CA1177313A - Slurry decaffeination - Google Patents
Slurry decaffeinationInfo
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- CA1177313A CA1177313A CA000378270A CA378270A CA1177313A CA 1177313 A CA1177313 A CA 1177313A CA 000378270 A CA000378270 A CA 000378270A CA 378270 A CA378270 A CA 378270A CA 1177313 A CA1177313 A CA 1177313A
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Abstract
SLURRY DECAFFEINATION
ABSTRACT
The object of the invention is to provide an improved method for removing caffeine from aqueous solutions such as coffee and tea extracts.
Decaffeination with water-immiscible fatty materials is impractical because the ratio of fatty material to aqueous caffeine solution will typically be about 20:1. Non-solvent systems employing solid adsorbents have not been commercially practical because they are either too non-selective or too expensive.
The process disclosed herein decaffeinates an aqueous caffeine solution by contacting it with a slurry comprising a solid caffeine adsorbent and a water-immiscible, caffeine-specific solvent. The caffeine is selectively extracted from the aqueous solution, leaving the solubles necessary for a good tasting beverage, and then removed from solution by the solid adsorbent. Because the solvent is selective, the adsorbent does not have to be. And, because the adsorbent continuously maintains a low concentration of caffeine in the solvent, much lower solvent to aqueous solution ratios can be employed, preferably less than 5:1.
ABSTRACT
The object of the invention is to provide an improved method for removing caffeine from aqueous solutions such as coffee and tea extracts.
Decaffeination with water-immiscible fatty materials is impractical because the ratio of fatty material to aqueous caffeine solution will typically be about 20:1. Non-solvent systems employing solid adsorbents have not been commercially practical because they are either too non-selective or too expensive.
The process disclosed herein decaffeinates an aqueous caffeine solution by contacting it with a slurry comprising a solid caffeine adsorbent and a water-immiscible, caffeine-specific solvent. The caffeine is selectively extracted from the aqueous solution, leaving the solubles necessary for a good tasting beverage, and then removed from solution by the solid adsorbent. Because the solvent is selective, the adsorbent does not have to be. And, because the adsorbent continuously maintains a low concentration of caffeine in the solvent, much lower solvent to aqueous solution ratios can be employed, preferably less than 5:1.
Description
1 ,1773~3 DESCRIPTION
SLURRY DECAFFEINATION
Technical Field The present invention relates to d~caffeination, 05 and more particula~ly to a new process for de-caffeinating an aqueous solution by contacting it with a two phase extractant, namely a slurry of a solid adsorbent in a liquid caffeine-specific solvent.
The prior art has long sought a process to effectively and non-destructively remove caffeine from aqueous solutions, such as vegetable extracts from tea, coffee, and the like. All of the known procedures have at least two common problems.
First, they add cost to the final product, and it would be desirable to reduce that cost as much as possible. Secondly, they all affect the flavor and quality of the final product by either altering the chemical profile of the natural ingredients or possibly by leaving minor residues. Therefore, it would be desirable to provide an alternative procedure which is more economical than known technology for producing products of like or improved flavor and quality.
~ ~i77313 Background Art Commercial decaffeination techniques often involve solvent extraction from whole green beans such as described by Patel et al. in u.s. 3,671,263 - 05 who use a chlorinated hydrocarbon solvent, and by serry et al. in U.S. 2,309,092 who use a caffeine-deficient solution of coffee solubles. Also of commercial importance is the extraction of caffeine from aqueous solutions with a water-immiscible solvent as described by Adler et al. in U.S. 2,933,395.
However, a wide variety of other processes have been described in the patent literature to enable the use of alternative solvents or eliminate the need for solvent/ product contact. For example, in Belgian Patent 835,556 there is disclosed a process wherein aqueous caffeine solutions are contacted with liquid, water-immiscible fatty extractants at ratios of liquid extractant to caffeine solution of about 20:1. The high volumes of extractant seriously detract from the commercial utility of such a process because of the high added costs.
In an alternative to the use of highly caffeine-specific solvents, Katz suggests in U.S. 4,113,886 that a selective membrane can be employed to effect separation. The solvent is used only to transfer the caffeine from the feed solution to an aqueous phase for collecting the extracted caffeine.
As a total alternative to liquid extractants, a number of patents teach solid adsorbents. For example, U.K. Patent 1,448,340 describes removing caffeine from an aqueous solution by means of polymeric non-ionogenic adsorption resins. While certain of these resins are effective and produce high quality products, they are more costly than desired. Other _ ~ J773~3 patents, such as U.S. 2,391,981 and U.S. 2,416,484 to Kremers, discuss clay as an adsorbent, however, clay is not satisfactorily selective for commercial use as such. Similarly, the hydrated silicates as 05 disclosed by Grossman in U.S. 2,375,550 remove valuable coffee solids other than caffeine. Other patents, such as U.S. 2,472,881 to Bender, U.S.
