Characterization and classification of Western Greek olive oils according to cultivar and geographical origin based on volatile compounds

The aim of the present study was to characterize and classify olive oils from Western Greece according to cultivar and geographical origin, based on volatile compound composition, by means of Linear Discriminant Analysis. A total of 51 olive oil samples were collected during the harvesting period 2007-2008 from six regions of Western Greece and from six local cultivars. Forty-five of the samples were characterized as extra virgin olive oils. The analysis of volatile compounds was performed by Headspace Solid Phase Microextraction-Gas Chromatography/Mass Spectrometry (HS-SPME-GC/MS). Fifty-three (53) different volatile compounds were tentatively identified and semi-quantified. Using selected volatile compound composition data (selection was based on the application of ANOVA to total volatiles to determine those variables showing substantial differences among samples of different geographical origin/cultivar), the olive oil samples were satisfactorily classified according to geographical origin (87.2%) and cultivar (74%).     

Simultaneous determination of volatile and semi-volatile aromatic hydrocarbons in virgin olive oil by headspace solid-phase microextraction coupled to gas chromatography/mass spectrometry

A reliable, simple and relatively fast method for the simultaneous determination of volatile and semi-volatile aromatic hydrocarbons in virgin olive oil was developed, based on headspace solid-phase microextraction (HS-SPME). The investigation regarded eco-contaminants such as alkylated monoaromatic hydrocarbons from C1- to C4-benzenes and light polyaromatic hydrocarbons up to four aromatic rings. Sampling and chromatographic conditions were optimized by using standard solutions in deodorized olive oil and the analytical performances of the method were determined. The proposed method was then applied to real samples of virgin olive oil were the target hydrocarbons could be identified and quantified. Several of them had not been previously quantified in virgin olive oil. Moreover, by the analysis of olive oil samples an additional number of C4-benzenes could be tentatively identified.     

Application of solid-phase microextraction to the analysis of volatile compounds in virgin olive oils

Solid-phase microextraction was used as a technique for headspace sampling of extra virgin olive oil and virgin olive oil samples with different off-flavours. A 100 microm coated polydimethylsiloxane fiber was used to extract volatile aldehydes, the sampling temperature was 45 degrees C and the fiber has been exposed to the headspace for 15 min. Nonanal and 2-decenal were present in all the olive oils with extraction off-flavours but were not in extra virgin olive oil sample.     

Evaluation of two commercial solid-phase microextraction fibres for the analysis of target aroma compounds in cooked beef meat

The aroma profile of cooked beef meat has been investigated by solid-phase microextraction (SPME) combined with gas chromatography-mass spectrometry (GC-MS). Out of more than 200 volatile compounds, 36 key odour-active compounds were selected for analysis. Several extraction times, desorption times, temperature conditions and fibre types were tested to achieve a fast and reproducible extraction, and a representative analysis of the aroma profile of cooked beef. Extraction conditions and fibre type significantly affected the majority of the target compounds. Divinylbenzene-carboxen-polydimethylsiloxane (DVB-CAR-PDMS) fibre presented a better reproducibility at all extraction times and extracted more efficiently the less volatile compounds than the carboxen-polydimethylsiloxane (CAR-PDMS) fibre. The high molecular weight compounds seemed to achieve faster the equilibrium between the headspace and DVB-CAR-PDMS fibre. The use of SPME was shown to be a simple, sensitive, selective, representative, fast, and low-cost method for the evaluation of key odour-active compounds in cooked beef meat, even if further research on quantitative analysis of volatiles using SPME on solid samples has to be done.     

