GB2089639A - Process for recovery of aroma volatiles - Google Patents

Abstract

A process for the treatment of an aqueous coffee extract wherein the extract is subjected to concentration by evaporation and the vapors resulting from said concentration are condensed to form an aqueous liquid. The aqueous liquid is passed through an adsorbent comprised of non-iogenic macroreticular cross-linked resin particles to adsorb aroma volatiles. Preferably, the resin is a divinylbenzene polymer and the aroma volatiles are desorbed from the resin particles with steam as the desorbent. The aroma volatiles which are recovered are added to the concentrated extract which may then be dried.

Description

SPECIFICATION Process for recovery of aroma volatiles This invention relates to a process for producing soluble coffee of improved flavor and taste and more particularly to an improved process for recovery of aroma volatiles which are lost during conventional soluble coffee princesses.

The production of soluble coffees, also referred to as instant coffees, both spray dried and freeze dried, has advanced significantly in recent years. Thus, soluble coffees are able to be obtained in increased yields due to improved roasting, extraction and drying techniques. However, such yields are obtained sometimes with a consequent loss of flavor, taste and aroma volatiles when the dry soluble coffee products are reconstituted. Thus, by utilizing techniques in which dilute extracts are produced increased yields of the dry soluble coffee products may be obtained. However, the drying and other procedures have to be adjusted to accommodate the more dilute extracts since it is known that less aroma volatiles are lost when higher concentration extracts are dried.These are achieved by a variety of techniques principal of which are concentration methods in which the dilute extracts that are obtained according to various methods including split-stream drawoff processes as shown, for example, in U.S. Patent No.

3,965,269 or as conventional extracts from percolator sets are then concentrated employing various types of concentrators, evaporators or the like.

The more concentrated extracts are subsequently dried as, for example, by spray drying or freeze drying. The more concentrated extracts may also be blended with the more dilute extracts prior to drying.

During the concentration of the dilute extracts coffee volatiles may be recovered and added to the extract that is being dried. However, the recovery of such aroma volatiles is and has been extremely difficult because of the volume of condensate or distillate.

Moreover, during the distillation only those aroma volatiles that are able to be condensed or distilled under the general operating conditions employed can be recovered with the result that certain noncondensable aroma volatiles are lost also. These non-condensable aroma volatiles may also contain valuable components for providing flavor and taste in the dry soluble coffee products. Further, if the extract or extracts to be dried are at least than optimal concentration, usually 40% to 50% for spray drying and 20% to 35% for freeze drying, retention of valuable aroma volatiles may also be a problem.

Prior art methods for absorbing aromatic compounds in coffee extracts are disclosed in Rooker, U.S. Patent No. 3,418,134 and Kleeman et al., U.S.

Patent No.3,531,463. The Rooker patent teaches the use of activated charcoal as an adsorbent. However, desorption of aromatic compounds is a problem.

The Kleeman et al. patent indicates ion exchange resins may be employed. However, such resins do not appear to trap aromas that are later added back, instead the ion exchange-treated condensate is recycled and used as an extraction medium. Published German patent application No. DT 2452 693 mentions that macroreticular cross-linked resins may be employed to recover aroma substances from tomato concentrate and also cocoa butter. However, desorption of the resins appears to be accomplished using an organic solvent. All of the just-mentioned processes thus have serious processing disadvantages. It would therefore be very desirable to have an improved method for the treatment of aqueous coffee extracts so as to recover sought-after aroma volatiles.

A process for the treatment of an aqueous coffee extract has now been discovered wherein the extract is subjected to concentration by evaporation and the vapors resulting from said concentration are condensed to from an aqueous liquid. The aqueous liquid is passed through an adsorbent comprised of non-ionogenic macrorecticular cross-linked resin particles to adsorb aroma volatiles.

Preferably, the resin is a divinylbenzene polymer and the aroma volatiles are desorbed from the resin particles with steam as the desorbent. The aroma volatiles which are recovered are added to the concentrated extract which may then be dried.

Referring to block diagram Figure 1, in the process of the present invention, primary and secondary percolator draw-off extracts, one at about 20% coffee soluble solids and the other at about 12% soluble coffee solids are mixed yielding a 16% soluble coffee solids extract. This extract is then concentrated to about 45% soluble solids in an evaporator such as a Centritherm* evaporator. The evaporate containing volatile coffee aromas is condensed. The aroma rich condensate is passed through a column containing non-ionogenic macroreticular cross-lined resin particles for example, Amberlite* XAD4 resin available from Rohm and Haas Co., Philadelphia, Pa. The aromas are removed from the condensate water by the resin. The column effluent is discarded.

After the feed cycle is completed the aromas are removed from the resin with steam. The column is steamed in the reverse back flush direction until 1/20th the volume of the feed is condensed and collected. The aromas are effectively concentrated in 5% of the original amount of water.

