CA1074331A - Process for separating oils and fats into liquid and solid fractions - Google Patents

Abstract

ABSTRACT OF DISCLOSURE

Separation of an edible oil into liquid and solid fractions. The edible oil is dissolved in about 0.5-4 parts by weight of a solvent being a C2-C3 alkanol containing about 2 to 10% by weight of water and the solution is cooled to a temperature at which it separates into two liquid phases and a solid fraction crystallizes. The crystallized solid fraction floats in the upper liquid phase and is recovered therefrom. The liquid fraction of the oil is re-covered from the lower liquid phase.

Description

10'74;~

This invention relates to fractional crystal-lization of vegetable and animal oils and fats.
More particularly, the invention provides a new and efficient process for separating such oils and fats, by crystallization, into a less saturated fraction (herein-after "liquid fraction") and a more saturated fraction (hereinafter "solid fraction").
The present invention is of particular value for the production of "salad oil", i.e. liquid unsaturated edible oil, from such natural or semi-processed oils and fats as contain relatively large proportions of saturated fatty acids (in the form of triglycerides).
A high quality salad oil is required to have a good "chilled stability", i~e. a resistance to crystalli-zation when kept for at least 72 hours at a relatively low temperature. The chilled stability of an oil, is a function of its degree of unsaturation, convention-ally measured as the "iodine value". The higher the iodine value, the lower the temperature at which the oil resists crystallization. Thus, in order to obtain from comparatively saturated oils and fats a liquid fraction having the desired c~racteristics of a salad oil, it is necessary to increase the degree of unsatura-tion of the oil or fat by separating therefrom a solid fraction containing a desirably large proportion of the saturated fatty acids. Fractional crystallization techniques have been used for this purpose.

- 2 -10~7~33~

In accordance with the known methods, the oil or fat is dissolved in several times its volume of a solvent, such as acetone or hexane, at an elevated temperature, and the selective crystallization of a solid fraction is induced by cooling the solution.
The main disadvantage of such known processes resides in the need to resort to filtration or centrifugation for the separation of the solid fraction crystals from the residual solution. Owing to the low melting points and to the sticky consistency of the crystals, the aforesaid operations are very cumbersome and the separation of the phases is inefficient.
Furthermore, in these processes it is, as a rule, necessary to produce the crystals in the branched-out beta-form, in order to make the filtration at all possible. However, the production of the crystals in the beta-form is a time consuming operation as distinguished from the ready formation of the spherically-shaped alpha-form. This then constitutes a further disadvantage of the prior art processes.
The present invention provides a process which is free from the aforesaid drawbacks in that it does not involve any filtration or centrifugation and permits neat and easy separation of the liquid and the solid fractions by a simple decantation.

107~331 According to one ~spect of the in~ention a process for separating an edible oil, selected from the group consisting of natural and semi-processed animal and vegetable oils and fats and mixtures thereof, into a less saturated fraction (liquid fraction) and a more saturated fraction (solid fraction), which method in-cludes the steps of: dissolving one part by weight of the oil in about 0.5 to about 4 parts by weight of a solvent consisting of a ~2 ~ C3 alkanol containing about 2~ to about 10% by weight of water at a dissolutiGn temperature above about 40C; rapidly cool-ing the resulting solution to a crystallization temperature lowerthan the dissolution temperature, thereby to cause formation of substantially spherical-shaped alpha-form crystals of the more saturated fraction of the oil capable of floating in the solvent;
allowing the mixture to separate into three phases consisting of a lower liquid layer comprising the less saturated fraction of the oil and a part of the solvent, an upper liquid layer comprising another part of the solvent, and a solid phase consisting of the crystals of the more saturated fraction of the oil, the solid phase floating in the upper liquid layer to form a suspension therein; and separating the lower liquid layer from the suspension by decantation.
The edible oil and the aqueous alkanol solvent, at the above specified weight ratios, are completely miscible only at elevated temperatures. When the resulting solution is cooled, the solvent partially separates as an upper layer above the heavier oil layer which still contains some solvent. At the same time the cooling also causes crystallization of the solid fraction of the oil. The formed crystals contain considerable amounts of al-kanol (probably as solvent , ,~ ~, "

