Odp 2

The aroma-active compounds in the samples and control were screened using GC-O identification with an Agilent 6890 gas chromatograph equipped with an Agilent 5973 N mass selection detector (Wilmington, DE, USA) and a sniffing port (ODP-2; Gerstel, Inc., Linthicum, MD, USA), based on the previous description of Gao et al., (2020) [3 (link)].
The flavor dilution factor (FD) represents the highest split ratio (most dilution) of GC injection at which the odorant could be noticed (even if not identified) by at least two out of three panelists [3 (link)]. In this study, the split ratios of GC injection were 1:1, 2:1, 4:1, 8:1, 16:1, 32:1, 64:1, 128:1, 256:1 and 512:1.

A GC (Agilent 6890, Santa Clara, CA, USA) equipped with a flame ionization detector (FID), a mass selective detector (Agilent 5973 MSD) and a Gerstel ODP 2 (Linthicum, MD, USA) sniffing port using a deactivated capillary column (30 cm × 0.3 mm) heated at 240 °C and supplied with humidified air at 40 °C was used to analyze aroma and aroma-active compounds. Helium was used as a carrier gas with a flow rate of 1.5 mL min⁻¹. Aroma compounds were separated on DB-Wax column (30 m length × 0.25 mm i.d. × 0.5 μm thickness, Santa Clara, CA, USA). The program conditions were as follows: The oven start temperature was 50 °C (1 min), the subsequent gradient was 5 °C min⁻¹ to 200 °C and then at a rate of 8 °C min⁻¹ to 260 °C with a final hold at 260 °C for 5 min (DB-WAX column, Santa Clara, CA, USA). Afterwards, GC effluent was split 1:1:1 among the FID, MSD, and sniffing mode via a Dean’s switch. A total of 3 μL of extract was injected each time in pulsed splitless (40 psi; 0.5 min) mode. Mass spectra in the electron ionization mode were recorded at 70 eV and a mass/charge range of 30–300 amu at 2.0 scan s⁻¹ scan rate. The identification of compounds was carried out using mass spectral database (NIST 98, Wiley 6), retention index, and chemical standards. Concentration of each compound was calculated using internal standard method [11 (link)].