Comparison and analysis of fatty acids, sterols, and tocopherols in eight vegetable oils

The similarities and differences of eight vegetable oils produced in China were investigated in terms of their fatty acid, sterol, and tocopherol compositions and subsequent data processing by hierarchical clustering analysis and principal component analysis. The lipid profiles, acquired by analytical techniques tailored to each lipid class, revealed great similarities among the fatty acid profiles of corn and sesame oil as well as few differences in their sterol profiles. It turns out that not only was there great similarity between the fatty acid profiles of corn oil and sesame oil but also there were not too many differences for the sterol profiles. Sunflower and tea-seed oil showed similar sterol compositions, while the tea-seed oil tocopherol was very similar to palm oil. The results demonstrated that the use of only one of these profiles was unreliable for indentifying oil origin and authenticity. In contrast, the use of the sterol or tocopherol profile together with the fatty acid profile more accurately discriminates these oils.     

Quantification of tocopherols and tocotrienols in portuguese olive oils using HPLC with three different detection systems

Three different HPLC detection systems were compared for the determination of tocopherols and tocotrienols in olive oil: fluorescence and diode array connected in series, ultraviolet, and evaporative light scattering. The best results were obtained with the fluorescence detector, which was successfully applied in the quantification of tocopherols and tocotrienols in 18 samples of Portuguese olive oils. To support the validity of the method, the parameters evaluated were linearity, detection limits, repeatability, and recovery. All of the studied samples showed similar qualitative profiles with six identified compounds: alpha-T, beta-T, gamma-T, delta-T, alpha-T3, and gamma-T3. Alpha-tocopherol (alpha-T) was the main vitamin E isomer in all samples ranging from 93 to 260 mg/kg. The total tocopherols and tocotrienols ranged from 100 to 270 mg/kg. Geographic origin did not seem to influence the tocopherol and tocotrienol composition of the olive oils under evaluation.     

Fluorescence of vegetable oils: olive oils

Fluorescence spectra of undiluted extra virgin olive oil obtained with the traditional setup (right-angle fluorescence) show considerable artifacts and deformations due to self-absorption phenomena, even when the spectra are corrected for inner filter effects. On the other side, front-face fluorescence spectra are much less affected by self-absorption. Front-face fluorescence of native olive oil reveals the presence of different fluorophores and can provide information about their amount. From the intense emission at ca. 315-330 nm, it is possible to detect fluorescent polyphenols and pherols and to evaluate their overall content. Low-intensity emission bands at 350-600 nm are correlated to vitamins and other important molecules. Among them, the fluorescence of the riboflavin fluorophore can be used to evaluate its concentration. The intense emission of chlorophyll derivatives, measured in the 640-800 nm spectral region, can provide information on their concentration.     

Influence of deep frying on the unsaponifiable fraction of vegetable edible oils enriched with natural antioxidants

The influence of deep frying, mimicked by 20 heating cycles at 180 °C (each cycle from ambient temperature to 180 °C maintained for 5 min), on the unsaponifiable fraction of vegetable edible oils represented by three characteristic families of compounds (namely, phytosterols, aliphatic alcohols, and triterpenic compounds) has been studied. The target oils were extra virgin olive oil (with intrinsic content of phenolic antioxidants), refined sunflower oil enriched with antioxidant phenolic compounds isolated from olive pomace, refined sunflower oil enriched with an autoxidation inhibitor (dimethylpolysiloxane), and refined sunflower oil without enrichment. Monitoring of the target analytes as a function of both heating cycle and the presence of natural antioxidants was also evaluated by comparison of the profiles after each heating cycle. Identification and quantitation of the target compounds were performed by gas cromatography-mass spectrometry in single ion monitoring mode. Analysis of the heated oils revealed that the addition of natural antioxidants could be an excellent strategy to decrease degradation of lipidic components of the unsaponifiable fraction with the consequent improvement of stability.     

