Packaging material that can extend edibility of processed food

Abstract

To provide two-dimensional and three-dimensional food packaging materials that can maintain the freshness of fresh foods or extend edibility of foods by using complex silver anion water together with nonwoven fabrics made of 100% synthetic fibers or 100% polyester fibers and polyester films with highly effective and safe antibacterial functions, and also to provide a product packaging material that can reduce the addition of preservatives for retort foods.MEANS FOR SOLVING THE PROBLEM: A small amount of surfactant with nonionic or anionic hydrophilicity is mixed into 100% synthetic fiber nonwoven fabric as a pretreatment, which is then coated and dried, and then coated with a liquid agent (silver anion water) that contains almost entirely complex silver anions to obtain a packaging material; alternatively, if water-soluble polyester resin and the silver-ion water are mixed and adjusted and coated on the side of polyester nonwoven fabric that comes into contact with retort food, the antibacterial function of the silver anion can be fully utilized, making it possible to at least reduce the amount of preservatives added, contributing to not impairing the flavor of the food, and both of these make it possible to extend food edibility. Also, by laminating a polyester film as the surface material, a three-dimensional food packaging material with waterproof properties can be obtained.

Description

[Technical field] Food waste has become a social issue, which is a particularly serious problem in Japan, where the country has a low rate of food self-sufficiency. This invention relates to a packaging manufacturing technology that can contribute to reducing the economic loss caused by Japan's reliance on imports for much of the food consumed in Japan, and can contribute to the economy.The invention also relates to a food packaging manufacturing method that can suppress the proliferation of microorganisms, which account for the majority of food spoilage and deterioration, particularly bacteria related to food spoilage, using a complex silver anion that does not react with thiol groups derived from cysteine, halogens such as chlorine contained in salt, or organic ions, and has a sustained antibacterial function that can inhibit bacterial proliferation or kill bacteria, extend the edibility of the food, reduce food spoilage and deterioration, and reduce food loss. Furthermore, retort foods can be stored for long periods even at room temperature, but during production, preservatives are added, heat treatment is performed for a certain period of time, or radiation is applied to prevent the food contained therein from spoiling or deteriorating due to microorganisms. However, the addition of preservatives in particular can impair the flavor of the food itself and can also give off an unpleasant odor or taste. This invention relates to a technology for manufacturing food packaging material that solves these problems and can be used for the long-term storage of cooked foods. [Background technology]

[0001] It goes without saying that storage temperature has a major impact on the shelf life of not only fresh foods but also cooked foods. The oxygen in the air also oxidizes food, causing it to spoil. In recent years, vacuum packing technology has come into widespread use as it cuts out oxygen, which is involved in food spoilage, and prevents the growth of aerobic bacteria.

[0002] Condiments such as vinegar, salt, sugar, and spices such as pepper and chili peppers have been used since ancient times to extend the edibility of food in general. However, these not only enhance the flavor of food, but also have a history in food culture of being used to protect the food itself from bacteria that cause spoilage and inhibit bacterial growth, thereby extending the edibility of food.

[0003] Furthermore, in Japan, food has long been packaged in bamboo bark, which has safe antibacterial properties that inhibit the growth of microorganisms other than those mentioned above. This is because the safe natural antibacterial agents contained in bamboo bark reduce the activity of bacteria and inhibit their growth. If artificial, yet safe and inexpensive food packaging materials and containers were to have this function, it would be possible to reduce food spoilage and deterioration, and as a result, contribute to reducing food waste.

[0004] Not only food packaging materials, but also Patent Document 2, which is a prior art document described below, describes a plastic food container made by injection molding, in which flat pure silver-containing powder, which contains a layer of evaporated pure silver sandwiched between polyester resin, is blended with the powder kneaded into the plastic resin, and silver cations are eluted from the powder kneaded into the plastic resin in the moisture contained in the food placed in the container, and if the food contains a small amount of cysteine ​​as a component, or if the protein contained in the food is not all cysteine, the food is sold commercially as being able to extend the life of the food. If a silver-based antibacterial agent is blended into the polymer resin and there is a small amount of moisture in the food, the silver cations will elute through the molecules of the resin, and the antibacterial function will kill or inhibit the growth of bacteria involved in food spoilage, thereby extending the life of the food. In particular, if the silver ions are anionized, they can suppress the reaction with the thiol group contained in cysteine ​​and the precursor methionine, even if the amount varies in all ingredients, and the antibacterial function can be more effectively demonstrated by preventing insoluble silver sulfide formation. Of course, moisture will not leak through containers or lunch boxes that are sprinkled with antibacterial agents.