107~33~

of crystallization) and consequently their density is sufficiently low so that they float up into the upper solvent layer in which they form a suspension. The floating of the crystals and the sharp separation of the layers are also facilitated by the decreased viscosity of the oil layer owing to its aqueous alkanol content.
It was surprising to find in accordance with the invention that this unexpected effect occurs upon selection of the above specified parameters. The simple separation of the floating crystals in accordance with the invention constitutes a non-obvious and significant technical progress.
The process of the invention is applicable to any vegetable or animal oil or fat or mixtures thereof, either in the crude or in a semi-processed (e.g. partially hydrogenated) state. The term "edible oil" will be used herein to embrace all these types of oils and fats. Examples of edible oils which are suitable starting materials for the process of the invention are palm oil, cottonseed oil, sunflower seed oil, rice bran oil, kapok seed oil, partially hydrogen-ated soybean oil as well as animal fats such as tallow, lard and marine oils.
The edible oil starting material should be ~07433t degummed, dried and preferably deacidified. Although the process of the invention can be carried out success-fully with crude edible oil containing up to about 10~ free fatty acids (F.F.A.), it has been found that a decreased F.F.A. content leads to an easier crystalli-zation, a sharper separation of the layers on decantation and increased yields. Tllus, edible oils which had undergone a physical refining or a caustic neutralization and drying, proved to be most suitable as starting materials for the process of the invention.
It has also been found in accordance with the invention that best results are obtained if the oil is pretreated so as to reduce the amount of mono-glycerides contained therein. ~lonoglycerides, are degradation products of natural oil which are formed together with the free fatty acids by hydrolysis of the triglycerides, and they are thus present in all oils and fats having a considerable F.F.A. content. It has been found that a monoglyceride content of more than about 2% has adverse effects on the crystalli-zation of the solid fraction and consequently on the efficiency of phase separation in accordance with the invention. The monoglyceride content of the oil can be reduced by caustic neutralization or by steam dis-tillation under vacuum. In this way th~ mono-~07~33~

glyceride content of crude palm oil can be reduced,for example, from 8.15~ to 0.7%. A preferred method for eliminating the monoglycerides is to convert them to di- and triglycerides by esterification with the free fatty acids already contained in the crude oil.
This can be accomplished by heating the crude oil for several hours at 250 under vacuum in the presence of a catalyst, e.g. 0.2% of stannous chloride.
In accordance with the invention, the degummed and dried oil, preferably after being deacidified and pretreated as described above to reduce its mono-glycerides content, is dissolved in the aqueous C2-C3 alkanol solvent by heating the mixture at about 40 to 70C., preferably with stirring. The solvent can be ethanol, n-propanol or isopropanol, containing from about 2% to about 10% by weight of water, preferably from 4 to 6% by weight. For each part by weight of oil 0.5 to 4 parts, preferably 1 to 2 parts by weight of solvent are used. Isopropanol is the preferred solvent. The solution is then cooled to the crystalli-zation temperature which depends on the composition of the oil being processed. Thus, for example, cottonseed oil, sunflower seed oil, and kapok seed oil are successfully crystallized at about 0 to 10C.
Certain edible oils which contain comparatively

