FRACTIONAL CRYSTALLISATION-THE FAT MODIFICATION PROCESS
FOR THE 21ST CENTURY
Ralph E. Timms
Consultant – Oils & Fats, Nocton, Lincoln, UK
[Republished with copyright permission of European Journal of Lipid Science and Technology,
original reference: Timms RE (2005) Fractional crystallisation – the fat modification process for the 21st century.
Eur J Lipid Sci Technol 107:48-57. Dol: 10.1002/ejlt.200401075]
Abstract: The historical development of fractionation, from the use of fractionated tallow in Mège-Mouriès’
margarine to the modern dry fractionation process used to produce steep-melting palm fractions for cocoa butter
equivalents, is described.
The principles of fractionation by fractional crystallisation are explained. The fractionation process is carried out in
two stages: firstly, a crystallisation stage; secondly, a separation stage. Crystallisation may be effected without any
solvent (dry fractionation) or in the presence of a solvent. It can be shown that the efficiency of separation of
triglycerides is more or less independent of the solvent so that dry fractionation is, in principle, capable of giving as
good a fractionation as solvent fractionation. However, separation of the solid phase (crystals) from the liquid phase is
easier in the presence of a solvent, which dilutes the oil and lowers the viscosity. It is mainly developments in
separation over the last 25 years that have led to the improved effectiveness of dry fractionation so that it can achieve
results that rival solvent fractionation. The concept of ‘entrainment’ is explained with reference to the different
separation methods and to their different efficiencies.
Today, hydrogenation is in decline, due to nutritional concerns about trans fatty acids and to environmental
concerns about nickel catalysts and their disposal. Increasingly, oils with reduced linolenic acid (C18:3) can be
produced agriculturally so that stable frying oils may be produced without hydrogenation. With the decline in
hydrogenation, interesterification has seen a renaissance, although it is only partially able to replace hydrogenation.
Additionally, interesterification suffers from the ‘chemical’-process image and environmental drawbacks of
hydrogenation.
Fractionation is a purely physical process which satisfies today’s increasing environmental and health concerns. It is
the main modification process used for palm oil, whose production is still increasing rapidly and which is likely to
become the world’s most-produced oil within 10 years. If hydrogenation is to be avoided, then only palm stearins can
supply the higher solid fat content components required to produce the margarines and shortenings essential to produce
the bread, pastries and cakes we like to eat. Fractionation is therefore set to become the dominant modification process
of the 21st century.
Keywords:
Fractionation, crystallisation, palm,
hydrogenation, separation.
1. Historical background
Fractional crystallisation, usually known simply as
fractionation, is undoubtedly the oldest fat modification
process and was the foundation of the modern edible-oil
and fat-processing industry. On 15 July 1869, Hippolyte
Mège-Mouriès applied for the French patent number
86480 entitled: “Demande d’un brevet d’invention de
quinze ans pour la production de certains corps gras
d’origine animale”, that is: Application for a patent of
fifteen years for the production of certain fats of animal
origin”. The patent was granted in October 1869. The
product was what we know today as margarine. MègeMouriès had been working at the Imperial farm at
Faisanderie in Vincennes. The French emperor,
Napoleon III, had offered a prize to anyone who could
produce a cheap substitute for butter. He wanted to
improve the diet of his people, and particularly his
soldiers, to strengthen France for the impending war
with Germany. Having observed that the fasting cows
still produced milk, Mège-Mouriès concluded that butter
must be derived from cows’ tissues and hence from
tallow. He found that tallow itself was too high-melting
and had a waxy mouthfeel, but by separating a liquid
fraction from it, a suitable fat, oleo-margarine, was
obtained.
In July 1870, Napoleon III declared war on Germany,
or strictly speaking on Prussia, and a margarine factory
was quickly built at Passy, near Paris. However, with the
complete defeat of the French army at the Battle of
Sedan in September and the entry of the Prussian army
into Paris, the emperor was deposed and the factory was
closed. Napoleon fled to Britain where he died on 9
January 1873. He is buried in the Imperial Crypt at Saint
Michaels’ Abbey, Farnborough.