[0005] The silver ion described in claim 1 is a complex silver anion, and the silver ion that can be dissolved while being evenly mixed in the water-soluble polyester resin described in claim 2 is also a complex silver anion. The silver anion does not react with the thiol group of cysteine ​​or the precursor methionine, and can kill bacteria that cause food spoilage at a lower concentration than silver cations, making it possible to extend the life of food. Foods such as beef, pork, chicken, and fish are mostly made up of proteins, some of which are amino acids. Almost all foods, whether vegetables or fruits, contain cysteine, an amino acid, to a greater or lesser extent, and both fresh foods and cooked foods contain organic ions with negative charges, so the complex silver anion does not react with organic ions and can exert an antimicrobial function, thereby extending the life of cooked foods. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5988476 [Patent Document 2] Patent No. 4175486 Summary of the Invention [Problem to be solved by the invention]

[0007] The problem that this invention aims to solve is, simply put, to provide a two-dimensional food packaging material and a three-dimensional retort food packaging material that have artificial antibacterial properties that far exceed the safe antibacterial properties of traditional Japanese bamboo bark.

[0008] The lightweight nonwoven fabric made of 100% synthetic fiber described in claim 1 is highly hydrophobic and does not mix with the complex silver anion water, which is almost water without any treatment. The water containing the silver anion cannot be absorbed or retained by the anion itself, and almost all of it falls off the nonwoven fabric during the drying process. To prevent this, it is necessary to mix a surfactant that is safe to eat with the complex silver anion water, which has been adjusted to a slightly higher concentration, at just under 1%, to make the silver anion support the nonwoven fabric.

[0009] The lightweight nonwoven fabric made of 100% synthetic fibers that has been treated as described above is cut to the size of the food to be packaged, or slightly larger, and is wrapped in a PVDC film that is prevented from drying so that it is as closely attached to the food as possible, for example, a tuna fillet (product name: Krewrap, manufacturer: Kureha Corporation). The complex silver anions can sterilize the bacteria that cause spoilage on the surface of the tuna, and prolong the discoloration, odor, and edibility of the tuna. Furthermore, the silver anions do not adsorb to the nonwoven fabric made of 100% synthetic fibers, and by closely wrapping the food with the food, the silver anions can migrate to the surface of the food and exert their bactericidal power.

[0010] Next, the problem to be solved by claim 2 will be specifically described below. In order to implement claim 2, it is necessary to limit the substrate to 100% polyester nonwoven fabric. By mixing and blending silver anion water containing complex silver anions with a water-soluble polyester resin liquid approved for use in food packaging materials, a mixture of very weakly viscous water-soluble polyester resin and silver ion water (hereinafter referred to as silver PET resin liquid) in which the silver anion concentration of 0.5 to 1.0 ppm is uniformly dispersed in the resin is obtained, and the water-soluble polyester resin acts as an adhesive between the silver anions and the nonwoven fabric when the mixture is applied to the nonwoven fabric by the above-mentioned coating method. As described in claim 1, there is no need to pretreat the surfactant or dilute the silver anion water, mix it with the surfactant, and apply it. As to which of claims 1 and 2 can realize manufacturing rationality and low cost, it can be said that the latter is superior, considering the cost of the surfactant, the cost of the water-soluble polyester, the pretreatment of the nonwoven fabric, the mixing with the silver anion water, the coating process of the mixed liquid, the mixing of the water-soluble polyester resin and the silver anion concentration, and the coating and drying of the mixed liquid on the nonwoven fabric. In addition, both polyester and silver are included in the positive list under the revised Food Sanitation Law.

[0011] Although 100% polyester nonwoven fabric is like oil and water-soluble polyester is like water, the adhesion between nonwoven fabric made of oil-based polyester fibers and water-soluble polyester resin is very strong, regardless of whether silver anion water or silver anion coating is used, and there is no need to worry about peeling.

[0012] The problem with claim 3 will be specifically described below. As described in claim 2, when applying silver PET resin to polyester nonwoven fabric, it is possible to apply silver anions evenly to the entire nonwoven fabric using known coating methods, and since there is no problem with the adhesion between the nonwoven fabric itself and the water-soluble polyester, it is not difficult to apply the silver anion water and then laminate a waterproof polyester film to one side of the dried fabric. In addition, when the laminated film processed as described in claim 2 is used for retort foods, which can extend the edibility of cooked foods by adding preservatives, it is possible to eliminate or reduce the addition of the preservatives, reduce or eliminate the effect of the preservatives on the flavor of the food, and greatly reduce the odor caused by the preservatives themselves. In addition, the product name and instruction manual can be printed on the laminated film, and since the nonwoven fabric with silver anions is on the inside, there is no need to use a laminated film with a metal layer such as aluminum for the purpose of blocking ultraviolet rays.

[0013] The silver anion concentration is adjusted to 0.5 to 1.0 ppm relative to the solid content of the silver PET resin to obtain a silver PET solution with extremely low viscosity, and the adhesion between the nonwoven fabric obtained by the coating method described above and the polyester film is strong, as both are polyester and there is no effect on the adhesive strength or adhesion. Similarly, the silver ion water is applied to the silver PET solution-coated surface of the polyester nonwoven fabric described above so that it comes into contact with cooked food, and a laminate film of the nonwoven fabric and polyester film is obtained by drying, which is cut to a size appropriate for the packaging material, folded, and bonded on three sides by well-known heat welding, to obtain food packaging materials such as three-dimensional packaging bags and containers that can extend the freshness or edibility of food as described above.

