Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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-1-
CONTROLLED ATMOSPHERE PACKAGE WITH DOUBLE COVER
This is a divisional of Canadian Patent Application Serial No. 2,223,232
filed June 6, 1996.
BACKGROUND OF THE INVENTION
The present invention relates generally to packages for fresh red weak
s Particularly, this invention is directed to the packaging of food products
such that
the packaged product may be maintained in one condition under certain
circumstances and then converted to another condition. Specifically, packages
in
accordance with the present invention provide for distribution of a packaged
product in a low oxygen environment and for introduction of oxygen to the
~o product surface at a supermarket or other retail outlet Such introduction
of
oxygen is achieved either by permeation of oxygen through a film in contact
with
the product surface or through an exchange of atmospheric oxygen with a low
oxygen gaseous atmosphere contained around the product_
While a wide variety of food products can be packaged in accordance with
is the teachings of this invention, it is particularly advantageous in
connection with
the packaging of fresh red meat such that the meat may be transported in a low
oxygen atmosphere, that is, preferably 0.5% OZ or less, most preferably 0.05%
OZ or
less, and then caused to bloom when it reaches a supermarket by exposure to
oxygen.
2 o Historically, large sub-primal cuts of meat have been butchered and
packaged in each supermarket. This, however, can be inefficient and result in
certain undesirable additional costs. For example, all cuts from a large sub-
primal
must be sold at once. Instead it would be preferable to permit the meat to be
butchered and packaged at a central facility which benefits from economies of
scale
25 and thereafter shipped to individual supermarkets such as is done, for
example,
with many poultry products.
In the past, the goal of central fresh red meat processing has not been
achievable because most consumers prefer to buy meat which is reddened in
color
as a result of exposure to oxygen. However, the meat maintains its reddened
color
3o for approximately one to three days and, thereafter, turns a brown color
which is
undesirable to most consumers.
Therefore, if the meat was butchered and packaged in a gas permeable
(hereinafter "permeable") film, as is typical at retail, at a central location
and then
shipped to another location for eventual sale, in all likelihood, by the time
the
35 package reached the retail outlet the meat would have undergone the
transformation to the brown color and would be effectively unsalable.
Conversely,
if the meat was butchered and packaged at a central location in a gas-
impermeable
(hereinafter "impermeable") film, either under vacuum or with vacuum and a low
oxygen gas flush, and then shipped to another location for eventual sale, the
meat
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2
would reach the retail outlet having a purple color which is typical of meat
prior to
exposure to oxygen. Heretofore, marketing efforts to teach the consumer about
the
harmlessness of the purple color have proved to be difficult And, if the gas
impermeable film was a component of a conventional package having a tray which
s is overwrapped or lidded with a film and which contains a low oxygen
atmosphere, the impermeable film would have to be removed and replaced with a
permeable film in order to allow for bloom of the meat to a bright red color
prior to
display for the consumer, negating to a large extent the benefits of a central
processing facility.
o A variety of packages have been developed in an effort to provide a means
for transporting meat in a low oxygen environment and for quickly and easily
introducing oxygen to the meat at the retail outlet immediately prior to
display to
the consumer.
One approach to solving this problem has involved the development of
s peelable films. That is, films have been developed which readily delaminate
into
permeable and impermeable portions. Such a film is sealed to a support member,
such as a tray, which contains the meat product, thereby forming a gas
impermeable package for distribution. At the retail outlet, the gas
impermeable
portions are peeled from the film leaving a permeable film sealed to the tray
and,
2 o therefore, a gas permeable package which allows the meat to bloom to
bright red
because of the exchange with atmospheric oxygen.
