JP7850541B2 - Packaged foods, packaging materials, laminates - Google Patents

Description

This invention relates to packaged food products that have been subjected to pressure treatment while sealed in packaging material.

It has long been known that applying heat, pressure, or electron beams to packaged foods allows for long-term storage. In particular, in recent years, high-pressure processing, which inactivates microorganisms by applying extremely high pressure to packaged foods, has become popular. This method can inactivate microorganisms even at room temperature or near room temperature. Therefore, it has the advantage of preventing thermal denaturation of the treated material (proteins and starch, etc.), preserving flavor, nutrients, and color, and allowing for uniform and even processing.
On the other hand, because extremely high pressure is also applied to the packaging material, various types of packaging materials have been proposed.

Patent Document 1 describes a packaging material for high-pressure processing having a base material such as PET film, a gas barrier layer such as aluminum foil, and an innermost layer such as cyclic polyolefin or amorphous polyester.
Patent Document 2 describes a packaging material used in a high-pressure sterilization method, which has a hydrophobic layer such as polypropylene and a saponified ethylene-vinyl acetate copolymer layer.
Patent Document 3 describes a multilayer structure for ultra-high pressure processing having an ethylene-vinyl ester copolymer saponified layer between a base film such as PET and a heat-seal layer.

Japanese Patent Publication No. 2019-11098 Japanese Patent Application Publication No. 3-290175 Japanese Patent Publication No. 2018-58298

Applying high-pressure processing to food products, especially sliced meat products like ham, allows for microbial control. However, compared to meat products that have not undergone high-pressure processing, these products tend to discolor more easily over time, resulting in a deterioration of their appearance (color) during storage.

The objective of this invention is to provide packaged food products that suppress discoloration over time, particularly meat products, that have undergone high-pressure processing, thereby maintaining their appearance (color).

As a result of diligent research into the above-mentioned problems, the inventors discovered that by using packaging materials with a specific oxygen permeability for the processed material, it is possible to suppress the aging of the processed material due to high-pressure processing and obtain packaged food with excellent stability during storage, thus completing the present invention.
In other words, the present invention relates to the following packaged food, packaging material, and laminate.

The present invention, which solves the above problems, is a packaged food comprising a product to be treated and a packaging material for packaging the product to be treated, wherein the packaging material has an oxygen permeability of 1.0 mL/ ^m² ·day·atm or less and a moisture permeability of 1.0 to 10 g/m² ^· day, and comprises a laminate having (a) an outermost layer, (b) an intermediate layer and (c) an innermost layer, wherein the (b) intermediate layer includes at least one of a layer selected from a layer containing a resin having oxygen gas barrier properties and a layer containing an oxygen absorber, and the product to be treated is subjected to pressurized treatment while sealed with the packaging material.
According to the present invention, it is possible to suppress the aging of the processed material due to pressure treatment and provide a packaged food with excellent stability during storage.

The present invention, which solves the above problems, is a packaged food comprising a product to be processed and a packaging material for packaging the product to be processed, wherein the packaging material has a ratio of moisture permeability (g/ ^m² ·day) to oxygen permeability (mL/ ^m² ·day·atm) of 3.5 or more (moisture permeability/oxygen permeability), a moisture permeability of 1.0 to 10 g/m² ^· day, and comprises a laminate having (a) an outermost layer, (b) an intermediate layer and (c) an innermost layer, wherein the (b) intermediate layer includes at least one of a layer selected from a layer containing a resin having oxygen gas barrier properties and a layer containing an oxygen absorber, and the product to be processed is subjected to pressurized treatment while sealed with the packaging material.
According to the present invention, it is possible to suppress the aging of the processed material due to pressure treatment and provide a packaged food with excellent stability during storage.

