Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~J
Case 3286
DESCRIPTION
ROASTED COFFEE EXTRACT
DECAFFEINATION METHOD
TECHNICAL FIELD
05
The present invention relates to a roasted
coffee extract decaffeination method providing a
soluble coffee of improved flavor. A roasted coffee
extract is contacted with a caffeine solvent. The
separated caffeine-containing solvent is contacted
with an aqueous suspension of caffeic acid so that
caffeic a~id/caffeine complex crystals grow in the
water phase. The then decaffeinated caffeine solvent
containing non-caffeine solubles is separated and
added to the decaffeinated roasted coffee extract.
Residual solvent is stripped therefrom and the
extract is dried.
BACKGRQUND A~T
One of the more widely practiced decaffeination
methods is the process disclosed by Berry et al. in
U.S. Pat. No. 2,309,092, ~he so-called water decaf-
feination technique. Green coffee beans are first
moistened and then extracted with a caffeine-deficient
green coffee extract in a multi-stage countercurrent
extraction battery. ~hile progressing through the
extraction battery, the green coffee extract becomes
increasingly rich in caffeine and contacts decreas-
ingly decaffeinated beans. Periodically, the stage
3~ 37
- 2 -
containing the most highly decaffeinated coffee is
isolated from the battery and a stage containing
fresh green beans is placed on stream. Caffeine-laden
coffee extract is withdrawn from the last stage of
05 the extraction battery, processed so as to remove
the caffeine therefrom and returned to the system as
caffeine-deficient green coffee extract. The caffeine
is removed from the caffeine-laden extract by contact
with an organic solvent, most preferably a halogenated
hydrocarbon solvent, such as trichloroethylene or
methylene chloride. The water decaffeination tech-
nique, although it currently has wide application in
the industry, is directed only to the decaffeination
of green coffee beans and is not suited to the more
efficient decaffeination of roasted coffee extracts.
While techniques are known for decaffeinating
roasted coffee extracts, the methods are not without
certain drawbacks. For example, Belgian Patent
Disclosure 865,488 of Bolt et al. describes a process
wherein the coffee extract is first decaffeinated
with a solvent; the solvent is then contacted with
water to transfer the caffeine and unavoidably, some
non-caffeine solubles; the decaffeinated solvent is
returned to the cof~ee extract and stripped therefrom;
and the caffeine is crystallized from the water
phase, which is then discarded. The water phase
inevitably contains some non-caffeine solubles which
would contribute importan-t body notes to the soluble
coffee but are instead discarded. A similar though
supposedly improved method is disclosed in U.S. Pat.
No. 4,409,253 to Morrison et al. The improvement
consists of recyclying the water phase from which
the caffeine has been crystallized back to the
original caffeine-containing extract. The water
phase apparently cannot be combined with the decaf-
~ ~ S3 ~ ~ ~
feinated extract because the crystallization leaves
substantial caffeine in the water. Hence, the
inefficient recycle oE the water phase, with the
accompanying increase in the amount of caffeine to
be removed, is needed.
A complexation approach to the decaffeination
of roasted coffee extracts is also known. Caffeic
acid is suspended in the roasted coffee extract or
the caFfeic acid may be dissolved in water and the
solution added to the extract. An insolublel colloidal
caffeic acid/caffeine complex forms almost instantane-
ously, but it is virtually impossible to separate
the colloidal complex from the coffee extract.
Larger crystals of the complex which are more easily
separable will grow on standing but the growth is
quite slow, taking upwards of two weeks. Manipula-
tion of the extract p~ or temperature promotes more
rapid crystal growth but ~he process is not as fast
as is commercially desirable. The chief advantage
of the complexation approach is that essentially
only the caffeine is removed and virtual]y all of
the non-cafeine coffee solubles initially present
remain in the decaffeinated roasted coffee extract.
