Activated carbon improved vegetable oil refining process

Phospholipid-containing vegetable oils, especially soya oil, are treated by an improved refining method comprising the steps of degumming the crude vegatable oil, passing the degummed oil through a bed of granular activated carbon, and finally subjecting the treated vegetable oil to steam assisted vacuum distillation deodorization. The process yields a final product acceptable in taste, odor and color and storage stable for normal shelf life periods.

BACKGROUND OF THE INVENTION 
The present invention is concerned with an improved process for refining 
phospholipid-containing vegetable oils which employs treatment with 
activated carbon during the preliminary stages. 
More particularly, the present invention is concerned with an improved 
refining process for edible phospholipid-containing vegetable oils, 
especially soya oil, which comprises the steps of degumming the crude 
vegetable oil, passing the degummed oil through a bed of activated carbon, 
and finally subjecting the treated vegetable oil to vacuum steam stripping 
and deodorization. 
The vegetable oils to which the present invention is applicable are those 
having a phospholipid level of 0.05% by weight and above. Phospholipids, 
or phosphatides, are lipoid substances that occur in cellular structures 
and contain esters of phosphoric acid. The aminophosphatides, or 
lecithins, which are mixed esters of glycerol and choline with fatty acids 
and phosphoric acid, are especially common. For example, the phospholipid 
content of crude soybean oil ranges from 1.1 to 3.2% by weight, and 
averages 1.8%, while the phospholipid content of peanut oil ranges from 
0.3 to 0.4% by weight. 
Thus, the improved refining process of the present invention is applicable 
to such edible vegetable oils as soya or soybean oil, corn oil, cottonseed 
oil, peanut oil, sesame seed oil and rapeseed oil, among others. On the 
other hand, the refining process of the present invention is not 
applicable to such oils as olive oil, palm oil, palm kernel oil, coconut 
oil, and babassu oil, among others. 
The process of the present invention has proven especially suitable to 
refining of soybean oil, and it is, therefore, particularly applicable 
thereto. Soybean oil is, moreover, the most important vegetable oil 
produced in the United States, comprising about 82% of the present total 
annual vegetable oil production.. Thus, production of soybean oil in the 
United States is an important and extensive industry, with current annual 
production of edible soya oil being approximately 9.5 billion pounds. 
While crude soybean oil is stable and nonreverting in nature, it has a 
dark color and a strong odor and taste which make it regarded as 
unpalatable in that state. Consequently, a number of techniques have been 
employed previously in the art to refine the crude soybean oil. The 
resulting product, while initially a light colored oil with a bland and 
agreeable flavor, in many cases unfortunately reverts by stages to more 
unpleasantly flavored forms after standing for a short period of time.

In accordance with the improved refining process of the present invention, 
it is possible to eliminate two conventional refining steps which are 
cumbersome and wasteful, and yet at the same to obtain an end product 
refined oil having a phosphorus concentration below 2.0 parts per million 
(p.p.m.), an iron and copper concentration below 1.0 and 0.05 p.p.m., 
respectively, and a peroxides concentration level of less than 2.0 meq. 
per 1.0 kg. of oil. As a result, the end product refined oil is acceptable 
with respect to prevailing industry standards for taste, odor, and color, 
and is, moreover, storage stable over the normal shelf life period of from 
one to three or more months. The end product refined oil produced in 
accordance with the present invention is thus comparable to oils produced 
by conventional refining processes in these respects. 
Conventional processes heretofore employed for refining vegetable oils, 
particularly soybean oil, have employed a number of distinct treatment 
steps. However, most often these have consisted of degumming, alkali 
neutralization, water washing, bleaching, and deodorizing, employed in 
that order. See, for example, U.S. Pat. No. 3,629,307. 
1. The step of degumming removes various mucilaqinous products, primarily 
protein or albuminoid substances and phospholipids, from the crude 
vegetable oil. These phospholipids, primarily lecithin, cephalin and 
inositol phosphatide, are primarily responsible for the rather strong and 
bitter flavor and aroma of the crude oil. They are responsible, moreover, 
for fouling of processing equipment employed in subsequent refining 
operations, if they are not successfully removed. The degumming process is 
primarily carried out at the extraction mill, where alkali refining may or 
may not be carried out. To a much lesser extent, degumming may be done by 
the refiner at another location. In general, the degumming process 
consists of adequately mixing with the crude vegetable oil, an organic 
acid such as phosphoric acid or acetic acid, followed by a little water. 
The resulting hydrated, mucilaginous globules are subsequently removed 
from the oil by centrifuging. The step of degumming may also be carried 
out without the use of acid, by simply adding water. Both types of 
degumming will be described in more detail hereinafter. While 
substantially all of the phospholipids should be removed, to a level at 
least below 2.0 p.p.m., as phosphorus, it has not been considered possible 
to accomplish such a result by conventional water degumming alone. Unless 
substantially all of the phospholipids are thus removed, a dark colored 
oil will be produced by decomposition of the remaining phospholipids at 
the elevated temperatures encountered during the final step of vacuum 
steam stripping and deodorizing. This dark colored material is very 
difficult to remove by ordinary refining or bleaching and imparts an 
off-flavor to the refined vegetable oil final product. In addition, the 
phospholipids tend to chelate any metal ions contained in the vegetable 
oil being refined, and will tend to carry these over into the refined oil 
final product, where they can cause undesired oxidation of the refined 
vegetable oil final product. Moreover, the phospholipids recovered, 
particularly lecithin, continue to possess good market value as a 
by-product for sale in non-related fields, for use, for example, as an 
emulsifying agent. 
