METHOD OF ENCAPSULATING FLAVORS AND FRAGRANCES BY CONTROLLED WATER TRANSPORT INTO MICROCAPSULES
RELATED APPLICATIONS
This application is a Continuation-ln-Part application of U.S.
Application Serial No. 08/947,694 filed October 9, 1 997, now pending.
FIELD OF THE INVENTION
This invention relates to a method of encapsulating flavors or
fragrances into microcapsules having a hydrogel shell and an oil core.
BACKGROUND OF THE INVENTION
Microcapsules incorporating a flavor or fragrance compound are
useful to provide a controlled release of the contained flavor or fragrance.
Such products may be used in the food processing industry, where
encapsulated flavor particles may provide a flavor burst upon chewing the food
or may allow taste evaluation of a botanical or food/beverage aroma. Such
products may also be used in the cosmetic and toiletry industries, where
encapsulated fragrance particles may provide a burst of scent upon capsule
fracture. The capsule may comprise a shell surrounding a core material in
which the flavor or fragrance compound is contained.
Microcapsules may be formed by a coacervation or crosslinking
process, in which lipids are coated by tiny droplets of proteins, carbohydrates,
or synthetic polymers suspended in water. The process of coacervation is,
however, difficult to control and depends on variables such as temperature,
pH, agitation of the materials, and the inherent variability introduced by a
natural protein or carbohydrate.
In the manufacture of microcapsules containing a flavor or
fragrance compound, several features are desirable. It is desirable to produce
microcapsules that have strong walls and that do not agglomerate. It is
desirable that the compound be readily loaded into an oil microparticle, that is,
be readily absorbed into the oil core of the microcapsule. Once absorbed, it
is also desirable that the compound be irreversibly retained in the oil core of
the microcapsule, that is, be adsorbed into the microcapsule.
The amount of compound that may be encapsulated depends
upon several factors including its solubility in a fluid such as a gas or water,
partition coefficient, molecular weight, water content, volatility, and the ratio
of blank capsule to water amounts. Flavors and fragrances may be mixtures
of hundreds of components, each of which may widely in these properties. A
flavor or fragrance compound that is lipophilic may be readily contained in an
oil core of a microcapsule, while a flavor or fragrance compound that is
hydrophilic may be less readily contained in an oil core. For example, the
flavor compound diacetyl (DA) is about 20% to about 30% water soluble. For
diacetyl, typical maximum absorption into an oil is up to only about 55%. A
highly water soluble compound such as diacetyl is also more difficult to retain
in the oil core once it is loaded.
A compound's solubility in an aqueous phase versus an oil phase
is determined by its partition coefficient, abbreviated as K. The partition
coefficient of a compound is the ratio of the compound's concentration in one
liquid phase to the compound's concentration in another liquid phase (K|iquιd/Iιquιd)
or in one gaseous phase to another liquid phase (Kgas/hquιd). The partition
coefficient thus is an inherent property of the compound with two given liquid
phases, such as a lipid phase and an aqueous phase, or a lipid and a gas
phase, and reflects the compound's distribution at equilibrium between the
water or gas phase and the lipid phase. Any means of decreasing the water
solubility of a compound will shift the equilibrium of the compound and thus
shift its partitioning between an aqueous or gas phase and a lipid phase. For
example, addition of a salt will decrease the water solubility of a compound
and will increase its partitioning into the lipid phase. Similarly, crosslinking a
protein membrane to strengthen the membrane and physically decrease the
amount of water, or physically removing water from the environment, causing
capsule wall or membrane shrinking, will decrease the water solubility of a
compound and will increase its partitioning into the oil phase.
Flavors or fragrances that are water soluble may interfere with
encapsulation of an oil particle. For example, flavor or fragrance compounds
that are water soluble cannot be encapsulated using gelatin coacervation. This
is because for coacervation to occur, there must be a droplet to coat, and for
these water soluble materials, there are no droplets to coat. In addition, the
water soluble flavor or fragrance may partition so as to locate the flavor or
fragrance compound in an aqueous environment outside the encapsulated oil
particle rather than inside the oil particle. If a flavor or fragrance compound
is too water soluble, the coacervation process ceases to function due to the
colloid becoming either too thick or too thin. A colloid that is too thick has no
flow, and thus cannot properly coat the oil surface. A colloid that is too thin
is not retained on the oil surface. In the extreme, a water soluble flavor or
fragrance compound can totally solubilize the colloid, leaving no wall material
to deposit on the oil surface.
