Note: Descriptions are shown in the official language in which they were submitted.
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IMPROVED METHOD FOR
AROMATIZING SOLUBLE COFFEE
TECHNI CAL F I ELD
The invention relates to a method for aromatizing
soluble coffee and more particularly to a method for
producing an improved aromatized glyceride for use
in the aromatization of soluble coffee.
BACKGROUND ART
. .
Grinder gas, that is the gas which is released
from roasted whole coffee beans when their internal
cell structure is disrupted, such as during grinding
of the beans and which also continues to be evolved
from the disrupted and/or fractured beans for a
short period thereafter, has long been recognized in
2~ the art as a highly desirable natural coffee aroma.
The coilection and stabilization of this aroma
has, however, proven -to be a difficult undertaking,
especially when it is desired for use in a commercial-
sized soluble coffee system.
The use of grinder gas as a means -to enhance
the jar aroma of a soluble coffee powder is disclosed
in U.S. Patent No. 3,021,218 to Clinton et al. which
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f ~
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aromatiæes the jar headspace and U.S. Patent No. 2,306,061
to Johnston which condenses grinder gas aromatics
onto chilled soluble coffee powder. The use of
grinder gas condensates which are added to a liquid
05 extract and dried in order to produce an improved
cup aroma when the powder is dissolved in hot water
is disclosed in U.S. Patent No. 3,244,533 to Clinton
et al. which homogenizes coffee oil in extract and
then adds condensed grinder gas aromatics. Condensed
grinder gas frost can be mixed with a liquid glyceride
which mixture is then processed to remove excess
water, such as by centrifugation, prior to being
combined with soluble coffee solids ~e.g., soluble
powder).
The addition of the condensed aromatics to a
glyceride carrier is a known method for stabilizing
the aromatics. Such glycerides as coffee oil,
bland-tasting vegetables oils and triacetin have
proven especially useful for this purpose; however,
other oils and low melting point fats may also be
used. U.S. Patent No. 4,119,736 to Howland et al.
discloses-removal of a water phase from a pressure
vessel containing condensed grinder gas at a pressure
of in excess of 506~2 psia and a temperature of
greater than 32F, contacting the demoisturized
grinder gas with a glyceride, and slowly venting
the pressure vessel. Mahlmann in U.S. Patent No.
3,979,528 discloses a method for aromatizing a
glyceride by contacting it with a grinder gas frost
in a pressure vessel at various conditions. Among
the conditions disclosed by Mahlmann is a rapid
pressure release of the pressure vessel to atmos-
pheric pressure at a tempera-ture below room temper
ature.
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It has, however, be~n desired to maximize the
amount of aromatics that are fixed in the glyceride
carrier so as to minimize aroma loss and reduce the
amount of glyceride which would be incorporated with
05 a soluble coffee product so as to obtain a desired
level of aromatization. Moreover, it is desirable to
increase the quantity of aromatics generally but
especially the aromatics having or imparting a
"lighter", "high impact", "groundsy", "buttery",
"less sulfury" character to the soluble coffee.
SUMMARY OF THE INVENTION
According to the invention there is prQvided a
much improved method for aromatizing soluble coffee
powder with a glyceride aromatized by contact with a
grinder gas frost concentrate, comprising the steps
of:
(a) condensing, as a frost, grinder gas
which has a high carbon dioxide content;
(b) placing the grinder gas frost in a
pressure vessel;
(c) supplying heat to the contents of the
vessel and allowing the frost to equilibrate at
a pressure in excess of 750 psi, thereby forming
2s three phases, a water phase, a liquid carbon
dioxide phase and a gaseous carbon dioxide
phase;
(d~ draining the water phase from the
vessel;
(e) venting quickly the gaseous carbon
dioxide phase from the vessel until a pressure
of about 300 psi to about 375 psi is reached,
then resealing the vessel;
(f) introducing a glyceride into the
vessel;
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(g) supplying heat to the vessel and
pressuri2ing the vessel;
(h) slowly venting the vessel;
(i3 obtaining an aromatized glyceride; and
05 (j) combining the aromatized glyceride
with soluble coffee powder.
