Pigment parameters determining spanish virgin olive oil authenticity: Stability during storage

The chlorophyll and carotenoid pigment composition in 12 mono-variety virgin olive oils was examined every 30 d during 1 yr of storage at 15°C in darkness. The oil authenticity parameters, as defined by the ratio of chlorophylls/carotenoids and the ratio of minor carotenoids/lutein, remained stable throughout storage, irrespective of the variety and degree of ripeness of the source fruit. The percent of violaxanthin, percent of lutein, and total pigment content, the classifying variables chosen as the best possible discriminators among olive varieties, also remained stable during storage. The prediction model for olive variety, which was based on a discriminant multivariate analysis of the observed values of these variables, gave a correct classification in 99.6% of the oils analyzed. The discriminant criterion established remained valid after 1 yr of oil storage. The detection of chlorophyll derivatives other than those associated with the physical extraction process was seen as a quality index, as small, analytically detectable transformations in the structure of pigments were indicative of oil storage.     

Effect of growing area on pigment and phenolic fractions of virgin olive oils of the arbequina variety in Spain

The purpose of this investigation was to study differences in the chlorophyll, carotenoid, and phenolic fractions of virgin olive oils from the Arbequina variety cultivated in different olive growing areas of Spain. Virgin olive oil from Lleida was less heavily pigmented, and these oils showed more negative values for the ordinate a^* (of the CIELAB colorimetric system). Pheophytin a was the major chlorophyll pigment, and lutein was the major component of the carotenoid fraction in all oils analyzed. The chlorophyll a concentration in virgin olive oils from Lleida was 700 μg kg⁻¹, but was 175 μg kg⁻¹ in oils from Jaén, and 200 μg kg⁻¹ in oils from Tarragona. Finally, the chlorophyll a/chlorophyll b ratio was 9 in oils from Lleida and around 0.6 in the other two Arbequina olive oils. In relation to the phenolic fraction, the hydroxytyrosol and tyrosol contents were significantly higher in olive oils from Jaén (grown at higher altitude and precipitation rates). The secoiridoid derivatives showed a significantly higher concentration in olive oils from Tarragona, probably due to the low altitude where they grow, and finally the ratio of (dialdehydic form of elenolic acid linked to tyrosol)/lignans had a value of 1.4 in olive oils from Lleida, whereas this value was around 0.7 in the other Arbequina olive oils.     

Distribution of chlorophylls and carotenoids in ripening olives and between oil and alperujo when processed using a two-phase extraction system

The present work has studied the content and type of pigments present in olive fruits and the respective oils and alperujos. The concentration of isochromic pigment fractions—chlorophylls and carotenoids—decreased with fruit ripening, more markedly in the former than in the latter. This implied that the ratio between the two pigment fractions also decreased in parallel in the three products studied. However, the value in the oil was lower than in the fruit, and that in the alperujo was much higher. During the extraction process, the release of acids may have caused pheophytinization reactions in the chlorophyll fraction, increasing pheophytin content in alperujos and oils, whereas the carotenoid fraction was affected only in the alperujo. Chlorophyll b derivatives were destroyed in greater proportion than chlorophyll a derivatives during transfer to the oil. During processing the destruction of lutein was greater than that of β-carotene. The balance of matter between fruit, alperujo, and oil indicated that not all the fruit pigmentation was released from the structures, and most remained occluded in the alperujo. The rest of the pigmentation, and particularly the chlorophyll fraction, was partly destroyed during its transfer to the oil.     

Effect of crop season on the composition of virgin olive oil with protected designation of origin “Les garrigues”

In recent years a growing demand for agricultural produce with an identifiable geographical origin has developed. The aim of this work was to study differences in quality and composition of virgin olive oils produced over four consecutive crop seasons in the region of the protected designation of origin “Les Garrigues” (Catalonia, Spain), taking the harvesting period and the climatic conditions of the year into consideration. The results obtained in this study indicate that virgin olive oil composition is greatly influenced by climatic conditions, mainly the cumulative rainfall in the case of FA composition and phenolic compounds, and the minimum temperatures during harvest period in the case of chlorophyll, carotenoid pigments, and α-tocopherol content. The harvest period influenced most of the parameters analyzed, apart from the PV and FFA content. Prediction models for carotenoid pigment content, oxidative stability, and bitter index were found.     