Various methods of degumming have been employed in the past, including the 
use of various aliphatic and aromatic hydrocarbon and other compositions 
which are solvents for the vegetable oil, but nonsolvents for the 
phospholipids and other mucilaginous products. Acetone is an example of a 
suitable solvent. As the solvent is added to the vegetable oil, the 
decreased solubility of the phospholipids and other impurities causes them 
to precipitate out of the oil. Separation can then be achieved simply by 
filtration. The separated oil is then treated to remove the added solvent, 
for example, by distilling under a moderate vacuum. See, for example, U.S. 
Pat. No. 2,117,776. However, such methods have the serious drawback of 
requiring the use of often hazardous solvents. 
The preferred method of degumming for use in the improved refining process 
of the present invention is one whereby the phosphollipids and other 
mucilaginous products are simply hydrated, precipitated, and separated, 
desirably by a continuous process. As before stated, an acid such as 85% 
phosphoric acid is also used before the addition of the water. The amounts 
used may vary from 300 to 2,000 p.p.m. by volume of oil. The amount of 
water may be from 1.0 to 3.0% by volume. The temperature may be from 
100.degree. to 160.degree. F. The refining process of the present 
invention may employ either (1) the simple degumming method using water 
alone, (2) the acid degumming method using water and acid together, or (3) 
a combination or sequence of the degumming methods (1) and (2). The 
mixture is introduced into a continuous centrifuge in which it is heated 
and caused to circulate continuously, whereby the mucilaginous products 
are completely hydrated and the aqueous phase containing these hydrated 
mucilaginous products is finally discharged. See U.S. Pat. No. 3,206,487. 
2. The second step in the conventional oil refining process is alkali 
neutralization of the oil to remove free fatty acids and other impurities. 
Usually, this neutralization is accomplished simply by treating the oil 
with an aqueous solution of sodium hydroxide or other strongly alkaline 
reagent. The free fatty acids in the oil, generally present in amounts of 
from 0.5 to 3.0% by weight, are removed as precipitated soaps produced by 
the reaction of the fatty acids and alkaline reagent. The soap thus formed 
may be removed by centrifuging and the separated soapstock disposed of in 
some manner. However, handling of these soapstocks has presented 
considerable problems to the vegetable oil refiner. Usually, these 
soapstocks are acidulated and free fatty acids are recovered. 
Nevertheless, waste-products are produced which cannot be readily disposed 
of without creating problems of environmental pollution. As a final step, 
the oil is then washed with water to remove virtually all traces of soap, 
and the oil is then dryed to remove any dissolved or emulsified water 
which may be present. 
3. The third step in the conventional vegetable oil refining process is 
bleaching to remove pigments remaining in the oil after the previous 
refining steps. Such pigments comprise the carotenoids and chlorophyll, 
among others. Typically, the bleaching step is carried out under vacuum at 
a moderate temperature in the range of 210.degree. to 250.degree. F., and 
in the presence of an activated earth such as fuller's earth, perhaps 
admixed with a lesser amount of activated carbon. After the bleaching has 
been carried out, it is necessary to filter out the bleaching earth and 
activated carbon and pigment products adsorbed thereon. It has been found 
that during bleaching some free fatty acid products are generated and that 
the acid value of the oil is raised to about double that existing at the 
end of the alkali neutralization process. 
4. The fourth step in the conventional refining of vegetable oils is 
deodorizing. During this step live steam is passed through the vegetable 
oil while it is maintained under a high vacuum and at elevated 
temperatures. The temperature usually ranges from 460.degree. to 
530.degree. F. and the vacuum is maintained at 4 to 6 mm. Hg. The process 
may require from one and onehalf to seven hours. During the process most 
of the free fatty acids remaining in the vegetable oil are distilled off. 
Most of the remaining pigment products are destroyed during this step as 
well. The acid value and color of the oil are thus improved, and the odor 
and flavor are made acceptable. However, if any appreciable quantity of 
phospholipids remains, the elevated temperatures experienced during this 
step would result in a darkening of the oil. For most vegetable oils it 
has been considered necessary to utilize both alkali neutralization as 
well as deodorization in order to remove most of the free fatty acid 
content of the vegetable oil, as well as to get a bland-tasting and 
odorfree edible oil. 
The conventional deodorizing step has been improved by variation of the 
parameters involved and other modifications. See, for example, U.S. Pat. 
No. 3,506,696. 
The vegetable oil refining method of the present invention is an 
improvement over the conventional refining process described in the 
paragraphs above since it eliminates both the conventional alkali 
neutralization and water washing step and the conventional bleaching step. 
This conventional process step elimination is possible because the carbon 
treatment of the present invention reduces the phospholipid concentration 
of the degummed oil sufficiently to result in a final product which is 
both stable and acceptable from the standpoint of taste, color and odor. 
In addition, the final product is satisfactory as a consequence of the 
removal of other impurities in the oil, especially peroxide compounds, by 
the activated carbon treatment step. Thus, the step elimination 
improvement may be illustrated by reference to the flow sheet set forth in 
FIG. 4. 