Now without a patron, Mège-Mouriès sold his
invention for 60,000 francs to two Dutchmen, Simon van
den Bergh and Anton Jurgens. They quickly established
margarine factories in The Netherlands and in other
European countries. Thus, as a result of Napoleon III’s
failed imperial ambitions, The Netherlands, not France,
became the centre of Europe’s margarine, edible-oil and
fat-processing industries, and our modern industry had
begun.
Malaysian Oil Science and Technology 2005 Vol. 14 No. 1
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Fractional crystallisation: Fat Modification for the 21st Century
Mège-Mouriès’ patent describes most of the steps that
are familiar to us in a modern refinery, e.g. bleaching or
decolourising of the tallow (by treatment with dilute
hydrochloric acid) and deodorisation or removal of offflavours (by treatment with an acidified infusion of pig’s
stomach), to give a fat that “has no longer the odour of
animal fat and has all the flavour of the most delicate
fat”, although clearly the modern technology for these
various steps is quite different from that recommended
in the patent. For the present purpose the section on
pressing is the most important.
“Pression - Cette opération est destinée a
séparer la partie dure qui rend le corps gras
grenu, le fait figer rapidement, et se colle au
palais. On sait que I’industrie ordinaire fait
cette opération très difficilement; elle devient
industrielle par les moyens suivants: le corps
gras liquide et limpide est versé dans les caisses
qui ont une ouverture au bas, et contiennent
une couche d’eau tiède; on les couvre, et
lorsque,
par
le
refroidissement,
la
cristallisation est faite, on enlève l’eau par
l’ouverture, on renverse la caisse, on laisse
tomber la messe sur une table, on la coupe en
gâteaux de 1 à 2 centimètres d’épaisseur, on
enveloppe ces gâteaux dans une toile et on les
met sous presse entre les plaques chaudes; on
obtient ainsi environ 60p. % d’un mélange de
margarine et d’oléine, d’une composition
identique au saindoux, mais d’une saveur bien
supérieur; quant à la partie solide, elle reste
dans ses toiles.”
Which I translate as:
“Pressing – This operation is meant to separate
the hard part that makes the fat grainy, makes it
congeal rapidly and stick to the palate. It is
known that it is very difficult to do this
operation by ordinary industry methods; it must
be done by the following means: the clear and
liquid fat is poured out into boxes that have an
opening at the bottom and contain a layer of
lukewarm water; they are covered, and when,
by chilling, the crystallisation is done, the water
is raised by the opening, the box is turned over,
the mass is let fall on a table and cut into cakes
of 1 to 2 cm thickness; the cakes are wrapped in
a linen cloth and placed under pressure between
warm plates; thus one obtains about 60% of a
mixture of margarine (note: stearic acid or
harder fat/fatty acid) and olein (note: oleic acid
or liquid fat/fatty acid) with a composition
identical to lard, but with a very superior
flavour; as for the solid part, it remains on the
cloths”
In more detail added in 1874, the best size for the boxes
is given as 20 L of rectangular shape and the
crystallisation conditions as 25-30°C for about 24 h.
Mège-Mouriès described the product as butter in a
primitive state. To make “beurre supérieur” or
margarine: “The fat is mixed (at animal heat, i.e. about
40°C) with its weight of water in which has been mixed
1
/50 of mammary tissue (note: cow’s udder), 1/100 of
bicarbonate of soda, 1/50 of fresh milk curds (French:
caséum de lait) and a sufficient quantity of yellow
colour. It is allowed to digest for at least 3 h, while
agitating and maintaining it at animal heat; when the
transformation is done, it is chilled, preventing the
brittle and grainy state…” and making it soft and
pliable by a scraping process that he describes as used
in soap-making. Apart from the cow’s udder, this
process is immediately recognisable as the same as we
use to make margarine today, although he does say that
it you omit the cow’s udder you get an inferior product.
Something for the modern margarine industry to think
about?!
At the beginning of the 20th century, cottonseed oil
became the most important edible oil in the USA.