Effect of storage on the original pigment profile of spanish virgin olive oil

The present study was carried out on 12 virgin olive oils to determine whether one year's storage under mild conditions of 15°C and darkness affected the initial pigment composition of recently extracted virgin olive oil. Although the total pigment content remained constant, the individual contribution of each pigment changed. The acid compounds liberated from the fruits during the oil extraction process promote the beginning of chlorophyll pheophytinization and the isomerization of the 5,6-epoxide groups of the minor xanthophylls. During the first 3 mon of storage, there was a generalized increase in pheophytinization that was different for each oil (P<0.01, Duncan test) but was not correlated with the free acidity measured in them. At the same time, isomerized xanthophylls and allomerized pheophytins increased slightly. Following this stage, pyropheophytin a (a pigment not present in the initial oils), was detected; its concentration increased during storage. There were no significant differences in the final percentages of pyropheophytin a among the 12 oils, and the concentration of this new compound represented around 3% of the chlorophyll fraction. The pheophytin a/pyropheophytin a ratio always exceeded 20. All these small pigment transformations were signs that the oil had been stored. The content and class of pigments present in virgin olive oil are authentic indicators of its history prior to marketing.     

Chromatic evolution of virgin olive oils submitted to an accelerated oxidation test

Six samples of virgin olive oil obtained from several varieties of olive fruits (Picual, Manzanilla, Lechín, and Arbequina) were submitted to an accelerated oxidation process during a 63-h period under the conditions of the oil stability index (OSI), as measured by a Rancimat (100°C) apparatus. Spectra were measured every 3 h, and chlorophyll and carotenoid indexes and CIFLAB color ordinates were calculated. As oxidation time increased, remarkable changes in the spectral characteristics and color ordinates were observed. Oxidation provoked less vivid colors (lower values for chroma, C _* ^ab ) in all the samples; however, only some varieties became darker (lower values for lightness, L^*). The pigment loss calculated for oxidized oils was 67% for the carotenoid index and 58% for the chlorophyll index. Mathematical models are offered to predict color changes with time of storage at 20°C.     

Validation of the oxygen radical absorbance capacity (ORAC) parameter as a new index of quality and stability of virgin olive oil

The induction period (IP), determined using accelerated methods such as the Rancimat test, is a parameter that has been used to predict the shelf life of virgin olive oil. The oxygen radical absorbance capacity (ORAC) has recently been proposed as a quality index of virgin olive oil because it measures the efficiency of phenolic compounds in the protection against peroxyl radicals. This study aims to investigate relationships between the ORAC and IP values and proposes ORAC as a new parameter of virgin olive oil stability. The concentrations of phenolics, o-diphenols, tocopherol, β-carotene, lutein, and ORAC and IP values were determined in 33 virgin olive oils. Regression analyses showed that both ORAC and IP values correlate with total phenols and o-diphenols with highly significant indices, whereas the correlations of both ORAC and IP with tocopherols, β-carotene, and lutein were not significant. The ORAC values correlate with the IP values with low but significant indices (R=0.42; P<0.02). The results confirm the key role of phenolic compounds in accounting for the shelf life of virgin olive oil and suggest that the ORAC parameter may be used as a new index of quality and stability.     

Chlorophyll and β-carotene pigments in moroccan virgin olive oils measured by high-performance liquid chromatography

Chlorophyll and β-carotene concentrations were determined by high-performance liquid chromatography (HPLC) in virgin olive oils, which were press-extracted from green and semi-black olives. Pheophytin A was found to be the major chlorophyll isomer in all oil samples. The occurrence of this pigment at higher concentrations in oil extracted from green olives is a possible indication of its time-related destruction during olive ripening. Some evidence for thein vivo existence of pheophytin A is also presented. Beta-carotene concentration in oils was found to decrease during olive ripening.     

Color-pigment correlation in virgin olive oil

The chlorophyll and carotenoid content of virgin olive oils from five varieties harvested at varying degrees of ripeness were determined. Colors were evaluated from the chromatic ordinates L*, a*, b* of the absorption spectrum. Oil color changes for different varieties or stages of ripeness are directly related to pigment content and a* and b* values. The statistical study made on both series of parameters proves that there is a good correlation between them. The carotenoid content and b* have one of the best correlation coefficients (r) and is easily measured. This methodology evaluates chlorophyll and carotenoid content, an additional attribute for evaluation of virgin olive oil quality.     

