Note: Descriptions are shown in the official language in which they were submitted.
PROCESS FOR_EXTRACTING_OLEAGINOUS SEED MATERIAL
Field of the Invention
This invention relates to the solvent extraction of
oleaginous seed materials, and more particularly to a novel
process for extracting oleaginous seed materials utilizing
aqueous alcohols to produce protein flours or protein concen-
trates~
Back~round of the Invention
In earlier disclosures, exemplified by U.S. Patents
Nos. 4,144,229 and 4,219,470 assiyned to the same assignee as
the present invention, I have described the use of aqueous
solutions of alcohols, such as ethanol and isopropanol to
extract carbohydrates, non-oil lipids and oil in three or
four sequential extraction steps.
In U.S. Patent No. 4,219,470 there are disclosed
processes for preparing a protein concentrate from oleaginous
seed material. In the four step process thereof, the oleagi-
nous seed material is sequentially extracted in the steps
comprising: contact with a relatively dilute aqueous alcohol
to remove carbohydrates and phosphatides; contact with
concentrated alcohol to displace dilute alcohol; contact with
undistilled, recycled concentrated alcohol at or near the
boiling point to partially remove oil; and contact with
distilled concentrated alcohol at or near the boiling point
to complete oil removal. The novel protein concentrate is
obtained by desolventizing the extracted residue.
In U.S. Patent NoO 4,144,229 there are disclosed
processes for preparing a novel protein Elour under condi-
tions such that, some but not all oE the carbohydrates and
non-oil lipids are extracted to produce a proteln flour and,
in particular, a soy flour, which is a product of unspeci-
fied, but lower protein content than the 70% specified for
soy protein concentrate. This soy flour has cer-tain desired
characteristics. These characteristics are: a reduced
content of the non-oil lipids that give soybean products a
beany flavor, a reduced content oE those carbohydrates which
cause flatulence, and color which is whiter than that of
commercially available soy flours.
In such processes, after extraction in a first step
with 50 ~o 70 weight percent alcohol of all or some of the
carbohydrates and non-oil lipids from the full fat flakes,
the flakes are contacted in a second step with concentrated
alcohol to displace the dilute alcohol, consequently making
it feasible to extract oil in a third step. The second step
is mandatory in such process because even at or near the
solution boiling temperature, oll has limited solubility in
92 weight percent aqueous ethanol, the highest concentration,
because of azeotrope formation, that can be recovered from
ethanol solutions by simple rectification. At ethanol
concentrations only slightly lower than 92 percent, the
solubility of oil is reduced to an impractical amount. Any
dilution of the concentrated alcohol by water entering with
--2--
the flakes from the second step effectlvely reduces oil
solubility.
Similar considerations apply to the other alcohols,
i.e., isopropanol, in whose aqueous solutions oil has limited
solubility, and which forms an azeotrope with water that
limits the practical maximum alcohol concentration.
Oil is extracted in the aforesaid third step with
92 percent alcohol. The oil-rich solution is cooled to
precipitate most of the oil, which is removed from the
process; and the lean solution, still containing some oil, is
recycled to the third step. Extraction of oil from the flakes
is completed in a fourth step, where the solvent is distilled
92 percent alcohol.
If the protein product can tolerate some or most of
the carbohydrates, the first step may be minimized or elimi-
nated, as was disclosed in U.S. Patent No. 4,144,229.
If the water solubility of the protein in the
protein product is to be preserved, both such first and
second steps should be carried out at the lowest feasible
temperature. It is well known that protein denaturation is
accelerated, particularly at increased temperature, by
contact with aqueous alcohol ranging in concentration from 50
to 70 percent, whereas protein denaturation is little
affected by 90 percent alcohol even at its boiling point.
Objects of the Invention
An object of the present invention is to provide
an improved process for treating oleaginous seed materials
using aqueous alcohols as the extraction solvent for the
carbohydrates, non-oil lipids and oil.
Another object of the present invention is to
provide an improved process for extracting oleaginous seed
material with aqueous alcohol solutions to produce a pro-
teinaceous flour.
Still another object of the present invention is to
provide an improved process or extract.ing full-fat soybean
flakes with aqueous alcohol solutions to remove a portion of
the carbohydrates and non-oil lipids and substantially all of
the oil.
Another object of the present invention is to
provide an improved process for extracting full-fat soybean
flakes with aqueous alcohol to remove substantially all of
the alcohol soluble carbohydrates and non-oil lipids and
substantially all of the oil to produce soy protein con-
centrate.