The present invention, which solves the above problems, is a packaged food comprising a product to be treated and a packaging material for packaging the product to be treated, wherein the packaging material satisfies the conditions of the following formula (1) for oxygen permeability (mL/ ^m² ·day·atm) and moisture permeability (g/ ^m² ·day), the moisture permeability being 1.0 to 10 g/m² ^· day, and comprises a laminate having (a) an outermost layer, (b) an intermediate layer and (c) an innermost layer, wherein the (b) intermediate layer includes at least one of a layer selected from a layer containing a resin having oxygen gas barrier properties and a layer containing an oxygen absorber, and the product to be treated is subjected to pressurized treatment while sealed with the packaging material.
Y>4.2X+z Formula (1)
(However, X represents oxygen permeability, Y represents water vapor permeability, and z is -1.5.)
According to the present invention, it is possible to suppress the aging of the processed material due to pressure treatment and provide a packaged food with excellent stability during storage.

Furthermore, in one embodiment of the packaged food of the present invention, the pressure during pressurization is 50 MPa or more and 1000 MPa or less, and the temperature during pressurization is 5°C or more and 60°C or less.
This feature allows for sterilization without heat treatment of the object being processed.

Furthermore, in one embodiment of the packaged food of the present invention, the processed product is a meat product.
This characteristic further enhances the effect of suppressing fading over time.

Furthermore, one embodiment of the packaged food of the present invention is characterized in that the processed product is a sliced food product.
Slicing the processed material increases its surface area, making it more susceptible to discoloration over time. Therefore, the effects of the present invention are even more pronounced when the processed material is a sliced food product.

Furthermore, in one embodiment of the packaged food of the present invention, the packaging material comprises a laminate having (a) an outermost layer, (b) an intermediate layer, and (c) an innermost layer, wherein the (b) intermediate layer includes at least one of a layer selected from a layer containing a resin having oxygen gas barrier properties and a layer containing an oxygen absorber.
This feature allows the outermost and innermost layers to protect the gas barrier intermediate layer, thus further enhancing the effect of suppressing discoloration over time.

Furthermore, in one embodiment of the packaged food of the present invention, (c) the innermost layer is characterized by being a layer made of a heat-sealable resin or resin composition.
This feature allows for easy packaging using a heat sealer.

According to the present invention, it is possible to provide packaged foods that suppress discoloration over time, particularly meat products, that have undergone high-pressure processing, and maintain their appearance (color).

This is a schematic diagram illustrating the structure of the laminate of the present invention. This is a schematic diagram illustrating the structure of the packaged food product of the present invention. This graph shows the color changes of high-pressure packaged food products using the packaging material of the present invention, high-pressure packaged food products using conventional packaging materials, and unpackaged food products using conventional laminates. This graph shows the relationship between oxygen permeability and moisture permeability of packaging materials, as well as whether or not there is a change in the color of packaged food after high-pressure processing.

[Laminate]
The laminate of the present invention is characterized by having an oxygen permeability of 1.0 mL/ ^m² ·day·atm or less. The oxygen permeability is a value measured in the laminate before filling with contents, based on the Japanese Industrial Standard (JIS) K 7216-2 "Coulometric Method (MOCON Method)" (isobaric method). The measurement conditions were 23°C and 0% RH humidity.
The oxygen permeability of the laminate is preferably 0.7 mL/ ^m² ·day·atm or less, and more preferably 0.5 mL/ ^m² ·day·atm or less.
When the oxygen permeability is 1.0 mL/ ^m² ·day·atm or less, packaged foods using the packaging material made of the laminate of the present invention, particularly packaged meat products (such as ham), can maintain their appearance (color) immediately after high-pressure processing.

The moisture permeability (g/ ^m² ·day) of the laminate of the present invention is not particularly limited, but for example, it is 0.1 to 10 g/ ^m² ·day. The lower limit of moisture permeability is preferably 1.0 g/ ^m² ·day or more, more preferably 1.5 g/ ^m² ·day or more, even more preferably 2.0 g/ ^m² ·day or more, and particularly preferably 2.5 g/ ^m² ·day or more. The upper limit of moisture permeability is preferably 8.0 g/ ^m² ·day or less, more preferably 6.0 g/ ^m² ·day or less, and even more preferably 5.5 g/ ^m² ·day or less.
The moisture permeability was measured on the laminate before filling with contents, according to Japanese Industrial Standard (JIS) Z 0208-1976 "Test Method for Moisture Permeability of Moisture-Proof Packaging Materials (Cup Method)". The measurement condition was 25°C.

