WO2023004523A1 - Biodegradable, antifungal coating for liner or kraft paper, corrugated cardboard and waterproof corrugated cardboard box comprising same, suitable for the transport of fresh fruit, especially grapes and berries - Google Patents

Abstract

The present invention relates to a biodegradable antifungal coating comprising an emulsion of a polymer selected from a copolymer of ethylene and poly(vinyl alcohol) (PVOH) and a volatile antimicrobial agent selected from cinnamaldehyde, for application to liners (Kraft paper) used to manufacture corrugated cardboard and corrugated cardboard containers or boxes for the transport and sale of fresh fruit, specifically for grapes and other berries sensitive to the action of Botrytis cinerea, without affecting the recyclability thereof, and a waterproof corrugated cardboard container or box comprising same.

Description

BIODEGRADABLE ANTIFUNGAL COATING FOR KRAFT PAPER OR LINER, CORRUGATED CARDBOARD AND WATER-RESISTANT CORRUGATED CARDBOARD BOXES, WHICH INCLUDE IT, USEFUL FOR TRANSPORTING FRESH FRUITS, ESPECIALLY, GRAPES AND BERRIES FIELD OF THE INVENTION

The present invention relates to food packaging. In particular, the packaging of fresh fruits, in a biodegradable container, with mechanical resistance for handling, stacking, transport, storage/collection in high humidity conditions, typical of the distribution chains of fresh fruit and vegetable products with an internal coating comprising a volatile natural antifungal agent, which allows extending the shelf life of fresh fruit sensitive to Botrytits cinerea, especially grapes and berries, and paper I inerque comprising said coating, corrugated cardboard comprising said liner with coating and corrugated cardboard box comprising said liner with covering. The biodegradable antifungal coating comprises an emulsion of a polymer selected from copolymer of ethylene with poly(vinyl alcohol) (PVOH) and a volatile antimicrobial agent selected from cinnamaldehyde, to be applied on liners (kraft paper), corrugated cardboard and corrugated cardboard boxes. , especially, that are used for the manufacture of corrugated cardboard containers or boxes. BACKGROUND

Food packaging has as one of its objectives, to position quality food in the market. To meet this objective, it is necessary to select the most suitable material to obtain a packaging system for the specific food. In the case of fresh fruits such as: grapes, berries and others, one of the main requirements that packaging materials must meet is, on the one hand, providing adequate mechanical resistance during handling, stacking, transport and storage, and , on the other hand, to deal with the main mechanism of deterioration, which determines the useful life, and which, in these products, is through contamination by fungi, and in the specific case of grapes it is due to the attack of Botrytis cinerea . As a consequence of high humidity in the distribution chain, an environment conducive to the development of unwanted microorganisms is generated, producing irreversible alterations and for the deterioration of the mechanical properties of corrugated paper and cardboard. For this reason, you must address the problem by addressing solutions for packaging material as well as for the protection of fresh fruit.

The commercialization of fresh fruits is carried out in corrugated cardboard boxes, which have properties suitable for the demands of use and present a competitive advantage over other materials, for example, plastic, due to its lower environmental impact, as it is a packaging material. from natural renewable sources and be a recyclable, biodegradable and compostable material. The main problem associated with paper and cardboard containers is related to their hygroscopicity, since they absorb moisture and lose their resistance. during the distribution chain, in addition to favoring the growth of fungi (Botrytis cinerea) in fruits such as grapes or berries, reducing their useful life.

It should be noted that the hydrophilic nature of cellulose, the base material of corrugated cardboard boxes for fresh fruits, especially for export, limits the water vapor barrier properties, which, in turn, negatively affects the mechanical properties of the boxes. Corrugated cardboard. The hydroaffinity and porosity of the substrate can pose challenges in controlling the absorption and transport of water, gases and oils, particularly for packaging purposes. Control over the wetting and barrier properties is relevant to preserve the shape and mechanical properties of the package by limiting the swelling of the fiber and the loss of quality of the packaged products during the stages of the distribution chain. These functionalities can be achieved by internal sizing or treating the paper with external barrier coatings, or on the corrugated box directly.

Currently, the coatings used to control the moisture barrier property and water absorption of papers are petroleum-derived polymers, including polyolefins, waxes, ethylene vinyl alcohol (EVOH), polyvinylidene chloride (PVDC), which provide a significant barrier. against water and oxygen permeation for food packaging materials. Although surface hydrophobicity is improved by employing these polymers, they are not favored due to limitations in fossil petroleum resources, poor recyclability, and environmental concerns about non-biodegradable waste generated.

On the other hand, the use of cinnamaldehyde has been recorded since ancient Egypt as flavorings and spices (Cocchiara, J., Letizia, CS, Lalko, J., Lapczynski, A., & Api, AM (2005). Fragrance material review on cinnamaldehyde. Food and Chemical toxicology, 43(6), 867-923). This essential oil was used in volumes of 2 to 12 μL, with percentages of microbial inhibition of 81.72% to 100%. The suggested mechanism of action of cinnamaldehyde against Botrytis cinerea being the inhibition of cell wall biosynthesis, membrane function and specific enzymatic activities (Di Pasqua, R., Betts, G., Hoskins, N., Edwards, M., Ercolini, D., & Mauriello, G. (2007).Membrane toxicity of antimicrobial compounds from essential oils.Journal of agricultural and food chemistry, 55(12), 4863-4870;Di Pasqua, R., Hoskins, N., Betts, G., & Mauriello, G. (2006). Changes in membrane fatty acids composition of microbial cells induced by addiction of thymol, D, limonene, cinnamaldehyde, and E in the growing media. Journal of agricultural and food chemistry, 54(7), 2745-2749.; Gilí, AO, & Holley, RA (2006a). Disruption of Escherichia coli, Listeria monocytogenes and Lactobacillus sakei cellular membranes by plant oil aromatics. International journal of food microbiology, 108(1 ), 1-9, Gilí, AO, & Holley, RA (2006b). Inhibition of membrane bound ATPases of Escherichia coli and Listeria monocytogenes by plant oil aromatics. International journal of food microbiology, 111 (2), 170-174; Shreaz, S., Wani, WA, Behbehani, JM, Raja, V., Irshad, M., Karched, M., ... & Hun, LT (2016). Cinnamaldehyde and its derivatives, a novel class of antifungal agents. Phytotherapy, 112, 116-131). In addition, a recent study reported evidence that cinnamaldehyde disturbs calcium [Ca ²⁺ ] homeostasis. Functionally, Ca ²⁺ regulates several cellular processes, such as sporulation, spore germination, hyphal branching, tip growth, and structural differentiation (Hu, L, Wang, D., Liu, L, Chen, J. ., Xue, Y., & Shi, Z. (2013). Ca ²⁺ efflux is involved in cinnamaldehyde induced growth inhibition of Phytophthora capsici. PloS one, 8(10), e76264; Courchesne, WE, Tune, M., & Liao, S. (2009). Amiodarone induces stress responses and calcium flux mediated by the cell wall in Saccharomyces cerevisiae. Canadian journal of microbiology, 55(3), 288-303; Heusinkveld, HJ, Molendijk, J., van den Berg, M., & Westerink, RH (2013). Azole fungicides disturb intracellular Ca ²⁺ in an additive manner in dopaminergic PC12 cells. Toxicological Sciences, 134(2), 374-381; Liu, S., Hou, Y. , Liu, W., Lu, C., Wang, W., & Sun, S. (2015). Component of the calcium- calcineurin signaling pathway in fungal cells and their potential as antifungal targets. Eukaryotic cell, 14(4) , 324-334).

To inhibit the growth of Botrytis cinerea in fresh fruits, different solutions are also applied, such as incorporating modified atmosphere packaging - which implies a higher cost, or incorporating sulfur dioxide generators - which in many countries is prohibited due to the allergen condition. of sulfur dioxide.

Among the patent documents that address this or other similar problems, is the US patent No.:8268391B2 (Lifschitz Yakov Mark Nanotech Industries Inc) refers to a method for manufacturing a biodegradable nanocomposite with cellulose nanoparticles to form a protective coating on natural materials. One of its objectives is to form a protective coating layer on a biodegradable natural material, providing waterproofing properties and resistance to grease. It only focuses on improving mechanical properties and does not address improving coating properties to combat biofouling.

