Note: Descriptions are shown in the official language in which they were submitted.
1289806
DESCRIPTION
METHOD FOR THE E~TRACTION OF
ROASTED AND GROUND COFFEE
TECHNICAL FIELD
oS The present invention relates to a method for
extracting roasted and ground coffee. More particu-
larly, the invention involves feeding extraction
water to one end of an extraction vessel containing
roasted and ground coffee while withdrawing coffee
extract from the other end of the vessel. The
invention yields a roasted and ground coffee extract
of improved flavor quality and at a higher concen-
tration than conventional extraction systems. Flow
to and from the vessel may be periodically inter-
rupted, and unextracted coffee is intermittently
charged to the extraction vessel, while a portion of
extracted coffee is simultaneously discharged.
BACKGROUND ART
The extraction of roasted and ground coffee for
soluble coffee processing is most often carried out
in a fixed bed co~ntercurrent extraction battery
having between six and eight columns. Hot extraction
water, typically at a temperature in excess of
160C, is fed to the column containing the most
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spent roffee (that is, the coffee that has had the
most solids extracted) so as to thermally hydrolyze
the coffee. The extraction liquid progresses through
columns containing increasingly less extracted coffee,
becoming richer in coffee solids. The final column in
the extraction train, from which coffee extract is
withdrawn, contains the freshest (least extracted)
coffee, which coffee is then atmospherically
extracted. Periodically, after all the solids that
are practically soluble and extractable have been
removed from the spent coffee, the column containing
said coffee is isolated from the battery and a new
column containing fresh coffee is brought on stream.
The flow of the extracting liquid is adjusted so that
the hot extraction water is fed to the new most spent
column and the corresponding adjustments made
throughout the battery. Thus, the countercurrent
extraction ~attery is not continuous and such a system
requires considerable valving and piping (a complex
manifold) to permit the desired flow adjustments.
Typical countercurrent extraction batteries are
described in U.S. Pat. No. 2,515,730 to Ornfelt and
U.S. Pat. No. 2,915,399 to Guggenheim et al. as well
as in "Coffee Processing Technology" by Sivetz and
Foote, AVI Publishing, Westport, Conn., 1963, Vol. 1,
pp. 281-294.
SUMMARY OF THE INVENTION
In accordance with one embodiment of the present
invention there is provided a method of extracting
roasted and ground coffee in a more efficient manner
than by conventional column extraction to produce a
highly flavourful coffee extract closer to initial
roast and ground coffee flavour which comprises: (a)
feeding extraction water to the bottom end of an
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elongated vertical column extraction vessel containing
the most spent extracted roasted and ground coffee,
the most spent coffee being extracted at the highest
extraction water temperature employed in the
extraction as is done in a countercurrent extraction
system; (b) contacting the extraction water having a
superficial velocity between 0.03 m/min. and 0.3
m/min. at a temperature of 70C to 232C, the
temperature being maintained constant through the
column or being allowed to decrease during extraction,
with the extracted roasted and ground coffee in a
countercurrent nearly continuous operation for a
period sufficient to produce a final extract
concentration of about 5% to about 55% coffee solids
by weight and produce a substantially better flavoured
product closer in flavour and balance to the
unextracted roasted and ground coffee extracted by
this process than is conventionally produced in
multicolumn, countercurrent extractions; (c)
withdrawing a coffee extract from the top end of the
vessel, the extract having greater aroma retention and
higher quality being closer to the unextracted roasted
and ground flavour; (d) intermittently discharging
4% to 20% of the volume of extracted roasted and
ground coffee at the bottom of the extraction vessel
into a bottom blow case, the discharged extracted
coffee containing feed water; (e) simultaneously
charging a volumetric portion of unextracted dry
roasted and ground coffee sufficient to allow swelling
upon moistening in the extraction column or an
approximately equal volumetric portion of premoistened
roast and ground coffee from a top blow case into the
extraction column, the process operating in an
essentially continuous countercurrent fashion while
intermittently introducing fresh coffee to the top of
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~289806
- 3a -
the extractor and discharginy moist spent extracted coffee and
wash water from the bottom of the extractor.
