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Characterization of Bioactive Compounds from Monovarietal Virgin Olive Oils: Relationship Between Phenolic Compounds-Antioxidant Capacities
International Journal of Food Properties
Abstract and Figures
The characterization of bioactive components of virgin olive oil from nine varieties (Cuquillo, Empeltre, Manzanilla, Cornicabra, Picual, Arbequina, Lechin, Picudo, and Hojiblanca) has been carried out. Carotenoids, chlorophylls, α-tocopherol, fatty acids, total phenols, and individual phenols were determined. The antioxidant capacity was evaluated by 2,2′-diphenyl-1-picrylhydrazyl and 2,2′-azinobis (3-ethylbenzothiaziline-6-sulfonate) radical scavenging capacity assay, ferric reducing antioxidant potential assay, and oxygen radical absorbance capacity assay. Twelve phenolic compounds were detected and quantified by high-performance liquid chromatography with diode-array detection. Dialdehydic form of elenolic acid linked to tyrosol and hydroxytyrosol, oleuropein, and ligstroside aglycones were the major components in all the samples. Principal component analysis confirmed that Manzanilla, Lechin, Cuquillo, and Hojiblanca var. were the most similar. Furthermore, these results showed that the antioxidant capacity measured by different assays was highly influenced by the phenolic content, especially the dialdehydic form of elenolic acid linked to tyrosol and hydroxytyrosol.
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... Myristic (C14:0), heptadecanoic, and eicosanoic acids are also present in small amounts [6][7][8][9][12][13][14]. See Table S1 for further information on the percentages of fatty acids present in EVOO from the main cultivars in the Mediterranean Area [6,[15][16][17][18][19][20][21][22][23][24][25][26]. ...
... Smaller amounts of simpler phenolic compounds-such as caffeic, vanillic, and ferulic acids-have the role of protecting and enhancing the bioavailability of α-tocopherol [6][7][8][9][12][13][14]33,34]. See Table S2 for further information regarding antioxidants in the unsaponifiable fraction of EVOO from the main cultivars in the Mediterranean Area [17,[19][20][21][22][23]25,[35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51]]. ...
Extra virgin olive oil (EVOO) is a cornerstone of the Mediterranean diet (MedD). In this narrative review, we synthesize and illustrate the various characteristics and clinical applications of EVOO and its components—such as oleic acid, hydroxytyrosol, and oleuropein—in the field of clinical nutrition and dietetics. The evidence is split into diet therapy, oleic acid-based enteral nutrition formulations and oral supplementation formulations, oleic acid-based parenteral nutrition, and nutraceutical supplementation of minor components of EVOO. EVOO has diverse beneficial health properties, and current evidence supports the use of whole EVOO in diet therapy and the supplementation of its minor components to improve cardiovascular health, lipoprotein metabolism, and diabetes mellitus in clinical nutrition. Nevertheless, more intervention studies in humans are needed to chisel specific recommendations for its therapeutic use through different formulations in other specific diseases and clinical populations.
... The oxygen radical absorbance capacity (ORAC) assay is one example of method to assess the antioxidant capacity of compounds since it tests their ability to protect a fluorescent probe from oxidative degeneration [129]. A study utilized this assay to verify the antioxidant capacity of VOO and obtained values in the range of 183-949 µ mol TE/100 g, while a distinct study found that the values for EVOO were between 178 and 620 µ mol TE/100 g [130]. Although we would expect to see higher values for EVOO due to the higher content of phenolic compounds, these results do not illustrate that. ...
Neurodegenerative diseases are a significant challenge to global healthcare, and oxidative stress plays a crucial role in their development. This paper presents a comprehensive analysis of the neuroprotective potential of olive oil, with a primary focus on its antioxidant properties. The chemical composition of olive oil, including key antioxidants, such as oleuropein, hydroxytyrosol, and oleocanthal, is systematically examined. The mechanisms by which these compounds provide neuroprotection, including counteracting oxidative damage and modulating neuroprotective pathways, are explored. The neuroprotective efficacy of olive oil is evaluated by synthesizing findings from various sources, including in vitro studies, animal models, and clinical trials. The integration of olive oil into dietary patterns, particularly its role in the Mediterranean diet, and its broader implications in neurodegenerative disease prevention are also discussed. The challenges in translating preclinical findings to clinical applications are acknowledged and future research directions are proposed to better understand the potential of olive oil in mitigating the risk of neurodegenerative conditions. This review highlights olive oil not only as a dietary component, but also as a promising candidate in preventive neurology, advocating for further investigation in the context of neurodegenerative diseases.