SLURRY DECAFFEINATION
Technical Field The present invention relates to d~caffeination, 05 and more particula~ly to a new process for de-caffeinating an aqueous solution by contacting it with a two phase extractant, namely a slurry of a solid adsorbent in a liquid caffeine-specific solvent.
The prior art has long sought a process to effectively and non-destructively remove caffeine from aqueous solutions, such as vegetable extracts from tea, coffee, and the like. All of the known procedures have at least two common problems.
First, they add cost to the final product, and it would be desirable to reduce that cost as much as possible. Secondly, they all affect the flavor and quality of the final product by either altering the chemical profile of the natural ingredients or possibly by leaving minor residues. Therefore, it would be desirable to provide an alternative procedure which is more economical than known technology for producing products of like or improved flavor and quality.
~ ~i77313 Background Art Commercial decaffeination techniques often involve solvent extraction from whole green beans such as described by Patel et al. in u.s. 3,671,263 - 05 who use a chlorinated hydrocarbon solvent, and by serry et al. in U.S. 2,309,092 who use a caffeine-deficient solution of coffee solubles. Also of commercial importance is the extraction of caffeine from aqueous solutions with a water-immiscible solvent as described by Adler et al. in U.S. 2,933,395.
However, a wide variety of other processes have been described in the patent literature to enable the use of alternative solvents or eliminate the need for solvent/ product contact. For example, in Belgian Patent 835,556 there is disclosed a process wherein aqueous caffeine solutions are contacted with liquid, water-immiscible fatty extractants at ratios of liquid extractant to caffeine solution of about 20:1. The high volumes of extractant seriously detract from the commercial utility of such a process because of the high added costs.
In an alternative to the use of highly caffeine-specific solvents, Katz suggests in U.S. 4,113,886 that a selective membrane can be employed to effect separation. The solvent is used only to transfer the caffeine from the feed solution to an aqueous phase for collecting the extracted caffeine.
As a total alternative to liquid extractants, a number of patents teach solid adsorbents. For example, U.K. Patent 1,448,340 describes removing caffeine from an aqueous solution by means of polymeric non-ionogenic adsorption resins. While certain of these resins are effective and produce high quality products, they are more costly than desired. Other _ ~ J773~3 patents, such as U.S. 2,391,981 and U.S. 2,416,484 to Kremers, discuss clay as an adsorbent, however, clay is not satisfactorily selective for commercial use as such. Similarly, the hydrated silicates as 05 disclosed by Grossman in U.S. 2,375,550 remove valuable coffee solids other than caffeine. Other patents, such as U.S. 2,472,881 to Bender, U.S.
2,508,545 to Shuman, and U.S. 4,168,324 to Roselius et al, disclose the attraction of caffeine by activated carbon. However, none of these patents suggest decaffeination of an aqueous extract by direct contact with activated carbon because the activated carbon is not specific to caffeine and picks up many other solids.
Thus, the prior art attempts with liquid fatty extractants need improvement to reduce the large amounts of extractant required, and the systems employing solid adsorbents are either too costly or not ~elective enough. Accordingly, there is a present need or improvement and the provision of an alternative process for decaffeination.
Disclosure of Invention The present invention provides a new method for decaffeinating an aqueous caffeine-containing solution comprising the steps of: (a) contacting an aqueous caffeine-containing solution with a slurry containing a ~olid caffeine adsorbent and a liquid, water-immiscible, caffeine-specific solvent; (b) maintaining the aqueous caffeine-containing solution in contact with the slurry for a time sufficient for at least a portion of the caffeine to be extracted from the aqueou~ solution and adsorbed by the solid caffeine adsorbent; and (c) separating the aqueous caffeine-containing solution from the slurry.
~ ~ ~77313 The process is useful for removing caffeine from any aqueous caffeine-containing solution, but finds its primary utility for decaffeinating agueous vegetable extracts such as coffee and tea. Because - 05 of its high specificity for caffeine, the coffee extracts can be from green or roasted beans. Where the extract is from roasted coffee, it is preferred to strip and collect volatile flavors and aromas from the aqueous extract before contacting the extract with the slurry for removing the caffeine.
Then, the decaffeinated extract can be combined with the collected volatiles and dried to soluble powder form as described in U.S. 2,933,395 to Adler et al.
There are envisaged, however, products for which this will not be necessary and alternative processes wherein the volatiles can be removed from the water-immiscible solvent employed in the slurry.
The liquid, water-immiscible caffeine-specific solvent employed in the extractant slurry provides two principal functions. First, it extracts the caffeine from the a~ueous feed solution; and secondly, its high selectivity for caffeine screens out other valuable material~ present in the feed solution. An advantage of the invention is that the solvent need not have a high capacity for holding caffeine.
