Tunisian Extra Virgin Olive Oil Research Articles

The performance of the Tunisian olive oil exports within the new distribution of world demand

The present work aims to analyze the performance of the Tunisian olive oil exports compared to its main competitors (Spain, Italy, Greece, Turkey and Portugal) during the last fifteen years, on the European market and four potential markets: the United States, Canada, Japan and Brazil using the Shift Share Analysis, in order to identify the main sources of change. The period 2011-2015 was a boom period for Tunisia in all studied markets. The gain in Tunisian competitiveness on the new markets (Canada, Japan and Brazil) is related to the growth of their global imports and the competitiveness of Tunisian exports reinforced by the superior quality of Tunisian extra virgin olive oil and the recourse to packaged oil. The results indicate that the maintenance of a sustainable international competitiveness of Tunisia on the olive oil market depends on its domestic production and that of its European competitors, to which is added recently the Turkish competition, policies and trade agreements that must be negotiated and requires the improvement of its non-price competitiveness.

Market Segmentation Using Intrinsic Product Attributes: Evidence From the Tunisian Olive Oil Market

Market segmentation using consumer preferences is important for the marketing strategy. For staple foods, like olive oil in the Mediterranean region, intrinsic attributes of the product lead these preferences and should prevail in determining consumer groups. In this paper, we apply conjoint analysis and clustering methods to identify olive oil consumer segments in the Tunisian market. A survey was carried out among 274 consumers who were required to blind taste of samples and give scores for 12 different samples of Tunisian Extra Virgin Olive Oil (EVOO). Results revealed three differentiated segments of consumers; 43.8% of consumers prefer strongly flavored olive oil with deep green color while 38.9% support light yellow olive oil with lower flavor. These preferences are described by age, income category, and consumption frequency. Our results indicate that in countries where olive oil is a traditional food ingredient, the marketing strategy must focus on the product’s intrinsic attributes to better target customers.

The effects of geographic region and cultivar on oxidative stability and elemental analysis of Tunisian extra virgin olive oil

Metals contents were determined in 18 samples of Extra Virgin Olive Oil (EVOO) collected from different regions in Tunisia, after microwave digestion with nitric acid and hydrogen peroxide. In oil obtained by the detection power of the ICP–MS technique was sufficient for the determination of trace metals. Oils were extracted using Lab Olive Oil Extractor Machine. The amounts of trace metals in EVOO were lower than the maximum values recommended by FAO/WHO expert committee on food and addictives and US environmental protection agency. Acidity value, K270 and K232 were also determined. The assessment of metal contents in EVOO showed significant differences (p < 0.0001) between the diverse regions and cultivars. ANOVA Test of Cochran is duo to affect by the agro-environmental conditions and the genetic cultivars. Indeed in this study, metals have shown no negative effects on the oxidative rate of the oils and no potential risk for the health of the consumers.

Multiblock chemometrics for the discrimination of three extra virgin olive oil varieties

To discriminate samples from three varieties of Tunisian extra virgin olive oils, weighted and non-weighted multiblock partial least squares – discriminant analysis (MB-PLS1-DA) models were compared to PLS1-DA models using data obtained by gas chromatography (GC), or global composition through mid-infrared spectra (MIR). Models performances were determined using percentages of sensitivity, specificity and total correct classification. The choice of threshold level for the interpretation of PLS1-DA results was considered. PLS1-DA models using GC data gave better results than those using MIR data. Even with the most conservative threshold, PLS1-DA on GC data allowed very good predictions for Chemlali variety (99% correct classification), but had more difficulty to discriminate Chetoui and Oueslati samples (95% and 84% correct classification respectively). Non-weighted MB-PLS1-DA models benefiting from the synergy between the two sources of data were more discriminative than simple PLS1-DA, yielding better prediction for Chetoui and Oueslati varieties (98% and 90% correct classification respectively).

Effects of treadmill training and EVOO enriched diet on cartilage degeneration in rats with ACLT.

