IE43744B1

IE43744B1 - Process for manufacture of mild coffee

Info

Publication number: IE43744B1
Application number: IE2291/76A
Authority: IE
Original assignee: D E J Int Research
Priority date: 1975-08-27
Filing date: 1976-10-18
Publication date: 1981-05-20
Also published as: IT1067576B; DE2638383A1

Abstract

Caffeine is brought into an aq. soln., extd. with supercritical or liq. CO2 and recovered from CO2 soln. Crude coffee is first treated, at higher temp., with water contg. same concn. of soluble coffee constituents, with exception of caffeine. Caffeine is stripped from aq. exn. soln. by using liq. CO2, at >15 degrees, or super-critical CO2. Residual soln. is re-used s extractant. Caffeine is recovered from extract, pref. with water. Caffeine-free or caffeine-deficient coffee can be prepd. without loss in quality and with simultaneous recovery of caffeine. When using liquid CO2, aq. extn. soln. is pref. treated at 20-31 degrees C and 80-300 (250) bar. With super-critical CO2, temp. is esp. 31-95 (60-95) degrees C under 75-400 (120-300) bar.

Description

The present invention relates to a process for the manufacture of mild coffee.

It is a well-known fact that roasted coffee contains compounds which act as irritants in the gastro-intestinal tract of a not inconsiderable percentage of potential users. Many attempts have been made to submit the green beans to a treatment for removal of the irritating components and/or their precursors, preferably without reducing the caffein content, in order to produce what is known as mild coffee.

The irritating effect has been linked to substances which are for the most part present in the waxy layer surrounding the green coffee beans. Some investigators are of the opinion that these substances are carboxyl-5-hydroxy tryptamides (in abbreviation CgHT's). At any rate these C^HT's are used as indicators for the presence of the waxy layer,which has to be removed in order to reduce the irritating effect of the coffee. For more details see e.g. the litera20 ture mentioned in O.S. Patent Specification No.3,770,456, in which also the older - unsatisfactory - methods are mentioned for the manufacture of mild coffee.

An entirely satisfactory process for the removal of the coffee wax or at least the irritating substances 3 7 4 4 - 3 contained therein has to meet many requirements, among which are the following: 1. The processing should not leave, in the green beans, substances which after roasting of the coffee give rise to a. organoleptic deviations of the brew made from that roasted coffee; b. deviations in appearance of the roasted beans; c. health hazards. 2. Preferably the process should leave the caffein content substantially unaltered. 3. The loss in solid content should be negligible. '4. The processing should be economical requiring a. little time and b. simple equipment.

In the German Patent Application No.1,960,694 a method is described whereby the CgHT's are removed for a large part by treating preheated green beans with preheated chlorinated hydrocarbons for 25-40 minutes. According to German Patent Application No.2,031,830, the green beans are treated with methylene dichloride under pressure at a temperature of 5O-8O°C.

A fundamental drawback common to both processes is that chlorinated hydrocarbons are not naturally occurring in coffee and that it is difficult to remove these potentially hazardous -substances so thoroughly that only traces remain. This also presupposes a strict control of the process. Even so, the regular ingestion of 3 7 4 4 - 4 chlorinated hydrocarbons, or substances Lo which they may give rise in the roasting process, even in very small amounts, is not recommendable, and if the aim is - as it should be - to completely avoid potential health hazards in foods and beverages wherever possible, their presence in coffee is particularly unacceptable.

According to the present invention, there is provided a technically and hygienically advantageous process for removing , from green coffee beans, components which after the roasting of the beans contribute to the presence of gastro-intestinally irritating compounds, which process comprises washing the beans at elevated temperatures (as hereinafter defined), and at substantially atmospheric pressure with a solvent being an ester or a ketone naturally occurring in freshly roasted coffee in amounts higher than 10 ppm and having a boiling range between 50°C and 100°C, mechanically separating the beans from said solvent and, by application of heat and/or vacuum and/or steam, lowering the concentration of said solvent in the green beans to such a level that, after roasting, the beans will have a content of the solvent which lies substantially within the normal range for freshly roasted coffee.

The washing of the beans is desirably effected at elevated temperatures, i.e. at temperatures above ambient temperature but not more than the boiling point of the solvent, preferably at temperatures at or near the boiling point of the solvent.

That the process is hygienically advantageous over the processes cited above follows from the fact that it lacks the drawbacks already discussed. 3 7/44 - 5 The process according to the present invention is moreover technologically advantageous over these in that shorter treatment times can be achieved for washing the beans and also shorter treatment times for the removal of the excess solvent. While according to the processes of the prior art cited above the content of solvent has to be brought back to traces of chlorinated hydrocarbons, using the process according to the present invention the content of solvent remaining in the green beans may be higher without running into health hazards.

An additional advantage of the method according to the present invention is that the loss of solids is negligible (about 0.3% by weight).

Other processes for the manufacture of mild coffee are mentioned in Belgian Patent No.795,949 and Netherlands Patent Application No.74,07658. These involve oxidation processes in which the green beans are heated under pressure and at temperatures above 100°C with water vapour and air, oxygen or ozone. It is however difficult with these methods to obtain an organoleptically satisfactory product. Advantageously,in the process according to the present invention, the time and temperature of the washing process are chosen so that there is substantially no loss of caffein.