... Fuentes et al. [10] presented a model of antioxidant capacity measured using an oxygen radical absorbance capacity assay with fluorescein as the target molecule (H-ORACFL), dependent on hydroxytyrosol and an oleuropein derivative. Ramos-Escudero et al. [11] reported that the antioxidant capacity measured using different assays, including the H-ORACFL assay, is highly influenced by the phenolic content, especially the dialdehydic form of elenolic acid linked to tyrosol and hydroxytyrosol. ...
The frequency of early frosts has increased in recent years, which are injurious to olive growing, causing losses in the yield and quality of virgin olive oil. In this research, it was studied how the management of agronomic factors mitigates frost damage in Arbequina olives, minimizing the loss of phenols and volatiles in virgin olive oil, at different fruit ripening stages. A Box–Behnken design and multivariate analysis were performed, with three levels of irrigation, potassium fertilization, and foliar copper application (15 treatments). Virgin olive oil was extracted from fresh and frozen olives. Light frost caused a significant decrease in the total phenols and secoiridoid compounds in and the antioxidant capacity of the frost-affected oils, which were perceived as more pungent and had the slight defect of “frostbitten olives”. According to the Box–Behnken design, an 86% reference evapotranspiration (ET0) or higher with 100 potassium oxide units (UK2O) and a 100% ET0 or higher with 250 UK2O would be required to minimize the effect of light frost on phenols and volatiles. Partial Least Squares Regression–Discriminant Analysis (PLS-DA) differentiated the virgin olive oils according to their ripening stage and fresh and frost conditions. Moreover, PLS-DA positively correlated a 75–100% ET0 and 0 Uk2O with the dialdehydic form of the decarboxymethyl ligstroside aglycone (p-HPEA-EDA), the dialdehydic form of the decarboxymethyl oleuropein aglycone (3,4-DHPEA-EDA), the dialdehydic form of the ligstroside aglycone (p-HPEA-EDA-DLA), and with fruity, pungent, and bitter attributes. Precision agronomic management based on the needs of the crop itself would avoid unnecessary stress on olive trees and oil damage.
... PCs are the primary antioxidants that maintain the stability of the VOO and are carriers of bitterness and pungency and, together with the volatiles, influence flavour and aroma [20,21]. Although the proportion of total phenolic compounds (TPCs) in olive oil mostly depends on the cultivar [22,23], several studies confirm that oils obtained by processing low-ripeness fruits contain a higher proportion of these compounds [21,24,25]. Due to the known inhibitory effect of PC on the enzyme LOX [26], one of the objectives of this work was to observe the change in TPC concentration during fruit ripening. ...
The lipoxygenase pathway has a significant influence on the composition of the volatile components of virgin olive oil (VOO). In this work, the influence of the maturity index (MI) on the activity of the lipoxygenase enzyme (LOX) in the fruits of the autochthonous Dalmatian olive cultivars Oblica, Levantinka and Lastovka was studied. The analysis of the primary oxidation products of linoleic acid in the studied cultivars showed that LOX synthesises a mixture of 9- and 13-hydroperoxides of octadecenoic acid in a ratio of about 1:2, which makes it a non-traditional plant LOX. By processing the fruits of MI~3, we obtained VOOs with the highest concentration of desirable C6 volatile compounds among the cultivars studied. We confirmed a positive correlation between MI, the enzyme activity LOX and the concentration of hexyl acetate and hexanol in cultivars Oblica and Lastovka, while no positive correlation with hexanol was observed in the cultivar Levantinka. A significant negative correlation was found between total phenolic compounds in VOO and LOX enzyme activity, followed by an increase in the MI of fruits. This article contributes to the selection of the optimal harvest time for the production of VOOs with the desired aromatic properties and to the knowledge of the varietal characteristics of VOOs.