iL253737
DISCLOSURE OF THE INVENTION
~:v
In accordance with one particular aspect oE ~he
present invention, there is provided a roasted cofEee
extract decaf~eination method which involves first
contacting the extract and a caffeine solvent so that
caffeine and a lesser proportion of non-caffeine
solubles are transferred to the solvent. After
separation the then cafEeine-containing solvent is
concentrated and contacted with an aqueous suspension of
caffeic acid so that caffeic acid/caffeine complex
crystals form in the water phase. The complex crystals
are filtered out and the solvent and water phases are
separated~ The caffeine solvent may be further
decaffeinated by a second contact with an aqueous
caf~eic acid suspension. The decaffeinated caffeine
solvent containing some non caffeine solubles is
ultimately added to the decaffeinated coffee extract and
the residual solvent is stripped therefrom. The water
phase may also be added to the decaffeinated coffee
extract which is then dried into a soluble coffee of
improved flavor.
Roasted coffee extracts are decaffeinated by the
method of the present invention. Suitable roasted co~fee
extracts include extracts derived from commercial coffee
extraction systems such as those wherein roasted and ground
coffee is extracted with water in a multi-stage
countercurrent extraction battery. Water at a temperature
in excess of about 175C is typically fed to the stage
containing the most spent coffee so as to hydrolyze the
same. As the water progresses through the extraction
battery, it becomes increasingly rich in coffee solids, so
as to form the roasted coffee extract, while contacting
increasingly fresher (less extracted) coffee. The
freshest coffee is contacted with the extract in the
~2 537 3~'
- 5 -
first stage and the roasted coffee extract is with-
drawn therefrom. Periodically, after a previousl~
determined cycle time, the stage containing the most
extracted coffee is isolated, a new stage containing
05 fresh roasted and ground coffee is added to the
bat-tery and the flow is adjusted to conform to the
above description. The stage of fresh coffee may be
contacted with steam prior to being placed on stream
so as to recover some of the more volatile flavor
and aroma compounds. The roasted cofee extract so
produced, which in any event contains much of the
flavor-and aroma of the starting roasted and ground
coffee, typically contains between about 10% and 50%
b~ weight total coffee solids and up to about 5% by
weight caffeine.
Inasmuch as the roasted coffee extract does in
most cases contain much of the flavor and aroma of
the roasted and ground coffee, it ma~ be preferable
to strip the roasted coffee extract before the
contact with the caffeine solvent. Conventional
stripping techniques as are known in the art are
particularly suitable. The roasted coffee extract
may be stripped with steam and the steam condensed
as a flavor and aroma condensate for subsequent
addition to the decaffeinated co~ee extract.
Alternatively, the roasted coffee extract can be
vacuum evaporated and the evaporate condensed as the
flavor and aroma condensate. ~hile such flavor and
aroma recovery techniques are useful for the recovery
of the volatile flavor and aroma compounds, said
techniques are not useful for recovering the non-
volatile body notes which contribute to the overall
desirable flavor of the roasted coffee extracts.
Some of these body notes do tend to be transferred
to the caffeine solvents and are lost in those prior
3 7 37
- 6 --
art processes in which no provision is made for
their recovery. The soluble cof~ees produced by
such prior art processes are typically characterized
as thin and lacking in body.
05 Whether or not the roasted coffee extract is
first stripped of the volatile flavor and aroma
compounds, the extract is contacted with a ca~feine
solvent. Suitable caffeine solvents are those
having relatively low miscibility with water, moderate
to high solubilities for caffeine and relatively
lower solubi.lities for caffeic acid. Preferred
caffeine solvents are also relatively specific for
caffeine. That is, the solubility of caffeine in
the solvent is appreciably higher than the solubility
of non-caffeine solubles. Specific useful caffeine
solvents include the halogenated hydrocarbon solvents
such as trichloroethylene. Me-thylene chloride is a
particularly preferred caffeine solvent as it is
generally water-immisible, has a fairly good solubility
for caffeine and is relatively specific. Methylene
chloride is approved for use in decaffeinating
coffee and has a long history of such use in the
art. Moreover, methylene chloride is relatively
inexpensive and readil~ available.
Contact of the roasted coffee extract and
caffeine solvent may be carried out by any method
and in any apparatus pro~iding good liquid-liquid
contact. For e~ample, the two liquids can be contacted
in an agitated batch tank and subsequently separated.
