Content Of Virgin Olive Oil Research Articles

Study of the olive β-glucosidase gene family putatively involved in the synthesis of phenolic compounds of virgin olive oil.

Hydrolysis of the fruit phenolic glucosides occurring during the oil extraction process is the main biochemical reaction affecting the biosynthesis and accumulation of secoiridoid compounds in virgin olive oil. An integrated approach at the molecular, biochemical, and metabolic level was used to study the olive β-glucosidase gene family in seven olive cultivars selected by their different phenolic profiles. Eight β-glucosidase genes have been identified by in silico analysis of an olive transcriptome. Their expression levels were analyzed by reverse transcription quantitative polymerase chain reaction in olive fruits at different ripening stages: I, green fruits, 16-19 weeks after flowering (WAF); II, yellow-green fruits, 22-25 WAF; III, turning fruits, 28-31 WAF; and IV, fully ripe fruits, 35-40 WAF. Gene expression was compared with the level of β-glucosidase activity in the fruit and with the phenolic composition of fruits and oils from different olive cultivars. Phylogenetic analysis of the encoded proteins and differences found among the β-glucosidase genes based on Gene Ontology enrichment analysis data suggests maximum involvement of two genes, OeBGLU1A and OeBGLU1B, in the phenolic composition of virgin olive oil. Positive correlation coefficients were found within each olive cultivar between OeBGLU1A and OeBGLU1B gene expression data and the phenolic content of the oil. The results obtained suggest that the expression pattern of specific β-glucosidase genes may be an accurate predictor for the phenolic content of virgin olive oil that could be used in olive breeding programs. © 2021 Society of Chemical Industry.

Evaluating the reliability of specific and global methods to assess the phenolic content of virgin olive oil: Do they drive to equivalent results?

Despite the huge number of different published methodologies, there is an open debate regarding which one is the most convenient analytical strategy for the determination of phenolic compounds from virgin olive oils. Diverse technical issues together with the disparity of criteria regarding results expression cause a lot of confusion. Herewith, a systematic comparison between specific (a powerful and LC–MS method) and global methodologies (the Folin-Ciocalteau (FC) colorimetric assay, the International Olive Council (IOC) method and hydrolysis plus HPLC-DAD) has been carried out. Thus, these strategies have been applied to the analysis of 50 extra virgin olive oils (covering all the possible quantitative ranges of these substances). This is the first time in which the individual LC–MS quantification of so many phenolic substances is included in this kind of comprehensive comparison. The outcomes of all the strategies have been thoroughly confronted and their equivalence (or divergence) has been carefully evaluated, establishing possible correspondence factors.The LC–MS individual determination with the pure standard of every analyte represented the ideal situation; when only the commercially available standards were used, a drastic change was observed in the absolute concentrations of oleuropein derivatives (in terms of hydroxytyrosol). Total phenolic content (summing individual levels) proved to be higher (1.9–3.0 times when data was expressed in mg/kg) than the values given by the three non-specific methods (with R2 from 0.84 to 0.90). In any case, the IOC method, the FC assay and the hydrolysis approach could be considered as feasible strategies when a global value is pursued. Good correlations between their results were found (R2 > 0.89), with the following equivalence factors: FC(mg caffeic acid/kg) ≈ 0.60 IOC(mg TY/kg); IOC(mg TY/kg) ≈ 1.27 Sum acid hydrolysis(mg TY+HTY/kg); FC(mg HTY/kg) ≈ 1.04 Sum acid hydrolysis(mg TY+HTY/kg).

The oxidative stability of flavoured virgin olive oil: the effect of the water activity of rosemary

Flavoured olive oil gained has importance in terms of its sensorial properties and oxidative stability in recent years. However, the water activity level of the flavouring agent can be important for oxidative stability. Therefore, the aim of this study was to determine the effect of the water activity of rosemary, which was used as a flavouring agent, on the oxidative stability of olive oil. For this purpose, rosemary samples were adjusted to different levels of water activity (0.17, 0.24 and 0.44) and used for the aromatization of virgin olive oils. At the end of the aromatization, the olive oil samples were exposed to an accelerated oxidation test at 60 °C for 28 days. The peroxide, p-anisidine, TOTOX (total oxidation index), free fatty acid, chlorophyll, carotenoid and specific extinction values of the samples were determined. According to the results, the oxidation of olive oils is limited by decreased water activity values in the rosemary samples. Moreover, unflavoured oils were identified as being more sensitive to oxidation when compared to flavoured oils. Additionally, storage time had important effect on all of the analysed parameters. The present research showed that the water activity of rosemary, when used as condiment, affected the oxidative stability and carotenoid content of virgin olive oil. Using rosemary with a low water activity value to flavour olive oil was more effective in terms of oxidative stability. These findings implied that the oxidation of flavoured olive oil could be decreased by decreasing the water content of the condiment used.