Further, according to a feature of one embodiment of the
present invention, soluble solids are extracted from the
roasted and ground co~fee in a manner effective to maintain
the flavourful quality of the coffee solids. Further, because
of the improved efficiency of the extraction, a roasted an~d
ground coffee extract is produced of a high soluble solids
concentration, thereby reducing the degree to which said
extract may be concentrated prior to drying. Thus, a roasted
and ground coffee extract of excellent flavour quality is
produced, said excellent flavour quality being reserved to the
finished soluble coffee product because of the high
concentration at which the coffee extract is produced.
In the above method, there may be included the further
step of halting the flow of liquid to and from the extraction
- vessel during the period that the coffee is being chargçd and
discharged. A preferred embodiment of the invention is where
the extraction vessel is a vertical, elongated column having a
length between about 7.5 and 23.0 m, and a diameter whereby
the superficial velocity is between 0.03 m/min. and 0.3 m/min.
and extraction water flow is continuous.
The above method may also include premoisturizing the
unextracted roasted and ground coffee to a moisture between
35% by weight and 60% by weight prior to charging said coffee
to the extraction vessel. In the premoisturizing step,
preferably water is used to premoisturize the unextracted
roasted and ground coffee. In an alternate arrangement,
coffee extract may be used to premoisturize the unextracted
roasted and ground coffee.
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In a pre~erred form of the method outlined above, the
superficial velocity is 0.06 m/min. to 0.15 m/min. and the
extract water temperature is 70c to 232OC to produce a final
extract concentration of greater than 10~ to about 55% coffee
solids by weight and produce a higher solids concentration
than is conventionally produced in multicolumn, countercurrent
extraction of the same coffee. In this preferred form,
preferably the extraction water temperature is 70C to 180~C.
In particularly preferred embodiments, the extraction
water temperature is 70C to 180C to produce a final extract
concentration of 4% or greater and approaching 10% or more
having a substantially improved flavour and balanced flavour
compared to conventionally extracted coffee said flavour and
flavour balance approaching unextracted roasted and ground
coffee employed for extraction in this process. Preferably,
the extraction water is fed to the extraction vessel at a
temperature between about 70C and 180C. Particularly
preferred embodiments are where the temperature in the ,
extraction vessel is maintained between about 70C and 100C.
In the above described methodl another preferred
embodiment, is where the extraction water is fed to the
extraction vessel and maintained in the extraction vessel at a
temperature of between about 70C and 180C, and said
extraction water concentration is increased to about 10% to
about 55~ by weight. A more specific preferred embodiment, is
where the extraction water is fed to the extraction vessel at
a temperature between 100C and 180~C, which temperature is
reduced throughout the height of the vessel.
In another aspect of the present invention, in the above
method, the extraction water is fed to the extraction vessel
at a temperature between 100C and 180C so as to hydrolyze
the coffee in the lower portion of the extraction vessel,
which temperature falls to between 70C and 100C at the upper
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~289~30~
portion of the column so that the roasted and ground coffee in
said upper portion is atmospherically extracted.
The method may also include the further step of
atmospherically extracting the roasted and ground coffee in
the extraction vessel and, subsequently, hydrolyzing the
intermittently discharged portion of roasted and ground coffee
in a countercurrent fixed bed extraction battery.
Still further, the method may also include the step of
discharging the extracted roasted and ground coffee into a
blow case and, charging unextracted roasted and ground coffee
to the extraction vessel through a blow case that has been
pressurized to a pressure equal to or slightly above the
pressure in said extraction vessel.
BRIEF DESCRIPTION OF THE DRAWING
Figure 1 is a front view of an extraction vessel for the
extraction of roasted and ground coffee.
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i~:898(~6
DISCLOSURE OF THE INVENTION
Roasted and ground coffee is extracted in an
extraction ~essel. Suitable vessels include those
which allow for the contact of the roasted and
05 ground coffee and the extracting liquid as said
liquid flows through the vessel, as well as for the
intermittent charging of the fresh coffee and dis-
charging of the extracted coffee. The preferred
vessel is an elongated column in which the roasted
and ground coffee is maintained as a bed and the
extracting liguid passes through the bed. The
elongated column preferably has a length between
about 7.5 m and 23.0 m. The diameter of the column
is determined by the desired capacity and in view of
the preferable superficial velocity range hereinbelow
described. Said column is situated vertically to
provide the most convenient countercurrent flow of
the extracting liquid and the roasted and ground
coffee.
