Note: Descriptions are shown in the official language in which they were submitted.
~33436
The present invention relates to packaged foods and
more particularly to a package or popping corn in a microwave
oven.
In recent years manufacturers have begun distribut-
\ ing popcorn ln gusseted paper bags. The corn is popped by
\ placing the entire bag in a microwave oven. In this way, the\ corn is heated by microwave energy while it remains in the
\ bag. As the corn pops, the bag expands to accommodate the
popcorn kernels.
` One shortcoming of commercial products is the prob-
lem of maintaining the best possible volumetric yields. The
volumetric yield is measured by popping a standard quantity of
corn in its package within a microwave oven, pouring the
popped kernels into a graduate and noting the total volume.
The resulting final volumes have not always been satisfactory
and all too often a disappointingly high number of kernels
remain unpopped. Moreover, those that do pop are often less
than maximum volume.
U.S. Patents Nos. 3,973,045 and 3,835,280 are repre-
sentative of the prior art. The packages described in the
patent do not, when heated, achieve maximum potential volumet-
ric yield.
In view of these shortcomings the present invention
provides a package for improving the volumetric yield of pop-
corn dlstributed and popped in flexible bags. The present
invention also achieves the improved yields while in no way
interferring with the flexibility of the bag or substantially
increasing its cost. The present invention again provides a
way to relate to the charge of popcorn and fat in a package to
a microwave inductive member to maximize heating of the pickup
member and the transEer of the heat efficiently to the popcorn
while allowing the package to be collapsed to a very small
oh
. - 1 -
33~36
volume for shipment and yet the pickup means will permit free
expansion during heating to a large enough volume to accommo-
date the popped kernels while the pickup sheet remains
throughout heating efficiently thermally coupled to the pop-
corn.
According to the present invention there is provided
a popcorn package suited for shipment in a collapsed state and
for heating in a microwave oven to accomplish popping of pop-
corn kernels within the package comprising, a collapsible bag
formed from flexible sheet material transparent to microwave
energy, said bag having a food heating compartment therein
containing a charge of popcorn and fat and having a bottom
surface during heating that includes a flexible sheet of
paper, a flexible and foldable microwave concentrating induc-
tive pickup sheet only on the bottom of the compartment con-
taining the charge, said inductive sheet being composed of a
base material in sheet form having a flexible microwave induc-
tor material thereon characterized by becoming hot to effect
concentrated heating of a localized portion of the charge when
exposed to microwave energy, the pickup sheet being substan-
tially flat and being bonded to said paper sheet for dimen-
sional support to prevent shriveling and scorching during
localized heating of a food and defining a substantially flat
flexible bottom for the food heating compartment containing
the charge of fat and popcorn, the pickup sheet being in heat
transfer relationship with the charge contained in the com-
partment and being flexible enough while bonded to the paper
to permit the bag to bend freely during shipment and during
popping while the bag expands from a collap5ed state to an
expanded state, the portlons of the package other than the
bottom surface being freè from microwave receptive material to
Eacilitate locallzed absorption of microwave energy my -the
. - 2 -
:~Z33~36
pickup shee-t to thereby concentrate absorbed microwave energy
at the bottom of the charge.
In one embodiment of the present invention the
charge of popcorn and fat is spread out lat:erally so that ls
presents a broad face resting on the flexible inductive sheet
and the lower bag panel adjacent the floor portion of the
microwave oven during popping whereby microwave energy is
absorbed by the inductive pickup sheet and transferred to the
popcorn and fat above it. Suitably the microwave inductive
lo pickup sheet comprises a film of plastic resinous material
having a microwave inductive metal electrodeposited thereon as
a thin layer. Desirably the electrodeposited layer is trans-
parent to light.
In a particular embodiment of the present invention
said bag is folded transversely into three sections of approx-
imately equal size including a central section and two end
sections, each end section being empty and being folded cen-
trally to a position in proximity to the charge contained in
the central section of the bag, said transverse folding defin-
ing a means as a part of the bag to temporarily restrain thecharge at the center of the bag and in only one tube and said
microwave inductive sheet material being located at least
within the central section of the bag below said charge.
The present invention thus provides a popcorn pack-
age for shipping and popping popcorn within a microwave oven.
