Comparison of Two Analytical Methods for Assessing Antioxidant Capacity of Rapeseed and Olive Oils

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 552–95.6 μmol TE/100 g) were higher than for olive oils (949–123 and 167–32.1 μmol TE/100 g). 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%.     

Characterization of cold-pressed onion, parsley, cardamom, mullein, roasted pumpkin, and milk thistle seed oils

Cold-pressed onion, parsley, cardamom, mullein, roasted pumpkin, and milk thistle seed oils were characterized for their fatty acid (FA) composition, tocopherol content, carotenoid profile, total phenolic content (TPC), oxidative stability index (OSI), color, physical properties, and radical-scavenging capacities against peroxyl (oxygen radical-scavenging capacity) and stable DPPH (diphenylpicrylhydrazyl) radicals. Parsley seed oil had the highest oleic acid content, 81 g/100 g total FA, and the lowest saturated fat among the tested oils. Roasted pumpkin seed oil contained the highest level of total carotenoids, zeaxanthin, β-carotene, cryptoxanthin, and lutein at 71 μmol/kg and 28.5, 6.0, 4.9, and 0.3 mg/kg oil, respectively. Onion seed oil exhibited the highest levels of α- and total tocopherols under the experimental conditions. One of the parsley seed oils exhibited the strongest DPPH scavenging capacity and the highest oxygen radical absorbance capacity (ORAC) value of 1098 μmol Trolox equiv/g oil. However, ORAC values of the tested seed oils were not necessarily correlated to their DPPH scavenging capacities under the experimental conditions. The highest TPC of 3.4 mg gallic acid equiv/g oil was detected in one of the onion seed oils. The OSI values were 13.3, 16.9–31.4, 47.8, and 61.7 h for the milk thistle, onion, mullein, and roasted pumpkin seed oils, respectively. These data suggest that these seed oils may serve as dietary sources of special FA, tocopherols, carotenoids, phenolic compounds, and natural antioxidants. An erratum to this article is available at .     

Validation of the oxygen radical absorbance capacity (ORAC) parameter as a new index of quality and stability of virgin olive oil

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.     

Evaluation of the Antioxidant Properties of Micronutrients in Different Vegetable Oils

Micronutrients (tocols, sterols, and total phenolic) and antioxidant activities of 15 varieties of common vegetable oil samples obtained from different countries are investigated. All methanol extracts are assayed for total antioxidant ability and cellular antioxidant activity (CAA) using oxygen radical absorbance capacity (ORAC) method and CAA assay. CAA has been widely used in the evaluation of food antioxidants recently. It quantifies antioxidant capacity utilizing a HepG2 cell model, which is more biologically representative. Linseed and sesame oils show much higher CAA values than the others tested; however, levels of walnut, sunflower, and coconut oils are extremely low, which are hard to be quantified. A significant correlation between the ORAC and CAA values and total phenolic content (p < 0.05) is observed. High‐phenolic olive oil has the highest level of phenolics and the highest ORAC, while linseed oil has the highest CAA value. Based on this, choosing proper edible oil consumption may reduce oxidative damage of human body and promote the precision processing of edible oil such as retaining beneficial ingredients moderately. Practical Application: This study demonstrates the evaluation of the universality of vegetable oils by the cellular antioxidant model and provides a data reference for the selection of edible oils with excellent antioxidant properties.     

Fatty Acid Composition, Antioxidant Properties, and Antiproliferative Capacity of Selected Cold-Pressed Seed Flours

Cold-pressed seed flours from pumpkin, parsley, mullein, cardamom, and milk thistle were examined for total oil, fatty acid profile of the oil, total phenolic content (TPC), scavenging activities against peroxyl (ORAC), hydroxyl (HOSC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) (RDSC) radicals, and antiproliferative capacity against HT-29 human colon cancer cells. The cold-pressed parsley seed flour contained a very high concentration of total oil—17.6 g/100 g flour—with primarily C18:1 fatty acid at 86.2 g/100 g fatty acids. All other flour oils had relatively high levels of saturated fats, ranging from 39.0 to 62.9 g/100 g fatty acids. The tested seed flours demonstrated significant TPC and free radical scavenging activities. Milk thistle seed flour had the highest TPC value of 25.2 mg gallic acid equivalent per g flour (GAE mg/g) followed by that of parsley seed flour at 8.1 GAE mg/g. Milk thistle seed-flour extract also had significantly higher antioxidant activities than all other extracts against all tested radicals. The milk thistle seed-flour extract had an ORAC value of 1131 μmol trolox equivalents (TE) per g flour (TE μmol/g), a HOSC value of 893 TE μmol/g, and an RDSC value of 61 TE μmol/g. Also, ORAC, HOSC, and TPC values were significantly correlated (P < 0.01) under the experimental conditions. The cold-pressed milk thistle seed flour inhibited the proliferation of HT-29 cancer cells in a dose-dependent manner. Results from this study suggest that these cold-pressed seed flours may serve as natural sources of antioxidants and may be used to improve human health.     

