Fractionation of commercial frying oil samples using sep-pak cartridges

Commercial frying oil samples were fractionated by column chromatography on hydrated silicic acid according to the standardized DGF-IUPAC-AOAC method. The non-polar fraction was isolated using a mixture of petroleum ether:diethyl ether (87:13), while the polar fraction was eluted by diethyl ether. These used frying oil samples were also fractionated using Sep-Pak cartridges. The non-polar fraction was eluted with 20 ml of a mixture of petroleum ether:diethyl ether (92:8), while the polar fraction was eluted with methanol. The purity of each fraction was studied by thin layer chromatography (TLC) and by the Iatroscan TLC/FID system using a mixture of hexane:tetrahydrofuran:acetic acid (97:3:1) as solvent system. The Sep-Pak and the standardized methods gave similar results. This indicates that the state of degradation of a frying oil (detection of polar components) could be studied using Sep-Pak cartridges, which is less time- and solvent-consuming than column chromatography.     

Quantitative determination of Tri-, Di-,monooleins and free oleic acid by the thin layer chromatography-flame lonization detector system using internal standards and boric acid impregnated chromarod

The separation conditions for hydrolysates of triglycerides by lipase and their quantitative determination are discussed for a thin layer chromatography-flame ionization detector system utilizing internal standards. The complete separation of glyceride hydrolysis mixtures (triolein 1,3-diolein, 1,2-diolein, 1-monoolein and oleic acid) was achieved on a 3% boric acid-impregnated Chromarod S-II by development with benzene/chloroform/acetic acid (70∶30∶2, v/v/v) (mobile phase A) or hexane/ ether/acetic acid (70∶30∶1, v/v/v) (mobile phase B). Mobile phase B had an advantage over mobile phase A in terms of free space to add internal standards for simultaneous quantitation and was employed.p-Hydroxybenzoic acid andp-carboethoxy benzyl alcohol, which appeared between 1,2-diolein and 1-moloolein, were adopted as the internal standards. The calibration curves relating internal standards to each glyceride were all approximated by the equations Y=aX^b giving high correlations. The method was applied to hydrolysis of triolein by pancreatic lipase. Part of this investigation was reported at the annual meeting of JOCS in Tokyo, November 1982.     

Separation of neutral lipid,free fatty acid and phospholipid classes by normal phase HPLC

Normal phase high performance liquid chromatography methods are described for the separation of neutral lipid, fatty acid and five phospholipid classes using spectrophotometric detection at 206 nm. Separations were accomplished in less than 10 min for each lipid class. A mobile phase consisting of hexane/methyltertiarybutylether/acetic acid (100∶5∶0.02) proved effective in separating cholesteryl ester and triglyceride with recoveries of 100% for radiolabeled cholesteryl oleate and 98% for radiolabeled triolein. Free fatty acid and cholesterol were separated by two different mobile phases. The first, hexane/methyltertiarybutylether/acetic acid (70∶30∶0.02) effectively separated free fatty acids and cholesterol, but did not separate cholesterol from 1,2-diglyceride. A mobile phase consisting of hexane/isopropanol/acetic acid (100∶2∶0.02) effectively separated free fatty acid, cholesterol, 1,2-diglyceride and 1,3-diglyceride. Recoveries of oleic acid and cholesterol were 100% and 97%, respectively. Five phospholipid classes were separated using methylteriarybutylether/methanol/aqueous ammonium acetate (pH 8.6) (5∶8∶2) as the mobile phase. The recoveries of phosphatidylinositol, phosphatidylethanolamine, phosphatidylcholine, sphingomyelin and lysophosphatidylcholine were each greater than 96%.     

