Volatile compound analysis
The volatile compounds extracted using SPME with DVB/CAR/PDMS (Supelco,
Inc.) fiber following to previously described (Yanget al., 2017).
Individual oil samples (5g) were chosen and placed into a sealed bottle
and water bath at 50°C immediately. The aroma compounds were extracted
using SPME method for 30 min. The fiber was then removed and transferred
into the GC/MS injector For the GC–MS measurements, GC HP 6890 (Calif,
USA) attached to an HP5973MSD detector with a DB–1 column (60 m×0.25
mm×0.25 μm, Agilent, Palo Alto, CA, USA) was used. Helium was operated
at flow rate of 1 mL/min. The ionization potential used was 70 eV, and
the temperature of the ion source was at 230 °C. The condition of the
oven temperature was as follow: I) 40 °C as initial temperature, then
increased to 120 °C (speed of 3°C/min) and II) then set to a rate of
increase to 200 °C (speed of 5°C/min), the temperature which then was
held for 10 min. The linear retention indices (RIs) were calculated from
the retention times of n–alkanes
(C5–C25), and the volatiles
Identification by matching the RI with data found other literature
(Yehet al., 2014). The quantities of volatile compounds were indicated
using the peak area.