PAHs content in sunflower,soybean and virgin olive oils: Evaluation in commercial samples and during refining process

Polycyclic aromatic hydrocarbons (PAHs) are environmental carcinogenic compounds that may contaminate vegetable oils and their levels can be reduced by refining. In order to understand the influence of the refining steps, the content of 15 PAHs was assessed throughout alkaline refining in soybean, sunflower and olive oil samples. Eight commercial brands of these oils were also analysed. The analytical method involved a liquid–liquid extraction, a solid-phase clean up (C₁₈ and Florisil) followed by RP-HPLC with fluorimetric detection. The total PAHs content in the studied samples can be considered generally low. The light PAHs (2–4 rings) were predominant. Virgin olive oils showed the highest values (max. 26 μg/kg). An evident decrease of PAHs contents during alkaline refining was observed (71%, 88% and 85% in sunflower, soybean and olive oils, respectively) being more pronounced in light PAHs. Neutralization and, particularly, deodorization were the more effective steps contributing to the PAHs decrease. Bleaching was responsible for a slight increase in the PAHs content in soybean and olive oils.     

Analysis of polycyclic aromatic hydrocarbons in vegetable oils combining gel permeation chromatography with solid-phase extraction clean-up.

A semi-automatic method for the determination of polycyclic aromatic hydrocarbons (PAHs) in edible oils using a combined gel permeation chromatography/solid-phase extraction (GPC/SPE) clean-up is presented. The method takes advantage of automatic injections using a Gilson ASPEC XL sample handling system equipped with a GPC column (S-X3) and pre-packed silica SPE columns for the subsequent clean-up and finally gas chromatography-mass spectrometry (GC-MS) determination. The method was validated for the determination of PAHs in vegetable oils and it can meet the criteria for the official control of benzo[a]pyrene levels in foods laid down by the Commission of the European Communities. A survey of 69 vegetable oils sampled from the Danish market included olive oil as well as other vegetable oils such as rapeseed oil, sunflower oil, grape seed oil and sesame oil. Levels of benzo[a]pyrene in all the oils were low (<0.2-0.8 microg kg(-1)), except for one sample of sunflower oil containing 11 microg kg(-1) benzo[a]pyrene.     

Sources of contamination by polycyclic aromatic hydrocarbons in Spanish virgin olive oils

The presence of polycyclic aromatic hydrocarbons (PAHs) in virgin olive oils results from contamination on olive skins and the oil itself during processing. Determination of nine PAHs was carried out by isolation of the hydrocarbon fraction and subsequent clean-up by solid phase extraction, followed by RP-HPLC analysis using a programmable fluorescence detector. Contamination of olive skins depends directly on environmental pollution levels and inversely on fruit size. In the oil mill, PAHs levels were increased by contamination from combustion fumes during the extraction process. Other procedures, such as washing or talc addition during extraction, did not affect PAHs levels. High concentrations of PAHs were only found as a consequence of accidental exposure to contamination, such as direct contact of olives with diesel exhaust and oil extraction in a polluted environment.     

Sources of contamination by polycyclic aromatic hydrocarbons in Spanish virgin olive oils

The presence of polycyclic aromatic hydrocarbons (PAHs) in virgin olive oils results from contamination on olive skins and the oil itself during processing. Determination of nine PAHs was carried out by isolation of the hydrocarbon fraction and subsequent clean-up by solid phase extraction, followed by RP-HPLC analysis using a programmable fluorescence detector. Contamination of olive skins depends directly on environmental pollution levels and inversely on fruit size. In the oil mill, PAHs levels were increased by contamination from combustion fumes during the extraction process. Other procedures, such as washing or talc addition during extraction, did not affect PAHs levels. High concentrations of PAHs were only found as a consequence of accidental exposure to contamination, such as direct contact of olives with diesel exhaust and oil extraction in a polluted environment.     

