PT1092532E - Process for packaging fresh meat - Google Patents

Description

Method for packing fresh meat "

BACKGROUND OF THE INVENTION The present invention relates to ethylene copolymer compositions useful in the manufacture of films for the fresh red meat packaging and a process for packaging fresh red meat.

More particularly, the ethylene copolymer compositions of the present invention are based on a copolymer of ethylene with carboxylic acid and partially neutralized with ions and are thus capable of reacting with the surface of fresh red meat under certain processing conditions and preventing blood or the water contained in the meat accumulate between the meat and the wrapping film.

The ethylene copolymer compositions used in the present invention are well known in the packaging industry for the packaging of cooked and fresh meat (Publication Dupont H56747 9/94). Examples of such uses are as sealants or filler films in mono or multilayer food packaging films or even, more specifically, as a sealant for secondary sealing to prevent flesh juice from extending between the two layers of film, avoiding so micro-channel spills. They are known for their alleged superior adhesion to cooked meat and are used in pack 1 of cooked ham and turkey. Dupont Publication H-56747, 9/94, mentioned above relates more specifically to the packaging of processed meat products.

A process for packaging and cooking a meat product in a bag made from an adherent film material, which includes a sealant ionomer material, is described in US-A-4 820 536. The package of meat product includes filler hot and vacuum sealed at temperatures of from 175.4 ° C to 98.9 ° C (175 ° F to 210 ° F) for about 6 to 120 seconds (0.1 to 2 minutes).

A process for packaging and cooking a meat product in a bag of which the food contact layer is an ionomeric material is also described in US-A-4 606 922. The cooking time-temperature conditions involve immersion in water at 70-80 ° C, or in steam, for 4-6 hours.

An ionomeric film material containing a concentration of acidic monomers from 0.2 mol percent to 25 mol percent of a monobasic carboxylic acid, and of which at least 10% of the carboxylic acid groups are neutralized with metal ions such as, Na, K, Li, Mg, Ca or Zn, are as such described in US-A-3,355,319.

However, these known processes and packaging films do not completely prevent meat juice from flowing out of the meat once the packaging is opened or damaged because of its insufficient adhesion to fresh meat. The process of the present invention overcomes the above-mentioned problems and produces packages which effectively increase the retention of meat juice within the packaged fresh meat.

The present invention relates to a process for packaging fresh red meat as claimed in claim 1.

Preferred embodiments are defined in dependent claims 2 to 6. The present invention provides a package which utilizes this film to pack fresh red meat which is heated with fresh red meat for seconds above the Vicat temperature, closes the cells of the red meat without modifying its color thereby significantly reducing the loss of flesh or blood juice from the meat when compared to other sealant materials.

Detailed Description of the Invention

This invention consists in the use of ionomers with high acidic comonomer content and neutralized with certain metal ions as sealing layers for multilayer films for packaging fresh meat with increased juice retention or meat purging and a process for their performance. It has been found that, for this use, the most convenient one is the use of a copolymer of ethylene and a C3-C8-OC, β-unsaturated carboxylic acid, preferably in an amount of 1-30% by weight, of a Preferred form is acrylic acid or methacrylic acid, which carboxylic acid is partially neutralized with at least one metal ion. The copolymer may further contain an acrylate and may be processed, e.g. by pressing or casting a layer or blowing a film. The ionomer is described below:

Copolymer Acid and Ionomer

The acidic and ionomer copolymers of the present invention are derived from direct copolymers of ethylene and C3-C8-CC, β-ethylenically unsaturated carboxylic acid (" ethylene-acid copolymers ") by neutralization with metal ions

&Quot; direct copolymer " it is understood that the copolymer is produced by the polymerization of monomers together, at the same time, differing from " polymer graft " wherein a monomer is attached or polymerized over an existing polymer chain. Methods of preparing such ionomers are well known and are described in U.S. Patent No. 3,264,272. The preparation of the direct ethylene-acid copolymers on which the ionomers are based is described in U.S. Patent No. 4,351,931.

The ethylene acid copolymers used to produce the ionomeric copolymer of the present invention may be E / X / Y copolymers wherein E is ethylene; X is an attenuating comonomer and Y is the C3-C8-Î ±, β-ethylenically unsaturated carboxylic acid, in particular acrylic or methacrylic acid. Preferably, however, the ethylene acid copolymer is a dipolymer (non-softening comonomer). Preferred acidic moieties are methacrylic acid and acrylic acid. 4

By " softener ", it is meant that the polymer is produced less crystalline. Comonomers " softeners " (X) are monomers selected from alkyl acrylate and alkyl methacrylate in which the alkyl groups have 1-12 carbon atoms which, when present, may be up to 30% by weight of the ethylene acid copolymer (preferably up to 15, most preferably up to 5).

