Application of supercritical fluid chromatography in the quantitative analysis of minor components (carotenes,vitamin E,sterols, and squalene) from palm oil

The application of supercritical fluid chromatography (SFC) coupled with a UV variable-wavelength detector to isolate the minor components (carotenes, vitamin E, sterols, and squalene) in crude palm oil (CPO) and the residual oil from palm-pressed fiber is reported. SFC is a good technique for the isolation and analysis of these compounds from the sources mentioned. The carotenes, vitamin E, sterols, and squalene were isolated in less than 20 min. The individual vitamin E isomers present in palm oil were also isolated into their respective components, α-tocopherol, α-tocotrienol, γ-tocopherol, γ-tocotrienol, and δ-tocotrienol. Calibration of all the minor components of palm as well as the individual components of palm vitamin E was carried out and was found to be comparable to those analyzed by other established analytical methods.     

Noncarotenoid hydrocarbons in palm oil and palm fatty acid distillate

Column chromatographic and gas chromatographic-mass spectroscopic (GCMS) analyses for minor and trace noncarotenoid hydrocarbons of crude palm oil and palm fatty acid distillate revealed the presence of a wide range of n-alkanes (C₁₂H₂₆ to C₃₆H₇₄) and n-alkenes in addition to the major component, squalene. Hydrocarbon components concentrated in palm fatty acid distillate where squalene was dominant, but degradation products such as alkenes (from fatty acids or glycerides), aromatic hydrocarbons (from carotenes) and diterpene hydrocarbons (from tocotrienols) were detected in significant quantities, superseding the naturally occurring n-alkanes. Mechanisms proposed suggest that degradation of the valuable vitamin E or tocotrienols needs to be minimized in physical refining.     

Supercritical fluid chromatographic analysis of fish oils

Various natural and processed fish oil triglyceride mixtures have been analyzed by capillary supercritical fluid chromatography (SFC). The analyses were performed on nonpolar columns to separate the components by lipid class and by the number of carbon atoms. The compounds separated included free fatty acids, squalene, α-tocopherol, cholesterol, wax esters, cholesteryl esters, di- and triglycerides. This kind of analysis is not possible by gas chromatography or high-performance liquid chromatography methods without prior treatment of the fish oil, making SFC superior for this application. Applications of SFC to fish oils are given, including a control analysis of the various process steps in the refining of a fish oil, analysis of a lipase-catalyzed transesterification of a fish oil and the detection of polymeric artifacts.     

Carotinanalysen in rohem Palmöl

Analysis of Carotenes in Crude Palm Oil Structure and properties of natural carotenes as well as their behaviour especially towards adsorbents are discussed. Literature on the occurrence of carotenes in palm oil is reviewed and a short history of the development of analytical methods for the separation of carotenes is presented. A tentative method of the DGF for the analysis of minor components is reported, which enables quantitative determination of the total carotenes as well as α and β-carotenes, separately in fats and oils. Usefulness of this method is shown in the analysis of 10 samples of crude palm oil from various sources. Determination of free fatty acids and peroxides round up the analytical picture of palm oil samples.     

A spectrophotometric method for determination of solid fat content of palm oil

A new spectrophotometric method has been developed for determining solid fat content (SFC) of crude palm oil based on the different solubilities of the inherent carotenes in the solid and liquid components of the oil. The sample to be analyzed is tempered according to usual procedures and then either filtered or centrifuged to liberate the liquid component (olein). The carotene contents of the palm oil and olein as determined by spectrophotometry are then fitted into an equation to obtain the SFC. The carotenes are apparently insoluble in the solid component of palm oil. The standard deviation of analysis on palm oil samples at 25 C is 0.5% which is almost comparable to that of the wide-line NMR technique. The correlation coefficient of SFC measured by these 2 methods over a range of temperatures is 0.99. The new method can also be used to determine SFC of hybrid palm oil (Elaeis guineensis ×E. oleifera) and different palm oil-stearin blends.     

Continuous supercritical carbon dioxide processing of palm oil

Crude palm oil was processed by continuous supercritical carbon dioxide. The process reduces the contents of free fatty acids, monoglycerides and diglycerides, certain triglycerides, and some carotenes. The refined palm oil from the process has less than 0.1% free fatty acids, higher carotene content, and low diglycerides. Solubility of palm oil in supercritical carbon dioxide increased with pressure. A co-solvent improves the refining process of palm oil.     