Alternatively, a continuous operation may be used.
A rotating disc contactor column is one suitable
example. A reciprocating plate column, such as a
Karr column, is another e~ample. In either such
column, the denser of the two liquids enters the top
of the column, passes therethrough and is removed at
~53'~q
- 7 -
the bottom of the column. The less dense liquid is
fed to the bottom of the column, rises therethrough
and is removed at the top of the columrl. The liquid
from which something is to be extracted, i.e. the
05 roasted coffee extract, is typically maintained as
the dispersed phase in the continuous extracting
phase. A distinct separation step is not necessary
as the continuous operations provide for the separ
ation after contact of the two liquids. It may be
desirable to treat the exiting streams 5 such as by
centrifuging, in order to remove entrained caffeine
solvent from the extract and entrained extract from
the caffeine solvent.
One of the more important parameters of the
contact of the roasted coffee extract and caffeine
solvent is the weight ratio of solvent to extract.
The most preferred ratio in a given instance depends
on -the desired degree of decaffeination as well as
the concentration of the roasted coffee extract. It
has been found though that a range for the weight
ratio between 3:1 and 10:1 caffeine solvent to
roasted coffee extract is sufficient for a roasted
coffee e~tract having between 10% and 50% by weight
coffee solids and up to 5% by weigh~ caffeine.
weight ratio from the above range provides a degree
o~ decaffeination of from less than 50% to better
than 97% of the caffeine initially present for a
roasted coffee extract within the specified concen-
tration range. The temperature of the contact is
not especially important and does not affect the
preferred weight ratio of solvent to extract. It is
preferable though to maintain a temperature below
the boiling points of the two liquids.
After contact with and separation from the
roasted coffee extract, the caffeine solvent contains
5 37 3
- 8 -
anywhere from about 0.1% to 1.0% by weight caf~eine
and a lesser proportion of non-caffeine solubles.
It is, of course, an object as the invention to
remove the caffeine from the caffeine solvent by
05 complexation with caffeic acid. In order to do so
efficiently, it has been found that the initial
concentraction of caffeine in the solvent must be
above a certain level, depending on the desired
degree of decaffeination. For example, in the case
of methylene chloride) it has been discovered that
an initial caffeine concentration in the solvent of
about 2% by weight is needed to achieve a 75% by
weight degree of decaffeination. An initial caffeine
concentration of at least about 4% by weight has
been found to be necessary to achieve a 90% by
weight degree of decaffeination of the caffeine
solvent. Increasing the concentration much above ~/O
by weight does not provide a significantly higher
degree of decaffeination, with an initial caffeine
concentration of about 6% by weight giving only
about a 93% by weight degree of decaffeination. The
concentration step of the caffeine-containing caffeine
solvent may be by the techniques known in the art
such as vacuum evaporation, thin film evaporation,
and like methods.
Once the caffeine-containing caffeine solvent
has been evaporated to the desired caffeine concen-
tration, the caffeine solvent is contacted with an
aqueous suspension of caffeic acid so as to form an
insoluble caffeic acid/caffeine complex in the water
phase, thus decaffeinating the solvent. Caffeic
acid is a yellow crystalline material which begins
to soften at about 195C. It is only sparingly
soluble in water at less than about 25C and freely
soluble in alcohol across a wide range of temper-
atures. The crystalline caffeic acid/caffeine
7 ~7
complex that forms when caffeine and caffeic acid
are brought together in the presence of water is
also insolubl.e in water over a wide range of temper-
atures. Although the existence of the caffeic
05 acid/caffeine complex had been reported in the
literature (in, for example, I. Horman and ~. Viani,
"The Nature and Conformation of the Caffeine-Chloro-
genate Complex of Coffee", J. Food Sci. 37 (1972)
925-27), ~he complex has apparently not been reported
to be insoluble in water. In addition, it was
surprisingly found that the complex will not typically
form in the caffeine solvent alone but will form if
there is at least some water present. It has further
been found that the complex is insoluble in water
and immediately precipitates therefrom. Most conven-
iently, it is only the caffeic acid/caffeine complex
that precipitates, so that essentially no non caffeine
solubles are lost.
