Note: Descriptions are shown in the official language in which they were submitted.
- 1 - A~401
FAT REFINING
Technical Field
The field of the invention is the refining of fat,
particularly but non-exclusively the refining of vegetable
5 butters.
From whatever source they are obtained, fats require
purification in a refining process, to remove impurities
and improve both the appearance and performance of the fat.
In the edible context with which the invention is
10 concerned, taste also is improved by refining. The
invention is particularly concerned with a class of fats
known generally as vegetable butters from their relatively
high melting characteristic~, compared with the majority of
fats from vegetable sources which are generally liquid at
15 ambient temperature~ and are usually described as vegetable
oils.
Oil~ and fats may be classified into two distinct
groups differing markedly both in their properties and
stability and require very different approach~s in detail
20 to refining proces~es applied to them. Those high in
polyunsaturation, including linoleic and more highly
unsaturated fatty acids, and prized accordingly for their
dietetic value, may contain 40~ or more of the~e acids in
their glyceride~, they are liquid at ambient temperature
HBE15F
- 2 - A.401
and are susceptible to the development of reversionary
flavours after refining, owing to their susceptibility to
oxidation arising from their high degree of unsaturation.
Examples of these high PUFA vegetable oils include soyabean
5 containing 52% polyunsaturated fatty acids, cottonseed
(53%), groundnut (32%), linseed (65% including no less than
53% of triunsaturated fatty acid), safflower (77~) and
sunflower (64%). Marine oils are also notable for their
high PUFA content.
In contrast, most animal fats are substantially less
unsaturated. They are accordingly, high meltiny and less
prone to flavour reversion as are vegetable butters. Like
most other vegetable fats, vegetable butters consist
principally of triglycerides of predominantly Cl6 and
15 Cl8 fatty acids, but vegetable butters contain more
saturated fatty acids. These are distributed principally
in the alpha- or l- and 3-positions of the triglycerides
which constitute the principal component of fats and in
this vegetable butters closely resemble cocobutter and in
20 their refined form are therefore used as cocoabutter
substitutes since the close similarity of their structure
is matched by similar melting performance including most
importantly, organoleptic response. Examples of vegetable
butters include cocobutter itself with only 4~ linoleic
25 acid, shea ~lO~), sal (2.8~) manqo kernel (5%) and mowrah
(up to 18%), with palm oil (lO~).
The application of selective adsorption methods for
the removal on an industrial scale o~ impurities from
glyceride oils and fats is a relatively recent event in
30 refinery practice. A miscella is made of the fat or oil in
a suitable organic ~olvent, usually a hydrocarbon 6uch as
hexane, and the solution brought into contact with an
apprQpriate~ adsorbent material of æuitable particle size.
The process necessitates removal of the solvent from the
7~7
~ 3 ~ A.401
raffinate solution and is therefore expensive to operate.
The cost of the process may also be prohibitively high if
the effective life of the adsorbent is short.
~evertheless, the removal of the small quantities of polar
5 compounds present may have a dramatic effect, particularly
on the melting characteristics o:E vegetable butters and is
not readily achieved by alternative methods. The invention
is particularly useful therefore in reducing the cost of
achieving high ~uality fats for edible purposes such as
10 chocolate manufacture and also for pharmaceutical
application by enhancing the effective lie of adsorbents
used for producing such fats.
Background art
USP 2,976,156 discloses a method of refining liquid
15 vegetable oils by contact with alumina adsorbent in which
it is recommended that bleaching treatment can be omitted,
USP 3,955,004 discloses a similar process to that of
~SP 2,976,156 and in addition discloses as adsorbent
mixtures of silica and alumina. The oils, which include
20 coconut, palm kern 1 and palm oil, are dissolved in a
suitable solvent. After contact with the adsorbent, the
refined oil is separated from the solvent and bleached.
French Patent 990704 discloses bleaching a solution
of glyceride oil and subjecting the solution to silica
25 treatment. None of these references reveals the necessity
for combining the application of adsorption and bleaching
steps with regeneration as provided for by the present
invention and applied to vegetable butters to be
fractionated.
