Residual Free Fatty Acid Research Articles

Separation of eicosapentaenoic acid and docosahexaenoic acid in fish oil by kinetic resolution using lipase

AbstractThe objective of this study was to investigate the use of lipases as catalysts for separating eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in fish oil by kinetic resolution. Transesterification of various fish oil triglycerides with a stoichiometric amount of ethanol by immobilized Rhizomucor miehei lipase under anhydrous solvent‐free conditions resulted in a good separation. When free fatty acids from the various fish oils were directly esterified with ethanol under similar conditions, greatly improved results were obtained. By this modification, complications related to regioselectivity of the lipase and nonhomogeneous distribution of EPA and DHA into the various positions of the triglycerides were avoided. As an example, when tuna oil comprising 6% EPA and 23% DHA was transesterified with ethanol, 65% conversion into ethyl esters was obtained after 24 h. The residual glyceride mixture contained 49% DHA and 6% EPA (8:1), with 90% DHA recovery into the glyceride mixture and 60% EPA recovery into the ethyl ester product. When the corresponding tuna oil free fatty acids were directly esterified with ethanol, 68% conversion was obtained after only 8h. The residual free fatty acids comprised 74% DHA and only 3% EPA (25:1). The recovery of both DHA into the residual free fatty acid fraction and EPA into the ethyl ester product remained very high, 83 and 87%, respectively.

Low‐temperature properties of alkyl esters of tallow and grease

AbstractThe low‐temperature properties of mono‐alkyl esters derived from tallow and recycled greases were determined for neat esters and 20% ester blends in No. 2 low‐sulfur diesel fuel. Properties studied included cloud point, pour point, cold filter plugging point, low‐temperature flow test, crystallization onset temperature, and kinematic viscosity. Compositional properties of the alkyl esters determined included water, residual free fatty acids, and free glycerol content. In general, the secondary alkyl esters of tallow showed significantly improved cold‐temperature properties over the normal tallow alkyl ester derivatives. The low‐temperature flow test did not show a 1:1 correlation with cloud point as previously observed with methyl soyate and methyl tallowate. For the homologous series methyl to n‐butyl tallowate, ethyl tallowate had the best broad‐spectrum low‐temperature properties, both neat and when blended in diesel fuel. For the greases studied, both the normal and branched alkyl ester derivatives showed improved properties over corresponding tallow esters, especially with neat esters.

Effects of Phospholipase A2 and Albumin on the Calcium‐Dependent ATPase and the Lipid Composition of Sarcoplasmic Membranes

1. The calcium-dependent ATPase activity of phospholipase-A2-digested sarcoplasmic vesicles decreases concomitantly with the contents of residual lysophospholipids and fatty acids when increasing albumin concentrations are applied. 2. Delipidated albumin preferentially removes unsaturated fatty acids and lysophosphatidylcholine. A complete removal of the phospholipids by albumin does not occur. 3. The membrane-bound lysophospholipids were analysed with respect to type of phospholipid, plasmalogen content and fatty acid chains by means of thin-layer chromatography and gas chromatography. 4. While the fatty acid composition of the lysophospholipids is independent of the degree of delipidation, the composition of the residual free fatty acids is found to change with the albumin concentration. 5. Reactivation of the Ca2+-ATPase by oleate leads to reasonable activities at room temperature as long as a minimum of about 30 lysophospholipid molec-les per ATPase is left. The course of the residual Ca2+-ATPase activity with the degree of delipidation is related to the presence of unsaturated fatty acids. 6. No specific role of either sphingomyelin or the plasmalogens has been found.