Metabolism of linoleate versus linoelaidate in the laying hen

The metabolic fate in the laying hen of linoelaidic acid, thetrans,trans-geometric isomer of linoleic acid, was compared to that of the naturally occurringcis,cis linoleate. In two experiments, mixtures of radioisotope-labeled linoleate and linoelaidate were orally administered to a set of three laying hens. A third mixture consisting of linoleate-³H and linoleate-¹⁴C was fed to three hens to measure biological isotope effects. Isotopic ratios (³H/¹⁴C) of the neutral lipid and phospholipid fractions isolated from egg yolks and of the octadecadienoic acids from these fractions were compared to those of the administered mixtures. The³H/¹⁴C ratiosindicate that linoelaidic acid and linoleic acid are equally incorporated into egg yolk neutral lipids and phospholipids. Arachidonic acid was found exclusively in the phospholipid fraction and was radiolabeled with the isotope from thecis,cis octadecadienoate isomer only. Further detailed analysis of individual neutral lipid components indicated: (a) discrimination against thetrans,trans isomer in cholesteryl esters and (b) no discrimination against either isomer in triacylglycerols. Presented at the AOCS Meeting, Chicago, September 1976.     

Hydrolysis of linoleate geometric isomers byGeotrichum candidum lipase

Lipase (EC 3.1.1.3) from the microorganismGeotrichum candidum preferentially hydrolyzescis-9 18∶1 andcis,cis-9,12 18∶2 from triacylglycerols, largely ignoring all other positional isomers ofcis 18∶1 as well astrans-9 18∶1. To obtain additional information about the specificity of the enzyme, two triacylglycerols were prepared and utilized as substrates. The lipase hydrolyzed 85%cis,cis-9,12 18∶2 and 15%trans,trans-9,12 18∶2 from the triacylglycerol, containing ca. 50% of each acid. From the triacylglycerol containing 46.3%cis,trans-9,12 18∶2 and 53.7%trans,cis-9,12 18∶2, 44.8 and 55.2% of the two acids were hydrolyzed. Therefore the enzyme discriminated against thetrans,trans isomer but not between thecis,trans andtrans,cis isomers. Scientific contribution No. 535, Agricultural Experiment Station, University of Connecticut. ARS, USDA.     

Study on the effect of antioxidants in the autoxidation of methyl nonconjugated octadecadienoates

Many studies have been published on the effect of antioxidants on unsaturated fatty acid esters but the differences of the effects of antioxidants on geometric isomers have never been investigated. In this study, methylcis-9,cis-12-octadecadienoate and itstrans isomer methyltrans-9,trans-12-octadecadienoate were used as methyl nonconjugated dienoates, and BHA, BHT, PG, NDGA, 4,4′-dihydroxy-3,5,3′,5′-tetratert-butyl diphenyl methane, L-thyroxine sodium salt,a-tocopherol and sesamol were used, as antioxidants. The differences of the effects of antioxidants on both geometric isomers were investigated by determining the induction period using the weighing method. Also determined were the infrared and ultraviolet spectra, peroxide values, conjugated diene contents, isolatedtrans double bond contents and molecular weights for the controls and the samples containing antioxidants. Thecis,cis isomer was more easily autoxidized and had a shorter induction period than thetrans,trans form. By the end of the induction period, no isolatedtrans double bond forms in thecis,cis isomer, but a considerable amount of isolatedtrans double bond decreased in thetrans,trans isomer. In general, the effects of antioxidants, except NDGA, on thecis,cis isomer were larger than thetrans,trans form.     

trans-Polyunsaturated fatty acids in French edible rapeseed and soybean oils

The fatty acid compositions of rapeseed and soybean oils marketed in France have been determined by gas liquid chromatography on a fused-silica capillary column coated with a 100% cyanopropyl polysiloxane stationary phase. Under the operating conditions employed, methyl esters of linolenic acid geometrical isomers could be separated and quantitated easily without any other complementary technique. With only one exception, all samples under study (eight salad oils and five food samples) contain geometrical isomers of linolenic acid in measurable, although variable, amounts. Totaltrans-18:3 acids may account for up to 3% of total fatty acids. This value corresponds to a degree of isomerization (percentage oftrans isomers relative to total octadecatrienoic acids) of 30%. Examination of our data indicates that the distribution pattern of linolenic acid geometrical isomers does not depend on the degree of isomerization. The two main isomers always have thec,c,t and thet,c,c configurations. These isomers occur in the almost invariable relative proportions of 47.8±1.7% and 41.1±1.0%, respectively. The third mono-trans isomer is present in lower amounts−6.5±0.7%. The only di-trans isomer that can be quantitated with sufficient accuracy is thet,c,t isomer (4.9±1.5%). Mono-trans isomers of linoleic acid are also present in these oils. However, their maximum percentages are lower than those determined for linolenic acid geometrical isomers. In the oils showing the highest degrees of isomerization,trans isomers of linoleic acid account for 0.5% (rapeseed oils) and 1% (soybean oils) of total fatty acids. Taking into account all data, it would appear that the probability of isomerization of linolenic acid is about 13–14 times that of linoleic acid.     