81~3~0~
~ 4 ~ ~.401
USP 4,284,580 describes the fractionation o~
triglyceride mixtures by selective adsorption on surface-
aluminated silica gel adsorbent. The process disclosed in
this reference relies upon differential adsorption
5 characteristics exhibited by different degrees of
unsaturation between the many triglycerides of glyceride
oils and fats in order to obtain fractions of different
lodine Values.
Indian Oil Soap Journal (1969), 34 (7), pages 147-
10 150. Laboratory scale purification of sal oil is describedin which crude sal oil is purified by chromatography in
benzene solution over an alumina column. No column
regeneration is described, nor was the solution
pre-bleached.
USP 2,589,097 describes the removal of reversionary
flavours from soyabean and similar highly unsaturated oils,
which may first be bleached, using column adsorption
treatment.
European Patent Application 53016 published
20 2nd June 1982 describes refining sal fat by contact with a
specially prepared particulate adsorbent in a column.
General description of the invention
This invention relates to fat refining, particularly
but not exclusively to refining vegetable butters.
Fats may be refined by contact, in a solution or
miscella of a non-polar solvent, with an adsorption agent,
usually packed in a column and ba6ed on silica and/or
alumina activated by heat treatment. The adsorption agent
selectively retain~ polar impurities, for example partial
, ,.
37~
- 5 - A.401
glycerides and colouring matter, and oxidised compounds
which are highly polar, whereas the triglycerides
constitutiny the principal components of the fats remain
unabsorbed in a raffinate from which the purified fat is
5 recovered by removing the solvent.
The absorption agents become less effective with
prolonged and/or repeated use, a~ polar compounds
accumulate on them. Desorption of these po~ar compounds by
treatment with polar solvents is incompletely effective
10 with the more tenacious polar compounds absorbed from
vegetable butters such as shea, sal and others. We have
now found that regeneration is facilitated by subjecting
the fat or the fat miscella to pretreatment by contact with
bleaching earth and/or active carbon, to adsorb the more
15 highly polar compounds before treatment with the adsorption
agent, preferably packed in a column through which the
miscella is percolated. The less highly polar compounds,
e.g. diglycerides, adsorbed by the adsorption agent may
then be readily removed in a subsequen-t desorption step,
20 e.g. ~y percolation with a polar solvent. The refined fat
may be separated from the raffinate, for example by
distilling off the non-polar solvent, or by fractiona
crystallisation, preferably to recover a fat fraction
having a slip melting point of at least 35C.
Excepting the lauric fats, e.g. palm kernel and
coconut oil, about 1/3 of the triglycerides of the fats
with which the invention is chiefly concerned are
symmetrical, disaturated C16/C18 triglycerides-
Generally they contain less than 20~ l.inoleic acid and, for
30 the most part, not ~ore than 10% and are low in
polyun~aturated fatty acids generally.
Such fats are usually expelled or extracted from
tropical or sub-tropical fruit, either the fruit ~eeds or
,.
6 ~ 01
whole fruit. Although sometimes cultivated in plantations,
as for palm oil, usually the fruit grows wild and is
collected at irregular intervals in the forests after
having fallen. Due to the preva:iling elevated temperature
5 and the moisture content of the earth, extensive enz~nic
reaction can occur, converting the natural triglycerides of
the fats contained in the fruit seeds or in the pericarp by
hydrolysis to mono- and diglycerides and free fatty acids.
Other common reactions encountered in the fruit are
10 hydroperoxidation, epoxidation and hydroxylation of the
unsaturated fatty acid radicals contained in the
triglycerides of the fat. These enzymic reactions produce
a host of highly polar compounds which adhere tenaciously
onto adsorbents, both on their surface and in their pores,
15 which makes their desorption very difficult and which
consequently result in the failure to regenerate the
adsorbents for re-use.
The solvent in the fat miscella is preferably hexane
or other inert aliphatic hydrocarbon compositions,
20 preferably with a boiling point below 100C to facilitate
evaporation from the miscella without exposing the fat to
excessively high temperatures. The fat in the miscella may
be in crude form or undergo some preliminary refining
beforehand, preferably neutralisation.
