Note: Descriptions are shown in the official language in which they were submitted.
2~8~23
PROCESS FOR REMOVING STEROLS FROM VEGETABLE AND ANIMAL FAT
This application claims priority from German Patent P 41 39 398.8, filed on November 29, 1991, which
is hereby incorporated by reference.
The present invention relates to a process for removing sterols from and respectively for enriching sterols
in vegaable and animal fats. As cholesterol is by far the most important fat among the sterols, in the
following the removal/enrichment of cholesterol is discussed as being representative for the rernovallenrich-
ment of sterols in general.
Recently the fractionation and the removal of cholesterol from milk fat has found great interest with respect
to possible new utilities and markaing milk fat. Due to health hazards mainly with respect to athero-
sclerosis the reduction of the cholesterol content has found considerable attention. It has been generally
suggested to reduce the cholesterol content of milk fat by 90 % so that several of the dairy products may
be classified in the category of cholesterol-free products.
Cholesterol (5-cholestone-3n~1), molecular weight 386.64, melting point 148.5C, boiling point 360C,
is essentially insoluble in water, it is little soluble in cold alcohol while being better soluble in the heat. In
ether, benzene, petroleum ether and chloroform cholesterol is easily soluble. Cholesterol may be found in
large amounts in bile calculi. As main representative of the zoosterines cholesterol is also present in the
other organs: in the cerebrum (about 10 9 i of the dry matter), in nerve cells, in the suprarenal glands and
in the skin. Egg yoke and wool wax are also rich in cholesterol. Blood contains 150 to 250 mg%, the heart
2000 rag% of cholesterol (maximum amount around about the 60th year). Altogether the human body
contains an average of 0.32 % of cholesterol, partly free and partly esterified with fatty acids; the esters
are considered blood fats. The body of an average adult person synthezises about I to 2 g of cholesterol
per day, absorbing 0.04 to 0.1 g with a low-fat diet and with a high-fat diet up to 1.4 g.
Per 100 g of foodstuff, butter contains 240 mg, margarine 186 mg, fat beef 90 mg, fat pork 99 mg,
codfish 58 mg, shellfish 64 mg and codliver oil 570 mg of cholesterol. In minor amounts cholesterol also
occurs in vegetable fats. The biosynthesis of cholesterol starts from squalene via lanosterol. The main site
of its formation is the liver, but cholesterol is also formed in the suprarenal cortex, in the skin, gut, testes
and aorta.
~holesterol is also the biogenetic precursor of biliary acids, vitamin D3, androsterone, testosterone,
progesterone and other steroids. In the organism cholesterol is also a protective for the skin, a regulator
for swellings, nerve insulator etc.
Pathologically elevated cholesterol concentrations in the serum may result from a wrong diet but also from
certain enzyme defects which are considered partly responsible for the occurrance of atherosclerosis;
however, the theories about relationships between the take-up of cholesterol-containing foodstuffs and
hypercholesterolemiae are controversial. According to Heyden oils having a high content of unsaturated
fatty acids (such as sunflower oil, corn oil, linseed oil, soybean oil and wineseed oil) are said to decrease
2 2~3~2~
the blood cholesterol content, thus in being frequently active against atherosclerosis.
A high percentage of milk fat is marketed in the form of butter. According to the German Butter Regul-
ation of June 2, 1951 butter is "the plætified mixture obtained from milk, cream or whey cream, sweet or
acidified, optionally with the use of specific lactic bacteriae cultures, water and table salt from wbich, by
heating to 45C, a substantially clear layer of milk fat and a minor layer containing water and milk
components are separated." Butter is not permitted for marketing when 100 g thereof contain less than 82
g of fat or more than 16 g of water. In salted buKer 100 g thereof contain more than 0.1 g of table salt.
As coloring agent only alpha-, beta- and gamma-carotines are permitted. Although butter was already
known in early historic times (if only æ a cosmetic) its consumption æ one of the most inportant edible
fats became popular in zones of moderate climate only in the 16th century. In the Federal Republic of
Germany the consumption of butter is decreasing in favour of other foodstuffs (margarine, edible oils and
vegetable fats).
Starting material for the preparation of butter is cream, a milk emulsion enriched in fat and having a fat
content of 20 to 25 %. It is obtained by le~ting the milk stand or by centrifuging it. By continuous churning
in a churn or in a churning machine cream is converted to butter, the fine fat particles gradually associating
to larger lumps. From 25 1 of good milk 1 kg of butter is generally obtained. The forming aqueous phase
is buttermilk. The ready unsalted butter contains an average of 82 to 84 ~o of fat and 15 % of water as
well as minor amounts of lactose, lactic acid, casein, egg white and mineral substances. Expressed in terms
of the colloid chemistry butter is a water-in-oil emulsion, whereas milk is an oil-in-water emulsion. In the
latter case very fine fat particles float in an aqueous solution.
For several purposes butter is converted to clarified butter which contains 99.3 % of butter fat. Clarified
butter contains at most 0.5 % of water and is substantially free from lactose, casein and salts. Clarified
butter is obtained by melting butter and separating the aqueous phæe while heating to 100 to 105C. It is
mainly used æ frying and baking fat.
The colour of butter is dependent on the type of fodder for the milk cows and the vitamin content of the
fodder. Butter fat contains 0.2 to 0.45 æ of lecithin, 0.22 to 0.41 % of cholesterol and the fat soluble
vitamins A and E. Lactic bacteriae are present in butter in amounts of up to 100 millionslg, which,
however, is unobjectional to the health. As a protection against becoming rancid it is best to keep butter
in a dark and cool surrounding. If heavy metal ions (in particular copper) are present and if the butter has
a higher content of acids it may acquire a fish-like odour already after 2 to 3 days because the lecithin in
the butter is decomposed to trimethyl amine by hydrolysis and oxidation.
About 98 % of the milk fat consist of triglycerides. The number of carbon atoms of the triglycerides is
in the range of 26 to 54. The remaining 2 % consist of a great number of other compounds, such as
lecithin, cholesterol, vitamins A and E, and a great number of other components, which contribute to the
characteristic flavour of the milk fat and are present in low concentrations.
Flavour substances of the butter are formed partly by enzymatic processes during the ripening of the cream
~83723
and partly by autioxidation of the unsaturated fatty acids. The main flavour substances of the cream.are
diacetyl (2,3-butane dione) and acetoin (3-hydroxy-2-butanone). Furthermore the following flavour
substances are important: unsaturated aldehydes, such as cis~heptenal and homologues, esters and
lactones. Among the lactones delta-decalactone, delta-dodecalactone, delta-tetradecalactone and delta-
hexadecalactone have been identified.
