US2397874A - Refining fatty oils - Google Patents

Description

Patented Apr. 2, 1946 UNITED STATES PATENT OFFICE REFININ G FATTY OILS Katherine Lloyd, Chicago, and Havard L. Keil; Clarendon Hills, Ill., assignors to Armour and Company, Chicago, Ill., a corporation of Illinois No Drawing. Application March 23, 1940,

Serial No. 325,784

Claims. (01. 195-3) cial processes as inthe manufacture of foods or soap, it is first necessary to remove these other substances which in thi discussion will be referred to as impurities. Without removal of such impurities the oil cannot be hydrogenated or bleached in a commercially successful way and is otherwise not suitable for use in commercial processes.

The method which has been in universal use for the removal of these impurities is the caustic.

alkali method wherein the caustic alkali reacts with the free fatty acids to form soaps and may possibly react with the impurities, the soaps and impurities being separated out and removed as foots. By this method of oil refining the fatty acids are necessarily removed, and as a practical matter some glycerides are always removed in the foots; and these features result in a relatively high refining loss. I

A method of refining the natural oils so as to enable their use in commercial processes without th removal of free fatty acids would be of great commercial importance, and its value would 5 be further enhanced if such a method were effective to remove in the impurities substantially all those substances which act as hydrogenation inhibiting factors or bleach inhibiting factors in the later processing steps.

In the past various kinds of treatments have been suggested for the refining of oils without removal of the free fatty acids, but none of these suggested treatments have ever had any commercial significance. Some of the suggested processes consist of treatment with bacteria of one or another type such as in Ekhard Patent No. 2,172,531, and others have consisted of yeast treatment such as disclosed in 'Babcock Patent No. 156,404, and others, as in Ayres Patent No. 1,737,402, consist of treatment with water only. All of these have fallen short and have failed to displace the caustic alkali methods already in commercial use.

We have discovered processes which are effective in the removal of impurities from the oil without removal of free fatty acids. Furthermore our processes are effective to remove in the impurities those substances which are contained in the naturally occurring Oils and fatty acids of such oils and which inhibit hydrogenation or bleaching action. Our improved'methods depend upon the action of enzymes of the proteolytic type in causing the precipitation or flocculation of the impurities.

In carrying out the process we subject the crude 'oil to treatment with a small amount of a 'proteolytic enzyme, in the presence of water.

Through the peculiar action of this enzyme the water and impurities combine, probably in a kind of hydration, to form insolubles. The insolubles may then be removed by centrifuging or by allow-- ing the oil to stand until the insolubles have settled and then decanting the purified oil. We do not now know the exact mechanism by which this insoluble union is formed through action by the proteolytic enzyme. It is possible that the enzyme acts to sever certain protein bonds in the impuri- I ties to permit hydration of the impurities not before possible because of such bonds, or it i possible the proteins themselves being acted upon by the proteolytic enzyme hydrate and form about the other impurities to remove them from the oil. Also we do not now know whether the hydrogenation-inhibiting and the bleach-inhibiting factors removed by our improved process are themselves proteins or are removed only through the proteolytic enzyme action on the proteins. Evidently, the proteolytic enzymes do coact with the water in some way to convert the oil-soluble impurities into an oil-insoluble combination which can be separated off.

To be effective in our process the enzyme used must be a 'proteolytic enzyme; that is, it must be of a type having proteolytic activity. Papain, trypsin, pepsin, bromelin or ficin are examples of types which can be used. Various mixtures of such proteolytic enzymes may be used advantageously. These examples given are not intended as inclusive and any other enzymes or mixtures of enzymes having proteolytic activity may also'be used. The proteolytic enzymes here referred to do not necessarily include all enzymes which act on proteins but do include those enzymes which hydrolyze or cleave the protein molecule. We have found that those enzymes without proteolytic activity are of no use in the practice of our invention and do not serve the desired function in our processes; for example, yeasts are chiefly a casein coagulant and does not have proteolytic activity, is altogether ineffective in our process.

Of the proteolytictype of enzymes which may be used we and papain particularly advantageous. we now believe that this can be explained by the fact that papain' has proteolytic activity I over a wide pH range, and since the pH of the oil is normally not the optimum for proteolytic action, papain is more effective to perform the desired function under the ordinary operating conditions of purificatiom We find also that the enzyme trypsin is very effectively used in our processes.

The amount of proteolytic enzyme necessary to perform the desired function is very small and is of the order of .002 to .01 per cent by weight of the oil being purified. vIn the case of papain only about 1 pound of the powdered enzyme material now marketed as having a proteolytic strength of 1:200 is required to thoroughly refine 30,000 pounds of oil. Of the other proteolytic enzymes which may be used in our method, we find that in general about the same amount or possibly a slightly larger proportion of enzyme is desirable.