Characterization of Turkish Virgin Olive Oils Produced from Early Harvest Olives

Olives were collected from various districts of Turkey (North and South Aegean sub-region, Bursa-Akhisar, South East Anatolia region) harvested over seven (2001–2007) seasons. The aim of this study was to characterize the chemical profiles of the oils derived from single variety Turkish olives including Ayvalik, Memecik, Gemlik, Erkence, Nizip Yaglik and Uslu. The olive oils were extracted by super press and three phase centrifugation from early harvest olives. Chosen quality indices included free fatty acid content (FFA), peroxide value (PV) and spectrophotometric characteristics in the ultraviolet (UV) region. According to the FFA results, 46% (11 out of 24 samples) were classified as extra virgin olive oils; whereas using the results of PV and UV, over 83% (over 19 of the 24 samples) had the extra virgin olive oil classification. Other measured parameters included oil stability (oxidative stability, chlorophyll pigment, pheophytin-α), cis–trans fatty acid composition and color index. Oxidative stability among oils differed whereas the cis–trans fatty acid values were within the national and international averages. Through the application of two multivariate statistical methods, Principal component and hierarchical analyses, early harvest virgin olive oil samples were classified according to the geographical locations categorized in terms of fatty acid profiles. Such statistical clustering gave rise to defined groups. These data provide evidence of the variation in virgin olive oil quality, especially early harvest and cis–trans isomers of fatty acid profiles from the diverse agronomic conditions in the olive growing regions of Turkey.     

Change in the natural ratio between chlorophylls and carotenoids in olive fruit during processing for virgin olive oil

Different varieties of olives from different sources, harvested in a similar ripeness state, have been characterized by their chlorophyll and carotenoid pigment profile and content. Pigment richness is inherent to the variety and enables great differences or similarities to be established between them. In all the fruits, ripening involves pigment loss, with the disappearance of chlorophylls always being slightly greater than that of carotenoids. However, independently of variety and the different pitment content of the fruits, the ratio between chlorophylls and carotenoids tends to remain more or less constant, within a range of 2.5 to 3.7 mg total chlorophyll/mg total carotenoid. Pigment loss caused by the extraction process is more marked for the chlorophyll fraction than for the carotenoids, changing the ratio in the oil to around one unit, whatever the variety of soruce fruit.     

Analytical characteristics of virgin olive oil from young trees (arbequina cultivar) growing under linear irrigation strategies

The effect of a linear (vs. effective crop coefficient, K _c), irrigation strategy applied to young olive trees (Arbequina cv.) on the qualitative and quantitative parameters of virgin olive oil quality was studied. Although linear irrigation strategy did not affect the quality indexes used to classify olive oil by commercial grades, it did influence other important parameters such as total phenol content, bitter index oxidative stability, and the sensorial appraisal. All of these of olive oil qualities were negatively associated with the amount of applied irrigation water. Pigment content of oils determined by carotenoid and chlorophylls also was negatively associated with the amount of water supplied. No consistent relation was found for α-tocopherol and fatty acid content of olive oil in relation to these treatments.     

Fast quality screening of vegetable oils by HPLC-thermal lens spectrometric detection

Isocratic reversed-phase HPLC with thermal lens spectrometric (TLS) detection enabled identification of linseed, olive, sesame, and wheat germ vegetable oils to control the authenticity of the oils based on characteristic carotenoid/carotene profiles. Four characteristic regions of carotenoids (i.e., lutein, xanthophyll, carotene, and lycopene) have been identified in each type of oil. The concentrations of total β-carotene (BC) and α-carotene (AC), together with trans-to cis-isomers of β-carotene (TBC/CBC) and BC/AC ratios were shown to be reliable and useful indices for fast screening of oils for nutritional quality. The oil TBC/CBC ratio and the BC concentration (in μg/mL) should meet the following numerical criteria: linseed (≽2∶1, ≽1.7), olive (≽3∶1, ≽0.4), sesame (≽1∶1, ≽0.1), and wheat germ oil (≽1∶1, ≽1.7). Based on the above criteria, unsatisfactory olive oils differed significantly from the consumable ones. Likewise, the concentration of AC in consumable wheat germ and sesame oil should not be lower than 0.6 and 0.02 μg/mL, respectively. The AC level in safflower oil should not be higher than 0.04 μg/mL. The BC/AC ratios exceeding 3∶1, 6∶1, and 8∶1 should be used as an additional quality requirement for consumable wheat germ, sesame, and safflower oil, respectively.     

