US2524056A - Process for bleaching compounds of fatty acids or the like - Google Patents

Description

Patented Oct. 3, 1950 UNITED STATES PROCESS FOR BLEACHING COMPOUNDS OF FATTY ACIDS OR THE LIKE Vagn Jespersen, Copenhagen, Denmark No Drawing. Application March 15, 1947, Serial No. 735,021

6 Claims. 1

This invention relates generally to the bleaching of fats and the like. More particularly, the instant invention pertains to an improved process for bleaching such compounds with relatively small amounts of hydrogen peroxide at temperatures approximating the boiling point of water.

= In its broad aspect, my novel bleaching process involves forming a two layer system comprising water and the fatty substance to be bleached, adding relatively concentrated aqueous hydrogen peroxide thereto, and heating said system to reflux the aqueous portion thereof through the fatty portion thereof until bleaching of the latter occurs. Advantageously, the foregoing process not only permits using hydrogen peroxide in the order of 0.1 per cent to 0.5 per cent H202 (by weight of fatty substance), but also results in rapid bleachinga quarter hour generally being sunicient to adequately bleach the fatty substance.

Accordingly, it is the principal object of my invention to provide a method for bleaching fats, oils, free fatty acids, which are substantially immiscible in and of lower specific gravity than water and compounds thereof, which method is rapid and only requires in the order of 0.5 per cent H202 or less, calculated on the weight of the material being bleached.

It is another object of the present invention to provide a hydrogen peroxide bleaching process 5 which eliminates the step of washing the fatty substance subsequent to the bleaching operation.

Yet another object of my invention is to provide a bleaching process for fatty acids and compounds thereof, wherein suspended impurities are deterged from the fatty charge during the bleachiing operation by refluxing water therethrough.

These and other objects will be apparent from a consideration of the following specification and claims, and the nature of the process disclosed therein.

In order that the nature of my invention may be more fully understood, the following examples are provided which, for purposes of clarity in exposition and completeness in guiding these desiring to use my invention, are made specific in detail. It is strictly to be understood, however, that I do not limit my invention to any of said details, except insofar as they are expressly included in the appended claims.

Example I Brown grease is heated until melted, after which approximately ten per cent (by weight) of water is added. The mixture is then heatedto about 65 ,centigrade, at which temperature 0.44 per cent by weight of aqueous hydrogen peroxide containing H202 is introduced to the system. Sufiicient heat is then applied to boil the water thereby achieving a high degree of agitation with in the system. The bleaching action produces a characteristic surface frothing which grows in intensity as the water is brought to a boil. Conversely, as the bleaching agent is expended, the surface frothing abates. Accordingly, when the surface of the grease becomes comparatively quiet, the bleaching may be considered complete. In general it requires about 12 minutes to bleach a brown grease from an initial F. A. C. colorof 39 to an F. A. C. color of 31;

Example II Approximately, 3500 pounds of fish oil and 350 pounds of water are placed in an open kettle. Sufficient heat is then added to the contents of the kettle to raise their temperature to approxi mately oentigrade. At this temperature the water and oil separate into two more or less distinct strata, with the water at the bottom of the kettle. Approximately twelve pounds of aqueous 40 per cent hydrogen peroxideare then added. to

the H202, heat is added to the contents of the kettle in an amount sufficient to. cause the aquea ous stratum to boil. A temperature gradient normally exists between the top and bottom inter: faces of the fish oil by virtue of the type of apparratus (open kettle) employed, and preferablyis of a magnitude which insures'a temperature at the upper surface just under centigrade. Hence, as wet steam evolves from the watery lay-f er and passes up through the oil, it normally con-. denses just short of the upper surface of the fish oil. This condensed steam tends to form into water droplets which coalesce and work down through the oil. Accordingly, as further heat is applied to the water, a counter-flow of ascending wet steam and descendin condensate is set up a and maintained within the fish oil. This counterflow results in a violent internal agitation and hence an efficient distribution of the unused bleaching agent throughout the oil. Consequentj ly, the elapsed time for the total process generally need not be in excess of ten to twelve minutes. The foregoingprocess yields an edible bleached fish oil which is purged of mechanical impurities through the action of the descending water screen, stable against subsequent rancidity, and free from the objectionable sharp aftertaste metim s resent in oils and fats which have been bleached by other hydrogen peroxide processes.