A rapid,automated method for the determination ofcis andtrans content of fats and oils by fourier transform infrared spectroscopy

A rapid Fourier transform infrared (FTIR) method was developed to simultaneously determine percentcis andtrans content of edible fats and oils. A generalized, industrial sample-handling platform/accessory was designed for handling both fats and oils and was incorporated into an FTIR spectrometer. The system was calibrated to predict thecis andtrans content of edible oils by using pure triglycerides as standards and partial least squares as the chemometric approach. The efficacy of the calibration was assessed by triglyceride standard addition, by mixing of oils with varyingcis/trans contents, and by analyzing fats and oils of known iodine value. Each of the approaches verified that the FTIR method measured thecis andtrans content in a reproducible (±0.7%) manner, with the measured accuracies being 1.5% for standard addition and 2.5% for the chemically analyzed samples. Comparisons also were made to the conventional American Oil Chemists’ Society (AOCS) method for the determination oftrans isomers by IR spectroscopy. The FTIR-partial least squares approach worked well over a wide range oftrans contents, including those between 0 and 15%. The sample-handling accessory designed for this application is robust, flexible, and easy to use, being particularly suited for quality-control applications. In addition, the analysis was automated by programming the spectrometer in Visual Basic (Windows), to provide a simple, prompt-based user interface and to allow an operator to carry outcis/trans analyses without any knowledge of FTIR spectroscopy. A typical analysis requires less than two minutes per sample. The derived calibration is transferable between instruments, eliminating the need for recalibration. The integrated analytical system provides a sound basis for the implementation of FTIR methods in place of a variety of AOCS wet chemical methods when analytical speed, cost, and environmental concerns are issues.     

cis andtrans Analysis of fatty esters by gas chromatography: Octadecenoate and octadecadienoate isomers

A gas chromatographic method has been developed for quantitative determination of thecis andtrans percentages in octadecenoate and octadecodienoate esters. To separatecis- andtrans-monoene and diene isomers on a packed GC column, the fatty esters were stereospecifically epoxipized with peracetic acid. A simple and quantitative epoxidation procedure allows thecis- andtrans-epoxyoctadecanoates to be analyzed without prior isolation from the reaction mixture. No positional or geometric isomerization of the double bond occurred during epoxidation. Synthetic mixtures containingcis- andtrans-6,-9 and-12 octadecenoate isomers were completely separated intocis andtrans fractionstrans-15-Octadecenoate was the only isomer investigated that partially interfered in the analysis. Diene mixtures containingrans,trans-, cis,trans- andcis,-cis-9,12-octadecadienoates were also successfully analyzed by gas liquid chromatography (GLC) after epoxidation with peracetic acid. Each diene isomer formed two pairs of diepoxy diastereomers, some of which could be separated. Onecis,cis-diepoxyoctadecanoate diastereomer peak overlapped thecis,trans-diepoxyoctadecanoate peaks. The totalcis,-cis-diepoxyoctadecanoate percentages were calculated by using the ratio of the twocis,cis-diepoxyoctadecanoate diastereomers. Other positional octadecadienoate isomers were also epoxidized and analyzed by GLC. The large number of possible octadecadienoate isomers requires that some preeiminary fractionation be made before GC analysis is practical for diene isomers. Presented at the AOCS Meeting, Atlantic, City, October 1971 N. Market. Nutr. Res. Div., ARS, USDA.     

