Note: Descriptions are shown in the official language in which they were submitted.
~0'~ '7(~
This invent1on relates to a method of manufacturing
coffee aroma materlals.
This invention is related to commonly-assigned Patent
Appllcation, lB2062 wherein is disclosed a method for
condensing the aromatic gases given off during the comminution
of freshly roasted coffee in a vertically-mounted, scraped-wall
heat exchanger which is cooled by means of liquid nitrogen. The
condensed gases are collected at the bottom of the heat exchanger
in the form of a frost or snow and this frost is mixed with a
1~ liquid glyceride and then combined with a coffee extract prior
to drying the extract (e.g. freeze drying) or combined with a
soluble coffee powder.
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
bean for a short period thereafter, has long been recognized in
the art as a higly desirable natural coffee aroma. The collec-
tion and stabilzation 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 United States
Patent No. 3,021,218 to Clinton, et al. which aromatizes the jar
headspace and United States Patent No. 2,306,061 to Johnston which
condenses grJnder gas aromatics onto chilled soluble coffee powder.
The use of grinder gas condensates which are added to a liquid
extract and dried in order to produce an improved cup aroma when
the powder is dissolved in hot water is disclosed in United
States 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
whi~h mixture is then processed to remove excess water, such as
-1-
~o4~70~
be 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 attempting to
stabilizing the aromatics. Such glycerides as coffee oil,
bland-tasting vegetable oils and triacetin have proven
especially useful for this purpose; however other oils and low
melting point fats may also be used. It has, however, been
desired to maximize the amount of aromatics that are fixed in
the glyceride carrier, since this would minimize aroma loss and
would reduce the amount of the glyceride which would be
incorporated with the soluble coffee product to obtain a
desired amount of aromatization.
According to the invention there is provided a method
for aromatizing soluble coffee with an aromatized glyceride
comprising the steps of:
a) condensing, as a frost, an aroma-containing gas which
has a high carbon dioxide content;
b) placing the aroma-containing frost in a pressure
vessel, the amount of frost being sufficient to provide a
saturated carbon dioxide phase within the vessel, and the
pressure vessel being directly connected with an overhead
packed column and a condenser located above the column;
c) isolating the vessel from the atmosphere;
d) supplying heat to the contents of the vessel to
produce an internal temperature which is above the congeal
point of the glyceride;
~ -2-
1~)4Z7~6
e) contacting within said heated vessel the frost aromas
and a liquid glyceride phase, said glyceride being present in
the vessel at a level of about one gram of glyceride to 0.5 to
6 grams of the frost; thereafter,
f) slowly releasing pressure from the vessel so that the
glyceride is maintained in a liquid state;
g) refluxing the pressurized gas exiting the vessel by
-2a-
means of the condenser and then
h~ combining the aromatized glyceride with coffee solids.
Thus this invention is directed to fixing in a glyceride
carrier aromatics contained in an aroma-bearing gas which has a
high (e.g., above 80% by weight) carbon dioxide content, and
which gas has been condensed as an aroma-bearing frost. This
invention is particularly described in terms of coffee grinder
gas, which is in excess of 90% by weight CO2; 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 con-
sidered to be within the scope of this invention.
The process of this invention employs high pressure
together with reflux as a means to increase absorption of the
volatile compounds present in an aroma-bearing carbon dioxide
frost by a glyceride carrier. The process, which may be conduct-
ed as a simple batch operation in a suitable pressure vessel, or
as a semi-continuous, countercurrent operation in a battery of
pressure vessels, eliminates the need for laborious mixing of
the frost and the glyceride. This mixing operation has proven
to be troublesome in commercial operation, since contact between
the condensed frost and the glyceride quickly congeals the gly-
ceride thus making uniform mixing of the two components quite
difficult.
Contacting the gaseous frost and a liquid glyceride
phase within an isolated pressure vessel has proven to be a desi-
rable method to increase the level of aromatics fixed in the
glyceride; however, the end temperatures and pressures (e.g.,
~ _ 3 _
7(~;
70F. and 855 psig.) permit the presence of liquid carbon
dioxide. Conditions which permit the presence of liquid CO2
within the pressure vessel also allows some of the
- 3(a) -
~ 7~)~
aromatics to be dissolved in the liquid CO2 phase accordin~ to
equilibrium partition conditions based on complex relationships
between vapor pressures, solubilities, and chemical potential.
When a pressure vessel containing an aroma-bearing liquid C02
phase is vented, nearly all of the desirable organic materials
dissolved in the liquid CO2 will co-distill and be lost in the
vent gas.