Assessment of phenolic compounds in virgin olive oil by response surface methodology with particular focus on flavonoids and lignans

This work deals with the combined effect of agronomical and technological variables on the content of virgin olive oils in phenolic compounds with special attention to flavonoids (luteolin and apigenin) and lignans (pinoresinol and 1-acetoxypinoresinol). Olives from irrigated or rainfed trees at different fruit ripening were studied using Response Surface Methodology. Relevant variables included malaxation temperature (20–60 °C); time (20–60 min); and talc dosage (5–25 g/kg g olives). According to the models, the highest concentrations were 7.83, 289.4, 38.0 and 4.70 mg/kg of hydroxytyrosol, oleocanthal, luteolin and pinoresinol, respectively. Results show that the content of phenolic compounds is mostly affected by the malaxation temperature, increasing when the temperature rises; however, the time exerts an irregular influence, while the dosage of adjuvant has little influence. The flavonoid content, both luteolin and apigenin, decreased with increasing temperature and malaxation time. The pinoresinol content increased with temperature and malaxation time. Non-irrigated olive oils have a higher content in phenolic compounds. The flavonoid contents presented a maximum around maturity index 4. Moreover, the contents usually were higher for olives coming from rainfed. Pinoresinol content decreased with the increase of the index of maturity, the oils from fruits grown in rainfed containing more pinoresinol.

Settling of virgin olive oil from horizontal screw solid bowl in static conditions.

This work was aimed to study the clarification efficiency of natural decantation in settling tank on virgin olive oil obtained from a two-ways continuous process. For this purpose, the impurities content of the virgin olive oil were monitored during settling process in settling tank at two different depths. Efficiency of purging system was determined for two days. The experiments were performed at industrial scale during three crop years. During the first minutes of settling was observed an ascent of the smaller organic particles of the oil. Then, most of the virgin olive oil impurities were settled at 300min, independently of the initial content of virgin olive oil. Finally, oil decantation showed slower rate. Higher clarification values were obtained for those decanter oils with higher impurities content, achieving clarification percentages between of 62.69 and 95.91% at 48h of settling. The highest settling efficiency was observed for those decanter oils with initial higher impurities content. The purging system used in the settling tanks was not able to remove the most of settled impurities since a considerable amount of the impurities remained in the tank after 48h, between 13.6 and 71.41% for the studied oils. In the tank purges was observed important oil losses. Therefore, decantation was not an efficient system for oil clarification since its settling capacity varied depending on the initial impurities content and due to the settled impurities can not be removed fully by purging system.

The Sterol and Erythrodiol + Uvaol Content of Virgin Olive Oils Produced in Five Olive‐Growing Zones of Extremadura (Spain)

AbstractThe content of sterols and erythrodiol + uvaol was studied in 273 virgin olive oil samples from 40 mills in five olive‐growing zones of Extremadura (Spain). An analysis of variance showed significant differences at a confidence level of 95 % between the different zones in each of the main sterols and in the sum of erythrodiol + uvaol. The results of a linear discriminant analysis, considering the different olive‐growing areas as categorical dependent variables and the different sterols as independent variables, explained 78.2 % of the variance with the first two discriminant functions. The resulting model correctly classified 86.9 % of the samples analysed. A validation study was conducted to verify the goodness of the discriminant analysis, resulting in 79.3 % of the new samples used for validation being correctly classified. In the graphical representation of the different groups studied considering the proposed model's first two discriminant functions, the centroids of the Sierra Norte de Cáceres, Vegas del Guadiana and Tierra de Barros olive‐growing zones were clearly separated, but this was not the case for the other two zones—La Serena and La Siberia.

Correlation of fatty acid composition of virgin olive oil with thermal and physical properties

Physical properties (dynamic viscosity and density) of virgin olive oil (VOO) from fourteen olive varieties were studied as a function of their fatty acid (FA) compositions and temperature. Moreover, for these same VOOs, were evaluated the thermal properties by Differential Scanning Calorimetry (DSC): cooling, heating, and oxidation profiles. The composition of VOO analyzed corresponded to the normal range for these varieties. Also, for all VOOs, the temperature effect on oil density decreased linearly as a temperature increased, achieved a good correlation. Arrhenius model describes the effect of temperature on viscosity showing a Newtonian behavior. Correlations between temperature of the major peak of crystallization phase (Pc) and their content in oleic and linoleic FAs were found. In addition, although a not very good correlation was observed between FA composition and viscosity, it was observed that the viscosity tends to increase with the amount of oleic acid.Practical applications: Knowledge of thermal and physical properties of the virgin olive oils (VOOs) is essential to improve some aspects of the extraction process in olive oil mill. Therefore, the information in this work is important for many applications such as equipment design (settling and storage tanks, centrifuges, pumps, etc.).Correlations between the oleic acid (C18:1) content of VOOs and the corresponding to (A) temperature of the major peak of crystallization phase (Pc) and (B) dynamic viscosities (µ). The aim of this work is to study not only thermal properties from thermal profiles (crystallization, melting, and oxidation curves) by DSC measurements, but also physical characterization (density and viscosity) as a function of temperature of VOOs from 14 different olive cultivars, in order to relate thermal and physical properties with chemical composition (FA). As can observed, there is a high correlation between temperature of the peak of crystallization phase, Pc, and FAs composition (C18:1). Moreover, although non good correlations between oil viscosity and fatty acid composition could be found, the viscosity tends to increase as the amount of C18:1 fatty acid.

