Note: Descriptions are shown in the official language in which they were submitted.
L7
Thi.s invention relates to the stabilization of edible
animal and vegetable oils and fats against oxidation by atmos-
pheric oxygen, and more specifically it relates to a method
of stabilizing oils and fats by heating them with cereals,
starch and/or protein at a temperature above 150C.
Anti-oxidants such as BHA, 2(3)-butyl-4-hydroxy-
anisole and BHT, 2,6-di-tert butyl-p-cresol, most of which
are chemical synthetic products are normally used to stabilize
oils and fats, especially edible oils and fats, and to prevent
them from deterioration. TheAe anti-oxidants are usad for the
purpose~ mentioned under the regulation provided for food
additives. Lately, there was a tendency to seek natural non-
toxic substances as anti-oxidants for stabilizing oil~ and fats.
If the stabilizing effect for oils and fats could be achieved
using a natural, ~on-toxic substance, and moreover at moderate
cost, such a method of stabilization might become more inter-
esting and the value of the product prepared by that method
might be increased to be truly comparable to edible oils and
fats~
The stabilization of edible oils and fats using
natural substances has been studied and it has been found that
it can be achieved by heating said oils and fats with cereals,
starch and/or protein, or mixtures thereof at a temperature
above about 150C.
More specifically, in accordance with this invention,
there is provided a method of stabilizing an animal or vegetable
fat or oil which comprises:
mixing said fat or oil with at least onq substance
selected from the group consisting of cereals, starch and pro-
teins, and mixtures thereof, and
heating the mixture to a temperature above 150C until
said fat or oil is stabilized.
The term "cereals" i~ used in a broad sense and in-
cludeq a ~ery wide ran~e of products generally called cereals
such as wheat flour, defatted soybean Elour, rice flour, corn
flour barley flour, rice bran, wheat bran, rice, barley, wheat,
corn or the like. These cereals can be used not only in the
form of powders or grains but also as roughly crushed particles.
They can be used alone or as a mixture of more than two kinds
of cereals.
All the cereals seem to have a stabilizing effect on
oils and fats althou~h there are some differences in the effect
produced by each of these cereals and the stabiliziny effect
can be increased depending on the amount of cereals which will
be added to oils and fats. The amount of cereals which is
added to oils and fats is preferably between 0.002 and 9 parts
of cereals for 1 part of oils and fats.
According to the invention, starch, protein or a
mixture of starch and protein, in any suitable ratio can also
be u~ed to form a mixture which is heated with oils and ~ats.
A starch which has been found effective in the method
o~ the invention is derived from plants which dif~ex ~reatly
in their botanical classifications, such a~ wheat, corn, potato,
sweet potato and it goes without saying that simi~ar stabilizing
e~fects can also be achieved when starches of ~hs other oriyi~
are used. The starches are desirably puri~ied in ord~r to
give a sufficient stabilizing effect.
The protein which have been ~ound ef~ective in carry-
ing out the method of the invention can be selected from a wide
range of proteins and include vegetable proteins derived from
soybean, wheat and the like, and animal proteins derived from
meat, fish, egg and the like.
The above-mentioned starch and protein can be used
independently or as mixtures thereof in any suitable ratios.
- 2 -
The stabilizing effect of the invention varies depending on
the mixing ratio of the components. This e~fect is always
greater in the oil treated by the method of the invention than
that in a n~n-treated oil ~egardle3s of the mixing ratio of
the components.
In the drawings which illustrate the invention,
Figure 1 shows the relationship between the mixing
ratio of starch and protein, and the stabilizing effect.
A test was carried out using a mixture of wheat starch
and isolated soybean protein t95% protein) as the stabilizing
agent, and soybean oil. The amount of soy~ean oil was 500 g and
the stabilizing agent amounted to 20% by weight of the oil.
The mixture of stabilizing agent and soybean oil was heated for
30 minutes at a temperature of 250C, after which the oil was
separated by filtration.
The mixing ratio of starch and protein varied between
0 to 100%. The stability of the resultant oil was measured by
the "Active Oxygen Method", fully identified below.
Figure 1 shows the result of the test.
2~ The stability of soybean oil which was not treated
by the method of the invention i9 shown at line (A), and the
stability of the oil treated by the method of the invention
was notably increased regardle~s o~ the mixing ratio of ~tarch
and protein.