A perusal of the foregoing examples demonstrates that my improved hydrogen peroxide bleachin process is both rapid and economical. n the other hand, suggested prior processes which bleach fatty compounds with hydrogen peroxide have been handicapped by their inability to combine small quantities of the bleaching agent (as compared to the total charge being processed) with rapid bleaching action. While it has previously been suggested to use concentrations of hydrogen peroxide of the order of 0.5 per cent, such prior processes are stated to require at least several hours, and often as long as several days for bleaching. The salient disadvantage of such an extended period of processing, other than from the standpoint of economy, is the increased susceptibility of the fatty matter to development of rancidity, due to oxidation or other chemical reactions. Even where the bleached matter does not become rancid during bleaching, rancidity may develop at any future time, since the long heating tends to impair the chemical stability of the fat or oil.

Attempts have also been made to reduce the bleaching time through the media of mechanical agitation used in combination with larger proportions of H202. It is apparent that such methods have definite commercial limitations, since the use of larger amounts of H202 necessarily increases the cost unduly.

Regardless of the concentration of hydrogen peroxide which is used or the length of time required for the bleaching operation, it is necessary to remove any residual hydrogen peroxide if the bleached material is to be used as a nutritive. Where large proportions of hydrogen \peroxide are used, the thoroughness with which the hydrogen peroxide is purged from the, fatty substance takes on increased significance,v since even a minute quantity of hydrogen peroxide imparts a sharp aftertaste to the fatty substance. While the washing operation customarily used to remove these traces of the bleach does not result in any significant loss of the fatty substance, it is nevertheless desirable to avoid this cleansing operation where possible. if only from the viewpoint of economy of operation.

In addition, the prior art teaches that hydrogen peroxide bleaching of fats must be \performed at temperatures lower than the boiling point of water, and that as little water as possible should be used. The latter teaching proceeds on the theory that the water tends to isolate the H202 from the fat-like substances and thereby reduces the efficiency of the over-all chemical reaction.

Now I have discovered that, contrary to the teachings of the prior art, the use of a relatively large quantity of water refluxing through the charge achieves unsuspected economy, efficiency and rapidity of bleaching.

The initial step in my process preferably comprises placing the unbleached fatty matter and the requisite amount of water within a jacketed kettle open to the atmosphere. While the e act quantity of water to be added is largely governed by the typeof apparatus used and the duration of the bleaching operation, I have found that an amount approximatin ten per cent of the weight of the fatty matter is generally sufficient. The water and fatty substances are substantiall immiscible and hence separate into two more or less distinct, strata, with the water stratu ly b neath'the stratum of fatty matter by virtue of its greater specific gravity. Should the fat-like matter be a solid at ordinary temperatures, it may be either melted prior to placing it within the kettle or else melted within the kettle. In any event, after the fatty matter and the water are placed within the kettle sufficient heat is added to the charge to bring it up to some intermediate temperature, as for example 65 centigrade.

Following this initial heating, the hydrogen peroxide is added, preferably to the fatty matter, in order to cause the peroxide to percolate therethrough before reaching the aqueous layer beneath. My experiments indicate, moreover, that addition of one pound of a 40 per cent hydrogen peroxide solution to the fatty matterto cite an exampleproduces a bleaching action which is superior to that obtained by adding two pounds of a 20 per cent hydrogen peroxide solution to an identical charge. Since the bleaching effect obtained is afunction of the concentration of H202 in contact .with the molecules being bleached (other factors being constant), the foregoing example apparently indicates that best results are achieved when the hydrogen peroxide is highly concentrated. Actually, however, when the concentration of the hydrogen peroxide solution approaches 60 per cent, the chemical reactivity of the solution becomes so great as to pose difficult problems of handling and storing the same. Also, the use of absolute hydrogen peroxide of ex cessively high concentration often adversely affects the hardening properties and taste of the bleached :product. This effect is especially to be avoided in the processing of edible fats or other foodstuffs. Actual performance indicates, however, that a highly satisfactory balance between the foregoing and conflicting factors is obtained by adding to the fatty matter an aqueous solution containing from about 30 per cent to about 40 per cent by weight of hydrogen peroxide.

