Characterization and quantification of 4-methylsterols and 4,4-dimethylsterols from Iberian pig subcutaneous fat by gas chromatography-mass spectrometry and gas chromatography-flame ionization detector and their use to authenticate the fattening systems

► Characterization and quantification of 4-methylsterols and 4,4-dimethylsterols. ► Differentiation between extensive and intensive fattening systems of Iberian pigs. ► Analysis by GC-MS in full scan mode and GC-FID. ► Pattern recognition techniques have been applied.