US2029722A - Method of refining fats and oils - Google Patents

Description

' Patented Feb. 4,1936

- UNITED STATES,-

2,029,722 mrrnon or un -name Mrs Ann oms 'Vernon Jersey, Cleveland, Ohio, ass ignor' to S. M. A. Corporation, Cleveland, Ohio, a corpora-- tion of Ohio No Drawing, Application June 7, 1933,.

sol-a m. 674,777

Claims. (01. 87-12) This invention relates to atmethod for remov ing'free fatty acids from fats and oilscontaining valuable substances subject to destruction by oxidation or decomposition. More particularly,

5 the invention relates to a newv and improved method for removing such fatty acids,v either 2o extracted from sweet potatoes and from pump- 7 kins, and in other sources., However, since the sodium hydroxide-although other alkalies, such proportion of carotene in these natural sources. israther low, in proportion to the amount of 3 vehicle present, it isimportant to preserve .as' much of the carotene as possible. Furthermore,

the hydrocarbon, carotene, is'very susceptible to oxidation, and serious losses in the amount of pi ment realized in the finished product are experienced due to- -this oxidation. The same, is true of other natural pigments, such as the readily oxidizable xanthophyll, found in egg yolk oil, and the pigment lycopin, found in-tomato pulp oil, since these pigments are, similarly to carotene, subject to partial destruction during 35 reflning of the oils which contain them. A process by which the oil or fat carrying these fatsoluble pigments, can be refined so as to remove objectionable ingredents, particularly free fatty acids, with ut destroying morethana minimum amount of the pigments present, is needed and the present invention contemplates providing such a method.

It is, accordingly, an object-of the present inyention to provide a process of refining fats and It is known that free fatty acids, inparticular,

are unpalatable in a fatty substance when is inoils containing oxidizable pigment-like substances. without harmiully affecting these substances" ducing the proportional carotene naturally prestended to be taken into the alimentary tract and cause digestive disturbances when present in gRater amounts than about 5%. Consequently,

it has been attempted to remove these free fatty acids from oils containing carotene in order that the oils might serve as a source of vitamin Ain the human system. Suchmethods as have harptofore been used to effect this, haveresulted in the destruction of a portion of the carotene content of the oil, so that a substantial amount of 10 the pigment is lost and e'xerts no therapeutic effect; In the presentmethod, however, it is possible to conduct the purification so that substantially all of the readily oxidizable pigment will be 'retained' in the oil. 1 In accordance with the improved method, the

oil obtained from a natural source, e. g carrot oil expressed from air-dried carrot pulp, containing free fatty acids often in amount exceeding 5% of the oil,-is treated with an aqueous solution of a soluble alkaline material, preferably as sodium carbonate, etc., may be used to neutralize these free acids. The alkali is added slowly to prevent rise of temperature, preferably at such a rate that the heat of reaction is dissipated, as fast as generated, by the cooling water in the jacket or coils surrounding the reaction vessel. A temperature below 25? C. and, if conditions-permit, nearer 20 C. desirable for fats that are liquid at this temperature; somewhat higher temperatures are required for fats having higher melting points, .in order to maintain them in liquid condition. This comparatively low temperature, in most cases not far removed from ordinary room temperature, prevents oxidation or decomposition. of the pigment.

, and also "prevents emulsiflcation of the oil with the soap which is formed by the neutralizationf Of course, the temperature must be high enough 40 so that thefatty material does not solidify but remains liquid throughout the operation. Fur: ther to prevent emulsification, which would result in loss of-some of the fator oil,- the necessary agitation to mix the alkali and fatty material'is conducted slowly so as to produce a uni- -form distribution of the alkali, butxnot fast enough to produce any emulsiflcation of the fat, with the soap. Such gentle, stirring of the reaction mass also" avoids incorporating air into the fat; which would have a tendency to promote" oxidation of the pigment After all of the alkli has been added, agitation is continued: for about twenty minutes, 'or'even longer,v to permit completion lot the reaction. to

is found to be most 30.

