US2075807A - Oleaginous stabilization by the ester of glycerin with phosphoric and higher fatty acid - Google Patents

Description

Patented Apr. 6, 1937 UNITED STATES PATENT OFFICE OLEAGINOUS STABILIZATION .BY THE ESTER OF GLYCERIN WITH PHOS- PHORIC AND HIGHER FATTY- ACID Albert K. Epstein and Benjamin B. Harris; Chicago, Ill

No Drawing.

Application June 3, 1935, Serial 18 Claims.

as oils and fats and materials in which oils and fats are a constituent, are adversely affected by the presence of oxygen in the air, in that decomposition, presumed to be caused directly by oxidation, takes place and, in general, renders the article unfit for its intended use. This decomposition or spoilage sometimes manifests itself as rancidity, sometimesby'discoloration, and sometimes by the loss or destruction of some important constituent, as, for'example, the vitamin A constituent of cod liver oil.

Although considerable work has been done looking toward the development of anticatalysts or antioxidants in oils, fats, and the like, normally subject to oxidation, the art has not developed sufiiciently to enable one to predict what substances, or even what types of substances, will have a retarding or inhibiting effect. It is known, however; that certain substances, which have some antioxidant effect in oils and fats normally subject to oxidation, will not function in the presence of other substances, as for example relatively heavy metals such as copper, iron and cobalt. These metals, as well as other substances, are said to poison the anticatalyst or antioxidant. It has been found, also, that if, in a given chemical substance which acts as an antioxidant or anticatalyst, a new chemical group or radical be introduced, or the position or character of groups present in the antioxidant molecule be changed, then the potency of the chemical substance as an antioxidant or anticatalyst is decreased or entirely destroyed.

Accordingly, the principal object of our invention is the provision of an improved class of antir, oxidants of an edible innocuous nature.

Another object is to retard or prevent the oxidation of organic substances, particularly oils and fats, and substances having oils and fats as constituents thereof.

so Other objects and features of the invention are apparent from the foregoing description of problems involved and the following description of the manner in whichthese problems are overcome.

We have discovered that esters of phosphoric .3; acid, produced by esterifying relatively high molecular weight fatty acid glycerides having at least one free hydroxy group with a derivative of phosphorus capable of producing an ester of phosphoric acid, have a definite antioxidant efiect, particularly in oils and fats and compositions having an oily or fatty constituent. Certain of the phosphoric acid esters seem, in general, to be more potent than others, as will be pointed out. These phosphoric acid esters may be treated with alkaline materials in varying amounts without afiecting their action as antioxidants in oils and fats and similar organic materials.

In general, the preferred type of phosphoric acid ester used in accordance with our invention is that wherein glycerine is esterified with a relatively high molecular weight fatty acid to form a monoglyceride, diglyceride, or mixture thereof, at least one remaining hydroxy group being esterified with phosphoric acid. In general, reaction products comprising mixtures seem to be as potent as relatively pure substances. Those reaction products produced by re-esterifying oils and fats with glycerine to produce a mixture of relatively high molecular weight monoand diglycerides and then esterifying the mixture with a derivative of phosphorus capable of forming an ester of phosphoric acid, not only produce improved results, but have the advantage of being relatively inexpensively prepared. For further explanation, this class of materials will be described in further detail.

In general, the substances described in the copending application of Harris, Serial No. 705,825, filed January 8, 1934, now Patent No. 2,026,785, are all suitable for use as antioxidants, as well as the reaction products described in Harris copending application, Serial No. 14,528 filed April 3, 1935 as a continuation in part thereof and which is now Patent No. 2,025,986. While the composition of the phosphate substances employed in the present invention may vary, the substances should in themselves be relatively stable and particularly should be devoid of choline groups, as substances having choline groups in themselves may introduce an additional type of spoilage due to the liberation of choline and the production of amines.

The following examples are illustrative of types of reaction products which can be employed to advantage in the present invention.

Example A 175 parts of refined deodorized cottonseed oil are heated with 10 parts of glycerine (United States Pharmacopoeia grade) in an inert, that is, non-oxidizing atmosphere, with stirring, to about 200 C. .17 part of flaked caustic soda is then added with stirring. The mixture is then raised to about 250 C. and maintained at this temperature with continuous stirring for about two hours, and cooled to room temperature in an inert atmosphere.