In addition to the conventional refining process described above, other, 
often more direct, methods have been put forward in the art as improved 
methods of vegetable oil refining. For example, U.S. Pat. No. 2,746,867 
describes a two step refining process comprising a first step of carefully 
controlled partial degumming by means of hydration, followed by steam 
deodorizing at a moderate temperature. However, this process is intended 
to leave at least some of the free fatty acids in the product. Similarly, 
U.S. Pat. No. 2,117,776 describes a two step process comprising removal of 
the phospholipids from the crude oil, preferably by precipitation with a 
non-solvent, followed by high vacuum-short path distillation of the oil. 
As already noted above, it is known to employ activated carbon 
conventionally as a bleaching agent, that is, as a decolorizing agent to 
remove various pigment products. When employed as a bleaching agent, the 
activated carbon is typically utilized in powder form in a batch or 
continuous batch-type operation. Conventionally, such use takes place 
before the vaccum distillation deodorization step. Nevertheless, the art 
has preferred to employ activated clays as bleaching agents rather than 
activated carbons due to their greater cost effectiveness, a result of the 
much greater holding capacity of the activated carbons for the vegetable 
oil, is compared to the activated clays. 
However, it is known to employ activated carbons in various ways in 
vegetable oil refining processes. For example, John P. Harris and Bernard 
N. Glick, in "Crude Cotton Oil Filtration," Oil & Fat Industries, pp. 
263-265, Sept., 1928, suggest activated carbon filtration of crude cotton 
oil to remove certain colloids and other impurities prior to the 
conventional refining process. U.S. Pat. No. 3,455,975, concerned with a 
refining process wherein deacidification and deodorization of glyceride 
oils is accomplished by distillation in a steam current under vacuum, also 
discloses decolorization pretreatment with artificially activated 
montmorillonite earth and activated carbon. However, the pretreatment is 
applied to olive oil, and where maize germ oil is treated, it is described 
as being prerefined until reaching a yellow color. U.S. Pat. No. 3,354,188 
describes a refining method comprising the steps of dispersing an acid 
refining agent in the vegetable oil to form an emulsion, adsorbing the 
dispersed refining agent phase on a particulate solid such as fuller's 
earth, activated clay, or charcoal, and separating the continuous oil 
phase which is then subjected to steam distillation. U.S. Pat. No. 
2,980,717 describes a refining method comprising the steps of mixing the 
crude oil stock with a bleaching adsorbent, for example a mixture of 
decolorizing earth and activated carbon, and subjecting the mixture to a 
sudden rise in temperature by bringing the mixture, while falling in a 
subdivided state, into contact with a separate hot mixture of crude oil 
stock and bleaching adsorbent, the contact taking place at sub-atmospheric 
pressure and elevated temperatures and in the presence of a countercurrent 
stream of superheated steam. 
In contrast to methods heretofore employed in the art, the method of the 
present invention uniquely provides for a straightforward and efficient 
means of preparing refined vegetable oils having a final phospholipid 
level of less than 5.0 p.p.m., measured as phosphorus especially less than 
2.0 p.p.m., measured as phosphorus, a peroxides concentration level of 
less than 2.0 meq. per 1.0 kg. of oil, and having reduced contents of 
other impurities which would result in an unstable product and one 
unacceptable in color, taste and odor. 
SUMMARY OF THE INVENTION 
In accordance with the method of the present invention, crude edible 
vegetable oils having a phospholipid content of 0.05% by weight and above 
are refined by the successive steps of degumming, passing of the degummed 
oil through a bed of activated carbon, and subjecting of the thus treated 
vegetable oil to vacuum steam distillation and deodorization. An edible 
vegetable oil refined by this process will have a final peroxides 
concentration level of less than 2.0 meq. per 1.0 kg. of oil, and a final 
phospholipid content of less than 5.0 p.p.m., measured as phosphorus and 
particularly less than 2.0 p.p.m., measured as phosphorus. A phosphorus 
level below 2.0 p.p.m. has been found especially desirable for refined 
vegetable oils which are to be hydrogenated, which is the case for a 
substantial majority of all refined oils. However, for non-hydrogenated 
oils the phosphorus level should not be more than 5.0 p.p.m. 
For purposes of the present invention, the phosphorus level of the refined 
vegetable oil final product is measured in accordance with the procedure 
specified in A.O.C.S. Official Method Ca 12-15 "Phosphorus," Sampling and 
Analysis of Commercial Fats and Oils, modified as suggested in C. D. Evans 
et al., "Iron and Phosphorus Contents of Soybean Oil . . . ," J. of the 
American Oil Chemists' Society, Vol. 51, No. 10, pp. 444-448 (1974). This 
method determines phosphorus or the equivalent phosphatides content by 
asking the sample in the presence of zinc oxide followed by colorimetric 
measurement of phosphorus as molybdenum blue. The modification of C. D. 
Evans et al. provides for hydrolyzing of the magnesium pyrophosphates by 
gentle boiling in sulfuric acid solution before proceeding with the 
phosphorus color determination. 
The peroxide value of the refined vegetable oil final product, for purposes 
of the present invention, is measured in accordance with the procedures 
specified in A.O.C.S. Official Method Cd 8-53 "Peroxide Value," Sampling 
and Analysis of Commercial Fats and Oils. This method determines all 
substances, in terms of milli-equivalents of peroxide per 1000 grams of 
sample, which oxidize potassium oxide under the conditions of the test. 
The degumming step of the method of the present invention may be carried 
out using any conventional procedure for removing various mucilaginous 
products, primarily protein or albuminoid substances and phospholipids, 
from the crude vegetable oil. Typically, the degumming step will reduce 
the phopholipid content of the vegetable oil to about 200 to 250 p.p.m., 
measured as phosphorus. However, it has been possible to obtain 
phospholipid levels in this degumming step for the present invention in 
the range of from about 50 to about 100 p.p.m. of phospholipids, and even 
lower, measured as phosphorous. 