Besides water solubility, a flavor or fragrance compound that
contains fatty acids affects the pH of a coacervation reaction. If a base is
added in an attempt to adjust pH, the fatty salts produced in the reaction
impart an undesirable soap taste to a flavor compound. If a flavor or fragrance
compound contains water soluble esters, the coacervation temperature is
affected and hence the final gelation temperature is altered. While it is
therefore desirable to limit compounds that contain either fatty acids or water
soluble esters, there is a tradeoff in the potency and profile results for the
encapsulated compound. This limits the range of formulations that are able to
be effectively encapsulated.
Currently, flavor or fragrance compounds that are difficult to
encapsulate are diluted with oils such as vegetable oil or mineral oil. This
alters its oil to water partition coefficient, in which the compound attempts to
reach an equilibrium between the oil and aqueous phases. The oil serves to
reduce the natural water solubility of most compounds and, in many cases,
reduces it below the level at which it interferes with coacervation. A flavor or
fragrance compound that is highly water soluble, however, does not have this
effect. A compound that has a water solubility greater than 25% prefers to
partition in an aqueous phase, and a ratio of lipid:water greater than 90% is
needed to encapsulate these compounds. The coacervation process, however,
is generally limited to about 22% lipid. Thus, this technique is of only limited
applicability for water soluble flavor or fragrance compounds.
Several techniques are known in the art for absorbing compounds
into a microcapsule, such as cyclodextrin entrapment or silica plating. A
drawback of the cyclodextrin entrapment technique is that the binding effect
varies widely depending upon the particular flavor or fragrance compound. A
drawback of the silica plating technique is that there is no barrier to protect the
flavor or fragrance compound from evaporation. Thus, there is a need for an
efficient method of absorbing the many types of flavor and fragrance
compounds to the desired level of loading in an encapsulated oil. There is also
a need for an efficient method of adsorbing flavor and fragrance compounds
once they have been encapsulated.
SUMMARY OF THE INVENTION
This invention relates to a method of encapsulating a flavor or
fragrance compound by controlled water transport of the compound into a
capsule having an oil core. The method comprises preparing a microcapsule
having a hydrogel shell and an oil core, and thereafter adding an amphiphilic
flavor or fragrance compound in a liquid or gaseous state in the presence of
water to the microcapsule to transport the compound through the hydrogel
shell and into the oil core. The compound is transported into the core by
aqueous diffusion through the hydrogel shell. The oil core is retained in the
hydrogel shell during the aqueous diffusion. A flavor or fragrance compound
is thus encapsulated in the hydrogel shell containing the retained oil core.
The shell may consist of a carbohydrate or a protein, which may
be crosslinked or non-crosslinked, or a synthetic polymer such as polyvinyl
pyrollidone or methyl cellulose. The oil core may comprise, for example,
vegetable oil, mineral oil, benzyl alcohol, or mixtures thereof. In a preferred
embodiment, the oil is a short chain triglyceride of fractionated coconut oil.
As more particularly defined hereinafter, "oil" is meant to include a wide range
of substances that are dispersible in water due to their hydrophobic nature.
In an alternative embodiment of the invention, the microcapsule
may be prepared in a dry form. An amphiphilic volatile flavor or fragrance
compound is added, in the presence of a controlled volume of water, to a
substantially dry microcapsule having a hydrogel shell surrounding an oil core.
The compound is solubilized in a fluid, either a liquid or gas, is transported
through the hydrogel shell by aqueous diffusion into the oil core and is retained
in the core. The microcapsule having the flavor or fragrance compound
retained in the oil core is used as is. Alternatively, the capsule wall may be
treated to prevent loss of component and then dried.
