Note: Descriptions are shown in the official language in which they were submitted.
l~2~7
CASE 2830
DESCRIPTION
PROCESS FOR THE PREPARATION OF SOLUBLE COFFEE
TECHNICAL FIELD
This invention relates to a process for the
05 preparation of soluble coffee by spray drying a
concen~rated aqueous coffee extract obtained from
roasted and ground coffee.
Work done by Huste et al., U.S. Patent
No. 3,345,18~, indicates that volatile retention
across spray drying is improved with higher solids
concentration o~ aqueous coffee extract. However,
since it is economical to operate the percolators at
high drawoff factors giving high yields, a low
concentration extract is produced. Therefore, a
more effective method of concentrating extract is
desirable. However, capturing and retaining volatile
coffee flavor and aroma compounds is also essential.
~he present invention may be used in an improved
version of the process disclosed in Shrimpton, U.S.
Patent No. 4,107,339. According to the process as
described in the patent, a small percent evaporation
is followed by a bulk evaporation to produce a high
concentration extract. The condensate from the
first evaporation is then added back to the concentrate
and subsequently is spray dried.
The process as described in the patent is
affected by three factors pertaining to the capture
~}~
3 ~, 7
and retention of flavor and aroma. First is the
small percen~ evaporation which favors removal of
compounds with a high relative volatility (relative
to water). Relative volatility (~) is defined as
05 Kl/K2 where K is the ratio of vapor concentration to
liquid concentration; subscript 1 refers to the
1avor and aroma compound being distilled and
subscript 2 refers to water. Compounds with ~'s,
i.e., relative volatilities, less than 40 are not
removed well. Secondly, condensation favors compounds
with low ~'s. Compounds with high a's are lost.
Thirdly, any compounds that were not removed by the
small percent evaporation, are subsequently removed
by the large percent evaporation and are discarded.
If one assumes that all flavor compounds are
important, then the process as disclosed in the
aforementioned U.S. Patent No. 4,107,339 has two
areas that need improvement. The first area is the
small percent evaporation. A larger percent
evaporation could remove heavier volatiles (low
~'s), however the increased water load would dilute
the product. Therefore, a means to separate and
concentrate the volatiles before addback such as a
distillation column is needed. Secondly, the
condenser could be improved by providing a means of
capturing the highly volatile compounds that are
normally lost.
This invention relates to the use of an absorption
column for capturing and retaining volatile coffee
flavor and aroma compounds by absorption of the
compounds into cold coffee extract. By "cold" is
meant coffee extract at a temperature of about 10
to 15C and having a solids concentration of about
10% to 40%, preferably about 35/O. As a processing
step, the use of the absorption column permits
Ip~3
-- 3 --
transfer of desirable coffee flavor and aroma compounds
from a venting gaseous stream to a product liquid
stream of coffee e~tract. These flavor and aroma
volatiles can then be retained through further
OS processing to the finished product obtained by spray
drying the concentrated extract. The gaseous aroma
stream can be from any source of volatile aromas,
e.g., the vent from a condenser, percolator vent,
grinder, etc. Preferably the volatile aromas are
the non-condensed flavor and aroma compounds from
the condenser. The absorp~ion column is designed
for operation at or slightly above atmospheric
pressure; but if the gaseous aromas are produced
under a vacuum, a sealed gas compressor such as, for
example, a diaphragm pump is used to compress the
aroma stream, uncontaminated, to atmospheric pressure
prior to entering the absorption column.
The invention is based on the finding that
highly volatile coffee flavor and aroma compounds
have a strong affinity for cold coffee extract.
This invention is designed to prevent the loss
o desirable flavor and aroma volatiles during
processing. IT1 particular, in processes such as,
for e~ample, in Shrimpton U.S. Patent No. 4,107,339,
it solves the problem of flavor losses during extract
evaporation due to poor condensation of highly
volatile flavor and aroma compounds in the aroma
condenser. It can also be used to solve the problem
of losses due to poor ccndensation of volatile steam
aromas in processes such as steam stripping of roast
and ground coffee, and for collection of grinder gas
aromas for jar or brew aroma.