During and subsequent to the adding of the bleaching agent to the fatty matter, the charge is further heated to and maintained at the ebullition temperature of the aqueous layer. The comparatively large amount of water present establishes the boiling point of this aqueous layer as the maximum temperature that may be obtained throughout the total charge; hence the application of heat may be most rapid without overheating or scorching the fatty matter. For example, I have found that my process can be very conveniently conducted by circulating saturated steam at approximately five atmospheres centigrade) within the jacket of the kettle. Where the heat input is too rapid and/or the quantity of bleaching agent is large it is sometimes necessary to reduce the surface frothing,

particularly during the latter stages of the process, by means of a cold water spray played over the top of the kettle.

As pointed out above, most of the hydrogen peroxide which is added to the kettle apparently initiall remains within the fatty substance, rather than passing into the watery layer. When the hot steam which evolves from the boiling water passes upward through the fatty substance and the bleaching agent therein, the action of the heat and the violent internalagitation of the refluxing results in very efficient dispersion of the H202 throughout the fatty substance. In the open kettle method preferably used, the steam leaving the aqueous underlayer is of a low quality; hence, as it rises through the fatty matter it readily condenses, provided the temperature gradient which exist between the two interfaces of the fatty matter is appropriate. The desired temperature .--.g ra dient is obtained through the proper design of the apparatus, control of the heatinput, proper quantity of charge, etc. Upon condensing, the water droplets, because of their greater specific gravity, descend through the fatty matter, and

hence a reflux action, orcounterflow between the ascending wet steam and the descending condensed steam is set up within the system.

The reflux action also effectively removes sediment and other undesirable mechanical impurities from the fatty matter. Apparently the violent internal agitation of the fatty matter facilitates wetting of the suspended impurities by the water and steam. These wetted impurities are then picked up by the descending water screen and carried down into the aqueous stratum.

In actual practice, it has been found that between 0.1 per cent and 0.5 per cent of the H202 (by weight of the fat-like substance) is sufiicient to adequately bleach the fat-like substance within a quarter hour. Generally speaking, the lower limits of the above range may be used when brown or yellow coloring bodies in the fat are to be bleached. Red, and green pigments usually require a somewhat greater proportion of hydrogen peroxide, but less than 0.5 per cent hydrogen peroxide invariably yields appreciable bleaching. For example, using my novel process a very dark green oil may be rapidly bleached with a quantity of hydrogen peroxide approximating 0.5 per cent of the weight of the oil. This efiicient bleaching of green pigments is especially advantageous, since the oil and fat industr is occasionally beset by large quantities of soya oil and other vegetable oils having a green coloring. Heretofore conventional bleaching methods such as fullers earth filtration have generally proven inadequate in processing such highly colored oils.

Since my improved process uses less H202 than was the case heretofore, it is correspondingly less likely that any unreacted H202 will remain in the bleached material. The reflux feature of my invention is effective in removing any trace of H202 from the bleached fatty substance. Hence, fat-like substances which are bleached in the foregoing manner need not be subjected to a Washing operation subsequent to the bleaching operation, as is the case in conventional peroxide bleaching processes. Nevertheless, fatty matter bleached by my novel process possesses far less residual peroxide than substances which have been bleached conventionally. The products of my improved process are free from the sharp aftertaste which even a minute quantity of hydrogen peroxide imparts to fatty substances.

While my novel process employs temperatures higher than those used heretofore, the duration of the bleaching operation is so brief that the quality of the fat is not injured. For that reason, there is less rancidity in the products of my process than is ordinarily present in bleached fatty substances, and rancidity develops more slowly during storage.

From the foregoing specification, it will be ap- 16 v parent te- -thos'e'skilled in th'eart that I have invented and describedanew and improved method for bleaching fattyacids and compounds through the use of hydrogen peroxide. My invention not only results ina diminution of process-time and quantity of bleaching agent required, but also effectively'purges the bleached product both of unused bleaching agent and of mechanical impurities.

