Method of producing a substantially sterol free fat or oil

A process for removing sterols and specifically cholesterol from fats or oils such as anhydrous milk fat by passing liquid fat or oil over an absorbent or adsorbent material, where the ratio of fat or oil to absorbent or adsorbent is from preferably about 0.8:1 to 0.3:1.

FIELD OF THE INVENTION 
This invention relates to methods of removing compounds at least one of 
which is a selected compound from fats and oils and/or fats and oils from 
which such compounds have been removed, and in particular for the removal 
of cholesterol from milkfat. 
BACKGROUND OF THE INVENTION 
It is generally well known to treat various edible oils and fats to remove 
objectionable color or flavors. For example, U.S. Pat. No. 692,283 
discloses the removal of color impurities with powdered animal charcoal by 
mixing such charcoal with fish oil, olive oil and the like which are 
typically used for dietetic or medicinal purposes. In Bailey's Industrial 
Oil and Fat Product. Swern, pp.771-77 (1964), various materials such as 
clay, activated clay, activated carbon are taught as useful in bleaching 
oils. In particular, Swern teaches using carbon in an amount of about 0.2% 
to the oil. The use of carbon is preferably always with a bleaching earth. 
Further, the activity of an adsorbent can be measured by the Freundlich 
constant,.sup.1 K, the value of which in the examples given varies between 
0.25 and 7.2 (with a mean of 1.48) for most active adsorption bleaching 
processes. 
Freundlich equation Kc.sup.n =x/m where x=the amount of substance adsorbed, 
m=amount of adsorbent, c=amount of residual substance and K and n are 
constants. 
Other processes for improving or enhancing edible and nonedible oils are 
known in the art. See, for example, U.S. Pat. Nos. 4,112,129 (reducing 
free fatty acid and color degradation in cooking oils); 3, 450,541 
(separating sterols from a liquid mixture); 2,418,819 (removal of water 
and soaps from oil or fat by percolation); 3,519,435 (fractionation of 
milk fat); 4,443,379 (adsorptive bleaching of edible oils using Group VIII 
metal cations and bleaching clays); and 4,005,228 (milk fat 
crystallization using an acetone solution). Also, PCT application 
GB82/00327 (method for refining fats using organic solution with 
adsorption agent). 
A number of processes have been directed to the reduction of cholesterol in 
egg products, for example, U.S. Pat. Nos. 3,987,212; 3,941,892 and 
3,563,765. However, few, if any, processes have been successful in 
reducing or eliminating sterols such as cholesterol in milk fats and like 
products. In Belgium patent 862,264, however, a method for reducing the 
cholesterol content of butter by using molecular vacuum distillation is 
disclosed. It is reported that initial cholesterol content can be reduced 
by 70-90% using this method. 
Granulated carbon processes have been used with dairy products to remove 
antibiotics or residues from milk, rancidity, and for acid hydrolysis and 
purification of lactose in whey. The action of bleaching earths on 
cholesterol was reported in Alteration of Sterol by Industrial Processing 
of Fats and Oils. by E. Homberg, Fette, Seifen, Anstrichmittel v.76 
pp.433-35 (1974). The report focuses on the formation of cholesterol 
derivatives during the treatment with active earth. 
Notwithstanding the dietary advantages in reducing or eliminating 
cholesterol and its derivatives and other sterols from milk fat products, 
there have been few processes which provide for large commercial scale 
removal. Moreover, it is desirable to reduce such cholesterols in fats in 
such a way as to leave a product useful for the production of edible 
processed foods. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a method of removing at 
least some of compounds at least one of which is a selected compound from 
fats and oils and/or fats and oils from which such compounds have been 
removed which will at least provide the public with a useful choice. 
Accordingly, one aspect of the invention consists in a method of removing 
at least some of the objectionable compounds, one of which is a selected 
compound from fat and/or oil. This method comprises the steps of 
maintaining the fat and/or oil in a liquid condition and passing the 
liquid fat and/or oil over a large amount of absorbent or adsorbent 
material. The absorbent or adsorbent material is such as to remove at 
least the selected compound from the fat or oil. 