近红外光谱快速检测食用油必需脂肪酸

为了建立食用油必需脂肪酸快速检测的方法,该研究提出了基于近红外光谱技术检测食用油中α-亚麻酸和亚油酸含量的快速测定方法。对光谱信息分别采用偏最小二乘回归方法(PLS)和最小二乘支持向量机(LS-SVM)建立模型。比较了多种光谱预处理方法对模型预测能力的影响。结果表明对于亚油酸含量的预测,采用Savitzky-Golay平滑法结合多元散射校正(MSC)的光谱预处理所建立的LS-SVM模型最优。预测集的决定系数(R2)、预测均方根误差(RMSEP)和剩余预测偏差(RPD)分别达到了0.989,0.0161和9.4783。对于α-亚麻酸含量的预测,采用Savitzky-Golay平滑法结合标准正态变换(SNV)的光谱预处理所建立的LS-SVM模型最优。α-亚麻酸含量预测结果的R2、RMSEP和RPD为0.972,0.0036和6.0561,据此表明,应用近红外光谱技术能够检测食用油中α-亚麻酸和亚油酸的含量,为快速检测食用油的必需脂肪酸提供了参考。     

NIR spectroscopy and partial least-squares regression for determination of natural alpha-tocopherol in vegetable oils

Near-infrared (NIR) spectroscopy and partial least-square regression were used for determination of alpha-tocopherol in edible oils after extraction with ethanol. The standard error of calibration and the standard error of prediction were calculated for evaluation of the calibration models. The chemometric calibration model was prepared in spectral region 6500-4500 cm(-1) for standard alpha-tocopherol solutions (0.54-53.54 mg/mL). Obtained mean concentrations of natural alpha-tocopherol in different types of oils varied from 17.53 to 57.10 mg/100 g. Net analyte signal calculation was used to estimate detection limit (DL = 0.12 mg/mL), quantification limit (QL = 0.40 mg/mL), sensitivity (SEN = 0.045 mg/mL), and selectivity (SEL ranged between 0.24 and 0.54% of the measured reflectance signal) of the proposed NIR method. The comparable precision (RSD = 0.68-2.80% and 0.79-3.06%) and accuracy (recovery, 97.2-102.4% and 96.8-103.2%) for the proposed NIR and standard HPLC methods, demonstrate the benefit of the NIR method in the routine analysis of alpha-tocopherol in vegetable oils.     

Determination of coenzyme Q10, coenzyme Q9, and melatonin contents in virgin argan oils: comparison with other edible vegetable oils

Virgin argan oil possesses high antioxidant capacity (AC), which may be partially explained by its high content in antioxidant molecules such as polyphenols and tocopherols. However, the content in other antioxidant molecules, for example, coenzyme Q10 (CoQ(10)), coenzyme Q9 (CoQ(9)), and melatonin (Mel), which have been identified in other edible vegetable oils, have not been evaluated in virgin argan oil. Consequently, it was decided to evaluate the contents of CoQ(10), CoQ(9), and Mel in virgin argan oils and compare the results to those obtained in extra virgin olive oils and some varieties of seed oils. By the use of sensitive HPLC-EC/F methods, the results showed that virgin argan oil is a rich source of CoQ(10) and Mel, but no CoQ(9) was detected. Extra virgin olive oil showed higher levels of CoQ(10) and lower levels of Mel than virgin argan oil. Between the seed oil samples, only virgin soybean oil showed higher CoQ(10) and Mel levels than virgin argan oil. The results may be relevant for the contribution of CoQ(10) and Mel to the biological activities of virgin argan oil.     

Determination of aflatoxins in vegetable oils

A simple method is proposed for determination of aflatoxins in vegetable oils. The method was successfully applied to both crude and degummed oils. The oil sample, dissolved in hexane, was applied to a silica column and washed with ether, toluene, and chloroform; aflatoxins were eluted from the column with chloroform-methanol (97 + 3). As quantitated by thin layer chromatography and liquid chromatography, the oils analyzed contained aflatoxin B1 at levels of 5-200 micrograms/kg. Recoveries of aflatoxin B1 standards added to aflatoxin-free oils were between 89.5 and 93.5%, with coefficients of variation of 6.3-8.0%.     

