W. M. N. Ratnayake

The “basic” fatty acid composition of atlantic fish oils: Potential similarities useful for enrichment of polyunsaturated fatty acids by urea complexation

It is known that the 20:1 and 22:1 fatty acids of fish oils from temperate and northern latitudes are of exogenous origin. By discounting these two fatty acids, calculation shows that the remaining fatty acids are a “basic” composition for these fish oils, with similar totals for saturated (14:0, 16:0), monounsaturated (16:1, 18:1) and polyunsaturated (primarily n-3) fatty acids. Thus, any of these oils are potential raw materials for urea complexing of acids or esters to give concentrates enriched in eicosapentaenoic and docosahexaenoic fatty acids.

Novel branched-chain fatty acids in certain fish oils

Methyl-branched fatty acids, which are usually minor components (≤0.1%) in fish oils, were concentrated in the non-urea-complexing fraction along with polyunsaturated fatty acids during the enrichment of omega-3 fatty acids from certain fish oils via the urea complexation process. The methyl-branched fatty acids in the omega-3 polyunsaturated fatty acid concentrates, which were prepared from three fish body oils, were characterized by gas chromatography and gas chromatography/mass spectrometry. Among the major branched-chain fatty acids expected and identified were the known isoprenoid acids—mainly 4,8,12-trimethyltridecanoic, pristanic, and phytanic—and the well-known iso and anteiso structures. Two novel phytol-derived multimethyl-branched fatty acids, 2,2,6,10,14-pentamethylpentadecanoic and 2,3,7,11,15-pentamethylhexadecanoic, were identified in redfish (Sebastes sp.) oil. These two fatty acids were absent in oils from menhaden (Brevoortia tyrannus) and Pacific salmon (mixed, but mostly from sockeye,Oncorhynchus nerka). The major branched-chain fatty acid in the salmon oil, 7-methyl-7-hexadecenoic acid, was also present to a moderate extent in menhaden oil. A novel vicinal dimethyl-branched fatty acid, 7,8-dimethyl-7-hexadecenoic was detected in all of the fish oils examined, but was most important in the salmon oil. Three monomethyl-branched fatty acids, 11-methyltetradecanoic acid, and 11- and 13-methylhexadecanoic, hitherto undescribed in fish lipids, were also detected in salmon, redfish and menhaden oils.

Eicosapentaenoic acid geometrical isomer artifacts in heated fish oil esters

Gas liquid chromatography (GLC) on polar capillary columns showed that the ester of eicosapentaenoic acid (EPA) in distilled fish oil methyl and ethyl esters sometimes is accompanied by several artifacts. The same EPA artifacts did not arise from saponification and/or esterification but were formed in a significantly high yield during prolonged heating of the authentic acid. Physicochemical studies, isolation and partial degradation showed that these artifacts are mainly geometrical (cis-trans) isomers of the naturalcis ethylenic bonds of eicosapentaenoic acid. Several C20 mono-and diethylenic geometrical isomers were prepared and the GLC equivalent chain length values determined. On the basis of measured and calculated equivalent chain length values on two different GLC phases, some of the EPA artifacts were identified as 20:5-Δrans-5,cis-8,cis-11,cis-14,cis-17; 20:5-Δcis-5,trans-8,cis-11,cis-14,cis-17; and 20:5-Δcis-5,cis8,cis-11,cis-14,trans-17. No evidence was found for any positional isomers.

Stability of lipids and polyunsaturated fatty acids during smoking of atlantic mackerel (Scomber scombrus L.)

Fall Atlantic mackerel (Scomber scombrus L.), non-smoked and hot smoked according to the method of Torry (Aberdeen, Scotland) Advisory Note #82, in an AFOS-Torry Mini Kiln, were used to study changes in oxidative rancidity and composition of major lipid classes and fatty acids. After smoking there was an increase in thiobarbituric acid (TBAM) value and peroxide (PO) value, but the values were still indicative of acceptable quality. The percentages of triglycerides (TG) and phospholipid (PL) did not change significantly, and free fatty acids could barely be detected. The overall fatty acid composition remained virtually unchanged after the smoking process. This included the longer chain C20 and C22 n-3 fatty acids, now regarded as potentially essential fatty acids for humans.

