WO1997036798A1 - Modifier transfer film and method of cooking a food product - Google Patents

Abstract

A film article suitable for cook-in packaging and a method of cooking a food product are described. The film article contains a food-contact layer which includes a copolymer which retains a food product modifier. The copolymer includes substantially water-insoluble segments and substantially hygroscopic segments. The copolymer is capable of transferring at least a portion of the modifier to a food product in contact with the food-contact layer. The film article is particularly well-suited for use as a cook-in film. In this regard, it is capable of sorbing and then transferring a modifier to a packaged food product in sufficient quantity that a separate, post-cooking application of modifier to the food product is unnecessary. Thus, only one package is necessary to cook, ship, and store the food product until it is to be consumed or further processed for retail display. Contamination risks associated with handling and repackaging a cooked food product can be altogether avoided.

Description

MODIFIER TRANSFER FILM AND METHOD OF COOKING A FOOD PRODUCT

BACKGROUND INFORMATION 1 Field of the Invention

This invention generally relates to packaging films and to processes employing such films More specifically, this invention relates to films that can retain and then, during a cook-in process, transfer a modifier to a food product as well as to methods of cooking and transferring a modifier to a food product in such films

2 Background of the Invention

Food products often are processed in thermoplastic film packages by subjecting the packaged products to elevated temperatures For example, such packaged products can be immersed in hot water or placed in a steam-heated environment Such thermal processing often is referred to as "cook-in", and films used in such processes are known as cook-in films The processed and packaged food product can be refrigerated, shipped, and stored until the processed food is to be consumed or, for example, sliced and repackaged into smaller portions for customer display (Many sliced luncheon meats are processed in this fashion.) Alternatively, the processed food can be removed immediately from the cook-in package and consumed or further processed for customer display (e g , sliced and repackaged)

Cook-in films must be capable of withstanding exposure to rather severe temperature conditions for extended periods of time while not compromising their ability to contain the food product. Cook-in processes typically involve a long cook cycle Submersion in hot water for up to about 4 hours at about 55° to 65°C is common, and submersion in water or steam at 70° to 100°C for up to 12 hours is possible

Following the cook-in process, the film preferably conforms, if not completely then at least substantially, to the shape ofthe contained food product Often, such conformation is achieved by allowing the film to heat shrink under cook-in conditions to form a tightly fitting package In other words, the cook-in film desirably possesses sufficient shrink energy such that the thermal energy used to cook the food product also shrinks the packaging film snugly around the contained product Alternatively, the cook-in film package can be caused to shrink around the contained food product pπor to initiating the cook-in procedure by, for example, placing the package in a heated environment prior to cooking

The cook-in film also preferably possesses sufficient adherence to the food product to inhibit or prevent "cook-out" during the cook-in process Cook-out involves the collection of juices (sometimes referred to as "purge") between the surface of the contained food product and the food-contact surface ofthe packaging material Preventing cook-out can increase product yield and provide a more aesthetically appealing packaged product

Often, application of a modifier (I e , a substance that can change the odor, color, taste, texture, etc , of the packaged product) to the outer surface of a packaged food product is desired For example, where the food product is poultry or ham, one might wish to impart a smoke color, flavor, and/or odor to the outer surface thereof This can be accomplished by applying a substance referred to as "liquid smoke" to the outer surface ofthe food product, normally after the cooking process Certain characteristics of conventional cook-in films can limit their range of potential uses For example, many films cannot successfully transfer modifier(s) to a food product during the cook-in process Previous attempts have been largely unsuccessful, resulting in (at best) non-uniform transfer of modifier Several explanations have been posited Merely identifying materials that can sorb and retain a modifier and then, during the cook-in process, transfer the same to a food product has proven problematical In addition to this selective retention requirement, the ultimate location ofthe material further complicates the search for prospective candidates Specifically, such a material necessarily contacts the packaged food product As such, it must be capable of being formed into the food-contact layer of a cook-in film, withstanding the rather extreme conditions involved in cook-in processes, and providing a sufficient level of adhesion with the packaged food product Sufficient adhesion can be a particularly difficult requirement to meet Specifically, the film must be able to prevent cook-out and also be removable from the food product once it is cooked Some presently available cook-in films can prevent cook-out However, such films tend to adhere to the surface of the food product with such tenacity that portions, or even an entire surface layer, of the food product are torn away when the film is peeled from the food product As a result, product yield is reduced, and the resulting food product has an unsightly appearance (e.g , a pitted surface)

Because conventional cook-in films have not heretofore successfully transferred modifier to a food product during cook-in, any desired modifier generally must be applied to the food product after the cook-in process This necessitates stripping the cook-in film from, applying the modifier to the surface of, and then repackaging the cooked food product which adds time, expense, and complexity to the cooking/packaging process This procedure also increases the likelihood that the food product, which is sterilized by the cooking process, will become contaminated Eliminating the necessity of removing the food product from its cook-in package, handled, and potentially exposed to microbial contact prior to its consumption or processing for retail display is highly desirable

Accordingly, a need exists for a cook-in packaging film that can facilitate the transfer of a modifier to a food product during the cook-in process, minimize or prevent cook-out, and yet still peel away from the food product without tearing portions from the surface thereof

SUMMARY OF THE INVENTION

Briefly, the present invention provides a film article having a food-contact layer that includes a copolymer with a modifier retained therein The copolymer includes segments that are substantially insoluble in water and other segments that are substantially hygroscopic. The copolymer retains the modifier in such a manner so that at least a portion ofthe modifier can be transferred to a food product in contact with the food-contact layer

In another aspect, the present invention provides a method of cooking a food product A food product is enclosed in the above-described film and heated so as to at least partially cook the food product During this cooking process, at least some of the modifier is transferred from the food-contact layer to the food product

In yet another aspect, the present invention provides a method for making a multilayer film having a food-contact layer which contains therein a modifier The method includes the step of laminating on a film article a food-contact layer impregnated with a solution including a modifier Preferably, the food-contact layer includes a copolymer that has substantially water-insoluble segments and substantially hygroscopic segments

In a still further aspect, the present invention provides a method for impregnating a food-contact layer with a modifier whereby a solution including a modifier is coated on the food-contact layer which retains at least a portion ofthe modifier Again, the food-contact layer preferably includes a copolymer that has substantially water-insoluble segments and substantially hygroscopic segments The film article ofthe present invention is particularly well suited for use as a cook-in film The film is capable of retaining and then transferring a modifier to a packaged food product in sufficient quantity that a separate, post-cooking application of modifier to the food product is unnecessary This eliminates the contamination risks associated with such an operation Thus, only one package is necessary to cook, ship, and store the food product until it is to be consumed or further processed for retail display

Also, the film provides a desirable level of adhesion with the packaged food product The film adheres sufficiently to the food product during cook-in to minimize or prevent cook-out but still can be peeled from the cooked food product without tearing away a surface layer or portions ofthe food product The film article also can be made shrinkable and is capable of withstanding the rather severe conditions associated with cook-in procedures To assist in understanding the more detailed description ofthe invention that follows, certain definitions are provided immediately below These definitions apply hereinthroughout unless a contrary intention is explicitly indicated