[0014] In addition, preservatives are usually added to retort foods, which can extend the edibility of cooked foods. However, if this food packaging material could be obtained, it would be possible to eliminate or reduce the addition of preservatives, thereby reducing or eliminating the impact on the flavor of the retort foods, and also significantly reducing or eliminating the odor caused by the preservatives themselves.

[0015] Fresh foods are broadly divided into meat, seafood, vegetables, and fruits, and all of these fresh foods contain the amino acid cysteine, although the amount may vary depending on the type of food. Also, cysteine ​​has a functional group consisting of sulfur and hydrogen, called a thiol group, although the amount may vary depending on the type of food. Silver is listed as a food additive in the Food Sanitation Act and is also listed in the positive list of food contact plastics in the revised Food Sanitation Act, but when silver is ionized, it usually becomes a silver cation, which reacts with the thiol group to form silver sulfide, quickly losing its antibacterial function. Water-soluble polyester resin is also listed in the positive list, so there is no problem with safety, and the silver anion does not react with salt, thiol group, or organic ions, and can fully fulfill its antibacterial function, delaying food spoilage and deterioration and prolonging the life of edible food.

[0016] In the silver ion water of Patent Document 1, silver is dissolved by dilute citric acid solvent, but the carboxyl group constituting citric acid is a ligand, and citric acid has three carboxyl groups. The silver ion in the silver ion water becomes a complex silver anion having a negative charge monovalent by a total of two-coordinate bonds between the carboxyl group and the carboxylate anion in which the proton is dissociated. The silver cation is a monovalent cation, but the silver ion in the dilute citric acid solvent forms a total of two-coordinate bonds between the carboxyl group and the carboxylate anion, so that the silver anion contained in the silver ion water of Patent Document 1 can be almost entirely complexed and maintained in a negative charge monovalent silver anion state when adjusted to an appropriate concentration with water up to a pH of about 2.5 to less than 4.0.

[0017] The thiol group has a negative charge, so it does not react with the silver anion, and can exert its antibacterial function against a wide spectrum of bacteria that silver ions inherently possess. Also, since the above-mentioned foods contain organic ions with a negative charge, the silver anion does not react with the organic ion, and can exert its antibacterial function over a wide spectrum in the same way as above. Incidentally, silver cations are unstable and are affected by ultraviolet rays, and react with the thiol group and organic ion contained in all foods, losing their antibacterial function.

[0018] However, when a liquid agent containing silver cations or silver anions is applied, it is adsorbed by nonwoven fabrics containing cellulose fibers such as cotton, linen, and rayon (hereinafter referred to as cellulose-based nonwoven fabrics). For example, if a fabric or nonwoven fabric made of cellulose fibers is gravure coated or soaked, and then dried and food is packaged, the silver ions are adsorbed by the cellulose fibers in the nonwoven fabric and cannot be transferred to the food being packaged. Although the nonwoven fabric or fabric itself can exhibit antibacterial and deodorizing properties, it cannot kill bacteria present on the surface of the food. Fresh foods do not have bacteria inside, but only on the surface. If bacteria are present inside, it may have already spoiled or deteriorated, so it should not be consumed. Meat inspections are carried out to stop shipment to the consumer market, except for meat for pet food, if bacteria are present inside. It is thought that vegetables and fruits among fresh foods can only ripen and spoil from the inside if microorganisms enter through the calyx or if tiny insect eggs hatch and invade the inside.

[0019] Therefore, the synthetic fiber nonwoven fabric used in implementing claim 1 of the present invention and the synthetic fiber woven fabric used in retort food storage bags are optimal, and the optimal example of the nonwoven fabric material is 100% polyester. Furthermore, the silver anions encapsulated in the silver PET resin applied to the nonwoven fabric used in the food packaging material of the present invention by the various coating methods described above can dissolve through the gaps between the polymer molecules of the polyester resin toward the moisture when they come into contact with food containing moisture, thereby exerting an antibacterial function. Incidentally, in the JIS L 1902 antibacterial test for textiles, an effective value can be obtained with silver anions at 2 to 5 ppb. [Means for solving the problem]

[0020] The silver ion water described in Patent Document 1 is in fact almost entirely a liquid containing complex silver anions. First, in order to obtain the food packaging material described in claim 1, complex silver anion water must be prepared by diluting the synthetic fiber nonwoven fabric with ion-exchanged water or purified water so that the pH is within the range of 2.5 to less than 4.0 at a concentration of 0.5 to 1 ppm. When silver ion water is produced using a solvent containing 2% by weight of citric acid monohydrate, the silver anion water contains approximately 25 ppm of dicarboxyargent(I) acid ion. If this is diluted to, for example, the 1 ppm concentration described in claim 1, it will be diluted by more than 25 times, and protons will dissociate from the carboxyl groups, increasing the amount of carboxylate anions. This is thought to be one of the reasons why the pH of organic acids rises and falls randomly, but even if the pH can be maintained, the carboxyl groups will decrease and the balance of the bidentate coordination will be lost, so it is more preferable to increase the concentration of citric acid monohydrate to about 3% when producing silver ion water. Furthermore, the complexed silver anions are broken down at around 200°C and become silver cations while emitting carbon dioxide. However, as described above, the water that evaporates during drying after coating removes the heat of vaporization, so the silver anions on the coated nonwoven fabric are not broken down and become cations.

