Note: Descriptions are shown in the official language in which they were submitted.
_ETHOD FOR AROMATIZING SOLUBL~ COFFE~
TECHNICAL FIELD
This invention relates to a method for aromatiz-_
ing 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
shor~ period thereafter, has long been recognized in
the art as a highly desirable natural coffee aroma.
A great deal of effort has been directed toward the
development of a method for recovering and fixing a
high percentage of grinder gas aromas on a substrate
for subsequent addition to coffee products, particu-
larly soluble coffee powder.
Clinton et al. in U.S. Patent No. 3,021,218
disclose a method whereby a coffee aroma condensate
is vaporized to admit the more volatile coffee aromas
into void spaces of a container filled with soluble
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coffee. Johnston teaches addition of condensed
grinder gas to chilled soluble coffee powder in
U.S. Patent No. 2,306,061. These two methods are
similar in that grinder gas aromas are contacted
directly with coffee particles in order to improve
the aromatics of the coffee product. However, both
methods fail to provide the convenience, stability,
and high level of grinder gas fixation, desired in
the coffee field.
Several methods for fixing grinder gas aromatics
in a glyceride substrate are known in the art, such
glycerides as coffee oll, bland-tasting vege-table
oils, and triacetin being especially useful for this
purpose. Katz in U.S. Patent No. 3,939,291 -teaches
contacting condensed grinder gas and a glyceride in
a pressure vessel at a temperature above the critical
temperature of liquid carbon dioxide, then slowly
venting the vessel while maintaining the temperature
above carbon dioxide's critical temperature. Katz'
method effectively prevents the formation of liquid
carbon dioxide at any point during the glyceride
aromatization procedure. Mahlmann discloses, in
U.S. Patent No. 3,97~,528, contacting a glyceride
and condensed grinder gas in a pressure vessel at a
temperature of 70 to 75F and a pressure above
100 psia to enable aromatic transfer from the liquid
carbon dioxide phase to the liquid glyceride phase,
and then venting the vessel. Mahlmann's procedure
involves repeated venting of said pressure vessel
from a high pressure ranging from 75 to 120 psig, to
a low pressure of O psig. Siedlecki et al. in U.S.
Patent No. 4,007,291 teach a procedure whereby a
glyceride is contacted with condensed grinder gas in
a pressure vessel at a temperature of 70 to 85F and
a pressure in excess of 700 psig, then slowly venting
1,
the pressure vessel, preferably isothermally.
Howland et al. in U.S. Patent No. 4,119,736 disclose
removal of a water phase from a pressure vessel
05 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. Howland et al. disclose that it is possible
to separate aromas from the removed water phase,
such as by vacuum distillation, and to reclaim or
recycle vented aromatics.
It is an object of the present invention to
produce an aromatized glyceride of improved quality
which may be used to aromatize soluble coffee.
It is a further object of the invention to
improve the organoleptic character of an aromatized
glyceride such that it is more like freshly roasted
and ground coffee grinder gas.
It is an additional object that the aromatized
glyceride exhibit good stability both prior to and
subsequent to its application to a coffee substrate.
It is yet another object that the process by
which an aromatized glyceride is produced satisfying
the above criteria, be controllable, reproducible,
safe and efficient.
