Olive Oil Authenticity Research Articles

Scattering-based optical techniques for olive oil characterization and quality control

Olive oil is a major fat source of the Mediterranean diet. For its unique functional and technological properties, olive oil is highly appreciated all over the world. Very sensitive techniques are currently required to determine chemical composition, to evaluate olive oil authenticity and to quantify vegetable adulterants or degradation compounds. A class of techniques that can be particularly interesting in olive oil characterization is represented by those based on light scattering. These techniques can provide important information on physical properties, conservation state and possible adulteration without complicate or time expensive procedures. Among these, static and dynamic light scattering, diffuse wave spectroscopy, different kinds of Raman spectroscopy are the most used. In this short review, basic concepts about the experimental aspects of these techniques are presented together with some of the most generally used data analysis procedures. Some selected examples of the most interesting applications of these techniques are also proposed.

Microsatellite High-Resolution Melting (SSR-HRM) to Track Olive Genotypes: From Field to Olive Oil.

The need to support food labelling has driven to the development of PCR-based techniques suitable for food analysis. DNA-based markers have been successfully employed for varietal tracing in Protected Designation of Origin (PDO) olive oils. In this study, we report a fast, sensitive, and easy-to-use strategy for PDO olive varietal identification. To achieve this aim four different DNA extraction methods were tested and compared, based on initial volume, extraction time, the gDNA concentration, and quality ratios. The optimized DNA extraction protocol from extra virgin olive oils, based on CTAB-hexane-chloroform extraction, proved to be the most effective. High-resolution melting (HRM) DNA assay was developed based on nuclear microsatellites (gSSR) and plastid DNA (cpDNA) aiming an accurate identification of the olive varieties present in the olive oil samples. After PCR reproducibility evaluation, six molecular markers: three SSRs and three cpDNA loci were chosen based on their discrimination power. The SSR-HRM strategy assays were designed to target UDO99-011, UDO99-039, UDO99-024, and ssrOeUA-DCA16 loci. All SSR-PCR products generated from these primers were analyzed by capillary electrophoresis (CE) for HRM data validation. The SSR coupled with HRM melting curve analysis generated 14 HRM profiles sufficient to genotype all varieties, highlighting their potential use for varietal discrimination. The locus ssrOeUA-DCA16 generated a specific melting curve that allow a high-throughput discrimination of the Picual and Cobrançosa varieties in olive oil samples. Further, the UDO99-024 was also tested by SSR-HRM assay in commercial olive oil samples with promising results. Considering time, cost, and performance SSR-HRM proved to be a reliable method suitable for varietal tracing of olive oils. PRACTICAL APPLICATION: Olive oil authenticity is a form of protecting producers and consumers against fraudulent practices. Herein, we present a DNA barcode suitable for the identification of olive varieties, allowing an accurate identification of the olive varieties in olive oil samples using SSR-HRM assay. Its applicability in commercial olive oil samples is viable. This methodology can be used as a tool for Extra Virgin Olive Oil (EVOO) adulterations detection.

Ultrasonic method for identifying oil types and their mixtures

The study focused on the efficacy of ultrasonic method for identifying vegetable oils and their mixtures in the formulation of frying oil and its ability in authentication of virgin olive oil. The ultrasonic propagation properties (velocity and Time of Flight (TOF)) were used to classify oil samples and their mixtures at 1 MHz. The results revealed the ability to classify oil types in terms of their level of un-saturation, besides it is to identify oil mixtures. Each oil sample could be grouped into different clusters using ultrasonic parameters. Hence, ultrasonic could be used to discriminate the vegetable oil types and their mixtures effectively as a rapid and continuous method in the industrial in-line quality control system of vegetable oils and their mixtures.

The OLEUM Project: ensuring olive oil quality and authenticity

The OLEUM Project: ensuring olive oil quality and authenticity

Vibrational spectroscopy and chemometric procedures for the rapid assessment of olive oil authenticity

Vibrational spectroscopy and chemometric procedures for the rapid assessment of olive oil authenticity

Authentication and Quantitation of Fraud in Extra Virgin Olive Oils Based on HPLC-UV Fingerprinting and Multivariate Calibration.

