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L’oliveraie tunisienne est riche en variétés, mais en dépit de cette richesse, aucune évaluation biochimique des huiles issues de ces variétés n’a été entreprise jusqu’à l’heure actuelle. C’est pourquoi nous procédons dans le présent travail à l’étude de la composition chimique des huiles de sept variétés à huiles cultivées en Tunisie. Outre la caractérisation variétale, cette étude a pour objectif l’amélioration de la qualité de nos huiles par le choix de variétés performantes du point de vue de la composition chimique de l’huile, pour répondre aux exigences du marché international relatives à la norme commerciale. Dans ce premier travail, nous nous intéressons à la composition de l’huile en acides gras et espèces moléculaires de triacylglycérols. Notre étude confirme qu’aussi bien la teneur en huile des olives que la composition en acides gras et triacylglycérols des huiles sont étroitement liées à la nature du cultivar. Parmi les variétés étudiées, la Sayali et la Chemchali se distinguent par un rendement élevé en huile, supérieur à 50%. Ces deux variétés possèdent les taux les plus élevés en acide oléique (82 et 71%) et les taux les plus bas en acide linoléique (respectivement 4 et 10%). Elles possèdent aussi les taux les plus faibles de trilinoléine, respectivement 0,05 et 0,19%. Par conséquent, les huiles de ces deux variétés sont à recommander pour des coupages permettant de corriger la composition chimique des huiles des autres variétés

Background: The aim of the present work was to investigate the influence of fruit ripening on oil quality in an attempt to establish an optimum harvesting time for Chétoui olives, the second main olive variety cultivated in Tunisia., Results: Our results showed that many analytical parameters, i.e., peroxide value, UV absorbance at 232 and 270 nm, chlorophyll pigments, carotenoids and oleic acid contents decreased during ripening, whilst oil content and linolenic acid increased. Free acidity remained practically stable with a very slight rise at the highest maturity index. The trend of oxidative stability, total phenols and o-diphenols, showed an increase at the early stages followed by a reduction at more advanced stages of maturity. The major phenolic compounds, such as hydroxytyrosol, ligstroside aglycon, elenolic acid, acetoxy-pinoresinol and oleuropein aglycon, seemed to have the same behaviour. In the case of tyrosol, a strong decrease was observed directly related with the ripening progress., Conclusion: On the basis of the evolution of the analytical parameters studied, the best stage of Chétoui olive fruits for oil processing seems to be at ripeness index higher than 2.0 and lower than 3.0., ((c) 2009 Society of Chemical Industry.)

Treatment of rape seedlings with increasing CdCl2 concentrations in the culture medium resulted in a cadmium accumulation within plant tissues, which increased with external metal dose; such accumulation was more important in roots than in leaves. Biomass production was severely inhibited, even at low cadmium concentration. In leaves, quantities of chloroplastic lipids, monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), sulfolipids (SL) and phosphatidylglycerol (PG) decreased sharply under metallic treatment. However, contents of extrachloroplastic lipids, mainly phosphatidylcholine (PC) and phosphatidylethanolamine (PE) increased significantly. In contrast to leaves, contents of root phospholipids decreased. Likewise, levels of tri-unsaturated fatty acids: linolenic (C18:3) and hexadecatrienoïc (C16:3) dropped in leaves of treated seedlings as compared to those of controls, suggesting that heavy metals induced an alteration in the fatty acid desaturation process or a stimulation of their peroxidation. Also, trans palmitoleic acid (C16:1-trans) level in PG decreased considerably. In roots, there was a slight decrease in C18:3 level, with a concomitant increase in the C18:2 percentage. Radioactive labelling of leaf lipids with (1-14C) acetate allowed to show that fatty acid biosynthesis was noticeably altered at the highest cadmium dose used (50 microM). Biosynthesis of tri-unsaturated fatty acids was also inhibited which may explain the decline in non-labelled lipid contents. Results showed that metallic ion seems to affect selectively chloroplastic membranes due to an inhibition of polyunsaturated fatty acid biosynthesis. Moreover, a lipid peroxidation occurred in our case because of the spectacular increase of malondialdehyde (MDA) content observed in cadmium treated leaves.