In a preferred form of the invention, a flavor or fragrance
compound is encapsulated by preparing a microcapsule of a coacervate of an
oil core and a hydrogel shell, adding the flavor or fragrance compound in the
presence of water to the microcapsule for transportation of the compound into
the oil core, transporting the compound through the hydrogel shell by aqueous
diffusion, and retaining the oil core in the hydrogel shell during the
transportation to provide the encapsulated flavor or fragrance and retained oil
core in the hydrogel shell.
The invention is also directed to a method of encapsulating a
volatile flavor or fragrance compound by preparing a microcapsule having a
hydrogel shell surrounding an oil core for retention of the oil in the shell, adding
the compound in its gaseous state in the presence of water to the
microcapsule for transportation of the compound into the retained oil core,
transporting the compound by aqueous diffusion through the hydrogel shell
into the retained oil core, and retaining the oil core in the hydrogel shell during
said transportation to provide the encapsulated compound in the hydrogel shell
containing the retained oil core. The compound, such as an aroma chemical,
is in a stream of a gas such as air, carbon dioxide, nitrogen and/or argon that
is passed over the microcapsule.
The invention is additionally directed to a method of encapsulating
a volatilized compound by capturing the volatilized compound in a gas stream
and passing the gas stream containing the volatilized compound in the
presence of water over microcapsules having a hydrogel shell surrounding an
oil core for retention of the oil in the shell for transporting the volatilized
compound into the microcapsule retained oil core, and retaining the oil core in
the hydrogel shell during transport to provide the encapsulated volatile
compound in the hydrogel shell containing the retained oil core.
The invention is also directed to the products produced by the
methods of the invention.
One advantage of the invention is that the microcapsule may
contain a concentration of the flavor or fragrance compound in either a liquid
or gaseous state, that heretofore has not been feasible. A second advantage
is that the walls of the blank microcapsules have a substantially uniform
thickness, strength, and resiliency. Another advantage is the increased yield
of encapsulated flavor or fragrance, since essentially no flavor or fragrance
compound is lost to the environment. Still another advantage is the economy
in manufacturing the flavor or fragrance compounds of the invention, since the
same technology is used for all flavors and fragrances. Yet another advantage
is that the encapsulated material is edible, allowing direct tasting without
further chemical modification.
The objectives and other advantages of this invention will be
further understood with reference to the following detailed description and
examples.
DETAILED DESCRIPTION
In a preferred practice of the invention, microcapsules containing
a desired flavor or fragrance compound are formed by a coacervation process.
In coacervation, there is separation of a colloid into a colloid-rich phase (the
coacervate) and an aqueous solution of the coacervating agent (the equilibrium
liquid), forming an oil coated with protein, carbohydrate, or polymeric droplets
so as to suspend the oil in water. In the process, two lipid phases and one
aqueous phase are ultimately absorbed into one lipid phase and one aqueous
phase. The first lipid phase forms the microcapsule core. The core is
surrounded by a hydrogel capsule, defined herein as a colloid in which the
dispersed phase (colloid) has combined with the continuous phase (water) to
produce a viscous jellylike product. The core consists of an oil which is a term
used herein to define a wide range of substances that are quite different in
their chemical nature. Oils may be classified by their type and function and
encompass mineral oils (petroleum or petroleum-derived), vegetable oils (chiefly
from seeds and nuts), animal oils (usually occurring as fats; the liquid types
include fish oils), essential oils (complex volatile liquids derived from flowers,
stems, leaves, and often the entire plant), and edible oils (chiefly vegetable oils
as well as some special fish oils). Oils derived from living organisms are
chemically identical with fats, the only difference being one of consistency at
room temperature. In one embodiment, the oil may be mineral oil, vegetable
oil, or benzyl alcohol. In a preferred embodiment, the oil is a short chain
triglyceride of fractionated coconut oil, available under the trade names
Migylol® (Huls Corp., Piscataway, NJ) or Captex® (Abitec Corp., Janesville,
Wl) . The hydrogel shell may be either carbohydrate, protein, or a synthetic
polymer such as polyvinyl pyrollidone or methyl cellulose. In a preferred
embodiment, the oil is Migylol® or Captex® and the shell is gelatin. The second
lipid phase is the desired flavor or fragrance compound, which is to some
extent both water-soluble and lipid-soluble, that is, it is amphiphilic, which is
the term used herein to define its dual solubility properties. The aqueous
phase is used to transport, by partition coefficient equilibrium, the slightly
water soluble flavor or fragrance compound into the oil core of the
microcapsule by aqueous diffusion. Equilibrium dynamics continue until the
three phases (two lipid and one aqueous) are absorbed into two phases (one
lipid and one aqueous).
