Extra Virgin Olive Research Articles

Development and Stability Assessment of Coenzyme Q10-Loaded Oil-in-Water Nanoemulsions Using as Carrier Oil: Extra Virgin Olive and Olive-Pomace Oil

Coenzyme Q10 (CoQ10) presents multiple health benefits as an essential molecule for every cell and as an excellent antioxidant compound; however, its oral intake is challenging due to its low water solubility. Oil-in-water (o/w) nanoemulsions are considered excellent delivery systems for CoQ10, offering high protection and controlled release of the bioactive compound. In the present study, CoQ10 nanoemulsions were prepared using extra virgin olive (EVOO) or olive-pomace oil (OPO) with Tween 20 and Tween 40. It was investigated the effect of environment (25 °C) and refrigerated (4 °C) storage on the nanoemulsion physical and chemical stability. The results showed that it is possible to form fine o/w nanoemulsions with the two oils and various emulsifiers’ concentrations. The physicochemical properties of the nanoemulsions were evaluated in terms of mean droplet diameter (MDD), polydispersity index (PDI), ζ-potential, turbidity, and CoQ10 physicochemical stability (RCoQ10%). EVOO proved able to form kinetically more stable nanoemulsions with high CoQ10 retention (74.01%), while OPO led to nanosized emulsions with lower CoQ10 retention (71.99%). It was also observed that CoQ10 retention increases as the oil concentration increases (6% w/w EVOO, RCoQ10 = 77.17 and 8% w/w EVOO, RCoQ10 = 79.89%). All the nanoemulsion formulations, after storage either at 4 °C or at 25 °C, remained in the nanosized range after 3 months, with high physical (MDD < 500 nm) and chemical stability (RCoQ10 = 52.87%). Finally, nanoemulsions with 4% w/w emulsifier concentration appeared kinetically and chemically more stable as they presented lower MDD variations during storage.

From the Chief Executive and News

From the Chief Executive and News

Kinetic Study of the Scavenging Reaction of the Aroxyl Radical by Eight Kinds of Vegetable Oils in Solution

AbstractA detailed kinetic study was performed for the reaction of the aroxyl radical (ArO•) with eight vegetable oils 1–8, which contain different concentrations of α‐, β‐, γ‐, and δ‐tocopherols and ‐tocotrienols (‐Tocs and ‐Toc‐3s). The second‐order rate constants (ks) and aroxyl radical absorption capacity (ARAC) values for the reaction of ArO• with vegetable oils 1–8 (rice bran 1, perilla 2, rapeseed 3, safflower 4, grape seed 5, sesame 6, extra virgin olive 7, and olive oils 8) were measured in ethanol/chloroform/D2O (50:50:1, v/v/v) solution at 25 °C using stopped‐flow spectrophotometry. The ks value (16.1 × 10−3 L g−1 s−1) of rice bran oil 1 with the highest activity was 8.0 times larger than that (2.02 × 10−3) of olive oil 8 with the lowest activity. The concentrations (in mg 100 g−1) of α‐, β‐, γ‐, and δ‐Tocs and ‐Toc‐3s contained in the vegetable oils 1–8 were determined using high performance liquid chromatography‐mass spectrometry/mass spectrometry (HPLC‐MS/MS). From these results, it was clarified that the ArO•‐scavenging rates (ks) (i.e., the relative ARAC value) obtained for the vegetable oils 1–8 may be well explained as the sum of the product of the rate constant () and the concentration ([AOH‐i]/105) of AOH‐i (Tocs and Toc‐3s) included in vegetable oils. The results suggest that the ARAC assay method might be used in the evaluation of antioxidant activity of general food extracts.

Extra Virgin Olive oil as carbon negative product: Experimental analysis and validation of results

To reduce greenhouse gas (GHG) emissions, the Kyoto Protocol identifies several activities that are closely related to land use, included into the category called Agriculture, FOrestry and Land Uses (AFOLU). In this framework, a multidisciplinary study has been performed about the carbon footprint of extra virgin olive (EVO) oil in Italy. This study aims to promote process innovation by implementing eco-friendly techniques and technologies along a more sustainable production chain. Life Cycle Assessment approach was used to quantify the environmental impacts during the entire life cycle, starting from olive cultivation up to transformation processes and packaging. Each operation was monitored in terms of energy and material flows; the data were normalized on the basis of 1 L of olive oil, chosen as functional unit. Forest survey methodologies were applied to estimate the biomass and the respective carbon stocked in olive tree permanent (trunk, branches, twigs and root collar, roots) and non-permanent components (prunings and fruits). Added value of this study was coupling the resulting impacts with carbon sequestrations in order to: i) estimate the net balance between the equivalent carbon dioxide (CO2-eq) emissions and absorptions; ii) identify the break-even point, after which the amount of sequestered carbon exceeds the energy investments linked to human activities. Results from the study give important contributions towards the preliminary assessment of potential benefits in terms of avoided CO2-eq from agriculture.