Fast simultaneous determination of capsaicin,dihydrocapsaicin and nonivamide for detecting adulteration in edible and crude vegetable oils by UPLC-MS/MS

Capsaicinoids are pungent components in hot peppers, which have been detected in waste cooking oil. However, trace analysis of capsaicinoids in edible and crude vegetable oils is a challenging task due to the complex matrix. In this study, a simple liquid-liquid extraction and solid phase extraction (SPE) coupled with RP-UPLC-ESI-MS/MS method was developed for the quantification of capsaicinoids in edible and crude vegetable oils to screen the adulteration with waste cooking oil. This method was used to simultaneously determine 3 capsaicinoids (capsaicin, dihydrocapsaicin, and nordihydrocapsaicin) with capsaicin-d₃, and dihydrocapsaicin-d₃ as internal standards. This method allows the complete analysis of a sample in only an hour, even including sample preparation and chromatographic separation. The linear range of 3 capsaicinoids ranged between 0.5 and 40 µg/kg. The limit of detection (LOD) and limit of quantification (LOQ) for capsaicinoids were calculated as 0.15 and 0.5 µg/kg, respectively. Quantitative recoveries ranging from 92.9% to 105% were obtained by the analysis of spiked oil. The relative standard deviations were less than 5% (n = 6). The established method can potentially overcome the interference of triacylglycerols and fatty acids in edible and crude vegetable oils, and have been successfully applied to analyse real oil samples. This method provided a rapid and reliable method for the detection of adulteration of vegetable oils with waste cooking oils.     

Evaluation of polycyclic aromatic hydrocarbons content in different stages of soybean oils processing

A study was conducted in order to determine the levels of 13 polycyclic aromatic hydrocarbons (PAHs) in crude soybean oils produced in Brazil and to evaluate the influence of the refining process in their reduction. Analysis of intermediary products (neutralized, bleached and deodorized oils) showed that all compounds were reduced through refining (up to 88%). Neutralization and deodorization steps contributed effectively to the PAHs decrease. The mean total PAHs content in crude and deodorized oil samples ranged, respectively, from 10 to 316 and 3 to 69μg/kg. Since vegetable oils have been shown to be the major sources of PAHs in the diet, a monitoring program should be developed by the refining industries and the use of activated carbon during oil processing is highly recommended.     

Determination of polycyclic aromatic hydrocarbons in edible oils and barbecued food by HPLC/UV–Vis detection

Determination of nine polycyclic aromatic hydrocarbons in corn, sunflower, olive oils and barbecued meat and fish by HPLC/UV–Vis method is described. The extraction procedure included a saponification, liquid–liquid extraction and finally purification of PAHs through a house-made silica–alumina column. Chromatographic determination was based on separation of PAHs on ODS column and measurement at 254 nm. All polycyclic aromatic hydrocarbons were separated and analyzed in 12 min on reversed phase ODS column with acetonitrile/water mobile phase at 1.5 mL min⁻¹ flow rate. The detection limits of nine polycyclic aromatic hydrocarbons ranged from 0.26 to 1.15 μg L⁻¹ at a signal/noise ratio of 3. The linearity of the method was between 0.9951 and 0.9996. Oil samples contain different PAHs ranging from 0.44 to 98.92 μg L⁻¹. Barbecuing process increased the concentration (in the range of 2- to 8-fold) and caused the formation of PAHs in food samples.     

脂肪酸含量对植物油介电特性的影响

为了提供植物油在微波和射频等介电加热技术和通电加热技术中的应用基础数据,考察脂肪酸含量对植物油介电特性的影响,分别利用LCR阻抗测试仪和网络分析仪(同轴探针法)测量了4种植物油(橄榄油、自制橄榄油、橄榄调和油、大豆油)和5种脂肪酸(棕榈酸、硬脂酸、油酸、亚油酸、亚麻酸)在低频段(1 000 Hz~2 MHz)和高频段(300~10 000 MHz)的介电特性。结果表明:低频下,植物油的介电常数比较稳定,其均值为(1.56±0.02),介电损耗随着频率的增加而下降,其中0.7 MHz时橄榄油具有最大的介电常数(1.67±0.00)和介电损耗(7.31±0.02);高频下,植物油的介电特性随着频率的上升而缓慢下降,4种植物油之间的介电特性的差异不显著(p0.05);低频下,在植物油中加入油酸后,植物油的介电常数和介电损耗呈现先上升后下降的趋势,而添加亚油酸呈现相反的趋势。添加脂肪酸会加快油脂的氧化反应。     