According to Bailey, writing in 1950 in his classic book
‘Melting and Solidification of Fats’1: “The American
trade requires a salad oil that will remain fluid at the
temperature of mechanical household refrigerators (4045°F), and produce a mayonnaise which is likewise
stable at low temperatures. For various reasons,
cottonseed oil must serve in large measure as a source
for salad oils, yet the unprocessed oil solidifies
relatively easily. Hence, fractional crystallization is
required to obtain a suitable salad oil. Formerly, a
sufficient supply of ‘winterised’ oil was produced by
allowing the refined oil to stand in outside storage tanks
in cold weather, and drawing the liquid portion off from
the partially solidified material settling to the bottom of
the tanks. Now, however, the oil is generally
refrigerated artificially.” Bailey goes on to say: “The
fractionation of edible beef fat to produce low melting
oleo oil… is an old process… and formerly a highly
important one before catalytic hydrogenation provided
means of producing comparable products from liquid
vegetable oils.” Concluding his short review of
fractionation, he says: “there is a considerable quantity
of lard fractionally crystallized… Coconut and palm
kernel oils are separated into low and high melting
fractions with the latter being used as a confectionery
fat. In each of these cases the liquid fraction must be
separated from a relatively large solid fraction, hence
the operations of crystallizing and pressing resemble
those employed for the production of oleo oil, rather
than the operations of winterizing…”
Rossell2 gives some background on the origins of the
fractionation of lauric oils to produce confectionery
fats. He says: “The advantages of fractionation were
first appreciated by European fat companies who
imported coconut oil from Sri Lanka in long wooden
barrels called ‘Ceylon Pipes’. The pipes were filled
with warm fluid oil which cooled slowly during the sea
voyage to cooler European climates. This slow cooling,
perhaps coupled with gentle agitation of the ships’
movement, allowed the fat to crystallize and separate
into fractions.”
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Fractional crystallisation: Fat Modification for the 21st Century
In contrast to fractionation, hydrogenation of oils
was not invented until 1901 and patented by Wilhelm
Normann in 1903 while working in Leprince &
Siveke’s factory in Herford, Germany.3 The first
production trials took place in 1905 and 1906 at Joseph
Crosfield’s factory in Warrington, England. Like van
den Bergh’s and Jurgens’ factories, it was later to
become part of Unilever. Large-scale production of
hydrogenated fats began at Crosfield’s in 1908. In
1908, hydrogenated whale oil and, in 1909,
hydrogenated cottonseed oil were produced in Herford.
Interesterification was the last of the three fat
modification processes to be developed. In the 1920’s
it was introduced in the USA and in Europe, like
hydrogenation as a means of improving the functional
properties of blends for shortenings and margarines and
extending the range of raw materials that could be used.
Indeed one of the first patents on the topic was taken
out by Normann. It was developed further in the USA
in the 1940’s and 1950’s by combining it with a
fractional crystallisation step to give the so-called
directed interesterification process for the improvement
of lard as a shortening.
All the fractionation processes mentioned show the
same principles and features we use today:
 complete melting of the fat,
 slow cooling,
 gentle or no agitation to encourage the
development of large crystals,
 separation into liquid and solid fractions with
differing physical and chemical compositions.
As we shall see, there have been tremendous
developments in the technology, particularly in the last
25 years, but the principles and the objectives have not
changed. Only the use of organic solvents, as patented
by Unilever in the late 1950’s for the production of fats
to replace cocoa butter, used a process not
foreshadowed by the early processes.4
the temperature. The situation is illustrated in Fig. 2,
which shows a schematic phase diagram of a binary
mixture of triglycerides A and B which form a
continuous solid solution, i.e. they are completely
miscible in the solid state. Holding the mixture at
temperature T1 results in the formation of a solid phase
(crystals) of composition c in a liquid of composition a.
The fraction of solid phase = (ab/ac).
Figure 1. Schematic diagram of the fractionation process,
indicating factors that are important at each stage (from
reference 5)
To obtain crystallisation, it is necessary to increase the
concentration of the triglycerides to be crystallised above
the saturated-solution concentration at a given
temperature. In practice, this is not sufficient to cause
crystallisation, and solutions can exist indefinitely with
concentrations above the saturation level without
forming any crystals. Such solutions are called
‘supersaturated’.
Figure 2. Simple schematic phase diagram illustrating
the principles of fractionation.
2. Principles of fractionation
2.1 Preliminaries
The process of fractionation consists of two steps:5
 crystallisation to produce solid crystals in a liquid
matrix,
 separation of the crystals from the liquid matrix.
