JPS6322145A - Decaffeination of raw coffee - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for decaffeinating green coffee by extracting the coffee with water and treating the aqueous extract with activated carbon.

In addition to the conventional method of decaffeinating green coffee using commercially available chlorinated hydrocarbons, a method of decaffeinating green coffee using activated carbon is attracting attention.

In such a method, a green coffee extract is first prepared which, in addition to caffeine, contains dry substances that are readily soluble in water. The extract thus prepared is then treated with activated carbon, which in any case involves adsorption of the caffeine or a large part of it onto the carbon.

According to European Patent Application No. 111 375, this process is carried out using activated carbon having an intrinsic adsorption capacity for caffeine of at least 100 g of caffeine per kg of carbon and an intrinsic selectivity of at least 0.2, shows a direct proportional relationship between the concentration of the bean extract on the one hand and the loading ratio of caffeine/non-caffeinated extractant on the adsorbent on the other hand when it is in equilibrium with the extract.

According to European Patent Application No. 8398, before the caffeine is recovered from the extract, activated charcoal is preloaded with sugar, if necessary in combination with treatment with acid. Use of such a method prevents too much non-caffeinated dry matter from being removed from the extract. A disadvantage of this method is that reuse of activated carbon requires thermal regeneration and reactivation.

European Patent Application No. 40712 relates to the decaffeination of green coffee beans by the method described in the opening section using "substantially neutral activated carbon". This application further defines it as an activated carbon that reacts substantially neutrally when dispersed in water. One of the drawbacks of this method is that the concomitant decomposition of the chlorogenic acid components in the extract can result in a noticeable bias in taste.

Various methods are known for the recovery of caffeine from bulk activated carbon, essentially resulting in a specific choice of solvent. European Patent Application No. 42295 is particularly concerned with the use of acetic acid or a mixture with other components to recover caffeine from activated carbon.

As explained in European Patent Application No. 76620, the disadvantage of this method is that acetic acid has a very low flash point;
This means that it cannot be applied commercially, or it is almost impossible to apply it commercially. The European patent application therefore relates to a method to reduce this problem, which is achieved by discarding some of the positive effects of acetic acid by diluting it with at least 30% water. As a result, the flash point is significantly lowered, but this is a loss in extraction efficiency. however,
Furthermore, according to these methods, the activated carbon must be thermally regenerated or reactivated after recovering the caffeine.

European Patent Application No. 129609 relates to the use of formic acid and/or formic acid-containing solutions for caffeine recovery.

Although this method has fairly moderate efficiency, it is still necessary to thermally regenerate the activated carbon in due course.

The object of the present invention is to provide a method for decaffeinating green coffee using carbon, which does not have the disadvantages mentioned above.

The method of the invention comprises: a) treating the extract with activated carbon from step C to fully absorb the caffeine into the activated carbon; and b) treating the caffeine-loaded activated carbon with an acid liquid to remove the caffeine from the activated carbon. C) Add activated carbon to water until pH of activated carbon reaches 3-6 (ASTM 03838)
-80) washing, and d) returning the washed carbon to step a.

Surprisingly, it has been found that the combination of specific steps according to the invention results in an effective decaffeination process and furthermore has several advantages over the prior art.

One of its advantages is that intermediate thermal regeneration of the carbon can be omitted or that this regeneration is only occasionally needed.

A second advantage is that the claimed method does not pose problems with the formation of substances that would bias the taste of processed coffee after roasting, which is likely due to the reduced decomposition of chlorogenic acids. It probably depends on the facts.

The extraction used according to the invention consists of: green coffee with water;
Alternatively, it can be carried out in a conventional manner by treating with an aqueous solution at a temperature of 50 to 100°C.

The carbon used in the method according to the invention may be commercially available carbon. The carbon should be selected according to its properties having a pH of 3 to 6, preferably 3 to 5.5, as determined by ASTM standard D3B38-80 after acid regeneration and washing with water.

As a first choice, activated carbon can be selected that essentially meets the pH requirements. This in itself is still not sufficient, since in step C it must also be ascertained whether the pH requirements imposed by the invention can be met.

It is well known that activated carbon contains oxygen-containing groups and has acidic or basic properties depending on its nature and structure. For use in the present invention, it is important that the activated carbon's basic groups are optimally shielded.

In this regard, the activated carbon described in European patent application no. It is recognized that it must have both functional groups.

Such carbons are not suitable for the present invention since they have additional disadvantages in catalyzing the formation of by-products.

It is clear from the examples of this European patent application that the use of carbon as described here increases the pH of the extract and that the basic groups are not, or are only partially, shielded. means.

From a taste standpoint, this is a huge disadvantage.

