JP2858016B2 - Freshness preserving packaging material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a packaging material useful for maintaining freshness of fresh foods, particularly fruits and vegetables.

[Related Art] As a technology for maintaining freshness in the distribution stage of fruits and vegetables and preservation in each household, a number of methods have been proposed as a result of research on the alteration mechanism. For example, a bag to which a water-absorbing resin is applied to prevent the adhesion of dew condensation water on a storage container (Japanese Patent Application Laid-Open
58-209934), a device containing an oxygen scavenger to prevent oxidation by oxygen generated by respiration (Japanese Patent Application Laid-Open No. 63-82967, etc.), and a device containing an adsorbent for ethylene, which is a physiological metabolite, No. 63-233748) has been proposed. However, these methods vary in effectiveness depending on the type of fruit and vegetable,
Nothing useful for a wide range of fresh foods has been obtained.

[Problems to be solved by the invention]

Since fruits and vegetables, fish, meat, dairy products, and the like have different maturities depending on the harvest time and distribution conditions, it has been difficult to find an effective method for maintaining the freshness of a wide range of fresh foods. In general, the freshness of fruits and vegetables is determined not only by temperature conditions for preservation, but also by microorganisms causing decay, moisture, gas composition by respiration, and physiological metabolites. A packaging material that satisfies all these conditions and can ensure the safety of the material used from the viewpoint of food hygiene is preferable. Accordingly, an object of the present invention is to provide a packaging material having a high freshness retaining effect for a wide range of fresh foods.

[Means for solving the problem]

The object of the present invention is achieved by a freshness preserving packaging material comprising a polymer film containing 3 to 30% by weight of zeolite containing silver ions and having a water content of 10% or less (hereinafter referred to as silver zeolite).

 Hereinafter, the present invention will be described.

The silver zeolite used in the freshness preserving packaging material of the present invention has an antibacterial effect by silver ions, has a porous and humidity controlling action, has a property of adsorbing oxygen when its oxygen concentration is increased, and is a typical physiological metabolism. It has the property of adsorbing ethylene gas as a substance. Furthermore, it is extremely safe for the human body, and is excellent as a component of packaging materials for maintaining freshness.

In the present invention, as the "zeolite", any of natural zeolites and synthetic zeolites can be used. Zeolite is generally an aluminosilicate having a three-dimensional skeleton structure, and has a general formula of XM _{2 / n} O.Al ₂ O _3.
Displayed as YSiO ₂ · ZH ₂ O. Here, M represents an ion-exchangeable ion and is usually a monovalent or divalent metal ion. n is the valence of the (metal) ion. X and Y
Denotes the coefficient of each metal oxide and silica, and Z denotes the number of water of crystallization. Specific examples of the zeolite include, for example, A-type zeolite, X-type zeolite, Y-type zeolite, T-type zeolite, high silica zeolite, sodalite, mordenite, analcyme, clinoptilolite, chabazite, erionite and the like. Can be mentioned. However, these are not limited. The ion exchange capacities of these exemplary zeolites are A-type zeolite 7meq / g, X-type zeolite 6.4meq / g, Y-type zeolite 5meq / g, T-type zeolite 3.4meq / g, sodalite 1
1.5meq / g, mordenite 2.6meq / g, analcyme 5meq / g
g, clinoptilolite 2.6meq / g, chabazite 5meq / g
g and erionite 3.8 meq / g, all of which have sufficient capacity for ion exchange with silver ions.

Silver zeolite used in the present invention, ion exchangeable ions in the zeolite, for example, a part or all of sodium ions, potassium ions and the like, silver ions, preferably, in addition to silver ions, copper, manganese, at least nickel It is replaced by a kind of ion. here,
It is preferable to include copper, manganese, and nickel ions because the amount of ethylene gas adsorbed increases and the ability to decompose ethylene gas also increases.

The amount of silver ions contained in the zeolite is suitably from 0.1 to 15% by weight of the zeolite from the viewpoint of antibacterial properties. Further, it is more preferable to contain 1 to 10% by weight of at least one ion selected from copper, manganese and nickel.

When carbon dioxide is caused to flow through the silver zeolite used for the freshness-keeping packaging material of the present invention, the gas composition by respiration is made rich in carbon dioxide, and the freshness-retaining effect of fruits and vegetables is further improved.
The carbon dioxide content is suitably from 0.4 to 2 g / g. In addition, in this specification,% means weight% of 110 degreeC dry basis.

