JPS61187748A - Decaffeination of coffee extract - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a process for decaffeinating caffeinated liquids and in particular aqueous coffee extracts. In particular, the caffeic acid of the invention is mixed with a caffeinated coffee extract to form an insoluble colloidal caffeic acid/caffeine complex. Growing crystals of the caffeic acid/caffeine complex followed by min. m-r;b from decaffeinated coffee.

Conventional technology There are many decaffeinating techniques available in this field.

One widely used method is called the water decaffeination technique and is described by Berry et al. in U.S. Pat.
No. 9,092. In the water decaffeination process, hydrated green coffee beans are extracted with caffeine-depleted green coffee extract in a multi-stage countercurrent extraction device. As the green coffee extract progresses through the device, it becomes progressively richer in caffeine, while becoming progressively less in contact with the decaffeinated coffee beans. The caffeinated coffee extract withdrawn from the last stage of the device is processed to remove caffeine and then returned to the system. Caffeine is removed from green coffee extract by contacting it with an organic solvent (typically a halogenated organic solvent such as methylene chloride). Although water decaffeination techniques are widely used, it is becoming increasingly desirable to avoid the use of organic solvents in food processing.

Furthermore, the water decaffeination technique is for green coffee beans and is not suitable for decaffeinating roasted coffee extract.

Alternative decaffeination techniques exist but have drawbacks.

For example, the use of activated carbon adsorbents supported on sugar is 198
European Patent No. 0.00 granted on May 19, 2017
No. 8,398. Although this method avoids the use of organic solvents, the activated carbon tends to adsorb decaffeinated coffee dissolved matter as well as caffeine, which significantly inhibits the economics of this method. Furthermore, the flavor of the finished coffee will not be exactly the same as that obtained by de-decaffeination.

The complexation method, only for the decaffeination of aqueous black tea extracts, is described by Husiani et al. in US Pat. No. 4,315,036.

The aqueous black tea extract is cooled to precipitate the cold water-insoluble complexes of caffeine and tannins already present in the black tea. This method has the advantage of using complex-forming compounds that are already present in the black tea and do not need to be added separately. The tannin/caffeine complex will become insoluble and therefore precipitate, but such tannins are not present in the aqueous coffee extract.

Many compounds (some of which are naturally present in coffee) are known to form complexes with caffeine. The properties of ':
I7 Hol-'/E7'', T, F'ood Sci, 3
7 (1972) 925-27 (1 containing a water-soluble chlorogenic acid/caffeine complex being studied).
0 such caffeine complexes are recognized.

Problem the invention seeks to solve: If the complex-forming compound forms a water-insoluble caffeine complex, it would be beneficial in the decaffeination process. No such compound has been identified so far. Furthermore, such naturally present complex-forming compounds must compete with the chlorogenic acid and/or must be relatively robust to break up the chlorogenic acid/caffeine complex.

Means for Solving the Problem - A method of decaffeinating caffeine-containing liquids, especially aqueous coffee extracts, using the complex-forming compound caffeic acid - the caffeine naturally present in coffee, especially roasted coffee, has now been discovered. Ta. Caffeic acid is mixed with a caffeine-containing extract to form an insoluble, colloidal caffeic acid/caffeine complex. Crystals of the caffeic acid/caffeine complex are grown and subsequently separated from the decaffeinated coffee extract.

Caffeic acid is a yellow crystalline substance that begins to soften at about 195C. It is only slightly soluble in water below about 25C, but freely soluble in water above about 80C, and freely soluble in alcohol over a wide range of temperatures. However, it has been unexpectedly discovered that caffeic acid/caffeine complexes are insoluble in aqueous solutions over a wide range of temperatures. Although caffeic acid is reported to be as high as 0.5% by weight in roasted and ground coffee, in reality it is only present in trace amounts in green coffee, and in roasted coffee it is relatively high but still in small amounts. It has now been found that only about a few hundred parts per million exist in roasted coffee beans or in typical soluble coffee grounds. The large amount of acid in roasted coffee is caffeic acid, which is one of the decomposition products of roasting, and lorogenic acid is abundant. Although the caffeic acid used in the present invention may be chemically synthesized, it is best to use compounds from roasted coffee or chlorogenic acid, since decaffeination can be carried out using compounds that naturally exist in coffee. It was obtained by acid hydrolysis.

Caffeic acid is an insoluble compound, despite the presence of large amounts of chlorogenic acid in coffee extracts, and despite the fact that the caffeic acid/caffeine complex has a smaller association constant than the chlorogenic acid/caffeine complex. It is particularly suitable because it forms a complex. In the previously cited paper, Horman et al. report that the association constant of the chlorogenic acid/caffeine complex is 16.9 and the association constant of the caffeic acid/caffeine complex is 12.2. Since the association constant is a measure of the relative strength of the complexes, the added caffeic acid is clearly able to break up the chlorogenic acid/caffeine complexes already present in the coffee extract, subsequently making them insoluble. Forming a Colloidal Caffeic Acid/Caffeine Complex is a very surprising book.