Antithrombotic lipid minor constituents from vegetable oils. Comparison between olive oils and others

Many epidemiological studies suggest that vegetable oils and especially olive oil present a protective effect against atherosclerosis. In this study, total lipids (TL) of Greek olive oils and seed oils of four kinds, namely, soybean, corn, sunflower, and sesame oil, were separated into total polar lipids (TPL) and total neutral lipids (TNL) via a novel extraction procedure. TPL and TNL of olive oil were fractionated by HPLC for further study. Each lipid fraction from HPLC separation along with TL, TPL, and TNL lipid samples from oils were tested in vitro for their capacity to induce or to inhibit washed rabbit platelet aggregation. Comparison between olive and seed oils supports the superiority of olive oil as high levels of platelet activating factor (PAF) antagonists have been detected, mainly in TPL. In addition, the structure of the most active fraction from olive oil was elucidated, as a glycerol-glycolipid. Because it has already been reported that PAF plays a pivotal role in atherogenesis, the existence of PAF agonists and antagonists in vegetable oils may explain their protective role against atherosclerosis.     

One-pot synthesis of chemically modified vegetable oils

Vegetable oils are promising candidates as substitutes for petroleum base oils in lubricant applications, such as total loss lubrication, military applications, and outdoor activities. Although vegetable oils have some advantages, they also have poor oxidation and low temperature stability. One of the ways to address these issues is chemical modification of fatty acid chain of triglyceride. We report a one-pot synthesis of a novel class of chemically modified vegetable oils from epoxidized triacylglycerols and various anhydrides. In an anhydrous solvent, boron trifluoride etherate is used as catalyst to simultaneously open the oxirane ring and activate the anhydride. The reaction was monitored and products confirmed by NMR, FTIR, GPC, and TGA analysis. Experimental conditions were optimized for research quantity and laboratory scale-up (up to 4 lbs). The resultant acyl derivatives of vegetable oil, having diester substitution at the sites of unsaturation, have potential in formulation of industrial fluids such as hydraulic fluids, lubricants, and metal working fluids.     

Quantification of total furocoumarins in citrus oils by HPLC coupled with UV, fluorescence, and mass detection

Furocoumarins or psoralens represent a class of photosensitizers whose use level is likely to be restricted to 1 ppm in cosmetic products by the EU. A reversed-phase HPLC method was developed to separate the 15 main furocoumarins present in citrus oils. Quantification by UV, fluorescence, or mass detectors was compared in terms of linearity and limit of detection. Cold-pressed oils of different citrus species were analyzed using this method. This method could be implemented in quality control laboratories equipped with an HPLC system and a UV diode array detector. Because of possible coelutions, the UV-spectral data should be carefully examined to avoid misleading interpretations of peaks.     

酶法脱胶在植物油脂精炼中的应用进展

酶法脱胶作为一种新型的植物油脂脱胶工艺,与传统脱胶工艺相比,具有脱胶完全、用水量和废水排放少、耗能低、精炼得率高等经济、环保的优点,因而备受各国油脂加工业的关注。随着酶法脱胶技术的发展,已有多种磷脂酶（A1、A2、B、C）应用于植物油脂脱胶;酶法脱胶工艺也从简单地优化基本参数（脱胶温度、酶添加量、pH值和加水量等）到结合优化酸预处理、水酶和油脂混合程度来提高脱胶效率,从单一酶脱胶工艺发展到复合酶脱胶工艺,由游离酶脱胶发展到固定化酶脱胶。该文介绍了植物油脂酶法脱胶工艺中使用的磷脂酶,综述分析了酶法脱胶工艺设计与应用现状及存在的问题。提出需综合考虑脱胶效果、磷脂改性副产品加工价值及植物毛油品质等因素,选择合适的磷脂酶和脱胶工艺才能使酶法脱胶同时达到低耗和经济的效果。目前制约酶法脱胶工艺大规模应用的一个重要因素是现有磷脂酶催化性能差,可通过酶人工改造技术提高磷脂酶活性和抗逆性从而解决目前酶法脱胶时间长,脱胶温度低等问题。因此开发性能优良的磷脂酶,并且相应地设计更节能、环保的脱胶工艺是未来植物油脂酶法脱胶研究的主要目标。     