High performance liquid chromatography method with ultra-violet detection (HPLC-UV) fingerprinting was applied for the analysis and characterization of olive oils, and was performed using a Zorbax Eclipse XDB-C8 reversed-phase column under gradient elution, employing 0.1% formic acid aqueous solution and methanol as mobile phase. More than 130 edible oils, including monovarietal extra-virgin olive oils (EVOOs) and other vegetable oils, were analyzed. Principal component analysis results showed a noticeable discrimination between olive oils and other vegetable oils using raw HPLC-UV chromatographic profiles as data descriptors. However, selected HPLC-UV chromatographic time-window segments were necessary to achieve discrimination among monovarietal EVOOs. Partial least square (PLS) regression was employed to tackle olive oil authentication of Arbequina EVOO adulterated with Picual EVOO, a refined olive oil, and sunflower oil. Highly satisfactory results were obtained after PLS analysis, with overall errors in the quantitation of adulteration in the Arbequina EVOO (minimum 2.5% adulterant) below 2.9%.

Classification of olive oils using chromatography, principal component analysis and artificial neural network modelling

Classification and addressing, and geographical origin of different olive oils is of great importance due to their differentiation in quality, and for commercial concerns. In this study, quantification of sterols, fatty acids, and triacylglycerol composition of forty-nine olive oils collected from six different locations of western part of Turkey (Izmir, Manisa, Aydin, Mugla, Bursa, and Edremit Bay) were performed by using chromatographic methods. Data for those olive oil samples were compiled, and classified with the artificial neural network (ANN) modelling and principal components analysis (PCA). The analytical results included resourceful information about determining geographical origin and traceability of olive oil in Turkey by using ANN and PCA. The ANN model for sterol composition showed the highest accuracy with 85.71%. The FAME and TAG profiles followed this with 83.67 and 81.63% accuracy respectively. However, Izmir and Manisa regions have poor sensitivity values with all ANN models since they are geographically very close to each other. Furthermore, the PCA results of the sterol composition have provided separation and clustering between locations. β-sitosterol, campesterol, stigmasterol and 24-metilen cholesterol have an important role in determining the separation of the locations of origin. While separation of the Bursa location has been under the pressure of FAME composition, the TAGs have been effective on the clustering of the Aydin and Edremit Bay. In conclusion, the geographical authentication of Turkish olive oils can be done with high accuracy by using ANN and PCA.

Discrimination of Tunisian and Italian extra-virgin olive oils according to their phenolic and sterolic fingerprints

In the last years, olive oil authentication issues have become topics of prominent importance, not only for consumers, but also for suppliers, retailers, and administrative authorities, and particularly for assurance of public health. In this work, the sterolic and phenolic profile of Tunisian and Italian extra-virgin olive oil (EVOO) samples was depicted using an untargeted UHPLC-ESI/QTOF mass spectrometry approach. Polyphenols and sterols were quantified according to their chemical sub-classes, with high sterols (around 1000 up to 2000 mg/kg) and tyrosols (on average 420.2 mg/kg) contents detected. The metabolomics data were elaborated by means of multivariate statistics, i.e. unsupervised hierarchical cluster analysis and orthogonal projections to latent structures discriminant analysis (OPLS-DA). This approach allowed identifying the best markers (i.e. hydroxybenzoic acids, cholesterol and stigmasterol derivatives) of the geographical origin able to discriminate Tunisian and Italian EVOO samples, showing the potential of sterolic and phenolic fingerprints for olive oil authenticity evaluations.

基于受激布里渊散射及紫外-可见吸收光谱的橄榄油等级鉴别与分析

基于受激布里渊散射及紫外-可见吸收光谱的橄榄油等级鉴别与分析

FTIR spectroscopy coupled with chemometrics of multivariate calibration and discriminant analysis for authentication of extra virgin olive oil

ABSTRACTThe objective of this study was to develop FTIR spectroscopy combined with chemometrics for the authentication of extra virgin olive oil (EVOO) from grape seed oil (GSO), soybean oil (SO), and walnut oil (WO). FTIR spectra of EVOO and that mixed with GSO, SO, and WO were scanned at mid infrared region (4000–650 cm−1). The optimized wavenumbers region was used for the quantification of oil adulterants using multivariate calibration of partial least square (PLS) and principle component regression (PCR) as well as for classification using discriminant analysis (DA). PLS at optimized wavenumbers was used with R2 for the relationship between actual and predicted values of GSO, SO, and WO was >0.99. The values of root mean square error of calibration (RMSEC) were relatively low, i.e. 0.308%, 0.658%, and 0.101% for GSO, SO, and WO, respectively. DA at the optimized frequency region could successfully classify EVOO and EVOO adulterated with GSO, SO, and WO.

