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.