As obviously shown in Figure 1, when the ~ixing ratio
was above 50%, the stability o the oil was excell~nt.
Similar effects can be observed when o~er kinds of
starch and protein or mixtures of more than two kinds of these
components are used. Moreover, it was ascertained that the
stabilizing effect of the invention was far superior to that
of an oil which was heated with protein and sugars.
The stabilizin~ effect of the invention varies accord-
3 --
7~
iny to the ratio of the amount of s-tarch and/or protein to the
amount of oils and fats. The higher the ratio is, the more the
stabilizing effect increases. The stabilizing effect increases
when the amount of oils and fats increases under unchanged rat7O.
The amount of starch and/or protein to be added to oils and
fats is preferably between 0.002 and 9 parts of s~arch and/or
protein against 1 part of oils and fats.
The stabilizing effect of the invention already
appears when heating the mixture at about 150C, a ~emperature
above 160C is preferred. Higher temperature can give better
results. ThQ maximum temperature depends on the heating condi~
tions, whether heating is performed in open air, under normal
atmospheric pressure, or in an inert gas under reduced pres-
sure. It is about 300~C when the heating is performed in open
air.
A longer heating time is usually more advantageous
for the stabilization of oils and fats. An excessive heating
time, however, is not recommended. The heating time is pref-
erably within 300 minutes depending on the temperature, and less
than 300 minutes are preferred in practice. Longer heating
time may, of course, be required when the heating is performed
under special conditions.
For example, 20% by weight of wheat flour, or starch,
and/or protein is added to the oil and the mixture is heated
at a temperature of 250C. The stabilizing effect appears in
the oil after heating for 5 minutes. When the mixture with the
same amount of flour, or starch, and/or protein is heated at a
temperature of 160C under reduced pressure, the stabilizing
effect appears after heating for 3 hours.
Heating can ~e carried out under normal pressure, in
open air, under reduced pressure and in a stream of an inert gas.
It is preferred to heat oils and fats with cereals, or starch,
7~
and/or protein under reduced pressure or in an inert gas in order
to prevent the oils and fats from degradation (oxidation) caus-
ed by the contact of the oils and fats with air (oxygen). Such
operation under reduced pressure or in an inert gas can signif-
icantly inhibit coloration and generation of odor in the heated
oil.
Agitation during heating is not always necessary, but
the agitation of the mixture is preferred in practice to per-
form homogeneous and efficient heat treatment.
Ater heat treatment, the oils are usually filtered
or clarified by conventional methods of filtration or centri-
fugation and the like.
In special cases, clarification after heat treatment
is not performed and the suspension of insolubles tcereals,
starch, proteins or mixtures thereof) in the oil can be used
for stabiliziny oils.
When a large amount of cereals, or starch and/or
protein is added to oils and fats, for example, 9 parts of
cereals, or starch and/or protein added to 1 part of oils
and fats, the oil can be separated from the heated mixture by
centrifugation or the heated mixture as such can be dispersed
in the oils and fats intended to be stabilized without separa-
ting the heated cereals, or starch and/or protein from the oil.
The stabilized oil is dissolved or transferred into an untreat-
ed oil and the insoluble residue is thereafter separated and
r~moved from the oil. me stabilizing effect of the oils can
be improved to a desired degree, if a suitable amount of the
heated mixture i9 added to an untreated oil.
Stabilized oils and ~ats prepared by the method
according to the invention and txeated under suitable condi-
tions/ are much more stable than those prepared by the addition
of conventional synthetic antioxidants. The activity of the
.~ ~ 2~L7
conventional synthetic antioxidants in the oil will disappear
due to decomposition during heating such as frying. On the
other hand the stabilized oils of the invention have a high
resistance to heat and these oil~ and the efective consti-
tuents assumed to be ~ormed in the oil do not evaporate nor
decompose during heating, thus the oxidation of oil during heat-
ing is avoided.
The stabilizing effect of the invention can of course
be observed in the products fried with the stabilized oil,
and the stability of the product is far superior than that of
the product fried with an oil to which antioxidants have been
added.
