CA1075262A - Vegetable oil extraction - Google Patents

Abstract

Abstract of the Disclosure:
A process for extracting oilseeds, particularly pea-nuts, said process comprising dividing the oilseeds into thin slices, and thereafter extracting the oil from said slices with a solvent. The defatted product possesses a white color, a bland taste, high protein solubility, and may be used in vari-ous food and industrial products.

Description

1075;~Specification:
This invention relates to the processing of vegetable oilseeds to obtain an oil fraction and a protein fraction there-from. This invention has particular application to the proces-sing of peanuts in order to obtain peanut oil and peanut flour.
Oil-bearing vegetable seeds, such as soybeans and cottonseeds, have long been extracted by either application of mechanical pressure, or by solvent extraction, or by a combina-tion of these two techniques. Both techniques are suitable for obtaining a high quality oil fraction. However, when a high quality solids fraction is desired, in addition to the oil fraction, mechanical expression of the oil cannot be utilized.
This is because the pressure and heat generated during such me-chanical extraction causes substantial denaturation of the pro-tein content such that the protein loses its functionality, and particularly its solubility in water. Therefore, when a high functionality protein solids fraction is desired, as for use in food products, the oil-bearing vegetable seeds are extracted by means of a suitable solvent such as hexane or alcohol. Such extractions can generally be carried out under temperature/time conditions sufficiently mild to minimize protein denaturation, and thus minimize loss of protein solubility and other functional properties of the protein.
Unlike soybeans and cottonseeds, peanuts have never been able to be feasibly solvent extracted. This is because peanuts have an extremely high oil content, in the order of 48-50% by weight, as compared to other oil-bearing vegetable seeds such as soybeans and cottonseeds which have an oil con-tent of less than 20% by weight. Thus when peanuts are fla~ed in accordance with prior art procedures, the flakes tend to disintegrate during solvent extraction, resulting in a fine dispersion of the solids material (marc) in the solvent/oil miscella. The presence of this solids dispersion in the ~07S;~Z

miscella makes it extremely difficult to separate the æolids from the liquid miscella in accordance with typical separation procedures. The solids dispersion can be separated from the liquid miscella only by the application of sophisticated and expensive techniques not common to the vegetable oil extrac-tion industry. Because of these problems in solvent extrac-tion of peanuts, very little high functionality peanut protein material is manufactured today. Rather, almost all peanuts which are processed to remove the oil content, are mechani-cally extracted in a screw-press, leaving a substantially non-functional protein residue which is used almost exclusively as an animal feed. In view of the foregoing, there is a continu-ing need in the vegetable oil extraction industry for an im-proved method of extracting peanuts.
It is therefore a principal object of this invention to provide an improved method for the solvent extraction of oil-bearing vegetable seeds.
It is a further objective of this invention to pro-vide an improved method for the solvent extraction of peanuts.
It is also an objective of the present invention to provide an improved method for extracting peanuts with hexane.
It is an additional okjective of the present inven-tion to provide a protein material derived from solvent ex-tracted peanuts, which protein material may be used as a food additive.
It is another objective of the present invention to provide a peanut protein material characterized by an extreme-ly high protein water solubility.
Briefly, the objectives of this invention are car-ried out by solvent extraction of oilseeds which have been given a physical form that is resistant to disintegration dur-ing the solvent extraction process. The process comprises thinly slicing the oilseeds, as opposed to flaking same, and

