No abstract

A modified low-temperature solvent crystallization process was employed for the enrichment of polyunsaturated fatty acids (PUFA) in borage and linseed oil fatty acids. The effects of solvent, operation temperature, and solvent to free fatty acid (FFA) ratio on the concentration of PUFA were investigated. The best results were achieved when a mixture of 30% acetonitrile and 70% acetone was used as the solvent. With an operation temperature of −80°C and a solvent to FFA ratio of 30 mL/g, γ-linolenic acid (GLA) in FFA of saponified borage oil can be raised from 23.4 to 88.9% with a yield of 62.0%. At a yield of 24.9%, α-linolenic acid in linseed oil can be increased from 55.0 to 85.7%. The results of this work are comparable to the best results available in the literature.Paper no. J9786 in JAOCS 78, 485-488 (May 2001).

A two-stage, low-temperature solvent fractional crystallization process was developed in this work for the enrichment of γ-linolenic acid (GLA, 18:3 n6) in free fatty acids (FFAs) derived from saponified borage oil. Acetonitrile was the solvent in the first stage. At an acetonitrile to FFA ratio of 62.5 mL/g and after 48 h of storage at -40 °C, the GLA content in the liquid phase can be increased from 23.4% to 66.1% with a corresponding yield of 93.0%. In the second stage, a mixture of 30% acetonitrile and 70% acetone was employed as the solvent. At a solvent to FFA ratio of 90 mL/g and after 24 h of storage at -80 °C, the GLA content in the liquid phase was further raised from 66.1% to 93.9% with a corresponding yield of 92.4% (overall yield 86.0%). More than half of the GLA in the solid can be recovered after the second-stage operation was applied to the solid phase.

High-purity γ-linolenic acid (GLA) was obtained by employing a modified low-temperature solvent crystallization process, followed by a lipase-catalyzed esterification, to borage oil fatty acid. By applying a two-stage solvent crystallization process to the borage oil fatty acid, GLA content was increased from 23.4 to 92.1% with a yield of 89.3%. After the esterification of GLA-rich fatty acid with butanol catalyzed by Lipozyme IM-60, GLA content in the fatty acid was further raised from 92.1 to 99.1%. The overall yield of the combined process was 72.8%. The effects of operation parameters on the Lipozyme IM-60 catalyzed esterification between fatty acid and alcohol were systematically investigated.Paper no. J9953 in JAOCS 79, 29-32 (January 2002).

Eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, in free fatty acids (FFA) derived from saponified menhaden oil were concentrated by the solubility differences of FFA-salts in organic solvent. FFA-salts were formed by adding NaOH to a solution containing FFA. A Buchner funnel was used to separate solid phases from liquids containing FFA-salts. FFA that are rich in EPA and DHA can be recovered from the liquid phase by the addition of 12 N HCl. The effects of reaction time, the amount of NaOH, and solvent used on the concentration of EPA and DHA were systematically investigated. With a total volume of 112 mL, made up of 1.85% 15 N NaOH, 88.1% acetone, and 10.0% FFA, a reaction temperature of 30°C, and a reaction time of 1 h, the resulting liquid phase contained 65.4 wt% EPA and DHA, with a corresponding yield of 41.5%. By replacing the acetone with a mixture of 45% acetone and 55% acetonitrile and then storing the liquid phase at −70°C overnight, the content and yield of EPA and DHA in the final liquid phase were 61.4 wt% and 66.2%, respectively.Paper no. J9271 in JAOCS 77, 425-428 (April 2000).KEY WORDS: DHA, EPA, menhaden oil, solubility difference, solvent extraction.Polyunsaturated fatty acids (PUFA) have been the subject of much attention in recent years because of their special physiological functions in human (1). Fish oil is an important natural source for PUFA, especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The health-promoting effects of EPA and DHA in human subjects have been reviewed (2,3). Various methods are available for obtaining concentrated EPA and DHA from fish oil, such as urea adducts (4), iodolactonization (5), high-performance liquid chromatography (6), supercritical fluid extraction (7), extraction by silver nitrate (8), and solvent extraction (9). Enzyme methods, including esterification (10), hydrolysis (11), and transesterification (12), have also been employed for the concentration of EPA and DHA. Although enzyme methods usually require more steps, thermal degradation of PUFA can be minimized because of their mild operating temperatures.The solubility of a free fatty acid (FFA)-salt in solvent depends on factors such as the polarity difference between the FFA-salt and the solvent, the chain length, and the number of double bonds in the FFA. In this study, the solubility differences of FFA-salts in organic solvent were employed for the concentration of EPA and DHA in FFA derived from saponified menhaden oil. The effects of reaction time and the amounts of NaOH and solvent used on the concentration of EPA and DHA were studied systematically. MATERIALS AND METHODS Materials.Refined menhaden oil and all fatty acid standards were purchased from Sigma Chemical Co. (St. Louis, MO). All solvents and reagents used were of high-performance liquid chromatographic or American Chemical Society grade. Preparation of FFA. FFA were prepared according to the method described by Haagsma et al. (13) with some modifications. Typically, a 3.7 N NaOH solution was pr...