WO20170106984 (Universidad de Santiago de Chile) refers to a film for packaging fruit or vegetables that comprises a polyolefin-based polymeric matrix that incorporates an antimicrobial active agent (biocide or fungicide) of essential oil selected from the group consisting of: carvacrol, cinnamaldehyde, cineole, sabinene, thujaplicin or a mixture thereof. It proposes treatments to improve both the water barrier properties and the antifungal properties, however, conventional materials that are neither recyclable nor biodegradable are used.

CA2935497A1 (Western Michigan University Research Foundation WMURF) relates to a chitosan coating for paper and board and the method of using it as a surface coating or pulp additive to improve the properties of paper and board products. Furthermore, it shows methods for obtaining unique chitosan compositions from chitin and chitosan-containing fungal biomass. Addresses the improvement of water barrier and antifungal properties, from coatings for cardboard containers. material is used biodegradable, which needs to be in direct contact with the fruit or the packaged product to develop antifungal properties, unlike essential oils that generate an atmosphere due to their volatility, so with this material direct contact is not needed to provide said improvement. Then, the antimicrobial effect of this proposal is exerted only on that fruit or section of the fruit that is in direct contact with the container, however, this is only a section of the fruit and in the case of fungal growth, it develops. in the internal part of the berries (or berries) that are not in direct contact with the container.

MX368720 (Universidad Autónoma De Nuevo León) refers to an edible formulation to coat and extend the shelf life of fruits and vegetables based on chitosan and nanocapsules of essential oil from Lippia berlandieri (oregano). It focuses on protecting fresh fruit from damage due to humidity and other environmental conditions on the shelf and not for transport.

CL2019002215A1 (Universidad de Santiago Chile) refers to an antimicrobial active container for fresh vegetables or fruits, preferably berries, comprising a partial or total interior coating of water-soluble polymer containing cinnamaldehyde and linalool and one or more surfactants, method of preparation and use to extend their useful life avoiding damage and deterioration by microorganisms, preferably Botrytis cinerea. It does not refer to the water resistance of the container.

WO20180010038 (Moser Rossel Roberto) refers to a multilayer structure with antimicrobial properties that comprises at least one polymer sheet, where the last sheet, which remains as the interior of the multilayer and in contact with food, is an antimicrobial polymer sheet that eliminates microorganisms on the surface of the food in contact with it. The antimicrobial effect is exerted only on that fruit or section of the fruit that is in direct contact with the container, however, this is only a section of the fruit and in the case of fungal growth, this develops in the internal part. of the berries (or berries) that are not in direct contact with the container.

WO1997047702A1 (Alcell Technologies Inc.) relates to a vapor barrier formulation suitable for coating and lamination onto a substrate paper and comprises lignin in a dispersion, mica and latex, and is recyclable. It only focuses on improving mechanical properties and does not address improving coating properties to combat biofouling.

EP2609252A1 (Basf SE) refers to a single or multiple corrugated cardboard gummed on one or both sides and preparation method, where at least one of the upper or corrugated folds is a paper film composite comprising: i) a material of paper that has a grammage of 30 to 600 g/m ² and ii) a biodegradable plastic coating that is 1 to 100 pm thick. Preferably, the paper material is an outer layer and an inner layer and the biodegradable plastic coating is an intermediate layer. Thus, a corrugated cardboard is obtained with surfaces comparable to paper, but resistant to water and oil with high moisture resistance and easy to recycle. The structural reinforcement sits within the composite and improves barrier properties such as resistance to moisture, water vapor, oil, among others. The plastic coating is selected from one or more polymers selected from: aliphatic-aromatic polyester, aliphatic polyester, polylactic acid, polyalkylene carbonate, polycaprolactone, and polyhydroxyalkanoate, and a selection of natural polymers. The paper film composite is prepared by laminating preheated paper webs with a plastic film, optionally with the aid of a laminating adhesive. Alternatively, the coating is prepared by extrusion, where the biodegradable plastic is applied in a hot melt. It does not refer to antifungal properties.

US20100051674A1 (Cascades Canada ULC) refers to a composite material that is water repellent and has gas barrier properties and comprises a core portion and a face member attached to one of the surfaces of the core portion. The core portion has wood fiber based on a geometric pattern structure defining two substantially spaced apart planar surfaces and including a hydrophobic additive. The face member has a wood fiber based linerboard including a hydrophobic additive and a nylon coating film on one surface of the linerboard. A polymeric water vapor barrier layer is located between the linerboard and the nylon cover film. The nylon coating film is applied to the outer surface of the linerboard. The wood grain is based on a geometric pattern structure selected from a honeycomb or corrugated shape. The composite material is useful for packaging applications and, more particularly, it is substantially water repellent and has gas barrier properties and can be used for the manufacture of containers, such as containers for perishable goods, facilitating their storage and transport from the site of production to that of consumption. The water repellent properties protect the container against infiltration of liquids and water vapor, among others. It also has gas barrier properties that prevent infiltration and odor release. It is lightweight, low cost, recyclable, repulpable, and with adequate mechanical properties. The nylon coating film is applied to the surface of the linerboard so that one side is substantially water repellent; and attaching the face member to a surface of a core portion having wood fibers based on a geometric pattern structure, which is substantially water repellent. The nylon cover film is extruded. The hydrophobic agent is added on the paper making machine or sizing press. Alternatively, a sizing agent may be added between at least two plies of a linerboard for the manufacture of the geometric pattern structure and face member. Alternatively, it comprises applying an adhesive to at least one face member and the core portion and thus bonding them together. It does not refer to antifungal properties.

WO2020241417A1 (Daio Seishi KK) refers to a liner for board with at least an upper surface layer containing 80% by mass of softwood artisanal pulp, a sub-surface layer containing 25-25% by mass of softwood artisanal pulp and pulp of cardboard waste paper and a back surface layer containing 30-70% by mass of cardboard and magazine waste paper pulp. The proportion on a weight basis of the top surface layer to the overall, on a weight basis is 20-35%, and the gust rate in the atmosphere at 80% RH and 60°C is greater than or equal to 3.45 kPa ^* m ² /g. It does not refer to antifungal properties. US7927458B2 (International Paper Co) refers to paper and board and process for preparing it, which incorporates a composition of one or more hydrophobic polymers where the ratio by weight of starch to polymer is selected such that the paper and board exhibit an equal Cobb value or less than 25 and a contact angle equal to or greater than 128 ^e . The paper or cardboard comprises a network that includes cellulose fibers and the aforementioned composition where the hydrophobic polymer is selected from alkylated melamines, paraffin wax, polyurethane, polyethylene and polymethyl methacrylate. Alkyd melamine contains an alkyl moiety that is linear or branched and has at least 7 carbon atoms. Alternatively, the composition comprises a sizing agent which may be selected from starch, and the network may include expandable microspheres. It does not refer to antifungal properties.

