US2259968A - Method of decolorizing oils - Google Patents

Description

Patented Oct. 21, 1941 METHOD OF DECOLORIZING OILS Carl N. Andersen, Wellesley Hills, Mass., assignor to Lever Brothers Company, a corporation of Maine No Drawing. Application September 30, 1938, Serial No. 232,533

-13 Claims. (Cl. 260424) The present invention relates to a process of refining oils and fats of vegetable and animal origin, and more particularly, to that portion of the refining process in which the oil is decolorized.

An object of my present invention is to provide a process of decolorizing oils and fats to produce a refined product of a particularly light color.-

In addition it is particularly an object of my invention to provide a decolorizing process capable of affecting the more diillcultly removable coloring matter in an oil, such as the carotenoid pigments.

A further object of my invention is the provision of a decolorization process that is simple and inexpensive in its operation, and which may be integrated readily with conventional methods of oil and fat refining.

The conventional method of refining oils and fats of vegetable and animal origin, hereinafter referred to as glyceride oils, includes the neutralization or removal or both of the various impurities such as free fatty acids, some of the coloring matter and gums. The fatty acids and gums, for the most part, are removable by conventional refining processes such as the neutralizing and precipitating action of caustic soda solution or other alkaline reagent. The color of the oil treated by such refining steps, in many cases, shows but a slight improvement, and it is necessary to treat the oil by other methods or with other materials,

sequence of conjugated bonds, which conjugations function as chromophore groups.

The carotenoid pigments vary in color from a bright yellow through a deep red or even a 'violet, to a dark blue, and it is believed that the that they are decomposed with the formation of reagents, comprises. the so-called carotenoid pigas polyene pigments. They are naturally occurring pigments and are found widely distribut ed in both vegetable and animal material.

There are other coloring pigments associated with oils and fats, and to distinguish carotenoids from these other types of coloring materials, they may be defined more specifically as nitrogen-free polyene pigments consisting wholly or chiefly of a long acyclic chain of carbon atoms united in a products of high molecular weight. Oil containing carotenoid pigments is improved in color upon subjection to oxidation. Oxidation. of the carotenoid pigments may be accelerated by the application 01. heat,,and heat bleaching of oils has become well known in the art. The process is not generally used, however, because the necessary high working temperatures have a deleterious effect upon theoil being treated. At lower processing temperatures the destruction of the carotenoids or their removal to improve the color of the oil is not complete enough for present day commercial standards. g

It has also been proposed to use bleaching clay for the removal of carotenoid pigments, but this is an expensive operation because an appreciable amount of the clay'isrequir'edl The process is inconvenient because the clay must be removed by filtration. It also results in a considerable loss of oil through absorption of oil by the clay.

Palm oil is one of the glyceride oils that contains a relatively large amount of carotenoid pigments, and it is the decolorization of palm oil in accordance with my invention that produces the most striking results. The treatment of all glyceride oils is included in my invention, however, and oils such as cottonseed oil, sesame oil, soya bean oil, kapok oil, peanut oil, lard, tallow and animal oils such as whale oil, may be treated by my process.

I have described my invention as applicable particularly to the removal of carotenoid pigments because these pigments are so difilcult to remove by processes heretofore available, but my invention is not so limited and may be employed to remove other pigments if desired.

In accordance with the present invention, the reduction of the color in the oil is accomplished by the use of reducing'agents effective for decolorizing oil. I have discovered that additions of a small amount of a strong reducing agent of the abovetype to an oil will result in a marked reduction of the color of the oil. After completed refining, the oil is in many casespractically void of color.

Suitable reducing agents that may be used in accordance with the present invention include those phosphorous compounds that comprise hypophosphorus acid (HaPOz) and its monobasic salts such as sodium hypophosphite (NazPOa). The relatively high activity of these compounds as reducing agents is-well known in' the art. It is not intended that other reducing agents of the type described shall be excluded from the scope of the present invention.

