The aim of this work was to ascertain the amount of oxidized triglycerides and triglyceride dimers in virgin and "lampante" olive oils: to this effect, 38 samples were collected from different oil-mills. No data on the above compound classes in "lampante" olive oils have ever appeared in literature up to now. However, fat autoxidation is known to imply polymerization reactions; so. low amounts of oligopolymers may be formed in oil at a given state of oxidation. This aspect also applies to virgin olive oils because the very few data reported in literature are mainly related to extra virgin olive oils which are classified as high quality oils. Column chromatography and highperformance size exclusion chromatography were used for oil analysis in this work. Triglyceride dimers were either absent or present in traces in virgin olive oils, but were found in "lampante" oils with a mean value of 0.07 %. Oxidized triglyceride percentages in "lampante" oils were more than twice as high as those present in virgin oils. The data obtained suggest the following consideration: the presence of dimers in vegetable oils reveals a rather high oxidation level and is confirmed by the higher oxidized triglyceride values. This is a reliable index of oxidative degradation in oil.
I n t r o d u c t i o n
So far, the commercial quality of virgin olive oil has been assessed mainly by the following methods of analysis: determination of % free fatty acids (FFA) by which oil types are differentiated; determination of the peroxide value (PV) and U V spectrophotometric analysis.
Though still valid, however, these routine methods do not define thoroughly the quality of an olive oil.
While FFA provide a determination of hydrolytic degradation, they are however quite inadequate to characterize oil quality'. The same is true for PV which measures the primary products of oxidation and does not therefore give an exhaustive picture of the product's state of oxidation. Spectrophotometric analysis too deserves some criticism: refined olive oils have recently appeared on the market with spectrophotometric constants that are very close to those of edible virgin olive oils'.
Recent lines of research have shown presence, in refined oils, of polymer triglycerides the percentage of which seems to be related to the level of oxidation of