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.     

Application of solid-phase microextraction to the analysis of volatile compounds in virgin olive oils from five new cultivars

Evaluation and identification of wild olive genetic resources allowed us to select new olive varieties and to recognize Tunisian grove richness and diversity. Five new olive cultivars were previously selected among populations of wild olive plants on the basis of agronomic and chemical evaluations. Their virgin olive oils were analysed for their fatty acid composition, quality indices (Free acidity, PV and UV characteristics) and oxidative stability. They were then submitted to solid phase microextraction (SPME) and their volatile compositions were determined.     

DNA diversity in olive (Olea europaea L.) and its relationships with fatty acid,biophenol and sensory profiles of extra virgin olive oils

Olive (Olea europaea L.) is gaining importance worldwide primarily for the production of virgin olive oil (VOO), the main lipid source of the Mediterranean diet.We evaluated the genetic diversity of 20 traditional varieties of Southern Italy using 10 SSR markers. We also produced 382 monovarietal extra virgin olive oils (EVOOs) from the same varieties and studied their chemical profiles by analysing 13 fatty acids (FAs) and 6 olive biophenols (OBPs). In addition, the sensory profile of EVOOs was also assessed.Significant differences among the 20 varieties were found in terms of DNA polymorphism, chemical composition and sensory profile of the EVOOs, highlighting that the genetic variability in olive is detected also in different EVOO features. The chemical variation of EVOOs throughout different years suggested a genotype-specific level of environmental stability and adaptation. The comparison of pairwise distances between varieties obtained by genetic, chemical and sensory data indicated a significant correlation of sensory attributes with the other parameters.The genetic and EVOO composition data underlined the significant diversity present in the varieties under investigation, suggesting that traditional varieties specialized to particular environmental conditions have distinctive, unexplored features. Our work also shows the efficacy of establishing integrated compositional databases as a means to make evident differences among VOOs from traditional varieties. This multidisciplinary information is highly useful to differentiate origin-linked products from others of the same category.     

Sterols and triterpene diols in olive oil as indicators of variety and degree of ripening

Sterols and triterpene diols in olive oil as indicators of variety and degree of ripening derived from three olive varieties and produced at three different harvesting periods were studied. In order to test the stability of the proposed indicators, oils obtained were stored for 12 months at three different temperatures. Thirty-six samples in total were subjected to GC analysis and results were processed by multivariate chemometric methods (MANOVA, PCA, and SLDA). Campesterol, β-sitosterol, Δ⁷-campesterol/Δ^5,24-stigmastadienol, clerosterol, uvaol, and campestanol/Δ⁷-avenasterol were established as the indicators of variety of fresh oils, while when stored oils were included in the model, the final three compounds were substituted by 24-methylene-cholesterol/stigmasterol. The most important variables for differentiating fresh oils according to degree of ripening were Δ⁷-campesterol/β-sitosterol, uvaol/stigmasterol, clerosterol/Δ⁵-avenasterol and sitostanol/uvaol, while stored oils were differentiated by campestanol/stigmasterol, erythrodiol, stigmasterol/Δ⁷-campesterol, Δ⁵-avenasterol, 24-methylene-cholesterol/β-sitosterol and 24-methylene-cholesterol. Results demonstrated that sterols and triterpene diols can be used as indicators of variety and degree of ripening among virgin olive oils.     

28份国产特级初榨橄榄油中多酚含量及其变化规律北大核心CSCD

为了对我国油橄榄产业提供基础数据支持,采用国际油橄榄理事会推荐的HPLC法检测特级初榨橄榄油中的多酚含量,分析了我国不同产地的28份市售食用特级初榨橄榄油样品的多酚含量,并对不同生产年度和不同产地单果级特级初榨橄榄油中多酚含量变化规律进行了分析。结果表明:市售国产特级初榨橄榄油中均含有较为丰富的多酚类化合物,多酚含量范围为(63.885±2.345)mg/kg~(307.325±6.865)mg/kg;特级初榨橄榄油中多酚含量受贮存时间的影响较大,同时不同产地中适合生产高多酚含量特级初榨橄榄油的品种具有差异。不同特级初榨橄榄油样品之间多酚含量波动较大,需要通过多种方法来防止油脂中多酚类化合物的降解,以保证油品的质量,并因地制宜对油橄榄品种进行优化筛选。     

