Note: Descriptions are shown in the official language in which they were submitted.
CA 02229768 1998-02-17
CANADIAN PATENT APPLICATION
HILL & SCHUMACHER
Title: SKIN PACKAGE AND METHOD OF PRODUCTION
Inventors: David Richard WOTTEN
Robert John DERKACH
CA 02229768 1998-02-17
SKIN PACKAGE AND METHOD OF PRODUCTION
FIELD OF THE INVENTION
This invention relates to skin packaging and in particular vacuum skin
packaging that may be used for packaging frozen foods and the like.
BACKGROUND OF THE INVENTION
A wide variety of packaging techniques are used in the food industry.
Different techniques are used with frozen foods and fresh foods. Each different
packaging technique has advantages and disadvantages.
The majority of frozen food products sold in retail stores are packaged in
10 a plastic bag or vacuum packed in a bag. The advantage with this technique is that
plastic bags are relatively inexpensive and readily available. However, most freezers in
retail stores have an auto defrost feature to avoid frost build up. During the auto defrost
cycle the temperature of the product is increased which causes the protective ice
coating on the product to melt or disappear thus leaving the frozen food unprotected.
15 In a short time ice crystals will form in the bag and the product will start to dehydrate
causing freezer burn. Freezer burn lowers the quality of the product and eventually the
product becomes inedible and unsaleable. Therefore, frozen food packaged in thismanner will have a limited shelf-life. Another disadvantage of packaging the product in
a bag is that it is difficult to attach a label to a bag that will not slip when the product is
20 put through the defrost cycle.
Alternatively, some frozen foods are bagged or vacuum packed and then
placed in a printed cardboard box. The addition of the box will provide some added
protection, however, the same disadvantages discussed above with regard to freezer
CA 02229768 1998-02-17
burn in a bag alone will occur. The shelf-life will be somewhat longer than with the bag
alone because the box does provide some added protection. A disadvantage of this
method of packaging frozen food is that the box is very expensive. Further, the
consumer is unable to see the product or7 at best, where a window is provided in the
5 box, the consumer has a limited ability to view the product. Still further, the product is
packed, not only in a box, but also in a bag and therefore the product is packed in two
mediums which could be considered to be over packed and therefore unnecessarily
harmful to the environment.
Another alternative used by many retail stores is to pack their frozen
10 product on StyrofoamTM trays and over wrap the product and the tray with stretch
plastic wrap. This method provides very little protection against ice crystal formation
and dehydration. Further, this method does not provide an air tight seal. In addition,
the package does not prevent the product from moving therein and movement of the
product in the package can easily damage the plastic wrap. It is also unattractive
15 particularly over time.
Another type of packaging which is quite popular is referred to as skin
packaging wherein the product is vacuum packed or skin packed on a supporting
member. The most common packages are those wherein the product is held between
two thermoplastic materials (flexible and/or semi-rigid - printed or plain); the product is
20 placed on a poly-coated polystyrene or StyrofoamTM tray placed between the two
thermoplastic materials; or the product is placed on a cardboard or plastic insert placed
between two thermoplastic materials. The product is held in place by a supporting
CA 02229768 1998-02-17
member and a seal between the two thermoplastic materials. The product is then
distributed as is or repacked into a pouch, box or inserted into a sleeve for protection
and for display purposes. The product is only held in place on the supporting member
by the tightness of the pack. During the defrost cycle the product will shrink in size,
5 especially in the case of seafood due to its high water content, and after shrinkage the
product will slide in the pack to another location. When the product refreezes, it may
expand in a smaller area in the package and break the seal. When the seal is broken
the product is exposed to air and is unprotected and will degrade.
A specific example of a skin package is shown in US Patent 3,966,045
issued June 29, 1976 to Richard R. Perdue. This patent is directed to a skin package
which includes a gas impervious support member with product held to opposed sides
of the support member by films. The main objective of this patent is to provide a skin
package with product positioned on both sides of a support member. The film can be
pulled back from the support member without damaging the support member so that a
15 user can access the product on one side of the support member without disturbing the
product on the other side thereof. Therefore the seal between the film and the support
member is a tack type seal. Since the product is packaged on both sides of the
support member, printed material that will be visible when the product is on the shelf
cannot be applied to the support member. The method of packaging shown in this
20 patent is batch type which uses individual sheets of film. This type of packaging
method is more costly than a continuous method which uses a continuous roll of film.