The important parameters for the contact of the
caffeine solvent and aqueous caffeic acid suspension
are the mole ratio of caffeic acid in suspension to
caffeine in the solvent and the volume ratio of
aqueous suspension to solvent. If the operation
were perfectly efficient, the mole ratio would
preferably be 1 0:1 moles caffeic acid to caffeine
so that every mole of caffeine in the solvent would
complex with all the caffeic acid, leaving the
caffeine solvent and water phases free of caffeic
acid and caffeine. Perfect efficiency is impossible
and so, it is preferable that the mole ratio be
anywhere from 1.0:1 to 2:1 caffeic acid to caffeine.
~It is possible to use a mole ratio higher than 2:1
but there is no particular advantage in doing so.
The volume ratio of aqueous suspension to caffeine
solvent is also related to efficiency. It is desir-
~ ~ 3 7 ~ ,
- 10 -
able to minimiæe the volume ratio so as to minimi~e
the volumes handled b~t at the same time, the volume
ratio must be sufficiently large to permit efective
contact. Althou~h any volume ratio upwards o~ 0.5:1
05 aqueous suspension to caffeine solvent is useful,
the most preferred volume ratio is between l.0:1 and
2.0:1 aqueous suspension to caffeine solvent.
Contact of the aqueous caffeic acid suspension
and caffeine solvent may be by any manner providing
good liquid-liquid contact but is most preferably
batch. The concentrated caffeine solvent is placed
in the batch tank and the aqueous suspension is then
added thereto. If the aqueous suspension is more
dense than the caffeine solvent, the suspension will
settle to the bottom of the tank and the insoluble
complex crystals will settle to the bottom of the
aqueous layer. If the aqueous suspension is less
dense than the caffeine solvent~ the aqueous suspen-
sion will remain on top and the complex crystals
will tend to settle at the interface of the aqueous
suspension and caffeine solvent. The tank contents
are maintained undèr moderate agitation until equi-
librium is reached, typically in under one hour at
ambient temperature.
When the aqueous caf~eic acid suspension and
caffeine solvent have been contacted for a sufficient
period of time, the caffeic acid/caffeine complex
crystals are removed and the two liquids are separ-
ated. The preferred method of removing the complex
crystals is by filtration, although any of the ~nown
solid-liquid separation techniques are generally
~acceptable. In the case of batch contact, the
contents of the batch tank are simply drained and
passed through a filter. The complex crystals
3~ recovered in the filter may be processed further to
~ ~3'7~ 7
,
- 11 -
recover the caffeic acid and caffeine. It is prefer-
able to rinse the crystals in a small portion of
fresh caffeine solvent so as to remove adhering
non-caffeine solubles. The solvent rinse may be
05 held for subsequent combination with the decaffein-
ated caffeine solvent. The complex crystals may
then be refluxed in fresh caffeine solvent which has
the effect of slowly breaking the complex so that
caffeine dissolves in the solvent and solid caffeic
acid remains behind. This may be carried out at the
boiling point of the caffeine solvent or at ambient
temperature under a reduced pressure. The caffeine
is then easily crystallized from the caffeine solvent
by techniques well known in the art.
The aqueous suspension and decaffeinated caffeine
solvent from which the complex crystals have been
removed are then separated into a solvent and water
phase. The phases will separate of themselves on
standing but the process is relatively slow and
inefficient. Preferably, the liquids are passed
through a centrifuge designed to separate a denser
liquid from a less dense liquid, such as are well
known in the art. After separation, the water phase
contains a small portion of non-caffeine solubles.
The caffeine solvent contains some non-caffeine
solubles and perhaps some caffeine, depending on the
degree of decaffeination achieved in the contact
with the aqueous caffeic acid suspension.
Inasmuch as the maximllm degree of decaffeination
in a single batch stage (without concurrent evapora-
tion of the caffeine solvent) has been found to be
about 93% by weight of the caffeine initiall~ present,
it may be preferable to re-contact the caffeine
solvent with a second aqueous suspension so that in
excess of 97% by weight decaffeination is achieved.