Sterol and alcohol components of seed,pulp and whole olive fruit oils. Their use to characterise olive fruit variety by multivariates

Sterols, triterpene dialcohols, long‐chain aliphatic alcohols and higher triterpene alcohols were determined in three fruit oil kinds (seed, pulp and whole fruit oils). Seven major Italian olive fruit varieties from the same environment were considered. Results of this research suggested that the compositional data concerning the above analytical fractions were effective in discriminating between seed and pulp oils. The seed oil fraction did not substantially modify the sterol and alcohol composition of the whole fruit oil (mixture of seed and pulp oils), the percentage weight of the seed (～2%) being far lower than that of the pulp (～85%) (whole fruit weight basis). Based on the concentrations of the above components and using appropriate statistical parametric or non‐parametric multivariate techniques, the genetic origin (olive variety) of the three fruit oil kinds was characterised. © 2002 Society of Chemical Industry     

Changes in volatile compounds and oil quality with malaxation time of Tunisian cultivars of Olea europea

While there has been considerable work examining the effect of malaxation time on different characteristics of olive oils, there have been few that deal with all the major aspects. Here, the influence of malaxation time was evaluated using major local Tunisian (cv. Chemlali and Chetoui) cultivars. Standard characteristics were measured as well as detailed analyses of volatile compounds were conducted. Headspace solid‐phase microextraction (HS‐SPME) was applied to the analysis of volatile compounds of virgin olive oils from Chemlali and Chetoui varieties with differing malaxation time. Twenty‐seven compounds were characterised by GC‐FID and GC–MS. Compounds belonging mainly to alcohols, esters, aldehydes, ketones and hydrocarbons chemical classes characterized the volatile profile. Significant differences in the proportion of volatiles from oils of different malaxation time were detected. The results suggest that besides genetic factors, malaxation time influences volatile formation. The main variables that were affected by malaxation time were the total amount of phenols and composition of the volatile compounds. At malaxation time of 30 min, Chemlali and Chetoui olive oils presented the highest total phenol content (244.19 and 877.63 mg kg^?1, respectively), while the lowest content was observed at 60 min from regardless of cultivars. In turn, this influenced the oxidative stability and peroxide value. It was also clear that the cultivars behaved differently and this prevented general conclusions being made for all of the quality characteristics.     

Sensory Authentication of European Extra-Virgin Olive Oil Varieties by Mathematical Procedures

Multidimensional scaling and a fuzzy filter qualifier were used together for authenticating and characterising four olive oil varieties—Picual and Arbequina (Spain), Coratina (Italy) and Koroneiki (Greece)—representative of the most important producer countries. Twenty four samples were evaluated by five panels of different nationalities—British, Greek, Italian and Spanish—these being representatives of traditional and potential consumers of virgin olive oil. Each sample was initially characterised by 74 sensory attributes. The paper analyses the most outstanding attributes and their evaluation intensities that characterise the varieties and gives the sensory profiling of each variety. Green attributes characterise Koroneiki variety, Arbequina variety is characterised by sweet–fruity sensory attributes, the bitter–pungent sensory attributes can identify Coratina while a strong fruity odour explains the sensory characteristics of Picual variety.     

