U.S. patent number 3,615,657 [Application Number 04/759,647] was granted by the patent office on 1971-10-26 for process for producing cottonseed protein concentrate.
This patent grant is currently assigned to N/A. Invention is credited to Esler L. D'Aquin, Paul H. Eaves, Edward A. Gastrock.
United States Patent |
3,615,657 |
Gastrock , et al. |
October 26, 1971 |
PROCESS FOR PRODUCING COTTONSEED PROTEIN CONCENTRATE
Abstract
A process for producing a high protein cottonseed concentrate
from cottonseed meats which process is characterized by an
integrated sequence of drying, flaking, disintegrating, screen
separating and gravity separating steps. The process accomplishes
the substantially complete removal of intact cottonseed pigment
glands and as a consequence thereof, the isolation of gland-free
material, which material can be exalted to exhibit a protein
content as high as 73 percent by weight on an oil and moisture free
basis.
Inventors: |
Gastrock; Edward A. (Metairie,
LA), D'Aquin; Esler L. (New Orleans, LA), Eaves; Paul
H. (Metairie, LA) |
Assignee: |
N/A (N/A)
|
Family
ID: |
25056433 |
Appl.
No.: |
04/759,647 |
Filed: |
September 13, 1968 |
Current U.S.
Class: |
530/377; 426/472;
426/486; 426/430; 426/473 |
Current CPC
Class: |
A23J
1/142 (20130101) |
Current International
Class: |
A23J
1/00 (20060101); A23J 1/14 (20060101); A23j
001/14 () |
Field of
Search: |
;99/17,98,2E |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
2482141 |
September 1949 |
Boatmer et al. |
|
Other References
Smith, Walton, "Precautions to Minimize Damage and Deterioration to
Oil and Protein in Processing" from Proceedings of the Twelfth
Cottonseeed Proceeding Clinic, Held at New Orleans, Louisiana, Feb.
11 and 12, 1963, Printed by U.S. Department of Agriculture in
January, 1964..
|
Primary Examiner: Monacell; A. Louis
Assistant Examiner: Simons; William Andrew
Claims
We claim:
1. A process for producing from cottonseed meats a protein
concentrate product having a low gossypol content and a protein
content not less than about 65 percent, which process comprises the
following steps carried out in sequence:
a. drying the cottonseed meats at a temperature below about
180.degree. F. to a moisture content of not above about 4 percent
by weight,
b. immediately flaking the still warm dried cottonseed meats to
produce flakes with a thickness within the range of about 0.008 to
about 0.012 inch,
c. extracting the flakes with a nonpolar hydrocarbon solvent, to
obtain extracted flakes with a residual oil content below about 2
percent by weight,
d. adding solvent to the solvent-damp extracted flakes from step
(c) and mixing to produce a pumpable free-flowing slurry,
e. disintegrating the solid particles in the slurry from step (d)
by passing the slurry through a high speed rotary stone mill with
opposed stone faces set at a clearance within the range 0.002 to
0.015 inch.
f. adding solvent to the slurry of disintegrated material from step
(e) and mixing to produce a screenable slurry containing not more
than about 15 percent by weight of solids,
g. screening the material from step (f) to obtain three separate
streams of material segregated with respect to particle size as
follows:
1. a first stream of material comprised of solvent-wet particles
which remain on a screen of about 24 mesh, which material exits the
process at this step,
2. a second stream of material comprised of solvent-wet particles
which remain on a screen of about 80 mesh, which stream of material
is returned to step (f) of the process,
3. a third stream of material comprised of solvent-wet particles
which pass through a screen of about 80 mesh,
h. diluting the said third stream of material from the preceding
step (g) with solvent to produce a slurry material containing from
about 3 to about 10 percent of solids, and
i. feeding the diluted slurry material of step (h) at a pressure of
at least about 15 pounds per square inch to a liquid cyclone, which
liquid cyclone is adjusted to produce an overflow stream and an
underflow stream in the ratio by weight range of about six parts of
overflow to one part of underflow to 20 parts of overflow to one
part of underflow, with the solids content of the overflow being in
the range of 3 to 10 percent by weight and the solids content of
the underflow being in the range of about 25 to about 45 percent by
weight, which said underflow stream exits the process at this step
for meal and solvent recovery,
j. feeding the overflow stream from the liquid cyclone of the
preceding step (i) to a solids concentrator wherein the solids are
partially freed from solvent, and then to a filter for further
solvent removal to produce a solvent-damp material of a solids
content of about 50 percent by weight,
k. removing the residual solvent from the solids of the preceding
step (j) by volatilization to produce a protein concentrate having
a protein content of at least about 65 percent by weight, a total
gossypol content of less than about 0.30 percent by weight, and an
oil content of less than about 2 percent by weight.