The peelable film may extend over the contained product and be sealed to
the periphery of the tray as a lid or it may be heated and draped over the
product
under vacuum to form to a vacuum skin package. However, for both types of
25 packages the principal drawback is the relatively low gas transmission rate
of the
permeable film portion after removal of the impermeable portion. That is,
although the permeable portion of the peelable film has a much higher gas
transmission rate than that of the entire film prior to delamination, 5,000 to
25,000
cc/m2/24 hrs./atm. at 73°F as compared to 0 to 50 cc/m2/24 hrs./atm. at
73°F prior
so to delamination, it is still too low to effect bloom of the packaged meat
in a low
oxygen gaseous atmosphere in a short period of time, except in areas of
intimate
permeable film to meat contact
Most of the other approaches to achieving the goal of central fresh red meat
processing have involved the development of a variety of dual web packages of
the
35 type having a permeable film covering the meat product and an impermeable
film,
which is removed at the retail outlet, covering the permeable film wherein the
permeable film and the impermeable film are separate, discreet films.
Examples of these types of packages include dual overwrap packages
wherein a permeable film is wrapped around the meat and its support member
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3
and an impermeable film is wrapped about the permeable film; dual lid packages
which include a permeable lid and an impermeable lid sealed to the periphery
of
the support member; and packages with a head space which allows for the
introduction of a treating gas, typically nitrogen, carbon dioxide or some
mixture
s of the two, between a permeable film adjacent to the meat product and an
impermeable upper web. But, as is the case with the peelable films discussed
above, each of these dual web packages are limited in their effectiveness by
the
permeability of the permeable film. Typical gas transmission rates for
commercially viable gas permeable films are 5,000 to 25,000 cc/mi/24 hrs./atm.
at
73°F which is too low to effect rapid red meat bloom by exchange of the
low
oxygen gas and/or gases out and the atmospheric oxygen in.
A further package developed to allow for central fresh red meat processing
includes a gas impermeable upper lid with a valve defined in the lid. The
package
may include a treating gas between the packaged meat and the upper lid during
~s distribution which is withdrawn through the valve and replaced with an
oxygen-
rich gas. Although a rapid bloom is possible with this system, it has the
disadvantages of requiring trained operators at the retail outlet and
relatively
expensive equipment to exchange each package thus negating the cost savings of
a
central processing facility. The presence of the valve has the further
disadvantage
2 0 of creating a package appearance which is different from that which
consumers are
accustomed to seeing for meat packaging. Further, a gas space between the meat
product and the impermeable film is required to maintain a bloomed color which
yields an underfilled package appearance.
Yet another package developed to allow for central fresh red meat
2s processing provides for an excellent exchange of gases and rapid
introduction of
oxygen in which an upper impermeable web covers a lower permeable web which
includes unsealed areas in the seal of the permeable web to the tray. However,
the
intermittent sealed and nonsealed areas are formed by an alfiered sealing head
which comprises a series of sealing "fingers" rather than a conventional,
continuous
3 o sealing surface.
Thus, it is an object of the present invention to provide a package which
allows for central processing of fresh red meat with minimal processing
required at
retail.
It is yet another object of the present invention to provide a package which
3 s is similar in appearance to that which consumers are accustomed to seeing
for meat
packaging.
It is a further object of the present invention to provide a package which
allows for rapid bloom of fresh red meat
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4
It is yet another object of the present invention to provide a package which
may be assembled, filled and sealed at a central processing facility on
conventional
equipment.
s SUMMARY OF THE INVENTION
These as well as other objects are achieved by providing a package for a
product which includes a product, an impermeable support member supporting
the product, a first film sealed to the support member for enclosing the
product,
means defined within the first film for exchanging gases into and out of the
~ o package, such means for exchanging gases having a gas transmission rate of
at
least about 50,000 cc/m~/24 hrs./atm. at 73°F, and a second impermeable
film
enclosing the first film and the means defined therein for exchanging gases,
such
that removal of the second impermeable film provides for the exchange of gases
into and out of the package.
15 Such objects are further achieved by providing a package for a product
which includes a product, an impermeable support member supporting the
product, a multilayer web sealed to the support member for enclosing the
product,
the multilayer web being delaminatable into a permeable portion and an
impermeable portion with the permeable portion being directly adjacent and
2o sealed to the support member and the impermeable portion, whereby the
permeable portion remains sealed to the support member upon delamination of
the impermeable portion therefrom, and whereby delamination of the
impermeable portion from the permeable portion defines at least one channel
within the permeable portion allowing for a free flow of gases through the at
least
2 s one channel, into and out of the package.
