High performance size-exclusion chromatography analysis of polar compounds applied to refined, mild deodorized, extra virgin olive oils and their blends: An approach to their differentiation

An investigation was carried out to evaluate the use of High Performance Size-Exclusion Chromatography (HPSEC) of polar compounds of refined, mild deodorized, extra virgin olive oils as well as of their blends, in attempting to reveal significant differences in the amounts of the substance classes constituting polar compounds among these oils. Two sets of blends were prepared by mixing an extra virgin olive oil with both refined and mild deodorized olive oils in increasing amounts. The obtained data highlighted that the triacylglycerol oligopolymers were absent or present in traces in the extra virgin olive oil, while their mean amount was equal to 0.04 g/100 g and 0.72 g/100 g in mild deodorized and refined olive oils, respectively. Oxidized triacylglycerols and diacylglycerols were more abundant in mild deodorized oil and refined oil than in extra virgin olive oil. The Factorial Discriminant Analysis of the data showed that the HPSEC analysis could reveal the presence of refined/mild deodorized oils in extra virgin olive oils. In particular, the classification functions obtained allowed designation of mixtures containing at least 30 g/100 g of mild deodorized oil and all those containing refined olive oil as deodorized oil, therefore as oils subjected to at least a mild refining treatment.     

Statistical analysis on Sicilian olive oils

A robust multivariate statistical procedure applied to an accurate gas chromatography (GC) analysis was used to analyze 1004 monovarietal and multivarietal Sicilian extra virgin olive oils coming from 22 cultivars of different geographical areas of Sicily and collected in nine years (1993, 1995, 1996, 1997, 1998, 1999, 2000, 2001 and 2002). The effect of the cultivar, of pedoclimatic conditions as well as of the year of harvesting on the olive oil fatty acid composition and therefore on their classification was investigated. Oleic, linoleic and palmitic fatty acids, important for the nutritional properties of an olive oil, showed a crucial rule in the characterization of olive oils.     

Multivariate analysis of NMR fingerprint of the unsaponifiable fraction of virgin olive oils for authentication purposes

A new approach to the geographical characterisation of virgin olive oils (VOOs) based on the ¹H NMR fingerprint of the unsaponifiable matter is presented. The ¹H NMR spectra of the unsaponifiable fraction of virgin olive oils from Spain, Italy, Greece, Tunisia, Turkey, and Syria were analysed by several pattern recognition techniques (LDA, PLS-DA, SIMCA, and CART). PLS-DA (PLS-1 approach) obtained the best classification results for all classes. Moreover, ¹H NMR spectra of the bulk oil, and its corresponding unsaponifiable fraction, as well as the subfractions of the unsaponifiable fraction (alcohol, sterol, hydrocarbon, and tocopherol fractions) were studied in the search for the markers that multivariate techniques revealed to be related to the geographical origin of olive oils. Additionally, a preliminary study regarding ¹H NMR data of the bulk oil and the corresponding unsaponifiable fraction of VOOs suggested that these spectral data contained complementary information for the geographical characterisation of VOOs.     

Review of the use of phytosterols as a detection tool for adulteration of olive oil with hazelnut oil

Adulteration of virgin olive oil with less expensive oils such as hazelnut oil is a serious problem for quality control of olive oil. Detection of the presence of hazelnut oil in olive oil at low percentages (<20%) is limited with current official standard methods. In this review, various classes of phytosterols in these two oils are assessed as possible markers to detect adulterated olive oil. The composition of 4-desmethyl- and 4-monomethylsterols is similar in both oils, but the 4,4′-dimethylsterols differ. Lupeol and an unknown (lupane skeleton) compound from 4,4′-dimethylsterols are exclusively present in hazelnut oil and can be used as markers via GC–MS monitoring to detect adulteration at levels as low as 2%. The phytosterol classes need to be separated and enriched by a preparative method prior to analysis by GC or GC/MS; these SPE and TLC methods are also described in this review.     