The soluble coffee product is found to have a
higher quantity of aromatics generally and especially
aromatics having or imparting a "light~r", "high
lo impact", "groundsy", "buttery", "less sulfury"
character to the soluble coffee.
DETAILED DESCRIPTION OF THE INVENTION
.. . . . _ _
The present invention is directed to combining
with coffee solids an aromatized glyceride contain-
ing grinder gas aromatics which have been concen~
trated and condensed from a grinder gas frost. This
invention is particularly described in terms of
coffee grinder gas, which contains 80% to 90% by
weight carbon dioxide; however, it is to be under-
stood that other aroma~beaxing gases which have a
high carbon dioxide content such as coffee percolator
vent gas and coffee roaster gas, may likewise be
employed and are considered to be within th~ scope
of this invention-
The most readily available source of grindergas may be obtained by enclosing or hooding coffee
grinding equipment, such as commercial grinders.
The gases liberated from the ground coffee may be
removed by a pump or rotary blower; additionally,
when desired, a stream of inert, preferably moisture
free, gas may be used to sweep gas from the coffee
and to have the yrinding operation take place in a
substan-tially inert atmosp~ere. Such a process is
described in U.S~ Patent No. 2,156,212 which describes
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a me~hod of collecting gases evolved during roastlng,
but which can be equally applied to the collection
of gase6 evolved during the grinding or cellular
disruption o whole freshly roasted coffee beans.
05 If pumpiny is employed, it may be deslrable to cool
the gas ahead of the pump so that the heat added by
pumping will not deteriorate the aromatics contained
in the gas.
The chemical composition of the evolved gas is
lo largely carbon dioxide together with water vapor and
the characteristic aromatic constituents of roasted
coffee. The amount of moisture in the gas may be
lowered by ~he use of dry roasting conditio~s and
low-moisture quenches or quenching mediums. The
evolved gas is preferably passed through a first
condenser where it is cooled to between 35 and 50F
and where substantial quantities of water are removed.
The relatively low-moisture gas is then fed to a
condenser, such as a jacketed, vertically-mounted,
scraped-wall heat exchanger, which is cooled by
means of a liquid gas refrigerant.
Preferably the condenser is cooled by means of
liquid nitrogen and the gas flow into the exchange
is maintairled within the range of about 1 to 5 cubic
feet per minute per square foot of heat exchanger
surface. The nitrogen gas that evolves from the
cooling system is useful as an inert gas stream
which might be used elsewhere in the soluble coffee
process, such as sweeping grinder gas from the
grinder or inert gas packaging of the soluble coffee
product.
The aroma bearing gas is condensed into the
form of a frost as it comes into contact with the
heat transfer wall of the condenser. Typical grinder
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gas frost is collected at a liquid nitrogen jacket
temperature of -195F to ~225F contains approxi-
mately 87% carbon dioxide, approximately 10% water,
and approximately 3% coffee aromas. The frost is
05 removed from the condenser wall and collected for
combina-tion with a glyceride carrier. The frost may
be held for a short period at low, such as liquid
nitrogen, temperatures without deteriorating; however,
it is preferred to immediately utilize the rost in
lo accordance with this invention.
According to this invention, the grinder gas
frost is placed in a pressure vessel. A sufficient
amount of the grinder gas frost is added to avoid
the presence of an unsaturated carbon dioxide vapor
phase. Heat is added to the contents of the vessel,
such as by means of a 70F to 85F water jacket, to
sublime the grinder gas frost and form a headspace
pressure. At approximately 75 psia solid carbon
dioxide changes to liquid. The temperature corres-
ponding to this phase change is -70F. At this
condition, water and any trace glyceride present, as
well as some of the organic aromatics, are in the
solid state. The temperature of the vessel contents
is raised preferably to about room temperature, at
which condition the grinder gas aromatics will
diffuse and establish an equilibrium among the
gaseous carbon dioxide, liquid carbon dioxide, and
water phases. Temperatures in excess of about 85F
should be avoided as degradation of the coffee
aromatics may result. ~fter the frost within the
vessel has reached the desired temperature, and
possibly after an equilibrium period of up to several
hours, a peak pressure is reached.