In order to keep the washing time as short as possible, the washing is preferably accomplished at a temperature near or at the boiling point of the solvent and preferably, the washing time remains below 12 minutes.

Very good results have been obtained with methyl ethyl ketone as a solvent and satisfactory results with methyl acetate.

After having been washed, the beans are mechanically separated from the solvent e.g. by a filtering process and preferably treated with steam to remove excess solvent. Conveniently the content of methyl ethyl ketone may be lowered to below 24 ppm, preferably to about 18 ppm, and the content of methyl acetate may be lowered to-below 16 ppm, preferably to about 6 ppm.

The present invention lends itself very well to a continuous process in which the washing is performed by moving the beans and the solvent countercurrently.

Conveniently, the volume of solvent used when the process according to the present invention is performed batchwise may be from 0.4 to 1.5 times the bulk volume of the coffee, or 0.5 to 2 by weight.

The present invention also encompasses green coffee beans treated according to the present invention and roasted coffee manufactured from these beans.

The present invention will now be further illustrated by way of the following examples: Example 1 250 g green beans of blended coffee were extracted for 10 minutes with 500 ml of methyl ethyl ketone at 70°C. The CgHT content was reduced from about 800 ppm to 174 ppm. The loss of caffein was negligible and the loss of solids 0.21% by weight.

After mechanically separating the beans from the solvent the beans were heated with steam at atmospheric pressure and subsequently dried in a fluid bed dryer at 90°c. 3 7 4 4 - 7 With a steam treatment of 0.5 hour the content of methyl ethyl ketone in the beans was reduced to 18 ppm, and with a steam treatment of 1 hour to 6 ppm.

It was found that, after roasting the green 5 coffee obtained in this way, only a few percent (less than 5%) of its original content of C^HT was decomposed (by pyrolysis). There would appear to be indications that the irritating effect of conventional roasted coffee may be caused, not primarily by Cj-HT itself, but by substances formed during the roiisting process by pyrolysis of CgHT. If this is indeed the case, it is desirable that the coffee treated in accordance with the present invention, after the roasting process, contains a low percentage of pyrolysis product of CgHT.

Appearance and cup quality of this roasted product were not impaired, when tested by experts, when compared with roasted coffee of the same blend without the pretreatment according to the invention.

Example 2 The process parameters were the same as in Example 1, except that methyl acetate was used, at a temperature of 50°C instead of methyl ethyl ketone.

In this case a steam treatment of 0.5 hour left 3.6 ppm of the solvent in the beans and a steam treat25 ment of 1 hour left 0.5 ppm.

The CgHT content was reduced from about 800 ppm to 259 ppm. The loss of caffein was negligible and the loss of solid was 0.18% by weight. 437 4 4 - 8 Example 3 g of green. Santos beans were extracted for 10 minutes with 150 ml of methyl ethyl ketone at. 75°C The Cj-ΪΙΤ content was reduced from 1048 ppm to 186 ppm on dry solids basis. The loss of caffein was 0.01% by weight and the loss of solids 0.4% by weight, calculated on dry solids basis.

Thereafter the beans were further processed as described in Example 1.

Claims

1. CLAIMS:1. A process for removing , from green coffee beans, components which after roasting of the coffee contribute to the presence of gastro-intestinally irritating 5 compounds, which comprises washing the beans at elevated temperatures (hereinbefore defined), and at substantially atmospheric pressure with a solvent consisting of an ester or a ketone naturally occurring in freshly roasted coffee in amounts higher than 10 ppm and having a boiling range 10 between 50°C and 100°C, mechanically separating the beans from said solvent and, by application of heat and/or vacuum and/or steam, lowering the concentration of said solvent in the green beans to such a level that, after roasting, said beans will have a content of the solvent which 15 lies substantially within the normal range for freshly roasted coffee.

2. A process as claimed in Claim 1 wherein the washing is accomplished at a temperature near or at the boiling point of the solvent. 20

3. A process as claimed in Claim 1 or Claim 2 wherein the solvent is methyl ethyl ketone.

4. A process as claimed in Claim 3 wherein the green beans, after having been washed, are treated with steam in such a way that the content of mpthyl ethyl ketone is 25 lowered to below 24 ppm.

5. A process as claimed in Claim 1 or Claim 2 wherein the solvent is methyl acetate.

6. A process as claimed in Claim 5 wherein the green beans, after having been washed, are treated with steam in - 10 such a way that the content of methyl acetate is lowered to below 15 ppm.

7. A process as claimed in any one of the preceding Claims wherein the beans are washed with a volume of the solvent which is from 0.4 to 1.5 times the bulk volume of the coffee beans.

8. A process as claimed in any one of the preceding Claims, wherein the washing time is less than 12 minutes.

9. A process as claimed in any one of the preceding Claims which is continuous and wherein the beans and. the solvent are moved counter-currently.

10. A process as claimed in any one of the preceding Claims wherein the time and temperature of the washing process are chosen so that there is no substantial loss of caffein.

11. A process as claimed in Claim 1 for removing, from green coffee beans, components which after roasting of the coffee contribute to the presence of gastrointestinally irritating compounds substantially as hereinbefore described and with reference to any one of the examples.

12. Green coffee beans whenever treated by a process as claimed in any one of the preceding Claims.

13. Roasted coffee manufactured from green coffee beans as claimed in Claim 12.