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).     

Protective effect of olive oil and its phenolic compounds against low density lipoprotein oxidation

The protective effect of phenolic compounds from an olive oil extract, and of olive oils with (extra-virgin) and without (refined) phenolic components, on low density lipoprotein (LDL) oxidation was investigated. When added to isolated LDL, phenolics [0.025–0.3 mg/L caffeic acid equivalents (CAE)] increased the lag time of conjugated diene formation after copper-mediated LDL oxidation in a concentration-dependent manner. Concentrations of phenolics greater than 20 mg/L inhibited formation of thiobarbituric-acid reactive substances after AAPH-initiated LDL oxidation. LDL isolated from plasma after preincubation with phenolics (25–160 mg/L CAE) showed a concentration-dependent increase in the lag time of conjugated diene formation after copper-mediated LDL oxidation. Refined olive oil (0 mg/L CAE) and extra-virgin olive oil (0.1 and 0.3 mg/L CAE) added to isolated LDL caused an increase in the lag time of conjugated diene formation after copper-mediated LDL oxidation that was related to olive oil phenolic content. Multiple regression analysis showed that phenolics were significantly associated with the increase in lag time after adjustment for effects of other antioxidants; α-tocopherol also achieved a statistically significant effect. These results indicate that olive oil phenolic compounds protect LDL against peroxyl radical-dependent and metal-induced oxidation in vitro and could associate with LDL after their incubation with plasma. Both types of olive oil protect LDL from oxidation. Olive oil containing phenolics, however, shows more antioxidant effect on LDL oxidation than refined olive oil.     

Lipid characteristics and phenolics of native grape seed oils grown in Turkey

Grape seed oils of seven native Turkish cultivars (namely Atfi, Mazruna, Black Kerkü?, Zeyti, Verdani, Karfoki, and Kerkü?) were evaluated for their fatty acids, tocols, phytosterols as well as total phenolics and oxygen radical absorbance capacity (ORAC) values. Among the fatty acids, linoleic acid (18:2ω6) was the most abundant (56.38–68.56%), followed by oleic acid (16.45–29.38%, 18:1ω9), palmitic acid (8.19–9.44%, 16:0), and stearic acid (3.74–4.98%, 18:0). Total tocopherols and tocotrienol amounts varied in the range of 102.30–305.43 and 251.47–468.22 mg/kg, respectively. Beta‐sitosterol was the most abundant sterol among grape cultivars whose concentration ranging from 64.19 to 71.62%. Total phenolic content ranged from 2.19 to 4.70 mg of gallic acid equivalents/100 g oil, being lowest in Zeyti and highest in Verdani. With respect to antioxidant activities, a large variation in ORAC values was observed among grape seed oils (ranging from 1048 µmol of Trolox equivalents (TE)/100 g in Karfoki to 2569 µmol of TE/100 g in Mazruna). Practical applications: The crude grape seed oils extracted from different cultivars are a good source of nutrients, fat‐soluble bioactives, and health‐promoting components.     

Effect of growing area on pigment and phenolic fractions of virgin olive oils of the arbequina variety in Spain

The purpose of this investigation was to study differences in the chlorophyll, carotenoid, and phenolic fractions of virgin olive oils from the Arbequina variety cultivated in different olive growing areas of Spain. Virgin olive oil from Lleida was less heavily pigmented, and these oils showed more negative values for the ordinate a^* (of the CIELAB colorimetric system). Pheophytin a was the major chlorophyll pigment, and lutein was the major component of the carotenoid fraction in all oils analyzed. The chlorophyll a concentration in virgin olive oils from Lleida was 700 μg kg⁻¹, but was 175 μg kg⁻¹ in oils from Jaén, and 200 μg kg⁻¹ in oils from Tarragona. Finally, the chlorophyll a/chlorophyll b ratio was 9 in oils from Lleida and around 0.6 in the other two Arbequina olive oils. In relation to the phenolic fraction, the hydroxytyrosol and tyrosol contents were significantly higher in olive oils from Jaén (grown at higher altitude and precipitation rates). The secoiridoid derivatives showed a significantly higher concentration in olive oils from Tarragona, probably due to the low altitude where they grow, and finally the ratio of (dialdehydic form of elenolic acid linked to tyrosol)/lignans had a value of 1.4 in olive oils from Lleida, whereas this value was around 0.7 in the other Arbequina olive oils.     