2. A process for producing from cottonseed meats a protein
concentrate product having a low gossypol content and a protein
content not less than about 70 percent, which process comprises the
following steps carried out in sequence:
a. drying the cottonseed meats at a temperature below about
180.degree. F. to a moisture content of not above about 4 percent
by weight,
b. immediately flaking the still warm dried cottonseed meats to
produce flakes with a thickness within the range of about from
0.008 to about 0.012 inch,
c. extracting the flakes with a nonpolar hydrocarbon solvent to
obtain extracted flakes with a residual oil content below about 2
percent by weight,
d. adding solvent to the solvent damp extracted flakes from step
(c) and mixing to produce a pumpable free-flowing slurry,
e. disintegrating the solid particles in the slurry from step (d)
by passing said slurry through a high speed rotary stone mill with
opposed stone faces set at a clearance within the range 0.002 to
0.015 inch,
f. adding solvent to the slurry of disintegrated material from step
(e) and mixing to produce a screenable slurry containing not more
than about 15 percent by weight of solids,
g. screening the material from step (f) to obtain three separate
streams of material segregated with respect to particle size as
follows:
1. a first stream of material comprised of solvent-wet particles
which remain on a screen of about 24 mesh, which material exits the
process at this step, for meal and solvent recovery,
2. a second stream of material comprised of solvent-wet particles
which remain on a screen of about 80 mesh, which stream of material
is returned to step (e) for further disintegration,
3. a third stream of material comprised of particles which pass
through a screen of about 80 mesh,
h. diluting the said third stream of material from step (g) with
solvent to produce a slurry material containing from about 3 to
about 10 percent of solids,
i. feeding the diluted slurry material of step (h) at a pressure of
at least about 15 pounds per square inch to a liquid cyclone, which
liquid cyclone is adjusted to produce an overflow stream and an
underflow stream in the ratio by weight range of about six parts of
overflow to one part of underflow to 20 parts of overflow to one
part of underflow, with the solids content of the overflow being in
the range of 3 to 10 percent by weight and the solids content of
the underflow being in the range of about 25 to about 45 percent by
weight, which said underflow stream exits the process at this step
for meal and solvent recovery,
j. feeding the overflow stream from the liquid cyclone of step (i)
to the first stage of a series of stages of small diameter liquid
cyclones at a pressure of at least about 30 pounds per square inch,
which first stage of small diameter liquid cyclones produce an
overflow stream and an underflow stream, the said overflow stream
exiting the process at this step for meal and solvent recovery,
k. feeding the said underflow stream from step (j) at a pressure of
at least about 30 pounds per square inch to the first stage of the
remaining series of stages of small diameter liquid cyclones, which
series of stages of small diameter liquid cyclones each produces an
overflow stream and an underflow stream, and are so arranged that
the underflow stream from each of the stages of small diameter
liquid cyclones is fed to the next succeeding stage of small
diameter liquid cyclones of the series at a pressure of at least
about 30 pounds per square inch, while the overflow stream of each
of the successive stages of small diameter liquid cyclones exits
from the process for meal and solvent recovery, each of the stages
in the series of small diameter liquid cyclones including that of
step (j) being adapted to yield a weight ratio of overflow to
underflow within the range of 1 to 1 to 1.5 to 1, with solids
content of the respective underflow streams from each stage of
small diameter liquid cyclones being successively exalted in each
succeeding stage until the solids content of the underflow stream
from the final stage of small diameter liquid cyclones of the
series has reached at least about 30 percent by weight, and
1. feeding the underflow stream from the final stage of small
diameter liquid cyclones of the preceding step, step (k), to a
filter wherein the solids of the said underflow stream are
partially freed from solvent to obtain a solvent-damp material of a
solids content of about 50 percent by weight, and
m. removing the residual solvent from the filtered solids of the
preceding step (step 1) by volatilization to produce a protein
concentrate having a protein content of at least about 70 percent
by weight, a total gossypol content of less than about 0.30 percent
by weight, and an oil content of less than about 2.0 percent by
weight.
3. A process for producing from cottonseed meats a protein
concentrate product having a low gossypol content and a protein
content not less than about 65 percent, which process comprises the
following steps carried out in sequence:
a. drying the cottonseed meats at a temperature below about
180.degree. F. to a moisture content of not above about 4 percent
by weight,
b. immediately flaking the still warm dried cottonseed meats to
produce flakes with a thickness within the range of about 0.008 to
0.012 inch,
c. adding a nonpolar hydrocarbon solvent to the flakes from step
(b) and mixing to produce a pumpable free-flowing slurry,
d. disintegrating the solid particles in the slurry from step (c)
by passing said slurry through a high speed stone mill with opposed
stone faces set at a clearance within the range of 0.002 to 0.015
inch,
e. adding solvent to the disintegrated material from step (d) and
mixing to produce a screenable slurry containing not more than
about 15 percent by weight of solids,
f. screening the material from step (e) to obtain three separate
streams of material segregated with respect to particle size as
follows:
1. a first stream of material comprised of miscella-wet particles
of solids which remain on a screen of about 24 mesh, which material
exits the process for oil, meal, and solvent recovery, and
2. a second stream of material comprised of miscella-wet particles
of solids which remain on a screen of about 80 mesh, which stream
of material is returned to the fourth step (step d) of the process
for further disintegration.
3. a third stream of material comprised of the major portion of the
solvent and oil (miscella) and the particles which pass through a
screen of about 80 mesh, and
g. diluting the said third stream of material with solvent to
produce a slurry material containing about 3 to about 10 percent of
solids, and
h. feeding the diluted slurry material of the preceding step (g) at
a pressure of at least about 15 pounds per square inch to a liquid
cyclone, which liquid cyclone is adjusted to produce an overflow
stream and an underflow stream in the ratio by weight range of
about six parts of overflow to one part of underflow to 20 parts of
overflow to one part of underflow, with the solids content of the
overflow being in the range of about 3 to about 10 percent by
weight, and the solids content of the underflow being in the range
of about 25 to about 45 percent by weight, which said underflow
stream exits the process for oil, meal, and solvent recovery,
and
i. feeding the overflow stream from the liquid cyclone of the
preceding step (h) to solids concentrator wherein the solids are
partially freed of solvent and oil to produce a thick but flowable
slurry comprised of solids and oil-rich miscella, which flowable
slurry is filtered and washed essentially free of oil to yield a
solvent-wet solids material of a solids content of about 50 percent
by weight, and
j. removing the residual solvent from the solids of the preceding
step (i) by volatilization in a dryer, to produce a product
material having a protein content of about 65 percent or more by
weight, a total gossypol content of less than about 0.30 percent by
weight, and an oil content of less than about 2 percent by
weight.
