Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1~9~5(~
I'here has long been a recognized demand for decaffein-
ated vegetablc materia].s, partic~llarly in producing beverages
such as coffee and tea.
In the search for lmproved means for producincJ these de-
caffeinated products, a -technique utllizing a cafEeine solven-t
comprising liquid, water-immiscible fat-ty material has been in-
~ vented. This technique is desc:ribed in detail in copending
-. Canadian patent application Serial No. 239,458, filed November
12, 1975.
This technique involves con-tac-ting a liquid, water- - -
~ immiscible fatty material with thecaffeine-containingvegetable
material, maintaining -the fatty and vege-table materials in con:tact
for a period of time sufficient to transfer caffeine into the fatty
.~ material, and then separating the resultant, caffeine-laden fatty
.`. material from the decaffeinated vegetable material.
.....
This technique has wide application in the decaffeination
art; virtually any form of vegetable material may be used. Thus,
~` for example, an aqueous extract of tea, green or roast coffee beans
may be decaffeinated. Alternatively, solid vegetable materials
... 20 including green or roast coffee beans -- preferably beans which
~ contain a total moisture content of from about 20 -to 60~ by
-.- weight-- may be decafEeinated by direct contact with the liquid,
water-immisci.ble fatty material.
. The composition of the fatty material may also vary. This
;~: .
.- material may be any of the animal, vegetable or synthetic fats,
.: oils, admixtures or fractions thereof which assume liquid form at
. the temperature of contact with the vege-table material. This fatty
material is cus-tomarily composed essentially of esters of fatty
;~ . acids -- primari:Ly triglyceride esters -- and may be utilized in
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either native chemical form or in a form resultant from conven-
tional treatments as are known in the art. Exemplary of these
fatty materials are safflower oil, soy bean oil, corn oil, peanut
oil, coffee oil, triolein, olive oil and lard.
The degree of decaffeination achieved through this
technique may be varied, as desired, by modifying the conditions
of vegetable/fatty material contact. The particular fatty
material, the weight ratio of fatty material to vegetable mater-
ial, the temperature and the ~ime of contact each directly
influence the efficiency of decaffeination.
In the foregoing decaffeination process, the caffeine-
-laden fatty material is ordinarily regenerated. By contacting
~ . .
used and therefore caffeine-laden fatty material with water, its
caffeine content is reduced. The resultant aqueous solution may
then be treated for recovery of caffeine by-product, while the
fatty material is recycled for further use in decaffeination.
Although this aqueous regenerative technique is effec-
tive, it hàs beerl discovered to have certain drawbacks. It often
slows the overall rate of decaffeination. Also, handling and
disposal of the liquid media and recovery of valuable by-product
constituents -- particularly caEfeine -- are tedious and expensive.
Further, some degradation of the fatty material occurs under the
condltions of treatment. All these decomposition products are
not always removed during theregeneraltiion cycle and consequently
their presence may adversely a~fect the process.
This invention relates to the decaffeination of
vegetable material with a recirculating caffeine solvent comprising
a liquid, water-immiscible fatty material.
It is an object of this invention to provide an im-
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proved means for regenerating used fatty material employed in the
decaffeination of vegetable materials. Particularly, it is
desired to extend the useful life of the caffeine solvent without
detriment to the flavor of the vegetahle material being decaffein-
- ated.
Still further objects and advantages of the present
invention are evident from the description which follows.
` In accordance with the present invention, a liquid,
~ water-immiscible fatty material is utilized to extract caffeine
-~ 10 from a vegetable material. After extraction, the caffeine-laden
- fatty material is regenerated for further use by remov;ng the
caffeine by vaporization. In this manner, the fatty material
may be recycled in a continuous manner in an improved process
for the decaffeination of vegetable materials.
A key factor of efficient and economic decaffeination
is utilization of a recirculating caffeine solvent. To be re- -
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s circulatable, used fatty material must be ~reated to reduce its
.:. . .
