Note: Descriptions are shown in the official language in which they were submitted.
Descr~ tion
AROMATIZE~ SOLUBLE COFFEE
Technical Field
The present inven~ion p~rtains to soluble
05 coffee and, more particulaxly, is directed to
freeze-dried soluble coffee solids. Specifically,
the invention is related to soluble coffee granules
having a unique porosity which provides these
granules with the capability of sorbing and retain-
ing roasted and ground coffee aromatics and control-
lably releasing these aromatic volatiles.
Background Art ~
Compared with roasted and ground coffee, the
source material, soluble coffee has very little
aroma.
Prior to the present invention, virtually all
commercial soluble coffee products have been Pn-
hanced with aromas by combining the soluble coffee
with pure coffee oil or aroma-enriched coffee oil in
an endeavor to provide the soluble coffee product
with an aromatic quality more akin to roasted and
ground coffee (cf. U.S.A. Patent No. 3,148,070).
Aromatizing soluble coffee solids with coffee
oil has several drawbacks. Many processing problems
are encountered in recovering the oil from the
roasted and ground coffee and, once obtained, the
glyceride has a tendency to become rancid. ALso,
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coffee oil, even in small amounts, adversely affects
the flowability of soluble coffee granules and
undesirable droplets of -the oil can, and do, appear
on the surface of the liquid beverages prepared from
05 the oil-containing soluble coffèe solids.
Prior suggestions, trials and other efforts
directed toward aromatizing soluble coffee solids
without the use of coffee oil as the aroma carrier
have not, within present knowledge, met with com-
mercial success. These attempts have been less thansuccessful, for the most part, because of the in-
herent lack of sufficient affinity of conventionally
produced soluble coffee solids for sorbing and
retaining volatile coffee aromatics.
Disclosure of the Invention
The thrust of the invention is the aromatization
of soluble coffee products wi~hout the use of coffee
oil. Surprisingly, it has been discovered that
soluble coffee solids, produced under a condition
which provides them with a unique porous structure,
have an affinity of heretofore unrealized large
magnitude for roasted and ground coffee aromas.
The porous soluble coffee particles of this
invention not only have the capacity to sorb large
quantities of volatile aromatics of roasted and
ground coffee, but also have the capability to
retain the aromatics for extended periods of time
and subsequently, to release the aromatics under
controlled conditions.
These highly aromatized soluble coffee particles,
when added in small amounts, and uniformly admixed
with typical unaromatized soluble coffee solids,
provide the composite product with the desirable
fragrant aroma of freshly roasted and ground coffee.
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The aromatized soluble coffee particles ind
their greatest utility as sor~ent for roasted and
ground coffee aromas which are to be released upon
opening a jar of aroma-enhanced soluble co~fee ? When
05 the jar is recapped, the uniquely porous particles
controllably release additional aromas which perm-
eate the contained remaining bulk product and void
spaces. On reopening the jar, the aromas are further
released to the a-tmosphere foretelling the consumer
of an enjoyable beverage.
The essence of the invention resides in the
discovery of a uni~ue microporous structure which
not only provides soluble coffee particles with
available exposed internal surface areas for solid
surface to vapor molecular attraction (adsorption of
the roasted and ground coffee aroma vapors) but also
the structure manifests micropores within a range of
sizes which extensively sorb and retain roasted and
ground coffee aromatics via capillary condensation.
The molecular structures of the aromas "fit" and
cooperate with the micropores to the extent the
aromatics are releasably retained within the
micropores substantially by capillary condensation
forces and by some surface contact attracting
forces.
Condensation of the aromas affords the
micropores the capability of sorbing significant
quantities of aromatics which are, subsequently,
controllably released as vapors.
For purposes of this invention, the term
"micropore" is intended to mean a pore having a
radius of 1000 A or less.
