Effect of the region of origin on the perceived quality of olive oil: An experimental approach using a control group

This study attempts to measure the overall effect of the image of an olive oil producing region and the effect of the components of this image on consumers’ perceived quality of an olive oil. Two successive experiments were performed in two different cultural contexts (France and Tunisia). To test the overall effect of the image, a quasi-experimental, pre-test/post-test type research design was developed, using a control group while the discrete choice method was used to study the effect of the components. The results confirm that the image of the product’s region of origin influences perceived overall quality regardless of the respondents’ nationality. The results partially confirm that each dimension of the image of the region of origin has a specific influence on consumers’ selection behaviors. The authors discuss the limitations of the results and the measurements commonly used to assess perceived quality.     

Microwave heating of different commercial categories of olive oil: Part II. Effect on thermal properties

The effect of microwave heating of commercial categories of olive oil for human consumption (extra virgin olive oil [EVOo], olive–pomace oil [Po] and olive oil [Oo]) on DSC thermal properties was evaluated at different times of microwave treatment.     

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.     

The detection of the presence of hazelnut oil in olive oil by free and esterified sterols

Genuine olive and hazelnut oils from diverse geographical origins, as single varieties and blends, were mixed at different percentages and analysed by the method based on the quantification of free and esterified sterols. Two formulas based on three sterols (Campesterol, Δ⁷-stigmastenol and Δ⁷-avenasterol) together with empirical decision rules were able to detect the presence of hazelnut oil in olive oil when the percentage of the former was more than 6–8%, although this figure was much lower in the most of the adulterations. Results of univariate and multivariate statistical procedures based on the analysis of 116 samples are presented in support of the method efficiency.     

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.     

Stability of avocado oil during heating: Comparative study to olive oil

The stability of the saponifiable and unsaponifiable fractions of avocado oil, under a drastic heating treatment, was studied and compared to that of olive oil. Avocado and olive oil were characterised and compared at time 0 h and after different times of heating process (180 °C). PUFA/SFA (0.61 at t = 0) and ω-6/ω-3 (14.05 at t = 0) were higher in avocado oil than in olive oil during the whole experiment. Avocado oil was richer than olive oil in total phytosterols at time 0 h (339.64; 228.27 mg/100 g) and at 9 h (270.44; 210.30 mg/100 g) of heating. TBARs was higher in olive oil after 3 h, reaching the maximum values in both oils at 6 h of heating treatment. Vitamin E was higher in olive oil (35.52 vs. 24.5 mg/100 g) and it disappeared earlier in avocado oil (at 4 vs. 5 h). The stability of avocado oil was similar to that of olive oil.     

Evaluation of potential and real quality of virgin olive oil from the designation of origin “Aceite Campo de Montiel” (Ciudad Real,Spain)

The potential and real qualities of virgin olive oils from the DO “Aceite Campo de Montiel” were evaluated. The regulated physicochemical and sensory parameters, the stability parameters and the fatty acid, sterol and triterpenic dialcohol compositions were analysed. The results of the regulated parameters in the potential quality study classified all the analysed oils into the “extra virgin” category. The varieties Picual and Cornicabra showed remarkably high stability, due to their high tocopherol and total polyphenol contents. Oleic and linoleic acids were the most useful fatty acids used to discriminate the predominant varieties, Picual and Cornicabra, from the others. The variety Cornicabra stood out due to its high campesterol content, Arbequina due to its low β-sitosterol content and high 24-methylenecholesterol, Δ5-avenasterol, Δ7-stigmastenol and total sterol contents, and Picual for its high sitostanol content. All the analysed samples in the real quality study were classified in the “extra virgin” category according to the regulated physicochemical parameters, but only 69% of them qualified if the sensory parameters were also taken into account. The predominance of the varieties Picual and Cornicabra in the study area was mainly responsible for the high oil stability and reflects the fatty acid and sterol compositions of the oils from the oil mills in the potential quality study.     

Blends of olive oil and sunflower oil: Characterisation and olive oil quantification using fatty acid composition and chemometric tools

A method capable of recognising the percentage of olive oil in a blend is required to verify whether its labelling complies with the statements set out by the Commission Regulation (EC) No. 1019/2002. In this study an analytical methodology was developed in order to define blends of olive oil and sunflower oil, which contain 50% of olive oil, compared to blends with 40% and 60% of it, respectively. Methyl esters of fatty acids were analysed by GC–FID and processed through chemometric tools (PCA, TFA, SIMCA and PLS). A strong differentiation of blends according to the amount of olive oil contained and a quantification model with a standard error of prediction of 1.51% were obtained. As this issue represents a significant analytical challenge, variability associated with the fatty acid composition of olive oil was first studied.     