The bag is formed from flexible sheet material transparent to
microwave energy and includes two opposed face panels of the
same width or of different widths. Sections of extensible
interconnectlng folded sheet materlal define centrally pro-
eating gussets that extend between the s:lde edges oE thefirst and second panels Jo allow the bag to expand as the corn
pops. One panel of the bag deflnes .Lower wall of the bag
-- 3
~33~6
which is placed downwardly when the corn is popped. A fle-
xible and foldable inductive microwave pickup sheet is pro-
vided. The sheet is paper or plastic film having a microwave
receptive pickup material thereon characterized by becoming
hot when exposed to microwave energy. The pickup shee-t is
present at least in the part of the bag where the charge of
popcorn and fat is located and is in heat transfer relation-
ship therewith. The pickup sheet is bonded to the lower wall
of the bag and is supported thereby so that it remains in
place beneath the charge to thus substantially line the pool
of hot fat during the cookiny operation. The pickup sheet in
this way substantially surrounds the lower aspect of the
entire pool of hot fat and because of its flexibility can be
folded or flexed upwardly around the sides and edges of the
pool as the bag is folded. The popcorn and fat contained in
the bag is positioned intermediate the ends of the bag and is
spaced apart from the ends. The charge is also located
between the centrally projecting gussets and the lower face
panel. The centrally projecting gussets approach each other
tending to divide the bag into a pair of collateral tubes.
The charge of popcorn and fat is confined substantially
entirely in -the lower tube. The tubes are in communication
with each other between the gussets so that the popcorn can
pass from the lower tube to the upper tube during popping. In
addition, the charge of popcorn and fat is spread out later-
ally, that is to say, from side to side so that it presents a
broad face resting on the inductive sheet and bag panel ad;a-
cent the floor portlon of the microwave oven during popping
whereby microwave energy i9 absorbed by the inductive pickup
sheet and transEerred to the popcorn and fat above it.
The present in~entlon will now be described by way
of examp:le with rcEerence -to -the accompanylng drawlngs, in
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23343Çi
which:--
Figure 1 is a perspectlve view of the packaye inaccordance with the invention fllled wlth a charge of popcorn
and fat;
Figure 2 is a transverse cross-sectional view taken
on line 2-2 of Figure l;
Figure 3 is a perspective view of the package in
accordance with another form of the invention prior to fill-
ing;
Figure 4 is a partial side elevational view of the
bag shown in Figure 3 as it appears in a flattened condition
prior to filling;
Figure 5 is a perspective view of the package of
Figures 3 and 4 after being filled and folded for shipment;
Figure 6 is a perspective view of the package of
Figure 5 after being unfolded and properly oriented in a
microwave oven preparatory to cooking;
Figure 7 is a transverse cross-sectional view taken
on line 7-7 of Figure 6;
Figure 8 is a view similar to Figure 7 as it appears
when the popcorn begins to pop;
Figure 9 is a view similar to Figure 8 in a later
stage in the popping cycle;
Figure 10 is a diagrammatic perspective view of one
method of filling the bags in accordance with the invention;
and
figure 11 is a highly magnified semidiagramatic
cross-sectional view of the induc-tive pickup sheet and under-
lying bag wall.
Figures 1 and 2 illustrate a form of the lnventlon
ln whlch a paclcage l employed havlng face panels oE equal
size. The embodimen-t of figures 1 and 2 comprises a package
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~L~33~3~i
10 composed of a bag 12 formed from flexible sheet material
such as paper whlch is of collateral tubular configuration,
that is to say, being composed of a pair of parallel longi-
tudinally extending tubes 14 and 16 which communicate with one
ano-ther along a central longitudinal opening 18. The two
parallel tubes 14 and 16 are separated by longitudinally
extending side indentions 20 and 22. When the package com-
prises a paper bag, the bag can be composed of upper and lower
face panels 24 and 2G, respectively of equal size, and the
indentions 20 and 22 comprise gussets. The bag shown in
Figure 1 has bottom seal 28. After being filled, the top 30
is also sealed conventionally by means of heat or a suitable
adhesive.
As best seen in Figure 2, a food product 32
comprising a mixture of popcorn and fat is placed in the
collateral
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~23;~36
tube 16 while the tube 14 is maintained substantially
free from the charge of popcorn and fit.
When the package is heated to pop the corn, tube
16 containing the charge 32 is placed downwardly in
the microwave oven. In this position panel 26 adjacent
the charge 32 faces downwardly and contacts the bottom
wall of the cooking chamber of the microwave oven as
will be described in more detail below. It will also
be noted that the charge 32 is located approximately
centrally with respect to the ends of the bag that is
to say, approximately halfway between the top 30 and
the bottom seal 28.