3~

107433:1 largeproportions of saturated fatty acids in their triglycerides, are best fractioned in tWG stages, i.e.
the liquid fractions obtained in a first fractional crystallization according to the present invention are submitted to a second such fractional crystalli-zation at lower crystallization temperatures. If solutions of oils of this type were cooled directly in the first stage to these lower crystallization temperatures, the amount of crystalline solid fraction separating would be too great to be accommodated as a suspension in the upper layer, and a sharp separation of the layers would not be possible. Examples are palm oil, tallow and lard which can be crystallized efficiently in two stages, the first at about 15 to 30C and the second at about 10 to 20C.
A similar case is that of edible oils con-taining appreciable amounts of waxes, such as rice bran oil which contains about 2 to 4% of waxes and about 2 to 3% of stearines. In these cases a single stage separation in accordance with the invention does not lead to satisfactory results, because the wax crystals (which have a higher melting point than the solid fraction of the oil) tend to remain in the lower layer.
It has now been found in accordance with a specific embodiment of the invention that the separation of the waxes can be achieved in a first stage iractionsl crystallization, if about 1 to 5% by weight of a 8011d fat having a comparatively high melting point (e.g.
42 to 45C) are added to the ~olution of the edible oil. Upon coollng, (e.g. 15C in the case of rice bran oil) the was~R crystallizR together with the ~olid fat which acts as a carrier for the waxes. The mixed ¢rystals sccumulate as a suspension in the upper solvent layer and a ~harp aeparation of the layers by decant-ation is made possible, The lower oil layer is then~ubmitted to a second fractional crystallization accord-ing to the invention, at a lower temperature (e.g. 5C
for rice bran oil) in order to separate the llquid fraction of the oil ~rom the ~olid fraction contain~ng the etearine~. The upper layer is heated to about 45C whereupon the mi~ed crystals of the solid fat and the ~aYes dis~olve and ths resulting ~olution separateR into two llquid phases: a lower layer o~
molten waxes containing ~ome aqueous alkanol and an upper layer consisting of a solution of the solid fat in the aqueous alkanol. The layer~ are separated by decantation at the elevated temperature (45C) and the upper layer i8 recycled for addition to the oil ~olution of a subse~uent batch. The lower layer can be distilled in order to recover as residue the pure waxes which have a considerable commercial value, and a~
distillate the aqueous alkanol which is recycled for u~e in the second 3tage or in a subsequent batch.
It has been found that the procee~ of the invention can be carried out more succe~sfully if the solid fraction of the oil is induced to crystallize in the alpha form of the crystals which, owi~g to their spherlcal shspe,~eparate much more easily than the branched-out cry~tals of the beta form. These alpha crystsl B may be i~duced to a~glomerste into small spherical ag~regates having an average diameter of 2-3 mm in order to facilitate their floating into the upper layer. Both these results csn be achieved by stirring the mixture at the crystallization temperature ~or 30me time, before allowing it to ~trati~yO Thun, in accordance wlth a preferred e~bodiment of the inven-tion, the cooling of the solution to the crystalli-zation temperature is effected rapidly in order to fa~our the formation of the alpha-crystals, and the resulting cooled mi~ture of pha~es ia stirred for several hours in order to i~duce ths agglo~eration of the cryntsls. The crystallization ti~e~ in accord-ance with thi~ preferred procedure range from about 2 to 6 hours, as compared with crystallization times f about 12 to 16 hours needed to obtain the filterable 1~)7~33~

beta-form of the crystals required in accordance with the prior art processes. Thus, the fact that the invention makes it possible, and even preferable, to use the alpha-form of the crystals, provides for a considerable saving of time, which is a further sub-stantial advantage of the invention.
The lower oil layer and the upper solvent layer containing the crystals of the solid fraction, are then separated by decantation and are submitted separately to distillation in order to remove the solvent (i.e.
the alkanol and the water) which can be recycled for re-use with a fresh batch of oil. The liquid and the solid fractions of the oil which are recovered as the distillation residues are preferably stripped of the residual amounts of alkanol and water by passing there-through a controlled stream of a dry inert gas at elevated temperatures and under vacuum (e.g. at 120C and 10 toor). The conventional direct steam stripping cannot be used in the present case, because this would increase the water content of the recycled alkanol. Dry carbon dioxide has been found to be most suitable for this purpose. If the liquid fraction is to be submitted to a second stage fractional crystallization, as described above, there is clearly no need to submit it to the stripping operation. In such cases it is even ~l)7~33:~

unnecessary to distill the lower layer in order to separate the solvent contained therein. The entir~
lower layer obtained in the first stage may instead be admixed with tha amount of sol~ent necessary to restore the aiore-specified weig~t ratio of oil to aqueou~ alkanol, and the ~olution thu~ obtained msy be ~ubmitted to the second-stage fractional crystallization.
In s~ch cases it ha8 been ~ound advantageous to heat the starting solution of the second stage, before it is oooled to the cry~tallization temperature, in order to ensure complete dis~olution of any solid ~ractlon crystal ~uclei whlch might be pre~ent therein.
By UBing ~n efficient sol~ent recovery system the solvent lo~es in the process of the in~ention can be decreased to practically negli~ible amount~. In a pilot plant u~ing 95~ a~ueou3 i~opropanol as solvent, the solvent lO~Be8 amounted to a mere 1 to 2 kg. per 1 ton o~ oil processed.
The invention is illustrated bg the iollo~ing non~ it~ng ~smplc~:
Bsam~le 1 200 g of degumm~d palm oil ~ere ml~ed ~th 200 g of i~opropa~ol contain~ng 5% by ~e$ght of ~atcr.
~he stirr~d mi~tur6 ~8S heate~ to 60C and stlrring was continued at that te~peratuI~ unt$1 a clear 901utlo~