; caffeine content or its ability to decaffeinate vegetable mater-
. ~... . .
ial soon decreases.
r~` 20 ~ In accordance with this invention, reclrclability is
achieved by providing two distinct and separate treatment zones
; lnvolving the fatty material.~ In the first decaffeination zone, -
the fatty material takes on caffeine from the vegetable material
w;th which it is contacted.~ The resultant, caffeine-laden fatty
material is then transferred to the second, regeneration zone.
There the caffeine is removed by vaporization. After this second
treatment, the fatty material may be returned to the first zone
for further use in decaffeination~
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I'he conditiolls and procedures pert:inent to the de-
caffeination zone are those which have already been described
in the cited, co-pending applications. ~nychanges -therein
pursuant to this invention are either routine modifications or
improved results due to the use of fatty material which has
been subjected to the instant condi-tions of regeneration.
Under ordinary conditions of opera-t:ion, the caffeine
content of fatty material which has been utilized for -the de-
caffeination of vegetable mat'erial may vary widely. At higher
caffeine concentrations, however, its solvent capacity declines.
It ls therefore desirab1y maintained below abou-t 10,000 parts
per million by weight, most perferably from about 2,000 to 5,000
parts per million. Regeneration involves removal of at least
some of thls caffeine from the fatty material. It does no-t,
however, require removal of all caffeine. As long as a content
below about 1,000 ppm, preferably between about 50 to 200 ppm,
of caffeine in the fatty material is obtained, the overall
process proceeds smoothly and efficiently.
In the regeneration zone, vaporization of cafEeine
is ordinarily performed in a continuous fashion after each cyclic
contact of fatty material with vegetable material'. This is not,
however, necessary. Regeneration can, for example, be performed
in batch-wise fashion. Thus a given volume of caffeine-contain-
ing vegetable ma-terial may be collected, regenera-ted and then
returned to the decaffeination zone. In another embodiment,
.~ .
regeneration of only a portion of the caffeine-laden fatty '~
'~ ~ 'material is performed in any given cycle.
Regeneration of the caffeine-laden fatty material may
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be accomplished under a variety of condi-tions. The threshhold
requirements ~or this step are that the temperature and pressure
to which the caffeine-containing fa-tty material is exposed be
adequate for the vaporization o caffeine ~- e.g., abou-t 170C
under atmospheric pressure. Preferably, however, conditions
above the minimum threshhold are utilized to increase the rate of
caffeine volatilization. This increase occurs with higher temp~
eratures and/or lower pressures. Extreme variation, however,
should be avoided.
Regeneration at very low pressures, for example, may
proceed with some loss of efficiency. The mechanical limits of
evacuation are such that minimal absolute pressures may be main-
tained during volatilization only if the rate of caffeine removal
::,
- is decreased. As the temperature of volatilization is increased,
it is the fatty material which may be effected~ These fatty
materials -- particularly where they contain water and/or non-
:: .
~ caffeine vegetable material constituents and other solute impur-
;:
`- ities -- exhibit increasing rates of degradation at elevated
- temperatures. It is therefore desirable to utiliæe conditions of -
vaporization which will minimize this effect, while still permitt-
ing efficient removal of the caffeine.
- Accordingly, although regeneration of the fatty mater-
~.
- ial will occur at from 50 to 450C with corresponding pressures
of 760 mm of Hg or less, it is ordinarily performed at a tempera-
` ture between 150 to 350C and pressures of 100 mm to 0.01 mm o~
Hg. More preferred conditions of volatilization comprise tempera-
tures of 150 to 250 C and pressures of 15 mm to 0.1 mm of Hg.
^ Because the temperature of regeneration is ordinarily
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above that at w~ich decaffeination occurs (usually 0 to 150C,
with 0 to 50C for aqueous extracts of vegetable ma-terials and
30 to 150C for solid vegetable ma-terials being preferred) it
is often desirable to heat ;the caffeine-containing fatty material
prior to its entry into, and cool the fatty material after exit
from, the regeneration zone. These steps may be performed by
.
means -- such as conventional indirect heat exchangers -- well
Xnown in the ar~. They are particularly desirable because they
- avoid the necessity of heating the fatty material in the regener-
ation zone before caffeine vaporization can occur. Also, promp-t
post-regeneration cooling minimizes degradation of the fatty
material.