... The amount of these pigments in OOs can vary widely depending on the primarily variety and harvest time [22] and also climatic conditions and processing methods [31]. Jolayemi et al. (2021) [32] reported that chlorophyll and carotenoid contents of a hundred samples of Turkish OOs from different olive cultivars obtained from five different production seasons varied from 0.6 to 5.6 and 0.6 to 3.3 mg·kg −1 , respectively, as a wide range. ...
Extra virgin olive oils (EVOOs) obtained from five Turkish olive cultivars widely produced in the Aegean and Marmara regions were investigated based on their total antioxidant capacity (TAC), total phenolic content (TPC), pigment contents, fatty acid (FA) profiles, phenolic compounds (PC), volatile compounds (VC), and sensory properties. The results showed that all properties of EVOO samples were significantly affected by the olive cultivar used. The pigment contents in Ayvalık (9.90 mg·kg−1) and Uslu (9.00 mg·kg−1) oils were higher than the others (p < 0.05). The greatest values for oleic acid (74.13%) and TPC (350.6 mg·kg−1) were observed in Gemlik and Domat oils, respectively (p < 0.05). Edincik oil showed the maximum hydroxytyrosol content (48.022 mg·kg−1) and TAC value (515.36 mg TE·kg−1) (p < 0.05). The Edincik, Domat, and Uslu oils were significantly not different for the total content of C6 compounds derived by lipoxygenase, which are the main volatiles responsible for the typical aroma of EVOOs (p > 0.05). Domat oil also exhibited the highest scores for bitterness and pungency perceptions (p < 0.05). The fruitiness scores of the oil samples (except for Ayvalık oil) were close to each other, even if they were statistically different (p < 0.05). Principal component analysis (PCA) indicated that the Ayvalık oil was separated from the others due to its poor-quality characteristics. As a result, it can be stated that Domat olive oil has better quality than the others.
... It has also been shown that in vitro antioxidant powers vary according to teas and antioxidant capacity and the content of total phenolics in tea is strongly correlated [23] as phenolic compounds are powerful chain breaking antioxidants that can directly contribute to antioxidative action [41]. Other studies also showed a strong relationship between antioxidant activity and total polyphenols content in tea leaf extracts [42,43] as well as in extracts of other plants [44][45][46] authenticating the role of leaf constituents, especially polyphenols as potential health benefitting compounds. ...
Objectives: The objective of the study was to estimate the seasonal variations in the antioxidant capacities, total polyphenol content (TPC), total flavonoid content (TFC), and tannin content (TC) of tea leaf extracts from two different plantation sites. Methods: Samples were collected from two tea gardens in Tuli and Ungma situated at N 26°39’19.3 E 094°39’22.7 and N 26°17’30.6 E 094°28’29.2, respectively, under the Mokokchung district of Nagaland, India. TPC, TFC, and TC from sample extracts were determined using Folin–Ciocalteu reagent, aluminum chloride colorimetric, and Folin–Ciocalteu assay. Apart from these, antioxidant capacities were analyzed using ferric reducing ability of plasma (FRAP) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. Results: The concentrations of total polyphenol, flavonoid, and tannin varied from 552.029±8.079 to 305.647±1.744 mg gallic acid equivalent/g, 238.770±0.508–148.457±1.653 mg catechin equivalent/g, and 26.453±0.485–20.173±0.173 mg tannic acid equivalent/g, respectively. FRAP and DPPH assay displayed value ranging from 2.564±0.023 to 1.074±0.023 mmol Fe(II) equivalent/g and 3.612±0.053–2.076±0.028 mmol Trolox equivalent/g. Significant seasonal variations in concentrations of these compounds were observed and a positive correlation between antioxidant capacities and phenolics of tea leaf extracts was established. Conclusion: Tea (Camellia sinensis (L.) O. Kuntze) has been regarded as a plant of immense medicinal and therapeutic value since time immemorial. The tea leaf extracts analyzed in this study gave high TPC, TFC, and TC, as well as high antioxidant activity in terms of DPPH and FRAP value. Studying such properties in tea leaves contributes more to our understandings of health benefit potentials in tea leaves and the quality of tea leaves on the basis of seasons and sites where they are planted.
