IE45069B1 - Decaffeination process - Google Patents

Abstract

The aqueous extract having a high content of soluble materials is placed in contact with a water-immiscible liquid fat at a temperature of at least 65 DEG C for a period sufficient to transfer the caffeine from the aqueous extract towards the fat, and then the fat charged with caffeine is separated from the aqueous extract. After possible reincorporation of the volatile aromatic materials which were separated off before decaffeination, it is possible to dry the extract by spraying or by freeze-drying in order to obtain an instantly-dissolving powdered coffee or tea.

Description

This .invention relates to the decaffeination of aqueous extracts of vegetable materials.

There has long been a recognized demand for decaffeinated vegetable materials, particularly beverages such as cof5 fee and tea. The customary prior art techniques for decaffeination generally involve the use of organic solvents such as. .-. trichlorethylene or chloroform, which solvents are contacted either with the vegetable material or with an aqueous extract thereof. When sufficient caffeine has been transferred to the10 solvent, the resultant solution of caffeine is separated so as to allow, further processing of the decaffeinated material or extract.

A technique for utilizing fatty materials for the removal of caffeine from, inter alia, caffeine-containing aqueous extracts is described in German Patent Application NO. 2548916.

In brief, this technique involves contacting the liquid, water-immiscible fatty material with the aqueous extract of vegetable material, maintaining these liquids in contact for a period of time sufficient to approach or reach equilibrium caffeine distribution, and then separating the two liquids. 3y this sequence, the caffeine initially present in the aqueous extract is partially transferred to the fatty material. When .the caffeine-laden fatty material is then separated, the extract exhibits a correspondingly reduced Concentration of caf25 seine. .-.In accordance with the present*, invention, however, it has been found that use of elevated temperatures while the fatty material and aqueous extract are in contact not only substantially improves the decaffeination efficiency, but additionally fails to cause adverse flavor effects which might otherwise be expected. Advantageously, higher caffeine distribution coefficients and greater ease of separation of the two immiscible liquids into separate phases can be achieved where these liquids are held at elevated temperature during the time they are in contact and then separated into their respective phases. In this manner, the occurrence of inclusion or entrain' ment of one liquid in the other, which results in retention of amounts of one of the liquids within the phase of the other is reduced or avoided. The term ''inclusion designates the phenomenon whereby one liquid is dispersed essentially uni15 formly in gel-like form in the phase of the other liquid. Although less stable than emulsions, such entrainments would normally require additional steps to separate or resolve them.

The present invention thus provides a process for decaffeinating a caffeine-containing aqueous extract of a vegetable material comprising a) contacting the aqueous extract with a liquid, waterimmiscible fatty material; b) maintaining the aqueous extract and fatty material in contact for a time sufficient to transfer caffeine from the aqueous extract to the fatty material; and c) separating caffeine-laden fatty material from the aqueous extract, wherein the liquid fatty material 4$°θ° and aqueous extract are at or are brought to a temperature of at least about 65°C while they are maintained in contact.

By fatty material, as the term is utilised herein, is 5 meant any of the animal or vegetable fats or oils or admixtures or fractions thereof which are liquid at temperatures of about 65°c (and above). These fatty materials are customarily composed essentially of esters of fatty acids -- usually glycerol esters — and may be utilised in either their na10 tive form or in those resultant from conventional treatments as are known in.the art. Desirably, the fatty materials are essentially non-solvents for non-caffeine constituents of the vegetable material.

For example, the fatty materials may be unsaturated or saturated fats or oils. Similarly, unrefined or conventionally refined oils as well as oils with, or without, such normal additives as anti-oxidants and preservatives are within the scope of the present invention. It is preferred, however, that the fatty materials be essentially exempt of surfact20 ants, either natural or added. These materials may stabilize emulsions which form upon agitation of the liquid fatty -material and aqueous extract, and therefore increase the difficulty of such steps as liquid-liquid separation. Edible fatty materials are particularly preferred, including, for example, safflower oil, soy bean oil, corn oil, peanut oil, olive oil, coffee oil, triolein (oleic aeid ester of glycerol) and lard.