Therefore, solvents with high selectivity, but low capacities for holding caffeine can be employed with good effectiveness. The solvent is constantly cleaned of caffeine by the solid caffeine adsorbent.
Another advantage of the invention is that the selectivities of the solvent and the solid adsorbent are additive and the slurry is more ~elective than either would be separately.
- ~ 177313 Selection of the proper combination of solvent, solid adsorbent, ratio of solvent to adsorbent, and conditions of contact is important to maintain the most effective driving force and rate of decaffeination.
05 As a general guide, it is desirable to operate with suitable solvents and solid adsorbents in suitable relative amounts and at suitable conditions of time and temperature of contact, to maintain the concentration of caffeine in the solvent at levels of less than 0.03% based on the weight of the solvent.
Preferably, the caffeine concentration will be maintained at a concentration of less than 0.015%.
Ultimately, economics must dictate this value, and concentrations outside of these limits may be preferred in some situations.
The solvent must be a liguid undér the proposed processing conditions and must be immiscible in the aqueous caffeine-containing feed solution. It is important for the solvent to be liquid so that liquid-liquid contact with the feed solution can be establiRhed. Preferably, the viscosity of the solvent will be sufficiently low that the level of mixing shear normally encountered in liquid-liquid extraction will keep it adequately dispersed within the aqueous feed solution. The quality of immiscibility is important so that the solvent is not dissolved in the aqueous caffeine-containing solution in any amount which will have a significant impact on the flavor or quality of the final product. Preferably, the solvent is sufficiently immiscible to prevent any measurable amount of it to be dissolved in the aqueous caffeine-containing solution. Also, it is important for the solvent and the solid adsorbent to be mutually attracted sufficiently to maintain the , ~77313 solid adsorbent in the solvent phase and out of aqueous phase.
Among the materials which can be employed as solvents according to the present invention are 05 petroleum oils, triglycerides, fatty acids, fatty alcohols and other caffeine-specific, water-immiscible materials which are liquid at the conditions of treatment. The triglycerides can be derived from vegetable or animal sources. Among the suitable triglycerides are the usual vegetable fats typically encountered in food processing, such as soybean oil, corn oil, coconut oil, cottonseed oil, peanut oil, safflower oil, palm kernel oil, sun-flower oil, palm oil, rapeseed oil~ coffee oil, and mixtures of these. Preferably the fat will be naturally low in emulsifying potential or will be treated such as by an initial emulsification in water under high shear conditions and separating out all portions which do not readily recoalesce with the major portion of the oil. It is also preferred that the caffeine-specific solvent have a partition coefflcient above 0.02, and more preferably above 0 .1.
While hydrogenated fats can be employed, they are not preferred because they may smoke and break down under the high temperatures employed in processing, especially those encountered during periodic purification of the oil. Similarly, animal fats such as tallow, chicken fat, lard and butter fat can conceivably be employed, but they contain large amounts of impurities which are costly to remove.
However, economics is the primary reason for their non-preference. Among the suitable petroleum oils are mineral oils known to the art as light mineral ~77313 oils. These oils are desirable because they have good stability. Among the fatty acids are oleic acid, stearic acid, octanoic acid, and the like. In general, the longer chain acids will be prefe~red 05 within this group. Similarly, longer chain fatty alcohols, such as stearyl alcohol, are preferred within that group.
The solid caffeine adsorbent employed in the slurry of the present invention can be selected from any of those known to adsorb caffeine and ~e physically stable under the conditions of processing. Among the know~ caffeine adsorbents are clays such as discussed in U.S. 2,391,981 and U.S. 2,416,484 to Kremers; zeo~ites and ion exchange resins as taught in U.S. 3,108,876 to Turken et al; hydrated silicates as taught in U.S. 2,375,550 to Grossman; polymeric non-ionogenic adsorption resins, especially styrene divinylbenzene macroreticular resins of the type disclosed by Gustafson in U.S. 3,531,463; activated carbon, especially finely-divided activated carbon derived from coconut or coal. Among these, activated carbon is preferred because of its desirable balance between cost and effectiveness.
The solid adsorbent should have the highest possible surface area consistent with physical strength necessary under the processing conditions and the facility with which it can be separated from the water-immiscible solvent after contacting the slurry with the aqueous caffeine-containing solution for the desired period of time. In the case of activated charcoal, especially derived from coconut or coal, particle sizes of from 100 to 300 U.S. mesh have been found effective. The natural porosity of these materials further increases their surface area . ~J77313 and increases the efficiency with which they remove caffeine from the solvent.
The concentration of the solid adsorbent in the water-immiscib~e solvent will depend upon a number 05 of factors including: the concentration of caffeine in the aqueous feed solution, the combined capacity of the solid adsorbent and the liquid solvent to hold caffeine, the individual capacity of the solvent to hold caffeine and yet maintain a high driving force to continue extraction, the individual capacity of the solid adsorbent to hold caffeine and yet maintain a high driving force to continue removing the caffeine from the solvent, the desired reduction in caffeine concentration in the aqueous feed solution, the rate at which the solid adsorbent is renewed in continuous processing, the available quantities of slurry for contacting with the aqueous liquid, and various other factors, including economics, which can affect or control any of the listed factors.