... As shown in Table 5, prolonged consumption of OPO, HOSO and SO did not induce significant changes in ABTS, ORAC, FRAP and oxLDL values in both groups, except for FRAP (p = 0.018), which showed differences between the study groups, so that the hypercholesterolemics showed a general greater improvement compared to the normocholesterolemics. FRAP, ORAC and ABTS are three complementary methods commonly used to evaluate the antioxidant capacity of different oils, such as olive or sunflower oil, among others [59], as well as in foods naturally containing or enriched with phenolic compounds, such as hydroxytyrosol in olive oil [60]. Although these techniques have not been applied in previous clinical studies with OPO, HOSO or SO, they have been used in long-term studies carried out with other food products naturally high in antioxidants, rich in phenolic compounds, such as cocoa [61,62], green/roasted coffee [35] or in post-prandial studies with hydroxytyrosol-enriched biscuits [63]. ...
Olive pomace oil (OPO) is mainly a source of monounsaturated fat together with a wide variety of bioactive compounds, such as triterpenic acids and dialcohols, squalene, tocopherols, sterols and aliphatic fatty alcohols. To date, two long-term intervention studies have evaluated OPO’s health effects in comparison with high oleic sunflower oil (HOSO, study-1) and sunflower oil (SO study-2) in healthy and cardiovascular risk subjects. The present study integrates the health effects observed with the three oils. Two randomized, blinded, cross-over controlled clinical trials were carried out in 65 normocholesterolemic and 67 moderately hypercholesterolemic subjects. Each study lasted fourteen weeks, with two four-week intervention phases (OPO versus HOSO or SO), each preceded by a three-week run-in or washout period. Regular OPO consumption reduced total cholesterol (p = 0.017) and LDL cholesterol (p = 0.018) levels as well as waist circumference (p = 0.026), and only within the healthy group did malondialdehyde (p = 0.004) levels decrease after OPO intake versus HOSO. Contrarily, after the SO intervention, apolipoprotein (APO) B (p < 0.001) and Apo B/Apo A ratio (p < 0.001) increased, and to a lower extent APO B increased with OPO. There were no differences between the study groups. OPO intake may improve cardiometabolic risk, particularly through reducing cholesterol-related parameters and waist circumference in healthy and hypercholesterolemic subjects.
... According to our results, the aguaje oil obtained from these morphotypes ranged from 153.41 to 328.89 mg/kg and was much higher than the value (107.0 mg GAE/kg) reported previously by Speranza et al. (2016). The polyphenol content of aguaje oil is higher than those of other vegetable oils, such as palm (31.20 to 70.18 mg/kg), linseed (61.76 to 85.24 mg/kg), and sacha inchi (17.75 to 62.0 mg/kg) (Kaur et al., 2017;Abdullah et al., 2018;Ramos-Escudero et al., 2021) and is comparable with that of olive oil (86.90 to 367.60 mg/kg) (Ramos-Escudero et al., 2015). Vegetable oils possess a wide range of polyphenolic compounds including simple phenols, phenolic acids, tannins, phenylethanoids, esters of hydroxycinnamic acids, coumarins and chromans, stilbenes, flavonoids, lignans, and secoiridoids (Ramos-Escudero et al., 2021;Zeb, 2021). ...
The chemical composition and CIELAB color parameters of oil from three aguaje morphotypes (Mauritia flexuosa L.f.) extracted by supercritical carbon dioxide was investigated. By chromatography (HPLC and GC), spectrometry (UV/vis), and digital image colorimetry (digital camera), carotenoids, tocopherols, tocotrienols, fatty acids, total polyphenols, and CIELAB color space were analyzed. These findings showed that the oil obtained from morphotype 3 was superior in several analytes (carotenoids, polyphenols, oleic acid, β-sitosterol, campesterol, and stigmasterol), while morphotype 2 and morphotype 1 showed very close profiles. The most similar chemical components in the oils of the three morphotypes were stigmasterol (16.00 to 17.81%), β-sitosterol (66.39 to 68.94%), palmitic acid (15.56 to 20.69%), and oleic acid (73.29 to 79.54%). The chromatic parameters (L*, a*, b*, and Cab*) were quite different except for the hue angle (hab) (66.55 to 69.71 U), which showed some similarity. Aguaje oil is an interesting resource that stands out for its high content of carotenoids. All three morphotypes may be suitable for potential commercial applications.