As cholesterol is made responsible for the occurrance of atherosclerosis and other circulatory defects the
possibilities for its removal from milk fat have frequently been examined. In various papers the extraction
of cholesterol by means of carbon dioxide under high pressure has been studied. A cholesterol solution in
milk fat is treated at high pressure with the sub- or supercritical CO2 dissolving, beside cholesterol, also
portions of the milk fat in the dense carbon dioxide. Subsequently the carbon dioxide is contacted ~Yith an
adsorbent for the cholesterol. Salts of basic metals, such as oxides, hydroxides, carbonates, sulfates etc.,
are suitable adsorbents for cholesterol. From the solution, which is freed from cholesterol in this manner,
the milk fat is removed by pressure reduction. In this way cholesterol has been removed from butter oil by
fluid carbon dioxide at 220 bar and 45C using Ca(OH)2 (WO 90/02788).
A further suggested process relates to the dissolut;on of the cholesterol-containing material in an unpolar
solvent, such as hexane, and the subsequent adsorption of the cholesterol on silica gel aP-B~2-039593).
In another article it is reported that cholesterol is adsorbed at the heptane/water interface together with
alkyl ammonium (cetyltrimethyl ammonium, dioctyl dimethyl ammonium) IYu.A. Shchipanow, A.N.
Popow, Latv. PRS Zinat. Akad. Vestis, Kim. Ser (4), 445-51 1980)].
Pormer investigation has concentrated on systems with batchwise extraction using dense supercritical carbon
dioxide. More recently also the extraction of cholesterol from anhydrous milk fat with supercritical dense
C2 has been examined for continuous processes, working in countercurrent as well as in continuous cur-
rent. At 60C and 172 bar a loading of CO2 of about 0.3 weight% was observed, and at 40C and 241
bar the loading was about I weight%. Together with the cholesterol also the triglycerides of short chain
fatty acids go into solution to a considerable extent whereby the fatty acid pattern of the raffinate and
extract is thus modified. A reduction of the cholesterol content in the rafflnate by 7.5 % was associated
with the extraction of 57 % of the fat. Thus the selective solubility of cholesterol in CO2 was not sufficient.
Thelefore the loaded gas phase was passed over an adsorptive column filled with magnesium silicate. In
this way a removal of cholesterol from milk fat by about 88 % was obtained (Sangbin Lim, Gio-Bin Lim,
Syed S.H. Rizvi, Proceedings of the 2nd International Conference on Supercritical Fluids, Boston,
Massachusetts, May 20 to 22, 1991, pages 292-296). The flavour substances of the milk fat were,
however, also partly adsorbed. The problem of recovering the adsorbed cholesterol and resp. the regenera-
tion of the adsorbent has not yet been solved.
In the magazine ''New Scientist" of May 18, 1991, there is the following note:
"Eggs and milk products having a low cholesterol content may soon be available for health-aware
consumers. Australian researchers are in the process of perfecting two technologies which, as they say,
may remove up to 90 % of the cholesterol from certain foodstuffs without affecting the taste, the nutritional
value or the structure thereof. Charn Sidu, a biochemist of CSIRO (Research Organisation of the Australian
4 2~3723
Government), and his colleague David Oakenfull have developed a polymer on the basis of beta-cyclod-
extrin (BDC - a non-toxic substance obtained from starch - which binds to cholesterol in broken eggs and
milk). The binding occurs due to the doughnut-like structure of the BCD-molecule. The cholesterol is
drawn into the center of the molecule where it is smoothly accomodated like in the hole of the doughnut.
Then the foodstuff is centrifuged to remove the cholesterol-loaded BCD. In commercial processes 80 to
90 % of the cholesterol may be removed according to Sidhu.
According to Sidhu, it is a true advantage of the BCD-technique that it operated at temperatures of down
to 5C. This means, that foodstuffs do not spoil by heating and that they may be cooled during their
preparation to inhibit the growth of microorganisms. He says that many foodstuff processing companies do
already possess the necessary equipment and that BCD may be prepared in a cheap way.
At the beginning of this year CSIRO signed a licence agreement with an Australian company, National
Eggs Products. The company is about to start the production of eggs in liquid or dried form with a low
cholesterol content. The health-favourable eggs may be used in a wide variety of foodstuffs from egg flip
and ice-cream to confectionary goods and mayonnaise.
Neil Foster, a chemical engineer at the University of New South Wales, uses a technique known as
supercritical fluid-technology to extract cholesterol from fats and oils. In their supercritical fluid state gases
show the characteristics both of gases and liquids. CO2, for instance, becomes supercritical at 31C and
about 73 at. According to Foster, the trick of the supercritical fluid-technology resides in the fact of
finding the proper balance between pressure and temperature for specific applications.
To remove cholesterol Foster percolates supercritical CO2 into a vessel similar to a household pressure-
cooker which contains the fats or oils. The liquid-like characteristics of the CO2 dissolve the cholesterol.
Then the supercritical fluid is brought back into its gaseous state by reduction of pressure and tempera-
ture. The gas penetrates the oil entraining the dissolved cholesterol. Then the cholesterol is deposited on
an adsorptive bed and the CO2 is recycled. Foster asserts that the process removes all cholesterol which is
not bound to lipides - about 90 % of the total cholesterol. Since CO2 becomes a supercritical fluid near
room temperature, temperature-sensitive foodstuffs are not damaged during the process. "
It is known that sterols, such as cholesterol, stigmasterol, sitosterol, lanosterol, agnosterol etc. are soluble
in alcohol.
In EP-A-329 347 i.a. the extraction of cholesterol from milk fat is described. Said extraction is preferably
effected with pure methanol or methanol/water-mixtures at temperatures of from 40 to 45C (little above
the melting point of butter). In a blender/separator-extractor in particular milk fat and solvent are continu-
ously and thoroughly admixed with a solvent to fat ratio of 5:1 and with a residence time of 30 minutes
in the blender. Then the admixing was interrupted and the separation of the phases was allowed to occur.
The extracted fat phase, the raffinate, was withdrawn, weighed and admixed with a second portion of fresh
solvent (weight ratio of solvent:fat = 5:1). The admixing, separation and withdrawal was repeated six
2~3723
times. In this crosscurrent extraction altogether 88 to 97 % of cholesterol were removed from the butter
fat. About 35 to 48 % of the feed were obtained as cholesterol-free butter fat.
Ihe distillation of the solvent phase resulted in a pure methanol/water-mixture and a residue slightly
enriched in cholesterol which contained a few flavor components and fats.
After the extraction the milk fat was stripped with steam of 70C for 15 minutes to remove all remaining
traces of the organic solvent. At this point the milk fat was ready to be used in the preparation of various
products.