[0021] Regarding the food packaging material described in claim 2, the water-soluble polyester resin (manufactured by GOO Chemical Industry Co., Ltd.: product name PLUSCOAT) is an anionic solution with about 10-25% polyester resin solids and about 90-75% water, and is in the weak acidic range with a pH of less than 4.0. The water-soluble polyester resin has a certain degree of viscosity. The silver ion water described in Patent Document 1 has an ion concentration of about 25 ppm after production, but this is adjusted to 0.5 to 1 ppm in the silver anion concentration in the silver PET resin with ion exchange water or purified water, etc., to increase the adhesion and adhesion between the 100% polyester nonwoven fabric and the silver PET resin, and when a known coating such as gravure coating or fine dot printing is performed, the silver anion is distributed throughout the nonwoven fabric, and when it is dried, the nonwoven fabric exhibits antibacterial properties on the side that comes into contact with food.

[0022] Regarding the content of claim 3, conventional packaging materials for retort foods have been laminated films having an aluminum vapor deposition layer sandwiched between two polyester films. The present invention uses 100% polyester 20 to 30 g / m 2 The method is to apply 0.5 to 1.0 ppm of silver anions to a very thin nonwoven fabric using water-soluble polyester as an adhesive, laminate a polyester film on one side, fold the coated nonwoven fabric inward, seal the three sides together by heat welding, inject retort food, and seal the injection port by heat welding. Of course, care must be taken to prevent the polyester fiber that makes up the nonwoven fabric from being mixed into the product, but there is no need to worry about this because the adhesion between the nonwoven fabric and the water-soluble polyester resin is strong.

[0023] What makes it different from conventional retort food containers is that what comes into contact with the food is not an aluminum vapor-deposited film, but a polyester nonwoven fabric containing the silver anions, and the product name, names of the product's constituent materials, instructions for use, and warnings can also be printed on the laminated polyester film. The difference is that the preservatives have been reduced or eliminated, which has reduced the odor of preservatives, or it can be stated that no preservatives are used, and it is possible to block ultraviolet rays and prevent deterioration of retort foods. Silver and polyester are included in the positive list of materials that can be used for food containers in the revised Food Sanitation Act.

[0024] To reiterate, the laminated film that is the base material of the retort food packaging material as described above is sandwiched between two polyester films with aluminum by vacuum deposition, and the product name, cooking method, ingredients, etc. are printed on the front and back of the packaging bag, and ultraviolet rays are also blocked, but the side that comes into contact with food is a polyester film with no printing or other processing, and when the silver PET resin containing the above-mentioned pretreated silver anions is coated by a known method, the adhesion between the polyesters is strong so that the coated water-soluble plastic resin and the silver anions do not get mixed into the food to be sealed, and the silver anions dissolve, making it usable. The difference from the present invention is that the retort food comes into contact only with the presence of complex silver anions that adhere to the water-soluble polyester and dissolve to kill food spoilage bacteria. In 2003, the WHO issued a statement stating that no adverse health effects would occur to humans even if they lived for 70 years consuming only water containing 0.1 ppm of silver ions, and the maximum amount of silver ions that can be contained in Japan's tap water is 1 ppm. Effect of the Invention

[0025] Naturally, food packaging forms vary depending on the food to be packaged. Food may simply be wrapped in a two-dimensional packaging material and then wrapped in plastic wrap, or it may be placed in a packaging bag or container and stored in the refrigerator or freezer, or it may be stored for long periods at room temperature as a retort food. However, regardless of the packaging material, different packaging forms are used to extend the edibility of food, with the ultimate goal being, either alone or in combination, to prevent microbial contamination of the food, to prevent deterioration of the food due to ultraviolet rays, and to prevent oxidation due to oxygen in the air. The packaging material of the present invention makes it possible to eliminate or at least reduce the amount of preservatives added to retort foods. Regardless of the packaging form of the present invention, the complex silver anion does not react with thiol groups or organic ions that all food ingredients possess to a greater or lesser extent, and the silver anion effectively exerts an antibacterial effect, thereby extending the shelf life of the food, reducing food waste and eliminating the economic loss caused by waste.

