快速气相色谱法测定食用油中的未衍生化长链脂肪酸

建立了利用短的微径色谱柱直接测定食用油中未衍生化长链脂肪酸的快速气相色谱方法。C12~C22脂肪酸在2 min之内实现基线分离，定量标准曲线的相关系数大于0.988，最低检测限（S/N=3）为2.80~9.60 mg/L,回收率为74.5%~86.5%。该方法快速、简便、准确，分析通量大，已成功地用于香油、色拉油及调和油等3种食用油中长链脂肪酸含量的测定。     

Utilizing biotechnology in producing fats and oils with various nutritional properties

The role of dietary fat in health and wellness continues to evolve. In today's environment, trans fatty acids and obesity are issues that are impacted by dietary fat. In response to new information in these areas, changes in the amount and composition of edible fats and oils have occurred and are occurring. These compositional changes include variation in fatty acid composition and innovation in fat structure. Soybean, canola, and sunflower are examples of oilseeds with varied fatty acid composition, including mid-oleic, high-oleic, and low-linolenic traits. These trait-enhanced oils are aimed to displace partially hydrogenated vegetable oils primarily in frying applications. Examples of oils with innovation in fat structure include enzyme interesterified (EIE) fats and oils and diacylglycerol oil. EIE fats are a commercial edible fat innovation, where a lipase is used to modify the fat structure of a blend of hard fat and liquid oil. EIE fats are aimed to displace partially hydrogenated vegetable oils in baking and spread applications. Diacylglycerol and medium-chain triglyceride (MCT)-based oils are commercial edible oil innovations. Diacylglycerol and MCT-based oils are aimed for individuals looking to store less of these fats as body fat when they are used in place of traditional cooking and salad oils.     

Evaluation of a rapid method for preparation of fatty acid methyl esters for analysis by gas-liquid chromatography

The major limitation to fatty acid analysis by gas-liquid chromatography is associated with preparation of fatty acid methyl esters (FAME). In the present study, FAME preparations were made from plant oils (corn, olive, sunflower), sunflower oil margarine, lard and various animal tissue fats by a rapid transesterification involving tetramethylammonium hydroxide in methanol, and also by a longer conventional saponification-esterification method. Fats from animal (beef, mutton, pork) adipose tissues were extracted by a simpler modified procedure and also by the Folch method prior to the rapid and the conventional FAME preparations, respectively. FAME analysis on a gas-liquid chromatograph equipped with a Silar 10C glass capillary column indicated similar fatty acid composition of a given fat or oil, whether FAME was prepared by the rapid or the longer conventional method. The data obtained by both methods were very highly correlated for all the fats (r = 0.9895 - 0.9999). However, the rapid method showed a tendency for enhanced recoveries of lower chain fatty acids (e.g. 14:0), and also of unsaturated C18 isomers. Possibly, losses of fatty acids that occurred during the lengthy fat extraction, fatty acid esterification or ether-evaporation FAME concentration steps (conventional method) were minimised by the single transesterification step (rapid method). This rapid transesterification method appears to be an attractive alternative to FAME preparation from a wide variety of different fats for gas-liquid chromatographic analysis.     

Untargeted fatty acid profiles based on the selected ion monitoring mode

Fatty acids are potential biomarkers of some diseases and also key markers and quality parameters of different dietary fats and related products. Thus, untargeted fatty acid profiles are important in the study of dietary fat quality and fat-related diseases, as well as in other fields such as bioenergy. In addition, accurate identification of unknown components is a technological breakthrough for the selected ion monitoring (SIM) mode for untargeted profiles. In this study, we developed untargeted fatty acid profiles based on SIM. We also investigated mass spectral characteristics and equivalent chain lengths (ECL) to eliminate the influence of non-FAMEs for identifying fatty acids in samples. As an application example, fatty acid profiles were used to classify three edible vegetable oils. The results indicated that SIM-based untargeted fatty acid profiles could yield accurate qualitative and quantitative results for more fatty acids and benefit related studies of metabolite profiles.     