Different factors are important at each stage, as shown
in Fig. 1. At this point, it is useful to note that the
‘quality’ of the liquid fraction depends only on the
crystallisation step, whereas the ‘quality’ of the hard
fraction depends on both the crystallisation and the
separation step. By quality, the degree of concentration
of the desired triglycerides in the separated fraction is
meant. Quality is usually assessed by physical criteria,
such as cloud point or solid fat content.
When a liquid fat is cooled, a solid phase separates,
whose composition and amount depend principally on
For any system, we can draw a saturationsupersaturation diagram as shown schematically in
Figure 3 for the crystallisation of partially hardened
soybean oil.6 The continuous line is the normal solubility
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Fractional crystallisation: Fat Modification for the 21st Century
or saturation curve. Below this line, crystallisation is
impossible because the solution is not saturated and the
situation is stable indefinitely. The dashed lines divide a
metastable zone from an unstable or crystallisation zone.
In the metastable zone crystallisation is possible, but will
not occur spontaneously or immediately without
assistance, such as stirring or seeding. Crystallisation
will occur spontaneously and immediately in the
unstable zone. It can be seen that the position of the
dashed-line boundary between the metastable and the
unstable zones is variable and depends on process
variables such as cooling rate and agitation.
third power (size3), it is clear that the solubility must
depend on the size of the crystal. Using data for a typical
triglyceride, we can calculate the effect of crystal size on
solubility, as shown in Tab. 1. Supercooling is the
decrease in temperature below the solubility temperature
required to get small crystals (in a supersaturated
solution) to crystallise. The ‘critical size’ is the
minimum size of a crystal that is stable at the prevailing
temperature. We can see that small crystals have an
enormously increased solubility and require a lot of
supercooling to make them crystallise.
Table 1. Variation of solubility and supercooling with
radius of crystals of a triglyceride (from ref.15).
Radius of crystal
[μm]
[Å]
10
100,000
1
10,000
0.1
1,000
0.01
100
0.001
100
Figure 3.
Saturation-supersaturation diagram for
crystallisation of partially hardened soybean oil. Effect
of cooling rate on metastable/unstable boundary (dashed
line). Numbers are rates of cooling [°F/min] at an
agitation speed of 120 rpm. (Adapted from reference 6).
The reason for the existence of the metastable zone
can be understood if crystallisation is treated as a twostep process: Nucleation followed by crystal growth.
2.2 Nucleation
Supercooling
[oC]
0.004
0.036
0.36
3.6
7.2
Increase in
solubility
1.001
1.007
1.1
2.1
1380
In practice, such spontaneous or homogeneous
nucleation rarely occurs in fats. Instead, heterogeneous
nucleation takes place on solid particles, such as already
existing seed crystals, dust, walls of the container or
foreign molecules.
Once crystals have formed due to primary nucleation,
secondary nucleation can also occur. Secondary nuclei
form whenever small pieces of crystal are removed from
the growing crystal surface. If the pieces are smaller than
the critical size, they redissolve; if larger, they act as
nuclei and grow to become crystals. Secondary
nucleation is undesirable in fractionation. Agitation or
stirring is the primary cause, and therefore agitation is
usually kept to the minimum required to facilitate heat
transfer.
2.3 Growth
A crystal nucleus is the smallest crystal that can exist in
a solution of a certain concentration and temperature.
Aggregates of molecules smaller than a nucleus are
called embryos and will redissolve if formed.
When molecules come together to form a crystal,
there are two opposing forces. Firstly, energy is evolved
due to the heat of crystallisation, which favours the
process. Secondly, the surface of the crystal increases as
the molecules aggregate together. Just as when a balloon
is blown up, increasing the surface requires energy to
overcome the surface tension or pressure. A stable
crystal will form only when the energy due to the heat of
crystallisation exceeds that required to overcome the
surface energy. Since the surface energy is proportional
to the surface area, and hence to size (here: linear
dimension of the crystal, e.g. the diameter for spherical
crystals) to the second power (size2), and the heat of
crystallisation to the volume, and hence to size to the
Once a crystal nucleus has formed, it will start growing
by the incorporation of other molecules. These
molecules are taken from the adjacent liquid layer,
which is replenished continuously from the surrounding,
supersaturated liquid by diffusion. The growth rate is
proportional to the amount of supercooling and inversely
proportional to the viscosity, which affects the rate of
diffusion.