[0026] Silver is also recognized as a food additive, and polyethylene, polypropylene, polyester, and silver are included in the positive list of food contact plastic packaging materials and containers in the revised Food Sanitation Act. When complex silver anions are chewed in the stomach along with food, the complex is broken by dilute hydrochloric acid, which is gastric acid, and changes into silver cations, which react with the chlorine in the dilute hydrochloric acid, which is gastric acid, and changes into silver chloride, which is excreted as an insoluble substance. Neither silver cations nor complex silver anions are harmful to human health, and this is also clear from the WHO statement in 2003 that water containing 0.1 ppm of silver cations is harmless to humans even if they live alone for 70 years. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] First, a method for obtaining silver anion water using a dilute citric acid solvent containing almost all complex silver anions will be described below. Patent Document 1 describes that a solution containing silver anions can be obtained by vacuum-depositing pure silver on unprocessed polyester film using dilute citric acid, and then stirring a group of silver-deposited film fragments cut without protecting the silver surface in a dilute citric acid solvent; however, the silver ions in the solution obtained by this method are complexed silver anions (dicarboxyargentate(I) ions). It is common knowledge in coordination chemistry that both the carboxyl groups that make up citric acid and the carboxylate anions resulting from the dissociation of protons are ligands with negative charges, and the more protons dissociate, the more acidic the citric acid monohydrate solution becomes.

[0028] First, a 60 nm thick pure silver vapor deposition film is formed on a 9-12 micron thick polyester film substrate by vacuum deposition without any pretreatment. In the vacuum deposition method, a vapor deposition vessel is placed in an electric crucible inside the vessel, and pure silver ingots are melted and vaporized by low-temperature heat if the atmosphere is much closer to a vacuum than normal pressure. The silver atoms are individually laminated on the polyester film, and the film that does not protect the vapor deposition layer surface is cut into a roughly square shape with a side length of about 2 cm in preparation for stirring. At this time, the pure silver atoms are piled up individually, like powdered snow, and the metallic bonds are weak, so when lightly rubbed, ultra-fine silver powder is transferred to the friction paper. Since the pure silver atoms are clogged and form layers almost independently of each other, when the cut film is stirred in a dilute citric acid solvent with a concentration of 1-2%, silver ion water, which is almost entirely composed of complex silver anions, can be obtained. For example, the silver ion water can be obtained by adding 30,000 pieces of the above-mentioned cut film, each approximately 2 cm square, to 130 L of a 2% concentration dilute citric acid solvent and stirring it. When the base film is removed, the solvent liquid is also taken along, so in reality there is some loss, but silver ion water is obtained in which almost all of the dissolved silver is complex silver anions, and the original solution after production is about 120 L, with a silver anion concentration of around 25 ppm and a pH of about 2.1 to 2.2.

[0029] Although it is a little late, the reason why the stirring tank is made of plastic such as polyethylene, the motor part of the stirrer will not get wet if it is stirred at 300 to 400 times per minute, the shaft is Teflon coated, and the stirring screw is made of polycarbonate is that if a metal has a lower tendency to ionize than pure silver, it will dissolve faster than silver, and the complex anion of that metal will be formed first and become an impurity of the complex silver anion, and this is one of the important points to note when producing the silver anion water.

[0030] In the case of nitric acid or dilute nitric acid, which are strong inorganic acids, even if the metallic bond has returned to the silver atom, even if the deposited silver has become a silver salt, the silver atom dissolves and a liquid containing all silver cations can be obtained by stirring the above film fragments. However, as mentioned above, silver atoms with very weak metallic bonds or no metallic bonds are dissolved by stirring in dilute citric acid, which is an organic acid and a weak acid, with a concentration of 1 to 2%, and the carboxyl group that constitutes citric acid and the carboxylate anion that is the dissociated proton form a total of two-dentate coordinate bonds, and the dissolved silver ions are complexed and anionized. In this way, silver anion water in which almost all of the dissolved silver in the dilute citric acid solvent is complexed with silver anions can be obtained. Incidentally, the concentration of complex silver anions obtained by the above method is about 25 ppm, so it is sufficient to dilute it with ion-exchanged water to adjust the silver anion concentration for each application. However, if the dilution ratio must be increased, it is more preferable to increase the concentration of the citric acid monohydrate solution to about 3%.

[0031] The complex silver anions contained in the silver anion water obtained as described above have weak coordinate bonds that cause them to revert to silver cations as the pH approaches neutral, and metallic silver gradually precipitates when the pH exceeds neutral, so it is important to maintain the pH below 4.0 when using the water. The change of complex silver anions to silver cations as the pH approaches neutral can also be clearly understood from enveloped virus inactivation tests using influenza virus (H3N2) as a surrogate for the new coronavirus.

[0032] Prepare pH 2.6 and pH 4.9 with a silver ion concentration of 500 ppb. 1) The same amount of the silver anion water was inoculated onto cotton cloth whose cleanliness had been confirmed by the Japan Product Quality and Technology Center (a non-profit foundation). ▲2▼The test results showed that the antiviral activity value was 4.3 at pH 2.6, but 2.1 at pH 4.9. Silver cations have lower anti-enveloped virus activity than silver anions. Both pass the test in terms of anti-viral activity, but it is clear that the amount of silver anions is affected by the pH level.

