[Show abstract][Hide abstract] ABSTRACT: At the industrial scale, the major source of olive oil deterioration is the poor handling of the raw material during the time separating harvesting from processing. The objective of this work was to verify the effect of modified atmospheres and cold storage in relation to quality parameters of the extracted oils. Olives (cv Chétoui) intended for oil extraction, were stored for 21 days at two different temperatures (ambient temperature 14 ± 2 °C and 5 °C) and under two different modified atmospheres 21% O₂ - 0% CO₂ and 2% O₂ - 5% CO₂. Oils quality was ascertained with analytical parameters: free fatty acids, peroxide value, K₂₃₂, K₂₇₀ as suggested by European regulation. Oxidative stability, total phenols content, radical scavenging activity and fatty acids composition were carried out in order to measure the hydrolytic and oxidative degradation of oils. Olive oils quality parameters were significantly affected by treatments with especially a beneficial effect on primary oxidation indicators and free acidity. Most efficient treatments, with regard to oils phenolic content and involved parameters, were 21% O₂ - 0% CO₂ at ambient temperature (636.25 mg ca/kg) and 2% O₂ - 5% CO₂ under 5 °C (637.50 mg ca/kg). Those two treatments improved individually oil samples phenolic content of 25% but not at the same storage period.
No preview · Article · Aug 2012 · Food Science and Technology International
[Show abstract][Hide abstract] ABSTRACT: One hundred and fifty accessions belong to six wild olive populations from Tunisia were analyzed using fruit pomological traits and oil chemical characteristics. Analysis of variance revealed significant differences among olive accessions for the main studied parameters, indicating a high degree of variability among oleasters. Cluster analysis revealed no clear relationships between accessions according to their geographical origin. Among the screened oleasters, three stand out for their interesting oil parameters, as compared to traditional varieties with high oleic and low linoleic acid contents, high triolein level, large total phenol content, high oxidative stability and high oil content. ZI2 had the highest values of oleic acid (78.5%), whereas H3 was noteworthy for its higher content of phenolic compounds (435.3 mg/kg). Accordingly, oil from H3 presented the highest oxidative stability (83.5 h). A significant relationship was observed between phenolic compounds and oxidative stability.
The identification of new cultivars and their oil composition is a key point in the improvement of olive oil production. This is the first study of chemical composition of virgin olive oils from wild olives. The paper is a study on the quality characteristics of olive oils obtained from wild olive trees growing in Tunisia to define new cultivars well adapted to Tunisian environment and yielding high quality oils. Although the study was carried out in Tunisia, it might be applied to other countries with wild olive trees, in order to contrast productivity and oil quality with those resulting from native cultivars and transplanted foreign varieties.
No preview · Article · Nov 2010 · Journal of Food Biochemistry
[Show abstract][Hide abstract] ABSTRACT: In this study, eighteen olive varieties, originating from Spain, France, Italy, Greece and Algeria, and maintained at the olive experimental station of Boughrara (arid region of Tunisia) were evaluated for their oil yield and fatty acid composition. The analysis of variance revealed significant differences among varieties for all traits (p < 0.01). The Hierarchical Cluster Analysis (HCA) classified the varieties into three main groups. The first group included a subgroup which is composed of seven olive varieties (Cornezuelo, Verdial de Vélez-Málaga, Leccino, Coratina, Koroneiki, Lechín de Granada and Changlot Real) characterized by high oil yield with high oleic, low palmitic and linoleic acid contents. The fatty acid compositions of the oils from these varieties comply with international standards and show more beneficial characteristics than the oil obtained from Chemlali: the most abundant olive cultivar in Tunisia. Finally, the main fatty acids (palmitic (C16:0), oleic (C18:1) and linoleic (C18:2)) of nine of the studied virgin olive oils were compared to those sampled from their traditional areas. Except for Koroneiki and Olivière oils which showed an unchanged fatty acid composition and for Cornezuelo oil in which the level of oleic acid raised and the level of linoleic acid decreased, most of oils showed a decrease in oleic acid rates and an increase in palmitic and linoleic acid percentages as compared to those from their original sites.
No preview · Article · Dec 2009 · Grasas y Aceites
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study was to evaluate differences in the chemical composition of virgin olive oils from the Chemlali variety cultivated in different olive growing areas of the Centre of Tunisia. All samples were harvested using the same controlled procedures and were submitted to a controlled processing in the same laboratory mill. Several analytical parameters and indices were determined. Results showed that the oils quality was attributed not only to the olive variety but also to the plantation site, therefore to climatic and pedologic factors. All these parameters showed an important effect on the fatty acid, phenol, α-tocopherol, sterol and volatile contents of the oils.
No preview · Article · Jan 2009 · Asian Journal of Biochemistry
[Show abstract][Hide abstract] ABSTRACT: A study on the characterization of virgin olive oils from wild olives (Olea europaea L. subsp. Oleaster) was conducted in order to define new cultivars which are welladapted to the Tunisian environment and yield high quality oils. The study was done during the crop years 2003/04, 2004/05 and 2005/06. The main analytical parameters of the oils were evaluated: fatty acid compositions, chlorophylls, carotenoids, tocopherols and phenolic compounds as well as their relationship with oxidative stability. The fatty acid composition of all the wild olive trees tested produced virgin olive oil which compiles with commercial standards, as well as for their appreciable amounts of tocopherols and phenolic compounds. Tocopherol analysis by HPLC revealed the presence of a, β, γ and δ tocopherols In all the studied olive oils. Total tocopherol content was significantly influenced by the varietal factor. It ranged from 310 (SB12) to 780 mg/kg (H3). As for total tocopherols, the amount of each tocopherol varied according to genotype, a tocopherol is the most prominent, whereas β, γ and δ tocopherols are less represented. Results showed a clear influence of total phenols and o-dlphenols on virgin olive oil stability (R = 0.905, 0.963 P< 10-3, respectively), and a much lower contribution of tocopherols (R = 0.568) and acidic composition (R = 0,563).