Lesser amounts of the enzymes, of the order of 1 pound of enzyme material to 60,000 pounds of oil, may be used, depending on the character of the oil being treated, but if the amount is too greatly reduced the oil will-be incompletely purifled. Also greater amounts such as 2, 4, or 6 pounds of enzyme powder per 30,000 pounds of oil, may be used, but the additional amounts usually result in no substantial benefits; and if the amount used becomes too great, digestion of the proteins proceeds to a stage not desirable and this results in the impurities being again released and rendered soluble in the oil which defeats the purpose for which the enzymes are used. It will therefore be clear that our process involves not a ,proteolysis to the point of decomposition but only such action as enables or facilitates the forma- ,tion of compounds insoluble in the oil.

Though our invention in its broadest aspects from as low as 1 or 2% of the oil up to 40 or 50% or even higher, we have further discovere that 1 by limiting the amount of water employed we ob- When we use such limited amount of water the.

flocculent water-impurity formation is of a gelatinous nature, appears to cohere more effectively, and produces a cleaner separation from the body of the oil. Too, the agglomerated particles are relatively large in size when the water is limited, and will settle into a layer of lesser volume; To distinguish this oil-insoluble compound-of improved character we will call it a gelatinous flocculation. It will be understood'that by this term we do not mean the compound is necessarily stiif or like jelly, and in most cases it is On the other hand when the amount of wate is more than 20 per cent of the oil, the character of the flocculation is entirely different. In these cases the layer occupied by the compound after settling, is larger, and instead of being an ag- J I a v is best to use for obtaining the impurity compounds of improved character will vary somewhat depending on the oil purified and the amount of impurities contained in it. but having in mind the character of the impurity compound desired it is simple to adjust the specific quantity 'of water used to obtain this result.

Though as above stated we prefer to use a 7 .limited amount of water to produce the fiocculation of improved character, we need not so limit the water used and can use larger amounts of 1 water while still obtaining great advantage ter to employ temperatures between 100 to 110 F. though the temperature of greatest activity for papain is in the range of about 145 to 155 F. Indeed when the temperature is raised to about 115 F. we have noticed a very marked difference in the functioning of the .enzyme to form the insoluble flocculation. When we are working with may be practiced using water in the amount of normally hard fats we must, of course. use temperatures suillciently high to melt the fat reducing it to a liquid.

While as above stated we prefer to employ temperatures in the range of 100 to 110 F., temperatures outside this range result in effective operation. -It will, of course, be recognized-by those familiar with enzymes that the temperature employed should not be below that at which the enzymes have any activity and should not be above that at which they are destroyed.

Our process maybe practiced by heating the oil in a large tank to a desired temperature such as 105 F., and then mixing into the oil the enzymes and water by mechanical agitation. Alternatively the enzyme and water may be added before the oil is heated, but this way a longer time is required for processing since the enzyme has very little proteolytic activity until the temperature is raised toabout90F.

One good way of performing the treatment is to start 'a mechanical stirrer, in the processing tank and apply heat, then when the operating temperature is reached add the water containing the enzyme, continuing the stirring. to mix the water and enzyme with all parts of the oil. Another way is to first add the major portion of the water and then .add an'aqueous solution of the enzyme. Within usually about lO minutes after the addition of the enzyme a break" I 'will occur, as evidenced'by the presence of small of a soft gelatinous nature.

glomeration of fairly large particles of gelatinous less advantageous. The amount of water which it masses which tend to collect within the oil, causing the oil to have a mottled appearance. These small collected masses are the product of the union of the water and impurities as created by the action of the proteolytic enzyme. This mottled effect then becomes more pronounced during the period of enzyme activity. Preferoil to stand overnight. The purified oil 'is then drawn on and thus separated from the oil-insoluble substances. .The losses may be further drogenation or bleaching of the purified oil.

reduced by stirring the insoluble mass which con-.

tains a certain amountof oil. and then allowing time for settling, after which a further quantity of purified oil can be drawn'ofi. 1

We find it advantageous to employ the mechanical stirrer in mixing in the enzyme and water, and so far as possible to avoid beating air into the mass. Oxidation produced by the air is a chemical change which we find undesirable. Not only does oxidation adversely aflect the character of the oil, but it also restricts or inhibits the full action of the proteolytic enzyme. I

Instead of allowing the oil to stand until the insoluble fioc has precipitated to the bottom,

the oil may be passed through a centrifuge to separate the insoluble compound from the oil. This operation enables the oil to be refined in a shorter period of time.

