Determination of copper with 5,5-dimethylcyclohexane-1,2,3-trione 1,2-dioxime 3-thiosemicarbazone in olive oils by adsorptive stripping square wave voltammetry

In the present paper a method for the determination of Cu in olive oil samples by adsorptive stripping square wave voltammetry (Ad-SSWV) is presented. It has been proven that Cu reacts with 5,5-dimethylcyclohexane-1,2,3-trione 1,2-dioxime 3-thiosemicarbazone, DCDT, in strongly acid media giving rise to a complex. In Ad-SSWV the complex Cu–DCDT experiments an adsorptive reductive process which promotes the appearance of a peak at −0.570 V. The extraction process of Cu from olive oil is carried out with hot concentrated HCl. Calibration graph has been constructed from 0 to 35 ng mL⁻¹ and the detection limit was 0.49 ng mL⁻¹. The method has been applied to commercial olive oils samples and the amounts of Cu found are very similar to those obtained when samples are analysed by AAS.     

High-power gradient diffusion NMR spectroscopy for the rapid assessment of extra-virgin olive oil adulteration

A high gradient diffusion NMR spectroscopy was applied to measure diffusion coefficients (D) of a number of extra-virgin olive, seed, and nut oils in order to ascertain the suitability of this rapid and direct method for discrimination of adulterated olive oils. Minimum adulteration levels that could be detected by changes in D were 10% for sunflower (SuO) and soybean oil (SoO), and 30% for hazelnut (HO) and peanut oil (PO). Qualitative and quantitative prediction of adulteration was achieved by discriminant analysis (DA). The highest prediction accuracy (98–100%) was observed only when two DA models were concomitantly used for sample classification. The first DA model provided recognition of high adulterated EVOO with more than 20% of SuO or SoO, and 30% with PO, whilst the second model could differentiate EVOO adulterated with 10% of SuO or SoO, and more than 30% of HO. The validation test performed with an independent set of randomly adulterated EVOO samples gave 100% classification success. The high accuracy levels together with minimal requirements of sample preparation, and short analyses time, prove the high-power gradient diffusion NMR spectroscopy as an ideal method for rapid screening of adulteration in valuable olive oils.     

Gas chromatography screening of bioactive phytosterols from mono-cultivar olive oils

Phytosterols (PS) from nine samples of olive oil from Olea europaea L., the Carolea, Cassanese and Coratina mono-cultivars, have been analyzed by gas chromatography. Coratina virgin olive oil (VOO) from the month of November showed highest contents of β-sitosterol (5491 mg kg⁻¹) and Δ⁵ avenasterol (1767 mg kg⁻¹). Olive pomace oil had the lowest total content of all PS, when compared to VOO. These results suggests that, PS can be an important regulatory factor for the functional quality of olive oil along the agro-industry chain from the orchard to nutraceutical.     

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.     

Traceability of olive oil based on volatiles pattern and multivariate analysis

An automated head-space solid-phase microextraction (HS-SPME)-based sampling procedure, coupled to gas chromatography–ion trap mass spectrometry (GC–ITMS), was developed and employed for fast characterisation of olive oil volatiles. In total, 914 samples were collected, over three production seasons, in north-western Italy—Liguria (n = 210) and other regions—in addition to the rest of Italy, Spain, France, Greece, Cyprus, and Turkey (n = 704) with the aim to distinguish, based on analytical (profiling) data, the olive oils labelled as “Ligurian” (protected denomination of origin region, PDO) from all the others (“non-Ligurian”). For the chemometric analysis, linear discriminant analysis (LDA) and artificial neural networks with multilayer perceptrons (ANN-MLP) were tested. Employing LDA, somewhat lower recognition (81.4%) and prediction (61.7%) abilities were obtained. The classification model was significantly improved using ANN-MLP. Under these conditions, the recognition (90.1%) and prediction (81.1%) abilities were achieved. The diagnostic value of the data obtained by one-dimensional GC–ITMS were compared with those generated by two-dimensional gas chromatography–time-of-flight mass spectrometry (GC × GC–TOFMS), allowing a comprehensive analysis of olive oil volatiles.     