Having thus described my invention and in dicated its utility, I claim: l. A method of bleachin fats or the like which utilizesaquantity of water underlying said fats or the like which is sufficient to generate steam for at least ten minutes when boiled, said method comprising the steps of adding. aqueous hydrogen peroxide to said fats or the like, heating said hydrogen peroxide, said fats or the like, and said water until said water boils, and maintaining said boiling until said substances are adequately bleached-said hydrogen peroxide being of about 30 per cent to 40 per cent concentration and in an amount such that the quantity of H202 is between 0.1 per cent and 0.5 per cent of the weight of said fats or the like.

2. A method of bleaching fats or the like which are solid'at room temperature, in which steam rises through and condensed steam falls through said fats or the like, whereby hydrogen peroxide less than 0.5 per cent and greater than 0.1 per cent by weight of said fats or the like bleaches the same in approximately a quarter hour, said method comprising adding said hydrogen peroxide to said fats or the like, and heating said hydrogen peroxide, said fats or the like, and a quantity of water underlying the same to cause said water to boil.

3. The method of bleaching fats or the like with small quantities of hydrogen peroxide, in which rising and falling countercurrents of steam and condensate respectively impregnate said hydrogen peroxide throughout the mass of said fats or the like, said method comprisin boiling a mass of water underlying said fats o the like admixed with H202 until said fats or the like are sufiiciently bleached by said H202-said H202 being in an amount between 0.1 per cent and 0.5 per cent of the Weight of said fats or the like.

4. The method of bleaching fats or the like which have a specific gravity less than that of water and which are substantially immiscible therewith, with small quantities of H202, said method comprising: heating a quantity of water underlying said fats or the like to approximately 65 centigrade, said quantity of water being about ten per cent of the weight of said fats or the like; adding aqueous hydrogen peroxide of about 30 per cent to about 40 per cent H202 concentration. to said fats or the like in an amount such that the quantity of absolute H202 is between 0.1 per cent and 0.5 per cent of the Weight of said fats or the like; further heating said water until boiling commences; and maintaining said water at its boiling temperature until said fats or the like are sufiiciently bleached.

5. The method of bleaching fish oil, which consists of heating said fish oil with approximately ten per cent by weight of water to approximately 65 centigrade, introducing aqueous hydrogen peroxide of about 40 per cent H202 concentration to said oil in an amount such that the quantity of H202 is about 0.2 per cent of the weight of said oil, heating the aggregate until the water boils, and maintaining said boiling until said oil is sufficiently bleachedsaid bleachingrequiring approximately a quarter hour.

v.6. The method of bleaching brown grease or the like, which comprises heating said grease with approximately ten per cent by weight of 0 .water to at least that temperature necessary to melt said grease, addin to said grease approximately 0.4 per cent H202 in the form of an' aqueous 30 per cent solution thereof, and further heating the aggregate until the watery layer thereby formed boils, and maintaining said boiling until said grease is sufficiently bleached.

VAGN JESPERSEN.

8 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 446,117 Race Feb. 10, 1891 619,020 Henderson Feb. 7, "1899 2,204,109 Thurman June 11, 1940 2,221,140 Jahrstorfer et a1. Nov. 12, 1940 FOREIGN PATENTS Number Country Date 595,126 Germany Mar. 27, 1932

Claims (1)

1. A METHOD OF BLEACHING FATS OR THE LIKE WHICH UTILIZES A QUANTITY OF WATER UNDERLYING SAID FATS OR THE LIKE WHICH IS SUFFICIENT TO GENERATE STREAM FOR AT LEAST TEN MINUTES WHEN BOILED, SAID METHOD COMPRISING THE STEPS OF ADDING AQUEOUS HYDROGEN PEROXIDE TO SAID FATS OR THE LIKE, HEATING SAID HYDROGEN PEROXIDE, SAID FATS OR THE LIKE, AND SAID WATER UNTIL SAID WATER BOILS, AND MAINTAINING SAID BOILING UNTIL SAID SUBSTANCES ARE ADEQUATELY BLEACHED-SAID HYDROGEN PEROXIDE BEING OR ABOUT 30 PER CENT TO 40 PERCENT CONCENTRATION AND IN AN AMOUNT SUCH THAT THE QUANTITY OF H2O2 IS BETWEEN 0.1 PER CENT AND 0.5 PER CENT OF THE WEIGHT OF SAID FATS OR THE LIKE.

Images