The beneficial effects of Extra Virgin Olive Oil (EVOO), the main fat source in Mediterranean diet, are widely studied thanks to its anti-inflammatory and antioxidant properties. Lubricin is a chondroprotective glycoprotein, with lubricant properties. A joint injury causes an increased cytokine expression, associated with decreased lubricin synthesis and predisposition to cartilage degeneration. The aim of this study was to evaluate the beneficial role of EVOO-enriched diet and physical activity, on osteoarthritic cartilage of rats. These effects were assessed through lubricin and interleukin-6 expression in rat joint tissues. Osteoarthritis was induced mechanically by anterior cruciate ligament transection (ACLT). Forty-eight 3-month-old male Wistar rats were used for this study. Experiments and surgical procedures for ACLT were performed in accordance with the guidelines of the Institutional Animal Care and Use Committee (I.A.C.U.C.) of the University of Catania, European Community Council Directive and the Italian Animal Protection Law (Protocol n. 2112015-PR, Italian Ministry of Health). The 48 animals were divided into 6 groups: 1 – control rats (no ACLT, common die); 2 – rats with ACLT and common diet (experimental control); 3 – rats with ACLT, common diet and treadmill training; 4 – rats with ACLT, Sicilian EVOO and treadmill training; 5 – rats with ACLT, Tunisian EVOO and treadmill training; 6 – rats with ACLT, Tunisian EVOO and leaves extract and treadmill training. To this purpose, we performed histomorphometric, histological, immunocytochemical, immunohistochemical and biochemical analysis for lubricin and interleukin-6 evaluations in articular cartilage and synovial fluid of rats. Furthermore, skeletal muscle (anterior tibial) and liver tissue were used to perform histological analyses to exclude respectively hepatic steatosis and sarcopenia. The results showed the beneficial effect of physical activity and EVOO supplementation on the rat articular cartilage. ACLT determined an increase in interleukin-6 expression and a significant decrease in the lubricin expression, while physical activity and EVOO supplemented diet, determined that the values returned to a normal level when compared to the control group. Moreover, EVOO does not cause hepatic steatosis and muscle fibers of all groups did not show damaged histological structure. Our findings suggest that mechanical stimulation is able to increase the release of lubricin in articular cartilage, while the anti-inflammatory properties of EVOO reduces the expression of interleukin-6. In conclusion, the results showed a beneficial effect of the conjunction of EVOO-based diet, corresponding to the Mediterranean diet, and physical activity on the preservation of articular cartilage tissue. Support or Funding Information This study was supported by the University Research Project Grant (Triennial Research Plan 2016–2018), University of Catania, Italy. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Physical activity and Mediterranean diet based on olive tree phenolic compounds from two different geographical areas have protective effects on early osteoarthritis, muscle atrophy and hepatic steatosis.

Osteoarthitis (OA) leads to progressive loss of articular cartilage, pain and joint disability. An acute injury constitutes an important risk factor for early OA, determining an inflammatory process responsible of cartilage degeneration and muscle atrophy, due to the joint pain and immobility. The study aims to assess the effects of conjugation of physical activity and diet enriched by olive tree compounds [extra virgin olive oil (EVOO) and olive leaf extract (OLE)], on the musculoskeletal system in OA rat model. OA was induced by anterior cruciate ligament transection and confirmed by Mankin and OARSI scores. Rats were subjected to physical activity on treadmill 5 days a week for 10min daily and fed with experimental diets (standard diet enriched with Sicilian EVOO, Tunisian EVOO and Tunisian EVOO-OLE) for 12 weeks. Immunohistochemistry was used to evaluate IL-6 and lubricin expression in cartilage tissue and ELISA was used to quantify these proteins in serum at different time points. Histology and histomorphometry analysis were done to valuate liver steatosis, muscle atrophy and cartilage pathological changes. Compared to the OA group, the experimental groups showed general increased lubricin and decreased IL-6 expression, significant muscle hypertrophy and no signs of liver steatosis, suggesting the beneficial effects of physical activity coupled with EVOO-enriched diets on rat articular cartilage. Interestingly, the best result was shown for Sicilian EVOO-enriched diet. In conclusion, the conjugation of physical activity and EVOO-enriched diet determines a significant articular cartilage recovery process in early OA.

Tunisian Extra Virgin Olive Oil Traceability in the EEC Market: Tunisian/Italian (Coratina) EVOOs Blend as a Case Study

In order to check the reliability of an NMR-based metabolomic approach to evaluating blend composition (and declaration), a series of 81 Italian/Tunisian blends samples at different percentage composition (from 10/90 to 90/10% Coratina/Tunisian oil by 10% increase step) were prepared starting from five Coratina (Apulia) and five Tunisian extra virgin olive oil (EVOO) batches. Moreover, a series of nine binary mixtures blend oils were obtained, starting from the two batches’ oil sums. The models built showed the linear relationship between the NMR signals and the percentage composition of the blends. In particular, a high correlation with the percentage composition of blends was obtained from the partial least squares (PLS) regression model, when the two batches oil sums were used for the binary mixtures of blend samples. These proposed methods suggest that a multivariate analysis (MVA)-based NMR approach—in particular PLS regression (PLSR)—could be a very useful tool (including for trading purposes) to assess quantitative blend composition. This is important for the sustainability of the goods’ free movement, especially in the agrifood sector. This cornerstone policy of current common markets is also clearly linked to the availability of methods for certifying the origin of the foodstuffs and their use in the assembly of final product for the consumer.