[0033] In antibacterial tests of ordinary fabrics, nonwoven fabrics, and textile products, silver cations exhibit a wide spectrum of antibacterial properties. For example, the required concentration of silver cations to be dissolved in cotton textile products such as towels is said to be 5 to 10 ppb. However, complex silver anions can easily permeate bacterial cell membranes with a concentration of 2 to 5 ppb, and therefore exhibit antibacterial properties greater than those of silver cations.

[0034] When gravure coating the nonwoven fabric using only the above-mentioned complex silver anion water, if a nonionic or anionic surfactant is applied as a pretreatment as described above, the hydrophobicity of the 100% hydrophobic synthetic fiber nonwoven fabric can be destroyed and the silver anion water can be prevented from being repelled, so it is important to pretreat with the surfactant solution at a concentration of just under 1%, but it is not necessary to apply a surfactant in such an amount that it affects the silver anion concentration or pH, and a small amount of the surfactant is sufficient. Of course, the surfactant used must be harmless if consumed by humans.

[0035] The water-soluble polyester resin described in claim 2 has a low molecular weight of about 15,000, is in a liquid form of 80-75% ion-exchanged water and 20-25% water-soluble polyester resin solid content, is anionic, and the original solution is in a weak acidic range of about pH 4.0. The silver ion water is also a liquid, and the mixing of the two liquids for coating the nonwoven fabric will be described later, but both liquids are anionic, have an acidic pH, and are highly compatible.

[0036] The mixed solutions of both liquids described in the above paragraphs contain a lot of water, so when mixing, it is sufficient to calculate the silver ion concentration based on the complex silver anion concentration and the solid content of the water-soluble polyester resin. It is sufficient to calculate so that the complex silver anion is contained in the solid content of the polyester resin after the water has evaporated. The solid content of the water-soluble polyester resin is 20-25% per 1L of the original solution, so if the specific gravity of the polyester resin is about 1.4, the solid content of the polyester resin in 1L of the original solution will be 280-350g.

[0037] When preparing silver PET resin liquid using silver ion water containing complex silver anions with a silver ion concentration of 5 ppm, the water will evaporate when the silver ion water is dried, and there is no significant error in calculating the specific gravity of the silver ion water as 1 even if silver anions are dissolved and about 2% citric acid is dissolved. The water content of 1L of water-soluble polyester resin stock solution that can be used for food also evaporates, so the amount of polyester resin dissolved in the water is 280 to 350g. In order to adjust the silver anion concentration to the appropriate amount, it is sufficient to calculate based on the specific gravity, with some error, and since the silver anion concentration is preferably 0.1 to 1.0 ppm or less, some error will occur. If the polyester resin solid content in 1L of silver PET resin solution is 350g, and the silver anion concentration in the solid polyester resin of 350g is adjusted to 1 ppm, if silver anion water with a silver anion concentration of 5 ppm is used, both water contents will evaporate after coating as mentioned above, so 70 ml should be added and stirred well. Of course, the water in which the water-soluble polyester resin is dissolved is heavy, so in order to stir the excess silver PET resin solution without increasing its viscosity, it is preferable to discard as much of the water in which the resin is dissolved as possible before adding the silver anion water.

[0038] If we think about it differently from the above, the weight of 1L of water-soluble polyester resin would be 1,100g (750g water + 250g PET resin x 1.4 = 1,100g). That 750g of water evaporates after coating, and the silver anions remain in the polyester resin. To evenly incorporate 1.0ppm of silver anions into the polyester resin at 1,100g without discarding the water, 350g of solids should be targeted, and if it is 5ppm silver-ion water, just over 70ml should be added and stirred. Which calculation is more preferable can be determined by checking the viscosity of the silver-PET resin solution, and then selecting the coating method to be used to coat the silver-PET resin on the nonwoven fabric.

[0039] Regardless of the silver anion concentration of the silver ion water, when storing silver ion water in a plastic container, the container itself should be shaken well 5 to 6 times before use. If the container is left stationary during storage, the silver anions will enter the gaps between the molecules of the plastic that makes up the container, lowering the apparent concentration, so if you shake it just before use as described above, the silver anion concentration will return to its original concentration. Once opened, silver ion water should be used up, but if the air is removed and the water is sealed with nitrogen gas, it is believed that the quality will not deteriorate for 2 to 3 months.