In order to produce a satisfactory and success
ful result within the precepts of the invention, it
has been determined that the particles of soluble
coffee to be initially aromatized with roasted and
~round coffee aromas must have a porosity such that
from 3 to 30 microliters per gram of the dry soluble
coffee solids is comprised of micropores which have
05 a radius of 150 A or less. That is, the soluble
coffee solids must have 0.3 to 3% (v/w) of useful
pore space comprised of pores having a
radius of 150 A or less.
Inherently, when the soluble coffee solids are
prepared so as to have from 0.3 to 3% (v/w) of the
pore space comprised of pores having a radius of lS0
A or less (useful pore space for purposes of the
invention), a gradation of pore sizes results with
those pores having a radius of less than 30 A most
frequently occurring and contributing to the useful
pore space.
The fact the useful pore space is comprised of
pores of gradual sizes adds to the overall capability
of the useful pore space to sorb and retain aromas
associated with roasted and ground coffee. The
aromas are a mixture of compounds of various molecular
size and structure, each of which is preferentially
sorbed and retained by capillary condensation in
pores of a size most suitable for this purpose.
Those pores in the soluble coffee solids having
a radius greater than 150 A have been determined to
be substantially incapable of sorbing any of the
components of roasted and ground coffee aromas by
capillary condensation and are, therefore, considered
to be outside the useful range.
It has now been determined that from 0.05 to 20
milligrams of roasted and ground cof~ee aromas can be
sorbed by capillary condensatlon per gram of dry coffee
solids having a useful pore space of 0.3 to 3% (v/w).
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The specific amount of aromas sorbed is primarily a
factor of the type aroma, the magnitude of the
useful pore space, and the pore size distribution
within the useful pore space.
05 Further, for those soluble coffee solids having
a useful pore space of 30 microliters/~ram of solids,
when sorbing within each gram of soluble solids as
much as 10 milligrams of dry aromas from roasted and
ground coffee via capillary condensation, it has been
determined that only 30-35% of the useful pore space
is filled with aroma components.
The capillary condensation forces which sorb
and retain the aromas have been determined to be
less than the aroma vapor pressure forces strivin~
to release the aroma from the useful pore spa~e.
Thus, upon confining a small quantity of the
aromatized soluble coffee solids within a closed
container, the aroma will be driven from the solids
in vapor form until an equilibrium partial vapor
pressure is attained within the container. Upon
opening the container the vaporized aroma is further
released to the proximate atmosphere. Reclosing the
container brings about a second equilibrium condition.
Thus it can be appreciated that a readily calculated
small amount of aromatized microporous sol-lble
coffee solids of the invention can be admixed and
jarred with unaromatized conventional soluble coffee
to provide sufficient roasted and ~xound aroma to
pass from the aromatized solids into the headspace
of the jar and be released each time the jar is
uncapped.
Measurement of Pore Size and Useful Pore Space
The porosity of a material is the ratio of the
volume of the interstices of -the material to the
volume of its mass. To extend this definition to
include the number of interstices (pores), their
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shape and size (particularly micropores), requires
sophisticated measurement and calculation
techniques.
The characteristics of the porosity of the dry
05 soluble coffee solids for the present invention have
been calculated from responses from model systems
employing C02 and N2 gases according to the well
recognized and authoritative methods of S. Brunauer,
"The Adsorption of Gases and Vapors" Vol. 1
Princeton University Press, 1945 and ~arre-tt, E.P.,
et al. Journal American Chemical Society 73 373
1951.
Best Mode for Carryin~ Out_the Invention
The microporous particles of soluble coffee of
the invention are prepared by shock freezing a
concentrated coffee extract followed by
freeze-drying the resultant frozen particles of
extract.
Spraying an aqueous coffee extract, preferably,
but not necessarily, having a soluble solids content
less than 40% by weight, typically 25% to 35% by
weight, into a cryogenic fluid having a temperature
below -100C, preferably liquid nitrogen, and
subsequently freeze-drying the frozen particles of
solution produces dry microporous soluble coffee
solids having the required useful pore space whereof
from 3 to 30 microliters per gram of the solids is
comprised of micropores which have a radius of 150 A
or less.