4. A process for producing from cottonseed meats a protein
concentrate product having a low gossypol content, and a protein
content not less than about 70 percent, which process comprises the
following steps carried out in sequence:
a. drying the cottonseed meats at a temperature below about
180.degree. F. to a moisture content of not above about 4 percent
by weight,
b. immediately flaking the still warm dried cottonseed meats to
produce flakes with a thickness within the range of about from
0.008 to about 0.012 inch,
c. adding a nonpolar hydrocarbon solvent, to the flakes from step
(b) and mixing to produce a pumpable free-flowing slurry,
d. disintegrating the solid particles in the slurry from step (c)
by passing said slurry through a high speed rotary stone mill with
opposed stone faces set at a clearance within the range 0.002 to
0.015 inch,
e. adding solvent to the disintegrated material from step (d) and
mixing to produce a screenable slurry containing not more than
about 15 percent by weight of solids,
f. screening the material from step (e) to obtain three separate
streams of material segregated with respect to particle size as
follows:
1. a first stream of material comprised of miscella-wet particles
which remain on a screen of about 24 mesh, which material exits the
process for oil, meal, and solvent recovery, and
2. a second stream of material comprised of miscella-wet particles
which remain on a screen of about 80 mesh, which stream of material
is returned to the fourth step (d) of the process for further
disintegration, and
3. a third stream of material comprised of the major portion of the
solvent and oil (miscella) and the particles of solids which pass
through a screen of about 80 mesh, and
g. diluting the said third stream of material with solvent to
produce a slurry material containing from about 3 to about 10
percent of solids, and
h. feeding the diluted slurry material of the preceding step (g) at
a pressure of at least about 15 pounds per square inch to a liquid
cyclone, which liquid cyclone is adjusted to produce an overflow
stream and an underflow stream in the ratio by weight range of
about six parts of overflow to one part of underflow to 20 parts of
overflow to one part of underflow, with the solids content of the
overflow being in the range of about 3 to about 10 percent by
weight and the solids content of the underflow being in the range
of about 25 to about 45 percent by weight, which said underflow
stream exits the process for oil, meal and solvent recovery,
and
i. feeding the overflow stream from the liquid cyclone of the
preceding step (h) to the first stage of a series of liquid
cyclones at a pressure of at least about 30 pounds per square inch,
which first stage of liquid cyclones produces an overflow stream
and an underflow stream, the said overflow stream exiting the
process for oil, meal, and solvent recovery, and
j. feeding the said underflow stream from the preceding step (i) at
a pressure of at least about 30 pounds per square inch to the first
stage of the remaining series of stages of liquid cyclones, which
series of stages of liquid cyclones each of which produces an
overflow and an underflow stream and are so arranged that the
underflow stream from each of the stages of liquid cyclones is fed
to the next succeeding stage of liquid cyclones of the series at a
pressure of at least about 30 pounds per square inch, while the
overflow stream of each of the successive stages of liquid cyclones
exits the process for oil, meal and solvent recovery, each of the
stages in the series of liquid cyclones, including that of step
(i), being adapted to yield a weight ratio of overflow to underflow
within the range of 1 to 1 to 1.5 to 1, with the solids content of
the respective underflow streams from each stage of liquid cyclones
being successively exalted in each succeeding stage until the
solids content of the underflow stream from the final stage of
liquid cyclones of the series has reached at least about 30 percent
by weight, and
k. feeding the underflow stream from the final stage of liquid
cyclones of the preceding step (j) to a filter wherein the solids
of the said underflow stream are washed essentially free of oil
with solvent and partially freed from solvent to obtain a
solvent-damp material of a solids content of about 50 percent by
weight, and
1. removing the residual solvent from the solids from the preceding
step (k) by volatilization in a dryer to produce a protein
concentrate having a protein content of about 70 percent by weight,
a total gossypol content of less than about 0.30 percent by weight,
and an oil content of less than about 2 percent by weight.
Description
The salient features of the process, which process is applicable to
either defatted or undefatted cottonseed prime in quality and free
of deleterious contaminants as a starting material, comprise:
rigorous control of moisture in the starting material (meats) at
moisture levels well below those levels previously considered
feasible in conventional oilseed milling practice; precisely
controlled, practically instantaneous disintegration of the
material being processed while maintaining the integrity of the
gland structure to avoid dispersal of gland contents in the
processed material; disintegration in a nonaqueous, nonpolar, fluid
medium by use of a high-speed stone mill; and the use of vibrating
screens and liquid cyclones in series.
A nonexclusive, irrevocable, royalty-free license in the invention
herein described throughout the world for all purposes of the
United States Government, with the power to grant sublicenses for
such purposes, is hereby granted to the Government of the United
States of America.
This invention relates to an industrially practical, continuous
method of processing cottonseed to produce as a major end product,
an edible grade of cottonseed concentrate that is high in protein
content and essentially free of gossypol, oil, and hulls. The said
end product is eminently suited for use as a high protein dietary
supplement for human nutrition, and is of a quality and purity,
with respect to its protein content, that have not hitherto been
possible of attainment by contemporary processing methods.
Cottonseed is unique among oilseeds in that distributed throughout
the oil and protein bearing kernel are numerous small ovoid sacs,
commonly known as pigment glands. These pigment glands contain
about 35 percent to 45 percent by weight of gossypol and
gossypol-like compounds.
By chemical analysis whole mill run cottonseed, with linters
removed, contain up to about 1.5 percent of gossypol. Since the
hulls contain little or no gossypol, the gossypol content of
dehulled kernels is higher. If the protein content, only, of the
cottonseed kernel is considered, its content of gossypol may be as
high as 3 percent. This is an important consideration because as
the protein content of any cottonseed product is increased by the
removal of hulls, oil and other nonprotein constituents, the
gossypol content will rise proportionally unless concurrent steps
are taken to remove gossypol.
Gossypol is a highly reactive material, and under the processing
conditions normally used including, but not limited to, moisture,
heat, pressure and time, the pigment glands of cottonseed are
ruptured, the gossypol is discharged and some or most of it
combines with various constituents of the meal. The most usual
combination appears to be with lysine, one of the essential amino
acids present in cottonseed. When combined with gossypol, this
essential amino acid is rendered nutritionally unavailable. Two
methods of gossypol analysis are presently in use and these methods
permit the determination of gossypol with a high degree of
accuracy. One method determines the "free" or uncombined gossypol
present. The other method determines the "total" gossypol content.
The difference between the two values is referred to as the "bound"
gossypol.
