Note: Descriptions are shown in the official language in which they were submitted.
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MODIFIED ATMOSPHERE PACKAGE
Field of the Invention
The present invention relates generally to modified atmosphere packages for
storing food. More particularly, the invention relates to a modified
atmosphere package
for extending the shelf life of raw meats or other food.
Background of the Invention
Containers have long been employed to store and transfer perishable food prior
to presenting the food at a market where it will be purchased by the consumer.
After
perishable foods, such as meats, fruits, and vegetables, are harvested, they
are placed into
containers to preserve those foods for as long as possible. Maximizing the
time in which
the food remains preserved in the containers increases the profitability of
all entities in the
chain of distribution by minimizing the amount of spoilage.
. The environment around which the food is preserved is a critical factor in
the
preservation process. Not only is maintaining an adequate temperature
important, but the
molecular and chemical content of the gases surrounding the food is
significant as well.
By providing an appropriate gas content to the environment surrounding the
food, the
food can be better preserved when maintained at the proper temperature or even
when it
is exposed to variations in temperature. This gives the food producer some
assurance that
after the food leaves his or her control, the food will be in an acceptable
condition when it
reaches the consumer.
Modified atmosphere packaging systems for one type of food, raw meats, exposes
these raw meats to either extremely high levels or extremely low levels of
oxygen (02).
Packaging systems which provide extremely low levels of oxygen are generally
preferable
because it is well known that the fresh quality of meat can be preserved
longer un --
2 5 anaerobic conditions than under aerobic conditions. Maintaining low levels
of oxygen
minimizes the growth and multiplication of aerobic bacteria. Heretofore, low-
level
oxygen systems, such as the systems proposed in U.S. Patent No. 3,574,642 to
Weinke
and U.S. Patent No. 5,115,624 to Garwood, have obtained extremely low levels
of
oxygen by relying upon oxygen evacuation techniques.
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In typical prior art packaging systems, a package composed of flexible or
rigid gas
barrier materials is loaded into an evacuation chamber. The package in the
evacuation
chamber is subjected to a vacuum which removes as much of the gases
surrounding the
package as possible. At this point the package is sealed. After the evacuated
package is
sealed, the raw meat either can be maintained in a "zero" atmosphere
environment
(commonly referred to as vacuum packaging) or can be refilled with a gas or
mixture of
gases to provide a modified atmosphere environment. To provide a modified
atmosphere
environment, the air-evacuated package is typically filled with a mixture of
gases
consisting of about 30 percent carbon dioxide (C02) and 70 percent nitrogen
(N2).
Refilling the air-evacuated package with such a mixture of gases is believed
to suppress
the growth of anaerobic bacteria. The meat in the modified atmosphere package
takes on
a less desirable purple-red color which few consumers would associate with
freshness.
This purple-red color, however, quickly "blooms" to a bright red color
generally
associated with freshness when the package is opened to oxygenate the fresh
meat by
exposure to air. The package is typically opened immediately prior to display
of the fresh
meat to consumers so as to induce blooming of the fresh meat just prior to
display to the
consumers.
Low-level oxygen systems relying upon evacuation techniques to diminish oxygen
levels suffer from several disadvantages. For example, such systems operate at
exceptionally slow speeds because they require the use of an evacuation device
along the
packaging line. The evacuation process is time-consuming. Typically, only
about four to
six evacuated packages can be prepared on a packaging line in one minute. In
addition,
the evacuation techniques render it difficult to remove any oxygen within a
previously
wrapped package such as an overwrapped meat tray. The trapped oxygen raises
the
residual oxygen level in the package and can also cause billowing and
subsequent damage
to the package during evacuation.
A need therefore exists for a modified atmosphere package and a system for
making that package which overcome the aforementioned shortcomings associated
with
existing modified atmosphere packages and existing systems for making those
packages.
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Summary of the Invention
Briefly, the present invention is directed to a new and improved modified
atmosphere package for extending the shelf life of food, especially raw meats.