Pesticide residue assessment in different types of olive oil and preliminary exposure assessment of Greek consumers to the pesticide residues detected

In this study the occurrence and levels of multi-class pesticides in different types of virgin olive oil quality and origination were determined and the contribution of olive oil in the chronic risk of pesticide residues consumption in the Mediterranean diet was estimated. For this purpose, a multiresidue method for the determination of 35 pesticides in olive oil was evaluated and applied to a total number of 100 olive oil samples. Ten percent of the samples produced from fruits of conventional cultivations contained no detectable residues whereas in the rest samples were detected residues of 20 insecticides. The highest detection rates were observed for the residues of fenthion, dimethoate and endosulfan. The highest occurrence and levels of pesticides were observed in extra virgin olive oil whereas results pointed that residues in olive oil from variety of olives with high oil yield may be higher. Furthermore, olive oil from organic cultivations could be contaminated with pesticide residues and/or contain low levels of pesticide residues that are not registered for use in olive cultivations. For there were multiresidues of pesticides present in olive oil, there is no zero risk in consumption of olive oil. However, the exposure of olive oil consumers to each detected residue is far below the acceptable daily intake (ADI).     

Oxidative stability of olive oil during the thermal process: Effect of Pistacia khinjuk fruit oil

The oxidative stability of refined olive oil with incorporated Pistacia khinjuk fruit oil (PKFO; 0.5%, 1%, 2%, 5%, and 10%) during thermal processing at 170ºC for 8 h was evaluated. The conjugated diene values, carbonyl values, acid values, oil/oxidative stability indices, and total tocopherol content were measured during thermal processing. Olive oil containing 0.5% PKFO was identified as the most oxidative stable oil followed by oils containing 100 ppm TBHQ and 1, 5, 10, and 2% PKFO. No significant difference between samples of olive oil containing 100 ppm TBHQ and 1% PKFO was observed. Thus, it was concluded that PKFO at levels lower than 1% could provide stronger antioxidation activity in comparison with TBHQ (the strongest syntactic antioxidant used in the food industry). Moreover, reduction in tocopherol compounds during thermal processing was higher in olive oil containing TBHQ as compared to those in pure olive oil.     

Ultrasound assisted maceration: An original procedure for direct aromatisation of olive oil with basil

Aromatisation of olive oil is a new trend in the Mediterranean area, both for sensory and for nutritional improvement. This work presents the development of a green enrichment of an olive oil with basil. In fact instead of a solvent extraction of the aromas, purify them and add them to the olive oil or instead of doing steam distillation prior to add the essential oil into the olive oil, basil leaves were directly put into the olive oil. Ultrasounds were then applied to the mixture in order to accelerate diffusion of the basil volatile compounds into the olive oil. The processing time is reduced from hours or days to few minutes when comparing traditional maceration and ultrasound assisted aromatisation. GC/MS chromatographs have similar profiles between macerated and ultrasounds assisted macerated oils. Concentration of linalool and eugenol were calculated into the aromatised oils and used as indicators of the aromatisation.     

The potential of different techniques for volatile compounds analysis coupled with PCA for the detection of the adulteration of olive oil with hazelnut oil

This paper investigates the effectiveness of three rapid methods of volatile compounds analysis with subsequent principal component analysis (PCA) treatment of data for differentiation between virgin olive oil samples adulterated with hazelnut oil. Tested methods included comparison of chromatograms of volatiles obtained using SPME-fast GC-FID, volatiles analysis by electronic nose based on MOS sensors (HS-Enose), and by direct coupling of SPME to MS (SPME-MS). Volatile compounds were analyzed also by SPME-GC/MS technique. Data obtained as a result of SPME-GC/MS was subjected to PCA. SPME-GC–MS analysis with subsequent PCA yielded good results, however being time consuming. The three methods of analysis of volatiles, with subsequent PCA treatment of data, allowed detection of olive oil adulteration with different contents of hazelnut oil ranging from 5 to 50% (v/v).     

The effect of citric acid on the phenolic contents of olive oil

Response surface methodology was used to optimise the combined effects of malaxation time (t) and aqueous citric acid solution (C_A) added at the beginning of the malaxation step on total polyphenols (TP) and o-diphenols (OD) content and the antiradical power (ARP) of the olive oil extracted from the Italian olive fruits of Coratina cultivar. Different tests were performed according to a 3² full factorial design, varying t from 30 to 90 min and the C_A from 5 to 15 ml/kg_paste. Overall optimal conditions identified by a numerical optimisation for the three responses were found to be at t = 30 min and C_A = 13.79 ml/kg_paste under which the model predicted TP = 604.52 μgCAE/g_oil, OD = 80.44 μgCAE/g_oil and ARP = 28.73 μgDPPH/μlextract. There were also linear correlations between TP (R² = 0.8176) and OD (R² = 0.8633) values of olive oil and waste water. The results of this study demonstrate that considerably short malaxation time and relatively small amounts of citric acid were required to enhance the quality of olive oil. The outcome of our study will therefore be of great value for the commercial production of olive oil with high level of polyphenols and o-diphenols.     