In the present invention it has been found that a very large amount of 
absorbent is required to achieve successful removal of cholesterol and its 
derivatives such as cholesterol oxides. In fact, the Freundlich constant K 
is about 63 for the adsorption of cholesterol from milk fat. This is to be 
contrasted with a value of about K=7 for decolorization of milkfat using 
carbon. Generally, the present invention involves maintaining the oil or 
fat in a liquid state and thereafter contacting it with an adsorbent to 
remove the sterol. Preferably the adsorbent is selected from the group 
consisting of granulated carbon, activated carbon, carbon adsorbents 
impregnated with metal salt or organic compounds, porous glass, porous 
glass impregnated with metal salts or organic compounds or containing 
chemically bonded groups, porous ceramic, porous plastics, aluminas, 
silicates, magnesia's and derived compounds including Florisils. 
In order to remove substantially all of the cholesterol from milkfat (that 
is, for example, to levels of approximately 50 ppm cholesterol), it is 
necessary to use a very large quantity of adsorbent. Generally, it has 
been found that with unenhanced adsorbents such as an activated carbon, a 
batch process using 5% carbon based on the weight of the oil will remove 
between 40 and 50% of the cholesterol. In such a process cholesterol 
levels of 50 ppm and less are achievable by successive treatments which 
require the use of at least 35% by weight adsorbent. In a continuous 
process using the same carbon these levels of cholesterol are achieved 
with 10% by weight of adsorbent or absorbent. In a preferred embodiment of 
the invention using a continuous process a greater than 90% reduction in 
cholesterol was effected when the ratio of oil to adsorbent was from 0.8:1 
to 0.3:1 depending on the adsorbent used. In conventional color removal 
from fats and oils the ratio is typically 20:1 to 100:1 and in the case of 
milkfat a ratio of 176:1 is typical. Enhanced adsorbents can achieve 
substantial removal of cholesterol using reduced amounts of adsorbents. 
The present invention can take advantage of either a fixed column or a 
pulsed column of adsorbent to achieve a reduction or elimination of the 
sterols from the fat or oil. However, the advantages of the present 
invention will become apparent from a perusal of the following detailed 
examples set forth in the preferred embodiments. The preferred embodiments 
also disclose the best mode of carrying out the method above-described.

PREFERRED EMBODIMENTS OF THE INVENTION 
In one of the preferred forms of the invention it is envisaged that an oil 
and/or fat, for example fats and oils of vegetable and/or animal origin 
(including fish fats and/or oils), is treated with an absorbent. This 
method is described in relation to the removal of cholesterol from 
anhydrous milkfat. 
To put the method into operation, the oil and/or fat is maintained at a 
temperature which maintains the fat and/or oil liquid and preferably which 
reduces the viscosity of the liquid fats and oils to a value which 
facilitates adsorption or absorption of the desired components on to or 
into the active adsorbents or absorbents. Preferably the treating material 
comprises an adsorbent which include active carbons, earths and clays, 
aluminates, silicates, magnesia's and synthetic compounds from these 
(e.g., florisils), either pulverized or granulated, or porous glass, 
plastics or ceramics. Most preferably the absorbent is in particulate 
condition. 
During repeated or continuous contact with the adsorbent some oils and fats 
may lose their characteristic flavor, color and oxidative stability. After 
deodorization for example by using equipment common to the vegetable oil 
industry, undesirable flavors are removed from the treated oil or fat. 
Both desired color, flavor and oxidative stability may be added back using 
natural, nature identical, or artificial components. 
The process may be carried out either as a continuous or batch process. As 
an example of the continuous method, a hot milkfat such as anhydrous 
milkfat is maintained at a temperature above its melting point (e.g., 
40.degree. C.) and preferably between 70.degree.-90.degree. C. and is 
slowly percolated through a column of granulated (12.times.40 mesh) active 
carbon (type APC, Calgon Corporation, Pittsburgh, PA, U.S.A.). The initial 
fractions obtained were substantially cholesterol free. 
In a batch procedure, a quantity of milk fat, such as anhydrous milkfat, is 
held at 70.degree.-90.degree. C. and is vigorously stirred with 2.5% 
active pulverized carbon (type NAP, Calgon Corporation, Pittsburgh, PA, 
U.S.A.) for one hour. After this period of time the pulverized carbon is 
removed by filtration and the process is repeated a number of times until 
the milkfat is cholesterol free or substantially free of cholesterol. 