It is one~of the advantages of the invention that a
highly stabilized oil can be obtained by adding a desirable
amount of the heated oil according to the method of the invention
to an untreated oil, and the resultant oil is far more stable
than an oil mixed with synthetic antioxidants.
It is a matter of choice that the oil treated by the
method of the invention can be employed simultaneously with
conventional antioxidants.
The oils and fats to be treated by the method of the
invention include a very wide range of animal and veget~ble oil
and fats such as soybean oil, rape seed oil, lard, palm oil,
rice oil, corn oil, sunflower oil, cotton seed oil, safflower
oil, coconut oil, palm, kernel oil, olive oil, cacao butter,
beef tallow, mutton tallow, fish oil, whale oil and the like.
The oils and fats which can be treated by the method according
to the invention also include crude oils, deacidified oils, de-
colorized oils, hydrogenated oils and fractionated oils obtained
during any stage of the ref ining proce~s.
It has also been found that the stabilizing effect of
the invention can be obtained by adding the volatile substance
generated in the cours~ of heating cereals, or starch and/or
p~otein with oils and fats, to untreated fresh oilO
When oils and cerealq, or starch and/or protein are
heated in a flask, the volatile material released from the hot
mixture is recovered and collected in a cooler1 The .stability
of the fresh oil combined with the distillate and the oil re-
maining in the flask is significantly improved. The nature of
the cereals, or starch and/or protein, the amount of oil and
the condition o heating to collect the volatile material are
the same as described above and the condensation and collection
of the volatile material are carried out under normal pressure,
reduced pressure or in a stream of inert gas. The volatile
material can be introduced directly into fresh oil in the form
of a gas. The degree of stabilization of the oil can be con-
trolled by the amount of volatile material added to the fresh
oil.
Soybean oil, rape seed oil, lard and palm oil were
selected as the samples to be treated. Wheat flour, defatted
soybean flour, rice flour, potato starch, powder of wheat
gluten, and an equal mixture of starch and gluten were added
to these oils and fats.
The amounts of cereals, starch, gluten and their
mixture to be added to the oil was 20% by weight of each oil.
m e mixture of oils and additives was kept agitated and heated
at a temperature of 250C for 30 minutes after which the solid
matter was filtered off. The stability of the filtered oil is
illustrated in Tables 1 and 2 in hours measured by the method
defined in the O~M--test, A. O. C. S. Official Method CD 12-57
(Active Oxygen Method), (Oil & Soap, 10, 105-9, 1933) reapproved
in 1973.
m e samples of oils and fats used for the test were
obtained by refining crude oil by the conventional refining
processes such as deacidification, decolourization and deodoriza-
ization. No anti-oxidant was added to these oils,
TABLE 1
(Cereal 9 ) AOM (Hour 8 )
before after heat- after heating with
heating ing without wheat defatted rice
cereals flour soybean flour flour
soybean
oil 16 8 84 64 54
rape seed more than more than more than
oil 20 17 100 100 100
more than more than more than
lard 8 4 lQO 100 100
more than more than more than
palm oil64 50 100 100 100
TABLE 2
(Starch and Protein) AOM (Hours)
after heating with
before after heat- the mixture
heating ing without po~ato whea~ of the same
starch and starch gluten - amoùnt o~ po-
protein tato starch and
wheat gluten
soybean more than more than more than
oil 15.5 9.0 100 100 100
rape seed more than more than more than
oil 18.0 14.0 100 100 100
more than more than more than
lard 4.5 1.0 100 100 100
more than more than more than
palm oil72.0 65.0 200 2Q0 200
As shown in Tables 1 and 2, the AOM hours of the oils
which were heated with cereals, starch and/or protein were sub~
stantially increased and the stability of the treated oils was
also increased, although some differences were found in the AOM
hours among cereals used. The AOM hours were naturally shorter
when the oils were heated without cereals, starch and/or protein.
- 8 -
1~7~
Cereals have a ~tabilizing effect on oils and fats
only when these oil3 and fat~ are heated with cereals. If the
cereals are heated beforehand and then added to the oil, no
stabilizing effect can be observed in the oil. Cereals such as
wheat flour, defatted soybean flour and rice flour are heated
respectively at a temperature of 250C for 30 minute~. These
heated cereals themselves or the extracts of theqe cereals with
solvents such as chloroform, acetone or normal he~ane are added
to the aforementioned ~oybean oil and the AOM test is carried
out on the oil. The results of the test are shown in Table 3.
