Detection of low‐quality extra virgin olive oils by fatty acid alkyl esters evaluation: a preliminary and fast mid‐infrared spectroscopy discrimination by a chemometric approach

A set of eighty‐one extra virgin olive oils (EVOOs) was analysed according to the new quality parameters relative to the total amount of methyl and ethyl esters of fatty acids [Σ (FAMEs + FAEEs)] and the ratio between ethyl and methyl esters [ratio of FAEEs/FAMEs (RFF)]. Acquisition of the mid‐infrared spectra was also performed by Fourier Transform Infrared Spectroscopy (FT‐IR). Chemical and spectroscopy data were chemometrically elaborated, and FT‐IR coupled by Partial Least Square (PLS) methodology was developed. Results were statistically similar to official procedure in terms of analytical performance for Σ (FAMEs + FAEEs) and RFF in EVOOs: a good agreement between predicted and actual values on calibration data sets was found (0.98 and 0.83, respectively) and the limit of quantification was low enough (29.3 mg kg^?1) considering the actual limits for Σ (FAMEs+ FAEEs). This new approach, time‐saving and environmentally friendly, can be considered as a useful tool for screening procedures.     

Characteristics of olive fruits and extra‐virgin olive oils obtained from olive trees growing in Appellation of Controlled Origin ‘Sierra Mágina’

Olives and olive oils from Appellation of Controlled Origin (ACO) ‘Sierra Mágina’ have been analysed during the 1997/98 harvest. The territory of this ACO has been subdivided into four zones of different characteristics. The olives were harvested on two occasions (November 1997 and January 1998). Various parameters were analysed, such as the ripening index, the average volume, the average weight of 100 olives and 100 stones, the pulp/stone ratio, the industrial yield, etc. From these olives, olive oils were extracted using an Abencor system, and the free acidity, the peroxide index, the coefficients K₂₇₀ and K₂₃₂ and the fatty acid composition were determined. The analysis of the results obtained, as well as principal component analysis, demonstrates a marked variability in the fruits, but the corresponding olive oils show fairly homogeneous compositions that are difficult to distinguish by sensory analysis. The olive oils from this ACO are extra‐virgin olive oils characterised by low acidity, a high content of oleic acid and a high ratio of unsaturated to saturated fatty acids. The most important sensory attributes are fruity, woody‐fig, green, bitter and pungent. Copyright © 2003 Society of Chemical Industry     

Quality assessment of edible vegetable oils used as liquid medium in canned tuna

An experimental investigation was conducted to assess the quality of vegetable oils used as liquid medium in preserved fish. Sixteen tuna preserves were tested, including two in extra virgin olive oil, nine in olive oil (refined olive oil plus virgin olive oil) and five in refined seed oil. Next to the traditional routine analyses prescribed by the EEC Regulation N° 2568/91 (useful for a preliminary characterisation of oils used as liquid medium), the content of trans isomers of unsaturated fatty acids was determined and the analysis of polar compounds was performed by HPSEC (high performance size-exclusion chromatography). The acid composition showed the presence of highly unsaturated fatty acids, typical of fish lipids. Trans isomers were always absent in extra virgin olive oils, whereas they were always present in olive oils and in refined seed oils. Triglyceride oligopolymers, oxidised triglycerides and diglycerides, measured by means of the HPSEC analysis of polar compounds, ranged within 0.13-1.07%, 0.51-2.36% and 0.96-4.02%, respectively. The HPSEC analysis of polar compounds and the determination of trans isomers enabled better assessment of the quality of different types of oils used as liquid medium for canned tuna.     