The extraction according to the process described in EP-A-329 347 is successful essentially only with
methanol/water-mixtures. But also in this case, after interrupting the mixing operation, the phase separation
is very slow. Furthermore a relatively well-defined intermediate layer is formed between the two phases
which has to be added to the extract and increases the losses of fat.
With a growing number of carbon atoms the emulsifying action of primary alcohols increases. When using
ethanol/water-mixtures as extractant in the above process the butter fat phase as well as the ethanol/water
phase remain turbid for several hours. Therefore alcohol/water-mixtures at first seemed unsuited for the
removal of cholesterol from milk fat.
Surprisingly it has now been found that the phase separation may be greatly accelerated when a hydrocar-
bon is added to the above system. Said hydrocarbon dissolves essentially completely in the butter fat
leading to solutions of low viscosity also at temperatures below the melting point of the butter fat of 40C.
In the extractant alkonol/water only negligible amounts of hydrocarbons dissolve. The intermediate layer
between the two phases disappears essentially completely. Thus a multistage countercurrent process
becomes possible with a high space-time yield. The addition of a certain amount of hydrocarbons also
shifts the distribution coefficient of the sterol (cholesterol) towards an enrichment in the water/alcohol
phase.
Accordingly the present invention provides a process for the removal of sterols, in particular cholesterol,
from vegetable and animal fats, in particular milk fat, and the enrichment of these sterols therein, which
process is characterized in that it comprises the following steps:
a) admixing sterol-containing fat with a mixture consisting of a hydrocarbon, a water miscible solvent
and water;
b) separating the two phases forming,
c) removal of the solvent from the hydrocarbon-rich phasé (preferably by distillation), thus obtaining
a fat having a reduced sterol content, and/or
d) complete or partly removal of the solvent (preferably by distillation) from the hydrocarbon-depleted
phase at least until a sterol-rich fat precipitates and, optionally, removal of said fat from the
remaining solution (preferably by decanting and/or centrifugation).
6 2~3~3
The term "water miscible solvent" in this connection means an organic solvent which is liquid at 20C and
atmospheric pressure and which is miscible with water preferably in any desired ratio. In any case,
however, at least 10 weight% of water should dissolve in the solvent (under the just mentioned conditions).
Preferably used hydrocarbons are easily volatile (preferably saturated) hydrocarbons having from 1 to 12,
e.g. l to 8, especially 1 to 4, carbon atoms. Specific examples thereof are methane, ethane, propane and
butane, i.e. hydrocarbons which are admitted in the foodstuff technology without any restriction. After the
e~traction these hydrocarbons may easily be removed from the fat at low temperatures. With hydrocarbons
boiling at temperatures below the extraction temperature, the extraction has to be effected at the respective
vapor pressure or above. The concentration of the above preferred alkanes in the fat may easily and
dependably be controlled by means of the pressure.
This is of great advantage in the commercial operation. With propane and butane pressures below the vapor
pressure suffice to adequately reduce the viscosity of the fat phase. Therefore, in this case, pressures
between only 2 and 15 bar are necessary between room temperature and 40C. But also when using ethane
and methane the pressures necessary for a fast phase separation do not exceed the value of from 50 to 60
bar.
Water miscible solvents suitable for the process according to the invention are e.g. alcohols, ketones,
carboxylic acid esters and their mixtures. Particularly suitable are alcohols, particularly alkanols having I
to 6, preferably I to 3, carbon atoms, such as e.g. methanol, ethanol and propanol. Particularly preferred
are ethanol and isopropanol, ethanol being the alcohol of choice in most cases. The alcohol may also
contain more than one (e.g. two or three) hydroxy groups as well as ether bridges. Examples thereof are
ethylene glycol, diethylene glycol, propane diol etc. Among the ketones those having 3 to 5 carbon atoms,
such as acetone and butanone, are preferred, while with carboxylic acid esters the overall number of carbon
atoms should not exceed 5 (such as e.g. in the case of methyl formiate and ethyl acetate). Since alcohols
ar~ most preferred as water miscible solvents according to the invention the following description, for
simplicity's sake, mentions "alcohol" and resp. "alkanol" as rcpresentatives of "water miscible solvents"
which, however, does not mean that the respective embodiments are restricted to those cases where
alcohols and alkanols, respectively, are employed.
During the extraction the alcohols are dissolved to a remarkable extent in the fat phase and have to be
removed from the raffmate after the extraction of the sterols. This is usually done by stripping at elevated
temperatures and reduced pressure (at about 70 to 80C; 0.1 to 0.5 bar). The duration of stripping is
generally about 15 minutes. This temperature stress may now be avoided according to the process of this
invention by using methane, ethane, propane or butane as hydrocarbons. To remove tne dissolved alkane
the raffinate phase is heated to about 20C above the process temperature and then depessurized via a
depressurizing valve to a pressure of 0.5 to t bar. This liberates the gaseous alkane and removes the
dissolved alcohols substantially completely from the fat phase. Thus a moderate temperature increase of
short duration is sufficient to free the raffinate from the solvents. However, if traces of the alcohol are still
retained in the fat it suffices to redissolve one of the mentioned alkanes (e.g. methane at a pressure of 5
bar) and to then effect a depressurization in order to remove the last traces of the alcohol.
7 ~`~83723
In the process according ~o the invention the weight ratio of the fat to the hydrocarbon empolyed is
generally in the range of 10:1 to 1:5, particularly in the ral;ge of 6:1 to 1:3. In this context two cases
should suitably be distinguished:
(A) If the fat-enriched phase is the light phase the weight ratio of fatlhydrocarbon is generally in the
range of 1:1.5 to 1:5, in particular of 1:1.8 to 1:4 and especially preferred of 1:2 to 1:3.
(B) If, however, the fat-enriched phase is the heavy phase then the weight ratio fat/hydrocarbon is
generally in the range of 10:1 to 1:1, preferably of 8:1 to 1.5:1, especially preferred of 6:1 to 3:1.
The weight ratio of alcohol used to water used in the process according to the invention is generally 1:0.05
to 1:1, in particular 1:0.07 to I :O.S, a ratio in the range of 1:0.1 to 1:0.35 being particulary preferred. The
Breater the ratio of water to aikanol the lower the alcohol content of the fat will be. At the same time the
solubility of the hydrocarbon in the alcohol decreases with increasing water content of the alcohol. Vice
versa the alcohol content of the fat and the hydrocarbon content in the alcohol increase with decreasing
water content of the alcohol. For practical reasons water. concentrations of more than 15 weight% will not
be used e.g. in the extraction of cholesterol from milk fat by means of ethanol because otherwise the
solubility of the cholesterol is too low and the re~juired amounts of extractant become too great.