SUMMARY OF THE INVENTION
It has been found according to the present
invention that a vastly improved method for aroma-
tizing solwble coffee powder with a glyceride,
aromatized by contact with a grinder gas frost, is
attained by a process comprising the steps of:
(a) condensing, as a frost, grinder gas
which has a high carbon dioxide content;
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(b) placing the grind~r gas frost in a
pressure vessel;
(c) supplying heat to the contents of the
vessel and allowing the ~rost to equilibrate at
a pressure in excess of 506.2 psia and at a
temperature of greater than 32~F, to form three
phases: (l) gaseous carbon dioxide plus
aromatics, (2) liquid carbon dioxide plus
aromatics, and (3) liquid water containing
aromatlcs;
(d) draining the water phase which contains
aromatics from the vessel;
(e) contacting a glyceride with the water
phase of step (d) to transfer aromatics ~rom
said water phase to the glyceride;
(f) introducing the glyceride, which
contains aromatics transferred from the water
phase, into the pressure vessel of step (b);
(g) supplying heat to the contents of the
pressure vessel if necessary in order to raise
the temperature to between 70 and 85F, and `
thereby increase the pressure to about 750 to
850 psia, to form three phases: (1) gaseous
carbon dioxide plus aromatics, (2) liquid
carbon dioxide plus aromatics, and (3) liquid
glyceride which contains water phase aromatics;
(h~ reflu~ing, in a packed column, liquid
carbon dioxide and gaseous carbon dioxide
phases, while slowly venting, thereby removing
"lean" carbon dioxide from the vessel and
concentrating aromatics in the glyceride, until
the pressure drops to about 650 to 700 psia;
(i) depressurizing the vessel;
~j) obtaining an aromatized glyceride; and
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(k) combining the aromatized glyceride
with soluble coffee powder.
The method for aromatizing soluble coffee
05 described above represents at least a two-fold
improvement over the prior art. First, the aromatic
transfer from water phase to glyceride of step (e)
and the reflux system of step (h) result in about a
25 to 70% increase in the quantity of coffee aromatics
transferred to the glyceride, as measured by gas
chromatography, over the glyceride aromatization
systems described in the art, specifically
Siedlecki et al. and Howland et al. Said 25 to 70%
increase in aromatic recovery transla-tes to a
significant increase in the aromatized glyceride
yield from a given amount of grinder gas frost, thus
greatly improving the efficiency of a grinder gas
aromatization system and the economies thereof.
Second, the quality of the aromatized glyceride
and thereby the aromatized soluble coffee powder
produced by the present invention is largely improved
over previous aromatization systems. The aromatized
soluble coffee powder of the present invention, when
compared to prior art coffee aromatization processes
at an equivalent quantitative aroma level, as measured
by gas chromatography, is found to impart a superior
coffee aroma, with a more "groundsy", "roasted and
ground", "high impact" coffee aroma character. The
improved qualitative coffee aroma character of the
present invention is directly attribiltable to the
aroma balance of the aromatized glyceride which
results from (1) recovering the aromatics from the
water phase in step (e), and (2) concentration of
the coffee aromatics through reflux in step (h).
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to combining
with coffee solids an aromati~ed glyceride contain-
ing grinder gas aromatics which have been concentrated
and condensed from a grinder gas frost. This inven-
tion is particularly described in terms of coffee
grinder gas, which contains 80% to 90% by weight
carbon dioxide; however, it is to be understood that
other aroma-bearing 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 the scope of this
invention.
The most readily available source of grinder
gas may be obtained by enclosing or hooding coffee
grinding equipment, such as coNmercial grinders.
The gases liberated from the ground co~fee 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 grinding operation take place in a
substantially inert atmosphere. Such a process is
described in U.S. Patent No. 2,156,212 which describes
a method of collecting gases evolved during roasting,
but which can be equally applied to the collection
of gases evolved during the grinding or cellular
disruption of whole freshly roasted coffee beans.
If pumping is employed, it may be desirable 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
largely carbon dioxide together with water vapor and
the characteristic aromatic constituents of roasted
coffee. The amount of moisture in the gas may be
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lowered by the use of dry roasting conditons and
low-moisture quenches or quenching mediums. The
evolved gas is preferably passed through a first
05 condenser where it is cooled to between 35 and 50F
and where substantial quantities of water are removed.
The removed water, typically termed "knockout water",
may be subsequently contacted with a glyceride, as
described below, to recover any coffee aromatics
lo contained therein. 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.
PreEerably the condenser is cooled by means of
liquid nitrogen and the gas flow into the exchanger
is maintained within the range of about 1 to 5 cubic
feet per minute per square foot of heat exchanger
surface. The nitrogen gas that evolves rom 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
gas frost is collected at a liquid nitrogen jacket
temperature of -195F to -225F con~ains approxi-
mately 87% carbon dioxide, approximately 10% water,
and approximately 3% coffee aromas. The frost is
removed from the condenser wall and collected for
combination 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 frost in
accordance with this invention.