The amount of heated cereals or of the extracts, which
is added to the oil, corresponds to 20% cereals by weight of
the oil and is added to the oil as shown in Table 1.
TABLE 3
AOM hours
Control, Addition of Addition of extracts of
heated with heated heated cereals extracted with
cereals cereals
and oils chloroform n-hexane acetone
Wheat
flour 84 17 16 16 16
Defatted
soybean 64 16 16 16 16
flour
Rice
flour 54 16 16 16 16
It is obvious from Table 3 that the heated cereals or
the extracts thereof with solvents are not effective to improve
the stability of oils and fats. It ha~ been found that ~h~
stabilizing effect of the invention can only be obtained by
heating cereals with oils and ats. The stabilizing effect of
the invention was heretofore not known and is siynificant from
the aspects not only of technology but also of industrial
availability.
The invention will now be illustrated by means of the
following examples.
_ g _
~z~
EXAMPLE 1
Wheat, wheat flour, wheat bran, rice flour, rice bran,
corn flour, soybean flour and defatted soybean flour extracted
at low temperature were added ~espectively to 500 g of soybean
salad-oil, rape seed salad-oil, corn salad oil, refined palm
oil and lard (no anti-oxidant is contained) a~ shown in Table 4.
The amount of cereal~ added to the o~l~ and ~ts i5
also illustrated in Table 3. Tha heat treatment was carried
out in a 1 litre beaker at 250C for 30 minute~ in open air
under agitation with a small ayitator at 400 r.p.m. After heat
treatment, each sample was cooled down to about 60C and centri-
fuyed, and then a clarified oil was obtained. The stability
of the oil was examined by the AOM test. The results are shown
in Table 4.
-- 10 --
7~
TABLE 4
Sample Amount AOM stability (hours)
(%) Soybean rape corn re~ined lard
salad salad salad palm
oil oil oil oil
control* - 817 19 50 4
more than more than
wheat 20 2581 96 100 100
wheat mor-e than more than morP than more than
flour 20 84100 100 100 100
more than more than more than more than
wheat bran10 40100 100 100 100
more than more than more khan more than
rice flour20 54100 100 100 100
more than more than more than more than
rice bran 10 ' 40100 100 100 100
more than more than more than more than
corn flour20 53100 100 100 100
soybean more than more than more than more than
flour 10 42100 100 100 100
defatted
soybean more than more than more than more than
flour 20 64100 100 100 100
at low
temperature
.. .. .... . _.. . .
* Heat treatment is carried out without adding cereals
under the same condition.
As evidently shown in Table 4, although there are
some di~ferences among the kinds of fats and oil, and the kinds
and forms of cereals, the oils and fats trea~ed by the method
of the invention have a remarkably improved stability in com~
parison to those treated without cereals.
EXAMPT.E 2
~ he heat txeatment was applied to soybean salad oil
with different amounts of wheat flour under the same condition
as in Example 1. The results of the AOM test are shown in
Table 5.
T~LE 5
amount of AOM stability
wheat flour in soybean
~%) calad oil ~hour)
1 16.0
2 21.5
35.0
55~
84.0
100.0
As clearly shown by these result~, the stabilit~
of oils and ~ats can be obtained by the addition of a wide
range of amounts of cereals: stability is increased with an
increased amount of cereals.
EXAMP E 3
Soybean salad oil and wheat flour which were used
in Example 1 were intimately mixed in a ratio of 1 to 1, 1 to 2
and 1 to 5 based on the weight of oil and flour. These mixture~
were heated for ten minutes in the frying pan, ma~ntaining the
temperature of the mixture at 230C under agitation.
The mixture was left standing to cool and was
filtered with filter paper. One part of each heat treated oil
wa~ added to ten parts of untreated oil and mixed, and the hC~
stability was examined on the heat treated oil and the mixture
of the heat treated and untreated oil. The results of the test
are shown in Table 6.