Bioactive compounds detected for the first time in corn oil: Cyclic dipeptides and other nitrogenated compounds

Eleven edible oils, namely extra virgin olive, virgin olive, olive, sunflower, virgin soybean, refined soybean, virgin linseed and four corn oils were studied in order to analyze the occurrence in them of minor nitrogenated components. The study was carried out by using Solid Phase Microextraction (SPME) followed by Gas Chromatography/Mass Spectrometry (GC/MS). Apart from fatty amides no other nitrogenated compound was found in the first seven oils cited. However, it has been discovered that the four corn oils studied contain cyclic dipeptides or 2,5-diketopiperazines (DKPs), and other nitrogenated compounds such as oxazolines, pyrrolidines and other pyrrol derivatives, as well as indol, pyrazol, pyridine and β-phenylethylamine derivatives. DKPs were the most numerous and some of them were the most abundant of all nitrogenated compounds detected. All these compounds are bioactive and for this reason they can give corn oil interesting properties from a technological, nutritional and health points of view. Cyclic dipeptides could be considered as corn oil markers in authentication and fraud studies and their concentration can be used for differentiation and classification of corn oils. This is the first time that the presence of these bioactive compounds has been reported in corn oils.

Lipid oxidation-related characteristics of gim bugak (Korean fried cuisine with Porphyra) affected by frying oil.

The effect of frying oil on the lipid oxidation, antioxidants, and in vitro antioxidant activity of gim bugak was studied. Bugak was prepared by pan-frying at 180°C in unroasted sesame, soybean, extra virgin olive, or palm oil. The degree of lipid oxidation based on conjugated dienoic acid and p-anisidine values was higher in the bugak fried in soybean or sesame oil with high contents of polyunsaturated fatty acids and tocopherols. However, the oil oxidation was lower in olive and palm oils, which showed higher degradation of tocopherols and polyphenols than in sesame or soybean oil during frying. Although the bugak fried in palm oil contained less antioxidants than that fried in soybean or sesame oil, the in vitro antioxidant activity was not different (p>0.05). Results suggest that palm oil can replace unroasted sesame oil for the preparation of gim bugak with improved lipid oxidative stability and health functionality.

Formation of cholesterol oxides in lipid medium during microwave heating

Microwave (MW) heating of foods may cause the formation of cholesterol oxidation products (COPs). COPs formation depends on the conditions of MW heating and the composition of the food matrix. The aim of this work was to study the formation of major COPs from cholesterol incorporated into palm, extra virgin olive, soybean, or fish oils during MW heating, and to monitor changes in peroxide value and fatty acid (FA) profiles. Model systems composed of mixtures of cholesterol and oil (2.5 mg of cholesterol/g oil), were heated for 20 min in multimode (900 W), unimode MW (≈300 W) ovens, or convection oven at 180°C. Maximum total COPs contents largely varied (46.4–250.4 µg/g lipids), depending on the type of heating system and oil matrix. Multimode MW heating caused greater COPs formation than unimode MW. COPs formation trends in the conventional oven were similar to those of MW heating, except for fish oil. Results indicated that soybean oil, compared with the other oils tested, did not promote cholesterol oxidation during MW heating, while the opposite trend was observed for extra‐virgin olive oil and palm oil. FA profile and natural antioxidants influenced cholesterol and surrounding media oxidation during MW heating.Practical applications: This work explores the formation of oxysterols by microwave heating in model systems. This will help assess the possible risks for formation of these compounds during industrial and home cooking practices.Microwave (MW) heating of foods may cause formation of cholesterol oxidation products (COPs). In this work, a model system consisting of four types of edible oils with added cholesterol was employed and heated with three different forms (unimodal and multimodal MW, and conventional heating) for different time periods. Generation of COPs in all the model systems was monitored.

