Antimicrobial packaging films

Abstract

The present invention is directed to packaging films having accelerated migration rates of an antimicrobial agent through a product-contact layer which extends the shelf-life of products packaged therein. The product-contact layer includes an ethylene vinyl acetate (EVA) copolymer having a melt flow index of greater than 6 dg/min at 190 C/2.18 kg, an antimicrobial agent and a wetting agent. In some preferred embodiments, greater than 30% of the initial amount of antimicrobial agent present in the product-contact layer can be released after 21 days upon contact with water. The packaging films can be converted into bags, pillow pouches, stand-up pouches, quad pouches, zipped pouches, over-wraps, lidding films, thermoformed trays, vacuum packages, vacuum skin packaging and the like. These films can be used for any product in which it would advantageous to reduce harmful microbial contaminants.

Claims

1. A packaging film comprising: at least a product-contact layer comprising: i) an ethylene vinyl acetate copolymer having melt flow index of greater than 6 dg/min at 190° C./2.16 kg; ii) an antimicrobial agent; and iii) a wetting agent; wherein the wetting agent comprises a fatty acid adduct selected from the group consisting of glyceryl monostearate, polyoxyethylene monooleate, polyoxyethylene monostearate, polyoxyethylene monolaurate, lisorbitan monooleate, potassium oleate, sodium lauryl sulfate, sodium oleate, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan tristearate, sorbitan monooleate, sorbitan trioleate, triethanolamine oleate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, and combinations thereof, and wherein the wetting agent further comprises an ethoxylated alkyl phenol.

2. The packaging film according to claim 1, wherein the average cumulative amount of antimicrobial agent released from the product-contact layer upon contact with water is greater than 10% of the initial amount of antimicrobial agent present in the food-contact layer after 2 days at 23° C. and 1 atm.

3. The packaging film according to claim 1, wherein the average cumulative amount of antimicrobial agent released from the product-contact layer upon contact with water is greater than 20% of the initial amount of antimicrobial agent present in the product-contact layer after 14 days at 23° C. and 1 atm.

4. The packaging film according to claim 1, wherein the average cumulative amount of antimicrobial agent released from the product-contact layer upon contact with water is greater than 30% of the initial amount of antimicrobial agent present in the product-contact layer after 21 days at 23° C. and 1 atm.

5. The packaging film according to claim 1, wherein the film has an antimicrobial activity of less than log.sub.10 7 CFU/g as measured by the total plate count (TPC) up to 20 days after the film is in contact with a food product.

6. The packaging film according to claim 1 wherein the amount of antimicrobial agent present in the product-contact layer is between 0.08 and 9.3 g/m.sup.2.

7. The packaging film according to claim 1, wherein the ethylene vinyl acetate copolymer has melt flow index equal to or greater than 8 dg/min at 190° C./2.16 kg.

8. The packaging film according to claim 1, wherein the ethylene vinyl acetate copolymer has a vinyl acetate content of at least 18 wt.-%.

9. The packaging film according to claim 1, wherein the antimicrobial agent comprises a proton donator or derivative thereof.

10. The packaging film according to claim 9, wherein the proton donator is an organic acid selected from the group consisting of acetic acid, adipic acid, benzoic acid, citric acid, glycolic acid, glutaric acid, p-hydroxybenzoic acid, maleic acid, malic acid, malonic acid, phenols, polymeric acids, propionic acid, sorbic acid, sulfurous acid and mixtures thereof.

11. The packaging film according to claim 9, wherein the proton donator derivative is a salt of an organic acid.

12. The packaging film according to claim 11, wherein the organic acid is selected from the group consisting of potassium sorbate, sodium bisulfite, sodium methyl hydroxybenzoate, sodium propyl hydroxybenzoate, sodium sulfite and mixtures thereof.

13. The packaging film according to claim 9, wherein the proton donator is a mineral acid selected from the group consisting of boric acid, hydrobromic acid, hydrochloric acid, hydrofluoric acid, hydroiodic acid, nitric acid, phosphoric acid and mixtures thereof.

