Note: Descriptions are shown in the official language in which they were submitted.
DESCRIPTION
PROCESS FOR AROMATIZING FOOD SUBSTRATES
- BACKGROUND OF THE INVENTION
Soluble beverage powders such as spray
05 dried coffee or tea products are relatively devoid
of aroma as compared to their source or parent
material - namely, roasted and ground coffee and
fermented tea leaves. The same low aroma situation
exits with dried fruit juices, such as freeze-dried
orange juice, as compared to natural fruit from
which the juice is obtained. Low aroma intensity
also exists in certain types of roasted coffee
material such as most decaffeinated coffees and the
compressed roasted coffee materials described in
U.S. Patent Nos. 1,903,362 to McKinnis, 3,615,667 to
Joffe and 4,2619466 to Mahlmann et al. These low
aroma beverage products have an initially low
quantity of aroma~ such that upon the initial open-
ing of the product by the consumer only low aroma
impact is detected, and whatever amount of aroma is
present in the product is rapidly given up after
initial opening of the container, such that sub-
sequent openings of the container during a typical
in-use cycle for the product evolve little or no
aroma.
It should be ~oted that the terms '?coffee
product" and/or "tea product" as used in this in-
vention is meant to refer to not only those materials
consisting of 100% coffee and/or tea but also to
05 substitute or ex~ended coffees or teas which may
contain roasted grain, chicory and/or other veget-
able materials alone or in combination with coffee
and/or tea.
To date most efforts to add natural aroma
to food products have focused on the addition of
roasted cofee aroma to soluble coffees such as
spray or freeze-dried coffee. Understandably then
the thrust of the present invention is in the area
of aromatizing soluble coffee products; however, the
application of this invention for the aromatization
of other food products i5 contemplated.
At the present time, virtually all com-
mercial soluble coffees are combined with coffee oil
such as by spraying the soluble coffee prior to
packaging with either a pure or an aroma-enriched
coffee oil. In this manner the soluble coffee
material will have an aroma more akin to non-
decaffeinated roasted and ground coffee. The
addition of oil is usually effected by the well-
known oil plating technique (shown in U.S. PatentNo. 3,148,070 to Mishkin et al.) or by oi] injection
(shown in U.S. Patent No. 3,769,032 to Lubsen et
al.).
Coffee oil with or withowt added aromas
3~ has been the preferred medium employed to aromatize
coffee material since such products could still be
designated as being pure coffee; however, techni~ues
developed for the production of coffee oil (see
Sivetz, Coffee Processing Technology, ~ol. 2, Avi
Publishing Company, 1963, pages 21 to 30) such as
Z~8
solvent-extracting or expelling coffee oil ~rom
roasted coffee are not particularly desira~le since
the manu~acturer is left with either solvent-
containing roasted coffee or e~pelled cake, both of
05 which must be either further processed or discard~d.
The addition of oil to a coffee product has also
proven troublesome in that, un~esirably, oil drop-
lets can appear on the sur~ace of the liquid ~ev-
erage prepared from the oil-containing product.
Thus, it would be advan~ageous if processes for
aromatizing coffee products were developed which
employed all coffee or other vegetable materials~
but which did no~ require the production or use of
coffee oil or other glyceride material.
A method of aromatizing food products
which does not have to rely on synthetic materials
or chemical modification of natural materials would
have applications in the food industry in addition
to coffee and tea products. Powdered fruit juices,
powdered fruit-flavored beverage concentrates and
gelatin dessert mixes are bu~ some of the possible
applications. The use of expressed aromatic oils
such as orange oil and lemon oil has been practiced
in the food art, but the instability of these oils
has limited their use. If the aromatics contained
in either these oiis or elsewhere in a foodstuff
material were capable of being held in a stable
manner within natural vegetable materials, natural
aromas could be incorporated into a multitude of
food products.
While the majority of the description
presented herein relates to aromatizing coffee
products, such a presentation is for convenience of
description only and the invention is not meant to
be limited thereby.
- 4 -
DESCRIPTION OF THE INVENTION
Water-soluble particles of edible materials
are obtained by drying aqueous solutions of vegetable
materials such as coffee, tea, chicory, fruits, and
05 the like. These particles are prepared in such a
manner that the particles have an average (basis
distribution of % by weight) diameter which is below
200 microns ~ ) preferably below 150~ , usually
between about 50~ and 150,h , and possess a micro-
10 porous structure containing micropores having a most
probable radius of less than 150 angstroms (A)
preferably less than about 110 A, more preferably
less than 50 A. A most probable radius of between
10 and 35 A has been found to be most preferred for
15 this invention. Micropores smaller than about 15 A
while thought to be desirable for purposes of this
invention have not been found to be readily attain-
able and is seen ~o constitute a practical lower ;
limit for the most probable radius parameter. A
20 pore radius of less than about 3 A is not desirable
since such a small size would exclude molecules of
aromatic compounds sought to be fixed within the ;
microporous structure.
