Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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. ~ 15 BACKGROUND OF THE INVENTION
This invention relates to a process for preparing a '
~ ' decaffeinated coffee extract. More'particuiarly, it relates to
'~ a process for the preparation of a decaffeinated coffee extract
of the soluble or instant type.
, Numerous metho,ds for the decaffeination of,coffee have
been desc~ibed in the art.' For example, U.S. Reissue Patent 13,261,
' issued September 1, 1908 to ~eyer et al., describes a process involv
' ing direct contact between green coffee and a solvent for caffeine.
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~loistened green coffee beans are contacted with an or~anic
solvent, residual solvent is removed from the green beans, and
the decaffeinated beans are roasted for preparation of a coffee
extract and product therefrom. Another approach to decaffeina-
tion of coffee has involved the formation of an aqueous extract ofgreen coffee solubles followed by a liquid/liquid decaffeination
operation utilizing an organic solvent. This method is described
in detail in U.S. Patent 2,309,092, issued January 26, 1943 to '
Berry et al.
10Green bean decaffeination methods, while effective to
remove caffeine from the coffee beans, involve the handling of
large amounts of coffee and solvent materials and require the
; utilization of expensive equipment and facilities. Moreover, the
decaffeination and desolventizing steps employed in green bean
decaffeination methods are slow operations tending to reduce
process efficiency.
Certain of the economic considerations and processing
inefficiencies of green bean decaffeination methods have been
overcome by resort to liquid/liquid decaffeination of roast and
ground coffee extract. Extract decaffeination methods are rela-
tively fast in operation and require less capital equipment
and expense than green bean decaffeination methods. Examples
of extract decaffeination methods are described in U.S. Patent
2,472,121 (issued June 7, 1949 to Ornfelt); U.S. Patent 2,472,881
(lssued June 14, 1949 to Bender); and U.S. Patent 2,933,395
(issued April 19, 1960 to Adler et al.). In general, these methods
involve the preparation of an extract of roast and ground coffee
and decaffeination of the extract by utilization of a water-
immiscible organic solvent for caffeine. The resulting decaf-
3~ feinated extract, separated from the caffeine-laden organic
solvent, can be utillzed in the preparation of a soluble coffee
in conventional manner.
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while extract decaf~eination methods per-Jni~
certain ~conomlc aind practical limitations of green ~ean decaf-
feination methods to be overcome, extract decaffeination methods
are attended by the same problems of flavor quality as exist
in the case of decaffeination methods in general. Thus, it
has been generally appreciated that decaffeinated coffee products
tend to lack the flavor and aroma qualities of their non-
decaffeinated counterparts. The tendency of decaffeinated coffee '
products to be diminished with respect to flavor and aroma
principles that contribute materially to cup aroma and flavor
has heen attributed for the most part to the tendency of caffeine
solvents to remove certain desirable non-caffeine constituents
of coffee.
It is an object of the present invention to provide
a process for the decaffeination of coffee.
It is another object of the invention to provide an
economical and efficient process for preparin~ a decaffeinated
coffee extract.
Still another object of the invention is to provide
a process for the preparation of a coffee extract deprived of its
caffeine content while retaining to the extent practicable its
non-caffeine constituents.
These and other objects of the invention will become
apparent from the detailed description provided hereinafter.
SUMM~RY OF THE INVENTION
The present invention is based in part upon the dis-
covery that important non-caffeine flavor and aroma constituents
normally removed from an aqueous coffee extract in the course of
liquid/liquid decaffeination can be efficiently recovered and
restored to the coffee extract with the result that an extract
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having improved flavor and aroma characteristics is obtained.
Thus, the recovery and restoration to a coffee extract of these
important coffee and aroma principles can be effectively
utilized in extract decaffeination methods. These methods
generally comprise the steps of forming an aqueous extract of
roast and ground coffee, decaffeinating the extract by contact
with a water-immiscible organic solvent for caffeine, and
separating the decaffeinated aqueous coffee extract from the
caffeine-containing water-immiscible organic solvent. It
has been found that desirable flavor and aroma principles can
be effectively recovered by partitioning the caffeine content
of the water-immiscible organic solvent into water. The
resulting organic solvent and its content of flavor and aroma
principles can thereafter be restored to the coffee extract.
The extract can then be desolventized and dried in a conventional
manner to a soluble coffee product having improved flavor and
aroma characteristics.