Volatile chemicals such as aroma flavor or fragrance chemicals
may be encapsulated by head space partitioning. This may be useful, for
example, in taste evaluation of a botanical material or food/beverage aroma,
since the perception by smell and by taste may be very different.
Microcapsules containing an absorbed aroma chemical prepared according to
the invention can be tasted directly or can be dissolved in water or another
solvent and then tasted. Microcapsules provide an effective absorbent for an
aroma chemical and a sanitary and safe medium for sensory evaluation.
Examples of aroma chemicals include but are not limited to dimethyl sulfide,
acetic acid, furfuryl, mercaptan and ethylbutyrate.
Encapsulation is achieved by passing a gaseous stream containing
the aroma compound through a chamber containing the sorption capsule
material in the form of microcapsules, prepared as previously described, in the
presence of water. The gas is preferably air for economic reasons, but other
gases such as nitrogen, carbon dioxide or argon may be used. The
microcapsules may contain as little as about 0.5% to 1 % water when a highly
water soluble aroma or flavor such as acetic acid is to be encapsulated. More
preferably, about 5% to about 1 0% of moisture may be added to
microcapsules to activate them to conduct the transportation of the volatilized
flavor or fragrance by aqueous diffusion through the hydrogel shell. The
moisture to conduct aqueous diffusion may be present in the microcapsules
and/or may be in the gas stream passing over the microcapsules, for example,
by adjusting to a relative humidity of between about 40-80%. Transport of
the compound may occur at temperatures from 0°C-1 00°C, but usually will
occur at temperatures in the range of about 20°C-25°C and under atmospheric
conditions. In one embodiment, the sorption capsule material is gelatin
coacervated migylol.
The compound is transported through the hydrogel shell by
aqueous diffusion into the oil core and is retained in the core. The
microcapsules having the aroma flavor or fragrance compound retained in the
oil core may be used as is. In another embodiment, the capsule wall may be
rendered less susceptible to leakage of the retained components. This may be
accomplished by drawing off moisture from the hydrogel shell with salts such
as sodium chloride, sodium sulfate, sodium citrate, etc. or other dehydrating
agents. The amount of the salt used is from about 5% to about 95% by
weight of the capsules, depending upon the amount of moisture to be captured
or drawn away from the shell. The microcapsules containing the retained
flavor or fragrance may be air dried.
Blank microcapsules are added to a chamber that is configured to
capture the aroma compounds by way of controlled water transport into the
capsule having an oil core. The chamber may be of any size and of any
material, for example, glass, plastic, stainless steel or other material to contain
the microcapsules and allow passage of a gaseous stream. In one
embodiment, microcapsules are packed into a glass tube and the ends of the
tube are covered by a metal or other type of screen, allowing access of the
gaseous stream containing the volatilized compound to the microcapsules
contained therein. In another embodiment, two 55 gallon stainless steel tanks
contain microcapsules and are connected to a gaseous stream.
The chamber may be connected either directly or indirectly to a
gas source that captures the desired aroma chemical in the gaseous stream.
The source of the aroma chemical, which may be in any physical form, is
placed in a container of any size and composition connected to the gas source.
Standard types of connectors are used such as plastic, glass or stainless steel
tubing. The aroma chemical in the headspace of the container is captured by
the flowing gas and is then provided to the chamber containing the
microcapsules, again using any type of standard connector. The gaseous
stream containing the aroma chemical is passed over the microcapsules using
either positive (e.g., pumping) or negative (e.g., vacuum) pressure. In one
embodiment, the gaseous stream may be recirculated. The time during which
the aroma chemical is encapsulated can vary but is typically from about 0.5-5
h. This time depends upon factors such as the aroma intensity of the sample
and the aroma notes of interest, for example, total aroma, top notes, bottom
notes or in between.