The preferred method of degumming the crude vegetable oil in accordance 
with the method of the present invention is by simple hydration of the 
mucilaginous product impurities contained in the vegetable oil. The 
hydrated mucilaginous products form a precipitate which can be separated. 
The amount of water employed ranges from about 1 to about 2% by weight, 
based on weight of crude vegetable oil to be treated. In has been found 
that certain agents improve the rate and amount of mucilaginous product 
precipitation. For example, certain acids, such as acetic acid and 
phosphoric acid, have been found to improve the efficiency of the 
degumming step. These precipitation enhancing agents are most easily 
employed by simply adding them before the water employed for hydration of 
the crude vegetable oil mucilaginous products (gums). 
The degumming step may be carried out at normal temperatures and pressures. 
However, it is preferred to carry out the step at a temperature of from 
about 100.degree. to about 160.degree. F. 
While separation of the precipitated, hydrated mucilaginous products may be 
accomplished simply by filtration, the rate and efficiency of separation 
is greatly improved by the use of equipment which permits continuous 
centrifuging of the hydrated crude vegetable oil gums. Indeed, it is 
preferred to employ equipment which will provide for high speed mixing and 
agitation of the acid, water and vegetable oil mixture, with subsequent 
centrifugal separation. Thus, pumps or other devices may be utilized to 
form an initimate physical mixture or emulsion of the water and oil, 
whereby the area of surface contact between the water and mucilaginous 
products in the oil is substantially increased. Then, centrifugal 
separators remove the water and hydrated mucilaginous products to yield 
demucilaginated oil. In association with such centrifugal separators there 
may also be employed static separators which permit gravimetric 
classification of the emulsion of vegetable oil and water. 
Desirably, the various types of equipment described above will be utilized 
in such a way that they operate to provide continuous processing of the 
vegetable oil. Also, multiple cycling of the oil and water can improve the 
performance results of the process. 
Alternatively, the degumming step may be carried out using steam to replace 
the water for hydration of the mucilaginous products in the vegetable oil. 
The emulsion formed is then separated by centrifuging in the same manner 
as for the emulsion formed with water in the conventional process. 
Subsequent to the degumming step, there may be employed, desirably, a step 
of water washing of the degummed vegetable oil, for the purpose of 
removing additional amounts of precipitated mucilaginous products and any 
contaminants that may have been introduced into the vegetable oil during 
the degumming step. 
The step of activated carbon treatment comprises contacting the previously 
degummed or demucilaginated vegetable oil with granular activated carbon 
by passing the oil through a bed of granular activated carbon. The use of 
granular activated carbon in a bed to treat vegetable oil is a basic 
departure from the conventional use of activated carbons as bleaching 
agents, where they are normally employed in powder form and in batch or 
continuous batch-type operations, which is a less complicated manner of 
utilizing activated carbon than the bed system. However, as has already 
been pointed out, the activated carbon treatment step of the present 
invention has an entirely different objective, and achieves an entirely 
different result, from the bleaching treatment step in which activated 
carbons have been utilized in the past. 
By using a bed of granular activated carbon, it is possible to achieve an 
acceptably small effective dosage of carbon for a given quantity of oil to 
be treated, by reason of the possibility of regeneration of the granular 
activated carbon, and also by reason of the significantly lower effective 
equilibrium concentration adsorption levels which exist in a bed of 
granular activated carbon as compared to powdered activated carbon used in 
a batch-type operation. Thus, phospholipids could not be removed from 
degummed vegetable oils to the extent achieved by the activated carbon 
treatment step of the present invention by use of powdered activated 
carbon in the amounts normally employed in conventional batch-type 
bleaching operations. 
The granular activated carbon which may be employed in the activated carbon 
treatment step of the present invention should fall within the mesh size 
range of 12.times.40, U.S. Sieve Series. However, the size of the 
activated carbon granules is not especially critical, so long as it does 
not vary considerably from the indicated range. The activated carbon 
material itself should be a conventional liquid phase activated carbon 
prepared from any suitable source, including petroleum, coal, wood and 
other vegetable raw materials. Coal based activated carbons have been 
found especially suitable. A preferred granular activated carbon material 
for use in the present invention is CAL 12.times.40, available from the 
Pittsburgh Activated Carbon Division of Calgon Corporation. 
The size of the column vessels used to establish the bed of granular 
activated carbon may be varied in size, depending, essentially, on the 
volume of vegetable oil to be processed. 
The total contact time of granular activated carbon with the vegetable oil 
being treated may be from about 4 to about 24 hours, and preferably will 
be from about 6 to about 12 hours. 
A preferred manner of employing the bed of granular activated carbon in the 
process of the present invention is the pulse-bed system. This system 
duplicates the action of a large number of filters in series in a clean, 
continuous, closed system. In this system, a small amount of spent 
activated carbon is removed (slugged) from the bottom of each column once 
during every eight-hour period. The removed activated carbon is then 
regenerated for further use. At the same time that the spent activated 
carbon is removed from the bottom of each column, a corresponding amount 
of regenerated or virgin activated carbon is added to the top of each 
column bed from charge tanks located above each column. 