S ο ΰ 3 The caffeine-containing extracts to be decaffeinated in accordance with the present invention are aqueous extracts of vegetable materials such as roast coffee, green coffee and tea. In the cases of roast coffee and tea, it is the solubles remaining in the extracts after decaffeination which are further processed to provide beverage products.

With green cofree, an acusots solution is used to remove caffeine selectively from ths grain beans. Preferred extraction cf caffeine from green coffee may be performed by use, for example, of closed aqueous recirculation in the manner set forth in United States Patent Ko. 2,309,092 of Berry et al., the disclosure of which is incorporated by reference herein, as if it were set forth at length, to describe that process. The aqueous extract is then itself decaffeinated with fatty material whiIo ths decaffeinated green beans, upon subsequent roasting etc·., are converted into a comestible beverage product.

It is preferred that an extract of a vegetable material such as roast coffee or tea which contains sensitive, volatile flavor&nts be treated to avoid their loss. Thus, prior to decaffeination, it is desirable to isolate volatile flavors by, for example, stripping ths fresh extract with steam, suitably in accordance with known techniques. The isolated volatiles may bs returned to the extract or product at a later stage.

The transfer of caffeine from an aqueous extract of vefatty material is partially dependent - 5 gatable material to a upon the caffeine distribution coefficient between the two liquids. The value of the caffeine distribution coefficient varies with the particular liquids and the attendant conditions. It reflects the relative affinities of the fatty material and aqueous extract for caffeine, and is defined by the following equilibrium relationships Caffeine Concentration in Fatty Phase Distribution Coefficient = -----— Caffeine Concentration in Aqueous Phase In concert with the distribution coefficient, the relative amounts of the two liquids control the total weight of caffeine transferred -between them.

In accordance with the invention, transfer of caffeine is effected at an elevated temperature of about 65°C or above. The extract flavor constituents of coffee and tea have been found to be sufficiently stable at temperatures upwards of 65°C to permit holding times of up to, about 3 hours, although, less than about 1 hour is preferred. At still higher temperatures, the advantages of this invention increase further, and it is also possible to utilize correspondingly shorter processing times at such higher temperatures. No substantial advantage is derived by maintaining the two liquids at a temperature in excess of about 150°C while they are in contact, and temperatures in the range of about 65°C to 150°C are. accor dingly preferred. Once the aqueous extract has been separated from the fatty phase, the aqueous phase is desirably dried or chilled, suitably to below about 30°C, as soon as practicable thereafter as a precaution against flavor loss and degradation It is unnecessary that the aqueous extract and fatty material be at such elevated temperatures before they are maintained in contact and then separated. They may, for example, be contacted at lower temperature and then heated to this range. Similarly, for example, extract at a lower temperature may be contacted with fatty material of a temperature sufficient to bring both liquids within the desired temperature range during the tire they are maintained ia contact.

It was heretofore known that temperature affects the 10 caffeine distribution coefficient. For example, in the previously identified German Application distribution coefficients at different temperatures are given. The relationship there set forth, however, are only for temperatures of 20°C and below, and the distribution coefficient at those tempera15 tares may either increase or decrease with temperature, according to the specific fatty material utilized. At the elevated temperatures of this invention, however, substantially greater differences, which are always increases in the caffeine distribution coefficient, have been observed.

The significantly increased rate of transfer of caffeine from the aqueous extract to the fatty material substantially improves tha efficiency cf the decaffeination process. The caffeine.concentration in the initially caffeine-poor fatty material rapidly increases and approaches its equilibrium va25 lue. This permits caffeine transfer in liquid-liquid contact times of as little as a few seconds, although a contact time of at least 2 minutes is preferred when operating on a commercial scale.