Polycyclic aromatic hydrocarbons in Brazilian commercial soybean oils and dietary exposure

In this study the 13 polycyclic aromatic hydrocarbons (PAHs) identified as being genotoxic and carcinogenic by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) were determined in different brands of soybean oils available on the Brazilian market, totalling 42 samples. A solid-phase extraction (SPE) method for sample clean-up with a C₁₈ cartridge, followed by reversed-phase HPLC with fluorescence detection, was used for determination. The method showed good recoveries for most PAHs studied with values between 74% and 111%. Good intra- and inter-day precisions (0.5?<?RSD?<?11.9) and high correlation coefficients (r ^2?>?0.999) were obtained. The presence of PAHs was detected in all 42 samples with mean summed PAH levels ranging from 10.4 to 112.0?µg?kg^?1. The mean and maximum dietary exposures for total PAHs were estimated as 12.4 and 19.1?ng?kg?bw^?1?day^?1, respectively.     

冷冻除脂-气相色谱-串联质谱法检测食用植物油中30 种多环芳烃

建立冷冻除脂--气相色谱-串联质谱检测食用植物油中30?种多环芳烃（polycyclic aromatic hydrocarbons,PAH）的方法。选用6?种氘标记PAH为内标,样品经乙腈--丙酮溶液（4∶1,V/V）于离心管中涡旋提取,10?000?r/min离心5?min,－80?℃对油脂冷冻固化,倾出提取液,再经减压浓缩和氮气吹干,以二氯甲烷复溶,气相色谱--串联质谱多反应监测方式进行检测。结果表明,在相应质量浓度范围内30?种PAH均有良好线性（R2＞0.998）,检出限为0.10～1.83?μg/kg,定量限为0.35～6.11?μg/kg,在5、20?μg/kg和50?μg/kg添加水平下的回收率为67.77%～119.28%,相对标准偏差为1.18%～12.47%。采用本方法对市售11?类38?个食用植物油样品的检测显示,萘、1-甲基萘、2--甲基萘、联苯、2,6--二甲基萘、苊烯、苊、2,3,6--三甲基萘、芴、二苯并噻吩、菲、蒽、1-甲基菲、荧蒽、芘、环戊烯[c,d]芘、苯并[a]蒽、屈、苯并[b]荧蒽、苯并[k]荧蒽、苯并[e]芘和苯并[a]芘的检出率均为100%;5--甲基屈、苝、茚并[1,2,3--c,d]芘、二苯并[a,h]蒽、苯并[g,h,i]苝和二苯并[a,l]芘的检出率分别为86.84%、63.16%、81.58%、21.05%、81.58%和26.32%;二苯并[a,e]芘和二苯并[a,h]芘未检出;PAH总量为92.56～905.16?μg/kg,其中苯并[a]芘含量为1.94～7.40?μg/kg,依据食品安全标准限量,PAH处于较安全水平。     

Survey of polycyclic aromatic hydrocarbons of vegetable oils and oilseeds by GC-MS in China

