Variability of 4-Monomethylsterols and 4,4'-Dimethylsterols in Olive Oil and Their Use as Indicators of Olive Variety, Ripening Degree, and Oil Storage Temperature.

To investigate the variability of 4-monomethylsterols and 4,4'-dimethylsterols in olive oil as a result of variety, ripening, and storage temperature, 36 samples were subjected to gas chromatography with flame ionization detection (GC-FID) and with mass spectrometric detection (GC-MS), and results were processed by univariate and multivariate statistics. Relative amounts (percent) of β-amyrin, cycloartenol, and 24-methylenecycloartanol accounted for the most variation due to variety, while citrostadienol (percent) and 24-methylenecycloartanol (milligrams per 100 g) were strongly affected by ripening. Multivariate statistics differentiated olive oils regardless of storage conditions, which implied the possibility to use 4-monomethyl- and 4,4'-dimethylsterols as indicators of variety and ripening degree for fresh and stored oils. Absolute changes in 4-monomethyl- and 4,4'-dimethylsterols after storage were of a much smaller magnitude, meaning the investigated olive oils essentially retained health-beneficial features that derive from these compounds. Relative changes caused by storage were specific for each storage temperature and were useful in discriminating oils by linear discriminant analysis.