The spray should preferably produce particles
having an average particle size of below about 200
microns diameter so that the entire particle will be
instantaneously frozen on contact with the cryogenic
fluid.
It is not strictly essential the particle be
formed from a spray or the particle size be below
200~ --what is essential is the rapidity at which
all of the moisture within ~he particle freezes.
05 It is believed that rapid freezing, approaching
instantaneous, forms minute ice crystals exclusively
throughout the particle. To assure this condition,
the cryogenic fluid should have a temperature of
-100C or below.
The moisture content of the shock frozen particles
of concentrated coffee extract which is in the form
of minute ice crystals is sublimed from the particles
to yield solid coffee granules with the microporous
structure of the invention. It is essential that
moisture removal be accomplished substantially
completely by sublimation (no liquid water present)
to produce the desirable pore structure. Also, freeze-
drying processing conditions must be carefully
controlled to insure there is insignificantly little,
or no melting of the ice crystals during dehydration
of the frozen coffee extract particles.
The aromas associated with roasted and ground
coffee, whether natural or synthetic, may be derived
from many sources well-known to those skilled in the
art. Depending on the method of contact to be
employed, the aromas may be present as a component
of a gas, a liquid condensate or a condensed frost.
The method of contacting the microporous
particles with roasted ground coffee aromatics for
the purpose of sorbing aroma within the particles
can also be many and varied. The use of high pressure
and/or low particle temperatures may be employed in
order to maximize the quantity of aroma sorbed or to
shorten the period of -time required to achieve a
desired level of aromatization; however, such
conditions are not usually required.
Among the techniques useful to date for the
05 sorption of aromatics by the porous solu~le coffee
particles, the most preferable is to contact the
microporous particles of soluble coffee with grinder
gas frost (frozen roasted and ground aromatics plus
frozen C02 obtained during the grinding of the
roasted coffee).
This is accomplished by placing both the porous
particles and condensed CO2 aroma frost well mixed
in a vented vessel, preferably above -40C, and
permitting the CO2 portion of the frost to sublime.
The microporous coffee granules of the in-
vention have the capability of sorbing as much as 2%
(w/w) of roasted and ground coffee aroma. This is,
in general, in excess of that which is required and,
depending on how the aromatized soluble coffee
solids axe utilized, the aromatized particles will
contain aromatics at a level of from 0.05 to 20
milligrams per gram of solids.
When the level of aromatics sorbed is 1 milli-
gram/gram of aromatized solids, it requires about 5
grams of aromatized solids to be admixed with 95
grams of conventional soluble coffee -to provide
sufficient headspace aroma in the jar for release
each time the jar is uncapped throughout the average
periodic use of the beverage-making product.
Since it has been determined to be more prefer~
able to admix 2% or less of aromatized microporous
soluble coffee solids with the conventional soluble
coffee, the aromatized mixture should preferably
contain aromatics at a level of 0.2 to 0.5% (w/w).
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If the aromatized rnicroporous soluble coffee
granules are present in the product of the invention
in excess quantity, they provide desirable flavor
effects to the liquid beverage upon reconstitution
05 of the granules with hot water.
As stated before, during storage of the
aromatized soluble coffee granules admixed with the
bulk unaromatized materials, the sorbed aromatics
exert a vapor pressure which overcomes the porosity
binding forces and a small quantity of aroma is
released until a partial vapor pressure equilibrium
condition exists within the jar. Upon opening the
jar, the aroma is further released to the atmosphere
foretelling the consumer of an enjoyable beverage.
Upon capping the jar, the aroma-retention and
releasing processes are repeated. Thus, the inven-
tive granules are capable of sorbing, retaining, and
releasing roasted and ground coffee aromas to pro-
duce desirable soluble coffee jar package "head-
space" aroma.