The laminate of the present invention is characterized in that the ratio of moisture permeability (g/ ^m² ·day) to oxygen permeability (mL/ ^m² ·day·atm) (moisture permeability/oxygen permeability) is 3.5 or higher.
The ratio of water vapor permeability to oxygen vapor permeability (water vapor permeability/oxygen vapor permeability) is preferably 4.0 or higher, and more preferably 4.5 or higher. There is no particular upper limit to the ratio of water vapor permeability to oxygen vapor permeability (water vapor permeability/oxygen vapor permeability), but for example, it is 10.0 or lower.
When the ratio of moisture permeability to oxygen permeability (moisture permeability/oxygen permeability) is 3.5 or higher, packaged foods using the laminated packaging material of the present invention, particularly packaged meat products (such as ham), can maintain their appearance (color) immediately after high-pressure processing.

Furthermore, the laminate of the present invention is characterized in that its oxygen permeability (mL/ ^m² ·day·atm) and moisture permeability (g/ ^m² ·day) satisfy the conditions of the following formula (1).
Y>4.2X+z Formula (1)
(However, X represents oxygen permeability, Y represents water vapor permeability, and z is -1.5.)
When the oxygen permeability and moisture permeability satisfy the conditions of formula (1) above, packaged foods using the packaging material made of the laminate of the present invention, particularly packaged meat products (such as ham), can maintain their appearance (color) immediately after high-pressure processing.

In formula (1), z is preferably -0.52, more preferably ±0.00, and particularly preferably +0.50.

As shown in Figure 1, the laminate 1 of the present invention includes a laminated structure in which an oxygen barrier layer is present in the intermediate layer 3 located between the outermost layer 2 and the innermost layer 4 that is in contact with the contents. Depending on the purpose, other layers can be arbitrarily provided as the intermediate layer.

(outermost layer)
The outermost layer is susceptible to mechanical forces. Therefore, it is preferable to include a resin that has toughness, pinhole resistance, and puncture resistance, as well as a function that protects the inner layer from water and oxygen.
Therefore, resins used as the outermost layer include polyolefins, cyclic polyolefin resins, ethylene-(meth)acrylic acid ester copolymers, ethylene-(meth)acrylic acid copolymers, ethylene-(meth)acrylic acid ester-(meth)acrylic acid copolymers, ethylene-vinyl acetate copolymers, acrylic resins, ionomer resins, styrene polymers, polyvinylidene chloride polymers, fluororesins, polyimides, polyimidoamides, silicones, polyesters, polycarbonates, polyamides (nylon), polyurethanes, acetal resins, polysulfone resins, polyarylene ether resins, and cellulose resins. These may be used individually or mixed in combination as a composition.
Among the above resins, polyester, polyolefin, and polyamide are preferred due to their ease of availability, processability into films or sheets, and superior mechanical strength and internal visibility when formed into films or sheets.

Specifically, examples of polyolefins include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene (ethylene-butene copolymer, ethylene-hexene copolymer, and ethylene-octene copolymer, etc.), ethylene-propylene copolymer, and polypropylene.
Examples of cyclic olefin resins include ring-opening metathesis polymers (such as norbornene ring-opening polymers) and addition copolymers of cyclic olefins and olefins (such as ethylene).
Examples of styrene-based resins include polystyrene, acrylonitrile-styrene copolymer, and acrylonitrile-butadiene-styrene copolymer.
Examples of polyesters include polyethylene terephthalate, polytrimethylene terephthalate, polytetramethylene terephthalate, polyethylene naphthalate, polytrimethylene naphthalate, and polytetramethylene naphthalate.
Examples of polyamides include nylon-6 and nylon-6,6.