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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 70~F to 85F water jacket, to
sublime the grinder gas frost and form a headspace
pressure. At approximately 75 p.s.i.a. solid carbon
dioxide changes to liquid. The temperature corre-
sponding 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. After 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
2 be in three distinct phases including a bottom water
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
reachecl its peak, generally at about 750 psia to
3 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 o-f the vessel.
The removed water phase is contacted with a
glyceride, preferably coffee oil, in any apparatus
that provides efficient liquid-liquid contact.
2~
g
Optinally, the knockout water previously recovered
may be incorporated herein. An agitated batch tank
or a continuous apparatus such as a rotating disc or
05 reciprocating plate column may be employed to contact
the water phase with the glyceride. In a preferred
embodiment of the invention, coffee oil is atomized
into a batch tank containing the water phase, and
the mixture is agitated mechanically with an impeller
to ensure sufficient liquid-liquid contact.
Effective partioning of grinder gas aromatics
from the water phase to the glyceride, preferably
coffee oil, is achieved by contacting the water
phase with the glyceride at a volume ratio of about
0.5:1 to about ~:1, and preferably about 1:1 to
1.5:1, water to glyceride. Said contact is generally
conducted at a temperature of about 35F (1.7C) to
about 120F (48.9C), typically at a temperature of
about 50F (10.0C) to about 100F (37.8C), and
preferably at about ambient temperature. The transfer
of coffee aromas to the glyceride is,primarily by
diffusion and the rate thereof is generally improved
at higher temperatures. However, it is essential to
the present invention that degradation of the coffee
aromas contained in the removed water phase be
prevented, and therefore that temperatures in excess,
of 120F, and preferably 85F, be avoided during the
liquid-liquid contact.
The contact time necessary for effective parti-
tioning of the coffee aromas from the water phase tothe glyceride is primarily dependent upon the contact
temperature, contact ratio of water to glyceride,
type of liquid-liquid contact apparatus employed,
and degree of agitation supplied. However, in order
to partition the coffee aromas which have been found
by the present invention to be necessary to deliver
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a "groundsy" aroma character to the final aromati~ed
soluble coffee, it has been found that a certain
minimum contact time is requi.red. For example, in
one embodiment of the present invention wherein a
05
water phase containin~ grinder gas coffee aromas was
contacted with coffee oil at a volume ratio of l::L,
in an agitated batch reactor at a temperature of
75F, it was found that a minimum contact time of
8 minutes, and preferably at least 15 minutes, was
needed to transfer sufficient grinder gas aromas to
the coffee oil to achieve the desired "groundsy"
aroma character in the aromatized soluble coffee
powder. Generally, minimum contact times in excess
of four minutes and effective to transer sufficient _
aromatics from the water phase to the glyceride to
deliver a groundsy coffee aroma are required in
batch reactors. Shorter contact times, as low as
about ~0 seconds, can be effective to transfer said
groundsy coffee aromas to the glyceride in continuous
reactors. Minimum contact times may vary as a func-
tion of the processing conditions such as contact
temperature, contact ratio, etc., employed, but such
variations are seen to fall within the scope of the
present invention.
The glyceride phase which now contains parti-
tioned grinder gas coffee aromas from the water
phase is separated therefrom by any suitable liquid-
liquid separation technique, typically by centrifu-
gation. The separated water phase may contain trace
amounts of desirable grinder gas coEfee aromas which
may be recovered by recyclin~ said water phase into
a second liquid-liquid contact with a glyceride,
either alone or in combination with an additional
grinder gas coffee aroma-containing water phase.