EPA and DHA contents of encapsulated fish oil products

Seventeen brands of encapsulated fish oil or fish oil concentrate products, purchased during the period 1984–88 over the counter in the United States United Kingdom or Canada, were analyzed for their mg contents of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids per g of capsule contents. The mg contents were determined with respect to methyl tricosanoate internal standard by gas liquid chromatography (GLC) on a SUPELCOWAX-10 flexible fused silica capillary column. The alkyl ester and free fatty acid products showed very high levels of EPA (259–300 mg) and DHA (172–254 mg) whereas in the triglyceride oils EPA ranged from a low of 80 to a high of 250 mg, and DHA ranged from 78 to 156 mg, per g of capsule contents. The mg/g results indicate that the label claims for EPA and DHA for the majority of the products sampled are presented with reasonable accuracy.

Cod lipids, solvent systems and the effect of fatty acid chain length and unsaturation on lipid class analysis by Iatroscan TLC-FID

The chromatographic behavior of molecular species of free fatty acids, triglycerides, sterol esters and wax esters on Chromarods-SII was investigated in four developing solvent systems of different polarities. In accordance with previous reports it was observed that molecular species within a lipid class are partially separated according to the chain length and degree of unsaturation of the acyl groups. The separation is more affected by the degree of unsaturation than the chain length, especially in nonpolar solvent systems. In polar solvent systems the separation within a lipid class is less efficient; a slight separation according to the chain length was observed, and the degree of unsaturation had little or no influence. The partial separation of molecular species within a class leads to the superimposing of certain lipid classes, for example glyceryl ethers and highly unsaturated fatty acids of marine origin. This poses a potential problem in identification of Iatroscan peaks. However, with totally hydrogenated marine lipid samples a complete separation of the lipid classes was achieved when developed in a nonpolar solvent system. It is proposed that at least two kinds of authentic standards varying in the degree of unsaturation and chain length should be used for the identification of the peaks of natural lipid samples of unknown composition, and that total hydrogenation be applied to improve separations and ensure sample stability, and probably to improve quantitation accuracy.

Triacylglycerols of evening primrose oenothera biennis seed oil

AbstractsThe triacylglycerol (TG) composition of evening primrose(Oenothera biennis) seed oil (EPO) was studied using a combination of silver nitrate thin layer chromatography (AgNO```3``-TLC), reverse phase high performance liquid chromatography (HPLC) and capillary gas liquid chromatography (GLC). The important TGs in EPO are LLL (24.4%), LLO (23.9%), LLP (11.5%), LOO (7.2%), LOP (6.8%), LLS (4.8%), γLnLp (3.7%), LOS (3.3%), γLnLS (2.0%), γLnLL (2.0%), LPP (1.9%), OOO (1.7%), LSP (1.3%) and γLnLO (1.0%).

Rapid Analysis of Canola Gum Lipid Composition by Iatroscan Thin Layer Chromatography — Flame Ionization Detection

Abstract The combination of silicic acid separation of lipids on Chromarods-SII with flame ionization determination in the Iatroscan offers a simple, fast and economical approach to the determination of composition of canola gums. An initial analysis with a wax ester internal standard gives the proportions of triglyceride in the sample from only two peak areas. Samples from five Canadian oil processors had 8.4-12.4% triglyceride but only traces of free fatty acids. The latter could be measured as part of the same analysis, if present. Since they were not, the phospholipids in the sample could be taken as the difference in weight. For examination of phospholipids, the neutral lipids were first eluted with acetone to the upper part of the Chromarod, and removed by a partial scan. The phospholipids were then moved from the origin by a second development in a polar solvent system, and scanned for individual weight determinations. Samples from two out of five processors had little or no phosphatidic acid, whereas the others contained about 25% of this lipid class in the total sample. The high phosphatidylcholine in these two samples relative to the other three suggested this as the origin of the phosphatidic acid.

Hydrazine reduction in the gas liquid chromatographic analysis of the methyl esters of cyclopropenoic fatty acids

Hydrazine was used to hydrogenate the double bond of cyclopropenoic fatty acids (CPEFA) without cleaving the cyclic system. Using gas liquid chromatography (GLC), quantitation studies showed that it was possible to accurately determine CPEFA at concentrations as low as 0.1%. Studies with kapok seed oil methyl esters illustrated the potential application of such a technique to selectively hydrogenate the CPEFA to cyclopropanoic fatty acids (CPAFA), rendering them stable on the column, with a minimum effect on the degree of unsaturation of the remaining double bonds. Hydrazine reduction was found to be a simple and accurate method of measuring CPEFA in seed oils. Decomposition of pure methyl sterculate (methyl 9,10-methylene-9-octadecenoate) on GLC columns of various polarities also was examined.