Fatty acids were evaluated as their methyl esters after cold alkaline transesterification with methanolic potassium hydroxide solution (Commission Regulation (EEC) no. 2568/91) and extrac- tion with n-heptane.
The fatty acid profile was determined with a Chrompack CP 9001 chromatograph equipped with a split-splitless injector, a FID detector, an autosampler Chrompack CP-9050 and a 50m×0.25mm i.d. fused silica capillary column coated with a 0.19 m film of CP-Sil 88 (Varian).
Helium was used as carrier gas at an internal pressure of 110 kPa. The temperatures of the detec- tor and injector were 250 ◦ C and 230 ◦ C, respectively.
The split ratio was 1:50 and the injected volume was of 1 L.
The results are expressed in relative percentage of each fatty acid, calculated by internal normalization of the chromatographic peak area eluting between myristic and lignoceric methyl esters.
A standard mixture (Supelco 37 FAME Mix) was used for identification and calibration purposes (Sigma, Spain)