Alkali isomerization of linoleate isomers: Characterization of products

Geometrical isomers of methyl linoleate were reacted with alakli, and the resulting conjugated isomers were separated intotrans,trans;cis,trans; andcis,cis fractions. The position of double bonds in the various fractions was determined by reductive ozonolysis.trans-9,trans-12-Isomer of linoleate formedtrans,trans- andcis,trans-conjugated dienes, whereascis-9,trans-12- andtrans-9,cis-12-isomers in addition formedcis,cis-conjugated dienes. The formation of the products is in accordance with the theoretical predictions. During conjugationtrans double bonds shifted to form atrans bond preferentially. During conjugation ofcis-9,trans-12- andtrans-9,cis-12-linoleate isomers, thecis double bond shifted preferentially over thetrans double bond. A small amount of diene not conjugated was probably a geometrical and positional isomer of the starting material.     

Effect of ingestion of isomeric fatty acids on cholesterol and lipids of serum and liver

The effect of the ingestion of large amounts of thetrans, trans isomer of linolein upon the cholesterol and lipid levels of the blood and liver was investigated using hypercholesterolemic rats. The serum levels of esterified fatty acids and cholesterol of rats fed the diets containing 30% oftrans, trans linoleic acid glycerides and safflower oil were 15 and 25%, respectively, lower than those fed coconut oil. However, a weight loss associated with less intake of thetrans isomer as compared with a gain with the other two fats must be considered. The serum levels of labeled cholesterol of rats administered radioactive cholesterol along with thetrans isomer were intermediate in maximum value as compared to the levels obtained with coconut and safflower oils. These results suggest that thetrans isomers are not as effective as thecis isomers in lowering the cholesterol and lipids of the blood. The livers of the former group had a lower fat content than the latter which might be accounted for in part by the lower fat intake Presented at AOCS Meeting, Houston, Texas, 1965.     

Separation and spectral data of the six isomeric ozonides from methyl oleate

The structures of the products obtained on ozonation of methyl oleate have been re-examined. The assignments for the six isomeric ozonides of methyl oleate have been made by¹H and¹³C nuclear magnetic resonance (NMR), which were consistent with the retention times observed in high-performance liquid chromatography; the assignments were confirmed by mass and infrared spectroscopy. Two triplets for the ozonide ring protons of thecis andtrans isomers in the normal (MOO1) and the two cross ozonides (MOO1 and MOO3) can be resolved by 400 MHz NMR. For MOO1 and MOO3, where the two ring carbons are equivalent, two peaks for the ring carbons of each cross ozonides are resolved in the¹³C NMR spectra, one for thecis and one for thetrans isomer. For MOO2, four peaks for the ring carbons are resolved in the¹³C NMR spectra, two for thecis and two for thetrans isomer.     

Revisiting the formation of trans isomers during partial hydrogenation of triacylglycerol oils

The decisions to limit (Europe) or declare (USA) the trans isomer content of certain fatty foodstuffs have caused a demand for hardstocks with a reduced trans isomer content. One way to produce such hardstocks is by interesterifying high‐melting components such as palm stearin or fully hydrogenated vegetable oils with lauric or liquid oils. Another way is to modify the hydrogenation process. Possible modifications are reviewed. A moderate reduction in trans isomer content results from operating the hydrogenation process at much reduced temperature, but this also leads to an increase in saturates. Larger reductions in trans isomers may well be made possible by the recent development of new catalysts. One development involves the use of zeolites that allow the rather straight trans isomer to enter the pores while keeping the more curved cis isomers outside. The other development involves a precious metal catalyst that may have been modified in such a way that it has a reduced affinity for monounsaturated fatty acid moieties.     

Heat-induced geometrical isomerization of α-linolenic acid: Effect of temperature and heating time on the appearance of individual isomers

The formation of linolenic acid geometrical isomers (LAGIs) was studied in linseed oil that was heated under vacuum in sealed ampoules at different temperatures (190–260°C) for several durations (2–16 h). A temperature of about 190°C seems to be necessary to induce the formation of LAGIs. At higher temperatures, disappearance of linolenic acid follows a first-order kinetic. The formation of LAGIs increases with both heating time and temperature, degrees of isomerization of linolenic acid higher than 50–60% could easily be obtained by simply heating the oil under vacuum. Side reactions remain at a low level. The mean probabilities of isomerization of individual ethylenic bonds are similar to those determined in linolenic acid-containing oils marketed in European countries, 41.9, 4.7 and 53.3% for double bonds in positions 9, 12 and 15, respectively. The di-trans t,c,t (trans,cis,trans) isomer is formedvia the mono-trans c,c,t andt,c,c isomers by a two-step reaction. The proportions of thec,c,t andt,c,c isomers (relative to total LAGIs) decrease linearly with the heating time. The proportion of thec,t,c isomer is only slightly affected by this parameter; however, it increases with temperature. The proportion of thet,c,t isomer increases linearly with heating time at each tested temperature, at the expense of thec,c,t andt,c,c isomers. However, there is no simple relationship linking the disappearance of each of the mono-trans isomers and the formation of the di-trans isomer.     