Lipid class separation by HPLC combined with GC FA analysis: Comparison of seed lipid compositions from different <Emphasis Type="Italic">Brassica napus</Emphasis> L. varieties

A reliable HPLC method was established to evaluate the lipid composition of useful plants modified by breeding techniques. This study focused on the polar lipid distribution and polar lipid FA compositions of four rapeseed varieties. Structure and quantity of the distinct lipid classes were compared by HPLC using ELSD followed by a GC FA analysis. A baseline separation of 14 lipid classes could be achieved within one step by using an eluent gradient of hexane, tert-methylbutyl ether, isopropanol, acetonitrile, chloroform, triethylamine, acetic acid, and water supplemented with ammonium sulfate with a polyvinyl alcohol column. After automatic fractionation, the FA compositions of the distinct lipid classes were characterized by a subsequent complementary GC FA analysis through direct acetylchloride methylation. The rape varieties analyzed showed diversity in polar lipid content and distribution, dominated by PC, PE, PI, monoglycosyldiacylglycerols, and phytosterols. Extensive variations were detected in FA within the lipid classes of rape varieties with predominantly oleic acid, linoleic acid, and α-linolenic acid observed followed by palmitic acid and gondoic acid. Oleic acid was mainly connected to PC and linoleic acid to PE, whereas α-linolenic acid and γ-linolenic acid were predominantly linked to PI in all varieties.     

Oxidation kinetics of β-carotene in oleic acid solvent with addition of an antioxidant, α-tocopherol

Oxidation experiments with β-carotene were performed in oleic acid solvent with addition of an antioxidant, α-tocopherol. A kinetic model was proposed based on a reaction mechanism consisting of the oxidation of β-carotene, oleic acid, and α-tocopherol; the antioxidation reactions of β-carotene and oleic acid by α-tocopherol; the cross-reaction of β-carotene and oleic acid; and the radical-exchange reaction of β-carotene and α-tocopherol. The model quantitatively described the oxidation behavior of β-carotene over a wide range of temperatures, oxygen compositions, and initial antioxidant concentrations. The model simulated well the time over which β-carotene was almost totally consumed under practical storage conditions at room temperature in air.     

Extraction and Characterization of Seed Oil from Naturally Grown Chinese Tallow Trees

Seeds were collected from locally and naturally grown Chinese tallow trees (CTT) and characterized for general physical and chemical properties and fatty acid composition of the lipids. The effects of four different solvents (petroleum ether, hexane, diethyl ether, and 95 % ethanol) and two extraction methods (supercritical carbon dioxide (SC-CO₂) and conventional Soxhlet) on the properties of the CTT seed oil, including Chinese vegetable tallow (CVT) and stillingia oil (SO), were also investigated. In general, the yields of CVT and SO did not vary based on solvent for Soxhlet extraction and solvent-free SC-CO₂ extraction, except that the yield of CVT from SC-CO₂ extraction was substantially lower. Nevertheless, the CTT seed oil, extracted by SC-CO₂ displayed better quality than those extracted by Soxhlet extraction in terms of color, residual precipitation, and acid value of the oils. The pretreatment of CTT seed by 3 % aqueous sodium bicarbonate solution likely promoted the hydrolysis of triglyceride and caused the high acid value in the CVT samples. The iodine value at around 180 indicated that the SO is a highly unsaturated drying oil. Palmitic (76 %) and oleic (23 %) are two dominant fatty acids in CVT while linolenic (43 %), linoleic (31 %), and oleic (13 %) are the dominant fatty acids in SO.     

Phase investigations of fats. II. Systems containing oleic and stearic acids and an organic solvent

1. The ternary systems oleic acid-stearic acid-commercial hexane and oleic acid-stearic acid-acetone containing varying amounts of the three components have been equilibrated at 0°C., −10°C., −20°C., −30°C., and −40°C.
2. From compositional data of the liquid and solid phases in equilibrium at each isotherm, ternary phase diagrams have been constructed. From these diagrams it is possible to predict the degree of separation which can be obtained with any given mixture of oleic and stearic acids, using either acetone or commercial hexane as solvent.
3. With practical solvent ratios the phase diagrams at −20°C., −30°C., and −40°C., exhibit closed areas representing liquid phase composition. The liquid phase boundaries have been established for each isotherm investigated.
4. The intersolubilizing effect of oleic acid on stearic acid, greater in commercial hexane than in acetone, and the possible formation of mixed crystals of oleic and stearic acid have been noted.
5. Oleic acid of high purity can be obtained as one of the practical applications of these data.

