Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to an enhanced microwave popcorn package which
achieves greater popping efficiency at less expense than predecessor packages.
In particular, this
invention relates to a highly efficient arrangement of kernels and associated
oils and seasonings
across a susceptor embedded in such a package. More particularly, this
invention relates to the
creation of a moisture and grease resistant barrier which isolates the greasy
kernels and oils from
the package and surrounding environment until the popping cycle is initiated.
ackground of The Invention
Popcorn has long been a favorite snack item, the popularity of which supports
a
large and profitable sector of the food industry. However, as consumers have
become increasingly
health and time conscious, traditional cooking methods involving pans of hot,
messy cooking oil
that take relatively long to heat, have steadily become less popular. Though
these concerns have
been somewhat addressed with healthier oils and hot air poppers, far and away
the most dramatic
innovation in this area was the creation of containers that enable popcorn to
be prepared in a
conventional microwave oven.
Popcorn is commonly sold and stored in ready-to-use, shelf stable, leak-proof
packages which also serve as microwaveable cooking containers. These packages
are designed
to store a charge of popcorn kernels along with other edible ingredients such
as shortening,
cooking oils and seasonings/flavorings, (collectively the "slurry") in a
collapsed configuration that
reduces storage requirements and shipping costs. The material forming these
packages is
transparent to microwave energy so that the entire package can be placed in a
microwave oven for
the heating process. When microwave energy is applied to the product, the
popcorn kernels
rupture and assume the familiar shape of popped popcorn while the flexible
package expands to
accommodate the increased volume of the popped kernels.
A popular microwave popcorn package is described in U.S. Patent No. 4,571,337
to Cage. This is a traditional "grocery-bag" style with a flat bottom end and
a crimp-sealed top
end. Inwardly folded gussets provided on the sides permit the package to
assume a relatively flat
shape for shipping and storage. During the cooking process, steam generated by
the slurry and
kernels is held in the bag causing the gussets to unfold and the bag to
inflate. To the extent that
excess steam is generated, the corresponding pressure creates vent holes in
the corners of the top
seal. When the popcorn kernels have popped and are ready to be served, the top
end of the inflated
bag can be opened by pulling on diagonally opposite corners of the package.
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Another common package style is the wedge-bottom, or pinch-bottom, bag
illustrated in U.S. Patent No. 4,596,713 to Burdette. Both the top and bottom
ends of this package
are sealed by crimping and/or high temperature adhesive (there is no bottom
panel), and the edges
of the front and back panels are joined by side panels with gussets extending
into the package. The
charge of popcorn is placed in the center portion of this package between the
top and bottom ends,
and the top and bottom ends are folded over the center portion to maintain
this placement during
shipping and storage. Unlike the package described in the Cage patent supra,
the Burdette
package cannot sit upright on the bottom end. Thus it must be placed in the
microwave oven on
either the front or back panel. As the kernels are popped, the steam and
increased popcorn volume
cause the ends and gussets to unfold and the package to inflate. This package
is likewise opened
at one of the ends after cooking to provide access to the popped kernels
within.
Fundamental differences in the heating mechanisms of microwave ovens and
traditional stoves initially hindered the success of microwaveable popcorn
products. In a common
skillet or pan, a flat, very hot surface quickly heats the unpopped kernels
causing vapor pressure
inside the kernels to rupture the tough exterior causing the kernels to assume
the familiar "popped"
configuration. When a kernel pops, it quickly assumes a much larger and
lighter consistency that
causes it to jump from the pan's surface to be replaced with the denser
unpopped kernels. This
natural process is effective because the kernels that still require heat
gravitate toward the pan while
the kernels that are prone to burn rise to relatively cool areas above the
pan. Microwave ovens,
on the other hand, do not typically create such a temperature gradient.
Rather, microwave ovens
disperse microwave energy relatively evenly throughout the popcorn package.
Moreover, while
most microwave ovens generate enough energy to eventually pop the kernels, it
is typically too
low to pop them very fast. Since some variance in kernel structure is
inevitable, some of the
kernels will pop quite faster than others. Thus while the slower kernels
absorb microwave energy
toward popping, the faster kernels dry out and eventually scorch or burn.
Most currently available microwaveable popcorn containers use a susceptor to
address the heating problems associated with microwaves. A susceptor is a very
thin sheet of
material, usually vacuum metalized polyester, that rapidly increases in
temperature and radiates
heat energy when subjected to microwave energy. When affixed to the package
panel below the
popcorn, a susceptor emulates the heated surface of a pan. The susceptor
rapidly increases the
temperature of the panel and adjacent kernels which in turn hastens the
popping process. Since
the cooking time is thereby shortened, the early popped kernels are subjected
to less unnecessary
energy. Moreover, since the susceptor concentrates most of the heat on the
bottom surface, the
lighter popped kernels can ascend to the higher, relatively cool areas in the
package.
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Experimentation has also shown that packages employing susceptors cause
kernels to pop with
greater volume than packages without susceptors.
In wedge-bottom packages such as that illustrated in the Burdette patent,
supra, the
susceptor and kernels are placed near the middle of the package so that the
popped kernels have
S sufficient space to escape the susceptor's heat. Thus the manufacturing
processes used to make
these packages must position the kernels adjacent the susceptor rather than
permitting gravity to
pull them to either end of the package. This is currently accomplished through
a vertical filling
process in which the bottom portion of the package length is folded over the
middle section and
the kernels and slurry are poured in the open top. The top section of the
package is then sealed and
folded over the middle section to hold the kernels in place. This keeps the
unpopped kernels from
lodging in the ends, and reduces the required susceptor size. This process is
illustrated and
described in more detail in European Patent Application Number 88304722.7.
Though the vertical filling process positions the kernels and slurry generally
in the
middle of the package adjacent the susceptor, it does not do so very well.