Not all of these factors and their interrelation-ships have been studied in detail, however, it appear~ desirable to maintain the combined capacity of the solvent and the adsorbent at a level at least equal to the total amount of caffeine in the system.
And, the solid adsorbent should be present in an amount effective to provide a capacity to hold at least half of that total caffeine. Preferably, the combined capacity should be at least 50% greater than the amount of caffeine in the solution in contact with the slurry. Preferably, the slurry will contain from about 2 to about S0% solid adsorbent ba~ed on the weight of the slurry. Most preferably, the slurry will comprise from about S to 20% of the ~ ~773~3 g solid caffeine adsorbent, based on the weight of the slurry.
An advantage of the present invention is the reduced level of solvent reguired as compared to 05 prior art processes employing water-immiscible fatty materials as solvents. Ratios of the weight of slurry to the weight of a~ueous caffeine-containing solution can be considerably less than 20:1 and ratios of 1:1 and lower can be used with some effectiveness. More preferred ratios are within the range of from about 2:1 to about 10:1. It is most preferred to maintain the ratio of the weight of the solvent to the weight of the solution to less than 5:1, and this can be achieved with facility according to the invention where the amount of solid adsor~ent added to the solvent to form the slurry is effective to maintain the concentration of caffeine in the solvent at a level of less than 0.03%, based on the weight of the solvent. Where the adsorbent is activated carbon, and the a~ueous caffeine-containing solutio~ is a typical coffee extract containing from about 10 to about 35%, and most typically from 15 to 28%, solids including caffeine, carbon concentrations of from about 5 to about 20% of the weight of the slurry will be effective.
The process of this invention can be employed to obtain any desired degree of caffeine removal.
The process is adaptable to batch, semi-continuous and continuous processing with concurrent or counter-current flow. Preferably, however, it is performedcontinuously by countercurrently passing the slurry and a caffeine-rich agueous solution into a liguid-li~uid contactor such as a rotating disc contactor or a Karr column. The slurry and the agueous solution ~ l 7731 3 are easily separated due to their requisite im-miscibility. The slurry is then continuously filtered to remove the adsorbent and fresh activated carbon is continuously added prior to recycling the solvent 05 to the liquid-liquid contactor. The carbon can be renewed by known processes such as heating and solvent regeneration.
The oil remains relatively clean and needs no treatment to remain effective. However, over a period of time, the oil may degrade or be filled with other undesirable components and can be discarded or renewed according to known techniques. For example, it can be heated to sublime the caffeine.
It is an advantage of the present invention, however, that the soivent does not need to be specially processed simply to remove the caffeine to maintain a high driving force for the extraction. The solid caffeine adsorbent continuously removes excess caffeine levels from the solvent to maintain a good extraction rate.
Al~o important for obtaining good extraction according to the invention is the temperature maintained during contact between the slurry and the aqueous caffeine solution. The temperature will affect the rate of extraction, the selectivity of the solvent, and the relative capacities of the slurry components for holding the extracted caffeine. The temperature will also affect the flavor of any desired coffee or tea flavors present in the agueous solution. Accordingly, it is not possible to identify a single temperature or range of temperatures as universally defining optimum conditions. It is believed, however, that temperatures within the range of from about 50 to about 100 C will provide good results. The selection l~77313 of an exact temperature will depend on the materials and processing equipment and conditions employed, and may be within this range or outside of this range.
05 Total contact time, or residence time within a liquid-liquid contactor, will depend upon the factors discussed above as well as the desired degree of caffeine extraction. While economics is the controlling factor, it must be borne in mind that excessively long contact times adversely affect coffee and tea flavors. Those skilled in the art will be able to balance these factors as necessary, given the exemplary situations set forth in the Example.
Best Mode For CarrYinq Out The Invention The following Example is provided to illustrate and explain what is presently considered the best mode for carrying out the invention. The data is for illustrative purposes to guide the person of ordinary skill in the art and is not to be taken as limiting in any regard. Unless otherwise indicated, all parts and percentages are by weight.
Example A series of green and roasted coffee extracts were decaffeinated by contacting them with slurries containing the indicated water-immiscible solvents and 10%, by weight of the slurry of DARCO 51 fine activated carbon.
The green coffee extracts had total solids contents of 25% and a ratio of total solids to caffeine of 25 . 2.
The roasted coffee extracts had total solids contents of 20% and a ratio of total solids to caffeine of 20.8.
