Fatty acids and sterols evolution during the ripening of olives from the Moroccan Picholine cultivar.

Abstract

From june to february 13 olive samples from Moroccan Picholine olive trees were collected. The oils from the first samples have high acidity levels (>1%). But this latter decreases rapidly then stabilizes between 0.36 and 0.44%. The evolution of the total fatty acids shows a relatively high rates of C18:3 in the first samples. These proportions decrease during the ripeness process and stabilize at 0.8 - 0.9% from begining november. The C16:0 decreases while C18:2 increases during the ripening. Monoinsaturated fatty acid predominate in the Sn 2 glycerol position. The sum of the palmitic and the stearic acids proportions in this position become less than 1.5% between mid november and begining January. The chemical composition of the mesocarp fatty acids is quantitatively and qualitatively similar to that observed for the total fatty acids of the whole olives. However, the total fatty acids of the olive seed are quantitatively different from those of the mesocarp. The proportions of these fatty acids remain stable since mid September. The β sitosterol is the main sterol in all our samples with a proportion exceeding 84%. The Δ5 avenasterol reaches a maximum at January 2 nd at this time the β sitosterol have its lowest rate. The campesterol rates vary between 3 and 3.5% and the rates of the stigmasterol stabilize around 1 % until the begining november then it decreases to 0.5%.