NZ272187A - Polymeric, heat shrinkable casing comprising an oxygen-barrier polymeric layer having a lay-flat width less than 3 inches, use as a food casing - Google Patents

Description

New Zealand Paient Spedficaiion for Paient Number £72187 * «• 7 Priority Date(s): ft.

Complete Specification Filed: .aals.tes Class: (6) o..6fe33>.$!.1.3Ht".

Publication Date: P.O. Journal No: J ±\Z.

NO DRAWINGS NEW ZEALAND PATENTS ACT, 1953 No.: Date: COMPLETE SPECIFICATION SEAMLESS, HEAT SHRINKABLE CASING WITH NARROW LAY-FLAT WIDTH We, W R GRACE & CO-CONN, a corporation organised and existing under the laws of the State of Connecticut, United States of America, of 1114 Avenue of the Americas, New York, NY 10036-7794, United States of America, hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is tol2£.perforffiS3T^beF- ; • *7 r ■ ... — particularly described in and by the following statement:- 2 3 MM 1995 -l- (followed by page la) ""272 SEAMLESS, HEAT SHRINKABLE CASING WITH NARROW LAY-FLAT WIDTH FIELD OF THE INVENTION The present invention relates to casings and packages made from casings, and more particularly to casings and packages made from casings, and used in cook-in processes.

BACKGROUND OF THE INVENTION Cook-in packaged foods are essentially foods cooked in the package in which they are distributed to the consumer or other purchaser, and which may be consumed with or without warming. (In some cases, the food product is removed from the original package after cooking, and repackaged in another packaging material for distribution.) Cook-in time-temperature conditions typically refer to a long slow cook, for example, heating the product to an internal temperature of between about 55 degrees C and 75 degrees C in e.g. hot water or hot air for between about 1 and 4 hours. These conditions are representative of institutional cooking requirements. Under such conditions, a cook-in packaging material should maintain its integrity, i.e., the product should maintain its interply adhesion, and any heat sealed seams should resist being pulled apart during cook-in. Additionally, it is desirable that the 3/940429.1/SPECFLDR la "27, * packaging film be substantially comformable to the contained food product. Preferably, this substantial conformability is achieved by the film being heat shrinkable under these conditions so as to form a tightly fitting package, i.e., the film should be heat shrinkable under these time-temperature conditions and should possess sufficient shrink energy so that the packaging film will shrink snugly around the contained product, and especially up to about 55% monoaxial aud/or biaxial shrinkage.

Several types of casings are supplied commercially for cook-in applications. One type is fibrous casing, which tends to be expensive, and does not include a shrink characteristic. Polymeric casings made from thermoplastic materials are also available. Commercial examples include CN 510 and CN 610 cook-in casings available from the Cryovac Division of W.R. Grace & Co.- Conn. Cook-in packaging materials are described in U.S. Patent Nos. 4,469,742 (Oberle et al); 4,448,792 (Schirmer); 4,606,922 (Schirmer); 4,762,748 (Oberle); and 4,855,183 (Oberle); and USSN 189,475 filed January 31,1994, and USSN 043,417, filed April 6, 1993, all assigned to the assignee of the present application, and incorporated herein by reference in their entirety.

As described in these patents, conventional shrinkable cook-in packages are used to prepare meat products such as bologna, sausage, and mortadella in casings or bags. The filled casing is sometimes placed horizontally or in external molds to control the final shape of the package, and sometimes hung vertically. Hot water and hot air are typical cooking media.

Both seamed (i.e. backsearned) and seamless (no backseam) casings are available. Backseamed casings are those 3/940429 .1/SPECFLDR 2 272 in which a casing material is produced in a tubular shape, typically in a relatively large lay-flat width, and the tubular material is then slit open longitudinally, and then further slit into selected widths, and one or more of the slit portions is converted back to tubular form by lap sealing the portion longitudinally. This results in backseamed tubular casings of narrower lay-flat width than the original tubular material. In contrast, seamless casings are those which are formed by a tubular extrusion of thermoplastic material, either cast or blown, and used in their original tubular state as casings without the need for slitting and subsequent backsearning.