Performance of Choline-Based Deep Eutectic Solvents in the Extraction of Tocols from Crude Palm Oil

Deep eutectic solvents are emerging green solvents that have potential in many separation processes. This study investigates the performance of choline‐based deep eutectic solvents in the extraction of tocopherols and tocotrienols (collectively known as tocols) from palm oil, a major natural source of tocols. Deep eutectic solvents comprised of choline chloride salt and selected carboxylic acids as hydrogen bond donors were prepared and used in the extraction of tocols from crude palm oil by liquid–liquid extraction. Tocols concentration in the extracted product was at least double that in the control (8671 mg/kg compared to 3285 mg/kg, respectively). Increasing the amount of the deep eutectic solvents increased the tocols concentration in the extracted product up to 18,525 mg/kg, but the yields lowered from 4 % to less than 1 %. The tocols profile was significantly improved by the increase of the tocotrienols fraction in the products from 80.8 to 99.8 %. This study showed that unique interaction between the selected deep eutectic solvents with the tocols make it possible to selectively separate individual tocols in palm oil, where products with fractions rich in tocotrienols and low in tocopherols (particularly α‐tocopherol) are favorable.     

Analysis of tocopherols by capillary supercritical fluid chromatography and mass spectrometry

Tocopherol-containing mixtures were analyzed by gas chromatography (GC) and capillary supercritical fluid chromatography (SFC). GC analysis of tocopherols required the formation of the silyl derivatives, while SFC analysis of the tocopherol-containing mixtures was accomplished on neat samples. SFC analysis conditions were optimized with respect to column type and density/pressure programming. Enhanced resolution of many components was achieved by using inverse temperature programming during the SFC analyses. Both SFC and GC analyses permitted the separation and quantitation of alpha-, beta-, gamma- and delta-tocopherols. In addition, SFC proved particularly applicable for characterizing the composition of a deodorizer distillate and commercial antioxidant formulation. Coupling of a quadrapole mass spectrometer with a supercritical fluid chromatograph was also achieved; the mass spectrometer provided electron impact mass spectra on the underivatized tocopherol and sterol moieties. Both SFC and SFC/mass spectrometry proved effective for the analysis of complex lipid-containing mixtures, requiring minimal sample preparation prior to analysis. Presented at the 82nd Annual Meeting of the American Oil Chemists’ Society, Chicago, IL, May 12–15, 1991.     

Colorimetric determination of total tocopherols in palm oil,olein and stearin

By using a preliminary heat-bleach at 250 C the Emmerie-Engel method has been adapted for the determination of total tocopherols (including tocotrienols) in crude as well as refined palm oil, olein and stearin. Total tocopherol contents found were: Crude palm oil, 794 ppm (n=10); RBD palm oil, 563 ppm (n=13); RBD palm olein, 643 ppm (n=40); RBD palm stearin, 261 ppm (n=19), where n is the number of samples analyzed. During the detergent fractionation no tocopherols were lost, but the tocopherols were concentrated in the olein fraction. The fate of the tocopherols during degumming, bleaching and steam refining/deodorizing of Crude palm olein containing 978 ppm total tocopherol was studied. Over the whole refining process only 8% of the tocopherols were lost, 62% of the original tocopherols were retained in the RBD palm olein, while the remaining 30% were concentrated in the fatty acid distillate which contained 7,040 ppm tocopherol.     

Frying performance of a sunflower/palm oil blend in comparison with pure palm oil

The aim of this study was to test the performance of a vegetable oil blend formulated as alternative to pure palm oil as frying medium. For this purpose, the evolution of many analytical parameters (free acidity, spectrophotometric indices, total polar components, fatty acid composition, short‐chain fatty acids, tocopherol and tocotrienol content and composition, color, flavor evaluated by means of an electronic nose) of the selected blend (sunflower/palm oil 65 : 35 vol/vol) has been monitored during a prolonged frying process (8 h discontinuous frying without oil replenishment) in comparison to pure palm oil. Sensory attributes of the fried food were also evaluated. The blend proved to keep qualitative parameters comparable to those shown by palm oil during the prolonged frying process. Even if some oxidation indices, such as spectrophotometric indices, short‐chain fatty acids and total polar components, increased faster in the blend, it showed a higher tocopherol content and a lower increment in free fatty acids as compared to pure palm oil. Chips fried in the two oils did not show significantly different sensory profiles.     

