Phenolic Composition and Antioxidant Activity of Monovarietal and Commercial Portuguese Olive Oils

Olive oil composition has been investigated using chemical approaches, since the composition has a direct impact on its quality and safety and it may be used for certification purposes. In this paper, eleven monovarietal and twelve commercial Portuguese olive oils were analyzed to determine spectrophotometrically their total polyphenol content, ortho-diphenols and antioxidant activity. The phenolic profiles of these olive oils were also studied by high performance liquid chromatography. The lowest phenolic content and antioxidant activity were observed for monovarietal olive oils, however, among these group, ‘Cobrançosa’ and ‘Redondil’ cultivars showed the highest values of these two chemical parameters. In commercial olive oils, the concentration of polyphenols, determined according to the Folin–Ciocalteu method, and the antioxidant activity (ABTS method) ranged from 97.37 ± 1.10 to 219.7 ± 1.50 mg GAE/kg of oil and from 387.2 ± 20.00 to 997.5 ± 30.90 µmol Trolox/kg, respectively. The study of the phenolic profile demonstrated that the highest concentrations of the most abundant compounds in olive oil (tyrosol, hydroxytyrosol and oleuropein) are present in commercial olive oils. The correlation coefficient between total phenolics and antioxidant activity was statistically significant (r = 0.95, p < 0.0001). The same was observed for ortho-diphenol content and antioxidant capacity (r = 0.94, p < 0.0001).     

Characterization of the Volatile, Phenolic and Antioxidant Properties of Monovarietal Olive Oil Obtained from cv. Halhali

Volatile and phenolic compositions of olive oil obtained from the cv. Halhali were investigated in the present study. Fruits were harvested at the optimum maturity stage of ripeness and immediately processed with cold press. Simultaneous distillation/extraction (SDE) with dichloromethane was applied to the analysis of volatile compounds of olive oil. Sensory analysis showed that the aromatic extract obtained by SDE was representative of olive oil odour. In the olive oil, 40 and 44 volatile components were identified and quantified in 2010 and 2012 year, respectively. The total amount of volatile compounds was 18,007 and 19,178 μg kg^?1 for 2010 and 2012, respectively. Of these, 11 compounds in the 2010 and 12 in the 2012 harvest presented odour activity values (OAVs) greater than 1, with 1‐octen‐3‐ol, ethyl‐3‐methyl butanoate, (E)‐2‐heptenal and (E,Z)‐2,4‐decadienal being those with the highest OAVs in olive oil. The high‐performance liquid chromatographic method coupled with diode‐array detection was used to identify and quantify phenolic compounds of the olive oil. A total of 14 phenolic compounds in both years were identified and quantified in olive oil. The major phenolic compounds that were identified in both years were hydroxytyrosol, tyrosol, elenolic acid, luteolin, and apigenin. Antioxidant activity of olive oil was measured using the DPPH and ABTS methods.     

Phenolic Compounds and Antioxidant Capacity of Monovarietal Olive Oils Produced in Argentina

Virgin olive oil has high levels of phenolic compounds that are highly bioavailable; these compounds are receiving considerable attention for their antioxidant activity, closely related to the prevention of non‐communicable chronic diseases. The aim of this work was to characterize the phenolic profile and antioxidant capacity of monovarietal olive oils cvs. Arauco, Arbequina, Farga and Empeltre produced in Argentina. This study focused on the relationship between the single molecules or classes of molecules quantified by SPE‐CZE, the corresponding Folin‐Ciocalteu results, and antioxidant capacity using three different tests. Fifteen compounds were simultaneously determined: tyrosol, vinylphenol, oleuropein, hydroxytyrosol, rutin, catechin, naringenin, cinnamic acid, chlorogenic acid, syringic acid, luteolin, apigenin, vanillin acid, quercetin, and caffeic acid. The phenolic contents of the monovarietal olive oils show significant differences between different varieties (p < 0.05), with positive and significant Pearson's correlation found between Folin–Ciocalteu and CZE. Besides, the correlation between the content of total polyphenols and antioxidant capacity was high for all the antioxidant assays performed. When analyzing the correlation coefficients of the different families of phenolic compounds studied, simple phenols and cinnamic acid derivatives show a higher correlation with antioxidant capacity. Thus, findings obtained in this study demonstrated that Arauco olive oil, autochthonous for Argentina, possesses the highest antioxidant/free‐radical scavenging properties, which are very likely due to the presence of high contents of phenolic compounds.     