Such objects are also achieved by providing a package for a product which
includes a product, a support member supporting the product, a first film
sealed to
the support member for enclosing the product, a second, impermeable film for
enclosing the first film, at least one channel defined within the first film
and
so enclosed by the second, impermeable film whereby removal of the second,
impermeable film allows for a free flow of gases through the at least one
channel,
into and out of said package, and a patch for enclosing the channel after the
gases
flowing into and out of the package have achieved a desired equilibrium.
Such objects are further achieved by providing a package for a product
3s which includes a product, a support member supporting the product, a first
film
sealed to the support member, a second film sealed to the first film, the
second film
having a gas transmission rate of at least about 50,000 cc/m2/24 hrs./aim. at
73°F,
the product being enclosed within the support member by the first and second
films, a third, impermeable film for enclosing the first and second films,
whereby
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removal of the third, impermeable film allows for a free
flow of gases through the second film, into and out of the
package.
In one aspect, there is provided a package for a
5 product, comprising: a support member supporting the
product; a first film sealed to the support member, said
first film having at least one opening therein; a second
film sealed to the first film such that said second film
covers said atleast one opening in said first film, said
second film having a gas transmission rate of at least
50,000 cc/m2/24 hrs.jatm. at 73°F, said product being
enclosed within said Support member by said first and second
films; a third, substantially gas-imperrneable film for
enclosing the first and second films; whereby removal of the
third, impermeable film allows for a flow of gases through
said second film and said at least one opening, into and out
of the package.
In a second aspeot, there is provided a package or
product comprising: a product; a support member supporting
the product; a first, substantially gas-impermeable film
sealed to said suppoxt member to enclose the product between
said support member and said first film, said first film
having at least one opening therein; a patch sealed to said
first film such that said patch covers said at least one
opening in said first film, said patch having a gas
transmission rate of at least 50,000 cc/m2/24 hrs./atm. at
73°F; and a second, substantially gas-impermeable film that
encloses said patch, whereb~r, removal of said second,
substantially gas-impermeable film allows for a flow of
3~0 gases through said patch and said at least one opening, into
and out of the package.
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5a
In a third aspect, there is provided a web,
comprising: a first, substantially gas-impermeable film
having at least one opening therein; a patch sealed to said
first film such that said patch covers said at least one
opening in said first film, said patch having a gas
transmission rate of at least 50,000 cc/m2/24 hrs./atm. at
73°F; and a second, substantially gas-impermeable film that
encloses said patch and is sealed to said first film,
whereby, removal of said second, substantially gas-
impermeable film allows for a flow of gases through said
patch and said at least one opening.
BRIEF DESCRIPTION OF THE DRAWINGS
A detailed description of preferred embodiments of
the invention follows, with reference to the accompanying
drawings, wherein:
Fig. 1 is a perspective view of a package,
according to the invention;
Fig. 2 is a partial cross-sectional view of the
package of Figure 1;
Fig. 3 is a partial cross-sectional view of
another package in accordance with the px°esent invention;
Fig. 4 is a partial cross-sectional view of yet
another package in accordance with the present invention;
Fig. 5 is a perspective view of a further package
in accordance with the present invention;
Fig. 6 is a cross-sectional view of the package of
Fig. 5;
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5b
Fig. 6A is a cross-sectional view of the package
of Fig. 5 following removal of the impermeable web and
application of the patch;
Fig. 7 is a perspective view of a still further
package in accordance with the present invention;
Fig. 8 is a cross-sectional view of the package of
Fig. 7; and
Fig. 9 is a cross-sectional view of a further
embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is directed to a tray-type
package suitable for the central processing of fresh red
meat which includes a gas impermeable (hereinafter
"impermeable") support member or tray, a first film sealed
to the tray which includes a means defined therein for
providing for an exchange of gases into and out of the
package, and an impermeable film which encloses the first
film and means for exchanging gases defined therein. The
package most preferably contains a low oxygen gaseous
atmosphere such as, for example, a nitrogen/carbon dioxide
mix. Thus, removal of the impermeable film allows for a
release of the low oxygen atmosphere and for introduction of
oxygen to the packaged meat product.