Positioned adjacent to the panel 26 which serves
as the lower or bottom panel during the heating opera-
tion is a microwave pickup sheet 27. Sheet 27 is flexible
and foldable and is composed of a plastic film having a
microwave receptive metallic material 29 thereon (Figure
11). The microwave receptive material 29 is characterized
by becoming hot when exposed to microwave energy. The
sheet 27 and metallic layer 29 may, if desired, be bonded
to a paper backing 31 which serves as a support and the
entire laminate composed of the film , the metallic layer
29 and the paper backing 31 is secured preferably by ad-
hesive bonding to the lower wall panel 26 of the bag as
shown in Figures 2, 7, 8 and 9. The inductive sheet 27-29
is present at least in the portion of the bag where the
charge of fat and corn 32 is located and is in heat transfer
relatiQnship thcrewith. l`he sheet 27-29 is bonded to the
lower wall 26 ox the ba~3 ancl is supported thereby to
remain in place and to s~lbstantially line the pool of hot
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~Z3~3~i
fat in which the corn is suspended during the cooking
operation. In this way, the microwave inductive sheet
substantially surrounds the entire lower surface of the
pool of hot fat andr owing to its flexibility,can be folded
i.e., curved upwardly around the sizes and edges of the
heated fat 52 shown in Figures 8 and 9.
The metal coating 29 is usually very~thin, transparent
or semitransparent but partially reflective of light. It
can be formed, for example, by vacuum metali~ing a plastic
film-such as a polyester film. Various metals can be used
such as aluminum, copper, gold and various ferrous materials.
Other suitable inductor sheet materials can be obtained
from Jomergin, Inc. of St. Albans, Vermont, and Camvac
International of Brewster, New York. It should be under-
stood that layer 29 is not a continuous uninterrupted
metal which is a good conductor of electricity. It is
instead thin enough to be transparent to light.
Thus, the microwave inductive heat pickup sheet
absorbs the microwave energy signals generated in the
microwave oven and becomes extremely hot, probably due
to internal losses in the metal layer 29 which causes it
to heat up rapidly to a much higher temperature than an
equivalent quantity of water, fat or other common food
substance and this heat is transferred by conduction to
the food.
It is important to note that the product rests in
heat transfer relationship with the underlying inductive
sheet 27 and that the hot layer of flexible sheet material
27-29 substantially surrounds the entire lower surface
of the pool of hot fat. Moreover, because of its flexibility,
it can be transferred through all of the bag forming
operations without damage and without requirement for
additional forming or handling operations. In addition,
when the bag is folded it will, if large enough, follow con-
tours of the bag and will fold upwardly if desired around
the side edges of the pool 52 of fat which forms at the
bottom ox the bag as the popcorn is heated. While the
inductive sheet has been shown laminated to a paper
backing 31 in Figure 11, it should be understood that
the paper backing is optional, provided, however, the
plastic sheet 27 is in some way supported dimensionally,
for example,by bonding it directly to the wall 26 of the
bag. The microwave inductive pickup sheet 27 can be of
various shapes, rectangular, round or in strip form. In
any event, it should be bonded to the wall 26 of the
bag because if it is not held in place, it will tend to
float away from the wall 26 and may become charred be-
cause heat is not conducted efficiently to the charge
of food present in the bag. While the sheet 27 can be
spot bonded to the bag, it is particularly important to
bond at least the edges to the bag wall 26 to provide
dimensional stability. If it is not supported firmly
as, for example, by bonding at -the edges or over its
entire area, it will -tend to shrink to a small size and
will overheat.
Refer now to Figures 3 through 9 which illustrate
another form of the invention and in which the same
numbers refer to corresponding parts. As sllown best
in Figllres 3 and I, a packaye on is providecl comprising
a bag forrned from flexible sheet materials s-lch as
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paper preferably with a greaseproof paper liner of
suitable known construction and including first and
second parallel collateral tubes 42 and 44 both of which
cxtend longitudinally and comm~lnicate with one another
along midline at 46. The bag is sealecl by means of a
bottom seal 48 and prior to filling is open at the top
50 such that a charge of popcorn and fat 52 can be
introduced as shown in Figure 5. After the charge has
been introduced, the top 50 is sealed as shown at 50a in
Figure 6. It can be seen in Figures 3 and 4 that the
collateral tubes 42 and 44 are separated by indentations
54 and 56 and although not essential to the invention,
the indentations are conveniently formed by construct-
ing the bag with longitudinally extending centrally
projecting gussets at 54 and 56. The bag after being
constructed will usually be flattened to the condition
shown in Figure 4 with the innermost aspect of the
gussets 54 and 56 comprising folds indicated by dotted
lines 54a and 56a. The bag is in this case provided
with two longitudinally extending face panels; panel 58
and panel 60 which is smaller in width and area than
face panel 58. While size is not critical, it is pre-
ferred that the panel 60 be about 18% to 50% smaller
in area than the panel 58. Consequently, tube 44 is
smaller in cross-section than tube 42. The term "cross-
section" herein has reference to the tubes when fully
expanded to circular configuration as shown in Figure 3.