A laboratory study of the bleaching process in stigmasta-3,5-diene concentration in olive oils

The bleaching effect was simulated in pilot plant by measuring the influence of temperature (40, 50, 60, 70, 80, and 90°C), time (5, 10, 15, 20, 25, and 30 min), and concentration of solid adsorbent [1.5 and 8% (w/w) of Tonsil supreme NFF] on stigmasta-3,5-diene (STIG) obtained by dehydration of steroidal compounds. Conditions were chosen to simulate those used in industrial operations. The presence of refined oils in extra virgin olive oil can be detected by these newly formed steroid hydrocarbons. Experimental results indicated that STIG did not exceed an imposed limit of 0.15 mg/kg in extra virgin olive oil, when oils were bleached with 1.5% earth at temperatures ≤80°C for 30 min in admixed to oils sold as virgin. A large proportion of the adulterations were not detectable by the official methods. Color determinations (CIE-1931) chromatic coordinates) were replicated on a refined oil and in admixed extra virgin olive oil. Color of olive oil was not significantly affected by mixing with refined oil (≤20%).     

Use of high-resolution 13C nuclear magnetic resonance spectroscopy for the screening of virgin olive oils

¹³C Nuclear magnetic resonance (NMR) spectra of 104 oil samples were obtained and analyzed in order to study the use of this technique for routine screening of virgin olive oils. The oils studied included the following: virgin olive oils from different cultivars and regions of Europe and north Africa, and refined olive, “lampante” olive, refined olive pomace, high-oleic sunflower, hazelnut, sunflower, corn, soybean, rapeseed, grapeseed, and peanut oils, as well as mixtures of virgin olive oils from different geographical origins and mixtures of 5–50% hazelnut oil in virgin olive oil. The analysis of the spectra allowed us to distinguish among virgin olive oils, oils with a high content of oleic acid, and oils with a high content of linoleic acid, by using stepwise discriminant analysis. This parametric method gave 97.1% correct validated classifications for the oils. In addition, it classified correctly all the hazelnut oil samples and the mixtures of hazelnut oil in virgin olive oil assayed. All of these results suggested that ¹³C NMR may be used satisfactorily for discriminating some specific groups of oils, but to obtain 100% correct classifications for the different oils and mixtures, more information than that obtained from the direct spectra of the oils is needed.     

Detection of pressed hazelnut oil in admixtures with virgin olive oil by analysis of polar components

Analysis of the polar fraction from virgin olive oil and pressed hazelnut oil by high-performance liquid chromatography showed marked differences in the chromatograms of the polar components in the two oils. Six commercial samples of pressed hazelnut oil and 12 samples of virgin olive oil (or blended olive oil including virgin olive oil) were analyzed. The phenolic content of the pressed hazelnut oil samples was 161±6 mg·kg⁻¹. Inspection of the chromatograms showed that the pressed hazelnut oil extracts contained a component that eluted in a region of the chromatogram that was clear in the olive oil samples, and consequently this component could be used to detect adulteration of virgin olive oil by pressed hazelnut oil. The component had a relative retention time of 0.9 relative to 4-hydroxybenzoic acid added to the oil as an internal standard. The ultraviolet spectrum of the component showed a maximum at 293.8 nm, but the component could not be identified. Analysis of blends of oils showed that adulteration of virgin olive oil by commercial pressed hazelnut oil could be detected at a level of about 2.5%.     

Pigment Profile,Color and Antioxidant Capacity of <Emphasis Type="Italic">Arbequina</Emphasis> Virgin Olive Oils from Different Irrigation Treatments

Olive fruits and virgin olive oils from a super‐high‐density olive orchard cv. Arbequina under different irrigation treatments (Control, RDI1, RDI2) were characterized by their pigment profile, CIElab colorimetric coordinates, oxidative stability and antioxidant capacity during the olive seasons 2011 and 2012. The control treatment were irrigated according to the total evapotranspiration of the olive grove (100% ETc), while RDI1 and RDI2 consisted of moderate and severe deficit irrigation, respectively. Olive fruits from severe water deficit irrigation treatment (RDI2) showed a significantly greater concentration of pigments compared to the others. In addition, the ratios a*/chlorophylls and chlorophylls/carotenoids indicated a delayed maturation in these olives. Irrigation treatments significantly affected the yellow component (b*) of the virgin olive oils contained. A reduction of 75% in the water applied (RDI2) produced a strong increase in lutein‐zeaxanthin content (38%) and chlorophyll a (50%), oxidative stability, that ranged from 8.37 h (Control) to 13.23 h (RDI2) and antioxidant activity compared to Control. However, the oil production from RDI2 decreased approximately a 49%.     