The separation and determination of fatty acids by isotopic dilution and radiogas-liquid chromatography

A number of static phases have been evaluated for the GLC separation of fatty acids. Of those investigated, only AT 1200 was capable of resolving the isomeric forms of the acids. A radiogas-liquid chromatographic method incorporating isotopic dilution analysis has been developed for the determination of n-butyric acid. The proposed method has been applied to the determination of the acid in hydrolysed butter fat and milk chocolate extracts.     

Update on solid-phase extraction for the analysis of lipid classes and related compounds

This article provides information on the different procedures and methodologies developed when solid-phase extraction (SPE) is used for lipid component separation. The analytical systematics, established by different authors and designed to separate groups of compounds and also specific components by using a combination of chromatographic supports and solvents are presented. The review has been divided into three parts, which we consider well defined: edible fats and oils, fatty foods and biological samples. Separations of non-polar and polar lipids is the most extensive systematic, although many other published methods have been established to isolate specific components or a reduced number of components from edible fats and oils, fatty foods or biological samples susceptible to further analysis by other quantitative techniques.     

Automated determination of fatty acid methyl ester and cis/trans methyl ester composition of fats and oils

The determination of the fatty acid composition (as methyl esters, FAMEs) of fats and oils and their cis/trans (CTME) distribution requires a simple, but manual and time-consuming sample preparation. The so-called BF3 method is often the preferred procedure. Because FAME/CTME analyses are encountered very frequently in the food industry, an automated, robot-based alternative is proposed which uses the sodium methylate procedure. After sample weighing and the (manual) addition of heptane (2 min), a XYZ robotic autosampler is used for all remaining work, which includes reagent addition, agitation, sample settling and the final injection into the gas chromatograph (10 min). The performance of the sodium methylate and BF3 methods are compared by analysing some 30 oil and fat samples. The novel procedure is much faster (less than 15 min versus ca. 1 h) and manual sample handling is drastically decreased. The experimental results obtained with the two methods frequently are the same, while small differences can be explained by (known) differences of the two methods in the conversion of minor oil/fat constituents, such as free fatty acids, wax esters and sterol esters. In case of FAME analyses, a hot injection is to be preferred over a cold injection. The RSDs of the peak areas were 1.5% for the major fatty acids to 11% for peaks that were just above the noise level. The detection limit were approximately 0.03%.     

Capillary electromigration methods for fatty acids determination in vegetable and marine oils: A review

Fatty acids determination is of paramount importance for quality control and suitable labeling of edible oils, required by regulatory agencies in several countries, and fast methods for this determination are worldly desired. This review article aimed to explore the available analytical methods for vegetable and marine oils analyses employing CE, which can be a straightforward and faster alternative than GC methods for fatty acid determination, considering some purposes. CE usually offers the possibility of a rapid analysis with a simple preparation of the sample, without requiring specific columns, which are inherent advantages of the technique. Instrumental conditions and the key points about fatty acids determination employing the technique are highlighted, and the main challenges and perspectives are also approached. Potential use of CE for edible oil analyses has been demonstrated for research and routine, which can be of interest for industries, regulatory agencies, and edible oil researchers. Therefore, we have explored the analytical approaches described in the last decades, intending to spread the interest of CE methods for fatty acid monitoring, label accuracy assessment, and food authenticity evaluation of edible oils.     

Analysis of steroidal lipids by gas and liquid chromatography.

This article describes the most commonly used procedures and recent laboratory methodologies using gas and liquid chromatography developed for separation and quantitation of non-saponifiable steroidal lipids from clinical (human) studies, edible fats and oils or fatty foods.     

Direct analysis of fatty acid profile from milk by thermochemolysis-gas chromatography-mass spectrometry

The fatty acid composition of milk is of considerable interest due to their nutritional and functional properties. Although rapid milk fat separation and transesterification procedures have been developed, the overall procedure remains time consuming, specially, for the analysis of a large number of samples. In this work, a fast and simple method for direct profiling of fatty acids from milk using thermochemolysis has been developed. This method has the capability of directly analyse fatty acids from one drop of milk without fat extraction or cleanup. Our approach for thermochemolysis is based on thermal desorption integrated with a cold trap inlet. The optimized method does not present isomerisation/degradation of polyunsaturated fatty acid and shows milk fatty acid profiles comparable to the conventional method based on fat extraction and alkaline transesterification. Overall, this method has demonstrated significant potential for high throughput analysis of fatty acids in milk.     