45 parts of the above product, which consists essentially of a mixture of diglycerides, and 3 parts of finely divided phosphorus pentoxide are mixed at a temperature of about 50 to 60 C., and

then heated with vigorous stirring in a substantially dry, inert atmosphere to about 115 to 120 C., or, if desired, somewhat higher, and maintainedat this temperature for two to three hours.

The reaction mixture is then allowed to remain at-rest and to cool in an inert atmosphere. A small proportion of insoluble matter settles to the bottom of the container and, while the mixture is still liquid, the liquid is poured oil from the sediment. The decanted material may be used as such with good results, or a somewhat more stable product may be produced and employed, in which case the reaction product is further treated as follows:

The reaction product is chilled until it is semisolid and plastic, and a 50% aqueous sodium hydroxide solution is added with stirring in sufiicient proportions to render the product as a whole substantially neutral to methyl orange or methyl red.

Example B 600 pounds of cottonseed oil, hydrogenated to 5 an iodine value of about 69, and 150 pounds of cottonseed oil are heated together with 250 pounds of glycerine to a temperature of about 200 C. with constant stirring and preferably in the presence of an inert atmosphere. 12 ounces of sodium hydroxide fiakes are added and the temperature raised to about 250 C. and held at that temperature for about two hours with constant stirring. The inert atmosphere may be maintained and stirring accomplished by bubbling the inert gas, such as carbon dioxide, through the reaction mixture, but generally, when processing relatively large batches, mechanical stirring should be employed. In general, the product should be keptout of contact with atmdspheric air at all temperatures in the region of 90 C. and above. Under the conditions given, a product consisting essentially of a mixture of mono-glycerides with some di-glycerides is produced, some free unreacted glycerine remaining. This glycerine may be removed by allowing it to settle out, by centrifuging, or in any other suitable manner. 1

700 pounds of the esterified product produced, as described directly hereinabove, are now transferred to a jacketed kettle. Approximately '75 pounds of finely divided phosphorus pentoxide are added at a temperature of about 55 C., under thorough and continuous agitation. The temperature rises to about to 90 C. Steam is then 5 circulated in the jacket to raise the temperature to about 115 C. and the mixture is maintained at that temperature with constant agitation for one-half hour. The reaction product is then centrifuged to remove the uncombined phosphorus 7 pentoxide and adhering organic matter. With the proportions given, about 150 pounds of a very viscous brown mass is centrifuged out. Analysis shows that the product remaining ordinarily contains only about 0.1% to 0.2% combined phos- 75 phorus calculated as P205. A clear liquid results from the removal of the phosphorus pentoxide and adhering organic matter and this clear liquid may then be treated further to form the phosphoric acid ester.

The clear liquid obtained from this pretreatment step is transferred back to the kettle and cooled to about 50 to 60 C. '75 pounds of finely divided phosphorus pentoxide are then added with agitation. At the same time, cold water is circulated in the jacket. The temperature rises to about to C. in about five to ten minutes and remains at this temperature for several minutes and then begins to cool. It is allowed to cool to about 65 C. The total time required from the time the phosphorus pentoxide is added to the time it reaches its maximum temperature and then cooled to about 65 C. is about one-half hour. This is found to give the best results when finely divided phosphorus pentoxide is used. If coarse phosphorus pentoxide is used, it is added at about 70 C. and the temperature rises slowly to approximately C. in about twenty minutes. At

this point, there is a tendency for the temperature to rise; but this rise is checked by circulating cool water in the jacket. The maximum temperature obtained in this way is approximately 100 to C. The reaction mixture is allowed to remain at this temperature for several minutes and is then allowed to cool to about 65 C. This takes approximately another twenty minutes. A dark, reddish-brown viscous liquid is obtained, comprising essentially esters of phosphoric acid, the proportion of combinedphosphorus being high.