The fine pore structure of the porous
25 particles of this invention was determined from `
analysis of the adsorption-desorption isotherms of
carbon dioxide gas on these particles at -78C. A
standard all-glass volumetric gas adsorption ap- 5
paratus was used following the procedures recognized
3 by those skilled in the field of surface chemistry
(Brunauer, S., "THE ADSORPTION OF GASES AND VAPORS"
Vol. 1, Princeton Univ. Press, 1945). Normally one
determines the adsorption isotherms first, by
measuring the amounts of CO2 adsorbed at various but
successively increasing equilibrium pressures, and
,: ; . : . .
- 5 -
then reduces the pressure to obtain the desorption
branch of the isotherm.
The desorption isotherms are usually the
result of ordinary multilayer adsorption and con-
05 densation in porPs, in which case the Kelvinequation, which evaluates the lowering of the ad-
sorbate (CO2) vapor pressure due to the concavity of
the ]iquid meniscus in ~he pore, can be applied. In
its simple form and assuming a complete wetting of
the surface (zero contact angle) the pore radium (r)
is given by
r = -2 ~ V
RT ln Pd/Po
where ~ is the surface tension of liquid sorbate
(CO23, V is its molar volume, Pd is the pressure at
the desorption branch of the isotherm and PO is the
saturated vapor pressure (760 mm Hg for CO2 at
-78C). The Kelvin equation shows that there is a
logarithmic relationship between the pore radius and
the relative pressure (Pd/Po). Narrower pores fill
at lower relative pressures, wider pores at higher
pressures, and the entire pore space is filled at
the saturation pressure. Further refinements of the
Kelvin equation have to be applied to correct for
gas adsorption which occurs simultaneously with gas
condensation (Barrett, E.P., L.G. Joyner, P.P.
Halenda; J. Amer. Chem. Soc. 73, 373 (1951).
Computation is then performed to obtain the relative
pressures and hence gas volumes (v~ adsorbed cor-
responding to selected pore radii(r). Plots of -
) vs r (A) provide pore volume distributioncurves. The shape of these distribution curves
reflect the uniformity or the spread of pores of
different sizes in a given sample. As will be
-
~ 8
- 6 -
recognized by those skilled in the art, the pore
size distribution within a given porous material
generally follows a bell-shaped curve distribution
pattern, and the term "most probable radius" is
05 meant to refer to the radius corresponding to the
top of the pore volume distribu~ion curve.
The aqueous solutions used to prepare the
dry particles will usually be obtained by means of
an aqueous extraction of a vegetable material such
as roasted coffee or fermented tea, or by expressing
a juice from a vegetable material such as oranges,
apples, grapes and the like.
Various techniques such as those herein-
after set forth will be available for producing
lS particles having the desired microporous structure.
Conventional spray drying yields dry particles which
do not possess a microporous structure. Convention-
al freeze drying yields particles wherein the most
probable pore radius is well in excess of 10,000 ~.
Pores below 150 A are necessary in order to trap
volatile aromatic compounds, such as those found in
coffee and tea aroma, within the microporous
structure of the dry particle. The entrapment of
aromatics by the dry particles of this invention is
believed to be a result of both adsorption and more
importantly, capilIary condensation (i.e., the
li~uefaction of vapors in pores). The aromatics are
held within microporous structure without the
necessity of any coating on the surface of the
particles. A small percentage of these aromatics
will, however, be released as a result of the slight
partial pressure exerted by the trapped aromatics.
The mechanism of capillary condensation will not
occur in pores of excessive size where surface
- 7 -
coating of the particles will be necessary to retain
aromatics.
The dry porous particles produced in
accordance with this invention are, after being
05 contacted with desirable aromatics, used to provid~
headspace aroma for packaged low-aroma food product5
such as the aforementioned soluble coffee or tea
products. These particles will be combined with the
food product at a preferred level by weight of from
0.1% to 2%, most preferably from about 0.2% to 1%.
Typically the dry aromatized soluble particles of
this invention will be merely blended with a dry,
low-aroma, powdered food product.
