CA1177314A - Decaffeination process - Google Patents

Abstract

ABSTRACT Moist coffee is decaffeinated by extraction with a hygroscopic material.

Description

l ~ 7~31 4 DESCRIPTION

DECAFFEINATION P~OCESS

TECHNICAL FIELD
This invention relates to a decaffeination 05 process. More particularly, it relates to the decaffeination of green or roasted coffee. This invention especially relates to coffee decaffeination by dehydration with a hygroscopic material.
BACKGROUND ART
Current commercial decaffeination of coffee is effected by the removal of caffeine from whole, green coffee beans. The beans are first moistened and then extracted with a solvent which is relatively specific for caffeine. The solvents employed commercially are either a chlorinated hydrocarbon solvent, such as discussed in U.S.
Patent No. 3,671,263 to Patel et al. or a caffeine-deficient water solution of green coffee solubles, such as disclosed in U.S. Patent No. 2,309.092 to Berry et al.
In the decaffeination process of U.S.
Patent No. 2,309,092 which is commonly referred to as the water extraction system (Note: Sivetz, Coffee Processing Technology, Vol. 2, p. 208, AVI
Publishing Co., Inc., 1963) the caffeine laden water extract, resulting from contract between caffeine-containing green coffee and the caffeine-deficient ~ ~ 77314 water solution, is directly extracted with a solvent in order to remove caffeine. Typically these solvents are the same chlorinated hydrocarbons which are employed in the direct solvent extraction 05 processes, exemplified by the aforementioned U.S.
Patent No. 3,671,263.
It is also known to produce decaffeinated soluble coffee by first stripping and collecting volatile flavor and aromas from an aqueous extract of roasted coffee and then directly contacting the stripped extract with an organic water-immiscible caffeine solvent such as methylene chloride. The decaffeinated extract can then be combined with the collected volatiles and dried to a soluble powder form. Such a process is described in U.S. Patent No. 2,933,395 to Adler et al.
Decaffeination technigues which avoid the use of a solvent such as the resin technigue of U.S.
Patent No. 3,108,876 to Turken et al. and the microbiological technique of U.S. Patent No. 3,749,584 to Kurtzman et al. are known to the art but have not yet been developed commercially.
Other technique~ for decaffeination are disclosed in the prior art, U.S. Patent No. 3,669,679 to Panzer et al. teaches the use of fluorinated hydrocarbons to remove caffeine from green coffee while Belgian Patent No. 835,556 and Belgian Improvement Patent No. 848,635 teach the use of liquid fatty materials, such as safflower oil, ~oybean oil, corn oil and the like, to extract caffeine from either coffee beans or coffee extract. Diethyl succinate is the caffeine extraction medium employed in the process of U.S. Patent No. 4,087,562 to Jones et al.
Membrane diffusion is disclosed as an effective decaffeination means in U.S. Patent No. 4,113,886 to I .! 773 1 4 Katz where the caffeine, in aqueous extracts of green or roasted cof~ee, diffuses through a porous, hydrophilic membrane filled with a water immiscible caf~eine-selective ~olvent into a water phase on the 05 other side of the membrane.
U.S. Patent No. 3,953,615 to Gupta et al.
relates to a hydration drying process for a juice concentrate, such as orange juice or coffee. Anhydrous dextrose is admixed with the aqueous concentrate to produce a dry, free flowing powder, viz., powdered coffee, with the water being removed in the form of hydrated dextrose. In all embodiments, the anhydrous dextrose is contacted with an aqueous solution, there is no suggestion that the dextrose will remove water present in a solid mass, such as moist coffee beans.
It is an object of this invention to provide a decaffeination process for coffee.
It is another object of this invention to provide a process for decaffeinating coffee which eliminates the direct or the indirect use of organic solvents.
It i5 a further object o this invention to provide a process that removes the caffeine directly from the coffee beans.
It is still another object of this invention to provide a dry proce~s for decaffeinating green or roasted coffee beans.