"polymer" means the polymerization product of one or more monomers and is inclusive of homopolymers, copolymers, terpolymers, tetrapolymers, etc , and blends and modifications of any ofthe foregoing,

"mer unit" means that portion of a polymer derived from a single reactant molecule (e.g., a mer unit from ethylene has the general formula — H₂CH₂— ), "homopolymer" means a polymer consisting essentially of a single type of repeating mer unit,

"copolymer" means a polymer that includes mer units derived from at least two reactants (normally monomers) and is inclusive of random, block, segmented, graft, etc , copolymers, "polyvinyl alcohol", abbreviated herein as "PVOH", means the material formed by partial or complete hydrolysis of poly(vinyl acetate),

"hydroxy propyl cellulose", abbreviated herein as "HPC", means a thermoplastic, non-ionic cellulose ether formed by the reaction of propylene oxide with alkali cellulose slurried with an aliphatic hydrocarbon and alcohol or propylene oxide, "polyolefin" means a polymer in which some ofthe resulting mer units are derived from an olefinic monomer, which can be linear, branched, cyclic, aliphatic, aromatic, substituted, or unsubstituted (e.g , olefin homo-polymers, copolymers of two or more olefins, copolymers of an olefin and a non-olefinic comonomer such as a vinyl monomer, and the like), "(meth)acrylic acid" means acrylic acid and/or methacrylic acid,

"(meth)acrylate" means acrylate and/or methacrylate, "(meth)acrylamide" means acrylamide and methacrylamide, "anhydride-modified polymer" means one or more ofthe following (1 ) a polymer obtained by copolymerizing an anhydride-containing monomer with a comonomer, (2) an anhydride-grafted copolymer, and (3) a mixture of a polymer and an anhydride-containing compound, "hygroscopic" means the ability to sorb and retain water (either in liquid or gaseous form) and/or aqueous solutions,

"water insoluble" means the ability to substantially resist dissolution in water and/or aqueous solutions, "free shrink" means the percent dimensional change, as measured by

ASTM D 2732, in a 10 cm x 10 cm specimen of film when subjected to heat,

"laminate" means to affix or adhere two or more layers of a film article to one another and can be accomplished by a variety of means including, for example, coextrusion, casting and coating, adhesive bonding, pressure bonding (e g , via calendering) etc ; and

"cook" means to heat a food product thereby effecting a change in one or more ofthe physical or chemical properties thereof (e g , color, texture, taste, and the like)

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Films used in the food packaging industry often are categorized according to the number of layers that make up the film Some films are made from a single polymer or blend of polymers and thus have only one layer However, most films include more than one layer and are referred to as multilayer films In general, the layers of a multilayer film can be classified as "interior" or

"exterior" An interior layer is one in which each ofthe primary surfaces ofthe layer directly contacts some other layer ofthe film In other words, an interior layer is sandwiched by two other layers ofthe film On the other hand, an exterior layer is one in which only one ofthe principal surfaces ofthe layer is adhered directly to another layer ofthe film while the other principal surface of each ofthe two exterior layers forms a principal exterior surface ofthe film

If desired, one or more additional interior layers can be included to provide additional or different properties to the film In addition, any number of tie layers (i e , internal layers having the primary purpose of adhering two other layers to one another) can be included in the film Such tie layers can be present primarily on the outside of an interior layer or can be a layer itself The tie layer preferably includes modified polyolefin and/or polyurethane, more preferably at least one of modified ethylene/α-olefin copolymer, modified ethylene/unsaturated ester copolymer, and modified ethylene/unsaturated acid copolymer Anhydride- modified ethylene/α-olefin copolymer and anhydride-modified enthylene/unsaturated ester copolymer are particularly preferred Specific examples include anhydride-grafted linear low density polyethylene (LLDPE) or anhydride-grafted ethylene/vinyl acetate copolymer

With respect especially to films to be used for cook-in processes, one exterior layer acts as a food-contact layer while the other acts as an outer layer The former serves as the inner layer of a package formed from the film and is in direct contact with the packaged food product The latter provides abuse resistance by serving as the outer layer ofthe package, I e , that layer which is most distant from the food-contact layer

To form a multilayer film, the individual layers are laminated, i e , bonded together Lamination can be accomplished through the use of adhesives, the application of heat and/or pressure, corona treatment, and even spread or extrusion coating Lamination also can be accomplished by coextrusion, which involves extruding two or more materials through a single die with two or more orifices arranged so that the extrudates merge and weld together into a laminar structure before cooling Coextrusion can be employed in film blowing, free film extrusion, and extrusion coating processes

Some films, including many which are used in cook-in processes, are oriented prior to use Orientation involves stretching a film at an elevated temperature (the orientation temperature) followed by setting the film in the stretched configuration (e g , by cooling) When an unrestrained, unannealed, oriented polymeric film subsequently is heated to its orientation temperature, heat shrinkage occurs and the film returns almost to its original, i e , pre-oriented, dimensions

An oriented film has an orientation which is the multiplication product ofthe extent to which the film has been expanded in several directions, usually two directions peφendicular to one another Expansion in the longitudinal direction, sometimes referred to as the machine direction, occurs in the direction the film is formed during extrusion and/or coating Expansion in the transverse direction means expansion across the width ofthe film and is peφendicular to the longitudinal direction

Turning now specifically to the film ofthe present invention, the food- contact layer includes a copolymer having mer units derived from at least two co- reactants The first co-reactant is capable of homopolymerizing to a material which is substantially water insoluble while the second co-reactant is capable of homopolymerizing to a material which is substantially hygroscopic In this manner, when the two co-reactants are copolymerized (by any suitable copolymerization technique known in the art), the resultant copolymer is believed to contain two distinct types blocks or segments, some of which provide water insolubility and other which provide hygroscopicity to the polymer The two types of segments function both interdependently, in that they are inseparable parts ofthe same polymer, and independently, in that they provide the polymer ofthe food-contact layer with water insolubility and hygroscopicity This is highly advantageous for the several reasons

The hygroscopic, i e , water sorbing or swellable, segments ofthe copolymer sorb and retain at least some of a modifier, particularly aqueous modifiers, I e , those which are suspended or dissolved in an aqueous carrier, when the modifier is brought into intimate contact therewith (Of course, where the modifier is not aqueous in nature, the water-insoluble segments can provide the desired sorption and retention Also, where the modifier is, for example, an emulsion, both types of segments can be involved in sorption and retention ) Subsequently, when the food-contact layer is brought into contact with a food product, at least a portion ofthe modifier transfers from the copolymer to the food product Although such transfer most readily occurs during the cook-in process, cook-in is not required to effect transfer

The water-insoluble segments ofthe copolymer prevent the food-contact layer from being solubilized by the food product during and after cook-in and do not themselves dissolve or solvate in the aqueous modifier In this regard, the water-insoluble segments serve to anchor the hygroscopic portions to the rest of the copolymer and thereby maintain the integrity ofthe food-contact layer during cook-in

Thus, a copolymer including both water-insoluble and hygroscopic segments advantageously (1) allows for sorption and subsequent transfer (to a food product during cook-in) of a modifier, and (2) remains intact (or at least substantially intact) so that the food-contact layer can be separated from the food product at any desired time after cooking