Casings that are shrinkable offer many advantages. One is a reduction in wrinkles formed at the clipped or sealed longitudinal ends of the package. These wrinkles result in product yield loss, which is an economic loss to the producer and packager of products such as smoked and processed meats. Shrinkable casings provide improved yield to the end user.

Additionally, shrinkage results in a tighter package with a better appearance following cooking, especially when the casing is not fully filled prior to cooking. Reduced purge (exudation of meat juices from the product inside the casing) is another benefit.

Finally, shrinkable materials also tend to have better optics and oxygen barrier properties as the result of the orientation process used to supply the casing or film with shrink properties.

Seamless, shrinkable polymeric casings of the CN 510 and CN 610 type are currently commercially available only in lay-flat widths of 6 1/2 inches or more. This may be the 3/940429.1/SPECFLDR 3 result of perceived higher costs, and extreme difficulty in processing narrow width tubing in a film orientation process. It has heretofore been considered impractical, if not impossible, to produce such materials on a commercial basis.

Shrinkable polymeric casings of narrower width are available, but only in backseamed format. Backseaming includes a lap seal, which presents a different, sometimes undesirable appearance. Abuse resistance can also be impaired because of the presence of the backseam. The cost of processing the casing material to create the backseam, seal integrity, and barrier integrity are other factors which have made it desirable, and created an unmet market need, to provide to the marketplace a narrow lay-flat width (i.e. less than 6 1/2 inches) seamless, shrinkable, polymeric casing suitable for cook-in applications. able, seamless casing suitable for cook-in applications, and having a lay-flat width of less than 6 1/2 inches, can be made. heat shrinkable, seamless casing suitable for cook-in applications, the casing comprising at least one oxygen barrier polymeric layer, wherein the casing has a lay-flat width of about 3 inches or less.

In another aspect, the invention comprises a package comprising a food article, and a polymeric, heat shrinkable, seamless casing which encloses the food article, the casing comprising at least one oxygen barrier polymeric layer, the casing having a lay flat width of about 3 inches or less.

The inventor has found that a polymeric, heat shrink- SUMMARY OF THE INVENTION In one aspect, the invention comprises a polymeric 3/940429.1/SPECFLDR N.? r-ATENT OFFICE 4 1 6 OCT 1996 42303 27 21 The term "cook-in" as used herein is intended to refer to procedures in which a package, usually a casing filled with a food product such as meat, is exposed to time-temperature conditions suitable for cooking the food product.

"Lay flat width" is used herein to mean the transverse width of a casing after it has been extruded to create a tubular material, and then collapsed or flattened. For prior art casings that have been backseamed, the lay-flat width is the width of the final backseamed and collapsed casing. Lay flat width should be measured at least about 12 hours after extrusion, or in the case of oriented casings, at least about 12 hours after orientation, to allow for "shrink back" of some materials, such as nylon-containing materials.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A CN 610 casing, having a film structure as described in USP 4,855,183 was produced by the process described therein, stuffed with a meat product, and cooked in a cook-in process. The casing had an initial width of 6.1 inches (155 mm) as measured immediately after production of the casing, and a lay-flat width of 5.4 inches (145 mm) after 24 hours at 70 degrees F. The casing was seamless, and heat shrinkable, and shrunk around the meat product during the cook-in cycle. The casing had an innermost sealant layer (for contact with the surface of the food product) comprising a blend of nylon 12 and nylon 6,12; a core layer of ethylene vinyl alcohol copolymer; a maleic anhydride graft copolymer as polymeric adhesive layers on both sides of the core layer; a bulk layer, disposed between the sealant layer and one of the polymeric adhesive layers, comprising a blend of a metallocene DEFINITIONS 3/940429.1/SPECFLDR •218 7 catalyzed polymer and a maleic anhydride graft copolymer, and an outer abuse-resistant layer comprising a blend of ionomer and linear low density polyethylene. The resultant package was a commercially acceptable package.