Regeneration comprises desorption and reactivation,
preferably effected in two steps. In the first step
adsorbed polar compounds are desorbed from the adsorbents
by contact with a polar organic solvent which preferably
comprises a monohydric fatty alcohol containing up to 6
30 carbon atoms and particularly methanol J ethanol and
isopropanol, and alcohol hydrocarbon mixtures, preferably
aliphatic, which may be miscible or immiscible, preferably
azeotropi~ mixtures to facilitate removal from the
regenerated adsorbent by evaporation. In the second step,
, ,,
- 7 - A 401
residual polar solvent (eOg. methanol) used for the
desorption operation is driven out of the column by
heating and preferably a volatile aliphatic hydrocarbon,
e.g. hexane either in the vapour phase or as a superheated
5 liquid. The formation of a~eotropic mixtures is also
helpful in this case. Herein the first step is called
"desorption" and the second step "reactivation".
Pretreatment, adsorption and desorption are
preferably carried out at temperatures from 15 to 75C,
10 more preferably not in excess of 65C, but pretreatment in
particular may be carried out at temperatures from 30 to
110C and adsorption and desorption at 40 to 80C.
Adsorption is preferably effected in particular at 30 to
60C, particularly approximately between 20 and 50~.
Reactivation is preferably carried out between 50 to
170C. Substantially less bleaching aid or active carbon
is used in the pre-treatment step than adsorption agent,
from 0.5 to 5% by weight of the fat being adequate for the
former, but with preferably a fat:adsorbent ratio from 10:1
20 to 1:1 by weight of the fat. Preferably both the pre-
treatm~nt and adsorption steps are applied to the same
solution of fat.
Suitable bleaching earths for use in the invention
include activated Fuller' 5 earth, for example Tonsil and
25 Fulmont, Lucilite, Kieselsaure of Degussa. Granulated or
non-granulated active carbon, e.g. Norit~ may alternatively
or in addition be used. Bleaching earths are usually
acid-activated natural earths of structures typified by
Montmorillonit and Bentonit. Acid treatment increases
30 their propensity for adsorption of highly polar organic
compounds including highly polar pigments, e.g.
chlorophyll. These earths are not ~uitable for the
adsorption of bulk amounts of diglycerides etc, but very
rr~~ S
~ 8 - A.401
useful in the preliminary treatment step for the removal of
small amounts ~f highly polar organic compounds prior to
the treatment of the fat with adsorbents like silica gel or
A1203. These highly polar compounds otherwise prevent
5 the regeneration of the adsorbents like silica gel and make
their reuse difficult; if not imE~ossibleO
Active carbon also adsorbs highly polar compounds
both by surface adsorption (e.g. pigments etc~ and also by
~ -electron interaction (e.g. aromatic compounds, polyene
10 compounds, etc). All active carbons, both granulated and
non-granulated, are suitable for this purpose and may be
used in conjunction with bleaching earths.
The adsorption agent may comprise silica gel,
alumina or mixtures thereof including co-precipitates.
15 Examples of aluminas include gibbsite and bayerite and
among proprietary examples include Aluminiumoxid 504C.
Suitable silica gels include Sorbsil of Messrs J Crosfield
& Sons Limited, Warrington, England and Kieselgel-M of
Messr~ Herrmann, Cologne, Germany.
Preferably adsorption is effected by percolating the
miscella through a column packed with the adsorbent and
with a length:diameter ratio of 5:1 to 1:2, particularly
approximately equal diameter and length, with a residence
time in the column of 5 to 30 minutes, especially 15
25 minutes.
Adsorbents suitable fox use in the process of the
invention preferably exhibit a specific surface area of 300
to 500 m /g, a pore volume of 0.7 to lo 5 mls/g, an
average pore diameter of 30 to 2000 A, preferably 60 to
30 180 A, a weight-volume ratio of 0.2:0.5 g/ml and pH of
6.5 to 7.5. Preferably silica gel adsorbent u~ed in this
invention contains more than 95~ SiO2 with not more than
.1; ~c~d~ ~Q~k
~ 9 - A.401
approximately 4 to 8% of volatiles removed at 140C after
4 hours. Particle size by sieve analysis should preferably
include not more than approximately 5% of 0.3 mm and not
more than 25% of 0.2 mm.