Another factor which greatly influences the efficiency
; of regeneration is the form of the caffeine-containing fatty
material during treatment. A thin film of the caffeine-contain-
ing fatty material provides for a greatly accelerated rate of
- caffeine removal. Moreover, this acceleration permits reduction
of the period of time during which the fatty material is exposed
to~higher, degradative temperature. It is therefore also a means
for preserving the fatty material.
Ordinarily, film thicknesses of less than about 20 mm,
;~ more preferably less than 3 mm, of the caffeine-containing Eatty
material should be employed during vaporization. Most preferably,
the thickness of caffeine-containing fatty material is less than
1 mm.
Several means for obtaining thin films are available.
,. .
On a commercial scale, for example, falling Eilm and wiped film
` apparatus have been employed to produce such films for different
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applications. Most perferably, however, packed columns are
: utilized. They represent a compact means for forming large
areas of these thin films and a:lso are particularly accessible
to provision and maintenanoe of vaporization temperatures and
pressures.
The period of time of exposure of fatty material to
,, ,
:;~ temperatures and pressures sufficient to effect vaporization in
- part governs the`efficiency of caffeine removal. Under any of
.~
~ the conditions set fort~ above, su~stantial caffein removal from
- 10 the fatty material can be obtained in up to about 1 to 4 hours.
. Within such period, however, some degradation of the fatty
~ material can occur, particularly if the temperature ranges well
-- o
. above 150 C. ~t is therefore desired that a residence time li.e.
:` time of exposure to regenerative vaporization conditions) of
-
.... from about 0.3 to 20 minutes, most preferably 0.5.to 5 minutes
` be utilized. By operating through the conjunctlve use of h.igher ~ ~
~ temperatures, lower pressures, and thinner film thicknesses as ~ :
previously set~forth, essentially lOQ% removal of caffeine from
` the veyetable material can be achie~ed even within these severly
.l 20. shortened residence times.
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It has also been discovered that th.e efficiency of
~- regenera~tion of the caffeine-containing fatty material may be
improved by passage of a carrier or sweep gas over and/or through
th.e fatty material. ~h.ere a carrier gas such as nitrogen or pre-
`.?
. ferably (because it is more read~ly condensible and thus aids in
; maint~ining a low pressure in the regeneration zone) steam is
.' swept rapidly past the.fatty material, the effective rate of
~ removal of caffeine solute into gaseous phase is greatly in-
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creased.
Large amounts of carrier gas may be employed where
regeneration is performed at or near atmospherlc pressure. Where
a vacuum is utilized, however, correspondingly lower amounts of
gas are required for the same effect. The op-timum amount of gas
also depends upon the free space or volume surrounding the fatty
material and which may be occupied by gases volatilized from the
fatty material. Because the function and mechanism of a carrier
gas are well known, the determination of optimum amounts for in-
creasing the rate of caffeine sublimation are readily determin~
able.
Because of the conditions to which they are subject-
ed during this process, the fatty materials undergo some degrada-
tion -- the amount being determined largely by the severity and
time of regenerative vaporization conditions. In particular,
the fatty acid triglycerides of which the fatty materials are
primarily composed undergo hydrolysis, with release of free fatty
acids. Other degradation products which may be produced within
.;
~ the fatty material are a number of oxidation products. These
-~ 20 oxidation products -- particularly aldehydes -- are responsible
for at least some of the off-flavors and rancidity naturally
common to fatty materials.
A high content of these free fatty acids and other
degradation products within the fatty material is ~ndesirable.
Their presence may change the solvent characteristics of the fatty
material and/or contaminate the vegetable material. It has been
discovered, however, that these deleterious impurities are also
removed during vaporization of the caffeine.
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This colncident removal of impurities from the fatty
material during regeneration substantially extends the period
' of time during which the fatty material may be utilized within
~ the decaffeination process. Indeed, exposure to conditions of
', caffeine vaporization so completely purifies the fatty material
~ of undesirable ingredients that, instead of requiring weekly or -,
- frequent exchanges of fresh for used fatty material, virtually
endless use of the fatty material decaffeination solvent is
' possible. Only an occasional addition of fresh fatty material
is desirable; this to replace th,e small fraction of the fatty
,
material which are lost during the process. Thus it merely
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' insures-an essentially constant volume of recirculating fatty
material.