Means-end chains analysis of extra virgin olive oil purchase and consumption behavior

Consumption and purchase behavior towards extra virgin olive oil are not well understood in the US. Soft laddering interviews were conducted with 63 Northern California consumers and means-end chains analysis on the interview data revealed common grounds of consumption and buying motivations for three different a priori defined consumer segments. Consumption motivational structures were more similar across the different consumer segments than purchasing ones. Consumers who purchased only local extra virgin olive oil had simpler perceptual orientations than consumers who purchased imported extra virgin olive oils or both imported and local oils. Several different consumer values could be associated with consequences that were linked to just one attribute. On the other hand, one particular value could also be associated with a few different attributes. These findings provide opportunities for the olive oil industry to design products that will better satisfy consumer values and needs.     

Geographical classification of Greek virgin olive oil by non-parametric multivariate evaluation of fatty acid composition

Fatty acid compositional data for Greek virgin olive oils from 24 years of harvest and various regions and cultivars were evaluated using chemometric methods. Non-parametric discriminant analysis after proper transformation of the data seems to be a suitable approach to characterise the oils according to the geographical origin and may produce a scientific basis for the assignment of an ‘appellation d'origine’ trade mark.     

Use of capillary electrophoresis with UV detection to compare the phenolic profiles of extra‐virgin olive oils belonging to Spanish and Italian PDOs and their relation to sensorial properties

BACKGROUND: There is much interest in foods that belong to Protected Designations of Origin (PDO) because the quality and other essential and exclusive characteristics are guaranteed because of a particular geographical environment. We have used a capillary electrophoretic method for the simple, rapid and simultaneous characterization and quantification of the polyphenolic fraction of extra‐virgin olive oil from different PDOs (18 compounds in less than 7 min). To demonstrate the usefulness of this method, we have analyzed 16 samples of a Spanish PDO and nine other samples belonging to an Italian PDO (n = 5). RESULTS: In this way, it was possible to compare the phenolic profiles of the oils of different zones of the same PDO, as well as the phenolic profiles of Spanish and Italian extra‐virgin olive oils. Univariate statistics were used for differentiating the oils produced in each PDO. Furthermore, the correlations among several of the phenolic compounds present in the extracts of olive oil and its sensorial properties were checked. decarboxylated oleuropein aglycon (DOA) (b) (peak 6) was the compound more related to the bitterness of the oils, Ac Pin (peak number 4) and the unidentified peak with t_mig 4.025 min played an important role in the pungent taste of the oils, and these two latter compounds and the peak 13 seemed to be related to the fruitiness of the oils. CONCLUSIONS: The electrophoretic method described in the current work has the ability to detect and quantify simultaneously 18 phenolic compounds (belonging to five different families) in less than 7 min. This technique could improve the characterization of this polar fraction and determine the geographical origin of olive oils or detect possible ‘PDO markers’. In fact, capillary electrophoresis coupled to statistical analysis enabled discrimination among olive oils belonging to two different PDOs considering eight phenolic compounds present in the extracts, and also identification of the phenolic compounds which could have more influence on several sensory attributes such as bitterness, pungency and fruitiness. Copyright © 2009 Society of Chemical Industry     

Infrared spectroscopy for quantitative analysis and oil parameters of olive oil and virgin coconut oil: A review

Vegetable oils are major lipid sources with high nutritional and calorific values for human diet. Specifically, virgin coconut oil and extra virgin olive oil are the functional oils widely used in food and pharmaceutical products, either as vehicles or main components. The quality of edible oils is determined by its contents and parameters inherent in vegetable oils. Infrared spectroscopy is an ideal technique for quantitative analysis of vegetable oils as well as for determination of oils parameters as the changes in infrared spectra can be associated with the changes of oils parameters. Infrared spectra in complex samples are difficult to interpret, as a consequence, spectroscopist uses additional tools called with chemometrics to analyse edible oils qualitatively and quantitatively. This article reviews the use of infrared spectroscopy combined with chemometrics (multivariate analysis) for quantitative analysis and determination of oil parameters of virgin coconut oil and extra virgin olive oil. Although infrared spectra for edible oils are similar, they exhibit some differences which enable spectroscopist to differentiate due to the nature property of infrared spectroscopy spectra as fingerprint spectra which can be understood that there are no different edible oils having the same infrared spectroscopy spectra.     