Several methods have been identified for
producing dry soluble particles of edible material
obtained from aqueous solutions of vegetable
materials such that the resulting dry particles are .
below 200,~in diameter and contain a porous structure
wherein the most probable pore radius is below
150 A.
Spraying of an aqueous solution, prefer-
ably having a 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 micro-
porous particles having a most probable pore radius
of less than 50 A. The spray should produce
particles having an average particle size of below
200~ in diameter so that the entire particle will be
instantaneously frozen on contact with the cryogenic
fluid. It is believed that instantaneous freezing
will result in the formation of only minute ice
crystals throughout the particle. Should the spray
-
~z~
- 8 -
droplets e~ceed 200 in average diameter then, even
at liquid nitrogen temperature the frozen particle
will possess ~he desirably minute ice crystals only
at its surface and not throughout its structure.
05 Sublimation of these minute ice crystals is seen to
yield the desirable microporous structure of this
invention. Use of a cryogenic fluid having a tem-
perature above -100C has not been found to produce
a most probable pore radius of less than 150 A
regardless of the diameter of the spray droplets.
Another method for producing the dry
microporous particles is to spray the aqueous 901u-
tion into a anhydrous organic solvent, such as 100%
ethanol, which will both deh~drate the extract and
form porous spheres of soluble solids. Soluble
coffee particles prepared in this manner have been
found to possess a most probable pore radius of less
than 50 A. It is also possible to begin with ground
spray dried particles, such as soluble coffee, and
boil these particles in an edible organic solvent
such as ethanol, preferably after grinding, in order
to etch the surface of the particles and produce a
desirably porous structure. ~gain, it will be
desirable to produce or utilize particles which have
an average diameter below 200~ in order to provide
sufficient surface area for the solvent to etch such
that a sufficient number of desirable micropores are
produced.
The microporous particles produced accord-
ing to this invention could entrap volatile aromatic
compounds up to about 2% by weight. In actual
practice amounts of aromatics in excess of 1% are
difficult to obtain. Entrapment of aromatics at a
level of less than about 0.1% by weight would re-
quire the addition of aroma~ized particles to thesoluble food product at a level of 5% or more. It
will usually be preferred to add the aromatized
particles at a level of less than 2% by weight.
05 Preferably the aromatized particles of this invention
will contain aromatics at a level of 0.2% or more,
typically about 0.5%.
The method of contacting the porous
particles with aromatics for the purpose of en-
trapping aroma within the particles can be many andvaried. The use of high pressure and/or low particle
temperatures may be employed in order to maximize
pick-up of aroma or shorten the period of time
required to achieve a desired level of aromatization;
however, such conditions are not required. It will
be desirable, however, to minimize the amount of
moisture which comes into contact with the soluble
porous particles both before, during and after
aromatization. Suitable condensation, vaporization,
sweeping and/or other separation techniques may be
employed to separate the moisture and aromatics
contained in aroma-bearing gas streams, aroma frosts
or liquid aroma condensates. It may also be desir-
able to separate aromatics from any carrier gas
(e.g. CO2 in which they are entrained. Among the
techniques useful for adsorbing aromatics onto the
porous substrates are: (1) placing both the porous
particles and a condensed CO2 aroma frost well-mixed
in a vented vessel, preferably above -40C, and
permitting the CO2 portion of the frost to sublime
off, (2) enclosing both the adsorben-t and a con-
densed aroma frost in one or two connected pressure
vessels and then raising the temperature wi~hln the
frost containing vessel to vaporize the frost and
- 10 -
provide an elevated pressure, (3) combining a highly
concentrated aqueous aroma condensate with the
porous particles at a level at which it does not
unduly moisten the particles, (4) condensing
05 aromatics onto chilled porous par~icles, (5) passing
a stream of aroma-bearing, low-m~isture gas through
a bed or column of porous particles.
The aromatics which may be used for this
invention may be derived from any of the 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. Among the aromas
which may be used are coffee oil aromas, as des-
cribed in U.S. Patent No. 2,947,634 to Feldman et
al., aromas obtained during the roasting of green
coffee, as described in U.S. Patent No. 2,156,212 to
Wendt, aromas obtained during the grinding of roast-
ed coffee, as described in U.S. Patent No. 3,021,218
to Clinton et al., steam-distilled volatile aromas
obtained from roasted and ground coffee, as described
in ~.S. Patent Nos. 2,562,206 to Nutting, 3,132,947
to Mahlmann, 3,244,521 -to Clinton et al., 3,421,901
to Mahlmann et al., 3,532,5~7 to Cascione and
3,615,665 to White et al., and the vacuum-distilled
aromas obtained from roasted and ground coffee as
described in ~.S. Patent Nos. 2,680,687 to Lemonnier
and 3,035,922 to Mook et al. It would, of course,
also be possible to employ volatile synthetic
chemical compounds which duplicate or simulate the
aromatic compounds naturally present in roasted
co~fee, fermented tea or other aromatic food
products.