The Chemical Properties and Volatile Compounds of Virgin Olive Oil from Oueslati Variety: Influence of Maturity Stages in Olives

The aim of the present work was to investigate the influence of fruit ripening on oil quality and volatile compounds in an attempt to establish an optimum harvesting time for Oueslati olives, the minor olive variety cultivated in Tunisia. Our results showed that many analytical parameters, i.e., peroxide value, UV absorbance at 232–270 nm, chlorophyll pigments, carotenoids and oleic acid contents decreased during ripening, whilst linolenic acid increased. Free acidity remained practically stable with a very slight rise at the highest maturity index. The volatile compounds emitted by the Oueslati olive oil were characterized and quantified by HS‐SPME‐GC‐EIMS. Twenty‐three volatile compounds were identified, mainly aldehydes, sesquiterpenes and esters. The results show variations in the volatile fractions and quality parameters of Oueslati extra virgin olive oil obtained at different olive‐ripening stages. Fifteen sesquiterpenes were identified for the first time in this cultivar, mainly hydrocarbon derivatives, but also oxygenated ones. On the basis of the quality parameters and volatile fractions studied, the best stage of Oueslati olive fruits for oil processing seems to be at ripeness index about 3.0. Indeed, these results suggested the possibility of using sesquiterpenes for olive authenticity and traceability and demonstrated that the volatile fractions can be used as indicators of the degree of ripening of the olives used to obtain the corresponding virgin olive oils.     

Chemical Composition of Turkish Olive Oil––Ayvalik

Although large amounts of olive oil are produced in Turkey, not much information on its chemical composition is available in the literature to date. The aim of this study was to evaluate the chemical composition of commercial olive oils produced from the Ayvalik olive cultivar in Canakkale, Turkey. Five different samples corresponding to the olive oil categories of extra virgin (conventional, extra virgin olive oil (EVOO), and organic extra virgin olive oil (OGOO) production), virgin olive oil (OO-1), ordinary virgin olive oil (OO-2) and refined olive oil (RFOO) were evaluated. Olive oils were collected from two consecutive production years. According to the free fatty acids, the absorbance values (K₂₃₂ and K₂₇₀), and peroxide values of all the samples conformed to the European standards for olive oil. The level of oleic acid was in the range of 68–73%; while the linoleic acid content was significantly lower in the refined olive oils. The tocopherol and polyphenol content was in the lower range of some European olive oils. However, pinoresinol was a major phenolic compound (5–77 mg/kg depending on the oil category). Its content was markedly higher than in many other oils, which would be a useful finding for olive oil authentication purposes.     

Determination of sterols by capillary column gas chromatography. Differentiation among different types of olive oil: Virgin,refined, and solvent-extracted

Compositional analysis of the sterol fraction of olive oil can be used to assess the degree of purity of the oil and the absence of admixture with other plant oils. This determination also permits characterization of the type of olive oil in question: virgin, refined, or solvent-extracted. In the present work, 130 samples of olive oil were analyzed, the sterol fractions were separated from the unsaponifiable fraction by silica gel plate chromatography, and later they were analyzed as the trimethylsilyl ether derivatives by capillary column gas chromatography. From the results obtained, it was concluded that this methodology is able to differentiate among virgin, refined, and solvent-extracted olive oils. Stigmasterol, clerosterol, Δ5-avenasterol, Δ7-stigmasterol, and Δ7-avenasterol permit the differentiation of the three types of oil from one another. Campesterol, Δ5, 23-stigmastadienol, β-sitosterol, and Δ5,24-stigmastadienol permit the differentiation of only two oils from each other but confirm the conclusions obtained for other sterols. Correlations between the different sterols of virgin, refined, and solven-extracted olive oil also have been obtained.