W02020056124A1 (SM Tech Holdings LLC) refers to an adjustable method of treating cellulosic materials with a barrier coating comprising: a prolamine and at least one polyol fatty acid ester that provides increased resistance to oil and grease without sacrificing biodegradability. The method proposes to adhere the barrier coating on articles comprising cellulosic materials. Materials thus treated have increased lipophobicity and can be used in applications for the treatment of materials containing cellulosic compounds to render them hydrophobic/lipophobic and provide barrier coatings that are used in replacement of known prolamin solvents or plasticizers, and prolamins, Useful for modifying the surface of cellulose-based materials, including paper, cardboard, and packaging products. Prolamins are selected from the group consisting of zein, hordein, gliadin, kafirin, and combinations thereof. The polyol comprises a carbohydrate or a mono-, di- or trisaccharide, or sucrose or lactose. The fatty acid is an unsaturated fatty acid. Optionally and additionally, it comprises one or more of polyvinyl alcohol (PVOH), polylactic acid (PLA), clay, talc, precipitated calcium carbonate, ground calcium carbonate, natural and synthetic latex, glyoxyl, and combinations thereof. The fatty acid may be obtained from a natural source, including an oilseed, which in turn may be selected from soybean, peanut, rapeseed, barley, canola, sesame seed, cottonseed, palm kernel, grapeseed, olives, marigold, copra, corn, coconut, flaxseed, hazelnuts, wheat, rice, potatoes, cassava, legumes, camelina seeds, mustard seeds, and combinations thereof. The article may be selected from a paper, cardboard, paper pulp, carton or food storage bag, shipping bag, coffee or tea container, tea bag, bacon board, barrier/blocking film or cloth of weeds, mulching film, pot for plants, among others. It does not refer to antifungal properties. US7427444B2 (Wacker Chemical Corp) relates to a cellulosic product such as a coating composition for paper comprising aqueous-based semi-crystalline ethylene-vinyl acetate polymer emulsions containing crystalline ethylene segments, which are useful for imparting oil resistance , grease, solvent, water and steam. Polymer emulsions are prepared via aqueous-based free radical direct emulsion polymerization of ethylene with various other co-monomers. It can be used directly as a paper or cardboard coating to print resistance to oil, grease, solvents, water and water vapor, and it is repulpable. The polymer coating comprises: an ethylene vinyl acetate polymer comprised of crystalline ethylene segments prepared by aqueous emulsion polymerization of ethylene and vinyl acetate in the presence of a stabilizing agent consisting essentially of a surfactant or a protective colloid in combination with a surfactant, said ethylene vinyl acetate polymer, having: (a) a crystalline melting point in the range of 35 to 110°C. measured at a heat rate of 20°C per minute; and,

(b) a storage modulus of stress of at least 1 x ^{10 5} dynes/cm ² at a temperature of 115°C and measured at 6.28 rad/sec. It does not refer to antifungal properties.

WO2019160429A1 (Ulti Forms Corp) refers to paper products that could be made into bags, wrappers, receptacles, cups, boxes, or the like. The paper is coated with an oil and water resistant coating. Allows the use of heat seal bonding adhesives or the use of ester-styrene copolymer. It is safe for contact with food, compostable and recyclable. In particular, it is a barrier coating for cellulosic substrate with resistance to water and grease, even at 160 °C ^, comprising hydrolyzed polyvinyl alcohol, a metal salt of fatty acid, a crosslinking agent, and water-dispersible hydrophobic polyester resin. water. It does not refer to antifungal properties.

US20080003384A1 (Polymer Ventures Inc) refers to a method for improving the gas, water, water vapor and/or grease resistance of a porous material comprising treating the material with a first treatment with an agent followed by the application of wax and poly (vinyl alcohol) and optionally a polyamine. Also, the multilayer porous material obtained from said method is disclosed, and includes paper, asphalt, wood, textiles, among others. In the case of paper, it is selected from cardboard, bakery board or sweets, butter or margarine chips, among others. The first treatment agent comprises a fluorochemical compound or a polymeric binder. The polymeric binder can be selected from poly(vinyl alcohol), polyacrylate, polystyrene/polyacrylic copolymer, cellulose derivative, nitrocellulose, vinyl chloride, protein, starch, among others. Likewise, the first treatment may also comprise one or more pigments, minerals, organic opacants, lubricants, starch, saturants, rheology modifiers, dispersants, plasticizers, and insolubilizers. The plasticizer may be selected from dioctylphthalate, tricresyl phosphate, castor oil, and mixtures thereof. The mineral may be selected from calcium carbonate, titanium dioxide, kaolin, clay, montmorillionite clay, gypsum, or a mixture thereof. The wax can be selected from wax animal, vegetable wax, synthetic wax or a mixture thereof. The poly(vinyl alcohol) is selected from hydrolyzed, fully hydrolyzed, partially hydrolyzed or intermediate hydrolyzed poly(vinyl alcohol). The polyamine comprises one or more of polyoxyalkyleneamine, polyoxyalkylenediamine, polyoxyalkylenetriamine, or an amine-aldehyde condensate that is the product of the reaction of an amine containing an active hydrogen atom and an aldehyde. KR101769000B1 (Adams Company; Yejin Communications Co., Ltd) refers to an antimicrobial coating composition containing an antimicrobial agent and method for preparing it. The coating comprises 1 to 20% by weight of an inorganic antibacterial agent, which in turn comprises 50 to 95% by weight of a silicate mineral, 1 to 40% by weight of mineral clay and 1 to 10% by weight of a metal ion. It does not refer to a volatile natural antimicrobial agent.

ES2405360T3 (Kemira Oyj) refers to a method for preventing or retarding bacterial sporulation in a waste paper system on a machine to produce paper or board that comprises reducing the level of transition metals in the waste paper by chelation. It does not refer to volatile natural antifungal agents.

CN111497409A (MYS Group Co ltd) refers to Glue Starch Antibacterial Mildew Proof Corrugated Paper and Preparation Method, comprising in % by mass: 9-13% Octyl Isothiazoline, 13-18% nano zinc oxide , 8-12% emulsion and water. Starch glue is prepared from cassava flour, mold preventative, caustic soda, a stabilizer, a strong adhesive, and water. Corrugated paper comprises a surface layer, a middle layer, and an inner layer. The paper has excellent waterproof effect and broad-spectrum high-efficiency antibacterial effect, and absorbs moisture in high-temperature and high-humidity environment, maintaining cushioning and wet effect and compressive strength. It does not refer to a volatile natural antifungal agent.

CA1185031A (Okayama Paper Mill Co Ltd Unitika Ltd) refers to adhesives prepared by dissolving polyvinyl alcohol, a filler and a water-soluble boron compound. These adhesives are "cold set", they are liquid at a temperature of 60°C or more but do not lose their fluidity when cold gelatinized at a temperature greater than 20°C, they are very useful for cold corrugated systems. The adhesive essentially consists of polyvinyl alcohol, a filler, a water soluble boron compound and water, are mixed at a weight ratio of 20/80 to 70/30 polyvinyl alcohol to filler, and the amount of soluble boron compound in water it is from 0.2 to 4 parts by weight per 100 parts by weight of polyvinyl alcohol plus filler, the filler being able to be an inorganic filler, which in turn can be selected from clay, titanium dioxide, aluminum hydroxide, sulfate barium, calcium sulfate, magnesium oxide and magnesium hydroxide, among others. It does not refer to a volatile natural antifungal agent.

CN111206457A (Huang Xiying) refers to a waterproof and stain resistant corrugated carton and a preparation process thereof. The corrugated cardboard box is formed by gluing surface paper, inner paper, core paper and corrugated paper. processed into corrugated corrugations. The surface paper, inner paper, core paper and corrugated paper processed into corrugated corrugations are each coated with a stain resistant water resistant emulsion layer before bonding to form a stain resistant film layer waterproof; The stain resistant water resistant emulsion comprises the raw materials in percent by mass: 8 to 12 percent waterproof stain resistant agent, 25 to 30 percent methyl acrylate, 5 to 8 percent methyl methacrylate. methyl, 10 to 15 percent ethyl acrylate, 3 to 5 percent initiator, 0.5 to 1.2 percent emulsifier, and balance deionized water; then stain resistant waterproof corrugated cardboard is obtained by bonding, pressing, cutting and binding, it has good waterproof, antibacterial and stain resistant properties, and is relatively practical. It does not refer to a volatile natural antifungal agent.