(Middle class)
The intermediate layer includes a layer containing a resin with oxygen gas barrier properties, a layer consisting of a metal or metal oxide with oxygen gas barrier properties, or a layer containing an oxygen absorber (hereinafter collectively referred to as the "oxygen barrier layer").
<Oxygen barrier layer>
The oxygen barrier layer prevents oxygen from entering the inside of the package.
The oxygen barrier layer may consist of only one layer or two or more layers. If two or more oxygen barrier layers are provided, they may be of the same type or different types, and their thicknesses may be the same or different.

In this specification, a resin having oxygen gas barrier properties means one in which an unstretched sample with a film thickness of 20 μm has an oxygen permeability of 5.0 mL/ ^m² ·day·atm or less when measured at 23°C and 0% RH.
Resins having oxygen gas barrier properties include, for example, resins having a polyvinyl alcohol (EVA) structure such as vinyl acetate polymer saponified, trifluorovinyl acetate polymer saponified, vinyl formate polymer saponified, vinyl pivalate polymer saponified, butyl vinyl ether polymer saponified, and trimethylsilyl vinyl ether polymer saponified; resins having an ethylene vinyl alcohol copolymer (EVOH) structure such as ethylene vinyl acetate copolymer saponified, ethylene trifluorovinyl acetate copolymer saponified, ethylene vinyl formate copolymer saponified, ethylene vinyl pivalate copolymer saponified, ethylene butyl vinyl ether copolymer saponified, and ethylene trimethylsilyl vinyl ether copolymer saponified; polyvinylidene chloride polymers containing vinyl chloride as a constituent monomer; and polyamide MDX6 (a condensed polymer of m-xylenediamine and adipic acid).

Layers made of metals or metal oxides that have oxygen gas barrier properties include layers manufactured by depositing metals or metal oxides. Examples of metals or metal oxides include aluminum, silicon, magnesium, and tin, as well as their oxides.
Examples of layers containing an oxygen absorber include a layer in which Ageless (registered trademark, Mitsubishi Gas Chemical Co., Ltd.) is dispersed in the resin listed in the outermost layer section or in a resin having oxygen gas barrier properties.
The oxygen barrier layer is preferably made of a resin having oxygen gas barrier properties due to its ease of availability and processing, and its excellent visibility of the contents. Resins having an ethylene-vinyl alcohol copolymer (EVOH) structure and polyvinylidene chloride polymers are more preferred.

A deposited film of metal or metal oxide can be formed on a substrate that forms the innermost or outermost layer, or an intermediate layer, by, for example, vacuum deposition, sputtering, ion plating, plasma chemical vapor deposition, or thermochemical vapor deposition.
(Other middle class)
In addition to the oxygen barrier layer, any other layer can be provided in the intermediate layer depending on the purpose (e.g., toughness, pinhole resistance, puncture resistance, moisture barrier properties, or rigidity).
For example, the resins or resin compositions listed in the outermost layer section can be cited.
Furthermore, generally, vinyl alcohol polymers, ethylene-vinyl alcohol copolymers, and polyamide MDX6, which have oxygen barrier properties, experience a decrease in oxygen barrier properties due to moisture absorption. For this reason, a layer containing a hydrophobic resin may be provided on one or both sides of the oxygen barrier layer.

(Innermost layer)
Since the innermost layer comes into contact with the packaged item and seals it by the seal, it is preferable that the innermost layer be a resin or resin composition with excellent heat-sealing properties and chemical stability.
Examples of innermost layers include polyolefins, cyclic olefin resins, acrylic resins, cyclic olefin resins, ethylene-vinyl acetate copolymers, ethylene-(meth)acrylate alkyl copolymers, ethylene-(meth)acrylic acid copolymers, ionomer resins, unsaturated carboxylic acid-modified polyolefin resins, ethylene-(meth)acrylate alkyl ester-unsaturated carboxylic acid copolymers, and amorphous polyesters.
Specifically, examples include low-density polyethylene, high-density polyethylene, linear low-density polyethylene (ethylene-hexene copolymer and ethylene-octene copolymer, etc.), ultra-low-density polyethylene, ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-4-methyl-1-pentene copolymer, polypropylene, cyclic olefin ring-opening polymer, ethylene-cyclic olefin addition copolymer, ethylene-(meth)acrylic acid 2-ethylhexyl copolymer, and ethylene-(meth)acrylic acid copolymer. These may be used individually or mixed in groups of two or more to form a resin composition.
Due to their availability, hydrophobic properties for protecting the oxygen barrier layer, and sealing capabilities, polyolefins and cyclic olefin resins and their resin compositions are preferred, and low-density polyethylene, high-density polyethylene, linear low-density polyethylene, ultra-low-density polyethylene, ethylene-propylene copolymers and ethylene-butene copolymers and their resin compositions are more preferred.