DISCLOSURE OF INVENTION
In accordance with the present invention, it ha8 been found that green or roasted coffee beans can be decafeinated by moistening the coffee beans with water and then contacting the bean~ with a hygro~copic material to remove water, along with ~ !77314 . . .
caffeine dissolved therein, from the coffee beans.
The invention is directed to a method of decaffeinating coffee comprising:
~a~ moistening the coffee, 05 ~b) contacting the moistened coffee with a hygroscopic material for a period of time sufficient to remove caffeine-containing water from the coffee;
and (c) separating the coffee from the hygroscopic material.
The present invention relates to a decaffeination process which eliminates the direct or indirect contacting of the coffee with such hydrocarbon solvents as tricholoroethylene or methylene chloride which have been employed commercially heretofore. There has been increasing interest recently in providing decaffeination processes which do not employ either of these solvents-.
The present invention achieves decaffeination by a hydration process. A hygroscopic material, viz., a hydra~able salt, such as sodium chloride, is brought into contact with coffee beans which have been contacted previously with water so as to increase their water content. Since caffeine is water soluble, the water which is contained within the coffee bean contains a significant quantity of caffeine.
Apparently, because of the water concentration gradient which exists when the hygroscopic material is brought into contact with moist coffee beans, water passes from the coffee bean to the salt. The water soluble caffeine is carried from the coffee bean along with the water thereby effecting decaffeination. By repeating this process a number ~ ~7314 of times, a significant reduction in the caffeine content of the coffee bean can be effected.
This invention may be employed to decaffeinate either green or roasted coffee in the 05 form of whole beans, cracked beans, beans in sub-divided form or ground coffee. As used herein, the term "coffee" is meant to include green or roasted coffee in any of these forms. As with other decaffeination processes, the process of this invention is based on the solubility of caffeine in water and the ability to remove or extract water, along with dissolved caffeine, from the coffee.
The coffee is initially contacted with water to increase its free water content. This step is known in the art as "premoistening" or "moistening."
The water penetrates the beans and dissolves the caffeine contained therein. The extraction of the caffeine-loaded water from within the beans is accomplished in the prior art with a variety of solvents, viz., chlorinated hydrocarbons, fluorinated hydrocarbons, diethyl succinate and the like, or by other means, viz., diffusion through a porous, hydrophilic membrane. In the process of this invention, the water iB extracted from the coffee by means of a hygroscopic material, such as, salt. Following the extraction, the coffee and the hygroscopic material are separated by such means as screening and the coffee is water-washed, where necessary, to remove residual quantities of the hygroscopic material.
The decaffeinated coffee is then cooled and dried or if the coffee is to be roasted, the cooling and drying may be eliminated and the decaffeinated coffee sent directly to the roaster for processing by well known procedures. The roasted coffee i~
suitable for use as either regular coffee or for I l77314 extraction in making soluble coffee.
The moistening operation involves uniformly incorporating water in the green or roasted coffee.
This water is thought to swell the coffee, solubilize 05 the caffeine and, in general, to render the green or roasted coffee caffeine-extractable. Moistening can be accomplished by adding water and mixing the coffee, by using humidified air or other gases, and/or by employing steam. The particular method employed for moistening the bean is not critical, so long as a uniform and relatively even penetration of water is obtained throughout the coffee and no free or excess water is permitted to exist on the external surfacè of the coffee at the completion of the moistening step. No free water should be present when the extraction step is initiated. One effective means to prevent the presence of such free water is to introduce into the vessel containing the coffee, the precise amount of water required to obtain the desired moisture content in the coffee and then to permit sufficient time for equilibrium to be achieved.
If steam is employed, extra care should be exercised since free water forms rather easily with this moistening procedure. Steam is therefore nat preferred.
One particularly effective means of moistening the coffee is to contact it with boiling water.
Effective moisture levels can be obtained by this means in a relatively short time, usualy about 5-15 minutes. Coffee may be moistened to any desired degree, but it has been found that the greater the moisture content of the coffee, the more rapid is the caffeine extraction. Thus, while moisture contents of about 15 to about 55% may be employed, moisture contents gre~ter than 30% are preferred and those greater than 40% are particularly preferred.