Appropriate upper limits of temperature and time of contact of the fatty material with aqueous extract are readily determinable by those of ordinary skill in the art, having regard to the mechanical means employed for maintaining and then separating the two liquids. Thus, for example, where high degrees of decaffeination are sought by multi-stage admixtures of extract with fatty material, the repeated contacting and separating steps may consume a substantial amount of processing time. On the other hand, a single stage decaffeination technique utilizing a counter-current extraction column or like apparatus having a high number of theoretical plates or stages may permit much shorter overall processing times.

It is possible, with efficient processing means permitting short periods of contact, to employ temperatures of, for example, about ,150°C (where the temperature exceeds 10Q°C, suitable conditions of superatmospherie pressure are of course required to maintain the materials in liquid form). Ordinarily, however, temperatures of about 75° to 120°C are preferred. Tern- 1 peratures of from about 85 up to about 100°C are still more ( I preferred and do not require pressurization to maintain the fatty material and aqueous extract in liquid form.

Another factor which, in conjunction vzith those described above, affects decaffeination efficiency is the soluble solids concentration of the aqueous extract. - 8 ¢.'4: 42QGQ Increases in the solids concentration of tne aqueous extract also lessen the tendency to form emulsions with the fatty material. At an extract concentration of, for example, % soluble solids by weight, it has been found that emul5 sion-formation problems, which might otherwise interfere with the separation of fatty material from the aqueous extract, are materially lessened or eliminated. Moreover, such emulsions as may fern during decaffeination of suca nigh solids extracts are of substantially stability. 'i'he twc liquids may thus be readily resolved into separate and distinct phases by conventional techniques.

At particularly high extract concentrations, more inclusion, as distinct from amulsior. formation, may occur upon intimate admixture of the aqueous extract and fatty material.

Accordingly, extract concentrations in axcess of about 55 3 by weight ara preferably avoided. This does not mean, however, that still higher extract concentrations are inoperable. Concentrations of up to about 70 o may oe employed, particularly at the nignest temperatures of this invention. It has been found that entrainment which may occur at such concentrations is faeilely overcome by subjecting at least the separated phase of fatty material (and preferably also the aqueous extract) to a simple purification step such as centrifugation.

This purification of the separated phases may ordinarily be performed after the extract has reached the ultimate, desired degree of decaffeination (ordinarily, for example, about Λ (3 Ο g.a’» 97 % for coffee). Alternatively, the extract and/or fatty material may be purified of included liquid after any·, or each, of ths decaffeination cycles.

It is accordingly preferred that the concentration of soluble solids in the aqueous extract of vegetable material be within the range of from about 30 % to 70 -¾ by weight. Most preferably, however, concentrations of about 35 to 55 % are employed to maximize efficiency of caffeine removal, and minimise inclusion effects.

The effects of contacting temperature and solids concentration of the aqueous extract are interrelated. Aqueous extracts having concentrations above about 40 % (with some variation dependent upon the particular kind or blend of vegetable material extracted) are more difficult to decaffeinate at ambient temperatures. For example, ambient temperature aqueous extracts of roas-c coffee having a solids concentration of about 40 % have viscosities and surface tensions which tend to interfere with their intimate admixture vzith the fatty material. At the elevated temperatures of decaffeination of this invention, however, it has been found that efficient admixture and decaffeination of the extracts are achieved. Thus, in addition to the other advantages achieved by use of the higher temperatures of the present invention, they also promote physical characteristics vzhich permit more rapid and quantitative transfer of caffeine from the extract to the fatty material. ίϊ <3 Ο 6 9 A still further advantage of this invention is increased processing flexibility. At the elevated temperatures herein described and particularly where the preferred, higher extract solids concentrations are also employed, it is feasible to utilize more efficient means of contacting the fatty material and aqueous extract. The decreased propensity of these liquids to form stable emulsions allows improved agitation or like means for more intimately contacting the liquids, thereby increasing the rate of decaffeination without undue corresponding detriment to the ease of separation therein.