14. The packaging film according to claim 13, wherein the proton donator is a salt of a mineral acid.

15. The packaging film according to claim 9, wherein the proton donator derivative is an anhydride of an organic acid.

16. The packaging film according to claim 9, wherein the proton donator derivative is an alkyl ester of an organic acid.

17. The packaging film according to claim 16, wherein the alkyl ester of an organic acid is selected from the group consisting of methyl p-hydroxybenzoate, propyl p-hydroxybenzoate, butyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, isopropyl p-hydroxybenzoate, isobutyl p-hydroxybenzoate, benzyl p-hydroxybenzoate and mixtures thereof.

18. The packaging film according to claim 1, wherein the ethoxylated alkyl phenol is ethoxylated nonyl phenol.

Description

WORKING EXAMPLES

(1) The Polymer Matrix of the Product-Contact Layer

(2) The use of an ethylene vinyl acetate (EVA) copolymer having a melt flow index of greater than 6 dg/min at 190° C./2.16 kg is an important aspect of the packaging films described herein. Melt flow index (MFI) is a measure of how many grams of a polymer flow through the die in ten minutes expressed as decigrams per minute (dg/min) at a given temperature under a specific mass. The test is performed at a given temperature depending on the plastic. The force used to push the plastic through the system is supplied by a weight which sits on top of a ram. One particularly useful method of determining melt flow index of a thermoplastic material is described in ASTM D1238-13 test method titled Standard Test Method for Melt Flow Rates of Thermoplastics by Extrusion Plastometer by ASTM International, West Conshohocken, Pa. It should be understood that a person skilled in the art can determine the melt flow index of ethylene vinyl acetate (EVA) copolymers by any method known in the art without undue experimentation and is not limited to the aforementioned ASTM test method.

(3) In some preferred embodiments, the ethylene vinyl acetate (EVA) copolymer has a melt flow index of 8 dg/min at 190° C./2.16 kg or higher. In other preferred embodiments, the ethylene vinyl acetate (EVA) copolymer has a melt flow index of 14 dg/min at 190° C./2.16 kg or higher. In still other preferred embodiments, the ethylene vinyl acetate (EVA) copolymer has a melt flow index of 30 dg/min at 190° C./12.16 kg or higher. Suitable examples of these ethylene vinyl acetate (EVA) copolymers which are commercially available include, but are not limited to those sold under the trademark DuPont Elvax® 3174 and 3176 from E. I. du Pont de Nemours and Company, Wilmington, Del. Other suitable commercially available ethylene vinyl acetate (EVA) copolymers include those sold under the trademark Escorene™ Ultra LD 726 by ExxonMobil Chemical Company, Inc., Houston, Tex. It is envisioned that the product-contact layer can also serve as a heat sealing layer in the packaging films described herein.

(4) The Antimicrobial Agent

(5) The antimicrobial agent is one which does not deteriorate during film fabrication, distribution, and storage. The antimicrobial agent is preferably heat stable during extrusion at temperatures that may exceed 200° C., and stable to the shear forces and pressure involved in the process conditions. Also, in some embodiments, the antimicrobial agent used must not adversely affect or discolor the package polymeric materials. The term “antimicrobial agent” describes any water soluble material capable of killing or inhibiting of the growth of bacteria, yeast, fungi, algae, viruses, and/or mold.

(6) In some preferred embodiments, the antimicrobial agent is a GRAS (generally recognized as safe) food additive by the United States Food and Drug Administration (FDA).

(7) The antimicrobial agent used herein are considered a proton donator or derivative thereof. In general, a proton donor is any species capable of donating a proton, for example, Bronsted-Lowry acids which include organic acids such as, but not limited to those selected from the group consisting of acetic acid, adipic acid, benzoic acid, citric acid, glycolic acid, glutaric acid, p-hydroxybenzoic acid, maleic acid, malic acid, malonic acid, phenols, polymeric acids, propionic acid, sorbic acid, sulfurous acid and mixtures thereof. Bronsted-Lowry acids may also include mineral acids such as, but not limited to those selected from the group consisting of boric acid, hydrobromic acid, hydrochloric acid, hydrofluoric acid, hydroiodic acid, nitric acid, phosphoric acid and mixtures thereof.