- ~2 _ 10743;~

wa~ obta~ned. The ~olution was cooled rapidly to 22a under stirring and the stlrring wa~ continued at that temperature for 2 hours. The misture wa~
trans~erred into a cooled decantat~on vessel where it separated into two layer~ within 5 minutes. The layers were separated irom sach other by decantation.
The lower layer had a weight of 174 g snd contained 36 g oi isopropanol which was distilled off.
The dlstlllation residue con~isted Or 138 g Or liquid fraction havln~ a chilled stability at 22QC, an lodine ~alue of 57.2 and a ~.F.A~ of 3.72%.
The upper layer t226 g) was distilled to yield 164 g o~ aqueoue lsopropanol ln the distillate and, in the resldue, 62 g oi solld fraction having a slip polnt oi 49C, an iodine ~alue of 42.6 and a F.F.A.
oi 8.06%.
~m~le 2 ~ ) 200 g oi deacidi~ied palm oil were mi~ed with 200 g o~ leopropanol contalning 5~ by welght o~
water. ~he etirred mi~ture wac heated to 60C and ~tlrr~ng was oontlnued at that temperature until a clear solut~on ~a~ obts$ned. The Bolution WR~ then cooled rapldly to 25a under ~tirr~ng and the stirr~g wa8 contlnusd at that temperature ~or two hours. ~he mi~ture was tr~n~ferrsd lnto a cooled decantation 107433~

vessel where it deparated within a few minutes into two layers which were separated from each other by decantation.
The lower layer had a weight of 194 g and contained 44 g of isopropanol which was distilled off.
The distillation residue consisted of 150 g of liquid fraction having a chilled stability at 25C and an iodine value of 55.
The upper layer (206 g) was distilled to yield 156 g of aqueous isopropanol in the distillate and 50 g of solid fraction in the residue, having a slip point of 48~C and an iodine value of 36.
B) 150 g of the liquid fraction obtained above were mixed with 150 g of isopropanol containing 5~
by weight of water and the mixture was heated with stirring to 60C. After a clear solution was obtained, it was cooled rapidly to 15C with stirring and stirred at that temperature for 2 hours. The mixture was then transferred into a decantation vessel, precooled to 15C, where it separated in less than 10 minutes into two layers which were separated by decantation.
The lower layer (143.6 g) contained 23.6 g of aqueous isopropanol which was distilled off to leave 120 g of a residue consisting of a liquid fraction having a chilled stability at 18~C, an iodine value of 107~331 63 and a cloud point of 5C. The yield of thls liquid iractlon (based on the weight of initial palm oil) wa~
60~o.
The upper layer (156.4 g) wa~ separated by distillation into 126.4 g oi aqueous i~opropanol and 30 g of ~olid iraction having a ~lip point o~ 34C
and a~ iodine ~alue oi 47.
The two solid fractions were combined to yleld 80 g (40% of lnitial palm oil) oi a solid iraction having a ~lip point oi 42 to 43a and an iodine value oi 41.5.
The ~atty acid composition oi the deacidified palm oil starting material and of the variou~ iractions obtained as dee¢ribed above were determined by ga~
chromatography and are represented in the following Table I in per¢entages by weight:

Table I

Deacidi- Liquid Solid Solid 301id Fatty Acid~ ~ied Palm Fraction Fraction Fraction Fraction Oil I II I + II
combin.