Classification of different quality virgin olive oils by metal-oxide sensors

The European Union classifies virgin olive oils into three categories, extra virgin, virgin and lampante; lampante being the only oil that cannot be consumed before undergoing a refining process. A mathematical model based on two metal-oxide sensors has been designed and checked in order to detect on-line lampante oils inside the production systems. The model was developed using 114 samples and was successfully tested with an external test set of 55 samples taken from different single varietal olive oils and geographical origins. The model was able to detect 100% of non-lampante virgin olive oils and 89.5% of lampante virgin olive oils.     

Detection of the adulteration of olive oils by solid phase microextraction and multidimensional gas chromatography

The presence or absence of filbertone in 21 admixtures of olive oil with virgin and refined hazelnut oils obtained using various processing techniques from different varieties and geographical origins was evaluated by solid phase microextraction and multidimensional gas chromatography (SPME–MDGC). The obtained results showed that the sensitivity achievable with the proposed procedure was enough to detect filbertone and, hence, to establish the adulteration of olive oil of different varieties with virgin hazelnut oils in percentages of up to 7%. The very low concentrations in which filbertone occurs in some refined hazelnut oils made difficult its detection in specific admixtures. In any case, the minimum adulteration level to be detected depends on the oil varieties present in the adulterated samples. In the present study, the presence of R- and S-enantiomers of filbertone could be occasionally detected in olive oils adulterated with 10–20% of refined hazelnut oil.     

Has the use of talc an effect on yield and extra virgin olive oil quality?

The maximization of both extraction yield and extra virgin olive oil quality during olive processing are the main objectives of the olive oil industry. As regards extraction yield, it can be improved by both acting on time/temperature of malaxation and using physical coadjuvants. It is well known that, generally, increasing temperature of malaxation gives an increase in oil extraction yield due to a reduction in oily phase viscosity; however, high malaxation temperature can compromise the nutritional and health values of extra virgin olive oil, leading to undesirable effects such as accelerated oxidative process and loss of volatile compounds responsible for oil flavor and fragrance. The addition of physical coadjuvants in olive oil processing during the malaxation phase, not excluded by EC regulations owing to its exclusively physical action, is well known to promote the breakdown of oil/water emulsions and consequently make oil extraction easier, thus increasing the yield. Among physical coadjuvants, micronized natural talc is used for olive oil processing above all for Spanish and Italian olive cultivars. The quality of extra virgin olive oil depends on numerous variables such as olive cultivar, ripeness degree and quality, machines utilized for processing, oil storage conditions, etc. However, the coadjuvants utilized in olive processing can also influence virgin olive oil characteristics. The literature highlights an increase in oil yield by micronized natural talc addition during olive processing, whereas no clear trend was observed as regards the chemical, nutritional and sensory characteristics of extra virgin olive oil. Although an increase in oil stability was reported, no effect of talc was found on the evolution of virgin olive oil quality indices during storage. © 2016 Society of Chemical Industry     