Inasmuch as the column is most conveniently
situated vertically, it is also preferable to feed
the extraction water to the bottom of said column
and withdraw the coffee extract at the top of the
column so that the extracting liquid flows upward
through the bed of roasted and ground coffee and the
movement of said coffee is downward. Periodically,
flow to and from the vessel may be halted and
unextracted coffee is intermittently charged to the
extraction vessel, as a portion of spent coffee is
discharged. The feeding of extraction water to and
withdrawal of extract from the vessel may then be
resumed. The coffee moves, of course, as a result
of the intermittent discharging of extracted coffee,
and the subsequent charging of the fresh roasted and
ground coffee. In the case where the extraction
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water is fed to the bottom of the vessel, the fresh
coffee is charged to the top of the vessel and the
extracted coffee is withdrawn from the bottom in
order to provide countercurrent movement of said
05 coffee relative to the flow of the extractin~ uid.
Thus, situating an elongated column vertically
allows the movement of the coffee through the column
to be primarily caused by gravity. Of course, the
flow of the extracting liquid and roasted and ground
coffee can be reversed so that the extraction water
is fed to the top of the vessel, but it is simply
not as convenient to do so.
Intermittently, after a pre-determined period
of time as described hereinbelow, the feeding of
extraction water to the extraction vessel and the
withdrawal of coffee extract therefrom may be tempo-
rarily halted. A portion of extracted roasted and
ground coffee is discharged from one end of the
vessel while a portion of fresh, unextracted roasted
and ground coffee is charged to the other end of the
extraction vessel. In the case of an elongated
column, said portion is measured as against the
volume of the coffee bed in said column where, for
example, 10% of the total volume o the column is
intermittently discharged. The preferred portion of
extracted roasted and ground coffee intermittently
discharged is between 4~ and 20% of the volume of
the coffee bed contained in the elongated column.
An e~ual volume of unextracted roasted and ground
coffee cannot be charged to said column if the
coffee is dry, because roasted and ground coffee
swells to nearly twice its original volume upon
wetting, also concentrating and reducing the volume
of the extracting liquid. So, if an equal volume of
dry, fresh roasted and ground coffee replaces the
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discharged extracted coffee, said coffee cannot
properly expand and will therefore not extract
properly. Thus, the charge of dry coffee should be
approximately one-half of the volume of extracted
05 coffee that is discharged. Moreover, the flow rate
of the extracting liquid must be adjusted so as to
compensate for the water adsorbed by the roasted and
ground coffee. Most preferably, the unextracted
roasted and ground coffee is premoisturized prior to
being charged to the elongated column, in which
event, the volume of coffee simultaneously charged
and discharged should be about equal.
Once the charging of the unextracted roasted
and ground coffee and the discharging of the extracted
coffee is completed, the flow of the extraction
water to the vessel and the withdrawal of extract
from the extraction vessel is resumed (assuming said
flow had been previously halted). The whole operation
can be made quite brief, genexally not lasting more
than a few minutes (depending on the size of the
portion discharged), so that the method is more
nearly continuous than conventional countercurrent
fixed bed extraction. Alternatively, based on the
specific equipment configuration and if the super-
ficial velGcity of the extracting liguid is toward
the lower end of the range as described hereinbelow,the flow of the liquid to and from the extraction
vessel need not be halted, making the method of the
present invention essentially continuous. The
superficial velocity at which it becomes necessary
to halt the flow will be apparent to a worker skilled
in the art. The charging of the fresh coffee and
discharging of the extracted coffee may be by any of
several methods. For example, in the case where the
fresh roasted and ground coffee is charged at the
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top of an elongated column, a ~alve is briefly
opened at the bottom of said column to discharge the
desired portion of extracted roasted and ground
coffee. Simultaneously, a valve at the top of the
05 column is opened to charge the proper amount of
unextracted roasted and ground coffee by the force
of gravity. Both valves are then shut. This tech-
nique is not appropriate when the extraction vessel
is maintained at a pressure greater than atmospheric.