The olive oil oxygen radical absorbance capacity (DPPH assay) as a quality indicator

The antioxidant properties of some single components and the total antioxidant activity of extra‐virgin olive oil have been evaluated by the oxygen radical absorbance capacity (ORAC) method. The total ORAC of the extra‐virgin olive oil was found to be positively correlated with the concentration of total polyphenols, which are important to the shelf life of the product. Among the single phenolic compounds studied, gallic acid showed a higher ORAC than caffeic acid and oleuropein, while among the derivates of oleuropein, hydroxytyrosol was found to be the most active compound among all the phenols studied. The total ORAC of commercial olive oils differed according to the concentration of total polyphenols. The total ORAC of extra‐virgin olive oil was constant during 1 year of storage in rational conditions, whereas it worsened dramatically in olive oil damaged by the lipase‐producing yeast Williopsis californica or by lipase from Pseudomonas spp. The study accomplished on the oily fraction of the fruits before harvesting demonstrated that the total ORAC of the oil of under‐ripe green olives is higher compared to that shown by mature fruits; therefore, through the choice of the harvesting time, it is possible to define also the future content of polyphenols of the oil. The total ORAC test, together with other analyses, can be considered as a qualitative parameter that can contribute to the expression of technological and health virtues of extra‐virgin olive oil.     

Detection of polycyclic aromatic hydrocarbons in commonly consumed edible oils and their likely intake in the Indian population

Edible oils such as coconut, groundnut, hydrogenated vegetable, linseed, mustard, olive, palm, refined vegetable, rice bran, safflower, sesame, soybean, and sunflower were analyzed for the presence of light and heavy polycyclic aromatic hydrocarbon (PAH) residues using liquid-liquid extraction, cleanup on a silica gel column, and resolution and determination by HPLC using a fluorescence detector. Ten PAH viz. acenaphthene, anthracene, benzo(a)pyrene, benzo(e)pyrene, benz(ghi)perylene, chrysene, coronene, cyclopenta(def)phenanthrene, phenanthrene, and pyrene were monitored. Analysis of 296 oil samples showed that 88.5% (262) samples were contaminated with different PAH. Of 262 contaminated edible oil samples, 66.4% of the samples showed PAH content of more than the 25 μg/kg recommended by the German Society for Fat Science. The total PAH content was highest in virgin olive oil (624 μg/kg) and lowest in refined vegetable oils (40.2 μg/kg). The maximum content (265 μg/kg) of heavy PAH was found in olive oil and the minimum (4.6 μg/kg) in rice bran oil. Phenanthrene was present in 58.3% of the oil samples analyzed, followed by anthracene (53%). Among the heavy PAH, benzo(e)pyrene was observed in 31.2% of the samples followed by benzo(a)pyrene (25.5%). The intake of PAH was highest through olive oil (20.8 μg/day) followed by soybean oil (5.0 μg/day) and lowest through refined vegetable oil (1.3 μg/day). Based on these monitoring studies, international and national guidelines for permissible levels of PAH can be prepared so as to restrict the intake of these toxic contaminants.     

Frying Quality Characteristics of French Fries Prepared in Refined Olive Oil and Palm Olein

The objective of this study was to compare two oils with different polyunsaturated/saturated (P/S) fatty acid ratios, refined olive oil (P/S 0.75) and palm olein (P/S 0.25), in frying French fries. The chemical qualities of the oil residues extracted from the French fries were assayed for five consecutive batches fried at 1-h intervals. The levels of total polar compounds, free fatty acids, p-anisidine value and phytosterol oxidation products (POPs) were elevated in French fries fried in both oils. The level of total polar compounds increased from 4.6 in fresh refined olive oil to 7.3% in final batches of French fries. The corresponding figures for palm olein were 9.8–13.8%. The level of free fatty acid in fresh refined olive oil increased from 0.06 to 0.11% in final products. These figures for palm olein were 0.04–0.13%. The p-anisidine value increased from 3.7 to 32.8 and 2.5 to 53.4 in fresh oils and in final batches of French fries in refined olive oil and palm olein, respectively. The total amount of POPs in fresh refined olive oil increased from 5.1 to 9.6 μg/g oil in final products. These figures were 1.9 to 5.3 μg/g oil for palm olein.     