When growth is under way, there is a large evolution
of heat. Especially in the absence of stirring, local
temperature rises can be very significant. As a result, the
volume adjacent to a growing crystal surface may cease
to be saturated and/or existing nuclei may redissolve,
because the critical size has increased with the rise in
temperature. The nucleation and growth sequence may
become erratic, leading to imperfect and variable-size
crystals. In the industrial fractionation of fats, it is an
important aim of the process to limit this exotherm by
Malaysian Oil Science and Technology 2005 Vol. 14 No. 1
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Fractional crystallisation: Fat Modification for the 21st Century
varying the rate of heat removal and agitation with
temperature.
2.4 Separation
To complete the fractionation process, the desired solid
triglycerides in the crystals need to be separated from the
triglycerides that are liquid at the temperature of
crystallisation. These liquid triglycerides are distributed
in three locations:



in solid solution with the solid triglycerides,
in the uncrystallised bulk oil,
in the uncrystallised oil that is physically trapped or
‘entrained’ in the crystals.
The extent and type of solid solutions formed depend
primarily on the fundamental phase behaviour of the fat
being crystallised, although high degrees of supercooling
will tend to increase the extent of formation of solid
solutions. However achieved, once the solid solution has
formed in the crystals, the separation step can do nothing
to change the composition of the solid phase of the
crystals.
The uncrystallised bulk oil is relatively easily
removed from the crystals, but it should be noted that
some liquid oil will always remain as a surface layer.
The surface oil retention is proportional to the total
surface area of the crystals, which depends on their
shape and size – the smaller the crystals the greater their
surface area. The entrained oil is more difficult to
remove. The separation step must address the problem of
reducing the level of entrained oil in the final solid
fraction. Three methods have been developed to achieve
this: centrifugation, vacuum filtration and pressing.
2.4.1 Centrifugation
Although there is a useful density difference of about
10% between solid and liquid, oils are relatively viscous
materials at the temperatures of fractionation. In a
method now rarely used (the Lanza or Lipofrac TM
process), the crystal slurry is mixed with a detergent
solution so that the crystals are wetted and move into the
aqueous phase. Separation is then easily effected
between the oil and aqueous phases.
In a newer procedure, the crystal slurry itself is
centrifuged using a nozzle centrifuge, which allows the
separated crystals to be discharged through nozzles on
the outer edge of the centrifuge bowl. Effective and
useful separations can be achieved, but results are
strongly influenced by viscosity and by crystal size,
shape and amount.
2.4.2 Vacuum filtration using a rotary drum or a
belt filter
through, similar to the operation of a laboratory vacuum
filter. Such filters operate in two stages. In the first stage,
the crystallised bulk oil is removed and the filter or
crystal cake builds up. In the second stage, the residual
liquid is sucked out and air or nitrogen sucked through
the cake. It is in this second stage that the entrained oil is
reduced. Although more complex and expensive, the belt
filter has the advantage that more time can be given to
this second stage, and the differential pressure can vary
along the belt. As a result, the belt filter yields a solid
cake fraction with a lower level of entrainment than the
drum filter.
2.4.3
Pressing
Vacuum filters are necessarily limited to a pressure on
the crystals of less than 1 bar. If the pressure is
increased, it is possible to squeeze out more of the
entrained oil. As noted earlier, improved separation
improves the yield but not the quality of the liquid
fraction, whereas for the solid fraction, the separation
step has a decisive effect on quality. The mechanical or
hydraulic pressing process was therefore developed
particularly for the production of palm kernel stearin
where the quality of the stearin determines its utility and
value as a replacement for cocoa butter. Conventional
vertical hydraulic presses capable of 100 bar pressure
have been used for many years. The process is applied in
practice by crystallising the fat statically in blocks, e.g.
in trays, in a cold room circulating cold air around the
blocks to cool the fat and to remove the heat of
crystallisation. The crystallised blocks of fat are then
wrapped in filter cloths with a mesh size able to retain
the crystals while allowing the entrained oil to flow out,
and hydraulic or mechanical pressing is applied just as
Mège-Mouriès described. The practical limit on pressure
is determined by the point at which no further oil can be
squeezed out and/or the solid crystals begin to extrude
through the cloth. Such a process is labour intensive, and
because of the need to surround the crystals completely
with the cloth, it is only feasible for solid crystalline
masses with a solid fat content of at least approximately
25%.