The vessel contents at this peak pressure may
be in three distinct phases including a bottom water
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phase, a liquid carbon dioxide phase, and a gaseous
carbon dioxide phase with aroma present in each
phase. After the pressure within the vessel has
reached its peak, generally at about 750 psia to
05 about 950 psia, the water phase is removed from the
vessel. This can be done by simply draining the
water through a valve in the bottom of the vessel.
The removed water phase may be contacted with a
ylycerlde, preferably coffee oil, in any apparatus
that provides efficient liquid-liquid contact to
recover aromatics contained therein. However, in a
preferred embodiment of the invention, the removed
water phase is discarded without being contacted
with a glyceride.
The pressure vessel is maintained at a temper-
ature of about 75F (23.9C) to about 85~F (29.4C)
and thereby at a pressure of about 750 psia to abou-t
950 psia, for a period sufficient to ensure the
existence of vapor~ uid equilibrlum within the
pressure vessel. After equilibrium has been
established, and possibly after a holdup period of
up to several hours, the pressure vessel is rapidly
vented to the atmosphere without restriction, until
a pressure of between about 300 and 375 psia, and
preferably between about 325 and 350 psia, is attained,
at which point the pressure vessel is again sealed.
It has been discovered according to the invention
that the gaseous carbon dioxide stream vented from
the pressure vessel during this rapid venting step
is very nearly free of grinder yas coffee aromatics.
Fur-ther, it has been found that the pressure within
the pressure vessel rapidly drops from a startiny
pressure of between about 750 psia and 950 psia to
about a pressure of about 300 to 375 psia, at which
point the pFessure reduction within the pressure
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vessel ceases briefly despite the restriction-free
opening to the atmosphere. Thereafter, if the
vessel is allowed to continue to vent freely to the
atmosphere, a large amount of grinder gas aromatics
05 are lost in the vented gaseous carbon dioxide stream
as the vessel vents from between about 300 and
375 psia to atmospheric pressure.
Generally, the rapid venting step is accom~
plished as rapidly as is practicable. However, for
lo the proper functioning of the invention, it is
important that the pressure vessel be qui.ckly
resealable during the brief cessation in pressure
reduction which occurs at a pressure of about 300 to
375 psia. Therefore, the pressure vessel is
typicalLy rapidly vented by opening a valve in a
large diameter pipe, said valve being easily sealable
at the point when the pressure reduction briefly
ceases. However, automated systems as may become
apparent to one skilled in the art which enable a
more rapid venting of the pressure vessel and a
guick resealing capability are considered to be
within the scope of the invention. The period of
duration of the rapid vent step depends upon the
internal volume of the pressure vessel and the size
of the unrestricted vent line. Typically, however,
the rapid vent step is less than about one minute ir
duration, and preferably extends for about 10 to
20 seconds.
The rapid expansion of carbon dioxide yas
during ~he rapid vent step requires a supply of
heat. This heat is generally supplied by the ir~er
walls of the pressure vessel, the liquid carbon
dioxide phase within the pressure vessel, and the
gaseous carbon dioxide phase. ~s a result, -these
22
g
hea~ sourc s are subs~antially cooled and, in fact,
the subs~antial cooling is accompanied by phase
changes, i.e., a fraction of the gaseous carbon
dioxide phase is liquified and a percentage of the
05 liquid carbon dioxide phase is solidified. At the
point when the pressure reduction briefly ceases,
i.e., at a pressure of between about 300 psia and
375 psia, the pressllre vessel contains a slushy,
predominantly frozen, mixture of solid and liquid
carbon dioxide which is concentrated in grinder gas
aromatics. It has been found that this slushy
mixture maintains its phase condition, i.e., does
no-t vaporize or sublime to any measurable degree,
for a brief interval, untll heat begins to re-enter
the pressure vessel system from the surrounding
environment. It is at this point that the pressure
vessel is resealed from the atmosphere according to
the invention.