(8) A proton donator derivative may include a salt of an organic acid and a salt of a mineral acid. Non-limiting examples of salts of an organic acid suitable for use may be selected from the group consisting of potassium sorbate, sodium bisulfite, sodium methyl hydroxybenzoate, sodium propyl hydroxybenzoate, sodium sulfite and mixtures thereof. Other non-limiting examples of proton donator derivatives include anhydride of organic acids and alkyl esters of an organic acids. In some preferred embodiments, the proton donator derivative is selected from the group consisting of methyl p-hydroxybenzoate, propyl p-hydroxybenzoate, butyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, isopropyl p-hydroxybenzoate, isobutyl p-hydroxybenzoate, benzyl p-hydroxybenzoate and mixtures thereof.

(9) In some preferred embodiments, the product-contact layer comprises between 0.08 g/m.sup.2 and 9.3 g/m.sup.2 (0.124 mg/in.sup.2 and 14.42 mg/in.sup.2), or between 0.155 g/m.sup.2 and 1.55 g/m.sup.2 (0.1 mg/in.sup.2 and 1 mg/in.sup.2), or between 0.31 g/m.sup.2 and 1.24 g/m.sup.2 (0.2 mg/in.sup.2 and 0.8 mg/in.sup.2) of antimicrobial agent. In some preferred embodiments, the product-contact layer comprises between 0.1 wt. % and 15 wt. %, or between 0.5 wt. % and 10 wt,%, or between 1 wt. % and 5 wt. % of antimicrobial agent relative to the total weight of the product-contact layer.

(10) The Wetting Agent

(11) It should be understood that the term “wetting agent” used herein may include any substance which increases the mobility of the antimicrobial agent incorporated within the ethylene vinyl acetate of the product-contact layer. The wetting agent may also facilitate or enhance the hydration or contact with an aqueous medium along a face of the product-contact layer. Examples of suitable wetting agents include polyoxyalkylenes (such as those available from BASF under the designation PLURONICS, or those available from Union Carbide under the designation CARBOWAXES, including those with PEGs), ether capped polyoxyalkylenes, e.g., polyoxyethylene lauryl ether, ester capped polyoxyalkylenes, e.g., polyoxyethylene stearate, sorbitan esters (such as certain products commercially available under the designations SPAN and TWEEN), phosphatides (such as lecithin), alkyl amines, glycerin, water soluble polymers such as polyethylene oxides, carboxymethyl cellulose, polyvinyl alcohol, and polyvinyl pyrrolidone, surfactants such as alkyl (C.sub.6-C.sub.20) sulfate salts, e.g., sodium lauryl sulfate, aryl (C.sub.6-C.sub.10) sulfate salts, and alkaryl (C.sub.7-C.sub.24) sulfate salts, and the like.

(12) In some preferred embodiments, the wetting agent comprises a fatty acid adduct selected from the group consisting of glyceryl monostearate, polyoxyethylene monooleate, polyoxyethylene monostearate, polyoxyethylene monolaurate, lisorbitan monooleate, potassium oleate, sodium lauryl sulfate, sodium oleate, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan tristearate, sorbitan monooleate, sorbitan trioleate, triethanolamine oleate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, and combinations thereof.

(13) In such preferred embodiments, the wetting agent may also further comprise an ethoxylated alkyl phenol. Non-limiting examples of suitable ethoxylated alkyl phenols are ethoxylated nonyl phenols. A particularly useful combination of substances suitable for use as a wetting agent includes a mixture of sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, lisorbitan monooleate and ethoxylated nonyl phenol which is sold under the trademark Atmer™ 645 by Croda International Plc, Edison, N.J.

(14) In some preferred embodiments, the product-contact layer comprises between 0.0155 g/m.sup.2 and 4.65 g/m.sup.2 (0.01 mg/in.sup.2 and 3 mg/in.sup.2), or 0.078 g/m.sup.2 and 3.88 g/m.sup.2 (0.05 mg/in.sup.2 and 2.5 mg/in.sup.2), or between 0.155 g/m.sup.2 and 3.1 g/m.sup.2 (0.1 mg/in.sup.2 and 2.0 mg/in.sup.2) of wetting agent. In some preferred embodiments, the product-contact layer comprises between 0.1 wt. % and 5 wt. %, or between 0.25 wt. % and 3.5 wt. %, or between 0.5 wt. % and 2.5 wt. % of wetting agent elative to the total weight of the product-contact layer.