Horizontal centrifuge with screw conveyor (decanter): Optimization of oil/water levels and differential speed during olive oil extraction

Olive oil extraction using a horizontal centrifuge with a screw conveyor is an essential operation to reduce production costs. However, proper control of the plant is required to maintain a high level of extraction yield and olive oil quality. Rheological characteristics of the olive paste, which change in relation to water content, fruit variety, maturity level and seasonal temperature variations, greatly affect the efficiency of centrifugal extraction. If olive paste is fed to a decanter without automatic control, then non-optimal extraction is performed.     

Potential of olive oil phenols as chemopreventive and therapeutic agents against cancer: A review of in vitro studies

Olive oil is a common component of Mediterranean dietary habits. Epidemiological studies have shown how the incidence of various diseases, including certain cancers, is relatively low in the Mediterranean basin compared to that of other European or North America countries. Current knowledge indicates that the phenolic fraction of olive oil has antitumor effects. In addition to the ability to be chemopreventive, with its high antioxidant activity, the antitumor effects of olive oil phenols (OO‐phenols) has been studied because of their capacity to inhibit proliferation and promote apoptosis in several tumor cell lines, by diverse mechanisms. This review will summarize and discuss the most recent relevant results on the antitumor effect of OO‐phenols on leukemia tumor cells, colorectal carcinoma cells, and breast cancer (BC) cells. In particular, very recent data will be reported and discussed showing the molecular signaling pathways activated by OO‐phenols in different histopathological BC cell types, suggesting the potential use of OO‐phenols as adjuvant treatment against several subsets of BC. Data summarized here represent a good starting point for more extensive studies for better insight into the molecular mechanisms induced by OO‐phenols and to increase the availability of chemopreventive or therapeutic drugs to fight cancer.     

The production of hydrogen peroxide is not a common mechanism by which olive oil phenols induce apoptosis on HL60 cells

We have recently demonstrated that hydroxytyrosol (3,4-DHPEA), the most representative olive oil phenol, induces apoptosis on HL60 cells through the production of considerable amount of extracellular hydrogen peroxide (H₂O₂). The aims of the present investigation were first to assess the ability of different phenolic compounds to both produce extracellular H₂O₂ and induce apoptosis on HL60 cells, and second to elucidate whether the pro-apoptotic activity was mediated by the production of H₂O₂ in the cell culture medium. Based on the results phenols can be classified as follows: (1) those which were not able to induce both apoptosis and H₂O₂ accumulation (tyrosol, homovanillic alcohol and protocatechuic, o-coumaric, vanillic, homovanillic, ferulic and syringic acids); (2) those which showed a pro-apoptotic activity mediated, at least in part, by the production of H₂O₂, as evidenced by the ability of catalase to inhibit apoptosis (3,4-DHPEA, dopamine, 3,4-dihydroxyphenylacetic, 3,4-dihydroxy-hydrocinnamic, caffeic and gallic acids); and (3) those which induced apoptosis without the involvement of H₂O₂ (the secoiridoid derivatives of both hydroxytyrosol and tyrosol). Oleuropein showed a peculiar behaviour since, and although it caused an abundant production of H₂O₂ in the cell culture medium, it exerted a weak pro-apoptotic effect. From these results we may conclude that the cathecol moiety of the phenol molecule is necessary for the H₂O₂ producing activity, and that the 3,4-DHPEA metabolism to homovanillic alcohol and homovanillic acid may significantly reduce its pro-apoptotic potential. The real in vivo meaning of the phenol-induced H₂O₂ production remains to be investigated.     

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%.     

Evaluation of potential and real qualities of virgin olive oil from the designation of origin (DO) “Aceite Montes de Alcaraz” (Albacete,Spain)

The potential and real qualities of virgin olive oils, from the designation of origin (DO) “Aceite Montes de Alcaraz”, were evaluated. The regulated physicochemical and sensory parameters, the stability parameters and the fatty acid, sterol and triterpenic dialcohol compositions were analysed. The results of the regulated parameters in the potential quality study classified all the analysed oils into the “extra virgin” category. The varieties Picual and Cornicabra showed remarkably high stability, due to their high total polyphenol content. The fatty acid contents fell within the intervals required by the EU regulations in all the analysed samples. The distribution of fatty acid composition covered the normal range expected for olive oil. Oleic and linoleic acids were the most useful fatty acids used to discriminate the varieties Picual and Cornicabra from the others. The variety Cornicabra stood out due to its high campesterol content. All the analysed samples in the real quality study were classified into the “extra virgin” category according to the regulated physicochemical parameters, but only 67% of them qualified if the sensory parameters were also taken into account. The predominance of the variety Picual in the study area was mainly responsible for the high oil stability and reflects the fatty acid and sterol composition of the oils from the oil mills in the potential quality study.     

The potential of coupling information using three analytical techniques for identifying the geographical origin of Liguria extra virgin olive oil

The combined use of data obtained from different analytical instruments is a complex problem.