[0040] When food is packaged with a two-dimensional polyester nonwoven fabric with residual silver anions, as shown in the example below, a gap will inevitably be created somewhere between the nonwoven fabric and the packaged food. The silver anions remaining on the nonwoven fabric cannot become a gas when they evaporate like water and cannot come into contact with the food, so care must be taken to keep them in contact with the packaged food as much as possible. In other words, silver anions cannot move through the air in their silver anion form unless they are contained in the water of the solvent. EXAMPLES

[0041] A comparative experiment was conducted to compare the disinfecting power of chopped green onions by washing cut vegetables (chopped green onions) with (A) an aqueous solution of sodium hypochlorite at a concentration of 200 ppm (hereafter referred to as hypochlorous water) and (B) an aqueous solution of silver ion water with a silver anion concentration of 0.1 ppm. The chopped green onions were washed by stirring with both solutions (A) and (B) for 8 minutes at room temperature, and then further washed with well water to wash off the solutions adhering to the chopped green onions, the specimens from (A) and (B). Hypochlorous water is a well-known antibacterial and disinfectant agent. Note that this example was conducted with n=3. Experimental Example 1

[0042] The initial bacterial count of freshly chopped green onions was about 4.0 in logarithmic value, but both samples (A) and (B) showed almost the same sterilization rate of 99%, and the logarithmic value of the bacterial count decreased to about 2.0. Since chopped green onions are stored at 10°C in retail stores, sample (B) was able to extend edibility for at least 2 days, similar to conventional washing with hypochlorous water. If the bacterial count after sterilization with hypochlorous water and then washing with well water is about logarithmic value 2, it is allowed to be sold at retail stores for 2 days after arrival when the bacterial count reaches logarithmic value 5. At retail stores, chopped green onions that have been in stock for 2 days are either used in cooked foods sold at the store, or are discarded because the bacterial count reaches logarithmic value 6 after 3 days of storage after arrival. Since there may be silver anions that cannot be transferred to the food, it is desirable to keep the concentration at 0.1 to 1 ppm when manufacturing packaging materials. Washing with hypochlorous water or subsequent disinfectant cleaning is not routinely possible at home or in chopped leek retail stores, and washing with 0.1 ppm silver ion water is not harmful, as stated by the WHO in a statement below, and the temperature inside a typical household refrigerator is around 10°C, so it may be possible to use it at home after washing with silver ion water that has almost no acidity. Incidentally, even when tap water was poured into 0.1 ppm silver anion water, no silver chloride was formed. This is evidence that the silver ions have become anions. The silver anion concentration immediately after production of the complex silver anion water was 20 ppm, and the pH was around 2.1. Example 2

[0043] 20g / m 2 A thin 100% polyester nonwoven fabric was cut into approximately A4 size to prepare 12 sheets as antibacterial test samples. First, a water-soluble polyester resin solution was prepared by diluting silver anion water with a silver anion concentration of 5 ppm in the solid content of the water-soluble polyester resin by 5 times with ion-exchanged water to obtain a silver ion concentration of 1 ppm, and lightly sprayed onto the nonwoven fabric. Approximately 1.5 g of silver PET resin solution (a mixture of silver anion water, water-soluble polyester resin, and water) was sprayed onto each of six A4 size sheets. There was no dripping. The packaging material obtained in this way was subjected to the following antibacterial test. The antibacterial test itself was carried out in accordance with JIS-L-1902, simulating a slightly dirtier condition than the standard.

[0044] Normally, the medium concentration for the JIS-L-1902 antibacterial test is performed by making the agar medium with consommé soup or the like and diluting the soup by 1 / 20, but to simulate a dirty situation (to increase the nutrition of the test bacteria), the medium concentration was diluted 5 times and the same test method was applied to perform the antibacterial test with n=3. This also mimics the packaging conditions for fresh and cooked foods that contain proteins, various amino acids, lipids, carbohydrates, and organic ions. Experimental Example 2

[0045] The results of the above antibacterial test were as follows: The antibacterial activity value was calculated by counting the number of colonies formed on the culture medium (n=3) after 18 hours of testing, and calculating the simple average value by logarithmizing the sterilization rate. The antibacterial activity value of the test result was obtained from a sample in which a water-soluble polyester resin solid content with a silver anion concentration of 1.0 ppm was sprayed onto a polyester nonwoven fabric, and was effective as shown below. From this result, since it is difficult to leave a large amount of silver anion water on the nonwoven fabric, it was judged appropriate to set the silver anion concentration of the silver anion water to 1.0 ppm. <Against Staphylococcus aureus> Antibacterial activity value: 6.7 <Against E. coli> Antibacterial activity value: 7.0 All of the data was excellent, showing that the number of surviving bacteria was close to zero. Example 3

[0046] The packaging material obtained in

[0043] was cut horizontally to form a sample packaging material. A pear purchased from a supermarket was cut into 6 equal parts and, without peeling, 3 of the pears were wrapped tightly in the packaging material. Kitchen paper was tightly wrapped to catch any drips, and then this was wrapped in cling wrap (manufactured by Kureha Corporation) to prevent the pears from drying out, and the pears were stored in a household refrigerator at a room temperature of 10°C.

[0047] As a blank, the remaining three pears were wrapped in kitchen paper to absorb drips, and then wrapped in cling wrap to prevent drying, and stored in the same manner as above.