酶处理对初榨橄榄油品质及抗氧化活性的影响

将纤维素酶、果胶酶应用于橄榄油提取工艺,旨在生产具有较高总酚含量及较强抗氧化活性的高质量初榨橄榄油。随着果胶酶和纤维素酶添加量的提高,橄榄油的过氧化值及K_(232)均出现下降的趋势,油酸比例有一定程度提高,并在添加0.2%纤维素酶时油酸比例达到最高(65.85%)。结合主成分分析,确定了在油橄榄融合过程中添加0.5%纤维素酶得到的初榨橄榄油总酚含量和抗氧化活性最高。这是由于果胶酶和纤维素酶能有效降解橄榄细胞壁,减少亲水酚类物质与细胞壁多糖的络合,有助于橄榄果皮中的游离酚的释放,从而提高橄榄油中总酚含量及抗氧化活性。     

Use of lambda DNA as a marker to assess DNA stability in olive oil during storage

Filtered olive oil samples spiked with three different concentrations of λDNA were stored at 25 °C under a 12 h photoperiod for up to a year. These samples were used for DNA extraction and PCR amplification of λDNA amplicons of 107, 415 and 691 bp length. The amplification signal was gradually decreased with longer storage periods, while the strength of the signal was related to the initial concentration of spiking λDNA particularly during longer storage periods. The 107 bp amplicon was the only one successfully amplified from all the samples, regardless of both concentration of spiking λDNA and storage period. The amplification of 415 and 691 bp amplicons was not successful for samples stored longer than a threshold period of 20 and 10 days, respectively. These results suggest that detection of polymorphic markers requiring DNA templates shorter than 100 bp might have a wider range of applications in DNA fingerprinting of olive oil. In addition, the DNA extracts were tested for the presence of inhibitors in PCR amplification reactions of yeast DNA amplicons. The inhibitory effect of olive DNA extracts was partial and gradually increased with the storage period of the olive oil samples used for the DNA extraction.     

Using Lipid Profiles for the Characterization of Turkish Monocultivar Olive Oils Produced by Different Systems

The aim of this study was to characterize the biochemical profiles of the virgin olive oils produced in various districts of Aegean and South East Anatolia regions of Turkey over two growing seasons (2001–2002). The olive oils were extracted by classic hydraulic pressing, three phase continuous system, Abencor oil method at laboratory scale, and foot oil process from monocultivar Turkish olives, including Ayvalik, Memecik, Nizip Yaglik, Gemlik, Domat, and Uslu. Total phenolics, ortho-diphenols, oxidative stability, and total chlorophylls of the oils differed by location. The cis-trans fatty acids, triacylglycerols, and the actual versus theoretical equivalent carbon number of 42 (ECN 42) triglycerol content (ΔECN42) were within national and international averages. Oil samples from the three phase continuous system had higher total phenolic contents than those of the hydraulic pressure system. Turkish monocultivar virgin olive oil samples were classified by biochemical profiles using the principal component and hierarchical cluster analyses multivariate statistical methods. Clustering analysis defined groups according to growing location. Triacylglycerols and fatty acid profiles can be used for identification of monocultivar olive oils with regard to authenticity and classification.     

Identification of 3-MCPD esters to verify the adulteration of extra virgin olive oil

ABSTRACT

The adulteration of olive oil is an important issue around the world. This paper reports an indirect method by which to identify 3-monochloropropane-1,2-diol (3-MCPD) esters in olive oils. Following sample preparation, the samples were spiked with 1,2-bis-palmitoyl-3-chloropropanediol standard for analysis using gas chromatograph-tandem mass spectrometry. The total recovery ranged from 102.8% to 105.5%, the coefficient of variation ranged from 1.1% to 10.1%, and the limit of quantification was 0.125 mg/kg. The content of 3-MCPD esters in samples of refined olive oil (0.97–20.53 mg/kg) exceeded those of extra virgin olive oil (non-detected to 0.24 mg/kg). These results indicate that the oil refining process increased the content of 3-MCPD esters, which means that they could be used as a target compound for the differentiation of extra virgin olive oil from refined olive oil in order to prevent adulteration.     

Direct analysis of glucuronidated metabolites of main olive oil phenols in human urine after dietary consumption of virgin olive oil

In the present study we report on a UPLC-MRM validated method for the simultaneous direct analysis of main glucuronidated metabolites of olive oil phenols: tyrosol, hydroxytyrosol and its O-methyl metabolite homovanillyl alcohol in human urine after dietary olive oil ingestion. The developed method was linear within the concentration range 20–2000 ng/mL with adequate recovery of analytes (>86%). Intra- and inter-day precision and accuracy were according to standard requirements for method validation criteria. Using the developed method, urinary concentrations and excretion rates of glucuronides of olive oil phenols were successfully estimated in an intervention study with 11 healthy volunteers supplemented with a dietary dose of virgin olive oil (VOO) (50 mL). Therefore, about 13% of the consumed olive oil polyphenols were recovered in 24-h urine, where 75% of them were in the form of glucuronides (3′- and 4′-O-hydroxytyrosol glucuronides, 4′-O-glucuronides of tyrosol and homovanillyl alcohol) and 25% as free compounds.     