The relative amounts of water-insoluble and hygroscopic segments in the copolymer can be selected to provide any desired balance of water insolubility and hygroscopicity Generally, the water-insoluble segments can be present in the copolymer at a weight percentage ranging from about 1 to about 99 while the hygroscopic portions can be present at a weight percentage ranging from about 99 to about 1 , more preferably, the water-insoluble segments can be present at a weight percentage ranging from about 20 to about 95 while the hygroscopic segments can be present at a weight percentage ranging from about 80 to about 5, most preferably, the water-insoluble portions can be present at a weight percentage ranging from about 40 to about 90 while the hygroscopic portions can be present at a weight percentage ranging from about 60 to about 10

Preferably, the water-insoluble segments ofthe copolymer have a solubility in an aqueous medium of less than 10%, more preferably less than 5%, more preferably still less than 1%, even more preferably less than 0 1%, yet more preferably less than 0 05%, more preferably still less than 0 01%, even more preferably less than 0.005%, and most preferably less than 0 001%. (All ofthe foregoing percentages are weight percentages ) The water-insoluble segments preferably are derived from one or more of amides, olefins, esters, alkyl

(meth)acrylates, vinylics, dienes, alkynes, lactides, sulfides, sulfones, urethanes, siloxanes, and silanes Ofthe foregoing, amides, olefins, and esters are particularly preferred, with amides such as nylon 6, nylon 6/6, nylon 12, nylon 6/12, and the like being most preferred. The hygroscopic segments ofthe copolymer preferably have a water sorption capacity of greater than 5%, more preferably greater than 10%, more preferably still greater than 20%, even more preferably greater than 30%, yet more preferably greater than 40%, even more preferably still greater than 50%, yet more preferably still greater than 100%, still more preferably greater than 500%, even more preferably greater than 1000%, and most preferably greater than 5000% All ofthe foregoing percentages are weight percentages

Preferably, the hygroscopic segments are at least somewhat water soluble The hygroscopic segments preferably have a solubility parameter greater than 9 (g/cc)"², more preferably greater than 12 (g/cc)^1/2, and even more preferably greater than 14 (g/cc)¹'² The substantially hygroscopic segments preferably are derived from one or more of ethers, cellulosics, saccharides, anhydrides, caprolactones, imines, (meth)acrylic acid, (meth)acrylamides (such as, for example, N,N-dimethylacrylamide, N-isopropylacrylamide, etc ), cinnamides (such as, for example, N- (meth)acrylylglycinnamide), succinimides (e g , N-vinylsuccinamidic acid), piperidines (such as, for example, N,N-dimethyl-3,5-methylenepiperidinium chloride, 2- vinylpiperidine, 4-vinylpiperidine, and the like), vinyl acetates, vinyl pyrrolidones, vinyloxazolidones (such as, for example, vinylmethyloxazolidone), sulfonic acids (such as, for example, 2-methacryloyloxyethane-l -sulfonic acid, 3-methacryloyloxypropane- 1 -sulfonic acid, 3-(vinyloxy)propane-l -sulfonic acid, and the like), phosphoric acids, phosphonic acids (e g , ethylenephosphonic acid), silicic acids, vinylamines (such as, for example, 2-vinylpyridine, 4-vinylpyridine, and the like), vinyl sulfuric acids (e g., 4- vinylphenyl sulfuric acid), benzoic acids (e.g , 4-vinylbenzoic acid as well as derivatives such as 4-vinylbenzyltrimethylammonium salt), maleic acid, and phenols (e g , 4-vinylphenol) Ofthe foregoing, ethers are preferred Hygroscopic segments derived from one or more of ethylene glycol, propylene glycol, and tetramethylene glycol are particularly preferred

From the foregoing description of preferred water insoluble and hygroscopic reactants, one can see that a particularly preferred copolymer is one which includes mer units derived from esters and mer units derived from amides, i e , an ether/amide copolymer which is the polymerization product of (at least) an ether compound and an amide compound The amide and ether portions can be present in the copolymer in any desired amount depending upon the particular application for which the film article is to be used The copolymer can include between about 1 to 99 weight percent mer units derived from an ether and between about 99 to 1 weight percent mer units derived from an amide Preferably, however, the copolymer includes between about 20 to 80 weight percent mer units derived from an ether and between about 80 to 20 weight percent mer units derived from an amide

A particularly preferred type of ether/amide copolymer is a block copolymer, i e , poly(ether block amide) (PEBA) This type of block copolymer can be produced from a molten state polycondensation of a dicarboxylic polyamide and a polyether diol Preferred PEB As include PEB AX™ MX 1074 and 6031 (Elf-Atochem North America, Inc ; Philadelphia, PA), both of which contain blocks of nylon 12 and poly(ethylene glycol)

In accordance with another embodiment ofthe invention, the food-contact layer can include HPC or a blend of HPC and another polymer Commercially available HPCs include Klucel™ (Aqualon Division of Hercules, Inc , Wilmington,

Del ) and Nisso™ resins (Nippon Soda Co Ltd , Tokyo, Japan)

Chemical or radiative crosslinking ofthe HPC to an extent sufficient to render the food-contact layer substantially water insoluble is preferred In this manner, the HPC food-contact layer remains intact and does not dissolve into the food product Preferred chemical crosslinking agents include, e g , aldehydes, diisocyanates, glyoxal, boric acid, and sodium borate Radiative crosslinking means are well known to those of ordinary skill in the art

In general, the food-contact layer can have a thickness ranging from about

025 to 250 μm (001 to 10 mils), preferably from 1 3 to 25 μm (005 to 1 mil), more preferably from 2 5 to 13 μm (0 1 to 0 5 mils), and most preferably from about 5 to

7.5 μm (about 0.2 to 0 3 mils)

To withstand cook-in time and temperature conditions, the polymer(s) from which the food-contact layer is formed preferably has/have a melting point ranging from about 70° to 250°C, more preferably from about 85° to 230°C, even more preferably from about 100° to 200°C, and most preferably from about 120° to 180°C Other polymers optionally can be blended with the materials described above for the food-contact layer to obtain either a diluted effect or a synergistic effect Thus, other moisture absorbing polymers or relatively water-insoluble polymers can be blended with any ofthe polymers or copolymers described above to form the food- contact layer The blend can include any desired amount of additional polymer Suitable water-insoluble polymers include polyolefins, polyamides, polyesters, etc , with polyamides being preferred Suitable moisture absorbing polymers can include one or more ofthe following water-soluble polymers poly(ethylene imine), poly(acrylic acid), polyacrylamide, poly(methacrylic acid), polymethacrylamide, poly(N,N-dimethylacrylamide), poly(N-isopropylacrylamide), poly(N- (meth)acrylylglycinnamide), poly(vinyl acetate), polyvinylpyrrolidones, polyvinyloxazolidone, polyvinylmethyloxazolidone, poly(ethylene sulfonic acid), poly(phosphoric acid), poly( silicic acid), poly(styrenesulfonic acid), polyvinylamine, poly(2-vinylpyridine), poly(4-vinylpyridine), poly( vinyl sulfuric acid), poly( vinyl alcohol-co- vinyl sulfuric acid), poly(N,N-dιmethyl-3 , 5-methylenepiperidinium chloride), poly(ethylene phosphonic acid), poly(maleic acid), poly(2- methacryloyloxyethane- 1 -sulfonic acid), poly(3-methacryloyloxypropane- 1 -sulfonic acid), poly(4-vinylbenzoic acid), poly(4-vinylbenzyltrimethylammonium salts), poly[3- (vinyloxy)propane-l -sulfonic acid], poly(4-vinylphenol), poly(4-vinylphenyl sulfuric acid), poly(2-vιnylpiperidine), poly(4-vinylpiperidine), and poly(N-vinylsuccinamidic acid) In some circumstances, forming the food-contact layer solely from one or more ofthe foregoing moisture absorbing polymers might be possible