In a preferred embodiment of this invention, for the preparation of decaffeinated extracts of roast coffee, the aqueous extract has a caffeine content equal to at least about 5 %, more desirably at least 6 %, by weight of total soluble solids present. Extracts having such caffeine contents are conveniently prepared by extracting coffee with aqueous media at relatively low temperatures, usually not exceeding about 120°C, for example in the range 90 - 120°C. At these temperatures, all the caffeine present is extracted, but only a part of the noncaffeine solids, so that the caffeine content of the total extracted solids is greater. The extracts are preferably concentrated to the higher soluble solids content previously described prior to decaffeination, whereas the coffee may be subjected to a second extraction at higher temperatures, preferably of at least about 140°C. The second extract may thereafther be added, preferably after concentration, to the decaf11 fainated low temperature extract. In this manner, a decaffei; nated extract of conventional composition may be produced, even though only part of its constituents has been subjected to decaffeination.

A further optional embodiment of the invention involves .stripping non-caffeine components of the extract from the separated, caffeine-containing fatty material. Although the fatty caffeine solvents utilized in this invention are essentially selective for caffeine, they may also remove minor amounts of other constituents of the vegetable material from the aque.ous extracts. Some of these constituents may merit recovery for subsequent return to the decaffeinated extract.

Stripping of volatile flavors from the caffeine solvent fatty material may be either an alternative or a supplement to the already discussed, preferred prior treatment of the aqueous extract for removal of volatile flavors. In general, only in decaffeination cf tea extracts does the fatty material contain non-volatile flavors which merit recovery.

Stripping of extract constituents from the separated fatty material may be performed by subjecting the fatty material to conditions of temperature and pressure sufficient' selectively co vaporise them. Preferred conditions of stripping are from about 85 to about 125°C with corresponding pres- . sures of about 1 to about 150 mm of Hg. These conditions per25 mit separation of the flavor constituents, which may then be collected, as by condensation. - 12 4 3 0 6 9 The invention is illustrated by the following examples, in whioh, unless otherwise noted, percentages and proportions are on a weight basis.

EXAMPLE 1 An aqueous extract of roasted and ground coffee beans prepared at extractive temperatures of up to 160°C and having a soluble solids concentration of 17 % is stripped with steam to remove volatile flavors. The stripped extract is then subjected to vacuum evaporation to increase its solids concentra10 tion to 45.8 % by weight. The extract is then introduced to the decaffeination system.

The decaffeination system is composed of six serially connected stages, each stage being composed of a static inline mixer for contacting corn oil and extract, connected to a jacketed, vertical holding column for gravity separation of these admixed liquids.

This system is operated for countercurrent passage of the streams Of fatty material and extract. Fresh extract and fresh fatty material are introduced into the system, and oaf20 feine-laden fatty material and decaffeinated extract are withdrawn from the system. Suitable pumps, piping and valves are provided.

Extract (at 90°C) is fed into the mixer at 120 g per minute, and corn oil (also at a temperature of 90°C) is fed in25 to the mixer at 1.7 kg per minute. After steady state operation has been reached, the residence time for extract in the decaffeination system is approximately 45 minutes. The extract is maintained at 90°C while being admixed with fatty material in each static mixer for about 2 minutes and permitted to settle in each separator column for about 5 minutes.

The extract exiting the decaffeination system is analysed and shows a caffeine content of less than 3 S of that contained in the original extract. After reincorporation of the volatile flavors stripped prior to decaffeination, the extract is spray-dried to produce an instant coffee powder. Upon recon10 stitution v/ith water, the powder yields a decaffeinated beverage comparable in flavor with commercially available products.

EXAMPLE 2 Ths stripped extract of Example 1 is concentrated by vacuum evaporation to a soluble solids concentration of 45 S by weight. The extract is then conveyed to the decaffeination system.

The decaffeination system consists of a vertical countercurrent extraction column having an internal packing composed of horizontal, circular plates affixed on a reciprocating ver20 tical shaft. The column has. a 2.2 meter length and a 5 centimeter internal column and plate diameter.

