Note: Descriptions are shown in the official language in which they were submitted.
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SEAMLESS CAPSULES
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention is related to a seamless capsule
comprising a shell material encapsulating a center-filled
core material, wherein the shell material is formed of a
carbohydrate in glassy state, and a method and an apparatus
for making the seamless capsule.
Description of the Prior Art
Traditionally, seamless capsules formed of a shell material
encapsulating a core material have been made by using as
the shell material film-forming materials such as gelatin
and gums. These shell materials present two disadvantages.
First, they are formed from an aqueous solution.
Consequently, when the capsules are formed, large amounts
of water must be removed, requiring great amounts of energy
and long drying times. Second, these shell materials
dissolve slowly when the capsules are being consumed,
thereby leaving a distasteful plastic film-like residue in
the mouth.
Seamless capsules are usually made by simultaneously
extruding the shell material and the core material through
concentrically aligned nozzles such that the extruded shell
material and the extruded core material exit the nozzles as
a coaxial jet with the shell material surrounding the core
material into a stream of cooled carrier liquid that is
flowing downward. While descending in the cooled carrier
liquid, the coaxial jet breaks into droplets with the shell
material encapsulating the core material. The droplets
then solidify in the cooled carrier liquid to form seamless
capsules. Such method is disclosed, for example, in U.S.
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Patent Nos. 4,251,195 and 4,695,466. However, when the
shell material is a material that solidifies quickly, this
prior art method is disadvantageous in that the shell
material in the coaxial jet may solidify prior to en-
capsulation. As a result, seamless capsules could not be
formed, and any capsules that were formed were not
spherical and did not have uniform size and shape.
An attempt to overcome this problem was proposed in U.S.
Patent No. 4,422,985, which describes a method that
modifies the prior art method by introducing a coaxial
triple jet consisting of a heated circulating liquid
surrounding the shell material which in turn surrounds the
core material into the cooled carrier liquid to allow
encapsulation to take place. In this method, since capsule
formation must still take place in the cooled carrier
liquid, if any solidification of the shell material occurs
prior to entering the cooled carrier liquid, encapsulation
will not occur.
Other methods used for making capsules typically involve
using a screw extruder to extrude an emulsion containing
the shell matrix and the material to be encapsulated.
However, in such process, it is difficult to make a capsule
formed of a shell material encapsulating a center-filled
core material. Instead, the encapsulated material is often
in the form of globules that are distributed within the
matrix.
U.S. Patent No. 2,857,281 describes a process for making a
solid flavoring composition in the form of globular
particles by extruding an emulsion containing a sugar base
and flavor oil into droplets.
U.S. Patent No. 3,971,852 describes a process for en-
capsulating oil in a cellular matrix that is formed of
polyhydroxy and polysaccharide compounds. The oil is in an
emulsified state with the cellular matrix, and the
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resulting emulsion is spray dried as droplets of the
emulsion.
U.S. Patent No. 5,009,900 discloses a process for en-
capsulating volatile and/or labile components with extruded
glassy matrices, wherein the encapsulated material is
distributed in the glassy matrices.
European Patent Application No. 0339958 discloses an
antifoaming composition containing an outer shell of a
meltable sugar in its crystalline state with an organo-
polysiloxane antifoaming composition imbedded therein.
This composition is formed by melting a sugar base and
dispersing the organopolysiloxane antifoaming composition
in the sugar melt as the discontinuous phase. The melt is
then solidified, thereby imbedding and entrapping the
antifoaming composition, which is dispersed in the melt.
U.S. Patent No. 5,300,305 relates to microcapsules that
provide long lasting breath protection.
SUMMARY OF THE INVENTION
A first aspect of the present invention provides a method
for making a seamless capsule comprising a shell material
encapsulating a core material comprising the steps of:
providing a concentrically aligned multiple nozzle
system having at least an outer nozzle and an inner nozzle;
supplying a shell material to the outer nozzle and a
core material to the inner nozzle;
simultaneously extruding the shell material through
the outer nozzle and the core material through the inner
nozzle, thereby forming a coaxial jet of the shell material
surrounding the core material;
introducing the coaxial jet into a flow of a heated
carrier liquid, thereby allowing the shell material to
encapsulate the core material to form capsules in the
heated carrier liquid; and
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introducing the capsules into a flow of a cooled
carrier liquid, thereby allowing the capsules to solidify.