Instead of distributing
evenly across the susceptor, the kernels tend to collect along the fold
between the bottom and
middle sections. Generally, the kernels and slurry in such vertically filled
packages cover
approximately 25% of the available susceptor. This uneven build-up reduces
popping efficiency
because the kernels positioned immediately adjacent the susceptor heat much
faster than the
kernels that start farther from the susceptor. Thus the overall cooking time
is lengthened, as is the
lag time between the early and late pops. This effect is mitigated to the
extent that the slurry
liquefies and disperses across the susceptor during heating, but this takes
time and energy that
could more efficiently be spent heating the kernels. Moreover, until the
slurry is spread across the
susceptor the "dry" areas of the susceptor will generate significant amounts
of unused heat. If
there are no adjacent kernels or oil to absorb this heat, the susceptor may
become hot enough to
scorch or even burn the package material. Unevenly dispersed kernels and
slurry also create
irregularly shaped packages that requires increased space for shipping and
storage.
U.S. Patent No. 4,038,425 to Brandberg et al. teaches a popcorn package which
is
not filled vertically, but is in communication with a smaller exterior
compartment that holds the
popcorn and slurry prior to popping. The idea is that by holding the kernels
in a small
compartment until they pop, heat will be more easily contained and higher
temperatures reached.
This design keeps the kernels and slurry from the package folds, but at the
costs of preventing the
unpopped kernels from evenly dispersing across the susceptor and inhibiting
the escape of the
popped kernels to the cooler areas of the package. Another problem with the
Brandberg package
is that since the storage compartment communicates freely with the inside of
the bag, it does not
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protect the popcorn slurry during shipping and storage and the kernels can
spill in the package if
the proper orientation is not maintained. Moreover, the external compartment
creates an irregular
shape that is difficult (and expensive) to manufacture and bulky to transport
and store.
Current microwave popcorn packages include a mechanism by which the oily
ingredients in the slurry are contained. Since the kernels and slurry are
typically loose in current
packages, the package panels themselves are designed to be sufficiently
impervious to the oily
ingredients to prevent them from soaking through (a phenomenon commonly called
"strike-
through"). To this end, high quality "grease-proof' paper is currently used.
Grease-proof paper is typically made with very long, tightly interwoven
fibers. The
longer the fibers, and the tighter they are woven, the more grease resistant
the paper will be.
Grease resistance can also be attained by treating the paper with a
fluorocarbon compound (e.g.
3M~ brand FC-807) during the papermaking process. The degree of grease
resistance is also a
function of the amount of fluorocarbon compound that has been applied.
High quality grease-proof paper can resist strike-through for six months or
more,
1 S but this protection comes at a significant material and manufacturing
cost. Printing on grease-
proof paper can also be difficult since the paper is resistant to ink. Thus,
dual-layered packages
having grease-proof paper on the inner surfaces, and ink receptive paper on
the outer surface are
popular. For example, the inner layer could be formed of bleached greaseproof
Kraft paper of
approximately 25 lbs./ream and the outer layer could be formed of plain
bleached Kraft paper of
approximately 30 lbs./ream. These layers, along with adhesive therebetween,
typically provide
sufficient grease resistance, but disadvantages include the relative heaviness
which increases
shipping costs, and stiffness which hinders the expansion of the package.
Single ply packages with
combined grease-proof paper and fluorocarbon treated surfaces have also been
used, but typically
these have had limited success containing the oils for commercially acceptable
periods.
U.S. Patent No. 5,461,216 to McDonald addresses grease-proofing in single ply
packages by increasing protection at the more vulnerable areas. McDonald
observed that prior
single ply packages failed to prevent strike-through, but typically these
failures were limited to the
seams, folds and corners where the fibers and/or fluorocarbon treating was
broken. Thus the
McDonald device teaches the use of highly refined fibers that tend to stretch
or bend rather then
break when the paper is folded. This limits the exposure of fiber ends which
wick grease through
the panel. In addition, McDonald teaches the application of "grease
protectors" that block the flow
of grease along the more vulnerable folded or creased areas. Grease protectors
are described as
strips of heat seal adhesive affixed to the inner and/or outer surfaces of the
package along folds or
creases.
WO 00/61456 CA 02369555 2001-l0-05 PCT/US99/07801
Another problem associated with storing the slurry loose in the package is
that the
slurry must be relatively solid at room temperature to prevent it from flowing
away from the
desired position adj acent the susceptor. Moreover, liquid slurries are
shunned because the package
would require very high grease-resistance to prevent strike-through, and the
ends would have to
5 be sealed particularly well to prevent leakage. Nonetheless, liquid slurnes
require less energy to
heat and are generally understood to impart a better taste to the finished
popcorn.
To maintain the popcorn's freshness, most commercially available popcorn
packages are overwrapped with polypropylene film for shipping and storage.
This overwrap
provides a needed moisture and volatile flavor barrier over the shelf life of
the product. This can
be important since the mechanics of popping popcorn require a certain degree
of moisture in the
kernels. Unfortunately, since current overwraps encase the entire package,
much of the moisture
in the popcorn and slung is lost to the package material and air within the
overwrap during
storage. Moreover, since the material used to create the overwrap is
relatively expensive, covering
the entire package to protect the relatively small volume of kernels and
slurry unnecessarily
increases the package's cost.
Multi-purpose packages have also been introduced which provide means for
converting the package into a convenient serving container after the kernels
have been popped.
One early such package is described in U.S. Patent No. 4,292,332 to McHam. One
of the panels
of the McHam package includes an "H" pattern of weaknesses that release excess
vapor during
popping. After the popping process is complete, the weaknesses assist the
consumer in opening
the package as the panel can be torn along the weaknesses to create two
"flaps" (i.e. the upper and
lower halves of the "H"). These flaps are then folded over to provide access
to the interior of the
container.
In practice, a McHam style package risks early ruptures along the pattern of
weaknesses as the expanding kernels exert pressure inside the package. If the
weaknesses can
withstand this pressure during popping, they will likely be too strong to
permit easy tearing after
the kernels are popped. Moreover, since there is no handle on the package with
which to remove
the panel, the consumer must initially push the flaps into the package before
reaching in to pull
an edge away. The McHam package also lacks means by which the panels and flaps
can be pulled
entirely off the package to create a large aperture through which the consumer
can obtain the
popcorn.