Coffee oil at 90°C is fed into the bottom of the column at a feed rate of 445 cc/min. The extract, also at 90°C, is fed into the top of the column at a rate of 30 cc/min, for an oil-to-extract weight ratio of 15:1. The two liquids remain at 90°C while in the column. 4ΰθ6θ After steady state operation of the column is achieved, extract exiting the.bottom of the column is centrifuged to remove included oil. Analysis of the centrifuged extract shows the degree of decaffeination to be about 97 %. Tlie ex5 tract is then recombined with volatile flavors separated prior to decaffeination and is spray dried. Upon reconstitution with water, the resultant beverage has a flavor substantially the same as that of commercially available products.

EXAMPLE 3 The effects of solids concentration of the aqueous extract and. temperature on decaffeination are illustrated in the Tables below. One part by weight of extracts containing the indicated concentrations of soluble solids are placed in separatory· funnels and 15 parts by weight of corn oil are ad15 ded, the materials being at the indicated temperatures. Each funnel is shaken twenty times over a 40 second interval and submerged in a water bath maintained at the same temperature. The funnels are held in the bath for one hour to ensure separation of the two liquid phases.

The ease and efficiency of separation of the two phases is reflected by the time required for the appearance of a distinct interface between the two liquids, by visual inspection for emulsion and by thin layer chromatography for inclusion. The results are set forth in the following tables; TABLE 1 * Coffee Extract Solids Concentration Temperature Separation Time Comments 5.5 % 20 °C 35 - 45 min. Emulsion 5.5 % 90 °C 4 - 6 rain. 17. S, 20 °C 45 - 55 min. — 17 % 90 °C 4 - 5 min. — - 30 % 20 °C 35 - 40 min. — 30 % 90 °C 4 - 5 min. — 49 S 20 °C 30 - 35 min. Substantial Inclusion 49 % 90 °C 3-4 min. — 64 & 20 °C 8-12 min. Inclusion 64 % 90 °C 3 - 5 min. Inclusion * Extract of the roasted and ground coffee was prepared by countercurrent extraction utilizing an,aqueous stream. having an initial temperature of 170°C'and a final temperature of about 100°C. The extract was then diluted or concentrated by vacuum evaporation, as required, to reach the indicated solids concentration.

TABLE 2 Coffee Extract Solids Concentration Temperature Separation Time Comments 5 % 20 °e 20 - 35 min. Emulsion . 5 δ 90 °C 4-6 mi». — 30 n. Ό 20 °C 35 - 45 min. __ 30 s SO °C 4.- 5 min. — •il <53063 Coffee Extract Solids Concentration Temperature Separation Time Comments 44 S . 20 °C 30 - 35 min. Inclusion. 44 % 90 °C 3 - 4 min. — ** Extract of the roasted and ground coffee was prepared by countercurrent extraction utilizing an aqueous stream having an initial temperature of about 110°C and a. final temperature of about 100°C. The extract was then diluted or concentrated by vacuum evaporation. Coffee Extract Solids Concentration TABLE 3 *** Comments Temperature Separation Time 21 % 20 °C 45 - 60 min. Substantial inclusion, Substantial Emulsion 21 % 90 °C 5-6 min. Substantial Inclusion, Lesser Emulsion 42 % · 20 °C 18 - 22 min. Substantial Inclusion 42 % 90 °C 3 - 4 min. Lesser Inclusion *** Extract of green beans of coffee was prepared utilizing an aqueous, stream having a constant temperature of 100°C and the extract was concentrated by vacuum evaporation.

Temperature Separation Time Comments TABLE 4 **** Tea Extract Solids Concentration 14 % 20 °C 25 - 30 min. — 14 % 90 °C 4 - 5 min. — 42 % 20 °C 16 - 20 min. High Inclusion 42 a o 90 °C 3 - 4 min. Inclusion In each of the 20°C runs, the separated oii phase has a cloudy appearance, indicating some inclusion of extract.

**** Extract of tea was prepared utilizing an aqueous stream having a constant temperature of 115°C. The extract was then concentrated by vacuum evaporation.