Thus, if a crystallised slurry of the consistency
produced in a stirred crystalliser is to be pressed, a
totally different design of press is required. Such presses,
membrane filter presses with compressible chambers for
the slurry, were developed in the early 1980’s for the
fractionation of palm oil. As a result of the development
of the membrane filter press, significantly lower
entrainment levels and, consequently, higher olein yields
can be achieved, as shown in Tab. 2, making this now
the preferred choice for new fractionation plants.7,8
Earlier, I mentioned the development of solvent
fractionation for the production of steep-melting fats to
replace cocoa butter. The advantages of using a solvent
are:
Here, the crystal slurry is applied to a perforated mesh or
cloth, and a vacuum applied to suck the liquid oil
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Fractional crystallisation: Fat Modification for the 21st Century




nucleation and growth are faster so that faster rates
of cooling can be used, thus favouring short
crystallisation times and continuous crystallisers;
lower viscosity of the liquid leads to easier
filtration;
dilution of the fat makes heat transfer easier and the
amount of oil in the entrained liquid smaller;
the ability to wash the cake repeatedly with fresh
solvent leads to very low levels (less than 10%) of
entrained oil.
Table 2. Comparison of vacuum filtration,
centrifugation and membrane press filtration in a palm
oil fractionation plant (adapted from Tab. 5.19, refs. 7
and 8; * author’s estimate).
Vacuum
Filtration
(drum/belt)
Filtration
Data
IV palm oil
IV olein
IV stearin
Liquid oil
entrained in
filter cake
Yield of olein
Centrifugation
(nozzle)
Press
Filtration
(standard
6 bar)
57
40
59%
52
57
38
53%*
57
34
45%
71%
74–75%
78%
The use of a solvent has been reviewed.9,10 The
selectivity of triglyceride separation in the crystallisation
step is little affected by the choice of solvent, and
indeed, solvent fractionation has no advantage over dry
fractionation here. The choice of solvent does affect the
selectivity of separation between lipid classes,
particularly the separation of triglycerides from
diglycerides, free fatty acids and other lipids more polar
than triglycerides. Of the two commonly used solvents,
acetone and industrial hexane, the more polar acetone is
more effective in separating lipid classes.
Due to improvements in separation efficiency using
membrane presses, especially if higher pressures and
smaller chamber widths are used, as shown in Tab. 3,
dry fractionation, i.e. fractionation without solvent, is
now capable of rivalling solvent fractionation, albeit
with more fractionation steps and lower yields.
Table 3. Effect of squeezing pressure and chamber
width on the separation efficiency during fractionation of
crude palm oil (adapted from Tab. 5.21, ref. 7).
Chamber
width
[mm]
Squeezing
pressure
[bar]
Liquid oil
entrained
in filter
cake [%]
Yield
of
stearin
[%]
IV of
stearin
(olein IV ~
57)
50
6
15
30
6
15
30
45
39
35
40
34
30
23.6
20.0
18.3
20.6
18.8
16.7
39.7
36.6
34.7
36.8
34.9
32.1
25
3. Comparison of fractionation with
hydrogenation and interesterification
For most of the last century, hydrogenation was the
major process used for the modification of oils. This
situation developed partly because of the great flexibility
that hydrogenation offers and partly because of the rise
of soybean oil to be the most widely produced and used
oil. Soybean oil is relatively unstable to oxidation and is
too liquid to be used as the hardstock in shortenings and
margarines. Hydrogenation can correct both these
deficiencies.
In the last ten years, trans fatty acids have been
implicated as a nutritional cause of coronary heart
disease. The majority of trans acids in our diet comes
from hydrogenated oils and, thus, the whole
hydrogenation process has come under a cloud. In 2004,
Denmark legislated for a maximum 2% trans fatty acids
in edible vegetable oils, and from 1 January 2006,
labelling of trans acids will be mandatory in the USA.
Even without legislation, consumer pressure has led to
the removal of trans acid from most retail margarines in
Europe. We now regularly see statements in the media
such as: “Nothing in our food supply is more dangerous
than trans fatty acids that are produced by the partial
hydrogenation of oils”.11 Whatever the truth of the
matter, I believe, like many others, that hydrogenation is
a dying process.
