GB2235121A

GB2235121A - Process for decaffeinating green coffee

Info

Publication number: GB2235121A
Application number: GB9002861A
Authority: GB
Inventors: Helmut Seidlitz; Eduard Lack
Original assignee: Schoeller Bleckmann GmbH; Schoeller Bleckman Stahlwerke AG
Current assignee: Schoeller Bleckmann GmbH; Schoeller Bleckman Stahlwerke AG
Priority date: 1989-02-09
Filing date: 1990-02-08
Publication date: 1991-02-27
Anticipated expiration: 2010-02-08
Also published as: GB2235121B; DE4003483A1; GB9002861D0

Abstract

A process for decaffeinating green coffee comprises extraction with fluid, supercritical CO2, which is supersaturated with 0.5-5% by weight of H2O. The coffee is optionally subsequently further treated in a second extraction step with water, preferably with water enriched with natural coffee flavor.

Description

1 4 1 The invention relates to a process for decaf."einating green coffee,

in which an extraction is performed wlth noist supercritical Con.

It has become known from AT-PS 290 962 that caffeine can be extracted.0-. on green coffee by moist M:, in supercritical state. Setting of- a defined water content of the coff ee beans is essential for perfor=ing such an extraction with supercritical C02. For this purpose, it is known to cook the coi'..oiee beans with live steam at increased temperature, and the beans greatly swell. 1 Also in moistening the coffee beans with hot water, a great swelling occurs and for the subsequent extraction with supercritical CC,, herep too, care must be taken to maintain a certain water content. It follows from this that the dampening or step rust be controlled relatively accurately. In the use of moist CC" in supercritical state, as proposed by AT-PS 290 962P the p-.cpert4-es of the supercritical C02 change so that moist supercritical Con no longer exhibits the properties of a ncnpolar fluid but the properties of an increasingly polar gas.

Use of moist C02 therefore is supposed to improve the absorbing capacity for the likewise polar caffeine. The moisture of the COn used results in this previously known process by recycling of the C02, since in extraction, the C02 absorbs moisturi5 from the previously dampened batch. From DE-PS 27 32 103 a series of drawbacks of this procesg can be seen and therefore a stationary treatment was proposed to eliminate the described problems by the coffee being passed through in a pressure vessel.

p The object of the invention is to provide a process of the initially mentioned type, in which, before the extraction phase with moist supercritical C02, the moisture adjustment can take place without any difficulty and with significant controls and optionally can be completely omitted. The invention has the further object to improve the extraction by a bed being passed through in a pressure vessel and especially to guarantee that the entire height of the bed in the vessel is homogeneously decaffeinated to the greatest extent possible.

According to the present invention there is provided a process for decaffeinating green coffee wherein the caffeine is extracted with fluid, supercritical C02 which is supersaturated with 0.5-5% by weight of H20Optionally the coffee is further treated with water, preferably with water enriched with natural coffee flavor. Since at the beg.,'==-,r-g oú the process a certain supersazuration of the superc-ritical C02 with water in the range of 0.3-5% by weight Is set, it has been surprisingly shoin that independently of the actual moisture content of the green coffee and especially independently of the question of whether previously a certain moisture content has been set for the extraction, durj .ng treammenz with such supersaturalted, supercritical CC, optimal moisture contents are set In the flow direction layer by layer, so that with the green coffee being passed through with such 4 supersaturn.ted, supercrit^cal CO 2 a largely quantitative decaleination extending ho=ogeneously layer by layer over the 4 entire height of Che batch takes place. Thus the additional cosl., 1 v It 3 I for moistening the coffee beans before the actual extraction step can be substantially reduced and the actual extraction always takes place in the bed layer at a moisture content of about 35% by weight which is optimal f6r the process according to the invention, As a result, by the extraction in layers the time necessary for complete decaffeination is substantially reduced, as a result of which the energy requirements and the energy costs are considerably lowered. Also the use of COI within the framework of the process according to the invention is less than with the usual extraction processes with supercritical C02, Since a presetting of the moisture to the relatively high values does not take place before the Utroduction of the extraction process according to the invention, no excess swelling of the cof!ee beans takes place and emptying of-the pressure vessel can be performed without any difficulty miter the completed treatment. Since the moistening is performed step by step by the extraction agent itself during the passage with supersaturated, SuPercritical C02 and therefore proceeds slowly, the coffee beans are not exposed to any shock effect, which surprisingly results in the lact that Wing subsequent roasting a reduced proneness to breaking was noted.