The gas source may be an air stream pump. The chamber may
be connected to a waste air duct for treatment of the waste air stream, such
as an air stream pumping over coffee grounds. The chamber may be
connected to an air source from a food processing operation, for example, to
capture desired natural flavor aroma chemicals such as natural tomato
essences of tomato stewing operations. The chamber may be connected to
an air source from a vessel containing chemicals dissolved in a low volatile oil
for the purpose of extracting the volatile chemicals without heat or distillation.
The chamber may be connected to a sample cell to capture flavor aroma
chemicals contained in vegetable matter, for example, as an oily mash or an
aqueous extract for the purpose of capturing only the aroma chemicals and
none of the waxes or bitter chemicals. The chamber may be connected to a
fermentation broth or a solution of an organic reaction for the continuous
removal and capture of aroma chemicals.
After exposure of the microcapsules to the aroma chemical in the
gaseous stream, the ends of the tube may be capped or otherwise sealed, for
example, by inserting Teflon or other types of plugs into both ends of the tube
or by other means. This embodiment is useful when aroma trapping is
performed in the field where microcapsule analysis is delayed, versus where
aroma trapping is performed in a laboratory where microcapsule analysis
occurs soon after exposure.
The volatile chemicals in a gaseous state exhibit partitioning
migration through the wall of the microcapsule and deposit in the oil core in
the same manner as do the chemicals in a liquid state, the difference being the
use of a gas phase transfer rather than a liquid phase transfer. Uses of this
embodiment include, but are not limited to, direct microencapsulation of
volatile chemical components, waste air stream treatment, selective
encapsulation of volatile aroma components from a nonvolatile solvent, and
capture of airborne organic compounds for analytical analysis. The method
may be used to capture flavor aroma chemicals in the field, or to capture
important natural flavor aroma chemicals from waste air streams of
commercial processes. Examples include the capture of beer or wine flavors
from the manufacturing waste air stream, capture of coffee or nut flavors from
roasting operations, capture of cereal notes from cereal manufacturing, capture
of fried notes from doughnut, fried snacks or french fry operations, and
capture of orange essences from orange oil.
For some water soluble compounds, less water is required for
absorption or partitioning into the oil phase. Conversely, for some highly lipid
soluble compounds, more water may be required for partitioning into the oil
phase. Thus, by transiently varying the amount of water that is available to
a compound, taking into account the compound's partition coefficient in either
a gaseous or liquid state, a compound may be absorbed through the hydrogel
shell into an oil.
Adsorption of the compound in the oil can be controlled.
Dehydration of the microcapsule or crosslinking of the capsule shell locks the
flavor or fragrance compound inside the microcapsule. In dehydration, a
substantial volume of the water is removed from the capsule, thereby reducing
the loss of the partially water-soluble flavor or fragrance compound from the
oil core into an aqueous environment. Alternatively, crosslinking of the
hydrogel shell of the coacervate renders the encapsulated oil thermostable,
since a capsule containing crosslinks is a stable structure. The use of known
chemical crosslinking agents, such as formaldehyde or glutaraldehyde, to
irreversibly crosslink the oil-containing capsule is known. Other crosslinking
agents such as tannic acid (tannin) or potassium aluminum sulfate (alum) are
similarly known. An optional capsule hardening step, as disclosed in U.S.
Patents no. 2,800,457 and 2,800,458, consists of adjusting a suspension of
capsular material to pH 9 to 1 1 , cooling to 0°C to 5 ° C, and adding
formaldehyde. Formaldehyde and glutaraldehyde are also effective chemical
crosslinking agents. For the food industry and the cosmetic/toiletry industries,
suitable cross-linking agents may be selected depending upon the specific
application.