The separated glyceride phase contains grinder
gas coffee aromas which are discarded in existing
prior art systems. Said glyceride is added to the
pressure vessel from whence the water phase was
previously removed, said addition generally being
via a high pressure pump. The pressure vessel
contains a gaseous carbon dioxide plus aromatics
phase and a liquid carbon dioxide plus aromatics
phase and is typically at a pressure of about
750 psia to about ~50 psia. The high pressure pump
must supply a pressure in excess of the vessel
pressure, typically by at least 50 psia, preferably
by at least 100 psia, and most preferably by at
least 200 psia, in order to supply the glyceride to
the pressure vessel.
The pressure vessel is maintained at a tempera-
ture of about 75F (23.9C) to about 85F (29.~C)
and thereby a pressure of about 750 psia to about
950 psia, for a sufficient period to allow the
establishment of vapor-liquid equilibrium. At
equilibrium there exists in the pressure vessel
three phases, each containing a percentage of grinder
gas coffee aromatics, the phases being (1) a gaseous
carbon dioxide phase, (2) a liquid carbon dioxide
phase, and (3) a liquid glyceride phase. Equilibruim
is generally established when the pressure in the
pressure vessel stabilizes.
Above the pressure vessel is mounted a packed
column and a partial or total condenser. The packed
column is generally loaded with any packing which is
suitable for vapor-liquid mass transfer and which
resists corrosion and does not catalyze unwanted
thermal degradation reactions (e.g., nickel-plated
packing). After the pressure vessel has reached
equilibrium, it is allowed to vent into the packed
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column and the partial or total condenser, which are
se~led from the atmosphere. In the case of a partial
condenser, a cooling fluid is passed through the
condenser, generally at a temperature of about 35F
(1.7C) to about 70F (21.1C), and typically at
about ~5F (7.2C) to about 60F (15.6C), thereby
condensing a portion of the gaseous carbon dioxide
phase containing aromatics to the liquid phase. In
the case of a total condenser, a cooling fluid
passes through the condenser at temperatures compar-
able to the partial condenser case, but the system
is operated so as to condense the entire gaseous
carbon dioxide stream passing therethrough. In this
way, a better condensation of coffee aromas is
effected and thus a higher degree of coffee aroma
recovery is enabled. In either case, the liquid
phase returns through the packed column to the
pressure vessel as reflux, becoming enriched with
aromatics from the rising gaseous phase through mass
transfer.
After liquid carbon dioxide begins to reflux
through the condenser, the condenser is slowly
vented to the atmosphere to allow removal of gaseous
carbon dioxide in the case of a partial condenser
and liquid carbon dioxide in the case of a total
condenser from the pressure vessel system. The
carbon dioxide which is vented is "lean" in aromatics
because the majority of aromatics are transferred to
the refluxing liquid carbon dioxide in the packed
column according to the invention. The pressure
vessel system is slowly vented from its equilibrium
pressure, generally about 750 psia to about 950 psia
and typically about 850 psia to abou~ 900 psia, and
at a temperature of about 75F (23.9C) to about
85F (29.4C), until the pressure drops to between
f~ 2~ ~ ~ 2 ~
about 650 psia to about 700 psia. The system is
vented slowly, generally over a period of several
hours and typically for about 3 to 4 hours. It is
05 essential to the invention that the gaseous carbon
dioxide not be vented from the pressure vessel
system too rapidly while the pressure is being
reduced to between about 650 psia to 700 psia,
because too rapid a vent results in insufficient
aromatic mass transfer from the gaseous carbon
dioxide phase to the liquid carbon dioxide phase in
the packed column. This, in turn, has been Eound to
result in an aromatized glyceride of inferior
quality. In a preferred embodiment of the invention,
"lean" gaseous carbon dioxide is vented through
small diameter capillary tubing to enable reliable
control of the vent rate.
After the pressure in the pressure vessel has
dropped to about 650 psia to 700 psia, the reflux of
liquid carbon dioxide is ceased according to the
invention. The pressure vessel is thereafter vented
to atmospheric pressure and the aromatized glyceride
is removed from the pressure vessel. Said aromatized
glyceride is typically filtered, standardized by
blending with a quantity of unaromatized glyceride,
and stored in cans for subsequent use on a soluble
coffee packing line.