EXAMPLE 4 The procedure of Example 3 is repeated with other fatty materials. The weight ratio of oil to extract is 15 : 1, and the solids content of the aqueous extract of roasted and ground coffee .is 30 3.

TABLE 5 ***** Fatty material Temperature Separation Time Comments Olive Oil 20 °C 25 - 43 min. Low Inclusiont Olive Oil 90 °C 1 - 2 min. — Safflower Oil. 20 °C 18 ~ 32 min. Low Inclusion Safflower Oil 90 °C 1 - 2 min. — 25 Blended Oil (Durkee 500} 20 °C 26 “ 36 min. Low Inclusion Blended Oil (Durkee 500) 90 °C 2 - 3 min. — - 18 αΰ069 ***** Extract of roasted and ground coffee was prepared by countercurrent extraction utilizing an aqueous stream having an initial temperature of 160°C and a final temperature of about 100°C and then concen5 trated.

EXAMPLE 5 Caffeine distribution coefficients at various temperatures are determined utilizing corn oil and an aqueous extract of roasted and ground coffee containing 50 % solubles.

This is accomplished by admixture of oil and extract in a weight ratio of 20 : 1 in bombs. The bombs are then maintained at the indicated temperatures (and superatmospheric pressure for 115°C) while being agitated for one hour. The results are set forth in the following table: 15 Temperature TABLE 6 ****** Percent Decaffeination Distribution ( 20 °C 31 % 0.022 50 °C 47 % 0.043 90 °C 64 % 0.091 20 115 °C 68 % 0.142 In the foregoing examples, vacuum evaporation of extract can be replaced by other concentration means, such as freeze concentration. Also, spray drying can be replaced by freeze drying or other suitable drying techniques.

****** Extract of roasted and ground coffee is prepared by countercurrent extraction utilizing an aqueous stream having an initial temperature of 160°C and a final temperature of about 100°C and then concentrated.

Claims (13)

. CLAIMS

1. A process for decaffeinating a caffeine-containing .aqueous extract of a vegetable material comprising a) contacting the aqueous extract with a liquid, water-im5 miscible fatty material? b! maintaining the aqueous extract and fatty material in contact for a time sufficient to transfer caffeine from the aqueous extract to the fatty material? and c) separating caffeine-laden fatty material from the aqueous 10 extract, wherein the liquid fatty material and aqueous extract are at or are brought to a tenperature of at least about 65°C while they are maintained in contact.

2. A process according to claim 1, in which the aqueous extract has a soluble solids concentration of 30 % to 70 % 15 by weight.

3. A process according to claim 2, in which the aqueous extract has a soluble solids concentration of 35 to 55 % by weight.

4. A process according to any preceding claim, in which the 20 liquid fatty material and the aqueous extract are at or are brought to a temperature between 75° and 120°C while they are maintained in contact.

5. A process according to claim 4, in which the liquid fatty material and the aqueous extract are at or are brought to 25 a temperature between 85° and 100°C while they afe maintained in contact, - 20 10 α ·Ϊ069

6. A process according to any preceding claim, in which the fatty material is selected from the group consisting of safflower oil, soybean oil, corn oil, peanut oil, olive oil, coffee oil, triolein and lard.

7. A process according to any preceding claim, in which the aqueous extract is an extract of tea or roasted coffee.

8. A process according to claim 7, in which volatiles are stripped from the aqueous extract prior to contact with the fatty material.

9. A process according to claim 7 or claim 8, in which the aqueous extract of roasted coffee has a caffeine content at least equal to 5 % by weight of total soluble solids.

10. A process according to claim 9, in which the aqueous extract is prepared by extraction of roasted coffee at temperatures not exceeding about 120°C.

11. A process according to any one of claims 1 to 6, in which the aqueous extract is of green coffee.

12. A process for decaffeinating aqueous extracts substantially as herein described with reference to any one of the Examples.

13. The decaffeinated extract obtained by a process according to any preceding claim.