US2820047A - Pretreatment of oilseed meats - Google Patents

Description

nited States Patent g 2,820,047 PRETREATMENT 6F OILSEED MEATS William H. King, Metairie, La., assignor to the United States of America as represented by the Secretary of Agriculture No Drawing. Application April 22, 1955 Serial No. 503,359

Claims. (Cl. 260-4123) (Granted under Title 35, U. S. Code (1952), see. 266) A non-exclusive, irrevocable, royalty-free license in the invention herein described, for all governmental purposes, throughout the world, with the power to grant sublicen'ses' for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to oilseeds. More particularly, it provides a process of pretreating the oilseed materials which involves little or no extensive heating.

Vegetable oilseeds are usually converted to oilseed meats, i. e., oilseed kernels substantially free of hulls, ends, etc., before their oil is removed by means of pressure and/or solvents. Whether the oil is pressed out, or is removed by an extraction with an oil solvent, the oilseed meats are usually subjected to a pretreatment to enhance the extractability of the oil, and/ or to aid in detoxification or inactivation of the gossypol contained in cottonseeds, and to improve the quality of the crude oil yielded by the meats. in general, the pretreatments are designed to increase the availability of the oil by improving the filtration and/or pressing characteristics of the meats. Ideally the pretreatment would convert the materials to porous solids, through which oil and oil solvents would flow with ease, impregnated with oil in the form of a homogeneous oil phase. In the case of cottonseed meats, a more extensive pretreatment, designed to aid in the detoxification of gossypol, is often employed.

Some of the previously proposed pretreatments involve heating the oilseed meats, in the presence of at least the amount of moisture present in the natural seeds, to a temperature of at least about 212 F. for at least about 30 minutes. Such extensive cooking pretreatments usually bring about the desired improvement in the filtration and/or pressing characteristics and, in the case of cottonseed meats, at least partially inactivate and detoxify the gossypol. However, the extensive cooking usually also causes an undesired reduction in the nutritive value of the meals that the meats will yield.

Previous work has demonstrated that the desired results of an oilseed meat pretreatment can be accomplished with a less extensive cooking. This is accomplished by first increasing the moisture content of the meats well above that ordinarily present in the meats or ordinarily used in a pretreatment process (e. g. to from about to 50% by weight), and then reducing the moisture content to one suitable for removing the oil by a mild dehydrative cooking usually involving less than 15' minutes at a temperature above 190 F. U. S. Patent Nos. 2,784,- 205 and 2,726,155 describe such high moisture and mild heat pretreatments, that are, respectively, adapted for rupturing cottonseed pigment glands in the course ofa severe mechanical agitation, inhibiting the dissolving. of gossypol in cottonseed oil by incorporating an inhibiting amount of lye in the liquid with which the meats are moistened, and improving the nutritive value of the meal yielded by the meats by adjusting the pH of the moist meats in a specified manner.

producing oil from vegetable 2,820,047 Patented Jan. 14, 1958 A primary object of the present invention is to provide a process of pretreating oilseed meats which accomplishes the results obtainable by a pretreatment process, without the necessity of subjecting the meats to a relatively severe cooking in the presence of moderate amounts of moisture, or to a mild dehydrative cooking in the presence of large mQUnts of moisture.

In general, according to the invention, oilseed meats are pretreated in preparation for removal of oil therefrom by forming a mixture containing the oilseed meats, from about 20% to 50% of the weight of the said oilseed meats, preferably about /3 of said weight, of a 1% to 10% aqueous solution of sodium hydroxide, and a water-miscible organic solvent of the group consisting of 2-propanol, preferably hot, and methanol, preferably at surrounding temperature, the said solvent being preferably employed in sufiicient amount to provide about 1 to 2 parts by weight of the solvent per part of the oilseed meats, thereby obtaining a liquid solution in which the said oilseed meats are suspended as solid oilseed particles. The oilseed particles are thereafter separated from the said liquid solution and freed from entrained liquid to yield oilseed particles having a moisture content of between about 4% and 12%.

In the preferred manner of carrying out the process, the oilseed meats are first mixed with about 20% to 50% of their weight of the- 1% to 10% aqueous sodium hydroxide solution and the resulting mixture then mixed with the water-miscible organic solvent, that is, 2-propanol, preferably hot, or methanol, preferably at surrounding temperature, and preferably in suthcient amount to provide about 1 to 2 parts by weight of the solvent per part of oilseed meats, thereby obtaining the liquid solution in which the said oilseed meats are suspended as solid oilseed particles. Thereafter, as above, the oilseed particles are separated from the liquid solution and freed from entrained liquid to yield oilseed particles having a moisture content of between about 4% and 12%.