Development of multiresidue analysis for twenty phthalate esters in edible vegetable oils by microwave-assisted extraction-gel permeation chromatography-solid phase extraction-gas chromatography-tandem mass spectrometry

A novel multiresidue analysis method is developed for the determination of twenty phthalate esters at the μg/kg level in edible vegetable oils by microwave-assisted extraction-gel permeation chromatography-solid phase extraction-high resolution gas chromatography-tandem mass spectrometry (MAE-GPC-SPE-HRGC-MS/MS). The samples were extracted with methanol under microwave incubation. Cleanup was carried out with GPC followed by a further C18 SPE column and then separated by the HP-5MS capillary column under a temperature program. The eluents were qualitatively and quantitatively determined by tandem mass analyzer with selected reaction monitoring (SRM) type and positive ion mode. The calibration curves showed good linearity in the range 5 μg/kg to 2.50 mg/kg with correlation coefficients larger than 0.999. Low detection limits (LODs) of 0.218-1.367 μg/kg and quantification limits (LOQ) of 0.72-4.51 μg/kg were achieved. The mean recoveries were in the range from 93.04% to 104.6% at 5, 15, and 40 μg/kg spiked levels, and the relative standard deviations (RSDs) were in the range of 1.01% and 5.26% (n = 7). This method could potentially overcome the interference from large amounts of lipids and pigment. The real sample test showed this method can be used for sensitive and accurate determination and confirmation of phthalate ester residues in high-fat and complex samples.     

Lubricant base stock potential of chemically modified vegetable oils

The environment must be protected against pollution caused by lubricants based on petroleum oils. The pollution problem is so severe that approximately 50% of all lubricants sold worldwide end up in the environment via volatility, spills, or total loss applications. This threat to the environment can be avoided by either preventing undesirable losses, reclaiming and recycling mineral oil lubricants, or using environmentally friendly lubricants. Vegetable oils are recognized as rapidly biodegradable and are thus promising candidates as base fluids in environment friendly lubricants. Lubricants based on vegetable oils display excellent tribological properties, high viscosity indices, and flash points. To compete with mineral-oil-based lubricants, some of their inherent disadvantages, such as poor oxidation and low-temperature stability, must be corrected. One way to address these problems is chemical modification of vegetable oils at the sites of unsaturation. After a one-step chemical modification, the chemically modified soybean oil derivatives were studied for thermo-oxidative stability using pressurized differential scanning calorimetry and a thin-film micro-oxidation test, low-temperature fluid properties using pour-point measurements, and friction-wear properties using four-ball and ball-on-disk configurations. The lubricants formulated with chemically modified soybean oil derivatives exhibit superior low-temperature flow properties, improved thermo-oxidative stability, and better friction and wear properties. The chemically modified soybean oil derivatives having diester substitution at the sites of unsaturation have potential in the formulation of industrial lubricants.     

Classification of edible oils by employing 31P and 1H NMR spectroscopy in combination with multivariate statistical analysis. A proposal for the detection of seed oil adulteration in virgin olive oils

A combination of (1)H NMR and (31)P NMR spectroscopy and multivariate statistical analysis was used to classify 192 samples from 13 types of vegetable oils, namely, hazelnut, sunflower, corn, soybean, sesame, walnut, rapeseed, almond, palm, groundnut, safflower, coconut, and virgin olive oils from various regions of Greece. 1,2-Diglycerides, 1,3-diglycerides, the ratio of 1,2-diglycerides to total diglycerides, acidity, iodine value, and fatty acid composition determined upon analysis of the respective (1)H NMR and (31)P NMR spectra were selected as variables to establish a classification/prediction model by employing discriminant analysis. This model, obtained from the training set of 128 samples, resulted in a significant discrimination among the different classes of oils, whereas 100% of correct validated assignments for 64 samples were obtained. Different artificial mixtures of olive-hazelnut, olive-corn, olive-sunflower, and olive-soybean oils were prepared and analyzed by (1)H NMR and (31)P NMR spectroscopy. Subsequent discriminant analysis of the data allowed detection of adulteration as low as 5% w/w, provided that fresh virgin olive oil samples were used, as reflected by their high 1,2-diglycerides to total diglycerides ratio (D > or = 0.90).     