Moreover,
the present invention is directed to a new and improved modified atmosphere
packaging
system for producing the foregoing packages which operates at significantly
higher speeds
than prior art systems and which reduces the oxygen level in the packages
without the use
of time-consuming evacuation techniques. The packaging system effectively
extends the
allowable time period between cutting and purchase of retail cuts of raw meat.
The raw
meat can be cut and packaged several weeks prior to being purchased at the
store and yet
remains fresh during this time period.
The modified atmosphere package maintains an appropriate contained atmosphere
around food being contained therein when stored in an ambient environment_ A
modified
atmosphere packaging system and method creates a modified atmosphere in the
package.
In one embodiment, the modified atmosphere package includes an inner container
and an
outer container. The inner container is composed at least partially of a
polymeric material
substantially perrneable to oxygen, while the outer container is composed of a
polymeric
material substantially impermeable to oxygen. After a food product such as raw
meat is
placed within the inner container, the inner container may be flushed with a
desired
mixture of gases to substantially remove oxygen from the inner container. The
flushed
inner container is then wrapped and inserted into the outer container without
sealing the
outer container. Next, the outer container is flushed with the desired mixture
of gases to
substantially remove oxygen from the outer container. After flushing the outer
container,
the outer container is sealed_ An oxygen scavenger is provided in the package
to
substantially absorb any residual oxygen within the package.
According to an aspect of the present invention there is provided a modified
atmosphere package, comprising a first container comprising polymeric material
substantially permeable to oxygen, and configured and sized to substantially
totally
enclose a retail cut of raw meat, a second container comprising polymeric
material
substantially impermeable to oxygen, the second container covering the first
container to
define a pocket between the first container and the second container, the
pocket being
substantially free of oxygen therein in response to substantially removing the
oxygen
from the pocket and introducing one or more gases creating a modified
atmosphere
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within the pocket, the first container being removable from at least a portion
of the
second container without destroying the first container, the first container
being
differently shaped than the second container, and an oxygen scavenger
positioned
external to the first container to substantially absorb residual oxygen within
the pocket,
the oxygen scavenger being activated with an activating agent for increasing
the rate of
oxygen absorption.
According to another aspect of the present invention there is provided a
method
of manufacturing a modified atmosphere package, the method comprising the
steps of
supplying a first container including a non-barrier portion substantially
permeable to
oxygen, placing a retail cut of raw meat within the first container, sealing
the first
container, supplying a second container substantially impermeable to oxygen,
covering
the first container with the second container without sealing the second
container so as to
create a pocket between the first container and the second container,
substantially
removing oxygen from the pocket and introducing one or more gases into the
pocket to
create a modified atmosphere therein, supplying an oxygen scavenger positioned
external
to the first container to absorb residual oxygen within the pocket, activating
the oxygen
scavenger with an activating agent for increasing the rate of oxygen
absorption, and
sealing the second container.
According to a further aspect of the present invention there is provided a
modified
atmosphere packaging system for creating a modified atmosphere in a package
including
a first container, a second container, and an oxygen scavenger, the first
container being
comprised of a polymeric material substantially permeable to oxygen, the first
container
being configured and sized to fully enclose a retail cut of raw meat, the
second container
being comprised of a polymeric material substantially impermeable to oxygen,
the
oxygen scavenger being active with an activating agent and positioned external
to the
first container to substantially absorb residual oxygen within the package,
the system
comprising means for sealing the first container with the retail cut of raw
meat enclosed
therein means, disposed downstream from the means for sealing the first
container, for
inserting the sealed first container into the second container without sealing
the second
container, the first container being removable from at least a portion of the
second container
without destroying the first container and being differently shaped than the
second container,
and means, disposed downstream from the means for inserting the sealed first
container,
for substantially removing oxygen from the second container and introducing
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one more or gases into the second container to create a modified atmosphere
therein, and
means, disposed downstream from the means for substantially removing oxygen
from the
second container, for sealing the second container.
The above summary of the present invention is not intended to represent each
embodiment, or every aspect of the present invention. This is the purpose of
the figures
and detailed description which follow.