The weight ratio of the fat to be extracted to the hydrocarbon/alcohollH20-mixture in the process according
to the invention is normally 1:0.5 to 1:10, in particular 1:1 to 1:7, a weight ratio of 1:2 to 1:5 being
especiaily preferred.
In step d) of the process according to the invention the partly removal of the solvent, which is preferably
carried out by distillation, is preferably effected to a residual alcohol content of 0.1 to 10, in particular of
0.5 to 3 weight%.
The process according to the invention is preferably effected continuously, in particular as a countercurrent
extraction. A particularly preferred process according to the invention for the removal of sterols and resp.
the enrichment of sterols in fats therefore comprises the following steps:
(i) dissolving fat in a hydrocarbon or an optionally hydrous hydrocarbon/alcohol-mixture;
(ii) extracting the solution obtained from step (i) with an optinally hydrocarbon-containing alcohol/water-
mixture leading to a hydrocarbon-depleted sterol-enriched extract and a hydrocarbon-enriched sterol-
depleted raffinate, and
(iii) removai of the solvent from the raffmate from step (ii) (preferably by distillation), and/or
(iv) removai of the solvent from the extract of step (ii) (preferably by distillation) at least until the
precipitation of a sterol-enriched fat, and optinally removal of this fat from the remaining solution
(preferably by decanting or centrifugation).
The above process is preferably carried out in such a way that the weight ratio of alcohol to water in the
2~'s'~
extractant used in step (ii) is in the range of 15:1 to 1:1, in particular of 10:1 to 1.5:1. The hydrocar'oon
which is optionally present in this extractant preferably does not constitute more .han 20 weight%, in parti-
cular not more than 10 weight%, of the extractant used.
In step (i) of the above process the weight ratio of the fat to be extracted to the hydrocarbon is preferably
8:1 to l:S, in particular 6:1 to 1:3. When a hydrocarbon/alcohol-mixture is used as solvent for the fat, the
alcohol content in the solvent for the fat is usually not more than 20 weight%, in particular not more than
10 weight%. The arnounts of water which are optiona.ly present in such a mixture usually derive from the
water content of the alcohol employed and tbus are in the range of traces up to about S weight%, in
particular up to about I weight%.
The weight ratio of the fat-enriched phase to t.be water/alcohol phase in the above extraction is preferably
in t.he range of 0.4:1 to 5:1. With increasing phase ratio the yield of sterol-enriched fat increases. With the
.^orrect selection of the phase ratio and the ratio of hydrocarbon:a.cohol:water:fat and, in particular, in
car.e of a countercurrent process with recycling, 95 to 99 æ of sterol-depleted and resp. sterol-free product
may be obtained, the sterol content thereof being decreased to 0.01 weight%. The process according to the
invention may be carried out e.g. in a way that the starting product, e.g. butter oil, is dissolved in a
hydrocarbon in a blender. The solution of the fat which is to be liberated from sterol (in particular from
cholesterol) is fed to the bottom of an extraction column, and the extractant (alcohol/water-mixture) is fed
to the head of the extraction column. The extractant normally forms the heavy phase and flows through the
column in countercurrent from head to bottom for dissolving the fat . As already mentioned above the
alcoho!/water-phase may also be the lighter phase. In this case the flow directions change.
The sterols dissolve in the extractant together with some fat. The higher the alcohol content of the
extractant the better the fat is dissolved. The extract is directed to a rectification column and the alcohol
is removed to a residual content of preferably about O.S to 2 70. If a mild thermal treatment is desired the
rectification is effected at reduced pressure or by stripping. As already mentioned above, the alcohols
methanol, ethanol and isopropanol (as well as acetone) are generally preferred because they have the lowest
boiling points.
After removing the alcohol the solubility of the fat in the extract phase has substantially decreased to zero.
Therefore the dissolved fat floats on top and is removed preferably by decanting or centrifugation. The
extracted sterol is dissolved, essentially completely in the precipitated oil (fat). Depending on the solvent
ratio products having a sterol content of up to 5 % and more may be obtained. These products are suitable
starting materials for the recovery of pure sterols (in particular pure cholesterol), if desired after repetition
of the process of the invention. Cholesterol is of commercial interest e.g. as starting product for the
synthesis of steroid hormones and of liquid crystals. After removing the fat the remaining water is
preferably admixed with the head product from the rectification of the extract phase and returned to the
head of the extraction column as extractant. The water soluble flavour substances e.g. present in butter oil
remain dissolved in the water during the course of the process of the invention and are thus returned to
the process. After a starting phase the flavour of the product which has been freed from sterols is sub-
stantially maintained. The fatty acid pattern may be influenced only with respect to the ratio of the fat
7 ?~ ~3
arnounts in the two phases. With a yield of g5 % and higher no important change is to be expected.
Another possibility of returning the flavour substances dissolved in water is distilling off so much water
during the removal of the alcohol from the alcohol-free phase by distillation that the resulting flavour-
containing amount of water is just sufficient to prepare a spreadable butter by emulsifying the water into
the sterol-free or sterol~epleted butter fat.
A preferred embodiment of the process according to the invention is now illustrated with respect to the
attached Fig. 1. This embodiment is to remove cholesterol from butter oil (milk fat).
Butter oil and hydrocarbon are admixed in the desired ratio in a blender (I) at a temperature little above
the melting temperature of the butter fat so that a homogenous solution results. The minimum pressure
prevailing in the blender is determined by the vapor pressure of the hydrocarbon above the solution. Under
certain circumstances is may be advantageous to add some alcohol to the solution. The homogenous
solution is introduced to the bottom of extraction column (2). It flows up in the column and countercur-
rently to the alcohol/water-phase and the cholesterol is absorbed by the alcohol/water-phase. A minor
amount of fat also enters into the alcohol/water-phase. The cholesterol-free light phase leaves the head of
the extraction column and enters column (3). The temperature in the extraction column may be below the
temperature in the blender. It may be chosen at will down to the freezing point.