In a preferred continuous procedure, a pulsed bed of APC granulated carbon 
(12.times.40 mesh) is used. Anhydrous milkfat (AMF) at an elevated 
temperature (e.g., 80.degree. C.) is pumped at a controlled rate up 
through the carbon column. The carbon column is pulsed (i.e.. a fresh 
portion of granulated carbon is added to the top of the column and an 
equivalent portion of spent carbon removed from the bottom of the column) 
at intervals selected to maintain the desired level of cholesterol (zero 
or relatively low) in the treated AMF. 
The treated AMF can then be deodorized in a vegetable oil deodorizer and 
stabilized against oxidative deterioration by the addition of a suitable 
antioxidant, preferably natural additives such as Eastmans (USA) Tenox 
GT-1 or Vitamin E 4-50. Yellow color (.beta.-Carotene) can be restored by 
the addition of .beta.-Carotene (Roche Switzerland). 
The following experiments set forth examples of cholesterol removal in 
milkfat using both batch and continuous processing. It should be noted 
that deodorization and decolorization are achieved at a very early stage 
in the processing whereas removal of the sterols requires a very large 
amount of processing. 
Experiment 1 
______________________________________ 
Active carbon treatment of milkfat 
No. of Total 
extractions 
Concentration 
Color percentage 
with 5% w/w 
of Cholesterol 
(.beta.-carotene) 
of active carbon 
active carbon 
.mu.g/g .mu.g/g used W/W 
______________________________________ 
0 2620 7.5 moderately 
0 
yellow 
1 1560 0.1 colorless 
5 
(water 
white) 
2 890 10 
3 460 15 
4 250 20 
______________________________________ 
Experiment 2 
______________________________________ 
Active earth treatment of milkfat 
No. of 
extractions Total 
with 5% w/w 
Concentration 
Color percentage 
active of Cholesterol 
(.beta.-carotene) 
of active earth 
absorbent 
.mu.g/g .mu.g/g used W/W 
______________________________________ 
0 2620 7.5 moderately 
0 
yellow 
1 2420 0.1 colorless 
5 
(water 
white) 
2 2350 10 
3 2140 15 
4 1900 20 
______________________________________ 
Experiment 3 
______________________________________ 
Active earth:carbon (10:1; w/w) 
treatment of milkfat 
No. of Total 
extractions percentage 
with 5% w/w 
Concentration 
Color of active 
active of Cholesterol 
(.beta.-carotene) 
adsorbent 
absorbent 
.mu.g/g .mu.g/g used W/W 
______________________________________ 
0 2620 7.5 moderately 
0 
yellow 
1 2340 0.1 colorless 
5 
(water 
white) 
2 2090 10 
3 1840 15 
4 1040 20 
______________________________________ 
Experiment 4 
______________________________________ 
Active carbon treatment of fish oil 
No. of extractions 
Concentration 
Total percentage 
with 5% w/w of Cholesterol 
of active carbon 
active absorbent 
.mu.g/g used W/W 
______________________________________ 
0 2310 0 
1 1550 5 
2 1300 10 
3 820 15 
4 430 20 
______________________________________ 
Experiment 5 
______________________________________ 
Continuous carbon column treatment 
of milkfat 
Amount of Quantity of milkfat 
Quantity of milkfat 
carbon used 
decolorized decholesterolized 
______________________________________ 
1 kg 176 kg 8 kg 
______________________________________ 
Referring to Experiment 5, 176 kg of milkfat was completely decolorized in 
a continuous column. However, only 8 kg of the milkfat was 
decholesterolized showing the larger ratios necessary to decholesterolize. 
In fact, in this experiment, 12% carbon adsorbent was used to reduce the 
level of cholesterol in the 8 kg of milkfat to approximately 50 ppm. 
In addition to the foregoing experiments, anhydrous milkfat (2375 .mu.g 
cholesterol/g milkfat) was passed through an APC carbon column (490 
mm.times.20 mm ID, 72.7g) at 70.degree. C. and the cholesterol level was 
reduced to 29.3 .mu.g/g milkfat. Likewise in a similar column when 
anhydrous milkfat was percolated through at 70.degree. C., the natural 
levels of cholesterol oxides.sup.2 present (5 cholesten-3 .beta.-01-7-one 
and cholesterol 5 .alpha., 6 .alpha.-epoxide) were completely eliminated 
in the first 5ml eluate collected. 