Furthermore, in order to facilitate the removal of the processed material, it is preferable that the innermost layer, either alone or together with other layers, has easy-peel properties. The easy-peel properties may be of the cohesive peeling type, interlayer peeling type, or interfacial peeling type.
Examples of resins or resin compositions having easy-peel properties include resin compositions containing ultra-low density polyethylene, linear low density polyethylene, and polypropylene; resin compositions containing 4-methyl-1-pentene-propylene copolymer and propylene-ethylene-butene copolymer; and resin compositions containing 4-methyl-1-pentene-propylene copolymer and linear low density polyethylene (ethylene-1-hexene copolymer).

The laminate of the present invention may contain ultraviolet absorbers, antioxidants, heat stabilizers, lubricants, fillers, reinforcing materials, plasticizers, crosslinking agents, light stabilizers, antistatic agents, mold release agents, surfactants, antibacterial and antifungal agents, flame retardants, desiccants, nucleating agents, coupling agents, antifogging agents, and colorants.

The thickness of the film or sheet when the laminate of the present invention is made into a film or sheet is not particularly limited. The film thickness is preferably 20 μm or more, more preferably 50 μm or more, and even more preferably 70 μm or more. By making the film thickness 20 μm or more, unexpected damage can be prevented and the strength of the film can be improved. The film thickness is preferably 300 μm or less, more preferably 250 μm or less, even more preferably 200 μm or less, and most preferably 150 μm or less. If the film thickness is 300 μm or less, the processability of the film during packaging is improved and the processed material can be easily removed.
Furthermore, for food packaging, it is preferable that the contents being processed can be seen from the outside. For this reason, the film or sheet using the laminate of the present invention is preferably transparent.

[Method for manufacturing laminates]
There are no particular limitations on the method for manufacturing a laminated film or sheet. For example, each layer may be manufactured and then laminated, with each layer being bonded together via an adhesive resin layer using an adhesive, heat, or pressure. Alternatively, single-layer films or sheets may be manufactured and then laminated, for example, by dry lamination, extrusion coating, co-extrusion coating, or sand lamination. Furthermore, all or part of the laminated film or sheet may be laminated by co-extrusion.
Methods for manufacturing each layer of film or sheet include, for example, film deposition methods such as casting, T-die method, cutting method, or inflation method.
Furthermore, each layer may be unstretched or stretched independently. Stretching may be uniaxial stretching, biaxial stretching, or stretching by inflation. Biaxial stretching may be sequential biaxial stretching or simultaneous biaxial stretching. Sequential biaxial stretching may be tubular stretching or tenter (T-die) stretching.
Furthermore, after manufacturing a laminate with each layer remaining unstretched, the entire laminate may be stretched by uniaxial stretching, biaxial stretching, or inflation.

To enhance adhesion between layers, each layer may be subjected to corona discharge treatment, ozone treatment, electron beam treatment, low-temperature plasma treatment, or glow discharge treatment. Furthermore, a primer coat layer, an undercoat layer, and an adhesive layer may be formed on the surface of each layer.

[Packaging material]
The type of packaging is not particularly limited as long as it can seal the contents to be processed. Examples include gas pack packaging and vacuum packaging, but vacuum packaging is preferred. Examples of packaging forms include deep draw packaging, skin pack, four-sided seal packaging, three-sided seal packaging, stick packaging, pillow packaging, gusset bag packaging, and standing pouch. Deep draw packaging and skin pack are preferred, with deep draw packaging being more preferred, because they allow for a tight, airtight seal between the contents and the packaging material.