Another advantage of this invention is that i~
involves the use of relatively low-cost e~uipment
whereas previous equipment for ~aseous aroma collectors
-- 4
were hi~h-cost items such as liquid nitrogen conclensers
or brine-cooled wiped film vapor-liquid contactors
such as a Votator. A further advantage of this
invention is its mul~iplicity of uses in processes
05 where it is desirable to capture non-condensable
gaseous flavor and aroma compounds for retention
through to the finished product.
DISCLOSURE OF INVENTION
-
A process for the preparatlon of soluble coffee
by spray drying a concentrated aqueous coffee extract
obtained from roasted and ground coffee has now been
discovered in which the improvements which comprise
the following steps result in capturing and retaining
volatile coffee flavor and aroma compounds:
(a) evaporating an aqueous coffee extràct
to produee an aqueous flavor a~d aroma solution;
(b) steam stripping the aqueous coffee
flavor and aroma solution in a distillation column
at a pressure of from 100 to 500 mm Hg absolute
~0 to strip flavor and aroma eompounds and to obtain
a eoneentrated flavor and aroma solution;
(e) eondensing the steam strippings in a
eondenser;
(d) compressing the gaseous non-eondensecl
flavor and aroma compounds from steps (a) and (e);
(e) passing the eompressed gaseous
non eondensed flavor and aroma eompounds to an
absorption eolumn;
(f) taking a portion of the coneentrated
stripped extraet of step (a);
(g) passing the eoncentrated extract of
step (f) to said absorption eolumn countercurrent so
as to absorb the eompounds of s~ep (e);
* Trade mark
3 ~ 7
-- 5
(h) combining the steam strippings of
step (c), the remainder of concentrated stripped
extract of step (a) and the portion of concentrated
e~tract containing the flavor and aroma co~pounds of
05 step (g); and
(i) spray drying the combined strippings
and extracts of s~ep (h).
Preferably, the extract of step (f) is maintained
at a temperature of about 10 to 15C, a concentration
of 10% ~o 40% solids, typically 35%, and a viscosity
of 70 to 150 cps. when passed to the absorption
column.
The evaporative concentration of step (a) may
be carried out in a single effect evaporator such as
a Centritherm*or a multiple effect evaporator.
The solids concentration of the combined
strippings and extracts of step (h) fed to the spray
dryer is about 35% to 60%, preferably 40% to 45%.
BEST MODE FOR CARRYING OUT THE INVENTION
This invention thus involves the use of a
moderately viscous liquid (70 to 150 cps), typically
35% solids concentration, at a temperature of 10 to
15C as the absorbing medium in a gas absorption
column. Generally, absorption columns are not
operated w~th viscous liquids. Previous attempts to
absorb gaseous aromas into a viscous liquid, such as
concentrated coffee extract were not too successful
due to poor operation and foaming, or were deemed
economically not feasible. A unique aspect of this
invention is the use of both gas and liquid streams
as continuous phases in the column, thus preventing
foam formation and yet providing enough contact area
between gas and liquid so as to effect mass transfer
of the volatiles from the gas to the liquid.
* Trade mark
The overall process allows coffee extract to be
concentrate~ from 10% to 20% initial upwards to 35%
to 60% solids ~ith minimal flavor and aroma loss.
The overall process involves an initial
05 evaporation step, carried out in a single effect
evaporator, followed by two recovery systems. The
condensate stream from the single effect evaporator
is sent to a distillation column where the volatiles
are separated and concentrated. The non-condensible
streams are recovered in an absorption column by
contacting with aroma lean concentra-ted extract
having a viscosity of 70 to 150 cps. and a
temperature of about 10 -to 15C. The concentrated
volatile streams are combined with the concentrated
extract stream before spray drying.