Lipid composition of selected margarines

Results of analytical studies on the composition of 10 selected margarines representative of consumeravailable hard and soft types are presented. Paired hard and soft products from the same manufacturer were chosen where possible. All of the margarines were compared on the basis of total fatty acid composition, polyunsaturated to saturated fatty acid ratios, totaltrans and thetrans content of the monoene and diene fractions, location of the double bond in the monoene isomers, per cent conjugation, distribution of the fatty acids at the 2 position of the triglycerides, tocopherol content, and the ratios of α-tocopherol to polyunsaturated fatty acids. As expected the soft margarines contained more polyunsaturated fatty acids than their companion hard types, but all soft margarines did not contain more polyunsaturated fatty acids than all of the hard margarines. The one margarine containing safflower oil had the highest polyunsaturated to saturated ratio. Eight of the ten margarines contained more than 15%trans monoene and nine contained less than 5%trans diene. Positional isomers in the monoene fraction were Δ6 toΔ12 with thecis Δ9 isomer predominating. All of the margarines contained less than 1.9% conjugation. The percentage oftrans monoene at the 2 position was greater for some margarines than that in the total fatty acid. This was attributed to the preferential placement of polyunsaturated fatty acids at the 2 position in the original vegetable oils. The forms of tocopherol found were characteristic of the original vegetable oils. Ratios of α-tocopherol to PUFA varied from 0.1 to 0.5 mg/g. Determination of the relationship of the amount of tocopherol content to either source or hardness is not possible on the basis of our data.     

Thermal polymerization of methyl linolenate,alpha- and beta-eleostearates

Summary The rates of polymerization of alpha and beta eleostearates agree with second order kinetics, as would be expected for a bimolecular Diels-Alder addition. The all-trans, beta isomer reacts faster than thecis, trans, trans alpha isomer, in agreement with knowncis, trans effects on diene activity. The polymerization of normal linoleate follows an apparent first order reaction. It is suggested that conjugation is the slow rate determining monomolecular reaction, as has been proposed for the non-conjugated linoleate isomers. Paper No. 177, Journal Series, Research Laboratories, General Mills Inc. Presented at the 28th fall (Paul Bunyan) meeting of the American Oil Chemists’' Society, Oct. 12, 1954, Minneapolis, Minn.     

Essential fatty acid-deficient rats: II. On the fatty acid composition of partially hydrogenated arachis,soybean and herring oils and of normal,refined arachis oil

The fatty acid composition of partially hydrogenated arachis (HAO), partially hydrogenated soybean (HSO) and partially hydrogenated herring (HHO) oils and of a normal, refined arachis oil (AO) was studied in detail by means of direct gas liquid chromatography, ultraviolet and infrared spectrophotometry and by thin layer chromatography fractionation on silver nitrate-silica gel plates followed by gas liquid chromatography. It was shown that the partially hydrogenated oils all contained fatty acids withtrans double bonds. In the plant oils, thetrans acids were present mainly as elaidic acid. The HHO showed an almost equal distribution betweentrans 18∶1 ω9,trans 20∶1 ω>9 andtrans 22∶1 ω>9. Sometrans configuration was also found in the C₂₀-and C₂₂-dienes and trienes of the HHO. In all the oils, conjugated fatty acids were present in minor amounts only (<0.5%). Special attention was given to the ω-acids known to be of specific nutritional value. The HSO contained about 32% linoleic acid, whereas the content ofcis, trans+trans, cis andtrans, trans octadecadienoic isomers was 1.7% and 0.5%, respectively. The amount of linoleic acid in the HSO was even higher than that of AO (29%). The HAO contained only 0.8% 18∶2 ω6 (linoleic acid). Further, two 18∶2 fatty acids with ω>6, acis, cis and atrans, trans isomer, were present in small amounts. The HHO contained 0.5% 18∶2 ω6 (linoleic acid). Isomers of 18∶2 ω>6 were also found in the HHO. They may be hydrogenation products of higher unsaturated C₁₈-acids orginally present. All the C₂₀- and C₂₂-dienes and trienes were shown to have an ω-chain greater than 6. Fatty acids with ω6-structure were not formed during partial hydrogenation of the oils studied.     