Cottonseed pigment glands normally are mechanically strong and
resistant to rupture; however, in the presence of moisture, and
particularly moisture in combination with heat, and pressure,
pigment glands readily rupture and discharge their gossypol content
which material is thereby brought into intimate contact with the
protein, oil, and other constituents making up the kernel.
Currently, cottonseed is processed by mechanical pressing (screw
pressing or hydraulic pressing), by solvent extraction with a
commercial grade of n hexane, or by prepress solvent extraction in
which a major part of the oil is first removed by screw-pressing
followed by solvent extraction of the resulting press cake with
commercial n hexane. The meal or cake produced by any of these
three processes is typically adjusted to contain 41 percent protein
(nitrogen .times. 6.25) by incorporation of cottonseed hulls that
contain little or no protein. Some few commercial cottonseed
crushing mills produce a meal with about 50 percent protein. The
cake or meals just described (41 percent to 50 percent protein) are
destined for use as animal feed. Processing conditions vary
considerably in the different mills and can affect, in a
significant manner, sometimes adversely, the quality and nutritive
value of the cottonseed meal being produced, especially if use as a
feed for nonruminants is intended.
The preparation and processing conditions employed in the
aforementioned methods all employ in some degree the addition of
moisture to either the kernels or the flaked meats, together with
heating or cooking and the application of pressure where screw
pressing, prepressing, or hydraulic pressing steps are employed.
These conditions of processing are in general ideally suited to
rupture the pigment glands, liberate the gossypol contained therein
into intimate contact with the other kernel components, and promote
the reaction of gossypol with the protein constituents of the
kernel.
The presence of cottonseed pigments together with attendant
processing conditions often cause the crude cottonseed oil produced
conventionally to have a color so dark that the normal alkali
refining and bleaching will not yield an oil prime in color. Such
colored oils must be sold under a price penalty.
There is limited production at one mill in the United States of a
cottonseed flour intended for human consumption. By dint of careful
selection of prime cottonseed kernels low in gossypol content from
an adjacent production line (producing oil and feed grade meals),
by the elimination of as many hulls as possible, and by diversion
of the fine meats fraction (containing much hull material) back to
the adjacent production line, and by careful screw pressing of the
selected kernels followed by fine grinding, a flour product is
produced which is higher in quality than the feed grade meal
collaterally produced. The flour product is nevertheless much
higher in gossypol content and much lower in protein content, in
protein quality, and is much darker in color than the cottonseed
flour produced by the process of this invention.
The high grade protein concentrate produced by the process of this
invention has approximately the following representative chemical
analysis:
---------------------------------------------------------------------------
COMPOSITION
Moisture, % 4.0 Protein (Nitrogen .times. 6.25) % 68.0 Nitrogen, %
10.8 *Nitrogen solubility, % 98.0 Total gossypol, % 0.25 Free
gossypol, % 0.05 Lipids, % 1.0 Crude Fiber, % 2.6 Ash, % 8.0 E.A.F.
Lysine, g./16 g. N 3.85 *in 0.02 N NaOH
__________________________________________________________________________
the above-listed compositional analyses are possible of achievement
by reason of new discoveries that relate to the handling,
preparation, and drying, of the cottonseed kernels and extraction
of the rolled flakes; by the discovery of new continuous techniques
in the application of equipment for disintegrating the cottonseed
whereby the pigment glands are freed from their enrobing tissue,
and the meal particles are finely comminuted without rupturing the
pigment glands; by the discovery of a continuous screening
technique whereby hulls can be removed and incompletely
disintegrated meat particles can be separated for additional
disintegration treatment, screening, and recycling to increase the
yield of final high protein product, if desired, and to reduce the
loss of protein in any diverted hull or concentrated pigment gland
fractions; by the discovery of a highly efficient, rapid, and
relatively inexpensive continuous process using 50 mm. and 10 mm.
liquid cyclones whereby a concentrated pigment gland fraction for
diversion from the process is instantly obtained from the underflow
of the 50 mm. liquid cyclone, the overflow from the 50 mm. liquid
cyclone being employed directly to produce a product of 65 percent
or higher protein contents or if a higher protein content product
is desired it may be passed through one or more stages of 10 mm.
liquid cyclones whereby the slurry is concentrated or thickened to
a total solids content of up to 30 percent or more and the protein
content of the solids is increased to 70 percent or more; by the
discovery that a slurry so thickened can be filtered on a vacuum
filter at capacity rates as high as or higher than 50 pounds of
solids per hour per square foot of filter area, which rate is
particularly suitable for continuous vacuum filtration on a
commercial-type rotary drum filter to produce a cake containing 50
percent of solvent or less which material is suitable for the final
removal of solvent in commercial-type continuous or batch meal
desolventizing equipment.
As an alternative to the use of the smaller, but higher gravity,
liquid cyclones for increasing the solids content of the process
stream prior to filtration and drying, it is possible to feed the
overflow stream at the 50 mm. liquid cyclone for thickening to a
filter, to an evaporator or to a settling chamber.
Since the smaller, but higher gravity liquid cyclones produce some
exaltation of the process stream with respect to protein content,
substitution of other methods of concentrating for the function of
these cyclones is made at the expense of ultimate protein content
(about 65 percent vs. more than 70 percent) but the total yield of
concentrate is enhanced.
We have found that a meats stream from the cottonseed hulling
equipment composed of the whole meats, cracked meats, and the bulk
of the fine meats can be used. This meats stream represents up to
90 percent of the protein originally present in the cottonseed.
Excess hulls present are removed in subsequent screening and liquid
cyclone operations.
We have discovered that when disintegrating either defatted or
undefatted material in order to prevent or minimize the concurrent
rupture of pigment glands it is essential first to dry the meats
below 4.0 percent by weight of moisture and then to feed a very
thick but flowable slurry of the cottonseed material and solvent to
the stone mill. The solids content of this slurry is preferred to
be from about 40 percent to 50 percent but is not limited to this
precise range. Before the slurry is fed to the stone mill, it must
be fluidized by vigorous agitation for about 5 to 15 minutes or
more. We have discovered that the high solids content is
particularly important when disintegrating defatted cottonseed
material in contrast to undefatted material. We have used n-hexane
successfully as a solvent but other nonpolar hydrocarbon solvents
are obviously operable.
