Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Process for restoring virtually caffeine-free coffee bean
extract substances into coffee beans which have been
extracted with an aqueous liquid and have thereby been
decaffe;nated
The decaffeination of coffee beans with water or
an aqueous extract of green coffee has been known for a
long t;me (compare French Patent Spec;f;cation No. 779~451,
published on 5th Apr;l 1935, and U.S~ Patent Spec;ficat;on
No. 2,309,09Z, patented on 26th January 1943). Neverthe-
less, extract;on of the caffein ~;th organic solvents,
;n part;cular methylene chloride has ga;ned acceptance
in recent decades. However~ decaffeination with aqueous
liquids has recently again ach;eved importance because
toxicolog;cal and ecological objections have lately ar;sen
to the use of organic solvents. For this reason, improve-
ments have been made to the process for decaffe;nation
w;th aqueous liqu;ds (compare European Patent A1-O,OOA,398
of Coffex AG, published on 5th March 1980, and European
Patent A1-0,040,712 of Societe des Produits Nestle S.Au~
zn published on Znd December 1981), which relate to the re-
duct;on ;n extract;on losses by ;ncreas;ng the selectiv;ty
of the active charcoal used for adsorpt;on of the caffeine.
~ wo processes for the decaffe;nation of coffee
beans w;th aqueous l;qu;ds have essentially gained accep-
tance, and are briefly described below:
The process of the GeneraL Foods Corporation(U.S. Patent Specification No. 2,309,092) uses as the ex-
traction solution an aqueous extract from green coffee
beans wh;ch is unsaturated in respect of caffeine but
quasi-saturated in respect of the extract substances from
coffee beans other than caffe;ne. Th;s extract ;s
passed over fresh coffee beans, essentially only caffeine
be;ng dissolved out of the coffee beans as a result of
the g;ven sa~urat;on cond;tions. The caffeine can be
removed from the resulting aqueous solution, in which ;t
is enr;ched, w;th the aid of processes which have been
known for a long time, such as by adsorption on active
charcoal or adsorption resins or by liquid/liqu;d extrac-
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tion by means of an organic solvent and the l;ker A dis-
advantage of this process is that the aqueous extraction
solution must be kept continuously at a high temperature,
in particular~ on the one hand, so that it does not cool
per;odically and have to be warrned again to the extra-ction
temperature, and, on the other hand, so that no micro-
organisms can develop~ After the aqueous extraction
solution has been ~sed several times, both color and
fLavor changes thel~eby occur. As a result, the cof~ee
beans decaffeinated with the aid of such solutions wh;ch
have been used several times have certain flavor and
color de~iciencies.
The other process uses pure water for the extrac-
tion of the caffeine. However, besides the caffeine,
other extract substances are also thereby dissolved out
of the coffee beans and must then be restored to the
coffee beans again. This is necessary ;n Sw;tzerland,
merely in view of the Swiss regulations on the treatment
of foodstuffs and commodities, list of permitted solvents
for the decaffeinat;on of coffee of 1st July 1981, para
graph II, line 3. For this purpose, the beans are partly
dried after the extract;on; the extraction solut;on is
decaffeinated ir the abovementioned manner and then con-
centrated, and is subsequently brought together with the
~5 extracted, partly dried coffee beans. However, the
coffee beans are additionally exposed to heat by the
intermed;ate drying, which leads to an impairment in
their flavor. In addition, the extract substances are
enr;ched at the surface of the coffee beans ~hen the
relatively concentrated extract solut;on is adsorbed, and
th;s impedes roasting and also impairs the cup quali~y.
The invention relates to a process for restoring
virtually caffeine-free bean coffee extract substances into
coffee beans which have been extracted with an aqueous
liquid and thereby decaffeinated, which does not have the
disadvantages of the two processes described above but,
because of a technically novel process procedure, combines
their advantages~ In particular, it has been found,
surprisingly, that rediffusion of the extract substances
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into the extracted cofeee beans is possible under quite
specif;c circumstances, even ~ithout predrying of the
beans, as long as the aqueous extract is present in an
excess in relation to the amount which the extracted
beans are capable o~ absorbing. Under these circumstances,
an equilibrium is established in the course of the pro-
cess between the extract substance content of the coffee
beans and the extract substance content of the caffeine-
free extract surrounding the beans. It is thereby possible
almost to re-establish the natural extract content of the`
coffee beans after decaffeination~ and as a result it is
also possible to achieve optimum cup quality by normal
roasting of the treated coffee beans.
The process according to the ;nvention thus com-
prises bringing the swollen extracted beans, without
intermediate drying, directly into contact with an amount
of a concentrated, decaffeinated aqueous coffee extract
which is gre~ter than the amount the extracted beans are
capable of absorbing, whereupon the extract content of the
beans is brought almost to the extract content of non-
extracted coffee beans, virtually ~ithout their caffeine
content being increased, and removing the excess coffee
extract from the coffee beans.
Another surprising fact is that even when the
excess coffee extract is used again in this process, no
reduction in qual;ty of the coffee beans occurs because
the extract substances are continuously renewed by mixing
the excess coffee extract of relatively low extract sub~
stance content with the fresh decaffeinated coffee extract
obtained in the extraction of the subsequent batch of
coffee beans with water. In particular, equilibrium con-
ditions are established between the extract substances
in the fresh decaffeinated coffee extract, the extract
substances in the circulating excess coffee extract and
the extract substances in the decaffeinated coffee beans~
so that the residence time of the extract substances in
the aqueous phase is shortened. This circumstance leads
to an addit;onal improvement in the cup quality in com-
par;son with the previously kno~n processes.
