Cere ed alcanoli nell'olio di oliva. Studio dell'influenza del tempo, temperatura ed illuminazione su contenuto e composizione

It is well known that the total content of waxes from linear alcohols in olive oil tends to increase with ageing. In this paper, we have shown that there is the same tendency in untreated olive oils for the single terms but more remarkably for the waxes C44 and C46. Consequently, with ageing, the composition per cent of C40 and C42 tends to decrease and that of C44 and C46 to increase. A similar behaviour is observed when the temperature increases under the same ageing time and, for the composition, especially for the increase of C40 and the reduction of C44 percentages. The content of waxes C36 and C38 from diterpene alcohols C20 (phytol and geranyl-geraniol) and fatty acids C16 and C18 also tend to rise with ageing, but not always. It often indeed occurs that, on the contrary, at the highest temperatures a diminution takes place or that, at a given temperature, at the beginning of ageing an increase is shown, followed by a lessening for longer periods. This behaviour is not so due to a displacement towards the hydrolysis of the equilibrium esterification hydrolysis, as to a degradation of waxes from diterpene alcohols. This hypothesis is supported by the diminution which is sometimes observed for diterpene alcohols content after a 6 months ageing, more often for the highest temperatures. No general trend is observed for waxes and alcanols contents by studying the possible influence of the light after a period of 6 months of the oils ageing at room temperature. The depressing effect of light on the C40-C46 waxes level found in the pomace olive oil and that of the C36-C38 waxes level observed in the extra virgin oil has not been confirmed in the other samples examined.