Hereinafter, a method for producing a silver ion-containing zeolite used in the present invention will be described. The zeolite is brought into contact with a mixed aqueous solution containing silver ions prepared in advance and metal ions such as copper ions, manganese ions, and nickel ions as necessary, thereby replacing the ion-exchangeable ions in the zeolite with the above ions. The contact is carried out at 10-70 ° C, preferably 40
The reaction can be carried out at a temperature of ℃ 60 ° C. for 3 to 24 hours, preferably 10 to 24 hours, by a batch method or a continuous method (for example, a column method). The pH of the mixed aqueous solution is 3-10, preferably 5-7.
Is suitably prepared. By adjusting the pH in this manner, precipitation of silver oxide or the like on the zeolite surface or in pores can be prevented. Each ion in the mixed aqueous solution is usually supplied as a salt. For example, silver ions are silver nitrate, silver sulfate, silver perchlorate, silver acetate, diammine silver nitrate, diammine silver sulfate, etc., and copper ions are copper (II) nitrate, copper perchlorate, copper acetate, potassium tetracyanocuprate, Manganese nitrate, manganese sulfate, manganese perchlorate, manganese acetate and the like can be used for manganese ions such as copper sulfate, and nickel perchlorate, nickel nitrate and nickel acetate can be used for nickel ions.

The content of silver ions and the like in the zeolite can be appropriately controlled by adjusting the concentration of each ion (salt) in the mixed aqueous solution. For example, when the zeolite contains silver ions and manganese ions, the silver ion concentration in the mixed aqueous solution is set to 0.002 M // 0.45 M /, and the manganese ion concentration is set to 0.3 M / 〜2.0 M /. By adding 100 to 500 g of zeolite and performing ion exchange, a silver ion-containing zeolite having a silver ion content of 0.1 to 15% and a manganese ion content of 1 to 10% can be appropriately obtained.

In the present invention, ion exchange can also be performed by using an aqueous solution containing each ion alone in addition to the mixed aqueous solution as described above and sequentially contacting each aqueous solution with zeolite. The concentration of each ion in each aqueous solution can be determined according to each ion concentration in the mixed aqueous solution.

It is preferable that the zeolite after the ion exchange is sufficiently washed with water and then dried so as to have a water content of 10% or less.
If the water content is higher than 10%, the water contained in the zeolite will evaporate at the film forming temperature when producing a polymer film, generating pinholes and the like, making it impossible to obtain a proper air permeability. In this specification, the appropriate air permeability means that the air permeability of oxygen, which is a representative gas species, is 40%.
It is within the range of 100 to 10,000 CC / m ² · 24 hrs · atm.

Silver zeolite having a water content of 10% or less can be used, for example, at 145
It is obtained by drying at 100 to 250 ° C under a reduced pressure (1 to 30 torr). Cooling after drying is preferably performed in a state of low oxygen, for example, in an atmosphere of nitrogen, carbon dioxide, an inert gas, or under a reduced pressure of 1 to 30 torr.
The silver zeolite is allowed to cool under a carbon dioxide atmosphere at a pressure of 50 kg / cm ² to add carbon dioxide to the silver zeolite in an amount of 0.4 to ² g / cm ^2.
g can be contained.

The silver zeolite used in the present invention has an average particle diameter of preferably 6 μm or less, and more preferably 0.5 to 4 μm, from the viewpoint of obtaining a polymer film having appropriate air permeability.

As the polymer for a polymer film used in the packaging material for keeping freshness of the present invention, any organic polymer compound that can be formed into a film can be used without limitation. For example, ionomer resin, EEA resin, EVA resin, vinyl chloride resin, chlorinated polyethylene, fluororesin, polyamide, polyurethane elastomer, polyetheretherketone, polysulfone, high-density polyethylene, low-density polyethylene,
Examples include linear low-density polyethylene, polycarbonate, butadiene resin, polypropylene, styrene-based transparent resin, polyacrylate, reinforced polyethylene terephthalate, polystyrene, vinylidene chloride resin, and conductive resin. Of these, it has moderate air permeability, and from the viewpoint that the effect of maintaining freshness is easy to maintain, oxygen permeability is 1000
High-density polyethylene, low-density polyethylene, linear low-density polyethylene, polycarbonate, polypropylene, styrene-based transparent resin, and polystyrene having CC / m ² · 24 hrs · atm or more are preferable. By containing 3 to 30% by weight of silver zeolite in the above polymer, the oxygen permeability becomes 4000 to
It is adjusted to ^{10000cc / m 2 · 24hrs · atm} . By adding an ion-exchanged normal zeolite together with the silver zeolite, the amount of silver zeolite can be reduced to obtain the same oxygen permeability.

The polymer film used in the present invention is obtained by mixing the above-mentioned silver zeolite and the above-mentioned polymer compound by a conventional method, and molding (forming a film) the obtained mixture. The film can be formed by, for example, a casting method, an extrusion method (for example, an inflation method, a T-die method, a calender method, a cutting method, and the like), and a stretching method. For example, in the casting method, a resin flake as a raw material is dissolved in a solvent, and an additive such as a silver zeolite and, if necessary, a plasticizer is added to the obtained solution. The resulting mixture is then filtered, defoamed and cast on a rotating flat metal support to obtain a thin film.

The polymer film used in the present invention has a thickness of 50 μm or less,
Preferably, the thickness is 10 to 35 μm.