FNT In addition to cholesterol, cholesterol oxides have been implicated as 
potent causative agents for atherosclerosis and have also been implicated 
as potential carcinogens. Accordingly, the removal of these oxides is 
extremely important. 
It has also been found that when carbon (Carbon APC 12.times.40) was 
impregnated* with a selection of metal salts of differing cations and 
anions the capacity of the carbon for cholesterol adsorption from 
anhydrous milkfat was increased, in some cases very significantly. This is 
illustrated in the following table: 
FNT *Granulated carbon was impregnated by immersion in a 10% (w/w) aqueous 
solution of the metal salt at 80.degree. C. for 2h. The carbon was removed 
by filtration and dried at 105.degree. C. for 24h before use. 
TABLE 
______________________________________ 
Concentration of Cholesterol 
Metal Salt used to 
(.mu.g/g milkfat) in the 28th 5 ml 
Impregnate Carbon 
fraction off column. 
______________________________________ 
Carbon Control 
534.0 
(mean of 3 exps) 
ZnSO.sub.4 330.6 
Zn(NO.sub.3).sub.2 
317.3 
ZnCl.sub.2 97.4 
Carbon control 
500.5 
CaCl.sub.2 294.0 
Carbon control 
674.0 
Mn(NO.sub.3).sub.2 
529.0 
MnSO.sub.4 330.6 
MnCl.sub.2 314.9 
______________________________________ 
Also carbon was impregnated with a number of water soluble or alcohol 
soluble organic compounds. It was found of these organic compounds; 
(a) amides, typified by urea, and 
(b) nucleotides such as GMP (Guanysine monophosphate) or IMP (Inosine 
monophosphate), 
were found to provide the greatest degree of enhancement to the process of 
the invention. In particular, urea and IMP markedly improved the ability 
of carbon to remove cholesterol from milkfat. 
______________________________________ 
Organic Compound 
Concentration of Cholesterol 
used to (.mu.g/g milkfat) in the 28th 5 ml 
Impregnate Carbon 
fraction off column. 
______________________________________ 
Control carbon 
288.5 
(mean of 2 exps) 
Urea* 59.0 
IMP.sub.+ 258.3 
______________________________________ 
*10% aqueous solution of urea (w/w) used to impregnate carbon. 
.sub.+ 5% aqueous solution of IMP (w/w) used to impregnate carbon. 
Thus selected organics can increase the efficiency of adsorbents to remove 
cholesterol (and cholesterol oxides) from anhydrous milkfat. 
It should be noted that Digitonin and Tomatine, two compounds known to form 
insoluble adducts with cholesterol in solution and used to remove 
cholesterol from solution when placed in/on an inert support (Celite 545) 
(U.S. Pat. No. 3,450,541), did not improve the performance of carbon. 
When anhydrous milkfat (2375 .mu.g cholesterol/g milkfat) was passed 
through a column packed with controlled porous glass (400mm.times.10mm ID, 
40g) at 70.degree. C. the cholesterol concentration was reduced to a mean 
of 370.3 .mu.g/g milkfat in the first 2ml of eluate. In the ninth 2ml 
fraction the cholesterol level was still reduced to a mean of 1650.2 
.mu.g/g milkfat. With the use of controlled pore glass it was observed 
that the color and some of the flavor compounds were only partially 
removed by the adsorbent. 
Porous Glass (Corning Vycor 30.times.60 mesh) 
Unlike carbon, under the conditions employed, metal salt impregnation.sup.3 
of porous glass evidenced little effect on the capacity of such glass to 
enhance cholesterol adsorption from milkfat. However, Zinc Chloride did 
show a slight productivity to enhance activation as was observed for 
carbon above. This is shown in the following table: 
______________________________________ 
Concentration of 
Cholesterol (.mu.g/g 
Metal Salt used Milkfat) in the ninth 
to Impregnate Porous 
2 ml fraction from the 
Glass column 
______________________________________ 
Porous glass control 
1650.2 
(mean of 2 exps) 
CaCl.sub.2 1734.5 
MnCl.sub.2 1622.1 
ZnCl.sub.2 1597.6 
______________________________________ 
Since the surface area for APC carbon (1525 m.sup.2 /g) is about 6.5 times 
greater than that of the porous glass investigated (230 m.sup.2/ g) it is 
contemplated that a more active porous glass may result by enhancing the 
capacity of the glass using different conditions or using solutions of the 
metal salts used to impregnate the glass which are correspondingly more 
dilute than those used to impregnate the carbon. 