Therefore the pTocess according to the invention is advantageously performed so that the water content for the extraction with C02 is set with the R20 portion, corresponding to the supersaturation, of the C02 used.

4 It has turned out to be particularly advantageous to select the supersaturation of the C02 with water between I and 2% by weight, as a result of which a particularly gentle dampening and an almost quantitative extraction of'the caffeine take place.

In an especially simple way the process according to the invention can be performed so that the extraction takes place with moist, supercritical COn supersaturated with water in a first extraction step at a pressure between 200 and 350 bars, preferably at about 235 bars, and a temperature is maintained between 40 and 80C, preferably about 601C, so that especially in comparison with the prior art it is possible to operate at a comparatively lower temperature.

To avoid an excess leaching of coffee flavor and to maintain the taste of the coffee beans to a considerably extent, advantageously the process according to the invention is performed so that after extraction with COW an extraction A perOrmed with water enriched with natural coffee flavor at a temperature between 70 and 904, preferably between 75 and SOIC, and a largely complete preserva;tion of the taste properties can even be improved in that the fluid C02 in the supercritical state is insignificantly laden with caffeine at the beginning of the extraction and is rRycled.

To facilitate the output the ndecaffeinated beans-alter completion of the extraction process and to counteract possibly disadvantageous swelling effects, following the extraction with COn a further treatment with enriched water is pericrmed so that 1 1 further treatMent with water enriched with coffee flavor is performed countercurrent to the extraction. This further treatment with enriched water results in the water-soluble part, of the saccharides, especially Oligosaccharides, adhering to the bean surface is washed away and in this way the stimulants arising during coffee roasming, especially carameliZzed saccharides, are reduced. In this connection, the total process can be performed in two isobaric process steps, as a result of which the tol.",al extraction time is shortened. As a result, the - is treated gently to the largest extent possible and end product the economic efficiency of th6 process is increased. Extractions of 80 to _07% off the originally present caffeine can be performed with the process according to the invention approximately in the same time, as is required for the extraction of 80% in the usual pure C02 high-pressure extraction process. Allso the subsequent water treament can be perforzted in the same high-pressure autoclave, as the extraction with supercritical Co.,> supersaturated with water and by the decaffeination in. layers the process can be controlled or regulated relatively simply by the process parameters of flow rate, pressure, temperature and bed thickness to obtain an optimal degree of extraction. The 'Aluid C02 in supercritical state can be conducted downward in the autoclave in the usual way, after which an optionally provided upward posttreatment or further treatment 'with water takes place upward. Especially this upward reversal of the flow d1rection thus results in a loosening up of the bean bed and a better 6 1 washing around the individual beans. Removal of the extracted caffeine from the fluid COq can take place in a known way, but does not have to be complete in any way. I'L the operation is in two consecutive steps, the first extraction step with7 supercritical COn does not have to take place completely by any means, since the res"C, of the caffeine is subsequently extracted in the water treatment. The caffeine can be scrubbed from the process water in an appropriate scrubber and optionally for complete removal of the caffeine residues an activated carbon filter can be used.

- The invention is explained below in detail by means of a device for perform.ing the process according to the invention dip-grar-matically represented in the drawing.

In the drawing, an extractor is represented by 1, which is 9-11--led with green unmoistened coffee beans. In a first process step the green coff.ee beans are dampened in extractor I with C02 supersaturated with water, which was enriched with coffee oils and CO6ee flavor. This water enriched with coffee flavor and coffee oils in this case is fed from a storage tank 2 by pipe 3, pump 4, a heat exchanger 6, valve 31 and by another pipe 5 into C02 circulation pipe 14 for water supersaturation of the C02 before it reaches extractor 1. The water laden with coffee oils and coffee flavor is derived from the raffinate separated from cato,eine treatment step 18, which reaches storage tank 2 by pipe 20. Dependent on this recycling, an equilibrium state is set relative to coffee oils and coffee flavor in extractor I as well p 1 7 1 -Per for these components as in scrubber 12, so that a mass trans. is excluded.