超高效合相色谱-质谱法快速分析食用植物油中常见脂肪酸

建立了超高效合相色谱-质谱(UPC²-MS)快速分析6种食用植物油(玉米油、葵花籽油、大豆油、茶油、菜籽油、花生油)中棕榈酸、硬脂酸、油酸、亚油酸、亚麻酸等5种常见脂肪酸的方法,并比较了这6种食用油中上述5种脂肪酸的含量差异。采用皂化反应对植物油进行前处理,以ACQUITY UPC² BEH 2-EP色谱柱(100 mm×2.1 mm, 1.7 μm)为分析柱,以超临界CO₂-甲醇/乙腈(1:1, v/v)为流动相进行梯度洗脱,流速为0.8 mL/min。在电喷雾负离子模式下进行检测,外标法定量。结果表明:5种脂肪酸标准物质在0.5~100 mg/L范围内呈现良好的线性关系,相关系数为0.9985~0.9998,定量限(S/N≥10)为0.15~0.50 mg/L;在3个添加水平下,样品的加标回收率为89.61%~108.50%;方法重复性的相对标准偏差(RSD)为0.69%~3.01%。该方法简单、快速、分离效果好,无需对脂肪酸样品进行衍生化,已成功地用于玉米油、葵花籽油、橄榄油、茶油、大豆油和花生油等6种食用油中常见脂肪酸含量的测定。     

Determination of azadirachtin and fatty acid methyl esters of Azadirachta indica seeds by HPLC and GLC

A simple and economical method has been developed to estimate the azadirachtin content and fatty acid composition of neem kernels. Neem kernels are crushed and soaked overnight in ethanol. The extract obtained is analysed by HPLC after filtering through a 0.22 micro m membrane. The peaks are separated using acetonitrile-water (40:60) 1 mL min(-1) as the mobile phase on an RP-18 column and monitored at 214 nm. For the determination of fatty acid composition, the fatty acids are directly transmethylated in the kernel powder by heating with methanol-acetyl chloride-benzene (20:1:4, v/v) for 1 h in a water bath. The fatty acid methyl esters (FAMEs) obtained are extracted in hexane and analysed using GLC. The separation of the FAMEs is achieved using an RH-Wax column using temperature programming, 170-200 degrees C at 2 degrees min(-1). The peaks are detected using an FID. Both the methods do not require any clean up or defatting of seeds. This results in faster, easier and more economical sample preparation.     

Overview of methods for the determination of trans fatty acids by gas chromatography, silver-ion thin-layer chromatography, silver-ion liquid chromatography, and gas chromatography/mass spectrometry

trans Isomers of naturally occurring cis-unsaturated fatty acids are produced when liquid vegetable oils or marine oils are partially hydrogenated to produce margarine, shortenings, and other hardened-fat products. Isomeric trans fatty acids are also formed in the intestinal tract of ruminants, and they appear in small amounts in dairy products and ruminant meat. Currently, satisfactory analyses for the fatty acid profiles of fats containing trans fatty acids are obtained by gas chromatography (GC) using capillary columns coated with highly polar cyanosilicone stationary phases. In capillary GC methods, the key limitation has been the incomplete separation of trans-monoenoic acid isomers from their cis isomers; however, recent reports have demonstrated that improvements in separation are attainable with the use of 100 m columns. In these columns, there is very little overlap of cis and trans isomers. More accurate trans fatty acid analyses can be obtained by coupling GC with either silver-nitrate thin-layer chromatography or silver-nitrate liquid chromatography.     