Another object of the present invention is to
provide an improved process, with reduced utility costs, for
extracting full-fat soybean flakes with aqueous alcohol to
remove substantially all of the carbohydrates and non-oil
lipids and substantially all of the oil to produce soy
protein concentrate.
A still further object of the present invention is
to provide an improved process, requiring shorter processing
time, for extracting full-fat soybean flakes with aqueous
alcohols to remove substantially all oE the alcohol soluble
carbohydrates and non-oil lipids and substantially all of the
oil to produce soy protein concentrate.
$till another object oE the present invention is
to provide an improved process for extracting Eull fat
soybean flakes with aqueous alcohol solutions using percola-
tion extraction techniques.
Another object of the present invention is to
provide an improved process requiring shorter processing time
for preparing a novel protein flour by extracting particulate
oleaginous seed materials using aqueous alcohol solutions as
extraction solvents.
Summary of the Invention
-
These and other objects of the present invention
are achieved by extracting particles of oleaginous seed
material with aqueous alcohol solutions, wherein displacement
of dilute alcohol in the flakes i5 completed by concentrated
alcohol at or near the boilin~ temperature thereof.
In one embodiment of the present invention, the
oleaginous seed material is sequentially extracted in Eive
steps, comprising: contact with relatively cool and dilute
aqueous alcohol to remove some or all of the alcohol soluble
carbohydrates and non-oil lipids; contact with relatively
cool and concentrated alcohol to displace dilute alcohol;
contact with concentrated alcohol at or near the boiling
point to complete displacement of dilute alcohol and to
initiate oil extraction; contact with undistilled, recycled
concentrated alcohol at or near the boiling polnt t~ par-
tially remove oil; and eontact with distilled concentrated
alcohol at or near the boiling point to complete oil removal;
followed by desolventizing of the residual solids to yield a
protein concentrate or flour.
Brief Description of the Invention
A better understanding of ~he present invention as
well as additional objects and advantages ~hereof will become
apparent upon consideration of the detailed disclosure
thereof when taken with the accompanying drawing which repre-
sents a schematic flow diagram of the present invention.
Detailed Descrlption of the Invention
Although the process is hereinafter more fully
described as applied to soybeans to produce a soy protein
flour, it is to be understood that it is equally applicable
to other oilseeds, such as cottonseeds, peanuts, sesame
seeds, sunflower seeds, i.e.~ seeds containing high concen-
trations of nutritious proteins.
Soybean flakes are prepared by first cracking clean
soybeans between corrugated rolls into 4 to 8 pieces which
are then Aehulled, softened by heat at about 160F~ and
flaked between smooth rolls. Soybean flakes are typically
about 0.5 inch in diameter and 0.010 inch thick. Other oil
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!. 3
seeds may be similary flaked or simply ground to a maximum
particle size of about 0.25 inch. Such flakes as now pre-
pared for hexane extraction are equally well suited for the
process herein disclosed.
Referring now to the drawing, particulate oleagi-
nous seed materials in line 1 are sequentially passed through
Steps I to V. Hot distilled aqueous alcohol, at least 92
weight percent ethanol at or near its boiling point, is
introduced through line 2 into Step V and contacts flakes
from Step IV. Carbohydrates and non-oil lipids have been
extracted from these flakes in Steps I and II, and most of
the oil extracted in Step IV. Extraction of oil is completed
in Step V. Deoiled flakes exit Step V in line 3. Miscella
from Step V is introduced into Step IV through line 4 at a
point downstream of a heated recycled alcohol stream in line
5. Miscella is withdrawn from Step IV by line 6 and intro-
duced into Step III, as more fully hereinafter discussed.
The remaining miscella from Step IV i5 withdrawn by line 7
and cooled in heat exchanger 8 to precipitate an oil phase.
Mixed phases in line 9 are separated in a decanter or centri-
fuge 10 from which are withdrawn an alcohol phase in line 11
and heavier oil phase in line 12. The alcohol phase in line
11 heated in heater 13 constitutes the heated recycled
alcohol introduced into Step IV by line 5.
While the alcohol soluble non-oil lipids appear to
be completely extracted in Steps I and II r it may be found in
--7--
commercial practice that some non~oil lipids may accumulate
in the recycled stream, since such non-oil lipids are very
soluble in 90% alcohol at 100F. In that event, a small
purge stream 14 is drawn off and passed to any suitable
process, such as evaporation, by which means the alcohol
could be recovered for recycle to the process.