Characterization of triacylglycerols in the seeds ofAquilegia vulgaris by chromatographic and mass spectrometric methods

A combination of analytical techniques is generally necessary to properly characterize complex lipid materials. Chromatographic separation in conjunction with spectroscopic characterization was utilized for the analysis of the triacylglycerols in the seeds ofAquilegia vulgaris. Reversed-phase high-performance liquid chromatography (HPLC), micropacked argentation supercritical fluid chromatography (SFC), and combinations of the two techniques were used. The fatty acid profile was determined by gas chromatography/mass spectrometry of the picolinyl esters and by gas chromatography/flame-ionization detection of the methyl esters. The major components were also identified by direct inlet mass spectrometry. The excellent selectivity of packed fused silica argentation SFC for the separation of triacylglycerols was demonstrated.     

Recovered oil from palm-pressed fiber: A good source of natural carotenoids,vitamin E,and sterols

Recovered fiber from pressed palm fruits, which is normally burned as fuel to provide energy for the palm oil mills, has now been found to be a rich source of carotenoids, vitamin E (tocopherol and tocotrienols), and sterols. Residual oil (5–6% on dry basis) extracted from palm press fibers contains a significant quantity of carotenoids (4000–6000 ppm), vitamin E (2400–3500 ppm), and sterols (4500–8500 ppm). The major identified carotenoids are α-carotene (19.5%), β-carotene (31.0%), lycopene (14.1%), and phytoene (11.9%). In terms of vitamin E, α-tocopherol constitutes about 61% of the total vitamin E present, the rest being tocotrienols (α-, γ-, and δ-). The major sterols present are β-sitosterol (47%), campesterol (24%), and stigmasterol (15%). The oil extracted from palm-pressed fiber is contaminated with about 30% of palm kernel oil. The quality of this fiber oil is slightly lower than that of crude palm oil in terms of the content of free fatty acids, peroxide value, and anisidine value.     

Determination of vernolic acid content in the oil ofEuphorbia lagascae by gas and supercritical fluid chromatography

Determination of the content of vernolic acid (12,13-epoxy-9c-octadecenoic) in the oil ofEuphorbia lagascae has been performed by gas chromatography of the fatty acid methyl ester derivatives of the triacylglycerols in the oil and by supercritical fluid chromatography (SFC) of the raw oil and the fatty acid derivatives of the oil. The content of vernolic acid was found to be 55 wt%. The three methods were compared, and SFC analysis of the fatty acid derivatives was found to be the most accurate method.     

Fractionation of palm oil

Because of its fatty acid composition, which includes 50% saturated and 50% unsaturated fatty acids, palm oil can readily be fractionated, i.e. partially crystallized and separated into a high melting fraction or stearin and a low melting fraction or olein. Three main commercial processes for fractionating palm oil are in use: the fast dry process, the slow dry process and the detergent process. All these processes lead to specific products of different quality with different yield and operating costs. The physical and chemical characteristics as well as the triglyceride compositions by high performance liquid chromatography (HPLC) of palm oil fractions from these industrial fractionation processes are given. Other varieties of products produced by specific fractionation are presented with analytical data: the superoleins, palm-mid-fractions and cocoa butter substitutes.     

Comparison of Methods for Separating Polar Lipids from Oat Oil

Polar lipids of crude oat oil were investigated. Oat oil was separated from oats by extraction with isopropanol. Polar lipids were fractionated from crude oil by supercritical CO₂-extraction, by ultrafiltration in hexane and by water degumming. The polar fraction from CO₂-extraction had the highest phospholipid and lowest tocopherol content. The polar fractions made by different methods possessed similar antioxidative properties. However, the polar lipids from oats were more powerful antioxidants than those made from soybean or rapeseed oil.     

Production of Tocopherol Concentrates by Supercritical Fluid Extraction and Chromatography∗

Abstract

Supercritical fluid extraction (SFE) has been combined with supercritical fluid chromatography (SFC) in a preparative mode to develop a system for fractionating and enriching high value constituents contained in seed oil matrices. The system consists of an extraction step sequenced on-line with a sorbent filled column, which permits a SFE-enriched tocopherol fraction to be diverted onto the chromatographic column for further enrichment of the tocopherols. For the SFE stage, the tocopherol enrichment was optimized at 25 MPa and 80°C for soybean flakes and rice bran. However, total tocopherol recovery and enrichment was also found to be a critical function of the mass ratio of CO₂/seed charge. Approximately 60% of the available tocopherols in soyflakes can be recovered in the SFE step, yielding enrichment factors of 1. 83–4.33 for the four tocopherol species found in soybean oil. Additional enrichment of tocopherol species can be realized in the SFC stage, ranging from 30.8 for delta-tocopherol to 2.41 for beta-tocopherol.