LC-DAD/ESI-MS/MS characterization of phenolic constituents in Tunisian extra-virgin olive oils: Effect of olive leaves addition on chemical composition

The aim of the present research is to evaluate the chemical characterization of main compounds from Tunisian monocultivar extra virgin olive oil (EVOO) (‘Chemlali’, ‘Chétoui’, ‘Zalmati’ and ‘crossbreeding Chemlali by Zalmati’) extracted after the addition of different amounts (0% and 3%) of olive leaves. As expected for extra virgin olive oil, the main sterols found in all analyzed samples were β-sitosterol, ∆-5-avenasterol, campesterol and clerosterol. Stigmasterol, 24-methylene-cholesterol, cholesterol, campestanol, sitostanol, ∆-7-stigmastenol, ∆-5,24-stigmastadienol, and ∆-7-avenasterol were also found in all samples, but in lower amounts. Most of these compounds were significantly affected by the cultivars but not to be affected by added leaves at 3% to olives prior to the extraction process. The obtained results revealed that 14 phenolic compounds belonging to different phenolic types were characterized and quantified by an effective HPLC-DAD-ESI-MS/MS method. In all the studied olive oil samples, dialdehydic form of elenolic acid linked to hydroxytyrosol (3,4-DHPEA-EDA), oleuropein aglycon (3,4-DHPEA-EA), and ligstroside aglycon (p-HPEA-EA) were the most abundant compounds. In addition, EVOO from ‘Chétoui’ cultivar extracted with 3% of olive leaves presented the highest amount of individual phenolic compounds.

Use of triacylglycerol profiles established by HPLC–UV and ELSD to predict cultivar and maturity of Tunisian olive oils

The usefulness of triacylglycerol (TAG) profiles established by high-performance liquid chromatography using both UV and evaporative light scattering (ELSD) detectors as a tool to discriminate between seven cultivars of Tunisian extra virgin olive oils (EVOOs) was evaluated in this work. Moreover, the discrimination of EVOOs from the cultivars Chemchali, Fouji and Zarrazi, characterized with different maturity indexes, was also studied. With both detectors, a total of 19 peaks, which were common to all the EVOOs studied, were observed. However, ELSD peaks, which provided a higher signal-to-noise ratio than the UV peaks, were selected to construct linear discriminant analysis models for cultivar and maturity index prediction. In all cases, an excellent resolution between all category pairs was achieved, which demonstrated that TAG profiles are a good marker of both cultivar and maturity index of EVOOs.

Sensory and Volatile Profiles of Monovarietal North Tunisian Extra Virgin Olive Oils from 'Chétoui' Cultivar.

The quality of olive oil is defined as a combination of characteristics that significantly determine its acceptance by consumers. This study was carried out to compare sensorial and chemical characteristics of sixty 'Chétoui' extra virgin olive oils (EVOOc) samples from six northern areas in Tunisia (Tebourba (EVOOT); Other regions (EVOON): Mornag, Sidi Amor, El Kef, Béjà and Jendouba). Trained panel taste detected ten sensory attributes. EVOOT and EVOON were defined by 'tomato' and 'grass/ leave notes, respectively. Twenty one volatile compounds from EVOOc were extracted and identified by Headspace Solid-Phase Microextraction followed by Gas Chromatography- Flame Ionization Detector. Principal component and cluster analysis of all studied parameters showed that EVOOT differed from EVOON. Sensory and volatile profiles of EVOOc revealed that the perception of different aromas, in monovarietal olive oil, was the result of synergic effect of oils' various components, whose composition was influenced by the geographical growing area.