(15) Fabrication of Product-Contact Compositions

(16) There are several methods which could be used to produce the product-contact layer compositions. All the components of the product-contact layer may be dry blended in the required weight ratio in a suitable device such as a tumble blender. The resulting dry blend is then melted in suitable equipment such as an extruder. Alternatively, a masterbatch could be prepared by metering the layer components directly into a single- or twin-screw extruder. The specific conditions for operating a single-screw extruder will differ from that of a twin-screw extruder, but those skilled in the art can readily determine the necessary operating conditions needed to prepare masterbatches suitable for use with the present invention.

(17) In some preferred embodiments, the desired amount of antimicrobial agent is dissolved in water and is introduced into a melt of the ethylene vinyl acetate copolymer via a first injection port on a single- or twin-screw extruder. Next, the wetting agent is dissolved in water and injected into the mixture of EVA copolymer melt and antimicrobial agent through a second injection port on the extruder. The water in this mixture is vaporized and exits the extruder via a vent opening on the extruder. The temperatures of the extruder and speed of mixing of the screw will control the quality of the mixing. A uniform dispersion of both antimicrobial and wetting agents within the polymer melt can be achieved. The specific conditions of operation can readily be determined by one skilled in the art. The extruder extrudes the product-contact layer composition as strands which can then cooled and cut into pellets for subsequent use. Particularly useful methods of incorporating the antimicrobial and wetting agents into ethylene vinyl acetate copolymers are described in U.S. Pat. Nos. 7,993,560 and 8,647,550. Finally, the pelletized layer compositions can be extruded as a monolayer film using a single-screw extruder fitted with a slot die head. Those skilled in the art can readily determine the necessary operating temperatures, screw speeds and other processing parameters needed to prepare such monolayer films without undue experimentation.

(18) Extraction Kinetics of the Product-Contact Layer

(19) In order to measure the efficacy of extraction of antimicrobial agent from the product-contact layer, films specimens were prepared by cutting a 120 cm.sup.2 sample from a 76.2 micron (3 mil) thick film having a specific product-contact layer composition. The specimens were placed inside a vial with 10 mL of deionized water. Potassium sorbate (C.sub.6H.sub.7KO.sub.2) was used as an antimicrobial agent and Atmer™ 645 was used a wetting agent. The cumulative amount of potassium sorbate extracted over time at 23° C. and 1 atm from each film specimen was determined using UV spectroscopy and recorded. The results are shown in Tables 1-5 below. Each value represents the average of three specimens. The product-contact layer composition of each film is identified in each table.

(20) TABLE-US-00001 TABLE 1 Product-Contact Layer Composition Example 1 96.7 wt. % EVA Copolymer-1 + 1.2 wt. % Atmer ™ 645 + 2.1 wt. % C.sub.6H.sub.7KO.sub.2 (EVA-1 Melt Index = 8 dg/min at 190° C./2.16 kg) Cumulative Total Amount of Amount of Cumulative Ave. Mass of C.sub.6H.sub.7KO.sub.2 C.sub.6H.sub.7KO.sub.2 % Extraction Time film Extracted in film of C.sub.6H.sub.7KO.sub.2 (Days) (grams) (mg/m.sup.2) (mg/m.sup.2) from film 2 0.421 68.2 722.23 9.5 ± 0.4 7 0.421 82.6 722.30 11.9 ± 0.3  14 0.421 91.45 722.30 12.9 ± 0.13 21 0.421 92.54 722.30 .sup. 13 ± 0.19

(21) EVA Copolymer-1 was an ethylene vinyl acetate copolymer having an 18 wt. % vinyl acetate content, a density of 0.940 g/cm.sup.3, a melting point of 65° C. which was sold under the trademark DuPont Elvax 3174 by E. I. du Pont de Nemours and Company, Wilmington, Del.