* Trade Mark ~ ~ 77313 All extractions were done in batches of 0.1 kilograms total weight for 20 hours at 82 C. Each extraction employed 0.02 kg aqueous coffee extract and 0.08 kg of the indicated solvent and carbon for OS a solvent to extract ratio of 4:1. The results are summarized in the table below and show good de-caffeination and good specificity.
Product Ratio of Apparent Solid Percent Total Process Adsorbent Decaffeina- Solid/ Partition Partition Extract Solve~t tion Caf- Coef- Coef-feine ficient ficient Green Mineral Oil 38.0 40.5 0.15 1.53 Green Corn Oil 49.4 49.7 0.24 2.44 Roasted Mineral Oil 52.g 44.1 0.28 2.80 Roasted Corn Oil 50,3 41.9 0.25 2.53 The above description i~ for the purpose of describing the invention to people having ordinary skill in the art to enable them to practice it. It is not meant to detail all of the obvious modifications and variations of the invention which will become apparent upon reading. It is intended, however, that these modifications and variations be included within the scope of the invention which is defined by the following claims.
Thus, the prior art attempts with liquid fatty extractants need improvement to reduce the large amounts of extractant required, and the systems employing solid adsorbents are either too costly or not ~elective enough. Accordingly, there is a present need or improvement and the provision of an alternative process for decaffeination.
Disclosure of Invention The present invention provides a new method for decaffeinating an aqueous caffeine-containing solution comprising the steps of: (a) contacting an aqueous caffeine-containing solution with a slurry containing a ~olid caffeine adsorbent and a liquid, water-immiscible, caffeine-specific solvent; (b) maintaining the aqueous caffeine-containing solution in contact with the slurry for a time sufficient for at least a portion of the caffeine to be extracted from the aqueou~ solution and adsorbed by the solid caffeine adsorbent; and (c) separating the aqueous caffeine-containing solution from the slurry.
~ ~ ~77313 The process is useful for removing caffeine from any aqueous caffeine-containing solution, but finds its primary utility for decaffeinating agueous vegetable extracts such as coffee and tea. Because - 05 of its high specificity for caffeine, the coffee extracts can be from green or roasted beans. Where the extract is from roasted coffee, it is preferred to strip and collect volatile flavors and aromas from the aqueous extract before contacting the extract with the slurry for removing the caffeine.
Then, the decaffeinated extract can be combined with the collected volatiles and dried to soluble powder form as described in U.S. 2,933,395 to Adler et al.
There are envisaged, however, products for which this will not be necessary and alternative processes wherein the volatiles can be removed from the water-immiscible solvent employed in the slurry.
The liquid, water-immiscible caffeine-specific solvent employed in the extractant slurry provides two principal functions. First, it extracts the caffeine from the a~ueous feed solution; and secondly, its high selectivity for caffeine screens out other valuable material~ present in the feed solution. An advantage of the invention is that the solvent need not have a high capacity for holding caffeine.
Therefore, solvents with high selectivity, but low capacities for holding caffeine can be employed with good effectiveness. The solvent is constantly cleaned of caffeine by the solid caffeine adsorbent.
Another advantage of the invention is that the selectivities of the solvent and the solid adsorbent are additive and the slurry is more ~elective than either would be separately.
- ~ 177313 Selection of the proper combination of solvent, solid adsorbent, ratio of solvent to adsorbent, and conditions of contact is important to maintain the most effective driving force and rate of decaffeination.
05 As a general guide, it is desirable to operate with suitable solvents and solid adsorbents in suitable relative amounts and at suitable conditions of time and temperature of contact, to maintain the concentration of caffeine in the solvent at levels of less than 0.03% based on the weight of the solvent.
Preferably, the caffeine concentration will be maintained at a concentration of less than 0.015%.
Ultimately, economics must dictate this value, and concentrations outside of these limits may be preferred in some situations.
The solvent must be a liguid undér the proposed processing conditions and must be immiscible in the aqueous caffeine-containing feed solution. It is important for the solvent to be liquid so that liquid-liquid contact with the feed solution can be establiRhed. Preferably, the viscosity of the solvent will be sufficiently low that the level of mixing shear normally encountered in liquid-liquid extraction will keep it adequately dispersed within the aqueous feed solution. The quality of immiscibility is important so that the solvent is not dissolved in the aqueous caffeine-containing solution in any amount which will have a significant impact on the flavor or quality of the final product. Preferably, the solvent is sufficiently immiscible to prevent any measurable amount of it to be dissolved in the aqueous caffeine-containing solution. Also, it is important for the solvent and the solid adsorbent to be mutually attracted sufficiently to maintain the , ~77313 solid adsorbent in the solvent phase and out of aqueous phase.