食用植物油脂肪酸的高分辨气相色谱分析

提出用一种经过改进的方法制备食用植物油的脂肪酸甲酯衍生物，并利用高分辨率毛细管柱分析其中脂肪酸的组成和含量。在确定的气相色谱操作条件下，所用的毛细管柱不仅能够测定食用植物油中的主要成分，而且可测得花生油中含量低至10mg／L数量级的痕量芥酸成分。     

应用脂肪酸甲酯快速筛选植物油中掺假地沟油

根据植物油和地沟油中脂肪酸酯存在方式的不同,建立植物油中地沟油掺假的快速筛选方法。植物油中脂肪酸是以甘油三酯的形式存在,地沟油中脂肪酸以脂肪酸甲酯的形式存在,利用气相色谱-质谱的全扫描模式,结合NIST 05标准谱库检索功能,对37 种脂肪酸甲酯进行测定。样品采用直接稀释-气相色谱-质谱全扫描分析脂肪酸甲酯,100 个植物油样品中均未检出脂肪酸甲酯;20 个地沟油样品中13 个检出肉豆蔻酸甲酯（C14∶0）、棕榈酸甲酯（C16∶0）和硬脂酸甲酯（C18∶0）等14 种脂肪酸甲酯,检出率为65%,且70%的检出脂肪酸甲酯的地沟油样品中脂肪酸甲酯种类多、含量较高。因此,若植物油样品脂肪酸甲酯种类多、含量高,则可判定为有地沟油掺假;若脂肪酸甲酯含量低或没有脂肪酸甲酯,则可以进一步用其他指标和方法进行检测,脂肪酸甲酯的检测方法可以作为地沟油掺假的快速粗筛方法。     

基于植物油中脂肪酸烷基酯含量变化鉴别废弃油脂

采用固相萃取柱净化,气相色谱-质谱联用法测定了6种植物油中脂肪酸烷基酯(包括脂肪酸甲酯和脂肪酸乙酯)的含量,并研究其在植物油煎炸、废弃及废弃油脂精炼等环节中的变化。结果发现,6种植物油中脂肪酸烷基酯的含量均低于30 mg/kg,而植物油在废弃过程中可能会形成大量脂肪酸乙酯,生成量与油脂是否烹饪及废弃物中乙醇含量有关。脂肪酸烷基酯在脱色工艺中不能被去除,但在脱臭中可被去除。因此,可以通过测定植物油中脂肪酸烷基酯含量发现废弃油脂,为废弃油脂的鉴别工作提供新的思路。     

Evaluation of potential and real quality of virgin olive oil from the designation of origin “Aceite Campo de Montiel” (Ciudad Real,Spain)

The potential and real qualities of virgin olive oils from the DO “Aceite Campo de Montiel” were evaluated. The regulated physicochemical and sensory parameters, the stability parameters and the fatty acid, sterol and triterpenic dialcohol compositions were analysed. The results of the regulated parameters in the potential quality study classified all the analysed oils into the “extra virgin” category. The varieties Picual and Cornicabra showed remarkably high stability, due to their high tocopherol and total polyphenol contents. Oleic and linoleic acids were the most useful fatty acids used to discriminate the predominant varieties, Picual and Cornicabra, from the others. The variety Cornicabra stood out due to its high campesterol content, Arbequina due to its low β-sitosterol content and high 24-methylenecholesterol, Δ5-avenasterol, Δ7-stigmastenol and total sterol contents, and Picual for its high sitostanol content. All the analysed samples in the real quality study were classified in the “extra virgin” category according to the regulated physicochemical parameters, but only 69% of them qualified if the sensory parameters were also taken into account. The predominance of the varieties Picual and Cornicabra in the study area was mainly responsible for the high oil stability and reflects the fatty acid and sterol compositions of the oils from the oil mills in the potential quality study.     

Determination of the content of wax esters in some sea foods and their molecular composition. A comparison with ω-3 enriched wax esters

Wax esters enriched in ω-3 fatty acids have been recently shown to be readily absorbed by rats after dietary supplementation. Wax esters are less prone to oxidation and can be better formulated than liquid ω-3 derivatives. All these characteristics suggest a possible use of wax esters enriched in ω-3 as food supplements. However, some naturally occurring wax esters are defined as scarcely digestible (jojoba oil, spermaceti). On the other hand, wax esters have been found in several sources of marine origin, which can enter normal foodstuff. In order to better understand the digestibility of wax esters, we have analysed some foods from marine sources. The content of triglycerides and wax esters of the foods has been determined. Moreover, wax esters have been analysed for their composition in alcohols and fatty acids. Wax esters have been shown to be a part of the neutral lipid extract of the foods analysed. Their content, if compared with the content in triglycerides, shows striking differences. In the case of two botargo preparations, it has been shown that wax esters are more than 90% of the total neutral lipid extract. The content of fatty acids and alcohols found in the foods analysed is consistent with published data.     