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Another advantage of the process according to the
invention is that an excess of decaffeinated coffee ex-
tract in relation to the amount which can be absorbed by
the extracted coffee beans is always used, so that the
beans in all cases conta;n sufficient extract substances
and fulfill the regulations in this respect in Switzerland
t22X by weight of extract substances)A In the simple
restoration process described above as the second known
process, this is no~ necessarily ensured, because the
losses of extract substances other than caffeine ~hich
unavoidably occur during decaffeination of the aqueous
extraction soiution are not compensated, so that these
extract substances are absent from the treated coffee
beans. Adsorbents which are charged with cof-fee extract
substances other than caffeine or with substitutes of
corresponding molecular structure and size are therefore
used for decaffeination of the aqueous extract in the
process according to European Patent A1-0,~08,398. An
active charcoal charged with sucrose and formic acid is
used in the example of this document. An act;ve charcoal
~hich is pretreated w;th hydrochlor;c acid for the purpose
~f neutral;zation is used ;n the known process accord;ng
to uropean Patent A1-0,040,712. These measures are
unnecessary ;n the present process.
In the process according to the ;nvention, the
excess coffee extract is preferably recycled to the pro-
cess by mix;ng with the fresh decaffe;nated coffee extract
obta;ned during extract;on of the subsequent batch of
coffee beans and concentrating the mixture.
The weight rat;o of extracted coffee beans to
concentrated coffee extract ;s as a rule in the range from
1:1 to 1:10, preferably ;n the range from 1:1 to 1:3,
and is~ in part;cular, about 1:2.
The decaffe;nated coffee extract usually has a dry
35 substance content of 15 to 50X by weight, preferably of 20
to 40% by we;ght, and in particular of about 30% by weight~
It is aLso poss;ble to follow a procedure in
wh;ch the deca-ffeinated cof-fee extract is circulated over
the swollen beans, which have been extracted but not
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inter~ediateLy dried, and through a vacuum evaporator so
that the concentration of the extract increases con-
tinuously, until the desired end value is reached.
The extracted beans and the decaffeinated coffee
extract can be brought into contact with one another at
temperatures of 40 to 90C. At 80 ~5C, the dif-
fus;on equilibrium is established after 3 to 4 hours,
and at 40C this period is correspondingly longer. The
process is preferably carr;ed out under normal pressure,
but pressures of 2 to 3 bar can also be applied~
Example 1
A) 60 kg of raw coffee ~ith a water content of 8X
by weight, a caffeine content of 1.0X by weight and an
extract content of 28% by weight, and 21û liters of pro-
cess water are introduced into an extractor of 250 liters
capacity. The beans are s~ollen at a temperature of 80C
for about 30 ninutes. The extraction solution is then
conveyed, via a pump and a filter~ alternately through
Z0 adsorption columns containing untreated ac~ive charcoal
and through ~he extractor. After 9 hours, the coffee
beans contain only 0.025% by ~eight or less of caffeine and
the aqueous extract contains only 0.010Z by weight or
less of caffeinea The extraction is ended and the de-
caffeinated extract, which has an extract content of 4.5to 5.0% by we;ght (refractometer value 5.5X) is pumped
off from the coffee beans and combined with the excess
extract from a preceding batch t100 liters, refractometer
value 25%).
B) The combined solutions~ includi,ng the water from
the lines, the adsorption columns and the like, are con-
centrated in vacuo to an extract content of about 30X by
weight (refractometer value 35%)~ The solution thus con-
centrated (about 125 liters) is conveyed to an ;nter-
mediate storage vessel, which is d~signed such that pro-
longed storage of the concentrated solut;on is possibleu
100 to 120 liters of this concentrated extract are now
added to the decaffeinated coffee beans, which have not
been intermed;ately dried, and are mixed therewith at
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80C for 4 hours. When diffusîon equ;libr;um has been
reached, the excess extract (100 liters, refractometer
value 25X) is pumped off again and stored in a tank at
70 to 80C for further use. The coffee beans are freed
from the adherin~ extract ~ith a little water and are
dried with hot air in the conventional manner. They have
a water content of 7X by weight, a caffeine content of
0.06X by weight an~ an ex~ract content of 23X by we;ght.
Example 2
A) The procedure followed is as described in Example
1, under A).
8) The combined solutions are brought toge~her with
the water from the lines, the adsorption columns and the
like in a vessel and are mixed throughiy, 420 to 450
l;ters of a solution ~;th an extract content of about
15% by weight (refraction value 12 to 15X) being obtained.
This solution is passed in circulat;on over the decaf-
feinated beans, which have not been intermediately dried,
and through a vacuum evaporator, so that absorption of
the extract substançe by the beans takes place simul-
taneously with concentration of the extractO After about
3 hours~ the beans have uniformly taken up the desired
amount of extract substance and the extract content of
the extract has been increased to about 30X by weight.
The process ;s now ended, and the excess extract (100
liters with a refractometer value of about 25Z) is pumped
off and stored in a tank at 70 to 80C for further use.
The coffee beans are freed from the adhering extract
with a little water and dried with hot air in the conven-
t;onal manner. They have a ~ater content of 7X by
weight, a caffeine content of 0.05% by weight and an ex- -
tract content of Z4Z by weight~
Ins~ead of active charcoal, adsorption resins
which are known per se can also be used in the Examples
with similar results.
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