More particularly, the present invention resides in
a process for preparing a decaffeinated coffee,
which comprises the steps of:
(1) decaffeinating an aqueous roast and ground coffee
extract by contact with a water-immiscible organic
solvent for caffeine;
(2) separating the decaffeinated aqueous coffee extract
from the caffeine-containing water-immiscible organic
solvent;
(3) concentrating the caffeine-containing water-immiscible
solvent to a solids content of from about 1~ to about
10% by weight;
(4) contacting the concentrated caffeine-containing water-
immiscible organic solvent with an amount of water
sufficient to partition caffeine into the aqueous phase;
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(5) recovering the water-immiscible organic solvent
containing flavor and aroma constituents;
(6) incorporating said water-immiscible organic solvent
and flavor and aroma constituents into the decaffeinated
roast and ground coffee extract; and
(7) desolventizing the decaffeinated coffee extract to
form a desolventized extract.
DETAILED DESCRIE'TION OF THE IN~IENTION
By the process of the present invention, an aqueous
extract of roast and ground coffee is subjected to a liquid/
liquid extraction with an organic water-immiscible caffeine
solvent. A resulting caffeine-laden solvent is separated from
the decaffeinated coffee extract and is subjected to a recovery
process whereby certain desirable flavor and aroma principles
in the organic solvent are retained after partitioning of a
caffeine content of the organic solvent into water.
The aqueous coffee extract can be prepared in conven-
tional manner from roast and ground coffee beans. Coffee beans
are roasted and yround to a suitable state of subdivision
for extraction by any of a number of known methods. Counter-
current extraction
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methods can conveniently be employed, and examples of such
methods are described in, for example, U.S. Patent 3,700,463
(issued October 24, lg72 to Bolt et al.), and U.S. Patent 3,700,466
(issued October 24, 1972 to Bergeron et al.). The extract
will normally have a concentration of soluble coffee solids in '
the range of from about 15% to 35%, although extracts having a
lesser or greater concentration of such coffee solids can be
employed.
The coffee extract can be devolatilized prior to the
liquid/liquid extraction operation. For example, the coffee extr~c
can be devolatilized by flashing-off volatiles at subatmospheric
pressure or by passing an inert gas such as carbon dioxide, nitro-
gen, or steam through the coffee extract. The coffee volatiles are
condensed for later addition to the coffee extract, kno~7n as the
add-back process. The ernployment of a devolatilization step,
whereby the volatiles are condensed in a suitably chilled conden-
ser for add-back to the coffee extract, constitutes a preferred
practice from the standpoint of optimizing flavor of the ultimate
coffee product and minimizing the possibly adverse affect of opera-
ting conditions upon the volatile components of the coffee extract.
A preferred devolatilization step involves the stripping of vola-
tiles from the coffee extract ~ ith the aid of steam.
If desired, the coffee extract can be concentrated prior
to the liquid/liquid decaffeination operation. For example, the
25 extxact can be concentrated into the range of about 30% to about
4596 coffee solids prior to the decaffeination step.
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The roast and ground coffee extract can be decaf-
- feinated by a number of methods. The decaffeination operation
involves a liquid/liquid extraction whereby contact of the
aqueous extract with a liquid water-immiscible organic solvent
5 effects substantial removal of the caffein~- content of the '
coffee extract. Any of a variety of water-immiscible organic
caffeine solvents can be employed. Examples include hydrocarbon
solvents such as benzene and toluene, halogenated hydrocarbons, such
a~ chloroform, methylene chloride, dichloroethylene, trichloro-
ethylene, difluoromonochloromethane, and l,l,l-trichloroethane.
Other suitable water-immiscible organic solvents for caffeine
include ethyl acetate and benzyl alcohol. It will be appreciated
that preferred solvents will include those which are effective to
remove caffeine from the extract while removing as small an amount
of non-caffeine coffee solids as practicable and leaving as little
residue of solvent in the ultimate coffee product.
The liquid/liquid extraction is preferably performed while
using as low a solvent to extract ratio as is practicable. The
employment of low solvent to extract ratios permits removal of the
caffeine content from the coffee extract while minimizing the
` amount of non-caffeine solids removed from the extract. Thus,
by controlling the amount of organic solvent contacted with the
coffee extract, the extraction of coffee solids having solvent-to-
water distribution coefficients smaller than caffeine is mini-
mized. Employment of high ratios of solvent to extract results
in the increased removal along with caffeine of coffee solids having
solvent to water distribution coefficients smaller than caffeine.