The oilseed meats resulting from this pretreatment exhibit good filtration properties and contain the desired amounts of moisture for oil removal by either a solvent extraction or a pressing operation. This pretreatment, furthermore, results in the production of meals and oils of exceptionally high quality. The proportion of oil which is extracted from the moist meats along with the aqueous sodium hydroxide solution can be readily recovered from the solvent solution by a phase separation procedure. Also, the oil which remains in the pretreated meats can be readily removed from the meats by a conventional pressing and/ or solvent extraction process.

Substantially any vegetable oil-bearing materials can be treated in accordance with the process of the present invention. The meats of vegetable seeds and nuts such as flaxseed, soybeans, castor beans, peanuts, cottonseed, tung nuts, sesame seed, and the like, are preferred starting materials. The hull content of the meats can vary over relatively wide ranges. The meats are preferably employed in the form of flakes, prepared by the usual decortication, cracking and flaking procedures, varying from about 0.005 to 0.040 in thickness.

The moisture contents of the vegetable oil-bearing materials are preferably adjusted by mixing the materials with the aqueous solution of sodium hydroxide as soon as they have been dehulled and comminuted to relatively small particles. The mixing can be accomplished by immersing the materials in the aqueous sodium hydroxide solution or spraying it onto thematerials, as long as the materials and the aqueous sodium hydroxide solution are agitated enough to obtain a substantially uniform mixture.

Where desirable, the aqueous solution of sodium hydroxide can be mixed with dilute aqueous solutions or dis.

persions of one or more compounds capable of reacting with gossypol and/or other components of the meats. Such compounds include oxidizing and reducing agents such as hydrogen peroxide andsodium sulfite amines and amino acids such as glycine, p-aminobenzoic acid, ethanolamine, and mechanical absorbents such as aluminum hydroxide gel and silica gel. Where the aqueous solution of sodium hydroxide contains a reactive component, the concentration of that component is preferably based upon the amount of the ingredients of the meats with which it will react.

During or following the adjusting of the moisture content of the meats, the processes of the above mentioned copending application can advantageously be combined with the process of the present invention. In the case of cottonseed meats, the gossypol contained in the pigment glands can be rendered available for chemicalconversion by subjecting the moist meats to the severe mechanical action that is more fully describde in U. S. Patent No. 2,726,155. Similarly, the gossypol containedin the pigment glands of cottonseed can be prevented from becoming dissolved in the oil'by employing in the aqueous sodium hydroxide solution with which the meats are moistened, the amounts of alkali specified in copending application Serial No. 390,098. By adjusting the pH of the moist meats in the manner specified in U. S. Patent No. 2,726,155 the present process can be employed to produce pretreated oilseed meats that yield meals of exceptionally high nutritive value.

As will be apparent to those skilled in the art: (1) the character of the water miscible organic solvent, (2) the temperature of the mixture of the solvent and the moist meats, (3) the proportion of solvent to meats, and (4) the time for which the moist meats remain in contact with the water miscible oil solvent comprise interrelated variables in relation to forming the liquid solution containing suspended solid oilseed particles having the specified moisture content, that is, between about 4% and 12%, after being separated from the liquid solution and then freed from entrained liquid. Any one of these can be varied within rather wide limits. In general, it is preferred to employ enough solvent, preferably an amount sulficient to provide about 1 to 2 parts by weight of the solvent per part of the oilseed meats, to form the liquid solution con taining suspended oilseed particles of the desired moisture content between about 4% and 12% withinabout to 15 minutes. Where the pretreated meats are to be pressed, the moisture content of the oilseed particles suspended in the liquid solution is preferably reduced to about 4 to 9%. Where the pretreated meats'are to be solvent extracted, the moisture content of the suspended particles is preferably reduced to from about 8 to 10%. The water miscible organic solvent can be mixed with the meats prior to or concurrently with the mixing of the meats with the aqueous sodium hydroxide solution. The mixture of the meals, aqueous sodium hydroxide solution, and organic solvent can be heated to temperatures above the boiling point of the mixture by using a short contact time and sufficient pressure to maintain the volatile components in the liquid phase. In general, it is preferable to employ a temperature below the temperature at which the liquid mixture boils at atmospheric pressure. The adjustment of the moisture contents of the moist meats, that is, the mixture of the meats and aqueous sodium hydroxide solution, by means of contacting them with the water miscible organic solvent, can be accomplished in one or a plurality of steps.

The mixing of the moist meats with the water miscible oil solvent can be accomplished by means of the usual procedures and apparatus for mixing a solid with a liquid. A conventional slurry mixer adapted to uniformly mix cottonseed meats with solvent is preferred. The resulting liquid solution can be separated from the solid particles of oilseed materials by means of the conventional procedures and apparatusfor removing; a solid-froma-liquid.-

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4 Straining, filtration, centrifugation, or the like procedures and apparatus usually employed in the solvent extraction of vegetable oilseed materials, are preferred.