Influence of oil type on formation, structure, thermal, and physical properties of monoglyceride‐based organogel

This research studied the possible relation between oil properties and structure and physical properties of saturated monoglyceride (MG)‐based organogels. To this aim different oils (castor, cod liver, corn, extra virgin olive, flax‐seed, peanut and sunflower oil, and mixture of medium chain triacylglycerols (MCT)) were used to prepare organogels by adding 10% w/w of monoglycerides. The fatty acid composition, viscosity, and dielectric properties of oils were measured. Then, organogels were characterized for crystallization induction time, dielectric properties, firmness, rheological behavior, thermal properties, crystal morphology by polarized light microscopy, and crystal polymorphism by synchrotron X‐ray diffraction (XRD) analysis.Results acquired showed that the addition of MG in different types of oils led to the formation of organogels with different properties. In all cases, β polymorph formed in the system irrespective of oil type. Regarding oils containing long chain fatty acids, gel firmness, and other structural parameters correlated well with the dielectric constant and/or viscosity of oils: increasing oil viscosity or decreasing oil dielectric constant, firmness and rheological parameters linearly increased. On the other hand, these correlations cannot be found including in the statistical analysis castor oil or MCT, probably due to the higher ability of these oils to make dipole–dipole rotation as well as the higher solubility of MG in castor oil.Practical applications: Oil gelation (organogelation) is a relative novel strategy to convert liquid oils into structured systems that has attracted food scientists and industry managers looking for solutions to reduce saturated/trans fats, deliver bioactive molecules, and minimize oil migration in foods. Results acquired in this research highlight that the choice of oil to be structured by means of saturated monoglycerides could affect the final gel structure. These findings could be useful in the attempt to applied organogels in different food products having different physical properties.This research studies the effect of oil properties on structure and physical properties of saturated monoglyceride‐based organogels. Results show that only the dielectric constant and/or viscosity of long chain fatty acid oils correlated well with gel firmness and other structural parameters.

Optimization of an Indirect Enzymatic Method for the Simultaneous Analysis of 3-MCPD, 2-MCPD, and Glycidyl Esters in Edible Oils.

We developed a novel, indirect enzymatic method for the analysis of fatty acid esters of 3-monochloro-1,2-propanediol (3-MCPD), 2-monochloro-1,3-propanediol (2-MCPD), and glycidol (Gly) in edible oils and fats. Using this method, the ester analytes were rapidly cleavaged by Candida rugosa lipase at room temperature for 0.5 h. As a result of the simultaneous hydrolysis and bromination steps, 3-MCPD esters, 2-MCPD esters, and glycidyl esters were converted to free 3-MCPD, 2-MCPD, and 3-monobromo-1,2-propanediol (3-MBPD), respectively. After the addition of internal standards, the mixtures were washed with hexane, derivatized with phenylboronic acid, and analyzed by gas chromatography-mass spectrometer (GC-MS). The analytical method was evaluated in preliminary and feasibility studies performed by 13 laboratories. The preliminary study from 4 laboratories showed the reproducibility (RSD R ) of < 10% and recoveries in the range of 102-111% for the spiked 3-MCPD and 2-MCPD in extra virgin olive (EVO) oil, semi-solid palm oil, and solid palm oil. However, the RSDR and recoveries of Gly in the palm oil samples were not satisfactory. The Gly content of refrigerated palm oil samples decreased whereas the samples at room temperature were stable for three months, and this may be due to the depletion of Gly during cold storage. The feasibility studies performed by all 13 laboratories were conducted based on modifications of the shaking conditions for ester cleavage, the conditions of Gly bromination, and the removal of gel formed by residual lipase. Satisfactory RSDR were obtained for EVO oil samples spiked with standard esters (4.4% for 3-MCPD, 11.2% for 2-MCPD, and 6.6% for Gly).