The aroma rich water is added back to the concentrated extract and the extract at 42% solids is spray dried at low temperature.

To obtain effective adsorption-desorption of aromas, certain process variables have been found to be essential. Thus, the residence time, that is, the amount of time the condensate is in contact with the resin is typically 1 to 5 minutes, preferably 2.5 to 3.0 minutes. The superficial velocity of condensate through the column containing the resin particles is dependent upon the height and diameter of the column containing the resin particles. The condensate to resin ratio is a measure of the capacity of the resin Trademark to absorb aroma volatiles.Generally, it has been determined that 1 pound of resin effectively adsorbes from 100 pounds f condensate. The cycle time is usually in the order of 60 to 120 minutes and the time for steaming is approximately 60 minutes so as to allowtimefor resin cooling and backflush ing. The condensate temperature is usually maintained within the range of 60 to 70"F (15to 21"C) for max imum adsorption of aroma volatiles. Condensates at much lower and at much higher temperatures appear to have less of their aromas adsorbed by the resin.To desorb the aroma volatiles steam is the preferred desorbent and it is employed at a ratio of approximately 1 to 20 of the volume of condensate feed passed through the resin particles.

The process may be carried out in a simple batch operation or by a continuous procedure. In a fixed bed batch operation, the resin adsorbent may be supported in a suitable adsorption cell or vessel which in most practical operations normally takes the form of a tower or column suitably packed with the resin particles which may be of any suitable size or mesh such as that which will pass through a 16-mesh screen but will largely be trapped buy a 100-mesh screen (U.S. Standard). The condensate is passed through the resin bed at a suitable rate, pref erably from top to bottom so that aroma volatiles may be adsorbed on the resin surfaces.

Besides the single contact or batch extraction sys tem just described, the condensate may be passed in succession through a plurality of fixed beds of the resign adsorbent or through a plurality of resin beds which are moved continuously or stepwise in coun tercurrent relation to the flow of condensate.

In another embodiment of the process, non condensable aromas, which are normally lost through the vacuum line during evaporate conden sation, are fed along with the condensate to a com posite column containing 5 parts resin to 1 part acticated charcoal. General operating conditions are the same as in the process in which all ofthe aromas are condensed.

The process is found to deliver high concentration, high quality extract to the dryers. Many workers have shown that volatile retention during spray drying is related to the solids concentration of the feed to the dryer. For example, 43% solids concentration dryer feed has been identified as desirable with regards to volatile retention. Economic production of coffee solids results in a solids concentration of 17% or less. Ordinary evaporation techniques used to concentrate coffee solids from 17% to 43% results in the loss of most coffee volatiles. The process thus recovers a substantial portion of the coffee volatiles that would be lost by ordinary evaporation.

EXAMPLE The principal aspects of the process are detailed in block diagram Figure 2. A dilute coffee extract (stream A) is obtained from a percolator set and is passed to an evaporator to produce a concentrated extract (stream B). Condensate from the evaporator (stream C) / (stream D), containing most of the easily condensed coffee volatiles, is fed to a column containing an absorbent comprised of non-ionogenic macroreticularcross-linked resin particles, specifically Rohm and Haas Amberlite* XAD4 resin, where most of these volatiles are adsorbed while the bulk of the condensate is discharged from the system (stream E). When the capacity of the resin is reached (after about one hour), the condensate (stream C) is diverted to a fresh column.While the second column is absorbing volatiles, the spent or loaded column is then desorbed with a small volume of steam (1/20 the volume of condensate) (stream F) that is then condensed (stream G)/ (stream H) and added to the concentrated extract (stream 1). After desorption and cooling, the column is considered fresh and ready to continue the process in an alternating fashion of one column adsorbing and one column desorbing. The net effect is a 20 to 1 folding capture of many of the coffee volatiles that would be lost by ordinary evaporation.

The concentrated extract (stream 1) to which the desorbed aroma (stream H) is added and now passed as stream J and, after heating, as stream K to a spray dryer. Dry soluble coffee product is recovered as L.

An expert panel evaluated spray dried soluble coffee product produced by the process. The expert panel consensus was that the process resulted in a productthat is less harsh with more real coffee taste.

Moreover, a 200 judgement test resulted in a 54% preferance for a spray dried soluble coffee product produced by the process as against a control.

The present invention thus provides a process for the recovery of aroma volatiles by passing an aqueous liquid containing such aroma volatiles through an adsorbent comprised of resin particles of a substantially non-ionogenic, water-insoluble suspension polymerized cross-linked polymer of polymerizable ethylenically unsaturated molecules comprising 2 to 100 weight percent of at least one poly(vinyl) benezene monomer which is divinylbenzene, trivinylbenzene, an alkyl-divinylbenzene having from 1 to 4 methyl or ethyl groups substituted in the benzene nucleus or an alkyl-trivinylbenzene having 1,2 or3 methyl or ethyl groups substituted in the benzene nucleus, which polymer has a porosity of at least 10% and a surface area of at least 10 square metres per gram.