The gaseous carbon dioxide stream which is
vented during the rapid venting step has been analyzed
for coffe~ aromatics content by gas chromatography
(GC). GC is an analytic technique routinely used to
measure the quantity of coffee aromas present in a
particular sample. Total GC counts measure the
total aromatic content of a sample whereas individual
GC "peaks" on a GC printout measure amounts of
individual compounds in a sample. Comparison of GC
peaks is often used to compare the quality of one
sample to another. It has been found that the
gaseous carbon dioxide stream vented during the
rapid vent step measures about 1.0 x 104 to about
7.0 x 104 total GC counts. However, if the pressure
vessel is thereafter allowed to vent from between
about 300 psia and 375 psia to atmospheric pressure,
after -the brief cessation in pressure reduction, as
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would be entirely contrary to the teachings of this
invention, it has been found that the vented gaseous
stream measures on the order of l.0 x 106 to~al GC
counts. Therefore, it is clear that the present
05 invention effectively prevents the venting of a
gaseous stream very rich in coffee aromatics (50 to
lO0 times more rich in coffee aromas than the rapidly
vented gaseous stream). Further, a comparison by
experts of the GC peaks of these two vent streams
(peak pressure to brief cessation versus brief
cessation to atmospheric pressure) indicates that
the aromas potentially lost after the brief cessation
by venting to atmospheric pressure are those aromatics
which yield a "buttery," "R&G like" cofee aroma,
whereas the rapid vented gaseous stream predominantly
carries with it aromatics which contribute to an
undesirable "pungent," sulfery" aroma.
Liquid glyceride is pumped into the sealed
pressure vessel which contains a slushy, predomi-
nantly frozen, mixture of solid and liquid carbondioxide at a pressure of about 300 psia to about
375 psia. The glyceride is pumped ln at a pressure
in excess of that within the pressure vessel,
preferably about lO0 psia greater than that within
the pressure vessel. In a preferred embodiment of
the invention, coffee oil is used as the glyceride
and is atomized into fine droplets as it is introduced
into the pressure vessel. The glyceride is general-
ly contacted with the slushy carbon dioxide mixture
at a ratio of about l:l to 6:l by weight, typically
about 2:l to 5:l, and preferably about 3:l to 4:l
glycerlde to slushy carbon dioxide.
The pressure vessel ls then heated to a temper-
ature of about 70F to about 85F, typically by
recirculatlng warm water through the pressure vessel
jacke~ing. This increased temperature results in a
new carbon dioxide phase equilibrium being established
within the pressure vessel, with some of the solid
and liquid carbon dioxide being sublimed and vaporized,
05 thereby increasing the pressure within the vessel~
Generally, the increased pressure does not exceed
about 500 psia, and typically it is less than about
450 psia. At this point, it may be desirable to
drain any residual water from the bottom of the
pressure vessel by opening a drain valve.
The transfer of coffee grinder gas aromatics
from the carbon dioxide phase to the glyceride phase
is accomplished by allowing the two phases to contact
within the pressure vessel for a period of about
30 minutes to 1 hour, or longer. Optionally, agitation
is employed within the pressure vessel to assist in
the transer of grinder gas coffee aromatics to the
glyceride. Thereafter, the pressure vessel is
slowly vented to atomspheric pressure, typically
over a period of about 2 to about 4 hours. Once
atmospheric pressure is attained, the aromatized
glyceride of improved quality is removed from the
pressure vessel, and is used to aromatize soluble
coffee.