When using hydrocarbons having a very low boiling temperature, such as e.g. propane or butane, as
solvent for the starting product, the working pressure in the extraction column may be above atmospheric
pressure. In these cases the solvent of the fat-enriched phase (the raffinate) is separated from the dissolved
fat in a flash process mainly in column (3) at a temperature which is about 20 to 40C higher than the
temperature in the extractor. Thereafter the liquid phase is depressurized to atmospheric pressure in the
depressurizing valve (4) and fed to the distillation column (5) in which the portions of hydrocarbon, alcohol
and water which are still dissolved in the fat are removed. The solvent separated in column (3) is returned
into the blender (1). The alcohol/water-phase (the extract), analogously to the procedure in the raffinate
phase, is essentially freed from easily volatile hydrocarbon by a flash process in column (6) at temperatures
of 20 to 40C above the temperature in the extraction column and then brought to atmospheric pressure in
the depressurizing valve (7). The extract leaving the bottom of extraction column (2) is directed to the
rectification column (8). It is a mixture of alcohol and water as the main components in which the extracted
cholesterol is dissolved together with same fat and hydrocarbon. The rectification column (8) operates at
atmospheric pressure. The extract therein is separated into a head product, containing alcohol as main
component together with water and minor amounts of hydrocarbon, and into a bottom product consisting
of water with a low alcohol content (about I %) and fat.
During the removal of the alcohol from the aqueous phase the fat becomes insoluble and separates in the
form of an oil. Surprisingly the latter contains the extracted cholesterol in essentially completely dissolved
form. The oil is removed in a separator (9) by decanting or centrifugation. The remaining aqueous phase
contains the extracted water-soluble flavour components of the starting product and traces of cholesterol.
Depending on how the process is carried out (solvent ratio) the fat obtained in the separator (9) may
2~37~
contain up to about 5 % of cholesterol. The water phase from the separator (9) is combined with the head
product of column (8) and returned to the head of the extraction column (2). In this way according to the
process of the invention a cholesterol-free fat may be obtained in high yield (96 to 98 ~o of cholesterol-
free fat may be obtained) and no environmental problems arise because the solvent and the extractant are
completely returned into the process.
With a high solvent ratio (i.e. a weight ratio of extract phasetrafflnate phase, e.g. of 4:1), a simple
countercurrent extraction, as schematically shown in Fig. 1, is able to reduce the cholesterol content of
milk fat to 0.02 weight~o and below. This procedure, however, is accompanied by high losses (S0 % and
more) of milk fat. This is also observed in the extraction with only ethanol/water-mixtures and has been
described in EP-A-329 347. High losses of milk fat, however, also lead to a considerable modification of
the fatty acid paKern of the raffmate, because the esters of short-chain faKy acids are more soluble in the
alcohol extractant than the esters of long-chain fatty acids.
Compared to other edible fats milk fat is characterized by a particularly broad fatty acid pattern, as may
be seen from the following table 1. A peculiarity are the relatively high contents of butyric acid and
capronic acid. This is one reason for the physiological valor of milk fat.
TABLE I
Composition of fatty acid mixtures obtained from several natural fatty acids
Proccntual portion in thc fatty acid mixturc
buucrlard coconut ~at olivc oil
Butyric acid (C4)3 - -
caproic acid (C6)2
Caprylic acid (C8) 1 - 8
Caprinic acid (C10) 2 - 7
Lauric acid (C12)4 - 47
Myristic acid (C14) lo 3 18
Palmitic acid (C16) 8 25 9 9
stcaric acid (cl8) lo lo 2 2
Sum of saturatcd
fatty acids 60 38 91 11
olcic acid (C18)35 52 6 85
Linolic acid (cl8) s lo z 4
. _
sum of unsaturatcd
ralty acids 40 62 8 89
11 2~
In case of a low solvent ratio, e.g. 1:1, the loss of milk fat may be decreased to e.g. S ~O wherefore the
fay acid pattern changes only little. Also the loss of flavours is less. But in this case it is not possible to
decrease the cholesterol content to extremely low values by a simple countercurrent extraction. The
achievement of both requirements, namely maintaining the fatty acid pattern and reducing the cholesterol
content by at least ~0 %, however, is possible by the fractionated extraction according to the process of
this invention, wherein part of the milk fat removed from the extract is returned to the extraction column
as recycle stream. This embodiment is illustrated in detail with respect to the schematic drawing in Fig. 4.
Butter oil (milk fat) and hydrocarbon in the desired ratio are admixed in the blender (10) at a temperatu-
re little above the melting temperature of the butter oil to a homogenous solution. It may probably be
advantageous to add so much alcohol (e.g. ethanol) to the solution that the equilibrium concentration is
obtained in the extractor. The pressure in the blender (10) corresponds to the vapor pressure of the
hydrocarbon above the solution. The homogenous solution is directed to the middle section of extraction
column (I l). The temperature in the extraction column (11) may be below the temperature in the blender
(10). It may be chosen at will down to the freezing point. Depending on the amount of alkane dissolved
in the butter oil and on the water content of the alcohol the extract phase may be the heavy or the light
phase. When using methane, ethane, propan or butane as hydrocarbon their content in the butter oil may
be adjusted and controlled by the pressure. With high alkane contents of the butter oil and higher water
contents of the alkanol the extract phase is the heavy phase. With lower alkane contents of the butter oil
and lower water contents in the alkane the extract phase is the light phase. The alkane content of the butter
oil and the water content of the alkanol are adjusted so that the difference in density between the extract
phase and the raffinate phase is at least 50 kg/m3.
The extract phase and the raffinate phase are directed countercurrently in extraction colurnn (Il), the
extractant consisting of alkanol and water absorbing the cholesterol. Furthermore a minor amount of fat is
dissolved in the extract. The raffinate phase freed from the cholesterol leaves the extraction column (I l)
and reaches the flash-evaporator (12). When using methane, ethane, propane or butane as alkane at the
working pressure and at a temperature which is about 10 to 20C higher than the temperature in the
extraction column (11) the prevailing amount of the alkane and the greater part of the alkanol dissolved in
the butter oil are removed in the evaporator (12) and returned into the blender (10).
Thereafter the butter oil is depressurized to atmospheric pressure in the depressurizing valve (13) and
directed to the rectification column (14).
In column (14) the portions of hydrocarbon and alkanol still dissolved in the fat are removed. The
separated solvent is returned into the blender (10). The cholesterol-free fat is withdrawn from column (14)
as bottom product.
The extract leaving the extraction column (Il) reaches the flash evaporator (15) where, in analogous
manner to the procedure in the raffinate phase, the dissolved alkane and part of the alkanol are removed
at elevated temperature and returned to column (Il). Subsequently the extract is brought to ambient
pressure in the depressurizing valve (16) and directed to the rectification column (17). The extract consists
2~723
12
of a mixture of alcohol and water, in which the extracted cholesterol and minor amounts of alkane are
dissolved beside some fat. In the rectification column (17) the extract is divided into a head product,
containing the alkanol a~s main component plus minor amounts of hydrocarbon be~side water, and into a
bottom product, consisting of water with a minor alkanol content (about I %) and fat.