Total lipid content and fatty acid composition of the seeds of some Vicia L. species

The seed oils of eight Vicia species (Leguminosae) were investigated for their total lipid contents and fatty acid compositions. The seed lipid contents were found to be between 2.30 and 3.91%. The fatty acid compositions of these eight different species were determined by gas chromatography of the methyl esters of their fatty acids. The seed oils of Vicia species contain palmitic and stearic acids as the major component fatty acids, among the saturated acids, with a small amounts of myristic, pentadecanoic, arachidic and behenic acids. The major unsaturated fatty acids found in the seed oils were oleic, linoleic and linolenic acids.     

Fatty acid esters of 3-chloropropane-1,2-diol in edible oils.

A series of 25 virgin and refined edible oils, obtained from retailers, was analyzed for levels of free 3-chloropropane-1,2-diol (3-MCPD) and 3-MCPD released from esters with higher fatty acids (bound 3-MCPD). Oils containing free 3-MCPD ranging from <3 microg kg-1 (LOD) to 24 microg kg-1. Surprisingly, bound 3-MCPD levels were much higher and varied between <100 (LOD) and 2462 microg kg-1. On average, virgin oils had relatively low levels of bound 3-MCPD, ranging from <100 (LOD) to <300 microg kg-1 (LOQ). Higher levels of bound 3-MCPD were found in oils from roasted oilseeds (337 microg kg-1) and in the majority of refined oils (<300-2462 microg kg-1), including refined olive oils. In general, it appears that the formation of bound 3-MCPD in oils is linked to preliminary heat treatment of oilseeds and to the process of oil refining. Analysis of unrefined, de-gummed, bleached, and deodorized rapeseed oil showed that the level of bound MCPD decreased during the refining process. However, additional heating of seed oils for 30 min at temperatures ranging from 100 to 280 degrees C, and heating at 230 degrees C (260 degrees C) for up to 8 h, led to an increase in bound 3-MCPD levels. On the other hand, heating of olive oil resulted in a decrease in bound 3-MCPD levels. For comparison, fat isolated from salami was analyzed for intact fatty acid esters of 3-MCPD. This fat contained bound 3-MCPD at a level of 1670 microg kg-1 and the fatty acid esters of 3-MCPD mainly consisted of 3-MCPD diesters; monoesters of 3-MCPD were present in smaller amounts. The major types of 3-MCPD diesters (about 85%) were mixed diesters of palmitic acid with C18 fatty acids (stearic, oleic, linoleic acids). These diesters were followed by 3-MCPD distearate (11%) and 3-MCPD dipalmitate (4%). Generally, very little 3-MCPD existed as the free compound (31 microg kg-1).     

A Capillary GC Determination of Cyclopropenoid Fatty Acids in Cottonseed Oils

A capillary gas chromatography (GC) method was studied for direct analysis for cyclopropenoid fatty acids (CPEFAs) as methyl esters. No thermal alterations were indicated in CPEFA methyl esters on a Supelcowax 10 or a DB-5 capillary column like other fatty acid methyl esters (FAMES), which obviated a second derivatization. GC conditions are described for a complete separation and quantitation of CPEFAs in cottonseed oils. CPEFAs of cottonseed oils from various refining steps were analyzed by the method. The reliability of the method was demonstrated with over 95% recoveries of CPEFA methyl esters diluted in corn oil FAMES at various levels as low as 0.017%.     