Quality and Composition of Virgin Olive Oils from Indigenous and European Cultivars Grown in China

The characteristics of eight varieties of virgin olive oil (Arbosana, Arbequina, Coratina, Cornicabra, Frantoio, Koroneiki, Picual, and Ezhi 8) obtained in two successive crops in the southwest of China (Xichang, Sichuan Province) were investigated. Significant differences (P < 0.05) were observed in physicochemical properties, fatty acid profile, minor component contents, and oxidative stability between different varieties of olive oils. The physicochemical properties of all samples met IOC standards for extra virgin olive oil, while in Koroneiki, olive oils were present the optimum oxidation stability among studied varieties. The results of hierarchical cluster analysis and principal component analysis (PCA) showed a good classification between varieties based on their qualitative characteristics. Koroneiki and Ezhi 8 olive oils were significantly different from other varieties mainly due to color, fatty acid profile, and minor components. PCA result also showed that harvest crop influences the characteristics of samples mainly due to the variance of temperature and rainfall.     

Effect of Agronomical Practices on the Nutritional Quality of Virgin Olive Oil at Different Ripening Stages

There is a need to verify the quality of organically produced olive oils and to compare them to conventional ones. The objective of this study was to assess possible differences in nutritional quality between agronomic practices in Picual and Hojiblanca olive oil varieties at different stages of olive ripeness. The results showed that organic versus conventional cultivation did not consistently affect acidity, peroxide index or spectrophotometric constants of the virgin olive oils considered in this study. On the contrary, phenol content, oxidative stability, tocopherol content and fatty acid composition were affected by the agronomical practices. Principal component analysis indicated that linolenic acid and β‐tocopherol were mainly responsible for discriminating Hojiblanca organic oils, whereas total phenols, palmitoleic acid and α‐tocopherol were the major contributors to differentiating Picual conventional oils. Lignoceric and stearic acids were related to oils from unripe and ripe olive fruits, respectively. Long‐term experiments are required to confirm these results.     

Effects of Cultivars and Location on Quality, Phenolic Content and Antioxidant Activity of Extra-Virgin Olive Oils

Quality characteristics of extra-virgin olive oils depend on several factors. In order to study the effects of genotype and growing location on olive oil quality, olives from cv. Coratina, Nocellara, Ogliarola, and Peranzana, picked in four locations of the Apulia region (Italy), were crushed by a three-phase system to produce mono-cultivar extra virgin olive oils that were analyzed for acidity, peroxide value, spectrophotometric indices, total phenolic content, phenolic profile and antioxidant activity. The experimental data concerning peroxide value, spectrophotometric indices, phenolic content and profile and antioxidant activity showed great variability among the cultivars grown in the same location and also among the oils produced with olives of the same cultivar but grown in different locations. For each cultivar, no significant differences were found among locations in terms of acidity and ΔK whereas peroxide value, K₂₃₂, and K₂₇₀ differ significantly among locations for both Ogliarola and Peranzana cv. Concerning the phenolic content of Ogliarola cv., no differences were highlighted between the locations whereas the phenolic contents of Peranzana significantly changed as a function of the place of growing. On the basis of these results, the statistical multivariate analysis did not allow the classification into homogeneous groups neither of the oils belonging to the same cultivar nor of those obtained from olives picked in the same location.     