(22) TABLE-US-00002 TABLE 2 Product-Contact Layer Composition Example 2 96.6 wt. % EVA Copolymer-2 + 1.1 wt. % Atmer ™ 645 + 2.3 wt. % C.sub.6H.sub.7KO.sub.2 (EVA-2 Melt Index = 14 dg/min at 190° C./2.16 kg) Cumulative Total Amount of Amount of Cumulative Ave. Mass of C.sub.6H.sub.7KO.sub.2 C.sub.6H.sub.7KO.sub.2 % Extraction Time film Extracted in film of C.sub.6H.sub.7KO.sub.2 (Days) (grams) (mg/m.sup.2) (mg/m.sup.2) from film 2 0.442 178.25 830.80 21.5 ± 0.11 7 0.442 232.50 830.80 28.02 ± 0.2  14 0.442 246.92 830.34 29.7 ± 0.71 21 0.442 251.10 957.90 30.15 ± 0.25 

(23) EVA Copolymer-2 was an ethylene vinyl acetate copolymer having an 18 wt. % vinyl acetate content, a density of 0.939 g/cm.sup.3, a melting point of 82.8° C. which was sold under the trademark Escorene™ Ultra LD 726.07 by ExxonMobil Chemical Company, Houston, Tex.

(24) TABLE-US-00003 TABLE 3 Product-Contact Layer Composition Example 3 95.7 wt. % EVA Copolymer-3 + 1.5 wt. % Atmer ™ 645 + 2.8 wt. % C.sub.6H.sub.7KO.sub.2 (EVA-3 Melt Index = 30 dg/min at 190° C./2.16 kg) Cumulative Total Amount of Amount of Cumulative Ave. Mass of C.sub.6H.sub.7KO.sub.2 C.sub.6H.sub.7KO.sub.2 % Extraction Time film Extracted in film of C.sub.6H.sub.7KO.sub.2 (Days) (grams) (mg/m.sup.2) (mg/m.sup.2) from film 2 0.419 120.90 957.90 12.6 ± 0.23 7 0.419 184.92 957.90 19.6 ± 0.97 14 0.419 230.95 957.90 24.17 ± 1.16  21 0.419 269.24 957.90 28.2 ± 0.86

(25) EVA Copolymer-3 was an ethylene vinyl acetate copolymer having an 18 wt. % vinyl acetate content, a density of 0.940 g/cm.sup.3, a melting point of 65° C. which was sold under the trademark DuPont Elvax 3176 by E. I. du Pont de Nemours and Company, Wilmington, Del.

(26) TABLE-US-00004 TABLE 4 Product-Contact Layer Composition Example 4 93 wt. % EVA Copolymer-3 + 4 wt. % Atmer ™ 645 + 3 wt. % C.sub.6H.sub.7KO.sub.2 (EVA-3 Melt Index = 30 dg/min at 190° C./2.16 kg) Cumulative Total Amount of Amount of Cumulative Ave. Mass of C.sub.6H.sub.7KO.sub.2 C.sub.6H.sub.7KO.sub.2 % Extraction Time film Extracted in film of C.sub.6H.sub.7KO.sub.2 (Days) (grams) (mg/m.sup.2) (mg/m.sup.2) from film 2 0.739 189.57 661.39  14.29 ± 0.67 7 0.737 253.74 622.64 20.14 ± 1.6 14 0.737 377.12 622.64 29.74 ± 2.9 21 0.737 496.00 622.64  38.8 ± 2.93

(27) TABLE-US-00005 TABLE 5 Product-Contact Layer Composition Comparative Example 1 97.08 wt. % EVA Copolymer-4 + 1 wt. % Atmer ™ 645 + 1.92 wt. % C.sub.6H.sub.7KO.sub.2 (EVA-4 Melt Index = 0.7 dg/min at 190° C./2.16 kg) Cumulative Total Amount of Amount of Cumulative Ave. Mass of C.sub.6H.sub.7KO.sub.2 C.sub.6H.sub.7KO.sub.2 % Extraction Time film Extracted in film of C.sub.6H.sub.7KO.sub.2 (Days) (grams) (mg/m.sup.2) (mg/m.sup.2) from film 2 0.497 52.70 803.37  6.6 ± 0.17 7 0.497 67.12 803.37 8.3 ± 0.4 14 0.497 69.29 803.37 8.6 ± 0.2 21 0.497 116.72 803.37 9.2 ± 0.3

(28) EVA Copolymer-4 was an ethylene vinyl acetate copolymer having an 18 wt. % vinyl acetate content, a density of 0.940 g/cm.sup.3, a melting point of 89° C. which was sold under the trademark DuPont. Elvax 3165 by E. I. du Pont de Nemours and Company, Wilmington, Del.

