Analysis of total FAMEs was performed on a GC 8000 Thermo Quest gas chromatograph coupled to a Voyager MD800 Finnigam Mass Spectrometer Detector.
The analytical column was a fused-silica TRB-WAX polyethyleneglycol capillary column (60 m × 0.25 mm I.D., 0.2 μm film thickness; Teknokroma, Barcelona, Spain).
1 μL of sample was injected in a split/splitless injector set at 250 °C. The GC was setup with helium as a carrier gas at a constant flow of 1.2 mL/min. The oven temperature programme was: 40 °C (5 min); to 100 °C (10 min) at 5 °C/min; to 190 °C (20 min) at 3 °C/min; to 240 °C (5 min) at 5 °C/min.
Detection was carried out with a MD800 mass-selective single quadrupole, using electron-impact ionisation (70 eV), detector at 550 V, source temperature at 200 °C, a scan range of 50–450 amu (scan time of 0.9 s and an inter scan delay of 0.1 s). Two replicates were injected for each sample.
Components identification was based on comparison of its mass spectra with those of the US National Institute of Standards and Technology (NIST) database 98 libraries of mass spectra, considering peak base, molecular masses and characteristic mass losses. Complementary, standard fatty acid methyl esters (FAMEs) of palmitic, stearic, oleic and linoleic acids were used for the confirmation of the GC–MS libraries results, by comparing the peaks in the analysed chocolate samples with the retention times and mass spectra of known standards (Supelco Bellefonte, USA). Quantification of the fatty acids methyl ester profiles was done considering the relative areas of peaks, expressed as the relative percentage of the individual area of each one relative to total area of compounds in the chromatogram.