GB2147911A - A process for the preparation of fatty substances - Google Patents

Abstract

The oil of pips of fruits of the Ribes genus is an abundant, cheap source of gamma -linolenic acid. It is extracted by pressing, or by using solvents, from dried and ground residues from the production of juices, preserves and jellies or brandies, liqueurs and schnapps of fruits, such as blackcurrant, redcurrant or gooseberry. The residues may be treated with a polar solvent, before being extracted with a non-polar solvent or supercritical fluid, in order to free the oil from most of the free fatty acids, waxes, colourings and odorous compounds. A preferred embodiment comprises flaking the washed pips and protecting them against oxidation before pressing the flakes prior to solvent extraction. The refined oil is a valuable ingredient in cosmetic, dermatological, dietetic and pharmaceutical compositions.

Description

SPECIFICATION A process for the preparation of fatty substances This invention relates to a process for the preparation of fatty substances from fruits of the Ribes genus.

Most vegetable oils contain linoleic (6,9-octadecadienic) and a-linolenic (9,1 2,1 5-octadecatri- enic polyunsaturated fatty acids. Only oils of the seeds of hops (Humulus), of hemp (Cannabis), of borage (Borage) and of evening primrose (Oenothera) are known as containing y-linolenic (6,9,12-octadecatrienic) acid, evening primrose being the only available source at, moreover, a high price.

y-Linolenic acid is an essential fatty acid which is metabolised by the organism into prostaglandins via dihomo-y-linolenic acid and arachidonic acid (5,8,11,14-eicosatetraenic), which is itself a constituent of cellular membranes, whereas a-linolenic acid does not take part in the same way in this metabolic process. The linoleic acid conversion into y-linolenic acid in the tissue is incomplete (4-20% compared to 90-98% for the conversion of y-linolenic acid into arachidonic acid) and may not even exist (for example in cats) in the case of the absence or the inactivation of the enzyme A-6-desaturase.

In effect, a lack of essential fatty acids results in a nutritional deficiency affecting all the metabolic processes which have been mentioned above and which may result in biochemical disorders or in organic lesions (for example coagulation disorders, dermatological lesions, endocrinal complaints, myocardiac lesions, and hepatic, articular, neurological and mental disorders). Therefore, it is possible to see the advantages provided by a supply of y-linolenic acid for the prevention or for the treatment of these anomalies.

The possibility of using y-linolenic acid and arachidonic acid as therapeutic and nutritional agents has been mentioned in, for example French Patents Nos. 2,197,605 and 1,603,383, ylinolenic acid being of a synthetic origin or being extracted from the oil of evening primrose (Oenothera) or officinal borage (Borage officinalis) seeds.

Moreover, French Patent No. 2,255,055 relates to cosmetic or pharmaceutical compositions based on the oil of raspberry pips, the anti-inflammatory activity of which is mentioned, but with no indication of the composition. Since the oil is preferably extracted using chloroform (a polar solvent), the anti-inflammatory activity is probably due to the presence of minor components.

Moreover, analysis of this oil has shown that it contained about 54% by weight of linoleic acid and 30% of a a-linolenic acid, but did not contain any y-linolenic acid.

Finally, Hungarian Patent No. T 1 3226 states that the addition of a pulp or a crude oil extracted from paprika, tomato or redcurrant pips to cosmetic products or table oils would inhibit their oxidation. The extraction, as it is described does not allow the separation of the undesirable waxes and colourings in the products which are envisaged, and the composition of the extract is not mentioned.

Surprisingly, it has been found that oils of pips of fruit of the Ribes genus contain an appreciable percentage, at least 4% by weight, of y-linolenic acid. Moreover, these pips are available in large quantities in the cakes resulting from squeezing fruit juices, from the production of preserves and jellies or from fermentation musts resulting from the production of brandies, liqueurs and schnapps, by-products which have been used up until now as fuel or forage.