Further, in the chamber type machine shown in the patent only one package can be
CA 02229768 1998-02-17
handled at one time. In addition, this package suffers from some of the shortcomings
discussed above with regard to skin packages.
Accordingly, it would be advantageous to provide a skin package that
would protect frozen food products in a retail environment during the auto defrost
cycle; that would display the product to the consumer as clearly as possible in an
attractive fashion; that would make the packaging visually appealing to customers; that
would use as inexpensive material as possible to keep costs down; and that would use
as little packaging as possible so as not to create excessive waste to be
environmentally responsible.
It is an object of the present invention to provide a skin package in which
an upper film conforms to the shape of the product and is fused to a coating on the
support member such that the product is protected from air and water during the auto
defrost cycle in a retail store.
It is an object of the present invention to provide a skin package that has
15 a support member with full color graphics on one side there of and a product on the
other side thereof held in place by a film that is fused to a coating on the support
member around the product.
SUMMARY OF THE INVENTION
The present invention provides a skin package for frozen food products
and the like. The skin package includes a support member, a top forming film and a
bottom non-forming film. The support member has a heat sealable plastic coating on
CA 02229768 1998-02-17
one side thereof. The frozen food is positioned on the heat sealable plastic coating.
The top forming film covers the frozen food and the plastic coating of the support
member in air tight relation. The top forming film is fused to the plastic coating with an
air tight and water tight seal. The bottom non-forming film is positioned on the other
5 side of the support member and is fused to the top forming film with at least a water
tight seal.
In another aspect of the invention there is a process for producing a skin
package for packaging food products and the like. The process includes the steps of:
providing a bottom non-forming film; placing a support member having a heat sealable
10 plastic coating on one side thereof on the forming film; positioning the food product on
the heat sealable plastic coating; stretching a forming film over the food product and
support member; fusing the forming film to the heat sealable plastic coating in an air
and water tight seal; and fusing the forming film to the non-forming film in at least a
water tight seal.
In a further aspect of the invention there is an alternate skin package for
packaging frozen food products and the like. The alternate skin package comprises a
water repellant support member and a top forming film. The support member has a
heat sealable plastic coating on one side thereof and the frozen food is positioned
thereon. A top forming film covers the frozen food and the plastic coating of the
20 support member in air tight relation and the top forming film is fused to the plastic
coating with an air tight and water tight seal.
Further features of the invention will be described or will become
CA 02229768 1998-02-17
apparent in the course of the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described by way of example only, with
reference to the accompanying drawings, in which:
Fig. 1 is a perspective view of a skin package constructed in accordance
with the present invention;
Fig. 2 is a cross sectional view of the skin package;
Fig. 2a is an enlarged cross section view of the edge portion of the skin
1 0 package;
Fig. 3 is a cross sectional view of an apparatus for producing the skin
package of the present invention; and
Fig. 4 is a cross sectional view of the skin package in a vacuum chamber
with the head in a closed position;
Fig. 5 is a cross sectional view of the skin package in a vacuum chamber
with the head in the open position;
Fig. 6 is a cross sectional view of the skin package in a vacuum chamber
with the head in a closed position and showing the head modified to package two
products;
Fig. 7 is a cross sectional view of the skin package in a vacuum chamber
with the head in the open position and showing the head modified to package two
products;
CA 02229768 1998-02-17
Fig. 8 is a perspective view of an alternative embodiment of a skin
package constructed in accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring to figures 1, 2 and 2a, a skin package produced in accordance
with the present invention is shown generally at 10. The package includes a planar
support member 12 having a heat sealable plastic coating 14 on one side thereof, a
top forming film 16, and a bottom non-forming film 18. Package 10 seals and protects
a frozen food product 20 such as fillets of fish and the like. During the packaging
10 process plastic coating 14 and top forming film 16 are fused together. Fused plastic
coating 14 and top forming film 16, referred to as fused coatingNilm 21, forms a bond
such that if the packaging is pulled apart the bond between the fused plastic coating
and the support member 12 will fail before the bond between the plastic coating 14 and
the top forming film 16.