Advantageously, the food-contact layer ofthe film article ofthe present invention not only can transfer modifier to a packaged food product but also can provide purge resistance, i e., inhibit or prevent cook-out during the cook-in process This is a significant advantage, especially where the food product is meat, poultry, or fish Preferably, the film article results in less than 20 weight percent cook-out, i e , less than 20% (by wt ) ofthe original weight of the food product is lost as purge More preferably, the film article results in less than 10% cook-out, even more preferably less than 5%, more preferably still less than 2% cook-out, and most preferably less than 1% cook-out To assist in reducing or eliminating cook-out, a food-contact layer having a surface energy of greater than 34 dynes/cm, preferably greater than 38 dynes/cm, more preferably greater than 42 dynes/cm, even more preferably greater than 46 dynes/cm, and most preferably greater than 50 dynes/cm is preferred At such surface energies, the food-contact layer is believed to provide sufficient adhesion with the food product to prevent or substantially minimize cook-out

If the film adheres so strongly to the cooked food product such that it cannot be peeled therefrom without tearing away portions ofthe same, the copolymer ofthe food-contact layer can be blended with one or more polymers that lower its adhesion In this regard, less polar polymers such as polyolefins having a surface energy of about 36 dynes/cm or less can provide beneficial results On the other hand, if adhesion between the film article and food product is too low, the surface energy of the food-contact layer can be increased This can be accomplished by, for example, subjecting the surface ofthe food-contact layer to sufficient energetic radiation (i e., of sufficiently high intensity or for a sufficiently long period of time) to achieve a desired increase in surface energy Examples of radiative techniques include plasma and corona treatments Alternatively, the surface energy ofthe food-contact layer can be increased by including one or more polar additives such as polyesters, polyamides, polylactic acid, and polar polyolefins such as ethylene/unsaturated acid copolymers, modified polyolefins, and blends thereof

When formed into a food-contact layer, PEBA advantageously has been found to provide sufficient adhesion with a packaged food product during cook-in to substantially prevent cook-out without the need for corona treatment At the same time, adhesion between PEBA and the food product is sufficiently low that the film article can be peeled from the food product after cook-in without substantial tearing of particles from the food product

As mentioned previously, modifiers are substances that can change the odor, color, taste, texture, etc , of a packaged product Normally, the modifier effects a change in the surface ofthe product to which it is applied when sorbed by that surface This sorption can occur either without, but preferably with (in the case of meat, poultry, or fish), a concurrent cook-in process Any desired modifier(s) can be included in the food-contact layer, especially those that are dissolved or suspended in an aqueous medium Non-limiting examples include colorants (e.g , dyes or pigments such as β-carotene), odorants, flavorants, antioxidants (to control rancidity), antimicrobial agents, enzymes, odor absorbents, or blends of any ofthe foregoing materials. Modifiers which impart more than one ofthe above properties also can be used An example of a modifier commonly used in the packaged food industry is "liquid smoke", a substance derived from wood and capable of being sorbed (i e , absorbed or adsorbed) by a food product such as, for example, beef, mutton, poultry, fish, cheese, and the like Liquid smoke is a colorant-flavorant-odorant which imparts a wood-smoked quality to red meat, poultry, ham, sausage, etc Various liquid smoke compounds, as well as the other modifiers listed above, are available from a number of different commercial sources The modifier can be sorbed into the food-contact layer either during or after production of the film article, e.g , by adding modifier to the pelletized or molten resin which will form the food-contact layer prior to extrusion or coextrusion thereof Preferably, sorption ofthe modifier takes place after the film article has been made This can be accomplished by any suitable means whereby a modifier or modifier solution is brought into contact with the food-contact layer for a time sufficient to allow the food-contact layer to sorb a desired amount of modifier Where the film article is in the form of a flat sheet, it can simply be immersed in a bath of a modifier or a solution that includes a modifier so as to impregnate the food-contact layer with modifier This can be done as a batch or continuous process Where the film is in the form of a tube with the food-contact layer on the inner surface thereof, the modifier can be contacted with the tube inner surface and sorbed thereby This can be accomplished in a number of ways such as, for example, by introducing a slug of modifier solution at a low position within a vertically oriented section of tube in the tube processing system, with a nip roll as a liquid seal at the lower end, and then passing the tube through the stationary slug See, e g , U S Pat No 2,901,358 Where the film article is fabricated into a bag, the modifier can be added by simply filling the bag or, as disclosed in U S Pat No 5,484,001, partially filling the bag and then squeezing the modifier between a moveable external roller and backing plate so that it is dispersed along and absorbed into a desired portion ofthe inside (i e , food- contact layer) ofthe bag Other means for sorbing the modifier into the food- contact layer include soaking the food-contact layer in a modifier or modifier mixture and then laminating it to the rest ofthe film structure, coating a modifier solution onto the food-contact layer by means of, for example, a flexographic printing press, a doctor blade, gravure coating, reverse roll coating, etc ; or spraying a modifier solution into the inside of a tube or bag formed from the film article

Surprisingly, the food-contact layer ofthe film article ofthe present invention has been found to be capable of sorbing, retaining, and then transferring a relatively large amount of modifier as a percentage ofthe total weight ofthe food-contact layer For example, a multilayer film having a PEBA food-contact layer that constitutes approximately 10% ofthe film's total weight and thickness, can sorb and retain between about 50 and 250 weight percent of a liquid smoke modifier, based on the total weight ofthe multilayer film If expressed as a percentage ofthe weight ofthe PEBA layer alone, the sorption ranges from about 500 to 2500 weight percent The amount of modifier retained by the food-contact layer often can vary with the viscosity ofthe modifier Generally, lower viscosity modifiers are sorbed and retained to a greater degree than higher viscosity modifiers

The values provided in the foregoing paragraph are based on the amount of modifier retained by the food-contact layer shortly after soaking the film article in a liquid smoke solution, i e , with little or no drying ofthe film article However, where a film article is allowed to dry (e g , at room temperature for a period of 12 to 18 hours), the amount of liquid smoke modifier retained by the food-contact layer is somewhat lower For a multilayer film having a PEBA food- contact layer, the amount of modifier retained after drying ranges from about 20 to 75 weight percent, based on the total weight ofthe film, or about 200 to 750 weight percent, based on the weight of the PEBA layer alone