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;- This purification effect has also been discovered
,~- to be desirable as a pre-treatment for fresh fatty material.
'' The fresh caffeine solvent is preferably treated to,regenerative
,i vaporization conditions (even though it contains no 'caffeine)
~ prior to its first instance of contact with caffeine-containing
.d vegetable material. Although this preliminary purification of
~'~' 20 the fatty material may be accomplished in a separate vaporiza-
: . .
',/ tion apparatus, it is most conveniently performed by adding the ,~
fresh replacement of fatty material to the recirculating, used
caffeine-laden solvent -- i.e. it is added at a point in the
cycle after the decaffeination zone but before the regeneration
~ zone. In this manner, the fresh fatty material does not contact
'''~ , vegetable material untll it has been passed at least once through
" the regeneration zone, where it is purified under the conditions
?,` of vaporization.
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Still additional pre-purification of fresh fatty
material may be performed prior to its addition to -the recircu-
lating solvent. Depending upon the source of a fatty material,
it may contain various non-glyceride constituents which would
decompose under the conditions of use in the present process.
Accordingly, the preliminary removal of these constituents pre
vents their introduction to the system and -- particularly where
their decomposition products are not volatile under condi-tions
of vaporization -- avoids their build-up within the solvent
itself.
The separate removal of these non-glyceride con-
stituents from a fatty material may readily he obtained by, for
. -. .
example, contacting the fatty material with an absorbent. Absor-
` bents such as activated charcoal and the like have essentially -
no affinity for the triglyceride content of fatty materials,
.: .
however, they readily remove other compounds, so as to produce
decaffeination solvents of improved stability and purity.
` As described in previously identified United States
application Serial No. 605,717, conjunctive to regenerative
removal of caffeine, it is desirable to eliminate moisture from
the caffeine-containing fatty material. This removal is readily
f,.: acGomplished under the conditions of temperature and pressure
~ for caffeine volatilization ln the regeneration zone.
:~,
In a preferred embodiment, however, the moisture is
separately removed from the caffeine-laden fatty material.
Evaporation of water in the regeneration zone may make low
pressures~difficult to maintain and/or induce turbulence entrain-
ing the fatty material in the vapor. Therefore it is desirable
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to remove at least most of the water from the caEfeine-laden
fatty material by, for example, flash distillation in convention-
al apparatus prior to its e~posure -to caffeine volatilization
conditions.
The regenerated fatty material (ordinarily a~ter
cooling to appropriate temperature) is recirculated to the de-
` caffeination zone for further contact with caffeine-containing
- vegetable material. No additional treatment is required. As
is also described in said application Serial No. 239,458, however,
it is often desirable first to incorporate a small amount of
water in it.
In the decaffeination of solid vegetable material,
higher efficiencies are obtained where the solid contains from
about 20 to 60% by weight of waterO Contact of such a solid
with essentially anhydrous fatty material, however, reduces this
-~- moisture content. Accordingly, where a solid is being decaffein-
ated, it is preferred to incorporate from 0~9 to 1.2~, most
preferably about 1~, by weight of water into the fatty material.
This amount acts to preserve the aqueous content of the solid
vegetable material and preserve optimum decaffeination efficiency.
.
- Removal of caffeine in accordance with the present
invention also permits an improved means for recovery of valuable
amounts of caffeine by-product~ The vapors removed during
regeneration are readily recondensed from gaseous form by chill-
ing in conventional condensers. Thus, in contrast to techniques
whereby, for example, caffeine-containing fatty material is
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regenerated by extraction with water (with the caEfeine and other
solubles being removed to aqueous phase~, no multi-step recovery
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procedure is required. The present invention permits simple
recovery of the materials -- lncluding caffeine -- removed from
the fatty material.
Many variations in the steps or materials comprising
the present process are possible without departing from the scope
of this invention. These variations are largely conventional,
-~ however, and are therefore largely absent from the specification.
In the following examples which are only illustrative of the
present invention, unless otherwise noted percentages are given
on the basis of we1ght.