Influence of the exposure to light on extra virgin olive oil quality during storage

An experimental investigation was carried out to study the influence that exposure to light has on the quality of extra virgin oil during a 12-month storage period by comparing it with the quality of extra virgin oil stored in the dark. The results showed that the oils stored in the light had significantly lower tocopherol, carotenoid and chlorophyll contents than did the same oils kept in the dark. Moreover, the oils stored in the dark mainly contained primary oxidation products, while the oils kept in the light contained secondary oxidation products as confirmed by the K₂₇₀ values which exceeded the legal limits even after purification by means of alumina. Overall, the results obtained showed that the shelf life of the oils exposed to light is shorter than that of oils kept in the dark, and that after only 2 months of exposure to light the oils examined could no longer be considered as extra virgin.     

Evaluation of potential and real qualities of virgin olive oil from the designation of origin (DO) “Aceite Montes de Alcaraz” (Albacete,Spain)

The potential and real qualities of virgin olive oils, from the designation of origin (DO) “Aceite Montes de Alcaraz”, were evaluated. The regulated physicochemical and sensory parameters, the stability parameters and the fatty acid, sterol and triterpenic dialcohol compositions were analysed. The results of the regulated parameters in the potential quality study classified all the analysed oils into the “extra virgin” category. The varieties Picual and Cornicabra showed remarkably high stability, due to their high total polyphenol content. The fatty acid contents fell within the intervals required by the EU regulations in all the analysed samples. The distribution of fatty acid composition covered the normal range expected for olive oil. Oleic and linoleic acids were the most useful fatty acids used to discriminate the varieties Picual and Cornicabra from the others. The variety Cornicabra stood out due to its high campesterol content. All the analysed samples in the real quality study were classified into the “extra virgin” category according to the regulated physicochemical parameters, but only 67% of them qualified if the sensory parameters were also taken into account. The predominance of the variety Picual in the study area was mainly responsible for the high oil stability and reflects the fatty acid and sterol composition of the oils from the oil mills in the potential quality study.     

橄榄油中脂肪酸烷基酯含量测定

采用商品化固相萃取柱净化,气相色谱-质谱联用法检测,建立了一种前处理简单快捷的橄榄油中脂肪酸烷基酯含量测定方法。该方法测定橄榄油中8种脂肪酸烷基酯的检出限均为1.0 mg/kg,加标回收率为99.05%~111.13%,相对标准偏差为0.50%~6.70%。方法重复性好,准确度高。通过测定橄榄油中脂肪酸烷基酯的含量,可以帮助区分橄榄油品质,为特级初榨橄榄油掺伪的鉴别提供技术支持。     

酶法合成植物甾醇酯工艺的研究进展

植物甾醇酯是一类具有降低血清胆固醇、预防心血管疾病等功效的新型功能食品添加剂。脂肪酶催化合成植物甾醇酯的途径包括与脂肪酸直接酯化、与三酰甘油酯或脂肪酸甲酯进行转酯化。介绍了国内外近年来脂肪酶催化合成植物甾醇酯的方法,并展望其开发前景,为研发环保、高效、可靠、安全的植物甾醇酯合成技术提供思路。     

Infrared spectroscopy for quantitative analysis and oil parameters of olive oil and virgin coconut oil: A review

Vegetable oils are major lipid sources with high nutritional and calorific values for human diet. Specifically, virgin coconut oil and extra virgin olive oil are the functional oils widely used in food and pharmaceutical products, either as vehicles or main components. The quality of edible oils is determined by its contents and parameters inherent in vegetable oils. Infrared spectroscopy is an ideal technique for quantitative analysis of vegetable oils as well as for determination of oils parameters as the changes in infrared spectra can be associated with the changes of oils parameters. Infrared spectra in complex samples are difficult to interpret, as a consequence, spectroscopist uses additional tools called with chemometrics to analyse edible oils qualitatively and quantitatively. This article reviews the use of infrared spectroscopy combined with chemometrics (multivariate analysis) for quantitative analysis and determination of oil parameters of virgin coconut oil and extra virgin olive oil. Although infrared spectra for edible oils are similar, they exhibit some differences which enable spectroscopist to differentiate due to the nature property of infrared spectroscopy spectra as fingerprint spectra which can be understood that there are no different edible oils having the same infrared spectroscopy spectra.     