Most preferably, the extraction vessel is
charged and discharged from so-called blow cases
located immediately above and below and communicat-
ing with said extraction vessel. Blow cases are
isolated vessels of about the same volume as the
unextracted coffee to be charged and the extracted
roasted and ground coffee to be discharged, which
blow cases are capable of withstanding a pressure
equal to or slightly above the pressure maintained
in the extraction vessel. The blow case above the
column is then filled with the appropriate amount of
fresh coffee and pressurized as with compressed air
or a portion of liquid to a pressure slightly greater
than the pressure maintained in said column. A
valve is opened on the bottom of the column so as to
fill the blow case with the discharged portion of
coffee whereupon, said valve is shut. Nearly simul-
taneously, a valve on the top of the column is
opened and the fresh roasted and ground coffee is
forced into the column under pressure. The top blow
case is subsequently isolated and flow to and from
the column is resumed. The use of said blow cases
is relatively simple, efficient and nearly as rapid
as charging and discharging the extraction vessel by
gravity.
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Figure 1 shows one of the preferred embodiments
for operating the method of the present invention.
At steady state conditions, the extraction vessel S
is filled with a bed of roasted and ground coffee
05 which has been extracted in varying degrees. Feed
water i~ fed to the first end of the extraction
vessel 6 and coffee extraction is withdrawn from the
second end of the extraction vessel 4. Unextracted
roasted and ground coffee is periodically admitted
through valve 1 into blow case 2. Valves 3 and 7
are simultaneously opened intermittently so as to
charge the unextracted roasted and ground coffee
from blow case 2 to the second end of the extraction
vessel 4 and discharge a portion of extracted roasted
and ground coffee from the first end of the extraction
vessel 6 to blow case 8. Valves 3 and 7 are then
closed. Valve 9 is then opened to discharge the
extracted roasted and ground coffee from blow case 8.
Additional unextracted roasted and ground coffee is
admitted through valve 1 into blow case 2 and the
procedure is repeated.
Having thus described the operation of ~he
present invention, the significantly improved process-
ing efficiency and coffee extract quality which
result from said operation are next considered. The
present method is more efficient for the extraction
of roasted and ground coffee solids because it
effectively has more stages then a conventional
fixed bed countercurrent extraction battery of six
or eight columns, the term "stage" being used in its
conventional chemical engineering sense as described
in Perry, Chemical Enaineers' ~andbook, 3rd Edition,
i
McGraw Hill, 1950, p. 716 . Said improved efficiency
results in an increased coffee solids concentration
in the withdrawn
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~28~306
g
coffee extract as compared to a conventional extrac-
tion battery with all operating parameters maintained
constant. Additionally, a higher level of coffee
aromatics is found in the coffe~ extract of the
05 present invention as measured by gas chromatograph
versus a conventional extraction battery, again with
all operating parameters maintained constant. The
increased co~fee solids concentration is particularly
important for the preservation of flavorful ~offee
aromas to a finished soluble coffee product because
a dilute coffee extract generally requires substantial
downstream concentration, as for example be evapor-
ation, prior to drying. Such downstream concentration
typically results in a significant loss and/or
degradation of flavorful coffee aromatics, said loss
and/or degradation generally being avoided by the
operation of the present invention. As such, the
higher soluble solids concentration of the invention
is much desired and preferred for flavor retention
in soluble coffee processing and has been found to
yield a soluble coffee product of excellent organ-
oleptic quality.
Extraction yield, that is, the weight of soluble
coffee solids extracted per weight of fresh roasted
and ground coffee charged, quantifies the degree of
the coffee extraction. In the present invention,
extraction yield is generally dependent upon the
superficial velocity of the extracting liquid through
the bed of roasted and ground coffee, the retention
time of the coffee in the extraction vessel, the
temperature of the extracting liquid ~as described
hereinbelow), and the total weight of extraction
water per weight of roasted and ground coffee charged.
"Extracting liquid" refers to the liquid flowing
through the vessel which is fed as extraction water
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1289806
-- 10 --
and becomes increasingly rich lnsoluble coffee solids until
being withdrawn from the vessel as coffee extract. The
superficial velocity of said liquid and the amount of liquid
fed through the roasted and group coffee contained in the
elongated colu~n are related to the degree of extraction and
washing to which the coffee is subjected. A lower superficial
velocity increases the retention time of the liquid in the
column and typically favors greater extraction. A higher
superficial velocity requires a taller extraction vessel to
achieve the same degree of extraction but provides better
washing of the coffee particles.