Such a result was not expected based on the reported association constants.

Caffeic acid is mixed with a caffeine-containing liquid (most typically an aqueous coffee extract) to form an insoluble, corobiform caffeic acid/caffeine complex. As noted earlier in this specification, acids are solids at typical room temperatures and are poorly soluble in water at the same temperatures. Solid caffeic acid may be mixed with the coffee extract and subsequently dissolved therein. Alternatively, it is also possible to first prepare an aqueous solution of caffeic acid (preferably at a temperature above 80'') and then mix the caffeic acid solution with an aqueous coffee extract. If the latter embodiment is followed, the coffee extract is somewhat diluted. However, the increased evaporation required to restore the original concentration is offset by the ease of mixing the caffeic acid and aqueous coffee extract.

The temperature at which the caffeic acid is mixed with the aqueous coffee extract is not a critical factor, but the lower temperature is bound by the solubility of the caffeic acid and the higher temperature is bound by the sensitivity of the coffee extract. It is well known that the flavor and other aspects of green coffee or roasted coffee extract tend to degrade above about 95C. Therefore, it is preferable to maintain the temperature below about 95C when mixing the caffeic acid and aqueous coffee extract. At the other end of the range, it is inconvenient to operate at temperatures below about 25C, since caffeic acid is poorly soluble in water or coffee extract at temperatures below about 25C. The solubility of caffeic acid increases significantly at about 50'C.

When first preparing an aqueous solution of caffeic acid, approximately 50C
It is best to dissolve the caffeic acid at a temperature between and 95 tZ' and mix the solution with the aqueous coffee extract within or below the same temperature range.

If the caffeic acid is dissolved directly in the coffee extract, it is best to maintain the extract between 50C and 950C.

The more important parameter is the molar ratio of caffeic acid to caffeine. Ideally, the caffeic acid should be mixed with the aqueous coffee extract in a 1:1 molar ratio of caffeic acid to caffeine so that all added caffeic acid forms a complex with the caffeine and is eventually separated as crystals. It is best to mix. This method, if successful, will remove essentially all the caffeine and leave no excess caffeic acid in the decaffeinated coffee extract. In practice, it is difficult to remove essentially all caffeine from coffee extracts, with 70% to 98% caffeine by weight most typically removed.

Furthermore, having a molar ratio as low as 1:1 is not advantageous as the kinetics of complex formation and subsequent crystal growth do not favor such a ratio. Although a molar ratio of at least 1:1 is desired, a molar ratio of caffeic acid to caffeine of about 1.5=1 has been observed to be particularly good. There is no upper limit to the molar ratio, but no particular benefit was observed for ratios above about 3=1. Since the solubility of caffeic acid is high at high pH, a ratio of caffeic acid and caffeine close to 3:1 was used for the high pH extract. Essentially all remaining caffeic acid uncomplexed with caffeine is later separated by lowering the temperature of the extract to about 10C to render it insoluble.

Once caffeic acid has been mixed into the caffeine-containing extract to form an insoluble, colloidal caffeic acid/caffeine complex, it is necessary to grow crystals of the insoluble caffeic acid/caffeine complex.

An insoluble, colloidal complex is formed almost immediately upon mixing caffeic acid and coffee extract, but it is extremely difficult to separate the colloidal complex from the coffee extract. Unexpectedly, colloidal complexes were observed to grow from the decaffeinated coffee extract into crystalline bodies that were more easily separated. Crystals will grow on their own if left alone, but this process is slow;
It takes two weeks to achieve 65% decaffeination of a roasted coffee extract aqueous solution. Crystal growth can be aided somewhat by maintaining the temperature of the coffee extract between about OC and 50C. Therefore, if the temperature of the extract increases significantly above 50C due to the mixing of caffeic acid and aqueous coffee extract, then the extract containing the insoluble, colloidal 9-form caffeic acid/caffeine complex will be used to assist the growth of crystals. It should be cooled properly. Crystal growth can also be made more rapid by the known technique of seeding the already formed caffeic acid/caffeine complex crystals. The proper amount of seeding depends on the particular coffee extract used and may vary depending on the individual involved. will be readily apparent after one or two trials.