Gas chromatographic (GC) analysis of the aroma-
tized glyceride produced by the invention prior to
standardization demonstrates a large increase in
aromatic intensity and an improvement in aromatic
quality over prior art methods. 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
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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 present invention yields an aromatized
glyceride with about 6.0 to 7.5 x 106 total GC
co~mts whereas prior art methods do not exceed about
4.5 to 5.0 x 106 total GC counts, when compared by
controlled experimentation. Further, the quality of
the aromatized glyceride, as reflected by individual
GC peaks, is improved by the present invention over
prior art methods. Said quality improvement has
been proven by expert oranoleptic comparison of
standardized control and improved (method of present
invention) aromatized soluble coffee samples, and by -
extensive consumer test comparisons thereof.
Standardization of aromatized glycerides is by
GC, thereby producing glycerides with equivalent
total quantities of coffee aroma compounds. However~
the quality of aromatized glycerides produced by the
present invention and prior art methods remains very
different because the balance of coffee aromatics in
the standardized glycerides as measured by individual
GC peaks remains quite different. The present
invention recovers and fixes the coffee aromatics of
grinder gas in a glyceride such that the resulting
aromatized soluble coffee exudes an improved coffee
aroma, described as "high impact" 3 "groundsy", and
"roast and ground" by panels of experts. It is
further noted that the product of the present inven-
tion lacks the pungent, sulfury character associated
with prior art methods due to the balanced character
of the aromatized glyceride.
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EXAMPLE 1
Grinder gas collected from roast and ground
coffee grinders was condensed in a battery of liquid
05 nitrogen jacketed, scraped-surface heat exchangers.
The knockout water was discarded. The condensed
grinder gas frost was loaded into a pressure vessel
with an internal volume of about 8~ ft3 and allowed
to reach vapor-liquid equilibrium. A peak equilibrium
pressure of 900 psig was attained at 85F. The
liquid water phase was drained ~rom the bottom of
the pressure vessel through a drain valve, which was
thereafter immediately closed to maintain the liquid
and gaseous carbon dioxide at equilibrium within the
pressure vessel. The liquid water phase was placed
in a batch tank, wherein coffee oil was added at a
volume ratio of 1:1. The liquid water and coffee
oil were contacted with agitation at ambient temper-
ature for 15 minutes. The oil was then separated
from the water by centrifugation and injected back
into the pressure vessel by a high pressure pump at
a pressure of 1050 psig.
The pressure vessel was then vented into a
packed column and a partial condenser, said partial
condenser cooled to 60F by recirculating water.
Gaseous carbon dioxide containing coffee aromatics
was condensed in the partial condenser, and passed
back down through the packed column to the pressure
vessel. Said return of the condensed liquid through
the packed column was observed through a site glass
and once a steady stream of returning liquid was
observed, the partial condenser was allowed to vent
slowly through capillary tubing to the atmosphere at
a rate of 3500 cc/min. The pressure vessel was
maintained at 80F throughout the controlled venting
and simultaneous refluxing period. Venting at the
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3500 cc/min rate was maintained until the pressure
in the pressure vessel dropped to 680 psig, at which
time the recirculating water supply to the partial
05 condenser was ceased and the partial condenser vent
rate was increased by ten-fold.
After the pressure vessel reached atmospheric
pressure, the aromatized glyceride was removed
therefrom and filtered. Analysis by gas chroma-
tography (GC) demonstrated 7.5 x 106 total GC counts.
The aromatized coffee oil was then blended with
unaromatized coEfee oil until a total GC level of
3.2 x 106 counts was obtained. This standarized
coffee oil was spray-plated on soluble coffee powder
at a level of 0.10% by weight, which was then packed _
in standard coffee jars. Expert evaluations termed
the aromatized coffee powder so produced to be of an
improved quality, having a "high impact", "groundsy",
"roast and ground" jar aroma. It was found that
this improved jar aroma was maintained over extended
storage as well.