According to the present invention, fatty substances are produced in practice from blackcurrants (Ribes nigrum), redcurrants (Ribes rubrum), gooseberries (Ribes ovacrispa or grossularia) or from hybrid fruits of these species. Of course, a mixture of these fruits may be used.

The lipid content of the by-products mentioned above is from 1 2 to 30% by weight, depending on the starting material. For its part, the lipid phase contains from 4 to 19% by weight of y-linolenic acid.

As an indication, the oil of the pips of these fruits comprises triglycerides of the following fatty acids, by weight: Fatty Acids Blackcurrants Red Gooseberries Currants C 16:0 6 - 7 % 4 - 5 % 7 - 8 % C 18:0 1 - 2 % 1 - 2 % 1 - 1 % C 18 :1 cis 9 - 10 % 14 - 15 % 15 - 16 % C 18 :1 trans 0.5 % 0.5 - 1 % 1 - 2 % C 18:2c36 47 47 - 49 % 41 - 42 % 39 - 41 % C 18:3wiz 15 - 19 % 4 - 5 % 10 - 12 % C 18:3 3W3 12 - 14 % 29 - 31 % 19 - 20 % C 18::4w3 3 - 4 % 2.5 -3.5 % 4 - 5 % Blackcurrant oil which is preferred due to its high content of y-linolenic acid also contains from 1 to 2% by weight of unsaponifiable substances, such as aliphatic alcohols, hydrocarbons, tocopherols, squalene, fi-sitosterol, campesterol and A-7 stigmasterol. Its density is 0.9215 g/cm3 (at 20"C), and its viscosity is 28.3 centipoise (at 20"C).

The present invention relates to a process for the preparation of fatty substances from pips of fruit of the Ribes genus, characterised in that a vegetable material containing these pips is pressed and/or is extracted by solvents in order to obtain a fatty substance containing at least 4% by weight of y-linolenic acid which is practically free from the odorous compounds, the free fatty acids, the colourings and the waxes of these fruits.

According to the present invention, the term "vegetable material" which is used is understood as designating the by-products which have been mentioned above. The starting material is generally in the form of strongly coloured cakes containing the waxes associated with the pips, waxes and colourings representing from 5 to 7% by weight of the crude oil which would be extracted therefrom, for example using hexane. The waxes are saturated and monounsaturated esters of long chain fatty acids with fatty alcohols which are solid at ambient temperature. The waxes and colourings in question are not desired in an oil incorporated in nutritive compositions.

A preferred starting material is the cake obtained by squeezing fruit juices, in particular blackcurrant juice. The cake is initially dried, for example in air for about 1 hour at about 60"C.

It is coarsely ground and sieved in order to obtain particles of from 1 to 1.5 mm, the sieving yield ranging from 60 to 80% by weight of the cakes. It is possible to separate advantageously the seeds from the chaff by gravity in a flow of air or by elutriation with a yield by weight of from 80 to 90%.

According to a preferred embodiment of the present process, the seeds are washed with a conventional polar solvent in order to free them from waxes, colourings and free fatty acids. For cosmetic uses, it is possible to use, for example methanol, isopropanol, acetone, ethanol or a mixture of these solvents, or a supercritical fluid, for example carbon dioxide under conditions which impart thereto a polar character. For nutritional and pharmaceutical uses, a food-grade solvent will be used, for example ethanol or supercritical carbon dioxide.

By way of example, washing is carried out by extracting the seeds with ethanol under reflux, either in batches, for example at first for about 2 hours and then for about 30 to 60 minutes, or continuously for about 2 hours, then the residue is drained.

In a variant, it is possible to extract the seeds using, for example, carbon dioxide under from 250 to 350 bars and at 60 to 80"C in a continuous cycle, the solvent being recovered in gas form by lowering the pressure, then being recompressed and recycled. It has been found that extraction makes it possible to remove most of the colouring materials and the waxes present in the skins and around the pips. In effect, the waxes are precipitated on cooling from the alcoholic extract, whereas said extract is very strongly coloured.