The step of steam stripping the aqueous flavor
and aroma solution resulting from the concentration/
condensation of extract may be carried out in a
distillation column. Volatiles are removed in the
lower section of the distilllation column called the
stripping or exhausting section. In this section a
large amount of the liquid is evaporated, and several
stages are provided so that volatiles can be removed.
In the upper portion of the distillation column,
called the enriching or rectifying section, the
volatiles are concentrated by refluxing liquid back
into the column and providing a sufficient number o~
stages to achieve a desired concentration.
Approximately 75% of the extract feed to an
evaporator may be evaporated. In this step, most,
perhaps as high as 90%, of the volatiles are removed
from the co~centrate. The extract leaving the
evaporator is at a concentration of approximately
52% solids. Staging of evaporators may be necessary
to achieve this concentration. A more efficien~
I :~ 8 ~
evaporator, such as a multiple effect, can be used
to perform the bulk of the evapora~ion.
The distillation column has been designed to
recover compounds with a lower limit of relative
05 volatility of 3 to 15. The number of actual trays
can be de~ermined using standard design method. An
advantage in using distillation, as a separating and
concentrating device is its flexibility. By altering
design and/or operating parameters, compounds with
other relative volatilities can be recovered, thus
altering the flavor of the final product.
Non-condensable vapors from both the evaporator
and the distillation column were analyzed and found
to contain a quantity of volatiles to impact flavor.
Recoveries on the absorber were above 95% for carbon
compounds.
Spray drying is performed using high concentration
extract (43% solids), high spray nozzle pressure
(70.3 kg/cm2, 1000 psi) and low temperature drying
conditions (205C in, 105C out, 400F in, 220F
out).
The spray dried products produced in accordance
with this invention have been described as being
similar to freeze dried. Flavor comments on the
products are: winey, buttery, aromatic, groundsy,
smooth and well rounded.
EXAMPLE
This invention is adapted to efficiently recover
non-condensable gaseous flavor and aroma compounds
venting from condensers on an evapora~or and
distillation column.
1. Feed extract (15% solids) from the percolator
scale tank i5 evaporated under vacuum (125 ~o 150 mm
Hg, absolute) in a single stage evaporator to 55%
concentration.
~ ~ ~2~
2. The vapors are condensed in a tower water
condenser.
3. The non-condensed gaseous aromas are then
compressed to atmospheric pressure and fed to the
05 bottom of the absorption column.
4. The flavor and aroma condensate from
step 2 is concentrated in a distillation column 20
fold under vacuum (360 mm Hg, absolute).
5. Non-condensed gaseous aromas from the
vacuum distillation column are compressed to
atmospheric pressure and fed to the bottom of the
absorption column.
6. A portion of the concentrated extract ~10%
by solids' weight from step 1) is diluted back to
35% solids concentration and fed into the top of the
absorber. Operation is conLinuous, counter-current.
5. The aroma-rich absorber product is then
combined with the liquid aroma from the distillation
column and the remainder of the concentrated extract.
6. The combined distillate and extracts are
then spray dried.
Gas chromatograph analyses of the gas streams
were performed. Taste comparisons of absorber feed
and absorber product showed the product to contain
significantly higher levels of coffee flavor notes
predominantly described as winey, buttery, aromatic,
and rich. Gas chromatograms further showed that
essentially all the gaseous aromas were recovered
from the gaseous stream fed to the absorber.
A study of the following products was then run
for product evaluation purposes.
1. Commercial freeze-dried coffee product
2. Spray-dried coffee product according to
process of invention (high Colombian blend)
1 ~2~
3. Spray-dried coffee product according to
- process of invention (moderate Colombian blend)
4. Commercial freeze-dried coffee product
A total of 576 judgements were conducted among
05 respondents who used either non-decaffeinated freeze
dried coffee or ground and freeze dried coffee.
No differences were found between the two user
groups (freeze dried and ground and freeze dried,
Dual Users~. Results from this test indicated equal
preference between products made according to the
process of this invention and the commercial
freeze-dried coffee products.