It has been found that a superficial velocity between 0.3
m/min and .3 m/min, desirably .15 to .3 m/min, is convenient
for use in the present invention, with a velocity of .06 m/min
being particularly preferred. Of course, a superficial
velocity outside the range may be used with a corresponding
decrease in extraction efficiency. The total weight of
extraction water per weight of roasted and ground coffee
charged is preferably maintained at about what it is for
conventional extraction, that is between about 15:1 and 90:1,
desirably 40:1 to 90:1. This is to say that each pound of
roasted and ground coffee preferably has about 15 lbs to 90
lbs, desirably 40 to 90 lbs, of extracting liquid flow past it
while in the extraction vessel.
Another operating variable effecting yield, the retention
time of the roasted and ground coffee in the extraction
vessel, is also preferably maintained at about what it is for
conventional extraction, between about 90 minutes and 240
minutes. Having thus set retention time and the portion of
extracted roasted and ground coffee that is intermittently
discharged as hereinbefore described, the frequency
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of the perlodic charging and discharging of the
roasted and ground coffee is fixed. This is because
the total retention time multiplied by the fraction
of the extraction vessel which is intermittently
05 discharged necessarily equals the interval between
the charging and discharging. For example, if a
total retention time is selected as 200 minutes and
about 12.5% of the height of the column is intermit-
tently discharged, the period between the periodic
operations amounts to 25 minutes. The net effect is
to provide the eguivalent of an eight column counter-
current extraction battery in a single extraction
vessel, eliminating the complexity of said battery.
As hereinbefore described, hydrolysis of the
coffee takes place in the column to which the ex-
traction water is fed in a conventional battery andatmospheric extraction takes place in the column
containing the fresh roasted and ground coffee from
which the coffee extract is withdrawn. The roasted
and ground coffee extraction method of the present
invention offers increased flexibility, the results
achieved being dependent upon the temperature at
which the extraction water is fed to the extraction
vessel. In a first embodiment, atmospheric extraction
of the roasted and ground coffee is accomplished by
feeding the vessel with extraction water at a tem-
perature of between about 70C and 100C and main-
taining said temperature throughout the full height
of the column. The pressure in the extraction
vessel is typically at or slightly above atmospheric
pressure. The extracted roasted and ground coffee
intermittently discharged may then be charged to
another extraction vessel so as to hydrolyze said
coffee and extract the remaining available soluble
coffee solids so produced. In the second extraction
12898Q6
- 12 -
vessel, hydrolysis is accomplished by feeding the
extraction water to the extraction vessel at a
temperature in excess of 100C and less than about
232C. Said temperature may be maintained throughout
05 the full height of the vessel such as by insulating
or jacketing the vessel, or the temperature may be
allowed to decrease through normal heat loss or
reducing the jacket temperature of said vessel. The
pressure in the column is significantly above atmos-
pheric, corresponding at least to the saturation
pressure of water at the temperature selected. Blowcases or other suitable means for charging and
discharging the coffee under the appropriate pressure
must, of course, be used.
In a second embodiment, the method of the
present invention may be varied so as to provide for
both atmospheric extraction and hydrolysis in a
single extraction vessel. The extraction water is
fed to the vessel at a temperature in excess of
100C so as to induce hydrolysis in the mostly
extracted roasted and ground coffee which is initial-
ly contacted by said water. The temperature in the
vessel is then progressively lowered by circulating
a cool liquid through the vessel jacket so that said
temperature is between about 70C and 100C by the
time the extracting liguid reaches the freshest
roasted and ground coffee at the opposite end of the
extraction vessel. In this way, the coffee which is
extracted at the lowest temperature is atmospherically
extracted and the most spent coffee is extracted at
the highest temperature in much the same way as in a
conventional extraction system. Although operation
in this manner is perhaps less complex, experience
indicates that precise temperature control within a
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single extraction vessel is often difficult to
achieve. Atmospheric extraction in one vessel
followed by hydrolysis in a second extraction vessel
or even in a fixed bed, countercurrent battery is
05 more flexible, particularly because most of the
coffee flavor and aromas are atmospherically extrac-
ted and so, the hydrolysis operation is not then
constrained by flavor considerations.