Improvement in the resolution of individualtrans-18:1 isomers by capillary gas-liquid chromatography: Use of a 100-m CP-Sil 88 column

Doubling the length of a CP-Sil 88 capillary column (Chrompack, Middelburg, The Netherlands) from 50 to 100 m remarkably improves the resolution of individualtrans-18:1 isomers from either ruminant fats or partially hydrogenated oils. Although the use of a 50-m column gives interesting results, it does not allow sufficient resolution of thetrans-10 andtrans-11 18:1 isomers. Moreover, thetrans-6 totrans-9 18:1 isomers emerge as a single group of peaks, whereas thetrans-12 isomer is only partly resolved from the adjacenttrans-11 andtrans-13 plustrans-14 isomers. With the 100-m column, thetrans-9,trans-10, andtrans-12 18:1 isomers are almost base-line resolved from other isomers. However, with both columns, it is not possible to separate the critical pair oftrans-13 andtrans-14 18:1 acids which co-elute under a single peak. Despite this minor drawback, the 100-m CP-Sil 88 column appears to be of great interest for the separation and the quantitation of most individualtrans-18:1 acids. Except for the use of argentation thin-layer chromatography, there is no need for complementary techniques, such as ozonolysis. This simple and powerful tool may be applied to ruminant fats, partially hydrogenated oils, and human tissue lipids.     

Chromatographic separation ofcis andtrans fatty esters by argentation with a macroreticular exchange resin

Methyl oleate and methyl elaidate, as well as other monoenecis andtrans isomers of fatty esters, can be separated quickly and conveniently by a preparative chromatographic procedure in which a silver-saturated ion-exchange resin is used. Separations are based on differences in stabilites of the silver-olefin complexes. Recoveries of better than 95% were made, and puretrans andcis monoene fractions were collected. This method can be used to separate saturates fromcis andtrans monoenes. Thecis,trans,cis,cis, andtrans,trans-9-12-octadecadienoates were separated. Whilecis,trans andtrans,trans dienes were cluted separately, thecis,cis diene isomer remained on the column. Presented at AOCS Meeting, in Minneapolis, 1963. A laboratory of the No. Utiliz. Res. and Dev. Div., ARS, USDA.     

trans fatty acids. 4. Effects on fatty acid composition of colostrum and milk

trans Isometric fatty acids of partially hydrogenated fish oil (PHFO) consist oftrans 20∶1 andtrans 22∶1 in addition to thetrans isomers of 18∶1, which are abundant in hydrogenated vegetable oils, such as in partially hydrogenated soybean oil (PHSBO). The effects of dietarytrans fatty acids in PHFO and PHSBO on the fatty acid composition of milk were studied at 0 (colostrum) and 21 dayspostpartum in sows. The dietary fats were PHFO (28%trans), or PHSBO (36%trans) and lard. Sunflower seed oil (4%) was added to each diet. The fats were fed from three weeks of age throughout the lactation period of Experiment 1. In Experiment 2 PHFO or “fully” hydrogenated fish oil (HFO) (19%trans), in comparison with coconut oil (CF) (0%trans), was fed with two levels of dietary linoleic acid, 1 and 2.7% from conception throughout the lactation period. Feedingtrans-containing fats led to secretion oftrans fatty acids in the milk lipids. Levels oftrans 18∶1 andtrans 20∶1 in milk lipids, as percentages of totalcis+trans 18∶1 andcis+trans 20∶1, respectively, were about 60% of that of the dietary fats, with no significant differences between PHFO and PHSBO. The levels were similar for colostrum and milk. Feeding HFO gave relatively lesstrans 18∶1 andtrans 20∶1 fatty acids in milk lipids than did PHFO and PHSBO. Only low levels ofcis+trans 22∶1 were found in milk lipids. Feedingtrans-containing fat had no consistent effects on the level of polyenoic fatty acids but reduced the level of saturated fatty acids and increased the level ofcis+trans monoenoic fatty acids. Increasing the dietary level of linoleic acid had no effect on the secretion oftrans fatty acids but increased the level of linoleic acid in milk. The overall conclusion was that the effect of dietary fats containingtrans fatty acids on the fat content and the fatty acid composition of colostrum and milk in sows were moderate to minor.     