US20200370244A1 (Mitsubishi HiTec Paper Europe GmbH) refers to a barrier paper having a paper substrate with a front and a back side, with a barrier substrate on the front side having a polymeric binder and a vegetable oil-based wax. The paper is useful as a wrapper, liner, internal packaging bag, interleaved paper, separating bakery products, fried products, snacks, sandwiches, hamburgers, meat products, fish and cured meats and/or cheese, and a manufacturing method. The vegetable oil based wax is selected from one or more of palm, coconut, poppyseed, olive, flaxseed, soybean, marigold, safflower and rapeseed oil. The mass fraction of the wax in the barrier layer is at least 6 to 98% based on the total weight of the barrier layer. Preferably said ratio is 20 to 90%, 50-59% or 20-78%. The polymeric binder is selected from starch, unmodified or modified polyvinyl alcohol, carboxyl ethylene-vinyl alcohol copolymer, or a combination of polyvinyl alcohol and ethylene-vinyl acetate copolymer, acrylate copolymer, unmodified or modified polyethylene glycol, a-isodecyl- ω-Hydroxy-poly(oxy-1,2-ethanediyl), styrene-butadiene latex, styrene-acrylate polymers and mixtures thereof. The acrylate copolymer is selected from methyl acrylate, methyl methacrylate, butylacrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, and styrene. The barrier layer further comprises a wax based on saturated hydrocarbons selected from at least one alkane selected from the group consisting of heneicosane, docosane, tricosane, tetracosane, pentacosane, hexacosane, heptacosane, octacosane, nonacosane, triacontane, hentriacontane, dotriacontane, tritriacontane, tetratriacontane , pentatriacontane, hexatriacontane, heptatriacontane, octatriacontane and nonatriacontane. It may further comprise an interlayer disposed between the paper substrate and the barrier layer. The selected barrier coating of a wax emulsion is applied to one side of the paper substrate, where substrate and barrier can be pre-prepared, and dried, and optionally an interlayer is first provided between the paper substrate and the layer of barrier. CN105780591 A (Zhejiang Jinchang Specialty Paper Co Ltd) refers to a method for the manufacture of vegetable/fruit preservative paper, comprising adding water for modulation in an appropriate amount of mesoporous silica as an immobilizing enzyme carrier, adding glucooxidase, transferring the liquid mixture to a constant temperature water bath device for adsorption; add glutaraldehyde to cross-link, centrifuge, wash substances adhering to a centrifuge wall, centrifuge again, spill, and repeat the operation more than two times to immobilize the glucoxidase; add water therein, add polyvinyl alcohol, polyether, carboxymethyl cellulose or a mixture of polyvinyl alcohol, polyether and carboxymethyl in any ratio as an adhesive, and a small amount of thickening agent, and mix evenly to obtain a coating; gum the surface of the piece of the substrate paper with the cover. Glucoxidase reacts with oxygen to generate gluconic acid and hydrogen peroxide in the presence of glucose. Oxygen removal and hydrogen peroxide generation play a sterilizing role. Thus, the wax-coated corrugated box was the solution in decades past, and currently, the use of wax is not accepted due to recyclability problems with wax-coated boxes. Furthermore, as published by Boxes, corrugated packaging (https://www.corrugated.org/recycling/recyclable-waxalternatives/), wax coatings do not dissolve in water, creating problems in the repulping process, to which they are subjected. recovered cartons for recyclability. This problem influences the percentages of recycled cardboard required in countries with regulations in this regard. Other information published by the Corrugated packaging Alliance (https://www.corrugated.org/recycling/recyclable-wax-alternatives/) indicates that the use of wax in 2018 has decreased by 45.9% since 2002.

Therefore, the existing solutions for the problem of loss of resistance and biological contamination that require the application of wax coatings must be overcome, which is currently not accepted by many legislations, which is very relevant. in fresh fruit exports since the material cannot be recycled, which is often a priority for the countries of destination. While, for the latter, to avoid biological contamination, in some countries, the application of sulfur dioxide is prohibited due to its allergenic condition.

In addition, there are currently treatments that improve the water barrier properties with the use of coatings in corrugated cardboard containers, although few use environmentally friendly materials, and there is a greater number of treatments that incorporate active agents - In general, essential oils, to the coatings of corrugated cardboard boxes or fruit containers to control biological contamination, however, there are no solutions that integrate both treatments in the same coating on corrugated cardboard containers and that use essential oils or recyclable and biodegradable materials. Taking into account the aforementioned characteristics and that were pending until the present invention, a corrugated cardboard container or box is provided that, together, shows desirable recyclability properties, inhibition of undesirable microbial action in food for human or animal consumption , and resistance to humidity. In particular, a corrugated cardboard box is provided with a coating based on a water resistant and antifungal emulsion against Botrytis cinerea, which reduces the absorption of moisture from the paper/cardboard, the losses of mechanical properties in the distribution chain and also decreases the incidence of appearance of Botrytis cinerea in fresh fruit packaged in corrugated cardboard box covered with said emulsion. This corrugated cardboard box is recyclable, biodegradable and compostable, and maintains its resistance to mechanical compression in high humidity conditions. Likewise, the antifungal biodegradable coating comprises an emulsion of a polymer selected from ethylene copolymer with poly(vinyl alcohol) (PVOH) and a volatile antimicrobial agent selected from cinnamaldehyde, to be applied on liners (kraft paper), and corrugated cardboard comprising said l//ier with coating and corrugated cardboard box comprising said liner with coating

Thus, the present invention refers to an active paper liner with low moisture absorption, for the export of fresh fruits, where the barrier function against moisture and mechanical resistance in high humidity conditions is complemented by the antifungal function against Botrytis cinerea, and the loss due to biological contamination of the packaged product.

In particular, the present invention relates to a paper with an active coating of 2-8 g/m ² , preferably 4-6 and even more preferably 4 g/m ² , of a biodegradable and recyclable polymer (PVOH/cinnamaldehyde) that manages to preserve the quality of fresh fruit and maintain for a longer time the properties of mechanical compression resistance in conditions of high humidity and low temperature in accordance with the mechanical, biological and environmental demands required of a liner, or layer of paper for cardboard, especially, corrugated cardboard, with which a corrugated cardboard box is manufactured comprising said liner with a coating for the transport of fresh fruit and vegetable products.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1. Shows a schematic of a prototype of a corrugated cardboard box comprising said liner with the present interior lining.

Figure 2. Shows diagram of corrugated cardboard box K1/P2-F (active box).

Figure 3. Graph shows permeation control paper and coated paper.

Figure 4. Sample setup of in vitro antifungal assays of volatile antifungal agent.

Figure 5. Shows water vapor permeability test scheme.

Figure 6. Shows a photograph of an active corrugated cardboard box to scale.

Figures 7A-7C. It shows photomicrographs of emulsion prepared at different times. Fig. 7A: 15 minutes, Fig. 7B: 30 minutes and Fig. 7C: 60 minutes.

Figure 8. Shows photomicrographs of the prepared emulsion. Figure 9. Shows a photomicrograph of an emulsion with problems stabilizing.

Figures 10A and 10B. They show scanning electron micrographs of 170 gram Kraft paper (PK 170, also known as K1).

Figures 11A and 11B. Scanning electron micrographs of K1 paper (or PK 170) with P2 are shown. Figures 12A and 12B. They show paper scanning electron micrographs K1 with P2 and F with 200x. Figure 13. Shows the in vitro antifungal assay setup of the volatile antifungal agent.

Figures 14A-14D. They show emulsions at different agitations 500 RPM (Fig. 14A), 750 RPM (Fig. 14B), 1000 RPM (Fig. 14C) and 1250 RPM (Fig. 14D).

Figures 1SA-15C. They show in vitro tests at different concentrations of F. Fig. 15A: Plate without active agent, control. Fig. 15B: Plate with half active agent, 0.151 µL/crrr. Fig. 15C: Plate with active agent, 0.302 mL/cm ³ .

Figures 16A-16H. They show the growth of Botrytis cinerea at 5 days, 7 days, 14 days and 30 days, in control plates (Figs. 16A-16D) and iiner plates with polymer and natural antifungal agent (K1-P2-F, Figs. 16E -16H).

DETAILED OF THE INVENTION

The present invention refers to a biodegradable antifungal coating for Kraft or Liner paper, corrugated cardboard and corrugated cardboard boxes, which comprises an emulsion of a biodegradable polymer and a volatile natural active agent with antifungal properties, especially against Botrytis cinerea, a fungus that attacks preferably grapes and other berries, and that allows the elaboration of liner with coating, and corrugated cardboard with liner comprising said coating and corrugated cardboard boxes comprising said liner with coating, hydro-resistant for packaging fresh fruit and showing less loss of properties in the distribution chain at high humidity conditions. This coating for liner kraft paper, corrugated cardboard and corrugated cardboard boxes has water resistant, antifungal properties and is recyclable.