However, the method according to the invention does not or hardly changes the pH of the extract. This is a clear advantage.

The activated carbon used according to the invention preferably has a large internal surface area, preferably an internal surface area (BET) of 2
/g is 800m or more.

Carbon having such an internal surface area allows the amount of adsorbed caffeine to be in a suitable ratio with respect to the amount of other adsorbed dry substances.

For example, European Patent Application No. 8398, European Patent Application No. 40712,
As can be the case with the conventional methods described in JP 111375 or JP 140629, the caffeine-bulking carbon is treated with an acid liquid after bulking with caffeine. This treatment is carried out at atmospheric pressure and at a temperature of at least 100°C, especially at 1°C.
It is preferable to work at temperatures above 10° C. and select acid liquids whose evaporation at these temperatures is rather limited. In practice, this means that the process is in principle carried out under atmospheric pressure and at most at the boiling point of the acid liquid.

The acid liquid may be just the acid itself or a mixture of two or more acids.
Alternatively, it may consist of a combination of an acid or a mixture of acids and one or more other substances.

Specific examples of acid liquids used are glacial acetic acid, acetic acid diluted with water, lactic acid, glycolic acid, citric acid.

Phosphoric acid, benzoic acid, or a combination of two or more of these acids, optionally with water.

However, suitably an acid liquid is used which contains from 50 to 85% by weight acetic acid, preferably at least 65% by weight, while the remaining liquid is water, citric acid.

It can consist of phosphoric acid, lactic acid, benzoic acid, etc.

After treatment with acid liquid, the activated charcoal is completely or almost completely freed from caffeine. The caffeine is then contained in the acid liquid, from which it can be recovered by well-known techniques.

The carbon released from the caffeine is then washed with water until the carbon meets the requirements imposed on its pH. This carbon is then used again to adsorb caffeine from the aqueous coffee extract. Of course, it is also possible to wash the carbon with a dilute aqueous solution of acid, for example the acid used in the process.

Activated carbon is preferably used without preloading. However, it is possible to treat the carbon with a carbohydrate solution before use in the decaffeination process. Preferably, no pretreatment using ethylcellulose as described in European Patent Application No. 140,629 is carried out.

After adjusting the conditions of equilibrium, the method described above results in adsorption of caffeine on carbon corresponding to 80-95% of the initial adsorption capacity.

This method reduces the residual caffeine content of coffee to 0.
1% by weight or less. If this number increases,
It can be returned to the initial level by readjusting the coffee/carbon ratio.

Next, the present invention will be explained by examples. This does not limit the invention.

Green coffee with a caffeine content of 1.2% by weight was heated to 70°C.
Extracted with water for 6 hours. The extraction was carried out by passing the liquid alternately over the coffee to be extracted and over a carbon column. The extract is thus treated with activated charcoal and then substantially freed from caffeine p)14.
8 extracts were obtained.

After the experiment was completed, the wet green coffee was dried and combined with the extract. The caffeine content of the finally obtained green coffee was 0.1% by weight (based on the green coffee). The activated carbon came from the previous cycle and was then regenerated in the manner described below.

Caffeine enriched activated carbon (23.4 g caffeine/kg activated carbon) was desorbed with acetic acid (100%) at 112°C. At that point, caffeine was almost completely absorbed. In this way, the carbon released from caffeine is transferred to a pH of 5.
．． 2 and then washed again with water and reused for the next cycle.

The method described above relates to stable situations in which such cycles have already been carried out ten or more times.

Claims (1)

[Claims] 1 a) Treat the extract with activated carbon from step C to fully absorb the caffeine into the activated carbon; b) Treat the caffeine-loaded activated carbon with an acid liquid to transfer the caffeine to the activated carbon. c) Add activated carbon to water until the pH of the activated carbon reaches 3 to 6 (A
d) decaffeinating the green coffee by extracting the coffee with water and treating the aqueous extract with activated carbon; Method. 2. The method according to claim 1, wherein the activated carbon is washed until the pH of the activated carbon becomes 3 to 5.5. 3. The method according to claim 1 or 2, wherein the caffeine-enhanced activated carbon is treated with an acid, a mixture of acids, or a mixture of one or more acids and other substances. 4. The method according to claim 3, wherein one or more acids selected from acetic acid, citric acid, lactic acid, glycolic acid, phosphoric acid, and benzoic acid are used. 5. A method according to any one of claims 1 to 4, characterized in that the activated carbon is treated with an acid solution that is liquid at atmospheric pressure at a treatment temperature of at least 100°C, preferably 110°C. 6 Carbon has a surface area of at least 800 m^2/g (BET
) The method according to any one of claims 2 to 5.