No preview · Article · Dec 2008 · Grasas y Aceites
[Show abstract][Hide abstract] ABSTRACT: Fruits from three Tunisian cultivars of Olea europea L. grown in the southeast of Tunisia were harvested at the maturity stage of ripeness and immediately processed with a laboratory mill. There are as yet no data on the chemical composition of virgin olive oils from the southeast of Tunisia, an area characterized by an arid condition of growth for olive trees. Our results showed significant differences in the analytical parameters examined for the three cultivars such as fatty acid composition, total phenols and o-diphenols, and the content of chlorophylls and carotenoids, confirming the importance of genetic factors in the chemical characteristics of the oil. Headspace solid-phase microextraction (HS-SPME) was applied to the analysis of volatile compounds of virgin olive oils. Forty-eight compounds were isolated and characterized by GC-RI and GC-MS, representing 94.1–98.1% of the total amount. (E)-Hex-2-enal, the main compound extracted by SPME, characterized the olive oil headspace for all samples. So, it was clearly shown that there were qualitative and quantitative differences in the proportion of volatile constituents from oils of the various cultivars.
Full-text · Article · Jan 2008 · European Journal of Lipid Science and Technology
[Show abstract][Hide abstract] ABSTRACT: Water relation parameters, leaf C02 assimilation rates, stomatal conductance (gs), internal CO2 concentrations (C i), and stomatal density were studied in two major Tunisian olive cultivars, Chemlali and Chetoui, under rain-fed, or rain-fed plus a moderate level of supplemental irrigation, conditions. Measurements were carried out throughout the season from January - September 2005, on 1-year-old leaves. CO2 assimilation rates showed substantial seasonal variation, but were similar in the two cultivars, with higher values during the Spring and lower values during the Summer. Stomatal conductance (g,) followed a similar trend to leaf CO2 assimilation rates, with an increase in March, followed by a decrease during August. Chetoui had the highest leaf CO 2 assimilation rate and g5 value (24.26 μmol m -2 s-1 and 0.35 mol m-2 s-1, respectively); but, compared to the supplemental irrigation treatment, Chemlali had a higher resistance to drought stress than Chetoui.
No preview · Article · Sep 2007 · Journal of Horticultural Science and Biotechnology
[Show abstract][Hide abstract] ABSTRACT: Characterization of virgin olive oils from two new olive cultivars obtained through controlled crossings on Meski variety was investigated. These two olive varieties have been selected among a progeny of 30 olive descendants after an evaluation of oil fatty acid composition and the content of their fruits. The study was achieved during the crop years 2001/2002 and 2002/2003. These two new cultivars (9D and 6H) had an improved oil composition compared to that of Chemlali, the dominant Tunisian olive oil variety; the latter is characterized by low rate of oleic acid and high rates of linoleic and palmitic acids. New cultivars are distinguished by: (1) good content of total phenols and oil yield; (2) a balanced fatty acid composition; and (3) a good content of OOO and a relatively low ΔECN42 as compared to that of Chemlali.
No preview · Article · Feb 2007 · Journal of Food Lipids
[Show abstract][Hide abstract] ABSTRACT: Evaluation and identification of wild olive genetic resources allowed us to select new olive varieties and to recognize Tunisian grove richness and diversity. Five new olive cultivars were previously selected among populations of wild olive plants on the basis of agronomic and chemical evaluations. Their virgin olive oils were analysed for their fatty acid composition, quality indices (Free acidity, PV and UV characteristics) and oxidative stability. They were then submitted to solid phase microextraction (SPME) and their volatile compositions were determined.Forty five compounds were isolated and characterized by GC–MS, representing 85%–98% of the total amount. The presence of some of these compounds in virgin olive oil had not been previously reported. The volatile compounds identified were mainly (E)-3-hexen-1-ol, (E)-2-hexen-1-ol, tricosane and β-selinene. Results demonstrated that the profiles of oleaster oils were distinctly different from those of European and Tunisian oils. All results indicate that there is a wide variability in the chemical and aroma characteristics of the selected oleaster virgin olive oils.
[Show abstract][Hide abstract] ABSTRACT: The effect of growing area on the natural antioxidant and oxidative stability of Chétoui virgin olive oil was studied. Total phenolic content, tocopherol composition, fatty acid composition and oxidative stability were analyzed. The results obtained in this study showed that Chétoui virgin olive oil composition is greatly influenced by growing environment, i.e., mainly by the climatic and pedologic factors. The cumulative rainfall appears to have a major influence on phenolic and o-diphenol content. Among studied samples, Amdoun oil had the highest total phenolic content, which exceeded 700 mg/kg. Moreover, it contained the highest amounts of o-diphenols 286.08 ± 6.74 mg/kg and total tocopherols 405.65 ± 4.17 mg/kg.
The amounts of total phenols and o-diphenols showed a good correlation (P ≤ 0.001) with stability while tocopherols showed a very low relation to oxidative stability.
No preview · Article · Nov 2006 · Journal of Food Biochemistry