The aromatized glyceride may be combined with
soluble coffee powder or with coffee extract prior
to drying the extract in accordance with any of the
kno~n prior art techni~ues. Typical levels of
addition are 0.1 to 2% by weight based on the weight
of soluble solids in the final product. The aromatiæed
powder of this invention may constitute all or only
a portion of the powder in the final product, as
will be apparent to those skilled in the art.
The soluble coffee product is found to have a
higher quantity of aromatics generally and especially
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aromatics having or imparting a "lighter", "high
impact", "groundsy", "buttery", "less sulfury"
character to the soluble coffee.
The terms "coffee powder" and "coffee extract"
05 used in the description of this invention are meant
to include material containing in whole or in part
coffee substitutes such as powders or extracts
obtained in whole or in part from roasted cereals
such as wheat, rye, barley and the like. One such
item is the water extract and resulting dried powder
of wheat, barley an molasses known as "Instant
Postum~."
EXAMPLE
After the grinders, grinder gas is sent through
a water knock-out condenser and demister to reduce
moisture content of the gas stream. The grinder gas
next enters the battery of liquid nitrogen jacketed,
scraped surface heat exchangers where the gas is
condensed and collected as a carbon dioxide "snow"
or Erost with coffee aromas trapped lnside. Grinder
gas frost collected at a liquid nitrogen jacket
temperature of ~195F to -225F typically contains
~87% carbon dioxide ~10% water, and ~3~ coffee
aromas.
1~ A pressure vessel ("Converter") having an
internal volume of 8l-2 ft3 was loaded with 152 lbs
of grinder gas frost. System was closed and sealed.
Jacket temperature was kept at 75F.
2. Peak pressure of 850-900 psig was reached
in 3-4 hours. The following three phase system was
formed at peak pressure:
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Phase I - CO2 vapor plus coffee aromatics
Phase II C02 liquid plus coffee aromatics
Phase III - Liquid ~2 plus coffee aromatics
05 Phase III was drained and discarded after
system was held at peak pr~ssure Eor 30 minutes.
3. The vessel was vented through a 1~l' diameter
vent line. The system was allowed to vent rapidly
for approximately 30 seconds until the pressure is
reduced to 350 psig. The sudden drop in pressure
recondensed the aromatics and a small quantity of
the carbon dioxide inside the converter into a
"concentrated frost." Approximately 20% of the
initial charge of grinder gas frost was recondensed
as concentrated frost; however, almost 95% of the
aromatics originally present were captured along
with the recondensed carbon dioxlde frost.
4. When the system pressure was 350 psiy a
brief cessation in pressure drop occurred and the
vent valve was closed.
5. Next, 95 lbs. of coffee oil was injected
using a high pressure pump.
6. The circulating water was pumped through
the jacket of the converter and the system was again
brought to 75F. A peak pressure of approximately
480 psig was reached which was too low or liquid
carbon dioxide to exist at 75F. A two-phase system
now existed consisting of gaseous carbon dioxide
twith some coffee aromas) in the headspace and
aromatized coffee oil.
7. After one hour, carbon dioxide (along with
some aromatics) was vented from the system through a
capillary vent. The vent rate was designed to mini-
mize oil foaming. Total venting time was 4 hours.
Aromati~ed oil rom the converter was drained,
filtered, standardized and stored in cans or subse-
quent use on a soluble coffee packing line.
Gas Chromatographic (GC) data for oil aromati-
05 zation runs made using the process was obtained.
The aromatized coffee oil of the invention measured
6.0 x 106 counts whereas a standard process can be
from 4.5 to 5.0 x 106 counts.
The aromatized oil is co~bined with soluble
1~ coffee powder at a level of from 0.1% by weight.
According to expert evaluations, jar aroma from the
process of the present invention lacks the pungent
sulfury character associated with a conventional
process jar aroma. In addition, there is an overall
quality improvement as contrasted with a product
made by a conventional process and, specifically, a
"lighter", "high impact", "groundsy", "buttery",
"less sulfury" character in the final soluble coffee
product as determined by panels of expert tasters.