The disintegration step is carried out with a high speed (3500
r.p.m.) stone mill wherein a rolling, torsional, or rubbing action
is applied to a thick n-hexane solvent slurry of the cottonseed.
Clearance between the stones may be as little as 0.002 in., which
clearance can be attained by precise adjustment of the spacing
between the stones. Surprisingly, this action is more gentle and
controllable relative to the effect on pigment glands than impact
or liquid shear as has previously been proposed for the
disintegration of cottonseed in solvent slurry. In addition,
previously investigated modes of disintegration using liquid shear
or impact (i.e., a high-speed blender) required 60 to 90 minutes,
batchwise, when operated to disintegrate 100 pounds of flakes.
Lengthy batchwise blending generates sufficient heat to cause
evaporation of solvent, and also results in appreciable rupture of
gossypol pigment glands with attendant binding of the gossypol so
released to protein components of the meal.
We have discovered that the proper degree of disintegration,
without gland rupture can be accomplished in a fraction of a second
with a high-speed (3500 r.p.m.) stone mill, using a continuous feed
and using discovered control techniques. In spite of the high
speed, the disintegration is gentle, due to the rubbing, rolling
and torsional action that takes place between the stones. It is
essential that the meats be dried to less than about 4.0 percent
moisture content, but they may be unextracted or extracted prior to
the disintegration step.
The presently accepted method of preparing cottonseed for
conventional commercial solvent extraction involves moistening the
cottonseed meats to about 10 to 12 percent H.sub.2 O, drying or
tempering these meats at temperatures of from 180.degree. to
210.degree. F. for up to 60 minutes to obtain a moisture content of
about 10 percent, and then flaking to a thickness of 0.007 in. to
0.012 in.
This preparation is held to be essential to the production of a
flake sturdy enough to permit satisfactory percolation in a basket
type of extractor and thin enough to extract satisfactorily.
However, this procedure is known to rupture pigment glands thereby
releasing gossypol which then combines with meal constituents to
produce bound gossypol. Ruptured glands are not detectable
visually. The gossypol released from the ruptured glands combines
chemically and preferentially with the essential amino acid lysine
thereby rendering it unavailable nutritionally. Contrary to the
above-described time-honored and industry-accepted concept, we have
discovered that drying the meats first to about 4.0 percent H.sub.2
O by weight or less (which drying is essential to prevent pigment
gland rupture) at a temperature below 180.degree. F. and then
flaking the dried meats to a thickness of about from 0.008 in. to
0.012 in. will produce a low moisture flake that crumbles, but
surprisingly results in a solvent percolation rate that is
comparable to the percolation rates obtained in conventional
commercial extractors.
The slurry from the stone mill is diluted to a consistency of
between 10 and 15 percent total solids to aid in the screening
operation. Dilution may be accomplished by the use of recycle
solvent streams of lower total solids content, by use of fresh
hexane, or by use of both.
Screening is accomplished with conventional, commercially available
continuous screening apparatus. Three fractions are separated in
the screening operation: (1) a coarse fraction consisting mainly of
hulls; (2) an intermediate fraction containing a few smaller hull
particles mixed with particles of the flakes that have not been
sufficiently disintegrated; and (3) a fine fraction composed
largely of small meats particles which have a large surface area
relative to their mass, disengaged but intact pigment glands, a few
smaller particles of insufficiently disintegrated flakes, and a few
fine hull particles.
A 24 mesh screen is used to collect the coarse fraction. The mesh
opening may be varied somewhat under different operating
conditions, with different varieties of cottonseed, etc.
An 80 mesh screen is used to collect the intermediate fraction.
Here, also, the mesh opening may be varied somewhat under different
operating conditions with different varieties of cottonseed,
etc.
The fine fraction is the material passing through the 80 mesh
screen. The principal purpose of the screening operation is to
obtain a slurry of fine meal particles mixed with pigment glands,
which glands have been freed from enrobing tissue, and which glands
are capable of separation from the fine gland-free meal particles
as separate entities under the intense centrifugal action in the 50
mm. liquid cyclone.
An ideal slurry of fine meal particles would have no protein
particles coarse enough or heavy enough to be removed along with
the freed pigment glands. An approach to such an ideal slurry is
obtained by careful attention to the disintegrating procedure.
The slurry feed is pumped at a pressure of at least 15 pounds per
square inch into the tangential feed port of the liquid cyclone at
its largest diameter. The resulting centrifugal action whirls the
feed stream around the periphery of the interior of the bowl and
exerts a centrifugal force of 5000 to 7000 times the force of
gravity, depending on the pressure and rate of feed of the slurry
material. This centrifugal action causes the larger, heavier, and
more compact particles having the lowest ratio of surface area to
mass (as typified by the ovoid-shaped pigment glands and the larger
particles of meats tissue) to travel rapidly to the outer periphery
of the liquid cyclone bowl. Thus these particles, which include the
bulk of the pigment glands, the larger meats particles, and hull
particles, are forced by the moving liquid down the tapered sides
of the lower portion of the liquid cyclone to the constricted tip,
or " apex," of the cyclone where they are discharged, together with
a minor portion of the solvent, as underflow. The finer meal
particles, which are essentially free of pigment glands and are of
lower effective specific gravity than the pigment glands and coarse
meal particles due to their relatively high ratio of surface area
to mass, move much more slowly towards the periphery of the bowl of
the liquid centrifugal and are forced upwards by the moving liquid
through the vortex finder at the center of the bowl and are
discharged through the vortex finder as overflow.