~ ~77314 Saturation is obtained at about 55% or above. All - percentage figures used herein are in terms of weight unless stated otherwise.
Extraction is accomplished by contacting a 05 hygroscopic material with the moist coffee to remove water from the coffee and concomitantly the caffeine which is dissolved in the water. As used herein the term hygroscopic material is meant a material which acts as a drying agent when brought into contact with the moist coffee whether the means by which it removes and binds the water to itself is chemical (absorption), physical (adsorption) or a combination of the two. Therefore, the hygroscopic materials which may be usefully employed in this invention can be selected from a very extensive list, limited only by the ingenuity of the artisan and the restrictions placed on the selection because of the foodstuff nature of the coffee beans and processing requirements of the particular embodiment of the invention being employèd. Thus, a hygroscopic material which deliquesces would not be a preferred material nor would an otherwise useful material which imparted an objectionable taste to the coffee beans. Therefore, bearing in mind such obvious limitations, the skilled artisan may select a hygroscopic material from such hydratable or desiccant salts as sodium chloride, copper sulfate, calcium sulfate, calcium ~ilicate, magnesium silicate, calcium chloride, zinc chloride, barium chlorate, magnesium chlorate, boron oxide, calcium oxide, magnesium oxide, barium oxide, calcium bromide and the like. Other inorganic materials which may #erve as a useful hygroscopic material in this invention include alumina, bauxite, fuller's earth, diatomaceous earth, kieselguhr, acid-treated clay, silica gel, crystalline aluminosilicates ~ ~ 77314 ~molecular sieves, zeolites) and the like. Activated c~arcoals prepared from shells, peat, coal or petroleum may also be used in this invention. Useful hygroscopic materials may also include such organic materials as 05 polystyrene, phenolic resins, acrylic resins, cellulose, cellulostic derivatives and the like.
Ideally~ the hygroscopic material should be anhydrous when initially brought into contact with the coffee in the extraction step so as to achieve a high degree of decaffeination. ~owever, as long as the moisture level of the hygroscopic material is below saturation, it will remove water from the coffee but certainly not as efficiently as if it were anhydrous or had a low water content.
The hygroscopic material should be provided in a size which will permit ready separation from the coffee following the ex~raction step. Physical separation of the coffee and the hygroscopic material can be readily achieved by screening or sieving where the particle size distribution of the hygroscopic material and the coffee are mutually exclusive to a sufficient degree.
Usually, the hygroscopic material will be of a particle size considerably smaller than that of the coffee. The capacity of the hygroscopic material for water as well as the effective surface area in contact with the coffee during the extraction will determine the effectiveness of the decaffeination.
The determination of optimum particle sizes for specific hygroscopic materials is a matter of routine experiméntation. In general, the hygroscopic material is of a particle size not larger than about 1/5 of that of the coffee beans and is preferably less than about 1/10. The particle size, however, should not be so small as to deliguesce on exposure to the ~ ~77314 moist beans.
In a particularly preferred embodiment, sodium chloride is employed to decaffeinate the cofee, especially green coffee. This "salt" is 05 commercially avàilable in numerous flake sizes thereby permitting the skilled artisan to select the salt in a particle size which will most efficiently decaffeinate the green coffee whether it is in whole bean or sub-divided form.
During the extraction step, the coffee and the hygroscopic material are, preferably, continuously contacted to achieve the most effective operation.
Since solid-solid contacting is employed in the extraction step, conventional equipment may be employed to conduct this operation in an efficient manner. Such commercially available eguipment as a tumbling barrel, a double cone mixer, a "V" mixer, a rotating pan with off~et blades, a mu~hroom mixer and the like may be employed. A "V" mixer has proven particularly effective.
In ~ome i~tances, particularly where the coffee treated has been roasted prior to decaffeination, the proce6s of this invention may remove significant quantities of non-caffeine solid~ from the coffee.
Where thi~ occurs, it may be desirable to recover the~e ~olids and recombine them with the extracted coffee. Additionally, the caffeine removed by the hygroscopic material may also be recovered as a valuable by-product for use in pharmaceuticals and soft drinks. Both the non-caffeine solids and the caffeine may be recovered and ~eparated by known technigues such a~ hydrophobic adsorption re~in~, reverse osmo~is or direct cry~tallization from a ~olvent employed to remove the~e material~ from the hygroscopic material.

~ ~77314 Following the separation of the coffee from the hygroscopic material at the end of the extraction step, it may be necessary to remove traces of the hygroscopic material remaining on the C5 coffee. Water washing has proven an effective means of accomplishing this, particularly where the hygroscopic material is water soluble. Preferably, cold water, i.e., below 50F. is empIoyed for the water washing. Other known separation means such as, elutriation, and the like may also be utilized.
The decaffeinated coffee may then be dried and sent to storage until it is roasted. The particular drying step employed should be such as to minimize the heat effect on the decaffeinated moist coffee, particularly where it is in the form of green beans. Where roasting is to be performed shortly after decaffeination, the drying step may be unnecessary and the moist beans can be sent directly to the roaster.
The practice of this invention can achieve various levels of decaffeination by repeated treatments o the coffee. It is not unusual to expect decaffeination levels of above 75% after a number of treatment~ as described herein.
Optionally, the process of this invention may be used in combination with other decaffeination processes. For example, such well known commercial processes as the organic solvent extraction process, such as that disclosed in Patel et al.'s U.S.
3,671,263 or the water extraction process, such as that disclosed in Berry et al.'s U.S. 2,309,092, could be practiced in combination with the present invention 60 as to utilize the advantages of several decaffeination processes.