The addition of olive leaves during processing of olive oil has been studied and reviewed from different perspectives but there is a paucity of information on the roles of particle sizes of the added leaves in phenolic content of the oil. Dry ground olive leaves with a range of particle size fractions (0.07–3.0 mm) were added to crushed olives prior to the malaxation to compare their effects on: (i) the content of total and selected polyphenols (particularly oleuropein and verbascoside), (ii) antioxidant capacity (in vitro), and (iii) physicochemical quality and the yield of the extracted olive oil. Besides particle size, that was the main factor of study, olive pitting and malaxation time (30 and 60 min) were also considered as independent variables. Olive leaves with 0.3 mm followed by 0.15 mm favorably exhibited significant effects (p < 0.001) in all assays. Indeed, the oil samples with 0.3 mm leaves produced from the pitted olives showed maximum values when the malaxation time was (i) 30 min – for oleuropein (5.85 mg per kg oil), verbascoside (4.02 mg per kg oil), luteolin (15.44 and mg per kg oil), and total phenolic content (TPC) (368.01 mg per kg oil), and (ii) 60 min – for hydroxytyrosol (19.14 mg per kg oil) and tyrosol (16.89 mg per kg oil). These findings indicate that the particle size of added olive leaves can play a significant role in the content of principal polyphenols of the resulting olive oil; a topic that has not been approached in the literature.
The sinami palm (Oenocarpus mapora H. Karst) is a plant from the South American Amazonia that has great potential for industrial applications in the development of functional foods, nutraceuticals and cosmeceuticals. In this manuscript, the physicochemical properties, total polyphenol content and antioxidant activity of sinami oil that was obtained using four extraction systems, namely expeller press extraction (EPE), cold press extraction (CPE), ultrasound-assisted extraction (UAE) and supercritical fluid extraction (SFE), were studied and compared. The oxidative stability (OSI) was statistically non-significant in EPE and SFE. The chromatic properties (CIELab) were influenced by the extraction methods and SFE presented high values of L* and a lower content of plant pigments. Ultrasound-assisted extraction showed a higher content of polyphenols and higher antioxidant activity. Different analyses for the evaluation of the physicochemical properties, the content of total polyphenols and antioxidant activity were used to classify sinami oil according to chemometrics using principal component analysis (PCA). For example, the sinami oil that was obtained using each extraction method was in a different part of the plot. In summary, sinami oil is an excellent resource for plant pigments. Additionally, the information that was obtained on the quality parameters in this study provided a good foundation for further studies on the characterization of major and minor compounds.
The aim of this study was to evaluate minor components (phenolic compounds, α-tocopherols and pigments), fatty acid contents and oxidative stability of virgin olive oil of Spanish cultivars: Arbequina, Arbequina I-18 and Arbosana and Greek cultivar: Koroneiki grown in Northern Tunisia under irrigated high-density plantation system. Thus, in order to have better knowledge about the quali-quantitative profiles of these components in samples obtained from the same collecting seasons and the same processing techniques. Fourteen phenolic compounds were detected and quantified by SPE RP-HPLC. Dialdehydic form of elenolic acid linked to tyrosol and hydroxytyrosol, oleuropein and ligstroside aglycones were the main components in all samples. Pinoresinol was the most abundant component in lignan fraction. These phenolic compounds, α-tocopherols, total phenols and o-diphenols showed significant correlations with oxidative stability. Furthermore, the majority of the studied analytical parameters were greatly influenced by the cultivar–environment interaction. In fact, significant differences between the studied oils were detected.