It was also observed that lowering the pH of caffeine-containing extracts promoted the growth of insoluble caffeic acid/caffeine complex crystals. The pH of coffee extract is typically between 4.7 and 5.2. Faster crystal growth was observed when adding sufficient acid to lower the pH of the extract to about 4.5 or below. However, below pH 3.5, irreversible decomposition of the coffee extract is likely to occur (which is the least desirable thing).Suitable acids include hydrochloric acid, sulfuric acid, phosphoric acid, as well as weak organic acids including formic acid and acetic acid. Examples include strong mineral acids such as nitric acid. Pressurized injection of carbon dioxide into the coffee extract also helps lower the pH.
Promote crystal growth. The pH may be adjusted both before or after mixing the coffee extract and Caffe-O. Coffee extract can be returned to its original pH after decaffeination.

Mineral acids are conveniently precipitated as salts, and the more volatile organic acids can be easily removed from the decaffeinated coffee extract by evaporation.

A variety of equipment can be used for both the growth of insoluble caffeic acid/caffeine complex crystals as well as the mixing of caffeic acid and caffeine-containing coffee extracts. The simplest treatment equipment is an agitation-type patch tank that has a means of regulating the temperature of the contents, such as by attaching a jacket to the tank. Caffeinated coffee extract is first placed in a tank and adjusted to the desired temperature. Caffeic acid is then added as a solid or solution while the tank contents are gently agitated. The contents are gently stirred and allowed to stand for a period of time determined by the degree of decaffeination desired and the particular aqueous coffee extract solution.

The tank is then drained and the coffee extract containing the insoluble caffeic acid/caffeine complex crystals is passed through a suitable separation device. Alternatively, the method of the invention can be carried out multiple times in series by allowing decaffeination to occur in connected columns. Caffeine-containing coffee extract and caffeic acid are introduced at the bottom of the column, which is maintained at a higher temperature than the rest of the column by appropriate use of a separate column jacket.

Insoluble caffeic acid/caffeine complex crystals grow as the extract is pumped to the top of the column, where it is removed for separation of the complex crystals.

Insoluble caffeic acid from decaffeinated coffee extract/
Separation of the caffeine complex crystals may be by any solid/liquid separation technique known in the art. Filtration of crystals is one example. Most preferably, the insoluble caffeic acid/caffeine complex crystals are separated from the coffee extract by centrifugation. Such centrifugation is relatively simple, effective and particularly inexpensive. Additionally, centrifugation provides a relatively "clean" separation, so that the decaffeinated coffee extract is essentially free of complex crystals and the separated crystals contain only a negligible amount of transferred coffee extract. Eliminating the loss of economically valuable coffee extract. Even so, it may be desirable to wash the separated complex crystals with cold water to recover the dislodged decaffeinated coffee lysate.

The insoluble caffeic acid/caffeine complex crystals may simply be discarded after separation, but both caffeic acid and caffeine are expensive and are worth recovering. The complex crystals are recovered by dissolving them in a solvent that can both dissolve and decompose the complex. Suitable solvents include acetate/alcohol along with low boiling alcohols such as methanol, ethanol or pronominol.
or other solvents such as ethyl acetate. The separated caffeic acid/caffeine complex crystals are dissolved in a solvent to decompose the complex and allow separate recovery of caffeic acid and caffeine. Separate recovery may be accomplished by adsorbing one component onto an adsorbent specific for one component or by extracting with a solvent specific for one component.

The method of the invention is applicable to caffeine-containing liquids, most particularly aqueous coffee extracts of roasted and green coffee. Green coffee extracts contemplated for use herein are obtained from the water film caffeine process previously described and typically contain between 20 and 30 inches by weight of coffee soluble components and 0.5 inches by weight. Contains 1 to 1 g of caffeine.

The present invention overcomes the shortcomings of that technology by replacing the solvent for caffeine removal in the water film caffeine process. The method is also useful for decaffeinating roasted coffee extracts typically used in the production of soluble coffee. Such roasted coffee extracts most often contain 10% to 30% by weight coffee soluble components and 0.5% to 5% caffeine by weight. The key advantages of the present invention regarding roasted coffee extracts are:
without causing any damage or loss to the desired roasted coffee flavor and aroma. Although it is typically desired to remove more than 97% of the caffeine initially present from the green coffee or roasted coffee extract, depending on the degree of decaffeination desired, the method of the present invention may be
It may be necessary to repeat it more than once.

The following examples illustrate specific examples of the invention. However, the examples do not limit the invention.

Example 1 30.09- of water, 1.65 f! - Chlorogenic acid and 0.9y- of caffeine were mixed to prepare an equimolar aqueous solution of chlorogenic acid and caffeine. The solution was heated to near boiling. An equimolar amount of 0.8554 caffeic acid was weighed out and dissolved in the hot solution.