An alternative film structure for casings of the present invention, CN 510, comprises an innermost sealant layer (for contact with the surface of the food product) comprising an ionomer; a core layer of ethylene vinyl alcohol copolymer; a maleic anhydride graft copolymer as polymeric adhesive layers on both sides of the core layer; a bulk layer, disposed between the sealant layer and one of the polymeric adhesive layers, comprising a blend of ionomer and an ethylene alpha olefin copolymer; and an outer abuse-resistant layer comprising a blend of ionomer and high density polyethylene. This alternative embodiment is less preferred, because it cannot be processed at the rate obtainable with the CN 610 formulation.

Examples of casings of the present invention wSre produced as described above, using the CN 610 formulation. These are shown in Table 1. The lay-flat width values, like the first example given above, represent the width of the material measured after 24 hours of aging.

TABLE 1 Example Lay-Flat Width 2 3.0 inches (76 mm) 3 2.5 inches (64 mm) 4 2.0 inches (51 mm) 3/940429.1/SPECFLDR 6 N.2. PATENT OFFICE 1 6 OCT 1996 nncr.! vcd The narrow width casings of the invention are preferably made by tubular cast coextrusion of a "tape", i.e. a relatively thick extrudate, of a polymeric material such as CN 510 or CN 610, or other suitable film material, followed by water quench, reheating to within the orientation temperature of the material, and blown bubble orientation. By proper attention to air ring insert size and tape (unoriented film) size at the orientation step, and relative location of the air ring, narrow width casings can be made. The air ring can be a conventional air ring, placed to provide a high degree of controlled cooling to the orienting material, and in turn helping to control and stabilize the orientation process.

Narrow width casings satisfy a long-felt need for a commercial casing for cook-in applications which combines the benefits of a seamless casing with the benefits of a shrinkable casing, in a width range narrower than that now currently offered. 3/940429.1/SPECFLDR N.2. PATENT OFFICE 1 6 OCT 1996 KCCEIVEO

Claims (9)

'272 f 423 __ " o O / Modifications will be obvious to those skilled in the art, after reviewing this description. The invention is defined by the claims which follow. For example, various polyolefins, including ethylene copolymers, and polyamides, including copolyamides, can be used as a sealant layer in connection with the casings of the present invention. Various oxygen barrier materials, including EVOH and saran, polyamides and copolyamides, can be used as an oxygen barrier material. Polyolefins and polyamides are also suitable for the outer abuse layer of a casing in accordance with the invention. The casing itself can be made by any appropriate tubular process. Films of the present invention are preferably cross-linked either before or after orientation. 3/940429.1/SPECFLDR 8 272187 WHAT WE CLAIM-IS:

1. A polymeric, heat shrinkable, seamless casing suitable for cook-in applications, the casing comprising at least one oxygen barrier polymeric layer, wherein the casing has a lay-flat width of 3 inches or less.

2. The casing of Claim 1 wherein the casing has a lay-flat width of 2 1/2 inches or less.

3. A package comprising a food article, and a polymeric, heat shrinkable seamless casing which encloses the food article, the casing comprising at least one oxygen barrier polymeric layer, the casing having a lay flat width of 3 inches or less.

4. The casing of Claim 3 wherein the casing has a lay-flat width of 2 1/2 inches or less. 27 2 1 8 7 42303

5. A polymeric, heat shrinkable, seamless casing suitable for cook-in applications, the casing comprising: a) an inner heat sealable layer; b) an intermediate oxygen barrier polymeric layer; and c) an outer abuse-resistant layer; wherein the casing has a lay-flat width of 3 inches or less.

6. The casing of claim 5 wherein the casing has a lay-flat width of between 2 inches and 3 inches.

7. The casing of claim 1 wherein the oxygen barrier polymeric layer comprises ethylene vinyl alcohol copolymer.

8. A polymeric, heat shrinkable, seamless casing as claimed in claim 1 substantially as herein described with reference to any example thereof.

9. A package as claimed in claim 3 substantially as herein described with reference to any example thereof.