The shape of the packaging material used for packaging is not particularly limited. For example, it can be in the form of a film, sheet, or tube.
Furthermore, surface treatment to improve tear resistance may be applied to facilitate the removal of the processed material.

The packaging material used for packaging may be a single laminate or a combination of two or more laminates.
For example, in three-side seal packaging, the object to be treated is placed on a film or sheet, and the package is sealed by folding it over so that the sealant layer is on the inside.
Furthermore, in skin packs, for example, the contents to be processed are sealed by sealing the lid and bottom. In this case, different packaging materials may be used for the lid and bottom.

Any known sealing method can be used. Examples include thermocompression sealing, high-frequency sealing, and ultrasonic sealing.

In the case of packaging using two or more types of packaging materials, it is preferable that the area of the packaging material using the laminate of the present invention accounts for 50% or more of the area in contact between the packaging material and the object to be processed (hereinafter referred to as the "contact area"). Here, the packaging material using the laminate of the present invention is a packaging material having an oxygen permeability of 1.0 mL/ ^m² ·day·atm or less, a packaging material having a ratio of water vapor permeability to oxygen permeability (water vapor permeability/oxygen permeability) of 3.5 or more, or a packaging material whose oxygen permeability and water vapor permeability satisfy the conditions of formula (1) above.
Additionally, other packaging materials with an oxygen permeability of 15 mL/ ^m² ·day·atm or less can be used.
Examples of packaging that uses two or more types of packaging materials include packaging that uses a base made of a packaging material using the laminate of the present invention and a base made of another packaging material.

[Packaged food]
The following explanation will use as an example a packaged food 10 in which the product to be processed 12 is deep-draw packaged using a bottom material 11A and a lid material 11B as packaging materials 11, as shown in Figure 2. The bottom material 11A is a packaging material with an oxygen permeability of 1.0 mL/ ^m² ·day·atm or less, and the lid material 11B is a packaging material with an oxygen permeability of 15 mL/ ^m² ·day·atm or less.

(Bottom material)
The base material is manufactured from the laminate of the present invention, occupies more than 50% of the contact area of the packaging material, and prevents oxygen from entering the inside of the package. The base material is a packaging material that shrinks to conform to the shape of the object being processed, making it possible to display the object in a three-dimensional manner.

In deep-draw packaging, the bottom material deforms to conform to the shape of the object being processed, resulting in a thinner film thickness and a tendency for unevenness. Therefore, it is preferable to apply the packaging material of the present invention (a packaging material with an oxygen permeability of 1.0 mL/ ^m² ·day·atm or less, a packaging material with a ratio of moisture permeability to oxygen permeability (moisture permeability/oxygen permeability) of 3.5 or more, or a packaging material in which the oxygen permeability and moisture permeability satisfy the conditions of formula (1) above) to the bottom material of deep-draw packaging. This further enhances the effect of the present invention in suppressing discoloration of the object being processed.

(lid material)
The lid material is a packaging material that functions as a lid for the bottom material, and its shape is not particularly limited, but it is preferable that it is a packaging material that maintains a flat shape. By making the shape of the lid material flat, it is possible to obtain packaged food in which the expiration date and ingredient list can be easily seen. The outermost layer of the lid material is preferably a layer containing a printable resin. The printable resin is a polar resin, and examples include nylon or polyester.
Additionally, the lid material can have a printed layer in the middle layer.

Because the lid material undergoes minimal deformation in deep-draw packaging, it is less susceptible to the effects of high-pressure processing. Therefore, packaging materials with an oxygen permeability exceeding 1.0 mL/ ^m² ·day·atm can be used for the lid material of deep-draw packaging. There is no particular upper limit to the oxygen permeability of the lid material of deep-draw packaging, but for example, it is 15 mL/ ^m² ·day·atm or less, preferably 10 mL/ ^m² ·day·atm or less, and more preferably 8 mL/ ^m² ·day·atm or less.