Among the materials which can be employed as solvents according to the present invention are 05 petroleum oils, triglycerides, fatty acids, fatty alcohols and other caffeine-specific, water-immiscible materials which are liquid at the conditions of treatment. The triglycerides can be derived from vegetable or animal sources. Among the suitable triglycerides are the usual vegetable fats typically encountered in food processing, such as soybean oil, corn oil, coconut oil, cottonseed oil, peanut oil, safflower oil, palm kernel oil, sun-flower oil, palm oil, rapeseed oil~ coffee oil, and mixtures of these. Preferably the fat will be naturally low in emulsifying potential or will be treated such as by an initial emulsification in water under high shear conditions and separating out all portions which do not readily recoalesce with the major portion of the oil. It is also preferred that the caffeine-specific solvent have a partition coefflcient above 0.02, and more preferably above 0 .1.
While hydrogenated fats can be employed, they are not preferred because they may smoke and break down under the high temperatures employed in processing, especially those encountered during periodic purification of the oil. Similarly, animal fats such as tallow, chicken fat, lard and butter fat can conceivably be employed, but they contain large amounts of impurities which are costly to remove.
However, economics is the primary reason for their non-preference. Among the suitable petroleum oils are mineral oils known to the art as light mineral ~77313 oils. These oils are desirable because they have good stability. Among the fatty acids are oleic acid, stearic acid, octanoic acid, and the like. In general, the longer chain acids will be prefe~red 05 within this group. Similarly, longer chain fatty alcohols, such as stearyl alcohol, are preferred within that group.
The solid caffeine adsorbent employed in the slurry of the present invention can be selected from any of those known to adsorb caffeine and ~e physically stable under the conditions of processing. Among the know~ caffeine adsorbents are clays such as discussed in U.S. 2,391,981 and U.S. 2,416,484 to Kremers; zeo~ites and ion exchange resins as taught in U.S. 3,108,876 to Turken et al; hydrated silicates as taught in U.S. 2,375,550 to Grossman; polymeric non-ionogenic adsorption resins, especially styrene divinylbenzene macroreticular resins of the type disclosed by Gustafson in U.S. 3,531,463; activated carbon, especially finely-divided activated carbon derived from coconut or coal. Among these, activated carbon is preferred because of its desirable balance between cost and effectiveness.
The solid adsorbent should have the highest possible surface area consistent with physical strength necessary under the processing conditions and the facility with which it can be separated from the water-immiscible solvent after contacting the slurry with the aqueous caffeine-containing solution for the desired period of time. In the case of activated charcoal, especially derived from coconut or coal, particle sizes of from 100 to 300 U.S. mesh have been found effective. The natural porosity of these materials further increases their surface area . ~J77313 and increases the efficiency with which they remove caffeine from the solvent.
The concentration of the solid adsorbent in the water-immiscib~e solvent will depend upon a number 05 of factors including: the concentration of caffeine in the aqueous feed solution, the combined capacity of the solid adsorbent and the liquid solvent to hold caffeine, the individual capacity of the solvent to hold caffeine and yet maintain a high driving force to continue extraction, the individual capacity of the solid adsorbent to hold caffeine and yet maintain a high driving force to continue removing the caffeine from the solvent, the desired reduction in caffeine concentration in the aqueous feed solution, the rate at which the solid adsorbent is renewed in continuous processing, the available quantities of slurry for contacting with the aqueous liquid, and various other factors, including economics, which can affect or control any of the listed factors.
Not all of these factors and their interrelation-ships have been studied in detail, however, it appear~ desirable to maintain the combined capacity of the solvent and the adsorbent at a level at least equal to the total amount of caffeine in the system.
And, the solid adsorbent should be present in an amount effective to provide a capacity to hold at least half of that total caffeine. Preferably, the combined capacity should be at least 50% greater than the amount of caffeine in the solution in contact with the slurry. Preferably, the slurry will contain from about 2 to about S0% solid adsorbent ba~ed on the weight of the slurry. Most preferably, the slurry will comprise from about S to 20% of the ~ ~773~3 g solid caffeine adsorbent, based on the weight of the slurry.
An advantage of the present invention is the reduced level of solvent reguired as compared to 05 prior art processes employing water-immiscible fatty materials as solvents. Ratios of the weight of slurry to the weight of a~ueous caffeine-containing solution can be considerably less than 20:1 and ratios of 1:1 and lower can be used with some effectiveness. More preferred ratios are within the range of from about 2:1 to about 10:1. It is most preferred to maintain the ratio of the weight of the solvent to the weight of the solution to less than 5:1, and this can be achieved with facility according to the invention where the amount of solid adsor~ent added to the solvent to form the slurry is effective to maintain the concentration of caffeine in the solvent at a level of less than 0.03%, based on the weight of the solvent. Where the adsorbent is activated carbon, and the a~ueous caffeine-containing solutio~ is a typical coffee extract containing from about 10 to about 35%, and most typically from 15 to 28%, solids including caffeine, carbon concentrations of from about 5 to about 20% of the weight of the slurry will be effective.
The process of this invention can be employed to obtain any desired degree of caffeine removal.