The aromas absorbed onto the microporous
particles in accordance with this invention have
been found to be stable during prolonged storage
undèr inert conditions such as that normally exist-
05 ing in packaged soluble coffee products. Theseabsorbed aromas are able to produce desirable head-
space aroma in packaged products and if present in
sufficient quantity can also produce desirable
flavor effects.
Example 1
An aqueous coffee extract having a soluble
solids content of 33% by weight was prepared by
reconstituting spray dried coffee solids. This
extract was sprayed into a 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.) using air as the pressurizing
fluid. The liquid nitrogen and particle mixture was
poured into freeze drier trays and the liquid nitro-
gen was allowed to boil-off leaving behind a flat
bed of frozen particles about 1/16 to 1/8 inches in
thickness. The trays were placed in a freeze drier
and subject to a vacuum of 10 microns of E~g. and a
plate temperature of 50C for a period of 18 hours.
The vacuum on the freeze drier was broken with dry
C2 and the dry particles having a moisture content
of below about 1.5% were removed from the freeze
drier and kept out of contact of moisture. The dry
particles were found to have a microporous structure
containing pores having a most probable radius of
about 24-28 A and a screen analysis as follows:
- 12 -
Standaxd U.S.
Mesh# % r~t,
n 80 7.5
on 100 15.0
on 200 67.3
pan 10.2
The dry particles were subseque~tly 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~erred to a prechilled jar having a pinhole
vent and the jar was stored at 0F 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 dried coffee
solids at the level of 0.75% by weight of spray dried solids.
The resulting jars were then stored at 95F. for periods of
eight weeks. Upon initial opening and during a standard
7 day in-use cycle, a pleasing headspace aroma is found which
is rated as being at least as good as the headspace aroma
possessed by jars of comparably stored aromatized, agglo-
merated spray dried coffee which coffee had been plated with
grinder gas-enriched coffee oil. This oil-plated sample was
prepared using an amount of grinder gas frost for each weight
~ unit of soluble product comparable to that employed in the
; inventive sample.
EXample 2
One hundred milliliters o~ a coffee extract
containing 50~ by weight soluble solids is sprayed
~o
- ,:
. .
~ 3
- 13 -
by means of a glass chromatographic nozzle into a
large beaker containing one gallon of pure ethanol.
The ethanol was a~ room temperature and was stirred
during the spraying operation. Thereafter particles
05 of soluble coffee were filtered from the ethanol and
these particles were put in a vacuum oven (25 inches
Hg. vacuum and about 90C) overnight to remove
residual ethanol. The resulting particles were
found to have a microporous structure wherein the
most probable pore radius was 33 A. The particles
were kept out of contact with mois~ure and contacted
with grinder gas frost at a level by weight of 2
parts frost to 1 part of particles in a Parr bomb
heated to about 20C. The resulting aromatized
particles were combined and packaged with unplated
and unaromatized spray dried coffee agglomerate at a
level of about 0.5/0 by weight. The jar aroma pos-
sessed by this sample after one week storage a~ room
temperature was found to be comparable to week-old,
grinder gas-enriched, oil-plated agglomerate.
Example 3
Agglomerated spray dried coffee was ground
and the particles passing through a 50 mesh (U.S.
Standard Sieve) screen were separated and 150 grams
of these particles were added to 2000 ml. of 100%
ethanol. This mixture was boiled for 24 hours in a
steam jacketed vessel equipped with an overhead
reflux condenser and a stirring rod. Thereafter the
coffee particles were filtered from the ethanol and
dried in a vacuum for 24 hours at 80C and a vacuum
of about 630 mm of Hg. The dry particles weighed a
total of about 90 grams (about 60 grams of coffee
solids having been dissolved by the ethanol) and
- 14 -
possessed a porous structure wherein the most prob-
able pore radius was about 102 A. Two parts (by
weight) of these particles were contacted with one
part of grinder gas frost in the manner set forth in
05 Example 1 and the resulting aromatized particles
were packaged with agglomerated spray dried coffee
at a level of about 0.5% by weight. The jar aroma
possessed by this sample after one week storage at
room temperature was found to be comparable to
week-old, grinder gas-enriched, oil~plated agglomerate.