Certain naturally-occurring enzymes are also good cross-linking
agents. Crosslinking using enzymes, such as transglutaminase, is disclosed
in co-pending application Serial No. 08/791 ,953 entitled Enzymatically Protein-
Encapsulating Oil Particles by Complex Coacervation, which is hereby
incorporated by reference in its entirety. Enzymes work by catalyzing the
formation of bonds between certain amino acid side chains in proteins. In
addition, because the enzymes are naturally occurring, encapsulated oils that
are enzymatically crosslinked do not suffer from the problems inherent with
formaldehyde and glutaraldehyde crosslinking, and hence may be ingested or
applied without the concern of toxicity of the crosslinking agent. Because
crosslinking is a enzyme catalyzed reaction, however, the proper environmental
conditions must exist for optimum enzyme activity.
For compounds with high water solubility, defined herein as at
least about 20% water soluble, it is preferable to concentrate the microcapsule
to 55% solids or to start with dry microcapsules and gravimetrically add water
and compound to get the desired results. For compounds with low water
solubility, defined herein as less than about 20% water soluble, a hydrated
microcapsule preparation may be used.
EXAMPLE 1
Blank capsules that are hydrated are prepared by pre-warming
deionized water to 50°C ± 2°C. A gum solution is prepared by vigorously
agitating prewarmed deionized water (87.201 8 g), carboxymethyl cellulose,
sodium salt (1 .8447 g), and gum arabic FCC powder SP Dri (0.1 845 g) . The
solution is mixed until the solids are completely dissolved, then the solution is
cooled to about 35°C to about 40°C. A gelatin solution is prepared by
vigorously agitating prewarmed deionized water (1 63.0453 g) and 250 Bloom
type A gelatin (1 8.4461 g) in a preemulsion tank until the gelatin is completely
dissolved, then the solution is cooled to about 35°C to about 40°C. Without
agitation, the gum solution is added to the gelatin solution in the preemulsion
tank and the foam is allowed to dissipate for about 1 5-20 min. The pH is
adjusted to about 5.5 with either a dilute sodium hydroxide solution (50%
w/w) or a dilute citric acid solution (50% w/w).
Vegetable oil (1 80.02 g of Captex® 355 mixed triglycerides or
Migylol®) is added with slow agitation, avoiding pooling of the oil. The capsule
size is adjusted to about 1 00 microns to about 400 microns and the size is
verified microscopically. The solution is slowly cooled at about 1 °C per 5 min
until the solution reaches about 28°C. If the capsule walls are intact, as
determined by microscopic examination of capsules showing uniform
deposition of protein with no free protein floating in the water phase, the
solution may be quickly cooled to about 1 0°C. If the capsule walls are thin,
as determined by microscopic examination of capsules showing nonuniform
deposition of protein and free protein floating in the water phase, the solution
is reheated to about 32°C to about 33°C. The solution is mixed at about 5°C
to about 1 0°C for 1 h. The solution is then heated to about 1 5 °C to about
20°C. Fifty percent glutaraldehyde is added and allowed to mix for about 1 6
h. Agitation is then discontinued and the capsules are allowed to separate by
flotation. Approximately 48% to 50% (approximately 379 lbs to 395 lbs) of
water is drained from the bottom of the tank into a separate vessel. If
capsules are present in the drained liquid, draining is stopped and agitation is
begun to resuspend the separated capsules into solution. The separation step
is then repeated. Once separation is complete, agitation is again begun in
order to resuspend the capsules into solution. Sodium benzoate (10% w/w)
is added with thorough mixing. If necessary, citric acid is added to adjust the
pH to less than 4.0.
Blank capsules, defined herein as encapsulated oil with no flavor
or fragrance value, that are dry are prepared by the following method. A syloid
solution is prepared by mixing a silica compound syloid 244 grade 68 powder
(1 5.9497 g) with deionized water (1 43.5477 g) until the powder is completely
dispersed and no lumps are present. The flavor is mechanically mixed until
smooth, then the syloid solution is mixed with the flavor until it is completely
dispersed with no lumps, thinning out after about 30 min of stirring. The
product is concentrated by centrifugation to about 50% or more solids. The
material is then dried in either a vacuum oven dryer at about 80°C or in a fluid
bed dryer at about 70°C.