C12 0075 0~05 0.85 0.7~ 0075 C14 ~.85 0.50 0.90 0.85 0085 C16 44.85 34.32 56.75 49.80 54.17 C18 2.15 2000 3.20 2.20 2.90 C18/1 40,70 51.10 31.33 37.72 33.70 ~18/2 10.70 12.0~ 6.97 8,7~ 7.6~

Fully 48.60 ~6.87 61.70 53.50 58.67 saturated Iodine 5~ 6~ 3B 47 41.50 value .
E~amPle 7 200 g o~ deacld~fied pPl m oil were mi~ed with 200 g o~ n-propanol containing 7.5% of water. The mixture wa~ heated under ~tirring to 60C and stirred at that temperature until a clear solution wa~ obtained.
The 301ution was then cooled rapidly to 25C under stirring and stirring was cont~nued at that temperature ~or 2 hours. The mi~ture was then transferred into a cooled decantation ~essel and allowed to settle for 30 minutes, whereupon two layer~ were formed. The layers were ~eparated by decantation and each wa~ di~tilled to ~(~7~331 remo~e therefrom the n-propa~ol and the ~ater.
The distlllation residue obtained from the lower layer consisted of 150 g o~ liquid fraction having a chilled stability of 25C.
The distillation residue of the upper layer consisted of 50 g of a solid fraction having a slip point of 48C.
E~am~le 4 The procedure described in E~ample 3 was repeated e~cept that instead of the aqu~ous n-propanol, 200 g of ethanol containing 2~ o~ ~ater were used as solvent.
~fter the mi~ture was transferred into the decantation ves~el, it eeparated into two layers in about 15 minutes. The layers were separated by decantation and distllled to yleld:
140 g of a liquid fraction having a chilled stability of 25C, and 60 g of a solid fraction having a slip point of 46C.
13Yam~le S
~ ~erie~ o~ e~per~ments were carried out with different p~l m oils ~c order to determ~ne the depend-ence of th~ yie~d~ o~ the variou~ fraction~ on the saturated fatty acid co~tent of the crude oil. Each type of palm oil was submitted both to the single stage procedure described in Example 1 above and to the double stage procedure described in Example 2. The solvent employed in all cases was isopropanol containing 5%
by weight of water, at a weight ratio of 1 part of solvent per 1 part of oil. The crystallization tempera-ture in the single stage experiments was 22JC and the crystallization temperatures in the first and the second stages of the double-stage procedure were 25DC and 15C respectively.
One set of experiments was conducted on crude oil which had been degummed, in which operation 2.5%
of the oil were lost. The yields (calculated on the initial crude oil) are represented in the following Table II:
Table II

Saturated Fatty SINGLE STAGE DOUBLE STAGE
Acids content Liquid Solid Liquid 1st Solid 2nd Solid in Crude Oil Fraction Fraction Fraction Fraction Fraction % % % % %

46 78 19.5 63.5 20 14 48 73 24.5 58 25 14.5 68.5 29.0 53 29.5 15 52 66 31.5 49 32 16.5 54 61.5 36 44 36.5 ~7 10~ 31 A second ~et of e~periments was carried out on crude oil which had been both degummed and deacidi~ied, which proce~ses ~nvolved a 108~ of 8~ of the crude oil. The yields (calculated on the initial crude oil) are repre~ented in the following Table III:
Table III