An improvement to the basic concept of a convertible package was recently
introduced by Hunt-Wesson, Inc. This Hunt-Wesson package includes two parallel
separation
lines extending longitudinally down the length of the package. These
separation lines are formed
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by reinforcing the adj acent areas with contact tape, whereby any tears
initiated along the separation
lines will tend not to deviate to other areas of the package. Thus after the
kernels have been
popped, the entire section of the panel between the separation lines can be
removed. This leaves
a relatively large aperture through which the consumer can access the popcorn
without having his
hand soiled by the greasy flaps. In addition, the intended tear lines can be
weakened to provide
added control. This product works well for its intended purpose, but the panel
reinforcement,
and/or weakening, to create the separation lines represent additional material
and manufacturing
costs that would preferably be avoided.
In view of the foregoing, it should be appreciated that there is a need for an
improved microwaveable popcorn product that pops a higher percentage of
kernels in a reduced
popping cycle, and does so without scorching the kernels. There is also a need
for a printable,
flexible and inexpensive package that contains the kernels adjacent the
susceptor, maintains the
moisture content in the pre-popped slurry, resists charring, permits the use
of liquid slurry, and
provides access to the popped kernels through a large opening in the panels,
while keeping
material and manufacturing costs to a minimum.
The present invention pertains to a microwaveable popcorn product that
addresses
many of the above-described deficiencies in currently available packages.
Moreover, these
objectives are accomplished with a package design that is inexpensive to
manufacture.
The primary structural components of the inventive product include a package
comprising multiple panels of flexible, microwave transmissive material joined
together to form
an inner cavity. A susceptor is mounted on one of the panels such that it is
adjacent an inner
surface of the package, and a charge of microwaveable popcorn kernels and
slurry is placed on the
inner surface of the cavity adjacent the susceptor. The susceptor is capable
of converting
microwave energy to heat, and the popcorn kernels are prone to pop and expand
when heated.
An important feature of this invention is that the slurry and popcorn kernels
are
dispersed in an even, uniform thickness relative the susceptor. Thus the heat
generated by the
susceptor will be evenly distributed to the kernels so that they will pop at a
substantially equal rate.
This aspect can be refined by dispersing the kernels in a single layer
adjacent the susceptor such
that all the kernels are as close to the susceptor as possible. This feature
can be further refined by
dispersing the charge of popcorn kernels and slurry across the entire
susceptor. Thus the heat
generated by the susceptor will be efficiently transferred to the kernels and
slurry with limited heat
transfer to the surrounding package material that could cause charnng.
In another embodiment of this invention, the charge is securely contained in
an
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envelope located within the cavity of the package. The envelope is strong
enough to contain the
charge of unpopped kernels until the popping process begins. However, when
subjected to the
steam, high temperatures and expansion pressure created by the kernels during
the popping
process, the envelope will burst and release its contents. Thus the unpopped
kernels will be
protected and held in place through shipping and storage, but when the popping
process is initiated
the popped kernels will escape into the larger cavity of the package.
In a refined embodiment of the invention, the envelope is created from two
sheets
of material that are entirely independent of the package material, yet reside
within the package.
This embodiment is advantageous in that it permits the envelope to be
manufactured separate from
the package, and subsequently inserted into the package.
In another embodiment of the invention, an envelope is created with a cover
that
overlies the charge of kernels and is adhered to the inner surface of the
package around the
perimeter of the charge. Thus the envelope is an integral part of the package
which ensures that
the charge will be located in the proper position and saves the cost of an
additional sheet of
envelope material.
In another embodiment of the invention, the envelope is created with only the
panels that form the package. This is accomplished by compressing the inner
surfaces of top and
bottom package panels together against the charge, and releasably sealing the
inner surfaces
around the perimeter of the charge. Thus, with the exception of the adhesive
layer, there are no
additional materials required over that which are already part of the package.
According to another aspect of the invention, the package is divided into
three
sections: a top section, a bottom section and a middle section that resides
between the top and
bottom sections. The susceptor and charge of kernels and slurry are positioned
in the middle
section of the package; and, the top and bottom ends are folded over the
middle section. Thus the
charge is retained in the middle section between the folds. This ensures that
the evenly dispersed
charge remains adjacent the susceptor, and in the best position for popping.
According to another aspect of the invention, side panels forming the package
include multiple gussets and the charge is placed along the channel at the
longitudinal center of
the package between the innermost folds of the gussets. This arrangement
enhances the freedom
of the kernels to move about the package during the popping process and
reduces the thickness of
the package. This also serves to hold the kernels in the center portion of the
package adjacent the
susceptor.
According to another aspect of the invention, a susceptor is mounted directly
onto
one of the surfaces of the envelope adjacent the charge. Thus the charge will
remain immediately
w0 00/61456 CA 02369555 2001-10-05 PCT/US99/07801
g
adjacent the susceptor no matter where the envelope is located in the package
ensuring that
susceptor's heat is efficiently transferred to the charge. This also permits
the use of a smaller
susceptor than if the susceptor was mounted on the package.
According to another aspect of the invention, the charge of popcorn kernels is
displaced in an even, uniform thickness inside the envelope and adjacent the
susceptor. Thus heat
generated by the susceptor when microwave energy is applied to the product
will be evenly
distributed to the kernels so that the kernels heat and pop at a substantially
equal rate. In a further
refinement of this aspect, the charge of popcorn kernels is dispersed in a
single layer adjacent the
susceptor.
According to another aspect of the invention, a panel of the package has a
susceptor
mounted thereon, and the envelope is placed adjacent the susceptor. Thus the
envelope can be
used with currently available package styles. Moreover, the envelope can be
produced at less
expense than if it included a susceptor.
According to another aspect of the invention, the envelope is secured to an
inner
surface of the cavity inside the package. Thus, after the package has burst
and the kernels have
popped, the consumer can empty the popped kernels from the package without
removing the
empty envelope in the process.
According to another aspect of the invention, the envelope is substantially
impervious to water. Thus the moisture content of the charge and slurry will
remain substantially
constant from the time that the charge and slurry are sealed in the envelope
until the envelope
bursts. This aspect can be refined by lining the envelope with polyester to
attain the moisture
barrier. This aspect can be further refined by evacuating the envelope of air
as this further
maintains a predetermined level of moisture in the envelope.