During the removal of the alkanol from the extract the fat becomes insoluble and separates as an oil. The
latter surprisingly contains the extracted cholesterol in essentially completely dissolved form. The oil is
separated from the aqueous pha~se in the separator (18) by decanting or centrifugation. The remaining
aqueous phase contains the extracted water-soluble flavour substances and traces of cholesterol. The milk
fat obtained in the separator (18) contains the extracted cholesterol in a concentration of up to 5 weight%.
Part of this product (about 50 to 70 %) is returned to the extraction column (I l) as recycle stream at tbe
site where the extractant exit~s.
The following examples are to illustrate the pre~sent invention without restricting it.
EXAMPLE I
61 g of butter oil having a chole~sterol content of 0.26 weight% were dissolved in 120 g of hexane and 10
g of ethanol. This solution was fed into a separation funnel and treated with a mixture of 26 g of water and
110 g of ethanol. Thorough admixture was obtained by shaking. The mixing operation completed two clear
phases separated within a short time (about 10 to 20 s). At the borderline there was a narrow turbid
interface layer (about 2 to 3 mm) which became clear only after prolonged standing. The weight ratio of
lighter butter fat-enriched phase to heavier ethanol-enriched phase wæ 1.14:1. The light phase contained
60 g of buner oil dissolved in a mixture of 106 g of hexane, 0.6 g of water and 9 g of ethanol. The butter
oil of the light phæe had a cholesterol content of 0.19 weight%. The heavy pha~se contained I weight% of
dissolved butter oil. The ratio of ethanol to water in the heavy phase was 4.3:1. Hexane and ethanol of the
light phase were distilled off, whereby 59.5 g of butter oil having a reduced cholesterol content of 0.19
weight% were obtained. This corresponds to a recovery of butter fat of about 98 %.
From the heav~ phase ethanol was distilled off to a residual content of about I weight% using a Vigreux-
column. The separated dissolved butter oil was decanted. It contained 3,7 weight% of cholesterol. The
water remaining after evaporating the ethanol contained only traces of cholesterol.
EXAMPLE 2
60 g of butter oil having a cholesterol content of 0.26 weight% were dissolved in 60 g of hexane and 180
g of ethanol. The ethanol used contained about 5 weight% of water. The resulting solution was fed into a
separation funnel, whereupon 10 g of water were added. After through admixing by vigorous shaking two
clear phases separated within a short time (about 20 s). Immediately at the interface there wæ a narrow
turbid layer (I to 2 mm) which clarifled only after prolonged standing. The heavy butter fat-enriched phase
contained 52 g of butter oil and 35 g of solvent (30 g hexane and 5 g ethanol). The butter oil of the butter
fat-enriched phase contained 0,11 weight of cholesterol. The main amount of the ethanol had entered into
the light phase. Surprisingly in this experiment the butter oil-enriched phase was heavier than the ethanol-
enriched aqueous phase. The weight ratio of butter fat-enriched phase to ethanol-enriched phase was
2~3~253
13
0.39:1. The light ethanol-enriched phase was introduced into a Vigreux-column, and ethanol was driven off
until only about I weight% remained. ~uring this the dissolved butter oil became insoluble and floated on
top. The cholesterol content of the butter oil separated from the heavy phase was 1.2 weight%. The portion
of water of the heavy phase contained only traces of cholesterol. The recovery of butter oil was 87
weight%.
EXAMPLE 3
60 g of butter oil having a cholesterol content of 0.26 weight% were dissolved in 170 g of propane at
40C and 14 bar. The solution was prepared in an autoclave provided with a window. Then 20 g of water
and 90 g of ethanol were pumped in. By shaking the autoclave thorough admixture was obtained. After
interrupting the mixing operation a very rapid separation of the mixture into two clear phases was observed
through the window. The weight ratio of lighter phase to heavier phase was 3.2:1. Samples were taken
from both phases and analyzed.
The light phase contained 59 g of butter oil which were dissolved in 148 g of propane, 24 g of ethanol and
2 g of water. The cholesterol content of the butter oil dissolved in the light phase was 0,22 weight%. The
heavy phase consisted of 18 g of water, 66 g of ethanol, 12 g of propane and I g of butter oil. The latter
contained the extracted dissolved cholesterol in a concentration of 2.2 weight%. The ethanol was removed
from the heavy phase by distillation during which the dissolved butter oil precipitated. After the distillation
the water contained about I weight% of ethanol and only traces of cholesterol.
EXAMPLE 4
In the blender of a laboratory apparatus, designed according to the diagram in Fig. 1, 200 g of butter oil
having a cholesterol content of 0.26 weight% were continuously dissolved in a mixture of 270 g of propane
and 57 g of ethanol per hour. At 40C the pressure in the blender was 15 bar. The thus obtained solution
was continuously pumped to the bottom of a 10 m high extraction column. The column contained a wirenet
packing, type CY, ex Sulzer company. As extractant a mixture of 328 g of ethanol, 70 g of water and 120
g of propane per hour was added to the head of the extraction column. The extractant flowed through the
column as heavy phase countercurrently to the solution of the butter fat (the light phase).
The light phase left the head of the extraction column as raffnate and was directed to a flash-column,
wherein the major portion of the propane was separated at 100C and 13.5 bar and returned into the
dissolution vessel. Part of the ethanol was entrained with the propane. After having left the flash~device the
raffinate was depressurized to 0.5 bar in a depressurizing valve, and at this pressure and a bottom
temperature of 100C ethanol and residues of propane were separated from the butter oil in a distiliation
column. In this distillation column 190 glh of butter oil were withdrawn as bottom product having a
cholesterol content of 0.027 weight%. The head product consisting of ethanol and propane was condensed
and returned into the dissolution vessel for the starting material.
At the bottom of the extraction column per hour 328 g of ethanol, 120 g of propane, 70 g of water and 10
g of butter oil were continuously withdrawn as extract and directed to a flash device in which the major
portion of propane and part of the ethanol were removed at 100C and 13.5 bar. After passing a de-
2~g372~
14
pressurizing valve the remaining mixture of ethanol, water and butter oil was separated in a distillationcolumn at atmospheric pressure. This resulted in a mixture of ethanol and water as he
ad product which had
about the same composition as the azeotrope. After removing the ethanol the dissolved butter oil precipita-
ted. The bottom product having a residual content of ethanol of about I weight% was directed to a
separator together with the precipitated butter oil and separated into a water phase and an oil phase. The
water phase was combined with the distillate and pumped back to the head of the extraction column as
e~tractant. Behind the pump the gaseous product from the flash-operation was admixed with the extractant
stream. The extracted cholesterol was dissolved essentially completely in the precipitated butter oil. The
water phase contained only traces of cholesterol. In the butter oil of the extract 5.1 weight% of cholesterol
were dissolved. The recovery of cholesterol-free butter fat was 95 %.