In particular, the present coating comprises a biodegradable polymer selected from a copolymer of ethylene with poly(vinyl alcohol) (PVOFI, P2) that incorporates a natural volatile antimicrobial agent selected from cinnamaldehyde, and which is classified as GRAS or generally recognized as safe, for be applied on liners (kraft paper), corrugated cardboard and corrugated cardboard boxes, which in turn are used for handling, stacking, transportation, storage, distribution and marketing of fresh fruits, especially grapes and other berries sensitive to the action of Botrytis cinerea, without affecting the recyclability of the final container or the organoleptic properties of the product. In addition, Kraft paper, corrugated cardboard, and recyclable coated corrugated cardboard box do not present changes in color that devalue it, and that could occur due to the presence of the coating with volatile natural antifungal agent.

The present invention deals with the loss of mechanical properties of corrugated cardboard boxes due to the absorption of humidity typical of the cellulosic base material, from a recyclable system that can be compared with existing wax solutions applied to different papers. In addition, the present invention adds a volatile natural antifungal oil, which inhibits the growth of Botrytis cinerea in fresh fruits, presenting an advantage over modified atmosphere packaging systems that are more expensive or incorporate sulfur dioxide generators. , prohibited due to its allergen status in many countries.

It should be noted that the materials that make up the entire coating and the final corrugated cardboard box, such as paper of natural forest origin and PVOH (hereinafter, it refers to the copolymer of ethylene with poly(vinylalcohol)) are biodegradable and recyclable. PVOH is recognized as one of the few water-soluble vinyl polymers that is also susceptible to ultimate biodegradation in the presence of properly acclimatized microorganisms Thus, the present invention comprises a formulation with specific components, in an application that effectively addresses the impact environment by using materials that are biodegradable and recyclable.

The present invention refers to a biodegradable polymeric coating selected from a copolymer of ethylene with poly(vinylalcohol) (PVOH, P2) that incorporates a volatile natural antimicrobial active agent (F), selected from cinnamaldehyde, to be applied on liners (kraft paper ), and corrugated cardboard and corrugated cardboard boxes comprising said coated liner used for the handling, stacking, transport, storage and distribution of fresh fruits, and specifically for grapes and other berries sensitive to the action of Botrytis cinerea, without affecting to the recyclability of the final container.

The biodegradable polymeric coating of the present invention for kraft liner paper, corrugated cardboard and corrugated cardboard boxes, comprises: a biodegradable polymer and a natural and volatile antifungal active agent, which when applied allows obtaining a kraft paper with water-resistant, antifungal and recyclable to be used as packaging in the distribution chain of fruit and vegetable products. See Figures 1 and 2.

Tests related to the inhibition of the growth of Botrytis cinerea were carried out in an in vitro compatibility test of the antimicrobial agent with the polymer; coating and characterization of the paper; water vapor permeability of the coated liner; water absorption; mechanical test on paper, ring crush test (RCT); optical properties (color); growth inhibition of Botrytis cinerea in in vivo assay; sensory analysis and in vivo testing of fresh fruit packaged in a corrugated cardboard box comprising a coated liner; among other.

A considerable decrease in permeability (47.12%) was observed when coating the Kraft paper (K1) with the biodegradable polymeric coating (P2). However, this decrease in permeability is not observed when coating the paper with a mixture of the polymer P2 and an active agent F (coating K1/P2-F), decreasing to 16.175%. Without being bound by theory, this would be because the active agent F is a volatile compound that leaves gaps in the coating. once volatilized, which can be best observed by scanning electron microscopy (SEM).

The present invention differs from others close to the prior art in that it addresses the antifungal properties, the resistance to humidity of the material, the mechanical properties and the recyclability properties, simultaneously, to obtain a product that shows all these properties at the same time. While prior art solutions address these properties and other parameters separately. The present biodegradable coating for liner paper, and corrugated cardboard and corrugated cardboard boxes provides water resistant and antifungal properties to corrugated cardboard boxes. .The aforementioned properties have been shown through permeability tests (desiccant method), in vitro, in vivo tests (at scale and under accelerated conditions) and mechanical resistance tests (RCT), mainly. The detail and general experimental design of these results are presented below:

1 ) Improvement of the water vapor barrier of the coated liner compared to an uncoated control. The water vapor permeability was determined according to the ASTM E96 standard by the desiccant method. The test was performed at 37.8°C under 95% relative humidity (RH) in permeability cells with 5.5 cm ² of exposed film surface. In this test a stainless steel container with 7.0 grams of silica gel was sealed with the sample film, adding silicone grease to achieve its adhesion to the edge. Two rings were placed on the film, one made of rubber and the other made of steel, which were secured with screws (Figure 5).

The different containers were placed in a desiccator set to 95% relative humidity and stored in an oven (Memmert, Schwabach, Germany) at 37.8°C. Each container was massed daily and the mass difference data over time were plotted to find their relationship through linear regression. The water vapor transmission rate was calculated using Equation 1:

WVT=(G/t)/A Equation 1 where G/t corresponds to the slope obtained through the graph of change in mass versus time and A is the area of the exposed sample.

On the other hand, Table 2 below shows the results obtained from the permeation of the untreated liner (K1), the coated liner P2 (K1/P2) and the coated liner plus the active agent F (K1 /P2-F). Figure 3 shows these data in a bar graph. The results obtained show the hydroresistant properties of the P2 polymer, either by itself or with the addition of the antifungal active agent F.

2) Improvement of the mechanical resistance of the coated liner compared to the uncoated control.

The maximum resistance of the paper to crushing was measured, according to the TAPPI 818 sp-07 standard at 50% ± 2.0% HR and 23.0 ± 1.0°C for day zero and at 90% ± 2.0% HR on days 2, 4 and 7 conditioned in the Barnstead air conditioner, analyzing the mechanical behavior of the coated papers over time under refrigeration conditions. 40 specimens were cut from 1 .27 x 15.24 cm (0.5 x 6 inches) per sample with a guillotine and left acclimating according to the day to be evaluated.

Table 4, included below, shows the results obtained by subjecting uncoated liner paper (K1) as a control, with P2 coating (K1/P2) and with coating plus active agent (K1/P2-F), under the previously mentioned conditions. described according to the TAPPI 818 cm-07 standard. This test was carried out in a Zwick Roell universal testing machine (model Allround Line Z005).

The results of the aforementioned Table 4 show that the incorporation of the coating in liner paper improves its mechanical properties with respect to crushing, either based on the polymer alone or with the addition of the active agent under high humidity storage conditions.

3) Effect of the coated liner in fruit packaging regarding the growth of Botrytis cinerea in vivo and on the sensory properties of the fruit.

An in vivo test was carried out simulating the packaging conditions of export grapes in 8.2 kg cardboard boxes at scale. These boxes were scaled to 25% of the real size, obtaining a template that was printed on the liner paper in a laser printer, to print 18 boxes (9 controls and 9 actives). Each paper box was assembled and glued with transparent super strong glue to a 12.5 x 10 cm corrugated cardboard base to reinforce its base. The assembled paper box is shown in Figure 6.

The paper boxes were placed in jacket bags, which have perforations for ventilation regulated by the USDA-APFIIS regulation. The shirt bags used were obtained from the manual perforation of 16.5 cm x 14.9 cm bags, following the aforementioned regulation.

137 grams of grapes were massed in each paper box and infected grapes were incorporated in the center so that a Botrytis cinerea nest could grow, to which 10 μL of a 1,2- Botrytis Cinerea spore solution was applied. 10 ⁶ spores/mL in a cut previously made.

One control liner paper prototype box and one coated liner box of the present invention were randomly selected every 15 days and both healthy and infected grapes in each box were massed and fungal contamination was measured by visual observation.

Table 6, included below, shows the data obtained in this test. A reduction in Botrytis cinerea infection was observed, expressed as the percentage (%) of inhibition, which increases from 13.59 (day 15) to 26.28 (day 30), showing the inhibitory potential of the active agent F, since it inhibits the growth of the fungus, even in the forced conditions in which it is carried out, that is, in much more suitable conditions for infection than those usual for shipping fruit in boxes.