Though the substances removed from the oil in our process have been designated as impurities, they are not to be understood as always being waste materials. Indeed, it has beendiscovered that this improved method presents a very effective way to recover lecithin from soya bean oil, and in many other instances the socalled impurities have valuable uses.

Our processes are applicable to any of the ve etable, animal, and marine oils such as soya bean, peanut, cocoanut, sardine and cottonseed oils and tallow and lard oils. but it is advantageous to vary the conditions in some instances depending on the oils being treated. In general the oils treated by our process can be hydrogenated and bleached by the usual processes applicable to oils. refined by the caustic method and in most instances we have found that the hydrogenation or bleaching operations proceed with greater ease and speed than in the case of caustic refined oils. To our knowledge no other process, excepting th caustic refining method, has ever been known which would permit the ready hy- By our method the free fatty acids remain in the oil and upon subjection to hydrogenation these free acids also take on hydrogen. In the past it has been thought that fatty acids occurring in oils inhibit the hydrogenation of the oils, but as demonstrated by our improved process. when the hydrogenation inhibiting substances are removed, not only will the purified triglycerides readily hydrogenate. but the fatty acids contained willthemselves readily-hydrogenate.

Soya bean oil is peculiarly susceptible to treatspecial bleaching agents. Alternativelythe cottonseed oil after being treated by our process may be given a very light caustic wash in removeany color holding bodies which it may then c ntai before it is subjected to the ordinary bleaching agents.

.The oils purified by this method and containingtl eir free fatty acids may be steam-distilled andthe'free fatty acids removed in vaporous form and separately condensed. This procedure yields a highly purified triglyceride which may be especially suitable for edible purposes, and

alsoa quantity of fatty acids which may be used in the manufacture of soaps or in other commercial processes. The possible uses of the relatively pure fatty acids recovered in this procedure are to be contrasted with the ineffective disposal of these acids in the caustic refining method where they are in chemically combined form with the impurity materials.

While our invention may be practiced without hydrogenation or bleaching of the refined oil,

ment by our improved processes, and it appears that the character of the impurities normally contained in the crude soya-bean oil are particularly responsive to combination with water by influence of a proteolytic enzyme. When purified by our method, soya bean oil with its free fattyacids content will react with hydrogen much more readily thanwill oil refined by the caustic method and having its free fatty acids removed. The enzyme purified soya bean oil may also be easily bleached using only the common colorabsorbing agents.

Though our process can be used to remove impurities from cottonseed oil we find that this oil when so purified may yet not bleach to the extent desired when'using the ordinary absorption we find that by carrying on the process to include the steps of hydrogenation, bleaching, or steam distilling, special and advantageous results can be accomplished.

Another advantage gained through the use of the proteolytic enzyme treatment is that the refined oil, though it retains its. fatty acid content, is more stable and develops rancidity less readily. This is'noticeable especially in the case of soya bean oil which after alkali refining has a tendency to develop poor taste and odor. The oil purified according to our, improved method remains swee for a greater period of time.

Followingare some examples of the practice of our invention to demonstrate specific ways of performing the steps involved:

- Example 1 50,000 pounds of soya bean oil are agitated and heated to 113 F. in a refining tank. Approximately 2,500 pounds of water are then added to the oil andas the water flows into the oil a mix- The foots are again allowed to settle and further quantities of oil recovered therefrom. The

total refining loss is under 2.5%.

I Exam le 2 H 500 parts by weight of crude peanut on are treated with 25 parts by weight of water and 0.018

parts by weight of commercial papain at 104 F. and the whole agitated for'about one hour. The oil is then allowed to settle and the refiningloss is 5.0%. The oil is bleached, using regular bleaching earth, from an original color of35 yellow and 7.6 red (Lovibond) to 20 yellow and 3 red.

Example 3 I 1,000 parts by weight of crude cocoanut, oil are treated at 104 F. with0.1 part by weight of com-.

mercial papain in 50 parts by weight of water.

Afterv settling overnight there are 98 parts by weight of foots recovered, corresponding to a 4.8 percent refining loss. A comparative run, using caustic refining in the regular way, shows a 12.4 percent refining loss.

rambl r" .To 500 para-a weight of crude cottonseed oil there is added with stirring to pa t by weightof water containing 0.2 part by weight trypsin saying 1:40 by the U. S. Pharmacopoeia test,

The temperature isvv maintained at 104 F.. for about one hour and'the oil then allowed to settle.