     

Stereospecific analysis of the major triglyceride species in the monounsaturated fraction of cocoa butter

A stereospecific analysis employing pancreatic lipase,Geotrichum candidum lipase and phospholipase A was applied to the monounsaturated triglyceride fraction of cocoa butter. Diacid triglycerides required additional analyses involving the gas liquid chromatographic determination of the proportions of digly ceride acetates produced by separately acetylating the α,α and α,β-digly cerides obtained from aG. candidum digestion mixture. Results indicated that the major triacid triglyceride in cocoa butter wasrac glyceryl-l-palmitate-2-oleate-3-stearate. Approximately 5% of cocoa butter was comprised of triglycerides which were solely or predominantly of one enantiomer, containing oleic acid in the 3 position. Scientific contribution No. 348 Agricultural Experiment Station, University of Connecticut, Storrs.     

Extracting long-chain fatty acids from a fermentation medium

Several solvents were evaluated for extracting free long-chain FA (LCFA) from a fermentation medium. Chloroform, chloroform/methanol (1∶1), hexane, and hexane/methyl tert-butyl ether (MTBE) (1∶1) were evaluated as alternative extraction solvents. Parameters considered for optimizing LCFA recoveries included pH and ionic strength. Maximal LCFA recoveries were obtained by adding 2 mL of the hexane/MTBE (1∶1) solvent mixture, 80 μL of 50% H₂SO₄, and 0.05 g NaCl to 1 mL of the aqueous sample and mixing for 15 min at 200 rpm. This method quantified saturated LCFA [capric acid (C_10∶0) to stearic acid (C_18∶0)] and unsaturated LCFA with 18 carbons [linoleic acid (C_18∶2) and oleic acid (C_18∶1)] with a 98 to 100% recovery. Caproic (C_6∶0) and caprylic (C_8∶0) acids were characterized by 27 and 76% recoveries, respectively.     

Changes in the structure of soybean triglycerides during maturation

Soybeans of the Hawkeye variety were picked at eleven periods from 30 to 111 days after flowering and extracted with chloroform-methanol. The triglyceride fraction of five pickings, selected 35 to 91 days after flowering (when synthesis of lipid was most active), were isolated by silicic acid thin layer chromatography (TLC) and species composition determined using argentation TLC and lipase hydrolysis. The triglyceride content of the total lipid increased from 6.5% at 30 days after flowering to 85% in the mature bean (111 days). The major changes in fatty acid composition of the triglycerides occurred during the first 52 days after flowering. During this period linolenic acid decreased from 34.2% to 11.7%, the percentages of linoleic and oleic acids increased, stearic remained fairly constant and palmitic decreased slightly. Large quantitative changes occurred in the molecular species of the triglycerides of the bean during maturation; some triglycerides containing linolenic acid could not be detected approximately 66 days after flowering. Although changes occurred in the percentage and amount of each triglyceride species, the positional distribution of fatty acids remained virtually unchanged throughout maturation. Linolenic acid was distributed fairly uniformly between the β-position and the α-positions, linoleate favored esterification in the β-position, and oleate the α-positions. Most of the stearic and palmitic acids were esterified in the α-positions. The consistency of the positional arrangement of the fatty acids indicated that the mode of glyceride synthesis was established very early during maturation and molecular species composition was controlled by the fatty acids available for synthesis.     

On Plate Identification of Coexisting Polyoxyethylene (20) Stearyl Ether,Cetyl Pyridinium Chloride,Tetradecyl Trimethyl Ammonium Bromide and Polyoxyethylene (9.5) Octyl Phenyl Ether Surfactants with Preliminary Separation by Planar Chromatography

Separation studies of four surfactants (nonionic and cationic) were performed on silica high-performance thin-layer chromatographic plates with various solvent systems. The most useful chromatographic system for the mutual separation of coexisting polyoxyethylene (20) stearyl ether (C18EO20), cetylpyridinium chloride (CPC), tetradecyl trimethyl ammonium bromide (TTAB) and polyoxyethylene (9.5), octyl phenyl ether (OPEO9.5) was formamide + 1 M formic acid (50:50 v/v). The nature of ‘H’ and ‘H⁺’ of formic acid (H–COO⁻H⁺) on the mobility of these surfactants was studied. The interference due to the presence of metal cations as impurities on the resolution of mixture of C18EO20, CPC, TTAB and OPEO9.5 was also examined. The limits of detection of C18EO20, CPC, TTAB and OPEO9.5 estimated were 0.0620, 0.0310, 0.0625 and 0.0312 μg/zone, respectively. The practical applicability of the proposed method was tested for the identification of four coexisting surfactants after their separation from the spiked aqueous systems.     