According to another aspect of the invention, the envelope comprises two
layers
of material that are placed on either side of the charge of kernels and
adhered to each other around
the perimeter of the charge. The adhesive used to join the layers has a
bonding strength that is
strong enough to hold the layers together during shipping and storage, but too
weak to contain the
expansion pressure created within the envelope when the kernels are popped.
Thus when the
popping process is begun, the layers of the envelope will separate thereby
releasing the kernels into
the package cavity.
According to another aspect of the invention, the adhesive used to bond the
layers
of the envelope is heat sensitive such that the bonding strength diminishes as
the temperature
increases. Thus the adhesive will be strongest when it is required to hold the
envelope together
(i.e. during the relative cool periods of shipping and storage); but will be
weakened by the very
WO 00/61456 CA 02369555 2001-l0-05 PCT/LTS99/07801
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process that requires its release. In a refinement of this aspect, a susceptor
is mounted to one of
the layers of the envelope adjacent the charge and the adhesive. Thus a
significant temperature
increase of the adhesive will be realized very early in the popping process.
According to another aspect of the invention, the package includes gusseted
side
panels that permit the front and back panels to converge onto the envelope
prior to popping, and
diverge during popping. Front and back layers forming the envelope are
securely attached to the
front and back panels such that as the front and panels diverge, the layers of
the envelope will be
pulled apart. This serves two functions: it opens the envelope to release the
unpopped kernels, and
it keeps the envelope layers from mixing with the popped kernels.
According to another refinement of the invention, the edges of the front panel
are
joined to the edges of the side panels along two lap seams, and the lap seams
are bonded together
with a releasable adhesive. The releasable adhesive is strong enough to hold
the package together
during shipping, storage and the popping process. However, the adhesive is
weak enough that it
will permit the front panel to be peeled from the remainder of the package
without tearing the
package material. This creates a large aperture in the package to provide
access to the interior
cavity. A similar arrangement can be created in which the back panel, as
opposed to the front
panel, is removably attached to the side panels.
Other features and advantages of the present invention will become apparent
from
the following description of the preferred embodiments, taken in conjunction
with the
accompanying drawings which illustrate, by way of example, the principles of
the invention.
Figure 1 is a plane top view of the exterior of the package of the invention.
Figure 2 is a cross-sectional side view of the package, taken along the line 2-
2 of
Figure 1, illustrating a first embodiment of the invention in which the charge
of kernels is arranged
in a uniform thickness.
Figure 3 is a plane side view of the package of Figure 1 taken after the end
sections
have been folded over the middle section.
Figure 4 is a cross-sectional side view of an envelope utilized in a second
embodiment of the invention to contain and protect the kernels and slurry.
Figure 5 is a cross-sectional side view, similar to that illustrated in Figure
2, of the
package incorporating the envelope illustrated in Figure 4.
Figure 6 is a cross-sectional side view, similar to that of Figure 5, in which
the
popping process is partially complete and the package is partially inflated.
WO 00/61456 CA 02369555 2001-l0-05 PCT/US99/07801
Figure 7 is a perspective view of the package of Figures 5 and 6 after the
package
has been expanded by the popped popcorn kernels.
Figure 8 is a perspective view, similar to that of Figure 7, of the package
after a
panel has been partially removed along with a portion of the envelope.
5 Figure 9 is a cross-sectional side view, similar to that illustrated in
Figure 2, of
another embodiment of the package in which a cover is draped over the kernels
and attached to the
inner surface of the package to envelope the kernels.
Figure 10 is a cross-sectional side view of similar to that of Figure 9 in
which the
popping process is partially complete and the package is partially inflated.
10 Figure 11 is a cross-sectional side view, similar to that illustrated in
Figure 2, of
another embodiment of the package in which the front and back panels of the
package are sealed
around the charge to envelope the charge.
Figure 12 is a cross-sectional side view, similar to that of Figure 1 l, in
which the
popping process is partially complete and the package has partially inflated.
Figure 13 is a top elevational view of the embodiment of Figures 11 and 12. A
corner of the back panel has been partially removed from the remainder of the
package for
illustrative purposes.
Figure 14 is a perspective view of the package of Figures 11, 12 and 13 after
the
package has been expanded by the popped popcorn kernels.
Figure 15 is a perspective view, similar to that of Figure 14, of the package
after
a panel has been partially removed to allow access to the popped kernels
within.
Figure 16 is an illustration of the preferred manufacturing process for
creating the
package of this invention.
These figures are provided to illustrate the concepts of the present invention
only.
The relative dimensions of the features will likely be modified in an actual
commercial
embodiment, but the need to make any such modifications will be well within
the understanding
of one skilled in the art. Numerals used in multiple drawings represent
alternate views of the same
or similar parts.
Consumer satisfaction with microwaveable popcorn has been overwhelmingly
evidenced by the large number of these products sold every day. Nonetheless,
several
characteristics of the currently available packages are still less than ideal.
For example, material
costs are still relatively high (especially in comparison to the cost of the
ingredients), and the
cooking process still requires a trade-off between popping a high percentage
of the kernels and
WO 00/61456 CA 02369555 2001-l0-05 PCT/US99/07801
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scorching the kernels that popped early. Described below are several
embodiments of Applicant's
invention, each incorporating slight structural variations on the overall
concepts. As will become
readily apparent, selection of a "preferred" embodiment will depend on
independent factors such
as the allowable material expenses and manufacturing costs, and the overall
level of complexity
S desired in the final product.
Embodiment 1
The present invention relates to a microwave popcorn product, generally
indicated
as 1 in the accompanying drawings. The package contains a charge of popcorn
kernels 2 that
expand into puffed edible popcorn 3 when heated in a microwave oven. As shown
in the
accompanying figures, the primary structural components of the package include
a rectangular
front panel 4, a rectangular back panel 5, and two rectangular side panels 6
and 7 which connect
the sides of the front and back panels to form inner cavity 8. For the
purposes of this description,
the front panel 4 is the panel that is to be placed downward when the package
is placed in a
microwave oven.