- 5~.2 S37 37
- 12 -
The procedure for the re-contact is the same as for
the initial contact. The caffeine solvent is further
evaporate~ so that the ca~feine concentration is
preferably 4% by weight or greater. An aqu~ous
05 caffeic acid suspension is prepared, preferably
using the water recovered after the initial contact.
The remainder of the processing is as hereinabove set
forth. ~y contacting the caffeine solvent in a
second batch stage, decaffeination in excess of the
commercially desirable 97% by weight is possible.
Alternatively, it is possible to reach or
exceed 97% by weight decaffeination in a single
stage if there is also concurrent evaporation of
some of the caffeine solvent. As hereinabove
described, the degree of decaffeination is related
to caffeine concentration in the caffeine solvent.
If there is some concurrent evaporation of the
caffeine solvent duuring the batch contact, the
caffeine concentration is maintained sufficiently
high to obtain the desired degree of decaffeination.
Typically, anywhere from about 50% to 75% of the
initial volume of the caffeine solvent is concurrently
evaporated. Such evaporation is easily carried out
~y maintaining the con~ents of the batch tank at or
near the boiling point of the caffeine solvent,
which boiling point is typically much lower than
that of water. The evolving caffeine solvent vapor
is conveniently condensed and recycled.
After one or two contacts with the aqueous
caffeic acid suspension, the decaffeinated caffeine
solvent containing a portion of non-caffeine solubles
~is added to the decaffeinated coffee extract so as
to recover important body notes. The caffeine
solvent has been considerably reduced in volume by
the previous evaporation needed to reach the desired
~2 5 3~ 37
- 13 -
initial caffeine concentration in the solvent. The
reduced volume of caffeine solvent makes it easier
to combine the generally immisible solvent in the
extract so as to transfer the body notes back to the
05 extract. Combinin~ the solvent with the extract is
also made easier by the fact that, depending on the
particular caffeine solvent, a small amount of
solvent will actwally be soluble in the extract.
After sufficient mixing, the caffeine solvent is
stripped from the extract and retained for recycling.
Such stripping may be carried out by passing steam
throug~ the extract and other known solvent stripping
techniques. It has been found that the non-caffeine
solubles, particularly those solubles contributing
the body notes, are not stripped along with the
caffeine solvent.
The water used in the aqueous caffeic acid
suspension also has a small portion of non-caffeine
solubles transferred to it upon contact with the
caffeine solvent. While it i5 not as important to
recover these non-caffeine solubles, their return to
the decaffeinated coffee extract does contribute to
an improved soluble coffee. After removal of the
complex crystals and separation from the decaffeinated
caffeine solvent then, the water used in the aqueous
caffeic acid suspension can be added to the decaffein-
ated coffee extract. As the concentration of non-
caffeine solubles in the water is typically quite
low, it is preferable to evaporate some and even
most of the water prior to the addition to the
decaffeinated coffee extract. If the water is not
evaporated prior to the combination with the coffee
extract, then the extract can simply be concentrated
prior to drying the extract into a soluble coffee.
Alternatively, the wa-ter may be recycled to the
method to make up a fresh aqueous caffeic acid
3~ 37
- 14 -
suspension. Under such a scheme, the water eventually
becomes saturated with non-caffeine solubles and
will not then absorb additional non-caffeine solubles
upon contact with caffeine-containing caffeine
oS solvent.
The decaffeinated coffee extract that has had
the decaffeinated caffeine solvent mixed therewith
and stripped therefrom and to which the non-caffeine
solubles-containing water has or has not optionally
been added may be dried into a soluble coffee. It
is preferable to enrich the flavor and aroma of the
decaffèinated extract with some of the more volatile
flavor and aroma compounds prior to drying the
extract. This is particularly true for those embodi-
ments wherein the volatile flavor and aroma compoundsare stripped from the coffee extract prior to decaf-
feination. As hereinabove described, such flavor
and aroma compounds are generally recovered as
liquid condensates. Such condensates are then added
to the decaffeinated roasted coffee extract shortly
before drying the same. ~rying of the decaffeinated
extract is carried out by known techniques, preferably
spray drying or freeze drying. The soluble coffees
so produced are characteri~ed as having more body
notes then decaffeinated soluble coffees produced by
known methods.