E-commerce retail of extra virgin olive oil: an hedonic analysis of Italian SMEs supply

Purpose– The purpose of this paper is to analyse the relationship between the price of extra virgin olive (EVO) oil and its main quality attributes, in the specific case of business-to-consumers electronic commerce (B2C EC) channel. The final objective is to provide useful insights for small and medium-sized enterprises (SMEs) interested in online selling of EVO.Design/methodology/approach– A hedonic price model was estimated considering the following attributes: packaging, cultivar composition, organic certification, oil extraction method, origin certification and localization of selling firms. A survey was performed in 2012 considering 169 virtual stores of SMEs (farms, mills and bottlers) located in all the main Italian olive-growing areas. A data set of 667 references was used to estimate the implicit prices of considered attributes.Findings– The EVOs sold through virtual stores are highly differentiated on the basis of several quality attributes among which the most important is the certification of origin (protected denominations of origin/protected geographical indication). Therefore the firm location could generate considerable advantages or disadvantages in adopting a B2C EC strategy.Research limitations/implications– Future researches should develop a comparison between the premium prices and costs associated to each attribute in order to find the best product differentiation strategy. An accurate analysis about the implementation and management costs of EC systems as well as an examination of interactions between online and offline sale channels is needed. It would be useful to compare the manufacturer direct sell business model with other business model.Originality/value– Few studies applied the hedonic price model to analyse the retail olive oil market. Nevertheless, no studies have analysed the market of EVO sold in virtual shops.

UPLC method for the determination of vitamin E homologues and derivatives in vegetable oils, margarines and supplement capsules using pentafluorophenyl column

A sensitive and rapid reversed-phase ultra performance liquid chromatographic (UPLC) method for the simultaneous determination of tocopherols (α‐, β‐, γ‐, δ‐), tocotrienols (α‐, β‐, γ‐, δ‐), α‐tocopherol acetate and α‐tocopherol nicotinate is described. The separation was achieved using a Kinetex pentafluorophenyl (PFP) column (150×2.1mm, 2.6µm) with both photodiode array (PDA) and fluorescence (FL) detectors that were connected in series. Column was thermostated at 42°C. Under a gradient system consisting of methanol and water at a constant flow rate of 0.38mLmin−1, all the ten analytes were well separated in less than 9.5min. The method was validated in terms of linearity, limits of detection and quantitation, precision and recoveries. Calibration curves of the ten compounds were well correlated (r2>0.999) within the range of 100 to 25,000μgL−1 for α‐tocopherol acetate and α‐tocopherol nicotinate, 10 to 25,000μgL−1 for α‐tocotrienol and 5 to 25,000μgL−1 for the other components. The method is simple and sensitive with detection limits (S/N, 3) of 1.0 to 3.0μgL−1 (FL detection) and 30 to 74μgL−1 (PDA detection). Relative standard deviations for intra- and inter-day retention times (<1%) and peak areas (≤4%) were obtained. The method was successfully applied to the determination of vitamin E in vegetable oils (extra virgin olive, virgin olive, pomace olive, blended virgin and refined olive, sunflower, soybean, palm olein, carotino, crude palm, walnut, rice bran and grape seed), margarines and supplements.

Deep-frying. A study of the influence of the frying medium and the food nature, on the lipidic composition of the fried food, using 1H nuclear magnetic resonance

Extra virgin olive, soybean and sunflower oils were used in three different series of fourteen experiments to deep-fry three foods of very different lipidic content and composition. The aim of this study was to analyze how much the composition of the frying medium influenced the lipidic composition of the fried food. To achieve this, the compositions both of the frying medium throughout fourteen deep-frying experiments carried out with each kind of oil, as well as that of the unfried food were studied by 1H NMR. This same technique was used to study the lipidic composition of each fried food. The study focussed on the changes in the molar percentage of the different kinds of acyl groups, sterols and diglycerides as well as on the occurrence of compounds or functional groups coming from lipid degradation, such as aldehydes, epoxy groups and primary and secondary alcohols, all of them determined from 1H NMR spectral data.

Determination of carbamates in edible vegetable oils by ultra-high performance liquid chromatography–tandem mass spectrometry using a new clean-up based on zirconia for QuEChERS methodology

In this study a fast, selective and sensitive multiresidue method based on QuEChERS methodology has been evaluated and validated for the determination of carbamate pesticides, in edible vegetable oils by UHPLC–MS/MS. A new clean-up sorbent, SupelTM QuE Z-Sep+, has been successfully applied in vegetable oil extracts. Z-Sep+ was compared with other sorbents (i.e. mixture of C18 and PSA) previously used for dispersive solid phase extraction of these matrices, reducing more effectively matrix effects without a significant decrease of analyte recoveries. Matrix effect was studied in different matrices (extra-virgin olive, sunflower, maize, linseed and sesame oil) being ≤│30│% for most of the studied pesticides. Under optimum conditions, recoveries ranged from 74% to 101%, with relative standard deviations lower than 10%. Limits of quantification ranged from 0.09 to 2.0µgkg−1, allowing their determination at the low concentration levels demanding by current legislation.