Various sheet materials may be used to form the panels, so long as the basic
requirements of the package are met. The package must be stiff enough to
resist tearing under the
expected loads, but at the same time it must be flexible enough that the
internal steam and popcorn
volume can expand the package from its compressed configuration. If the
kernels are loosely
stored in the package, the panels should resist leaking or staining for the
expected periods of
shipping and storage as well as during the popcorn process. A two-ply
construction with an inner
grease-proof paper layer of 20-25 lbs./ream adhered to an outer machine
finished paper layer of
25-30 lbs/ream is suitable. A suitable material for a single ply package is a
grease-proof paper
approximately 0.5 to 1.0 mils thick with a weight of about 35-60 lbs./ream
Machine glazed papers
are also suitable, but can be too rigid if too thick. The surface of the paper
can also be treated with
a commercially available fluorocarbon stain inhibitor such as 3M~ Inc. brand
FC-807. However,
as will be discussed in more detail below, if an envelope is used to contain
the charge and slurry,
lower grade grease-proof paper will be acceptable.
All four panels of the package 1 comprise a top end 9 and a bottom end 10.
Both
ends of front panel 4 and back panel 5 must be connected to close the package
and fully contain
the popcorn 2. The preferred design is the "tube" method in which the top and
bottom ends 9,10
are secured directly to each other. Alternatively, a bottom panel (not
illustrated) can be included
to create the "grocery-bag" style described in the background section supra.
The ends are closed
by crimping the material or applying a heat sensitive adhesive to the inner
surfaces and placing the
ends in a heated press. Typical adhesives used to close the ends include
polyvinyl acetate or
WO ~~/61456 CA 02369555 2001-10-05 PCT/US99/07801
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polyethylene vinyl acetate.
Referring to the cross-sectional view of Figure 2, a susceptor 11 is
preferably
adhered to the front panel 4 to enhance popping performance. As explained in
more detail in the
background section above, a susceptor consists of a thin layer of metal
adhered or evaporated on
S to a structural base such as a sheet of polyester. When subjected to
microwave energy the
susceptor rapidly increases in temperature and radiates heat energy to its
surroundings.
The contents of the package 1 principally include a charge of unpopped kernels
2
mixed with a slurry of shortenings, cooking oils and seasonings (not
illustrated) to enhance the
flavor and texture of the resulting popcorn 3. Room temperature stable
ingredients are preferable
so that refrigeration is not required, and if the slurry is to be loose in the
package it should be solid
at room temperature. If a leak-proof envelope, discussed infra, is used, the
slurry can be a liquid.
All of the kernels within a particular package would ideally fall within a
very
narrow range of strength and moisture content so that they will all pop at
approximately the same
time. However, since these variables cannot realistically be so strictly
controlled, the time and
heat requirement will vary from kernel to kernel. Energy will necessarily be
applied to the entire
collection of kernels after some of the kernels have already popped. If this
is continued for too
long, the earlier pops will become very dry and eventually scorch or even
burn. This invention
optimizes a short cooking cycle to avoid these problems.
Preferably the charge of kernels and slurry 2 is dispersed across the
susceptor 11
in a uniform thickness "x," and covers substantially the entire surface area
of the susceptor. (See
Figure 2) Thus, since the entire charge of kernels will be heated at
approximately the same rate,
the lag time between the early and late pops will be shortened which in turn
keeps the popped
popcorn 3 moist and reduces scorching. This arrangement has been
experimentally shown to
reduce standard cooking times to an average 2%2 minutes from an average 33/4
minutes for packages
in which the slurry is initially accumulated on only 25% of the susceptor.
Another advantage of
this arrangement is that the slurry will not have to melt and flow across the
susceptor. This ensures
that the heat from the susceptor 11 is efficiently transferred from the
beginning of the process, and
prevents any "dry" (i.e. uncovered) areas of the susceptor from becoming
excessively hot and
charring the package.
Popping performance can be further improved by using a susceptor 11 that is
large
enough to disperse all of the kernels 2 in a single layer. In other words, all
of the kernels would
preferably be laid side-by-side on the front panel 4 immediately adjacent the
susceptor. Each
kernel would thus receive the maximum amount of energy available from the
susceptor from the
beginning of the microwave cycle. Moreover, at least until the kernels start
to pop, each would
WO 00/61456 CA 02369555 2001-l0-05 PCT/US99/07801
13
receive an equal amount of energy, thus forwarding the goal of popping all the
kernels at the same
time. Depending on the number and size of kernels in the charge, the size of
the susceptor, and
front and back panels might have to be modified to accommodate this
arrangement.
As illustrated in Figure 2, the side panels 6, 7 each include multiple gussets
12
which allow the package 1 to maintain a collapsed configuration prior to the
preparation of the
popcorn kernels 2. These multiple gussets are formed in each side panel by
creating inwardly
directed folds parallel to the longitudinal axis of the package thereby giving
the side panel a
pleated or accordion-like configuration. The stiffness of the side panel
material causes the gussets
to remain compressed so that the package will remain relatively flat during
storage and shipping.
However, the side panel material must be flexible enough that the gussets will
expand when
subjected to the internal pressure created during the popping process. Thus
the package will
inflate to accommodate increased interior volume of the popped popcorn 3.
Since multiple gussets 12 do not protrude significantly into the inner cavity
8, they
do not hinder the free flowing movement of kernels 3 during popping. This
freedom can be further
improved by placing the entire charge and slurry between the inner folds of
the gussets whereby
the kernels will not get stuck under the gussets (See Figure 2). Moreover,
since the inner gussett
edges form a burner of sorts, the kernels will be held in the center portion
of the package adjacent
the susceptor. Another advantage of placing the slurry between the gussets is
that the overall
thickness of the package will be kept to a minimum. Depending on the number
and size of the
kernels used, this feature might also require modification of the package
dimensions and/or
susceptor size, but one skilled in the art could readily make these
modifications.
The susceptor 11 need not cover the entire front panel 4 to pop the kernels 2
efficiently, but if the susceptor covers only a portion of the panel, the
kernels must be held adjacent
that portion. As explained above, the gusset edges can be used to keep the
kernels from spilling
off the sides of the susceptor. It is also advisable to keep the unpopped
kernels from the ends 9,
10 as the pinched corners will restrict the kernels from fully popping. ' Thus
the package 1 is
longitudinally divided into three approximately equal sections: a top section
13, a middle section
14 and a bottom section 15; and, the susceptor and charge are placed on the
middle section. To
ensure that the kernels cannot escape the middle section until popped, the
package is folded
between the sections such that the top and bottom sections overlie the middle
section (as illustrated
in Figure 3). The combination of the gusset edges and these folds hold the
kernels in place until
the steam and expansion pressure of the popping process cause package to
unfold.