Cultivar discrimination and prediction of mixtures of Tunisian extra virgin olive oils by FTIR

Fourier‐transform infrared spectroscopy, followed by multivariate treatment of the spectral data, was used to classify Tunisian extra virgin olive oils (EVOOs) according to their cultivar. Moreover, these data were also employed to establish the composition of binary mixtures of EVOOs from different cultivars. For this purpose, the spectra were divided in 20 regions, being the normalized peak areas within these regions used as predictors. Using linear discriminant analysis, an excellent resolution between EVOOs from different cultivar was obtained. Moreover, multiple linear regression models were used to predict the composition of binary mixtures of EVOOs, being in all cases capable of predicting the percentage of one of the oils with average validation errors below 6%. Thus, the FTIR method proposed in this work, followed by chemometric analysis, could be used in an industrial setting since no complicated laboratory facilities are required, which could save great deal of time and money.Practical applications: EVOO quality can be affected by different parameters, such as cultivar and maturity index, among others, consequently, it is necessary to develop analytical methods able to verify EVOO quality, and also to control its origin since olive oil producers have to include in their manufactured products the cultivar (monovarietal oils) from which the oil was obtained. Currently, almost all the research related to Tunisian EVOOs has been mainly focused on the improvement and characterization of the two main cultivars (Chétoui and Chemlali). Thus, to diversify Tunisian olive oil resources and improve the quality of olive oil produced in Tunisia, research on additional cultivars needs to be conducted. Thus, the present methodology (including the application of chemometric techniques) could be used as an authentication tool for olive oil industry to assess cultivar of EVOO.ATR‐FTIR data of Tunisian EVOOs are used to predict EVOO cultivar using LDA.

Classification of Tunisian extra virgin olive oils according to their genetic variety and maturity index using fatty acid profiles established by direct infusion mass spectrometry

The usefulness of fatty acid profiles established by direct infusion mass spectrometry (DIMS) as a tool to discriminate between seven genetic varieties of Tunisian extra virgin olive oils (EVOOs) was evaluated in this work. Moreover, the discrimination of EVOOs from the genetic varieties Chemchali, Fouji, and Zarrazi, characterized with different maturity indices, was also studied. For DIMS, EVOO samples were diluted with an 85:15 propanol/methanol (v/v) mixture containing 40 mM ammonia and directly infused into the mass spectrometer using a syringe pump. The establishment of ratios of the peak abundances of the free fatty acids followed by linear discriminant analysis was employed to predict both genetic variety and maturity index. In all cases, an excellent resolution between all category pairs was achieved, which demonstrated that fatty acid profiles are a good marker of both genetic variety and maturity index of EVOOs.Practical applications: As EVOO quality can be affected by different parameters, such as cultivar and maturity index, among others, it is necessary to develop analytical methods able to verify EVOO quality, and also to control its origin as olive oil producers have to include in their manufactured products the cultivar (monovarietal oils) from which the oil was obtained. Currently, almost all the research related to Tunisian EVOOs has been mainly focused on the improvement and characterization of the two main cultivars (Chétoui and Chemlali). Thus, to diversify Tunisian olive oil resources and improve the quality of olive oil produced in Tunisia, research on additional cultivars needs to be conducted. Thus, the present method could be used as an authentication tool for olive oil industry to asses both cultivar and maturity index of Tunisian EVOO, which could be extended to EVOO from all around the world.DIMS data of Tunisian EVOOs were used to predict EVOO genetic variety and maturity index using LDA.

Effect of Addition of Olive Leaves before Fruits Extraction Process to Some Monovarietal Tunisian Extra-Virgin Olive Oils Using Chemometric Analysis

The analysis of the effect of cultivar and olive leaves addition before the extraction on the different analytical values revealed significant differences (p < 0.05) in some parameters, mainly in peroxide value, phenols and tocopherol contents, and oxidative stability. Aroma profiles were also influenced by the different varieties and the addition of different amounts (0% and 3%) of olive leaves. Twenty-three compounds were characterized, representing 86.1-99.2% of the total volatiles. Chétoui cultivar has the highest amount of (E)-2-hexenal, followed by Chemlali cultivar, whereas (E)-2-hexen-1-ol was the major constituent of Zalmati and crossbreeding Chemlali by Zalmati cultivars. Sensory analysis showed that Chemlali and Chétoui Zarzis possessed a high fruity, bitter, and pungent taste, whereas the Zalmati and crossbreeding Chemlali by Zalmati had a 'green' taste among its attributes. Indeed, the taste panel found an improvement of the oil quality when an amount of olive leaves (3%) added to the olives fruits.