Content and distribution oftrans-18:1 acids in ruminant milk and meat fats. Their importance in european diets and their effect on human milk

Thetrans-18:1 acid content and distribution in fats from ewe and goat milk, beef meat and tallow were determined by a combination of capillary gas-liquid chromatography and argentation thin-layer chromatography of fatty acid isopropyl esters. Thetrans isomers account for 4.5 ± 1.1% of total fatty acids in ewe milk fat (seven samples) and 2.7±0.9% in goat milk fat (eight samples). In both species, as in cow, the main isomer is vaccenic (trans-11 18:1) acid. The distribution profile oftrans-18:1 acids is similar among the three species. The contribution of ewe and goat milk fat to the daily intake oftrans-18:1 acids was estimated for people from southern countries of the European Economic Community (EEC): France, Italy, Greece, Spain, and Portugal. It is practically negligible for most of these countries, but in Greece, ewe and goat milk fat contributeca. 45% of the daily consumption oftrans-18:1 acids from all dairy products (0.63 g/person/day for a total of 1.34 g/person/day). Thetrans-18:1 acid contents of beef meat fat (ten retail cuts, lean part) and tallow (two samples) are 2.0 ± 0.9% and 4.6%, respectively, of total fatty acids (animals slaughtered in winter). Here too, the main isomer is vaccenic acid. Othertrans isomers have a distribution pattern similar to that of milk fat. Beef meat fat contributes less than one-tenth of milk fat to thetrans-18:1 acid consumed. The daily per capita intake oftrans-18:1 acids from ruminant fats is 1.3–1.8 g for people from most countries of the EEC, Spain and Portugal being exceptions (ca. 0.8 g/person/day). In France, the respective contributions of ruminant fats and margarines to the daily consumption oftrans-18:1 acids are 1.7 and 1.1 g/person/day (60 and 40% of total, respectively). These proportions, based on consumption data, were confirmed by the analysis of fat from milk of French women (ten subjects). The mean content oftrans-18:1 acids in human milk is 2.0 ± 0.6%, with vaccenic acid being the major isomer. Based on the relative levels of thetrans-16 18:1 isomer, we could confirm that milk fat is responsible for the major part of the daily intake oftrans-18:1 acids by French people. The daily individual intake oftrans-18:1 isomers from both ruminant fats and margarines for the twelve EEC countries varies from 1.5 g in Spain to 5.8 g in Denmark, showing a well-marked gradient from the southwest to the northeast of the EEC.     

Autoxidation of linoleic acid and behavior of its hydroperoxides with and without tocopherols

The autoxidation of linoleic acid dispersed in an aqueous media and the effect of α-, γ- and δ-tocopherols were studied. The quantitative analysis of the hydroperoxide isomers (13-cis,trans; 13-trans,trans; 9-trans,cis; 9-trans,trans) by direct high-performance liquid chromatography exhibited a prooxidant activity of α-tocopherol at high concentration (3.8% by weight of linoleic acid). On the other hand, α-tocopherol at lower concentrations (0.38 and 0.038%) and γ- and δ-tocopherols at high concentration (3.8%) were antioxidant. Furthermore, the addition of tocopherols modified the distribution of the geometrical isomers. The formation of thetrans,trans hydroperoxide isomers was completely inhibited by the highest concentration of the three tocopherols independently of their antioxidant or prooxidant activity and only delayed by the lower concentrations of α-tocopherol. The addition of tocopherols to hydroperoxide isomers reduced the decomposition rate of these isomers in the order α-tocopherol < γ-tocopherol < δ-tocopherol for thecis,trans hydroperoxide isomer and α-tocopherol ≪ γ-tocopherol ⋍ δ-tocopherol for thetrans,trans hydroperoxide isomer. With these hydroperoxides, as during linoleic acid autoxidation, α-tocopherol was completely oxidized whatever its initial concentration, while γ-tocopherol underwent partial oxidation and δ-tocopherol was practically unchanged.     

Linolenic acid artifacts from the deodorization of oils

Gas liquid chromatography on polar open tubular columns of the methyl esters of fatty acids from vegetable oils shows that the linolenic acid in deodorized oils is accompanied by two major artifacts identified as cis-9,cis-12,trans-15 and trans-9,cis-12,cis-15 isomers. Physicochemical studies, isolation, and partial degradation steps showed two additional isomers with trans-9,cis-12,trans-15 and cis-9,trans-12,cis-15 structures. Gas liquid chromatography also showed that linoleic acid was accompanied by the trans-9,cis-12 isomer. These artifacts were not present in unrefined oils or bleached oils but could be induced by deodorization in the laboratory. Proportions of the two major artifacts in total 18:3ω3 are given for some vegetable oils from the retail market. Presented in part at the AOCS Spring Meeting, New Orleans.