The foregoing sorption percentages are illustrative only Depending upon a particular set of circumstances (e g , the type of modifier, the composition ofthe food-contact layer, cook-in conditions, etc ), observed values can be higher or lower Actual sorption values can vary from 0 1 to 10,000 weight percent but generally range between 0 5 to 1000, or even 1 to 500, weight percent

The degree of sorption also can vary somewhat depending on the amount of time that the food-contact layer is exposed to the modifier as well as the temperature maintained during the sorption process The values reported above are based on soak times ranging from 30 seconds to 10 minutes (Generally, most sorption occurs within about 2 minutes ofthe time that soaking is initiated ) Where the modifier is liquid smoke compound, sorption times can range from seconds to several hours, e.g , 5 seconds to 24 hours Preferred soφtion times range from about 30 seconds to 30 minutes, more preferably from about 1 to about 10 minutes, most preferably from about 2 to about 5 minutes As illustrated in the Examples below, the film articles ofthe present invention advantageously provide adequate sorption of liquid smoke within about 1 to 10 minutes

Sorption temperatures generally range from about 0° to 70°C, with a temperature range of about 10° to 30°C being more preferred Depending on the circumstances, higher or Iower temperatures also can be employed

The food-contact layer preferably transfers at least 1% (by wt ), more preferably at least 5% (by wt ), even more preferably at least 10% (by wt ), more preferably still at least 20% (by wt ), even more preferably at least 30% (by wt ), yet more preferably at least 40% (by wt ), and most preferably at least 50% (by wt ) ofthe modifier retained therein is transferred to a food product packaged within the film article In general, a greater proportion ofthe retained modifier is transferred to the food product where a food product is cooked and packaged within the film article than where an already cooked food product is simply packaged within the film article About 45 to 95% (by wt ) of a liquid smoke modifier retained in the food-contact layer of a film article ofthe present invention is believed to be transferred to a food product cooked in the film article

The film article ofthe present invention can have a single layer or include a number of layers Preferably, the film article is a multilayer film having an outer layer comprising at least one of polyolefin, polystyrene, polyamide, polyester, poly(ethylene/vinyl alcohol), polyvinylidene chloride, polyether, polyurethane, and polycarbonate The outer layer preferably provides abuse resistance to the film article when it is formed into a cook-in package Polyolefins and/or polyamides often prove to be particularly useful in this regard Suitable polyolefins include polyethylene homopolyer or copolymer, polypropylene homopolymer or copolymer, and polybutene homopolymer or copolymer Preferred examples include ethylene/α-olefin copolymer, propylene/α-olefin copolymer, butene/α-olefin copolymer, ethylene/ unsaturated ester copolymer, and ethylene/unsaturated acid copolymer Specific examples of preferred polyolefins include one or more of LLDPE, ethylene/vinyl acetate copolymer (EVA), propylene/ethylene copolymer, and propylene/butene copolymer An ethylene/α-olefin copolymer includes mer units derived from ethylene and from one or more C to C₂₀ α-olefins such as 1 -butene, 1 -pentene, 1 - hexene, 1 -octene, 4-methyl- 1 -pentene, and the like The resulting polymer molecules include long chains with relatively few side chain branches and the side branching that is present is short compared to non-linear polyethylenes (e g , low density polyethylene homopolymer) Ethylene/α-olefin copolymers generally have a density in the range of from about 0.86 g/cc to about 0 94 g/cc LLDPE generally is understood to include that group of ethylene/α-olefin copolymers which fall into the density range of about 0 915 to about 0 94 g/cc Sometimes, linear polyethylene having densities of from about 0 926 to about 0 94 are referred to as linear medium density polyethylene (LMDPE) Lower density ethylene/α- olefin copolymers can be referred to as very low density polyethylene (VLDPE, typically used to refer to ethylene/butene copolymers available from Union Carbide with a density ranging from about 0 88 to about 0 91 g/cc ) and ultra-low density polyethylene (ULDPE, typically used to refer to ethylene/octene copolymers supplied by Dow Chemical Co.)

Ethylene/α-olefin copolymers also include homogeneous polymers such as metallocene catalyzed EXACT™ linear homogeneous ethylene/α-olefin copolymers (Exxon Chemical Co., Baytown, Texas), TAFMER™ linear homogeneous ethylene/α-olefin copolymers (Mitsui Petrochemical Corp , Tokyko, Japan), and AFFINITY™ long-chain, branched homogeneous ethylene/α-olefin copolymers (Dow Chemical Co , Midland, Michigan) Homogeneous polymers have relatively narrow molecular weight and composition distributions Homogeneous polymers are structurally different from heterogeneous polymers (e.g., ULDPE, VLDPE, LLDPE, and LMDPE) in that homogeneous polymers exhibit a relatively even sequencing of comonomers within a chain, a mirroring of sequence distribution in all chains, and a similarity of length of all chains, i.e., a narrower molecular weight distribution Furthermore, homogeneous polymers are typically prepared using single-site type catalysts (e.g , metallocenes) rather than Ziegler-Natta catalysts. Such single site catalysts typically have only one type of catalytic site, which is believed to be the basis for the homgeneity ofthe polymers produced thereby

Suitable polyamides from which the outer layer can be formed include one or more ofthe following polyamide (i e , nylon) 6, polyamide 66, polyamide 9, polyamide 10, polyamide 1 1, polyamide 12, polyamide 69, polyamide 610, polyamide 612, polyamide 61, polyamide 6T, polyamide MXD6, and copolymers thereof More preferably, the polyamide is selected from the group consisting of polyamide 6, polyamide 66 and polyamide 6/66 Even more preferably, the polyamide in the outer layer comprises a blend of polyamide 6, 66 or 6/66 with a second polyamide having a different crystalline structure from the first polyamide, including one or more of the following polyamide 6, polyamide 66, polyamide 9, polyamide 10, polyamide 1 1, polyamide 12, polyamide 69, polyamide 610, polyamide 612, polyamide 61, polyamide 6T, polyamide MXD6, and copolymers thereof. If the outer layer comprises polyamide, adding polymers that are compatible with the polyamide or polyamide blend so as to modify the properties ofthe polyamide can be beneficial for some applications Suitable polymers include polyolefins, such as those incorporating acids, esters, anhydrides or salts of carboxylic acids; and polar, non-polyolefinic materials such as polyesters, EVA, etc

If desired, additional layers can be included as interior layers Preferred materials from which such interior layers can be formed include polyolefin, particularly EVA, ethylene/alkyl acrylate copolymer (e g , ethylene/methyl acrylate, ethylene/ethyl acrylate, ethylene/butyl acrylate, etc ), LDPE, and ethylene/α-olefin copolymer (e g , LLDPE or VLDPE), polyamide, polyurethane, and blends of any ofthe foregoing In addition, any ofthe materials described above as suitable for use in the outer layer also can be used to form one or more interior layers If desired, the film article can contain an interior layer that acts as a barrier