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Brief Description of the DrawinEs
Other objects and advantages of the invention will become apparent upon
reading
the following detailed description and upon reference to the drawings in
which:
FIG. 1 is an isometric view of a modified atmosphere package embodying the
present invention;
FIG. 2 is a section view taken generally along line 2-2 in FIG. 1;
FIG. 3 is an enlarged view taken generally along circled portion 3 in FIG. 2;
and
FIG. 4 is a diagrammatic side view of a system for making the modified
atmosphere package in FIG. 1.
While the invention is susceptible to various modifications and alternative
forms,
certain specific embodiments thereof have been shown by way of example in the
drawings
and will be described in detail. It should be understood, however, that the
intention is not
to limit the invention to the particular forms described. On the contrary, the
intention is
to co'ver all modifications, equivalents, and alternatives falling within the
spirit and scope
of the invention as defined by the appended claims.
Description of the Preferred Embodiment
Turning now to the drawings, FIGS. 1-3 depict a modified atmosphere package
10 including an outer container 12 and an inner container 14. The inner
container 14
includes a conventional semi-rigid plastic tray 16 thermoformed from a sheet
of polymeric
material which is substantially permeable to oxygen. Exemplary polymers which
may be
used to form the non-barrier tray 16 include polystyrene foam, cellulose pulp,
polyethylene, polypropylene, etc. In a preferred embodiment, the polymeric
sheetused_ta-_
form the tray 16 is substantially composed of polystyrene foam and has a
thickness
ranging from about 100 mils to about 300 mils. The use of a common polystyrene
foam
tray 16 is desirable because it has a high consumer acceptance. The inner
container 12
further includes a stretch film wrapping or cover 18 substantially composed of
a
polymeric material, such as polyvinyl chloride (PVC), which is substantially
permeable to
oxygen. In a preferred embodiment, the stretch film used to form the cover 18
contains
additives which allow the film to cling to itself and has a thickness ranging
from about 0.5
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mil to about 1.5 mils. One preferred stretch film is ResiniteTm meat film
commercially
available from Borden Packaging and Industrial Products of North Andover,
Massachusetts.
The tray 16 is generally rectangular in configuration and includes a bottom
wall
20, a continuous side wall 22, and a continuous rim or flange 24; The
continuous side
wall 22 encompasses the bottom wall 20 and extends upwardly and outwardly from
the
bottom wall 20. The continuous rim 24 encompasses an upper edge of the
continuous
side wall 22 and projects laterally outwardly therefrom. A food item such as a
retail cut
of raw meat 26 is located in a rectangular compartment defined by the bottom
wall 20 and
contiriuous side wall 22. Prior to fully wrapping the tray 16 with the cover
18, the
partially formed inner container 14 may be flushed with an appropriate mixture
of gases,
typically a mixture of about 30 percent carbon dioxide and about 70 percent
nitrogen, to
lower the oxygen level in the inner container 14 to about 1.5 to 5.0 percent.
The
foregoing mixture of gases displaces the oxygen within the inner container 14
during the
flushing operation. After flushing the inner container 14, the tray 16 is
manually or
automatically wrapped with the cover 18. The cover 18 is wrapped over the
retail cut of
raw meat 26 and about both the side wall 22 and bottom wall 20 of the tray 16.
The free
ends of the cover 18 are overlapped along the underside of the bottom wall 20
of the tray
16, and, due to the cling characteristic inherent in the cover 18, these
overlapping free
ends cling to one another to hold the cover 18 in place. If desired, the
overwrapped tray
16, i.e., the inner container 14, may be run over a hot plate to thermally
fuse the free ends
of the cover 18 to one another and thereby prevent these free ends from
potentially-___
unraveling.
The outer container 12 is preferably a flexible polymeric bag composed of a
single
or multilayer plastics material which is substantially impermeable to oxygen.
The
polymeric bag 12 may, for example, include an oriented polypropylene (OPP)
core coated
with an oxygen barrier coating such as polyvinylidene chloride and further
laminated with
a layer of sealant material such as polyethylene to facilitate heat sealing.