As previously noted, jar aroma has been
provided to commercial soluble coffee products by
means of oil plating an aroma-bearing glyceride
(e.g. coffee oil) onto soluble powder. It has also
been contemplated 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 absorb or adsorb 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 conventional spray-dried,
foam-dried and freeze-dried products dealt with in
the Patel et al. patent. However, the same de-
ficiency does not e~ist in porous soluble coffee
particles having a most probable pore radius of less
than 150 A. As previously noted, conventional spray
dried coffee does not possess a microporous struc-
ture; while in conventional reeze dried coffee, the
most probable pore radius is on the order of lû,OOû
A.
05 As will be seen in the following Table
which compares the rate at which aroma is released
from aromatized particles of soluble coffee of
Examples 1 to 3 as compared to aromatized particles
of spray dried coffee which had been reduced ~o a
comparable particle size by being ground with dry
ice. The aroma release characteristics of the
different aromati~ed soluble coffee substrates can
be predicted by observing the amount of organic
carbon (micrograms) that was swept from the sub-
strate as a function of sweeping time. The carbonvalues were obtained by sweeping a known weight of
coffee (0.5 gms) with a stream of nitrogen (30 cc/min)
at 30C for 2000 seconds. The volatiles removed
were recorded every 200 seconds. The Table shows
the rate (expressed as % of total) of aroma release
(cumulative) as a function of sweep time, the aroma
released in 2000 seconds is taken as equal to 100%.
TABLE 1
% Aroma Released
Sweep Time ~u~m carbon/gm coffee) in respective
(Seconds) 'sweep time X I00 l~ Lm carbon/gm coffee)
in ~ûûu secon~s
Example 1 Example 2 Example 3 Control
200 51 36 55 69
400 74 56 74 87
600 82 67 82 94
800 8~ 76 87 96
1000 92 82 91 97
1200 94 87 93 98
14ûO 97 91 96 9g
1600 98 94 97 99
1800 99 97 98 99
2000 100 100 100 100
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As can be seen from the Tahle 1, the spray
dried control material, which does no~ possess a
microporous structure, gives up aroma most rapidly
and then would not be as suitable for providing an
05 in-use jar aroma.
~ e 4
A series of porous particles were made
according to the following procedures: 1) Spray
dried, agglomerated coffee powder was reconstituted
to 33% soluble solids and this extract was sprayed
into liquid nitrogen using a glass chromatographic
nozzle. The resulting frozen particles were freeze
dried at 10 mm microns of Hg. and 25C for 16 hours.
Particles in excess of 50 mesh (U.S. Standard Sieve)
were screened out. 2) Same as in 1 but powder
reconstituted to 50% soluble solids. 3) Spray
dried, agglomerated coffee powder was reconstituted
to 33% soluble solids and sprayed into 100% ethanol.
The resulting particles were collected and placed in
a vacuum drier at 100C and 25 inches Hg. vacuum for
16 hours. 4) 300 grams of the spray dried agglomer-
ate was ground and boiled in 2000 ml of 100% ethanol
The resulting particles were dried at about ~oac and
25 inches Hg. vacuum for 16 hours. A portion of
each of the four samples was aromatized by contact
with grinder gas frost at a ratio (by weïghtj of 0.4
parts frost per part substrate. Contact was effect-
ed by mixing the frost and substrate together in a
vessel chilled with dry ice. The aroma-bearing
particles were placed in separate chilled jars
equipped with a vent and placed in a 0F freezer
overnight. Thereaft~r 0.2 grams of each aromatized
,8
- - 17 -
sample was placed in a stoppered 250 cc flask and 1 cc of
the resulting headspace aroma contained in the flasks was
then evaluated using standard carbon gas chromatographic
techniques. A portion of each of the aroma-bearing par-
ticles was also subjected to the previously identified
nitrogen sweep test (2000 seconds at 30C) to assess the
level of aromatics contained therein. This nitrogen sweep
test was also performed on the unaroma~ized samples. The
results of these evaluations are set forth in Table 2.
TABLE 2
.. , . ... _ _
Sample # PorosityAroma Released~Ieadspace
(A)(4~gm carbon/ (GC counts
gm coffee) in millions)
1 23-28 28.5
l-aromatized " 1790 1.375
2 above 140 6.75
2-aromatized " 458 .304
3 33 2.11
3-aromatized "; 2055 .847
4 100 3.06
4-aromatized " 723 .448
Table 2 evidences the quantity of aroma which can
be absorbed by the porous particles of this invention as
compared to the amount of aroma present in the unaromatized
particles as well as the ability of these particles to
produce a headspace aroma comparable in quantity to the
headspace aroma produced by grinder gas-e~riched coffee
oil.