FNT Porous glass impregnated under exactly the same conditions as for carbon 
with the same strength metal salt solutions. 
Four porous glasses (Pierce, USA) each with different chemically bonded 
groups were investigated (column h.sub.t of bonded glass 362 mm, ID 10mm, 
weight of bonded glass 10.2g). Cholesterol values of 1652.3 .mu.g, 767.5 
.mu.g, 935.5 .mu.g and 1003.0 .mu.g per g of milkfat (original value 2375 
.mu.g cholesterol/g milkfat) were obtained in the first 2 mls of eluate 
obtained, respectively, from columns of control pore glass with the bonded 
groups, Alkylamine, Aminoaryl, Carboxyl and Glycophase. These results 
indicate that suitable columns of adsorbent with bonded groups would be 
able to eliminate cholesterol (and cholesterol oxides) from milkfat. (A 
control glass of the same porous specification was not available for 
comparison purposes). 
PRODUCTION OF DECHOLESTEROLIZED MILKFAT 
The following procedures describe a small production method for producing 
decholesterolized milk fat using a fixed and pulsed carbon column. 
1. Fixed Column Mode 
Anhydrous milkfat (2600 .mu.g cholesterol/g milkfat) at 40.degree. C. was 
pumped at 80ml/min through a column of carbon (APC 12.times.40 mesh) 13.7 
meters long by 5.1 cm internal diameter held at 70.degree. C. This column 
contained 9.1kg of granulated APC carbon. Approximately 74 kg of 
decholesterolized AMF (Cholesterol content&lt;10 .mu.g/g milkfat) was 
collected before cholesterol breakthrough occurred from the column. 
2. Pulsed Column Mode 
When breakthrough of cholesterol occurred from the column in 1 above 0.91 
kg of fresh APC carbon was added to the end of the carbon column in the 
form of an add-on column 1.37m.times.5.1cm ID and 0.91 kg of spent carbon 
was removed from the column as a detachable column 1.37m.times.5.1 cm ID. 
This procedure was repeated each time breakthrough of cholesterol occurred 
at the end of the new add-on column. This process is repeated until the 
desired amount of cholesterol free (&lt;10 .mu.g cholesterol/g milkfat) or 
low cholesterol milkfat is prepared. 
FILTRATION 
Micro particulate carbon present in the milkfat from experiments performed 
in both the fixed column mode and pulsed column mode was removed by 
filtration of the liquid milkfat. 
DEODORIZATION OF MILKFAT 
Before decholesterolized milkfat obtained from the carbon column can be 
utilized for the manufacture of most products it may be deodorized to a 
bland product. A small deodorizer with a total charge capacity of 15kg 
milkfat was utilized. The contents of the deodorizer were heated with an 
electric element to 210.degree. C. and a vacuum maintained at 8 m bar on 
the pump gauge. Steam was passed through the 15kg milkfat charge at 120 
grams/h for 4 h when deodorization was complete. The deodorized milkfat 
was cooled to 40.degree. C., packed off with added antioxident (Eastman 
Tenox GT-1) and stored at -5.degree. C. until required for the manufacture 
of cholesterol free or low cholesterol products. 
MANUFACTURE OF PRODUCTS WITH DECHOLESTEROLIZED MILKFAT 
1. Manufacture of Cheese 
Melted decholesterolized anhydrous milkfat (DCAMF) with added color 
(.beta.-carotene) and pasteurized skim milk together in a suitable ratio 
were homogenized at selected pressures and temperature to provide a cream. 
The cream was blended into a further quantity of pasteurized skim milk to 
provide whole milk with a standardized milkfat content. Cheese starter was 
added to the milk which was then set with rennet. The coagulum was cut 
into cubes and stirred continuously and the whey expelled. A portion of 
the whey may be removed (10-70%) and replaced with water (10-70%) so as to 
control the pH of the finished cheese. After the appropriate acidity 
increase, the whey was removed from the curd and salt applied for the 
final moisture control. After salting and further whey drainage the salted 
curd was pressed into blocks. After a suitable pressing period the cheese 
was wrapped in a nonpermeable barrier material for curing at a temperature 
in the range of 5.degree.-12.degree. C. (Actual curing time was dependent 
on the desired level of flavor development required). Cheeses were 
obtained with excellent flavor and texture and with very low cholesterol 
contents. 