The invention describes a process wherein the
pressure vessel is directly connected, such as through an open
vent, with an overhead packed column and a partial condenser
located above the column. A pressure or gas flow regulator
will be located upstream from the condenser and will usually
serve as the means for isolating the pressure vessel from the
atmosphere. Thus, instead of venting the pressure vessel
directly into the atmosphere where the aromatics will be lost,
the boiling CO2 passes through a packed column in which liquid
C2 is refluxing from the partial condenser. Contact in the
column between the gaseous C02 and the refluxing liquid CO2
enriches the liquid phase in aromatics. As the concentration
of aromatics increases in the liquid CO2 phase within the
pressure vessel, at least a portion of these aromatics will
pass into the liquid glyceride phase. Thus, by this technique,
a higher level of aromatics can be fixed within the glyceride.
According to the invention, a quantity of an aroma-
bearing carbon dioxide frost, which may be obtained from a
liquid nitrogen-cooled, scraped-surface heat exchanger, is
contacted in a pressure vessel with a liquid glyceride phase at
--4--
~ 0 4'~7 ~ 6
a ratio of grams of frost to grams of glyceride of about 0.5:1
to 6:1. The vessel is isolated from the atmosphere and the
vessel contents are continuously supplied with heat by such
means as a water jacket. Heat is supplied in sufficient
quantities to raise or maintain the temperature of the gly-
ceride above its congeal point, preferably the contents of the
pressure vessel will reach at least room temperature. As the
temperature of the frost increases, a gaseous phase on
increasing pressure is developed and as the temperature
increases above about -69.9F, the remaining condensed carbon
dioxide is converted from a solid phase to a liquid phase. As
the temperature of the vessel contents exceeds the congeal
point of the glyceride, the aromatics will readily dissolve in
the liquid glyceride phase. It may be desirable to hold the
vessel contents at a particular temperature above the congeal
point of the glyceride in order to lengthen by an hour or more
the contact time between the liquid glyceride and the aromatics.
Agitation of the vessel contents, such as by means of an
internal stirrer, may also be desirable in order to increase
absorption of aromatics by the liquid glyceride phase.
The frost and the glyceride may be placed in the
vessel at the same time (i.e. before any heat is supplied to
the vessel), or the frost may be permitted to warm within the
vessel, say to a temperature above the congeal point of the
glyceride, before the glyceride i5 placed within the vessel.
After the frost and glyceride within the vessel reach
the desired temperature, preferably about room temperature, and
possibly after a hold-up period, the pressure within the vessel
~ 042706
is slowly, preferably isothermally, released. Slow pressure
release is desirable in order to prevent the temperature of the
vessel contents from dropping below ~he congeal point of the
glyceride. This would hinder absorption of aromatics by the
glyceride. During pressure release, the condenser liquefies
and refluxes a portion of the aroma-containing gases (mostly
CO2) escaping from the pressure vessel and returns the
condensate to the vessel through the packed column.
The glyceride resulting from the above described
process is found to contain more than twice the amount of
aromatics obtained from manual mixing of the two components at
atmospheric pressure. The aromatized glyceride should then be
processed to remove excess water such as by centrifugation.
The aromatized glyceride may be combined with coffee
solids either in the fo~m of dry soluble coffeeJ such as by
conventional spray plating or any of the techniques disclosed
in United States Patent No. 3,769,032 or with a liquid coffee
or coffee-like extract, prior to drying the extract. The
aromatized glyceride may be solidified, such as by freezing,
and comminuted, such as by grinding, prior to being mixed with
the soluble coffee powderJ or prior to being combined with a
liquid coffee extract, a slushed coffee extract, or a partially
frozen slab of coffee extractJ such as disclosed in
- commonly-assigned United Stated Patent No. 3J809J766.
The invention will be better understood from the
accompanying illustration which shows in cross-section a
pressure vessel equipped with means for high pressure reflux
and also depicting the multiple phases which can exist within
the vessel.
10~'~706
The most readily available source of grinder gas may
be obtained by enclosing or hooding coffee grinding equipment,
such as the 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 grinding operation take place in a substantially
inert atmosphere. Such a process is described in United States
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
largeiy 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 the use of dry
roasting conditions 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 exchanger is maintained
1a)4~7~
within the range of about 1 to 5 cubic feet per minute per
sguare foot of heat exchange 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.
Ihe aroma bearing gas is condensed into the form of a
frost as it comes into contact with the heat transfer wall of
the condenser. 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 combine the frost with a glyceride
carrier in accordance with this invention. The glyceride,
which preferably is coffee oil or a bland-tasting vegetable
oil, such as cottonseed, corn or coconut oil, is combined with
the frost at a level of about O.S to 6 grams of frost per gram
of glyceride, preferably at about 1 to 4 gms. of frost per gm.
of glyceride.
According to this invention, contact between the
grinder gas frost and the liquid glyceride phase occurs in a
pressure vessel which is equipped for high pressure reflux. A
sufficient amount of the grinder gas frost is added to avoid
the pres~nce of an unsaturated CO2 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. Rapid heating of the vessel contents to
above the congeal point of the glyceride may be desirable in
~ 70 ~
order to increase the period of time during which a liquid
glyceride phase is present. At approximately 75 p.s.i.a. solid
C2 changes phase to liquid. The temperature corresponding to
this phase change is -70F. At this condition, water and any
glyceride present, as well as some of the organic aromatics,
are in the solid state. The temperatllre of the vessel contents
is raised to a point above the congeal point of the glyceride,
and preferably to about room temperature, at which condition
the grinder gas aromatics will diffuse and establish an
equilibrium among the gaseous C02, liquid C02, glyceride and
water phases which may be present within the pressure vessel.