Influence of olive cultivars and period of harvest on the contents of Cu,Cd, Pb,and Zn in virgin olive oils

Levels of four of the major pollutant heavy metals were assessed by ICP-OES in virgin olive oil monocultivar samples. The data showed high variability within cultivars for lead and zinc, whereas, for cadmium and copper, no statistical difference was observed. The influence of the cultivar and the stage of ripening of olives on heavy metal content was assessed; zinc was the only metal with a great variability within the first and the second harvest. All olive samples were processed with the same milling apparatus.     

High throughput flow injection bioluminometric method for olive oil antioxidant capacity

This paper describes a rapid flow injection automated method for the determination of olive oil total antioxidant capacity. The chemistry involved is the horseradish peroxidase (HRP) catalysed oxidation of luminol by hydrogen peroxide. Oxidation results in light emission (bioluminescence) that is enhanced using p-iodophenol sensitizer. Olive oil (0.7 mL) is extracted with two 0.7 mL aliquots of 80–20% (v/v) methanol–water solvent. A 17 μL aliquot of the extract containing hydrophilic antioxidants is injected in a phosphate buffer channel that subsequently merges with a luminol–HRP–p-iodophenol reagent stream. Bioluminescence resulting after merging the mixture with a hydrogen peroxide stream is suppressed upon increasing antioxidants’ concentration resulting in negative peaks due to hydrogen peroxide consumption by antioxidants. The method has been optimized on (a) number of manifold channels, (b) flow rates, (c) coil length and (d) HRP, hydrogen peroxide and p-iodophenol concentrations. Detection limit is calculated at 1.5 × 10⁻⁷ M gallic acid, linear range is between 1.0 × 10⁻⁶ and 1 × 10⁻⁴ M and precision is better than 2.8% RSD (n = 4). The fully automated method is achieving a rate of sampling equal 180 probes per hour. The proposed method is applied for the assessment of 50 extra-virgin olive oil samples of different Greek cultivars and regions.     

Determination of herbicide residues in olive oil by gas chromatography–tandem mass spectrometry

This paper reports a method for the analysis in olive oil of multiresidues of the herbicides of low-medium polarity most widely used by Andalusian olive growers. The method, which uses gas chromatography/tandem mass spectrometry (GC–MS/MS), was developed within the framework of Project CAO00-005, which spanned the period from 2000 to 2004. The results obtained for more than 3000 samples of virgin olive oil and organic olive oil analyzed over such a period are reported. Samples were extracted with an acetonitrile/n-hexane mixture and cleaned up by passage through Florisil columns prior to analysis. A linear determination range for the herbicides from 1 to 500 μg kg⁻¹ and a correlation coefficient better than 0.996 were achieved. The reproducibility, as relative standard deviation, was quite acceptable (8–11%), and so were herbicide recoveries (90–102%). The proposed method has been transferred to both public and private laboratories in the Andalusian region.     

Estimation of olive oil acidity using FT-IR and partial least squares regression

Olive oil characteristics are directly related to olive quality. Information about olive quality is of paramount importance to olive and olive oil producers, in order to establish its price. Real-time characterization of the olives avoids mixtures of high quality with low quality fruits, and allows improvement of olive oil quality. This work describes an indirect determination of olive acidity and that allows a rapid evaluation of olive oil quality. The applied method combines chemical analysis (30 min Soxhlet olive pomace extraction) in tandem with a spectroscopic technique (FT-IR) and multivariate regression (PLS1). The most suitable calibration model found used SNV pre-processing and was built with 4 Latent Variables giving a RMSECV of 8.7% and a Q² of 0.97. This accurate calibration model allows the estimation of olive acidity using a FT-IR spectrum of the corresponding Soxhlet oil dry extract and therefore is a suitable method for indirect determination of FFA in olives.     

Classification of olive oils according to geographical origin by using H NMR fingerprinting combined with multivariate analysis

Authentic extravirgin olive oils from 7 different regions (Italy – 3 regions, Greece – 4 regions) have been investigated by ¹H Nuclear Magnetic Resonance (NMR) fingerprinting in combination with multivariate statistical analysis. In order to cover the dominating lipid signals as well as signals from compounds of low abundance in the oil, both a simple one pulse experiment and an experiment with multiple saturation of the lipid signals was applied to each sample. Thus, the dynamic range of concentrations covered by the two experiments was of the order of 100,000 allowing for a more comprehensive NMR assessment of the samples. Monte-Carlo embedded cross-validation was used to demonstrate that a combination of principal component analysis, canonical analysis, and classification via nearest class mean can be used to predict the origin of olive oil samples from ¹H NMR data. Given the rather limited number of samples tested, correct prediction probabilities of 78% were achieved with region specific correct predictions between 53% and 100%.     