EXAMPLE 1
Green coffee beans were decaffeinated with coffee
oil in a zone comprising a four-chamber countercurrent extraction
system. Each chamber (or cell) contained 6.8 kilograms of beans
by dry weight, the beans having a moisture content of about 45%
by total weight. The coffee oil passed through the cells was
maintained at 105 C during decaffeination. A total oil to bean
` weight ratio of 10:1 was utilized and extraction was performed
over a total extraction period of 8 hours (2 hours for each cycle).
After each pass o~ the recirculating oil through
the decaffeination zone, the oil was passed consecutively through
- a flash dlstillation zone for removal of water, a heater which
raised its temperature to 180C, a regeneration zone and then a
cooler which returned it to 105C~ Immediately after passage
through the cooler and prior to return to the counter~urrent
extraction zone, 1% of water by weight was injected into th~ oil.
:;
The regeneration zone was composed of a jacketed
packed column 2 meters in height and 15 centimeters in diameter.
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It had an internal volume of approximately 0~033 cubic meters,
93% of which was free volume, the remaining percent being the
volume occupied by pall ring packing material.
The packed column WclS mainta ned at a jacket temper-
ature of 210 C and a pressure of 2.2 mm of Hg. As the oil was
monitored into the top of the column, 18 grams of steam per
kilogram of oil was injected into the bottom of the column.
The injected steam and vapors emitted from the oil passed through
an exit valve at the top of the column and were condensed in
a collection chamber maintained at 30C. The calculated film
thickness and residence time for the oil within the packed
column were 0.2 mm and 1.58 minutesO In the regeneràtion zone,
the caffeine content of the fatty material was reduced from
3,400 ppm to about 170 ppm. Thus the efficiency of regeneration
of the caffeine containing fatty material was about 95~. This
resulted in an overall efficiency in removal of caffeine from
-
the green beans of 97%.
The vapors condensed in the collection chamber were
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- analyzed. They consisted primarily of caffeine, water and a
mixture of fatty acids.
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EXAMPLE 2
Caffeine-containing coffee oil removed from the
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extraction system of Example 1 was subjected t~ sublimàtion
conditions in a wiped film evaporator. The evaporator consisted
of a glass evaporator tube 5 cm in diameter having a wiped
surface area of about 320 square centimeters. Four teflon blades
; rotated within the tube at high speed, maintaining an oil film
" thickness between 1 to 2 mm.
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The evaporator column and feed flask were heated
electrically to maintian the oil at the same temperature. A
condenser inside the evaporator tube was maintained at about
; 50C to condense the caffeine vapors removed from the oil. A
mechanical pump with condenser units was used to obtain lower
than atmospheric pressures.
A series of regeneration runs utilizing the wiped
film evaporator was performed with an oil feed rate of about
3.2 ml/min. The resultsof these runs -- for a single pass of the
oil through the column showed that regeneration at atmospheric
pressure required a temperature of about 260C in order to achieve
a 75% efficiency of regeneration. As the pressure in the column
'::
was reduced to 1 mm, 500 micron and 100 micron of Hg, the temper-
- atures required for this efficiency were reduced, respectively,
to about 190, 150 and 90C~
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EXAMPLE 3
Corn oil which had been utilized for the decaffeina-
tion of aqueous extract of roast coffee was utilized in a series
of runs to determine the effect of film thickness on the efficien-
cy of regeneration. The films of corn oil -- which contained
about lQ0 ppm caffeine -- were heated to predetermined vaporiza-
tion temperatures at atmospheric pressure. Nitrogen sweep gas
was continuously passed into and over the surfaces of the film
to remove caffeine vapors.
The conditions and results of the runs were as
follows:
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FILM PERCENT
THICKNESS RESIDENCE TIME, TEMPERATURE DECAFFINATION
17 mm 60 min. 190C 11%
3 mm 60 min. 190C 54
1 mm 40 min. 190C 77~
` 1 mm 15 min. 205C 86%
1 mm 30 min. 205C 86%
1 mm 60 min. 205C 100~
These results show the dramatic increase in efficien-
-- 10 cy of caffeine vaporization achieved with thinner film thick-
nesses.
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