Role of vitamin E and phenolic compounds in the antioxidant capacity,measured by ESR,of virgin olive,olive and sunflower oils after frying

The effect of lipid profile, vitamin E and total phenolic content was studied in relation to the antioxidant capacity (measured by ESR) of three edible oils (virgin olive, sunflower and olive oils), using short-time deep fat frying as a model. Physico-chemical changes in the oils were also studied. Samples were analysed before and after 15, 30, 45 and 60 min fryings. Determination of free radicals, by electron spin resonance spectroscopy, revealed the highest antioxidant capacity in virgin olive oil and sunflower oil. This parameter was mainly influenced by vitamin E content, followed by lipid profile and phenolic content. The frying procedure decreased the antioxidant capacity in all tested oils. Sunflower oil underwent more chemical changes by frying than did olive and virgin olive oils. Antioxidant capacity of the edible oils was correlated with polar components and ultraviolet indices but not with peroxide index or acidity value. The use of ESR, as a rapid and very sensitive method for determining antioxidant capacity of edible oils, is suggested.     

Effect of crushing on olive paste and virgin olive oil minor components

The present study focuses on the influence of the olive crushing technique on the minor composition of olive pastes and their corresponding virgin olive oils since these compounds are strongly related to their quality and characteristics. Two different cultivars, Arbequina and Cornicabra—known for their different minor component composition—were processed at laboratory scale using hammer mills at various breakage forces and grid hole diameters, a blade cutter and a mortar. Crushing and kneading produce a profound change in the composition of the phenolic compounds in the olive paste and in the final oil. Hydroxytyrosol derivatives in virgin olive oil were most affected by the crushing conditions. The stronger the crushing conditions (i.e. hammer crushers using smaller grid holes and a higher rotation speed), the higher the phenolic content in both olive paste and oil in both varieties. Interestingly, the effect on volatile compounds of milder or stronger crushing conditions was opposite to that described for the phenolic compounds.     

基于光谱法的特级初榨橄榄油快速鉴伪技术

本文研究了特级初榨橄榄油中掺入不同比例橄榄果榨油(精炼橄榄油)、菜籽油、玉米油和大豆油的光谱特征,采用荧光光谱和紫外光谱,对掺假样品及纯油样品进行了快速检测。结果表明,特级初榨橄榄油的光谱特征与其他植物油之间差异较大,且掺假体积与吸光度之间存在良好的线性关系(R²>0.89),实现了特级初榨橄榄油的定性鉴别与定量检测,建立了特级初榨橄榄油质量控制体系及其掺假检测分析技术,最低检出限为1%,线性范围为5%～100%(v/v)。系统聚类分析将所有特级初榨橄榄油准确地分为一个亚类,也佐证了此方法的稳定性与可靠性。这种简单快捷的检测技术,有助于特级初榨橄榄油实时、在线橄榄油检测分析技术的研发,为我国橄榄油品质鉴定及产业发展提供有利的技术保障。     

Volatile compounds characterising Tunisian virgin olive oils: the influence of cultivar

In this work, the volatile profiles of four Tunisian virgin olive oils were established by headspace‐solid phase microextraction and gas chromatography, using flame ionisation and mass spectrometer detectors. More than eighty compounds were isolated and characterised, representing 97–99% of the total GC area. The main volatile compounds present in the oil samples were determined quantitatively, the major constituents were often aldehydes, particularly (E)‐2‐hexenal (48–90%). Significant differences in the content of volatile constituents were observed. These quantitative differences were used to distinguish between virgin olive oils from different varieties.     

二相离心加工工艺对初榨橄榄油理化指标和氧化稳定性的影响

橄榄油的品质不但与品种有关,还受加工工艺的影响。以‘豆果’‘鄂植8号’‘克罗莱卡’3个品种油橄榄果为原料,研究了二相离心加工工艺对初榨橄榄油脂肪酸组成、色度、酸值、过氧化值、紫外吸光度、微量伴随物、抗氧化能力和氧化稳定性的影响,并与三相离心加工工艺进行对比。结果表明:在融合温度30℃、融合时间45 min条件下,初榨橄榄油的品质较好;‘克罗莱卡’初榨橄榄油中多酚含量最高,氧化稳定性最好,与三相离心加工工艺相比,二相离心加工工艺生产的初榨橄榄油多酚含量显著提高。     

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.     

