Fatty acid composition analysis
The previously reported method (Ichihara, et al., 1996) was followed to
convert oil samples to fatty acid methyl esters, which were analyzed by
gas chromatography (GC). Oil sample (10 mg) was dissolved in hexane
(about 1.4 ml), and 2 N KOH in methanol (200 μL) was added. The solution
was shaken with a Vortex mixer for 2 min and allowed to separate into
two phases. The hexane layer (top layer) was added to autosampler vials,
and the solution (1 μl) was injected into a capillary column (Supelco
SP-2560, 100 m × 0.25 mm, 0.20 μm film, Bellefonte, PA, USA) linked to
Shimadzu GC 2010 (Columbia, MD, USA). The program was set to have the
initial temperature at 165 °C for 30 min, then to increase at a rate of
2 °C/min to 200 °C, and to hold at 200 °C for 12 min. Helium (carrier
gas) flow rate was 2.0 ml/min, the injector temperature was 250 °C, the
FID temperature was 250 °C, and the split ratio was 1:100. Fatty acid
methyl esters peaks were identified using commercial standards.