(29) TABLE-US-00006 TABLE 6 Product-Contact Layer Composition Comparative Example 2 96.2 wt. % EVA Copolymer-3 + 3.8 wt. % C.sub.6H.sub.7KO.sub.2 (EVA-3 Melt Index = 30 dg/min at 190° C./2.16 kg) Cumulative Total Amount of Amount of Cumulative Ave. Mass of C.sub.6H.sub.7KO.sub.2 C.sub.6H.sub.7KO.sub.2 % Extraction Time film Extracted in film of C.sub.6H.sub.7KO.sub.2 (Days) (grams) (mg/m.sup.2) (mg/m.sup.2) from film 2 0.770 44.80 685.72 6.73 ± 0.36 7 0.754 67.27 687.43 9.78 ± 0.27 14 0.758 66.34 687.43 9.46 ± 0.37 21 0.754 72.39 687.43 10.5 ± 0.32

(30) As evident from Examples 1-4 and Comparative Example 1, the average amount of antimicrobial agent released from the product-contact layer upon contact with water was greater than 10% of the initial amount of antimicrobial agent present in the layer after 7 days when the ethylene vinyl acetate copolymer had a melt index of 8 dg/min at 190° C./2.16 kg or higher. In some preferred embodiments, greater than 20% of the initial amount of antimicrobial agent present in the food-contact layer was extracted after 14 days when the ethylene vinyl acetate copolymer had a melt index of 14 dg/min at 190° C./216 kg or higher. In other preferred embodiments, greater than 30% of the initial amount of antimicrobial agent present in the food-contact layer was extracted after 21 days when the ethylene vinyl acetate copolymer had a melt index of 30 dg/min at 190° C./2.16 kg or higher. When comparing the data for Example 4 with Comparative Example 2, it should be evident that when no wetting agent is present in the product-contact layer, the amount of potassium sorbate extracted from this layer is significantly lower than those compositions with wetting agent, i.e., at most 10% of the initial amount present after 21 days even though the melt index of the ethylene vinyl acetate was 30 dg/min at 190′ C./2.16 kg.

(31) Preparation of Packaging Films with Product-Contact Layer

(32) Multilayer packaging films having a product-contact layer as described herein were fabricated by blown film coextrusion methods. Other alternative conventional coextrusion methods can also be used including slot cast coextrusion, extrusion lamination, extrusion coating and combinations of blown film coextrusion with one or more alternative methods. In a preferred blown film coextrusion embodiment, the multilayer packaging film was produced using multiple extruders which fed into a multi-manifold circular die head through which the film layers are forced and formed into a cylindrical multilayer film bubble. The bubble was quenched, then collapsed and formed into a multilayer film. Blown film extrusion processes are known in the art and have been described, for example, in The Encyclopedia of Chemical Technology, Kirk-Othmer, 3rd ed., John Wiley & Sons, New York, 1981, Vol. 16, pp. 416-417 and Vol. 18, pp. 191-192.

(33) Seven-layer packaging films were fabricated by blown film coextrusion. The layer compositions are described in TABLES 7-8 below. Each of the two films included a product-contact layer comprising EVA-3 which has a melt index of 30 dg/min at 190° C./2.16 kg. The amount of potassium sorbate in the films was varied by the relative thickness of the product-contact layer, i.e., Example 2 had a product-contact layer thickness approximately twice that of Example 1, hence the amount of potassium sorbate in Example 2 was approximately twice that of Example 1.