Proteins in Olive Fruit and Oil

This paper is a comprehensive review grouping the information on the extraction, characterization, and quantitation of olive and olive oil proteins and providing a practical guide about these proteins. Most characterized olive proteins are located in the fruit, mainly in the seed, where different oleosins and storage proteins have been found. Unlike the seed, the olive pulp contains a lower protein content having been described a polypeptide of 4.6 kDa and a thaumain-like protein. Other important proteins studied in olive fruits have been enzymes which could play important roles in olives characteristics. Part of these proteins is transferred from the fruit to the oil during the manufacturing process of olive oil. In fact, the same polypeptide of 4.6 kDa found in the pulp has been described in the olive oil and, additionally, the presence of other proteins and enzymes have also been described. Protein profiles have recently been proposed as an interesting strategy for the varietal classification of olive fruits and oils. Nevertheless, there is still a lot of knowledge without being explored requiring new studies focused on the determination and characterization of these proteins.     

Derivative FTIR spectroscopy for cluster analysis and classification of morocco olive oils

Fourier transform infrared (FTIR) spectra were employed for differentiation and classification of olive oils from several producing regions of Morocco. A preliminary treatment of the FTIR data was done by a derivative elaboration based on the Savitzky–Golay algorithm to reduce the noise and extract a largest number of analytical information from the spectra. A multivariate statistical procedure based on cluster analysis (CA) coupled to partial least squares-discriminant analysis (PLS-DA), was elaborated, providing an effective classification method. On the basis of a hierarchical agglomerative CA and principal component analysis (PCA), four distinctive clusters were recognised. The PLS-DA procedure was then applied to classify samples from the same regions, picked in different times, or unknown olive oil samples. The model was optimised by applying the Martens’ Uncertainty Test that provided to select the wavelength zones giving the most useful analytical information. The proposed method furnished results reliable in classifying olive oils from different lands with the advantages of being rapid, inexpensive and requiring no prior separation procedure.     

Optimised off-line SPE–GC–FID method for the determination of mineral oil saturated hydrocarbons (MOSH) in vegetable oils

An optimised off-line SPE–GC–FID method based on the use of silver-silica gel was developed for the determination of mineral oil saturated hydrocarbons (MOSH) in vegetable oils, including olive pomace oil. The method is specific in not including the aromatic hydrocarbons. The performance of different silica gels (untreated, activated and treated with silver nitrate) was compared in terms of capacity to retain fat and retention of interfering olefins present in particularly large amounts in refined olive oils. A coefficient of variation of 9% was obtained performing six replicate analyses of an extra virgin olive oil fortified with an amount of MOSH near the estimated LOQ (15 mg/kg). Recoveries were close to 100%. The use of activated aluminium oxide as an additional tool to eliminate interference by endogenous long-chain n-alkanes, is discussed.     

Waxy fraction containing long-chain aliphatic aldehydes in virgin olive oils

Long-chain aliphatic aldehydes are natural minor components occurring in the cuticle of numerous plant species and also evidenced in virgin olive oils. The fraction containing these compounds can be isolated from the oil samples by using a solid-phase extraction silica-gel cartridge and then directly analysed by GC on a 5% diphenyl-95% dimethylsiloxane capillary column, using an on column-injection system. The proposed methodology showed that extra virgin olive oils contain long-chain aliphatic aldehydes, with even carbon-atom numbers from C₂₂ to C₃₀. Quantitative results, using the synthesised aldehyde C₂₁ as internal standard, give concentrations of total long-chain aliphatic aldehydes in a variable range below 116 mg kg⁻¹, being hexacosanal (C₂₆-al) the most abundant aldehyde. The different experimental conditions utilised during olive oil extraction processes influence the total aldehydes concentration. Besides contribution to the knowledge of the minor-component composition present in olive oil, their interest and relationship with wax esters, aliphatic alcohols and n-alkanes are discussed.     

Oxidative stability of olive oil and its polyphenolic compounds after boiling vegetable process

The changes in the stability and phenolic content of an extra-virgin olive oil and an olive oil following boiling operation in the presence of vegetables have been studied. After the boiling process, none of the olive oil samples was oxidized, independently of the olive oil quality used. However, in contrast with tocopherols, all polyphenolic components decreased in concentration with the thermal treatment and this decrease was dramatic in the presence of vegetables, probably because of their high content in metals such as iron and copper. The addition of olive oil only 15 min before the end of the boiling process was shown to bring benefits in general for the content of both elenolic acid derivatives, 3,4-DHPEA-EA and 4-HPEA-EA, and hydroxytyrosol acetate in the processed oils. Moreover, less destruction of the vegetables polyphenols was also observed when processing olive oils only 15 min before the end of the boiling process. Interestingly, and besides the use of EVOO instead of OO did not bring benefits to the stability of samples or a higher polyphenolic content in the samples after processing, an higher radical scavenging capacity of phenolic extracts obtained from EVOO samples could be observed.