JPH06248289A - Method for selectively separating and recovering highly unsaturated fatty acids - Google Patents

Abstract

PURPOSE:To obtain a simplified and efficient method for selectively separating highly unsaturated fatty acids from an aqueous solution of a silver complex. CONSTITUTION:A material containing highly unsaturated fatty acids is brought into contact and treated with an aqueous medium containing a silver salt to give an aqueous solution, which is extracted with supercritical carbon dioxide. Highly unsaturated fatty acids having three or more unsaturation degree are selectively separated. The highly unsaturated fatty acids can selectively be separated.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to highly unsaturated fatty acids having a degree of unsaturation of 3 or more such as eicosapentaenoic acid and docosahexaenoic acid, and the contents of highly unsaturated fatty acids such as their esters, preferably fish oil esters. The present invention relates to a method for selectively separating unsaturated fatty acids.

[0002]

2. Description of the Related Art Recently, highly unsaturated fatty acids, especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (D), which are contained in relatively large amounts in neutral lipids obtained from fish and shellfish.
The physiologically active action of HA) has received widespread attention, and establishment of advanced separation and purification methods for utilizing them as pharmaceuticals and health foods is strongly desired. However, seafood contains complex lipids such as phospholipids in addition to neutral lipids,
The amount of lipids, lipid composition, and the proportion of neutral lipids in total lipids differ depending on various factors such as the type of seafood, fishing season, fishing grounds, and oil collection methods. The neutral lipids are mainly glycerides (neutral fats). Carotenoids, hydrocarbons, sterols and their esters, free fatty acids, odorous components, etc. are contained in, and it is generally difficult to separate highly unsaturated fatty acids from seafood.

As a method for selectively separating highly unsaturated fatty acids from the contents of highly unsaturated fatty acids, a complex of water-soluble silver and highly unsaturated fatty acids is selected by utilizing highly unsaturated property. Methods have been developed for forming and extracting into an aqueous layer and separating from the aqueous layer (JP-A-4-103558, JP-A-4-159398, and JP-A-4-218).
596, etc.). The aqueous medium phase separated by this operation contains a silver salt-polyunsaturated fatty acid complex. It is difficult to recover the highly unsaturated fatty acid from the aqueous layer containing the complex with silver, and various proposals for recovery thereof, for example, various complex dissociating agents for dissociating the complex are used. Proposals have been made such as use (Japanese Patent Application Laid-Open No. 4-103558, Japanese Patent Application Laid-Open No. 4-218596, etc.) or adopting an organic solvent extraction method (Japanese Patent Application Laid-Open No. 4-159398). It is simply to dissociate and extract highly unsaturated fatty acid from highly unsaturated fatty acid forming a silver complex, and it is impossible to selectively separate a specific highly unsaturated fatty acid. It has not yet been adopted as an industrial operation that is difficult to say.

[0004]

The present invention is further improved by a method known prior to the present application for selectively separating only highly unsaturated fatty acids as a silver complex from inclusions of highly unsaturated fatty acids. The purpose of the present invention is to simplify and improve the efficiency of the subsequent step, that is, the step of selectively separating and recovering highly unsaturated fatty acids from the obtained aqueous silver complex solution.

[0005]

As a method for recovering highly unsaturated fatty acids from an aqueous layer containing the complex, the present inventors have adopted a supercritical carbon dioxide extraction method and selected highly unsaturated fatty acids. The present invention has been completed that can be separated efficiently and efficiently. That is, the present invention is a method for separating polyunsaturated fatty acids from the contents of polyunsaturated fatty acids, which is subjected to contact treatment with an aqueous medium containing a silver salt, and then subjecting the resulting aqueous solution to extraction treatment with supercritical carbon dioxide. . A method for selectively separating only highly unsaturated fatty acids from the content of highly unsaturated fatty acids as a silver complex utilizes the fact that silver ions form a complex with a carbon double bond of a fatty acid. A highly unsaturated fatty acid ester (eg, EPA, DHA, etc.) is obtained by contacting a highly unsaturated fatty acid content with an aqueous silver ion-containing solution.
Is a method known in the prior art of the present application in which is dispersed in an aqueous solution as a silver complex. This known method prior to the present application is adopted as the first step in the method for separating highly unsaturated fatty acids from the content of highly unsaturated fatty acids according to the present invention.