Modulating oxidoreductase activity modifies the phenolic content of virgin olive oil

The effect of modifying polyphenol oxidase (PPO) and peroxidase (POX) activity during the extraction of virgin olive oil has been assessed in terms of its influence on the phenolic profile of the oil produced. These enzymes were modified by adding exogenous enzyme or specific inhibitors during the milling and subsequent kneading step, studying the effect on specific phenolic compounds in the oils. PPO is the main enzyme involved in phenolic oxidation at the milling step whereas POX activity seems to be the main influence during the kneading step. The data obtained suggest it is possible to increase the nutritional and organoleptic quality of virgin olive oil by inhibiting these enzymes during olive fruit processing. Treatment with the PPO inhibitor tropolone produced a twofold increase in the phenolic fraction, which would therefore seem to be an interesting strategy to improve the nutritional and organoleptic properties of virgin olive oil.

Virgin olive oil ortho-phenols—electroanalytical quantification

An electroanalytical methodology was developed for the determination of the total ortho-phenol content of virgin olive oil (VOO) with high sensitivity and reproducibility. The VOO ortho-phenol content depends on its freshness and is normally expressed as HT equivalent. Screen-printed electrodes were used with cyclic voltammetry to investigate the oxidation of catechol, phenol, hydroxytyrosol (HT), tyrosol, caffeic acid and ferulic acid. The oxidation of ortho-phenols and mono-phenols occurs following different mechanisms, and at different potentials. Using screen-printed electrodes and square wave voltammetry, an HT detection limit of 0.40μM, was obtained. The electroanalytical methodology developed was applied to the determination of ortho-phenol content in fresh and old VOO. The HT equivalent determined for a two-year-old VOO sample was 3mg/kg, for one-year-old samples was 6–7 mg/kg, and for a fresh VOO sample 30mg/kg, recoveries in the range of 78–93% of HT standard being obtained. The effect of VOO matrix components on the HT standard response was investigated.

NOS3 Glu298Asp Polymorphism Interacts with Virgin Olive Oil Phenols to Determine the Postprandial Endothelial Function in Patients with the Metabolic Syndrome

Glu298Asp polymorphism of the endothelial nitric oxide synthase (eNOS) gene (NOS3) has been characterized as a risk factor of hypertension and coronary artery disease. Previous studies suggest that the higher risk observed in T allele carriers is due to endothelial dysfunction associated with a lower eNOS activity and that acute consumption of phenol-rich olive oil ameliorates postprandial endothelial dysfunction by reducing oxidative stress and increasing nitric oxide bioavailability. Nevertheless, how these facts may interact in a population with altered endothelial function such as metabolic syndrome patients remains unknown. The objective of the study was to evaluate whether the presence of NOS3 Glu298Asp polymorphism interacts with the phenol content of virgin olive oil (VOO) to influence postprandial endothelial function. Fifty-seven subjects with metabolic syndrome received three breakfasts based on VOO with different phenolic content. Baseline, incremental area under the curve, peak, and maximum parameters of postocclusive skin reactive hyperemia (PORH) were evaluated by laser Doppler, and the nitrate/nitrite [NO((x))] and eNOS concentrations were obtained during fasting and postprandially. A gene-diet interaction was found on maximum PORH and NO((x)) (P = 0.039 and P = 0.043, respectively). TT subjects showed lower values of eNOS, NO((x)), and maximum PORH as compared with GG and GT subjects, especially in the postprandial measurements (all P < 0.05). However, most of these differences were attenuated when high-phenol VOO was consumed. In a population with a compromised endothelial function, concentrations of phenols in dietary VOO interact with NOS3 Glu298Asp to ameliorate the endothelial dysfunction associated to the TT genotype.