The present method, although not strictly
continuous, is certainly more nearly so than a
countercurrent extraction battery, with the flow of
extract being interrupted intermittently and then
only for a brief period, preferably less than a few
minutes and, if conditions permit, not at all. The
nearly continuous operation permits a much closer
approach to steady state conditions so that the
withdrawn extract has a flatter more uniform concen-
tration profile than the extract withdrawn from a
countercurrent battery. Said concentration profile
may be made even flatter by premoisturizing the
roasted and ground coffee prior to charging the same
to the extraction vessel. Dry roasted and ground
coffee will typically adsorb about its own original
weight as moisture and so, if such coffee is charged
to the extraction vessel, said coffee will prefer-
entially adsorb water from the extraction liquidinitially contacting it, concentrating the liquid
and disturbing the concentration profile. Thus, the
roasted and ground coffee is preferably premoisturized
to between 35% by weight and 60% by weight before
being charged to the extraction vessel. The pre-
moisturizing may be with water or with coffee extract
having between about 10% by weight and 50% by weight
coffee solids. The use of extract for premoisturizing
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is preferred because said extract adds coffee solids
to the roasted and ground coffee, which tends to
increase the equilibrium concentration of the with-
drawn extract substantially. Regardless of the
05 liquid used for premoisturizing, said premoisturizing
also aids in determining the portion of unextracted
roasted and ground coffee intermittently charged to
the extraction vessel, as hereinbefore described.
The increased concentration of the withdrawn
extract of the present invention is essential to the
operation of the present invention. Said concentra-
tion ranges upwardly to about 55% by weight as it
exits the extraction vessel, particularly when the
roasted and grownd coffee is premoisturized with
coffee extract as hereinbefore described. In the
first embodiment described previously wherein solely
atmospheric extraction is accomplished in the extrac-
tion vessel, the exiting concentration is generally
greater than about 10%, -typically greater than about
20%, preferably greater than about 30%, and most
preferably greater than about 40% by weight coffee
solids. Similarly, in the case where atmospheric
extraction and hydrolysis are accomplished in the
same extraction vessel and in applications where
soley hydrolysis is accomplished, the exiting concen-
tration is generally greater than about 5%, typicallygreater than 10%, preferably greater than 20~, and
most preferably greater than about 30% by weight
coffee solids. In every instance, higher exiting
concentrations are achieved according to the present
invention than are achieved in conventional extrac-
tion batteries operated at identical conditions.
The benefit of said increased exit concentration
is realized in terms of downstream processing effici-
ency, cost savings, and flavor improvement. Typically,
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coffee extracts are subjected to substantial concen-
tration steps, generally evaporation, prior to
drying. Said concentration steps are energy inten-
si~e and generally result in a substantial loss of
05 flavorful coffee aromatics along with the water
phase which is being driven off. Methods are known
for recovering a percentage of these flavorful
aromatics, for example condensation, distillation,
and absorption, but these methods are capital and
energy intensive and less than 100% successful. The
present invention is extremely preferred over these
prior art systems in that coffee e~tracts are gener-
ated at such high concentrations and with such high
and balanced levels of coffee aromatics t~at either
limited or, preferably, no concentration is needed
downstream for the coffee extract to be suitable for
efficient drying, both from an energy and flavor
retention standpoint.
The following examples are intended to illustrate
certain embodiments of the present invention. The
examples are not meant to limit the invention beyond
what is claimed below.
EXAMPLE 1
1. For the purpose of comparison, a counter-
current fixed bed extraction battery having 6 columns
of 0.25 m. diameter by 5.5 m. height and charged
with 82 kg of roasted and ground coffee each was
operated after equilibrium was attained. The cycle
time was approximately 35 min. per cycle for a
total retention time of the coffee in the battery of
about 210 min. The extraction water was fed to the
battery at about 130C, effecting some thermal
hydrolysis as well as atmospheric extracton. The
total weight ratio of water per weight of roasted
and ground coffee was 29.6:1.
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128~8~6
The resulting extract had a soluble coffee
solids concentration of about 6.7% by weight. The
overall yield of the roasted and ~round coffee on a
dry basis was about 28% by weight.
