MX2014001285A - Compatibilized plastic films for antimicrobial and antioxidant activity. - Google Patents

Abstract

Described is an active packing material with dual antioxidant /antimicrobial characteristics including compatibilizing agents, the material being flexible or rigid, preferably for food or products susceptible to any type of oxidation and or microbial damage, which consists in a system for promoting the migration of the active agent towards the packed product during the storage or marketing thereof, which would increase he useful life thereof and would preserve the quality of the product. The present invention will replace the direct incorporation of antioxidant and/or antimicrobial agents to the products susceptible to oxidation and/or microbial damage. The material is formed by 80% of base polymer, 0.5-10% of GEGC and 0.1-20% by weight of any compatibilizing agent.

Description

PLASTIC FILMS COMPATIBILIZED FOR ACTIVITY ANTIMICROBIAL AND ANTIOXIDANT TECHNICAL FIELD OF THE INVENTION The present invention belongs to the area of active packaging technology using materials incorporated with compatibilizing agents to promote the controlled release of compounds with antioxidant and antimicrobial activity, such as epigallocatechin gallate (GEGC), in order to preserve the quality and extend the shelf life of foods susceptible to oxidation and / or deterioration of microbial origin.

The invention refers to an active material incorporated with a compatibilizing agent for antioxidant and / or antimicrobial packaging, which can be used in a wide range of food products such as: fresh red meat, products of marine origin (fresh and / or frozen) ), foods with a high content of saturated or unsaturated fatty acids (including cosmetics and pharmaceuticals). In general, they are products that have relatively smooth surfaces, which come into contact with the inner surface of the container, although not limited to this type of products.

BACKGROUND The main cause of deterioration in food is due to the presence of microorganisms, which produce low molecular weight compounds responsible for odors and flavors that negatively influence the quality of food. Lipid oxidation is the second cause of deterioration of foods, especially those with high fat content. The oxidation products of fats and oils normally have strong unpleasant odors and flavors, produced by aldehydes, ketones and other compounds formed in the oxidation reactions. The foregoing has the consequence of the loss of the quality and later the decrease of the shelf life of the food products and with this, material and economic losses are also produced.

The use of additives in food is carried out with the purpose of contributing to extend their useful life and improve food safety. An example of additives commonly used are antimicrobial agents, these are intended to inhibit or inactivate the growth of microorganisms of deteriorative and / or pathogenic origin. Antimicrobials can be classified according to their origin, say synthetic or natural. The vast majority of antimicrobial compounds of synthetic origin include organic acids as well as their salts, parabens, sorbates, phosphates, metal ions and nitrates.

The use of antioxidants to control oxidative rancidity has been one of the most used methods in the food, pharmaceutical and cosmetology industry. Traditionally, synthetic antioxidants, such as butylated hydroxytoluene (BHT) and butylhydroxyane (BHA) have been used in foods and polymers. However, due to the growing concern about the use of chemical products in foods and their effects on health, a greater interest has been generated by the use of natural antioxidants such as a-tocopherol and ascorbic acid. However, although the antioxidants mentioned above are effective and safe, they have the disadvantage of rapid degradation in the case of ascorbic acid, and tocopherols do not always provide effective protection, especially when there is contamination with trace amounts of metals (Fe 2+). or Cu 2+).

The FDA considers the active agents of natural origin as GRAS-type substances (Generally Recognized as Safe), among them we can find the GEGC, which is one of the most abundant compounds in green tea and, given its chemical and structural characteristics, presents greater antioxidant activity compared with the other catechins present in it, which results in a good option with potential for industrial and commercial use, as a possible antioxidant of natural origin. Another property that presents this compound is to inhibit the growth of microorganisms both pathogenic and of deteriorating origin.

There are several ways for the application of these compounds in foods, among them is the active packaging. Currently, this food packaging technology has a variety of systems that allow active interaction between the components of the container and the food, helping to slow deterioration processes. The active packaging allows the incorporation of antimicrobials and antioxidants to the packaging material for the gradual release of the compound. This allows reducing the addition of high concentrations of antimicrobials or antioxidants to foods or other susceptible products, which has an advantage over the direct application of the active compounds through the application of immersion or spraying methods to foods.