The a-sulfonation of pelargonic,stearic, and substituted stearic acids

Direct sulfonation of higher fatty acids with sulfur trioxide or chlorosulfonic acid, without use of solvent, is possible, but the product must then be isolated as the sodium salt. Use of a chlorinated solvent permits isolation of the α-sulfo acid. Sulfonation with dioxane sulfur trioxide in place of sulfur trioxide gave a nearly colorless α-sulfostearic acid. Substituted stearic acids derived from oleic or elaidic acids (phenyl-, 9,10-dichloro-, and 9,10-dihydroxystearic acids) were α-sulfonated with dioxane sulfur trioxide. Solubility, detergent, and surface-active properties were examined and related to structure. The surface-active properties of sodium α-sulfopelargonic acid are not very evident, but the octyl ester, with a much lower critical micelle concentration (0.08% compared to 1.00%), was found to be a very efficient wetting agent. Presented at the fall meeting, American Oil Chemists’ Society, New York, N. Y., October 17–19, 1960. Eastern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.     

Diffuse reflectance Fourier transform infrared spectroscopy of oleic acid adsorption on silicic acid

Diffuse reflectance Fourier transform infrared spectroscopy was used to observe adsorption complexes of oleic acid and isopropanol (IPA) on silicic acid in hexane. The spectra provide definite evidence of the molecular nature of the surface interaction. In addition, the effect on oleic acid adsorption of modifying the solvent with IPA, which competes for adsorption sites and modifies the solvent polarity, was studied. Oleic acid adsorption was reduced in the presence of an equimolar IPA concentration in hexane, relative to that from hexane alone. This could be explained by a combination of competitive adsorption of IPA and IPA interacting with oleic acid in solution. IPA, in solution, and silica are probably competing for the lipid. This is additional evidence that suggests that lipid adsorption onto silicic acid is influenced by competitive adsorption. The adsorption of oleic acid and IPA, from a mixture of the two in hexane, was controlled by (i) the equilibrium between surface-bound species and molecules in solution and (ii) the polar interaction between oleic acid and IPA in solution. Thus, washing pre-bound oleic acid with hexane removed only a small amount of oleic acid, while washing with a solution of IPA in hexane removed most of the pre-bound oleic acid.     

Effects of oleic,arachidonic and 5,8,11,14-nonadecatetraenoic acids on lipid secretion and ketogenesis in perfused rat liver

The effects of perfused oleic (18∶1n−9), arachidonic (20∶4n−6) and 5,8,11,14-nonadecatetraenoic (19∶4n−5) acids on triglyceride and cholesterol secretion and ketone body production were studied in isolated rat liver. As compared to oleic and 19∶4n−5 acids, both ketone body production and triglyceride secretion were significantly lowered when arachidonic acid was perfused. The concentration of triglyceride in the post-perfused liver was lower upon perfusion with arachidonic acid than upon perfusion with oleic acid or 19∶4n−5 acid. Cholesterol secretion in the liver perfused with arachidonic acid or 19∶4n−5 acid was significantly higher than with oleic acid. The concentration of cholesterol in the post-perfused liver was slightly but significantly higher with 19∶4n−5 acid than with the other fatty acids. The results suggest that 19∶4n−5 acid when compared with arachidonic acid affects lipid metabolism in liver differently.     

Solvent crystallization of α, β and γ polymorphs of oleic acid

The features of the solvent crystallization of α, β and γ polymorphs of ultra-pure oleic acid were examined in acetonitrile and decane. The solubilities of the three polymorphs were measured precisely, yielding a lower value for β than for the other two forms at any temperature. Thesolution- mediated transformation either from α to β or from γ to β was observed directly in the nearly saturated solution. It was found that this transformation occurred predominantly via the nucleation of the stable β form at the expense of the less stable ones. Finally the habit of the single crystal of each polymorph was determined for the first time. The results obtained were compared to the similar experiments of stearic acid polymorphs.     