This reaction product may be employed without being further treated, or it may-be treated with a suitable inorganic or organic alkaline material. For example, 12% to 15% of finely powdered anhydrous sodium carbonate (which is in excess of that theoretically required to completely neutralize the phosphate radical) is added, with stirring, to the above reaction product at about 50 C. The temperature rises to'65 or 70 C. and after the foam which forms disappears, the product is heated at 70 to 75 C. for thirty minutes. Uncombined sodium carbonate is removed by filtering with the ordinary filter press, centrifuging, or the like. In place of dry sodium carbonate, approximately 21 parts of ammonia gas may be introduced by bubbling the same through the mixture. Products prepared as described above, whether treated with an alkaline material as described above or not, are potent as antioxidants.

Example C 71 parts of mono-stearin, prepared in a suitable manner for example, from glycerine and commercial stearic acid, are treated with 54 parts of pyro-phosphoric acid at a temperature at which the monostearine is in a melted condition. The temperature rises spontaneously to about 85 C. in a few minutes. Thereafter, the product is heated to about to C. and retained at that temperature for one-half to three-quarters of an hour. The product so pro duced is essentially a glycerol ester .of pyrophosphoric acid in which one hydroxy group of the glycerine is replaced by a stearyl radical, a long chain radical of definite lipophile characteristics. This product may be used as prepared above, or it may be treated with an anti-acid substance of suitable character such as sodium carbonate, for example.

Example D Pure, fresh cod liver oil is treated by the addition of approximately A to /z% of the reaction products of Example B. So treated, the cod liver oil will keep for a very much longer period of time than cod liver oil not so treated. Furthermore, the vitamin A content of the cod liver oil will remain unaffected after comparatively long periods of storage. Even if the oil is contaminated with known oxidation catalysts such as copper, iron, nickel, and other common metal contaminants, our antioxidants exert their action and retard oxidation.

The particular phosphoric acid esters employed in accordance with our present invention are innocuous even if present in relatively high concentrations. This enables us to employ such phosphoric acid esters as oxidation inhibitors in substantially any type of organic substances which in themselves are employed as food or which are employed as ingredients of foods. When employed in proportions of one-half percent or less and up to based upon the oleaginous constituent of the product treated, remarkable and valuable properties are imparted to many types of materials, enabling them to be kept for much longer periods of time without suffering the type of deterioration usually accompanying oxidation.

Example E Fresh, pure lard is treated by the addition thereto of one-half percent. of a product prepared by treating a diglyceride (glycerol esterified with commercial stearic acid), with a proportion of phosphorus pentoxide, removing the phosphorus pentoxide and adhering organic matter, and then esterifying the remaining material with phosphorus pentoxide to form the ester. The reaction product may be used with good results in its acid condition or partially neutralized with sodium bicarbonate. In treating the lard, it is advisable that a thorough dispersion be obtained, and this is readily done by first mixing the ester with a portion of the lard and then incorporating this mixture into the balance of the lard. The preferred method, however, is to incorporate the ester while the lard is in a melted condition, employing suitable agitation, and then spreading the treated lard out on a so-called lard roll from which it is scraped in the customary manner. The lard so treated can be stored for much longer periods of time and with less precautions against spoilage than lard not so treated. Example F To 60 parts of cottonseed oil, 40 parts of the ester prepared as described in Example C are added with agitation and in a suitable manner to prepare a thoroughly. homogeneous mixture. This product will keep for long periods of time, the ester being of oleaginous character will not readily separate out, or if there should be any slight separation, simple mixing will restore homogeneity. The product may be used as such,

but preferably is adapted for treating other substances having an oleaginous constituent nor mally subject to oxidation. This affords a suitable vehicle for the treatment of substances with relatively'small amounts of an antioxidant.