05 2. A vertical, cylindrical elongated column
having a diameter of 0.1 m., a height of 15.2 m. and
holding about 44 kg. of roasted and ground coffee
was used. The steel column had two 10 cm. ball
valves mounted on either end for charging and dis-
charging the coffee. ~ hopper was mounted above the
column, communicating with said column through theball valve. An additional cylindrical length,
representing about 12.5% of the volume of the column
was mounted vertically below the column as a blow
case, communicating with the column through the
bottom ball valve. A third 10 cm. ball valve was
mounted on the bottom of the blow case. Water was
pumped through a heat exchanger and into the column
through a flow distributor such as a bayonet mounted
in the column, slightly above the bottom of said
column. The coffee extract was withdrawn through a
bayonet mounted in the column, slightly below the
top of said column. The extract was pumped into a
tank from the extraction column. Roasted and ground
coffee was placed in the hopper and premoisturized
by mixing manually with a liquid. The bottom most
ball valve on the blow case was closed. Flow to and
from the column was halted. The ball valves on the
two ends of the column were essentially simultaneously
opened, allowing the roasted and ground coffee to
charge to the column by gravity and the extracted
coffee to fill the blow case whereupon, both valves
were shut. Flow to and from the column was then
resumed. The contents of the blow case were allowed
to cool and the blow case was emptied by opening the
bottom most ball valve.
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For the first run, about 12.5% of the volume of
coffee in the column was intermittently discharged
into a blow case adjacent to the bottom of the
column every 25 min. for a total retention time in
- 05 the vessel of 200 min. An equal volume of unextrac-
ted roasted and ground coffee premoisturized with
water to 58% by weight moisture was then charged to
the top of the column through a blow case located
thereon. Extraction water was fed to the bottom of
the column at about 88 C, effecting atmospheric
extraction. The total weight ratio of water per
weight of roasted and ground coffee was 29.6:1.
The resulting extract had a soluble solids
concentration of about 13.8% by weight. The overall
dry basis yield of the roasted and ground coffee was
about 23% by weight.
A second run was carried out with identical
conditions except that the roasted and ground coffee
was premoisturized with a portion of the coffee
extract withdrawn from the top of the column. The
concentration of the resulting extract was about
36.6% by weight soluble solids. The simple expedient
of premoisturizing with extract increased the con-
centration nearly three-fold over what it was for
25 the first run. The results are shown in Table 1
below.
TABLE 1
Counter-
current
Run 1 Run 2 Battery
Extraction water temp. tC) 88 88 130
Water/coffee weight ratio 29.6:1 23.1:1 29.6:1
Drawn-off extract
concentration (%) 13.8 36.6 6.7
Yield in ~ dry basis 23 26 28
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Although the coffee extracted in the counter-
current battery gave a slightly hlgher yield, it is
attributable to the higher extraction temperature
for said method which was required because of equip-
05 ment limitations. The greater efficiency of the
present invention is seen in the higher concentra-
tion of the extract produced by the instant method,
which concentration was nearly twice that of the
conventionally produced extract in the first case
and six times that in the second case despite using
the same weight of water to weight of coffee in each
method. The higher concentration extract is bene-
ficial in that a high concentration extract exhibits
greater aroma retention and such an extract requires
less concentrating before drying, lowering equipment
reouirements and operating costs.
EXAMoeLE 2
1. The counterc~rrent fixed bed extraction
battery of Example 1 was operated with approximately
35 min. cycle times as before. The extraction water
was fed at approximately 180~C to the first column,
with atmospheric extraction conditions existing in
the final or freshest column. The total weight
ratio of water fed per weight of roasted and g~ound
coffee was 24.5:1.
The exiting extract was split into primary and
secondary extracts, the primary being the first 50%
by weight of the withdrawn extract and the secondary
being the final 50% by weight. The total yield was
about 53% by weight. The primary concentration was
19% by weight coffee solids and the secondary was
12% by weight.
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2. A third run was carried out in the elongated
column of E~ample 1, substantially similar to the
second run previously described. ~owever, the total
weight ratio o~ water fed per weight of roasted and
05 ground coffee was 22:1 and the total yield was 23.2~.
The roasted and ground coffee was premoisturized
with a portion of the coffee extract withdrawn from
the top of the column, diluted slightly to 41% for
handling ease, and the concentration of the resulting
extract was about 45% by weight. Due to an equipment
malfunction, the extract was not cooled as it exited
the extraction column. Generally, exiting extract
is cooled to about 18C to 24C to preserve the
flavor quality of the extract.
3. A comparison of the coffee aroma qùality
of the primary and secondary extracts of step 1 was
made versus the coffee extract generated in the
third run of step 2. The analysis of the extracts
was by gas chromatograph. The results are summarized
in Table 2.
TABLE 2
.