The dry crosslinked capsules (400 g) are placed in a stainless
steel mixing bowl (Hobart Lab Scale Mixer). The desired neat flavor (428.6 g)
is mixed with deionized water (1 71 .4 g) on a magnetic stirrer for 5 min. The
dry capsules are mixed with the water/flavor mixture on the Hobart Mixer at
power level 1 -2 for 5 min. The mixture is poured into a plastic storage
container, using a rubber spatula to scrap the sides of the mixing bowl, and
the container is closed. The mixture is allowed to incubate for 24 h for flavor
absorption before the product is used.
EXAMPLE 2
Blank capsules that are hydrated are prepared by pre-warming
deionized water to 50°C ± 2°C. A gum solution is prepared by vigorously
agitating prewarmed deionized water (87.201 8 g), carboxymethyl cellulose,
sodium salt (1 .8447 g), and gum arabic FCC powder SP Dri (0.1 845 g). The
solution is mixed until the solids are completely dissolved, then the solution is
cooled to about 35°C to about 40°C. A gelatin solution is prepared by
vigorously agitating prewarmed deionized water (1 63.0453 g) and 250 Bloom
type A gelatin ( 1 8.4461 g) in a preemulsion tank until the gelatin is completely
dissolved, then the solution is cooled to about 35°C to about 40°C. Without
agitation, the gum solution is added to the gelatin solution in the preemulsion
tank and the foam is allowed to dissipate for about 1 5-20 min. The pH is
adjusted to about 5.5 with either a dilute sodium hydroxide solution (50%
w/w) or a dilute citric acid solution (50% w/w) .
Vegetable oil (1 80.02 g of Captex® 355 mixed triglycerides or
Migylol®) is added with slow agitation, avoiding pooling of the oil. The capsule
size is adjusted to about 1 00 microns to about 400 microns and the size is
verified microscopically. The solution is slowly cooled at about 1 °C per 5 min
until the solution reaches about 28°C. If the capsule walls are intact, as
determined by microscopic examination of capsules showing uniform
deposition of protein with no free protein floating in the water phase, the
solution may be quickly cooled to about 1 0°C. If the capsule walls are thin,
as determined by microscopic examination of the capsules showing
nonuniform protein deposition and free protein in the water phase, the solution
is reheated to about 32°C to about 33°C. The solution is mixed at about 5°C
to about 1 0°C for 1 6 h, then agitation is discontinued and the capsules are
allowed to separate by flotation. Approximately 48% to 50% (approximately
379 lbs to 395 lbs) of water is drained from the bottom of the tank into a
separate vessel. If capsules are present in the drained liquid, draining is
stopped and agitation is begun to resuspend the separated capsules into
solution. The separation step is then repeated. Once separation is complete,
agitation is again begun in order to resuspend the capsules into solution.
Sodium benzoate ( 1 0% w/w) is added with thorough mixing. If necessary,
citric acid is added to adjust the pH to less than 4.0. The capsules are stored
at about 5°C to about 1 0°C.
The hydrated uncrosslinked beads (81 5.20 g) are added to a glass
reactor at about 5°C to about 1 0°C. Stirring at about 95-1 00 rpm is begun
while maintaining the temperature at about 5°C to about 10°C. Neat flavor or
fragrance (1 81 .8 g) is added to the glass reactor. The mixture is stirred for
about 2 h at about 5°C to about 1 0°C to allow the flavor or fragrance to
absorb into the capsules. Fifty percent glutaraldehyde (3.0 g) is then added
and allowed to mix at about 1 5°C to about 20°C for 1 6 h. Sodium benzoate
( 1 0.25 g of a 1 0% solution) is added to the reactor. Citric acid (20%) is
added to adjust the pH of the solution to 3.9. The capsules are stabilized by
adding a well-mixed xanthan gum/propylene glycol mixture (1 part xanthan to
2 parts propylene glycol). The mixture is stirred for about 30 min until the
capsules are stabilized. Once the capsules are stabilized, they are ready for
use.
EXAMPLE 3
Blank microcapsules were packed into a glass absorption tube
(3.5 mm I.D., 10 cm length) to be used as a "taste trap". The packing height
of the absorbent usually ranged from about 1 -5 cm (0.09-0.45 g
microcapsules), depending upon the experimental objective. After packing,
both open ends of the tube were plugged with metal screens. One end of the
tube was connected HOW? to a glass cover or container holding the subject
aroma chemical for analysis. The other end of the tube was connected by
plastic tubing to an air sampling pump. The air flowrate was about 30 ml/min.