Polycyclic aromatic hydrocarbons in Syrian olive oils and their likely daily intakes

The levels of 16 US Environmental Protection Agency polycyclic aromatic hydrocarbons (16 EPA PAHs) in Syrian olive oils have been determined. Forty-two samples including commercial extra virgin and virgin olive oils, and virgin olive oils from olive mills were analyzed. Only naphthalene (NAP) was detected in all olive oil samples under investigation. Among the studied 16 EPA PAHs, the highest maximum concentration was also observed for NAP (120 μg kg−1). Moreover, three samples exceeded the European Union (EU) maximum level of 2 μg kg−1 for benzo[a]pyrene (BaP) in oils and fats, and only one sample exceeded the EU maximum level of 10 μg kg−1 for the sum of benz[a]anthracene, chrysene, BaP, and benzo[b]fluoranthene (PAH4). The likely daily intakes of the total sum of 16 EPA PAHs, the sum of eight genotoxic PAHs, the sum of PAH4, the BaP, and the BaP equivalent through consumption of Syrian olive oils were estimated.

Feasibility of the determination of polycyclic aromatic hydrocarbons in edible oils via unfolded partial least-squares/residual bilinearization and parallel factor analysis of fluorescence excitation emission matrices

The possibility of simultaneously determining seven concerned heavy polycyclic aromatic hydrocarbons (PAHs) of the US-EPA priority pollutant list, in extra virgin olive and sunflower oils was examined using unfolded partial least-squares with residual bilinearization (U-PLS/RBL) and parallel factor analysis (PARAFAC). Both of these methods were applied to fluorescence excitation emission matrices. The compounds studied were benzo[a]anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenz[a,h]anthracene, benzo[g,h,i]perylene and indeno[1,2,3-c,d]-pyrene. The analysis was performed using fluorescence spectroscopy after a microwave assisted liquid–liquid extraction and solid-phase extraction on silica. The U-PLS/RBL algorithm exhibited the best performance for resolving the heavy PAH mixture in the presence of both the highly complex oil matrix and other unpredicted PAHs of the US-EPA list. The obtained limit of detection for the proposed method ranged from 0.07 to 2μgkg−1. The predicted U-PLS/RBL concentrations were satisfactorily compared with those obtained using high-performance liquid chromatography with fluorescence detection. A simple analysis with a considerable reduction in time and solvent consumption in comparison with chromatography are the principal advantages of the proposed method.

Capillary Electrophoresis of Free Fatty Acids by Indirect Ultraviolet Detection: Application to the Classification of Vegetable Oils According to Their Botanical Origin

A method for the determination of fatty acids in vegetable oils by capillary electrophoresis with indirect UV-vis detection has been developed. The separation of fatty acids was optimized in terms of Brij surfactant nature and concentration and organic modifier (2-propanol) percentage. The optimal background electrolyte consisted of 10 mM p-hydroxybenzoate, 5 mM Tris at pH 8.8, 80 mM Brij 98, 40% acetonitrile, and 10% 2-propanol. Under these conditions, vegetable oils from five botanical origins (avocado, corn, extra virgin olive, hazelnut, and soybean) were analyzed and the fatty acid contents established. Linear discriminant analysis (LDA) models were constructed using fatty acid peak areas as predictors. An excellent resolution among all category pairs was obtained, and all samples were correctly classified with assignment probabilities of >95%.

Use of triacylglycerol profiles established by high performance liquid chromatography with ultraviolet–visible detection to predict the botanical origin of vegetable oils

A method for the determination of triacylglycerols (TAGs) in vegetable oils from different botanical origins by HPLC with UV–vis detection has been developed. Using a core-shell particle packed column (C18, 2.6 μm), TAG separation was optimized in terms of mobile phase composition and column temperature. Using isocratic elution with acetonitrile/ n-pentanol at 10 °C, excellent efficiency with good resolution between most of the TAG peak pairs, within a total analysis time of 15 min, was achieved. Using mass spectrometry detection, a total of 15 peaks, which were common to oils of six different botanical origins (corn, extra virgin olive, grapeseed, hazelnut, peanut and soybean) were identified. These peaks were used to construct linear discriminant analysis (LDA) models for botanical origin prediction. Ratios of the peak areas selected by pairs were used as predictors. All the oils were correctly classified with assignment probabilities higher than 95%.