The means for exchanging gases defined within the
first film may be perforations defined within the first film
which are exposed upon removal of the impermeable film, an
enlarged opening defined within the first film which is
exposed upon removal of the impermeable film and is covered
with a patch or label following a period of time adequate
for sufficient exchange of gases, or a
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s
highly permeable film, sealed to the first film, which provides an area of
exceptionally high gas transmission upon removal of the impermeable film.
Looking to the first group of packages, Figures 1 through 4 illustrate
packages having a variety of multilayer webs which may be delaminabed into
s impermeable upper webs and perforated lower webs. Such multilayer webs allow
for a simplified packaging operation employing conventional single flange
trays, a
vacuum or, preferably, a vacuum and gas flush with a low oxygen atmosphere,
and sealing of a single web to the tray flange in a single sealing step. At
retail, the
upper layer of the web is peeled away revealing a perforated lower layer which
~o has a gas transmission rate of at least about 50,000 cc/m2/24 hrs./atm. at
73°F,
allowing for a rapid release of the low oxygen atmosphere and introduction of
oxygen for immediate blooming of the packaged meat product Following
blooming, the package may optionally be overwrapped with a gas permeable film
such as is employed in conventional retail overwrapping to act as a dust cover
for
~5 the packaged meat product.
Looking to Figure 1, a package 10 in accordance with the present invention
includes a support member or tray 12 having side walls 14 and a base 16
defining
an inner cavity 18 for receiving product 20. A peripheral flange 22 is defined
about
the upper portions of side walls 14. Multilayer web 26 is sealed to the tray
at the
2 o flange 22.
Figure 2 is a cross-sectional view of the package 10 of Figure 1 including
tray 12 with web 26 sealed to flange 22. For the present embodiment, web 26 is
a
single, coextruded multilayer film which may be delaminated into impermeable
and permeable portions. Films which may be so delaminated are well known in
2s the art and are formed by coextruding a multilayer film which includes two
Layers
immediately adjacent to each other and which demonstrate a weak force of
adhesion therebetween. Preferred bond strength equate to peel forces to
separate
these adjacent layers of from about 0.02 to about 0.05 tbs. Thus, web 26
delaminates into an upper impermeable portion 28 and a lower permeable portion
30 30, as is shown.
Web 26 has defined therein partial perforations 32 which extend through the
permeable portion of the film. Upon delamination it is seen that the
impermeable
portion 28 is substantially free of such perforations. Accordingly, when
pariiallv
perforating a film or web for use in the present inventive package it is
necessary to
35 know the extent and thickness of the permeable and impermeable layers
contained
therein and for the perforations to extend through the permeable layers but
not, to
any material extent, through the impermeable layers. That is, the perforations
may
extend partially, to a slight degree, into the impermeable layers but may not
interfere with the gas barrier properties of the impermeable portion of the
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7
tnultilayer film: Also included are perforations which extend substantially
but not
necessarily completely through the permeable portion, commonly Teferred to as
blind perforations.
Thus, when impermeable portion 28 is peeled away, perforations 32 defined
s within the remaining permeable .portion 30 allow for a rapid exchange of
gases and
consequent blooming of the packaged-meat products as is shown'.
It should be noted that web 26 is a multilayer film which delaminates into
permeable andv impermeable portions to uncover the permeable 'portion and
enhance 'tile flow of gases iaito and out of the package: It is also within
'the scope of
Z o the present invention, although less preferred; to provide a multilayer
film which
delaminates izito two impermeable pottioies, ~ne hat is i3irectly '-sealed to
the
support member having perforations. ~uchwalternative
is'vless:preferred~=because
the inherent peraieabflity'- of a perzneable° film portion also -aids=
iv gas exchange.
More importantly, in areas of intimate fil>n 'to wheat Contact 'ari
imperineable
15 perfarated'~fiim portion will preclude 'bloom of the'~rneat except in the
specific areas
of' perforafion, thus resulting in a non-bloomed at~ea containing dotted areas
of
bloo>r. ~Aiid, because of the expense 'involved 'in coextruding two gas
barrier
layeT°s ire a aingle znultilayer film when one will merely ~be.
perforated- to render it
perateable ''anyway, 'it is generally preferred that 'the perforated' portion
is
20 permeable.