EXAMPLE l
40 g of the neutralised solid fraction tO.1% free
fatty acids) remaining from dry fractionating crude sal fat
obtained by solvent extraction of the seeds of ~al fruits
~Shorea robusta) were dissolved to form a 20% solution in
10 hexane which was pretreated with 2% bleaching earth Tonsil
ACCFF and 0.4% active carbon Norit FND at 25 to 40C with
agitation for 45 minutes before the bleaching earth and the
carbon was filtered off and the pretreated hexane solution
passed at 40C down a column 3 cm in diameter and 21 cm
15 long, packed with silica yel (Kieselgel M o
Messrs Herrmann, Cologne), using a residence time of 12
minutes and a fat:gel ratio of 2:1. After collecting the
eluate raffinate the silica was regenerated by washing in
the column with isopropanol/hexane 20/80 mixture, removed
20 from the column and dried at 160C for 16 hours and reused
as before, adopting the same quantity of fat each cycle.
Particulars of the gel are as follows:- Specific surface
area 450 m2/g, pore volume 0.73 mls/g, average pore
diameter 60A weight:volume ratio 0.43 g/ml, pH 7.2,
25 SiO2 99.0%, volatiles as above 2.4%, sieve analysis 2%
of 0.2 mm, 75% of 0.1 mm, 18% of 0.063 mm and 4.5% of
O.05 mm and 0.5% of 0.04 mm.
5 cycles were completed and the fa* recovered from
the eluate raffinate and e~amined after each upon removi~g
30 the solvent.
The same fat and the same gel was used for a ~imilar
series of experiments în which the mîscella pretreatmen~
11887~6
~ X - CoOR3
HN " (VIII)
~x~ -CooR3
, x - CoOR3
HN (IX)
~Y-CN
Y CN
HN (X)
~Y"-CN
In the formulae ~VI) to CX), X, Y and R are as defined
s above; R represents an alkyl group having 1 to 8 carbon
atoms; a cycloalkyl group having ~ to 6 carbon atoms;
a benzyl group which may be substituted with a halogen
atom, an alkyl group having 1 to 3 carbon atoms or an
alkoxy group having 1 to 3 carbon atoms; a phenyl group
wh~ch may be substituted with a halogen atom, an alkyl
group having 1 to 3 carbon atoms or an alkoxy group
having 1 to 3 carbon atoms; or Z'-R4 , in which Z'
represents a carbonyl group or a sulfonyl group, and
` R4 represents an a,Lkyl group having 1 to 6 carbon
, 15 atoms, a phenyl group, a benzy]L group, an alkoxy group
-. having 1 to 6 carbon atoms or a phenoxy group (in which
the alkyl group and alkoxy group may be straight or
branched chain); R3 has the same meaning as in R3; X"
has the same meaning as in X; and Y" has the same meaning
as in Y.
,' - 1 1~ -
38~6
Representati~e examples of the amine compound
of the formula (VI) are N-methylglycine methyl ester,
N-methylglycine ethyl ester, N-methylglycine butyl ester,
N-ethylglycine ethyl ester, N-n-propylglycine ethyl
ester, N-isopropylglycine e~hyl ester, N-n-butylglycine
ethyl ester, N-isobutylglycine ethyl esteT, N-sec-butyl-
glycine ethyl ester, N-n-octylglycine ethyl ester, N-
cyclohexylglycine ethyl ester, N-benzylglycine ethyl
ester, N-(4-methylbenzyl)glycine ethyl ester, N-(4-
chlorobenzyl)glycine ethyl ester, N-phenylglycine ethyl
ester, N-(3-methylphenyl)glycine ethyl ester, N-(4-
methoxyphenyl)glycine ethyl ester~ N-methoxycarbonyl-
glycine ethyl ester, N-ethoxycarbonylglycine methyl
ester, N-ethoxycarbonylglycine ethyl ester, N-ethoxy-
carbonylglycine phenyl ester, N-phenoxycarbonylglycine
ethyl ester, ethyl N-methylaminopropionate, ethyl N-n-
propylaminopropionate, methyl N-isopropylaminopropionate,
ethyl N-isopropylaminopropionate, butyl N-isopropyl-
aminopropionate, 2-ethylhexyl N-isopropylaminopropionate,
methyl N-n-butylaminopropionate, ethyl N-n-butylamino-
propionate, ethyl N-isobutylaminopropionate, ethyl N-
sec-butylaminopropionate, ethyl N-t-bu~ylaminopropionate,
ethyl N-n-amylaminopropionate, ethyl N-isoamylamino-
propionate, ethyl N-n-hexylaminopropionate, ethyl N-
7 [3~
- 12 - A.401
EXAMPLE 2
A solution in hexane of neutral illipé fat was pre-
treated with bleaching earth and carbon as described in
Example 1 and passed down a column 0.85 m in diameter,
5 packed to a depth of 0.85 m with silica gel of the type
"Sorbsil" from Messrs J Crosfield & Sons Ltd, Warrington,
England, the weight of silica gel being the same weight as
the fat. The gel characteristics were as follows:
Total surface = 331 m /g, pore volume = 1.16 ml/g, pore
10 diameter = 140 R, pH = 7.6, wei~htOvolume ratio = 0.35 g/
ml, SiO2 content ~ 99.1~, particle size - 85.5~ between
0.05 and 0.2 J~m, 5.5% above 0.3 mm and 9% below 0.05 mm.