It will be appreciated by those skilled in the art that in the detailed
description herein we refer to a frozen food product 20. However, the skin package of
the present invention could be used with fresh food and this is of particular relevance
wherein the food product is cooked in the package of present invention.
Support member 12is a food grade cardboard. Typically the cardboard
is an eighteen point pressed cardboard. One side (not shown) may be printed with full
color graphics. Typically the color graphics is coated with a transparent plastic coating.
The color graphics side of cardboard support member 12is protected by bottom non-
CA 02229768 1998-02-17
forming film 18. Preferably there is a tack seal between support member 12 and
bottom non-forming film 18. The other side or top of cardboard support member 12 is
coated with a heat sealable plastic coating 14 which is a linear low-density
polyethylene and which has as low a melt temperature as practicable. Preferably
5 coating 14 has a matte finish. The matte finish is advantageous because when the
top film is fused to coating 14 the result is a high gloss finish. Therefore the high gloss
finish provides a visual indicator of fusion. Accordingly, any packages that do not have
a high gloss finish would be rejected. The user can choose the pigment of the coating
for aesthetic reasons. For instance, a dark pigment is preferable for such products as
10 white fish.
Top forming film 16 is preferably a 6 mil. to 8 mil. surlyn film with ethyl
vinyl acetate (EVA) coating. Bottom non-forming film 18 is preferably a 2.7 mil. surlyn
film with an EVA coating. The EVA acts as an adhesive and preferably is anhydride-
modified EVA sold as Dupont BynelTM adhesive resin Series 3000, specifically 3048.
15 Preferably coating 14 on support member 12 is an Ethylene Methyl Acrylate Copolymer
(EMAC) sold by CHEVRON TM Coating 14 could also be an EVA coating or another
low density polyethylene coating.
Top forming film 16, bottom non-forming film 18 and coating 14, when
processed under heat and in a vacuum chamber, form an air and water tight seal
20 therebetween. The width of support member 12 is less than the width of films 16 and
18 and a perimeter water tight and preferably air tight seal 22 is formed between films
16 and 18 around support member 12.
CA 02229768 1998-02-17
Top forming film 16 covers product 20 and support member 12 in air tight
relation. The seal between top film 16 and coating 14 extends between the peripheral
edge 15 of support member 12 and product 20. Where plastic coating 14 and top
forming film 16 are adjacent to each other they are fused together. Fused coating/film
5 21 forms a bond such that if the packaging is pulled apart the bond between the fused
plastic coating and the support member 12 will fail before the bond between the plastic
coating 14 and the top forming film 16.
Referring to figure 3, a vacuum packaging assembly is shown generally
at 24. Preferably a DIXIE UNION SKINPACK 100 & 100STM is modified and used in
10 the method of the present invention. Bottom non-forming film 18 is provided on roll 26.
Bottom film 18 is moved through the assembly 24 on a conveyor system 28. Bottom
film 18 acts as a transport medium as the product progresses through packaging
assembly 24. Support member 12, with plastic coating 14 facing upwardly, is placed
on bottom film 18. Product 20 is placed on the plastic coated surface 14 of support
15 member 12. Bottom film 18 is somewhat tacky to reduce the sliding movement of
support member 12 thereon and to provide a tack seal between the support member
and the bottom film. Top forming film 16 is provided on roll 30.
Top film 16 is passed under preheating station 32 so that top film 16 is
heated before it is applied over the product 20, support member 12 and bottom film 18.
20 The top film is heated to between 180 and 285~ C for approximately 20 seconds
before it is applied over the product.
The top film 16, product 20, support member 12 and bottom film 18 are
CA 02229768 1998-02-17
formed together in a vacuum chamber or station 34. In the vacuum chamber 34, thebottom film is heated to between 75 and 120~C for approximately 10 seconds by
heated seal plate 35 (shown in figures 4 and 5). Vacuum chamber 34 is provided with
a series of inletloutlet openings (not shown) so that the vacuum chamber can be
evacuated and vented. The air is removed or evacuated thereby creating a vacuum
and stretching the film away from the product 20. Then air is vented into the vacuum
chamber above the top film 16, so that top film is forced down against support member
12 and is smooth against product 20 and support member 12. It is important that the
top film 16 is wrinkle free because a wrinkle will act as a conduit for air which, if it
10 reaches the product 20, will cause it to degrade.