基于紫外可见光谱技术和色素组成区分橄榄油与其他食用油

目的 通过紫外可见光谱技术和色素组成,探究区分橄榄油与其他食用油的方法。方法 选择市售橄榄油(特级初榨橄榄油、混合橄榄油)和其他食用油(菜籽油、玉米油、葵花籽油、大豆油、花生油、调和油)作为研究对象,分别在220~800 nm的波长范围内进行全光谱扫描以及在波长为450 nm和670 nm处进行光度测量;通过比较不同食用油的紫外可见吸收光谱并结合主成分分析(principal component analysis, PCA)和偏最小二乘法判别(partial least squares discriminant analysis, PLS-DA)对不同橄榄油和其他食用油进行比较区分。结果 通过观察比较各食用油紫外可见吸收光谱的最大吸收波长所在位置,可以对不同食用油进行初步区分。并且PCA和PLS-DA结果显示,以波长450 nm和670 nm处的吸光度A450和A670以及A450/A670为变量,可用于区分不同橄榄油和其他食用油。结论 基于紫外可见光谱技术对不同食用油中色素的检测结果可以对食用油进行分类,并且A450、A670和A450/A670可以作为区分橄榄油与其他食用油的标记。     

Authentication of Olive Oil Adulterated with Vegetable Oils Using Fourier Transform Infrared Spectroscopy

Determination of the authenticity of extra virgin olive oils has become more important in recent years following some infamous adulteration and contamination scandals. The study focused on application of Fourier transform infrared spectroscopy to identify the adulteration of olive oils. Single-bounce attenuated total reflectance measurements were made on pure olive oil and olive oil samples adulterated with varying concentrations of sunflower oil (20-100 mL vegetable oil/L of olive oil). Discriminant analysis using 12 principal components was able to classify the samples as pure and adulterated olive oils based on their spectra. A partial least squares model was developed and used to verify the concentrations of the adulterant. Furthermore, the discriminant analysis method was used to classify olive oil samples as distinct from other vegetable oils based on their infrared spectra.     

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.     

Detection of hazelnut oil in virgin olive oil by a spectrofluorimetric method

The possibilities of a spectrofluorimetric method joined to multivariate analysis to assess the genuineness of olive oil in admixtures with hazelnut oils were studied. Virgin olive, virgin hazelnut and refined hazelnut oil samples and admixtures between them at 5, 10, 15, 20, 25 and 30% adulteration were analysed at _ex=350 nm. The precision of the method, in terms of repeatability and internal reproducibility, was established by means of the analysis of a virgin olive oil sample under different conditions, the RSD showing values less than 10%. Raw data of the spectra were subjected to mathematical treatment by calculation of the first derivative, selection of the maximum values and application of one-way ANOVA, to assess the most prominent variables in the discrimination process. The response to the addition of adulterant was linear, adjusted-R²=0.99 for virgin olive and refined hazelnut oil mixtures, and 0.98 for virgin olive and virgin hazelnut oil mixtures. Stepwise linear discriminant analysis applied to each admixture separately and to the whole set of samples allowed 100% correct classifications.     

特级初榨橄榄油基本质量指标及要求

目的 介绍2022年5月1日起实施的GB/T 23347—2021《橄榄油、油橄榄果渣油》,对当前市售进口特级初榨橄榄油质量情况进行评估。方法 采购20种市售标称意大利、希腊、西班牙等国进口的特级初榨橄榄油,检验酸价、过氧化值、消光系数变异值、水分及挥发物和不溶性杂质5个基础项目,对所得数据进行分析。通过与国际橄榄理事会标准的对比,讨论限量及测定方法等方面的细微差异,并说明这些项目对于橄榄油质量评估的现实意义。结果 所测样品的酸价、过氧化值、不溶性杂质3个项目均符合我国标准对该产品等级的限量要求。对比GB/T 23347—2021和国际橄榄理事会贸易标准,发现对于优质初榨橄榄油的酸价限量,国内标准比国外标准更为严格,橄榄油进口贸易需要注意这一差异。结论 2021年新颁布的GB/T23347—2021在质量要求上有所提高,消费者购买橄榄油时应优先选择“特级初榨橄榄油”。橄榄油质量初步评估需要加快时间和减少成本,检验以上5个项目为最低要求。     