EXAMPLE
An aqueous coffee extract having a soluble
solids content of 33% by weight was prepared by
reconstitu-ting spray dried coffee solids. This
extract was sprayed into an open vessel containing
liquid nitrogen whereupon the particles of extract
immediately froze and were dispersed. The extract
was sprayed by means of a two-fluid, glass atomizing
nozzle (a chromatographic nozzle obtained from SGA
Scientific, Inc., Fullerton, California) using air
as the pressurizing fluid. The liquid nitrogen and
particle mixture was poured into freeze drier trays,
and the liquid nitrogen was allowed to boil off
leaving behind a flat bed of frozen particles about
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1.16 to 3.2 mm. in thickness. The trays were placed
in a freeze drier and subjected to a vacuum of 10
microns of Hg. and a plate temperature of 50C for a
period of 18 hours. The vacuum on the freeze drier
05 was broken with dry CO~ and the dry particles having
a moisture content of helow about 1.5% were remo~ed
from the freeæe drier and kept out of contact of
moisture. The dry particles were found to have a
microporous structure such that 30 microliters per
gram of coffee solids of the pore space were com-
prised o pores having a radius of 150 A or less with
the most frequently occurring pore size within the
useable pore space being less than 30 A.
The dry particles were subse~uently chilled in
dry ice under a dry atmosphere and mixed with coffee
grinder gas frost, having a moisture content between
10 and 15% by weight, at a weight ratio of 0.2 parts
frost per part particle. The mixture was trans-
ferred to a prechilled jar having a pinhole vent, and
the jar was stored at-18~overnight during which
time CO2 was evolved. The chilled particles, having
a moisture content of below 6% by weight, were then
packaged in glass jars with unplated, agglomerated
spray-drled coffee solids at the level of 0.75~ by
weight of spray-dried solids. The resulting jars
were then stored at 35c for periods of eight
weeks. Upon initial opening and during a standard 7-
day, in-use cycle, a pleasing headspace aroma was
found which was rated as being at least as good as
the headspace aroma possessed by jars of comparably
stored, aromatized, agglomerated spray-dried coffee
which coffee had been plated with grinder gas-
enriched coffee oil. This oil-plated sample was
prepared in accordance with U.S. Patent No.
4,119,736 using an amount of grinder gas frost for
each weight unit of soluble product comparable to
that employed in the inventive sample.
As previously noted, jar aroma has been provided
05 to commercial soluble coffee products by means of
oil plating an aroma-bearing glyceride (e.g. coffee
oil onto soluble powder). -Lt has also been con-
templated to absorb coffee aromatics onto oil-plated
soluble coffee, and this technique is expressly
disclosed in U.S. Patent No. 3,823,241 to Patel et
al. It has, however, not previously been thought
possible to sorb high levels of aromatics directly
onto soluble coffee solids such that the aromatics
would be retained. The Patel et al. patent notes
the criticality of the oil so that upon successive
openings of the soluble coffee package (i.e., in~use
cycle), the consumer will continue to perceive a jar
aroma. This is in fact the situation for the con-
ventional spray-dried, foam~dried and freeze-dried
products dealt with in the Patel et al. patent.
However, the same deficiency does not exist with
microporous soluble coffee particles having a use-
able pore space as described for this invention. As
previously noted, conventional spray-dried coffee
does not possess a microporous structure; while in
conventional freeze-dried coffee, most of the pore
radii are on the order of 10,000 A and the useable
pore space (pores having a radius of 150 A or less)
is insignificantly small or entirely absent.
Indus_rlal Applicability
The microporous soluble coffee granules of the
invention find their greatest utility as sorbent for
roasted and ground coffee aromas which are to be
released upon opening a jar of soluble coffee. The
inventive product has no coffee oil as the aroma
sorbent and thereby avoids the processing
difficulties encountered with the
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glyceride. In this respect alone, the inventive
soluble coffee product comprising packaged low or no
aroma-containing soluble coffee admixed with a small
amount of highly aroma-enhanced microporous soluble
05 co~fee granules represents a major technical advance
in the art of soluble coffee manufacturing, part-
icularly in view of the fact the aromas sorbed by
the microporous granules have excellent stability
during prolonged storage under inert conditions such
as those which normally exist in packaged soluble
coffee products.