The combination of the heat, pressure from seal head 36, and the force
of the vacuum causes the top film 16 to fuse with the plastic coating 14 on support
member 12 to form an air and water tight fused coating/film 21. The heated top film 16
molds to the shape of the product 20. Fused coating/film 21 extends from the
15 peripheral edge 15 of support member 12 to and around product 20 so that
substantially no air remains within the package between top film 16 and support
member 12. Thus plastic coating 14 and top film 16 are fused from the perimeter of
the support member to the product 20. The fusing of the top film 16 to the coating 14 of
the support member 12 gives it a glossy appearance as discussed above.
Similarly, a perimeter seal 22 between top film 16 and bottom film 18 is
achieved by the combination of heat, pressure from the seal head 36 and the force of
the vacuum. The width of support member 12is smaller than width of top and bottom
- 10-
CA 02229768 1998-02-17
films 16 and 18. Thus, the peripheral edge 15 of support member 12 is spaced from
the edge of bottom film 18. The rubber contact portion 44 of the seal head 36
(described in more detail below) exerts a force on the top film 16 and bottom film 18
with no support member 12 therebetween to create a perimeter seal.
The finished package is cut to size by various cutting knives, with cross
cutting knives 38 and longitudinal cutting 40 knives.
The DIXIE UNION SKINPACK 100 & 100STM machine was modified for
the process of the present invention. The water cooling system was reduced so that
the temperature of the top film 16 and bottom film 18 were nrt reduced before entering
10 the vacuum station 34.
Referring to figures 4 and 5 a pliable resilient deformable material such
as foam 42 is inserted into head 36 of vacuum station 34. Preferably foam 42 is a
medium-dense closed cell foam. Foam 42 reduces the stretching of top film 16 in
vacuum station 34. In addition the foam applies some pressure on the top film 1615 when it is in the closed position as shown in figure 4. It is important that there is a
smooth seal between the top film 16 and the coating 14 on support member 12.
Wrinkles between the top film 16 and coating 14 act as air traps or conduits. If product
20 is exposed to air it will begin to degrade.
Head portion 36 of vacuum station 34 has a peripheral rubber contact
20 portion 44 which, in the closed position shown in figure 4, exerts pressure on heated
sealing plate 35 and on films 16 and 18 therebetween. This forms perimeter air and
water tight seal 22 (shown in figure 1).
- 11 -
CA 02229768 1998-02-17
Head portion 36 can also be modified so that two or more packages are
processed at one time (shown in figure 6 and 7). Head portion 36 is modified to
include a partition 37 with rubber portion 39 at the bottom thereof. Figures 6 and 7
show head 36 modified to allow for the processing of two packages simultaneously.
5 The process is modified such that two spaced apart support members are placed
adjacent to each other across the width of bottom film 18. The processing is as
described above and partition 37 exerts pressure on top film and bottom film wherein
there is no support member therebetween to form a perimeter seal.
The air flow around the vacuum station 34 was reduced by providing an
10 insulated hood 45 which extends from the preheating station 32 past the vacuum
station 34. This also reduces the air flow into the preheating station 32. Hood 45
serves to reduce the condensation from the frozen product 20 during the processing.
Temperature variations in the processing room can require various
adjustments to the equipment to achieve a seal of the top film to the support member.
15 It is important to reduce the condensation as much as possible during the processing
and this is controlled by the control parameters in the apparatus 24 and the conditions
in the room which houses the apparatus.
An alternative embodiment of the present invention is shown in figure 8 at
50. Package 50 is similar to that shown in figures 1, 2 and 2a. However, the support
20 member 52 is a water repellant support member with a heat sealable plastic coating 54
thereon. As discussed above top forming film 16 covers product 20 and plastic coating
54 in air tight relation. An air tight and water tight seal is formed between heat sealable
CA 02229768 1998-02-17
coating 54 and top film 16. The seal extends between the perimeter 56 of support
member 52 to product 20.