Our improved antioxidants have an advantage in being readily soluble or miscible with oily or fatty substances. Stock solutions or mixtures are therefore readily made up and easily handled containing a relatively large proportion of the antioxidant, for example, to

Among the classes of substances, the keeping qualities of which can be enhanced very satisfactorily in accordance with our present invention, are substantially all of the oils and fats of commerce, such as cod liver oil, halibut liver 'oil, sardine oil, salmon oil, and other fish oils, cotton seed oil, corn oil, peanut oil, sesame oil, rapeseed oil, lard, vegetable shortenings, and other animal and vegetable oils and fats. Many of these oils and fats are employed alone, while some of them are also employed in various ways in the food and other industries, as for example, in the form of emulsions in which they are in contact with moisture, which is known to cause oxidation to occur much more readily, while at other times these materials are mixed or associated with i'arinaceous or vegetable substances. Examples of such substances are the residues of oil extraction from'seeds, or animal fat renderings employed as cattle food and for other purposes, nuts which are often coated ortreated with oils, besides having an oil content of their own, dried milk powders, baked flour products of all kinds such as certain types of biscuits, crackers, and the like, which are kept for comparatively long periods of time, potato chips, and the like. Flour preparations of various kinds, such as biscuit or cake flours, containing proteins as in milk pow der, a shortening ingredient, etc., can be protected by the use of our antioxidant substances. In all materials of the character named, spoilage of a type promoted by spontaneous oxidation is definitely retarded by the use of phosphoric acid esters of the type described, and in some cases substantially complete inhibition for comparatively long periods is efiected.

When introducing our improved antioxidants into such materials, for example, as dried milk powder, the antioxidant may be dispersed first in the liquid milk so that when dried, it will be dispersed intimately throughout the milk powder. This procedure also protects the constituents of the milk against oxidation during the drying oper ation.

In general, all glycerine derivatives consisting essentially of relatively high molecular weight fatty acid monoand/or di-glycerides in which the hydroxy group or groups are esterified with a derivative of phosphorus capable of producing an ester of phosphoric acid are potent for our purposes. Furthermore, those reaction products which are produced by utilizing a pretreatment step, as shown illustratively in Example B, are more satisfactory than those in which a pretreatment step is not employed.

The substances which we employ are essentially phosphoric acid esters of glycerol esterified with relatively high molecular weight fatty acid radicals. Although carefully controlled laboratory processes can be employed which will produce a relatively pure substance of known and definite chemical structure, the reaction products produced commercially are in general mixtures of various phosphoric esters. Various amounts of phosphorus may be incorporated, even as much as 28%, based on weight and calculated as P205, when the pretreatment step is employed. The use of the pretreatment step makes the product more reactive in the esterifying step, and the amount of combined phosphorus can be increased. This increased amount of phosphorus does not decrease the antioxidant action of the product, but on the contrary enhances it. Besides the specific examples given, manyother reaction products may be employed with very good results.

Extensive additional examples of antioxidant substances employable in accordance with our invention appear unnecessary to a full understanding of the invention. It may be pointed out, however, that other methods of producing the prod- 5 ucts may be employed.

Example G to decompose the excess unreacted POC13 and also to remove the remaining chloride from the reacted POCl3. The product may then be treated with alcoholic potash in suitable amounts. The inorganic salts may be precipitated with petroleum ether. Excess solvents are then removed under vacuum.

Example H 7 parts of monostearine dissolved in 35 parts of pyridine are added to 12 parts of POCla dissolved in 50 parts of acetone and the mixture allowed to stand until the reaction goes to completion. The product is then washed with water and common salt.

Products consisting substantially of monoglycerides, or substantially diglycerides treated with a derivative of phosphorus capable of forming an ester of phosphoric acid, may be produced and used to good advantage. The diglycei'ide esters are valuable in certain instances, since in general they are soluble in oils and fats in at least relatively large proportions.

In treating a product consisting essentially of diglycerides, the fatty acid radicals of which are 40 of a type found in common oils and fats, for example having a relatively large content of fatty acids with 18 carbon atoms in the molecular structure, about 450 parts of the diglycerides are pretreated with 20 parts of fine P205, at about 125 C. for one-half hour, and then centrifuged. The remaining clear product is then reacted with about 12% of its weight of P205, at a temperature of '90 to 100 C. When the pretreatment step is not employed, 700 parts of the diglyceride are treated with 100 parts of P205 at about 130 C. for three quarters of an hour. The product made by either method may be treated with sodium carbonate or other innocuous alkali. In any event,

any of these products are quite freely soluble in oleaginous media. v

Products consisting essentially of monoglycerides of the same types of fatty acids may be given substantially the same treatment. In general, however, it is desirable to employ a considerably htigher percentage of P205 in the pretreatment s ep.