EXAMPLE $
In a laboratory blender-separator a solution of 23 weight% of butter fat having a cholesterol content of
0,26 weight% was treated in a mixture of 64 weight~O of hexane and 36 weight% of ethanol countercur-
rently to with an extractant consisting of 14 weight~O of water and 86 weight% of ethanol. The throughput
of the butter fat solution was 860 ml/h, that of the extractant 420 ml/h. The extraction was carried out at
30C. The raffinate was introduced into a rotary evaporator. Then at 120C and with water jet vaccum
hexane, ethanol and a small residue of water were driven off. The thus obtained solvent-free butter oil had
a cholesterol content of 0.04 weight%. The recovery of butter fat with a reduced cholesterol content was
96 %.
The extract contained 3 weight % of dissolved butter fat. It, too, was freed from the solvent in a rotary
evaporator at 120C and with a water jet vacuum. The remaining butter fat contained S.S weight% of
cholesterol.
EXAMPLE 6
20 g of butter fat having a cholesterol content of 0.26 weight% were dissolved in a mixture of 40 g of
isohexane (Cs-C,-isomer mixture of aliphatic hydrocarbons) and 40 g of isopropanol. The obtained solution
was introduced into a separation funnel, and 14 g of water were added. After thorough admixture by
vigorous shaking two clear phases separated in a short time (about 20 s). At the phase boundary a thin
turbid layer of I to 2 mm thickness remained for a prolonged time. The weight ratio of lighter phase
containing the major amount of the butter oil to the heavier alcohol-enriched phase was 1.6: I . The light
phase contained 19,7 g of butter fat dissolved in a mixture 36 g of isohexane, 12 g of isopropanol and 2.5
g of water. The solvent was distilled off resulting in 19.7 g of a butter fat having a cholesterol content of
0.21 weight% (recovery of butter fat 98.5 %). The weight ratio of isopropanol to water in the heavy phase
was 2.3:1.
From the heavy phase the isopropanol was distilled off to a residue of about I weight%, while the
dissolved butter oil precipitated which was subsequently decanted. It contained 3.5 % of dissolved
cholesterol. The aqueous phase remaining after the evaporation of the isopropanol contained only traces of
cholesterol.
EXAMPLE 7
20 g of butter oil having a cholesterol content of 0,26 weight% were dissolved in 40 g of butane and 40
g of ethanol in an autoclave at 40C and a pressure of 7 bar. Then 8 g of water were pumped in and
admixed thoroughly. After completed mixing two phases separated within a short time, as was observed
through a window. The weight ratio of the lighter phase to the heavier phase was calculated by the
determination of the interface and the density of the coexisting phases and amounted to 1.2:1. The light
phase contained 19.5 g of butter fat, 31.5 g of butane, 6 g of ethanol and 0.8 g of water. After removal
of the solvent 0.18 weight% of dissolved cholesterol were present in the butter oil of the light phase. The
recovery of buKer fat having a reduced cholesterol content was 97,5 9 i .
From the heavy phase the major arnount of the butane evaporated during depressurization to atmospheric
pressure. The ethanol was distilled off to a residual amount of about 1 9Z, at the same time driving off still
remaining residues of butane. The dissolved butter fat precipitated and was then decanted. It contained 3.4
weight% of cholesterol. The aqueous phase remaining after the evaporation of the ethanol contained only
traces of cholesterol. The weight ratio of ethanol to water in the heavy phase was 4.5:1.
EXAMPLE 8
In the blender of a laboratory apparatus, designed according to the illustration in Fig. 1, 200 g/h of butter
oil having a cholesterol content of 0.26 % were continuously dissolved with 27 g of ethanol at 25C. At
the same time propane was fed into the blender (I) at a pressure of 8 bar and dissolved in the butter
oil/ethanol mixture so that a solution consisting of 200 g of butter oil, 27 g of ethanol and 91 g of propane
was formed. The thus obtained solution was pumped continuously to the bottom of an extraction column
(2) of 12 m in height. The column contained a wirenet packing of type CY ex Sulzer company.
As extractant per hour a mixture of 673 g of ethanol and 127 g of water, which had been saturated with
propane at 8 bar and 25C, was introduced to the head of the extraction column (2). Under these condi-
tions the extractant flowed through the column as heavy phase in countercurrent to the solution of the
butter oil, the light phase.
The light phase left the head of the extraction column (2) as raft`inate and was first introduced into a flash
column (3) where the greater portion of the propane and part of the ethanol were separated from the butter
oil at 80C and 8 bar. After having left the flash-column (3) the raffinate was depressurized to 0.2 bar
with the aid of a depressurizing valve (4). In a distillation column (5) at this pressure and at a bottom
temperature of 80C ethanol and the residual propane were removed from the butter fat. From the
distillation column (5) 190 g/h of butter oil were withdrawn as bottom product. The butter oil had a
cholesterol content of 0.02 weight%. The head product consisting of ethanol and propane was condensed
and returned into the dissolution vessel (1).
From the bottom of extraction column (2) per hour 673 g of ethanol, 127 g of water, 25 g of propane and
10 g of cholesterol-enriched butter oil were continously withdrawn as extract and introduced into a flash
device (6) where, at 100C and 8 bar, the major amount of the propane and part of the ethanol were
removed. ~fter passing a depressurizing valve (7) the remaining mixture of ethanol, water and butter oil
2 ~ 3
16
was separated in a distillation column (8) at atmospheric pressure. As head product a mixture of ethanol
and water was obtained which had about the same composition as the azeotrope. During the removal of the
ethanol the dissolved butter oil precipitated. The bottom product having an ethanol content of about 1
weight% was introduced into a separator (9) together with the precipitated butter oil and separated into a
water phase and an oil phase. The water phase was combined with the distillate and pumped back to the
head of the extraction column (2) as extractant. Behind the pump the product from the flash operation wæ
admixed to the extractant stream. The extracted cholesterol was essentially completely dissolved in the
precipitated butter oil. The water phase contained only traces of cholesterol. In the butter oil of the extract
5,0 weight% of cholesterol were dissolved. The yield of cholesterol-free butter oil was 95 %.
EXAMPLE 9
In the blender (19) of a laboratory apparatus, designed according to the illustration in Fig. 2, 200 g/h of
butter oU having a cholesterol content of 0.26 % were dissolved continuously with 33 g of ethanol at 50C.
At the same time, at a pressure of 7 bar, propane was added to blender (19) and dissolved in the butter
oil/ethanol mixture so that a solution consisting of 200 g of butter oil, 33 g of ethanol and 20 g of propane
was formed. The thus obtained solution was pumped continuously into a 16 m high extraction column (20)
4 m below its head. The column contained a wirenet packing of type CY ex Sulzer company.
