Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
WO 94/12596 _ ~ ~ ~ ~ ,9 4 9 ~T~~3/03213
1
PROCESS FOR THE REFINING OF EDIBLE OILS
The present invention is concerned with a method for
refining~edible oils with the aim to avoid any refining
step which is not considered natural.
Background of the invention
The purification process of a crude edible oil usually
comprises the removal of phospholipids (degumming) by means
of water, acid and/or a sorbent. Oils for which degumming
was the first refining step still contain substances which
have a negative influence on taste, smell and keepability.
Those substances comprise inter alia free fatty acids and
destabilising peroxydes. For the removal of several unwan-
ted substances a process is used called deodorisation,
which can be performed by stripping the oil with a strip-
ping medium e.g. steam, at temperatures above 200°C.
Stripping at such relatively high temperatures has the
disadvantages that the oil may decompose and that unwanted
and sometimes even toxic compounds are formed.
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It has been realised that oils having a flavour which is
much alike the natural flavour might be much appreciated by
oil consumers. However, the natural flavour of an oil may
suffer from the presence of substances which contribute to
an off-flavour perception. The problem is to remove the
F 7125 (V) com ~ (amended 08.12.1994)
2
~1509~9
flavour deteriorating substances while preserving and
preferably increasing the flavour improving substances,
without being hindered_by the disadvantages of the
processes according to the state of the art.
The invention
The object of the invention is to provide a mild and cheap
refining method for the purification of edible oils and in
the same time to provide oils with a specific flavour
profile or even without any flavour (bland flavour).
Surprisingly a refining process has been found comprising
individual steps which are each considered as being
natural., which in spite of the mild conditions applied, can
afford a purified oil which is suited for direct consump-
tion and which can be qualified as "natural". Its
appearance and flavour are of a surprisingly high quality.
According to the invention a method is provided for
refining a triglyceride oil which comprises acidifying the
oil and removing substances which separate from the oil,
followed by gas stripping of the oil at a temperature of
60-160°C, characterised in that the stripping treatment is
preceded by a heat treatment, which consists of keeping the
oil at a temperature of 30-180°C.
With this method the flavour profile of the oil can be
modified, including the complete removal of flavour.
Detailed description
Without wanted to be limited by theory it is believed that
during the heating treatment decomposition occurs of
unwanted oil substances, particularly destabilising
peroxides, into harmless or even flavour imparting com-
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WO 94/12596 Z 1. 5 0 9 4 9 ~T~~3/03213
pounds such as ketones, aldehydes or alcohols.
The treatment of the invention is denoted as mild in
contrast to the usual, demanding refining treatments
comprising use of chemicals and/or high temperatures, such
as alkaline deacidification, bleaching and deodorising at
temperatures >200°C.
The temperature of the heat treatment preceding the
stripping of the oil is in the range of 30-180°C,
preferably 40-160°C and more preferably 60-160°C. A
suitable duration of the heat treatment may be in the range
of one hour to one week, and preferably is between 5-40 h.
It goes without saying that when the process temperature is
decreased, the process time should be increased to obtain
sufficient effect. Therefore time and temperature should be
properly attuned to each other so that a refined oil is
obtained with a satisfying flavour.
On behalf of the removal of substances which separate from
the oil an adsorbent, for example silica, may be admixed
before filtration.
When the heat treatment according to the invention is
carried out in the presence of an additive consisting of a
relatively small amount of an acid and/or an antioxidant,
preferably a tocopherol, the duration of the treatment may
be considerably shortened.
For example, without the additive a suitable time is 14-15
h at a temperature of about 120°C, but with the additive
the same effect is obtained within 7-8 h at the same
temperature. The amount of additive is 10-2000 ppm,
preferably 100-2000 ppm calculated on oil. A suitable
amount is 500 ppm. On behalf of its addition the acid may
be dissolved or dispersed in a suitable harmless liquid.
For acidifying the oil as mentioned above preferably
~F 712 (V) com ' 215 09 4 9 ~ amended 08. 1 2. 1 994 )
4
natural acids are used, which may advantageously be
selected from the group comprising citric acid, tartaric
acid, malic acid, lactic acid and acetic acid. Such natural
acids are preferred as they contribute to the 'green'
character of the refining method of the present invention.
In this respect also natural extracts or compositions
containing such acids are mentioned, like lemon-juice and
the like.
The gas stripping is carried out according to methods known
in the art with the proviso that preferably temperatures
are practised which are moderate. Moderate stripping
temperatures suitable for the purpose of this invention are
defined as being in the range of 30-200°C. The temperature
according to the invention is 60-160°C. A suitable period
of time for gas stripping is 1-100 h, preferably 1-10 h. By
properly attuning stripping time and temperature it is
possible to obtain an oil with a characteristic aid
attractive flavour profile or even an oil being completely
disposed of flavour (bland flavour).
Although the process according to the invention can be used
with any kind of edible oil, either from animal or
vegetable origin, it is particularly suitable for the
purification of natural oils which have been obtained from
a natural source and which after a mild refining treatment
are ready for direct consumption such as sunflower oil,
palm oil, olive oil, rape seed oil etc.
The present refining treatment may be combined with other
known mild treatments such as washing with water, centrifu-
ging or filtration, comprising membrane filtration.
Stripping is suitably effected by blowing steam or an inert
gas such as nitrogen through the oil.
During the heating period it is recommended to protect the
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WO 94/12596
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oil from the outer air by a nitrogen blanket to prevent oil
oxydation.
Bland flavour oils which have been obtained by the process
5 of the invention are characterised by a free fatty acids
content of at least 0.1 wt.% and a POV-value of less than 1
or even less than 0.5.
Thus, according to the invention, it is possible to improve
and to attune or to remove the flavour of an edible oil
applying mild processing conditions and without the
addition of non-natural flavour imparting substances to the
oil.