The following example is lntended to illustrate
certain embodiments of the present invention. The
example is not meant to limit the invention beyond
what is claimed below.
EXAMPLE
1. A roasted coffee extract, containing about
15% by weight total solids and 0.6% by weight caffeine,
was obtained from a countercurrent multi-stage extrac-
7 37
- 15 -
tion battery having 6 stages and a feedwater temper-
ature of about 180C.
2. The roasted coffee extract was concentrated
in a Centritherm evaporator to a concentration of
05 about 55% by weight solids to strip the aroma and
flavor therefrom.
3. The stripped roasted coffee extract was
then diluted to a concentration of about 25% by
weight total solids and about 1% by weight caffeine.
4. The roasted coffee extract was contacted
with methylene chloride in a Karr column at ambient
temperature. The weight ratio was 4.5:1 methylene
chloride to roasted coffee extract. The degree of
decaffeination was in excess of 97% by weight of the
caffeine initially present. The methylene chloride
withdrawn from the Karr column contained about 0.25%
by weight total solubles. The caffeine concentration
was 0.17% by weight with the remainder of the 0.25%
being non-caffeine solubles.
5. The methylene chloride was concentrated in
a still to 10.5% by weight total solids and 7.0% by
weight caffeine.
6. A 250 cc sample of the methylene chloride
was contacted in a beaker with 500 cc of an aqueous
caffeic acid suspension containing 23 g of caffeic
acid. Contact was at ambient temperature for about
30 minutes under moderate agitation. Crystals were
; seen to grow at the interface between the water and
the methylene chloride.
7. The crystals were then filtered from the
liquids using a coarse filter paper. The methylene
~chloride and water phases were allowed to separate
on standing and the water was decanted off. The
crystals ~ere analyzed and found to be an equimolar
complex of caffeic acid and caffeine. The methylene
~2 S3~ 3
- 16 -
chloride was analyzed and it was found that about
90% by weight of the caffeine initially present had
been remo~ed.
8. The water phase recovered above was washed
05 with two 50 cc volumes of fresh methylene chloride
to recover some non-caffeine solubles. This methylene
chloride washing step is a third and additional
alternative for dealing with the water used in the
aqueows suspension.
9. The two 50 cc volumes of methylene chloride
were combined with the solvent from above and the
solvent was vacuum distilled at 32C to 35C to a
volume of 110 cc.
10. The concentrated 110 cc sample of methylene
chloride was contacted in a beaker with 110 cc of an
aqueous caffeic acid suspension containing 5 g o
caffeic acid. A portion o~ the water from Step 8
was used to make the aqueous suspension. Contact
was again at ambient temperature for about 30 minutes
under moderate agitation. Crystals were again seen
to grow at the interface between the water and
methylene chloride.
11. The components were again separated as in
Step 7. An additional 70% by weight of the caffeine
present in the methylene chloride was found to have
been removed. In total about 97% by weight of the
caffeine initially present was removed by the two
stage decaffeination.
12. The methylene chloride from Step 11 was
added to the decaffeinated roasted coffee extract of
Step 4. The methylene chloride was then stripped
~therefrom by vacuum distillation at a temperature of
about 65C and at an absolute pressure of about 0.5
atm.
~2 S37 3
- 17 -
13. The water from Steps 8 and 11 was then
added to the extract of Step 12 and the extract was
diluted to normal cup strength, about 1% by weight
total solids.
05 14. A control sample of roasted coffee extract
which had been decaffeinated with methylene chloride
under the same conditions was prepared but the
methylene chloride was not then decaffeinated nor
added back. The control sample was also diluted to
about 1% by weight total solids.
15. The extract from Step 13 and the control
samples were tasted by an expert panel. The extract
of Step 13 was judged to have more body notes than
the noticably thinner control sample.