Embodiment 2
Figures 4-8 illustrate a microwaveable popcorn package 1 similar to Embodiment
WO 00/61456 CA 02369555 2001-l0-05 PCT/US99/07801
14
1, with the exception that the charge 2 is not loose in the package. Rather
the charge is securely
contained in an envelope 16 which in turn is located in the cavity 8 of the
package. The envelope
must be made of a material that is transparent to microwave energy, preferably
polyester, whereby
microwave energy will heat the popcorn kernels and slurry within. Since the
envelope is too small
to contain the kernels after they have popped, the structural constitution of
the envelope is
designed to burst when subjected to the heat, steam and expansion pressure
created by the kernels
during the popping process. After the envelope has ruptured, the kernels will
escape into the
surrounding package which holds the popped kernels 3 until they are removed by
a consumer.
A susceptor 11 is preferably included in Embodiment 2 to aid the popping
process.
The susceptor is preferably mounted to the lower surface of the envelope (as
is illustrated in
Figures 4-6). Thus no matter where the envelope is positioned in the package,
the susceptor will
be adjacent the kernels. An alternative design places the susceptor on the
front panel of the
package (as illustrated in Figure 2 of Embodiment 1), and a susceptor-free
envelope is secured to
the inner surface of the package adjacent the susceptor. In either event, it
is important that the
charge of kernels is positioned adjacent the susceptor.
As in Embodiment 1, the charge 2 is preferably dispersed in a uniform
thickness
inside the envelope. Thus no matter whether the susceptor is placed on the
envelop, or on and
adjacent panel, the kernels will be heated at a substantially even rate and
there will be little to no
dry area on the susceptor. Moreover, if the envelope is large enough that the
charge can be leveled
into a single layer, the heating efficiency will be further improved.
There are multiple ways to create an envelope that will burst to release the
kernels.
The difficulty comes in ensuring that the envelope is strong enough to
withstand the stresses
associated with manufacturing, shipping and storage, yet weak enough to burst
very early in the
popping process. One potential design utilizes a sheet of polyester of a
precise thickness and
strength that will burst at the opportune time. However, since microwave ovens
exert different
energy levels, and since the polyester manufacturing process will invariably
include some margin
of error, it would be difficult and expensive to produce envelopes with such
precision. An
alternative is to score the envelope along the desired rupture area. However,
this is not preferred
because the perforations increase the risks of premature rupture, moisture
transmission to and from
the charge, and leakage of the shortening and cooking oils.
The preferred envelope construction is illustrated in Figure 4. A front layer
17 has
the charge 2 positioned on the upper surface thereof, and a back layer 18 is
draped over the charge.
The edges 19 of the front and back layers are adhered together around the
charge with a releasable
adhesive 20.
W~ 00/61456 CA 02369555 2001-10-05 PCT/US99/07801
A releasable adhesive is used so that the envelope will split open when it is
subj ected to the internal expansion pressure created during the popping
process. Preferably the
bonding strength of the adhesive decreases when subjected to steam and
increased temperatures.
Thus the adhesive will be strongest during the relatively cool periods of
shipping and storage, and
5 weakest when it is intended to release. The releasing effect is further
improved if the susceptor
11 is mounted directly to the front layer 17 of the envelope so that the
adhesive will be quickly
heated. The preferred adhesive for creating the envelope is DuPont Brand Selar
PT 8307.
After the kernels 2 have popped, the consumer will need to gain access to
them.
This is traditionally accomplished by opening an end of the package l and
pouring the contents
10 into a bowl (See e.g. the Burdette patent discussed supra) . Since it would
be undesirable for the
spent envelope pieces to be mixed with the kernels 3, the envelope 16 is
securely mounted to the
inner surfaces of the package cavity 8 such that it will remain attached after
the popping process.
This can be accomplished with a heat resistant adhesive such as a modified
acrylic emulsion sold
by Basic Adhesives, Inc. product no. BR-3885. Note that the adhesive used to
secure the envelope
15 to the package should be considerably stronger than the releasable adhesive
used to seal the edges
of the envelope. As illustrated in Figure 5, strips of heat resistant adhesive
21 secure the front
layer 7 of the envelope to the inner surface of the front panel 4; and, strips
of heat resistant
adhesive 22 secure the back layer 18 of the envelope to the inner surface of
the back panel 5.
As illustrated in Figure 6, securing the envelope layers 17, 18 to the inner
surfaces
of the cavity 8 helps pull the envelope 16 apart at the proper time. As the
kernels 2 expand and
expel steam, the top and bottom sections 13, 15 of the package 1 unfold from
the middle section
14, the gussets 12 expand, and the package inflates. This inflating process
causes the front and
back panels 4, 5 to diverge from each other, which in turn pulls the front and
back layers of the
envelope apart.
Embodiment 2 also includes an improved method for allowing the consumer to
access the popped kernels 3. A pair of lap seams 23 extend the longitudinal
length of the package
1 and secure back panel 5 to side panels 6, 7. The lap seams are bonded
together with a releasable
adhesive which has a bonding strength great enough to hold the panels together
before and during
the popping process, yet weak enough to permit the back panel to be peeled
from the side panels
without tearing the package material. Figure 7 illustrates a package of this
embodiment after the
popping process has been completed. Figure 8 illustrates the same package with
the back panel
partially removed. Note that if the back layer 18 of the envelope 16 is
attached to the back panel
5, it too can be removed from the remainder of the package. Alternatively, if
the front panel 4 was
releasably attached to the side panels 6,7, the package could be turned over
and the front panel and
WO 00/61456 cA 02369555 2001-l0-05 PCT/US99/07801
16
front envelope layer could be removed.
The adhesive used along the lap seams 23 will not be subjected to as much
heat,
steam and internal pressure as the adhesive used to hold the envelope layers
17,18 together. Thus
the same releasable adhesive used for the envelope can be used for the lap
seams 23. Moreover,
depending on the bonding strength of the adhesive, the width of the lap seams
can be modified
until the appropriate strength is reached. Applicant has found that Franklin
Duracet 12 or Basic
Adhesives, Inc. product no. BR-3885 works well for this application.
