AU688015B2 - Seamless, heat shrinkable casing with narrow lay-flat width - Google Patents

Description

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION NAME OF APPLICANT(S): W. R. Grace Co.-Conn.

ADDRESS FOR SERVICE: DAVIES COLLISON CAVE Patent Attorneys 1 Little Collins Street, Melbourne, 3000.

INVENTION TITLE: Seamless, heat shrinkable casing with narrow lay-flat width The following statement is a full description of this of performing it known to me/us:invention, including the best method i 0* C

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42303 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 Soriginal package after cooking, and repackaged in another packaging material for distribution.) Cook-in time-temperature conditions typically refer to a long slow cook, for exam- S p: ple, 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, 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 I I 42303 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, 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 and/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 backseamed) and seamless (no backseam) casings are available. Backseamed casings are those 3/940429.1/SPECFLDR 42303 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 backseaming.

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.

n.d 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 VAO'ERADD\20212.SPf j11297 -4result 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 S created an unmet market need, to provide to the marketplace a .narrow lay-flat width, seamless, shrinkable, polymeric casing 15 suitable for cook-in applications.

The inventor has found that a polymeric, heat shrinkable, seamless casing suitable for cook-in applications, and having a lay-flat width of less than 76mm, can be made.

9 9 0, SUMMARY OF THE INVENTION In one aspect, the invention provides 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 76mm or less.

In a further aspect, the invention provides a polymeric, heat shrinkable, seamless casing suitable for cook-in applications, said casing comprising: ALf vo W 'w0 I'\OPER\ADD\20212-95.SPlE 1/12/97 a) an inner heat sealable layer; b) an intermediate oxygen barrier polymer layer; and c) an outer abuse resistant layer; wherein said casing has a lay-flat width of 76mm or less.

DEFINITIONS

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 15 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 20 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 c-oked in a cook-in process.

The casing had a lay-flat width of 3.0 inches (76mm) after 24 hours of ageing. The casing was seamless, and heat shrinkable, RA 30 and shrunk around the meat product during the cook-in cycle.

c, I':OPEWRADM0222-9SSP 1112197 -6- 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 siaes 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 catalysed 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 15 contact with the surface of the food product) comprising an We* 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, 20 comprising a blend of ionomer and an ethylene alpha olefin copolymer; and an outer abuse resistant layer comprising a blend **p 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.

Additional examples were produced as described above, using the CN 610 formulation. These are shown in Table 1. The layflat width values, like the first example given above, represent the width of the material measured after 24 hours of ageing.

'AOI'fR1IADDM2212-9iSPE I/12197 -7- TABLE 1 Example Lay-Flat Width 2. 2.5 inches (64mm) 3. 2.0 inches (51mm) 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 15 step, and relative location of the air ring, narrow width

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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.

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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.

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, 30 including ethylene copolymers, and polyamides, including 33^^

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7 PAOPERXADDA02129.SP'i- 1112197 -8- ~polyamides, 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.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", or o variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group 15 of integers but not the exclusion of any other integer or group of integers.

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Claims (11)

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 76mm or less.

2. The casing of claim 1 wherein said casing has a lay- flat width of about 64mm or less.

3. The casing of claim 1 or 2 wherein said oxygen barrier polymeric layer comprises ethylene vinyl alcohol copolymer. S.

4. A package comprising 15 a) a food article, and b) a polymeric, heat shrinkable seamless casing enclosing said food article, wherein said casing comprises at least one oxygen barrier polymeric layer and has a lay-flat width of 76mm or less.

The package of claim 4 wherein the casing has a lay- flat width of about 64mm or less.

6. The package of claim 4 or 5 wherein said oxygen barrier polymeric layer comprises ethylene vinyl alcohol copolymer.

7. A polymeric, heat shrinkable, seamless casing suitable for cook-in applications, said rasing comprising: a) an inner heat sealable layer; CY /k /VT S1 PO\'ErtADIDY2t2l .SPBJ3. 12/91 b) an intermediate oxygen barrier polymer layer; and c) an outer abuse resistant layer; wherein said casing has a lay-flat width of 76mm or less.

8. The casing of claim 7 wherein said lay-flat width is between 51 and 76mm.

9. The casing of claim 7 or 8 wherein said oxygen barrier polymeric layer comprises ethylene vinyl alcohol copolymer.

A polymeric, heat shrinkable, seamless casing substantially as hereinbefore described with reference to the Examples.

11. A package substantially as hereinbefore described with reference to the Examples. C. *i C DATED this 28th day of November, 1997 by W.R. Grace Co.-Conn. DAVIES COLLISON CAVE Patent Attorneys for the Applicants o 1-j T 0 SI, 42303 ABSTRACT OF THE DISCLOSURE A polymeric, heat shrinkable, seamless casing suit- able for cook-in applications has at least one polymeric lay- er, and a lay-flat width of less than 6 1/2 inches, and thus has a narrower lay-flat width than conventional heat shrink- able, polymeric seamless casings adapted for cook-in applica- tions. A narrow width casing of this type fills a long-felt market need. The invention is also a package having a food artic!e, and a polymeric, heat shrinkable, seamless casing whiciL encloses the food article, the casing having at least one polymeric layer, and the casing having a lay flat width of less than 6 1/2 inches. 0 o *o o* *ft