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When the caffeine-laden solvent is thereafter contacted with
water to partition the caffeine content from the organic solvent,
such coffee solids tend to partition along with the caffeine with
the result that such solids do not remain with the organic sol-
vent for restoration to the coffee extract. A ratio of water-
immiscible organic solvent to coffee extract in the range of from
about 0.3:1 to about 10:1 can be employed. The particular ratio
employed will depend upon the particular solvent selected for the '
extract decaffeination. For example, where the solvent is
10 methylene chloride, a preferred ratio will be from 0.5:1 to 1:1.
The liquid/liquid decaffeination operation can be con-
ducted in a batch or continuous operation, although a continuous
countercurrent liquid/liquid extraction of caffeine will be pre-
ferred. Liquidjliquid extraction techniques are well known and
15 generally involve continuous contacting of extract with the water-
immiscible organic caffeine solvent. The contact can be suitably
conducted in an elongated column. For example, where a solvent
heavier than the aqueous extract is employed, the aqueous extract
can be sprayed into the lower end of an elongated column containing
20 the caffeine solvent. The coffee extract is allowed to travel
upwardly in a manner countercurrent to the solvent and the decaf-
feinated extract is removed continuously from the top of the
decaffeination column. Such a method is described in detail in
U.S. Patent 2,933,395 (issued April 19, 1960 to Adler et al.l.
25 Other methods for effecting the liquid/liquid extraction can be
employed. For example, the coffee extract can be contacted with
the caffeine solvent by passing the extract and the organic
solvent in countercurrent fashion into a packed columnar bed
comprising an elongated tower fitted with Pall rings, Raschig
30 rings or the like.
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Pre~erred apparatus foL conducting the liquid/liquid
decaffeination comprises such liq~lid/liquid contacting devices as
the ~otary-disk Contactor, the"Oldshue-Rushto~' column, or the
"~ork-Scheibel~column. It will be appreciated that the feasibility
of the employment of low ratios of solvent to extract will depend
in part upon the nature of the solvent employed, the concen- ~
tration of the coffee extract, and the efficiency or mass transfer -
capability of the liquid/liquid contacting equipment. Thus, it
will be preferred to employ a liquid/liquid contacting device
which provides the mechanical agitation and turbulence necessary
for maximization of mass transfer. For this reason, a preferred
type of liquid/liquid contactor is the Rotary-disk Contactor.
It has been found that such a device will permit efficient decaf-
feination at low solvent-to-extract ratios, e.g., less than
1:1. The Rotary-disk Contactor and other suitable
liquid/liquid contacting devices are described in detail in
Perry's Chemical Engineers' Handboo~, McGraw-~ill Book Company,
4th Edition, Section 21, pp. 23-35.
The decaffeinated extract is separated from the caffeine-
laden solvent in known manner. Normally the separation will be
the result of continuous removal of countercurrent coffee extract
and solvent streams from the liquid/liquid contactor. The sepa-
rated caffeine-laden solvent is thereafter treated for recovery
of flavor and aroma principles.
The water-immiscible organic caffeine-laden solvent is
treated for separation of the caffeine therefrom. This is accom-
plished by contacting the caffeine-laden solvent with an amount
of water sufficient to remove or partition the caffeine from the
organic phase into the aqueous phase. Substantially complete
removal F partition of caffeine from the organic solvent is
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realized. The amount of water employed will vary with the parti-
cular nature of the solvent. Generally, an amount of water pro-
viding a ratio of water to caffeine-laden solvent of from about
0.5:1 to about 10:1 ~Jill be sufficient to effect the partition-
ing of caffeine into an aqueous phase. A preferred ratio in thecase of methylene chloride solvent is from 5:1 to 6:1.
Preferably, the caffeine-laden solvent will be concentrated prior
to caffeine removal so as to minimize the amount of caffeine-
laden solvent which must be handled and contacted with water for
10 the caffeine removal. In addition, concentration of the
caffeine-laden solvent permits maximization of mass transfer and
reduces capital equipment requirements. Concentration
can be effected by flashing of the organic solvent, hy
the use of conventional thin-film evaporators or the like. For
15 economy of operation, evaporated solvent will be condensed for
re-use in further liquid/liquid decaffeination. The concentrated
caffeine-laden solvent will preferably be concentrated such that
the solids content comprlses from about 1% to about 10% by weight
of the caffeine-laden solvent.
