Method for refining of palm oils

This invention relates to a method for the refining of palm type oils such as palm oil and other similar natural oils including palm kernel oil, coconut oil, and the like. The method includes adding a small quantity of phosphoric acid to a crude palm type oil, treating said oil with a small quantity of activated clay, and then subjecting said oil to steam refining of 200.degree. to 270.degree. C. with the blowing of superheated steam into the oil under high vacuum after the activated clay has been removed.

In previous methods for the refining of palm oils, a steam refining method 
has been used in addition to the ordinary alkali refining method. The 
former method is a steam distillation method under high temperature and 
high vacuum. In the steam distillation method, two refining processes, 
neutralization and deodorization are carried out at the same time. This 
method has been found to be a profitable one, since refining losses of 
neutral oil, such as entrainment in the soapstock and saponification by 
the alkali, which occur in the alkali refining method, can be eliminated. 
In the steam distillation method however, a large quantity of absorbent 
must be employed in the preliminary treatment process, and for this 
reason, the alkali refining method has been commonly used due to the 
economic advantages. 
A decolorizing process is necessary in all these common methods mentioned 
above, and in the steam refining method, the crude oil is subjected to a 
decolorizing process prior to steam distillation. For palm oils, a 
decoloring process is extremely important because such oils contain a 
considerable amount of coloring matters derived from raw materials. 
Particularly in the case of crude palm oil, it is difficult to decolorize 
this oil because of the large quantity of carotinoids contained therein. 
As a method for decolorizing palm oils, adsorption of the coloring 
materials by adsorbents, such as activated clay and active carbon, is 
generally employed. However, it is necessary to employ a large quantity of 
adsorbent for decolorizing palm oils in proportion to the quantity of 
coloring matters contained in them, and the refining losses which are 
caused by entraining neutral oil in the absorbent cannot be avoided. This 
is a bar to the economical use of the steam refining method for palm oils, 
in spite of the many advantages which are associated with this method. 
In the steam refining method, heat sensitive coloring matters such as 
carotinoids may be decomposed and decolorized by heat in the course of 
refining, but this has no effect on other heat insensitive matters. For 
the above reasons it is impossible to decolorize palm oils completely the 
steam refining method. Therefore, not only a heat treatment but also 
treatment by adsorbent cannot be omitted for refining palm oils. Moreover, 
for complete decoloration of palm oils it is necessary to use a large 
quantity of adsorbent for decolorizing thoroughly in spite of the fact 
that there is a loss of neutral oil caused by entrainment. 
The inventors of the present invention have studied the refining and other 
treatments of palm type oils, and invented a new method for refining of 
these oils, in which crude palm type oils are pretreated with a small 
quantity of phosphoric acid and then a small quantity of activated clay is 
mixed with the oil. The oil is subjected to steam refining at 200.degree. 
to 270.degree. C. under a high vacuum after the activated clay has been 
removed. The inventors of the present invention have discovered that, by 
the above treatment, palm type oils can be decolorized thoroughly using 
small quantities of activated clay.