Figure' 3 is directed to a- package 50 which is similar rin operation but
soW ewhat different in manufacture from that of package 10 of Figures l and
.2,
above.. Hereagain package 50 includes tray 52' having side walls 54 avd-a
base, not
shown, which defines a cavity 58°~for receiving a product, A
'peripheral flange b2 is
25 defined .about the upper portions ofside walls 54. MultilayeT webv 66 is
sealed to
the tray at flange 62: For the present eaiubodiment, web.6b' is wa coextruded;
niultilayer 'film or laminate of a nonpei~forated iaipe~eable' filirt E~8 and
a~~-film ?0
wlvch' includes perforations '72 defined - therein: As . Hrith' the single
film
embodi>nerat discussed aiiove, it is 'preferred that' film 70 is~ a'wpermeable
film
so because, although the perforations defined therethrough greatly-
lncrease.° the gas
trall5l?llssion rate of the fifm'such iriheTerit~pertneability' aids
°in gas exchange and
blooming will be hindered'in aTeas'of intiiriate film to meat coritacte"
However, a
nonperaieable film which is perforated to render pit 'permeable ns~ ~~lso
within the
scope of the present' invention. As is' shown 'in Figure 3; nonperforated fit-
m 68 is
35 peeled away to-reveal perforated film ~ 70 for a rapid :exchange of= gases
and
blooming of the packaged nneat at retail. -
" Figure 4 illustrates yet another °pa-ckage 1'00 in accordarsce with
~tlie~ present
invention which includes a support member or tray 11.2 having side yaIls 114
and
a base defiriing'an inner cavity 11$ far' receiving product: A :peripheral
°fiange 122
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8
is defined about the upper portions of side walls 114. Multilayer web 126 is
sealed
to the tray at the flange 122. For the present embodiment, web 126 is a
laminate of
impermeable film 128 and multilayer film 130 having perforations 132 defined
therein. Hereagain, multilayer film 130 is capable of delaminating into two
s separate film portions. However, for purposes of the present embodiment it
is
necessary that the force require to delaminate film 130 into two separate film
portions is less than the force required to delaminate impermeable film 128
from
the upper surface of multilayer film 130. That is, film 130 is formed by
coextrusion, is perforated, and is then laminated to impermeable film 128.
1 o However, unlike laminate 6b above, impermeable film 128 may not be readily
peeled from film 130. Rather, the bond strength between film 128 and
multiiayer
film 130 is greater than the interlayer strength of film 130 such that any
attempt to
remove film 128 results in the cohesive failure and inberlayer delamination of
film
130 into two separate film portions. Thus, upper portion 136 remains bonded to
s impermeable film 128 and lower portion 138 remains sealed to tray flange
122.
As with the webs discussed with respect to the embodiments set forth
above, the permeability of film 130 prior to its perforation is somewhat
optional
and may encompass a variety of combinations. Most preferably multilayer film
130 is a permeable multilayer film which is perforated, laminated to
impermeable
2o film 128 and, upon any attempt at removal of film 128, delaminates into two
film
portions, one of which remains bonded to film 128 and the other of which
remains
sealed to tray 112 enclosing the packaged meat product. Therefore, it should
be
understood that Figure 4 illustrates the separation of portions 136 and 138 as
shown but that film 130 being multilayer can be substantially separable right
at the
2 s layer-layer interface as well. However, it is also within the xope of the
present
invention to provide a multilayer impermeable film which delaminates into
permeable and impermeable portions. Such multilayer film is perforated,
laminated to impermeable film 128, preferably with the impermeable portion
being immediately adjacent to impermeable film 128 and the permeable portion
3o being sealed to tray 1I2, and, upon any attempt at removal of film 128,
delaminabes
into two film portions, the impermeable portion remaining bonded to film 128
and
the permeable portion remaining sealed to tray 112. Because the film 130 is
perforated all the way through it is also within the scope of the invention,
although
less preferred, to laminate film 130 to impermeable film 128 with the
permeable
3s portion being immediately adjacent to film 128 and the impermeable portion
being
sealed to tray 112. Similarly, it is also within the xope of the present
invention to
employ a multilayer film which delaminates into two impermeable portions such
that the film portion which remains sealed to tray 112 upon removal of film
128 is a
perforated impermeable film, which is, of course, rendered permeable by its
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64536-938D
9
perforations. As above, it is preferred that the remaining film portion 138 is
permeable because, although the perforations defined therethrough greatly
increase the gas transmission rate of the film, such inherent permeability
aids in
gas exchange and because of potential preclusion of bloom in areas of intimate
film
to meat contact.