The columns themselves are typically cone-bottomed columns ten feet in 
diameter and thirty feet in height, capable of holding approximately 2700 
cubic feet of granular activated carbon. A number of such columns would be 
required to process the normal output of a sizeable vegetable oil 
refinery, for example, approximately 60,000 pounds of vegetable oil per 
hour. Clearly, however, the dimensions of the columns are not especially 
critical and may be considerably varied to conform to space requirements 
or other considerations. 
The spent carbon which has been removed from each column is carried by 
gravity to an oil recovery tank where oil is removed from the spent 
activated carbon by washing with a C.sub.5 to C.sub.8 aliphatic 
hydrocarbon solvent, particularly hexane. It has been found that hexane is 
a uniquely suitable solvent for removal of the vegetable oil trapped in 
the spent activated carbon since the impurities adsorbed on the activated 
carbon are not eluted with the solvent. Hexane is also non-toxic, 
relatively inexpensive, and readily available. Several bed volumes washing 
with hexane will be sufficient to remove substantially all of the oil 
trapped in the spent activated carbon. In turn, removal of the hexane 
solvent from the activated carbon is readily accomplished using steam. 
After oil recovery from the spent activated carbon, regeneration is carried 
out. The spent activated carbon is conveyed away from the site of steam 
stripping to remove hexane by means of a dewatering screw to remove excess 
water. The spent activated carbon is carried into a multiple hearth 
furnace where it is regenerated as it passes through a controlled 
atmosphere at high temperatures. The regenerated carbon is then ready for 
reuse in the overall process. 
Before the regenerated carbon or virgin activated carbon is placed in the 
column vessels for use, it usually is necessary to deaerate the activated 
carbon during a preliminary wetting step. It has been found that air 
bubbles trapped between the granules of activated carbon interfere in a 
material way with the efficiency of the activated carbon treatment step. 
The air bubbles adhere rather tenaciously to the activated carbon 
granules, but it has been found that they can be satisfactorily removed by 
agitation of the activated carbon granules together with heated degummed 
vegetable oil in a preliminary step. 
After the step of activated carbon treatment of the degummed vegetable oil, 
the third step of deodorizing is carried out. The deodorization is 
accomplished by steam distillation under vacuum in accordance with well 
known procedures already established in the art. The distillation is 
generally carried out at temperatures in the range of from about 
400.degree. to about 550.degree. F., preferably at temperatures of from 
about 460.degree. to about 530.degree. F. The distillation is carried out 
at a reduced pressure of from about 1 to about 10 mm. Hg, preferably at 
from 4 to 6 mm. Hg. 
Vacuum steam distillation deodorization takes advantage of the significant 
differences in volatility between the basic triglyceride components of the 
vegetable oil and the various substances which give the oil its natural 
odor and flavor. Thus, the relatively volatile odor and flavor causing 
substances in the vegetable oil are stripped from the relatively 
nonvolatile oil during the process of steam distillation. The function of 
the steam in the distillation process is the conventional one of serving 
as a carrier for the odor and flavor causing substances being distilled 
from the oil. There is ordinarily no intended chemical reaction of the 
steam with the oil or its components. The steam distillation is usually 
carried out at high temperatures in order to increase the volatility of 
the odor causing substances in the oil. Carrying out the steam 
distillation process at significantly reduced pressure protects the oil 
from undue hydrolysis by the steam and from atmospheric oxidation. It also 
greatly reduces the quantity of steam required for the process. 
Deodorization by steam distillation also significantly reduces the color of 
the processed vegetable oil, since the carotenoid pigments responsible for 
the major portion of the oil color are unstable to heat. 
Along with odor, flavor and color causing substances, the steam 
distillation process also more or less completely removes the free fatty 
acids in the vegetable oil. The free fatty acid content of the oil can be 
reduced by the deodorization process to a level in the range of from about 
0.015 to 0.03% by weight, which is approximately the same level 
achieveable by conventional alkali refining. However, since the free fatty 
acid distillation rate is concentration dependent, and since the 
distillation process results in splitting of some oil to form additional 
quantities of free fatty acids, an equilibrium point is reached, resulting 
in a minimum content of free fatty acid in the oil. Odor and flavor 
causing substance removal from the vegetable oil generally parallels the 
free fatty acid removal during the process of distillation deodorization. 
Temperature significantly affects the efficiency of the distillation 
deodorization process since the logarithm of the vapor pressure of a 
volatile odor or flavor causing substance to be removed is proportional to 
its absolute temperature. Thus, an even progression in temperature will 
double and then quadruple the volatility of the odor or flavor causing 
substance. To achieve a given level of odor and flavor causing substances 
in a vegetable oil after processing by distillation deodorization, it will 
require approximately three times as long to deodorize at 350.degree. F. 
as at 400.degree. F., and nine times as long as at 450.degree. F. Since 
the amount of steam required in the distillation process is inversely 
proportional to the vapor pressure of the volatile components being 
removed from the vegetable oil, higher operating temperatures also result 
in a reduced requirement for steam in the distillation process. 
As already noted, the use of reduced pressure, that is, employing a vacuum 
distillation process, has a number of important advantages. In addition to 
these, the affect on the amount of steam required is significant. Since 
the amount of steam required in the deodorization process is proportional 
to the absolute pressure, the greatest economy of steam use results from 
the highest vacuum. The use of higher vacuums also significantly reduces 
the amount of time required for the deodorization process by increasing 
the maximum permissible rate of steaming. 