[0048] The samples and blanks stored as described above were taken out of the refrigerator after 6 days and 4 hours, and the packaging materials were opened and the odor, discoloration, fading, etc. were compared. ▲1▼The three pears wrapped in the specimen packaging still had a pear-like smell, and there was no discoloration of the skin or flesh. ▲2▼The three pears wrapped in blank packaging still had a pear-like smell, but two of them had brown discoloration in parts of the center. Although a small amount of juice was released from both the sample packaging and the blank packaging, it is thought that in an experiment using fruit that does not contain protein or fat, it is difficult to see a large difference in the experimental period of just under seven days. Example 4

[0049] 240g of steak beef was purchased and cut into 6 pieces of approximately equal weight for the test and blank, with n=3 for each. The test meat was wrapped in the same wrapping material as described in

[0047] , sprayed with the same amount of silver PET resin liquid / silver anion concentration 1ppm, dried, and wrapped in kitchen paper to absorb drips, and further wrapped in cling wrap to prevent drying. The blank meat was not wrapped in the nonwoven fabric wrapping material, but the other wrapping was the same as the three test samples, and stored on the same shelf in a refrigerator at room temperature of 10℃. The storage time was approximately the same as in the above experiment with pears.

[0050] ▲1▼All three blank packages were opened and checked for odor and color changes. Immediately after opening, all three had a slight putrid odor, and the color of the meat had changed from what it was at the start of the experiment, to a slightly dirty color between red beef and brown. 2. All three sample packages were opened. The smell was still similar to that at the start of the experiment, and all three had retained their beef-like color without any discoloration. (3) To absorb drips, the specimens were wrapped in kitchen paper before being wrapped in cling wrap. The specimen packaging material was breathable, and although beef drips were absorbed by both kitchen papers, there was no significant difference.

[0051] As shown by the data in paragraph

[0045] , this example demonstrates that the excellent antibacterial function can extend the edibility of foods, and the ability to extend the edibility of foods high in protein and fat is particularly notable. [Industrial Applicability]

[0051] Food packaging materials that utilize the complex silver anion of the present invention do not react with the thiol group of cysteine, an amino acid found in almost all fresh foods, and utilize their effective antibacterial properties to help maintain and extend the freshness of food, making it possible to maintain the freshness of food in food retail stores and ordinary households and extend the edible life of food, thereby reducing food waste and reducing food loss.

[0052] Retort foods are useful as emergency food or for easy cooking at home. However, after production, they are meaningless if they cannot withstand long-term storage or storage at room temperature, and for this purpose, various sterilization processes are carried out, but sometimes preservatives are added depending on the food. In particular, many consumers are concerned about the smell of preservatives when eating retort curry after heating it. The present invention can reduce the amount of preservatives added when packaging retort foods, and in some cases, can eliminate the need to add preservatives, which can contribute to the development of the retort food industry.

Claims

1. 15-30g / m2 made from hydrophobic synthetic fibers only ２ A thin and soft nonwoven fabric is first coated with a surfactant that can destroy hydrophobicity and is safe to eat, and the silver anion water described in the prior art document [Patent Document 1] described in the specification is actually complex silver anion water, so the complex silver anion water obtained by this method is diluted to an ion concentration of about 0.1 to 1.0 ppm, and then the nonwoven fabric is coated so that the ions are distributed throughout the fabric by a known coating method such as immersing the fabric in the diluted solution and squeezing and drying it, or spraying and drying it, and then cut to fit the size of the packaged material and wrapped in close contact with the packaged material to prevent drying, thereby prolonging the life of the packaged material, such as fresh food (meat, fish, vegetables, fruits), and a disposable two-dimensional food packaging material. (Note that the complex silver anion water will be referred to as silver anion water hereinafter, or as silver anion when describing only the ions.)

2. A nonwoven food packaging material comprising: a water-soluble polyester resin (product name: Pluscoat; manufacturer: GOO Chemical Industry Co., Ltd.) having a concentration of 0.1 to 1.0 ppm, which is evenly dispersed and mixed into the solid content of the resin; a coating method (dipping, spraying, gravure coating, etc.) is used to coat at least both sides of a 100% polyester nonwoven fabric so that the silver anions are distributed over the entire surface of the fabric; the coated nonwoven fabric can be cut to take into account the size of the material to be packaged; and the fresh food described in claim 1 is packaged in close contact with the food to prevent it from drying out, thereby extending the edible life of the food and allowing it to be disposable.

3. The food packaging materials shown in claims 1 and 2 are two-dimensional, but if the nonwoven fabric material is 100% polyester, there will be no moisture remaining after drying, so the silver anion described in claim 1 is applied to the solid content of the water-soluble polyester resin at a uniform concentration of 0.1 to 1.0 ppm. After coating and drying as described above, a polyester film is laminated to one side of the nonwoven fabric, and after cutting, the nonwoven fabric is folded with the fabric facing inward and bonded and sealed only on three sides using a well-known method such as heat fusion. This allows moist food materials such as retort foods to come into contact with the coated nonwoven fabric on the inside, making it possible to reduce or eliminate the amount of preservatives added to retort foods. After an appropriate amount of food is enclosed, the opening is heat fused or closed using other well-known methods to create a three-dimensional food packaging material that can extend the edible life of the retort foods.