We have found that the underflow stream ranges in solids content
from about 25 percent to about 40 percent by weight while the
overflow stream ranges in solids content from about 3 percent to
about 7 percent by weight, with the overflow stream amounting to
from about 80 percent to about 96 percent and higher by weight of
the feed stream, while the underflow stream amounts to from about 4
percent to about 20 percent of the weight of the feed stream. We
have also found that the ratio by weight of the overflow stream to
that of the underflow stream and the solids content of the
respective streams is controlled by the rate and pressure at which
the feed stream enters the tangential feed port of the liquid
cyclone, the cross-sectional area of the "apex" orifice through
which the underflow discharges, the makeup of the solids of the
feed stream with respect to particle size, and the solids content
of the feed stream. The larger, and more compact particles of the
slurry which include the bulk of the pigment glands, are forced by
the moving liquid down the tapered sides to the "apex," or small
lower end where they are discharged as underflow (UF). The finer
meal particles, practically free of pigment glands, are forced to
the center of the device and are discharged upward through the
vortex finder as the overflow (OF). The "apex" orifice may be
varied to adjust the ratio of the weight of OF to the weight of UF.
This ratio is called the "split." The underflow "apex" orifice of
the P50 liquid cyclone may be adjusted to the point where a "split"
(ratio of overflow slurry, lbs., to underflow slurry, lbs.) from
approximately 4 to 1 to approximately 30 to 1 is maintained. Under
certain conditions smaller or larger splits may be desirable.
Liquid cyclones are available in many sizes, usually designated by
the maximum inside diameter of the bowl, expressed in millimeters
(mm.). Two sizes of liquid cyclones have been used in this
invention, namely 50 mm. (P50) and 10 mm. (Doxie) cyclones. This
invention is not limited to the use of these two sizes because
other liquid cyclones, larger and smaller and also of intermediate
size, can be used.
It should be noted in the case of the P50 liquid cyclone and also
in the case of the 10 mm. Doxies the capacity of the system may be
greatly expanded by the use of multiple liquid cyclones in parallel
in any of the stages. The cyclones in any of the stages will be
served by a single pumping unit and supply tank.
The overflow from the P50 liquid cyclones is pumped under a
pressure of 30 p.s.i., or more, to two or more stages of 10 mm.
Doxies in series. The underflow from any one stage becomes the feed
for the next stage. The centrifugal action (up to 10,000 G) in the
smaller diameter 10 mm. Doxies is more intense than in the larger
diameter 50 mm. P50 liquid cyclones. Most of the protein particles
found in the overflow of the P50 liquid cyclones are now found in
the underflow of the Doxies. The total solids content of the
underflow is considerably greater than that of the feed. The total
solids content of the overflow is considerably less than that of
the feed.
We have discovered two other unexpected and surprising facts in the
operation of the Doxies:
1. the protein content of the solids in the underflow of each Doxie
stage is greater than that of the solids in the underflow of the
preceding Doxie stage and is greater than that of the solids in the
feed to the first Doxie stage; also, the protein content of the
solids in the corresponding overflows is reduced;
2. the total gossypol content of the solids in the underflow of
each Doxie stage is less than that in the solids of the preceding
Doxie stage and of the solids in the feed of the first Doxie stage;
also the total gossypol content of the corresponding solids in the
overflows is increased. By the use of two or more stages of Doxies
the total solids content of the underflow may be progressively
increased to a value as high as 30 percent.
An underflow slurry from the final Doxie stage having a total
solids content of about 30 percent is suitable as feed to a
continuous, vacuum drum filter. Filter tests have yielded rates as
high as 50 pounds of solids per square foot of filter area per hour
producing a filter cake with a solvent content of about 50
percent.
The Doxie overflows of lower total solids content may be recycled
to the system in whole or in part at appropriate points, to enhance
the yield of protein concentrate.
It will be obvious to those skilled in the art of oilseed
processing that the protein exalting operations of the process of
this invention should be applicable to other materials such as
soybeans, peanuts, sunflower seed, castorbeans, and rice.
LIQUID CYCLONE PROCESS FOR HIGH PROTEIN COTTONSEED CONCENTRATE
The more detailed description of the various steps of the process
that follow are more easily related one to the other by recourse to
the several flow diagrams (FIGS. 1-4 inc.) which of themselves are
self-explanatory.
We distinguish four embodiments of the process. A first process
embodiment wherein the cottonseed meats are dried, flaked, and
extracted for removal of the oil prior to the steps of
disintegrating the extracted material in a solvent, separating and
concentrating the protein fraction. This embodiment yields a
concentrate that exhibits a protein content of about 65 percent by
weight (see FIG. 1).
A second process embodiment parallels the several steps of said
first embodiment but incorporates the additional step of passing
the process stream of the protein concentrate through a series of
liquid cyclones for the purpose of exalting the protein content of
the finished concentrate product to at least about 70 percent by
weight (see FIG. 2).
A third process embodiment involves the steps of drying and flaking
the cottonseed meats but immediately thereafter the process stream
enters the phases of fluidization, disintegration in a solvent,
protein separation, and concentration, with oil enriched solvent
(miscella) being withdrawn from the process stream at several
appropriate steps. This embodiment like that of said first
embodiment is designed to yield a product concentrate of about 65
percent protein by weight (see FIG. 3).
A fourth embodiment parallels the several steps of said third
embodiment but like said second embodiment incorporates the
additional step of passing the process stream of the protein
concentrate through a series of liquid cyclones for the purpose of
exalting the protein content of the finished concentrate product to
at least about 70 percent by weight (see FIG. 4).
DRYING MEATS (ALL EMBODIMENTS)
Meats are dried preferably to 2- 4 percent moisture content at a
temperature not exceeding about 180.degree. F. Drying meats prior
to extraction prevents the increase in moisture of meats tissue
resulting from removal of oil, i.e., meats at 8 percent initial
moisture and 33.3 percent oil, when extracted "as is," would yield
oil free marc having a moisture content of about 12 percent. At
this high level of moisture, pigment glands are weakened and
ruptured simply by transfer of moisture to the gland walls. If the
same meats are dried to a moisture content of 3 percent before
extraction the moisture content of the oil free marc (on a solids
basis) produced is only about 4.6 percent, a concentration
insufficient to affect the pigment glands. It also appears that
drying the meats tends to toughen the pigment gland walls and to
loosen the attachment of the pigment glands to the enrobing meats
tissue.