Design of equipment utilized in the deodorization process can also be an 
important factor in improving the efficiency of the process. For example, 
the use of baffled apparatus permits stripping of the vegetable oil in 
shallow layers. Splashing of the oil against the baffles results in 
breaking up of the oil, thus creating a large oil and steam interface. By 
use of such equipment, the vaporization efficiency increases with the 
steaming rate. 
DETAILED DESCRIPTION OF THE INVENTION 
In order to correlate the extent of phosphorus and peroxide composition 
removal to effective activated carbon dosage, a sample of degummed soya 
oil was divided into aliquots and treated with varying amounts of 
activated carbon in accordance with the method of the present invention. 
The results of this evaluation are illustrated in the following table of 
values; 
______________________________________ 
Activated Carbon Peroxide 
Concentration 
Phosphorus Level 
(% by wt.) Level (p.p.m.) 
(mg. per kg. of oil) 
______________________________________ 
Blank 71.5 5.0 
0.1 57.2 3.2 
0.2 58.0 2.2 
0.4 56.8 1.8 
0.7 52.8 .2 
1.0 44.2 .2 
2.0 27.4 .2 
4.0 6.9 .2 
7.0 1.9 .2 
10.0 1.2 .2 
______________________________________ 
As may be seen, the amount, that is, the concentration of activated carbon 
required to result in a refined vegetable oil final product having a 
phosphorus level below 5.0 p.p.m. and a peroxide level of less than 2.0 
meq. per 1.0 kg. oil, will depend upon the phosphorus level of the 
vegetable oil after the initial degumming step. The amount of activated 
carbon required will vary somewhat depending upon the type of vegetable 
oil being refined, but will correspond generally to the values expressed 
in the table above. 
The activated carbon treatment method of the present invention provides a 
direct and inexpensive means for reducing the phosphorus level of a 
refined vegetable oil to desirably low levels. To illustrate this improved 
result, a sample of soya oil was removed after a degumming step where 
phosphorus levels varied between 75 and 125 p.p.m., and was subjected to 
storage for several days. During this period additional degumming took 
place by simple gravitational precipitation. The phosphorus level was 
measured and the sample was then subjected to the activated carbon 
treatment of the present invention, whereafter the phosphorus level was 
again measured. For comparison, a portion of the same sample of soya oil 
removed after a degumming step, but without being subjected to storage, 
was subjected to a caustic refining step and a bleaching step as described 
herein, whereafter the phosphorus level was measured. As already noted 
above, caustic refining has been commonly regarded heretofore as the 
method of choice for removing phospholipids, as well as free fatty acids, 
from a vegetable oil during the refining process. The following table of 
values shows that the activated carbon treatment method of the present 
invention provides an improved process, in terms of operation and result, 
for removing phospholipids from vegetable oils during the refining 
process. 
______________________________________ 
Phosphorus Level (p.p.m.) 
Sample Procedure A* Procedure B** 
______________________________________ 
Degummed 6.80 2.1 
Caustic Refined 
6.00 1.7 
Activated Carbon 
Refined 1.20 0.2 
______________________________________ 
*Procedure A was that specified in A.O.C.S. Official Method Ca 12-55 
"Phosphorus", Sampling and Analysis of Commercial Fats and Oils, modified 
as suggested in C. D. Evans et al., "Iron and Phosphorus Contents of 
Soybean Oil . . .", J. of the American Oil Chemists'Society, Vol. 51, No. 
10, pp. 444-448 (1974). 
**Procedure B was that specified by Fiske and Subbarow, J. Biol. Chem., 
Vol. 66, p. 375 (1925), modified as suggested in C. D. Evans et al. above 
 
Crude, that is, unrefined vegetable oils naturally contain antioxidant 
compounds, notably the tocopherols, which enhance their stability. It has 
generally been considered that a refined vegetable oil final product 
should contain at least 600 .mu.g. of tocopherols per gram of oil for good 
stability. Thus, an acceptable refining process will not remove or destroy 
tocopherols in the vegetable oil being refined to a level below 600 
.mu.g./g. of oil. The improved refining process of the present invention 
meets this important criterion of acceptability. Thus, when a sample of 
soya oil refined in accordance with the process of the present invention, 
except for the step of vacuum steam distillation deodorization, was 
analyzed for its level of tocopherols in accordance with the procedure 
described by P. A. Sturm in Analytical Chemistry, Vol. 38, p. 1244 (1966), 
it was found that the level was 874 .mu.g. of tocopherols per g. of oil. 
This level of tocopherols is well above that considered a necessary 
minimum. 
For the purpose of illustrating the refining process of the present 
invention more fully, reference will now be made in detail to the 
accompanying drawings which represent in schematic fashion the various 
stages of the activated carbon treatment step of the present invention. 
An appreciation of the various stages of these treatment steps can be 
gained from the Figures of the drawings when taken together with the 
detailed description which follows. 
EXAMPLE 1 
Crude soybean oil as available from an extraction plant is usually 
processed further at that location, for recovery of lecithin. 
In this process, water is the sole degumming agent. Reference should be 
made to FIG. 1 of the drawings, which illustrates a continuous system. The 
crude soybean oil from an extraction plant is at a temperature of 
125.degree. F. in tank 1. The phosphorus content is 650 p.p.m. which 
corresponds to a phosphatide content of 1.95%. It then goes into line 2 to 
pump 3 at a rate of 30,000 pounds per hour. Water is metered from line 3 
by the water flow controller 4 at a rate of 1.0% or 300 pounds per hour. 