The partitioning of caffeine from the caffeine-laden
solvent can be achieved by any effective contact of water
with the caffeine-laden solvent. The caffeine-laden solvent can
~e introdu ed in a countercurr2nt manncr into a colu~n
containing water. As in the case of the liquid/liquid
25 deca~feination operation, the separation of caffeine from the
caffeine-laden solvent can be facilitated by the use of other
conventional liquid~liquid contacting devices. A preferred
device is a continuous countercurrent extractor such as a Rotary-
disk Contactor. This device permits intimate contact between
30 water and the caffelne-laden solvent and efficient recovery of
aqueous and organic phases.
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The amount of aroma and Llavor principles restored to
the coffee extract will depend upon the amount present in the
organic solvent as the result of the extract decaffeination
operation. It will be appreciated that the advantages achieved
5 by restoration to a coffee extract of such principles will depend
upon the nature of the coffee e~tract and the selectivity of the
caffeine solvent used in the decaffeination operation. For
example, ethyl acetate will remove from a coffee extract, in
addition to caffeine, an appreciable content of aroma and flavor
1~ principles, relative to a more selective solvent such as metllylene
chloride. Accordingly, the benefits of the process of the inven-
tion will be most advantageous and the greatest contribu-
tion realized where relatively non-selective solvents are employed.
The process of the invention, thus, makes more feasible the use
of such solvents for the decaffeination of coffee.
The removal of caffeine from the caffeine-laden
solvent results in the recovery in the solvent of certain flavor -
and aroma principles. These principles, when restored to the
decaffeinated coffee extract, permit the preparation of a decaf-
feinated coffee extract having as much of the aroma and flavor
principles as is practicable. Thus, the extract when dried in a
conventional manner to a soluble or instant coffee product, pro-
vides a product having improved flavor and aroma properties.
While the precise chemical nature of the recovered flavor and
aroma principles is not entirely unAerstoorl, they are com.~rised
of numerous flavorful and aromatic principles resulting from
roasting and extraction or hydrolysis of coffee. The flavor
and aroma principles, although water-soluble, have a greater
affinity than caffeine for the organic solvent as is apparent
from the recover~ of such principles in the organic phase and
recovery of caffeine in the aqueous phase.
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The flavor and aroma principles recov~red by th~
process of the invention are incorporated into the decaffeinated
coffee extract prior to conventional drying thereof. The
production of a soluble coffee powder from a decaffeinated
coffee extract will be preceded by a solvent-stripping
operation whereby residual solvent can be removed from
the coffee extract. The flavor and aroma principles in the
organic solvent can be added to the decaffeinated extract prior
to the removal of residual solvent therefrom. Thus, the decaf-
1'~ feinated aqueous extract and the added solvent with flavor andaroma principles can be treated for simultaneous removal of
solvent. Preferably, the solvent will be stripped from the decaf-
feinated extract by passing the extract over a heated evaporating
surface under reduced pressure or by stripping with steam.
lS Conventional thin-film evaporation devices can be used for this
purpose. Other methods for volatilizing and recovering residual
solvent can, however, be employed.
Ater stripping of residual solvent, con~ensed vola-
tiles from the coffee extract obtained prior to the decaffeination
thereof, if any, can be added to the extract. The resulting
extract is then dried to a soluble coffee powder, e.g., by spray-
drying or freeze-drying, with or without a prior concentration stép.
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The invention is illustrated in the following specific
e~amples which are given by way of example only and not as
limiting the invention. All pcrcen~agcs and ratios expressed in
the specification and clai.-.ls are by weight.
EXAMPI.E I
An aqueous coffee extract having a solubles content
of 20% is prepared by conventional countercurrent extraction of
roast and ground coffee. The coffee extract is subjected to a
devolatilization step by contacting the extract with steam (0.1
lb. of steam/lb. of extract~ in a packed column maintained at a
vacuum of 21 inches of mercury. The steam-stripped volatiles
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are condensed, and the condensate is stored at less than 50F
for subsequent reincorporation into the coffee extract.
The stripped, i.e., devolatilized, coffee extract is
introduced as the dispersed phase into the bottom of a con-
tinuous countercurrent extractor (a Rotary-disk Contactor).