A variant of the separation and cleaning of pips from the fruit juice press cakes comprises treating the cakes enzymatically, for example with an aqueous solution containing 0.01 to 0.5% by weight of cellulose at pH 4 to 5, at a temperature of 38 to 42"C over a period of 1 to 4 hours or at ambient temperature over a period of 1 2 to 1 5 hours. The pips can be easily separated from the slurry and waxes and colourings are at least partly eliminated by this treatment.

It is advantageous to treat the washed and drained pips with an antioxidant. This treatment protects the oil against oxidation in the subsequent stages. Suitable antioxidants comprise for example aqueous dilute solutions of ascorbic or benzoic acids or sodium or potassium salts of these acids, ascorbic acid being preferred.

The protected pips may be pressed, for example in a continuous screw press at high pressure.

Depending on the type of press used, the number of pressing cycles and the pressing conditions applied, up to 90% of the oil may be recovered.

In a variant the pips are extracted with a solvent. Prior to solvent extraction, the drained residue is ground (particles from 100 to 300 ym), from about 10 to 15% by weight of water are added, and it is then made into pellets or granules by extruding the paste and cutting the strand. In a variant, it is possible to flake the seeds on a flattening cylinder from the non-ground drained residue. These forms prevent clogging and facilitate the subsequent extraction of the oil by providing the product with a porosity permitting a good penetration of the solvent, and the flakes in particular resist crushing.

A preferred variant of this stage comprises fiaking the protected pips and pressing the flakes prior to solvent extraction. The protected pips are dried and flaked, the flakes are preheated at a temperature of 80 to 90 C and pressed at 500 to 800 kg/cm2 with the press head temperature being kept below 90"C. In this way 50 to 60% of the oil present in the pips are obtained. The press-cake has a density of 0.58 to 0.65 which is about twice the density of the flakes. This is recommended for good percolation of the solvent. The press cake is milled and subjected to solvent extraction.

The next stage comprises extracting the oil with a non-polar solvent, for example, hexane, in a proportion of 200 to 250% by weight of hexane with respect to the residue. In a variant, it is equally possible to use in this stage liquid carbon dioxide or preferably supercritical carbon dioxide under conditions in which it is slightly polar, for example under from 200 to 300 bars and at 40 to 60"C. Of course, it is possible to use, for example, supercritical carbon dioxide in the washing stage and in the subsequent extraction stage, or in only one of these stages, the other being carried out using, for example ethanol or hexane.

After extraction, it is possible, although these measures are only preferred options, to neutralize the solution to remove the residual free fatty acids, after having partially evaporated the solvent, for example in the case of hexane, so that it contains about 10% by weight of oil, using (2N) concentrated potassium or sodium hydroxide, to cool the solution to about 0 to 4"C for about 24 hours and to filter it at this temperature in order to completely remove the residual waxes. Likewise, the subsequent decolorization and deodorization operations are preferred options: the solution is decolorized using 2 to 8% by weight of, for example active carbon or an activated aluminium silicate such as bentonite or montmorillonite with respect to the oil treated, at from 20 to 60"C, then the hexane is evaporated.The oil is then deodorized by steam stripping at from 140 to 220"C and preferably at about 1 80 C under a vacuum equal to or less than 1 torr.

According to one variant for the preparation of the oil, the seeds which have been ground are not previously washed, but are directly extracted with a solvent. In this case, the neutralization, the removal of the waxes by decantation, the decolorization and the deodorization as indicated above are essential for the production of a pale yellow refined oil.