4) Effect of the coated liner in fruit packaging on sensory properties of fresh fruit. A sensory test is carried out, in which 78 judges participate, 31 designated the grape sample from the covered corrugated cardboard box as the most intense (spicy aroma) according to the UNE-ISO 5495 standard.

Example 1. In vitro test

With this assay, the antifungal capacity of the antimicrobial agent is shown. On the lid of the Petri dish, a filter paper disc with a diameter of 2.5 cm is placed on which known quantities of the volatile natural antifungal agent F are deposited homogeneously. use (Figure 4).

The concentration of volatile active agent, necessary to inhibit the growth of Botrytis cinerea, called Minimum Effective Concentration (MEC) of a volatile compound against a fungus in solid medium, was studied. 3 μL of the fungus were seeded with a concentration of 10 ⁶ spores/mL at three equidistant points on the PDA plates. The plates were sealed with parafilm to prevent leakage of the volatile active agent from the edges. All experiments were carried out in triplicate. In parallel, a control was prepared with the same spore suspension without the active agent.

The plates are sealed with parafilm to prevent leakage of the active agent/volatile antifungal agent around the edges. All experiments are carried out in triplicate. The plates are incubated for 7 days at 22°C (see Fig. 15A-15C). The growth diameter of the fungus is measured over time and the inhibition percentage with respect to the control plate (without active agent/antifungal agent) is calculated. In particular, Fig. 15B shows an inhibition of 9.159 ± 5.897% with respect to the growth of the control plate.

Thus, once the emulsion of polymer P2 and active agent F was prepared, the in vitro test verified the effective antifungal activity of the coating. 3 μL of suspension of 10 ⁶ spores/mL were deposited at 3 equidistant points on the PDA agar in the lower zone of the plate. A sheet of the coating of the present invention is adhered to the upper part via coating (Figure 13), and the concentration of active agent/antifungal agent necessary to inhibit the growth of Botrytis cinerea or Minimum Effective Concentration (MCE) was calculated. In parallel, a control was prepared with the same spore suspension without the active agent. Both conditions were incubated at 20°C for 7 days. Figures 16A-16H show how the active agent F on paper allows growth inhibition at days 5, 7, 14 and 30 days (Figures 16E to 16H) versus the same days compared to a control (Figures 16A to 16D ).

This assay made it possible to determine the in vitro effectiveness of the coating P2 and the active agent F, which in this case was 100%, totally inhibiting the growth of the Botrytis cinerea fungus. After obtaining the minimum effective concentration (CME) of active agent from the in vitro test, the CME was calculated for the in vivo test with respect to the effective volume of air surrounding the grapes within the proposed system of boxes and bags.

The Figs. 15A-15C show that a minimum concentration must exist in the headspace of the plate for the inhibition of Botrytis cinerea to be effective. Example 2. Compatibility with the polymer

PVOH was used as the polymer, which already registers hydroresistance and its compatibility with cinnamaldehyde was evaluated. The stability of the emulsion was evaluated by observation under a microscope. Risch (1988) (Risch, S. J.; Reineccius, G. A. Spray-dried orange oil: effect of emulsion size on flavor retention and shelf stability. In Flavor Encapsulation; Risch, S. J., Reineccius, G. A., Eds.; ACS Symposium Series 370; American Chemical Society: Washington, DC, 1988; pp 67-77) which states that smaller droplets are more physically stable than larger emulsion droplets, so the chosen preparation time was 60 min of agitation. Solutions were prepared maintaining the concentration of volatile active agent, necessary for it to maintain its antifungal activity to evaluate the stability of the emulsion after 15, 30 and 60 minutes, after its preparation. Figures 7A-7C show photomicrographs of the emulsion prepared after 15, 30 and 60 minutes.

To prepare the coating, the following were studied: agitation times and use of surfactants, to achieve a homogeneous emulsion, and thus avoid phase separations such as those shown in Figure 8, which would cause the active agent F to stain the paper after coating. be applied. It is also necessary to evaluate the storage of the solution, observing that it does not separate in at least 24 h. See Fig. 9.

A 15% w/V PVOH (P2) solution was prepared at 90°C for 2 hours. Upon cooling, the volume of the volatile antifungal agent, cinnamaldehyde (10 mL of 15% w/V P2 + 361.5 μL cinnamaldehyde were prepared) was added directly to it and stirred for one hour. After this, the kraft paper was covered.

With constant stirring for one hour, the drop size was reduced, without adhering to any theory, this would be caused by the fact that P2 is a copolymer of ethylene with poly(vinyl alcohol), therefore it has hydrophobic sites related to the active agent molecule is oily in nature, so it is enough for them to stabilize without the need to use a surfactant. On the other hand, the hydrophilic sites of the polymer adhere to the hydroxyls of the cellulose molecules present in the liner paper, corrugated cardboard and corrugated cardboard box. Regarding the stirring speed (RPM), the reported 15% PVOH solution was stirred at a speed of 1250 rpm for 1 hour, and emulsion stability tests were performed only by varying the stirring speed. Figs. 14A-14D. It is observed that at the initially set speed (1250 rpm), a homogeneous emulsion is formed that presents a better disposition of the drops formed than at lower speeds.

The PVOH solution concentration was 15% like that of Christophiemk, et. al, 2017 (Christophliemk, H., Uilsten, H., Johansson, C., & Járnstróm, L. (2017). Starch-poly (vinyl alcohol) barrier coatings for flexible packaging paper and their effects of phase interactions. Progrese in Grganic Coatings, 111 , 13-22, & Christophliemk, H, Johansson, C., Uilsten, H., & Járnstróm, L. (2017) Oxygen and water vapor transmission rates oí starch-poiy (vinyl alcohol) barrier coatings for flexible packaging paper. Progress in Organic Coatings, 113, 218-224.), regarding the use of PVOH as a coating for packaging paper. But unlike the mentioned publication, in the present invention it does not need starch or any other additional polymer (using only PVOH) to make the coating. Furthermore, the concentration used is based on independently conducted tests.

Example 3. Coating and characterization of paper

Coating tests were carried out with an RK PRINT K303 unit at a speed of 5 m/min with the coating bar no. 2 and drying at room temperature. With a sheet size of 60 x 40 cm of Kraft paper (170 g/m ² ), obtaining grammage and thickness of control papers (K1), which refers to uncoated paper and papers only coated with polymer (K1/P2) and coated. with polymer emulsion with active agent (K1/P2-F). The results are shown in Table 1 .

Table 1 . grammage obtained.

It is observed that the grammage of both coatings does not exceed 5 g/m ² , which confirms properties for industrial use, in the preparation/manufacturing of cardboard boxes, preferably corrugated cardboard boxes, for fresh fruit, especially for export. .

When adding volatile active agent, the grammage did not vary significantly, however, the thickness of the coating decreases, due to the difference in the penetration of the emulsion coating compared to only the polymer. Similar results were observed by (Nowacka, M., Rybak, K., Wiktor, A., Mika, A., Boruszewski, P., Woch, J., Przybysz, K., & Witrowa-Rajchert, D. (2018 ). The quality and safety of food contact materials-paper and cardboard coated with paraffin emulsion. Food control, 93, 183-190) when applying the emulsion coating only a slight increase in thickness was observed.

Example 4. Permeability to water vapor

Table 2 shows the results obtained from the permeation of the untreated Kraft liner paper (K1), coated Kraft liner paper P2 (K1/P2) and coated liner plus active agent F (K1/P2-F). . Figure 3 shows these data in a bar graph. A considerable decrease in permeability (47.12%) is observed when coating the K1 paper with the P2 coating. However, this decrease is not preserved when coating the paper with a mixture of the polymer P2 and the active agent F (decreasing to 16.175%).

Table 2. Permeation to water vapor and percentage of variation with respect to the control.

An important factor is that the container to be developed is resistant to water vapor. The ability to prevent or at least reduce moisture transfer between food and the atmosphere in the surrounding area is critical to maintaining food quality and safety (Khwaldia, K., Basta, A. H., Aloui, H., & El-Saied, H. (2014).Chitosan-caseinate bilayer coatings for paper packaging materials.Carbohydrate polymers, 99, 508-516). The transport properties of coated packaging materials are influenced by the type of coating material used, the composition and the thickness of the coating (Tihminlioglu, F., Atik, í. D., & Ózen, B. (2010). Water vapor and oxygen-barrier performance of corn-zein coated polypropylene films.Journal of Food Engineering, 96(3), 342-347). Table 2 and Figure 3 (bar graphs) show the permeation of coated paper and control paper.

