Purifying polyunsaturated fatty acid glycerides

Details Purifying polyunsaturated fatty acid glycerides Purifying polyunsaturated fatty acid glycerides

1999-09-27

2001-03-20

Carr, Deborah (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Fatty compounds having an acid moiety which contains the...

C554S206000

Reexamination Certificate

active

06204401

ABSTRACT:

This invention relates to a process for treating compositions containing polyunsaturated fatty acid glycerides in order to recover a purified polyunsaturated fatty acid glyceride product therefrom.
The fractionation of fatty acids and their derivatives has been widely investigated in recent years. The reason for this interest lies in the recognition that some fatty acids, especially long chain polyunsaturated fatty acids, are precursors for so-called prostanoid compounds, including prostacyclins and prostaglandins, which play an important role in the regulation of biological functions such as platelet aggregation, inflammation and immunological responses.
In this specification polyunsaturated fatty acids are identified according to the system wherein the omega- or n-number denominates the position of the first double bond when counting from the terminal methyl group, e.g. in an omega-3 or n-3 fatty acid, the first double bond occurs at the third carbon atom from the terminal methyl group of the acid. Further, when a fatty acid is identified, for instance, as C18:3, this refers to a fatty acid having 18 carbon atoms in the chain and three double bonds.
Two commercially important polyunsaturated omega-3 fatty acids, EPA (eicosapentaenoic acid, C20:5) and DHA (docosahexaenoic acid, C22:6) are found in marine oils. The biological properties of these fatty acids have been discussed in many publications and patents, such as for instance GB 2221843 which teaches that concentrated mixtures of EPA and DHA are efficient products for the treatment and prophylaxis of multiple risk factors for cardiovascular diseases.
Correspondingly, the polyunsaturated fatty acids of the omega-6 series, such as linolenic acid and arachidonic acid, are also of growing commercial importance. The omega-6 acids are commonly produced from vegetable oils such as evening primrose oil and borage oil and are widely employed for pharmaceutical purposes.
These polyunsaturated fatty acids are found in marine and vegetable oils mainly as triglycerides.
As such triglycerides usually also contain unwanted fatty acids, it is often necessary to cut the triglycerides to obtain the fatty acids either in free acid form or as esters with monofunctional alcohols such as methanol and ethanol in order that a proper separation of the desired fatty acids from the unwanted fatty acids can then be accomplished.
On the other hand, for many commercial purposes it is desired that the polyunsaturated fatty acids should be used in the form of glycerides. Accordingly, it is common practice to reconvert purified fatty acids back to glyceride form by esterification with glycerol, or transesterification with glycerol if the fatty acids are present as monofunctional esters. The resulting glyceride products will be termed “synthetic glycerides” hereinafter, to distinguish them from the “natural glycerides” found in the original marine or vegetable oils, although of course they themselves have originated from natural sources as well.
Polyunsaturated fatty acids are extremely fragile when subjected to heat or light in the presence of oxygen and will readily undergo rapid isomerization, peroxidation and oligomerization reactions. Accordingly, even if great care is taken at all times during the manufacture of purified fatty acid glycerides for commercial use, it is almost impossible to avoid several types of organic impurities being present in either the natural or the synthetic glyceride products, eg in particular:
(1) oligomers of fatty acids, which normally are absent from natural products but typically present up to 3-5 weight percent, and sometimes at even higher levels, in synthetic products (they are formed particularly during the esterification or transesterification with glycerol),
(2) malodorous compounds giving an unpleasant smell and mainly consisting of aldehydes and other carbonyl compounds resulting from the breakdown of peroxides, and
(3) a wide variety of coloured decomposition products which have not been fully defined by chemical analysis but which typically impart a darker colour to synthetic glycerides than to natural glycerides.
Over the past decade a number of scientific groups have focused on the effect of oligomeric (often called “polymeric”) oxidation products on oil quality and on health. See, for example, Nawar et al “Stability of Fish Oils”, N-3 News, 1988, 3:3; Kragballe et al “Polyumaettede fedtsyrepraeparater pa det danske marked. Sammensetning og oksidativ stabilitet”, Ugeskr. Laeger, 1990, 152:894-897; and Hanmann “What's in those capsules”, Inform, 1990, 1:117-120. It is generally recognized that the presence of such comparatively large concentrations of these impurities is undesirable.
For these reasons it would be desirable to reduce the oligomer (polymer) content of both natural and synthetic fatty acid triglycerides to less than 1% by weight, preferably to less than 0.5% by weight.
The malodorous fatty aldehyde and other carbonyl components are responsible for the very unpleasant odour of many oils—they give the very typical “fishy” smell to marine oils, for example—and prevent these oils being directly usable in dietary and cosmetic products and even restrain their pharmaceutical utility. For this reason it is conventional to steam deodorise fatty acid glyceride compositions. However, this process has to be conducted at relatively high temperatures and can, by itself, give rise to the further production of oligomeric material (see Hanmann, supra). Moreover, it should also be noted that deodorising does not completely remove all oxidation/decomposition products. According to the authoritative Bailey's Industrial Oil and Fat Products (ed. Y. H. Hui, John Wiley & Sons, Inc., New York, 5 ed. 1996, Vol. 4, page 51): “While the deodorizer generally represents the final step in edible oil processing, and can make a good product from a less than perfect feedstock, the deodorizer cannot forgive the sins made in earlier processes. While the primary products of oxidation are removed (as indicated by the peroxide value), several damaged oil may contain secondary products of oxidation (measured as anisidine value).”.
The coloured by-products result in the fatty acid glycerides having an unpleasant appearance. Moreover, it is unsatisfactory to distribute products containing contaminants which have not been completely characterised chemically, particularly in the health or drug fields.
Metal compounds are often used as catalysts in the production of synthetic polyunsaturated fatty acid glycerides, and typically include zinc, silver, mercury and calcium as their salts or oxides. Residues from the catalysts can dissolve in the glyceride composition, typically in amount of 1-10 mg/g. Metals can act as unwanted catalysts for oxidation. Also, a purified product is not expected to contain residues from catalysts, and the health effects of any such residues should be documented.
In view of the state of the art it would be desirable to be able to provide a simple, effective process for removing at least some of the impurities which are commonly found in polyunsaturated fatty acid glycerides.
In accordance with the present invention there is provided a process for purifying a composition containing polyunsaturated fatty acid glycerides, comprising subjecting said composition to supercritical fluid fractionation in one or more countercurrent columns operated either with internal reflux achieved by a temperature gradient along the column or with an external reflux achieved through external regulation of the pressure, the solvent for said extraction being a mixture of supercritical CO
2
and a polar co-solvent; and recovering a purified composition containing said polyunsaturated fatty acid glycerides.
As is well known, it is possible to change from one state of a pure compound (i.e. solid, liquid or gaseous) to another state by changing the temperature and/or pressure of the compound. It is also well known that there exists a value, termed the “critical value” of temperature and/or pressure beyond which it is impossible t

Affiliated with

Also associated with

Rating

Purifying polyunsaturated fatty acid glycerides does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Purifying polyunsaturated fatty acid glycerides, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Purifying polyunsaturated fatty acid glycerides will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2468461