Total Phenolics of Virgin Olive Oils Highly Correlate with the Hydrogen Atom Transfer Mechanism of Antioxidant Capacity

Polar extracts of extra‐virgin olive oils (EVOO) contain a large number of phenolic compounds with antioxidant properties. The antioxidant capacity can be measured by different reaction mechanisms, as the single electron transfer (SET) or the hydrogen atom transfer (HAT). In this work, the total phenolic content (TPC) by the Folin‐Ciocalteu method and its correlation with four antioxidant capacity assays (FRAP, ABTS, DPPH^? and ORAC) were evaluated for EVOO polar extracts. It was observed that the higher the total phenolic compounds in the EVOO extracts, the higher the antioxidant capacities, regardless of the method employed. The reaction mechanism observed for TPC by Folin‐Ciocalteu method and also for FRAP, ABTS and DPPH^? antioxidant capacity assays is a single electron transfer, thus, a high correlation among their results is expected. However, the correlation between TPC and ORAC results was also high and significant, allowing to conclude that EVOO phenolic compounds are able to react by the hydrogen atom transfer mechanism, which indicates that they can act as effective radical chain‐breaking antioxidants. These results suggest that, for the EVOO polar extracts, TPC by Folin‐Ciocalteu and ORAC assays could be sufficient to evaluate their in vitro antioxidant capacity.     

The Effect of Harvesting Time on Olive Fruits and Oils Quality Parameters of Tortiglione and Dritta Olive Cultivars

Despite the fact that Italy holds the most important olives heritage in the world, with about 800 cultivars, most of them are still underestimated, in particular those from Abruzzo, a region located in the center of the peninsula. The aim of this work is to study the changes in quality parameters of olive fruits and related oils of two autochthonous Abruzzo olive cultivars, Tortiglione and Dritta during ripening (from September to November 2017). Both cultivar and ripening time affect the chemical parameters of olive fruits. Results highlight an increasing trend of the oil content with final values, based on fresh matter, of 38.7 ± 0.3% and 38.1 ± 0.9% for Tortiglione and Dritta, respectively. Olive oils chemical composition is also affected by ripening time and cultivar, with Tortiglione oils resulting generally richer than Dritta oils; on the first sampling time (30th of October) values for total phenolic content, antioxidant activity, and chlorophylls are 803.8 ± 68.2 mg gallic acid equivalent kg⁻¹, 2.7 ± 0.5 mmol trolox equivalent kg⁻¹, and 30.8 ± 1.6 mg pheophytin a kg⁻¹, respectively. Tocopherols seem to be more affected by ripening time than by cultivar, in particular for Dritta. Practical Application : The results on Abruzzo minor olive cultivars indicate that olive fruits and olive oil composition are strongly influenced by both cultivar and ripening time, giving rational indications about the optimal cultivar specific harvesting time and opening interesting opportunities for olive oil producers in a perspective of sustainable production to obtain high quality fruits and oils. The research provides detailed information about Tortiglione and Dritta olive cultivar, useful in the global context of revaluation of Italian minor olive varieties.     

Evaluation of Olive Preservation Methods on Bioactive Constituents and Antioxidant Properties of Olive Oils

The purpose of this study was to determine the effects of preservation methods on less salty natural black table olives by evaluating the extracted olive oils. For this purpose, olives of the Gemlik variety obtained in two harvest years were brined and dry salted with 2 and 4% levels of salt and packaged with vacuum and modified atmosphere (60% N₂ and 40% CO₂) and treated with gamma irradiation (0, 1, 3, 5 kGy). The olive oil extraction process was applied to raw olives, olives after fermentation and olives at 4th and 8th months of storage time. Bioactive component analyses including total carotenoid, total chlorophyll, α-tocopherol analyses and antioxidant properties were performed along with determination of free fatty acids content (FFA) and peroxide values (PV). FFA and PV increased while α-tocopherol (TO), total chlorophyll (TCH), total carotenoids (TC) and antioxidant activity (DPPH· radical scavenging assay) values decreased with storage and increment of irradiation dosage. Principal components analyses (PCA) showed that olive oils were discriminated clearly according to harvest year, salt content and processing type (dry-salting and brining). Overall, this study revealed that chemical parameters of olive oils as the main component of the olives were affected by the harvest year, processing and preservation conditions along with fermentation and storage period of olives.     