The test was performed at 37.8°C under 95% relative humidity (RH) in permeability cells with 5.5 cm ² of exposed film surface. In this test, stainless steel containers with 7.0 grams of silica gel were sealed with the sample film, adding silicone grease to achieve rim adhesion. Two rings were placed on the film, one made of rubber and the other made of steel, which were secured with screws.

The different containers were placed in a desiccator set to 95% relative humidity and stored in an oven (Memmert, Schwabach, Germany) at 37.8°C. Each container was massed daily and the mass difference data over time were plotted to find their relationship through linear regression.

Example 5 Water absorption test (Cobb)

The Cobb test was performed, according to the TAPPI 441 om-13 standard with samples pre-conditioned at 50% ± 2.0% RH according to the TAPPI 402 sp-13 standard. This test measures the amount of water absorbed by the paper in a time of 180 s, which allows knowing the water absorption per square meter of the paper. Next, Table 3 shows the results obtained by subjecting the control paper (K1), the coated paper (K1/P2) and the paper with P2 coating and active agent F (K1/P2 - F), to the test. of Cobb, determining the water absorption of each sample for each square meter.

Table 3. Water absorption of paper.

This test shows that the addition of the P2 coating does not provide significant barrier properties to water absorption. Also, it is observed how the addition of cinnamaldehyde active agent means a considerable increase in water absorption, compared to the control paper (K1) and with coating (K1/P2), without adhering to any theory, due to the fact that the active agent /antifungal agent (F), is a volatile compound that would leave gaps in the coating once volatilized. Said behavior is shown in the results of scanning electron microscopy (SEM) tests.

Example 6 Edge crushing (Ring Crush Test).

Table 4 shows the results obtained by subjecting K1 paper with and without P2 coating under the previously described conditions according to the TAPPI 818 cm-07 standard. This test was carried out in a Zwick Roell universal testing machine (model Allround Line Z005).

Table 4. Maximum force (N) of paper subjected to refrigeration conditions (2°C and 90% RH) for 2, 4 and 7 days, with and without P2 coating

It is observed that both the control and the coated paper, when subjected to high humidity, lose resistance to compression. In both cases, a decrease was observed as time increases in high humidity conditions, which responds to the expected trend. In general, the mechanical properties of laminated or coated films in a composite structure are controlled by the base film or substrate (Hong, S. I., Lee, J. W., & Son, S. M. (2005). Properties of polysaccharide-coated polypropylene films as affected by biopolymer and plasticizer types.Packaging Technology and Science: An International Journal, 18(1), 1-9). When performing the paper compression test using the ring test (RCT), it was observed that for the K1 paper under normal conditions (day 0), the maximum force supported was 295.95 ± 18.65 N, higher in a 25.4% to the force resisted by its control under the same conditions (220.28 ± 18.08 N). This trend is maintained over the days, varying between 24% and 32% increase in the maximum force supported by the coated paper. It is estimated that this sustained difference is due to the fact that the P2 coating gives the paper greater resistance to humidity, compared to the control, better supporting refrigeration conditions.

Example 7: Optical properties: Color

It was measured in order to evaluate the color changes produced by the paper coating. Six samples of each paper were analyzed in a CR-410 Minolta Chroma Meter, using the CIELab scale, measuring the luminosity (L ^* ) and chromaticity (a ^* and b ^* ). Table 5 shows the results of the optical properties of the active paper only in the case of the paper coated by emulsion of P2 and F caused by a slight decrease in luminosity and a slight increase in yellow and red coloration barely perceptible by the human eye, in all other samples there is no change in coloration.

Table 5. Optical properties of active K1 paper.

Example 8 Structural Properties: SEM

Figures 10A and 10B show the SEM micrographs of uncoated paper, where the porosity of the fibers could be observed.

It was observed in Figures 11 A and 11 B that when applying the coating of 4 g/m ² of P2 the surface becomes smoother and more uniform, which may explain the decrease in the water permeability of this coating. Surface micrographs show a homogeneous and relatively regular coating filling the pores of the cellulosic fibers. This can increase the resistance to water vapor and decrease the roughness of the paper. This smooth surface corroborated the results obtained in water permeability, this was also observed by (Flan, JH, & Krochta, JM (2001). Physical properties and oil absorption of whey-protein-coated paper. Journal of food Science, 66 (2), 294-299).

In Figures 12A and 12B, the scanning electron micrograph of the polymer with the active agent F is shown, in this case the polymer P2 with the active agent/antifungal agent F, being of different natures, forms an emulsion where the active agent remains. (oil) encapsulated in small droplets. This oil, being of a volatile nature, without proper storage, would volatilize leaving small holes, which can be seen in the right micrograph (Fig. 12B) with a higher magnification, where a homogeneous droplet size and good dispersion were observed. .

Example 9. In vivo test

An in vivo test was carried out simulating the packaging conditions of export grapes in 8.2 kg boxes at scale. The 8.2 kg box of grapes was scaled to 25% of actual size using Solid Works software. The assembled box is shown in Figure 6. 18 boxes (9 controls and 9 active) were prepared. In each box, 137 grams of grapes were packed in each box (organic grapes grown without the use of fungicides) and an infected grape was incorporated in the center so that a Botrytis cinerea nest could grow. These grapes were previously inoculated by making a cross cut in the peduncle with a sterile scalpel, applying 10 μL of a Botrytis cinerea spore solution at 1.2-10 ⁶ spores/mL to the cut, and then placing 2 grapes in each chamber. moist for 48 hours at 20°C. The boxes with grapes were stored refrigerated with a average temperature of 5 ± 2°C and with 54 ± 3% relative humidity (RH) average. The above conditions were used in order to carry out an accelerated shelf life study because the actual storage conditions of these fruits are 0°C and 90% RH. After 15 days of refrigeration, the organoleptic properties of the packaged grapes will be evaluated, according to the UNE-ISO 5495 standard. Evaluating the perception of strange aroma by means of the comparison in pairs.

The results obtained in the in vivo test are presented below. The temperature and humidity of the refrigerators where the samples are stored are monitored every 3 days by means of a thermohygrometer. Table 6 and Table 7 show the data obtained in this test.

Table 6 shows the results obtained in the in vivo test.

Table 6. Percentage of inhibition in boxes evaluated on days 15 and 30.

Table 6 shows a reduction in Botrytis cinerea infection, expressed as the percentage (%) of inhibition, which increases from 13.59 (day 15) to 26.28 (day 30), showing the inhibitory potential of the active agent F, since it inhibits the growth of the fungus, even under forced conditions in which it is carried out (average temperature of 5 ± 2°C and with 54 ± 3% relative humidity (RH) average), that is, in much more suitable conditions for infection than the usual ones for shipping fresh fruit, in cardboard boxes. Table 7. Percentage of dehydration of stored grapes.

For the time of decrease in the inhibition of Botrytis cinerea in vivo and in vitro, the effectiveness of the volatile natural antifungal agent was studied in vitro for 30 days, evaluating the growth at days 5, 7, 14 and 30 without growth. on the active paper plate on any of these days. On the contrary, in the control plate there is already a growth halo the size of the plate on day 7.

Due to the fungicidal action of F, which inhibits cell biosynthesis, it is established that its action is decisive in the elimination of Botrytis cinerea, leaving for granted its reappearance in samples exposed to this active agent (Shreaz, S., Wani, WA Cinnamaldehyde and its derivatives, a novel class of antifungai agents. Phytotherapy, 112, 116-131). It is necessary to emphasize that the tests carried out show that the control designed only with kraft paper or only with polymer-coated kraft paper - and, in both cases without active agent, the growth of Botrytis cinerea is not affected to any degree, growing is tai as in the aforementioned controls.