,A fine compact foots, dark and; resinous'in ap pearance, is obtained. The loss inthis'step is 0.55 percent. The oil recovered is rather dark in Y producefrom said water and proteins a gelatinous water-insoluble flocculation which is insoluble in said oil, and separating-said oil-insoluble I water-insoluble flocculation from the oil.

6. A process for refining fatty' oil containing oil-.- solubleproteins to obtain a refined oil substanstantially free of said proteins, comprising'subcolor but is clear and does not show any fiocculation when heated to 250 C'. A comparative test, but using no enzyme, gives a less compact foots and the oil recovered shows a considerable brown fioc upon being heated to 250 C. A batch of cottonseed oil treated, according to Example 1, with papain in the proportion of 5 pounds of commercial papain to- 60,000 poundsof oil gives an oil,

which, although not as-light in color as would be desirable for some purposes, does not darken nor ,shdw'a fioc upon,heating to 250 C.,.

Example 5 3,850 parts by weight of lard is heated to about 55 C. in order to melt the lard and there'is then added 190 parts by weight of water containing 0.2

parts by weight of trypsin with continuous agita- ,tion. The mixture is held at 131 F. for aboutan hour, with stirring, and then allowed to settle.

and the re that the improved treatment is applicable to other oils as well, and that various changes and adjustments can be made in the operation and conduct, of the processes without departing from the, spirit of the invention.

1. A process'for refining fatty oil containing oil-soluble proteins to obtain a refined oil sub stantially free of said proteins, comprising subjecting said oil to the action of a hydrolyzing proteolytic enzyme in the presence ofwater to produce from said proteins and water .a elatinous water-insoluble flocculationwhieh is insoluble in said oil, and separatingtsaid oil-insoluble waterinsoluble flocculation from the oil. 7

2. A process for refining fatty oil containing oil-soluble proteins to obtain a refined oil substantially free of said proteins, comprising'sub jecting said oil to the action of papain in the presence of water to produce from said proteins and water a gelatinous water-insoluble flocculation which is insoluble in said oil, and separating said' oil-insoluble water-insoluble flocculation tom the oil. i

3. A process for refining'fatty oil containing il-soluble proteins to obtain a refined oil subantially free of said proteins, comprising sub,- jectingsaid oil to the action oftrypsin in the presence of water to produce from said water and trypsin a gelatinous water-insoluble flocculation which is insoluble in' said oil, and separating said oil-insoluble water-insoluble flocculation from the oil. l r

4. A process for refining crude soya bean oil containing oil-soluble proteins to obtain a refined Jecting said oil to the action of a hydrolyzing proteolytic enzyme in the presence of water in the amount of less than 10% of said oil to produce from'said water and proteins a gelatinous water-insoluble flocculation which is insoluble in said oil, and separating said oil-insoluble water-insoluble flocculation from the oil.

6. A process for refining gatty oil containing oilsoluble proteins to obtain a reflnedf'oil substantially free of said proteins, comprising subject ing said oil to the action of a hydrolyzing proteo lytic enzyme in the presence of water to produce from said water and proteins a protein substance the form of a gelatinous flocculation separating said substance from the oil '7. In a process for refining fatty oil containing oil-insoluble proteins to obtain a refined oil substantially free of said proteins, the steps of bringing a hydrolyzing proteolytic enzyme and water into intimate admixture with said oil while agitating said oil while avoiding aeration thereof until said proteins are formed into a gelatinous flocculation and become oil-insoluble, and while said proteins remain in oil-insoluble water-insol- Y uble flocculated form separating them from said jecting, said oil to the action of a hydrolyz'ing proteolytic enzyme in the presence of "water at a temperature of from to F. to form a fiocculate oil-insoluble water-insoluble proteincontaining substance, and while said substance remains in flocculate oil-insoluble water-insolamount less than 10%of said oil to form a fiocuble form separating it from the oil. a

9. A process for refining fatty oil containin oil-soluble proteins to obtain a refined all substantially free of proteins, comprising subjecting said oil to the action of a hydrolyzing proteolytic enzymein the presence of water "in an culate oil-insoluble water-insoluble protein-containing substance, maintaining said oil in a quiescent state until said substance has settled,

oil-soluble proteins to obtain a refined oil sub-f stantially free of said proteins, comprising subjecting said oil to the action of a hydrolyzing proteolytic enzyme in the presence of waterto form a fiocculate oil-insoluble water-insoluble protein-containing substance, and before said substance has precipitated from said oil, and

while said substance is water-insoluble passing said oil in rapid centrifugal motion to said substance from said 011.

KATHERINE LLOYD.

HAVARD L.

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