One way to eliminate trans acids is to breed oilseed
varieties with reduced levels of linolenic acid so that
hydrogenation to improve oxidative stability is not
required. This has been successful and low-linolenic
rapeseed and soybeans oils are commercially available
and are used in the frying industry.
However, for the products we all enjoy – fancy
pastries, cakes, confectionery, biscuits, etc. – we do need
some solid fat. If we cannot get it from hydrogenated
oils, where else can we get it from? In Mège-Mouriès’
time, butter, lard and tallow were used, but due to fears
of cholesterol and saturated fatty acids, these have long
been considered undesirable. Thus, the only other
sources of harder fat are palm and palm kernel oils and
coconut oil. They may be simply blended with liquid
oils, but as we noted earlier, interesterification is a useful
process to improve the functionality and utility of such
blends.
The basic principles of the use of interesterification to
develop trans-free margarine hardstocks were outlined
by Unilever in British patent 1,245,539, filed on 28
February 1969. Note the date when there was already a
clear interest in eliminating trans fatty acids and
hydrogenated oils, long before the current nutritional,
media and consumer interest. The patent claims a
polyunsaturated margarine “free from hydrogenated hard
fat”. The last and most general claim is:
“Process for the preparation of a margarine
fat…which comprises interesterifying a mixture of
unhardened fats comprising a coconut fat, a palm fat
Malaysian Oil Science and Technology 2005 Vol. 14 No. 1
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Fractional crystallisation: Fat Modification for the 21st Century
and a constituent with at least 60% fatty acids of a
chain length of at least 16 carbon atoms, and
blending the interesterified mixture with 25-90% of
a liquid fat…”.
Essentially, the hardstock is to be a mixture of
unhydrogenated palm and lauric oils (about 2:1)
interesterified to produce trisaturated triglycerides.
However, interesterification is, like hydrogenation,
also a chemical process with environmental impacts.
There may also be health issues lurking, such as the
production of long-chain ketones12 or the placing of
saturated fatty acids in the nutritionally less desirable 2position in the triglycerides. It would clearly be good to
get rid of chemical processes altogether. For
interesterification, the option of using enzymic catalysis
to selectively keep the saturated acids at the 1- and 3positions of the glycerol molecule does now seem to be
economic and competitive with chemical catalysis, and
we may expect that most new interesterification plants
will use enzymic catalysis, as exemplified by the new
ADM plant built in the USA in 2002.
There is another trans-free source of hard fat – fully
hydrogenated liquid oils – and it is interesting to note
that ADM’s NovaLipidTM range of zero and low-trans
fats makes use of fully hardened soybean oil.
Hydrogenated oils are equated with trans acids in the
consumer’s mind and are therefore bad news; so
naturally, ADM did not want to label the oil as
‘interesterified and hydrogenated’. As a result, they
asked the Food and Drug Administration in the USA for
‘clarification’.13 The FDA has allowed the description to
be simply ‘interesterified soybean oil’ with the possible
addition of ‘high stearate’ or ‘stearic oil’. ADM are
quoted as saying: “This designation for NovaLipid TM
interesterified ingredients will allow customers to
replace the term ‘hydrogenated’ with the term
‘interesterified’ when describing these ingredients within
a finished product’s ingredient specification.” There is
surely some deception here, so we may expect some
manufacturers to specifically label their products as ‘free
from hydrogenated oils’. We may also expect some
backlash from consumer organisations and the public.
What a pity that neither ADM nor the FDA felt
sufficiently confident about the science behind the
process to educate the public about what they have really
done. In my opinion, clarity and openness in labelling
are vital if food manufacturers are to keep the trust of
their customers.
Fractionation has the advantage over both
hydrogenation and interesterification that it is a purely
physical process with a low environmental impact. It has
grown in line with the growth of palm oil, which is set to
be the dominant oil of the 21st century, as we shall see in
the last section.
Finally, we must not forget the economics.
Fractionation is a cheap process, as shown in Tab. 4.
Table 4. Comparison of the costs of fractionation,
hydrogenation and interesterification based on 100 t per
day plant capacity (adapted from Tabs. 5.10, 5.17, 5.22,
ref. 7).