Chemical Composition of Turkish Olive Oil––Ayvalik

Although large amounts of olive oil are produced in Turkey, not much information on its chemical composition is available in the literature to date. The aim of this study was to evaluate the chemical composition of commercial olive oils produced from the Ayvalik olive cultivar in Canakkale, Turkey. Five different samples corresponding to the olive oil categories of extra virgin (conventional, extra virgin olive oil (EVOO), and organic extra virgin olive oil (OGOO) production), virgin olive oil (OO-1), ordinary virgin olive oil (OO-2) and refined olive oil (RFOO) were evaluated. Olive oils were collected from two consecutive production years. According to the free fatty acids, the absorbance values (K₂₃₂ and K₂₇₀), and peroxide values of all the samples conformed to the European standards for olive oil. The level of oleic acid was in the range of 68–73%; while the linoleic acid content was significantly lower in the refined olive oils. The tocopherol and polyphenol content was in the lower range of some European olive oils. However, pinoresinol was a major phenolic compound (5–77 mg/kg depending on the oil category). Its content was markedly higher than in many other oils, which would be a useful finding for olive oil authentication purposes.     

Low molecular weight polypeptides in virgin and refined olive oils

Twenty-eight virgin olive oils—from different regions of Spain and prepared from olive drupes of different varieties—and six refined olive oils were analyzed to determine the presence of proteins in these oils. All oils studied showed the presence of proteins in the range of 7–51 μ/100 g of oil. There were no significant differences in protein content in oils from different varieties or between virgin or refined oils. In addition, all oils exhibited analogous amino acid patterns, suggesting a similarity among protein fractions obtained from different oils. A polypeptide with an apparent M.W. of 4600 Da was common to the isolated protein fractions. These results suggest that this polypeptide is a previously unknown minor component in olive oils. No clear influence of this component on oil stability was observed when oil stabilities were estimated as a function of phenol, tocopherol, phosphorus, and protein contents of the oils.     

The formation of oxo- and hydroxy-fatty acids in heated fats and oils

A fast-food fat (mostly tallow), olive oil and safflower oil were heated in air for 4 d and periodically analyzed for oxofatty acids (OFA), monohydroxy-fatty acids (HFA) and polyhydroxy-fatty acids (PHFA). After transmethylation, the OFA were estimated as 2,4-dinitrophenylhydrazones, and the HFA and PHFA were quantitated as pyruvic acid 2,6-dinitrophenylhydrazone esters. At least half of the maximum concentration attained for OFA, HFA and PHFA was generated between 16–24 h of heating of each oil. Safflower oil contained greater concentrations of HFA and PHFA than either olive oil or the fast-food fat. The fastfood fat sample contained a greater concentration of OFA than did the other oils. The sum of the concentrations of OFA, HFA and PHFA at the time of maximum formation in the oils was approximately 260 μmoles/g at 48–72 h for safflower, 200 μmoles/g at 48–72 h for olive and 170 μmoles/g at 72 h for the fast-food fat. Presented at the 79th Annual AOCS Meeting, Phoenix, Arizona, May 8–12, 1988.     