鲜榨山茶油与特级初榨橄榄油营养价值的比较

以鲜榨山茶油和特级初榨橄榄油为研究对象,对其理化指标、脂肪酸组成和营养成分进行测定并比较。结果表明:鲜榨山茶油在理化指标上与特级初榨橄榄油相当,脂肪酸组成与特级初榨橄榄油相似,但油酸含量高于特级初榨橄榄油,棕榈酸和硬脂酸含量低于特级初榨橄榄油;在维生素E、角鲨烯、植物甾醇等天然生物活性物质方面媲美特级初榨橄榄油。     

Phenolic content of commercial olive oils

The phenolic composition of commercial virgin olive oils (Picual, Hojiblanca, Arbequina and Cornicabra varieties) was studied by high performance liquid chromatography, sampling oils over 1 year. Oils sold in March displayed the lowest polyphenol concentration, particularly in secoiridoid aglycons. In contrast, lignans and tocopherols concentrations were not affected by sampling date. Among varieties, Picual and Cornicabra oils had slightly higher concentrations of polyphenols than Hojiblanca and Arbequina. Overall, the concentration of polyphenols in commercial Spanish virgin olive oils ranged from 330 to 500 mg/kg oil, which is higher than data reported previously. In contrast, "olive oil" and "pomace-olive oil" (mixtures of refined and virgin olive oils) had much lower concentrations in polyphenols than virgin olive oil, although higher than other edible vegetable oils. Thus, olive oil can be considered a good source of natural antioxidants. Moreover, the polyphenol and tocopherol contents of virgin olive oils were also found useful for the classification of the different commercial monovarietal oils when analysing the data by chemometric methods.     

Characterisation of the geographical origin of Western Greek virgin olive oils based on instrumental and multivariate statistical analysis

In this work, measurements of free acidity, peroxide content, spectrophotometric parameters, chlorophyll content, phenol, sterol, fatty acid and triacylglycerol composition, were carried out on samples of virgin olive oils (VOOs) coming from four different Greek Ionian islands, i.e. Zakynthos, Kefalonia, Lefkada and Kerkyra. An analysis of variance (ANOVA) highlighted statistically significant differences (p < 0.01) in the values of 26 analytical parameters amongst the VOOs produced in the four different geographical regions but a post-hoc test showed that no variable was able to distinguish all four origins. Analogously, a Principal Component Analysis (PCA) showed a modest grouping of VOOs according to geographical origin except for Kerkyra samples which were more distinct from others. Applying discriminant function analysis (DFA) a good separation of the four geographical groups was achieved with classification and prediction abilities equal to 97.7% and 95.3%, respectively. Moreover, the analysis of the standardised coefficients showed that the fatty acids and triacylglycerols were the most discriminant variables. This last outcome was confirmed by comparison of the prediction performances obtained applying DFA on four subdatasets containing fatty acids (69.8%), triacylglycerols (76.7%), sterols (62.8%), and remaining parameters (65.1%) together, respectively. As the results showed, the multidisciplinary approach that combines different types of analytical determinations improved the discrimination of geographical origin for Greek virgin olive oils.     

Sterolic composition of Chétoui virgin olive oil: Influence of geographical origin

The sterol profile of Tunisian virgin olive oils produced from Chétoui cultivar, the second main variety cultivated in the north of the country, grown under different environmental conditions, was established by gas chromatography using a flame ionisation detector. More than ten compounds were identified and characterised. As expected for virgin olive oil, the main sterols found in all Chétoui olive oils were β-sitosterol, Δ5-avenasterol, campesterol and stigmasterol. Cholesterol, 24-methylenecholesterol, clerosterol, campestanol, sitostanol, Δ7-stigmastenol, Δ5,24-stigmastadienol, and Δ7-avenasterol were also found in all samples, but in lower amounts. Most of these compounds are significantly affected by the geographical origin. The majority of the Chétoui virgin olive oils analysed respected EC Regulation No. 2568, and in all cases total sterol amounts were higher than the minimum limit set by legislation, ranging from 1017 to 1522 mg/kg.