Effects of Olive Trees Age on the Minor Components of Oueslati Virgin Olive Oils Produced from Olives Harvested at Different Ripening Degrees

Phenolics, volatiles, squalene, tocopherols, and fatty acids of virgin olive oils (VOO) from adult and young olive trees of the Oueslati variety, typically cultivated in the Center of Tunisia, were analyzed at three different harvesting periods. Significant differences in contents of saturated fatty acids (p < 0.05), squalene (p < 0.05), alpha-tocopherol and total tocopherol (p < 0.02) and oxidized form of decarboxymethyl oleuropein aglycon (p < 0.05) were seen between VOO from adult and young trees during maturation. Moreover, the volatile profiles of VOO from adult and young trees showed significant differences in the amounts of hexanal, 1-penten-3-ol (p < 0.05), (Z)-3-hexenal and (Z)-2-penten-1-ol (p < 0.01). Principal component analysis showed that olives from adult trees should be harvested at the cherry stage of maturation to obtain a satisfactory level of oil quality, while olives from young trees should be harvested at the black maturation stage.     

Fatty Acid Profiles of Virgin Olive Oils from the Five Olive-Growing Zones of Extremadura (Spain)

In this study, 278 samples of virgin olive oil from 40 mills belonging to five olive-growing zones of Extremadura were evaluated according to their fatty acid composition. An analysis of variance of the fatty acid contents, and their principal group subtotals and ratios revealed significant differences at the 95 % confidence level between zones. Means were compared using Tukey’s HSD test (p < 0.05). A discriminant analysis, taking the zone as the grouping variable and the different fatty acids and their ratios as independent variables, explained nearly 90 % of the variance with the first two functions. The model correctly classified 88.8 % of the analysed samples into their proper olive-growing zone. Validation against an extra test set of 30 samples resulted in 90 % being correctly classified; the results of the discriminant analysis were therefore considered to be validated. A two-dimensional graphical representation of the different groups studied using the first two resulting canonical discriminant functions clearly showed the Sierra Norte of Cáceres and Vegas del Guadiana each to be clearly separated from the rest and from each other, while the other three zones—Siberia, Serena and Tierra de Barros—overlapped considerably.     

Phenols and Volatiles of Istarska Bjelica and Leccino Virgin Olive Oils Produced with Talc,NaCl and KCl as Processing Aids

The effect of processing aids (2.5 % of talc, NaCl or KCl) on oil extractability and the profile of phenolic and volatile compounds of Istarska bjelica and Leccino oils was studied. Talc significantly increased extractability in both cultivars, while salts increased extractability in Leccino cv. In the laboratory extracted oils, phenols were determined by a RP‐HPLC–DAD method, whereas volatiles were determined by SPME/GC–MS. Talc addition significantly decreased hydroxytyrosol and increased ligstroside derivatives in produced oils, but did not affect the total phenol content. Among volatile compounds, only Z‐2‐penten‐1‐ol in Leccino and 1‐pentene‐3‐one in Istarska bjelica oils significantly increased by talc addition. Salts improved transfer of most individual phenols into oil, particularly oleuropein derivatives, and increased C6 aldehydes and C5 volatiles in Leccino oils. NaCl exerted a stronger effect in increasing individual phenols and volatiles than KCl.     

Effect of Agronomical Factors and Storage Conditions on the Tocopherol Content of Oblica and Leccino Virgin Olive Oils

The influence of agronomical factors (two growing areas and four harvest periods) and storage conditions of virgin olive oils (room temperature, +4 and ?20 °C) on tocopherols was investigated on two cultivars having significantly different tocopherol content (Oblica 269–443 mg/kg, Leccino 403–784 mg/kg). α‐Tocopherol accounted for 97 % of total tocopherols and its content decreased during ripening of both cultivars. In a warmer growing area both cultivars gained a higher γ‐tocopherol content while only Leccino showed a higher content of α‐tocopherol. After 12 months of storage α‐tocopherol content decreased by up to 27 %. Lower storage temperatures did not always contribute to the higher stability of α‐tocopherol compared to room temperature.     