Turning now to other means for exchanging gases which may be defined
within the first film of the present invention, Figure 5 illustrates a package
ISO
which includes a tray 152 having side walls 154 and a base 156 defining a
cavity
I58 for receiving a product 160. As will be discussed in greater detail below,
for
io purposes of the present embodiment, it is preferred that a dual flange 162
is
employed which includes outer flange portion 164 and inner flange portion 166
which are separated by depression 168.
As is shown better in the cross-sectional view of Figure 6,
a first film 170 is sealed to inner flange portion 166 and includes an
enlarged
i5 opening 172 defined therein. The opening 172 is of sufficient dimensions to
impart
of gas transmission rate of at least 50,000 cc/m2/24 hrs./atm. at 73°F,
and more
preferably at least about 75,000 cc/m~/24 hrs./atm. at 73°F, to the
film. For
purposes of the present embodiment it is preferred that film 170 is comprised
of a
gas permeable film, as will be shown below.
2o Impermeable film 174 encloses film 170 and opening 172 defined therein
and is sealed to outer flange portion 164. Preferably, the seal formed between
film
174 and outer flange portion 164 is such that film 174 may be easily peeled
away at
retail. Thus, upon removal of impermeable film I74, the enlarged opening 172
defined in film 170 allows for a rapid exchange of gases out of and into the
2s package and a concurrent blooming of the packaged meat product. Following
such gas exchange opening I72 is enclosed with a patch 176 as is shown in
Figure
6A. Alternately, opening 172 can be formed subsequent to removal of film 174
and
patch 176 then applied. Such patch may be permeable or impermeable. Generally,
it is preferred that either film 170 or patch 176 or both are permeable to
allow for a
so continued gas exchange during retail display. Also, a single impermeable
web
having a patch covering the hole is within the scope of the invention. If film
170 is
gas impermeable, then the patch 176 preferably comprises a permeable
mafierial.
However, since the opening I72 and its patch I76 define only a relatively
small
percent of the surface area of film 170, a preferred option is for film 170 to
be
ss permeable. Then patch 176 may be either permeable or impermeable, but need
not
serve as the sole means of gas exchange during retail display. Furthermore,
rather
than giving the appearance that something went wrong and the package was
"patched up" for retail display, it is preferred that the patch serve as all
or a portion
of a label identifying the product.
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64536-938D
Although a single enlarged opening is illustrated, two or more smaller.
openings may also be employed so long as they impart sufficient gas flux
capability to the film. However, it is generally preferred that multiple
openings be
grouped together such that they may be enclosed by a single patch or label.
.. Figure 7 illustrates yet a further embodiment of the present invention in
which a package 200 includes a tray 212 with side walls 214 and a base 216
defining a cavity 218 for receiving a product 220. For purposes of vthe
present
embodiment it is preferred that a dual flange 222 is employed which includes
outer flange portion 224, inner flange portion 226 and depression 228
separating
~ o the two.