(Object to be processed)
There are no particular restrictions on the processed material. Examples include meat products, seafood products, and vegetable products. Meat products are preferred. Specific examples of meat products include ham, bacon, prosciutto, roast pork, wieners/frankfurters, dried meat, sausages, hamburgers, meatballs, braised pork, salad chicken, smoked chicken, and yakitori. They may also contain liquids or gelatinous substances such as sauces, soups, or jellies. Specific examples of seafood products include sashimi, simmered fish, grilled fish, fish sausage, and dried seafood. Specific examples of vegetable products include cut raw vegetables, boiled vegetables, stir-fried vegetables, and pickles. Since the discoloration of red meat is particularly noticeable in meat and seafood products, the discoloration-suppressing effect of the present invention is even more pronounced.

The shape of the processed product is not particularly limited, but examples include block-processed foods, sliced foods, and minced foods. When the processed product is sliced or minced, the surface area increases, making it more susceptible to discoloration over time. Furthermore, since sliced foods are displayed with their cut surfaces facing outwards, discoloration is particularly noticeable. Therefore, the discoloration-suppressing effect of the present invention is even more pronounced when the processed product is a sliced food.

[Packaging method]
For packaging used in high-pressure processing, vacuum packaging is preferred because air pockets can cause whitening of the packaging material. Examples of degassing methods include chamber degassing, mechanical degassing, and nozzle degassing.

[High-pressure processing method]
High-pressure processing is a method of sterilization and disinfection that involves applying extremely high pressure at or near room temperature. Because this method minimizes heat-induced denaturation, it preserves flavor and nutrients, and allows for uniform processing of the entire object being treated.
<Pressure>
The pressure for high-pressure processing is, for example, between 50 MPa and 1000 MPa. The lower limit of the high-pressure processing pressure is preferably 100 MPa or higher, more preferably 200 MPa or higher, even more preferably 300 MPa or higher, and particularly preferably 450 MPa or higher. The upper limit of the high-pressure processing pressure is preferably 800 MPa or lower, more preferably 700 MPa or lower. At 100 MPa or higher, sterilization and disinfection are possible, and food can be preserved for a long period of time. Furthermore, at 1000 MPa or lower, the intrusion of oxygen and moisture into the inside of the package can be suppressed.
The pressurization may be carried out continuously or intermittently. The pressures may be the same or different.

<Temperature>
The temperature for high-pressure processing is preferably between 0°C and 60°C, between 3°C and 50°C, and more preferably between 5°C and 40°C. A temperature above 0°C prevents the processed material from freezing and prevents damage to the package during pressurization. A temperature below 60°C suppresses thermal denaturation of the processed material. The temperature may be uniform or varied during the pressurization process.

<Time>
The duration of the high-pressure treatment is not particularly limited. Preferably, it is 30 seconds to 1800 seconds, more preferably 60 seconds to 900 seconds, and even more preferably 150 seconds to 250 seconds. A duration of 30 seconds or more provides sterilization and disinfection effects, allowing the treated object to be stored for a long period. A duration of 1800 seconds or less prevents the treated object from being compressed and hardened. If the pressure is applied intermittently, the duration is the total time of pressure application.

<Pressurized media>
Water is generally used as the pressurizing medium in high-pressure applications. However, other chemically stable liquids besides water can also be used as the pressurizing medium. To prevent oxygen gas contained in the water from entering the package, it is preferable to use deaerated water or water purged of oxygen gas using an inert gas (such as nitrogen or argon).

The present invention will be specifically described below with reference to examples, but the technical scope of the present invention is not limited by these examples.

The measurement and evaluation methods used in this invention are as follows.
[1] Oxygen permeability: This value was measured at 23°C and 0% RH based on the Japanese Industrial Standard (JIS) K 7216-2:2006 "Coulometric method (MOCON method)" (isobaric method).
[2] Moisture permeability: This value was measured at 25°C based on Japanese Industrial Standard (JIS) Z 0208-1976 "Test method for moisture permeability of moisture-proof packaging materials (cup method)".
[3] Evaluation of discoloration After high-pressure treatment, the color of the treated material was visually evaluated.
(Evaluation criteria)
○: No change in color was observed.
△: The color has faded slightly.
×: The color has faded.