In some cases, a fatty substance is to be enriched with y-linolenic acid. In order to do this, the oil which is freed from waxes and free fatty acids is saponified with an alkali metal hydroxide, for example, potassium hydroxide in a medium of methanol/water in a concentration of about 11%, the resulting salts are acidified using a mineral acid, for example 2N sulphuric acid, the free fatty acids are extracted with hexane, and the organic phase is separated and dried, for example by the addition of sodium sulphate. In a variant, it is possible to directly treat the ground cake with an alkali metal hydroxide, to acidify it using a mineral acid, to extract the free fatty acids with hexane and to dry the organic phase as indicated above.The organic phase is fractionated by high pressure chromatography in liquid phase, by passage over columns of silica gel loaded with silver nitrate and elution preferably with a mixture of dichloromethane, toluene and diethyl ether 70:25:5-65:30:5 in isocratic manner, i.e., with recycling of the solvent mixture of fixed composition, and a fraction containing about 60% by weight of y-linolenic acid and about 40% of a-linolenic acid is thus obtained.

Practically, pure y-linolenic acid may be isolated by high pressure liquid phase chromatography with a C8 or C,8 support in inversed phase with a gradient of a solvent mixture acetonitrile/water, methanol/water or isopropanol/water.

The fatty substances prepared according to the invention may be used in nutritive compositions according to British Patent Application No. 83 09742 (Publication No. 2118567A).

The following examples illustrate the present invention. In these examples, the parts and percentages are based on the weight.

EXAMPLE 1 100 kg of residue obtained by the extraction of blackcurrant juice and drying are treated a first time for 2 hours under reflux with 250 kg of ethanol and a second time for 1 hour under reflux with 250 kg of ethanol. The extract is drained and is dried twice at 80"C over a period of 30 minutes in an air drier, and is finally ground in a hammer mill.

After moistening with from 10 to 15% of water and after extruding the paste in the form of pellets, the 89 kg of product which is obtained are extracted twice with 205 kg of hexane under reflux for 3 hours, then cooled and filtered. The hexane is then evaporated and 14.3 kg of a clear yellow oil are obtained, the weight content of free fatty acids of which is 0.16% .

EXAMPLE 2 100 kg of dried residue resulting from the extraction of blackcurrant juice are ground in a hammer mill, and the powder is sieved in order to obtain particles of from 1 to 1.5 mm with a sieving yield of from 60 to 80%. The product is moistened and made into pellets and then extracted with hexane, as in Example 1. Part of the hexane is evaporated, the free fatty acids are neutralized with a 2N solution of sodium hydroxide, the organic phase is separated, is left to settle at 4"C for 24 hours and is separated by filtration from the hard waxes which have settled.

The organic phase is treated with from 2 to 8% of active carbon based on the quantity of oil in solution, then the solvent is evaporated and the oil is deodorized by stripping with steam at 180"C under a vacuum of 0.1 torr. From 13 to 16 kg of refined oil are thus obtained.

EXAMPLE 3 100 kg of dried blackcurrant pulp resulting from juice squeezing are ground in a disc mill and the ground product is sieved in order to obtain 60.5 kg of particles of from 1 to 1.5 mm. The product is introduced into an elutriator and 49.5 kg of a heavy fraction essentially comprising seeds are recovered. The fraction is washed twice with each time 1 20 kg of ethanol under reflux. The process is continued as stated in Example 1, except that two times 1 20 kg of ethanol are used for the washing operation, the dried extract is made into flakes using a flattening cylinder mill instead of the extruder, and the flakes are extracted with two times 102.5 kg of hexane. 11.1 kg of a clear, yellow oil are obtained.

EXAMPLE 4 432 kg of dried blackcurrant pulp resulting from juice squeezing are ground in a disc mill and the ground product is sieved in order to obtain 261 kg of particles of from 1 to 1.5 mm. The product is introduced into an elutriator and 214 kg of a heavy fraction essentially comprising seeds are recovered. The fraction is washed twice with each time 520 kg of ethanol under reflux.