After distilling off the hexane a light-coloured
refined fat practically free of diglycerides was obtained
15 from the refined solution.
The spen~ silica column was then washed down at 80C
under pressure with an azeotrope mixture of isopropanol and
hexane in a weight ratio of 22:78, to desorb and remove the
material adsor~ed on the silica. The column was then
20 reactivated for reuse by passing down hexane at 180C and
13-bar. The reactivated silica column was used again to
refine a fresh batch of neutralised illipé, pre-treated as
described, the whole cycle of refining, desorption and
reacti~ation being repeated 15 times.
Neutralised illipé from the same batch was
similarly refined by treatment with silica but without the
pre-treatment. The silica progressively lost its
ad~orptive capacity with repeated reuse. This was shown by
the increasing ~iglyceride content of the refined fat and
30 its increasing colour and also by the considerable drop in
stabilised dilatation value~ D of the fat at 32.5C. These
results are shown in Table 2 and clearly demonstrate that
87al~7
- 13 - A.401
the miscella pre-treatment purifies the neutralised fat to
such an extent that after subsequent silica treatment the
spent sil~ca can be regenerated successfully by desorbing
with a mixture of isopropanol and hexane and reactivated by
5 superheated hexane. Such a regenerated silica gel can be
reused for satisfactory diglyceride removal from the
illipé fat. ~nission of the pre-treatment eventually
renders the spent silica non-reglenerable, as evidenced by
total failure to adsorb diglycerides after limited reuse.
~l8~
- 1 L~. _ A. 401
ol n 1 o ~ u~ o
O
O
1 0 ~ a~ o 00 ,,
O ~ O ----~--------~----~--~--~
o ~ o ~ I o o ~ o o
O ~ I ~; I o ~ ~D ~ ~
O I- ,----____ o
O I ~ I o o o O
0~ ~ N ~ N (`I ~`1
dP O ~ 0 ~ o ~
I ~ ,'~ !~
o --,------------- ____
O I ~ I ~ o o o
O o ~ ~D o
I O O 11 0 0 3 o
O
O O '~
O
O
N ~ ~ o Ll
- 15 - A.401
EXAMPLE 3
A solution of neutralised shea nut fat in twice its
weight of hexane, was bleached at 80C with 2% bleaching
earth "Tonsil ACCFF" from Messrs 5udchemie, Munich,
5 Germany. The filtered solution was passed through a column
as before, but packed with 8il ica "Kieselgel M" from
Messrs ~errmann, Cologne, Germany, using half as much gel
as fat by weight and a refined fat recovered by evaporating
the solvent from the treated solutions.
~he spent silica was desorbed in the column by
washing with a mixture of 85 vol % hexane and 15 vol %
methanol at 50C and reactivated by passing hexane vapour
under pressure at 90~C inlet temperature through th~
column, until methanol was completely driven out. The
15 column was reactivated and reused 5 times, the diglyceride
content being determined of the fat recovered after each
use.
In a control test the unbleached neutralised fat was
similarly refined and the diglyceride content of the
20 refined fat compared as shown in Table 3, from which it is
evident that bleaching prior to silica treatment exercises
a beneficial effect on regeneration and reuse of the silica.
7C~
- 16 - A. 40'1
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