-2-107S;~Z

thereafter extracting the thin slices ~ith an appropriate sol-vent.
The present invention, therefore, in one aspect, resides in a process for extracting peanuts comprising heating the peanuts to a temperature of from about 90-120F., dividing the peanuts into ultra thin slices having a thickness of from about .003 inches to about .02 inches, extracting the oil content therefrom with a solvent, separating the liquid oil-laden miscella from the extracted slices, desolventizing the slices at a temperature of less than about 185F., and thereafter grinding the desolventized slices to yield a peanut flour exhibiting a nitrogen solubility index of greater than 80 and an oil content of less than about 2% by weight.
In another aspect this invention resides in the peanut flour prepared in accordance with the above process.
It should initially be noted that the present process is applicable to the solvent extraction of all oil-bearing vegetable seeds, including soybeans, cottonseeds, sunflower seeds and tung seeds, as well as peanuts. However, as has been pre-viously pointed out, this invention has particular applicationto the solvent extraction of peanuts inasmuch as there is no known prior art technique for efficiently and inexpensively solvent extracting peanuts while retaining high functionality of the protein solids fraction. Therefore, this invention will be described in terms of solvent extraction of peanuts, but those skilled in the art will understand the invention to be equally applicable to the extraction of other oil-bearing vegetable seeds.
The peanuts utilized in the present process should first be dehulled in accordance with typical industry dehulling ~ _3_ procedures. The dehulled peanuts are then blanched to remove the thin outer skins. In accordance with prior art procedures, the peanut skins may be removed either by wet blanching or dry blanching. I have determined that it is preferably to employ a dry or mechanical blanching procedure. In such a procedure, whole peanuts with skins are heated in a hot air over to a temperature not in excess of about 120F. (49C.), and usually to a temperature within the range of from about 90-120F.
(32-39C.). Heating tends to dry the skin and make it brittle, and thus easily removable. The heated peanuts are then fed between two closely spaced, horizontally parallel rubber belts which rotate in such a manner so as to rub the dried skins from the peanuts. This type of blancher is also operable to split the peanut dicotyledon in half, resulting in two peanut cotyledons, along with the small peanut "heart". Although splitting of the peanut dicotyldeon into -3a-~,~

10752~2 halves is not mandatory, it is certa inly preferable in carry-ing out this invention. Once the skins have been rubbed off, and the individual cotyledons separated from the peanut hearts, the hearts are screenefl out and the skins are blown away or drawn off by vacuum.
The deskinned peanut cotyledons, with hearts re-moved, are then sliced. It is important that the peanuts be relatively warm during the slicing operation. If slicing i9 carried out immediately subsequent to blanching, the peanuts have already been warmed during the mechanical blanching and need not be reheated. However, if the peanuts have not been previously warmed, or have cooled in the interim, they should be reheated, as in a hot air oven, to a temperature within the range of 70-120F. (21-49C.), and preferably to a tem-perature within the range of 90-120F. (32-49C.).
As has been mentioned, flaking the peanuts in accord-ance with prior art procedures results in a physical form of the peanuts which will disintegrate during solvent extraction.
Flaking involves passing the peanuts between two closely spaced rollers which crushes the peanuts therebetween, breaking and crushing cell walls. Thus, upon extraction of the high oil content of the peanut flakes (48-50%), the crushe~ cell walls are unable to maintain their integrity, and thus disintegrate, forming a fine dispersion in the oil/solvent miscella.
I have suxprisingly discovered that by thinly slicing the peanuts, so as to avoid crushing of the individual cells, I can obtain a physical form of the peanut which can be solvent extracted without concomitant disintegration of the cellular structure. I have determined that the optimum slice thickness should be approximately just less than the thickness of two cell walls. In this manner, each cell wall in the peanut is exposed to the extracting solvent. Peanut cell walls are gen-erally about .0035 inches (.0089 centimeters) thick. Thus, an 1075~6Z
optimum slice thickness is about .007 inches (.018 cent~meters) thick. The lo~-er limit of slice thickness is determined by that thinness which will result in formation of a powder.
This is usually less than about .003 inches (.0076 centimeters).
The upper range of slice thickness is not particularly criti-cal; however, thicker peanut slices require longer e~traction perio~s in order to remove a given weight percentage of the oil content. We have determined, as a practical matter, that sliced thicknesses of greater than about .02 inches (.05 cen-timeters) are not particularly desirable.
The peanuts may be sliced by any cutting apparatus which is operable to uniformly slice the peanuts within the slice thickness range described above. We have discovered that conventional cutting machines utilized in the slicing of raw potatoes in the manufacture of potato chips are extremely suit-able for this purpose. In such machines, the charge of peanuts is fed from a storage hopper into an impeller zone which imparts a centrifugal motion to the peanuts. Extremely sharp, adjust-able blades are arranged about the periphery of the impeller zone, such that the centrifugal force imparted to the peanuts by the impeller drives them against the closely spaced blades, causing thin slicing of the peanuts. Due to the spaced arrange-ment of the blades, slices of desired thickness pass between the blades and are removed, while the remainder of the peanuts impinge upon ad~itional blades so as to create additional slices. Potato slicers of this type are manufactured by Urschel ~aboratories, Inc. of Valparaiso, Indiana, such as the Urschel ~odel CC Slicer or Urschel Comatrol. Slicers of this type have been used to slice nuts to obtain garnish slivers, e.g., al-mondine slivers, as well as potatoes. However, such sliced nuts and potatoes are substantially thicker than the thin slices envisioned by this invention.
The thinly sliced peanuts are now ready for solvent -_ " - 5 -~075Z6Z