As with Embodiment l, the kernels 2 (and envelope 16) are preferably located
in
the middle section 14 of the package 1 to aid the flow of popped kernels about
the package. The
best way to accomplish this is to place the envelope in the middle section,
and fold the top and
bottom sections over the middle section to hold it in place during shipping
and storage. Similarly,
if the envelope can be made small enough to fit between the gussets, as
illustrated in Figure 5, the
freedom of the kernels during the popping process will be improved.
The use of polyester for envelope 16 has also been shown to be very effective
in
preserving the freshness and popping performance of the kernels 2. The
mechanics of popping
popcorn rely on moisture within the kernels to expand and rupture the exterior
shell of the kernel.
Preferably sufficient moisture is present to reach a very high pressure and
cause a violent rupture
as this creates larger, puffier kernels. If the kernels are too dry due to
losee of moisture during
storage, insufficient internal vapor pressure will be generated leading to
smaller popped kernals
and increased number of kernels that do not pop at all. However, if the
moisture content is too
high, the pericarp will become pliable and rubbery and will split open with
little intensity. Thus
it is important to maintain the moisture content within set parameters. The
invention addresses
this goal by creating the envelope 16 out of polyester, which is substantially
impervious to the
transmission of water. This is advantageous over the prior art polypropylene
packets that covered
the entire package. The envelope 16 is much smaller and lighter, and does not
include the package
material or large volume of air which can absorb moisture from the kernels and
slurry. The
moisture content and slurry freshness can be further controlled by drawing a
vacuum in the
envelope.
The use of an envelope 16 is beneficial in that lighter, inexpensive materials
can
be used for the package panels 4, S, 6, 7. Since the envelope contains the
oily charge 2 for the vast
majority of the product's life, the need for expensive grease-proof panel
material is drastically
reduced. Strike-through protection has traditionally focused on the affected
elements of the
package (i.e. the panels). Rather than trying to protect the panels from the
oils, Applicant
contained the source of the oils. Thus the only time that the oils and
shortening come in contact
WO X0/61456 CA 02369555 2001-l0-05 PCT/LTS99/07801
17
with the panels is during and after the popping process. By this time, the
product's remaining
usefulness is typically less than %2 hour (or much less if the consumer pours
the contents into a
separate bowl). To prevent strike-through for such a short time requires far
less protection than
the prior bags which were designed to be stored for as long as six months or
more.
The use of an envelope 16 does not provide protection against strike-through
during
the popping process. Thus, depending on cost considerations, it might be
preferable to use a
moderately grease-proof material that can contain the oils for at least a few
minutes at
approximately 400 ° F. However, to the extent that strike-through
during popping is acceptable,
the panels can be made of inexpensive non-grease-proof paper. Regardless of
which material is
selected, the package will be considerably lighter and more flexible than the
traditional multi-ply
or heavily treated single-ply packages.
The envelope 16 also provides additional flexibility for the shortenings and
oils
used in the slurry. It was previously impractical to use liquid oils because
they tended to soak
through the panels and leak through any faults in the package. Solid
shortenings and oils were also
used because they helped to hold the charge in the intended position.
Applicant's polyester
envelope eliminates this reliance on solid shortening and oils. Since the
envelope is constructed
of polyester, it can hold the charge and associated ingredients regardless of
the whether it is in
liquid or solid form. Thus it is possible to use liquid shortenings and oils
which is advantageous
as the liquid oils are believed to impart better taste to the popcorn.
Embodiment 3
Figures 9 and 10 illustrate another embodiment of the invention. This package
is
similar to Embodiment 2 with the exception that front layer 17 of the envelope
16 is an integral
part of the front panel 4 of the package 1. Referring to the cross-sectional
view of Figure 9,
attached to the inner surface of the front panel 4 is a layer of polyester 24
on which a susceptor 11
has been evaporated. A strong, heat-resistant adhesive (not illustrated) holds
the front panel,
susceptor and polyester a single stratified unit. The back layer 18 of the
envelope, referred to more
appropriately in this embodiment as the "cover," is draped over the charge 2
and is releasably
bonded to the inner surface of the front panel to create a polyester-lined
envelope. A releasable
adhesive is used to bond the cover to the front panel as was described above
for Embodiment 2.
During the popping process, the mechanics of Embodiment 3 will behave much as
was described for Embodiment 2. When subjected to microwave energy, the
susceptor 11 will
heat the kernels 2 and the releasable adhesive 20. Through a combination of
the increased
temperature of the susceptor, and the steam and expansion pressure of the
kernels, the releasable
adhesive will permit to cover 18 to rise from the inner surface of the front
panel 4 thereby spilling
WO 00/61456 CA 02369555 2001-l0-05 PCT/LTS99/07801
18
the kernels into the cavity 8. As the process continues and the package
inflates, the back panel 5
will diverge from the front panel 4 to allow the popped kernels to fill the
inner cavity of the
package.
The package 1 of Embodiment 3 also preferably includes a removable panel for
permitting access to the popped kernels 3. If the back panel 5 is to be
removable, the popped
product will operate as described above (and illustrated in Figure 8).
However, for Embodiment
3 is preferable to make the front panel 4 removable. When the popping process
is complete, the
package can be rotated so that the front panel is on top and the package can
be opened by peeling
the front panel from the side panels along lap seams 23. This in turn removes
the susceptor 11 and
the lower layer of the envelope 16 from the remainder of the package. Thus,
even if the consumer
does not carefully peel the front panel from the side panels 6,7, or if the
releasable adhesive on the
lap seams is too strong, the susceptor will resist any tendency that the front
panel might otherwise
have toward tearing. For this reason, it is also preferable to extend the
susceptor all the way to the
edges of the front panel.
Embodiment 4
Embodiment 4 completes the progression of the configurations described above.