The macroreticular resins employed as the adsorbents herein are not new in themselves. Granular cross-linked polymers ofthe aforementioned type, prepared by suspension polymerization, are described in Gustafson U.S. Patent No. 3,531,463.

The macroreticular polymer, which preferably is of 35 to 50 mesh (U.S. Standard Sieve) in particle size, has a porosity of at least 10% (percent volume of pores in the resin body or bodies) and a surface area of at least 10 square meters per gram of the resin (up to 2000 square meters per gram). Suitable crosslinked resins have solubility parameters of at least 8.5 and those having such parameters up to 15 or more are satisfactory for use in the present invention.

The macroreticular resins employed as the aroma volatile adsorbents herein may be any of the known materials of this type. For example, there may be Trademark used the granular cross-linked polymers of this character prepared by suspension polymerization of polymerizable ethylenically unsaturated molecules comprising 2 to 100, preferably at least 50, weight percent of at least one polyvinyl benzene monomer which is divinylbenzene, trivinylbenzene, an alkyldivinylbenzene having from 1 to 4 methyl or ethyl groups substituted in the benzene nucleus or an alkyltrivinylbenzene having 1,2 or 3 methyl or ethyl groups substituted in the benzene nucleus.Besides the homopolymers and copolymers of these polyvinylbenzene monomers, one or more of them may be copolymerized with up to 98%, preferably less than 50% (by weight of the total monomer mixture) of (1) monoethylenically unsaturated monomers, or (2) polyethylenical ly unsaturated monomers other than the poly(vinyl)benzenes described above; or (3) a mixture of (1) and (2). Preferred polymers for use in this invention include those where the polymer is of at least 50 weight percent of divinylbenzene, for example, for example, a homopolymer of divinylbenzene or a copolymer of divinylbenzene and styrene.

It has been found that steaming a resin column "loaded" with Centritherm* condensate in the reverse direction provides an efficient, practical means for recovering the aromas. In addition, there are fractionations that occur in two parts of the process which can be used to modify the overall aroma, yielding a product of improved, less-harsh character.

In the first, some aroma compounds are not adsorbed by the resin leading to a modification of the flavor. Secondly, the steam effluent can be divided into fractions which are different in character as well as odor strength and can be chosen and blended as desired. These fractionations have been confirmed by gas chromatographic analysis.

Other aqueous streams in coffee processing may be treated by the process of the present invention for recovery of aroma volatiles. These include, inter alia, water condensation streams from freeze drying methods.

Claims (14)

1. A process for the treatment of an aqueous coffee extract in which said extract is subjected to concentration by evaporation, vapors resulting from said concentration are condensed to form an aqueous liquid and said liquid is passed through an adsorbent comprised of non-iongenic macroreticular cross-linked resin particles to absorb aroma volatiles.

2. A process according to claim 1 in which said resin is a divinylbenzene polymer.

3. A process according to either of claims 1 and 2 in which said aroma volatiles are desorbed from said resin particles with steam as the desorbent.

4. A process according to any one of claims 1 to 3 in which said aroma volatiles are recovered and added to the concentrated extract.

5. A process according to claim 4 in which the concentrated extract to which said recovered aroma volatiles are added is spray dried.

6. A process according to claim 4 in which the concentrated extract to which said recovered aroma volatiles are added is freeze dried.

7. A process according to any one of claims 1 to 6 in which non-condensable aroma volatiles are also passed through said particles.

8. A process according to claim 3 and any one of claims 4 to 7 as dependent on claim 3 in which said aroma volatiles are desorbed by passing said desorbent through said resin particles in a flow direction apposite that of said liquid.

9. A process according to any one of claims 1 to 8 in which two columns of resin particles are utilized simultaneously, one of said columns being desorbed after adsorbing aroma volatiles while the other of said columns is adsorbing aroma volatiles.

10. A process according to any one of claims 1 to 8 in which a composite column is employed, the lower portion of said column containing activated charcoal and the upper portion of said column containing resin particles.

11. A process according to any one of claims 4 to 10 in which the solids concentration of the concentrated extract is between about 40 to about 45%.

12. A process according to any one of claims 1 to 11 in which the ratio of said liquid to said adsorbent is 100 to 1, the time for passing said liquid through said desorbent is 1 to 5 minutes and the temperature of said liquid is 100 to 40"C.

13. A process for the treatment of an aqueous coffee extract substantially as hereinbefore described.

14. A coffee product containing aroma volatiles recovered from an aqueous liquid in accordance with a process as claimed in any one of claims 1 to 13.

Trademark