(Barrier layers inhibit the transmission of one or more gases, e.g., O₂ ) Such a layer can be advantageous for extending the shelf-life of an oxygen-sensitive product, such as beef, poultry, pork, or fish, when packaged in the film article of the present invention Such an oxygen barrier layer preferably is formed from at least one material selected from the group consisting of ethylene/vinyl alcohol copolymer, vinylidene chloride copolymer, polyamide, PVOH, polyhydroxyaminoether, polyalkylene carbonate, or a blend of any of the foregoing If desired, oxygen barrier functionality also or alternatively can be provided by appropriate material selection for the outer layer or other interior layers

Each ofthe foregoing materials from which the film article can be constructed are commercially available from a number of suppliers Specific examples are listed in the Examples below

If heat shrinkable, the film article preferably has a free shrink at 85°C ( 185°F), determined according to ASTM D 2732, of from about 5 to 70%, more preferably from about 10 to 50%, and most preferably from about 15 to 35% in at least one direction (i e , the longitudinal (L) or transverse (T) directions) Preferably, the film article is biaxially oriented, and preferably the film has a free shrink at 85°C of at least 10%, more preferably at least 15%, in each direction in each direction (L and T) Preferably, the film article has a total free shrink (L+T) of from about 30 to 50% at 85°C The film preferably is stretched in both the L and T directions at ratios ranging from about 1 1 5 to 1 7 and, more preferably, from about 1 2 to 1 4 Stretch orienting in the L and T directions can be followed by rapid quenching to lock in the molecular orientation The resulting film article is an oriented film which is heat shrinkable, preferably at the conditions at which the cook-in procedure is performed

Alternatively, the oriented film article can be heat-set Heat-setting can be done at a temperature from about 60° to 200°C, more preferably from about 70° to 150°C, and even more preferably from about 80° to 90°C

In general, the film article ofthe present invention can have any total thickness desired, as long as the film provides the desired properties for the particular packaging operation in which it is used Preferably, the film article has a total thickness (i.e., a combined thickness of all layers) of from about 13 to 250 μm (0.5 to 10 mils), more preferably from about 25 to 130 μm (1 to 5 mils), and still more preferably from about 50 to 75 μm (2 to 3 mils) The film article preferably has a Young's modulus ranging from about 34 to

3400 MPa (5,000 to 500,000 psi), more preferably from about 70 to 2100 MPa (10,000 to 300,000 psi), and most preferably from about 280 to 1400 MPa (40,000 to 200,000 psi) The food-contact layer itself can have a Young's modulus ranging from about 20 to 3400 MPa (3,000 to 500,000 psi) Preferably, the material from which the food-contact layer is formed has a melt flow index ranging from about 0 1 to 1,000 g/10 minutes, more preferably from about 0.5 to 500 g/10 minutes, and most preferably from about 1 to 50 g/10 minutes (ASTM D-1238, 235°C/1 kg)

Illustrated below are preferred examples of film structures in accordance with the present invention In each of these structures, the following abbreviations are used FC food-contact layer, as described above,

PA polyamide-containing layer, preferably having a thickness of from 2 5 to 130 μm (0 1 to 5 mils), more preferably from 5 to 75 μm (0 2 to 3 mils), most preferably from 13 to 25 μm (0 5 to 1 mils), PO polyolefin-containing layer, preferably having a thickness of from 2 5 to

130 μm (0 1 to 5 mils), more preferably from 5 to 75 μm (0 2 to 3 mils), most preferably from 13 to 25 μm (0 5 to 1 mils),

B oxygen barrier layer, preferably having a thickness of from 0 25 to 130 μm (0 01 to 5 mils), more preferably from 1 3 to 13 μm (0 05 to 0 5 mils), most preferably from 2 5 to 7 5 μm (0 1 to 0 3 mils), and

TIE tie layer having a preferred thickness of 0 25 to 25 μm (0 01 to 1 mils), more preferably 1 3 to 13 μm (0 05 to 0 5 mils), most preferably 2 5 to 7 5 μm (0 1 to 0 3 mils)

In the following film structures, the individual layers are shown in the order in which they would appear in the film

FC (monolayer)

FC / PA

FC / PO

FC / TIE / PO FC / B / PA

FC / TIE / PA

FC / PO / PA

FC / B / PO

FC / TIE / B / PO FC / TIE / B / TIE / PO

FC / PA / B / PA

FC / TIE / PO / TIE / PA

FC / TIE / B / TIE / PA

FC / TIE / PA / TIE / PA FC / TIE / B / PA / TIE / PA FC / TIE / PO / TIE / B / PA / TIE / PO

These representative film structures are intended to be illustrative only and not limiting in scope

The film article ofthe present invention can be produced by any suitable technique known in the art of film making, such as, for example, coextrusion, extrusion coating, or lamination Coextrusion is preferred

If desired, the film article can be chemically or radiatively crosslinked When electronically crosslinked, the film is subjected to an energetic radiation treatment, such as high energy electron treatment, which induces crosslinking of molecules ofthe irradiated material The irradiation of polymeric films is disclosed in U S Patent No 4,064,296 (Bornstein et al ) incoφorated herein in its entirety by reference thereto Bornstein et al discloses the use of ionizing radiation for crosslinking the polymer present in the film Radiation dosages often are expressed in terms ofthe radiation unit "RAD", megarads (MR), or kiloGrays (kGy), with one MR being equivalent to 10 kGy A suitable radiation dosage of high energy electrons is in the range of from about 16 to 166 kGy, more preferably from about 44 to 139 kGy, and still more preferably from about 50 to 80 kGy Preferably, irradiation is carried out by an electron accelerator with the dosage level being determined by standard dosimetry methods In carrying out a cook-in process in accordance with the present invention, a food product is enclosed in a film article as described above, with the food- contact layer being in contact with the food product Any suitable means of enclosing the food product in the film article can be employed Preferably, the film article is in the form of a bag or casing with a single opening Such a bag or casing can be formed by, e g , heat sealing one end of a length of tubular film or by sealing both ends ofthe tube and then slitting one edge to form the bag mouth Where the film article is made in the form of flat sheets, bags can be formed therefrom by heat-sealing three edges of two superimposed sheets of film That the food-contact layer be capable of being heat-sealed to itself is preferred PEBA, as well as HPC, are heat-sealable in this manner The food product is placed inside ofthe bag or casing and the opening is sealed closed, e g , by heat-sealing or clipping, so that the resultant enclosure is substantially liquid-tight The enclosed food product is then heated for a time and at a temperature sufficient to at least partially, but preferably fully, cook the food product During this process, at least some ofthe modifier retained within the food-contact layer is transferred to the food product Any suitable means of heating can be employed, including immersing the enclosed food product in a bath of heated water or steam, or placing the enclosed food product in a hot air or steam cabinet In one preferred embodiment, the film article is heat shrinkable so that the food-contact layer will be in close contact with the food product, thereby facilitating transfer of the modifier If the film is not heat shrinkable, the inside of the bag or casing can be evacuated and collapsed against the food product prior to sealing the bag or casing closed

After the desired degree of cooking has been achieved, the processed and packaged food product is removed from the heating means and allowed to cool The film article can be stripped from the food product at any desired time after the cooking process has been completed That is, the film article immediately can be stripped and the food product then can be either consumed or further processed, e.g , sliced and repackaged into smaller portions for customer display by a retailer Alternatively, the processed and packaged food product can be refrigerated, shipped to a retailer, and stored until the processed food is to be consumed or further processed as described above