J l77314 BEST MODE FOR CARRYING OUT TEIE INVENTION
The following examples illustrate embodiments of this invention:
EXAMPLE I

05 500 grams of green coffee beans were treated in a series of eight passes. In the first pass, the beans were placed in boiling water for five minutes to saturate them to a 55% water content.
The saturated beans were then removed from the boiling water and permitted to equilibrate for 25 minutes at room temperature, 75F. The bèans were placed in a "V" blender together with 5 pounds (2268 grams) of anhydrous sodium chloride and agitated for one hour at 75F. The bean~ and the salt were separated by screening and the beans were washed with a strong spray of 5 gallons (22.7 litres) of cold water ( 70F.). In the second through the eighth pass, the beans were treated in the same fa~hion as in the first pass except that the beans remained in the boiling water for only three minutes.
Following the eighth pass, the beans were placed in boiling water for three minutes and were then agitated bri6kly in 3 gallons (11.4 litres~ of warm water (95F.) for one hour. The beans recovered from the warm water showed a total decaffeination of 83.4%.
The beans were then roasted. Coffee prepared from these roasted decaffeinated beans had no salt flavor, a good overall flavor and a 0.70% solids content.

EXAMPLE II

A~ a control, S00 grams of green coffee beans were treated in the same fashion as in Example I
except that no salt was contacted with the beans.

~ ~77314 Instead of the 25 minutes equilibration and the l hour agitation with salt in the "V" blender, the beans were eguilibrated for 1 hour and 25 minutes.
In other respects the treatment of the beans during 05 the eight passes was the same as in Example I.
These beans showed a total decaffeination of 98% and a solids loss of approximately 70%. Coffee brewed from these beans had a solids content of 0.27%.

EXAMPLE III

An eight pass treatment of an additional 500 grams of green beans was conducted in a fashion similar to Example I with the following modifications:
1st pass - The equilibration af the beans (following the boiling water treatment) was conducted in water at 180-200F for one hour.
Contacting the moist beans with salt was performed in a jacketed "V" blender at 180P~.
2nd to 8th pass - The saturation and eguilibration of the beans wa~ conducted by agitation in the "V" blender with 200 ml of water at 180F.
for 25 minutes. The contacting with salt was the same a~ in the first pas~ of this example.
The treated beans showed a total decaffeination of 79%. Coffee brewed from these beans had no salt ta6te, a good overall flavor and a solids content of 0.88%.

Claims (10)

WE CLAIM:

1. A method of decaffeinating whole or divided coffee beans comprising:
(a) moistening the coffee beans to provide the beans with a water content of about 15 to 55%
(b) contacting the moistened coffee beans with a hygro-scopic salt for a period of time sufficient to remove caffeine-con-taining water from the beans, and (c) separating the coffee beans from the hygro-scopic salt.

2. A method according to claim 1 wherein step (a) is conducted by contacting the coffee with boiling water to effect water saturation of the coffee.

3. A method according to claim 1 wherein the hygro-scopic salt is a hydratable salt.

4 A method according to claim 3 wherein the hydrat-able salt is sodium chloride or copper sulfate.

5. A method according to claim 1 wherein the coffee is green coffee.

6. A method according to claim 1, wherein the coffee is roasted coffee.

7. A method according to claim 1, wherein step (b) is conducted at a temperature of about 35 to about 300 F.

8. A method according to claim 1 wherein step (c) is conducted by screening the coffee and the -scopic salt.

9. A method according to claim 1 including the following additional steps:
(d) decaffeinating the material of step (c) by contact-ing the material with a caffeine solvent, (e) dehydrating the decaffeinated material of step (d), and (f) recycling the dehydrated, decaffeinated material of step (d) to step (b).

10. A method according to claim 1 wherein steps (a), (b) and (e) are repeated with the same coffee beans until a de-caffeination of about 75% is effected.