Cluster analysis applied to the exploratory analysis of commercial spanish olive oils by means of excitation-emission fluorescence spectroscopy

Olive oil fluorescence is related to oil composition. Here it is shown that the natural clustering of different types of commercial Spanish olive oils depends on their fluorescence excitation-emission matrices (EEMs). Fifty-six commercial samples of olive oil (29 virgin olive oils, 20 pure olive oils, and 7 olive-pomace oils) were used. The clustering method was hierarchical agglomerative clustering using the Euclidean distance as a similarity measure and the average linkage. Two spectral ranges were considered (which either contained the fluorescence peak of the chlorophylls or did not), and various methods for preprocessing the fluorescence spectra were compared. The oils were clearly distinguished using the unfolded EEMs measured between lambda(ex) = 300-400 nm and lambda(em) = 400-600 nm. The optimal preprocessing was normalization of the unfolded spectra followed by column autoscaling. Also shown are the advantages of using second-order data (EEMs) instead of first-order data (a single fluorescence spectrum) for each sample.     

Acidolysis reactions lead to esterification of endogenous tocopherols and compromised oxidative stability of modified oils

For the first time, a possible mechanism responsible, in part, for the removal of endogenous antioxidants through the formation of tocopheryl esters during acidolysis reactions is proposed and confirmed. Tocopherols in the oils were found to react with carboxylic acids present in the medium, thus leading to the formation of tocopheryl esters that do not render any stability to the resultant modified oils as they lack any free hydroxyl groups on the phenolic ring of the molecule. Tocopheryl oleate, used as a standard, was synthesized through the reaction of acyl chloride of oleic acid with alpha-tocopherol (m/z 695.5 as evidenced by mass spectrometry). Subsequently, lipase-assisted esterification of alpha-, gamma-, and delta-tocopherols with oleic acid was carried out, and corresponding tocopheryl esters were isolated. In a real acidolysis reaction system involving docosahexaenoic acid single-cell oil and capric acid, high-performance liquid chromatography-mass spectrometry analysis demonstrated the presence of several tocopheryl esters. These included tocopheryl esters of myristic acid, namely, alpha-tocopheryl myristate, m/z 641.1, gamma-tocopheryl myristate, m/z 627.1, and delta-tocopheryl myristate, m/z 613.1, as well as those of palmitic acid, namely, alpha-tocopheryl palmitate, m/z 669.1, gamma-tocopheryl palmitate, m/z 655.1, and delta-tocopheryl palmitate, m/z 641.1. The mixture also contained different species of tocopheryl oleates, namely, alpha-tocopheryl oleate, m/z 695.5, gamma-tocopheryl oleate, m/z 681.1, and delta-tocopheryl oleate, m/z 667.2. Esters produced from reactions of docosahexaenoic acid and tocopherols were also detected, namely, alpha-tocopheryl docosahexaenoate, m/z 738.7, and delta-tocopheryl docosahexaenoate, m/z 710.7.     

Quantitative determination of hydroxy pentacyclic triterpene acids in vegetable oils

A simple and precise analytical method for the determination of hydroxy pentacyclic triterpene acids (HPTAs) in vegetable oils was developed. The acidic fraction was isolated by solid-phase extraction using bonded aminopropyl cartridges, and the extract was silylated and analyzed by gas chromatography. Repeatability and recovery of the method were determined. In virgin olive oils, similar amounts of oleanolic (3beta-hydroxyolean-12-en-28-oic) and maslinic (2alpha,3beta-dihydroxyolean-12-ene-28oic) acids and traces of ursolic (3beta-hydroxyurs-12-en-28-oic) acid were found. The main factor affecting HPTA concentration was the oil quality since that increases as the quality decreases, while olive variety, olive ripeness, and oil extraction system had less influence. In crude olive pomace oils, the concentrations were very much higher than in virgin olive oils. During refining processes, total or significant losses of HPTAs were observed. Esterified derivatives of HPTAs were not found.