Food products which can be packaged and cooked in accordance with the present invention can be any of those foods which are amenable to cook-in packaging, including whole muscle or chopped red meat, poultry, pork, or fish

Also included are foods which are not intended to be cooked-in but simply stored within the package, during which time a modifier is to be transferred to the packaged food product Such foods inlcude cheese, vegetables, fruits, and already cooked meat, poultry, pork, or fish In general, however, the invention is most advantageous when used as a cook-in package for, e g , poultry, ham, beef, lamb, goat, horse, fish, liver sausage, mortadella, and bologna, more preferably, poultry, ham, beef and bologna, even more preferably, poultry and ham

The invention will now be described with reference to the following examples, which are intended to be illustrative only and not limiting in scope

EXAMPLES

Example 1 A 6-layer film in accordance with the present invention was prepared The structure ofthe film was FC / I / TIE / B / TIE / O wherein FC represents a 38 μm (1 5 mils) thick food-contact layer of PEB AX™ MX 1074 poly(ether block amide) copolymer, I represents a 76 μm (3 0 mils) thick internal layer made from a blend of TYMOR™ 1203 anhydride-grafted LLDPE (Morton International, Chicago, IL) and EXACT™ 401 1 homogeneous ethylene/α-olefin copolymer (Exxon Chemical Co , Baytown, TX), each TIE represents a 28 μm (1 1 mils) thick tie layer of TYMOR™ 1203 anhydride-grafted LLDPE, B represents a a 28 μm (1 1 mils) thick oxygen barrier layer of EVAL™ LC-E105A ethylene/vinyl alcohol copolymer (Eval Co of America, Lisle, IL), and O represents a 190 μm (7 5 mils) thick outer layer made from a blend of PE 5269T™ ethylene/vinyl acetate copolymer (Chevron Chemical Co , Houston, TX) and FORTIFLEX™ J60-500C-147 high density polyethylene (Solvay Polymers, Inc , Deer Park, TX)

This film was prepared by coextruding each polymer (or polymer blend) at between 193° and 277°C (380° and 530°F) through a circular die held at a temperature of approximately 216°C (420°F) The extruded tube of film was cooled with water and flattened to a width of about 6 cm The flattened film was passed through the scanned beam of an electronic crosslinking unit where it received a total dosage of about 105 kGy After irradiation, the flattened tube was passed through hot water having a temperature of from about 97° to 99°C (206° to 210°F), inflated into a bubble, and oriented to result in a tube of oriented film, the tube having a lay flat width of about 16 5 cm (6 5 in ), with the multilayer film having a total thickness of 56 μm (2.2 mils)

The resulting film had about 20% free shrink in the longitudinal direction and about 30% free shrink in the transverse direction when immersed in hot water at 85°C (185°F) using ASTM method D 2732-83.

Example 2 Multilayer films made according to the teaching of Example 1 and monolayer PVOH films were subjected to cook-in testing by soaking 15 cm x 15 cm (6 in x 6 in ) film samples in a Charsol Select™ 24 liquid smoke solution having a pH of 2 4 (Red Arrow Products Co , Inc , Manitowoc, WI) for a predetermined period of time ranging from 1 to 10 minutes to allow the PEBA or PVOH food-contact layer to sorb some ofthe liquid smoke Some ofthe samples were simply shaken dry and then weighed to determine the amount of liquid smoke absorbed by the food-contact layer Others were allowed to dry for at least 12 hours before weighing This was done to replicate actual use conditions where, in some instances, the food-contact layer is impregnated with modifier shortly before packaging a food product (and will therefore be wet with modifier solution during the transfer ofthe modifier to the food product) and in other instances the modifier-soaked food-contact layer is dried by the time a food product is packaged in the film article

A chicken breast emulsion having 3% salt, 0 5% phosphate, and 35% water, the balance being defatted chicken breast meat (all percentages based on the total weight of chicken breast), was prepared Sections of 10 cm (4 in ) diameter poly(vinyl chloride) pipe were stuffed with the chicken breast emulsion and capped on one end with a 15 cm x 15 cm sample of liquid smoke-impregnated film The other end was capped with a control film having a food-contact layer comprising a 50 50 blend of nylon 12 and nylon 6/12 The control film did not contain modifier but was used as a basis for comparison of the meat- adhesion/cook-out prevention capabilities ofthe films ofthe present invention Restraining plates were placed over the capped ends ofthe stuffed pipe sections, and the resultant sample assemblies were subjected to a cook-in procedure wherein the sample assemblies were immersed in a hot water bath at 60°C (140°F) for 30 minutes, 65°C (149°F) for an additional 30 minutes, and then 70°C (158°F) for a final 30 minutes The sample assemblies then were chilled in an ice bath until cool, at which time the restraining plates were removed

Each ofthe tested film samples were inspected visually for their ability to prevent cook-out This was done by noting the extent to which any purge was trapped between the surface ofthe cooked chicken and the film The samples then were peeled from the cooked chicken During this procedure, the degree to which the food-contact layer of the film samples adhered to the surface ofthe chicken also was noted, in terms ofthe ability ofthe film to prevent cook-out by strong adherence with the chicken and also in terms ofthe ability ofthe film to release from the chicken without tearing away a surface layer or pieces therefrom After the films were removed, the chicken was examined to determine the extent to which the food-contact layer transferred liquid smoke to the chicken during the cook-in process

The test results are summarized in Tables 1 and 2, wherein each value is an average from three identically tested samples Table 1 sets forth the test results for film samples (identified according to their respective food-contact layers) which were allowed to dry for at least 12 hours after soaking in liquid smoke before initiating the cook-in procedure described above

a) 1030 PVOH (Mono-Sol Division of Chπs-Craft. Inc , Gary, Indiana) b) M 1040 PVOH (Mono-Sol Division of Chπs-Craft. Inc ) c) The weight of the film after being dried for at least twelve hours after being soaked in a liquid smoke solution d) The amount of modifier retained by the food-contact laver expressed as a percentage ofthe initial, pre-soaked weight of the film e) A qualitative measure of the degree to which the food-contact layer adhered to the surface ofthe cooked chicken product and prevented cook-out "Very high" represents essentially no cook-out but substantial tearing of chicken upon removal of the film, "high" represents essentially no cook-out and only some tearing of chicken upon removal of the film, "moderate" represents little or no cook-out and no tearing of chicken upon removal ofthe film, "low" represents some cook-out and no tearing, and "none" indicates no adhesion with substantial cook-out The comparative film having a blend of nylon 6 and nylon 6/12 for the food-contact layer exhibited "very high" to "high^" adhesion under this rating system f) A qualitative measure of the degree to which the food-contact layer trans-ferred liquid smoke to the chicken "Good" indicates a high degree, "fair" indicates a moderate degree, and "poor" indicates a low degree of transfer

Table 2 sets forth test results for films samples which had not been dried prior to commencement ofthe cook-in procedure Table 2

