US2269243A - Preparation of oils containing antioxidants - Google Patents

Description

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1.... mm.mia,x.r.,mrmn I Jakobsemmnneapoliablinnaa-lgnmtamstillatlonlroductalnc lloehestesymfaaeorporation of nelaware t No Application March 8, 1030, Serial No. ems r 5 Claims. (01.260424) rancidity. Oils containing a high content oi natural anti-oxidants are of value because of their good keeping qualities and also because they are excellent sources of anti-oxidants. Raw oils usually have an undesirable odor or taste.

Refining removes the taste etc., but also destroys the anti-oxidant. Also raw oils have the defect that they deposit non-volatile residues on the vaporizing surface of a high vacuum still which residues char and cause destruction of antioxidant and other diiiiculties such as gas formation and foaming. For these reasons high vacuumdistillation to recover anti-oxidant concentrates as described in application 201,018, filed April 8, 1938, in the name of Hickman and Baxter, has in many cases been attended with difiiculties.

Refining methods heretofore known have been found to cause substantial or complete destruction of the natural anti-oxidant content of the oil. For instance, conventional alkali refined oils are almost uniformly free of natural anti-v oxidant due to destruction caused by the refining treatment.

Examples of suitable organic acids are oxalic, tartaric, citric, maleic, adipic, fumaric, malonic,

' phthallc, gacetic, formic, butyric and benzoic acids. Polybasic and especially diand tri-basic organic acids and their hydroxylated derivatives are preferred. It is. best when using monobasicorganic acids to employ those having relatively low molecular weights. Examples of suitable weak inorganicacids are boric andortho phosphoric. The latter. represents the strongest inorganic acid which can be used and it causes rather substantial destruction unless used in small amounts at low temperatures.

Theacid is added to the oil in the solid or liquid state in which it naturally occurs or may be added to the oil in aqueous solution which is often preferred. The oil is then stirred or agitated and may be heated to elevated temperatures preferably below 100 C. The temperature employed will depend upon the particular acid selected. With the stronger acids lower temperatures will be found suitable. The impurities willthen have been coagulatedand/or precipitated .and' the oil can be decanted or directly filtered. Oil purified in this manner is found to be brighter in color than the crude oil and is free of substances which harmfully affect the subsequent distillation.

Stale oils or .oils which have been subjected to conventional refining treatment contain little or no anti-oxidant and should be avoided as source materials. Raw vegetable and animal oils contain relatively large amounts of anti-oxidant,

- particularly when freshly removed from the This invention has for its object to provide 'methods' for refining anti-oxidant-containing oils whereby substantial destruction of the antioxidant content is avoided. Another object is to provide a method for refining anti-oxidant-containing oils which results in a refinedv oil containing substantially its original anti-oxidant content and which is free of substances which cause charring and foaming during high vacuum distillation. Another object is to improve the art. Other objects will become apparent from the following description and claims.

These and other objects are accomplished in accordance with our invention which comprises subjecting the anti-oxidant containing oil to a refining treatment with an organic or weakinor-' 'ganic acid. Oils refined by treatment with these materials can be subjected to high vacuum distillation without dimeulty.

source, material. Examples of good. sources of anti-oxidant are corn oil, cottonseed, wheat germ, sesame, clove, thyme, and soy bean oils.

The distillation of the refined oil to concentrate the anti-oxidant is carried out by heating a thin film of the oil under a high vacuum and condensing vapors upon a condensing surface separated from the film by substantially unobstructed space. 1 The distance between the film and the condensing surface should be preferably short, such as 1-12 inches and preferably 1-6 inches, in which case the distillation is known as high vacuum. short path distillation. when this distance is less than the mean free path of the" residual gas molecules the distillation is molecular. Pressures below 1 mm. and preferably below .1 mm., such as .01-.0001 mm., are

HOW: I ever, it does not cause char-ring as do the stronger inorganic acids.

I The anti-oxidant'is obtained as a preliminary fractio which distills immediately after the free fatty a ds. It is desirable that the anti-oxidant fraction be collected as free of these fatty acids as possible since they have a pro-oxidant eflect. The temperature at which the anti-oxidant fraction is obtained varies considerably depending upon the pressure and other distillation conditions as well as upon the particular oil treated. The temperature is generally between 200 and 250 and particularly about 210 to 230 under molecular distillation conditions Further details of the distillation procedure etc. will be found in the Hickman and Baxter application referred to above.

When the refined oil is subjected to high vacuum distillation to conceri'trate'the anti-oxidant content thereof, the organic acids will bevolatilized in the early fractions and can thus be separated from the oil. The refined oil should preferably be degassed before introduction into the still but other treatment is ordinarily unoil which contains a natural anti-oxidant without simultaneously causing substantial destrucnecessary. Because of the possibility of collecting the organic acids as a first fraction, we prefer to employ these materials as refining agents. The inorganic acids are not volatile under the distillation conditions and, therefore, remain in the oil as undistilled residue. Since these acids are corrosive, it is best to remove them from the oil before the distillation treatment.

Example A crude oil which ordinarily deposited. slimy materials on the still columns was heated at.'70

with .4% of dry oxalic acid for one-half hour.

The major portion of the undesirable materials were coagulated and were deposited as sludge. The oil was withdrawn and filtered. The filtered .oil was brighter in color and'tests indicated that it contained the full anti-oxidant potency of the crude oil. J

Oxalic acid is very slightly soluble in oil and .and deposited as a sludge, separating the oil' from the impurities, subjecting the oil to high vacuum unobstructed path distillation and separating a fraction of the oil which contains at least a part of the natural antioxidant.

3. The method of preparing a natural 513'- oxidant concentrate .from a vegetable or animal oil which contains a natural anti-oxidant without simultaneously'causing substantial destruction of anti-oxidant which comprises in combination, treating the oil with an organic acid whereby the impurities therein are coagulated, separating the oil from these impurities, subjecting it to high vacuum, short path distillation and removing a fraction containing the anti-oxidant.

4. The process of refining an animal or vegetable oil which contains g. natural anti-oxidant which comprises treating the oil with an organic dibasic acid whereby the impurities are coagu-' lated separating the oil from these impurities, subjecting the oil to high vacuum unobstructed path distillation and separating a fraction of the oil which contains at least a part of the necessary antioxidant.

5. The process of refining an animal or vegetable oil which,contains a naturalranti-oxidant undoubtedly is present to a slight extent in oil purified as above. By molecular distillation of the aboveoil the small amount of oxalic acid was obtained in the first undesired fraction along with free fatty acids and other pro-oxidant compounds contained in the oil.

We claim:

which comprises treating the oil with oxalic acid, whereby the impurities are coagulated separating theoil from these impurities, subjecting the oil to high vacuum unobstructed path distillation and separating a fraction of the oil which contains atleast a part of the necessary antioxidant.

1. The method of preparing a natural anti oxidant concentrate from a vegetable or animal JAMIES G; BAXTER. JAKQB L. JAKOBSIEN'.