The antimicrobial packaging has the function of extending the phase of latency or delay, while reducing the rate of growth of microorganisms, this in order to preserve the quality and extend the shelf life of the food. Both safety and food quality are affected by the presence of deteriorating microorganisms and / or pathogens, which is why in vitro studies have been reported where the effectiveness of these systems is evaluated. Weng & Hotchkiss (1993. Anhydrides as antimycotic agents added to polyethylene films for food packaging, Packaging Technology and Science, 6: 123-128.), Developed LDPE-based films whose active compounds were benzoic acid and benzoic anhydride (0.5 - 2%) and evaluated their effect on strains of Rhizopus stolonifer, Penicillium spp. and Aspergillus toxicarius, reporting a null effect from benzoic acid; however, benzoic anhydride (1%) completely stopped the growth of these microorganisms. Vartiainen J, Skytta E, Ahvenainen-Rantala R, Enqvist J. (2003. Antimicrobial and barrier properties of LDPE films containing imazalil and EDTA, Journal of Plastic Film and Sheeting, 19: 249-261) evaluated the antibacterial activity of LDPE films incorporated with sodium nitrate (15%) against strains of Escherichia coli, Bacillus subtilis and Aspergillus niger, reporting only the absence of inhibition halos for the Escherichia coli strain.

Regarding the use of antimicrobial agents of natural origin in containers, Ramos, M., Jimenez, A., Peltzer, M. and Garrigós, MC (2012. Characterization and antimicrobial activity studies of polypropylene films with carvacrol and thymol for active packaging. of Food Engineering, 109: 513-519), evaluated the antibacterial activity of polypropylene films incorporated with thymol and carvacrol (8%) on E. coli, reporting the absence of zones of inhibition, due to the low diffusion of the active compound towards the middle. The aforementioned study exposes the need that exists for the controlled release of the active agents present in this packaging technology.

Because oxidation reactions in packaged foods or products are initiated on the surface, particularly the portion that primarily receives oxygen or light that diffuses through the container wall, systems have been developed where the container as a vehicle for the application of antioxidants, being the synthetic antioxidants the most used. Huang C.H. and Weng Y.M. (1998. Inhibition of lipid oxidation in fish muscle by antioxidant incorporated polyethylene film J. Food Processing Preserved 22: 199-209) produced polyethylene (PE) films added with the synthetic antioxidant butylhydroxytoluene (BHT) in concentrations between 30 and 50% , and evaluated the antioxidant activity in fish fillets during storage at different temperatures, observing a reduction of oxidation in said product. However, due to growing concern about the use of synthetic compounds, active packaging systems with compounds of natural origin have been developed. Barbosa L, Cruz JM, Sendón R., Bernaldo A., Ares A., Castro M., Abad MJ, Maroto J., and Paseiro P. (2013. Development of antioxidant active films containig tocopherols to extend shelf life on fish. Food Control 31: 236-243) developed LDPE films added with 1 and 5% tocopherols, where they evaluated the antioxidant activity in fish muscle.

Finding that the film with 1% presented a reduction of lipid oxidation above 30%, and 40% for the film with 5%. López de Dicastillo C., Gómez J., Catalá R., Gavara R., Hernández P. (2012. Active antioxidant packaging films: development and effect on lipid stability of brined sardines, Food Chemistry 131: 1376-1384) elaborated a container antioxidant active from the incorporated EVOH copolymer with ascorbic acid, ferulic acid, quercetin and green tea extract as active compounds, and its antioxidant effect in brine sardines was evaluated, finding that the green tea extracts provide greater protection against oxidation with respect to the other compounds present in the study. Patent 2009024846 A1 describes the preparation of an antioxidant active container with controlled release of tocopherol towards food products susceptible to oxidation, which consists of a system that promotes the migration of the active component to the packaged product during storage, extending its useful life and maintaining the quality of it.

Due to the above, there is an interest of the food industry to develop containers that have the ability to gradually release antimicrobial agents and / or antioxidants, this being one of the main objectives of the incorporation of compatibilizing agents in active packaging. In a study carried out by López de Dicastillo, C., Castro-López, M., Lasagabaster, A., López-Vilariño, J. M. & González-Rodríguez, MV (2013. Interaction and release of catechin from anhydride maleic-grafted polypropylene films, ACS Applied Materials &Interfaces, 5: 3281-3289) produced polypropylene (PP) and PP films compatibilized with maleic anhydride (PP-). PPgMA) added with green tea extract, where the evaluation of the release of the components of the extract towards different solvents was carried out, it was observed that for the compatibilized film the release was less with respect to the film without compatibilizing.

Recently, the use of this type of compounds in active containers has been evaluated, in order to improve the dispersion and decrease the electrostatic repulsion that occurs between the polymeric material and the active compound. due to load differences, which allows to promote the interaction between both components of the active container. This behavior was observed in a study carried out by Lee and Kim (1997), where the microstructural morphology of a mixture of LDPE and EVOH in a 70:30 ratio was evaluated, with the addition of the maleic anhydride copolymer (LDPE-AM) as a compatibilizer. In the unmatched mixtures large and thick EVOH agglomerates were observed, while in the samples with added LDPE-AM, the dimensions of these aggregates decreased from 5 to 6 times with respect to the sample without compatibilizer, this variation is dependent on the amounts of compatibilizer added. This is explained because the compatibilizer improves the adhesion between the two phases, and consequently a modification in the shape of the agglomerates occurred as the quantity of the LDPE-AM increased, so that the dispersed phase (EVOH) showed greater interaction with the continuous phase (LDPE). Patent US4950541 A describes the preparation of a compatibilizing agent obtained from polyethylene grafted with maleic anhydride. In this patent, the application of the compatibilizer is reported in order to stabilize mixtures of polymeric materials.

As seen above, the use of compatibilizing agents in polymeric mixtures allows a better distribution and greater interaction between immiscible materials. The use of compatibilizing agents in this new technology means an improvement in the distribution of the active component in the polymeric matrix, and with this an adequate release of the active compound towards the food is expected. Different active packages have been developed with the incorporation of compatibilizing agents, as is the case of antimicrobial containers made with polyethylene copolymers with acrylic acid and methacrylic acid and polypropylene antioxidant containers with maleic anhydride; the purpose in the use of compatibilizing agents in these packaging systems has been the improvement of the dispersion of the active compound and increase the affinity with the polymeric material.

In the present invention reference is made to a novel mechanism that gradually releases low concentration of agents with antimicrobial and antioxidant activity. The above is achieved by the use of a compatibilizing agent (LDPE or polylactic acid grafted with maleic anhydride, but not limited to these copolymers) and the active compound.

OBJECT OF THE INVENTION The general object of the invention is based on the development of a container with the dual characteristic of presenting antioxidant and antimicrobial activity, incorporating a compatibilizing agent whose purpose is to promote the release of GEGC.

Another object of the development of the invention is to provide a method for the production of rigid or flexible containers, mainly directed to the food sector, however, due to the general characteristics that it presents, it is possible to use them in products of the industry. pharmaceutical and cosmetological.

Another object of the invention is based on providing a method for the production of a single or multi-layer active packaging material, with the dual characteristic of presenting antioxidant and antimicrobial activity.

The above objects are carried out by producing an active container with the characteristic of presenting antioxidant and antimicrobial activity, which is based on the migration of the GEGC present in the flexible or rigid material towards the food or product susceptible to oxidation and / or microbial deterioration. The release of GEGC is favored by the incorporation of compatibilizing agents (LDPE or APL grafted with maleic anhydride), which have in their structure functional groups related to the antioxidant / antimicrobial agent, which promotes the formation of molecular interactions between both compounds, favoring a better distribution of active agent in the polymeric material and its subsequent release to the product. The controlled migration of the GEGC makes it possible to maintain a constant concentration of the active agent in the product, which represents an advantage over the direct addition of active compounds since it allows reducing the concentration of antioxidant / antimicrobial compound used.

DESCRIPTION OF THE INVENTION The developed materials can be used in monolayer or multilayer containers according to the required application, with the active layer being in contact with the product of interest, promoting the release of the active agent. These containers have the function of actively preserving the conditions of the food, since they are designed to deliberately incorporate active components destined to be transferred to food with the purpose of delaying or preventing the processes that reduce the shelf life of packaged foods, as are chemical processes (lipid oxidation) and / or microbiological. Through the application of the appropriate active packaging system the deterioration of the food can be significantly reduced. The controlled release of the GEGC present in the packaging material towards the food or product susceptible to microbial oxidation and / or deterioration is favored or directed by the incorporation of compatibilizing agents made with LDPE and polylactic acid (APL) grafted with anhydride. maleic or others of similar chemical structure whose use in materials in contact with food is approved for human or animal consumption, by regulatory organizations such as the FDA. The compatibilizing agents have in their structure functional groups related to the antioxidant / antimicrobial agent, which promotes the formation of molecular interactions between both compounds, favoring a better distribution of the active agent in the polymeric material and its subsequent migration to the product. The active agent used in the present invention has the advantage that it has the approval of the US Food and Drug Administration (FDA, for example). its acronym in English) for use in food as a substance GRAS (Generally Recognized As Safe, for its acronym in English).

The materials used in the development of the different flexible or rigid packages were LDPE, APL, and compatibilizing agents based on LDPE and APL grafted with maleic anhydride (PEBDgAM and APLgAM).

The active agent (GEGC) used must be food grade and have a high purity (> 94%). It can be added in the form of an approved concentrate or masterbatch for use in food packaging. The aforementioned active compound is added at the required concentrations to the mixtures of the polymers used (LDPE / PEBDgAM and APL / APLgAM) carrying out a physical pre-mixing process, to be subsequently introduced to the extruder feed hopper . The package can be manufactured by blow extrusion, flat film extrusion, cast molding, and blow molding. The above options consider the process of co-extrusion or lamination in the case of films or multilayer materials. The GEGC molecule is presented below: In order to increase and control the release of the GEGC present in the material, copolymers based on PEBD and APL grafted with maleic anhydride were used as compatibilizing agents, ie they are materials that have segments capable of promoting molecular interactions between the components of a polymeric mixture along the interface, reducing the interfacial tension while increasing the adhesion and dispersion during the mixing of the polymers by converting a polymer mixture into a useful commercial product. The structures of compatibilizing agents based on PEBD (PEBDgAM) and APL (APLgAM) have a hydrophobic part (the polymer chain) and a hydrophilic part (maleic anhydride) as can be seen below: The presence of the hydrophilic portion confers the ability to interact with the active agent and the hydrophobic part with the base polymer used for packaging (LDPE or APL) (Deng, JP, Yang, WT &Ranby, B. ( 2002) Melt-photografting polymerization of maleic anhydride onto LDPE film European Polymer Journal, 38: 1449-1455; Hwang, SW, Lee, SB, Lee, CK, Lee, JY, Shim, JK, Selke, S., Soto -Valdez, H., Matuana, L., Rubino, P. and Auras, R. (2012) Grafting of maleic anhydride on poly (L-lactic acid) Effects on physical and mechanical properties Polymer Testing, 31: 333 -344).

The described systems promote the release of the GEGC towards the product of interest contained in the container, and it is useful in products stored at different temperatures, however, under conditions of cooling and / or freezing the mobility of the compound (GEGC) in the polymer matrix is low. The composition of the active package material (either in its monolayer presentation or the layer intended to be in contact with the food of a multilayer material) is described below. The particular characteristic of this material is the presence of the compatibilizing agent: The materials developed in the present invention comprise flexible, rigid, mono or multilayer containers. Examples of possible applications of the above are rigid containers for storing liquids, such as milk, juice, drugs or cosmetics; In addition to the presentation in films, bags or envelopes composed of one or several layers of polymer, to contain and store solid and fresh foods such as beef, pork, fish and chicken; powdered foods, or prepared as hamburgers and sandwiches.

Other polymers that can be used in the manufacture of the active package according to this invention include low density polyethylene (LDPE, PELDB, metallocene, etc.), high polyethylene (HDPE) or medium density, polypropylene (PP, cast or bioriented) , polyvinyl chloride (PVC), polyvinylidene chloride (PCdC), polyamines (PA), polystyrene (PS, glass or high impact), polyethylene terephthalate (PET or PETG), polylactic acid (APL), among others.

EXAMPLE 1 To demonstrate the effectiveness of the system, the diffusion coefficients (D) of GEGC incorporated into LDPE and APL films in the absence and presence of the compatibilizing agents towards deionized water as a simulant of an aqueous food stored at 37 ° C were determined. The incorporation of the compatibilizing agent produced an increase in the migration rate of the GEGC towards the aqueous food simulant. The D values obtained for the LDPE films were 2.37x1010 and 2.86x1010 cm2 / s in the absence and presence of the compatibilizing agent (PEBDgAM). Regarding the APL films, the D values were 2.52x1010 and 5.03x1010 cm2 / s in the absence and presence of the compatibilizing agent (APLgAM).

EXAMPLE 2 In the evaluation of the antioxidant activity of monolayer films of PEBD added with GEGC to simulants of fatty foods (ethanol 95%) and aqueous (water) during storage at 4 ° C (simulating cooling conditions) for 14 and 28 days, respectively , a greater release of the active compound in the fat simulant was observed, and with it a greater antioxidant activity in this medium with respect to the aqueous. The developed containers had a thickness between 60 and 75 micrometers, and due to the presence of the compatibilizing agent an increase in the release of the compound was observed active towards both simulants of food, and with it a greater antioxidant activity.

EXAMPLE 3 The antibacterial activity of monolayer active films incorporated with GEGC on strains of Staphylococcus aureus and Pseudomonas spp. Was determined. The above was carried out using a liquid test system (culture broth), in order to simulate the activity of the film on a liquid food, the incubation conditions were 37 ° C for 15 hours. The effect of GEGC on bacterial morphology was evaluated, showing an increase in the area of S. aureus, 89.40 and 103.45 pm2 in the absence and presence of APLgAM, respectively. In Pseudomonas spp. a decrease in the length of the cells was observed, losing the bacillus form (obtaining values of 11.95 and 11.78 mm, in the absence and presence of APLgAM respectively). A similar effect was observed in active monolayer films made with LDPE, however the effect was less marked. A slight increase in the area of S. aureus cells was observed, obtaining values of 87.51 and 90.37 pm2 (in the absence and presence of PEBDgAM). In the case of the morphology of Pseudomonas spp. the bacillus form was lost, with a decrease in the length of the cell due to the presence of the PEBDgAM (12.12 and 11.45 pm in the presence and absence of the compatibilizer). The above results indicate that the presence of the compatibilizing agents had an effect on the antibacterial activity of the active films, which coincides with the results obtained in the release of the active compound, since a greater release of the GEGC implies a greater inhibition of growth bacterial.

EXAMPLE 4 The antibacterial activity of the films was evaluated by a direct contact technique, in order to determine its effect on the morphology of the bacterial cells by simulating direct contact with food or products susceptible to microbial spoilage. In relation to the results obtained, only in the APL treatments an effect was presented by the incorporation of the compatibilizer (APLgAM) on the antibacterial activity of the active films. As much of the cells of S. aureus as of Pseudomonas spp., Aggregation was observed in direct contact with the compatibilized films, without finding individual cells. The foregoing indicated that the presence of the active agent potentiated the antibacterial property of the active films.

Once the invention is described, it will be obvious that it can be varied in many ways. These variations should not be considered outside the scope of the invention, and all modifications that are apparent to a person skilled in the art, are considered to be included within the scope of the following claims.

Claims (14)

CLAIMS Having sufficiently described my invention, I consider it a novelty and therefore claim as my exclusive property the content of the following claims:

1. An active packaging material with dual antioxidant / antimicrobial characteristics incorporated with compatibilizing agents comprising at least 80% polymeric substrate to be contacted with a product susceptible to microbial oxidation and / or deterioration, characterized in that it comprises 0.5-10% by weight of GEGC and 0.1-20% by weight of a compatibilizing agent.

2. The active packaging material incorporated with compatibilizing agents according to claim 1, characterized in that the polymeric material is selected from low density polyethylene (LDPE, PELDB, metallocene, etc.), high polyethylene (HDPE) or medium density, polypropylene (PP, cast or bioriented), polyvinyl chloride (PVC), polyvinylidene chloride (PCdC), polyamines (PA), polystyrene (PS, glass or high impact), polyethylene terephthalate (PET or PETG), polylactic acid (APL) , etc.

3. The antioxidant / antimicrobial active container material according to claim 1, characterized in that the active compound GEGC is selected from the catechins of green tea, or another active compound of similar chemical structure, with a purity of at least 94% and of alimentary grade.

4. The material according to claim 1, characterized in that the compatibilizing agent is selected from the copolymer based on PEBD or APL grafted with AM or any other which has a polymeric chain grafted with maleic anhydride or another similar compound, for use in food or products susceptible to oxidation and / or microbial spoilage.

5. The antioxidant / antimicrobial active packaging material according to claim 1, characterized in that it is flexible or rigid.

6. The material according to claim 1, characterized in that it is a mono or multilayer material.

7. The antioxidant / antimicrobial active packaging material according to claim 6, characterized in that it is a monolayer material having a thickness between 60 and 75 micrometers.

8. The active packaging material with dual antioxidant / antimicrobial characteristics incorporated with compatibilizing agents according to claim 6, characterized in that it is a multilayer material and the additional layers are selected from low density polyethylene (LDPE, PELDB, metallocene, etc.), high polyethylene (HDPE) or medium density, polypropylene (PP, cast or bioriented), polyvinyl chloride (PVC), polyvinylidene chloride (PCdC), polyamines (PA), polystyrene (PS, glass or high impact), polyethylene terephthalate (PET or PETG), polylactic acid (APL) or combinations thereof obtained by the coextrusion or lamination process in which the appropriate adhesive has been used for the combination.

9. An active container with dual antioxidant / antimicrobial characteristics incorporated with compatibilizing agents for food or cosmetic products or a pharmaceutical composition susceptible to oxidation and / or microbial deterioration characterized in that it is made from a material according to any of claims 1 to 8 .

10. The active packaging with dual antioxidant / antimicrobial characteristics incorporated with compatibilizing agents according to claim 9, characterized in that the product susceptible to microbial oxidation and / or deterioration is selected from a food, a chemical compound, a cosmetic product or a pharmaceutical composition .

11. A process for the manufacture of an antioxidant / antimicrobial active packaging material, characterized in that it comprises: a) Provide a polymeric composition comprising at least 80% of a polymeric material and forming a surface in contact with a product susceptible to oxidation or microbiological deterioration, of 0.5-10% by weight of GEGC and 0.1- 20% by weight of a compatibilizing agent; Y b) Form mono or multilayer materials from the polymer composition.

12. The process for the manufacture of an active container with dual antioxidant / antimicrobial characteristics incorporated with compatibilizing agents according to claim 11, characterized in that the compatibilizing agent is added in the form of a concentrate or masterbatch.

13. The process for the manufacture of an active container with dual antioxidant / antimicrobial characteristics incorporated with compatibilizing agents, according to claim 11, characterized in that the material can be formed by extrusion-blowing, extrusion-flat film, casting or casting, or molding-spraying .

14. The process for the manufacture of an antioxidant / antimicrobial active packaging material, in accordance with claim 11 characterized in that the active compound is added to the plastic resin by physical pre-mixing, before being formed.