The oil may be featured as a "natural" oil for still
another reason because the process can dispose of the usual
bleaching treatment which removes carotenoids, so that the
natural colour of the oil is retained.
The oils according to the invention can be used as such for
consumption, or they may be processed further. The
invention therefore finally provides an edible composition
containing a refined oil according to the invention. The
refined oils according to the invention may be used for
example as ingredients in the preparation of edible
compositions, such as water and oil emulsions, e.g.
mayonnaise, dressings, fat spreads or processed cheese.
Since the fat component of such products may be quite
substantial, consequentially the flavour of the oil may
contribute considerably to the flavour of the end product.
The oil refined according to the invention still has most
of the original carotenoids present, whereas an oil refined
according to the art has no carotenoids left. The oil
refined according to the invention can therefore be used as
a natural colourant in products, e.g. spreads, having the
advantage that no taste is present which could interfere
WO 94/12596 PCT/EP93103213
150949
with the desired taste of. :~he~ product.
The following Examples illustrate some specific embodiments
of the present invention in greater detail. All percentages
are % by weight on oil unless indicated otherwise.
Example 1
A 5 kg sample of a crude sunflower oil, containing
phosphorous containing substances corresponding to 22 mg
P/kg oil and free fatty acids corresponding to 0.69 %, was
l5 degummed at a temperature of 90°C. 0.10 % of a citric acid
solution (50 % concentration) was added and after 15 min
0.2 % of water was added. After another 15 min 1.0 % of
Trisyl (Davidson Chemical Division of W.R. Grace & Co.) was
added and after 30 min water was removed from the mixture
by drying at subatmospheric pressure until the water
content was less than 0.1 %. After cooling the mixture to a
temperature of 40°C, the solids were filtered off.
The degummed oil heated to 120°C oil was stirred for 15 h
under N2-blanketing and subsequently stripped with steam at
120°C for 5 h. The flavour was completely removed.
A reference sample (A) comprising the same oil, was
subjected to the same degumming pretreatment, however,
after filtration it was deodorised immediately by stripping
with steam at 180°C for 5 h.
Another reference sample (B) comprising the same oil, was
treated like sample (A) but stripped at 120°C for 5 h.
The analytical data of the crude oil, the oil refined by
the method according to the invention and the reference
sample (A) are listed in Table I.
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The fresh taste of the oil prepared according to the
example and the oil of sample (A) was good: Even after 28
weeks of storage the taste was still acceptable for both
exemplified oils.
However, the oil sample (B) which had only been subjected
to stripping at 120°C, was immediately rejected by a test
panel.
Table I
Oil E268
FFA POV P Fe E232
(% (meq0_ (mg- (mg- (1%/- (
1%/-
wt) 2/kg) /kg) /kg) lcm)
lcm)
Crude 0.69 3.3 21.6 0.07 2.88 0.69
Inven- 0.55 0.3 <2 <0.01 2.77 1.11
tion
Referen- 0.03 0 <2 <0.01 2.57 1.33
ce (A)
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Example 2
To a 5 kg sample of crude palm oil at a temperature of 90°C
0.10% of citric acid solution (50%) was added and after a
residence time of 15 minutes 0.2% of water was added. After
another 15 minutes 1.0% of Trisyl (Davidson Chemical
Division of W.R. Grace & Co.) was added and 30 minutes
later water was removed from the mixture by drying at
subatmospheric pressure until the water content was less
than 0.1%. After cooling the mixture to a temperature of
40°C, the solids were filtered off. The oil was then heated
to 120°C, stirred for 15 hours under N2 blanketing and
subsequently deodorized for 5 hours at 120°C. The flavour
of the oil was completely removed.
For comparison, a reference sample containing the same oil
was subjected to traditional palm oil refining comprising
alkaline neutralisation and bleaching according to the art
and, after filtration, deodorizing at 240°C for 2 hours.
The fresh taste of both treated oils was good.
The analytical data of the crude oil, the oil refined
according to the invention and the reference are listed in
Table II
Table II
Caro
FFA POV E232 E268
tene
(% (meq0_ (1%/ (1%/-
(mg/
wt) 2/kg) lcm) lcm) kg)
Crude 4.40 4.3 1.82 0.45 497
Invention 3.97 0 1.43 0.35 377
Reference 0.08 0 2.10 1.19 0.4
~ .~ ~ .a . .,.
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Example 3
The same experiments as described in Example 1 were
repeated on pilot plant scale (75 kg) with good result: in
Table III the analytical data of the crude oil, the oil
refined according to the invention and reference sample (A)
are listed. After deodorization the fresh taste of the oil
treated according to the invention and the reference sample
A was excellent. After 6 months of storage at 15°C in
plastic bottles the taste of both treated oils was still
qualified as excellent.
Table III
FFA P Fe EZ32 $Z68 POV
Crude 0.69 13 0.14 2.39 0.24 4
Invention 0.65 <1 <0.01 2.54 0.61 0
Ref. A 0.03 <1 <0.01 n.m. n.m. 0
WO 94112596 ' PCT/EP93103213
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Example 4
A crude sunflower oil was split in two equal samples. To
one sample 0.1% citric acid (50% solution)~was added,
whereas to the second sample nothing was added.
Subsequently both oils were heated under nitrogen for 10
hours at 120°C. In Table IV the POV values at different
times are shown. This example clearly shows that the
presence of citric acid during the heating treatment
increases the decomposition rate of peroxides (indicated by
decreasing POV-value).
Table IV
pov (meq.oz/xg)
Time
(hours) ~lithout citric 500 ppm citric
acid acid
0 100 100
2 67 55
42 37
2g 23
g 20 11
10 18 2