There is a lack of information regarding the occurrence and content of contamination of polycyclic aromatic hydrocarbon (PAH) in edible vegetable oils and oilseeds used for oil production in China. By combining the advantages of ultrasound-assisted extraction, low temperature separation and silica SPE purification, a method for the determination of the USEPA, 16 PAHs was developed based on GC-MS to fill this gap. The method recoveries for oils and oilseeds were 84.4–113.8% and 84.3–115.3%, respectively. The LODs and LOQs for 16 PAHs were ranged from 0.06–0.17 and 0.19–0.56 μg kg^–1, respectively. Based on the established method, PAH concentrations in 21 edible oils and 17 oilseeds were determined. Almost all the PAHs were found in all the samples tested, especially the light PAHs (LPAHs). Three oil samples exceeded the maximum level of 10 μg kg^–1 for BaP set by China. However, five and six oil samples, respectively, exceeded the maximum limits of 2 and 10 μg kg^–1 set for BaP and PAH4 by the European Union. The concentrations of PAH16 in oilseed samples were 1.5 times higher than corresponding oil samples. The relationships between PAH4 and PAH8, PAH4 and PAH16 as well as PAH8 and PAH16 indicates that PAH4 is a sufficient surrogate for the contamination level of PAHs in edible oils when compared with PAH8.     

Polycyclic aromatic hydrocarbon content in commercial Spanish fatty foods

The levels of polycyclic aromatic hydrocarbons (PAHs) were determined by reversed-phase high-performance liquid chromatography with fluorescence detection in different fatty foods from a Spanish market. The average concentration of the sum of total PAHs in edible vegetable oils was below 25 ng/g, whereas the sum of heavy PAHs did not surpass 5 ng/g. Olive pomace oils obtained before the summer of 2001 were an exception because they were highly contaminated. The effects of different technological processes, such as bleaching, deodorization, and hydrogenation, on PAH concentration in edible oils have been studied. The PAH profiles, as well as the influence of cooking procedures, of other fatty foods (margarine, mayonnaise, and oils from canned fishes) have been examined.     

Changes in volatile compounds and oil quality with malaxation time of Tunisian cultivars of Olea europea

While there has been considerable work examining the effect of malaxation time on different characteristics of olive oils, there have been few that deal with all the major aspects. Here, the influence of malaxation time was evaluated using major local Tunisian (cv. Chemlali and Chetoui) cultivars. Standard characteristics were measured as well as detailed analyses of volatile compounds were conducted. Headspace solid‐phase microextraction (HS‐SPME) was applied to the analysis of volatile compounds of virgin olive oils from Chemlali and Chetoui varieties with differing malaxation time. Twenty‐seven compounds were characterised by GC‐FID and GC–MS. Compounds belonging mainly to alcohols, esters, aldehydes, ketones and hydrocarbons chemical classes characterized the volatile profile. Significant differences in the proportion of volatiles from oils of different malaxation time were detected. The results suggest that besides genetic factors, malaxation time influences volatile formation. The main variables that were affected by malaxation time were the total amount of phenols and composition of the volatile compounds. At malaxation time of 30 min, Chemlali and Chetoui olive oils presented the highest total phenol content (244.19 and 877.63 mg kg^?1, respectively), while the lowest content was observed at 60 min from regardless of cultivars. In turn, this influenced the oxidative stability and peroxide value. It was also clear that the cultivars behaved differently and this prevented general conclusions being made for all of the quality characteristics.     

Single-laboratory validation of a saponification method for the determination of four polycyclic aromatic hydrocarbons in edible oils by HPLC-fluorescence detection

An analytical method is reported for the determination of four polycyclic aromatic hydrocarbons (benzo[a]pyrene (BaP), benz[a]anthracene (BaA), benzo[b]fluoranthene (BbF) and chrysene (CHR)) in edible oils (sesame, maize, sunflower and olive oil) by high-performance liquid chromatography. Sample preparation is based on three steps including saponification, liquid–liquid partitioning and, finally, clean-up by solid phase extraction on 2 g of silica. Guidance on single-laboratory validation of the proposed analysis method was taken from the second edition of the Eurachem guide on method validation. The lower level of the working range of the method was determined by the limits of quantification of the individual analytes, and the upper level was equal to 5.0 µg kg^?1. The limits of detection and quantification of the four PAHs ranged from 0.06 to 0.12 µg kg^?1 and from 0.13 to 0.24 µg kg^?1. Recoveries of more than 84.8% were achieved for all four PAHs at two concentration levels (2.5 and 5.0 µg kg^?1), and expanded relative measurement uncertainties were below 20%. The performance of the validated method was in all aspects compliant with provisions set in European Union legislation for the performance of analytical methods employed in the official control of food. The applicability of the method to routine samples was evaluated based on a limited number of commercial edible oil samples.     