     

Investigations on physical refining of animal fats and vegetable oils

Alcohols, polyethyleneglycols, supercritical fluids, and some of their mixtures have been investigated as to their usefulness to purify animal fats and vegetable oils by extraction. The main impurities are free fatty acids. Phase equilibrium was measured as function of temperature and pressure. As primary substances abattoir fat and palm oil were used. Carbon dioxide, dimethylether, and mixtures thereof, likewise methanol and ethanol were tested as extractants for free fatty acids by counter-current extraction in a pilot plant including a high-pressure column and by cross-flow extraction on laboratory scale. With experiments and process simulations including the recovery of the extractants the deacidification of animal fats and vegetable oils was found to be possible. Polyethyleneglycols extract carotenes together with free fatty acids. With the physical refining methods investigated, the formation of waste materials was avoided.     

A Practical Method for Analysis of Triacylglycerol Isomers Using Supercritical Fluid Chromatography

Triacylglycerol (TAG) isomers have been reported to have differing physical and nutritional properties. The analysis of TAG isomers is therefore important for understanding the physical properties of lipids as well as their digestion and absorption. However, methods for the quantitative analysis of TAG regioisomers and enantiomers in vegetable oils and biological samples are still under development. Recently, methods using recycle high-performance liquid chromatography (HPLC) and silver ion column-HPLC have been reported. However the recycle HPLC method requires more than 1 hour, in general, for each sample that is analyzed. Furthermore, existing methods are unable to quantify regioisomers and enantiomers simultaneously. Thus, we aimed to develop a practical method to simultaneously quantify regioisomers and enantiomers of TAG. Three isomers of sn-POO, OPO, and OOP were separated by supercritical fluid chromatography coupled with triple quadrupole mass spectrometer (SFC/MS/MS) using a CHIRALPAK^® IG-U column with acetonitrile and methanol as mobile phase. The separation was completed in 40 min, which is a shorter run time than the conventional techniques published to date. Linear calibration curves with standards were obtained and used to quantify sn-OPO, sn-POO, and sn-OOP in extra virgin olive oil, refined olive oil, palm oil, palm olein, and interesterified palm olein.     

An improved micro-extraction cell for supercritical fluid extraction and chromatography of fatty acids

An improved supercritical fluid micro-extraction cell of increased reliability was designed for on-line supercritical fluid extraction and chromatography (SFE/SFC) of food and other lipid-related samples. The key components in the modified cell include a Swagelok stainless steel reducing union with a dual ferrule as the cell, with polyetherether-ketone (PEEK) ferrules and nuts to connect the cell to the control valve. The new cell did not leak under all conditions examined (100–500 atmospheres, 40–80°C), even after numerous extractions (>250). The quantitative performance of the cell was evaluated with fatty acid standard solutions, technical grade fatty acid sources and wheat flour. The percent relative error (%RE) for the fatty acid standards and technical-grade fatty acid samples was ≤6.0% for oleic, linoleic and linolenic acid. The %RE for oleic and linoleic acid in the whole-wheat samples was ≤10%. The results demonstrate that the new extraction cell can be used for quantitative extractions and that the sensitivity of the SFE/SFC technique is excellent. Similar SFE/SFC methods could prove useful in studying the interaction of free fatty acids with various food components such as enzymes, amylose and proteins.     

DC-Trennung von Ricinusölfettsäure-Estoliden

TLC Separation of Estolides of Castor Oil Fatty Acids Estolides of castor oil fatty acids (polyricinoleic acids) with varying degrees of condensation were synthesized by heating the castor oil fatty acids at 120° C–240° C under vacuum and CO₂ circulation. These products were analyzed by chemical constants and fractionated by TLC on silicagel 60 precoated plates into ricinoleic acid and di-, tri- as well as tetra-ricinoleic acids. Furthermore, the estolides were separated by two-dimensional TLC into two series of estolides, i.e. estolides containing only ricinoleic acid and those which contain fatty acids other than ricinoleic acid at the chain terminal. Hydrogenated castor oil fatty acids (technical 12-hydroxystearic acid) also form estolides which can be fractionated in a similar manner. Thus, TLC provides information on the oligomeric and polymeric character of the estolides of castor oil fatty acids and permits separation even of the decamers.