extraction. Although various prior art extraction solvents may be utilized, such as alcohols and hexane/alcohol azeotropes, I
have determined that hexane extraction is preferable when the oilseed material is peanuts. For one reason, peanut oil is more soluble in hexane than in alcohol. Also, the presence of water or alcohol in the miscella tends to have a detrimental effect on the functionality of the peanut protein. This is because alcohol and/or water makes the protein material more susceptible to denaturation.
Generally, it is desirable to extract the peanuts to an oil content of less than about 2% by weight and preferably less than 1~. Maximizing the oil extraction not only results in increased oil yields, but results in increased shelf-life of the peanut protein solids. It should be understood, of course, that the peanut slices can be extracted to any desired residual oil level. Extraction to a level of from about 0.5 to 2% by weight usually requires greater than two hours' ex-traction time, and typically r~guires an extraction time of 4-6 hours. Preferably, the hexane solvent should be heated prior to contact with the peanut slices marc, as extraction effi-ciency increases directly with miscella temperature. Since hexane flashes at approximately 155F. (69C.), the hexane should be heated to a temperature slightly less than this prior to contact with the marc. Also, the temperature of the oil-hexane miscella should be maintained as high as possible, with-out flashing, during the extraction procedure. Vsually, the miscella can be maintained at a temperature within the range of 155-160~. without flashing off the hexane, the miscella mixture having a higher flash point than pure hexane.
Any conventional extraction procedure may be utilized to extract the peanut slice marc, and this invention is not limited to any particular type of extraction technique. Typi-cal extraction procedures utilized in the extraction of soybeans 1075~6~

such as countercurrent extraction or deep bed extraction, are desirable. Deep bed extraction is preferable due to the excel-lent miscella contact with the peanut marc achieved during per-colation.
I have also determined that the solvent to solids ratio re~uired to efficiently extract peanuts is much higher than is normally used in conventional ext r action of other oil-bearing vegetable seeds such as soybeans. In particular, it has been detenmined that a solvent to marc ratio of from about