油橄榄鲜果中主要化合物随成熟度的变化

为阐明油橄榄果实成熟过程中主要化合物的变化,探索最佳成熟度,本试验以不同成熟度的皮瓜尔鲜果为材料,测定其蛋白质、还原糖、粗脂肪、总多酚的含量,以及果油中主要的脂肪酸和角鲨烯的相对含量。结果表明,随着成熟度的增加,蛋白质含量无较大差异,还原糖先降低后略有升高,粗脂肪先升高后趋于平稳,总多酚先降低后趋于平稳;各种脂肪酸相对含量在整个成熟过程中变化不一致;油酸、棕榈酸、亚油酸、亚麻酸、硬脂酸是橄榄油中含量较高的脂肪酸;角鲨烯先升高后降低。利用主成分分析对油橄榄果实品质进行综合评价,第四成熟度为油橄榄果的最佳成熟度。     

Microwave Heating Effects on Relative Stabilities of Tocopherols in Oils

The relative stabilities of individual tocopherols during microwave heating were investigated in fatty acid esters and tocopherol-stripped vegetable oils. The rate of tocopherol loss during heating was less from the highly unsaturated ethyl esters or vegetable oils than from ethyl laurate or olive oil. However, changes in chemical properties of the substrates depended on degree of unsaturation of esters and oils. The stability of tocopherols during microwave heating was δ > β > γ > α, and the order did not change with differences in the type of ethyl esters of fatty acids or oils.     

竹柏种仁油脂成分及其抗氧化活性分析

采用5种方法对竹柏种仁油脂进行提取,并通过核磁共振和气相色谱-质谱技术分别对其油脂成分和脂肪酸组成进行分析,同时采用DPPH自由基清除法和羟基自由基清除法对竹柏种仁油脂的抗氧化活性进行研究。结果表明,5种方法对竹柏种仁油脂的提取率存在显著差异(P 0.05),其中Folch法的提取率最高,为53. 81%。竹柏种仁油脂以甘油三酯为主,磷脂、游离脂肪酸和甾醇含量极低。竹柏种仁油脂经2 mol/L KOH-甲醇溶液室温衍生3 min,甲酯转化率即达99. 80%;且其脂肪酸以油酸(18. 65%)、亚油酸(43.49%)和花生烯酸(30.65%)为主,不饱和脂肪酸含量高达90%以上。竹柏种仁油脂对DPPH自由基和羟基自由基的IC_(50)分别为3.36 mg/mL和0. 38 mg/mL,表明竹柏种仁油脂具有较好的抗氧化能力,可作为健康植物油脂进行开发利用,具有良好的开发潜力和应用前景。本研究为竹柏种仁油脂的提取、成分分析和抗氧化活性研究提供了一定的参考。     

Changes in phenolic compounds and Rancimat stability of olive oils from varieties of olives at different stages of ripeness

BACKGROUND: Recently, diets rich in natural foods and food‐derived components, such as phenolic compounds, have received a great deal of attention because they are perceived as ‘safe’ and ‘non‐medicinal’. In fact, some are known to function as chemopreventive agents against oxidative damage, cerebrovascular disease, and aging. RESULTS: Phenolic compounds, natural antioxidants present in virgin olive oil, play an important role in oil quality by contributing significantly to protecting oil stability against oxidation. In addition, polyphenols are the main contributors to olive oil bitterness, astringency and pungency. The data were fit by linear regression, giving Rancimat stability (h) = 0.18× Total polyphenols (mg L^?1) in the virgin olive oil. CONCLUSIONS: The practice of harvesting ripe olives as soon as possible to produce oils of high phenolic contents and thus high oxidative stability implies bitter and piquant oils, this being admissible for oils of some varieties but detrimental to others appreciated in the market for being more fruity and sweeter. Copyright © 2010 Society of Chemical Industry