' 'the calculated amount or 'sodii'un hydroxide re- The amount of alkali added is closely regulated to correspond with the calculated or theoretical amount required 'to neutralize the determined free fatty acid content. An excess may be used, say to the extent 'of 5 or but it has been found that an excess of alkali results in a lower yield of refined oil and also. causes the destruction of some of the pigment which it is an object of the present method to preserve. Consequently, 10 a slight excess of alkali may be used to insure completion of the reaction, but such excess should be carefully controlled and preferably kept down to a minimum.

The concentration of alkali used to neutralize the free fatty acids also has an importantbear- .ing on the preservation of the carotene or other valuable pigments present in the oil. Thus, when a very dilute alkali solution is used, containing a large amount of water, emulsions are formed which areobiectionable due to the difllculty of separating oil therefrom, and it is observed that this emulsification also results in destruction of color, 1. e., pigment. .Ihis destruction of color results even when the amount of water used is reduced to a point where emulsions do not readily form, for example when the alkali is added in a concentration of 10% (10 parts of alakli to 90 parts of water). However, the destruction of pigment becomes less as the amount of water used to dissolve the alkali is reduced and may holds true up to a certain point, where anoth phenomenon occurs, namely, failure of the soap to separate sharply from the fat after completion .of the reaction; or in technical terms, the mixture fails to break,- This condition develops when the conce'ntratidn of alkali in, water is in' the nei hborhood of 50% and constitutes one limitation on the strength of alkali which may be used. In general, it may be said that recovery of a refined oil of good color may be achieved by the use of alkali solutions co'ntainingeven as little as .8% sodium hydroxide and from this minimum strength up to concentrations in the neighborhood of a point where the soap and fatty material fail to break, .For best results with the least destruction of color,'i-. e., pigment material, an alkali solution containing 14-20% of sodium hydroxide should be used.

After completion of the neutralization, the mixture of hydrolyzed fat and resulting soap is warmed to'a temperature of 50-60 0., depending on the stability of the pigment or pigments or other oxidizable material present in. the

. oil. At "the same time, the agitator or other 55 mixing means is stopped and the mass is permitted to stand and separate into a clear up'per layer of oil and a bottom layer of soap. when the mixture has thus stratified, the clear layer of oil may be decanted oil, or the entire mass may be run ofl into a solid bowl centrifuge to effect separation, or the mass may be clarified to separate .the'solid soap from theclear liquid fat.

I Any residue of soap remaining dissolved in'the oil is removed by well known methods. as by washingwithwater.

J As a practical illustration, but in no sense of limitation, of the new process, the following is given: Carrot oil or'other fattymaterial'inthe amount of 500 pounds is-placed in a suitable tank 70 and sodium hydroxide is run in to neutralize the free fatty acids. A titration indicates afatty acid content of. 6.5%, calculated m oleic acid, and

quired to neutralize this of free fatty 7" acids in the batch is 4.6 5.0 pounds the 011 01 me has been. presrvedflespitd;

readily oxidizable nature of these pigments.

of sodium hydroxide having a purity of 97% (a small excess) is dissolved in 3 gallons of water and, after cooling, is slowly added to the fat which has previously been brought to a temperature of "20 C. The temperature is kept near this point 5 by means of cooling water in a coil or jacket surrounding the tank until neutralization has been completed. The contents of the tank are slowly agitated during the process until the same is completed, whereupon agitation is stopped and the 10 mixture is brought to a temperature of 50-60 C. Separation of oil and soap may then'be carried out by any of the above mentioned procedures.

The method described in the foregoing example is applicable to fats or oils containing not ;over 15 about 10% of free fatty acids, although this value is not'fixed, it being possible to treat fatty materials containing slightly greater amounts of the free acids, say 11 or 12%, in this manner, However, where the proportion of free fatty acids 20.

present greatly exceeds this value, the procedure must be modified. Where the unrefined material contains up to 50% or more of free fatty acids, the large quantity of soap formed by the neutralization emulsifies theentire reaction mass and an 25 effective separation of soap solution and refined oil cannot be brought about. For this reason it is necessary to proceed by stages, adding in the first step only sufficient alkaline material to combine with about 10% of the oil as free fatty acid. Upon neutralization of this amount, the resulting soap is separated from the oil and an additional 10%, or thereabout, of alkaline material, is mixed with the oil. After another separation of formed soap, a further neutralization is effected and this 3 procedure of alternate neutralization and separation is continued until all of the free fatty acids have been removed from the oil. In this way, the amountof soap present at any time is not sufilcient' to emulsify the oil and separation by \40 stratification or otherwise can be conducted. An

oil containing 20 or 30% or more of free'fatty 'acids can be neutralized by this procedure.