The time during which the aroma chemical was trapped varied from about 0.5-
5 h, depending upon the aroma intensity of the sample and the aroma notes
of interest, for example, total aroma, top notes, bottom notes or in between.
When trapping was finished, the metal screens were removed and
the aroma encapsulated microcapsules were evaluated by taste. When aroma
trapping was performed in the field versus a laboratory type of environment,
the end of the glass tubes were securely sealed by inserting Teflon plugs into
both ends of the tubes before being transported to the laboratory for
evaluation.
EXAMPLE 4
The technique described in Example 3 was successfully used to
evaluate the aroma of the bark of Scorodophloeus zenkeri Huac. Fifty g of the
bark of Scorodophloeus zenkeri Huac was obtained on the commercial market
(Libreville, Gabon). A glass absorption tube was prepared with 0.27 g of blank
microcapsules. The exposure time was 2 h with an air flow rate of 30 ml/min.
Upon completion, the aroma encapsulated microcapsules were dissolved in
water. The solution was described by trained evaluators as having the taste
of onion spiced soup.
EXAMPLE 5
The technique described in Example 3 was successfully used to
collect and concentrate volatile aromas from roasting operations such as from
coffee, cereal or peanut processing.
EXAMPLE 6
The technique described in Example 3 was successfully used to
collect and concentrate volatile aromas from frying operations such as in the
manufacture of snack chips, doughnuts and meat.
EXAMPLE 7
The technique described in Example 3 was successfully used to
collect and concentrate volatile aromas from baking operations such as in the
manufacture of snack crackers, breads and cakes.
EXAMPLE 8
The technique described in Example 3 was successfully used to
collect and concentrate volatile aromas from materials whereby volatile
compounds are separated from non-volatile compounds, such as separation of
chocolate essence from bitter chocolate and volatile beer topnotes from
fermentation broths.
EXAMPLE 9
The technique described in Example 3 was successfully used to
collect and concentrate volatile hydrophilic aromas components from materials
whereby hydrophilic volatile components are separated from hydrophobic
components, as in separation of oxygenated volatile components from limonin
in orange and other citrus oils.
EXAMPLE 1 0
Sodium alginate (8.22 g, type FD 1 55, Grinsted Corp.) was
dissolved in deionized water (300 g). The solution was stirred until
homogeneous. Microcapsules (3.75 g) were added with stirring until a
homogeneous phase formed. Migylol® (99.9 g) was then added with vigorous
stirring to form an oil-in-water emulsion. The emulsion was fed through a
vibrating needle ( 1 .22 mm internal diameter) that was positioned about one
inch above the lowest point of an eddy generated in a glass beaker by vigorous
stirring of a 4% w/w aqueous CaCI2 solution ( 1 50 ml). The flow rate of the
emulsion through the needle was adjusted to prevent formation of a jet.
Emulsion droplets, upon entering the CaCI2 solution, immediately gelled,
yielding particles of about 800 μm diameter. After the emulsion was added,
the slurry of beads was permitted to stand for about 30 min to allow migration
of calcium ions into the microcapsules. The microcapsules were dewatered at
room temperature either by centrifugation or by vacuum filtration, and were
subsequently dried by techniques known in the art such as vacuum oven
drying or fluid bed drying.
The resulting microcapsules had a slight tendency to stick
together due to the presence of some surface oil. A free-flowing, dry alginate-
encapsulated flavor or fragrance compound was obtained by mixing the
microcapsules (about 58%) and water (about 7%) with the desired flavor or
fragrance compound (about 35%). The optimal absorption time is between
about one hour and ten hours, depending upon the partition coefficient of the
particular flavor or fragrance compound.
It should be understood that the embodiments of the present
invention shown and described in the specification are only preferred
embodiments of the inventors who are skilled in the art and are not limiting in
any way. Therefore, various changes, modifications or alterations to these
embodiments may be made or resorted to without departing from the spirit of
the invention and the scope of the following claims.
What is claimed is: