BR112020008373B1 - POLYSTYRENE FILM FOR APPLICATIONS IN CONTACT WITH FOOD PRODUCTS, ITS USE AND METHOD FOR ITS PRODUCTION, WRAP OR PACKAGING FOR FOOD - Google Patents

Abstract

The present invention belongs to the field of active polymeric materials. Specifically, it refers to an active polystyrene film that has antimicrobial or antioxidant activity and the method of producing said film. It also refers to wrappers, containers and slice separators (intercalators) comprising said film.

Description

DESCRIPTION FIELD OF INVENTION

[001] The present invention belongs to the field of polymeric materials releasing active substances for protecting and/or extending the shelf life of foods. Specifically, it refers to an active polystyrene film that has antimicrobial or antioxidant activity and the method of preparing said film. It also refers to wrappers, containers and films that separate slices (intercalators) comprising said film.

BACKGROUND OF THE INVENTION

[002] In order to improve the oxidative and microbial stability of food products and thus extend their shelf life, antioxidant agents and antimicrobial agents, respectively, are used as additives that are added directly to the products.

[003] Therefore, it is a common practice that, during the processing or before packaging of food products, antioxidants or antimicrobial agents are added directly in relatively high quantities, so that they exert protection for a prolonged time. During storage and marketing, this initial amount gradually decreases as it exerts its antioxidant or antimicrobial effect and eventually ends. This is the moment when oxidation reactions begin and the product begins to deteriorate, or when the microorganisms present in the product begin to grow.

[004] Oxidation reactions in packaged food products begin at the surface, particularly in the portion that first receives oxygen or light that diffuses through the container wall, for which systems have been developed where the packaging is used as a vehicle to the application of antioxidant agents.

[005] Likewise, the most vulnerable part of a packaged food to microbial contamination is its surface and different systems have been described in which the packaging is used as a vehicle for the application of antimicrobial agents.

[006] Producers of films and packaging for food products have spent decades trying to develop films and packaging with antioxidant or antimicrobial properties. Several products have been described in the literature.

[007] Document US 8,343,522 B2 describes coated sheets for antimicrobial treatment based on biopolymers, particularly cellulosic and proteinaceous (for example, collagen). The slide is antimicrobial in nature due to the fact that it is impregnated or coated with at least one a-amino acid ester, wherein said a-amino acid is covalently linked to the film. Due to said covalent bond, the antimicrobial agent does not have the ability to be released into the medium.

[008] Document WO 2017/049364 A1 describes a food packaging material comprising a polymeric material and an antioxidant agent. In particular, in the tests shown, the polymeric material is polyethylene resin and the antioxidant is a rosemary extract.

[009] Document US 2012/0276357 A1 describes a packaging material with antioxidant activity that comprises at least 89% of a polymeric substance, between 2 to 10% of tocopherol and between 0.1 to 1% of a chemical modification agent. surface. In particular, in the tests shown, the polymeric substance is low-density polyethylene.

[010] Document US 8,734,879 discloses a method for preserving a food product through a packaging material with preservative properties. Said packaging material comprises a salt of Nα lauroyl-L-arginine ethyl ester and an acyl monoglyceride comprising glycerol monolaurate incorporated in a polymeric material. In this document, a synergistic effect is shown in the preservative action only between the salt of Nα -lauroyl-L-arginine ethyl ester and glycerol monolaurate, there are no tests with other compounds.

[011] To date, inventors are unaware of the presence of these products on the market. In particular, they did not find any polystyrene slice separators with antioxidant or antimicrobial properties.

[012] Surprisingly, the authors of the present invention developed a film in which the active substances migrate to the surface of the film and maintain their functionality, despite the film manufacturing process. With this film, you can prepare slice separators, wraps and containers for food products with antioxidant or antimicrobial properties. Thus, these separators, wrappers and packaging provide food products with which they are in contact with antioxidant or antimicrobial properties. This entails important advantages, among which it is possible to emphasize the extension of the shelf life of these products.

OBJECT OF THE INVENTION

[013] The present invention relates, in a first aspect, to a polystyrene film for applications in contact with food products, characterized by comprising at least one layer comprising: - 60% to 75% (in w/pt) of crystalline polystyrene (hereinafter referred to as PS); - 10% to 35% (w/w) of ethylene copolymer with polar monomers (hereinafter referred to as EMP) with a comonomer content of 15 to 40% by weight in relation to the total weight of EMP (w/wEMP); - an active substance selected from the group consisting of antioxidant agent and antimicrobial agent; - 0.5% to 2% (in w/pt) of migration agent (hereinafter referred to as AdM); - 0% to 15% (in w/pt) of an emulsifying agent (hereinafter referred to as AE) with an HLB greater than 8, being 3 to 15% (in w/pt), when the active substance is an antimicrobial agent; and in which the ratio PS/(EMP+AE) is between 1.2 and 7.5.

[014] A second aspect of the present invention relates to a slice separator (interleaver) film comprising a film according to the first aspect of the invention.

[015] A third aspect of the present invention relates to a food package or wrapper that is manufactured from, or that comprises, a film according to the first aspect of the invention.

[016] A fourth aspect of the present invention relates to the use of a film according to the first aspect of the invention, for food packaging or food separator film.

[017] A fifth aspect of the present invention relates to the method for producing a film according to the first aspect of the invention.

[018] Other objects, characteristics, advantages and aspects of the present application will be evident to those skilled in the art from the description and the attached claims.

BRIEF DESCRIPTION OF FIGURES

[019] Figure 1: Graphical representation of bacterial growth (in log CFU/ml) as a function of time (in days), where the red square is the control, the blue triangle is the film without EMP and the green diamond is the film with EMP. In panel A, the initial concentration of Listeria was 101 and in panel B it was 105.

[020] Figure 2: Graphical representation of bacterial growth (in log CFU/ml) as a function of time (in days), where the red square is the control, the blue triangle is the film without PS and the green diamond is the film with PS. In panel A, the initial concentration of Listeria was 101 to 102 and in panel B it was 105 to 106.

[021] Figure 3: Graphical representation of bacterial growth (in log CFU/ml) as a function of time (in days), where the red square is the control, the blue triangle is the film without AE and the green diamond is the film with AE. In panel A, the initial Listeria concentration was 102 and in panel B, 106.

[022] Figure 4: Graphical representation of bacterial growth (in log CFU/ml) as a function of time (in days), where the red square is the control, the green diamond is the film with AE and the blue triangle is the film without AE. The initial concentration of lactic acid bacteria was 105.

[023] Figure 5: Graphical representation of bacterial growth (in log CFU/ml) as a function of time (in days), where the red square is the control, the blue triangle is the film without AdM and the green diamond is the film with AdM. The initial Listeria concentration was 105.

[024] Figure 6: Petri photographs with agar inoculated with the object of the analysis mold and a film control (Panel A) or a film according to the invention (panels B and C).

DETAILED DESCRIPTION OF THE INVENTION

[025] As used in the present application, the singular forms “a”, “a”, “the” and “a” include their corresponding plurals, unless the context clearly indicates otherwise. Unless otherwise defined, all technical terms used herein have the meaning that one skilled in the art to which this invention belongs generally understands.

[026] In order to facilitate understanding and clarify the meaning of certain terms in the context of the present invention, the following particular and preferred definitions and embodiments are provided, applicable to all embodiments of the different aspects of the present invention:

[027] “Crystalline polystyrene” (PS) (also known as amorphous polystyrene or general purpose polystyrene (GPPS)) is a polymer whose average molecular weight is between 100,000 g/mol and 400,000 g/mol . It is transparent, hard, brittle and glassy below 100 °C. Above this temperature, it is easily processable and can be given various shapes. It is completely atactic, that is, the phenyl groups are distributed on one side or the other of the central chain, in no specific order and, therefore, it is a completely amorphous polymer.

[028] “Modified Resistant Polystyrene” (HIPS, acronym for High Impact Polystyrene), also known as high impact polystyrene or medium impact polystyrene, is a graft copolymer, as it contains a main styrene chain and grafted polybutadiene chains. This copolymer is wear-resistant and has high impact resistance.

[029] “Emulsifying agent” (AE) refers to any emulsifier with an HLB greater than 8, is processable at a temperature of up to 200 °C and its use is permitted in contact with food and/or is edible. AE facilitates the solubility of the active substance and its release into the medium. In a particular embodiment, the AE is selected from the group consisting of polyethylene glycol 400 dioleate (PEG400DO), polyoxyethylene(20)sorbitan monolaurate (Tween® 20), polyoxyethylene(20)sorbitan monopalmitate (Tween® 40), monostearate polyoxyethylene(20)sorbitan, (Tween® 60), polyoxyethylene(20)sorbitan Tristearate (Tween® 65), polyoxyethylene(20)sorbitan monooleate (Tween® 80), polyethylene oxide stearate 40 (PEO40-S) , sorbitan monolaurate (Span® 20) and mixtures thereof. In a preferred embodiment, the AE is selected from the group consisting of PEG400DO, Tween® 80, PEO40-S and mixtures thereof, and more preferably, the AE is Tween® 80.

[030] “Migration agent” (hereinafter referred to as AdM) refers to a molecule that contains a hydrophobic and a hydrophilic portion, which makes it incompatible with the polymeric matrix and causes it to diffuse through it, accumulating on the surface with its hydrophilic part facing the outside and its hydrophobic part facing the polymer. Due to the tendency of such a molecule to orient itself, diffuse and accumulate on the surface, it causes entrainment of the active substance, which is attracted by the hydrophobic chain. In a particular embodiment, the AdM is selected from the group consisting of fatty acid amides (e.g., erucamide and oleamide), fatty acid esters (e.g., glycerol monostearate (MG)), metal stearates (e.g., zinc stearate), waxes and mixtures thereof. In a particular embodiment, the fatty acid esters do not include glycerol monolaurate. Preferably, the AdM is selected from the group consisting of erucamide, oleamide, MG, zinc stearate, waxes and mixtures thereof, and more preferably, the AdM is MG or erucamide.

[031] The “antioxidant agent” (hereinafter referred to as AO agent) is an agent with antioxidant properties that, among others, prevents fat from going rancid and/or browning in foods, especially meat. In a particular embodiment, the AO agent is selected from the group consisting of tocopherol, green tea extract, olive leaf extract, rosemary extract, grape seed extract, coffee extract, dried acerola (e.g., dried acerola powder with 17% to 25% vitamin C), citrus extracts with a flavonoid concentration greater than 45%, tomato extract with a lycopene concentration greater than 5% (e.g. LYCOSEEN®), fruit extract ( for example, Polyfence® 2), thymol and mixtures thereof. Preferably, the AO agent is selected from tocopherol, tea extract and mixtures thereof, and more preferably, it is tocopherol. The tocopherol may be α, β, Y or mixtures thereof (e.g. CAS 59-02-9, 1669835-4, 54-28-4, 119-13-1), preferably being a mixture of α -tocopherol, β-tocopherol and y-tocopherol.

[032] The “antimicrobial agent” (hereinafter referred to as an AM agent) is an agent active against bacteria (gram + and/or gram -), fungi or yeast. Thus, it can be an antibacterial, antifungal or antiyeast agent. It can also be an active agent against several of the said microorganisms. In a preferred embodiment, the AM is an antibacterial and/or antifungal agent.

[033] The “antibacterial agent” (hereinafter referred to as AB) is an agent with the ability to prevent bacterial growth (bacteriostatic effect) or with the ability to kill bacteria (bactericidal effect). In the present invention, a “bacteriostatic effect” is considered to exist when there is a difference in bacterial growth with and without AB agent of at least two logarithmic units. In a particular embodiment, the agent AB is selected from the group consisting of anhydrous sodium acetate, nisin, lysozyme, and its Ag salts, Zn and its salts, Nα -dodecanoyl-L-ethyl arginate (hereinafter referred to as LAE ), LAE salts and glycolipid biosurfactants. Among the salts of LAE is LAE hydrochloride (hereinafter referred to as LAE-Cl). Glycolipid biosurfactants include rhamnolipids, soporolipids, xylolipids, and mannoseitrite lipids. Preferably, the AB agent is selected from LAE, its salts, preferably LAE-Cl, and mixtures thereof, and more preferably, the AB agent is LAE or LAE-Cl (for example, CAS 60372-77-2).

[034] The “antifungal agent” (hereinafter referred to as an FA agent) is an agent with fungicidal (which kills mold) and/or fungistatic (which prevents the growth of fungi) properties. In a particular embodiment, the AF agent is selected from the group consisting of mixtures of medium chain mono-, di- and triglycerides, monolaurin, nisin, lysozyme, biosurfactant glycolipids, LAE and its salts, in particular LAE-Cl, and mixtures thereof. More particularly, the AF agent is selected from the group consisting of mixtures of mono-, di- and medium chain triglycerides, nisin, lysozyme, glycolipid biosurfactants, LAE and its salts, in particular LAE-Cl, and mixtures thereof. In the present invention, the term “medium chain glycerides” means those of the C8-C12 chain, preferably C8-C10. In a preferred embodiment, the agent is AF LAE, LAE-Cl, mono-, di- and tri-glycerides C8-C10 (e.g. CAS 91744-32-0).

[035] The food legislation applicable to each country restricts the number of substances that can come into contact with food and their limits. Substances must be suitable for contact with food, not only in their original form, but also after changes in pH, exposure to heat, humidity, etc. or hydrolytic breakdown. Thus, in the present invention, all components of the film of the invention must be suitable for contact with food and consumption, since the film of the invention is for those applications in which there is contact between the film and a food product.

[036] The objective of the polystyrene film of the invention is to provide the food product with which it is in contact with antioxidant or antimicrobial protection, in order to improve the appearance of the product, increase the shelf life of the product, etc. In order for the minimum amount of active substance to be released so that the film has functionality, it is necessary to replace part of the polystyrene with a compatible polymer, with appropriate polarity and viscosity. In this case, said compatible polymer is EMP with a certain comonomer content. The film of the invention comprises a polymeric matrix (also called plastic resin or resin hereinafter) comprising PS and EMP. Thus, the present invention refers, in a first aspect, to a polystyrene film for applications in contact with food products (hereinafter referred to as the film of the invention), characterized by comprising at least one layer comprising: - 60 to 75% ( in p/pt) PS; - 10 to 35% (w/w) EMP with a comonomer content of 15 to 40% w/w EMP; - an active substance selected from the group consisting of antioxidant agent and antimicrobial agent; - 0.5% to 2% (in w/pt) of AdM; - 0-15% (in w/pt) of AE, with a higher HLB greater than 8, being 3 to 15% (in w/pt), when the active substance is an antimicrobial agent; and where the ratio PS/(EMP+AE) is between 1.2 and 7.5.

[037] Said at least one layer comprises an active substance hereinafter referred to as “active layer”.

[038] The percentages used here are provided, unless otherwise specified, as a percentage by weight in relation to the total weight of the layer (w/pt), whether it is an active layer or not. The weight percentage is not given in relation to the total weight of the film due to the fact that the film may have one layer (being an active layer) or may have multiple layers (at least one of which is an active layer).

[039] The technical characteristics of the film of the invention defined above result in a film in which it was possible to maintain the functionality of the active substance it comprises, even if the substance is normally thermolabile and with good processability (for example, the polymeric mixture allows obtaining a homogeneous melt with the ability to flow through the extruder without phase separation and transformable by the forming methods used for thermoplastics). Furthermore, the particular composition specified for the active layer allows the active substance to be evenly distributed in the polymeric matrix of the layer and released into the medium (e.g. foods with which it is in contact), where it exerts its activity (e.g. antioxidant or antimicrobial). Thus, the film of the invention comprising an active layer as defined in the present invention efficiently provides antioxidant or antimicrobial protection to the food product that is in contact with said layer.

[040] In a preferred embodiment of the film of the invention, the PS content of 6470% is (w/pt), the EMP is 16 to 30% (w/pt) and the PS/(EMP+AE) ratio is between 1.5 and 4.4. As shown in the Examples, films according to this preferred embodiment provide antioxidant and antimicrobial protection in a surprisingly effective manner.

[041] As shown in the Examples, migration and antioxidant or antimicrobial activity depend on the composition of the film and it is essential that the film has a composition as defined in the present invention to efficiently provide antioxidant or antimicrobial activity. Specifically, regarding the PS component, it is essential that the active layer (or active layers) have crystalline polystyrene and not another polymeric material such as polyethylene (see Example 4). Thus, in a particular embodiment of the film of the invention, the active layer (or active layers) comprises as a polystyrene component (or components) only crystal polystyrene (PS), that is, PS is the only polystyrene-type material of the active layer. (or active layers) (e.g., the active layer does not understand HIPS). In another particular embodiment, according to any of the previous embodiments, the active layer (or active layers) does not comprise cellulose and/or polyethylene, more particularly, the film of the invention, according to any of the embodiments of the first aspect of the invention. , does not include cellulose and/or polyethylene. Preferably, the active layer (or active layers) does not comprise any other polymeric material other than PS and EMP.

[042] In a particular embodiment of the invention, the PS comprises different types of crystalline polystyrene, more particularly the PS comprises crystalline polystyrenes with different MFI (Melt Flow Index). In a preferred embodiment according to any of the above embodiments, the PS comprises PS with an MFI between 10 to 40 g/10 min at 200 °C and 5 kg (hereinafter referred to as PS1), more preferably 20 to 30 g/ 10 min at 200 °C and 5 kg, and/or PS with an MFI of 2-5 g/10 min at 200 °C and 5 kg (hereinafter referred to as PS2), more preferably 2.5 to 4 g/10 min at 200 °C and 5 kg. As shown in the examples, the use of these PS1 and/or PS2 advantageously provides a high release and activity of the active substance.

[043] In another preferred embodiment according to any of the above embodiments, PS comprises less than 37% (w/pt) of PS2, which advantageously provides the film of the invention with excellent processability, maintaining its high release and activity of active substance.

[044] It is also essential that the active layer (or active layers) have EMP, since, as shown in Examples 1 and 3, in the absence of EMP, neither a high release of the active substance nor an efficient antioxidant or microbial activity is achieved. . In a particular embodiment, the EMP is selected from the group consisting of ethylene vinyl acetate copolymer (EVA), ethylene methyl acrylate copolymer (EMA), ethylene ethyl acrylate copolymer (EEA), ethylene butyl acrylate copolymer (EEA), ethylene butyl acrylate copolymer (EBA) and mixtures thereof. EMP is preferably EVA. As shown in the examples, the use of EVA as EMP results in high release and activity of the active substance.

[045] In a particular embodiment of the invention, EMPs comprise EMPs with different IMFs. In a preferred embodiment according to any of the above embodiments, EMP comprises EMP with an MFI between 15 to 50 g/10 min at 190 °C and 2.16 kg (hereinafter referred to as EMP1), more preferably 30 to 45 g /10 min at 190 °C and 2.16 kg, and/or EMP with an MFI of 2 to 5 g/10 min at 190 °C and 2.16 kg (hereinafter referred to as EMP2), more preferably 2.5 at 4 g/10 min at 190 °C and 2.16 kg. Thus, when the EMP comprises EMP1, it may be EVA1, EMA1, EEA1, EBA1 or mixtures thereof, and when the EMP comprises EMP2, it may be EVA2, EMA2 , EEA2, EBA2 or mixtures thereof. As shown in the examples, the use of these EMP1 and/or EMP2 advantageously provides a high release and activity of the active substance.

[046] In another preferred embodiment according to any of the above embodiments, the EMP includes less than 5% (w/pt) of EMP2, which advantageously provides the film of the invention with good processability.

[047] As indicated above, the active substance is evenly distributed in the polymeric matrix of the active layer, and said active substance has the ability to migrate to the surface of the plastic. To control this migration and protect the active substance from any type of cleaning treatment to be carried out on the film, the active layer comprises 0.5% to 2% (in w/pt) of AdM. Surprisingly, as shown in Example 6, the presence of AdM affects the migration of the active substance, as it makes the migration of the active substance slower during the first few days due to the fact that its size is larger than that of AdM, and it also protects the active substance from the cleaning caused in the film, that is, it prevents or reduces the elimination/loss of the active substance due to any cleaning process, whether physical or chemical. Furthermore, as AdM is present, this favors the processability of the film, as it prevents the molten materials from sticking to the metal parts, facilitates the movement of the molten material through the extruder and prevents the bubble from blocking during its collapse, allowing the film to separate. same in two symmetrical films.

[048] In a particular embodiment, according to any of the embodiments of the previous paragraph, the migration agent is selected from the group consisting of fatty acid amides, fatty acid esters, except glycerol monolaurate (monolaurin), metal stearates , waxes and mixtures thereof. Preferably, AdM is selected from the group consisting of erucamide, oleamide, glycerol monostearate and zinc stearate; and more preferably, the AdM is glycerol monostearate and/or erucamide.

[049] In cases where it is desired for the film to provide antioxidant protection to the food product, the active substance will be an antioxidant agent. Thus, in a particular embodiment according to any of the above embodiments, the active substance is an antioxidant agent and this is selected from the group consisting of tocopherol, green tea extract, olive leaf extract, rosemary extract, grape seed, coffee extract, dehydrated acerola, citrus extract with a flavonoid concentration greater than 45%, tomato extract with a lycopene concentration greater than 5%, fruit extract, thymol and mixtures thereof. Preferably, the antioxidant agent is tocopherol or green tea extract.

[050] In a particular embodiment according to any of the previous embodiments, the active substance is an antioxidant agent and the content of the emulsifying agent is 0 to 5%, preferably 0 to 3%. The film of the invention is effective both in the absence of AE (see Examples 1 and 2) and in the presence thereof (data not shown). The presence of AE does not imply a great improvement in the release of the AO agent, since, as can be seen in Examples 1 and 2, the release of AO in the absence of AE is close to 100%. Therefore, in a preferred embodiment, the film with an antioxidant agent does not have AE, that is, the AE content is 0%, thus being an advantageous modality in economic and processing terms (the more elements in the mixture the processability becomes more complex).

[051] In cases where it is desired for the film to provide antimicrobial protection to the food product, the active substance will be an antimicrobial agent. Thus, in a particular embodiment of the invention, the active substance is an antimicrobial agent, more particularly an AB or AF agent selected from those given in the particular and preferred embodiments given at the beginning of the detailed description of the present invention. These embodiments are applicable to any of the embodiments of the first aspect of the invention in which the active substance is not an antioxidant agent.

[052] In a particular embodiment according to any of the embodiments of the previous paragraph, the active substance is an antimicrobial agent and the AE content is 3 to 12%, preferably 5 to 10%. As shown in the examples, with said AE content, it is possible to efficiently control the microbial population in the medium in contact with the film of the invention, while in the absence of AE, said antimicrobial control is not achieved (see Example 5).

[053] In a particular embodiment, the AE agent is selected from the group consisting of polyethylene glycol 400 dioleate, polyoxyethylene (20) sorbitan monopalmitate, polyoxyethylene (20) sorbitan, polyoxyethylene tristearate (20) sorbitan monooleate, polyoxyethylene ( 20)sorbitan, polyoxyethylene(20)sorbitan monooleate, polyoxyethylene sorbitan monooleate, polyethylene 40 stearate, sorbitan monolaurate and mixtures thereof. Preferably, the AE is polyoxyethylene sorbitan monooleate.

[054] Surprisingly, the films of the invention are antioxidant or microbiologically effective even incorporating, in their composition, low concentrations of active substance, for example, or less than 6% w/pt. Thus, in a particular embodiment according to any of the above embodiments, the content of the active substance is 0.5 to 6% (in w/pt). As shown in the Examples, films with active layers with concentrations as low as 0.9% tocopherol and 1.37% AM agent efficiently provide the medium with antioxidant and antimicrobial activity, respectively.

[055] In a preferred embodiment, the polystyrene film of the first aspect of the invention, according to any of the previous embodiments, comprises at least one layer consisting of: - 60% to 75% (in w/pt) of PS ; - 10% to 35% (w/w) EMP a comonomer content of 15 to 40% w/w EMP; - 0.5 to 6% of an active substance selected from the group consisting of an antioxidant and an antimicrobial agent; - 0.5% to 2% (in w/pt) of AdM; - 0% to 15% (in w/pt) of AE, with an HLB greater than 8, being 3 to 15% (in w/pt), when the active substance is an antimicrobial agent; where the ratio PS/(EMP+AE) is between 1.2 and 7.5; and wherein the total sum of the components is 100% by weight relative to the total weight of said at least one layer (i.e., the active layer).

[056] As shown in the Examples, films in which the active layer has a composition in accordance with the previous paragraphs, have the ability to release a functional active substance and to provide antioxidant or antimicrobial properties to the medium (e.g. food product) in contact with said film. Furthermore, the films of the invention have properties that allow good processability as indicated above, and have mechanical characteristics that result in excellent cutting properties. These cutting properties allow films to be cut at speeds in excess of 650 cuts/minute and, more particularly, at speeds of up to 1,200 cuts/minute, thus achieving excellent product stacking without burrs or irregular cuts. They are also highly non-stick films, with anti-static properties, allowing easy separation of the slices without sticking and are adjustable for all cutters available on the market.

[057] Thus, in a particular embodiment according to any of the previous embodiments, according to the first aspect of the invention, the film of the invention has a tensile strength in the machine and transverse direction greater than 20 MPa and an elongation at break in machine and transverse direction greater than 20%. More particularly, it has a tensile strength in the machine direction of more than 30 MPa and in the transverse direction of more than 20 MPa, and an elongation at break in the machine direction of more than 40% and in the transverse direction of more than 45%. These mechanical properties are widely known to those skilled in the art and were obtained in accordance with the UNE-EN ISO 527-3 standard.

[058] As indicated above, the film of the present invention can be single or multilayer. If the film is multilayer, the film comprises at least two layers, at least one of which is an active layer.

[059] In a particular embodiment according to any of the previous embodiments, the film is monolayer and has a total thickness of 10 to 300 microns, preferably 40 to 80 microns. In another particular embodiment, the film is multilayer and has a total thickness of 20 to 300 microns, preferably 30 to 80 microns. In monolayer and multilayer embodiments, the thickness of each active layer is at least 10 microns.

[060] The arrangement of the layers of the multilayer film must allow contact of at least one active layer with the food product (i.e., the active layer is at least one of the outer layers of the film) in order to provide antioxidant protection or antimicrobial for said product. Thus, in a particular embodiment, the film is multilayer and the active layer is an external layer of said film, that is, it can be in contact with the food product. In another particular embodiment, the film is multilayer and comprises at least one active layer and at least one layer without active substance (hereinafter referred to as “non-active layer”). The composition of the layer without active substance may be such that it provides beneficial properties for the processability of the film or for its cutting. This is the case of a film in which the non-active layer comprises glass polystyrene and high impact polystyrene (HIPS). Thus, in a particular embodiment, the multilayer film comprises at least one active layer according to any of the embodiments described in the first aspect of the invention and at least one non-active layer comprising crystal polystyrene and HIPS. More particularly, said non-active layer comprises 60 to 90% w/pt, preferably 65 to 75% w/pt of crystalline polystyrene and 10 to 40% w/pt, preferably 25 at 35% w/pt of HIPS. More preferably, said active layer is not 60 to 90% w/pt, preferably 65 to 75% w/pt, of crystalline polystyrene and 10 to 40% w/pt, preferably preferably 25 to 35% w/pt of HIPS, so that its composition is 100% w/pt.

[061] Preferably, the film of the invention, according to any of the previous multilayer embodiments, comprises three layers, wherein each of the two outer layers is an active layer, as defined in any of the previous embodiments, and in that the intermediate layer is a non-active layer as defined in any of the previous embodiments. Most preferably, trilayer film consists of the three layers defined in this paragraph.

[062] As shown in Example 2, the multilayer films defined in the previous paragraphs show excellent antioxidant and cutting properties, making them suitable for use as intercalators.

[063] Finally, in a particular embodiment according to any of the embodiments described in the first aspect of the invention, the film of the invention is in tube format.

[064] The film of the present invention can be used to prepare a slice separator film, since, as indicated above, it has excellent cutting properties and is capable of being cut by cutting machines at speeds greater than 650 slices/minute, and more particularly up to 1,200 cuts/minute. Furthermore, said slice separator thus supplies the active substance to each slice that is in contact with it through its active layer. Thus, a second aspect of the invention relates to a slice separator comprising a film according to any of the embodiments of the first aspect of the invention. More particularly, the spacer consists of a film according to any of the embodiments described in the first aspect of the invention.

[065] In addition to its use as a slice separator, the film of the invention can be used to manufacture a food wrapper or container. Thus, a third aspect of the invention relates to a food wrapper or container characterized by being manufactured from or comprising a film according to any of the embodiments described in the first aspect of the invention. As indicated above, the active layer of the film must be in contact with the food product in order to provide antioxidant or antimicrobial protection. In a particular embodiment, said food container consists of film according to any of the embodiments described in the first aspect of the invention. The food container can be in the form of a tray, bag, bag-in-box, doy-pack, flow-pack, etc. The food casing may be in the form of a strip, tube, etc.

[066] Taking all of the above into account, in a fourth aspect, the present invention relates to the use of a film according to any of the embodiments described in the first aspect of the invention for the packaging of food products or as a film that separates food products, particularly food product slice separator. As indicated above, using the film of the invention, an antioxidant or antimicrobial protection is efficiently provided to the food product in contact therewith.

[067] The microbiological risks of food products are still one of the main sources of foodborne illnesses today. Listeriosis is the most critical foodborne illness in the European Union and the USA, with a high mortality rate of around 13%. The fact that L. monocytogenes can grow at refrigeration temperatures (2 to 4 °C) causes the presence of this pathogen in ready-to-eat products with a relatively long shelf life, such as fish products, cooked meat products, sausages and Fermented cheeses are of particular concern for food safety. On the other hand, the presence of lactic acid bacteria in food products causes changes in their sensory attributes. Surprisingly, the film of the present invention provides excellent antimicrobial properties against lactic acid bacteria and Listeria (see Examples 3 to 6). Likewise, the slice separators, containers and packaging that make up the same.

[068] Finally, in a fifth aspect, the present invention relates to a method (method of the invention) for producing the film of the invention, characterized by comprising the following steps: a) providing a polymer composition comprising: - 60 to 75% (w/pt) PS, - 10 to 35% (w/pt) EMP with a comonomer content of 15 to 40% weight EMP, - an active substance selected from the group consisting of a antioxidant agent and an antimicrobial agent, - 0.5% to 2% (w/pt) AdM, - 0 to 15% (w/pt) AE, with an HLB greater than 8, with 3 to 15% , when the active substance is an antimicrobial agent, in which the ratio PS/(EMP+AE) is between 1.2 and 7.5; and b) forming a film with at least one layer comprising said polymer composition.

[069] The particular modalities of PS, PS1, PS2, EMP, EMP1, EMP2, AE, AdM, active substances and PS/(EMP+AE) ratio provided for the first aspect of the invention are applicable to the fifth aspect of the invention. Likewise, the modalities given in relation to the type of film (monolayer or multilayer) are applicable.

[070] In a particular embodiment of the method of the invention, the AE and/or the active substance are added to the composition of a) in the form of a concentrate or master batch, selecting the most suitable matrix according to its melting point, polarity and viscosity. Thus, in a preferred embodiment, the AE concentrate or master batch is prepared in PS, preferably in PS1, and/or the active substance concentrate or master batch is prepared in PS or in EMP, preferably in PS1 or EMP1. By preparing master batches in these components, very good stability of the AE and active substance and their homogeneous distribution in the polymer matrix are achieved. In a particular embodiment, the master batch comprises 15% to 40% AE or active substance, preferably 20 to 35%, by weight, based on the weight of the master batch.

[071] In a particular embodiment of the method of the invention, according to any of the previous embodiments, in step b) the film is formed by coextrusion, extrusion blow molding, extrusion of double or triple bubble film, flat film of extrusion or cast, thermoformed, laminated or blow molded.

[072] When the active substance is supplied to the polymer composition in the form of a concentrate and the film is formed by any type of extrusion, said active substance goes through two extrusion processes, one for the concentrate and the other for the final film . Surprisingly, despite the said double extrusion process, and thanks at least to the particular characteristics of the polymer composition, the active substance migrates to the surface of the film, is released and maintains its functionality.

[073] The active substance, AE and AdM can be added to the polymer composition by physically mixing in an in-line mixer, before entering the extruder hopper or without pre-mixing. Thus, in a particular embodiment of the method of the invention, according to any of the previous embodiments, the active substance is added to the plastic resin by physical premixing in an in-line conditioned mixer, before being formed. In another particular embodiment, the active substance is added without making said premix.

[074] Finally, the fifth aspect of the invention also refers to a film that can be obtained by the method of the invention, as defined in any of the previous embodiments. This film has excellent cutting properties and antioxidant or antimicrobial activity, depending on the active substance it comprises. This film, as well as the film of the first aspect of the invention, can be used as a slice separator and to prepare food packaging or packaging as indicated in the second, third and fourth aspects of the invention.

EXAMPLES

[075] Below are detailed specific examples of embodiments of the invention that serve to illustrate the invention without limiting its scope.

EXAMPLE 1: FILM WITH ANTIOXIDANT ACTIVITY - EMP COMPONENT

[076] Two monolayer films were prepared with the composition indicated in Table 1, where the components are hereinafter abbreviated as “comp.”, the content (“cont.”) of each is determined in percentage by weight based in the total weight of each layer (% w/pt). If the film is monolayer, this percentage is the same as if it had been given based on the total weight of the film. The EMP used was EVA. TABLE 1: COMPOSITION

[077] The film production process was by blown extrusion. In this process, resin pellets are fed through a hopper into an extruder. Here, heat and friction convert the pellets into a molten mass that is forced through a ring to form a bubble. The blister is then flattened by the collapse of the calender, stretched through pressure rollers and conveyed over the free rolls to a rewinder which produces the finished rolls of film.

[078] The EVA2 was purchased from the DuPont business house (ELVAX® 265A), while the PS1 was purchased from the Versalis business house (N3910). Furthermore, the PS2 was purchased from the Styrolution commercial house (PS 165N/L). HIPS was purchased from Styrolution (HIPS 486N). Glycerol monostearate was purchased from the Palsgaard trading company (Einar 204). The active substance is incorporated through a master batch that can be carried out in both PS1 and EVA1. Likewise, the AE additive is introduced into the film production process through a master batch manufactured at PS1. Master batches were prepared at a concentration of 30% AE or active substance (weight percentage based on the total weight of the master batch).

[079] In the other examples, these compounds PS1, PS2 and EVA2 are used and the same film production process, unless otherwise indicated.

[080] In the present case, the active substance was an antioxidant, specifically, it was a concentrate rich in natural tocopherols from non-GMO vegetable oil, in a concentration of 90% tocopherols from the commercial company BTSA (Nutrabiol® T90) with the following CAS numbers: 59-02-9 / 16698-35-4 / 54-28-4 / 119-13-1, and the antioxidant main batch was produced in PS1.

1.1.- RELEASE OF THE ANTIOXIDANT AGENT

[081] A sample of specific dimensions is taken from each of the films under study and is introduced into a certain amount of methanol, to reach a given ppm, during the indicated times. After this period, the sample is analyzed by HPLC and the amount of tocopherol released at each moment is determined. For each time a sample is prepared that is analyzed at a given time, that is, a single sample is not prepared from which an aliquot is taken each time. In this way, as many samples as scheduled times were prepared and analyzed.

[082] In this case, 150 mg of the film was introduced into 3 ml of methanol to reach a concentration of 500 ppm of tocopherol in the methanolic extract, considering that all the tocopherol migrated to the solvent and the samples were collected on days 1, 3 and 6. The results are shown in Table 2. TABLE 2. - PERCENTAGE OF TOCOPHEROL RELEASED PER DAY

[083] The results show that the film with EMP, in this case with EVA, has the ability to release tocopherol over the days, however, the film without EMP, in this case without EVA, does not have the ability to release tocopherol .

1.2.- IN VITRO ANTIOXIDANT ACTIVITY - DPPH TEST

[084] The DPPH test allows evaluating the ability to eliminate free radicals of antioxidant substances.

[085] 0.1 g of film was placed in tubes containing 2 ml of DPPH (1,1-diphenyl-2-picrylhydrazyl) in methanol (50 mg/l). The tubes were kept in the dark and under constant agitation for 30 minutes. Sample absorbance was measured at 515 nm on a spectrophotometer (UV-1700 Pharma Spec, Shimadzu) using methanol as a blank to remove solvent absorbance at this wavelength.

[086] As the DPPH present in the sample is reduced by the antioxidants present in the film, the solution loses its color proportionally to the presence of the antioxidant.

[087] The antioxidant activity of the samples was expressed as the percentage of oxidation inhibition (PI) according to the following formula: where Sample is the absorbance of the sample and Control is the absorbance of the DPPH solution. The higher the PI value, the greater the antioxidant capacity.

[088] The test was carried out in triplicate. Table 3 shows the average values of the results of the three tests. TABLE 3: PERCENTAGE OF OXIDATION INHIBITION

[089] The results show that the film with EMP, in this case with EVA, has an antioxidant activity of almost 100%, while the antioxidant activity of the film without EMP, in this case without EVA, is much lower, approximately 15%.

EXAMPLE 2: Film with antioxidant activity - Multilayer

[090] Two three-layer films were prepared with the composition shown in Table 4. TABLE 4: COMPOSITION OF THREE-LAYER FILMS

[091] Layers A and C are the outer layers and layer B is between them (intermediate layer). Thus, layers A and C, which may be in contact with food, comprise the antioxidant agent.

[092] The thickness of the film of the invention was 60 micrometers and the thickness of the layer a = b = 10 microns. The thickness of the control film was 60 microns, where the thickness of the layer A = B = C = 20 microns.

[093] The film was obtained by a blow extrusion process, as in Example 1, with the exception that the components of each layer are fed to a different extruder and the union of the layers occurs in the extrusion head before forming the bubble.

2.1. - RELEASE OF ANTIOXIDANT AGENT

[094] The test to determine the amount of tocopherol released by the film was carried out as explained in Example 1.1. In this case, films measuring 40x40 mm were introduced into 5 ml of methanol to achieve a tocopherol concentration of 79.46 ppm in the methanolic extract, considering that all the tocopherol migrated to the solvent and the samples were collected on days 0, 1, 2, 3, 6, 9, 15 and 21. The results are shown in Table 5. TABLE 5: PERCENTAGE OF TOCOPHEROL RELEASED PER DAY

[095] Thus, it is seen that the multilayer film (in this case, the trilayer) of the invention, like the monolayer, has the ability to release tocopherol as the days pass.

[096] This film has excellent cutting properties (tensile strength in the machine direction > 30 MPa and in the transverse direction >20 MPa and elongation at break in the machine direction >40% and in the transverse direction >45%), which makes it ideal for use as an interlayer in slicing machines that work at cutting speeds well above 650 cuts/minute, achieving excellent product stacking without burrs or irregular cuts. The cutting properties were characterized following the ISO 527-3 standard.

2.2. - IN VITRO ANTIOXIDANT ACTIVITY - TROLOX TEST

[097] The TROLOX test allows evaluating the ability to eliminate free radicals of antioxidant substances. This test was carried out as follows:

[098] The film measuring 110 mm x 110 mm is cut into small pieces, weighed with precision and crushed with an ultraturrax. Mix with 20 ml of methanol in 50 ml hawk tubes and vortex for 3 minutes and incubate at room temperature for 3 hours. Subsequently, it is vortexed for 3 minutes and centrifuged at 2,300 rpm for 10 minutes. The supernatant is collected for colorimetric determination.

[099] Before carrying out the colorimetric determination, a sample dilution test is carried out with the DPPH to know in which range it will enter the calibration. In addition, five serial dilutions are performed from the initial dilution and 0.9 ml of sample is taken from each dilution to which 0.9 ml of DPPH is added. Samples are incubated for 2.5 h in the dark and finally measured at 515 nm.

[0100] The calibration line is done with Trolox (0-60 μM) and the results are shown in Table 6 as meqTROLOX/100 g of sample. TABLE 6: ANTIOXIDANT CAPACITY

[0101] Thus, it is seen that the multilayer film (in this case, trilayer) of the invention has an antioxidant activity and has the capacity to consume 215 meq Trolox per 100 g of sample, while the control film does not have the capacity to consume some meq of the substance.

2.3. - IN VIVO ANTIOXIDANT ACTIVITY - CHALLENGE TEST

[0102] The trilayer film of the invention with tocopherol as an active substance which, according to the in vitro studies in Section 2.2, showed antioxidant activity, was used to evaluate the impact this has on the quality of a meat product (salami ) during its validity period.

[0103] A chopped cured product (salami) was used to ensure uniformity of the product. The product was vacuum packaged using the antioxidant film or control film in Table 4 as an interlayer.

[0104] An accelerated shelf life study in order to obtain validation of the films' activity was carried out. The product was kept at room temperature (22 °C) to speed up the test, since the product must be stored refrigerated at 8 °C, in displays under commercial lighting conditions. During the product's shelf life, sampling was carried out on days 1, 6, 13, 20, 27 and 41 to determine the evolution of product quality. Specifically, oxidation levels were analyzed (TBARS assay) and their organoleptic characteristics.

[0105] The TBARS index (thiobarbituric acid-reactive substances) was used as an indicator of the level of lipid oxidation of salami. The TBARS index was determined after an adaptation of the method proposed by Buege and Aust (Buege, JA and Aust, SD (1978) Microsomal Lipid Peroxidation. Methods in Enzymology, 52: 302310). 2 g of salami were homogenized for 30 s in an ULTRA-TURRAX® mixer using 20 ml of 1.2 M HCl, 0.1% (w/v) propyl gallate and 0.1% solution. in w/v EDTA. The homogenate was centrifuged at 5,000 rpm for 10 min. The supernatant was injected into a Futura System continuous flow analyzer (Alliance Instruments). A solution of 1.2M HCl, 0.327% thiobarbituric acid and 0.5% Brij-35 was also injected into the system. The system consists of a 90 °C bath to accelerate the reaction and a colorimeter set at 531 nm to detect the reaction product, malondialdehyde (MDA). The calibration line was obtained using 1,1,3,3-tetraethoxypropane as standard. The results were expressed in mg MDA/kg of salami.

[0106] The size of the interlayer was 90x90 mm and the weight of the salami slices was 7 g.

[0107] The results obtained were as shown in Table 7. TABLE 7: TBARS TEST RESULTS

[0108] During the test, the antioxidant effect of the trilayer film of the invention on salami can be detected. Samples of sliced salami packaged using the trilayer film of the invention as an intercalator and stored at room temperature (22 °C) under lighting conditions (870 lux on average; 12 h light + 12 h dark) showed lower oxidation values during product shelf life than the control batch samples. Significantly lower TBARS values (mg MDA/kg of product) were detected in the batches with the trilayer film of the invention compared to the control batch from day 13 of conservation and until the end of the study (t41).

[0109] A comparison between batches detected a less rancid aroma and flavor in batches with the trilayer film of the invention compared to the control batch. On the other hand, no differences in product color were detected between the types of film studied (instrumental and sensorial measurements). From the results obtained, it can be concluded that, under the test conditions (product, environmental conditions, manufacturing batches), the trilayer film of the invention allowed the lipid oxidation of salami to be delayed.

EXAMPLE 3: Film with antibacterial activity - EVA component

[0110] Three monolayer films were prepared with the composition specified in Table 8. TABLE 8: COMPOSITION

[0111] The antibacterial agent used was Mirenat® D from the commercial house VEDEQSA, which has between 53 and 57% ethyl Nα-dodecanoyl-L-argininate (LAE-Cl) (CAS 60372-77 -2). Mirenat® D was incorporated into the film using a master batch made from the EVA1 component. EVA1 was purchased from DuPont (ELVAX® 240A). Tween80® was purchased from Quimidroga (Polisorbato80.PS80). The rest of the components are the same as specified in Example 1.

3.1.- RELEASE OF AB AGENT

[0112] A sample of specific dimensions is taken from each of the films under study and is introduced into a certain amount of water, to reach a given ppm, during the indicated times. After this period, the sample is analyzed by HPLC and the amount of LAE released at each time is determined. Each time corresponds to one sample, that is, how many samples are analyzed according to the scheduled times.

[0113] In this case, 100 mg of film was introduced into 15 ml of water, which resulted in 117 ppm of LAE, considering that all LAE migrates to the solvent, and the samples were collected on days 0, 1, 2, 3, 6, 9, 15 and 28. The results are shown in Table 9. TABLE 9: PERCENTAGE OF LAE RELEASED PER DAY

[0114] The presence of EMP, in this case EVA, facilitates the release of LAE, reaching a release percentage greater than 80%, while if there is no EMP, in this case EVA, in the formulation, the maximum release percentage is only 50%

3.2.- ANTIMICROBIAL ACTIVITY

[0115] The antimicrobial activity of the films was evaluated using the broth culture method to determine the antimicrobial activity with in vitro capacity. The broth culture method allows monitoring the behavior of the microorganisms under study during storage in refrigerated conditions. Briefly, culture broth tubes (MRS/TSBYE) are inoculated with the selected strains at 2 levels (101 and 105 CFU/g) and a film sample is placed in these tubes to study the inhibitory effect of the films. The weight of the sample to be added will be determined based on the ppm equivalent of LAE (mg of LAE/kg of broth) that you wish to study. Samples are maintained at a temperature of 8 °C for a period of 35 days or until the stationary phase of growth is reached.

[0116] These methods were used to evaluate the antibacterial activity of AB (antibacterial) films against lactic acid bacteria (LAB) and/or against Listeria monocytogenes. BALs were used as indicators of spoilage of cooked meat products. Specifically, BAL isolated from spoiled cooked meat products (Lactobacillus sakei and Leuconostoc mesenteroides) was used. On the other hand, L. monocytogenes was used as a target pathogen due to its prevalence in meat products. The strains used were also isolated from meat products.

[0117] In this case, the test was performed with L. monocytogenes and 117 ppm of LAE. As can be seen in Figure 1, the film of the present invention (with EVA) shows bactericidal activity both at a concentration of 101 bacteria (Figure 1A) and at a concentration of 105 (Figure 1B). The study was carried out at two concentrations, one very high and harmful to humans, which could correspond to a contamination peak and another lower, in order to demonstrate the antimicrobial capacity of the films, regardless of the concentration of microorganisms present. With this example, it can be seen how, even if a very high Listeria peak is present, the film of the invention can reduce it to minimum values, thus avoiding future intoxication problems.

[0118] Figure 1 also shows that the EMP component is essential for the film to show said bactericidal activity, since, with the film without EMP, bacterial growth is the same as the control, regardless of the initial concentration of Listeria.

EXAMPLE 4: FILM WITH ANTIBACTERIAL ACTIVITY - PS COMPONENT

[0119] Three monolayer films were prepared with the composition specified in Table 10, as indicated in Example 3. In the film without PS, low density polyethylene (LDPE) (from Dow Chemical, class LDPE410E) was used instead of PS. TABLE 10: COIMPOSITION

4.1.- RELEASE OF AB AGENT

[0120] The test was carried out as explained in section 3.1, collecting samples on the days indicated in Table 11. The results obtained appear in Table 11. TABLE 11: LAE RELEASE RESULTS

[0121] The presence of the PS facilitates the release of the LAE, reaching a release percentage of almost 80%, whereas if there is no PS, the maximum release percentage is only approximately 40%.

4.2.- ANTIMICROBIAL ACTIVITY

[0122] The test was performed as in Section 3.2, with L. monocytogenes and 117 ppm LAE.

[0123] As shown in Figure 2, the film with PS (diamond) has a bactericidal effect, while the film with LDPE (triangle) has no effect, since bacterial growth is the same as with the film. control (square), regardless of the initial Listeria concentration (comparison panels A and B).

[0124] Therefore, it is essential that the layer with the active substance comprises PS.

EXAMPLE 5: FILM WITH ANTIBACTERIAL ACTIVITY - AE COMPONENT

[0125] Three monolayer films were prepared with the composition specified in Table 12: TABLE 12: COÍ MPOSITION

5.1.- RELEASE OF AB AGENT

[0126] The assay was performed as described in Section 3.1, sampling on the days indicated in Table 13. The results are shown in Table 13. TABLE 13: LAE RELEASE RESULTS

[0127] The presence of the AE facilitates the release of the LAE, reaching a release percentage of almost 80%, whereas, if there is no AE, the maximum release percentage is approximately 7%.

5.2.- ANTIMICROBIAL ACTIVITY

[0128] The test was performed as in Section 3.2, with 117 ppm of LAE and with L. monocytogenes at a concentration of 102 (Figure 3.A) or 106 (Figure 3.B) or with BAL at a concentration of 105 (Figure 4 ).

[0129] As for Listeria, as shown in Figure 3, the film with AE (diamond) has a bactericidal effect, while the film without AE (triangle) has no effect, since bacterial growth is the same as the control film (square), regardless of the initial Listeria concentration (comparison panels A and B).

[0130] As for BAL, as shown in Figure 4, the film with AE (diamond) has a bacteriostatic effect compared to the control film (square), while the film without AE (triangle) has no effect against BAL.

EXAMPLE 6: ADM COMPONENT

[0131] Three monolayer films were prepared with the following composition (Table 14), as indicated in Example 3. TABLE 14: COMPOSITION

6.1.- RELEASE OF ACTIVE SUBSTANCE

[0132] The test to determine the amount of LAE released by the film was carried out as explained in Example 3.1. In this case, 100 mg of film was introduced into 25 ml of water, resulting in 117 ppm of LAE and samples were collected on days 1, 2, 3, 6, 9, 15 and 20. The results are shown in Table 15

[0133] With the aim of evaluating the role of AdM in films subjected to a cleaning process (for example, with ethanol to sterilize the sample surface), two more samples were prepared like the previous ones, but were subjected to a cleaning process. chemistry with ethanol before introducing them into water, where they were kept for one day before determining the amount of LAE released by HPLC. The values obtained for these washed samples appear in parentheses in Table 15. TABLE 15: PERCENTAGE OF LAE RELEASED

[0134] As can be seen in Table 15, there was no significant difference in the release of LAE, in the presence or absence of AdM. However, after subjecting the samples to a chemical cleaning process with ethanol (see data in parentheses in Table 15), it is observed that the absence of AdM causes the loss of 31% of the active substance, while in the film with AdM it loses only 14% of said substance (after cleaning, 29% of LAE is released when, without cleaning, 60% was released in the absence of AdM and 43% in the presence of AdM). Thus, it is demonstrated that AdM acts as a physical protective barrier against the elimination or loss of the active substance.

[0135] Furthermore, Table 15 shows that AdM prevents the active substance from migrating too quickly in the first few days. This is a great advantage, since the first few days are the most critical for microbiological control, as in these days the active substance begins to act against bacteria during their dormant period.

6.2.- ANTIMICROBIAL ACTIVITY

[0136] The test was carried out as in Section 3.2, with 117 ppm of LAE and with L. monocytogenes at a concentration of 105, except that the surfaces of the films were subjected to cleaning with ethanol.

[0137] As shown in Figure 5, the film with AdM (diamond) has a bactericidal effect, while the film without AdM (triangle) has a bacteriostatic effect compared to the control film (square) due to the removal of part of the LAE during the surface chemical cleaning process.

EXAMPLE 7: FILM WITH ANTIFUNGAL ACTIVITY

[0138] The in vitro antifungal activity of the developed films was tested against Penicillium commune using the agar diffusion method. It is a qualitative method that allows the antifungal activity of films to be determined by the appearance of an inhibition halo or absence of growth on the contact surface between the film and a Petri dish with agar inoculated with the target microorganism.

[0139] Briefly, in the agar diffusion method, a basic contrast medium is used on which a layer of soft culture medium inoculated with a cocktail of the microorganism object of the study is deposited. Once the medium has solidified, a piece of film measuring 100 mm x 100 mm is deposited and the plate is incubated (in this case, for 11 days at 23 °C). Positive antifungal activity results in a halo of inhibition or absence of mold growth on the surface or around the deposited film.

[0140] In the present test, the following films were used, the composition of which appears in Table 16. TABLE 16. - COMPOSITION

[0141] As shown in Figure 6, in the control film (without fungicidal agent, panel A) the mold grows throughout the plate, while in the films according to invention 1 (with Glyceride 8 to 10 C atoms, the mold of panel B) and 2 (with LAE, panel C) does not appear on the surface of the plate in contact with the film of the invention. Thus, it is demonstrated that the film of the invention has fungistatic or fungicidal activity, that is, it has the ability to delay or inhibit the growth of the mold in the study. Note that there is a contaminating fungus (brown) that also does not grow on the surface of the plate in contact with the invention film.

Claims (31)

1. Polystyrene film for applications in contact with food products characterized by comprising at least one layer comprising: - 60 to 75% (in w/pt) of crystalline polystyrene (PS); - 10 to 35% (w/w) of ethylene copolymer with polar monomers (EMP) with a comonomer content of 15 to 40% w/wEMP; - an active substance selected from the group consisting of an antioxidant agent and an antimicrobial agent; - 0.5% to 2% (w/pt) migration agent (AdM) selected from the group consisting of fatty acid amides, fatty acid esters, waxes and mixtures thereof; - 0 to 15% (in w/pt) of emulsifying agent (AE) with an HLB greater than 8, being 3 to 15% when the active substance is an antimicrobial agent, where the ratio PS/(EMP+AE) is between 1.2 and 7.5, where the percentages are given as a percentage by weight in relation to the total weight of the layer (w/pt). 2. Film according to claim 1, characterized in that the PS content is 64 to 70% (in w/pt), the EMP content is 16 to 30% (in w/pt) and the PS ratio /(EMP+AE) be between 1.5 and 4.4. 3. Film according to any one of claims 1 or 2, characterized in that it is selected from the group consisting of ethylene vinyl acetate copolymer (EVA), ethylene methyl acrylate copolymer (EMA), ethylene ethyl acrylate copolymer ( EEA), ethylene ethyl butyl acrylate (EBA) copolymer and mixtures thereof. 4. Film, according to claim 3, characterized in that EMP is EVA. 5. Film according to any one of claims 1 to 4, characterized in that PS is the only polystyrene in said at least one layer. 6. Film according to any one of claims 1 to 5, characterized in that PS comprises PS with an MFI (Melt Flow Index) between 10 to 40 g/10 min at 200 °C and 5 kg (PS1) and/or PS with an MFI of 2 to 5 g/10 min at 200 °C and 5 kg (PS2). 7. Film according to any one of claims 1 to 6, characterized in that EMP comprises EMP with an MFI between 15 to 50 g/10 min at 190 ° C and 2.16 kg (EMP1) and/or EMP with an MFI from 2 to 5 g/10 min at 190 °C and 2.16 kg (EMP2). 8. Film according to any one of claims 1 to 7, characterized in that the content of the active substance in said at least one layer is 0.5 to 6% (in w/pt). 9. Film according to any one of claims 1 to 8, characterized in that the emulsifying agent is selected from the group consisting of polyethylene glycol 400 dioleate, polyoxyethylene(20)sorbitan monolaurate, polyoxyethylene(20)sorbitan monopalmitate, monopalmitate polyoxyethylene(20)sorbitan monostearate, polyoxyethylene(20)sorbitan monostearate, polyoxyethylene monoxide(20)sorbitan Tristearate, polyoxyethylene(20)sorbitan monooleate, polyoxyethylene sorbitan monooleate, polyethylene 40 stearate, sorbitan monolaurate and mixtures of the same. 10. Film according to claim 9, characterized in that the emulsifying agent is polyoxyethylene sorbitan monooleate. 11. Film according to any one of claims 1 to 10, characterized in that the active substance is an antioxidant agent and the emulsifying agent content is 0 to 5%, preferably 0 to 3%. 12. Film according to any one of claims 1 to 11, characterized in that the substance is an antioxidant and is selected from the group consisting of tocopherol, green tea extract, olive leaf extract, rosemary extract, seed extract grape extract, coffee extract, dehydrated acerola, citrus extract with a flavonoid concentration greater than 45%, tomato extract with a lycopene concentration greater than 5%, fruit extract, thymol and mixtures thereof. 13. Film according to claim 12, characterized in that the antioxidant agent is tocopherol or green tea extract. 14. Film according to any one of claims 1 to 10, characterized in that the active substance is an antimicrobial agent and the emulsifying agent content is 3 to 12%, preferably 5 to 10%. 15. Film according to any one of claims 1 to 10 and 14, characterized in that the active substance is an antimicrobial agent and this is an antibacterial agent selected from the group consisting of anhydrous sodium acetate, nisin, lysozyme, Ag and their salts, Zn and its salts, ethyl Nα-dodecanoyl-L-arginate (LAE), salts thereof, LAE hydrochloride, glycolipid biosurfactants and mixtures thereof. 16. Film according to claim 15, characterized in that the antibacterial agent is LAE hydrochloride. 17. Film according to any one of claims 1 to 10 and 14, characterized in that the active substance is an antimicrobial agent and this is an antifungal agent selected from the group consisting of C8-C10 mono, di, triglycerides, monolaurin ., nisin, lysozyme, glycolipid biosurfactants, LAE and its salts, LAE hydrochloride and mixtures thereof. 18. Film according to claim 17, characterized in that the antifungal agent is C8 -C10 mono-, di-, tri-glycerides or LAE hydrochloride. 19. Film according to any one of claims 1 to 18, characterized in that the migration agent is selected from the group consisting of erucamide, oleamide, glycerol monostearate (MG), zinc stearate, waxes and mixtures thereof, being preferably MG and/or erucamide. 20. Film according to any one of claims 1 to 19, characterized in that it is monolayer. 21. Film according to any one of claims 1 to 19, characterized in that it is multilayer. 22. Film according to claim 21, wherein the film is characterized by comprising at least one layer according to any one of claims 1 to 19 and at least one layer without active substance. 23. Film according to claim 22, characterized in that it comprises three layers, wherein each of the two outer layers is a layer, according to any one of claims 1 to 19, and wherein the intermediate layer is a layer without substance. 24. Film according to claims 22 or 23, characterized in that the layer without active substance comprises crystalline polystyrene and high impact polystyrene. 25. Film according to claim 24, characterized in that the layer without active substance comprises 60 to 90% crystalline polystyrene and 10 to 40% high impact polystyrene. 26. Slice separator film characterized by comprising a film according to any one of claims 1 to 25. 27. Food wrapper or packaging characterized by being manufactured from or comprising a film, according to any one of claims 1 to 25. 28. Use of a film according to any one of claims 1 to 25, characterized in that it is intended for packaging food or as a food slice separator. 29. Method for producing a film, according to claim 1, characterized by comprising the following steps: a) providing a polymer composition comprising: - 60 to 75% (in w/pt) PS, - 10 to 35 % (w/pt) EMP a comonomer content of 15 to 40% w/wEMP, - an active substance selected from the group consisting of an antioxidant agent and an antimicrobial agent, - 0.5% to 2% ( in w/pt) of AdM, - 0 to 15% (in w/pt) of AE, with an HLB greater than 8, being 3 to 15% when the active substance is an antimicrobial agent, in which the ratio PS/( EMP+AE) is between 1.2 and 7.5; and b) forming a film with at least one layer comprising the polymeric composition of a). 30. Method according to claim 29, characterized in that the emulsifying agent and the active substance are added to the composition of a) in the form of a concentrate or master batch. 31. Method according to claim 29 or 30, characterized in that the film is formed by coextrusion, blow extrusion, double or triple bubble film extrusion, flat or cast film extrusion, thermoformed, laminated or blow molded.