In practice, it is preferable that the decolorizing step utilizing the reducing agent be carried out prior to the usual refining operations with an alkaline reagent. In this manner, most of the products resulting from the reducing agent may be removed during the alkaline refining. Any remaining products are completely removed during the subsequent processing. For example, when hypophosphorous acid is used, there will be no trace of phosphorous compounds in the final product after conventional alkaline refining and subsequent treatments. In addition, the treatment with an alkaline reagent improves the color of the oil by further removing any pigments that remain after treatment with the reducing agent,

particularly the yellow pigments which are not acted upon as readily by the reducing agent as the red pigments.

As illustrative of the present invention, a reducing agent, such as hypophosphorous acid, in proportion of approximately from 1 to'1000, to 1 to 5000, is added to the oil heated to a desired bleaching temperature, preferably under vacuum. This may be done by adding the hypophosphorous acid to the oil in the treating tanks in a batch process, or by incorporating the acid as a step in a continuous process. Improved results are obtained by agitating the oil during the treatment with the reducing agent. The remainder of the refining process remains unchanged from that in general commercial use.

The above described bleaching process, followed by a conventional refining operation, has resulted in the lowering of the color of rapeseed oil from 2.6 red and 26 yellow, to 1.3 red and 13 yellow (5%," column) soya bean oil from 9.4 red, -'74 yellow and .5 blue, to 1.9 red, 30 yellow and .5 blue ('3" column) Sumatrapalm oil from 13 red, '75 yellow and 1.5 blue, to 1 red and 14 yellow (1" column); tallow from 23.5 red, 75 yellow and 4 blue to 6 red and 30 yellow (1" column), and African palm oil from 22 red and 70 yellow, to 1.5-2.3' red and 12-19 yellow (1" column).

In similar samples of tallow and African palm oil, which were treated by heat bleaching instead of the hypophosphorous acid bleach, the color was reduced only to 25 red, '75 yellow and 2 /2 blue (1''' column); and 2.4 red and 35 yellow (1" column), respectively. (All readings are on Lovibond scale.)

.As an illustration of my invention when applied to a complete method'of making an edible product, a crude Sumatra palm oil was heated to 235-255 C. at an absolute pressure of mm. of mercury with the addition of hypophosphorous acid in proportion of one to two thousand. This temperature wasmaintained for approximately five to ten minutes, after which the oil was cooled to 70 C. andthen refined in accordance with a conventional refining process including agitation with sodium hydroxide solution, bleached with earth, filtered, hydrogenated, and deodorized.

The final product exhibited a color reading on the Lovibond scale (5% column) of 1.0 red and 18 yellow.

As an additional illustration, a sample of crude palm oil, having a. dark color, was treated'with sodium hypophosphite in the proportion of 1 part to dissolved in water and heated under a vacuum. Heating was continued until the water was removed, and then the temperature was raised gradually to 255 C. which 'was maintained for approximately 5 minutes. The oil was then allowed to cool in a vacuum. A small amount of earth was added to insure a clear product. The finished oil exhibited a color reading of 1.4 red, 70 yellow (5%," column). After a conventional alkaline refining treatment the oil The use of an elevated temperature greatly facilitates the bleaching action. Its use shortens the time required for the color removal and is preferable in a commercial operation. The most favorable temperature, hereinafter referred to-as the bleaching temperature, at which, the bleaching action takes place is subject to considerable variation dependent on the type of oil being refined. In the case of palm oil, which is high in color, the range of 220 to 255 C. has been found to produce the best results. However, with peanut oil, the most favorable temperature was found to be approximately C. As a general rule, there is no advantage in maintaining the oil at a high temperature for an extended period of time, and

it is preferred that heating and cooling be accomplished as quickly as possible.

While it is not essential, the bleaching is preferably carried out under a vacuum of from 10 to 20 mm. of mercury pressure absolute, but the amount of vacuum has not been found to be critical. An atmosphere of inert gas may be em;-

ployed to obviate or supplement the use of a vacuum.

The amount of reducing agent used will depend somewhat-on the amount of coloring matter in the oil to be removed as well as on the conditions of operation, and may be varied over wide limits with satisfactory results. An excess does not accomplish any beneficial result. Quantities considerably less than that disclosed will produce a noticeable improvement in color.