FLAKING (ALL EMBODIMENTS)
Meats are flaked preferably to a thickness of 0.008-0.012 inch
while still warm from the drying operation. Flaking the meats while
they are still warm mitigates pickup of moisture following drying.
Flake thickness is controlled to prevent crushing or rupture of the
pigment glands in the flaking operation while still giving a flake
thin enough to expedite oil removal by extraction. The flakes
produced differ from those employed in conventional extraction, due
to their lower moisture content and are sandy and granular in
texture.
EXTRACTING OIL (FIRST AND SECOND EMBODIMENTS)
The oil is extracted from the flakes with hexane in a conventional
type of extractor to a residual lipids content of about 2 percent
or less. The miscella containing the oil is routed to a
conventional oil and solvent recovery system. The solvent damp
extracted marc is routed to a feeder which feeds the wet marc to
the liquid cyclone system through a fluidizer.
FLUIDIZING (ALL EMBODIMENTS)
Fluidizing of the wet marc to convert it into a thick, but free
flowing slurry, is necessary to obtain a material of the proper
consistency to feed evenly and smoothly to the stone mill and to
provide a material of the proper viscosity for maximum
disintegration in the mill without rupture of the pigment
glands.
Fluidization is accomplished by passage of the wet marc through a
pug type, baffled mixer which provides vigorous nonimpact
agitation. Best results have been obtained with wet marc containing
preferably about 45 percent solids and 55 percent hexane. Wet marc
from the extractor may contain less than 55 percent hexane, in
which case the requisite amount of additional hexane is added to
the marc at the point of entry into the pug mill mixer.
Once "on stream" conditions are reached shortly after startup, the
on-80 mesh material coming from the vibrating screen is also fed to
the pug mill mixer at the point of entry of the wet marc. The on-80
mesh material consists of a slurry of about 50 percent solids,
mostly of insufficiently disintegrated meats particles, and about
50 percent hexane. The solids in the on-80 mesh stream amounts to
about 15 percent of the total solids fed to the system initially in
the form of wet marc.
DISINTEGRATION (ALL EMBODIMENTS)
Disintegration of the meats into ultrafine particles of meats
tissue and intact glands, most of which are entirely free of
adhering meats particles, without rupturing the glands, is
accomplished by passing the fluidized marc from the fluidizer
through a high-speed stone mill. This mill consists of two
horizontally mounted coarse grit carborundum stones about
43/4-inches in diameter. The upper stone is stationary and has a
center hole about 21/3-inches in diameter through which the
fluidized marc is fed. The feed opening is in the form of an
inverted cone with the large end about 3 inches in diameter and
terminating in a flat horizontal surface seven-eighths of an inch
across. The lower stone is of the same diameter as the upper with
the center portion in the form of a cone, which fits into the cone
of the upper stone, and terminates in a horizontal flat peripheral
surface seven-eighths of an inch across. The lower stone is mounted
on an adjustable spindle which permits adjustment of the clearance
between the stones from contact of the horizontal plane surfaces to
0.25 of an inch. The lower stone revolves at 3600 r.p.m.
For this operation the stones are set for a clearance of from 0.002
to 0.015 inch (preferably 0.006 to 0.008 inch) so that there is no
actual contact between the stones and there is no grinding action
as such. The force exerted on the material passing between the
stones is a torsional, rolling, fluid shearing action which has
been found to effectively disrupt the meats tissue into micron size
particles and to separate the glands cleanly from the enrobing
meats tissue with essentially no breakage or permanent deformation
of the glands. For best results the fluidized marc should be of the
maximum solids content compatible with free flow.
The milled marc is discharged directly from the mill into a tank
provided with an agitator. Initially hexane is pumped to this tank
at a rate such as will provide a slurry containing about 15 percent
of total solids. When "on stream" conditions are attained a portion
of the overflow from the second liquid cyclone (a battery of 10 mm.
diameter cyclones known as the No. 1 Doxie) may be returned in
whole or in part to this tank to provide a portion of the solvent
for dilution and the hexane feed is correspondingly reduced.
SCREENING (ALL EMBODIMENTS)
The diluted milled marc (preferably 12-15 percent solids) is pumped
from the feed tank to a vibrating screener fitted with 24 mesh and
80 mesh screens. The vibrating screener discharges three streams of
slurry as follows:
A. on 24 mesh. The on-24 mesh material contains about 1 percent of
the solids in the feed to the screener and contains 60 percent to
70 percent solids. The solids of this material consist chiefly of
flat hull particles, with a small amount of meats particles too
large to pass through the 24 mesh screen. This on-24 mesh material
is combined with the underflow discharge from the first liquid
cyclone and filtered. For embodiments one and two this cake is
routed to dryers. For embodiments three and four it is washed free
of oil on the filter and is then routed to dryers.
B. on 80 mesh. The on-80 mesh solids amounts to 15 percent or less
(depending on the efficiency of disintegration) of the total solids
of the slurry fed to the screens and as discharged from the screen
contains about 50 percent solids and 50 percent hexane. The solids
consist of coarser particles of meats tissue containing embedded
glands plus a small amount of hulls. This material is returned in
toto to the system via the fluidizer for reworking as described
under "Fluidizing."
C. through 80 mesh. This stream contains 85 percent to 90 percent
of the total solids of the input wet marc. Total solids content
amounts to about 11 percent to 14 percent, with the solids being
made up of the ultrafine meats particles which are free of pigment
glands and constitute the desired end product, coarser meats
particles containing some embedded pigment glands, pigment glands
free of adhering meats particles, and some fine hull particles.
This through 80 mesh slurry discharges from the screen directly
into the feed tank for the first liquid cyclone, the 50 mm.
diameter P50.