The initial mixing of water and oil is done in pump 5. The mixture is 
pumped at a pressure of 120 PSIG into line 6. Flow control valve 7 is 
regulated for a flow rate of 30,300 pounds of crude soybean oil and water. 
The mixture is pumped upward into mixer 8. It is equipped with a 2 H.P. 
motor drive and two 14 inch diameter three-bladed propellers operating at 
180 R.P.M. There are two horizontal baffles for thorough mixing. 
The agitated mixture of oil and water than flows into line 9 to centrifuge 
10. A De Laval SRG 214 centrifuge operating at a speed of 4,400 R.P.M. is 
employed. The partially degummed soybean oil flows into line 11 and the 
back pressure on this oil phase is controlled by back pressure controller 
12 and then flows into the storage tank 16. The separated wet gums flow 
into line 13 and its back pressure is controlled by back pressure 
controller 14. The wet gums flow into tank 15. The back pressure 
controllers 12 and 14 are of known type and automatically control the 
operation of the separator. 
The partially degummed oil has a phosphorus content of 200 p.p.m.-which 
corresponds to 0.6% of phosphatides. The quantity of wet gums is 900 
pounds per hour or 3.0% of the oil feed. The analysis of the wet gums is 
33% water, 45% phosphatides and 22% soybean oil. The wet gums are then 
further processed for making commercial lecithin. The yield of partially 
degummed oil is 29,400 pounds per hour or 98% yield on a dry basis. 
A more complete degumming of crude soybean oil may be achieved by acid 
degumming as illustrated in the following example, and FIG. 2 of the 
drawings. 
EXAMPLE 2 
The feed material is the partially degummed crude soybean oil from Example 
1 which contains 200 p.p.m. of phosphorus which corresponds to 0.6% 
phosphatides, in feed tank 16. It flows into line 17 to pump 18 and then 
to heater 19 where it is heated to a temperature of 140.degree. F. The 
pressure at pump 17 is 130 PSIG. Flow control valve 20 is set to regulate 
the flow rate at 29,400 pounds per hour. Pipe line 21 has a supply of 85% 
phosphoric acid which is metered with metering pump 22 at a rate of 0.12% 
or 34.8 pounds per hour. This equals 0.10% on a 100% acid basis. The 
oil-acid mixture flows from line 23 into mixer 24. This mixer is similar 
to mixer 8 in FIG. 1 except that it is of stainless steel construction and 
there is only a 1 minute retention time. The flow is then into line 25 
where water supply 26 is regulated by means of flow control valve 27 to 
supply 3% of water or 882 pounds per hour. The flow is then into mixer 28 
which is similar to mixer 8 in Example 1, and then into the centrifuge 29 
which is similar to 10 in FIG. 1. The wetted gums flow out of line 32 into 
tank 34 through the automatic back pressure valve 33. The amount of wet 
gums is 1,285 pounds per hour containing 70% water, 10% phosphatides and 
20% crude soybean oil. It is processed further or otherwise disposed. The 
degummed oil flows from line 30 to pump 35 through the automatic back 
pressure valve 31. Pump 35 has an automatic equalizer 36. The pump 
pressure is 120 PSIG. The flow then is to heater 38 in which the oil is 
heated to 180.degree. F. Pipe line 39 has hot softened water at 
190.degree. F. and the flow is controlled by flow control valve 40 at a 
rate of 20% or 5,800 pounds per hour. The oil water mixture is then 
separated in centrifuge 42 which is identical to centrifuge 29. The wash 
waters flow from line 45 into waste water tank 47 through the automatic 
back pressure valve 48. The washed oil flows into pipe line 43 to tank 49 
through automatic back pressure valve 44. The washed oil yield is 29,014 
pounds per hour containing 0.3% moisture and 60 p.p.m. of phosphatides, 
measured as phosphorus. The dry weight is 28,927 pounds per hour. 
EXAMPLE 3 
Instead of a continuous system, the partially degummed crude soybean oil 
from Example 1 may be acid degummed using a batch process. 
For such a process, a cone bottom tank equipped with an efficient 
mechanical sweep-arm agitator is used. It has a closed steam heating coil 
and a bottom draw off line. The weight pumped into it for processing is 
58,800 pounds. The batch is heated to 140.degree. F. and 0.16% or 94 
pounds of 85% phosphoric acid is added to it. This is equal to 0.136% of 
100% acid. Mixing is done for 30 minutes. Then 3% of warm water or 1.764 
pounds of water is added to the mixer, at which time the temperature is 
raised to 155.degree. F. and mixing is continued for an additional 20 
minutes. The agitator is shut off and the mixture is allowed to settle 
until a definite separation of oil and water phase occurs. This requires 
about 6 hours. The water-gum phase is carefully drawn off. The agitator is 
then put on, 20% of hot soft water is sprayed on the batch while the 
temperature kettle is increased to 170.degree. F. The batch is allowed to 
settle again for 4 hours. At this time the wash water is drawn off. The 
washed oil yield is 58,028 pounds containing 0.3% of moisture and 70 
p.p.m. of phosphorus which corresponds to 0.21% of phosphatides. The dry 
weight is 57,854 pounds. 