Contribution of olive seed to the phenolic profile and related quality parameters of virgin olive oil

BACKGROUND: Conflicting results have been reported about the effect of fruit de‐stoning on the virgin olive oil (VOO) phenolic profile. The aim of the present study was to determine whether olive seed plays any role in the synthesis of this oil phenolic fraction. RESULTS: Increases of around 25% of total phenolic compounds were observed in oils obtained from de‐stoned olive fruits in three main Spanish cultivars. To investigate the involvement of olive seed in determining the phenolic profile of VOO, whole intact olive fruits were added with up to 400% olive stones. Excellent regression coefficients were found in general for the decrease of total phenolic compounds and, particularly, of o‐diphenolics in the resulting oils. On the other hand, it was found that olive seed contains a high level of peroxidase (POX) activity (72.4 U g^?1 FW), accounting for more than 98% of total POX activity in the whole fruit. This activity is able to modify VOO phenolics in vitro, similar to the effect of adding stones during VOO extraction. CONCLUSION: Olive seed plays an important role in determining VOO phenolic profile during the process to obtain an oil that seems to be associated with a high level of POX activity. Copyright © 2007 Society of Chemical Industry     

Gas chromatography-mass spectrometry (GC-MS) method for the determination of 16 European priority polycyclic aromatic hydrocarbons in smoked meat products and edible oils

A gas chromatography-mass spectrometry (GC-MS) method was developed for the analysis of 15 polycyclic aromatic hydrocarbons (PAHs) highlighted as carcinogenic by the Scientific Committee on Food (SCF) plus benzo[c]fluorine (recommended to be analysed by the Joint FAO/WHO Expert Committee on Food Additives (JECFA)) in fat-containing foods such as edible oils and smoked meat products. This method includes accelerated solvent extraction (ASE) and the highly automated clean-up steps gel permeation chromatography (GPC) and solid-phase extraction (SPE). Using a VF-17ms GC column, a good separation of benzo[b]fluoranthene, benzo[j]fluoranthene and benzo[k]fluoranthene was achieved. Furthermore, the six methylchrysene isomers and the PAH compounds with a molecular weight of 302 Daltons in fat-containing foods attained a better chromatographic separation in comparison with a 5-ms column. The reliability of the analytical method for edible oils was demonstrated by the results from a proficiency test. Measurements with GC-high-resolution mass spectroscopy (HRMS) and gas chromatography-mass selective detection (GC-MSD) led to comparable results. A survey of the 16 PAHs in 22 smoked meat products showed concentrations in the range <0.01–19 µg kg^?1. The median concentration for benzo[a]pyrene was below 0.15 µg kg^?1.     

Determination of polycyclic aromatic hydrocarbons (PAH) in edible vegetable oils by liquid chromatography and programmed fluorescence detection. Comparison of caffeine complexation and XAD-2 chromatography sample clean-up

Two clean-up procedures were compared for the analysis for polycyclic aromatic hydrocarbons (PAHs) in edible vegetable oils. One method comprises a liquid-liquid extraction followed by XAD-2 chromatography and the other a caffeine-formic acid complexation. The clean-up step is followed by gradient reversed-phase HPLC in combination with wavelength-programmed fluorescence detection. Due to better repeatability and simplicity, the XAD-2 method was selected for the determination of PAHs in 14 different vegetable oils. Between the different oil samples large differences were observed in PAH concentrations. PAH concentrations in vegetable oils sampled from the Dutch market appear to be comparable with those found in other countries.     