Stability of a phenol‐enriched olive oil during storage

The use of an emulsifier to stabilize the phenolic compounds added in the preparation of an enriched olive oil was evaluated. Two emulsifiers, lecithin and monoglyceride, were studied. The results showed lecithin to be the most convenient, due to the increase in the value of the oxidative stability of the phenol‐enriched oils in relation to the enrichments prepared with monoglycerides. After that, the shelf life of the prepared oils was evaluated during a period of 256 days of storage at 25°C in the dark. Oil quality parameters, total phenolic content, bitterness index and oxidative stability were studied during the storage period. Additionally, the phenolic composition and antioxidant capacity (by using the ORAC assay) were evaluated at the end of the storage. The phenolic enrichment of the oils allowed the shelf life of the oils to be extended compared with the control (virgin olive oil without phenol addition), delaying the appearance of peroxides and improving their oxidative stability. In addition, the higher content of phenolic compounds in the oils at all stages of storage is desirable in order to increase the intake of these beneficial compounds. Practical applications : The preparation of phenol‐enriched olive oils with a higher phenolic content than the commercial virgin olive oils is of special interest to increase the ingestion of these healthy compounds the daily intake of which is limited due to the high caloric value of olive oil. There are two key points in the development of this product: (i) the dispersion and stabilization of the phenol extract in the oil matrix and (ii) the stability of the phenols in the prepared oils to guarantee the phenol concentration during their shelf life. It is important to study the use of emulsifiers to determine if they allow an improvement in the dispersion of the phenolic extract, and their stabilization in the final product. In addition, the emulsifiers could mask the bitter taste of the enriched oils, which is desirable to increase consumer acceptance of the enriched oil.     

Fast quality screening of vegetable oils by HPLC-thermal lens spectrometric detection

Isocratic reversed-phase HPLC with thermal lens spectrometric (TLS) detection enabled identification of linseed, olive, sesame, and wheat germ vegetable oils to control the authenticity of the oils based on characteristic carotenoid/carotene profiles. Four characteristic regions of carotenoids (i.e., lutein, xanthophyll, carotene, and lycopene) have been identified in each type of oil. The concentrations of total β-carotene (BC) and α-carotene (AC), together with trans-to cis-isomers of β-carotene (TBC/CBC) and BC/AC ratios were shown to be reliable and useful indices for fast screening of oils for nutritional quality. The oil TBC/CBC ratio and the BC concentration (in μg/mL) should meet the following numerical criteria: linseed (≽2∶1, ≽1.7), olive (≽3∶1, ≽0.4), sesame (≽1∶1, ≽0.1), and wheat germ oil (≽1∶1, ≽1.7). Based on the above criteria, unsatisfactory olive oils differed significantly from the consumable ones. Likewise, the concentration of AC in consumable wheat germ and sesame oil should not be lower than 0.6 and 0.02 μg/mL, respectively. The AC level in safflower oil should not be higher than 0.04 μg/mL. The BC/AC ratios exceeding 3∶1, 6∶1, and 8∶1 should be used as an additional quality requirement for consumable wheat germ, sesame, and safflower oil, respectively.     

Antioxidant Activity and Total Phenolics of Propolis from the Basque Country (Northeastern Spain)

The purpose of this study was to evaluate the antioxidant activity (AA) of 19 propolis extracts prepared in different solvent (ethanol and propylene glycol). It was observed that all the samples tested had AA, although results varied considerably between extracts, i.e. 420–1,430 μmol Trolox/g (ABTS), 108–291 mg ascorbic acid/g (DPPH), and 1,573–4,669 μmol iron⁺⁺ sulfate/g (FRAP). The ethanol may enhance the potency of the AA, and the correlation coefficient between total phenolic content (TPC) (200–340 mg/g propolis extracts) and AA was statistically significant. Total flavonoids ranged from 72 to 161 mg/g propolis extracts. The results indicate that TPC and flavonoids contributed to AA.     

Antioxidant activity of rapeseed phenolics and their interactions with tocopherols during lipid oxidation

Commercial rapeseed press cakes are rich sources of phenolic compounds, namely, sinapic acid derivatives, which can be extracted as free sinapic acid and its bound forms (such as sinapine, the choline ester of sinapic acid). Fractionated rapeseed extracts rich in sinapic acid and sinapine were compared for their capacity to inhibit the formation of lipid oxidation products. Oxidation at 40°C was monitored by the formation of hydroperoxides (indicating primary oxidation products) and propanal (secondary oxidation products). The 70% methanolic extract of rapeseed meal, added as an equivalent of 500 μmol/kg oil (based on sinapic acid equivalent for sinapic acid-rich extracts or sinapine equivalent for sinapinerich extracts) showed good antioxidative activity compared with the addition of 500 μmol/kg oil sinapic acid. Apart from this, the interaction between a mixture of α-/γ-tocopherol and sinapic acid was investigated using response surface methodology for the experimental design. The experiments indicated that the addition of sinapic acid (concentration dependent) caused inhibition of peroxide formation, complementing further lower endogenous tocopherol concentration in oils. This paper was initially presented at the 95th AOCS Annual Meeting and Expo in Cincinnati, Ohio, May 1–4, 2004.