Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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
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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
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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
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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
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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
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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
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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
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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
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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
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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.