The freshness-keeping packaging material of the present invention comprising the silver zeolite-containing polymer film may be used in a sheet form,
It may be processed into a bag and used. Further, the film can be used in the form of a container laminated with cardboard, wood, foamed polymer, etc., unless the air permeability is extremely impaired.

The freshness-preserving packaging material of the present invention includes fruits such as melon, banana, strawberry, thigh, oyster, ume, apple, kiwi, mango, leafy vegetables such as cabbage, lettuce, chive, broccoli, cucumber, eggplant, tomato, etc. It is suitable for preserving many fresh foods such as rhizome vegetables such as fruits and vegetables, radish, turnip, burdock, carrot, etc., leafy vegetables such as spinach, komatsuna, spring chrysanthemum, mushrooms, beans, meat, fish and shellfish. In addition, it is also effective in maintaining the freshness of oil and fat foods, seeds, bulbs, cut flowers, and the like, and is thus suitable.

〔The invention's effect〕

The freshness-retaining packaging material of the present invention is a microorganism that affects freshness,
It controls moisture, gas composition, and physiological metabolites, has the effect of maintaining freshness over a wide range of fresh foods, and can extend the storage period for several days to several tens of days without reducing freshness. This makes it possible to stably supply a product having stable freshness quality even when transported from a production site.

〔Example〕

 Hereinafter, the present invention will be described in more detail with reference to Examples.

Reference Example (Preparation of silver zeolite) Zeolite made Shinanen New Ceramic Co. A- type zeolite _{(Na 2 O · Al 2 O} 3 · 2.0SiO 2 · ZH 2 O: Mean particle size
1.5 [mu] m), X- type zeolite _{(Na 2 O · Al 2 O} 3 · 2.5SiO 2
・ ZH ₂ O: average particle diameter 2.1 μm), Y-type zeolite (Na ₂ O)
・ Al ₂ O ₃・ 4.1SiO ₂・ ZH ₂ O: average particle diameter 0.7 μm, mordenite (Na ₂ O ・ Al ₂ O ₃・ 10.7 SiO ₂・ ZH ₂ O: average particle diameter 3.5
μm), commercially available natural clinoptilolite (average particle size 5
μm) were used. AgNO ₃ , Cu (NO ₃ ) ₂ , Mn (NO) are used as salts to provide each ion for ion exchange.
₃ ) Four types of ₃ and Ni (NO ₃ ) ₂ were used.

For each sample, water was added to 1 kg of zeolite powder heated and dried at 110 ° C. to make a slurry of 1.3, then stirred and degassed, and an appropriate amount of 0.5N nitric acid solution and water were added.
The pH was adjusted to 5-7 to make a 1.8 volume slurry.
Next, a solution 3 of silver, copper, manganese, and nickel at a predetermined concentration was added for ion exchange. The reaction is carried out at 20-60 ° C for 10
Stir for ~ 24 hours to reach equilibrium.

After the ion exchange, the zeolite phase was filtered and washed with warm water until the zeolite phase was free of excess metal ions such as silver. Next, after the sample was preliminarily dried at 110 ° C., moisture in the zeolite phase was eliminated at a predetermined temperature in a vacuum electric heating furnace. The atmosphere was allowed to cool, and cooled to room temperature to obtain 14 types of silver zeolites. Table 1 shows the preparation conditions.

Example (Production of polymer film containing silver zeolite) Silver zeolite obtained in Reference Example was mixed with various polymer substances from a hopper through which dry nitrogen flow was applied, and freshness of a predetermined thickness was formed by a T-die film forming machine. A holding film was made. The obtained film is heat-sealed to a size of 30 ×
The bag was made at 42 cm. Table 2 shows the film production conditions. As a comparative example, a film in which only untreated ordinary zeolite was mixed was similarly prepared.

Test example (storage test and bacterial test) Melon (1/4 fillet), banana, lettuce, cucumber, tomato, spinach, poultry (scissors part) and rice cake are put in the freshness preservation bag obtained in the example, respectively. Without
After closing the mouth with a stopper, refrigerator (inside temperature 4-7 ° C)
Saved. The state of each fresh food during the predetermined storage period was visually observed, and the number of bacteria in water droplets attached to the inner surface of the bag was measured. Table 3 shows the results.

As a comparison, the same test was performed on a commercially available freshness retaining bag containing Otani stone (Comparative Example 4).

Continuation of the front page (56) References JP-A-64-6031 (JP, A) JP-A-63-154746 (JP, A) JP-A-2-247239 (JP, A) (58) Fields investigated (Int .Cl. ⁶ , DB name) C08K 3 / 34,9 / 00-9/12 B65D 85/50-85/52

Claims (3)

(57) [Claims] 1. A freshness comprising a polymer film containing 3 to 30% by weight of zeolite having a water content of 10% or less, containing silver ions and at least one metal ion selected from the group consisting of manganese and nickel. Holding packaging material. 2. The packaging material according to claim 1, wherein carbon dioxide gas is adsorbed on zeolite containing silver ions. 3. The packaging material according to claim 1, wherein the packaging material is formed into a bag.