Determination of apolar and minor polar compounds and other chemical parameters for the discrimination of six different varieties of Tunisian extra-virgin olive oil cultivated in their traditional growing area

A study on the characterization of Tunisian extra-virgin olive oil varieties produced in their place of origin has been carried out. Due to the influence of the genotype and environmental, agronomic and technological factors on the chemical composition of olive oil and its quality, all the olives studied were collected on the same season, and the oil was obtained under the same processing technique. Several analyses were performed to characterize the different olive oils: free acidity, peroxide value, fatty acid composition, radical scavenging activity, Rancimat assay, pigments content and phenolic compounds by HPLC–MS. In order to evaluate all the results obtained (36 parameters for each variety), different statistical analyses were used to discriminate the extra-virgin olive oil varieties: one-way analysis of variance was performed to check significant differences among cultivars (p ≤ 0.05); PCA was applied to the data showing that variables such as oleic, linoleic, quinic and vanillic acids, apigenin, luteolin, taxifolin, oleuropein aglycon, pinoresinol acetate, elenolic acid and oxidative stability allowed discriminating among the different varieties of extra-virgin olive oil studied. Besides, LDA model was able to classify the samples depending on their geographical origin in Tunisia (North, Centre and South).

Chemical and thermal characterization of Tunisian extra virgin olive oil from Chetoui and Chemlali cultivars and different geographical origin

Application of differential scanning calorimetry (DSC) to discriminate among extra virgin olive oils on the basis of cultivar–environment interaction was preliminary evaluated on Tunisian samples from two varieties (Chetoui and Chemlali) and different geographical origin relating thermal properties obtained by cooling and heating thermograms to chemical composition. Higher content of triunsaturated triacylglycerols and oleic acid and lower amount of palmitic acid were detected in Chetoui samples in comparison with Chemlali oils. Cooling thermograms exhibited two well distinguishable exothermic peaks in all samples; the major event at lowest temperature was taller and sharper in Chetoui samples whereas the other peaking at highest temperature was more evident for Chemlali oils. Crystallization enthalpy did not account for the differences observed in chemical composition between the two cultivars. On the contrary, T on and T off of crystallization were found to significantly differ according to the compositional differences due to cultivars and geographical provenience interaction. Heating profiles exhibited a minor exothermic peak followed by multiple endothermic events and appeared also distinctive of oil samples from two cultivars. All thermal properties obtained by the analysis of heating thermograms significantly differed among oil samples from different geographical provenience. The application of DSC appeared useful to differentiate samples of different cultivars and/or geographical proveniences.

Effets des chlorophylles, du bêtacarotène, de l’alphatocophérol, du tyrosol et de leurs interactions sur la stabilité oxydative de l’huile d’olive tunisienne

Chlorophylls a and b, beta-carotene, alpha-tocopherol, tyrosol and their interactions effects on Tunisian extra virgin olive oil (EVOO) were studied. Beta-carotene, used at a level of 7 ppm, has an antioxidant effect more important at light than at obscurity. Chlorophyll a and b accelerate significantly the olive oil photooxidation, with a more important effect of chlorophyll b. When one or else of these chlorophylls is added with beta-carotene to oil, the global effect on peroxide value is attenuated. Both of alfa-tocopherol (0, 50, 100, 200, 400 ppm) and tyrosol (0, 5, 10, 20, 40 ppm) addition improved purified olive oil stability. On the other hand, alfa-tocopherol addition in EVOO has not significantly modified its oxidative stability, whereas that of tyrosol was very efficient. A factorial plane using three factors, beta-carotene (4 ppm), alfa-tocopherol (200 ppm) and tyrosol (50 ppm) is studied on EVOO and on purified olive oil. The results are different due to presence of various minor compounds on EVO.

Étude de la stabilité oxydative de l’huile d’olive vierge extra tunisienne au cours de son stockage

Tunisian extra virgin olive oil (EVOO) of Chetoui variety oxidation intensity depends on intrinsic composition, model packing and storage conditions. Thus, external factors such as kind of packing (glass, terephtalate polyethylene (PET), metal), full or attenuated day light, obscurity, air on bottles headspace, presence of metallic trace (iron and copper) and filtration influence on EVOO oxidative stability during two years storage at ambient temperature was studied. Peroxide value and ultraviolet specific extinction at 232 and 270 nm (K232 and K270) of oil bottled in PET and stored at obscurity for two years are significantly then the highest. On the other hand, oil bottled in glass bottles has shown the best physicochemical and organoleptic characteristics and also phenol and α-tocopherol contents were few higher than those of oil bottled into metal or PET packing. Oil exposure to light at storage increases quickly their photooxidation depending on EVOO chlorophylls levels. However, neither packing with nitrogen headspace nor filtration affects significantly oil stability.