FIRST LIQUID CYCLONE P50, 50 MILLIMETER (ALL EMBODIMENTS)
The through 80 mesh slurry from the screen, containing about 11
percent to 14 percent solids, is initially diluted with hexane in
this tank to a solids content of about 7.5 percent. When "on
stream" conditions are attained the hexane for dilution may be
replaced in whole or in part by overflow feedback from the second
liquid cyclone (the No. 1 Doxie), which contains about 1 percent
solids.
The diluted slurry is maintained under vigorous agitation in the
tank to keep all solids in suspension and is fed to the P50 cyclone
at 15-40 p.s.i. pressure (preferably 20- 30 p.s.i.) by a pump.
Classification and separation of the suspended particles in the
slurry takes place in the liquid cyclone to deliver an underflow
and an overflow stream. The underflow discharges from the lower
tip, or "apex" of the liquid cyclone. The underflow preferably
amounts to between 5 percent and 14 percent of the total slurry
entering the feed aperture of the P50 liquid cyclone and contains
from about 25 percent to 45 percent of solids. The overflow
discharges from the upper, or the vortex finder outlet, of the P50
liquid cyclone. This overflow stream preferably amounts to 86
percent to 95 percent of the total slurry entering the feed
aperture of the liquid cyclone and contains from about 3.5 percent
to 7.0 percent of solids. The weight ratio of overflow to underflow
is defined as the "split" and preferably ranges between from six
parts of overflow to one part of underflow to 20 parts of overflow
to one part of underflow.
The split ratio is controlled primarily by the relative
cross-sectional areas of the "apex" and vortex finder orifices and
the rate and pressure at which the slurry feed stream is pumped to
the liquid cyclone. The solids contents of the overflow and
underflow streams are also controlled by those factors but are also
strongly affected by the percentage of solids in the feed stream
and the degree of fineness of the solids.
The underflow contains essentially all of the intact pigment glands
of the feed slurry, relatively coarse (but smaller than 80 mesh)
particles of meats many of which contain embedded pigment glands,
and hull particles. These solids range from 3 percent to as much as
8 percent in gossypol content and from 45 percent to 60 percent in
protein.
The underflow stream is removed from the system and filtered. For
embodiments one and two the cake is routed to dryers. For
embodiments three and four it is washed free of oil on the filter
and then routed to dryers.
The overflow stream discharges from the upper, the vortex finder
outlet, of the P50 liquid cyclone into an agitated feed tank. This
overflow stream contains the extremely fine solids comprising the
desired high protein, low gossypol portion of the feed stream.
SECOND LIQUID cyclone, NO. 1 DOXIE BATTERY of 10 MILLIMETER
DIAMETER LIQUID CYCLONES (SECOND AND FOURTH EMBODIMENTS)
The overflow stream from the P50 liquid cyclone is maintained under
vigorous agitation in a tank and pumped from the tank through a
battery of 10 mm. diameter liquid cyclones mounted in parallel at a
pressure of at least 30 p.s.i. This battery of small liquid
cyclones serves to concentrate the solids. Overflow from the No. 1
Doxie battery, liquid containing about 1 percent of solids, amounts
to approximately 65 percent of the feed stream. The overflow stream
may be exited from the system at this point or may be returned to
the milled marc dilution tank, and/or the P50 feed tank in whole or
in part to serve as dilution solvent.
The underflow stream from No. 1 Doxie battery amounts to about 35
percent of the feed stream and contains about 10 percent of solids.
This stream discharges into a tank and comprises the feed to the
No. 2 Doxie battery.
THIRD LIQUID CYCLONE, NO. 2 DOXIE BATTERY OF 10 MILLIMETER LIQUID
CYCLONES (SECOND AND FOURTH EMBODIMENTS)
The underflow discharge from the No. 1 Doxie battery is maintained
under agitation in the receiving tank and is pumped to the third
liquid cyclone, the No. 2 Doxie battery, at a pressure of at least
30 p.s.i. The overflow from the No. 2 Doxie battery, containing
about 2 percent solids and amounting to about 60-65 percent of the
feed stream may be exited from the system at this point or may be
returned to the No. 1 Doxie battery feed tank.
The underflow from the No. 2 Doxie battery contains about 20
percent solids and amounts to about 40 percent of the input feed
stream.
FOURTH LIQUID CYCLONE, NO. 3 DOXIE BATTERY OF 10 MILLIMETER LIQUID
CYCLONES (SECOND AND FOURTH EMBODIMENTS).
The underflow discharge from the No. 2 Doxie battery is maintained
under agitation in the receiving tank and is pumped to the fourth
liquid cyclone, the No. 3 Doxie battery, at a pressure of at least
30 p.s.i. The overflow from the No. 3 Doxie battery containing
about 12 percent solids, and amounting to about 48 percent of the
feed stream may be exited from the system at this point or may be
returned, in whole or in part, to the No. 2 Doxie battery feed
tank.
The underflow from the No. 3 Doxie battery contains about 30
percent or more of solids, and amounts to about 52 percent of the
input feed stream. This high solids content stream is sent to a
rotary vacuum filter.
FILTERING
The high solids stream containing the desired protein concentrate
product is fed to a rotary vacuum filter which yields a cake
containing about 50 percent solids. For embodiments one and two
this cake is routed to the dryers. For the third and fourth
embodiments the cake contains oil and is washed free of oil with
solvent on the filter and is then routed to the dryers.
DRYING
The cake is heated in a suitable dryer to about 225.degree. F. in 1
hour to coincidentally remove solvent and destroy
micro-organisms.
GRINDING
After heat treatment as above, the cake is ground through a
sanitary stud mill to a fine flour and packaged. The final product
flour has a protein content on the order of 65 percent or higher
for embodiments one and three, and 70 percent or higher for
embodiments two and four, and for all embodiments, a total gossypol
content of 0.30 percent or less.
The Tables 1 through 5 that follow present operational data for
each of the several steps of the general process. The Tables are
entirely self-explanatory. ##SPC1## ##SPC2## ##SPC3##
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