Effect of the Organic Production and the Harvesting Method on the Chemical Quality and the Volatile Compounds of Virgin Olive Oil Over the Harvesting Season.

Organic production has increasing importance in the food industry. However, its effect on the olive oil characteristics remains unclear. The purpose of this study was to research into the effect of organic production without irrigation, the traditional harvesting methods (tree vs. ground picked fruits), and the harvesting time (over a six-week period) on the oil characteristics. Free acidity, peroxide value, K232, K270, ΔK, total phenols, oxidative stability and the volatile compound profile (by SPME extraction, gas chromatography and mass detection) of olive oils from the Verdial de Badajoz cultivar were analysed. The organic production affected the peroxide value, total phenols, oxidative stability and 34 out of 145 volatile compounds. Its effect was much less strong than that of the harvesting method, which affected severely all the chemical and physical-chemical parameters and 105 out of 145 volatile compounds. Conversely, the harvesting time was revealed as a factor with little repercussion, on the chemical and physical-chemical parameters (only peroxide value was influenced), although it affected 83 out of 145 volatile compounds. The larger content in total phenols in the organic oils than in the conventional ones could explain the increase in oil stability and the differences in the volatile compounds.

Volatile molecular markers of VOO Thermo-oxidation: Effect of heating processes, macronutrients composition, and olive ripeness on the new emitted aldehydic compounds.

Heating operation has been applied to Chétoui extra-virgin olive oils (EVOOs) extracted from fruits with several ripening stages (RS). The studied samples, were subjected to microwave and conventional heating. Results showed that heated VOOs after 2.5 h and 7 min of conventional and microwave heating, respectively, gave rise to a drastically decrease of LOX products and allowed the detection of toxic new formed aldehydic volatiles (alkanal: nonanal, alkenals: (Z)-2-heptenal and (E)-2-decenal, and alkadienals: (E.E)-2.4-decadienal), which can be used as markers of VOO degradation. Their abundance in the VOO headspaces depends on their boiling points, the rate of their possible degradation to yield other compounds, on the heating processes and on the rate of macronutrients. The emission rate of the new synthesized volatiles during heating processes was mainly attributed to enzymatic oxidation of some fatty acids. Hexanal, (Z)-2-heptenal, (E)-2-octenal, (E)-2-nonenal, (E,E) and (E,Z)-2,4-decadienal, and (E,E)-2,4-nonadienal, derived from linoleic acid, and heptanol, octanal, nonanal, decanal, (E) and (Z)-2-decenal, (E)-2-undecenal, and (E,E)-2,4-nonadienal, are emitted after degradation of oleic acid. During thermo-oxidation, the ECN44 (LLO, and OLnO), and the ECN46 (OLO, and PLO + SLL) compounds decreased, whereas, the ECN48 (OOO, and PPO), and the ECN50 (SOO) compounds increased when temperature and heating time increased. The several variations of the studied biochemical compounds depend to the heating processes. Ripening stage of olive fruits can be used as a tool to monitor the emission rate of the aldehydic volatiles, but cannot be used for a chemometric discrimination.

Improvement of the Sterol and Triacylglycerol Compositions of Chemlali Virgin Olive Oils through Controlled Crossing with Mediterranean Cultivars.

The chemical composition of extra virgin olive oils (EVOOs) from six new progenies, obtained through controlled crossings between the main Tunisian variety Chemlali and autochthonous (Chemcheli) and foreign cultivars (Sigoise, Coratina, Koroneiki, and Arbequina) used as pollen acceptor or pollinator, were compared with the EVOO of Chemlali cultivar known to be the main one cultivated in Tunisia as it is the most adapted to the arid climate. Several analytical determinations of major and minor components of EVOO were employed, especially triacylglycerol and sterol fractions. All the studied hybrid EVOOs showed an improvement in their chemical composition and stability by comparison with Chemlali EVOO. The main triacylglycerols were 1,2,3-trioleylglycerol (OOO), 2,3-dioleyl-1-palmitoylglycerol (POO), 2,3-dioleyl-1-linoleylglycerol (LOO) and 2,3-dioleyl-1-stearoylglycerol (SOO). ß-sitosterol, Δ5-avenasterol and campesterol were the principal sterols in all samples. Cholesterol, stigmasterol, clerosterol and Δ7-stigmastenol were also found in all samples. Oil samples examined showed inter-variability between the studied cultivars. Results of discriminant and principal component analyses appear to prove that genetic origin of the raw materials has a great influence on the final composition of the oil; especially triacylglycerol and sterol compositions.

Chemical composition of virgin olive oils according to the ripening in olives.

The aim of this study was the classification of olive oil according to the stage of ripeness of the olives used for its manufacture. A discriminant analysis was applied taking as dependent variables the fatty acids, triglycerides and sterols profile. The evolution of parameters of quality of the oils during ripening of the fruit has also been studied in three successive crops. The results of the classification shows that 88.5% of selected original grouped cases are correctly classified (85.7% green, 80% spotted and 78.9% ripe) and furthermore the validation classified the 69.6% of the unselected original cases. The most discriminating variables have been: avenasterol, linolenic acid, ß-sitosterol and gadoleico. Fig. 1 shows graphically the values of the canonical discriminant functions and the centroids of the intervals of three or the maturity index.