EXAMPLE 4 
The degummed soya oil, treated in accordance with the procedures of any of 
the preceding examples, is next subjected to the activated carbon 
treatment step of the present invention. Referring to FIG. 3 of the 
drawings, degummed soya oil is carried through line 101 to pre-filter feed 
tank 103 where it is stored until pre-filtration and subsequent processing 
is carried out. At that time the degummed soya oil is pumped by means of 
pump 105 through line 107 to pre-filter 109, which may be of any 
construction suitable for removing suspended particulate matter from the 
degummed oil. A paper filter may be employed. The sludge of removed 
suspended particulate matter is eliminated at 111. The pre-filtered oil is 
next transported through lines 113 and 117 to adsorber feed tank 119, 
which is insulated. If necessary, the oil may be refiltered by returning 
it through line 115 to the pre-filter feed tank 103. The oil is now ready 
for passage through the activated carbon adsorbers and is pumped through 
line 121 by pump 123 to adsorber columns 123, 125, 127 and 129. While four 
adsorber colums are depicted in the drawing, the actual number employed 
will vary according to the volume of oil being processed. The adsorber 
columns are insulated as well as being heat traced, primarily at the 
bottom conical portion, for example by small steam lines. After passing 
upwardly through the activated carbon adsorption columns, the oil is then 
transported through line 131 to post-filter feed tank 133. If additional 
activated carbon adsorption treatment is required, the oil may be 
transported back through line 135 to the adsorber feed tank 119. From the 
post filter feed tank 133 the oil is pumped through line 137 by pump 139 
to a post-filter 141. This filter is similar in construction to the 
pre-filter 109, and is especially suitable for removing any activated 
carbon fines which may have become entrained in the oil during passage 
through the activated carbon adsorber columns. The sludge of removed fines 
is eliminated at 143. The post-filtered oil is now ready for the final 
step of steam distillation deodorization and is transported through line 
145 to the apparatus for carrying out this step. The adsorber columns are 
operated as pulse beds and so require continual removal of exhausted or 
loaded activated carbon for reactivation, and a corresponding continual 
replenishing of fresh activated carbon for the adsorber column. Fresh 
activated carbon, either virgin carbon or reactivated carbon, is supplied 
to each of the adsorber columns through insulated charge tanks 147, 149, 
151 and 153. In these charge tanks the activated carbon is mixed with 
previously refined oil. This refined oil is carried to a refined oil 
storage tank 155 through line 157 from a location elsewhere in the process 
stream suitable for providing refined oil. The refined oil is pumped 
through line 159 to each of the charge tanks by pump 161. Fresh activated 
carbon is introduced into the charge tanks through line 163. The charge 
tanks are pressurized by a pressurizing medium supplied through line 165. 
The pressurizing medium is preferably compressed air, but may be, for 
example, nitrogen. The charge tanks are vented through line 167. 
After the activated carbon is loaded, that is, exhausted by adsorption to 
practical capacity, it is removed from the adsorber columns through line 
169 and carried to the product recovery column 171, which is vented 
through line 167. The product recovery column is insulated and is 
pressurized from line 165. A fraction of the oil is transferred under 
pressure through line 179 to the adsorber feed tank 119. Then the 
remaining oil is removed from the activated carbon by upflow desorption 
with hexane supplied from hexane storage tank 173, pumped through line 175 
by pump 177. The mixture of oil and hexane is recovered from the product 
recovery column. This mixture is carried through line 199 to hexane/oil 
storage tank 193. This hexane/oil mixture may subsequently be removed 
through pump 201 to an extraction plant or other location where the hexane 
and oil are, in turn, separated. The hexane is, in turn, removed from the 
activated carbon by steam stripping. The steam is introduced into the 
product recovery column 171 through line 181, and the mixture of steam and 
hexane is carried away from the product recovery column through line 183. 
The hexane is recovered from the steam and hexane mixture by condensing of 
the mixture in condenser 185, cooled by water supplied through line 187. 
The hexane is decanted in decanter 139 and carried through line 191 to 
hexane/oil storage tank 193. The separated water is sewered through line 
195. 
The desorbed carbon is now ready for reactivation and is transported 
through line 197 from product recovery column 171 to desorbed carbon 
storage tank 203. The desorbed carbon is transported as a slurry, prepared 
from water supplied through line 205. The slurry is then dewatered in 
dewatering screw 207, after which the carbon is introduced into 
reactivation furnace 209. The furnace is fueled by fuel from line 211, 
with combustion air supplied through fan 213. Steam is also utilized and 
is supplied through line 215. Air for cooling is supplied to the furnace 
through pump 217. The by-products of the reactivation are first treated in 
afterburner 229. They are then removed through line 231 to scrubber 233 
supplied with water from line 235 which is then sewered through line 239. 
Innocuous final products are exhausted to the atmosphere by means of 
induction fan 237. After reactivation, the carbon is carried through line 
219 to cooler 221, which employs water as a cooling medium, with the aid 
of water cooler 223 and pump 225. After cooling, the reactivated carbon is 
carried by means of the reactivated carbon transfer elevator 227 and line 
163 to the charge tanks 147, 149, 151 and 153. 
EXAMPLE 5 
The degummed and activated carbon treated soya oil prepared in accordance 
with the procedures of the preceding Examples is now ready for the final 
step of steam distillation deodorization under vacuum. The distillation is 
carried out at approximately 500.degree. F. and at a reduced pressure of 
approximately 1.5 mm. Hg. The distillation is carried out for 
approximately four hours while steam is supplied to the oil at the rate of 
10 pounds per minute. The recovered oil is of acceptable taste, odor and 
color, has a phospholipid content, measured as phosphorus, of less than 
5.0 p.p.m., and a peroxides concentration level of less than 2.0 meq. per 
1.0 kg. of oil.