Fatty acid composition analysis
Esterification of SPOMFs (50 mg) was achieved using 25% boron trifluoride (BF3) in methanol (2 mL) at 70 °C for 3 min. The resulting fatty acid methyl esters (FAMEs) were extracted with hexane (2 mL). The upper layer was separated and dried over anhydrous sodium sulfate, centrifuged at 8000 rpm for 5 min, and then used for gas chromatograph (GC) analysis.
The FAMEs were separated on a DB-Fast FAME column (30 m × 0.25 mm × 0.25µm) and quantified by a flame-ionization detector (FID) mounted in a gas chromatograph (7820A, Agilent, USA). The injector and FID temperatures were 250 °C, the initial column temperature was maintained at 80 °C for 0.5 min and then increased to 165 °C (at a rate of 40 °C/min), following which it was maintained at 165 °C for 1 min. Finally, the temperature was increased to 230 °C (at a rate of 4 °C/min) and held at 230 for 4 min. The running time of the entire program was 23.875 min. The FAMEs were identified and quantified by comparison of the retention times of the sample peaks with those of a mixture of the FAME standards.