Saturated Fatty SINGI~ STAG~ DOU~Ih ST~G~
Acids content ~iquid Solid ~iquid 1 t Solid 2nd Solid in Crude Oil ~raction Fraction Fraction Fraction Fraction o/O ~ 0~o ~ ~
.
46 7705 1405 6~ 15 14 48 72.5 1905 6105 16.5 14 67.~ 24.5 52 25 15 52 65.5 26.5 48 27 17 54 61 31 41.5 ~2 18~5 As could have been e~pected, the re~ults in Tablee II and III sho~ that the lower the saturated fatty acid content o~ the oil, the hlgher the yields of the liqu~d fraction and the lower the y~elds o~ the solid ~raction. The results also ~how that the yield~
obtalned ~rom deacidif$ed o$1 sre better than tho~e obta~ned with oil which had merely been degum~ed. ~hus, for e~ample, the degum~ed oil wlth the ~aturated fatty ac~d conte~t of 48% a~d contai~i~g 5~ F.F.~., when sub-mitted to the double-stage fractionsl crystallization after bei~g merely ds~u~med, yielded 59.4~ (based on 10~33 1 initial degummed oil) of liquid fraction containing about 1.5% ~.F.A. The yield calculated as oil with 0.1~
F.F.A. i~ 58.5~. If the ~ame oll is deacidi~ied prior to the fractional crystallization, the yield of the liquid fraction is 62.5% of deacidi~ied oil, the liquid fraction containing 0.1% F.~.A.
ExamDle 6 200 g of deacidified cottonseed oil were mi~ed with 120 g of isopropanol containing 5% by weight of water. The mlxture was heated under ~tirring to 60C
and the clear ~olution thus obtained was cooled rapidly to 5C and stirred at that temperature for 6 houreO
The mixture was tran~ferred into a cooled decantation vessel wherein it separated into two layers in less than 20 minutes. The layers were separated by decantation and each di~tilled in order to remove iRopropanol and water.
The lower layer (208 g) yielded 180 g of llquid fraction having a chilled stability of 6C and an $odine value o~ 115.
The upper layer (112 g) ylelded 20 g o~ a solid fraction having a ~lip point of 33C and an iodine value of 76.
Exa~ple 7 A) 200 g of deacldi~ied rice bran oll were m1xed with 10 g of a hard oil having a ~lip point of 48C
and with 120 g of isopropanol containing 5~ by ~eight of water. The mi~ture was heated under stirring to 60C and the ~olution thus obtained was cooled rapidly to 15C and stirred at that temperature for 2 hours.
The mi~ture wa~ then transferred into 8 cooled decantation vegsel where it ~eparated into two layers in less than 20 minutes. The layers were separated by decantation and the lower layer (221 g) distilled to yield a residue of 185 g of liquid fraction whic~l did not contain any wa~e~ and had a chilled stability of 20C.
The upper layer (109 g) was heated undsr stirring to 45C for 3~ minutes and transferred into a decantation ves~el whicn was maintained at a temperature of 45C.
After les~ than 20 minutes a separation into two layers took place. The layerQ were separated and distilled separately to remove tne i30propanol and the water.
The res~due from t~le upper layer consisted in 15 g of oil which contained the ~0 g of the hard oil, while the res~due from the distillation of the lower layer contained 8 ~ of wa~es and 2 g of triglyceriàes and had a slip point of 78C.
B) 185 g of the liquid fraction obtained above were submitted to a ~econd ~tage fractional crystalli-zation from 185 g of isopropa~ol containing 5~ by weight 3.~

of water in accordance with the procedure described in Example 6 (crystallization temperature 5C). The`re were thus obtained:
a liquid fraction (170 g) having a chille~
stability of 6C and an iodine value of 101; and a solid fraction (15 g) havin~ a slip point o~ 32C and an iodine value of 72.
E~am~le 8 200 g of partially hydrogenated soybean oil containing 0~5~ linolenic acid and having an iodine value of 90 were mixed with 200 g of i~opropanol containing 5% by weight of water. The mixture was heated with stirring to 60C and the clear solution thus obtained was cooled rapidly to 25C and stirred at thi~ tempera-ture for 2 hours. The mixture was then transferredinto a cooled decantation vessel wherein it separated into two layers in less than 10 minutesO The layers were separated by decantation and the lower layer (207 g) containing 47 g of aqueous isopropanol was mixed with additional 113 g of isopropanol containin~ 5~
by weight of water. The proceaure described above wa~ repeated at a crystallization temperature of 5C.
In the decantat~on vessel the separation of the two layers occurred in less than 20 minutes. The layers were separated by decantation.

10~7'~31 The lower layer (162 g) was distilled to yield as a residue a liquid fraction (140 g) having an iodine value of 100 and a chilled stability of 6C.
The upper layer (158 g) was combined with the upper layer obtained in the first stage and the mixture was distilled in order to remove isopropanol and water.
The obtained residue consisted of 60 g of a solid fraction having a slip point of 33C and an iodine value of 66.

Claims (29)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for separating an edible oil, selected from the group consisting of natural and semi-processed animal and vegetable oils and fats and mixtures thereof, into a less saturated fraction (liquid fraction) and a more saturated fraction (solid fraction), which method includes the steps of:
dissolving one part by weight of the oil in about 0.5 to about 4 parts by weight of a solvent consisting of a C2 - C3 alkanol containing about 2% to about 10% by weight of water at a dissol-ution temperature above about 40°C;
rapidly cooling the resulting solution to a crystallization temp-erature lower than the dissolution temperature, thereby to cause formation of substantially spherical-shaped alpha-form crystals of said more saturated fraction of the oil capable of floating in said solvent;
allowing said mixture to separate into three phases consisting of a lower liquid layer comprising said less saturated fraction of the oil and a part of said solvent, an upper liquid layer com-prising another part of said solvent, and a solid phase consisting of said crystals of said more saturated fraction of the oil, said solid phase floating in said upper liquid layer to form a suspen-sion therein; and separating said lower liquid layer from said suspension by decantation.