200 kg of ethanol washed blackcurrant pips obtained in this way are sprayed with 14 to 1 6 litres of water containing 30 to 50 ppm (parts per million) of ascorbic acid. The treated pips are dried at about 70"C over a period of 30 to 40 minutes and subsequently flaked. The flakes are heated in a toaster at 80 to 90"C over a period of 30 to 40 minutes. Their density is about 0.35. The flakes are pressed over a period of 30 to 50 minutes in a continuous screw press under a pressure of 500 to 800 kg/cm2, at a rotational speed of the screw of 10 to 20 r.p.m., the press head temperature being kept at 80 to 90"C. Under these conditions 26 to 31 kg of oil (about 50 to 60 percent of the total oil present in the pips) are obtained. The press cake has a density of about 0.60 which is quite suitable for percolation of the solvent during the subsequent solvent extraction. The press cake is milled, extracted twice with 370 to 400 kg of hexane under reflux for 3 hours and then cooled and filtered. The hexane is evaporated and 22 to 26 kg of additional oil are obtained.

Claims (13)

1. A process for the preparation of fatty substances from pips of fruits of the Ribes genus, in which a vegetable material containing such pips is pressed in order to obtain a fatty substance containing at least 4% by weight of y-linolenic acid which is substantially free from the odorous compounds, the free fatty acids, the colourings and the waxes of these fruits.

2. A process as claimed in claim 1, wherein the vegetable material which is used comprises residues from the production of juices, jellies, or preserves, brandies, liqueurs, or schnapps of blackcurrants, redcurrants, gooseberries, hybrids or mixtures of these fruits.

3. A process as claimed in claim 1, wherein the vegetable material which has been previously dried is ground, the ground vegetable material is washed with a solvent or a supercritical fluid in a polar condition in order to remove the waxes, most of the colouring materials and the free fatty acids, the material is drained, the drained residue is subjected to a sieving operation and an elutriation operation so that it essentially comprises pips of from 1 to 1.5 mm, and the pips are made into flakes, the flakes are pressed, the pressed cake is extracted with a non-polar solvent or a supercritical fluid in a slightly polar condition and the latter is removed by evaporation.

4. A process as claimed in claim 1, wherein the vegetable material which has been previously dried is ground and subjected to a sieving operation and an elutriation operation so that seeds of from 1 to 1.5 mm are obtained; the seeds are washed with a polar solvent or a supercritical fluid in a polar condition; the seeds are drained; and the washed and drained seeds are then treated with an antioxidant.

5. A process as claimed in claim 4, wherein after the seeds are treated with an antioxidant, the seeds are dried and flaked; the flakes are subjected to a pressing and heating step to obtain a first portion of the fatty substance; and the resulting pressed cake is milled and extracted with a non-polar solvent or a supercritical fluid in slightly polar condition to obtain a second portion of the fatty substance.

6. A process as claimed in claim 3, wherein the ground vegetable material is washed with ethanol under reflux.

7. A process as claimed in claim 3, wherein the ground vegetable material is washed with supercritical carbon dioxide in a polar condition under a pressure of above 250 bars and at a temperature of from 60 to 80"C.

8. A process as claimed in claim 3, wherein the pressed cake is extracted with hexane under reflux.

9. A process as claimed in claim 3, wherein the pressed cake is extracted with supercritical carbon dioxide in a slightly polar condition under a pressure of from 200 to 300 bars and at a temperature of from 40 to 60"C.

1 0. A process as claimed in claim 3, wherein the pressed oil and the extract of the pressed cake are joined together, the non-polar solvent is partially evaporated until a solution containing from 80 to 90% by weight of solvent is obtained, the solution is neutralized with a concentrated alkali, is maintained at a temperature of from 0 to 4"C for about 24 hours, is filtered, and the solvent is removed by evaporation.

11. A process as claimed in claim 10, wherein after the residue has been extracted, the solvent has been partially evaporated and the solution has been neutralized, the solution is decolorized using from 2 to 8% of active carbon based on the weight of the fatty substance in solution.

1 2. A process as claimed in claim 10, wherein after the solvent has been evaporated, the oil is deodorized at a temperature of from 140 to 200"C and under a vacuum of less than 1 torr.

13. Fatty substances from pips of fruits of the Ribes genus when extracted by a process as claimed in any of claims 1 to 12.