In carrying out the present invention, during the pre-treatment which is 
carried out before steam refining of the crude palm type oils, a small 
quantity of phosphoric acid is added to the melted crude palm oils and 
thoroughly mixed by agitation. Then a small quantity of activated clay is 
added while elevating the temperature of the oil, and the temperature of 
the oil is maintained at around 100.degree. C., for a certain period. 
Although there is no limitation for this period, it is usually selected 
within a range of about 5 to 30 minutes. Then, the activated clay is 
removed, and the resultant color of the oil is almost the same as that of 
the crude oil in spite of the above treatment having been carried out. 
Finally, decolorization, deodorization and deacidification are carried out 
at the same time by subjecting the above mentioned oil to a steam refining 
process with the blowing of super heated steam into the oil under high 
vacuum at above 200.degree. C. A thoroughly light coloured and odourless 
oil can then be obtained. 
Although the pre-treatment of the present invention looks like a 
decolorizing process that is made before a conventional steam refining 
method, there are substantial differences. In the conventional method, the 
color of the oil is removed by treatment with an adsorbent such as clay, 
contrary to the pre-treatment of the present invention in which the color 
of the oil is not removed by activated clay treatment and is the same as 
the color of the crude oil, in short, decolorization does not take place 
in the pre-treatment of the present invention. This can be understood more 
clearly from the visible absorption spectrum shown in the FIGURE. The 
pre-treated palm oil in the method of the present invention which has been 
treated with phosphoric acid and activated clay 3 and the untreated crude 
palm oil 2 have a peak of absorption, which originates from the presence 
of .beta.-carotine, at the same wave length as that of the absorption of 
.beta.-carotine 1. This indicates that it is not in the pre-treated palm 
oil that the decolorization takes place. On the other hand, palm oil which 
has been treated only with activated clay by conventional method 4 has no 
absorption peak corresponding to .beta.-carotine, and the height of the 
absorption curve is smaller, these facts showing that the oil has been 
decolorized. In the present invention, decoloration is carried out 
substantially in the steam distillation process following the 
pre-treatment. Thus the oil is thoroughly decolorized by the same 
distillation. This is one of the characteristics of the present invention, 
and offers a quite new idea for the refining process of oils, by which 
neutralization, bleaching, and deodorization of palm type can be 
accomplished in one operation involving steam distillation. 
If the use of phosphoric acid is omitted in the pre-treatment process of 
the present invention, the process becomes similar to a conventional 
decolorizing process and an extremely low decolorizing effect is attained 
by the subsequent steam refining process, which is carried out after the 
treatment with activated clay, though the oil is decolorized to some 
extent. In this case, to obtain a final product decolorized to the extent 
of palm oil which has been treated by phosphoric acid and activated clay 
it is necessary to use more than twice the amount of activated clay than 
that used in the present invention. In addition, the temperature must be 
kept higher than in the case of the present invention. 
The amount of phosphoric acid used in the pre-treatment process of the 
present invention has no specific limitation but depends upon the 
properties of the crude palm type oils to be used. The amount is however, 
generally within about 0.01 to 2.0 percent of the oil. The same effect is 
achieved even if more than 2.0 percent of phosphoric acid is used, but 
from an economical point of view, it is sufficient to use phosphoric acid 
in the amount of from 0.02 to 1.0 percent of the crude palm oil. 
The amount of activated clay used in the pre-treatment process is also 
variable depending upon the properties of the crude oils to be used. It is 
sufficient to use about one half the amount or less of that used in 
conventional decolorizing process. 
It has been known to use phosphoric acid in refining processes of oils. In 
these methods, however, phosphoric acid is always used with an alkali in 
alkali refining methods, reacting with phosphatides in the oil, and 
reducing the loss of neutral oil entrained in soapstock in the course of 
the neutralization process. 
It cannot be explained clearly as to the mechanisms of the effect of 
phosphoric acid used in the present invention comprising a method for 
refining of palm type oils which scarcely contain any phosphatide. It is 
clear that the mechanisms and action of phosphoric acid used in the 
present invention, in which alkalis are not used, are quite different from 
conventional alkali refining processes, using phosphoric acid with 
alkalis. And also, the method of the present invention is superior to 
conventional alkali refining methods in that it results in little loss of 
neutral oil and greater effect of decoloration. 
The refining method of the present invention is the most economical one 
because of the absence of complicated operation and special facilities, 
the low adsorption loss of neutral oil, and the fact that oil of good 
quality can be obtained easily. 
EXAMPLE 1 
The following four refining methods were applied to a Sumatra grown crude 
palm oil having acid value of 6.35. 
(1) Phosphoric acid-activated clay treatment and steam refining. (the 
method of the present invention) 
Phosphoric acid of 85% is added 0.05% to the crude oil with mixed for 30 
minutes. Then, 3% of activated clay was added to them, heated up to 
105.degree. C., with continual mixing for 15 minutes, and then activated 
clay was removed. The oil thus obtained was subjected to steam refining 
with the blowing of super heated steam into it under vacuum (5mm Hg 
absolute) at 270.degree. C., for 30 minutes, using conventional 
deodorization apparatus. 
(2) Activated clay treatment with steam refining (without the use of 
phosphoric acid). A control method for comparison with the present 
invention. 
Two crude oils were decolorized by a conventional decolorizing method with 
3% of activated clay, one at 105.degree. C., and the other at 150.degree. 
C., for 15 minutes. After clay was removed, the oils were subjected to 
steam refining under the same conditions as described in (1). 
(3) The crude oil was treated simultaneously with phosphoric acid and 
activated clay, and was steam refined. (Another control method) 
Phosphoric acid of 0.05% and activated clay of 3% were added simultaneously 
into the crude oil and mixed for 15 minutes at 105.degree. C. After clay 
was removed, the oil was subjected to steam refining under the same 
conditions as described in (1). 
(4) Alkali neutralization, decoloration and deodorization. (Another control 
method) 
The crude oil was neutralized with the alkali of 14.degree. Be. and the 
neutralized oil is subjected to decoloration with activated clay in an 
amount of 3% at 105.degree. C. for 15 minutes. After clay was removed, the 
oil was subjected to steam refining under the same conditions as described 
in (1). 
The resultant oils obtained from these four methods were measured for 
colors with a Lovibond 51/4 inch cell. The results are shown in Table 1. 
Table 1 
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Decolorizing effect according to the 
methods 
Color of 
refining the product yield (%) 
methods Yellow Red (to crude oil) 
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(1) 10 1.0 94.1 
(2) Decolorized at 
105.degree. C 
20 2.3 94.1 
150.degree. C 
15 1.5 94.1 
(3) 10 1.5 94.1 
(4) 10 1.2 92.0 
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It is clear that the method of the present invention (1) is superior to the 
methods (2) and (3), and to the alkali refining method (4) in its 
decolorizing effect and the small loss of neutral oil. 
EXAMPLE 2 
0.20% Of phosphoric acid was added to a crude coconut oil having acid value 
of 9.64, mixed for 10 minutes, the temperature increased to 105.degree. C. 
and there was added 1% of activated clay, and the operation continued as 
described in Example 1 (1). After the clay was removed, the oil was 
subjected to steam refining at 230.degree. C. for 30 minutes. The color of 
the resultant oil was Yellow 8, and Red 1.5 by Lovibond Tintmeter. 
Another control product was obtained by pre-treatment with only 1% clay 
(105.degree. C., 15 minutes) and carrying out the same steam refining 
method. This product had the color of Yellow 14, and Red 2.7. To obtain 
the product with the same color as the former product, it was necessary to 
use 3% of activated clay, and a 1.6% reduction in the yield resulted. 
As described above, it is clear that the method of the present invention 
provides a remarkable decolorizing effect, and it also has such advantages 
as a reduction in the quantity of activated clay to be used, and the 
improvement of the yield.