Our invention is by no means limited in the character of the fatty acid radical present in the molecule. Fatty acids which are themselves subject to oxidation may be employed such as the unsaturated fatty acids like oleic acid, linolenic or linoleic acid, for example. As sources of fatty acids, we may employ any of the usual oils and fats, such as cotton seed oil, corn oil, soy bean oil, lard, fish oils, like sardine oil, castor oil, etc. For best results, the fatty acid content of the oil or fat used should be of relatively high molecular weight, as previously stated, say from C8 up.

Considerable latitude is permissible in treating 75 any of the phosphoric acid reaction products with alkaline materials. At least a portion of the alkaline material functions to replace hydrogen in the phosphate radical. The products treated with alkali are in themselves more resistant to decomposition than those not so treated. The acid salts are active as antioxidants and in themselves are stable, with the result that the acid salts formed by partial neutralizationof the phosphate radical are suitable for some purposes for which the more acid, or more alkaline, products are not so satisfactory. While the partially neutralized products, for example the acid salts, are suitable, the ammonium salts, on the other hand, are better than the sodium salts.

The anti-acid substances employed, in addition to ammonia, etc., may be alkali metal carbonates, salts of fatty acids such as sodium stearate, calcium stearate, sodium acetate, alkali metal hydroxides, such as sodium hydroxide, alkali carbonates such as sodium carbonate, and other alkaline and potentially alkaline substances, etc.

It should be remembered that, instead of phosphorus pentoxide as the esterifying agent, we may employ any derivative of phosphorus capable of forming the ester. For example, by modifying the manner of treatment accordingly, we may use pyrophosphoric acid, phosphorus halides, ethyl meta-phosphates, phosphorus oxychloride, etc., and produce substances suitable for use as antioxidants in accordance with our invention.

It should be understood that the manner of employing antioxidant substances of our present invention, the amount used, and the degree of resistance to oxidation imparted depends upon a number of factors which it is unnecessary to.

set out in detail. For example, the antioxidant is readily introduced into an oil or fat in suitable proportions without special treatment. Should it be necessary to introduce the antioxidant substances into a material having other constitutents besides the oily or fatty constituent, the antioxidant can in general be incorporated by first introducing it into the oil or fat and then utilizing the oil or fat in the production of the final composition. In those cases where the oil or fat is raised to a relatively high temperature, it is advisable in some cases first to produce the article and then separately to incorporate the antioxidant.

Due to the innocuous character of our substances, they may, in general, be allowed to remain in the oils, fats, etc., even when ingested as food, without any special treatment.

Wherever the terms relatively long chain and relatively high molecular weight are employed herein, they will be understood to cover at least eight carbon atoms.

What we claim as new and desire to protect by Letters Patent of the United States is:

1. The method of retarding the oxidation of organic materials having an oleaginous constituent normally subject to oxidation, which comprises incorporating in said materials a nonneutralized or partially neutralized phosphoric acid ester of glycerol, wherein the hydrogen of at least one hydroxy group of the glycerol is replaced by a relatively long chain non-nitrogenous aliphatic lipophile radical.

2. The method of retarding the oxidation of organic materials having an oleaginous constituent normally subject to oxidation,- which comprises incorporating in said materials a nonneutralized or partially neutralized non-nitrogenous phosphoric acid ester of glycerol, wherein at least one hydroxy group of the glycerol is esterified with a relatively high molecular weight aliphatic organic carboxylic acid.

3. The method of retarding the oxidation of organic materials having an oleaginous constitu- 5 cut normally subject to oxidation, which comprises incorporating in said materials a nonneutralized or partially neutralized non-nitrogenous phosphoric acid ester of glycerol, wherein at least one hydroxy group of the glycerol is esterified with a relatively high molecular weight fatty acid.

4. The method of retarding oxidation of oils and fats in the'presence of oxidation catalysts such as heavy metals, which comprises introducing into said materials a proportion of a nonneutralized or partially neutralized ester in the form of a non-nitrogenous reaction product of a relatively high molecular weight glyceride having an unesterfled glycerol hydroxy group and a derivative of phosphorus capable of forming an ester of phosphoric acid.