While it is known that readily oxidizable substances, such as plant pigments or vitamins, may be protected from oxidation either by establishing a vacuum or by placing the material in an at mosphere of nitrogen or-other inert gas, these expedients are not applicable to a process of refining oils. In the process of removing free fatty acids from an oil containing oxidizable sub stances, such as carotene, both the action of the that no destructive action occurs. mcellent results are thus secured witha minimum ofcost and without the installation: of expensive gassing 'equlpment.-'. r7;

-dire/method results in a product containing practically'nc. free fatty acids, which are 'objectiqnablein iihledible oil, and in' which nearly all ofthe original pigment or-4 vitamin content (11f 'WhatI m. 1. The method of refining edible on; that are liquid at ordinary 'and'whichcou- 7 tain appreciable amounts of carotene and a substantial amount but not more than approximately 10% of free fatty acids which comprises adding an aqueous solution of an alkaline material to the oil in'the presence of air at substantially normal atmospheric pressure in an amount approximately just suflicient to combine with the free fatty acids present, slowly stirring the mixture to avoid inclusion of air, maintaining the temperature at about that of normal room temperature until neutralization is complete, warming the mixture to a temperature not greater than 60 0., allowing the mass to'stratify and separating the refined product.

2. The method of refining edible oils that are liquid at ordinary temperatures and which contain appreciable amounts of carotene and a substantial amount but not more than approximately 10% of free fatty acids which comprises adding an aqueous solution of an alkaline material to the oil in the presence of air at substantially normal atmospheric pressure in an amount approximately just sufiicient to neutralize all the free fatty acids present, gently mixing the ingredients of the mass to avoid aeration, maintaining the temperature at approximately 20 to 25 C. until neutralization is complete,'warming the mixture to a temperature between approximately and (3., allowing the mass to stratify and then separating the refined oil from the soap.

3. The method of refining edible oils that are liquid at ordinary temperatures and which contain appreciable amounts of carotene and a substantial amount but not more than approximately 10% of free fatty acids which comprises addin an aqueous alkaline solution containing about i 8% to 20% alkali in an amount not greatly exceeding that necessary to neutralize the free fatty acids present, agitating the mixture ,in the presence of air at substantially normal atmospheric pressureso as to mix the ingredients while minimizing contact with air, maintaining the tern,- perature at about 20 to 25 C. until neutralizationis complete, warming the to not a greater than 60 separating the soap and more than 60 0., allowing the mass to stratify and separating the carotene containing oil from the soap.

4. The method of refining palm oil which contains a substantial amount but not more than approximately 10 serving its carotene content which comprises adding an aqueous alkaline solution of about 14% to 20% alkali in approximately the amount necessary to neutralize the free fatty acidspresent. mixing the ingredients of the mass in the presence of air at substantially normal atmospheric pressure while minimizing the contact thereof with air, maintaining the temperature at about 20 to 25 C. until neutralization is complete, warming the mixture to not more than 60 C., allowing the mass to stratify and separating the carotene containing oil from the soap.

5. The method of removing free fatty acids from oils that are liquid at-ordinary temperatures and which contain appreciable amounts of carotene and substantially more than 10% free fatty acids while conserving the carotene content which comprises adding an aqueous alkaline solution in suflicient amount to react with approx imately 10% of the free'fatty ingredients in'the presence of air at substantially normal atmospheric pressure while minimizing contact with the air, dissipating the heat of reaction as lt is formed, heating the mixture after the reaction is completed to a temperature not 0., allowing the mass to stratify,

separating the soap formed from the oil, mixing an additional alkaline solution with the oil in an amount sufllcient to react with: not more than a 10% of the free fatty acids remaining, mixing the ingredients in the presence of air at normal atmospheric pressure while minimizing contact with the air, heating to a temperature of not more than 60 C. allowing repeating the operation. if necessary until the oil is substantially free from fatty acids.

' VERNON JERSEY.

the mass to stratify, v,

of free fatty acids while conacids, mixing the 7