The present invention employs a means for extracting the aqueous solution of the silver complex with supercritical carbon dioxide as a subsequent step. The extraction process is shown in FIG. That is, carbon dioxide is used as an extractant, and the carbon dioxide is pressurized and heated to a critical pressure of 75.
Carbon dioxide in a supercritical fluid region of ² kg / cm ² and a critical temperature of 31.1 ° C. or higher is brought into contact with an aqueous solution of a silver complex to selectively oxidize only specific highly unsaturated fatty acids. The method of extracting into carbon is adopted. The extraction pressure can be 350 Kg / cm ² from the critical pressure. The upper limit is due to the manufacturing of the device. It is necessary to remove the insoluble matter from the aqueous solution before starting the subsequent steps.

In the present invention, the polyunsaturated fatty acids mean fatty acids having an unsaturation degree of 3 or more. Examples of the polyunsaturated fatty acids having the degree of unsaturation of 3 or more include α-linolenic acid, arachidonic acid, eicosapentaenoic acid and docosahexaenoic acid. Therefore, polyunsaturated fatty acids include methyl ester, ethyl ester,
It includes ester type derivatives such as triglyceride, diglyceride and monoglyceride, carboxylic acid type derivatives such as amide and methylamide, and aliphatic alcohol. In the present invention, any raw material containing the polyunsaturated fatty acid having the degree of unsaturation of 3 or more can be used. Raw materials containing highly unsaturated fatty acids
Marine fish such as sardines, mackerel, saury, tuna, krill,
Crustaceans such as shrimp themselves, unpurified fish oil, animal and vegetable oils, lipids derived from microorganisms, and the like at any stage of purification can be used as a raw material.

The silver salt of the present invention capable of forming a complex with an unsaturated bond is not particularly limited, and is generally soluble in an aqueous medium such as silver nitrate, silver perchlorate, silver acetate and silver tetrafluoroborate. A silver compound is used. Water is preferable as the aqueous medium of the present invention, and other compounds having a hydroxyl group such as glycerin and ethylene glycol, or a mixture thereof can be used. The molar ratio of highly unsaturated fatty acids to silver salt may be in the range of 1: 100 to 100: 1, and the concentration of the silver salt in an aqueous medium may be 0.1 mol / 1 to the saturated state. At a concentration below this, the complex is not sufficiently formed,
Polyunsaturated fatty acids do not become aqueous soluble. From the recovery rate of highly unsaturated fatty acids, the molar ratio is 1: 5 to 1:
1, the concentration is preferably 1 to 20 mol / 1.

The former step of the present invention will be specifically described below.
An aqueous medium-soluble silver salt-polyunsaturated fatty acids is prepared by adding an aqueous medium solution of a silver salt capable of forming a complex with an unsaturated bond to a content of highly unsaturated fatty acids and stirring the mixture for 5 minutes to 4 hours. And the polyunsaturated fatty acids are selectively dissolved in the aqueous medium phase. The reaction temperature is such that the lower limit is liquid and the upper limit is up to 100 ° C. However, room temperature is considered in view of stability of highly unsaturated fatty acids, solubility of silver salt in water, rate of complex formation, etc. Near, reaction time 10 minutes to 2
Time is preferred. Further, in view of the oxidation stability of highly unsaturated fatty acids and the stability of silver salt, the present invention is preferably carried out under an inert gas such as nitrogen atmosphere and protected from light.

[0010]

Reference Example The distribution equilibrium of the fish oil ethyl ester and the 5M silver nitrate aqueous solution was measured by changing the silver nitrate concentration by fixing the volume ratio of the fish oil ester and the silver nitrate aqueous solution to be brought into contact with each other at an equilibrium temperature of 28K. As a result, as shown in Table 1, almost no fatty acid ester with a low degree of saturation and unsaturation was distributed in the silver nitrate aqueous solution, and only fatty acid ester with a high degree of unsaturation was distributed in the aqueous solution. The solubility of the whole unsaturated fatty acid ester in the aqueous solution increases with the silver concentration.
It reaches almost constant at M. It was found that EPA-Et.DHA-Et in the fish oil ester was almost completely transferred to the water phase even at a silver nitrate concentration of 5M. From these results, as the charging conditions when performing supercritical carbon dioxide extraction of the aqueous solution,
The concentration of silver nitrate used was 5M.