The decaffeination solvent, methylene chloride, is introduced at
the top of the extractor as the continuous phase. A solvent
ratio of 1.0 lb. of solvent/lb. of coffee extract is used at
a-temperature of 9QF, and caffeine removal of 98% is achieved.
The decaffeinated extract containing dissolved and entrained
solvent is withdrawn from the top of the extractor. The decaf-
feination solvent containing caffeine and flavor and aroma
constituents is withdrawn from the bottom of the extractor.
The decaffeination solvent containing caffeine and
flavor and aroma constituents is evaporated to a solids concen-
tration of about 5% by weight. The concentrated solvent is
then introduced as the dispersed phase into the top of a second
continuous countercurrent extractor (another Rotary-disk Contactor)
with water as the continuous phase. A water-to-solvent ratio of
5.0 is used at a temperature of 70F and a caffeine removal
of 99% i5 achieved. The decaffeinated concentrated solvent
stream containing the flavor and aroma constituents is withdrawn
from the bottom of the extractor and added to the decaffeinated
coffee extract. The resulting extract is then desolventized by
steam-stripping in another packed column maintained at a vacuum of
21 inches mercury and using 0.1 lb. of steam/lb. of extract. The
residual solvent level in the decaffeinated coffee extract is
reduced ~o less than 1 ppm on a solids basis. The decaffeinated
coffee extract is then concentrated to 63~ solubles by vacuum
evaporation. The condensate of steam-stripped volatiles is added
to the coffee extract, and the extract is spray-dried to a 97
decaffeinated soluble coffee powder.
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The resulting product is si~nificantly stronger and has
a more flavorful, balanced flavor than would a corresponding
product made without recovery of flavor and aroma constituents
from the caffeine-laden solvcnt and restoration thereof to the
decaffeinated coffee extract.
- EXAM~LE II
An aqueous coffee extract having a solubles content
of 20% is prepared by conventional countercurrent extraction of
roast and ground coffee. The coffee extract is subjected to a
devolatilization step by contacting the extract with steam (0.1
lb. of steam/lb. of extract) in a packed column maintained at a
vacuum of 21 inches of mercury. The steam-stripped volatiles
are condensed, and the condensate is stored at less than 50F
for subsequent reincorporation into the coffee extract.
The stripped, i.e., devolatilized, coffee extract is
introduced as the dispersed phase into the top of a continuous
countercurrent extractor (a Rotary-disk Contactor). The decaf-
feination solvent, ethyl acetate, is introduced at the bottom
of the extractor as the continuous phase. A solvent ratio of
1.3 lbs. of solvent/lb. of coffee extract is used at a tempera-
ture of 140~ F. and caffeine removal of 98% is achieved. The
decaffeinated extract containing dissolved and entrained solvent
is withdrawn from the ~ottom of the extractor. The decaffeination
solvent containi~g caffeine and flavor and aroma constituents is
withdrawn from the top of the extractor.
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The decaffeination solv~nt containing caffeine and
flavor and aroma constituents is evaporated to a solids concen-
tration of about 1.5~ by weight. The concentrated solvent is
then introduced as the dispersed phase into the bottom of a
5 second continuous countercurrent extractor (:another Rotary- :
dis.k Contractorl with water as the continuous phase. A water~
to-solvent ratio.~of ~7 is used at a temperature of 70 F. and
a caffeine removal of ~g% i.s ach.ieved. The decaffeinated con-
centrated solvent stre.am containing the flavor and aroma con~ ;
st~.tuti.ons is. withdrawn from the top of the extractor and added
to th.e.decafeinate.d coffee extract, The resulting extract is
then desolventized ~y steam-stripping in another packed column
maintaine.d at a vacuum of 21 inches mercury and using 0.1 1~.
of steam~lb-~ of extract. The residual solvent level in the
de.caffeinate.d coffee extract is reduced to less than 1 ppm on
a solids ~.asis, The de.caffe~.nated coffee. extract is then con-
centrated to ~3% solu~les ~.y vacuum evaporation, The condensate
of steam-stripped volatiles is added to the coffee extract, and
the extract ~s spray~drl:ed to a g7~ decaffeinated soluble coffee
20. po~der,
Th.e resulti.ng product is significantly stronger and
has a more ~lavorful, ~alanced flavor than ~ould a corresponding
product made without recovery of flavor and aroma constituents
from the caffeine~laden solvent and restoration thereof to the
deca~einated coffee extract,
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