PEBA PEBA PVOH-T PVOH-2^b

Soak time (min) 1 10 1 10

Initial film wt (g) 3 20 2 80 1 23 1 25

Wet film wt ^c (g) 6 04 5 5 5 36 4 84

Modifier sorbed (wt %) 89 96 336 287

Adhesion moderate moderate low low

Transfer good good good good

a) Same as in Table 1 b) Same as in Table 1 c) The weight ofthe film immediately after soaking, with excess liquid smoke having been onh shaken off of the film

The data of Tables 1 and 2 show that films ofthe present invention exhibit a high degree of modifier absorption and transfer In addition, the films provide a desirable balance of food adhesion, i e , cook-out is substantially prevented but removal of the film does not result in tearing of chicken particles

With respect to the films having a PEBA food contact layer, the percent absorption in Tables 1 and 2 is expressed as a percentage ofthe entire film weight In such films, the PEBA-containing food-contact layer accounted for approximately 10% ofthe total weight and thickness of the film Thus, the amount of liquid smoke absorbed by the PEBA as a percentage ofthe weight of the PEBA alone is much higher than the values reported in Tables 1 and 2

Example 3 Films made according to the procedure set forth in Example 1 (i e , having a PEBA food-contact layer) were formed into casings, weighed, filled with a liquid smoke solution, and allowed to soak for about 10 minutes The casings then were drained and allowed to dry for at least 12 hours before being reweighed to determine the amount of liquid smoke absorbed by the food-contact layer The casings were stuffed with a meat emulsion consisting of about 30-45% boneless, skinless turkey breast, 50-65% water, 2% NaCl, 0 5% sodium tripolyphosphate, 2% carrageenan, and 1% tapioca starch (all percentages being weight percentages) These stuffed casings were clipped to form a substantially liquid-tight enclosure and placed in a high-humidity thermal processing unit to cook the meat emulsion Cooking temperatures ranged from 60° to 82°C ( 140° to 180°F)

The meat emulsions were weighed before and after cooking to determine the amount purge loss (i e , cook-out) resulting from the cook-in process After cooking, the stuffed casings were chilled and then the casings were stripped from the cooked meat product Observations were made regarding meat adhesion, modifier transfer, and color uniformity of the surface of the modified and cooked meat product

The test results are summarized in Table 3, wherein each value is an average from three identically-tested samples

Table 3

a) LFBN Liquid Smoke having a pH of 6 1 (Red Arrow Products Co ) b) N52 Liquid Smoke having a pH of 5 4 (Red Arrow Products Co ) c) Select 5 Liquid Smoke having a pH of 5 5 (Red Arrow Products Co ) d) The weight ofthe casing after soaking in the liquid smoke solution and then drying for at least 12 hours e) Weight percentage of purge which collected between the meat and the casing, expressed as a weight percentage ofthe initial (1 e . pre-cooked) weight ofthe meat 0 A qualitative measure of the degree to which liquid smoke color uniformly transferred to the surface ofthe meat product, ranging from "uniform^"' (high degree of uniformity) to "mottled" (non-uniform transfer of modifier leading to a mottled or blotchy surface appearance)

This data from Table 3 show that films ofthe present invention can reduce cook-out to levels of approximately 1% or less Further, the films provide good absorption and subsequent transfer of modifier

Example 4 A film was made as in Example 1 but, instead of a food-contact layer formed from PEBAX ™ MX 1074, the food-contact layer was formed from

PEBAX™ 6031 (Elf-Atochem) The film was subjected to cook-in testing as described in Example 2 and exhibited "fair" modifier transfer and "high" adhesion, as those terms are defined above

Example 5

A monolayer film of Klucel™ HPC (Aqualon Division of Hercules, Inc ) was subjected to cook-in testing as described in Example 2 The film exhibited

"good" and "uniform" modifier transfer, and "low" adhesion, as those terms are defined above

While the invention has been described with reference to illustrative examples, those skilled in the art will understand that various modifications can be made to the invention as described without departing from the scope of the claims which follow

Claims

That which is claimed is

1 A film article comprising a food-contact layer, said food-contact layer comprising a) a copolymer comprising substantially water-insoluble segments and substantially hygroscopic segments, and b) a modifier retained by said copolymer, at least a portion of said modifier being capable of transferring from said copolymer to a food product in contact with said food-contact layer

2 The film article of claim 1 wherein said substantially water-insoluble segments are derived from one or more of amides, olefins, esters, alkyl (meth)acrylates, vinylics, dienes, alkynes, lactides, sulfides, sulfones, urethanes, siloxanes, and silanes

3 The film article of claim 2 wherein at least some of said substantially water-insoluble segments are derived from one or more of an amide, an olefin, and an ester

4 The film article of claim 3 wherein at least some of said substantially water-insoluble segments are derived from an amide

5 The film article of claim 4 wherein said amide is one or more of nylon 6, nylon 12, nylon 6/6, and nylon 6/12

6 The film article of claim 1 wherein said substantially hygroscopic segments are derived from one or more of ethers, cellulosics, saccharides, anhydrides, caprolactones, imines, (meth)acrylic acid, (meth)acrylamides, cinnamides, succinimides, piperidines, vinyl acetates, vinylpyrrolidones, vinyloxazolidones, sulfonic acids, phosphoric acids, phosphonic acids, silicic acids, vinylamines, vinyl sulfuric acids, maleic acid, benzoic acids, and phenols

7 The film article of claim 8 wherein at least some of said substantially hygroscopic segments are derived from an ether 8 The film article of claim 1 wherein said copolymer comprises mer units derived from one or more ethers and from one or more amides

9 The film article of claim 8 wherein said copolymer comprises blocks of ether and amide segments

10 The film article of claim 1 wherein said modifier comprises a colorant, odorant, flavorant, antioxidant, antimicrobial agent, enzyme, odor absorbent, or a blend of any ofthe foregoing

1 1 The film article of claim 1 wherein said modifier is a liquid smoke compound

12 The film article of claim 1 further comprising an outer layer

13 The film article of claim 12 wherein said outer layer comprises a polyolefin, polystyrene, polyamide, polyester, ethylene/vinyl alcohol copolymer, polyvinylidene chloride, polyether, polyurethane, or polycarbonate

14 The film article of claim 12 further comprising at least one interior layer positioned between said food-contact layer and said outer layer, said interior layer comprising a polyolefin, polyamide, or polyurethane

15 The film article of claim 12 further comprising an interior layer positioned between said food-contact layer and said outer layer, said interior layer comprising an ethylene/vinyl alcohol copolymer, polyvinylidene chloride, polyamide, polyvinyl alcohol, polyhydroxyaminoether, or polyalkylene carbonate

16 A package made from the film article of claim 1

17 A method of cooking a food product, said method comprising the step of sufficiently heating a food product enclosed in the film article of claim 1 so as to at least partially cook said food product, whereby at least some of said modifier is transferred from said food-contact layer to said food product

18 A method for making a multilayer film having a food-contact layer which contains therein a modifier, said method comprising the step of laminating on a film article a food-contact layer impregnated with a solution comprising a modifier

19 A method for impregnating a food-contact layer with a modifier, said method comprising the step of coating a solution comprising a modifier onto said food-contact layer so that at least a portion of said modifier is retained by said food-contact layer