Fatty acids by high-performance liquid chromatography and evaporative light-scattering detector

A high-performance liquid chromatographic (HPLC) separation method with an evaporative light-scattering detector (ELSD) has been developed for the separation and quantitative analysis of fatty acid methyl esters (FAME) in three different oils. Reverse-phased C18 HPLC separation of 13 FAME is achieved using a methanol/water eluent mixture. The retention times (RT) reflect the elution behavior of these compounds on C18 reversed-phase HPLC. The proposed method is tested on: soybean oil (Glycine max L.) as reference sample, rice bran oil (Oryza sativa L.), pumpkin seed oil (Cucurbita pepo L.) and algal oil (Arthrospira platensis Nordst.).     

Overview of infrared methodologies for trans fat determination

trans Fatty acids are present in a variety of foods like dairy products, but the major sources are products that contain commercially hydrogenated fats. Some studies have shown that trans fatty acids elevate levels of serum low-density lipoprotein (LDL)-cholesterol and lower high-density lipoprotein (HDL)-cholesterol. The quantitation and identification of trans fatty acid isomers is difficult because of the wide range of positional monoene, diene, and triene fatty acid isomers present in hydrogenated oils. This is complicated by the cis positional isomers that are also present, as well as the lack of commercial chromatographic standards for many fatty acid isomers. In this review, infrared methodologies for the determination of total trans fat are presented. Using an attenuated total reflection (ATR) infrared cell, a novel Fourier transform infrared (FTIR) spectroscopic method that was developed for the rapid (5 min) quantitation of the total trans fatty acid levels in neat (without solvent) fats and oils measured as triacylglycerols (TAG) is discussed. TAG required no derivatization, but had to be melted prior to measurement. The lower limit of trans quantitation was 5% of total fat. The precision of this ATR method was found to be superior to that of transmission infrared official methods. Accuracy was enhanced by generating a symmetric absorption trans infrared band at 966 cm(-1) on a horizontal background. This was achieved by "ratioing" the single-beam spectrum of the trans-containing fat or oil against that of a reference oil or standard having only cis double bonds. Attempts to apply this ATR-FTIR method to food matrixes with low trans fat and/or low total fat content were not satisfactory due to interfering infrared absorptions in the trans region. To overcome this interference, the method was modified by applying the standard addition technique to the ATR-FTIR determination. The modified procedure required more time, but eliminated any adverse impact on accuracy arising from interfering minor food components having absorption bands near 966 cm(-1).     

Preparation of biodiesel catalysed by KF/CaO with ultrasound

Biodiesel, chemically consists of fatty acid methyl ester (FAME) produced by methanolysis of natural triglycerides, such as animal fats and vegetable oils, is a kind of biomass energy, which is renewable and ecofriendly. In this article, KF/CaO was used as solid base catalyst for transesterification of soya bean oil and methanol, while ultrasound as supplementary means. Compared to mechanical stirring, ultrasound treatment is an effective method to increase the yield of FAME and shorten reaction time. By single-factor method, the optimisation of reaction conditions has been studied. The research showed that the optimum reaction conditions were: w(catalyst)/w(oil): 3%, reaction temperature: 65°C, n(methanol)/n(oil): 12, reaction time: 1?h, sound intensity: 1.01?W?cm(-2), frequency: 20?kHz, the yield of FAME could be 97%.     

Development of a DSC method for determination of certain technological parameters of margarine and mixed-fat spread

Nutritional-physiological research of near past decades had established the real nutritional value of fats and oils. In the former theory the nutritional value of fats and oils is influenced mainly by the rate of saturated/unsaturated fats. It was ruled out, and positive, inert or risk physiological effect of every single fatty acid had been established. The health-care effect of omega-3 fatty acid mainly by the favourable (<3:1) rate of omega-6/omega-3 was established, as inert was concerned the saturated C₁₆ fatty acid and the maximal amount of trans-fatty acids carrying health risk in fats was legally regulated in some countries. These nutritional-physiological requirements were mainly fulfilled by margarine producers and the elementary fats were selected in such a way that they should meet these requirements. Our method helps to the producers to quickly determine the amount of the liquid and solid fat at certain temperature and/or to adjust the technological temperature parameters. The main steps of our method are: a./ determination of cooling rate (K min^–1) of the crystallizer device; b./ determination of the rate of liquid/solid fat at 10°C temperature. This value is used for the determination of the rate of fats and oils as a function of technology and required consistency firmness (spread ability); c./ determination of the temperature from the cooling curve where the crystallization of most part of the fat has finished. This value is used for the determination of outlet temperature parameter of product coming out from the crystallizer device for margarines or mixed-fat spreads with water-in-oil system.     