A second aspect of the present invention provides an
apparatus for making a seamless capsule comprising:
a concentrically aligned multiple nozzle system
having at least an outer nozzle and an inner nozzle for
simultaneously extruding a shell material through the outer
nozzle and a core material through an inner nozzle, thereby
forming a coaxial jet of the shell material surrounding the
core material;
means for supplying the shell material to the outer
nozzle and the core material to the inner nozzle;
a first duct located beneath the multiple nozzle
J.5 system for receiving the coaxial jet;
means for delivering a heated carrier liquid to the
first duct to form a flow of the heated carrier liquid
surrounding the coaxial jet, thereby allowing the shell
material to encapsulate the core material to form capsules
in the heated carrier liquid;
a second duct, at least a part of which is located
beneath the first duct, for receiving the flow of the
heated carrier liquid carrying the capsules from the first
duct;
means for delivering a cooled carrier liquid into
the second duct to form a flow of the cooled carrier liquid
surrounding the capsules, thereby allowing the capsules to
solidify.
A third aspect of the present invention provides a seamless
capsule comprising a shell material encapsulating a center-
filled core material, wherein the shell material comprises
a carbohydrate in glassy state.
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BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 illustrates a schematic sectional side view of an
apparatus for making seamless capsules according to one
embodiment of the present invention.
Fig. 2 illustrates a schematic sectional side view of an
apparatus for making seamless capsules according to another
embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The present inventors have discovered that seamless
capsules can be formed by employing carbohydrates in glassy
state as the shell materials. Because carbohydrates in
glassy state are formed through solidification, capsule
drying is not required. In addition, the carbohydrate
shell materials dissolve rapidly and do not leave
distasteful residues in the mouth.
Because carbohydrates solidify rapidly in a cooled medium,
in the prior art method discussed above, prior to
encapsulating the core material, the carbohydrate shell
material already solidifies in the cooled carrier liquid.
As a result, seamless capsules could not be formed, and any
capsules that were formed were not spherical and did not
have uniform size and shape.
The present inventors have discovered a method and an
apparatus for making seamless capsules that overcome the
drawbacks in the prior art and are capable of forming
seamless capsules that are uniform in size and shape even
when carbohydrates are used as the shell materials. In
addition, this method and apparatus can make seamless
capsules formed of a shell material encapsulating a single
center-filled core material, i.e., the core material is not
distributed or dispersed within the shell material matrix.
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Fig. 1 illustrates an example of an apparatus that can be
used to make a seamless capsule according to the present
invention. The apparatus comprises a multiple nozzle
system having an outer nozzle 5 and an inner nozzle 6,
which are concentrically aligned. The inner nozzle 6 is
connected to a tank 1, which supplies the core material to
the inner nozzle 6 through a gear pump 3. The outer nozzle
5 is connected to a tank 2, which supplies the shell
material to the outer nozzle 5 through a gear pump 9. A
duct 9 is located beneath the multiple nozzle system. The
upper part of the duct 9 is surrounded by a heating
cylinder 8 in a concentric alignment. The heating cylinder
8 is connected to a tank 16, which is provided with a
heater 18 for heating a carrier liquid that is fed through
a feed pump 20 to the heating cylinder 8. The heating
cylinder 8 has an overflow over the duct 9, thereby
allowing the heated carrier liquid to flow from the heating
cylinder 8 into the duct 9.
The lower end of the duct 9 extends into a duct 10. The
upper part of the duct 10 is surrounded by a cooling
cylinder 7 in a concentric alignment. The cooling cylinder
7 is connected to a tank 17, which is provided with a
cooler 19 for cooling a carrier fluid. The cooled carrier
fluid is fed through a feed pump 21 to the cooling cylinder
7. The cooling cylinder 7 has an overflow over the duct
10, thereby allowing the cooled carrier liquid to flow from
the cooling cylinder 7 to the duct 10.
The lower end of the duct 10 forms a funnel-shape portion,
which is connected to a recovery pipe 11. The recovery
pipe 11 extends towards a circulating liquid tank 22 and
terminates at a small distance from the top of the
circulating liquid tank 22. Arranged on the circulating
liquid tank 22 is a net-like separator 23 for separating
capsules from the carrier liquid. The tank 22 is connected
through a pipe 12, which passes through a recycle pump 14,
to tank 16 for supplying the carrier liquid to be heated in
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tank 16. The tank 22 is also connected to a pipe 13, which
passes through a recycle pump 15, for supplying the carrier
liquid to be cooled in tank 17.