An extensive range of percentages of the acid portion may be used in the ethylene acid copolymer. The acid portion may be present in a range of about 1-30 weight percent of the acid copolymer, preferably in the range of about 12 to 25, alternatively about 15 to about 20. Ethylene acid copolymers with high acid levels are difficult to prepare in continuous polymerizers because of the monomer-polymer phase separation. This difficulty can, however, be avoided by the use of " co-solvent technology " as described in U.S. Patent No. 5,028,674 which is also set forth herein or by employing pressures somewhat higher than those in which copolymers with minor acids can be prepared. The copolymer may be neutralized in about 10 to 99.5% with metal ions selected from the groups Ia, Ib, IIa, IIIa, IVa, VIb and VIII of the Periodic Table of the Elements such as sodium, potassium, zinc, calcium, magnesium, lithium, aluminum, nickel and chromium. Preferred for better adhesion to the meat are ions such as zinc, calcium or magnesium selected from the groups IIa and IVa of the periodic table, zinc is most preferred. These neutralized ethylene-acid copolymers are known in the literature as " ionomers ". Typically, the neutralization will be 10-70%. Preferably, the copolymer has from about 35 to 70% of the ionic carboxylic acid groups by neutralization with metal ions.

Preferred ethylene dipolymers are ethylene / acrylic acid and ethylene / methacrylic acid. Other specific copolymers include ethylene / n-butyl acrylate / acrylic acid, ethylene / n-butyl acrylate / methacrylic acid, ethylene / isobutylacrylate / methacrylic acid, ethylene / isobutylacrylate / acrylic acid, ethylene / n-butylmethacrylate / methacrylic acid, ethylene / methylmethacrylate / acrylic acid.

Convenient ionomers for use in the present invention are commercially available under the trademark Surlyn®, suitable ethylene acid copolymers are available under the trademark Nucrel®, both from DuPont Company.

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In the present invention the above-mentioned polymer is used as the sealant layer in a multilayer structure with at least 3 X-type / tape / sealant layers, while X may represent one or more barrier or structural layers with corresponding layers of tape. The sealant layer will be in contact with fresh red meat. The structure may be comprised of the blown film or the molded film process or by the laminating of films together. 6

Processing

During the packaging process, after the sealing of the carton is complete, the entire carton is heated to temperatures between the Vicat temperature and the melting temperature of the sealant material. This process is called " secondary sealing " and is well known in the industry. In the case of the above mentioned ionomers this will be between 50-85 ° C. Warm-up time must be limited between 0.5-5 seconds. The secondary sealing operation will give rise to intense film-to-film contact where there is no flesh between the two films giving additional protection against spills and vacuum. This is particularly important if the packaging is damaged during dispensing. In addition, secondary ionomer sealing packages described in this invention prevent the migration of the meat juices into the package, minimizing the growth of bacteria, leading to a more aesthetic packaging.

However, once the package is opened and the vacuum is released, it is allowed to pour meat juice and blood from the fresh red meat, which results in a loss of the final weight of the meat.

The ionomers generally used in this application have low acid content (between 9 and 12% by weight) and are neutralized with Na and Zn.

It has surprisingly been found that using 7 ionomers with high acid content and zinc ions and applying secondary sealing temperatures above the Vicat temperature of these ionomers but below the melting temperature of the ionomers for short periods of time will occur the following effects: • The pores of the meat will be closed and the juice of the meat retained • The purge, once opened the packaging is reduced from 30- 100%. • Almost no meat juice is present between the meat and the inside of the wrapping film.

This effect can not be observed by the ionomers commonly used to package meat since the acid content of these ionomers is too low to allow sufficient adhesion of the meat and the melting point of these ionomers is too high to give a good reaction with the meat that leads to the closure of the pores but at the same time is low enough to avoid a color change of the meat during the treatment by secondary heating. The invention is further explained in the following examples. EXAMPLES:

The following materials were used:

PA6: Ultramid B35 Surlyn 1857, Surlyn tape layer PA LDPE adhesion: Stamylam from DSM EVA Elax from DuPont, featuring an MFI containing 18% VA

Na-based ionomer I with 10% by weight methacrylic acid content and having an MFI of 1 to 190 ° C.

Ionomer 2, Surlyn 1705, based on Zn, with 15% by weight methacrylic acid content and having an MFI of 5 to 190 ° C. Ionomer 3, Surlyn 9120, based on Zn, 19% by weight methacrylic acid content and having an MFI of 1 to 190 ° C.