The solution was allowed to cool to room temperature. Crystal growth was observed after about 1 hour. After 12-14 hours, the crystals were removed from the solution using coarse F paper. The analysis below shows that about 93% of caffeine was removed, while very little chlorogenic acid was removed.

Analysis of caffeine in this example and the following examples was performed by high performance liquid chromatography (HPLC), and removal of caffeine was measured by the change in the area of the peak identified as caffeine.

Separation column (5μ spherical C18; 3.9 mxX15c
1 rL) is approximately 280 nm of caffeine and caffeic acid.
It was used at a wavelength of Mobile phase is 010033MKH2PO
4, methanol, and acetic acid in a ratio of 80:20:4, respectively. The analysis was carried out at room temperature and in the same manner as 1.5 m11
5 μm was injected at a flow rate of 1 min. Solutions were diluted with mobile phase prior to analysis to a total solids content of 0.1 inch by weight.

Example 2 An aqueous solution was prepared by dissolving 0.9 fF of caffeic acid in 90.0y4) of water that was about to boil. Next, 10.5 grams, which contains 9.5 inches of caffeine by weight. Office lady? of atmospherically dried coffee extract was dissolved in the solution. A control sample was prepared by dissolving 10.01 P coffee in 90.0 P water.

Both coffee solutions were left to cool. Crystals were observed in the caffeic acid containing solution after 12-14 hours. No crystals were observed in the control sample. After one week, further crystal growth is observed in the solution containing caffeic acid, the supernatant liquid is decanted from the crystals, and the solution is left to stand for another week. When a portion of the solution was analyzed, it was found to contain approximately 30 grams less caffeine than the original. No crystals were observed in the control sample. After 2 weeks, crystal growth was again observed in the solution containing caffeic acid. The supernatant was decanted to separate the crystals. When a portion of the solution was analyzed, it was found that the caffeine content was reduced by approximately 65% compared to the original. Analysis of the crystals revealed essentially pure 1:1 molar ratio caffeic acid/caffeine complex. No crystals were observed in the control sample, and analysis found that all of the caffeine originally present remained.

A 10% by weight coffee solution was prepared from an atmospherically dried coffee extract containing 8.7% by weight of caffeine.

The solution was divided into four parts and heated to 70C. Caffeic acid was used in three samples with a molar ratio of caffeic acid to caffeine of 1.1:1.
It was added so that The four samples were then cooled to 40C. adding acetic acid to the two caffeic acid-containing samples;
The pH of the first sample is 4.5 and the pH of the second sample is 4.5.
．． I lowered it to 2. Four samples were stirred at 40C and sampled periodically. The results are shown in the table below.

After 5 days, the crystals were removed from sample 2-4 using ultracentrifugation at 350,000 P x 30 minutes. Analysis of the crystals revealed essentially pure 1:1 molar ratio caffeic acid/caffeine complex. No crystals were observed in the control sample (sample 1).

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Claims (1)

[Claims] 1) (α) mixing caffeic acid and a caffeic acid-containing liquid to form an insoluble colloidal caffeic acid/caffeic complex; (b) crystals of the insoluble caffeic acid/caffeic complex that can be separated from the liquid; (c) separating insoluble caffeic acid/caffeine complex crystals from the decaffeinated liquid; 2) The method according to claim 1, wherein the caffeine-containing liquid is a green coffee extract. 3) The method according to claim 1, wherein the caffeine-containing liquid is a roasted coffee extract. 4) At least 1:1 caffeic acid with caffein-containing liquid
The method according to claim 1, wherein the caffeic acid:caffein molar ratio is mixed. 5) A method according to claim 1, wherein the caffeic acid is mixed as a solid into the caffein-containing liquid and subsequently dissolved in the liquid. 6) The method according to claim 1, wherein caffeic acid is mixed into the caffein-containing liquid as an aqueous solution. 7) A method according to claim 6, wherein the caffeic acid solution is mixed with the caffein-containing liquid at a temperature of 50°C to 95°C. 8) Addition of a mixture of caffeic acid and liquid to further promote the growth of insoluble caffeic acid/caffeic acid complex crystals.
8. The method according to claim 7, wherein the method is cooled from .degree. C. to 50.degree. 9) The method according to claim 2 or 3, wherein an acid is added to the coffee extract to lower the pH to 4.5 or less. 10) The method according to claim 1, wherein the insoluble caffeic acid/caffein complex crystals are separated from the liquid by centrifugation. 11) The method according to claim 1, wherein after separating the caffeic acid/caffein complex crystals from the liquid, the caffeic acid/caffeic complex is broken, and then the caffeic acid and caffein are separately recovered. 12) The method according to claim 11, wherein the solvent used to dissolve the caffeic acid/caffein complex crystals is selected from the group consisting of methanol, ethanol, propanol, ethyl acetate and acetone.