Fig. 2 illustrates an alternative embodiment of an apparatus
that can be used to make seamless capsules of this
invention. In this embodiment, a cooler 18a cools a :fluid
in tank 16a and the cooled fluid is pumped by feed pump 20
directly into duct 10. A heater 19a heats a fluid in tank
17a and the heated fluid is pumped by feed pump 21 into
l0 heating cylinder 8. The heating cylinder 8 has an over flow
over duct 9 which allows the heated liquid to flow from the
heating cylinder 8 into duct 9. A seal 8a extending between
duct 9 and duct 10 and situated above the inlet from cooling
tank 16a and below the inlet from heating tank 17a ensures
the proper flow of the fluids.
The process of making the seamless capsules will now be
described in detail. The shell material is supplied from
tank 2 into the outer nozzle 5 and the core material is
supplied from the tank 1 into inner nozzle 6. The core
2o material and the shell material are then simultaneously
extruded to form a coaxial jet with the shell material.
surrounding the core material. The carrier liquid in tank
16 or 19a is heated to a temperature that is close or higher
than the temperature of the shell material and is supplied
to duct 9. Typically, the temperature of the heated carrier
liquid is from about 90 to 160°C. The coaxial jet is
introduced to the duct 9 containing the heated carrier
liquid flowing downward. Because the heated carrier liquid
is at a temperature that is close to or higher than the
temperature of the shell material in the coaxial jet, it
prevents the shell material from solidifying, thereby
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allowing the shell material to encapsulate the core material
to form capsules.
The carrier liquid in tank 17 or 16a is cooled to a low
enough temperature that can allow the capsules to solidify.
Preferably, the carrier liquid is cooled to a temperature of
from about 0 to 30°C. The cooled carrier liquid is supplied
from tank 17 or 16a to duct 10. The capsules from duct 9
are then carried by the heated carrier liquid into duct 10
containing the cooled carrier liquid that is flowing
downward. The final temperature of the combined streams is
low enough so that the capsules are then cooled sufficiently
to allow them to solidify in duct 10 to form the seamless
capsules. The thus-formed seamless capsules are then
transported through pipe 11 toward separator 23 located in
tank 22. The separator 23 separates the seamless capsules
from the carrier liquid to collect the seamless capsules.
The separated carrier liquid flows into tank 22 and is then
recycled to tanks 16 and 17 or tanks 16a and 17a through
pipes 12 and 13, respectively.
In an alternative embodiment, the coaxial jet simultaneously
extruded from the multiple nozzles is introduced into air
instead of a flow of the heated carrier liquid. As the
coaxial jet descends through air for a sufficient distance,
it breaks down into droplets, thereby allowing the shell
material to encapsulate the core material to form capsules.
Typically, the distance that the coaxial jet travels through
air is from about 3 to about 15 cm. The capsules then
descend into a flow of cooled carrier liquid to allow the
capsules to solidify. The temperature of the air should be
higher than that of the cooled carrier liquid and should be
maintained within a range in which the shell material .does
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not solidify within the travelled distance. The air
temperature may be maintained at ambient temperature, i.e.,
from about 25 to 35°C, or in another embodiment, the a.ir can
be heated above ambient, at a preselected set point, for
example, by the use of a tubular heater which maintains the
air within at the preselected temperature.
Any liquid that does not dissolve the shell material a.nd can
be heated and cooled to the appropriate temperatures without
undergoing phase change can be used as the carrier liquid in
to the present invention. Examples of suitable carrier liquids
include medium chain triglyceride (MCT)
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Prefe=ably; the shell material and the core material are
simultaneously extruded by setting the fluid volumetric
flux of the shell material through the outer nozzle equal
to the fluid volumetric flux of the core material through
the inner nozzle. The fluid volumetric flux of a material
flowing from a nozzle orifice is defined as the ratio of
the volumetric flow rate of the material through the nozzle
to the nozzle orifice area. As described in U.S. Patent No.
5,650,232, by setting the fluid volumetric flux of the shell
material equal to that of the core material through the
concentrically aligned nozzles, the mass ratio of the core
material to the shell material in the capsule can be
controlled by merely varying the size of the orifice areas
of the nozzles.