Up to 1700 samples of virgin olive oil from eight varieties at different ripening stages were analyzed for their colour, in terms of the CIEXYZ space, and pigments. The samples differed greatly in pigments contents (the chlorophylls index ranging from 0.15 to 61.96 mg/kg and the carotenoid one from 0.53 to 31.51 mg/kg) and therefore in colour, as it was inferred from the variations in X (16.19-91.39), Y (18.32-98.16), Z (0.17-81.14), purity of excitation (13.99-99.02), colorimetric purity (20.80-99.34) and dominant wavelength (566-575 nm). After exploring the relationships between the colour parameters and the indexes it was concluded that the purity of excitation and the colorimetric purity were better correlated with the carotenoid index than to the chlorophyll index and that λd was much poorly correlated to both. When multiple regression analyses were applied and the set of tristimulus values was considered altogether the best correlation was found with the carotenoid content.
This study aims to contribute to the knowledge of the commercial, sensory, and analytical characteristics of extra virgin olive oil (EVOO) from the Marche region (Italy), renowned since ancient times. The chemical composition of all the most typical monovarietal oils collected in four crop seasons, was studied in relation to the year of harvesting (from 2004–2007) and the genotype. In order to obtain a complete description of oil samples, free acidity, peroxide value, fatty acid composition, ultraviolet indices, carotenoids, chlorophylls, and phenols were determined. The main characteristics of these oils are large total phenol content, low acidity and peroxide values, low oxidative susceptibilities. All the chemical parameters fell within the limits established for the maximum olive oil category. Sensory evaluation showed that the total score of all the monovarietal extra virgin olive oils was always much higher than the 6.5 limit established for the ‘extra-virgin’ category. The overall quality indices support claims of excellence for monovarietal EVOOs from this geographical area. Results from the present study are of key importance for the specific Production Standards a document that contains regulations for supervising the entire olive oil production cycle and a prerequisite for both the European Protected Denomination of Origin (PDO) and Quality granted by the Marche region (QM) labels.
The beneficial health effects of extra virgin olive oil are due to both its high content of monounsaturated fatty acids and its high content of phenolic compounds, which have recently attracted research interest. In this context, the aim of this work was to examine the in vitro antioxidant and antiproliferative activities of the phenolic extract obtained from extra virgin olive oil from O. europea cultivar ‘Frantoio’ (samples 1–4), one of the main varieties cultivated in Italy. The total phenolic content was determined by Folin–Ciocalteu method and instead the phenolic profile was obtained by HPLC coupled to a diode array detector and mass spectrometry. Extra virgin olive oil extracts exhibited high antioxidant activity through different mechanisms of action and these activities are related to the phenolic content. Sample 3 demonstrated the strongest free radical scavenging activity with IC50 value of 56.5 μg/mL. The reducing ability measured with FRAP assay revealed that samples ranged from 91.3 to 156 μM Fe(II)/g. The same interesting trend was observed with Trolox equivalent antioxidant capacity value. Moreover, the virgin olive oils showed a good oxidative stability ranging between 19 to 32 h. Antiproliferative activity evaluated by SRB assay revealed that phenolic extracts from the cultivar ‘Frantoio’ showed a strong antiproliferative activity against CORL-23 cell line with an IC50 value of 14.5 and 55.9 μg/mL for samples 3 and 1, respectively, and these results are comparable to the positive control vinblastine. Overall, these results showed that extra virgin olive oils from the cultivar ‘Frantoio’, may represent an interesting source of phenolic compounds as functional components that could be consumed in diets and/or used for the elaboration of functional food and pharmaceutical industries.
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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.
The oxygen radical absorbance capacity (ORAC) and the ferric reducing antioxidant power (FRAP) methods were used for the determination
of antioxidant capacities (AC) of rapeseed oils at different steps of technological process and olive oils. The mean ORAC
and FRAP results obtained for rapeseed oils (1,106–160 and 552–95.6μmol TE/100g) were higher than for olive oils (949–123
and 167–32.1μmol TE/100g). Although, FRAP values were lower than ORAC values for all studied oils, there is a linear and
significant correlation between these two analytical methods (r=0.9665 and 0.9298, P<0.0005) for rapeseed and olive oils, respectively). Also, total phenolic compounds in rapeseed oils and olives correlated
with antioxidant capacities (correlation coefficient ranged between 0.9470 and 0.8049). The refining process of rapeseed oils
decreased the total phenolics content and antioxidant capacities by about 80%.
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 500mg/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.
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.