Saturated hydrocarbon content in olive fruits and crude olive pomace oils

Olive fruits contain an n-alkane series of saturated hydrocarbons mainly in the pulp. Lower amounts of a complex mixture of paraffins, unresolved by gas chromatography (UCM – unresolved complex mixture), have been found in cuticle, stone (woody shell and seed), olive leaves, and talc used as an aid to olive oil extraction. The amounts of both kinds of hydrocarbons are related to the olive cultivar and are transferred to oils in a proportion depending on the oil-obtaining process (centrifugation or solvent extraction). In olive oil obtained by centrifugation, only n-alkanes were detected. However, in olive oil extracted by second centrifugation, small amounts of UCM paraffins were detected together with the n-alkanes. Olive pomace oils showed a very variable content of both types of hydrocarbons according to the different obtaining process, such as double centrifugation, solvent extraction or centrifugation followed by solvent extraction. ‘White mineral oil’ used in oil extraction machinery is the source of the high concentrations of UCM paraffins found in some olive and olive pomace oils. In the case of second centrifugation olive oil, a maximum limit of 50 mg kg^?1 of UCM is suggested, whereas in the case of crude olive pomace oil, it amounts to 250 mg kg^?1 plus an additional minimum of 1.0 for the n-alkanes/UCM ratio.     

Differential scanning calorimetry thermal properties and oxidative stability indices of microwave heated extra virgin olive oils

BACKGROUND: The use of differential scanning calorimetry (DSC) for assessing the deterioration effect of microwave heating on vegetable oils, and on olive oils in particular, has been partially explored in literature. The aim of this work was to evaluate the potential of DSC to discriminate among microwaved extra virgin olive oils (EvOo from different olive cultivar and origin), according to changes on thermal properties (upon cooling and heating) and traditional oxidative stability indices (peroxide, p‐anisidine and TOTOX values). RESULTS: An elevated value of lipid oxidation was reached by the most unsaturated EvOo sample (9.5% of linoleic acid) at 6 min of microwave treatment. Free acidity significantly increased (0.42%) only for the oil sample with the highest water content (874 mg kg^?1 oil) at the longest time of treatment. Crystallisation enthalpies significantly decreased and the major exothermic peak shifted towards lower temperature, leading to enlargement of the transition range in all samples due to the formation of weak and mixed crystals among triacylglycerols and lipid degradation products. On the contrary, thermal properties upon heating appeared to similarly vary among samples. CONCLUSIONS: The analysis of DSC thermal properties upon cooling seemed to clearly discriminate among different EvOo samples after microwaving. The relation between changes of thermal properties and oxidation parameters should be further studied using additional oxidative stability indices on a larger set of oil samples, due to the complexity of EvOo composition. Copyright © 2010 Society of Chemical Industry     

Distribution and retention of phytosterols in frying oils and fried potatoes during repeated deep and pan frying

The retention and distribution of phytosterols in fried oils and French-fries during eight successive pan- and deep-frying sessions of pre-fried potatoes in sunflower oil, palm oil, cottonseed oil, virgin olive oil and a vegetable shortening were evaluated. Phytosterols (β-sitosterol, campesterol, stigmasterol, Δ⁵-avenasterol) were determined in the unsaponifiable fraction of frying oils and lipids extracted from French-fries by GC/FID after derivatization to trimethylsilyl ethers. French-fries were enriched with phytosterols due to the absorption of frying oil, with β-sitosterol predominating in both fried oils and potatoes. The amount of phytosterols decreased during frying, their overall retentions reaching 9.5–22.8% and 29.4–51.2% after eight successive pan- and deep-frying sessions, respectively, while their deterioration was found to be affected by frying time, frying technique, being more prolonged during pan-frying, and by the oils’ unsaturation, being more extended in polyunsaturated oils. Phytosterols were more or less uniformly distributed between the fried oil and the fried potatoes. The phytosterols dietary intake by consuming potatoes fried in the oils tested is discussed.