The above-mentioned materials were loaded onto a 50 mm Reifenhauser press. This press was part of a 3 layer Reifenhauser blown film line equipped with a 3 layer Barmag mold, where the following 3 layer structure was prepared: PA6 / PA6 tape / sealant Press loading 1 30 microns Film Press loading 2 10 microns Sealant Loading the press 3 50 microns The temperature profile that was established was as follows: 12345 Mold

Press 1 220 220 230 240 240 240 Press 2 170 180 190 200 210 220 Press 3 180 190 200 210 220 230

Types of fresh red meat, such as cow, pork, and deer, were packed in commercial meat packing equipment (Multivac Vacuum Chamber) using a film as the top membrane and another identical film as the bottom membrane. Other types of meats or even other types of cuts can lead to slightly different results with regard to the retention of meat juice. Meat was packed in a bag by a primary sealing operation which sealed the upper membrane to the lower membrane under the following conditions: sealing pressure 1-6 atm, time 0.3-5 seconds, temperature 80-100 ° C. This was followed by a second sealing operation where the surface areas between the upper and lower membranes which are in direct contact with one another are sealed without pressure application. The second seal may also be imperatively included or combined with the first sealing operation.

This was accomplished by reheating at 50-85øC of fresh vacuum-packed red meat piece for 0.8 seconds short enough to avoid discoloration of red meat 10 but long enough to seal the two areas together, as well as for closing the pores of the meat through contact with the low melt sealants of the Surlyn® types.

This reheating is performed using water of 50-85 ° C, hot air, infrared, steam injection or any other source of energy.

The hot air temperatures are higher because of the less intense heat conduction.

Thereafter, the following results were determined: The melt temperature of the sealant was measured by DSC according to ASTM D 1238. Purge retention was measured by keeping the pieces of meat packed for 4 weeks from 0-4øC in a refrigerator chamber . Then the packages were opened and the liquid was separated from the meat. The meat and liquid were then weighed separately. The purge is defined as the percentage of the weight of the liquid that was separated:% Purge = Total Weight - Meat Weight χ 100

Total Weight 11

Thermoformed bags / molds

Examples Vicat Temp. of melt Expansion (° C) (° C) of purge Ex 1 (comp.) LPE 100 120 no No Ex.2 (comp.) EVA 60 80 no No Ex.3 (comp.) Ionomer 1 85 94 no No Ex. 4 Ionomer 2 65 85 Yes Yes Ex. 5 Ionomer 5 60 88 Yes Yes

It has surprisingly been found that using specific ionomer types with high acid numbers and consequently low melting temperatures and Vicat gives sufficient temperature for an interaction between red meat and Surlyn® sealant which closes the pores of the meat and significantly reduces the loss of fluid. For red meat, of types such as cow, pork, deer, juice, blood or purge that leaves the meat after the cut is reduced. This can not be achieved by non-reactive sealants with similar melt temperatures and not even by ionomers which are currently used for this purpose because of their higher melt temperature.

This is observed during the preparation of so-called pouches, where the meat is simply vacuum packed in films, as well as during the packaging of the meat in trays or thermoformed forms.

Such sealant materials may therefore be used as sealant materials in optionally thermoformed reducing films which may optionally be oriented or bi-oriented together with at least one other structural or barrier layer and tape layer. 12

Examples include structures such as PA / tape / sealant, LDPE / tape / EVOH / tape / sealant, sealant / tape / EVOH / tape / sealant or PA / tape / EVOH / tape / sealant. EVOH is ethyleneoxyvinyl alcohol, a common oxygen barrier layer, used in the meat packaging instead of the more commonly used polyamide.

Lisbon, 13 December 2006 13

Claims (6)

A process for packaging fresh red meat into a bag containing as an inner layer an acidic copolymer or a ionomeric sealant having an acid content of at least 15% by weight by vacuum packaging and sealing the meat product in the bag said bag after which the packaged product is subjected to a heat treatment, referred to as secondary sealing, at a temperature between Vicat temperature and the melting temperature of the sealing ionomer layer for 0.5-5 seconds. A process according to claim 1, wherein said secondary seal is performed at a temperature of 50-85 ° C. A process according to claim 1 or 2, wherein the sealant ionomer layer is a copolymer of ethylene and up to 30% of a C3 -C8 -OC, β-unsaturated carboxylic acid, the acid groups being neutralized with 10 -99.5%, with metal ions selected from Na, K, Li, Mg, Ca or Zn. A process according to claim 3, wherein the C3-C8-CC, β-unsaturated carboxylic acid is present in an amount of 15-20%. A process according to claim 3 or 4, wherein the metal is Zn. 1, wherein the acrylate comonomer. A process according to claims 1 to 5, wherein the acid or ionomer copolymer further contains a softener selected from a (C1 -C12) alkylmethyl.