(34) TABLE-US-00007 TABLE 7 Multilayer Packaging Film Example 1 Total thickness = 44.45 μm (1.75 mil) Layer 1 86.6 wt. % of EVA-3 + 10.9 wt. % potassium sorbate + 2.5 (Product- wt. % Atmer ™ 645 contact/ [Thickness = 19.56 μm (0.77 mil) & Concentration of Sealant) potassium sorbate = 1.55 g/m.sup.2] Layer 2 80 wt. % of EVA Copolymer-4 + 20 wt. % of an anhydride modified linear low density polyethylene (mod-LLDPE) Layer 3 100 wt. % of Nylon 6 Layer 4 100 wt. % of Ethylene vinyl alcohol copolymer (EVOH) Layer 5 100 wt. % of Nylon 6 Layer 6 90 wt. % of a Very low density polyethylene (VLDPE) + 10 wt. % of an anhydride modified linear low density polyethylene (mod-LLDPE) Layer 7 53.2 wt. % of a Linear low density polyethylene (LLDPE) + 38 wt. % of ethylene vinyl acetate copolymer (EVA-5) having a melt index of 0.35 dg/min at 190° C./2.16 kg + 7.8 wt. % processing additives

(35) TABLE-US-00008 TABLE 8 Multilayer Packaging Film Example 2 Total thickness = 88.9 μm (3.5 mil) Layer 1 86.6 wt. % of EVA-3 + 10.9 wt. % potassium sorbate + 2.5 (Product- wt. % Atmer ™ 645 contact/ [Thickness = 35.6 μm (1.4 mil) & Concentration of Sealant) potassium sorbate = 3.1 g/m.sup.2] Layer 2 Same as Example 1 Layer 3 Same as Example 1 Layer 4 Same as Example 1 Layer 5 Same as Example 1 Layer 6 Same as Example 1 Layer 7 Same as Example 1

(36) Antimicrobial Activity of Packaging Films

(37) Antimicrobial tests were performed with the seven-layer packaging films of Examples 1-2 described above and a Control Example of a monolayer of low density polyethylene (LDPE) having a thickness of 50.8 μm (2 mil). For each of the three test groups, a total of nine packages were made containing a bone-less, skin-less chicken breast weighing approximately 200 grams each. It should be noted that the chicken was store brought and had lost 3 to 5 days of shelf-life. Each package had approximately 258.1 cm.sup.2 (40 in.sup.2) of surface area of film in contact with the chicken breast. Three samples of chicken breast from each test group were removed from their package for enumeration of bacteria colonies (CFU) after 3, 7, 10, 12, 14, 18, and 20 days. The remaining packaged chicken was maintained at 4° C. for the duration of the experiment. When the chicken was removed from the vacuum package, it was placed in a sterile bag containing 50 mL of cold Butterfield's buffer. The bag was vigorously agitated for 2 minutes and then opened in a biosafety cabinet. A one mL aliquot of solution was removed from the bag for serial dilution in additional buffer solution. A sample of the diluted solution was then spread across an agar plate. The plate was allowed to dry and incubated for 48 hours at 24° C. The total bacteria population on the plate was determined by visible inspection. The results are reported as colony forming units (CFU's) in exponential (log.sub.10) growth per gram of chicken. TABLE 9 below summarizes the measured antimicrobial activity test results of the studied films.

(38) TABLE-US-00009 TABLE 9 Antimicrobial Activity Total Plate Count (Log 10 CFU/g) Control Example Example 1 Example 2 Days after (non-vacuum (vacuum (vacuum Packaging packaged) packaged) packaged) 3 4.01 2.7 3 7 6.8 4.1 3.5 10 7.9 4.4 4.2 12 >8 4.8 4.8 14 >8 5.0 4.7 16 >8 5.2 4.3 18 >8 4.9 4.3 20 >8 5.3 4.9

(39) The above-described data demonstrate the antimicrobial efficiency of the packaging films at extending the shelf-life of a packaged meat product when the film includes a product-contact layer formed from an ethylene vinyl acetate copolymer with a melt index greater than 6 dg/min at 190′ C./216 kg, antimicrobial agent and a wetting agent. Also evident is that the packaging films have an antimicrobial activity of less than log.sub.10 7 cfu/g as measured by the total plate count (TPC) up to 20 days after the film is in contact with a food product.

(40) The above description and examples illustrate certain embodiments of the present invention and are not to be interpreted as limiting. Selection of particular embodiments, combinations thereof, modifications, and adaptations of the various embodiments, conditions and parameters normally encountered in the art will be apparent to those skilled in the art and are deemed to be within the spirit and scope of the present invention.