The bag illustrated is a tube type bag, that is, a bag
ormed from a continuous tube of paper manufacturecl on
a so-called bag tuber and cut transversely at: uniform
~33~36
intervals to define the top and bottom ends 50 and 48.
the bag can, however, be of the pasted bottom type with
folding panels at the top and bottom of the bag which
are pasted shut after the bag is filled. It should be
noted that the charge 52 is placed approximately inter-
mediate to the ends of the bag as shown in Figures 5 and
6. After filling and sealing the top 50 at 50a, the bag
is folded transversely at 62 and 64 to divide -the bag
roughly into three equal sections for convenient shipment
with the charge 52 in approximately the center of the bag
as best seen in Figure 6.
The charge 52 is placed in the tube 60 of smaller
cross-section, that is to say, laterally of the midline
of the bag. The larger tube 42 is maintained substantially
free of the charge of popped corn fat.
When the corn is to be popped, the package 40 is
positioned horizontally and placed in a microwave oven
68 with the panel 60 facing downward. The~charge 52 is
thus located adjacent the sheet 27 which is adjacent
the floor 69 of the cooking chamber 72 within oven 68.
The microwave oven 68 which is itself entirely conven-
tional, includes the usual oven controls 70, cooking
chamber 72 and door 74. After the door 74 is closed,
microwave energy will heat the charge 52 causing the
fat to melt as shown in Figure 8 and some of the popcorn
will pop while steam is generated filling the first
relatively large tubular section 42 with a combination of
steam and popped corn. As cooking continues, rnore and
more of the chance 52 will pop and the package wil:L
become filled with popped kernels 7~. The invention
result.s in a substantial increase in volumetric yields
as sllown in Tables L and 2.
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TABLE 1
FINAL VOLIJME OF POPPED CORN5'
Control
Bag
4 3" 4"x8'~" 3" With No
Square Square Strip Circle Inductive
Pickup Pickup Pickup Pickup Pickup
go 1040 840 1150 730 4~2
% increase135% 90~ 160~ 65% -0-
TABLE 2
FINAL VOLUME OF POPPED CORN
4" Square 4" Square Control
Pickup Pickup (Same Bag
Metalized Aluminized With No
Film 1 Mylar Inductive
0.5 Mil 0. 5 Mil Pickup)
__
c.c.2 1550 1250 860
increase
over control 80~ 45% -0-
536 gm. of corn and 16 gms. of fat heated in a 400 watt
mierowave oven for 3.5 minutes. Bags were yusseted paper
bags measuring 4" wide and 9~" long (gusse-ts were 1.5"
deep with bag collapsed). Panels were of equal size
(Figures 1 and 2).
6Average of 5 runs.
7In all samples, the inductive piekup was composed of
metalized plastic sheet 0.5 mil bonded to paper backing,
product from James River Corp. of Kalamazoo, Michigan.
Pickup was bonded to inside of the lower surface of the bag.
372 gm. of eorn and 25 gm. fat heated in 400 watt microwave
oven for 5 minutes. Bags were gusseted paper baqs mea~ur-
ing 5~" wide x 11~" tall with panels of unequal w:idth
(Figures 3~10). The smaller panel was 4 3/4" wide.
lProduct obtained Erom James River Corp. of Kalamazoo, Mich.
2Averaqe of 5 rulls.
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present invention. Depending upon circumstances, the
improvement may range from a volume increase of between
about 45% and 160%. It appears that not only more of the
popcorn kernels popped, but in addition the average volume
of the popped kernels is greater with the present inven-
tion.
Many variations of the invention within the scope
of the appended claims will be apparent to those skilled
in the art. For example, the term "metallic material" may
include metal compounds such as iron oxide, tin oxide, etc.
and the pickup shee-t can be loose in the bag and held in by
the weight of the product or bonded between plies or to the
outside of the bag.