Influence of olive paste preparation conditions on virgin olive oil triterpenic compounds at laboratory-scale

The influence of olive paste preparation conditions on the triterpenic content of virgin olive oils from Arbequina and Picual cultivars was investigated. For this purpose, three sieve diameters of the hammer mill (4, 5, and 6 mm), two malaxation temperatures (20 and 30 °C), and two malaxation times (20 and 40 min) were tested. Results obtained showed that for Arbequina oils, a finer crushing level resulted in higher maslinic acid and erythrodiol content. Increasing malaxing temperature and time lead to a rise in both oleanolic and maslinic acid concentration, whereas erythrodiol content increased only for the longer malaxation time. For Picual oils, higher concentrations of oleanolic acid, maslinic acid, and uvaol were obtained by prolonging the paste malaxation time. A finer crushing level resulted also in an increase of maslinic acid content. These findings suggest that virgin olive oil triterpenic composition can be improved by regulating olive paste preparation conditions.

Phenolic Content of Virgin Olive Oil Improves Ischemic Reactive Hyperemia in Hypercholesterolemic Patients

The goal of this study was to evaluate the effects of the phenolic content of virgin olive oil on endothelial reactivity. Endothelial-dependent vasodilatation is impaired during the postprandial state, and oxidative stress could play a key role in its development. Twenty-one hypercholesterolemic volunteers received two breakfasts, using a randomized sequential crossover design. Both arms received the same olive oil, but one had its phenolic acid content reduced from 400 to 80 ppm. Ischemic reactive hyperemia (IRH) was measured with a laser-Doppler procedure at baseline and 2 h and 4 h after oil intake. Postprandial plasma concentrations of lipid fractions, lipoperoxides (LPO), 8-epi prostaglandin-F(2alpha), and nitrates/nitrites (NO(x)) were obtained at baseline and after 2 h of the fat meal. The intake of the polyphenol-rich breakfast was associated with an improvement in endothelial function, as well as a greater increase in concentrations of NO(x) (p < 0.001) and a lower increase in LPO (p < 0.005) and 8-epi prostaglandin-F2alpha (p < 0.001) than the ones induced by the low polyphenol fat meal. A positive correlation was found to exist between NO(x) and enhanced endothelial function at the second hour (r = 0.669; p < 0.01). Furthermore, a negative correlation was found between IRH and LPO (r = -0.203; p < 0.05) and 8-epi prostaglandin-F2alpha levels (r = -0.440; p < 0.05). A meal containing high-phenolic virgin olive oil improves ischemic reactive hyperemia during the postprandial state. This phenomenon might be mediated via reduction in oxidative stress and the increase of nitric oxide metabolites.

Oxidative stability and phenolic content of virgin olive oil: An analytical approach by traditional and high resolution techniques

The characteristic resistance to oxidation of virgin olive oil is related to its unique fatty acid composition in addition to several minor components that have antioxidant properties. Among the latter, phenols are the most important. Several factors can influence the chemical or enzymatic oxidative processes that extend or shorten the shelf-life of olive oil. Furthermore, the amount of phenolic compounds extracted during production is fundamental for the oxidative and nutritional quality of the oil. In fact, it is well known that different steps used for preparation of virgin olive oil may determine differences in the quantities of phenol. At present, various analytical methods are available to analyze the hydrophilic components, including spectrophotometric assays (traditional) and high resolution chromatographic techniques (HRGC, HPLC, HPCE). In this review we summarize these different methodologies and demonstrate that the amount of phenolic compounds in virgin olive oil as determined by both traditional and high resolution techniques can be influenced by different factors including the olive cultivar and degree of ripeness, as well as by production and extraction technologies.

Sterol and erythrodiol + uvaol content of virgin olive oils from cultivars of Extremadura (Spain)

Sterol profiles were determined and the levels of erythrodiol + uvaol in 63 samples of oil elaborated in seven varieties of olives that predominate in the Extremadura Community Cornezuelo, Corniche, Cacereña, Carrasqueña, Morisca, Verdial de Badajoz and Picual at three ripening stages green, spotted, and ripe. The data were compared statistically, for differences by variety and ripeness. The data of 42 samples were subjected to a discriminant analysis with ‘variety’ as the grouping variable. This was found to explain 77% of the variance, with 100% success in classifying all the varieties. The model was validated with the data of the 21 remaining samples, with a mean of more than 90% of the samples correctly classified.

Effects of Olive Fruit Quality and Oil Storage Practices on the Diacylglycerol Content of Virgin Olive Oils

The evolution of 1,3- and 1,2-isomers of diacylglycerols (DGs) in olive oils obtained from healthy olives and the influence of the olive quality was studied. Healthy olive fruits yielded oils containing almost exclusively 1,2-isomers whereas altered olives produced oils with significant amounts of 1,3-isomers. Virgin olive oils obtained from various olive cultivars and stored at different temperatures showed triacylglycerol hydrolysis and diacylglycerol isomerization depending on the acidity and temperature. The results indicated that the relationship between acidity and total diacylglycerol content has scarce utility for detecting mild refined oil in virgin olive oil. On the other hand, the 1,3-/1,2-DG isomers ratio is useful for assessing the genuineness of virgin olive oils with low acidities during the early stages of storage.

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.