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

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

Influence of Irrigation Modalities (Irrigation Management and Dryland), Fruit Ripening,and Cultivation Modality (Organic and Conventional) on Quality and Chemosensory Profile of Hojiblanca and Picual Extra Virgin Olive Oils

A study with controlled field and authentic samples of olives, obtained in similar conditions of soil, climate, region, harvest, and with the same cultivation techniques and considering simultaneously different agronomic factors (olive variety, fruit ripening degree, irrigation, and organic or conventional production system) is performed to evaluate their influence on quality and added value of extra virgin olive oil (EVOO). Agronomical and physicochemical parameters, polyphenols, tocopherols, and fatty acid composition and volatile and sensory profiles are determined in Hojiblanca and Picual VOOs obtained from different fruit ripening degrees and different cultivation modalities (conventional with and without irrigation, and organic with irrigation). Among volatile compounds, 1-hydroxy-2-propanone, (E)-linalool oxide, and 2-acetylfuran are described for the first time in EVOO. The variable that most influences the chemosensory composition of EVOOs is the variety, followed by the stage of ripeness, and, within each variety, the cultivation modality. Organic irrigation differ from conventional modalities, showing significant differences in acidity, stability, tocopherol and polyphenol contents, fatty acid composition, and sensory attributes. Practical Applications: Results are of great importance, due to their applicability to the EVOO sector, allowing one to know the qualitative, chemical and organoleptic differences between organic and conventional EVOO, and factors that improve the quality and performance of EVOO.     

Changes in Quality Indices,Phenolic Content and Antioxidant Activity of Flavored Olive Oils during Storage

The chemical characteristics, phenolic content and antioxidant activity of olive oils flavored with garlic, lemon, oregano, hot pepper, and rosemary were evaluated during 9 months of storage. At the end of the storage period, the unflavored and the garlic-flavored oils maintained their chemical parameters within the limits fixed for extra-virgin olive oils. After 9 months of storage, a noticeable decrease in phenolic content was observed in all the oils. The highest (35.0 ± 3.9 mg/kg oil) and the lowest (6.3 ± 0.4 mg/kg) phenolic contents were detected in the unflavored and garlic-flavored oils, respectively. Compounds such as 3,4-DHPEA-EDA (3,4-dihydroxyphenylethyl 4-formyl-3-formylmethyl-4-hexenoate, the dialdehydic form of decarboxymethyl elenolic acid linked to hydroxytyrosol) and p-HPEA-EDA (dialdehydic form of the decarboxymethyl elenolic acid linked to tyrosol) were the most abundant in both unflavored and lemon-flavored oils up till 6 months of storage. At the end of the storage period, increases in 3,4-DHPEA (hydroxytyrosol) and p-HPEA (tyrosol) were measured in almost all the oils. During storage, the antioxidant activity coefficients of the phenolic extracts, calculated according to the β-carotene bleaching assay, significantly decreased and, after 9 months, were in a decreasing order: rosemary (51.3 ± 4.2), hot pepper, lemon, oregano, unflavored, and garlic (8.5 ± 0.7).     

A 3-year Study on Quality,Nutritional and Organoleptic Evaluation of Organic and Conventional Extra-Virgin Olive Oils

The quality of extra-virgin olive oils (EVOO) from organic and conventional farming was investigated in this 3-year (2001–2003) study. The oils were extracted from Leccino and Frantoio olive (Olea europaea) cultivars, grown in the same geographical area under either organic or conventional methods. Extra-virgin olive oils (EVOO) were produced with the same technology and samples were analyzed for nutritional and quality parameters. Volatile compounds were measured with solid-phase microextraction combined with gas chromatography and mass spectrometry (SPME–GC–MS). Sensory evaluation was also completed by a trained panel. Significant differences were found in these parameters between organic and conventional oils in some years, but no consistent trends across the 3 years were found. The acidity of organic Leccino oils was higher than conventional oils in 2001 and 2002 but not in 2003; Frantoio oils were never different. Organic Leccino oils had higher peroxide index than conventional oils in 2001 and 2002 but it was the reverse in 2003. Organic Frantoio oils had lower peroxide index in 2001, but values were not statistically different in the other years. The concentrations of phenols, o-diphenols, tocopherols, the antioxidant capacity and the volatile compounds showed differences in some years and no difference, or opposite differences, in others. Sensory analysis showed only slight differences in few aromatic notes. Our results showed that organic versus conventional cultivation did not affect consistently the quality of the high quality EVOO considered in this study, at least in the measured parameters. Genotype and year-to-year changes in climate, instead, had more marked effects.