A portion of the miscella rom Step IV in line 6 in
used in Step III to complete dehydration of and to initiate
oil extraction from the flakes. The miscella withdrawn from
1U Step III in line 15 is cooled, preferably to the temperature
used in Step I and II, in a heat exchanger 16 to precipitate
an oil phase. Mixed phases in line 17 are separated in a
decanter or centrifuge 18, from which the alcohol phase exits
in line 19 and the heavier oil phase exits in line 20. This
oil may be combined with the oil in line 12 for further
processing (not shown).
The alcohol phase in line 19 flows to Step II.
Miscella exiting ';tep II in line 21 is admixed with water in
line 22 and introduced by line 23 into Step I downstream of
the point of introduction of the dilute alcohol stream in
line 24. The amount of water added in line 22 is that
required to dilute the alcohol in stream 21 to the same
concentration as the alcohol in stream 24, which for aqueous
ethanol may be any concentration between 50 and 70 percent at
the option of the plant operator. Final miscella containing
--8--
carbohydrates and non-oil lipids in solution exits the
process in line 25.
Substantially all of the carbohydrates and non-oil
lipids soluble in aqueous alcohol dissolve in Steps I and
II. Oil which enters Step II in the liquid stream is almost
completely precipitated as the alcohol is diluted in Steps II
and I. Precipitated oil deposited on the flakes is recycled
to Step III and redissolved. Carbohydrate miscella exiting
in line 25 may be practically free of undissolved oil. Oil
exiting in lines 12 and 20, having been precipitated from a
solution containing little carbohydrate and non-oil lipids,
is pale yellow and free of "break".
As applied to soybeans, in Step I carbohydrates and
non-oil lipids are extracted from the full-fat flakes at
temperat~res preferably in the range of 95 to 175F., using
as the solvent in line 24 aqueous ethanol in the con~entra-
tion range of 50 to 70 weight percent. It has been found
that the extraction of carbohydrates and phosphatides in Step
I is not, and need not be, complete. Even in alcohol concen-
~0 trations as high as 70 percent, the flakes imbibe solvent and
become swollen. Consequently, extractionof the last of the
carbohydrates by diffusion into the alcohol solution that
surrounds the flakes is slow. Fortunately, the flakes shrink
considerably as they move through Steps II and III, thus
being in effect pressed. Dissolved carbohydrates in the
flakes leaving Step I are thus largely removed in Steps II
and III, even th~ugh the concentrated alcohol used in those
steps is not a good solvent for carbohydrates. Since the
solution in line 21 contains carbohydrates and non-oil
lipids, it is introduced, after dilution with water, into
Step I at a point downstream from the entry of distilled
solvent in line 24, optimally at the point where the miscella
flowing through Step I from the right has the same solute
concentration as that in stream 23.
In Step II, the flakes are dewatered, preferably at
~he same temperature as in Step I, by countercurrent extrac-
tion with aqueous concentrated alcohol from Step III,
generally, approximately 90 weight percent ethanol. Extrac-
tion temperature and alcohol concentration in Steps I and II
depend on the properties desired in the protein product.
High temperature and low alcohol concentration cause rapid
loss of protein dispersibility and water absorption, which it
is often desired to preserve. As taught in the hereinabove
mentioned U.S. Pat~ent No. 4,219,470, a soy protein concen-
trate with a high protein dispersibility index (PDI) can be
obtained by prolonged extraction with 70 percent ethanol at
95~F. If PDI is o~ no concern, extraction can be accelerated
and a lower ratio of solvent to flakes employed by extracting
with ethanol as dilute as 50 percent and at a temperature as
high as the boiling point.
I have found that complete displacement of dilute
alcohol by concentrated at low temperature in Step II, as
--1 0--
taught in my previous c1isclosures, is not necessary. Partlal
displacement at low temperature in Step II followed by
completion of the displacement at high temperature in Step
III is attended by little loss of protein dispersibility.
Complete dehydration of the flakes is effected in Step III at
the same temperature as that of Steps IV and V, preferably at
or near the boiling point of the concentrated alcohol. The
saving in cost of extractors is considerable, since complete
displacement of dilute alcohol is much more rapid at the
higher temperature.