As is better shown in the cross-sectional view of Figure 8, a first film 230
encloses the product and is sealed to the tray 212 at inner flange portion
226. An
enlarged opening 232 is defined ~~ithin the first film and a second film or
patch 234
is sealed to the first film enclosing opening 232. For all the embodiments of
a
~s permeable patch or a film covering a hole in a first film, the patch/film
permeable
material can comprise any permeable polymeric material compatible with the web
it is sealed to. It can comprise, for example, polyethylene or any of a
variety of
ethylene copolymers including, for example, ethylene vinyl acetate, ethylene
acrylate copolymers, ethylene acrylic acid copolymers including metal
neutralized
2o salts thereof, and ethylene alpha-olefin copolymers. Most preferred is a
patch/film
exhibiting a gas transmission rate of at least about 50,000 cc/m~/24 hrs./atm,
at
73°F, more preferably at least about 75,000 cc/m2/24 hrs./atm. at
73°f. Examples
of such include spun-bonded polyolefin or polyester materials, such as Tyvek'~
manufactured by DuPoni ana other microporous materials which are well known
2~ in the art Impermeable film 236 encloses the first film 230 and patch 234
and is
sealed to the outer flange portion 224 of tray 212. Preferably, the seal
between
impermeable film 236 and outer flange portion 224 is such that film 236 may be
peeled away from the package leaving first film 230 and patch 234 enclosing
the
product. The exceptionally high gas transmissibility of patch 234 provides for
a
so rapid exchange of gases and blooming of the package meat product Although
it is
preferred that film 230 is permeable, an impermeable film may be employed so
long as the enlarged opening and highly permeable patch are sufficiently large
to
allow for a free flow of gases into and out of the package.
Thus package 200 is formed by sealing a first film 230 to inner flange
3s portion 226 of tray 212 which contains product 220 therein. An enlarged
opening
is formed and is covered with the highly permeable second film or patch 234.
Impermeable film 236 is then sealed to outer flange portion 224. Optionally,
enlarged opening 232 may be formed prior to the application and sealing of
film
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230 to the tray. if such is the case, second film or patch 234 may also be
sealed to
the first film 230 prior to its application and sealing to tray 212.
An inventive package H-hich is similar in operation but different in
appearance and manufacture is illustrated in Figure 9. Package 250 includes
tray
252 which has side walls 254 and base 2S6 defining cavity 258 for receiving
product 260. Dual flange 262 includes outer flange portion 264 and inner
flange
portion 266 separated by depression 268. A first film 270 is sealed to inner
flange
portion 266. A second film 272, preferably a continuous strip, is sealed to
first film
270. As with the patch/film, discussed above, the present second film 272 is
is preferably comprised of a permeable material as described above, such as
Tvvek*
Impermeable film 274 encloses the first and second films and is sealed to tray
252
at outer flange portion 264. Impermeable film 274 may be peelably removed to
expose the first and second films. The highly permeable nature of second film
272
provides for a rapid exchange of gases out of and into the package and an
i~ immediate bloom of the packaged meat product.
Preferably, a series of perforations or slits 275 is introduced into film 270
underlying film 272, preferably after film 272 is sealed thereto, to augment
the free
flow of gases into and out of the package. Rather than being applied as a
patch,
the second film 272 of the present embodiment is preferably sealed to the
first film
2o prior to application and sealing of the first film to the tray.
For a1J embodiments of the present invention it should be generally noted
that dual flange trays are preferred whenever two separate H~ebs must be
sealed to
a single tray. However, a conventional, single flange tray may be employed
when
a precise means is available for sealing the first film to an inner portion of
the
25 single flange and for subsequently sealing the impermeable film to an outer
portion of the single flange. That is, the primary reason a dual flange is
preferred
for use as the tray of the present invention is that it facilities the
automated sealing
of two separate webs to the flange. A second circumstance under which a single
flange may be employed as the tray for dual web embodiments of the present
3e inventive package is when an adequate, peelable seal may be made between
the
impermeable film and the first film. Rather than sealing the impermeable film
directly to the tray, it is possible, with the proper selection of film
components, to
form a seal directly to the first film H~hich may be peeled away without
disturbing
the seal between the first film and the tray flange.
s5 The permeable film or web of the present invention is an oxygen permeable
or non-barrier film or skin which may be a formable or stretchable material.