The comparison of solid phase microextraction-GC and static headspace-GC for determination of solvent residues in vegetable oils

The objective of these investigations has been the determination of volatile organic compounds including residue solvents present in vegetable oil samples. Some olive oil, rape oil, sunflower oil, soy-bean oil, pumpkin oil, grape oil, rice oil as well as hazel-nut oil samples were analysed. Among residue solvents the following compounds have been mentioned: acetone, n-hexane, benzene, and toluene. Some experiments for the solid phase microextraction (SPME)-GC-flame ionisation detection (FID) were performed to examine extraction conditions such as fiber exposure time, temperature of extraction, and temperature of desorption. Various SPME fibers such as polydimethylsiloxane, Carboxen/polydimethylsiloxane and polydimethylsiloxane/divinylbenzene coatings were used for the isolation of tested compounds from vegetable oil samples. After optimisation of SPME, real vegetable oil samples were examined using SPME-GC/MS. Based on preliminary experiments the qualitative and quantitative analyses for the determination of acetone, n-hexane, benzene and toluene were performed by SPME-GC-FID and static head-space (SHS)-GC-FID methods. The regression coefficients for calibration curves for the examined compounds were R(2) > or = 0.992. This shows that the used method is linear in the examined concentration range (0.005-0.119 mg/kg for SPME-GC-FID and 0.003-0.728 mg/kg for SHS-GC-FID). Chemical properties of analysed vegetable oils have been characterised by chemometric procedure (cluster analysis).     

Recognition of volatile compounds as markers in geographical discrimination of Spanish extra virgin olive oils by chemometric analysis of non-specific chromatography volatile profiles

Chromatographic profiles obtained by headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography (GC) were processed as continuous and non-specific signals through multivariate analysis techniques in order to select and identify the most discriminate volatile marker compounds related to the geographical origin of extra virgin olive oils. The blind analysis of the chromatographic profiles was carried out on several steps including preliminary mathematical treatments, explorative analysis, feature selection and classification. The results obtained through the application of stepwise linear discriminant analysis (SLDA) method revealed a perfect discrimination between the different Spanish geographical regions considered (La Rioja, Andalusia and Catalonia). The assignment success rate was 100% in both classification and prediction by using cross validation procedure. In addition, it must be noted that the proposed strategy was able to verify the geographical origin of the samples involving only a reduced number of discriminate retention times selected by the stepwise procedure. This fact emphasizes the quality of the accurate results obtained and encourages the feasibility of similar procedures in olive oil quality and traceability studies. Finally, volatile compounds corresponding to the predictors retained were identified by gas chromatography-mass spectrometry (GC-MS) for a chemical interpretation of their importance in quality virgin olive oils.     

Electronic nose based on metal oxide semiconductor sensors as a fast alternative for the detection of adulteration of virgin olive oils

An “electronic nose” has been used for the detection of adulterations of virgin olive oil. The system, comprising 12 metal oxide semiconductor sensors, was used to generate a pattern of the volatile compounds present in the samples. Prior to different supervised pattern recognition treatments, feature selection techniques were employed to choose a set of optimally discriminant variables. Linear discriminant analysis (LDA), quadratic discriminant analysis (QDA) and artificial neural networks (ANN) were applied. Excellent results were obtained in the differentiation of adulterated and non-adulterated olive oils and it was even possible to identify the type of oil used in the adulteration. Promising results were also obtained as regards quantification of the percentages of adulteration.     

Gas chromatography-mass spectrometry analysis of volatile compounds from Houttuynia cordata Thunb after extraction by solid-phase microextraction, flash evaporation and steam distillation

Various sampling techniques including flash evaporation (FE), headspace solid-phase microextraction (HS-SPME) and steam distillation (SD) were compared for the gas chromatography-mass spectrometry of volatile constituents present in Houttuynia cordata Thunb (HCT). 2-Undecanone (22.21%) and houttuynum (7.23%) were predominant components of HCT samples obtained by HS-SPME whereas those levels were 3.95 and 3.60% in the same samples by FE and 25.93 and 6.60% in those by SD, respectively. SPME with polydimethylsiloxane (PDMS) fibre was more selective and particularly efficient for the isolation of biologically active compounds and afforded a higher yield of total compounds than FE and SD. A total of 60 compounds were detected in SPME extracts. While in FE and SD extracts, the detected compounds were 41 and 51, respectively. The total amount of compounds isolated by SPME was much larger than that isolated by FE or SD. Some minor constituents were isolated by SPME, but not by SD and FE. This carries great significance because of the importance of the oil volatiles to clinical therapy. HS-SPME is a powerful tool for determining the volatile constitutes present in the TCMs.     

Simple and fast determination of phenolic compounds from different varieties of olive oil by nonaqueous capillary electrophoresis with UV‐visible and fluorescence detection

In this article, we proposed very simple procedures to analyze important phenolic compounds in olive oil samples from different olive varieties. A nonaqueous CE method has been employed. The main phenolic alcohols in virgin olive oil (tyrosol and hydroxytyrosol) and some among the most abundant secoiridoid aglycone derivatives (dialdehydic form of decarboxymethyl elenoic acid linked to hydroxytyrosol, an isomer of oleuropein aglycone and the dialdehydic form of decarboxymethyl elenoic acid linked to tyrosol) were determined by a direct injection into the capillary of the olive oil dissolved in 1‐propanol 1:1 v/v. For the determination of compounds present at lower concentrations, a very simple liquid–liquid extraction method with ethanol has been proposed. The extraction was performed using a relationship 5:1 w/v olive oil/ethanol to achieve the necessary preconcentration of the analytes and the ethanolic extracts were directly injected into the capillary to obtain a very important time reduction. Good recoveries were obtained with both the procedures, using an internal standard. Finally, these procedures were applied to the analysis of these compounds in extra virgin olive oil samples from different varieties of olive.     

Multi-capillary column-ion mobility spectrometry: a potential screening system to differentiate virgin olive oils

The potential of a headspace device coupled to multi-capillary column-ion mobility spectrometry has been studied as a screening system to differentiate virgin olive oils (“lampante,” “virgin,” and “extra virgin” olive oil). The last two types are virgin olive oil samples of very similar characteristics, which were very difficult to distinguish with the existing analytical method. The procedure involves the direct introduction of the virgin olive oil sample into a vial, headspace generation, and automatic injection of the volatiles into a gas chromatograph-ion mobility spectrometer. The data obtained after the analysis by duplicate of 98 samples of three different categories of virgin olive oils, were preprocessed and submitted to a detailed chemometric treatment to classify the virgin olive oil samples according to their sensory quality. The same virgin olive oil samples were also analyzed by an expert’s panel to establish their category and use these data as reference values to check the potential of this new screening system. This comparison confirms the potential of the results presented here. The model was able to classify 97% of virgin olive oil samples in their corresponding group. Finally, the chemometric method was validated obtaining a percentage of prediction of 87%. These results provide promising perspectives for the use of ion mobility spectrometry to differentiate virgin olive oil samples according to their quality instead of using the classical analytical procedure.     

Monoterpene and sesquiterpene hydrocarbons of virgin olive oil by headspace solid-phase microextraction coupled to gas chromatography/mass spectrometry

In the present article, a headspace solid-phase microextraction method coupled to GC/MS was developed and applied for the simultaneous determination of mono- and sesquiterpenic hydrocarbons in virgin olive oils of different olive variety and geographical origin. Analysis of various oils resulted in the simultaneous detection of 15 monoterpenes and 30 sesquiterpenes. Some of these hydrocarbons were previously reported to be constituents of virgin olive oil terpenoid fraction, although we also detected some terpenic hydrocarbons that have not previously been documented as present in virgin olive oil. Significant differences were detected in the proportion of terpenic compounds in oils obtained from different olive varieties grown in different geographical areas. The monoterpene, and particularly the sesquiterpene composition of olive oil may be used to distinguish samples from different cultivar and geographical areas.     

The variability of composition of the volatile fraction of olive oil

Aroma of olive oil is a very complex mixture of components. Analysis of head space of a series of virgin olive oil samples indicate a great variability of volatile substances composition in olives and these data probably should be related to the story of olives after collecting.     

Direct olive oil authentication: detection of adulteration of olive oil with hazelnut oil by direct coupling of headspace and mass spectrometry, and multivariate regression techniques

Control of adulteration of olive oil, together with authentication and contamination, is one of the main aspects in the quality control of olive oil. Adulteration with hazelnut oil is one of the most difficult to detect due to the similar composition of hazelnut and olive oils; both virgin olive oil and olive oil are subjected to that kind of adulteration. The main objective of this work was to develop an analytical method able to detect adulteration of virgin olive oils and olive oils with hazelnut oil by means of its analysis by a headspace autosampler directly coupled to a mass spectrometer used as detector (ChemSensor). As no chromatographic separation of the individual components of the samples exists, a global signal of the sample is obtained and employed for its characterization by means of chemometric techniques. Four different crude hazelnut oils from Turkey were employed for the development of the method. Multivariate regression techniques (partial least squares and principal components analysis) were applied to generate adequate regression models. Good values were obtained in both techniques for the parameters employed (standard errors of prediction (SEP) and prediction residual error sum of squares (PRESS)) to evaluate its goodness. With the proposed method, minimum adulteration levels of 7 and 15% can be detected in refined and virgin olive oils, respectively. Once validated, the method was applied to the detection of such adulteration in commercial olive oil and virgin olive oil samples.     

Detection of hazelnut oil in virgin olive oil by assessment of free sterols and triacylglycerols

Free sterols were evaluated as factors for discriminating between genuine virgin olive oil and hazelnut-mixed virgin olive oil. Numeric analyses of the results amplified the differences between groups. The application of this method to virgin olive oil samples and their mixtures with 10% hazelnut oil distinguished between genuine and nongenuine virgin olive oil with statistical certainty. Triacylglycerol analysis was tested for the same purpose by using parameter deltaECN42, but although it possessed a discriminating capacity, it alone could not distinguish the aforementioned groups with sufficient certainty. Free delta7-sterols data were combined with deltaECN42 data into a single discriminating function to improve differentiation and bring more ruggedness, and for detection of low amounts (10%) of hazelnut oil in virgin olive oil. In fact, the values obtained by addition of delta7-sterol data and deltaECN42 data showed a higher discriminating capacity than single parameters. In a single operation the method produced all the oil fractions necessary for analysis of free sterols and triacylglycerols with ECN42. Solid-phase extraction was applied in substitution of traditional chromatography on a silica column.     

Preparation and application of in-fibre internal standardization solid-phase microextraction

The in-fibre standardization method is a novel approach that has been developed for field sampling/sample preparation, in which an internal standard is pre-loaded onto a solid-phase microextraction (SPME) fibre for calibration of the extraction of target analytes in field samples. The same method can also be used for in-vial sample analysis. In this study, different techniques to load the standard to a non-porous SPME fibre were investigated. It was found that the appropriateness of the technique depends on the physical properties of the standards that are used for the analysis. Headspace extraction of the standard dissolved in pumping oil works well for volatile compounds. Conversely, headspace extraction of the pure standard is an effective approach for semi-volatile compounds. For compounds with low volatility, a syringe-fibre transfer method and direct extraction of the standard dissolved in a solvent exhibited a good reproducibility (<5% RSD). The main advantage of the approaches investigated in this study is that the standard generation vials can be reused for hundreds of analyses without exhibiting significant loss. Moreover, most of the standard loading processes studied can be performed automatically, which is efficient and precise. Finally, the standard loading technique and in-fibre standardization method were applied to a complex matrix (milk) and the results illustrated that the matrix effect can be effectively compensated for with this approach.     

Synchronous fluorescence spectroscopy for quantitative determination of virgin olive oil adulteration with sunflower oil

Adulteration of extra virgin olive oil with sunflower oil is a major issue for the olive oil industry. In this paper, the potential of total synchronous fluorescence (TSyF) spectra to differentiate virgin olive oil from sunflower oil and synchronous fluorescence (SyF) spectra combined with multivariate analysis to assess the adulteration of virgin olive oil are demonstrated. TSyF spectra were acquired by varying the excitation wavelength in the region 270–720 nm and the wavelength interval (Δλ) in the region from 20 to 120 nm. TSyF contour plots for sunflower, in contrast to virgin olive oil, show a fluorescence region in the excitation wavelength range 325–385 nm. Fifteen different virgin olive oil samples were adulterated with sunflower oil at varying levels (0.5–95%) resulting in one hundred and thirty six mixtures. The partial least-squares regression model was used for quantification of the adulteration using wavelength intervals of 20 and 80 nm. This technique is useful for detection of sunflower oil in virgin olive oil at levels down to 3.4% (w/v) in just two and a half minutes using an 80-nm wavelength interval.     

Headspace solid phase microextraction for screening for the presence of resins in Egyptian archaeological samples

The aim of this study was to use headspace solid phase microextraction (SPME) to reveal the presence of resin in archaeological samples, such as mummification balms, from ancient Egypt. Experiments were first performed with fresh resins of known origin. The SPME fibre readily extracted mono- and sesquiterpenes and, to a lesser extent, diterpenes. Using mass spectra and retention indices of constitutive compounds, qualitative analysis of the volatile fraction allowed us to differentiate resins or gum-resins such as myrrh, olibanum, galbanum, labdanum, mastic, and conifer resins. SPME was then successfully applied to archaeological samples from ancient Egypt in which the presence of resins was detected. Volatile components were desorbed and trapped according to the same SPME procedure as was applied to fresh resins, after a sample preparation consisting of a fine grinding.     

Comparative elucidation of phenolic compounds in Albanian olive oils using LC-DAD-ESI-MS/MS

Abstract

Olive oils may provide health benefits, including the prevention of coronary heart diseases, cancers, and the modification of immune and inflammatory responses. These benefits mainly originate from the phenolic compounds found in olive oil. There has been no study on the advanced characterization of Albanian olive oils from various cultivars regarding phenolic compounds. Hence, a comprehensive characterization of phenolic compounds is carried out in Albanian monocultivar virgin olive oils from five different cultivars, including Kalinjot, Bardhi Tirana, Ulliri-i-Zi Tirana, Krips Kruja, and Bardhi Kruja for the first time. Liquid chromatography coupled to diode array detection and electrospray ?onization tandem mass spectrometry (LC-DAD-ESI-MS/MS) is employed for the determination of phenolic compounds. In total, 18 compounds were identified in all samples, including phenolic alcohols, phenolic acids, secoiridoids, flavonoids, and phenolic aldehydes. Significant quantitative differences were detected among the cultivars, with the highest concentrations detected in virgin olive oil (VOO) from cv. Ulli-i-Zi. Secoiridoids were found in abundance, in general, followed by phenolic alcohols, and in this group, 3,4-DHPEA-EDA and p-HPEA-EDA stood out as dominant compounds, especially in Kalinjot virgin olive oils. Regarding phenolic alcohols, 3,4-DHPEA-AC was determined as the main phenolic compound. Phenolic profiles were found to be significantly different among the olive oil samples of different cultivars. Principal component analyses (PCA) displayed the differentiation of samples in terms of phenolic compounds.     

Volatile compounds in virgin olive oil: occurrence and their relationship with the quality

The stimulation of the human sensory receptors by volatile compounds present in virgin olive oils gives rise to the sensory attributes that describe its delicate and fragrant aroma. The composition of the volatile compounds and their biogenesis is briefly illustrated. Analytical methodologies for evaluating the volatile fraction and the sensory properties of virgin olive oils are elucidated. Compounds responsible for typical flavours are examined and the influence of the main factors on the composition of volatile compounds is discussed. The origin of off-flavours are also described and the consequent changes of volatile composition and of sensory characteristics are analysed. The relationships between volatile compounds and sensory attributes are discussed.     

Effects of conventional heating on the stability of major olive oil phenolic compounds by tandem mass spectrometry and isotope dilution assay

The quality of olive oils is sensorially tested by accurate and well established methods. It enables the classification of the pressed oils into the classes of extra virgin oil, virgin oil and lampant oil. Nonetheless, it would be convenient to have analytical methods for screening oils or supporting sensorial analysis using a reliable independent approach based on exploitation of mass spectrometric methodologies. A number of methods have been proposed to evaluate deficiencies of extra virgin olive oils resulting from inappropriate technological treatments, such as high or low temperature deodoration, and home cooking processes. The quality and nutraceutical value of extra virgin olive oil (EVOO) can be related to the antioxidant property of its phenolic compounds. Olive oil is a source of at least 30 phenolic compounds, such as oleuropein, oleocanthal, hydroxytyrosol, and tyrosol, all acting as strong antioxidants, radical scavengers and NSAI-like drugs. We now report the efficacy of MRM tandem mass spectrometry, assisted by the isotope dilution assay, in the evaluation of the thermal stability of selected active principles of extra virgin olive oil.