Rapid characterization of edible oils by direct matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis using triacylglycerols

Direct matrix-assisted laser desorption/ionization time-of-flight mass spectrometric (MALDI-TOFMS) analysis of solutions of edible fats/oils yielded spectra useful for their rapid differentiation and classification. Results also reflected the individual fatty acid components and their degree of unsaturation. After dissolution in hexane, MALDI-MS analysis revealed spectra showing characteristic triacylglycerols (TAGs), the main fat/oil components, as sodium adduct ions. The Euclidean distances calculated using the mass and intensity values for 20 TAGs were used to evaluate and compare spectra. With cluster analysis, animal fats grouped together differently than vegetable oils and the individual oils grouped together by type. The ion abundances for the individual TAGs and their presumed compositions were used to approximate the overall fatty acid composition of canola, soybean, corn, olive and peanut oil, as well as lard. Using this approach the calculated fatty acid compositions and degree of unsaturation generally fell within about 4% of literature values. When the degree of saturation was compared with values calculated from the package labeling the differences were about 7%.     

Characterization of biodiesel and biodiesel blends using comprehensive two-dimensional gas chromatography

In this work the development of a comprehensive 2-D GC flame ionization detection (GC x GC FID) method for biodiesel fuels is reported. This method is used for the analysis of fatty acid methyl esters (FAMEs) in both biodiesel (B100) and biodiesel blend (B5) samples. The separation of FAME was based on component boiling point in the first dimension and polarity in the second dimension by using a BPX5/BP20 column set to provide a measure of 'orthogonality' in the 2-D space. Here the columns are coupled with a cryogenic modulator operating in a novel temperature programmed mode (T(M)) whereby the cryotrap is progressively incremented in temperature as the oven temperature is increased. The final method employs eight cryotrap temperature settings. The developed GC x GC method is able to successfully characterize and identify both B100 and B5 FAME components, which are produced from a variety of vegetable oils, animal fats and waste cooking oils, with high precision. The method is capable of analysing FAME with carbon numbers C4-C24, and is particularly suitable to characterize various types of biodiesel, making it possible to differentiate the origin and type of FAME used in the biodiesel samples.     

An improved method for sn-2 position analysis of triacylglycerols in edible oils and fats based on immobilised lipase D (Rhizopus delemar)

The use of lipase D (Rhizopus delemar) immobilised on microporous polypropylene as a replacement for the standard pancreatic lipases used in the stereospecific sn-2 position analysis of triacylglycerols from edible oils and fats is studied. Excellent hydrolysis characteristics are obtained in hexane/methanol solvents at reaction temperatures up to 60 degrees C with hydrolysis times of only 10-20 min. The favourable conditions for the hydrolysis reaction allow fats with higher melting points to be analysed and facilitate coupling of the hydrolysis reaction to the later steps in the analytical protocol. The performance of the new method is compared to that of the standard method using pancreatic lipase. The novel procedure is faster, manual sample handling is reduced, while the results obtained with both methods are comparable. The influence of alkyl-chain length on hydrolysis rates seems to be negligible for the most common vegetable fatty acids. Acyl migration was found to be absent. The short-term repeatability of the method ranges from 10% for fatty acids present at levels close to the detection limits to less than 1% for the major fatty acids. The detection limit is approximately 0.05%. Although the application of the immobilised enzyme in fully automated sn-2 position analysis seems to be promising, the attempts to do this using a packed bed reactor were not successful due to a rapid loss of enzyme activity.