The concentrically aligned multiple nozzle system that can
be used in the present invention can have more than two
concentrically aligned inner and outer nozzles. There can
be one or more concentrically aligned intermediate nozzles
positioned between the inner and outer nozzles, from which
one or more intermediate shell materials can be extruded.
In such embodiment, the shell material extruded from the
outer nozzle encapsulates the intermediate shell material
extruded from the intermediate nozzle, which in turn
encapsulates the core material from the inner nozzle. In a
preferred embodiment of this invention, the fluid
volumetric flux of the intermediate shell material through
the intermediate nozzle will be set to be equal to the
fluid volumetric flux of shell material through the outer
nozzle and the fluid volumetric flux of the core material
through the inner nozzle.
Examples of suitable carbohydrates that can be used as the
shell material in the present invention include sucrose,
glucose, fructose, isomalt, hydrogenated starch
hydrolysate, maltitol, lactitol, xylitol, sorbitol,
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erythritol, mannitol, and the like, and mixtures thereof.
Typically, the carbohydrate is fed into the outer nozzle as
the shell material in the form of a melt. When the
carbohydrate solidifies in the cooled carrier liquid, it
turns into a glassy state, i.e., amorphous state. When the
carbohydrate is in a glassy state, it exhibits an enhanced
ability to protect the center-filled core material from
vaporization and deterioration.
Suitable core materials are typically in liquid form or
meltable solid materials. Examples of suitable core
materials include MCT oils (e. g., such as coconut oil),
peppermint oil, cinnamon oil, fennel oil, clove oil, wheat-
gezm oil, vegetable oils (e. g., corn oil, cottonseed oil,
canola (rapeseed) oil, sunflower oil and the like),
silicone oils, mineral oils, fruit flavors, vitamins,
pharmaceutical solutions, natural and artificial
sweeteners, menthol, and the like.
Any material that is liquid at the operating temperature
and does not dissolve the core or shell materials and
further solidifies during the cooling process may be used
as an intermediate shell material. Examples of suitable
intermediate shell materials include waxes (e. g., paraffin
wax, microcrystalline wax, polyethylene wax, carnauba wax,
candellila wax and the like) and fats (e. g., hydrogenated
fats such as those known to persons of skill in the art).
The present invention is useful for making seamless
capsules for a variety of applications, such as center-
filled chewing gums, encapsulated medicines, foods,
cosmetics, industrial chemicals and the like.
The present invention will now be illustrated by the
following non-limiting Example.
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EXAMPLE
Seamless capsules were prepared by using a concentrically
aligned multiple nozzle system having an inner nozzle and
an outer nozzle. The inner nozzle had an inside diameter
of 0.20 cm, an outside diameter of 0.26 cm, and an orifice
area of 0.0314 cm2. The outer nozzle had an inside
diameter of 0.39 cm and an annular orifice area of 0.0664
cm2. A mixture of 90 wt. % isomalt and 10 wt. % xylitol
was melted at a temperature of 155°C and maintained in a
tank at 148°C. This mixture had an actual viscosity of 628
cps at 140°C. Generally, the methods of the present
invention would involve the use of shell materials having
an actual viscosity of less than about 1,000 cps at the
operating temperature. The resultant mixture had a density
of 1.00 g/ml. The mixture was then fed to the outer nozzle
as the shell material at a temperature of 145°C and a
volumetric flow rate of 2.37 ml/min. A mixture of 10 wt. %
cherry flavor and 90 wt. % cotton seed oil having a density
of 0.96 g/ml was supplied to the inner nozzle as the core
material at ambient temperature and a volumetric flow rate
of 5.01 ml/min. The shell material and the core material
were then simultaneously extruded from the outer and inner
nozzles, respectively, at the same fluid volumetric flux of
75.5 ml/min. cm2 into air, which was maintained at ambient
temperature. The coaxial jet descended through air for 10
cm and broke down into droplets to allow encapsulation to
take place. The capsules then descended into coconut oil
cooled to a temperature of 20°C and flowing downward at a
rate of 1,000 ml/min. The resultant capsules collected had
a diameter of about 4 mm and contained 68.78 wt. % of the
shell material in a glassy state and 31.22 wt. % of the
core material.
While the present invention has been described with respect
to what is presently considered to be the preferred
embodiments, it is to be understood that the invention is
not limited to the disclosed embodiments. The present
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invention is intended to cover various modifications and
equivalent mechanisms included within the spirit and scope
of the appended claims.