Breaking News on the Authenticity of Olive Oils by Means of Molecular Markers

Breaking News on the Authenticity of Olive Oils by Means of Molecular Markers

Chemometric characterization of virgin olive oils of the two major Cypriot cultivars based on their fatty acid composition

The effects of the geographical region and the botanical origin of olive oils on the profile of fatty acids isolated from monovarietal virgin olive oils from Cyprus were investigated, in order to establish, for the first time, promising models for authentication and classification of monovarietal virgin olive oils produced on the island. The two dominant Cypriot olive cultivars, Cypriot (ladoelia), and Koroneiki (lianolia), were analyzed for fatty acid composition by GC/FID after preparation of Fatty Acid Methyl Esters from olive oil, using a cold esterification method. The data obtained were analyzed statistically using multivariate and univariate ANOVA, principal components analysis (PCA) and hierarchical cluster analysis. Results showed that the olive oils can be separated into two distinct groups using the FAME data bank obtained from 225 samples. Significant differences in the proportion of some variables such as polyunsaturated linoleic acid, and the ratio C18:1/C18:2 from oils of different varieties and geographical regions were detected. The ratios C18:1/C18:2 and MUFA/PUFA, as well SFA, ω-9 and PUFA showed the higher discriminant power based on the cultivar.

Valuing Consumer Perceptions of Olive Oil Authenticity

ABSTRACTNowadays, while the authenticity of agri-food products becomes a major concern for consumers, given the increasing rate of food fraud reports across the world, olive oil records the highest adulterations. The high selling price of olive oil is the main reason for conducting adulteration, which is often caused through false indications on the packaging (mislabeling). On the other hand, consumers are well aware of the alteration, and they are looking for authenticity signals during the purchase process. Authenticity, therefore, becomes an evaluation and decision-making criterion that guides consumer choices. The aim of this paper was twofold: to highlight the attributes in which Greek consumers attach great importance during the evaluation of olive oil’s authenticity, and second, through consumers’ demographic segmentation, to gain more detailed knowledge about the attributes that consumers evaluate in olive oil authenticity. CUB (Covariates in a mixture of Uniform and Binomial random variables) models are employed for the interpretation of ordinal data due to the ability of comparing and clustering the rating distributions consumers express about olive oil features, and due to the ability of detecting significant similarities and differences in consumer responses. Moreover, with the introduction of respondents’ social, demographic, and financial characteristics, CUB models allow the measurement of the influence that the consumers’ profile has upon the attributes of olive oil authenticity. The results showed that consumers attached great importance to taste, acidity, country and region of origin, olive variety, color, organic production, and regional certification in the evaluation of olive oil authenticity. In addition, secondary school graduates tend to use taste and olive variety, also indicating confidence in the authenticity of organic olive oil.

Detection and quantification of extra virgin olive oil adulteration by means of autofluorescence excitation-emission profiles combined with multi-way classification

Within olive oils, extra virgin olive oil is the highest quality and, in consequence, the most expensive one. Because of that, it is common that some merchants attempt to take economic advantage by mixing it up with other less expensive oils, like olive oil or olive pomace oil. In consequence, the characterization and authentication of extra virgin olive oils is a subject of great interest, both for industry and consumers. This paper reports the potential of front-face total fluorescence spectroscopy combined with second-order chemometric methods for the detection of extra virgin olive oils adulteration with other olive oils. Excitation-emission matrices (EEMs) of extra virgin olive oils and extra virgin olive oils adulterated with olive oils or with olive pomace oils were recorded using front-face fluorescence spectroscopy. The full information content in these fluorescence images was analyzed with the aid of unsupervised parallel factor analysis (PARAFAC), PARAFAC supervised by linear discriminant analysis (LDA-PARAFAC), and discriminant unfolded partial least-squares (DA-UPLS). The discriminant ability of LDA-PARAFAC was studied through the tridimensional plots of the canonical vectors, defining a surface separating the established categories. For DA-UPLS, the discriminant ability was established through the bidimensional plots of predicted values of calibration and validation samples, in order to assign each sample to a given class. The models demonstrated the possibility of detecting adulterations of extra virgin olive oils with percentages of around 15% and 3% of olive and olive pomace oils, respectively. Also, UPLS regression was used to quantify the adulteration level of extra virgin olive oils with olive oils or with olive pomace oils.

Olive oil authentication: A comparative analysis of regulatory frameworks with especial emphasis on quality and authenticity indices, and recent analytical techniques developed for their assessment. A review

ABSTRACTOver the last decades, olive oil quality and authenticity control has become an issue of great importance to consumers, suppliers, retailers, and regulators in both traditional and emerging olive oil producing countries, mainly due to the increasing worldwide popularity and the trade globalization of this product. Thus, in order to ensure olive oil authentication, various national and international laws and regulations have been adopted, although some of them are actually causing an enormous debate about the risk that they can represent for the harmonization of international olive oil trade standards. Within this context, this review was designed to provide a critical overview and comparative analysis of selected regulatory frameworks for olive oil authentication, with special emphasis on the quality and purity criteria considered by these regulation systems, their thresholds and the analytical methods employed for monitoring them. To complete the general overview, recent analytical advances to overcome drawbacks and limitations of the official methods to evaluate olive oil quality and to determine possible adulterations were reviewed. Furthermore, the latest trends on analytical approaches to assess the olive oil geographical and varietal origin traceability were also examined.

Filtered vs. naturally sedimented and decanted virgin olive oil during storage: Effect on quality and composition

The aim of this study was to compare quality changes and compositional characteristics (fatty acids, total phenols, sensory profile) during 12 months storage of Buža and Istarska bjelica cv. virgin olive oils clarified by filtration at an industrial scale (filter press equipped with cellulose filters) and those clarified by natural sedimentation and decantation, as well as the influence of filtration of virgin olive oils on sterols and triterpene dialcohols composition. There were no significant differences in hydrolytic deterioration and sensory scores during the whole storage period between filtered and naturally sedimented oil samples. After 6 months, natural sedimentation was more favorable as regards delaying of oxidative deterioration, while filtration provided a more stable sensory profile. As regards total phenols the impact of the clarifying procedure was dependent on cultivar and fruit ripeness degree and it was more emphasized than the impact of storage. Filtration slightly affected the fatty acids composition, but natural sedimentation and decantation had no effect on it. Nevertheless, filtration did not compromise the confirmation of virgin olive oil authenticity according to the fatty acid composition, as well as according to sterols and triterpene dialcohols.

FT-NIR the method of choice to verify the authenticity of extra virgin olive oils

Fourier transform near infrared spectroscopy was recently demonstrated to be an excellent method to evaluate the authenticity and adulteration of extra virgin olive oil. Since this method is matrix dependent, it takes a chemical fingerprint of all the components which sets it apart from the targeted methods. Careful examinations of the Fourier transform near infrared spectra lead to the identification of a minor carbonyl overtone absorption at 5269 cm−1 associated with the volatile fraction in extra virgin olive oil that appears to be a reliable indicator of authenticity. The same spectra were used to identify the fatty acids present in the oil using models based on comparison to accurate GC data. Gravimetric mixtures of extra virgin olive oil with refined edible oils were then prepared to develop PLS1 calibration models to identify possible adulterants and by how much. The great varietal difference in olive oils made it necessary to develop four unique sets of PLS1 calibration models for each extra virgin olive oil variety. As a result, an extra virgin olive oil acceptance specification was established.

Development and optimization of an efficient qPCR system for olive authentication in edible oils

The applicability of qPCR in olive-oil authentication depends on the DNA obtained from the oils and the amplification primers. Therefore, four olive-specific amplification systems based on the trnL gene were designed (A-, B-, C- and D-trnL systems). The qPCR conditions, primer concentration and annealing temperature, were optimized. The systems were tested for efficiency and sensitivity to select the most suitable for olive oil authentication. The selected system (D-trnL) demonstrated specificity toward olive in contrast to other oleaginous species (canola, soybean, sunflower, maize, peanut and coconut) and showed high sensitivity in a broad linear dynamic range (LOD and LOQ: 500ng – 0.0625pg). This qPCR system enabled detection, with high sensitivity and specificity, of olive DNA isolated from oils processed in different ways, establishing it as an efficient method for the authentication of olive oil regardless of its category.

Fast Automated Determination of Total Tocopherol Content in Virgin Olive Oil Using a Single Multicommuted Luminescent Flow Method

Tocopherols are natural fluorophores of great importance for the characterization and authentication of virgin olive oil. Herein, a single automatic multicommuted flow method has been developed for the determination of total tocopherol content as well as the semi-quantitative estimation of α-tocopherol in extra virgin olive oil (EVOO) samples. Only appropriate dilution of samples with 2-propanol was necessary for their direct analysis by a multicommuted flow injection (MCFIA) manifold based on three solenoid valves with fluorescence detection. The peak height at λ em = 330 nm (emission) with λ exc at 296 nm was used as analytical signal. Linear response was observed within the range from 50 to 350 mg of tocopherols (expressed as α-tocopherol kg−1 olive oil), suitable to cover the usual range for tocopherols in (extra) virgin olive oil ((E)VOO)). The results were consistent with those obtained by reversed-phase HPLC reference method, whereas the analysis time was significantly reduced. The sample frequency of the proposed automatic method was close to 40 samples h−1, in contrast to typically 15–30 min required by HPLC. The method is fast, straightforward, cost-effective, and easy to implement in routine laboratories for screening purposes.

Special issue on olive oil

Lanfranco Conte Maria Tsimidou Virgin olive oil (VOO) is probably one of the most ancient foods of the Mediterranean area and it has been extensively studied for decades mainly with the aim to guarantee its purity and quality (sometimes just for taxation needs). The olive industry in the 21rst century has some unique characteristics. Production and consumption are in balance the last decades mainly because of the increasing evidence for the health benefits to the humans. Climatic changes affected the sector in recent years. This year's production is expected to drop by 7% (IOC provision), which is critical for the sustainability of exports from the major European producing countries. Research on the particular health properties of polar phenolic compounds of virgin olive oil has recently led the European Food Safety Authority to approve a health claim for their antioxidant activity. The interest in retaining organoleptic characteristics and a high content of these polar bioactive compounds became the driver for changes in the harvest and processing practices in the producing countries. The increasing demand for “high quality extra virgin olive oil” among certain groups of consumers from all over the world had a positive impact on the marketing of premium products that command high values/liter. Virgin olive oil is now appraised not only because of its high content in monounsaturated fatty acids and a balanced ratio of unsaturated fatty acids to alpha-tocopherol content but also for the fruity aroma and bitter/pungent taste related to the presence of valuable bioactive polar phenols. Freshness of the product and its maintenance is becoming important for producers, distributors and consumers. Recent innovations in the extraction system of olive oils are promising towards further improvement of quality. Legislation for olive oil characteristics is tight in the European Union since 1991. It involves the examination of different quality and authenticity characteristics, and also includes sensory scores. Similar regulations cannot be found for any other agricultural product, or for another edible oil and fat. Nevertheless, all interested parties work continuously on reducing the possibilities for fraudulent practices. This is reflected in a dedicated EU call on “Olive Oil Authenticity”. Analytics of olive oil cover a wide range of approaches and techniques. From the era of establishing indices of quality and authenticity, to the extensive application of separation techniques a century has elapsed. Thanks to GC-MS, sterols structure was adequately elucidated since the end of ‘60th, even if the presence of some sterols (e.g. delta 5 avenasterol) had been highlighted later, when more polar stationary phases became available. Sterols profile and concentrations of individual members has become a pertinent tool in olive oil authentication studies. Triacylglycerol analysis using HPLC together with the GC analysis of FAMEs were used for the calculation of a new index (Delta ECN 42) to detect adulteration with seed oils. The issue of “polyphenols” attracted the interest of the analysts since the end of ‘70s. Currently, new high throughput spectroscopic and molecular techniques have found application for different objectives. Ongoing research indicates that as far as analytical instruments performances improve, more and more knowledge is acquired on VOO composition that leads on one hand to a more perceptive control on its purity and quality and on the other hand to discover new compounds and to understand the biochemical mechanisms of their function in the human body. Still, the challenges in the olive sector never stop. Fair trade has many enemies within every country and region. One of the next goals is to protect the many different European Products of Denomination of Origin (PDOs) in a reliable objective way that guarantees the origin whereas some difficult frauds like the addition of deodorised oil must be combated through administrative and analytical approaches. We invited a number of researchers, who have been active for many years in this field to contribute to this Special Issue. The issue contains review articles and original research papers diverse in context. Authors from different countries and research groups contributed eagerly and we are indebted to them. We are also thankful to the reviewers, who supported this venture. Virgin olive oil, the olive juice, has a history that dates back to the very beginning of human presence on the earth as it has been used for multiple purposes, not only as a food item. Working on olive oil seems to be a life time endeavour for those researchers devoted to its chemistry, analysis and biological properties. We hope that you will enjoy reading the papers in this Special Issue. Lanfranco Conte University of Udine Maria Tsimidou Aristotle University of Thessaloniki