CA1289806C - Method for the extraction of roasted and ground coffee - Google Patents
Method for the extraction of roasted and ground coffeeInfo
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- CA1289806C CA1289806C CA000500621A CA500621A CA1289806C CA 1289806 C CA1289806 C CA 1289806C CA 000500621 A CA000500621 A CA 000500621A CA 500621 A CA500621 A CA 500621A CA 1289806 C CA1289806 C CA 1289806C
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Abstract
METHOD FOR THE EXTRACTION OF
ROASTED AND GROUND COFFEE
ABSTRACT
A method of extracting roasted and ground coffee is disclosed. Extraction water is fed to one end of an extraction vessel containing roasted and ground coffee, and coffee extract is withdrawn from the other end. Flow of water to and extract from the vessel is intermittently halted, and extracted roasted and ground coffee is intermittently discharged from the vessel while a portion of unextracted coffee is charged to the vessel at the other end.
The movement of coffee in the extraction vessel is countercurrent relative to the flow of the extraction water. The method of the present invention is less complex, is more easily controlled, requires a lower capital investment and produces a higher concentration and more aromatic coffee extract than prior art processes.
ROASTED AND GROUND COFFEE
ABSTRACT
A method of extracting roasted and ground coffee is disclosed. Extraction water is fed to one end of an extraction vessel containing roasted and ground coffee, and coffee extract is withdrawn from the other end. Flow of water to and extract from the vessel is intermittently halted, and extracted roasted and ground coffee is intermittently discharged from the vessel while a portion of unextracted coffee is charged to the vessel at the other end.
The movement of coffee in the extraction vessel is countercurrent relative to the flow of the extraction water. The method of the present invention is less complex, is more easily controlled, requires a lower capital investment and produces a higher concentration and more aromatic coffee extract than prior art processes.
Description
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 ~k - .
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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 , ' ~28~8~6 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 'C
~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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- 3b -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 T~
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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 ~ . : ', -~21~98C~6 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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1~898~6 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 .: - ' ~ '. : ' ' ' : . ' . ' ::
:: -~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 , , . ~ ' -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 D
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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 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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128913~6 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.
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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128~3~06 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.
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 n !-V
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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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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 ~k - .
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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 , ' ~28~8~6 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 'C
~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.
' ~ ' 1~89~306 "
- 3b -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 T~
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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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98~
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 ~ . : ', -~21~98C~6 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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1~898~6 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 .: - ' ~ '. : ' ' ' : . ' . ' ::
:: -~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 , , . ~ ' -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 D
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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 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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128913~6 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.
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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128~3~06 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.
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 n !-V
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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.
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.
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. 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, D
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~Z89806 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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~28g806 -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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. 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, D
.
~Z89806 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 .
',~ .
.
.
- . , -- .
- - - .
~28g806 -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.
D
:: ... .. ~ . .
. . : .
128980~
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.
~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.
. ' . , .
~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.
. ' . , .
Claims (17)
1. 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 elongated vertical column extraction vessel containing the most spent extracted roasted and ground coffee, said 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 said extraction water having a superficial velocity between 0.03 m/min. and 0.3 m/min. at a temperature of 70°C to 232°C, said temperature being maintained constant through the column or being allowed to decrease during extraction, with said 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 said vessel, said extract having greater aroma retention and higher quality being closer to said 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, said 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, said process operating in an essentially continuous countercurrent fashion while intermittently introducing fresh coffee to the top of the extractor and discharging moist spent extracted coffee and wash water from the bottom of the extractor.
(a) feeding extraction water to the bottom end of an elongated vertical column extraction vessel containing the most spent extracted roasted and ground coffee, said 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 said extraction water having a superficial velocity between 0.03 m/min. and 0.3 m/min. at a temperature of 70°C to 232°C, said temperature being maintained constant through the column or being allowed to decrease during extraction, with said 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 said vessel, said extract having greater aroma retention and higher quality being closer to said 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, said 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, said process operating in an essentially continuous countercurrent fashion while intermittently introducing fresh coffee to the top of the extractor and discharging moist spent extracted coffee and wash water from the bottom of the extractor.
2. A method as in claim 1 which further comprises halting the flow of liquid to and from the extraction vessel during the period that the coffee is being charged and discharged.
3. A method as in claim 1 wherein 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.
4. A method as in claim 1 which further comprises 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.
5. A method as in claim 4 wherein water is used to premoisturize the unextracted roasted and ground coffee.
6. A method as in claim 4 wherein coffee extract is used to premoisturize the unextracted roasted and ground coffee.
7. The method of claim 1 wherein the superficial velocity is 0.06 m/min. to 0.15 m/min. and the extract water temperature is 70°C to 232°C 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.
coffee solids by weight and produce a higher solids concentration than is conventionally produced in multicolumn, countercurrent extraction of the same coffee.
8. The method of claim 1 wherein the superficial velocity is 0.15 m/min. to 0.30 m/min. and the extraction water temperature is 70°C to 180°C 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.
9. A method as in claim 7 wherein the extraction water is fed to the extraction vessel at a temperature between about 70°C and 180°C.
10. A method as in claim 9 wherein the temperature in the extraction vessel is maintained between about 70°C and 100°C.
11. A method as in claim 1 wherein the extraction water is fed to the extraction vessel and maintained in the extraction vessel at a temperature of between about 70°C and 180°C, and said extraction water concentration is increased to about 10% to about 55% by weight.
12. A method as in claim 1 wherein the extraction water is fed to the extraction vessel at a temperature between 100°C and 180°C, which temperature is reduced throughout the height of the vessel.
13. A method as in claim 1 wherein the extraction water is fed to the extraction vessel at a temperature between 100°C and 180°C so as to hydrolyze the coffee in the lower portion of the extraction vessel, which temperature falls to between 70°C and 100°C at the upper portion of the column so that the roasted and ground coffee in said upper portion is atmospherically extracted.
14. A method as in claim 1 which further comprises atmospherically extracting the roasted and ground coffee in the extraction vessel of claim 1 and, subsequently, hydrolyzing the intermittently discharged portion of roasted and ground coffee in a countercurrent fixed bed extraction battery.
15. A method as in claim 1 which further comprises 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.
16. The method of claim 7 in which the extraction water temperature is 70°C to 180°C and the water to coffee ratio is 15:1 to 40:1.
17. The method of claim 8 in which the water to coffee ratio is 40:1 to 90:1.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US70335185A | 1985-02-13 | 1985-02-13 | |
| US703,351 | 1985-02-13 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1289806C true CA1289806C (en) | 1991-10-01 |
Family
ID=24825026
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000500621A Expired - Lifetime CA1289806C (en) | 1985-02-13 | 1986-01-29 | Method for the extraction of roasted and ground coffee |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1289806C (en) |
-
1986
- 1986-01-29 CA CA000500621A patent/CA1289806C/en not_active Expired - Lifetime
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