In a preferred
embodiment, the polymeric bag 12 is composed of a layer of polyethylene
laminated to
OPP film commercially available as product no. 325C44-EX861B from PrintPack,
Inc. of
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Atlanta, Georgia. The laminated OPP film has a thickness ranging from about 2
mils to
about 6 mils. Prior to sealing the peripheral edges of the polymeric bag 12,
the inner
container 14 is placed within the polymeric bag. 12. Also, the bag 12 is
flushed with an
appropriate mixture of gases, typically about 30 percent carbon dioxide and
about 70
percent nitrogen, to lower the oxygen level in the bag 12 to about 0.05 to 5.0
percent.
After flushing the bag 12, but still prior to sealing the bag 12, an oxygen
scavenger/absorber 28 is placed in the bag 12 external to the sealed inner
container 14.
The bag 12 is then sealed.
After a timelperiod of about one to two hours, the oxygen scavenger 281owers
the oxygen level in the bag 12 from the 0.05 to 5.0 percent oxygen level
described above
to less than about 0.05 percent and most preferably to about zero percent. If
there is still
oxygen in the bag 12 after this time period, the oxygen scavenger 28 absorbs
any
remaining oxygen in the bag 12 and any oxygen which might still be trapped
within the
inner container 14 so as to lower the oxygen level in the bag 12 to about zero
percent.
The_oxygen scavenger 28 also absorbs any oxygen which might permeate into the
bag 12
from the ambient environment. To optimize the rate of oxygen absorption, the
oxygen
scavenger 28 may be injected with a predetermined a:mount of activating agent
or by other
means to increase the rate of absorption prior to being placed in the bag 12.
In FIGS. 1-
3, the oxygen scavenger 28 is illustrated as a packet or label which is
inserted into the bag
12 prior to sealing the bag 12. Alternatively, an oxygen scavenging material
may be
added to the polymer or polymers used to form the bag 12 so that the oxygen
scavenging
material is integrated into the bag 12 itself. -
The retail cut of raw meat 26 within the package 10 takes on a purple-red
color
when the oxygen is removed from the interior of the package 10. The meat-
filled
modified atmosphere package 10 may now stored in a refrigeration unit for
several weeks
prior to being offered for sale at a grocery store. A short time (e.g., less
than one hour)
prior to being displayed at the grocery store, the inner container 14 is
removed from the
polymeric bag 12 to allow oxygen from the ambient environment to permeate the
non-
barrier tray 16 and non-barrier cover 18. The purple-red color of the raw meat
26 quickly
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changes or "blooms" to a generally acceptable bright red color when the raw
meat 26 is
oxygenated by exposure to air.
FIG. 4 illustrates a modified atmosphere packaging system used to produce the
modified atmosphere package 10 in FIGS. 1-3. The packaging system integrates
several
disparate and commercially available technologies to provide a modified
atmosphere for
retail cuts of raw meat. The basic operations performed by the packaging
system are
described below in connection with FIG. 4.
The packaging process begins at a thermoforming station 30 where a tray 16 is
thermoformed in coinventional fashion from a sheet of polystyrene or other non-
barrier
polyiner using conventional thermoforming equipment. The thermoforming
equipment
typically includes a male die member 30a and a female die cavity 30b. As is
well known
in the thermoforming art, the tray 16 is thermoformed by inserting the male
die member
30a into the female die cavity 30b with the polymeric sheet disposed
therebetween.
The thermoformed tray 16 proceeds to a goods loading station 32 where the tray
16 is filled with a food product such as a retail cut of raw meat 26. The meat-
filled tray
16 is then manually carried or transported on a conveyor 34 to a conventional
stretch
wrapping station 36 where a stretch film 18 is wrapped about the tray 16 to
enclose the
retail cut of meat 26 therein. The overwrapped tray 16 forms the inner
container 14. Just
prior to sealing the meat-filled tray 16 at the stretch wrapping station 36,
the tray 16 is
flushed with a mixture of carbon dioxide and nitrogen to reduce the oxygen
level in the
tray 16 to about 0.1 to 5.0 percent. The mixture of carbon dioxide and
nitrogen emanates
from a conventional gas supply hollow tube or rod 40 fed by a gas tank (not
shown): The_-
stretch wrapping station 36 may be implemented with a compact stretch semi-
automatic
wrapper commercially available from Hobart Corporation of Troy, Ohio.