Example 10: Replication of the test in vivo

Using the same methodology previously described in the previous example, the in vivo tests were repeated whose compared results are shown in the following Table 8:

Table 8. Comparative result of in vivo tests

In addition, an in vivo test number 4 was carried out, evaluating the useful life of the fruit, day by day and visually, determining that the grapes packed in cardboard boxes covered with P2-F, are considered infected on day 12, that is, they lasted 3 days longer than the control, giving it a 33% longer useful life.

Example 11 Sensory analysis

This test was carried out to determine the probability of similarity or difference between samples, using a one-sided pairwise comparison test designed based on the International Standard ISO 8587:2006. In this case, the objective is to determine if the amount added exceeds the maximum amount of agent so that the aroma of spice is with a reference product without the barely perceptible ingredient, and therefore does not have unfavorable consequences on the fresh fruit.

For this trial, a total of 78 untrained consumer judges were considered for a total of a couple, where one specimen corresponds to the control and the other to an active one. Each sample consisted of 130 grams of grapes packed for 30 days under refrigerated conditions in a prototype-scale box. At the time of the evaluation, a grape cut into 8 parts was packaged in a closed jar, covered and labeled with its respective coding.

Each judge was asked to select the sample with the highest intensity of the selected attribute, in this case the aroma of spices, even if the choice is a guess.

In testing, 31 judges designated Prototype Sample 1 the most intensely spicy. In table A.3 "Maximum number of correct or agreed answers necessary to conclude that two samples are similar, based on the pairwise comparison test" of the International Standard ISO 8587:2006, it can be seen that for n = 78 (number of judges) and for a pd of 20% and a b of 0.05, the maximum value to conclude that the samples are similar is 39. The response number is less than this value shows that there is a similarity between the samples, and the concentration of agent asset is apt to be accepted as an acceptable and tolerated value. Then, there is no undesirable effect on the flavor of the fruit, which alters the consumer's perception of the fruit, thus maintaining its quality and preference in the purchase.

Example 12 Other tests

Other polymers with the same active compound were tested, achieving a high inhibition of Botrytis cinerea but mixed results of hydroresistance and water vapor permeability, for which they were not used:

12.1 Polymer P1 (zein):

It is a sigma analytical polymer, soluble in a high ethanol:water ratio. The coating caused a decrease in water permeation by 4%. In the case of mechanical properties, 40% more was observed in the maximum resistance on the seventh day of refrigeration measured by RCT. But, it is discarded for safety reasons, as it is an organic solvent. Characterization:

12.1.1. Compressive mechanical resistance test (RCT)

Table 9. Maximum force (N) of K1 paper subjected to refrigeration conditions (2°C and 90% RH) for 2, 4 and 7 days, with and without P1 coating

Each value represents the mean of 10 replicates with its respective standard deviation.

On day 7, P1 showed a 40% increase in maximum resistance (247.18 ± 25.43 N) compared to Control (177.65 ± 12.86 N).

12.1.2. Water vapor permeation test Table 10. Water vapor permeation

Despite the fact that the coating with P1 decreases the water vapor permeation (by 4.14%), but for safety in the industry, it was discarded because it is only soluble in 70% ethanol and is not soluble in water. .

12.2 Polymer P3 (pea protein): The effects caused by this protein applied at 8 g/m ² increased water vapor permeation by 4%, however, the compressive strength is 15% higher than the control paper under refrigeration conditions.

Characterization: 12.2.1. Compressive mechanical resistance test (RCT)

Table 11: Maximum force (N) of K1 paper subjected to refrigeration conditions (2°C and 90HR) for 2, 4 and 7 days, with and without P3 coating

Each value represents the mean of 10 replicates with its respective standard deviation.

On day 7, P3 shows a 15% increase in maximum resistance (204.75 ± 17.00 N) compared to Control (177.65 ± 12.86 N).

12.2.2. Water vapor permeation Table 12: Water vapor permeation

P3 does not provide barrier properties to water vapor, increasing permeation by 4.47%, then it is discarded because it does not meet the desired properties.

12.3 Polymer P4 (chitosan):

Caused a decrease in water vapor permeation of 11%

Characterization:

12.3.1 Water vapor permeation Table 13: Water vapor permeation

P4 provides barrier properties to water vapor, but its very high value makes it not feasible.

12.4 Polymer P5 (starch)

It does not cause significant changes in the mechanical resistance of the paper, nor decrease in permeation.

Characterization: 12.4.1 Compressive mechanical resistance test (RCT)

Table 14: Maximum force (N) of paper subjected to refrigeration conditions (2°C and 90% FIR) for 2, 4 and 7 days, with and without P5 starch coating

Each value represents the mean of i Ó replicates with its respective standard deviation.

P5 shows on day 7, a significant change in the maximum resistance (176.01 + 17.81 N) with respect to the Control (177.65 + 12.86 N).

12.4.2 Water vapor permeation Table 15. Water vapor permeation

P5 does not provide barrier properties to water vapor, increasing permeation by 37.31% and, consequently, it is discarded.

12.5 Polymer P6 (gelatin)

It can be said that in the case of K1, P6 managed to maintain mechanical resistance under humidified conditions.

Characterization:

12.5.1 Mechanical resistance to compression test (RCT)

Table 16: Maximum force (N) of paper subjected to refrigeration conditions (2°C and 90HR) for 2, 4 and 7 days, with and without P6 coating

Each value represents the mean of i Ó replicates with its respective standard deviation.

P6 shows on day 7, an increase of 11.03% in maximum resistance (197.25 + 16.21 N) compared to Control (177.65 + 12.86 N) but it was discarded because it requires temperature for its ideal application, and otherwise gels.

In this way, the other polymers tested with the same antifungal agent F, achieved a high inhibition of Botrytis cinerea but varied results of hydroresistance and water vapor permeability: • P1 is a sigma analytical grade polymer, soluble in a high ethanol:water ratio. The coating caused a 4% decrease in water permeation, and a 40% increase in maximum resistance on the seventh day of refrigeration measured by RCT. But for safety reasons it is not recommended to use organic solvents. · P3, the effects caused by this protein applied at 8 g/m ² , increased water vapor permeation by 4%, however, the compressive strength is 15% higher than the control paper under refrigeration conditions.

• P4, caused a decrease in water vapor permeation of 11%.

• P5, does not cause significant changes in the mechanical resistance of the paper, nor decrease in permeation.

• P6, it can be said that in the case of K1, P6 managed to maintain mechanical resistance in humidified conditions. On the other hand, for K2, when day 7 of refrigeration arrives, the resistances are significantly the same.

Claims

1. Coating for Kraft paper or liner, corrugated cardboard, or corrugated cardboard boxes, recyclable, water-resistant and with antifungal properties, characterized in that it comprises an emulsion of a polymer selected from a copolymer of ethylene with poly(vinyl alcohol) (PVOH) and a volatile antimicrobial agent selected from cinnamaldehyde.

2. The coating of claim 1 characterized in that the emulsion comprises 15% w/V PVOH.

3. Corrugated, recyclable, waterproof cardboard with antifungal properties, characterized in that it comprises Kraft paper or liner with a coating comprising an emulsion of a polymer selected from a copolymer of ethylene with poly(vinyl alcohol) (PVOH) and a volatile antimicrobial agent selected from cinnamaldehyde.

4. Corrugated, recyclable, water-resistant cardboard box with antifungal properties for fresh fruit, characterized in that it comprises corrugated cardboard comprising Kraft paper or liner with a coating comprising an emulsion of a polymer selected from a copolymer of ethylene with poly(vinyl alcohol) (PVOH ) and a volatile antimicrobial agent selected from cinnamaldehyde.

5. Use of the coating of claim 1 characterized in that it is used in the manufacture of corrugated cardboard or corrugated cardboard boxes

6. The use according to claim 5, characterized in that said corrugated cardboard box is a recyclable, water-resistant corrugated cardboard box with antifungal properties.

7. The use according to claim 5 or 6 characterized in that said corrugated cardboard box of fresh fruit.

8. The use according to claim 6, characterized in that said corrugated cardboard box is a corrugated cardboard box for fresh fruit selected from grapes or berries or export fruits sensitive to Botrytis cinerea.