As extractant per hour a mixture of 667 g of ethanol and 100 g of water, which had been saturated with
propane at 7 bar and 50C, was introduced to the bottom of extraction column (20). Under these conditions
the extractant flowed through the column as light phase in countercurrent to the solution of the butter oil,
the heavy phase.
The heavy phase left the bottom of extraction column (20) as rafflnate and was first introduced into a flash
column (21), where, at 80C and 7 bar, the major portion of the propane and some ethanol were separated
from the butter oil. After having left the flash-device (21) the raffinate was depressurized to 0.2 bar with
the aid of a depressurizing valve (22), and at this pressure and at a bottom temperature of 80C ethanol
and residual amounts of propane were separated from the butter fat in a distillation column (23). As bottom
product from the distillation column (23) 183 g/h of butter oil were withdrawn. The butter oil had a chole-
sterol content of 0.02 weight%. The head product consisting of ethanol and propane was condensed and
returned into the dissolution vessel (19).
At the head of extraction column (20) per hour 667 g of ethanol, 100 g of water, 16 g of propane and 17
g of butter oil were continuously withdrawn as extract and directed into a separator (25) after the addition
of 130 g of water via a static blender (24). One half of the floating fat phase consisting of 17 g of butter
oil, 2 g of propane and 2 g of ethanol was introduced to the head of a separating column (20) as recycle
stream. The other half was transferred to a flash-device (26) where, at 100C and 7 bar, the major amount
of propane and part of the ethanol were removed. After passing a depressuring valve (27) the remaining
mixture of ethanol, water and butter oil was separated together with the bottom phase from the separator
(25) in a distillation column (28) at atmospheric pressure. This resulted in a mixture of ethanol and water
as head product which had about the same composition as the azeotrope. During the removal of the ethanol
the dissolved butter oil precipitated.
17 ~372~
The bottom product having an ethanol content of about I weight% wæ introduced into a separator (29)
together with the precipitated butter oil and separated into a water phase and an oil phase. The water phase
was combined with the distillate and pumped to the bottom of the extraction column (20) as extractant.
Behind the pump the product obtained from the flash process was admixed to the extractant stream. The
extracted cholesterol was dissolved essentially completely in the precipitated butter oil. The water phase
contained only traces of cholesterol. The butter oiJ of the extract contained 12 weight% of dissolved
cholesterol. The yield of cholesterol-free butter oil was 98 %.
EXAMPLE 10
200 g of butter oil having a cholesterol content of 0.26 weight% were dissolved with vigorous stirring in
825 g of acetone, 100 g of propane and 92 g of water in an autoclave at room temperature. The pressure
of the propane above the solution was 4 bar. After completed stirring two liquid phases formed. Phase
separation occurred within about 10 to 20 s, as observed through a window. The lower liquid phase
contained the major amount of the butter oil. It contained 188 g of butter oil, 90 g of propane, 91 g of
acetone and I g of water. The butter oil in the lower phase contained 0.20 weight% of cholesterol.
The upper liquid phase consisted of 12 g of butter oil, 10 g of propane, 739 g of acetone and 91 g of
water. The butter oil of this phase contained 1.21 weight% of cholesterol.
The weight ratio of the lighter (solvent-enriched) liquid phase to the heavier (butter oil-enriched) liquid
phase was about 3:1. The yield of butter oil having a reduced cholesterol content was 94 %.
From the solvent-enriched liquid phase the acetone was distilled off with the aid of a Vigreux-column to
a residual content of about I weight%. The precipitating butter oil was decanted. The water remaining
after the evaporation of the acetone contained only traces of cholesterol.
EXAMPLE I I
In the blender of a laboratory apparatus, designed according to the illustration in Fig. 3, 200 g/h of butter
oil having a cholesterol content of 0.26 ~6 were continuously dissolved at 50C with 33 g of ethanol. At
the same time, at a pressure of 7 bar, propane was added into blender (30) and dissolved in the butter
oil/ethanol mixture, so that a solution consisting of 200 g of butter oil, 33 g of ethanol and 20 g of propane
was formed. The thus obtained solution was pumped continuously into a 16 m high extraction column (31)
4 m below its head. Column (31) contained a wirenet packing of type CY ex Sul~er company.
As extractant per hour a mixture of 667 g of ethanol and 100 g of water, which had been saturated with
propane at 7 bar and 50C, was introduced to the bottom of extraction column (31). Under these conditions
the extractant flowed through the column as light phase countercurrently to the solution of the butter oil,
the heavy phase.
The heavy phase left the bottom of extraction column (31) as raffnate and was first introduced into a flash
column (32) wherein, at 80C and 7 bar, the major portion of the propane and some ethanol were removed
7 ~ 3
18
from the butter oil After having left the flash device (32) the raffmate was depressurized to 0.2 bar with
the aid of a depressurizing valve (33), and at this pressure and at a bottom temperature of 80C ethanol
and residual amounts of propane were removed from the butter fat in a distillation cotumn (34). From the
distillation column 183 g/h of butter oil were withdrawn as bottom product. The butter oil had a cholesterol
content of 0.02 weight~o. The head product of ethanol and propane was condensed and returned into the
dissolution vessel (30).
At the head of the extraction column (31) per hour 667 g of ethanol, 100 g of water, 16 g of propane and
17 g of butter oil were continuously withdrawn as extract, and after passing the depressurizing valve (35)
introduced into a flash-device (36) where, at 80C and atmospheric pressure, the major amount of propane
and 220 g of the ethanol were removed. The remaining mixture of ethanol, water and. butter oil was
transferred to a separator (37). The floating fat phase consisting of 8 g of butter oil, 1 g of propane and
1 g of ethanol was introduced as recycle stream to the head of separation column (31). The lower phase
from separator (37) was separated in a distillation column (38) at 100C and atmospheric pressure, yiel-
ding as head product a mixture of ethanol and water which had the approximate composition of the
azeotrope. During the removal of the ethanol the dissolved buner oil precipitated.
The bottom product having an ethanol content of about I weight~o was introduced in a separator (39)
together with the precipitated butter oil and separated into a water phase and an oil phase. The water phase
was combined with the distillate and pumped back to the bottom of extraction column (31) as extractant.
Behind the pump the product from the flash process was admixed with the extractant stream. The extracted
cholesterol was dissolved essentially completely in the precipitated butter oil. The water phase contained
only traces of cholesterol. The bulter oil of the extract contained 12 weight% of dissolved cholesterol. The
yield of cholesterol-free butter oil was 98 %.