The process is adaptable to batch, semi-continuous and continuous processing with concurrent or counter-current flow. Preferably, however, it is performedcontinuously by countercurrently passing the slurry and a caffeine-rich agueous solution into a liguid-li~uid contactor such as a rotating disc contactor or a Karr column. The slurry and the agueous solution ~ l 7731 3 are easily separated due to their requisite im-miscibility. The slurry is then continuously filtered to remove the adsorbent and fresh activated carbon is continuously added prior to recycling the solvent 05 to the liquid-liquid contactor. The carbon can be renewed by known processes such as heating and solvent regeneration.
The oil remains relatively clean and needs no treatment to remain effective. However, over a period of time, the oil may degrade or be filled with other undesirable components and can be discarded or renewed according to known techniques. For example, it can be heated to sublime the caffeine.
It is an advantage of the present invention, however, that the soivent does not need to be specially processed simply to remove the caffeine to maintain a high driving force for the extraction. The solid caffeine adsorbent continuously removes excess caffeine levels from the solvent to maintain a good extraction rate.
Al~o important for obtaining good extraction according to the invention is the temperature maintained during contact between the slurry and the aqueous caffeine solution. The temperature will affect the rate of extraction, the selectivity of the solvent, and the relative capacities of the slurry components for holding the extracted caffeine. The temperature will also affect the flavor of any desired coffee or tea flavors present in the agueous solution. Accordingly, it is not possible to identify a single temperature or range of temperatures as universally defining optimum conditions. It is believed, however, that temperatures within the range of from about 50 to about 100 C will provide good results. The selection l~77313 of an exact temperature will depend on the materials and processing equipment and conditions employed, and may be within this range or outside of this range.
05 Total contact time, or residence time within a liquid-liquid contactor, will depend upon the factors discussed above as well as the desired degree of caffeine extraction. While economics is the controlling factor, it must be borne in mind that excessively long contact times adversely affect coffee and tea flavors. Those skilled in the art will be able to balance these factors as necessary, given the exemplary situations set forth in the Example.
Best Mode For CarrYinq Out The Invention The following Example is provided to illustrate and explain what is presently considered the best mode for carrying out the invention. The data is for illustrative purposes to guide the person of ordinary skill in the art and is not to be taken as limiting in any regard. Unless otherwise indicated, all parts and percentages are by weight.
Example A series of green and roasted coffee extracts were decaffeinated by contacting them with slurries containing the indicated water-immiscible solvents and 10%, by weight of the slurry of DARCO 51 fine activated carbon.
The green coffee extracts had total solids contents of 25% and a ratio of total solids to caffeine of 25 . 2.
The roasted coffee extracts had total solids contents of 20% and a ratio of total solids to caffeine of 20.8.
* Trade Mark ~ ~ 77313 All extractions were done in batches of 0.1 kilograms total weight for 20 hours at 82 C. Each extraction employed 0.02 kg aqueous coffee extract and 0.08 kg of the indicated solvent and carbon for OS a solvent to extract ratio of 4:1. The results are summarized in the table below and show good de-caffeination and good specificity.
Product Ratio of Apparent Solid Percent Total Process Adsorbent Decaffeina- Solid/ Partition Partition Extract Solve~t tion Caf- Coef- Coef-feine ficient ficient Green Mineral Oil 38.0 40.5 0.15 1.53 Green Corn Oil 49.4 49.7 0.24 2.44 Roasted Mineral Oil 52.g 44.1 0.28 2.80 Roasted Corn Oil 50,3 41.9 0.25 2.53 The above description i~ for the purpose of describing the invention to people having ordinary skill in the art to enable them to practice it. It is not meant to detail all of the obvious modifications and variations of the invention which will become apparent upon reading. It is intended, however, that these modifications and variations be included within the scope of the invention which is defined by the following claims.
Claims (25)
1. A method for decaffeinating an aqueous caffeine-containing solution comprising the steps of:
(a) contacting an aqueous caffeine-containing solution with a slurry containing a solid caffeine adsorbent and a liquid, water-immiscible, caffeine-specific solvent;
(b) maintaining the aqueous caffeine-containing solution in contact with the slurry for a time sufficient for at least a portion of the caffeine to be extracted from the aqueous solution and adsorbed by the solid caffeine adsorbent; and (c) separating the aqueous caffeine-containing solution from the slurry.
(a) contacting an aqueous caffeine-containing solution with a slurry containing a solid caffeine adsorbent and a liquid, water-immiscible, caffeine-specific solvent;
(b) maintaining the aqueous caffeine-containing solution in contact with the slurry for a time sufficient for at least a portion of the caffeine to be extracted from the aqueous solution and adsorbed by the solid caffeine adsorbent; and (c) separating the aqueous caffeine-containing solution from the slurry.