As illustrated Figures 11 and 12, the front and back panels 4, 5 also serve as
the front and back
layers of the envelope 16. Preferably a polyester sheet with a susceptor
evaporated thereon is
attached to the inner surface of the front panel, and a strong, heat-resistant
adhesive holds these
layers in a single stratified unit. The back panel 5 is constructed of a
moldable material such as
polyester. The inner surfaces of the front and back panels are converged
together such that they
envelope the charge of kernels 2 and are in contact around the perimeter of
the charge of kernels.
Inner strips of releasable adhesive 25 surround the charge and hold the inner
surfaces of the front
and back panels together around the perimeter (as can seen in Figure 11). Thus
the envelope is
created simply by bonding the inner surfaces of the package together around
the charge. Note that
in this embodiment the charge will have to be positioned between the gussets
so that the inner
surface of the front and back panels can meet all the way around the charge.
During the popping process, the apparatus Embodiment 3 will perform in the
manner illustrated in Figure 12. The releasable adhesive strips that hold the
front and back panels
together to form the envelope will release, the kernels will spill into the
cavity 8, and the gussets
will expand to allow the package to inflate.
Embodiment 4 also preferably utilizes a removable panel. In this Embodiment
the
back panel 5 is the preferred choice since it will likely be of a different
material than the remainder
of the package 1, and will need to be attached to the side panels 6,7 anyway.
To the extent that
WO 00/61456 CA 02369555 2001-l0-05 PCT/iJS99/07801
19
a clear material such as polyester is used for the back panel, this package
will be visually
interesting in that it will be possible to watch the kernels 2 pop, and the
popped kernels 3 will be
visible through the panel after the popping process is complete. As
illustrated in Figure 13, the
back panel is attached to the side panels along lap seams 23 with a releasable
adhesive 26. Note
that the back panel in Figure 13 does not extend all the way to the package.
Depending on the
manufacturing process used to create this package, the back panel might
actually extent completely
to the top and bottom ends of the package. Figures 14 and 15 illustrate the
package of
Embodiment 4 after the kernels have been popped, and the back panel has been
partially removed
to expose the popped kernels 3.
Depending on the desired degree of complexity, and the available manufacturing
tools, any one of the above embodiments could be "preferable." However, to the
extent that an
envelope is to be used to contain the charge and slurry, Embodiment 4 is
arguably the best
arrangement in that it does not require additional panels or layers to create
the envelope.
Preferred Manufacturing ro a
Figure 16 illustrates the basic elements of a preferred manufacturing method
for
creating the apparatus of Embodiment 4.
The package 1 is constructed with the back panel S below the front panel 4.
Roll
30 deposits a continuous layer of polyester film onto conveyor belt 31. A
vacuum is drawn below
the surface of the conveyor such that the polyester film conforms to recesses
32. A charge of
popcorn and slurry 2 is then deposited in the recesses from popcorn hopper 33.
If a solid slurry
is used, it is preferably formed into solid cakes of popcorn and slurry sized
to fill the recess.
However, it is important to note that this horizontal manufacturing technique
is also well suited
to the use of liquid slurry since the recesses will contain the liquid until
it is sealed in the envelope
16. Moreover, since the ingredients will be depositied onto a horizontal
surface, gravity will
spread them evenly across the recess, and ultimately the susceptor, which
contributes to efficient
popping action.
The front panel 4 and side panels 6,7 are preferably constructed of a single
layer
of grease resistant paper, though non-grease-resistant paper could be used to
reduce material costs.
A continuous sheet of paper from roll stock 34 is used to create both the
front and side panels of
the package 1. A susceptor 4, preferably comprising a sheet of polyester with
a metalized film
evaporated on the surface thereof, is adhered to the centerline of the paper
stock at station 36.
Strips of high temperature adhesive (to seal the package ends) are then
applied to what will be the
top and bottom ends 9,10 of the package at station 37, and the paper stock is
fed through folding
device 38 which creates longitudinal gussets 12 in the sides panels.
WO ~~/61456 CA 02369555 2001-l0-05 PCT/US99/07801
Referring briefly to Figure 11, two separate patterns of releasable adhesive
strips
are required to attach the polyester film (i.e. the back panel S) to the
gusseted side panels in
Embodiment 4. Inner pattern 25 holds the inner surface of the paper stock to
the inner surface of
the polyester to create the envelope 16; and, outer pattern 26 holds the
polyester to both the ends
5 of the package and the edges of the gussets 12. Both of these releasable
adhesive patterns are
applied to the paper stock at station 39.
After the gussets, susceptor and adhesive patterns have been applied to the
paper
stock, the paper is rolled onto the conveyor and attached to the polyester
layer at position 40. Care
must be taken to synchronize the paper stock with the polyester film such that
the susceptor 11 and
10 adhesive patterns 25,26 are properly registered. Each susceptor 11 must be
positioned directly
above the recesses 32 and popcorn charge 2, each inner adhesive pattern 25
must register with the
circumference of a recess, and the outer adhesive pattern 26 must correspond
with the outer edges
of the polyester film. After the paper and polyester have been aligned, the
adhesives (releasable
and hi-temperature) are secured in heat press 41. Individual packages are then
cut off at station
15 42.
As will be readily apparent to one of skill in the art, the above described
manufacturing process has been provided for illustration purposes only. In
practice, these steps
will not necessarily be performed in this order, and they might not all be
performed in the same
process. For example the gussets and susceptor could be added to the paper
stock in a separate
20 process, and the releasable adhesive could be applied to the polyester as
opposed to the paper. One
of skill in the art will also readily recognize that this process can be
adapted to create the
package/envelope combinations of Embodiments 2 and 3. For example, if the
steps of applying
high temperature adhesive and gussets were removed, this process could be used
to create the
separate envelope that is to be inseted into a package (i.e., Embodiment 2.
Similarly, if the
polyester film was wide enough to seal around the charge without reaching the
gusset edges, and
an additional roll of paper stock was applied over to polyester film and
joined to the panels on
either side of the film, the package of Embodiment 3 would be created. Of
course, since this
process evenly distributes the charge relative to the susceptor, the concept
of Embodiment 1 will
also be realized.
Although the invention has been described in detail with reference only to
certain
embodiments, those skilled in the art will appreciate that various
modifications can be made
without departing from the spirit of the invention. With such possibilities in
mind, the invention
is defined with reference to the following claims.