Quantitative determination of 1,2-diacylglycerol in thoracic aorta of the rat using latroscan TLC/FID: Effect of norepinephrine

This study was undertaken to evaluate the use of the Iatroscan TLC/FID system for quantitating 1,2-diacylglycerol (DG) in the aorta. Cholesteryl acetate was chosen as an internal standard. In order to avoid interference of triglyceride and phospholipids with the separation of the internal standard and 1,2-DG, a stepwise elution of lipids from the silicic acid column was used. The development of Chromarods was done using two solvent systems and a three-step developing technique. Assay and recovery of both 1,2-DG and cholesterol (as compared to cholesteryl acetate) were sufficient to measure changes in the 1,2-DG content in blood vessels. After exposing the thoracic aorta to 10⁻⁵ M norepinephrine for 10 min, the 1,2-DG content increased nearly two-fold without significant change in cholesterol content.     

Soybean oil microemulsions with oleic acid/glycols as cosurfactants

The preparation of biocompatible microemulsions of soybean oil in systems made of anionic surfactant, oleic acid, water, and several glycols was considered. The selected glycols were ether derivatives (methyl, ethyl, dimethyl, and diethyl ether) of ethylene glycol and diethylene glycol. The study was performed using pseudoternary phase diagrams in which the three apexes were occupied by soybean oil, a combination of surfactant/oleic acid, and a combination of water/glycol, respectively. The widest regions of microemulsions were obtained for systems containing methyl ether and especially ethyl ether of both ethylene glycol and diethylene glycol. The two latter compounds allowed the preparation of oil-in-water, bicontinuous, and water-in-oil microemulsions with final surfactant contents of 3–4%.     

Fractionation of tallow fatty acids. Preparation of purified oleic acid and an inedible olive oil substitute

Summary Tallow fatty acids have been fractionally crystallized from acetone at temperatures ranging from 0° to −60° C. By crystallizing at 0° to −20° C., a saturated acid fraction which amounts to 40 to 50% by weight of the starting material has been obtained. This fraction corresponds to “double- or triple-pressed stearic acid.” The filtrate acids from the crystallization at −20° C. contain over 90% of the oleic acid present in the starting material, and in fatty acid composition this mixture is similar to olive oil. From this fraction. which amounts to about 50% by weight of the starting material, a synthetic triglyceride with, properties approximating those of olive oil has been prepared. By low-temperature crystallization of this oleic-acid-rich fraction at −50° to −60° C., followed by fractional distillation, a good yield of purified oleic acid (oleic acid content, over 95%) has been obtained. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, United States Department of Agriculture.     

Solvent Crystallization of the Fat and Fatty Acids of Schleichera trijuga Seed

The crystallizations of the kusum oil and the mixed fatty acids thereof were studied from several solvents at various temperatures (+10° C to ?60° C). The results indicate in general that in the range of temperatures studied, petroleum ether as a single solvent is comparable in efficiency to methanol and superior to both acetone and ethanol in respect of separation of the saturated and unsaturated components of the fatty acid mixture. The saturated and unsaturated fractions of the oil also are better separated by petroleum ether than acetone. Further, oleic acid essentially free from linoleic acid is obtainable by a preliminary crystallization of the fatty acid mixture from petroleum ether at ca. ?12° C, followed by two additional crystallizations from acetone at ca. ?55° C.     

Polymorphism of 1-behenoyldistearin and 2-stearoyldibehenin

The triglyceride 1 -behenoyldistearin shows α-2, β-2, β′-2 and β-3 forms in order of increasing stability. The previously unobserved β-2 form of the closely related homolog 1-stearoyldimyristin has now been observed on crystallization from hexane. The triglyceride 2-stearoyldibehenin shows an α-2 form and two modifications of β′-2 type. No β-3 form was observed such as has been previously observed for the related homolog 2-myristoyldistearin.