex fiber was used. This SPME fiber was purchased from Supelco (Oakville, ON, Canada).

The EVOO samples (2 g), spiked with 100 mg of internal standard solution of 4-methyl-2-pentanol dissolved in refined sunflower oil (50 µg/mL), were placed in a 20 mL glass vial, tightly capped with a polytetrafluoroethylene (PTFE) septum, and held for 5 min at 40 °C to allow for the equilibration of the volatiles in the headspace. After the equilibration time, the septum covering each vial was pierced with a solid-phase microextraction (SPME) needle, and the fiber was exposed to the headspace for 40 min. When the process was completed, the fiber was inserted into the injector port of the GC. The temperature and time of the pre-concentration step, performed in a HT280T (HTA s.r.I, Brescia, Italy), were automatically controlled by the software HT-COMSOFT (HTA s.r.I). The SPME fiber (2 cm length and 50/30 μm film thickness) was from Supelco (Bellefonte, PA, USA) and consisted of a stable flex stationary phase divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS). The fiber was previously conditioned following the instructions of the supplier.

The major flavor-associated compounds found in the headspace of untreated and treated samples of watermelon juice were analyzed by combining solid-phase microextraction (SPME) and gas chromatography-olfactometry-mass spectrometry (GC-O-MS).^{27 (link)} Watermelon juice (10 mL) was transferred to a 40 mL vial containing 3 g of NaCl. A SPME fiber (Supelco, Bellefonte, PA, USA), coated with 50/30 μm of divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS), was inserted into the headspace of each vial. Afterwards, the vial was heated at 50 °C for 40 min to facilitate the release of volatile compounds from the sample to the headspace volume.

The method was based on the literature and some optimizations as follows: Take 0.2 g of ground tea leaves, add 10 mL of hot distilled water (90 °C), and add 0.2 g of sodium chloride in a 15 mL headspace bottle, equilibrated for 3 min, and supplement with 5 μL of 1,3-dichlorobenzene (21 mg/kg in EtOH) as an internal standard [4 (link)]. The headspace SPME fiber (Supelco, Inc., Bellefonte, PA, USA) was 50/30 μm DVB/CAR/PDMS. Heating and extracting were performed in a 50 °C water bath for 40 min.

The volatile in the headspace of the culture supernatant was extracted using a poly- dimethylsiloxane/carboxen/divinylbenzene (PDMS/Car/DVB) SPME fiber (Supelco, Bellefonte, PA, USA) for 20 min at 37 °C. All samples were agitated at 250 rpm and incubated for 15 min before fiber exposure at the corresponding extraction temperature.