2. A process as defined in claim 1, which includes the step of stirring the mixture of said alpha-form crystals and residual solution, which results from said rapid cooling, at said crystallization temperature for about 2 to about 6 hours, thereby causing said crystals to agglomerate into small spherically shaped aggregates.

3. A process as defined in claim 1, wherein following said decanting, the lower liquid layer and the suspension are separately subjected to distillations thereby to remove the sol-vent as distillate and to recover, respectively, said less sat-urated fraction and said more saturated fraction of the oil as distillation residues.

4. A process as defined in claim 1, wherein the product solid and/or liquid fractions of the oil are stripped from residual amounts of alkanol and water under vacuum, by passing therethrough a controlled stream of a dry, inert gas.

5. A process as defined in claim 1, wherein a liquid fraction product obtained in a first separation operation is subjected directly to a second separation operation as defined in claim 1, in the course of which the solution is cooled to a lower temperature than in the first operation.

6. A process as defined in claim 1, 2 or 3, wherein the alkanol contains from about 4% to about 6% by weight of water.

7. A process as defined in claim 4 or 5, wherein the alkanol contains from about 4% to about 6% by weight of water.

8. A process as defined in claim 1, 2 or 3, wherein from about 1 to about 2 parts by weight of the aqueous alkanol are used for each part of the oil.

9. A process as defined in claim 4 or 5, wherein from about 1 to about 2 parts by weight of the aqueous alkanol are used for each part of the oil.

10. A process as defined in claim 1, 2 or 3, wherein the alkanol is isopropanol.

11. A process as defined in claim 4 or 5, wherein the alkanol is isopropanol.

12. A process as defined in claim 1, 2 or 3, wherein the oil is palm oil.

13. A process as defined in claim 4 or 5, wherein the oil is palm oil.

14. A process as defined in claim 1, 2 or 3, wherein the oil is cottonseed oil.

15. A process as defined in claim 4 or 5, wherein the oil is cottonseed oil.

16. A process as defined in claim 1, 2 or 3, wherein the oil is sunflower seed oil.

17. A process as defined in claim 4 or 5, wherein the oil is sunflower seen oil.

18. A process as defined in claim 1, 2 or 3, wherein the oil is kapok seed oil.

19. A process as defined in claim 4 or 5, wherein the oil is kapok seed oil.

20. A process as defined in claim 1, 2 or 3, wherein the oil is partially hydrogenated soybean oil.

21. A process as defined in claim 4 or 5, wherein the oil is partially hydrogenated soybean oil.

22. A process as defined in claim 1, wherein the oil is a dewaxed oil.

23. A process as defined in claim 22, wherein the oil is rice bran oil which is dewaxed by mixing it with about 1 to 5%
by weight of a hard fat of a comparatively high melting point, and submitting the mixture to a separation, the waxes being ob-tained together with the hard fat as solid fraction in the upper layer.

24. A process as defined in claim 23, wherein the waxes are recovered from the isolated upper layer by heating the latter to about 45°C whereupon it stratifies into a lower layer compris-ing the melted waxes and some of the aqueous alkanol, and an upper layer comprising a solution of the hard fat in the remainder of the alkanol, separating the two layers from each other by decantation at about 45°C and distilling the lower layer in order to remove the alkanol and the water and to recover the waxes as the distillation residue.

25. A process as defined in claim 24, wherein the upper layer is recycled for use in a subsequent dewaxing operation according to claim 24.

26. A process as defined in claim 1, 2 or 3, including the step of preliminary degumming and deacidification of the oil.

27. A process as defined in claim 4 or 5, including the step of preliminary degumming and deacidification of the oil.

28. A process as defined in claim 1, 2 or 3, comprising pretreating the oil for reduction of glycerides content.

29. A process as defined in claim 4 or 5, comprising pretreating the oil for reduction of glycerides content.