Temperatures in excess of about 85F should be avoided as
degradation of the coffee aromatics may result. After the
frost and glyceride within the vessel have reached the desired
temperature, and possibly after an equilibration period of up
to several hours, pressure is slowly released, with the use of
high pressure reflux.
Slow release of the pressure from within the vessel
is desirable in order to maintain the glyceride in a liquid
state. Frozen glyceride, which would result from rapid drops
in pressure, would not as readily accept transfer of aromatics
from the liquid C02 phase with which it is in contact.
According to this invention isothermal venting is thought to be
most preferred.
Referring to the drawing, the figure depicts
apparatus suitable for batch operation of this invention, the
figure showing the state that would exist at equilbrium with
the contents of the pressure vessel 1 at about 70F and a
1~4'~70~
pressure of about 855 p.s.i.a. The pressure vessel 1 is
surrounded by a water jacket 2 and the vessel is provided with
an outlet which directly communicates with ~ packed Column 3.
The partial condenser 4 is preferably adapted for counter-
current flow of a liquid heat transfer medium such as 30 to
40F brine or water. A pressure regulator 5 controls the exit
of gas from the system and may consist of a single on-off valve
and a capillary or small diameter tube which will provide a
sufficient pressure drop to prevent a rapid drop of pressure
within the vessel.
The vessel contents are shown in four distinct phases
including a bottom water phase 6, a liquid glyceride phase 7, a
liquid CO2 phase 8, and a saturated gaseous CO2 phase 9.
After the pressure within the vessel is reduced, the
aromatized glyceride phase is removed from the vessel. If
liquid, this can be done by simply decanting or by draining the
liquid through a valve (not shown) in the bottom of the vessel.
It would also be possible to permit residual pressure within
the vessel to force the liquid out of a vertical withdrawal
tube (not shown) which protrudes through the upper portion of
the vessel. The glyceride is then preferably processed so as
to remove excess water. If the glyceride is removed from a
pressurized vessel, any residual gas present in the vessel may
be retained for use in a subsequent pressure fixation cycle.
The aromatized glyceride phase and any water phase
which may be present in the vessel may be separated during
removal from the vessel. Alternatively, since water will be
the heaviest material within the vessel, it would be possible
-10-
104'~ 'Cs~
to remove the bottom liquid water phase at any point in the
pressure fixation cycle.
Removing water from the aromatized glyceride, prefer-
ably down to a level of 0.5% by weight or less, appears to
further stabilæe the grinder gas aromatics. Centrifugation,
ultracentrifugation, molecular fractionation, drying agents,
and like method have proven to be successful techniques for
removing water from the aromatized glyceride. As a further
refinement of this water removal process, it is possible to
separate any aromas from the removed water such as by vacuum
distillation and to add these separated aromatics back to the
aromatized glyceride.
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 known prior art
techniques. Typical levels of addition for the aromatized
glyceride are 0.1 to 2% by weight glyceride based on the weight
of soluble solids in the final product. The aromatized 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 terms "coffee powder" and "coffee extract" used
in the description of this invention is 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 and molasses known as "Instan~ Postum."
(Registered trademark)
1~4'Z7Vtj
This invention is further described but not limited
by the following Example:
Example
Coffee grinder gas which was evolved during grinding
of freshly roasted coffee beans was passed through a water
cooled condenser where 1.25 pounds of water per cubic foot of
gas was removed. The gas was then passed to a liquid nitrogen-
cooled, scraped-wall heat exchanger where it was condensed and
collected as a frost.
80 lbs. of the frost are placed in a 4 cubic foot
pressure vessel (as shown in the drawing) together with 40 lbs.
of expressed coffee oil. The pressure vessel is immersed in a
water bath maintained at about 70F. After 3 hours, the con-
tents of the vessel attain a temperature of about 70F and a
pressure of about 850 p.s.i.g. Water at 35F is then counter-
currently circulated through the condenser and the pressure
regulator valve is then opened slightly to slowly release
pressure over the course of 3 hours, care being taken to pre-
vent such rapid drops in pressure as would cause the oil to
solidify. During the venting process, reflux of CO2 was
observed, the liquid condensate returning to the vessel through
the packed column filled with ceramic Rasching rings. The
vessel contents are centrifuged and about 2 lbs. of water per
gallon of liquid is removed. This aromatized "dry" oil, when
frozen at -20F, is found to remain stable for at least 3 days
and to possess a pleasant coffee aroma which can be transferred
to a soluble coffee product by such means as spray plating.
-12-