In Steps IV and V oil is extracted by concentrated
alcohol, e.g. ethanol solution of at least 92 weight percent
alcohol, at or near the boiling temperature. Soybean oil has
a solubility of only about 3O5 percent in boiling 90 weight
percent ethanol, and since a practical maximum concentration
in line 2 of ethanol recovered by distillation is 92 percent r
it becomes apparent why Steps II and III are required to
effect almost complete displacement of dilute alcohol. Oil
is removed from the process by virtue of the difference in
its solubility at the boiling temperature and at the tempera-
ture in line 9, which without resort to refrigeration is at
least 100F. With 90 percent ethanol, this difference is
about 2.25 percent. While practical considerations limit the
concentration of aqueous ethanol that can be recovered by
simple rectification to 92 percent, stronger concentrations
can be realized by well known methods. The use of ethanol
solutions oE up to 100 weight percent ethanol is contem-
plated in the process of the present invention.
It is desirable to produce in Step IV an oil
solution as nearly saturated as possible. Consequently, an
oil concentration gradient must be developed in the alcohol
solution as the alcohol solution moves from right to left so
that the alcohol solution first contacting the flakes
entering Step IV is nearly saturated. I have observed that
the very first oil is rapidly extracted from the flakes,
after which the rate is reduced. However, the oil solution
flowing from Step IV to Step III in line 6 need not be fully
saturated since the oil solution becomes saturated in Step
III. That is why miscella in line 6 is removed from Step IV
before the end of the liquid path.
Even though the flakes are last contacted in Step
IV by a recycled solution in line 5 containing about 1
percent of oil in aqueous alcohol having a concentration as
high as 91 percent, there is a notable increase in the rate
of oil extraction when the flakes are contacted with only
~0 slightly stronger alcohol in Step V. Consequently, the
concentration of oil in the miscella leaving Step V in line 4
may well be over 1 percent. Thus, miscella in line 4 from
Step V is best introduced into Step IV at a point downstream
of the point of introduction of the recycled solution in line
5, and preferably at the point where the oil concentration
in the solution flowing through Step IV matches that in
stream 4.
- 1 2-
There has been dlsclosed and used a great variety
of equipment and methods for extracting particulate oleagi-
nous seed materials. In less preEerred methods, particulates
are immersed in and conveyed through the solvent, either in
countercurL-ent stages, each consisting oE a soaker followed
by solids-liquid separation, or ln a column or conveyor in
which there is counterflow of particulates and solvent.
When the particulates are flakes, there is considerable
breakage and fines in the miscella which are troublesome. It
has been the experience in the extraction of oilseeds that
percolation extraction, defined as a process in which the
particulates form beds through which solvent percolates, is
superior to immersion extraction. The reasons are that the
bed itself is an excellent filter for the miscella, that the
spent particulates can be drained by gravity prior to desol-
ventizing, that the bed affords efficient contact between
particulates and solvent, and that there is practically no
mechanical wear of the equipment.
Although the process of my invention may be
practiced in any suitable countercurrently operated liquid-
solids contractors used for washing or leaching, I prefer,
based on the experience of the oilseed industry, to employ
percolation extraction techniques. A commercially proven
extractor, particulatly suited for the practice of my inven-
tion, is the rotary extractor described in U.S. Patent No.
2,840,459.
-13-
In that extractor, a rotor divided into sector
cells rotates in a vapor-tight tank above stationary stage
compartments. Each cell is open at the top and closed at
the bottom by a hinged perEorated door. Solids are fed
con-tinuously into each cell as it passes under a loading
zone, and fall from the cell when its door opens above a
discharge zone almost completely around the circle from the
feed zone~ Solvent is advanced counter to the direction of
rotation by a series of stage pumps, which pump miscellas of
graduallly increasing concentration into distribution mani-
folds positioned over the free-draining beds formed in the
cells.
Extraction of 1akes in a percolation extractor can
be faithfully simulated in the laboratory by percolating
through a bed of flakes in a stationary vertical tube a
succession of miscellas of decreasing concentration, corre-
sponding to the miscellas collected in the stage compartments
and pumped to the manifolds by each stage pump. To establish
correct concentrati~ns of the miscellas, a first batch of
flakes is extracted with fresh solvent only, and the miscella
draining from the bed is collected in successive measured
cuts. The first cut, equivalent to final miscella, is
discarded, and other cuts are percolated in succession
through a second batch of flakes, followed by an amount of
fresh solvent whose ratio to flakes in the batch is the same
as the ratio of solvent to ~lakes fed in the continuous
process being simulated. After treating several batches of
flakes, the concentration of the miscella cuts reach a
steady state characterlstic of the operation of a continuous
extractor.