Next, the flushed and sealed inner container 14 proceeds to a high speed form,
fill,
and seal station 42 which may be implemented with a Fuji-Formost high-speed
horizontal
form-fill-seal machine commercially available as model no. FW-3700 from
Formost
Packaging Machines, Inc. of Woodinville, Washington. The inner container 14
may be
transported to the form, fill, and seal station 42 by a conveyor 44. At the
form, fill, and
seal station 42, a web 46 of oxygen barrier film from a roll 47 is arranged to
run along the
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direction of movement of the inner container 14. The web 46 of film is fed to
a
conventional forming box which forms a section 48 of the web 46 into a tube
configuration encompassing the inner container, 14. The tube-shaped section 48
of the
web 46 is thermally sealed along a lower fin 50 and is thermally sealed at one
end 52 by a
pair of vertically-oscillating heated sealing bars 54 or the like.
Just prior to sealing the other end 56 of the tube-shaped web section 48 to
complete formation of the polymeric bag 12, the web section 48 is flushed with
an
appropriate mixture of gases, typically about 30 percent carbon dioxide and
about 70
percent nitrogen, to lower the oxygen level in the bag 12 to about 0.05 to 5.0
percent.
The-mixture of carbon dioxide and nitrogen emanates from a conventional gas
supply
hollow tube or rod 58 fed by a gas tank (not shown). After flushing the web
section 48,
but still prior to sealing the end 56, the oxygen scavenger/absorber 28 is
placed in the web
section 48 external to the sealed inner container 14. The end 56 is then
conveyed
betuieen and sealed by the heated sealing bars 54 to complete formation of the
bag 12. In
addition to thermally fusing the web section 48 at the end 56, the heated
sealing bars 54
sever the web section 48 at the end 56 to separate the bag 12 from the next
upstream web
section being formed into another bag. The sealed bag 12 is substantially in
the form of a
sealed bubble or envelope loosely containing the inner container 14 and
providing a sealed
modified atmosphere surrounding the inner container 14.
The oxygen scavenger 28 lowers the oxygen level in the package 10 from the
previously described 0.05 to 5.0 percent oxygen level to approximately zero
percent
within a time period of about one to two hours. Although the oxygen scavenger
28 is
depicted in FIG. 4 as a packet or label inserted into the polymeric bag 12, an
oxygen
scavenger may altecnatively be integrated into the polymers used to form the
bag 12. One
preferred oxygen scavenger is a FreshPaxTm oxygen absorbing packet
commercially
available from Multiform Desiccants Inc. of Buffalo, New York.
The modified atmosphere packaging system in FIG. 4 can produce the modified
atmosphere packages 10 at cycle rates ranging from about 1 to 60 packages per
minute.
The maximum cycle rates which can be attained by the system in FIG. 4 are
significantly
higher than the cycle rates which can be achieved by prior art systems. The
attainment of
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high cycle rates is largely due to the fact that the packaging system in FIG.
4 relies upon
the use of simple, commercially available, and high-speed form, fill, and seal
equipment,
as opposed to the slower evacuation equipment employed by prior art systems.
Reducing
oxygen levels in the modified atmosphere package 10 by first flushing the
package 10 and
then subsequently introducing the oxygen scavenger 28 into the package 10 is
significantly faster and more cost-effective than the reliance upon slow
evacuation
techniques.
While the present invention has been described with reference to one or more
particular embodiments, those skilled in the art will recognize that many
changes may be
made thereto without departing from the spirit and scope of the present
invention. Each
of these embodiments and obvious variations thereof is contemplated as falling
within the
spirit and scope of the claimed invention, which is set forth in the following
claims.
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