. Primary Secondary
Extract Extract Run 3
"~ight" Coffee 6.35 x 104 3.71 x 105 l.7 x 106
Volatiles
~counts/gm coffee
solids)
"Heavy" Coffee 6.05 x 1085.15 x 1087 5 x 108
Volatiles
(counts/gm coffee
solids)
As is readily apparent, the extract of Run 3 is
richer in both light and heavy coffee volatiles than
either the primary or secondary extracts, despite
the absence of an aftercooler. For this analysis,
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2, 3 Pentanedione is the heaviest of the 1l light"
volatiles and Furfural is the lightest of the "heavy"
volatiles. Additionally, because the Run 3 extract
was at a 45% concentration when withdrawn from the
05 extraction column, concentration of any sort prior
to drying is unnecessary, thereby eliminating the
possibility of flavorful coff~e aroma loss or degra-
dation dùring concen tration. Further loss of
coffee aromas is certain for the primary and/or
secondary extracts during the concentration steps
which are needed to enable efficient drying of said
extracts.
EXAMPL~ 3
15 1. A vertical, cylindrlcal elongated column
having a diameter of 0.25 m, a height of 7.9 m, and
holding about 140 kg. of roasted and ground coffee
was used. The steel column had two ball valves
mounted on either end for charging and discharging
the coffee. A hopper was mounted above the column,
communicating with said column through the ball
valve. An additional cylindrical length, represent-
ing about 10% of the volume of the column was mounted
vertically below the column as a blow case, communi-
cating with the column through the bottom ball
valve. A third ball valve was mounted on the bottomof the blow case. Water was pumped through a heat
exchanger and into the column through a flow distri-
butor such as a bayonet mounted in the column,
~ slightly above the bottom of said column. The
coffee extract was withdrawn through a ba~onet mounted
in the column, slightly below the top of said column.
The extract was pumped into a tank from the extraction
column. Roasted and ground coffee was placed in the
hopper and premoisturized by mixing manually with a
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-liquid. The bottom most ball valve on the blow case
was closed. Flow to and from the column was halted.
The ball valves on the two ends of the column were
essentially simultaneously opened, allowing the
05 roasted and ground coffee to charge to the column by
gravity and the extracted coffee to fill the blow
case whereupon both valves were shut. Flow to and
from the column was then resumed. The contents of
the blow case were allowed to cool and the blow case
was emptied by opening the bottom most ball valve.
About 10% of the volume of coffee in the column
was intermittently discharged into a blow case
adjacent to the bottom of the column every 10.4 min,
for a total retention time in the vessel of 104 min.
An equal volume of unextracted roasted and ground
coffee premoisturized with water to 58% by weight
moisture was then charged to the top of the column
through a blow case located there-on. Extraction
water was fed to the bottom of the column at about
99 C and through the column at a superficial velocity
of 0.10 m/min., effecting atmospheric extract-ion.
The total weight ratio of water fed per weight of
roasted and ground coffee was 36.5:1.
The resulting extract had a soluble solids
concentration of about 14.9% by weight. The overall
dry basis yield of the roasted and ground coffee was
about 19.6% by weight.
2. A second extract sample was made from the
same roasted and ground coffee in a con~entional
extraction battery according to the procedure of
Example 2, step 2.
3. Another sample was prepared from the same
roasted and ground coffee by preparing a brew at a
recipe level of 75 cups/lb. in a conventional coffee
brewer.
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4. The three samples, i.e. two extracts and
one brew, were evaluated by gas chromatograph and by
an expert panel for flavor quality at a 1% solids
level by weight. The results are summarized in
05 Table 3.
TABLE 3
~All G.C. Data Measured In ug/g Solids)
RoastedConventional
and Extract
Ground(Primary &
Brew Secondary Combined) Column ~xtract
Total G.C.
Counts 2120 1090 2740
l52-Me-~uran 55 6 46
Furfural 84 85 81
Flavor
Evaluation groundsey, thin, flat, groundsey,
aromaticbland aromatic, less
harsh and acidic
than the brew
As is apparent, the extract prepared according
to the present invention (column extract) measures
signi-ficantly higher than conventionally prepared
extract and, remarkably, higher than a roasted and
ground coffee brew, in terms of total G.C. counts.
The nearly equal level of 2-Me-Furan in the column
extract as compared to the roasted and ground brew
shows the presence of those com-pounds that contribute
to the groundsey character of a coffee brew. This
analytical result is confirmed by organoleptic
evaluation, where the column extract is rated very
high in quality by an expert panel.
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