Simulation of the complete process of the present
invention -by extraction of successive batches is more com-
plexO Nevertheless the five-step process can be simulated by
accumulating five sets of miscella cuts, advancing miscella
from Step V to IV to III to II to I, and carrying out the
cooling, mixing, recycling, and reheating as shown in the
drawing.
The parameters that determine the steady state in
any one step of extraction are temperature, ratio of solvent
to feed, and time. Simulation of the five-step process of
the present invention is more complex in that additional
parameters must be selected, e.g. alcohol concentration and
flow rate in lines 2 and 24, recycle solution flow in line 5,
temperature of two-phase flow in line 9 and temperature and
retention time in each of the five steps~
E~
Full-fat dehulled soybean flakes were extracted in
accordance with the process of the present inventionO In a
number of successive batches, flakes were presoaked in the
solution equivalent to that in line 25 (Figure 1) for 10
minutes and then poured into a vertical glass tube closed at
the bottom by a screen. Each batch was treated in immediate
succession with aqueous ethanol solutions as in Figure 1.
Retention times in Steps I and IV were 60 minutes; in Steps
II, III and V, 30 minutes each. Temperature in Steps I and
II was 130F.; in Steps III, IV and V, 175F. (boiling
point). The runs were based on the following additional
parameters as set forth in the following Table I, using as a
basis 100 pounds of ~lakes in line 1.
Table I
Lines 2 11 19 24
Temperature F. 175 110 130134
Flow (pounds ) 135 775 - 86
ETOH Conc. (wt.%) 92 - ~ 60%
When the steady states was reached, the various streams were
measured as set forth in the following Table II:
Table II
Lines 3 7 1222 25
Flow (pounds)104 793 19.7 27 220
Solute (wt.%) - - - 0 8.5
Lipids (wt.%)0.9* 3.6 91 0 Neg.
ETOH Conc. (wt.%) - 91 - 0 62
Volatiles Iwt.%) 50 - 9
Protein (wt~)71.2* - - - 0.11.
* dr~ basis
-16-
The soy protein concentrate made in this Example 13
at least as good as the concentrate produced in the experi-
mental work described in U.S. Patent No. 4,219,470. The
concentrate was tasteless, and met or exceeded all oE the
5criteria now expected of commercial soy protein concentrate.
Comparison of the data in Tables I and II with the
corresponding data for the production of soy protein concen-
trate given in Table I of U.S. Patent No. 4,~19,470, clearly
showns that the innova~ions described in the present disclo-
10sure have improved the process. In UOS. Patent No. 4,219,470
the total retention time was four hours; it is now reduced to
three and a half hours. Probably even more important, the
flow in line 2, which was 170 pounds, is now reduced to 135
pounds. The flow in line 14 of the patent, which corresponds
15to the sum of the flows in lines 21 and 24 of the present
disclosure, was 230 pounds compared with the present sum of
157 pounds. Anoth~er easily understood improvement is that
the flow in line 15 of the patent, which corresponds to line
25 of the present disclosure, was 370 pounds compared ith 220
20pounds.
The reduction in aqueous alcohol flow results from
addition of the new Step III and the other innovations, which
are: (1) introducing miscella in line 4 at a point in Step IV
downstream from the point of introduction of miscella in line
255; (2) removing the net miscella advanced from Step IV to
Step III in line 6 at a point upstream Erom the end of the
.~ d ~
flow path in Step IV; (3) diluting the miscella in line 21
with water so that their mixture in line 23 has the same
concentration as the dilute distilled alcohol in line 24; and
(4) introducing stream 23 at a point in Step I downstream
from the point of introduction of stream 24.
This data can be the basis for a commercial process,
which includes in its entirety: distilling solvent from the
oil phases in line 12 and 20; desolventizing extracted flakes
in line 3 -to produce a novel protein concentrate; separating
phosphatides (if desired) from the carbohydrate-rich miscella
in line 25; and distilling the miscella in line 25 to recover
as distillates the strong alcohol required in line 2 and the
dilute alcohol required in line 24, and to recover the
carbohydrate as bottoms. Such distillation of carbohydrate
solutions may be best performed in accordance with the
teaching of U.S. Patent No. 3,993~535, assigned to the same
assignee as the present invention.
Although the invention is exemplified using soy-
beans and ethanol as the alcohol, other monohydric alcohols,
such as methanol, and particularly isopropanol, may be used
as aqueous solvents. The process can be applied equally well
to other oilseeds, such as cottonseed, peanuts and rape
seed.
l8