Two grams of each sample was weighed into a 22-mL vial and sealed with a silicon/PTFE
septum and open-top cap. A solid phase microextraction (SPME) fiber
(57301, Supelco, USA) coatedwith polydimethylsiloxane (100 μmthickness)
was used to absorb the headspace volatiles. Before extracting the
volatiles, the fiber was cleaned at 250 °C for 5 min in a GC injection
port and used immediately to prevent possible contamination. Samples
were preheated for 10 min at 50 °C in a heating block, and the SPME
fiber extracted the headspace volatiles for an additional 20 min. The
fiber was then injected into the GC and remained there for 2 min for
desorption. A Varian 4000 GC/MS (Varian, USA) and a Varian capillary
column (30 m × 0.32 mm, 0.25 μmfilm thickness) were used to quantify
the volatiles