2. Processed Cheese 
Method (a) 
Cheese manufactured in 1. above was added to a processed cheese kettle 
along with suitable emulsifying salts. After heating and mixing the molten 
processed cheese was packed in suitable containers and cooled. 
Method (b) 
Decholesterolized anhydrous milkfat, skim milk cheese, emulsifying salts, 
color, flavor and salt were added to a processed cheese kettle. After 
heating and mixing the molten processed cheese was packed in suitable 
containers and cooled. 
Both types of proccessed cheese had excellent flavor and texture and very 
low cholesterol contents. 
UHT - Treated Cream or Whole Milk 
Decholesterolized anhydrous milkfat (DCAMF) was melted and added to a 
predetermined amount of emulsifiers, stabilizers, skim milk, color 
(.beta.-carotene) and flavors. The appropriate amount of DCAMF was 
selected so as to obtain cream or whole milk with the desired milkfat 
content. The mixture of ingredients was heated to a selected temperature 
and homogenized at selected pressures to produce a stable emulsion. The 
resultant cream or whole milk was subjected to UHT treatment then 
aseptically packed. The cream and whole milk was kept refrigerated until 
required. The UHT products obtained had excellent flavor and physical 
properties in which the cholesterol content was extremely low. 
4. Butter 
Method (a) 
Decholesterolized milkfat is melted at minimum temperatures then maintained 
at 40.degree. C. in a suitable vat. The aqueous phase consisting of water, 
reconstituted skim milk solids, emulsifiers, stabilizers, color 
(.beta.-carotene), flavor and salt (if required) was pasteurized and added 
to the vat. The contents of the vat were agitated and passed through a 
scrapped surface heat exchanger and pin worker and the butter thus 
produced was packaged and cooled. A butter with excellent flavor and 
containing an extremely low cholesterol content was obtained. 
Method (b) 
In another variation of this procedure, the melted decholesterolized 
anhydrous milkfat was added to a calculated quantity of pasteurized fresh 
cream. An appropriate amount of color (.beta.-carotene) was added and the 
mixture processed as in (a). A butter with natural flavor and reduced 
cholesterol content was produced. 
5. Ice-Cream 
A suitable quantity of melted decholesterolized anhydrous milkfat was added 
to a formulation of reconstituted skim milk powder, sugar, emulsifiers, 
stabilizers, suitable flavors and corresponding colors which had been 
pasteurized. The mixture was passed through an ice-cream churn and the 
ice-cream produced packed and maintained suitably frozen. Ice cream with 
excellent flavor and with markedly reduced cholesterol content was 
obtained. 
Shortbread Cookies 
Butter from 4. above was blended with sugar, water, flour, baking powder 
and flavorings to a paste. The paste was chilled and then molded into 
portions on a baking tray. After baking in an oven at a suitable 
temperature for a short period of time shortbread cookies were obtained. 
Shortbread cookies with excellent flavor and with markedly reduced 
cholesterol content was obtained. 
7. Candies 
Butter from 4. above, liquid glucose, salt, brown sugar, white sugar, 
sweetened condensed milk, fondant and flavorings were placed in a pan and 
stirred over low heat. After gentle boiling to the correct consistency the 
contents of the pan were poured into a greased tray and allowed to cool. A 
chewy caramel was obtained. By omitting the Fondant a hard caramel was 
obtained. Candies with excellent flavor and with markedly reduced 
cholesterol content was obtained. 
A suitable milkfat is thus obtained which has been used for the manufacture 
of a wide range of products (including dairy products) which have zero or 
low levels of cholesterol, i.e.. butters, cheeses, cottage cheeses, ice 
creams, and low cholesterol liquid milks of varying fat content. Where 
necessary flavor (natural, nature identical or artificial) can be used in 
the formulation of the products in order to restore the expected flavor of 
the product which is absent due to the initial treatment of the AMF. 
While presently preferred embodiments have been described in particularity, 
the invention may be otherwise embodied within the scope of the appended 
claims.