The portion of the oil which is extracted from the moist meats along with the aqueous sodium hydroxide solution can readily be removed, so that the water miscible oil solvent can be recycled for re-use, by a phase separation procedure such as that employed in the phaseseparation solvent extraction processes. In typical phase separation solvent extraction processes, the oilseeds are extracted with a hot solvent such as an alcohol or aqueous alcohol and the hot extraction solvent is cooled to a temperature at which it separates into a phase consisting essentially of oil and another phase consisting essentially of solvent. See, for example, Patent Nos. 2,468,147; 2,584,108, and the'like.

The alkali present in the aqueous sodium hydroxide solution used to moisten the meats inhibits the passage into, and/or removes from the oil, acidic pigments, fatty acids and other impurities. Such impruities are usually present in the crude vegetable oils obtained by solvent extraction; and their presence is especially typical of the crude oils obtained by the phase-separation procedures using water miscible solvents without the alkali pretreament.

The solid oilseed particles that have been separated from the liquid solution in accordance with the process of the present invention, can advantageously be used as the oilseed starting material employed in a phase separation solvent extraction process, or in any of the conventional pressing and/or solvent extraction processes, for the production of a vegetable oil.

The following examples are illustrative of the details of at least one method of practicing the invention.

Example 1 Flaked oilseed meats obtained from raw cottonseed by conventional dehulling and flaking procedures are mixed with a water solution containing about 1 to 2% sodium hydroxide in suflicient amount to bring the total moisture content of the cottonseed meats to 31 weight percent. The meats and the aqueous sodium hydroxide solution are agitated for about 5 minutes in a conventional food mixing device. The treatment produces moist cottonseed meats having a moisture content of about 31%.

The moist meats are mixed with from about 1 to 2 parts by weight of the constant boiling (about 88% 2-propanol) mixture of 2-propanol and water per part of moist meats. After about 5 minutes of agitating the mixture consists of a liquid Z-propariol solution phase containing suspended particles of cottonseed meats in which substantially all of the cottonseed pigment glands are ruptured.

- The mixture is heated to about 170 F. and filtered.

:' The hot mixture consists essentially of a homogeneous 2-propanol solution of cottonseed oil and water, containing suspended particles of partially deoiled oilseed meats having a moisture content about equal to the natural moisture content of the meats. The filtrate produced by filtering the mixture contains about 25% of Water, 2-propanel and minor amounts of cottonseed oil and water and alcohol soluble components of cottonseed meats. This filtrate can readily be separated by conventional procedures for separating such a mixture to provide 2-propanol,

- for re-use as fresh solvent, cottonseed oil, and cottonseed meat by-products.

The partially deoiled meats which were filtered free of the hot solution are slurried with and filtered free of additional proportions of hot constant boiling aqueous isopropanol until the meats are converted to a meal containing less than about 1% residual lipids. The hot isopropanol solutions are combined and cooled to about F. Upon cooling. the solutions separate into an upper layer consisting essentially of aqueous Z-propanol saturated with cottonseed oil and a lower layer consisting essentially of cottonseed oil containing minor amounts of 2-propanol.

After separation by means of decantation or the like procedures the upper layer can be recycled for use as the constant boiling aqueous 2-propanol solution with which the moist meats are mixed, and the lower layer can be desolventized to produce 2-propanol and cottonseed oil.

Example 2 The procedure of Example 1 is repeated, using methanol in place of 2-propanol and filtering the mixture of moist meats and methanol at about room temperature. The meats which are filtered free of the mixture contain substantially all of their oil. They are drained free of methanol and desolventized by a conventional desolventization procedure. The desolventized meats are solvent extracted with hexane by one of the usual procedures for solvent extracting oilseed meats.

Example 3 The procedure of Example 2 is repeated except that the aqueous sodium hydroxide solution is mixed with the methanol before it is combined with the meats, so that the meats are mixed with both the aqueous sodium hydroxide solution and the methanol in a single step. The meats are drained free of liquid and desolventized by a conventional desolventization procedure. The desolventized meats are solvent extracted with hexane by one of the usual procedures for solvent extracting oilseed meats.

The meals produced by the procedures of each of the above examples contain from 0.002 to 0.030% free gossypol, from about 0.70 to 1.5% bound gossypol, depending upon the gossypol content of the seed used. These meals are characterized by a light yellow color and a freedom from the undesirable dustiness that often characterizes cottonseed meals extracted to a similar lipid content.