Dampening of the coffee beans takes place in layers in the CO,,) flow direction downward so that the extractlion takes plade only in this corresponding layer.

The isobaric COo ci=culation takes place after the discharge of the laden COn. by open valve 23 and by pipe 15 by circulating pump 10 and heat exchanger 11 into scrubber 12, in which caffeine is washed out countercurfirent from the C02 current by enriched water from storage tank 22, by activated carbon filter 13 for removal of the residue of the caffeine and by pipe 14 into extractor I for new charging witth opffel-ne. Valves 8 and 29 are closed in this process step.

Scrubber 12 is operated with raffinate from caffeine treatment step IS by storage tank 2, water ciroulating pump 4, pipe 3, heat exchanger 6 and valve 16 countercu=.-ent to the C02.

With the help of caffeine treatment step IS caffeina is serarated mainly from the water clrculation by pipe 17, and coffee oils and coffee flavor remain predominantly in the water circulation system. The caffeine separated in the coffee treatment step is thus discharged by pipe 19. The water consumed in the caffeine treatment is supplemented in storage tank 2 by!resh water supply by pipe 21.

This first process step is continued until about SOff/C of the caffeine has been extracted from the green coffee beans.

a After closing of valves 22, 23 and 24, the water laden with flavor and coffee ails is sucked from tank 2. by valve 25 and is delivered by pump 26 into the extractor. In pump 26 the water is now brought to t.he same pressure with which the CO.) left pump 10 before the first extraction step. The water is subsequently conducted by heat exchanger 27 where it is brought to the tenperature necessary for the second extraction step and from beat exchanger 217 by pipe 2S and open valve 8 is forced into -0 extractor 1. A.6tergoing through extractor I the water at the head of the extractor is fed by valve 29 and pipe 30 again, to the caffeine treatment. 'Valves 24 and 7 are closed in this operating step. It caffeine treatment IS the cafi5eine in turn is separated 0- .om the water of the second extraction step and the residual water is brought into the water storage tank by pipe 20. The second extraction step can optionally be performed even at lower pressures than in the first extraction step. The green coffee beans, now largely free of caffeine, can subsequently be removed fronn extractor 1 and further treated in a known way.

1 1. t 1

Claims

- CLAIMS:

1. A process for decaffeinating green coffee wherein the caffeine is extracted with fluid, supercritical C02 which is supersaturated with,0.55% by weight of H20-

2. A process as claimed in Claim 1 wherein the coffee is further treated with water.

3. A process as claimed in Claim 2 wherein the water is enriched with natural coffee flavor.

4. A process as claimed in any one of Claims 1 to 3 wherein the water content for the extraction with C02 is set with the H20 portion, corresponding to supersaturation, of the C02 used.

5. A process as claimed in any one of the preceding claims wherein the supersaturation of the C02 with water is selected between 1 and 2% by weight.

6. A process as claimed in any one of the preceding claims wherein the extraction is performed with moist, supercritical C02 supersaturated with water in a first extraction step at a pressure between 200 and 350 bars and at a temperature between 40 and 800C.

7. A process as claimed in Claim 6 wherein the pressure of the first extraction step is about 235 bars.

8. A process as claimed in Claim 1 or Claim 7 wherein the temperature of the first extraction step is about 600C.

9. A process as claimed in any one of the preceding claims wherein after extraction with C02, an extraction is 1 )l 10- performed with water enriched with natural coffee flavor at a temperature between 70 and 900C.

10. A process as claimed in Claim 9 wherein the extraction with water enriched with natural coffee flavor is at a temperature between 75 and 800C.

11. A process as claimed in any one of the preceding claims wherein the fluid C02 in the supercritical state is slightly laden with caffeine at the beginning of the extraction and is recycled.

12. A process as claimed in any one of the preceding claims wherein a further treatment with water enriched with coffee flavor is performed countercurrent to the extraction.

13. A process as claimed in Claim 1 substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.

Published 1991 atThe Patent Office. State House, 66/71 High Holbarn. U)ndonWCIR47P. Further copies may"be obtained from Sales Branch. Unit 6. Nine Mile Point. Cwmfelinfach. Cross Keys. NewpoM NPI 7HZ. Printed by Multiplex techniques lid. St Mary Cray, Kent.

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