[0011]

【Example】

Example 1 Supercritical Carbon Dioxide Extraction of Silver Nitrate Aqueous Solution Containing Highly Unsaturated Fatty Acid Ester A silver nitrate aqueous solution containing unsaturated fatty acid ester pretreated as shown in Reference Example was used as a semi-batch flow type supercritical carbon dioxide extractor (Fig. Using 1), the influence of the operating temperature and pressure on the extraction behavior was investigated. Unsaturated fatty acid ester had a high extraction rate in the early stage of extraction and then decreased in extraction rate, but finally all the fatty acid ester components in the aqueous solution were extracted. Water was also extracted at a constant rate at the same time. FIG. 2 shows an example of an extraction curve when supercritical carbon dioxide is used. From the result of measurement by the atomic absorption method, it was found that the extract did not contain silver and could be reused. The influence of the solvent flow rate on the extraction behavior was not observed in the measured range, indicating that the extraction was carried out under equilibrium. When supercritical carbon dioxide was used, the effect of extraction pressure was not significant. In addition, in an experiment in which the temperature was changed at a constant pressure, the extraction rate increased with temperature, and the extraction behavior was considered to be governed by the complex equilibrium in the aqueous solution rather than the solubility of unsaturated fatty acid ester in carbon dioxide. It was As shown in FIG.
A-Et had a purity of 60% at the initial extraction stage, and DHA-E
As for t, 90% or more was obtained in the latter stage of extraction. FIG. 4 shows an extraction curve using supercritical carbon dioxide.

Example 2 A sample prepared by ethyl esterification of sardine oil was brought into contact with an aqueous solution of silver nitrate at a volume ratio of 1: 2, shaken at 25 ° C. overnight, and allowed to stand, and then the amount and composition of fatty acid ester in the aqueous solution were measured. did.
From the partitioning experiment of the reference example, it was considered that the 5M silver nitrate aqueous solution was optimal for the preparation of supercritical extraction.
It fixed to M and extracted. About 8 g of an aqueous silver nitrate solution containing a fatty acid ester prepared by the above method was used with a semi-batch flow type supercritical carbon dioxide extraction device (FIG. 1).
Temperature (40-60 ° C), pressure (100-250Kg / c
m ² ) and carbon dioxide flow rate (400-800 ml / m
in [STP]) extraction was performed under a constant condition, and the time-dependent change of the extract was measured. The extraction was terminated when the fatty acid ester yield exceeded 95%. Since the extract is a mixture of fatty acid ester and water, after diluting it with 2-propanol to form a single phase, the amount of water is obtained by subtracting the amount of water from the extract with the Karl Fischer moisture meter, and the amount of ester extracted is obtained. The ester composition was analyzed by. It was also found that the presence or absence of silver in the extract was not extracted by the atomic absorption method.

INDUSTRIAL APPLICABILITY The present invention firstly utilizes the complex-forming ability of an aqueous medium-soluble silver salt capable of forming a complex with an unsaturated bond and a highly unsaturated fatty acid, and dissolves the complex in an aqueous medium. It is possible to selectively separate the part containing only highly unsaturated fatty acids by utilizing the property, and secondly, the aqueous solution of this complex is subjected to supercritical carbon dioxide extraction to extract highly unsaturated fatty acids from silver. It is achieved by separating. It is a method capable of selectively extracting, separating and purifying highly unsaturated fatty acids from a fatty acid-containing material on an industrial scale.

[Brief description of drawings]

Figure 1: Semi-batch flow type supercritical carbon dioxide extraction

FIG. 2 Supercritical carbon dioxide (313K and 24.
Extraction curve when using 5 MPa)

FIG. 3: Supercritical carbon dioxide (313K and 24.
Change in concentration of PUFA ester extracted using 5 MPa)

FIG. 4 Supercritical carbon dioxide (313K and 24.
Extraction curve of PUFA ester using 5 MPa)

[Explanation of Codes] 1 Fluid phase (Extract) 2 Water phase (Raffinate)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical display location C11B 7/00 2115-4H (72) Inventor Kaoru Nakano 2206-4 Minamiosawa, Hachioji, Tokyo 101 Kina Heights 101 (72) Inventor Satoshi Kikuchi 4-65-24 Kashiwa-cho, Tachikawa-shi, Tokyo

Claims (1)

[Claims] 1. A method for separating polyunsaturated fatty acids from contents of polyunsaturated fatty acids, which comprises contact treatment with an aqueous medium containing a silver salt, and then subjecting the resulting aqueous solution to extraction treatment with supercritical carbon dioxide. A method characterized by the following.