The invention relates to a package that tightly secures the product that it
encloses, using a heat sensitive coated film, to an inexpensive coated cardboard that
5 can be printed to convey product information. The package is designed to protect
frozen food products ( especially seafood) from degradation in a retail display freezer
and to provide a superior look for display and higher visibility of the product to the
consumer without over packing.
The package self seals itself to the perimeter of the product so that in
10 thaw/freeze situation the package is so tight around the product, the product is
completely immobilized and is prevented from moving and it is held in the same
position as originally placed. Further, during the thaw/freeze cycle the package is less
likely to break and expose the product to air than with prior art packages and thereby
the package of the present invention provides more protection. Since the integrity of
15 the package is not breached the appearance is not jeopardized and remains attractive
to the customer.
The product is covered in a clear skin tight film that molds to the contours
of the product, thereby making the product highly visible to the consumer. The skin
package seals around the product so that ice crystals do not form in the pack and
20 obstruct the view of the product. Further the package of the present invention is not
totally or even partially enclosed in a box or additional packaging material.
The side of the cardboard support member 12 which is not coated with
- 13-
CA 02229768 1998-02-17
the plastic coating 14 can be printed with high quality graphics making an attractive
display panel to attract a consumer's attention. In contrast, the bags, Styrofoam trays,
film and stretch wrap of the prior art can not be printed with such high quality graphics.
The type of cardboard and the size of the cardboard required and the
5 printing of the cardboard are inexpensive in comparison to a printed box. Films 16 and
18 used are only enough to cover the product and the support member and is also not
so expensive as to add a large cost.
The package uses the minimum amount of material as possible and still
performs all the functions that are required for the protection of the product and
10 conveying of product information. The small amount of material used reduces the
waste when the consumer finishes with it.
The package of the present invention is of particular importance in the
seafood packaging industry. Because of the high water content in seafood, seafood is
particularly susceptible in the thaw/freeze cycle of retail freezers and will experience
15 more dramatic changes than other frozen foods. Further, holding the product in place
and protecting it from the air is advantageous with seafood. The package of the
present invention could also be used with other frozen food items.
Product packaged in the package of the present invention can be cooked
in the package. Thus the producer can provide either frozen fish or cooked fish.
20 Previously product cooked in bags would result in curled bags and product that slides
and moves in the package. The package of the present invention includes a planar
support member 12 which holds the film flat and support the product through the
- 14-
CA 02229768 1998-02-17
cooking process. The fusion of the top film 16 with the coating 14 provides an air and
water tight seal thus during cooking there is no leakage of moisture into the product.
Further the package of the present invention allows the product to be placed in a single
layer on the support member which increases the likelihood of the product being
5 evenly cooked. This is especially relevant when packaging products such as shrimp or
scallops. Cooking the product in the package reduces the bacteria counts for an
extended period of time thus increasing the shelf life. The shelf life of the product may
be further extended by adding an oxygen barrier to top and bottom film. Cooking the
product in the package is somewhat analogous to a canning process.
Prior art packages which include a support member of board sealed
therein do not have the sealing characteristics which would allow the product to be
cooked in the package without the board degrading and or moisture being allowed into
the package. Prior art packages wherein the board degrades during cooking are not
suitable for displaying on a shelf thereafter. Prior art packages that allow moisture into
15 the package during cooking would allow bacteria into the package thereafter.
Accordingly, these prior art packages would not be suitable for cooking the food
product in the package and thereafter displaying it and selling it in a supermarket
thereafter. Alternatively, prior art "boil in a bag" type products have the sealing
characteristics to allow food to boiled therein but they do not include a support member
20 or board and thus are not suitable for displaying in a supermarket without some further
packaging to provide product information.
It will be appreciated that the above description is related to one
- 15-
CA 02229768 1998-02-17
embodiment by way of example only. Many variations on the invention will be obvious
to those skilled in the art and such obvious variations are within the scope of the
invention as described herein whether or not expressly disclosed.
- 16-