Effect of cultivar and ripening on minor components in Spanish olive fruits and their corresponding virgin olive oils

Phenolics and volatiles are the compounds mainly responsible for the desirable flavour of extra virgin olive oils and therefore to a large extent determine the degree of consumer preference for this highly regarded product. The effect of both (i) the nature of the cultivar and (ii) the degree of ripening of the olive fruit on the biophenolic and volatile profiles of six different Spanish varieties (Arbequina, Cornicabra, Morisca, Picolimón, Picudo and Picual) and their corresponding virgin olive oils was determined in this study. A clear and statistically significant difference was observed for the oleuropein content, the main phenolic component found in the olive varieties studied. Demethyloleuropein was only found in the Arbequina variety and its content doubled during the ripening process. Verbascoside steadily increased throughout fruit maturation and cyanidin 3-O-rutinoside was the most abundant anthocyanin in all the varieties studied. Within the same cultivar a relationship between the oleosides content in the fruit and the presence of secoiridoids in the virgin olive oils was observed; however, the ratio between biophenols content in the olive fruit and in the virgin olive oil varied significantly for each of the cultivars studied (ranging from 2.3 for Picudo and 28 for Picolimon). The major volatile component was the C6 aldehyde fraction whose content varied greatly between the different varieties studied: E-2-hexenal content ranged from 20.5 mg of internal standard (4-methyl-2-pentanol) per kg of oil in the Arbequina variety to 3.1 mg/kg for Cornicabra; the amount of hexanal ranged from 1.75 mg/kg in Morisca to 0.70 mg/kg for Picual samples.     

Use of 1-acetoxypinoresinol to authenticate Picual olive oils

Picual olive oils may represent 25% of the world olive oil production. This monovarietal oil is highly valued from a nutritional viewpoint because of its high content of monounsaturated acid and polyphenols. This study reports a method to authenticate virgin olive oils of the Picual variety. The method was based on the very low content of the lignan 1-acetoxypinoresinol in these oils. The compound, as well as the other phenolic substances, was extracted from oil by using N,N -dimethylformamide (DMF), the extract was washed with hexane and nitrogen was bubbled into the solution. The identification and quantification of the lignan used HPLC to separate, followed by UV, electrochemical, fluorescence and mass spectrometry detection or gas chromatography (GC) coupled to a mass spectrometry detector. UV detection offered low sensitivity and peaks coeluting with 1-acetoxypinoresinol were also observed. Mass spectrometry detection clearly discriminated between olive oils of Picual variety and other Spanish varieties. However, lignans show a very high response to fluorescence excitation, this detector is cheaper than mass spectrometry detectors and therefore it was considered as more appropriate for industrial uses. Thus, the latter method allowed discrimination between thirty-eight Picual olive oils and eight oils of the Hojiblanca, Cornicabra, Empeltre and Arbequina varieties. The paper also demonstrated the possibility of analysing all the phenolic compounds in virgin olive oil by fluorescence. Using this technique an easy methodology to authenticate Picual olive oils was developed.     

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.     

FTIR Spectroscopy and PLS-DA Classification and Prediction of Four Commercial Grade Virgin Olive Oils from Morocco

Fourier transform infrared (FTIR) coupled to chemometrics was shown to be a useful method to classify and predict the quality of four commercial grade virgin olive oils (VOO). FTIR and physicochemical data were collected using a set of 70 samples representing extra virgin (EV), virgin (V), ordinary virgin (OV), and lampante (L) commercial grade olive oils collected in Beni Mellal region (central Morocco). Two partial least squares discriminant analysis (PLS-DA) models using physicochemical data and FTIR data were established and compared. The PLS-DA model using only physicochemical data was not accurate enough to distinguish satisfactorily among OV, V, and EV olive oil grades. On the contrary, the PLS-DA model on FTIR data was better in the calibration, able to describe 98 % of the spectral information and predicting 93 % of the VOO grades. In the external validation, this PLS-DA model accurately classified VOO commercial grades with prediction accuracy of 100 %. The proposed procedure is fast, nondestructive, simple, and easy to operate, and it is recommended for the quick monitoring of olive oil’s quality.