Typical polymeric materials for the present permeable film may include any
material which may be securely sealed and bonded to the support member, such
as
polyethylene or any of a varieh~ of ethylene copolymers including, for
example,
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12
ethylene vinyl acetate, ethylene acrvlate copolymers, ethylene acrylic acid
copolymers including metal neutralized salts thereof, and ethylene alpha-
olefin
copolymers. Such ethylene alpha-olefins may be heterogeneous or homogeneous
in nature. That is, ethylene alpha-olefins which have been formed by
conventjonal
Zeigler-Natty*cacalysis and are heterogeneous in nature, such as linear loH~
density
polyethylene (LLDPE), are within the scope of the present invention as well as
such copolymers which are formed by single site catalysis, such as any of a
varieh~
of forms of metallocene catalyst technology, and are homogeneous in nature are
also within the scope of the present invention. A preferred permeable film for
use
~o in accordance with the present invention is a symmetrical, five layer
oriented film
having the structure:
EVA / LLDPE / EVA / LLDPE / EVA
although a Hide variety of permeable films may be employed.
The impermeable film or H~eb of the present invention may be any suitable
1s barrier layer, film or laminate ~~hich is substantially impermeable to gas
such as
oxygen so that a fresh meat product contained in a vacuum or other low oxygen
atmosphere possesses an enhanced shelf life over a package without the barrier
layer. Suitable polymeric materials having gas barrier properties for use in
the
present invention include ethylene vinyl alcohol copolymers, vinylidene
chloride
2o copolymers (PVDC) such as vinvlidene chloride vinyl chloride or vinylidene
chloride methyl acrvlate. Laminates of a sealable film and a barrier structure
which includes a barrier !aver and a tough, non-forming material such as a
biaxial)v oriented nylon or biaxiallv oriented polyester are especially
preferred for
use as the impermeable lidding of the present inventive packages. A preferred
2~ impermeable web has the structure:
biax nylon / PVDC // EVA / LLDPE / seal
wherein the double slashes (//) indicate adhesive lamination of the two webs,
although a variety of laminates and multilayer films may be employed as the
impermeable web of the present invention.
so Generally, the films or webs which may be employed in accordance with the
present invention may be monolaver or multilaver. Multilaver films may be
employed when all of the properties required of the film cannot be achieved by
a
single polymeric component or a blend of polymers in a single layer. For
example,
an impermeable film to be sealed to a tray in all likelihood will comprise a
3~ multilayer film because several properties are needed including peelable
sealability, oxygen barrier and impact properties, and outer abuse properties.
Thus, the film employed will most likely contain three !avers at a minimum: a
seal
!aver, a barrier !aver and an outer abuse !aver. Further internal !avers such
as
adhesive !avers and bulk !avers may also be included. Laminates of sealable
films
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13
and nonforming materials such as biaxially oriented polyester or biaxially
oriented
nylon are also within the scope of the present invention and are widely
recognized
as superior lidstocks for tray-type packages.
For all embodiments, the tray must be impermeable, but may be chosen
s from a variety of commercially available designs and compositions. That is,
the
tray may be formed of a rigid solid polymer, a barrier sealant coated polymer,
a
battier sealant coated foamed polymer, or a barrier sealant coated pulp or
paperboard tray. If foamed, a barrier film must be included, at least, on the
inner
surface of the tray in order to prevent outgassing of residual gases into the
io package.
Generally, the films employed in the present invention may be multilayer or
monolayer, although, of course, those films defined as delaminatable,
multilayer
films must include at least two layers. Typically, the films employed will
have two
or more layers in order to incorporate a variety of properties, such as, for
example,
15 sealability, gas impermeability and toughness, into a single film.
The foregoing description of preferred embodiments of the invention has
been presented for purposes of illustration and description. It is not
intended to be
exhaustive or to limit the invention to the precise form disclosed, and
modifications and variations are possible in light of the above teachings or
may be
2o acquired from practice of the invention. The embodiments were chosen and
described in order to explain the principles of the invention and its
practical
application to enable one skilled in the art to utilize the invention in
various
embodiments and with various modifications as are suited to the particular use
contemplated. It is intended that the scope of the invention be defined by the
25 claims appended hereto, and their equivalents.