3:1 to 6:1 by weight is preferable.
Once the peanut slices have been extracted to the desired residual oil content, the miscella and marc are separ-ated in accordance with conventional procedures. This is possible due to maintenance of the cellular integrity of the individual peanut slices. The miscella and marc are then in-dependently desolventized. The miscella is conventionally de-solventized so as to provide a hexane fraction which is recycled for further extraction, along with a peanut oil frac-tion. The marc is preferably desolventized under time/tempera-ture conditions which do not result in any appreciable denatura-tion of the peanut protein. ~his can best be accomplished by vapor or flash desolventization under a partial vacuum. Such vacuum desolventization enables flashing off of the hexane at lower temperatures than is possible with typical atmospheric desolventization. Usually, temperatures in excess of about 185F. (88C.) should be avoided in the desolventizing of the marc in order to avoid denaturation of the peanut protein.
The defatted, desolventized peanut slices are now in the form of white-colored peanut grits. These grits or slices may be ground to a peanut flour. Peanut flour manufactured in accordance with the present process typically has a white color, a very bland taste, a protein content of about 60% by weight, and a carbohydrate content of approximately 27%. Ideally, the 1075'~
flour will have a fat content of less than 2~ by weight, an ash content of less than about 5~ by weight, and a moisture content of from about 3-8~ by weight. Also, the peanut flour has a ni-trogen solubility index of greater than 80, and often greater than 90, indicating a highly functional protein. As compared to conventional prior art soy flours, peanut flour manufactured in accordance with the present process exhibits better color, better flavor, better water absorption (water binding) proper-ties, and a higher nitrogen solubility index.
If desired, the peanut flour may be further processed to obtain peanut concentrates, or peanut isolates, or textured peanut products. For example, peanut concentrates can be ob-tained by treatment of the peanut flour to remove water soluble sugars. L~kewise, peanut isolates can then be drived from the peanut concentrates by removal of the insoluble fiber residue.
Textured peanut products can be manufactured in accordance with prior art soybean technology by forming a dough from peanut flour and water, and thereafter extruding the dough under suit-able conditions of temperature and pressure into a zone of low-er pressure so as to obtain an expanded, textured product.
Peanut flour, along with peanut concentrates and pea-nut isolates derived therefrom, obtained in accordance with this invention have a wide range of food and industrial uses. As industrial raw materia~s, the peanut flour and its derivatives may be used in adhesives and synthetic fibers. ~ore importantly, due to the exceIlent functionality of peanut flour manufac-tured in accordance with this invention, it may be used as a whipping agent, a film-forming agent, a thickening agent and/or an emulsifying agent. In particular, the peanut flour can be used as a replacement for non-fat milk solids in food products.
For example, the present peanut flour may be used as a protein additive in breads, cakes, doughnuts, cookies and fillings.

With respect to processed meat products, the peanut flour may be 1075~62 used as a protein supplement in emulsified meat products such as frankfurters. In dairy products, the peanut flour may be used as a source of protein in imitation ice cream, imitation sherbets, soft serve ice creams, shakes and various frozen confectioneries.
Also, the peanut flour of the present invention may be used to replace sodium caseinate in non-dairy products such as coffee whiteners, imitation milks, whipped toppings, sour cream, imi-tation cheese and margarine.
It will be understood that levels of water soluble protein content in oilseeds recite~ hereinbefore, as expressed in Nitrogen Solubility Index ~NSI) Values, are measured by standard AOCS (American Oil Chemists Society) procedures. The standard procedures are based on the following calculation:

% soluble nitrogen in oilseed sample % total nitrogen in oilseed sample X 100 = ~SI Value Obviously many modifications and variations of the invention as hereinbefore set forth may be made without depart-ing from the spirit and scope thereof, and, therefore, only such limitations should be imposed as are indicated in the ap-pended claims.

Claims (7)

The embodiments of the invention in which an exclusive property is claimed are defined as follows:

1. A process for extracting peanuts comprising heating the peanuts to a temperature of from about 90-120° F., dividing the peanuts into ultra thin slices having a thickness of from about .003 inches to about .02 inches, extracting the oil content therefrom with a solvent, separating the liquid oil-laden miscella from the extracted slices, desolventizing the slices at a temperature of less than about 185° F., and thereafter grinding the desolventized slices to yield a peanut flour exhibit-ing a nitrogen solubility index of greater than 80 and an oil content of less than about 2% by weight.

2. The process of Claim 1 wherein the solvent is hexane.

3. The process of Claim 2 wherein the hexane-oil miscella is maintained at a temperature of from about 155-160° F. during extraction.

4. The process of Claim 3 wherein the peanut slices are extracted counter-currently for from about 2-6 hours.

5. The process of Claim 3 wherein the peanut slices are extracted in a deep bed extractor for from about 2-6 hours.

6. The process of Claim 3 wherein the solvent to marc ratio is from about 3:1 to 6:1 by weight .

7. The peanut flour prepared in accord-ance with Claim 1.