5. The method of retarding oxidationot organic materials having an oleaginous constituent normally subject to oxidation, which comprises introducing into said materials a proportion of a non-neutralized or partially neutralized ester in the form of a non-nitrogenous reaction product of a relatively high molecular weight glyceride having an unesterifled glycerol hydroxy group 39 and a derivative of phosphorus capable of forming an ester of a phosphoric acid.

6. The method .of retarding oxidation of organic materials having an oleaginous constituent normally subject to oxidation, which comprises introducing into said materials a proportion of a non-neutralized or partially neutralized ester in the form of a non-nitrogenous reaction prodnot of a relatively high molecular weight glyceride having. at least one free glycerol hydroxy 40 group and phosphorus pentoxida '7. The method of retarding oxidation of ,or-

ganic materials having an oleaginous constituent normally subject to oxidation, which comprises introducing into said materials a proportion of an unneutralized or a partially neutralized ester of phosphoric acid formed by pretreating a relatively high molecular. weight glyceride having a free glycerol hydroxy group with phosphorus pentoxide, and then reacting the resulting prodnot with a derivative of phosphorus capable of forming an ester of a phosphoric acid.

8. The method or retarding oxidation oforganic materials having an oleaginous constituent normally subject to omdation, which comprises introducing into said materials a proportion of an unneutralized or a partially neutralized ester of phosphoric acid formed by pretreating a relatively high molecular weight glyceride having a free glycerol hydroxy group with phosphorus having incorporated therein a proportion of an ester in the form of a non-nitrogenous reaction product of a relatively high molecular weight 0 glyceride having at least one glycerol hydroxy group and a derivative of phosphorus capable of forming an ester of a phosphoric acid.

10. A substantially dry product comprising oleaginous material normally subject to oxidation, having incorporated therein a proportion of an ester in the form of a reaction product of a relatively high molecular weight glyceride having at least one glycerol hydroxy group and a derivative of phosphorus capable of forming an ester of a phosphoric acid, said ester being reacted with a neutralizing agent.

11. A substantially dry product comprising a triglyceride normally subject to oxidation having incorporated therein a proportion of an ester in 'the form of a reaction product of a relatively high molecular weight glyceride having at least one glycerol hydroxy group and a derivative of phosphorus capable of forming an ester of a phosphoric acid, said reaction product being neutralized, at least in part, by an anti-acid substance.

12. A substantially dry product comprising oleaginous material of a character present in animal and vegetable oils and fats of commerce normally subject to oxidation, having incorporated therein a phosphoric acid ester of glycerol wherein the hydrogen of at least one hydroxy group of the glycerol is replaced by a relatively long chain, non-nitrogenous aliphatic lipophile radical. 4

13. A substantially dry product comprising oleaginous material of a character present in animal and vegetable oils and fats of commerce normally subject to oxidation, having incorporated therein a non-nitrogenous phosphoric acid ester of glycerol wherein at least one hydroxy group of the glycerol is esterified with a relatively high molecular weight aliphatic organic carboxylic acid.

14. A substantially dry product comprising oleaginous material of a character present in animal and vegetable oils and fats of commerce normally subject to oxidation, having incorporated therein a non-nitrogenous phosphoric acid ester of glycerol wherein at least one hydroxy group of the glycerol isjesterified with a relatively high molecular weight fatty acid.

15. The composition defined in claim 14, wherein said phosphoric acid ester is in the form of of glycerol, esterified with a ,fatty acid contain- I ing at least eight carbon atoms.

18. The method of retarding oxidation of organic materials having an oleaginous constituent normally subject to oxidation, which comprises incorporating in said materials an unneutralized or a partially neutralized ester of phosphoric acid prepared by treating a relatively high molecular weight'fatty acid diglyceride with phosphorus pentoxide, removing the phosphorus pentoxide, and thenesterifying the resulting diglyceride substance with phosphorus pentoxide.

ALBERT K. EPSTEIN. BENJAMIN R.