Having described my invention so that one skilled in the art may practice the same, it is not my intention to limit the scope thereof by reference to any particular theory of the chemical reactions involved or explanation of the results. As a possible explanation of the bleachingaction itis to'be'noted that the presence of a large number of double bonds or chromo phone groups in carotenoid pigments is prob ably the cause of the color of the pigments, and it is possible that the action of the reducing agents comprises a destruction of the double bonds by saturating the same with hydrogen, or by separating the compound at such points. Such saturation or breaking of the double bonds may cause the color reduction hereinbefore described.

It is to'be understood that the foregoing is given only as a possible explanation of the desirable results achieved by my invention, and it is not intended that any other explanation of the results or the chemical action involved is .to be excluded.

The invention being thus described, it will be obvious that the same may be varied in many ways, such as variations in reducing agents, oils treated, and treating conditions. Such variations are not to be regarded as a departure from the essence ofthe invention and all such varia- I tions are intended to be included in' the'scope or the following claims.

I claim:

1. In a'process of refining glyceride oils, the step of decolorizing the oil with a small amount of a reducing phosphorous compound selected.

steps which comprise heating the oil to a bleach- I ing temperature under a high vacuum with a small amount ofa reducing phosphorous com-- pound selected from the group consisting of hypophosphorous'acid and its salts, cooling .the

'oil under a vacuum, treating the oil with an alkaline solution and deodorizing the oil.

4. In a process of refining glyceride oils containing an appreciable amount of carotenoid pigments, the steps which comprise heating the oil to a bleaching temperature under a high vacuum with a small amount of a reducing phosphorous compound selected from a group consisting of hypophosphorous acid and its salts, and treating the oil with an'alkaline solution. p

5. In a process of refining glyceride oils con-' taining an appreciable amount of carotenoid pisments, the steps which comprise heating the oil to a bleaching temperature under a high vacuum with a small amount of a reducing phosphorous '1. In a process of refining glyceride oils, the

step of decolorizing the oil by treating it with a small amount of a'salt of hypophosphorous acid at a. bleaching temperature under vacuum. 8. In a process of refining palm oil, ,the step of decolorizing the oil with a small amount of hypophosphorous acid while the oil is at an elevated temperature and in a substantial absence of air.

9..In a process of refining palm oil, the step of decolorizing the oil by heating it with a small amount of hypophosphorous acid at a bleachin temperature under a vacuum.

10. In a process or. refining palm oil, the steps of decolorizing the oil by heating it with a small amount of hypophosphorous acid at a bleaching temperature under vacuum, and treating the oil with an alkalinesolution.

11. In a process of refining palm oil, the steps of decolorizing the oil by heating it with a small amount of hypophosphorous acid at a bleaching temperatureunder a vacuum, cooling the'oil under a vacuum, and treating the oil with an alkalinereflning agent.

12. In a'process oi refining palm oil, the steps which comprise treating the oil with hypo-' phosphorous-acid in a proportion of the order of 1 to 1000 and at a temperatureoi above 200 C.

under a high vacuum, cooling the oil underva vacuum, treating the oil with an alkaline solutlon, and deodorizing the oil to produce an oil .having a particularly light color.

' 13. In a process 01 refining palm oil,containing an appreciable amount of carotenoid pigcompound selected from a group consisting-of hypophosphorous acid and its salts, cooling the oil under a vacuum, and treating the oil with an alkaline solution.

6. In a process of refining glyceride oils, the step of decolorizing the oil by treating it with a small amount of hypophosphorous acid at a bleaching temperature under vacuum.

merits, the steps which comprise treating theoil with hypophosphorous acid iii a proportion of the order 01' 1 to 1000 and at a temperature-oi 220 to 235 C. under a vacuum of less than 20 mm. of mercury, cooling the oil under vacuum, treating the oil with a caustic solution to further refine the same and remove phosphorous compounds, washing the oil with water, and deodorizing the oil to produce a product having a particularly light color.

CARL N. ANDERSEN.