2. The method of claim 1 wherein the aqueous caffeine-containing solution is a coffee or tea extract.
3. The method of claim 2 wherein the aqueous caffeine-containing solution is a green coffee extract.
4. The method of claim 2 wherein the aqueous caffeine-containing solution is a roasted coffee extract.
5. The method of claim 4 wherein the roasted coffee extract has been stripped of volatiles.
6. The method of claim 1 wherein the solid adsorbent is continuously removed from the slurry and renewed adsorbent is continuously added.
7. The method of claim 6 wherein the temperature during contact is maintained within the range of from 50 to 100 C.
8. The method of claim 1 wherein the solid caffeine adsorbent comprises a member selected from the group consisting of activated carbon, clay, hydrated silicates, zeolites, ion exchange resins, non-ionogenic adsorption resins, and any combination of these.
9. The method of claim 8 wherein the solid caffeine adsorbent comprises activated carbon.
10. The method of claim 1 wherein the liquid, water-immiscible, caffeine-specific solvent comprises a member selected from the group consisting of petroleum oils, fatty acids, fatty alcohols, and triglycerides.
11. The method of claim 1 wherein the slurry comprises from 2 to 50% solid caffeine adsorbent based on the weight of the slurry.
12. The method according to any one of claims 9, 10 or 11 wherein the slurry comprises from 5 to 20%
solid caffeine adsorbent based on the weight of the slurry.
solid caffeine adsorbent based on the weight of the slurry.
13. The method according to claim 1 wherein the ratio of weight of the slurry to the weight of the aqueous caffeine-containing solution is within the range of from 1:1 to 20:1.
14. The method according to any one of claims 9, 10, or 11 wherein the ratio of the weight of the slurry to the weight of the aqueous caffeine-containing solution is within the range of from 2:1 to 10:1.
15. The method of claim 1 wherein the concentration of caffeine in the liquid, water-immiscible, caffeine-specific solvent is maintained at less than 0.03%
based on the weight of the solvent.
based on the weight of the solvent.
16. The method of claim 1 which further comprises the step of separating the liquid, water-immiscible, caffeine-specific solvent from the solid caffeine adsorbent.
17. The method of claim 16 which further includes the step of removing the caffeine from the solid caffeine adsorbent.
18. The method of claim 16 which further includes the step of removing the caffeine from the liquid, water-immiscible, caffeine-specific solvent.
19. The method according to claim 16 wherein concentration of caffeine in the liquid, water-immiscible, caffeine-specific solvent is maintained at a less than 0.03% based on the weight of the solvent.
20. The method according to claim 16 wherein the liquid, water-immiscible, caffeine-specific solvent comprises a member selected from the group consisting of petroleum oils, fatty acids, fatty alcohols, and triglycerides.
21. The method according to claim 20 wherein the solid caffeine adsorbent comprises activated carbon.
22. The method according to claim 21 wherein the ratio of the weight of the slurry to the weight of the agueous caffeine-containing solution is within the range of from 2:1 to 10:1.
23. The method according to claim 22 wherein the slurry comprises from S to 20% activated carbon based on the weight of the slurry.
24. The method according to claim 23 wherein the temperature during contact is maintained within the range of from 50 to 100 C.
25. The method of claim 24 wherein the ratio of liquid, water-immiscible, caffeine-specific solvent to aqueous caffeine-containing solution is less than 5:1.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US15990980A | 1980-06-16 | 1980-06-16 | |
| US159,909 | 1980-06-16 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1177313A true CA1177313A (en) | 1984-11-06 |
Family
ID=22574629
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000378270A Expired CA1177313A (en) | 1980-06-16 | 1981-05-25 | Slurry decaffeination |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPS5728089A (en) |
| CA (1) | CA1177313A (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0775593B2 (en) * | 1988-06-13 | 1995-08-16 | 松下電器産業株式会社 | coffee maker |
| DE602005015547D1 (en) | 2004-01-30 | 2009-09-03 | Kao Corp | COFFEE DRINK COMPOSITION |
| DE602005017361D1 (en) * | 2004-01-30 | 2009-12-10 | Kao Corp | COFFEE DRINK COMPOSITION |
| CN101227827B (en) | 2005-07-29 | 2012-06-13 | 花王株式会社 | Packaged black coffee drink |
| CN101227829B (en) | 2005-07-29 | 2011-06-22 | 花王株式会社 | Packaged milk coffee drink |
| JP4653587B2 (en) * | 2005-07-29 | 2011-03-16 | 花王株式会社 | Containerized coffee beverage |
| US8263149B2 (en) | 2005-07-29 | 2012-09-11 | Kao Corporation | Container-packed milk coffee beverage |
-
1981
- 1981-05-25 CA CA000378270A patent/CA1177313A/en not_active Expired
- 1981-06-15 JP JP9207281A patent/JPS5728089A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5728089A (en) | 1982-02-15 |
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