Process
Fractionation (to
produce palm
olein IV 57)
Hydrogenation
(to hydrogenate
soyabean oil to
IV 75
Interesterification
Capital
cost
[million
US$]
Operating
cost
[US$/t]
2.25
6.7
Operating
cost
including
investment
pay-off
[US$/t]
20
2.00
37.8
50
1.50
22.8
32
4. Implications for the 21st century
Fig. 4 shows that during the last 25 years of the 20 th
century, soybean oil maintained its position as the
world’s most important oil, but that palm oil grew
rapidly to challenge this position. Trade in palm oil
already exceeds trade in soybean oil, and during the next
10 years, production of palm oil is predicted to exceed
production of soybean oil. In line with the growth of
palm oil production has been the growth in fractionation
capacity and the production of palm olein and palm
stearin. As shown in Fig. 5, palm olein may now be
considered the world’s fourth favourite oil after soybean,
palm and rapeseed oil. Even palm stearin production
exceeds the production of olive oil.
Figure 4. Growth in world demand for leading
vegetable oils, 1976-2003 (source: J. Fry, A Hallam,
LMC International).
Although I have concentrated on the production of
the commodity grades of palm olein and stearin, there
are today a wide range of oleins and stearins, as well as
mid-fractions obtained by two, three or even four
fractionation steps. Fractionation plus palm oil is as
flexible as hydrogenation plus soybean oil.
Malaysian Oil Science and Technology 2005 Vol. 14 No. 1
7
Fractional crystallisation: Fat Modification for the 21st Century
Palm oil is currently the only major oil in the world
that claims to be ‘sustainably’ produced.14 Fractionation
is environmentally benign and meets the ‘green’
aspirations of today’s consumers. It has no known or
conceivable health issues associated with it.
5.
6.
7.
8.
Figure 5. Palm fractions are major oils (palm olein and
stearin production are estimated by using the production
figures from Malaysia proportionately for the total world
figures) (source: MPOB & USDA).
We can thus confidently predict that the dominant
modification process of the 21st century will be fractional
crystallisation, just as it was at the beginning of the
modern oils- and fats-processing industry after MègeMouriès invented margarine.
We have seen that the oils and fats industry
developed in many European countries and that it had its
origins in the fractionation of tallow at a key point in
European history.
Forty years ago, when I started my career as a
research scientist, the message of the time was: “Make
love, not war.” Today, taking our lesson from the history
of margarine, I give you my message for the 21st century
and for future European and world harmony: “Make
margarine, not war.”
With that thought, I offer this lecture in recognition of
the second Euro Fed Lipid Technology Award and of the
European Federation for the Science and Technology of
Lipids and its aim of “improving lipid science and
technology in Europe” with which I am pleased to have
been associated from its beginning.
References
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10.
11.
12.
13.
14.
15.
to cocoa-butter-substitutes. British Patent No. 827,
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Timms RE (1997) Fractionation. In: Gunstone FD,
Padley FB (eds) Lipid Technologies and
Applications ISBN 0-8247-9838-4. Marcel Dekker,
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Singh G (1974) Analysis of crystallization systems
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Kellens M (2000) Oil modification processes. In:
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Kellens M, Hendrix M (2003) Membrane press
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Hamm W (1986) Fractionation – with or without
solvent? Fette Seifen Anstrichm 88: 533-537.
Timms RE (1983) Choice of solvent for fractional
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www.bantransfats.com. Ban Trans Fats: The
campaign to ban partially hydrogenated oils.
Liu L (2004) How is chemical interesterification
initiated: nucleophilic substitution or alpha-proton
abstraction? J Am Oil Chem Soc 81: 331-37.
www77.ssldomain.com/twoi/newsmaker_article.
.asp?idNewsMaker=6042&fSite=A0545&category
=25&page=1. ADM to expand NovaLipidTM-line
of zero/low trans-fat oils and margarines. Receives
FDA clarification regarding interesterified trans-fat
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www.sustainable-palmoil.org.
Roundtable
on
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Timms RE (1991): Crystallisation of fats. Chemistry
& Industry. 20 May (1991) 342-45.
[Received: September 20, 2004; accepted: November 8,
2004 (Eur J Lipid Sci Technol) ]
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Bailey AE (1950) In: Melting and Solidification of
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