The oils produced by the procedures of the examples contain from about 0.001 to 0.023% gossypol and thus are not subjected to the color reversion upon storage characteristic of crude cottonseed oils containing appreciable proportions of gossypol. The colors of these crude oils (by the AOCS spectrophotometric method) vary from abut 9.4 to 40 red. Some of these crude oils are directly bleachable with bleaching earth to a color of 1.3 red. The free fatty acid content of these crude oils varies from about 0.1 to 0.34, as compared with a fatty acid content of 0.72% in oil directly extracted from the untreated seed.

1 claim:

1. A process of pretreating oilseed meats in preparation for removal of oil therefrom, comprising forming a mixture containing the oilseed meats, from about 20% to 50% of the weight of said oilseed meats of a 1% to aqueous solution of sodium hydroxide, and a Watermiscible organic solvent selected from the group consisting of methanol and Z-propanol thereby obtaining a liquid solution in which the said oilseed meats are suspended as solid oilseed particles, separating the said oilseed particles from the liquid solution, and freeing the separated oilseed particles from entrained liquid to yield oilseed particles having a moisture content of between about 4% and 12%.

2. A process of pretreating oilseed meats in preparation for removal of oil therefrom, comprising forming a mixture containing the oilseed meats, about /3 of the weight of said oilseed meats of a 1% to 10% aqueous solution of sodium hydroxide, and a sufficient amount of methanol to provide about 1 to 2 parts by weight of methanol per part of oilseed meats thereby obtaining a liquid solution in which the said oilseed meats are suspended as solid oilseed particles, separating the said oilseed particles from the liquid solution, and freeing the separated oilseed particles from entrained liquid to yield oilseed particles having a moisture content of between about 4% and 12%.

3. A process of pretreating oilseed meats in preparation for removal of oil therefrom, comprising mixing the oilseed meats with from about 20% to 50% of their weight of a 1% to 10% aqueous solution of sodium hydroxide, mixing the resulting mixture with a water-miscible organic solvent selected from the group consisting of methanol and Z-propanol thereby obtaining a liquid solution in which the said oilseed meats are suspended as solid oilseed particles, separating the said oilseed particles from the liquid solution, and freeing the separated oilseed particles from entrained liquid to yield oilseed particles having a moisture content of between about 4% and 12% 4. A process of pretreating oilseed meats in preparation for removal of oil therefrom, comprising mixing the oilseed meats with from about 20% to 50% of their weight of a 1% to 10% aqueous solution of sodium hydroxide, mixing the resulting mixture with a sufiicient amount of hot Z-propanol to provide about 1 to 2 parts by weight of 2-propanol per part of oilseed meats thereby obtaining a liquid solution in which the said oilseed meats are suspended as solid oilseed particles, separating the said oilseed particles from the liquid solution, and freeing the separated oilseed particles from entrained liquid to yield oilseed particles having a moisture content of between about 4% and 12%.

5. A process of pretreating oilseed meats in preparation for removal of oil therefrom, comprising mixing the oilseed meats with from about 20% to 50% of their weight of a 1% to 10% aqueous solution of sodium hydroxide, mixing the resulting mixture with a sufiicient amount of methanol at surrounding temperature to provide about 1 to 2 parts by weight of methanol per part of oilseed meats thereby obtaining a liquid solution in Which the said oilseed meats are suspended as solid oilseed particles, separating the said oilseed particles from the liquid solution, and freeing the separated oilseed particles from entrained liquid to yield oilseed particles having a moisture content of between about 4% and 12%.

References Cited in the file of this patent UNITED STATES PATENTS 705,785 Phillips July 29, 1902 1,161,481 Klein Nov. 23, 1915 1,347,870 Phillips July 27, 1920 1,648,670 Atwell Nov. 8, 1927 2,595,825 Williamson May 6, 1952 2,615,808 Rice Oct. 28, 1952

Claims (1)

1. A PROCESS OF PRETREATING OILSEED MEATS IN PREPARATION FOR REMOVAL OF OIL THEREFROM, COMPRISING FORMING A MIXTURE CONTAINING THE OILSEED MEATS, FROM ABOUT 25% TO 50% OF THE WEIGHT OF SAID OILSEED MEATS OF A 1% TO 10% AQUEOUS SOLUTION OF SODIUM HYDROXIDE, AND A WATERMISCIBLE ORGANIC SOLVENT SELECTED FROM THE GROUP CONSISTING OF METHANOL AND 2-PROPANOL THEREBY OBTAINING A LIQUID SOLUTION IN WHICH THE SAID OILSEED MEATS ARE SUSPENDED AS SOLID OILSEED PARTICLES, SEPARATING THE SAID OILSEED PARTICLES FROM THE LIQUID SOLUTION, AND FREEING THE SEPARATED OILSEED PARTICLES FROM ENTRAINED LIQUID TO YIELD OILSEED PARTICLES HAVING A MOISTURE CONTENT OF BETWEEN ABOUT 4% AND 12%.