비정제유 첨가가 참치유 보강 에멀젼의 산화방지활성에 미치는 영향

This study was conducted to evaluate the effects of adding unrefined oil on the antioxidant activity of a tuna oil-enriched emulsion by determining DPPH radical scavenging activity, reducing power, and inhibition of low-density lipoprotein (LDL) oxidation in vitro. The emulsion consisted of tocopherol-stripped canola (18.3 g) and tuna (9.1 g) oil, one of the unrefined oils (4.6 g), such as extra virgin olive, mustard, perilla, or sesame oil, 0.5% acetic acid (64 g), and egg yolk powder (4 g). The control emulsion contained only canola (21.4 g) and tuna oil (10.6 g), as oil sources,with the same composition of the remaining ingredients. The emulsion with added unrefined oil, particularly mustard oil, showed higher radical scavenging activity and reducing power than those of the control emulsion. The radical scavenging activity and reducing power of the emulsion with added unrefined oil were higher at 1,000 ppm than at 500 ppm thus, the effect was concentration-dependent. Adding sesame or perilla oil to the tuna oil-enriched emulsion resulted in higher inhibition of LDL oxidationwhereas adding olive oil increased LDL oxidation. The results clearly showed that adding roasted mustard, sesame, or perilla oil improved the antioxidant activity of a tuna oil-enriched emulsion by increasing free radical scavenging activity, reducing power, and inhibiting LDL oxidation. The results also suggest that adding unrefined oils produces a healthier fish oil-enriched salad dressing recipe.

Acrylate ester-based monolithic columns for capillary electrochromatography separation of triacylglycerols in vegetable oils

A simple and reliable method for the evaluation of triacylglycerols (TAGs) in vegetable oils by capillary electrochromatography (CEC) with UV–Vis detection, using octadecyl acrylate (ODA) ester-based monolithic columns, has been developed. The percentages of the porogenic solvents in the polymerization mixture, and the mobile phase composition, were optimized. The optimum monolith was obtained at the following ratios: 40:60% (wt/wt) monomers/porogens, 60:40% (wt/wt) ODA/1,3-butanediol diacrylate and 23:77% (wt/wt) 1,4-butanediol/1-propanol (14 wt% 1,4-butanediol in the polymerization mixture). A satisfactory resolution between TAGs was achieved in less than 12 min with a 65:35 (v/v) acetonitrile/2-propanol mixture containing 5 mM ammonium acetate. The method was applied to the analysis of TAGs of vegetable oil samples. Using linear discriminant analysis of the CEC TAG profiles, the vegetable oils belonging to six different botanical origins (corn, extra virgin olive, hazelnut, peanut, soybean and sunflower) were correctly classified with an excellent resolution among all the categories.

Formation of toxic alkylbenzenes in edible oils submitted to frying temperature

Abstract The influence of oil composition in the main components and of heating time at frying temperature on the formation of toxic alkylated monoaromatic hydrocarbons in oils is studied. Oils of very different compositions such as extra virgin olive, sunflower and virgin linseed oils were submitted to frying temperature in an industrial fryer for prolonged periods of time and the components of their headspace were periodically extracted by solid phase microextraction and studied by gas chromatography mass spectrometry; simultaneously, the formation of polar compounds was also monitored by means of dielectric constant measures. The results obtained evidence the formation of a very high number of alkylbenzenes with molecular weights ranging from 92 to 190. Evolution, during heating time, of the concentration of these compounds in the headspace of the three oils is reported for the first time. Taking these data into account, the ability of these oils to generate these kinds of compounds is evaluated. The formation of unsaturated alkylbenzenes in edible oils during heating at frying temperature is reported for the first time. Relationships between the nature and concentration of alkylbenzenes found and composition in the main components of the original oils are commented on. Significant increases in the concentrations of these toxic compounds in some of the oils studied, occurring before the oil reaches its permitted limit in polar compounds, suggests the advisability of analysing the safety of this limit, in order to protect public health.