- 12 -
:~27~
TABLE 6
Sample AOM stability (hours)
Heat treated oil (1) oil:flour=l:l more than 100
Heat treated oil ~2) oil:flour-1:2 more than 100
Heat treated oil (3~ oil:flour=1:5 more than 100
Mixed oil comprising 1 part of the oil (1)
with 10 parts of untreated oil 50
Mixed oil comprising 1 part of the oil (2)
with 10 parts of untreated oil 78
~xed oil comprising 1 part of the oil (3)
with 10 parts of untreated oil more than 100
As shown clearly in Table 6 even when an increased
amount of cereals was added to the oil, the stability of the
oil was significant~y increased, and it was also gxeatly im-
proved by adding heat treated oil to an untreated oil.
EX~MPLE 4
500 g of decolorized corn oil and 50 g of wheat
flour were put into a three neck flask with a stirrer, con-
denser (water-cooled system) and thermometer. The content was
agitated at a temperature of 270C for two hours. The volatile
substance produced in the heating process was introduced and
condensed in the condensor and wa3 collected therein. The yield
of the volatile substance was 3.12 g.
All of this volatile ~ubstance was added to soy-
bean salad oil (used in Example 1, AOM 16 hours~ and the AOM
stability was measured. The result shows that it has improved
to 39 hours.
EXAMPLE 5
Defatted soybean oil extracted at low temperature
was added to decolorized rape seed oil and the mixture was
heated under a reduced pressure of 1-2 mm Hg. The temperature
and the heatimg time are illustrated in Table 7.
- 13 -
TABLE 7
AOM stability (hours)
\ heating time
(C)~~_lminutes)
tempera- ~ 60 120 180 300
ture _
140 14 lS.5 17.5 18.5
200 15 23 28 40
260 38 4~ 62 95
. ~
AOM stability of decolorized rape seed oil before
heating: 14 hours.
EXAMPLE 6
Rice cr,acker was fried with the heat treated
soybean salad oil prepared as in Example 1. Soy~ean salad oil
beore heat treatment ~control 1), and the oil o~ control 1
to which 200 ppm of BHA (control 2) ha~ been added were also
used for frying rice cracker. ~he conditions used for rying
rice cracker are described in Table 8.
TABLE 8
Conditions used fox frying rice crac~er
weight of material for
frying rice cracker 2.5 g~piece
temperature of frying 260C
period for frying 4.5 seconds/piece
The fried rice cracker was preserved at a tempera
ture of 30C and the change of flavour and the peroxide value
of the products were observed. ~he results of the ob~ervation
are illustrated in ~able 9.
- 14
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-~ 15 --
EX~MPLE 7
Refined oils and fats free from conventio'nal anti-
ixodants were mixed with starch and/or protein and heated in a
flask. The amount of starch an~/or protein and the combination
of the oils with starch and/or protein are illustrated in
Table 10. The stability of the resultant oil was measured by
the AOM test.
The conditions during the heat treatment are as
follows:
Amount of treated oil : 500 g
Heat treatment carried out at 250C for 30
minutes in an open flask with stirring
at ~00 r.p.m.
Stability test : each sample was then cooled to
about 60C and centrifuged. The clear super-
natant was tested for oxidation resistance by
the method of the AOM test.
The results are shown in Table 10.
- 16 -
o
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-- 17 --
As evidently shown in Table 2, although there are
differences to some degree among the kinds of fats and oils,
and the mixing ratio of starch with protein and of starch and/
or protein to oil3 and fats, the resultant oils treated with
tne method of the invention have a remarkably improved stability
in comparison to those treated without starch and/or protein.
EXAM2LE 8
One part of each soybean salad oil treated as
described in Example 1 was added to ten parts of untreated
soybean salad oil, mixed and dissolved. The AOM hours of the
mixture was examined and the stability values are increased to
more than 40 hours.
EXAMPLE 9
500 g of decolorized corn oil and 100 g of a mix-
ture of the same amount of wheat s~arch and i~olated soybean
protein powder were placed in a three-neck ~la~X equipped with
a stirrer, water cooler and therm~meter. The mix~ure was agi-
tated at a temperature of 270C for two hours. The volatile
material generated during heatin~ was condensed and collected.
~0 All of the distillate was added to 100 g of soybean
salad oil. The AOM stability value of the fresh soybean salad
oil was 16 hours and it was improved to more than 75 hours
after the addition of the distillate.
- 18 -