<Test 1: Visual evaluation of the color of the treated object (1)>
[Example 1]
Sliced roast ham was used as the material to be processed. A film with an oxygen permeability of 0.5 mL/ ^m² ·day·atm and a moisture permeability of 3.3 g/ ^m² ·day (PP/EVOH/NY/PE-based EP, 160 μm thick) was used as the base material, and a film with an oxygen permeability of 1.0 mL/ ^m² ·day·atm and a moisture permeability of 5.1 g/ ^m² ·day (PP/barrier NY/LLDPE, 95 μm thick) was used as the lid material. The PE-based EP was used as the innermost layer of the base material, and the LLDPE was used as the innermost layer of the lid material. Sliced roast ham was placed on the lid material, the film that would serve as the base material was heated and drawn into shape, then the sliced roast ham was covered, a vacuum (1 kPa) was created between the base material and the lid material, and it was sealed to perform deep-draw packaging. The proportion of the contact area occupied by the base material was 50% or more.
The manufactured deep-drawn packaged food was subjected to high-pressure treatment by using water as the pressurizing medium and applying pressure at a hydrostatic pressure of 600 MPa for 210 seconds.
After leaving the treated materials at 10°C until each evaluation day, the color of the treated materials was visually inspected.

[Example 2]
The procedure was carried out in the same manner as in Example 1, except that a film with an oxygen permeability of 0.5 mL/ ^m² ·day·atm and a moisture permeability of 2.7 g/ ^m² ·day (NY/EVOH/NY/PE-based EP, 250 μm thick) was used as the bottom material and a film with an oxygen permeability of 4.5 mL/ ^m² ·day·atm and a moisture permeability of 3.4 g/ ^m² ·day (PP/KNY/LLDPE, 95 μm thick) was used as the lid material instead of the bottom material and lid material in Example 1.

[Example 3]
Sliced roast ham was used as the material to be processed, a film with an oxygen permeability of 0.5 mL/ ^m² ·day·atm and a moisture permeability of 2.7 g/ ^m² ·day (NY/EVOH/NY/PE-based EP, 250 μm thick) was used as the base material, and a film with an oxygen permeability of 6.5 mL/ ^m² ·day·atm and a moisture permeability of 3.6 g/ ^m² ·day (PP/KNY/LLDPE, 95 μm thick) was used as the lid material. The PE-based EP base material and the LLDPE lid material were used as the innermost layers. Sliced roast ham was placed on the lid material, the film that would serve as the base material was heated and pressed into shape, then the sliced roast ham was covered, a vacuum (1 kPa) was created between the base material and the lid material, and it was sealed to perform deep-draw packaging.
The manufactured deep-drawn packaged food was subjected to high-pressure treatment by using water as the pressurizing medium and applying pressure at a hydrostatic pressure of 600 MPa for 180 seconds.
After leaving the treated materials at 10°C until each evaluation day, the color of the treated materials was visually inspected.

[Example 4]
The procedure was carried out in the same manner as in Example 3, except that a film (NY/EVOH/NY/PE-based EP, 220 μm thick) with an oxygen permeability of 0.6 mL/ ^m² ·day·atm and a moisture permeability of 3.2 g/ ^m² ·day was used as the base material instead of the base material used in Example 3.

[Example 5]
In Example 3, instead of using the same base material, a film (NY/oxygen-absorbing layer/PE, 200 μm thick) with an oxygen-absorbing layer having an oxygen permeability of 0.0 mL/ ^m² ·day·atm and a moisture permeability of 3.6 g/ ^m² ·day as an intermediate layer was used as the base material, and the PE base material was used as the innermost layer. Otherwise, the procedure was the same as in Example 3.

[Comparative Example 1]
In Example 1, instead of the bottom material and lid material, a film with an oxygen permeability of 2.0 mL/ ^m² ·day·atm and a moisture permeability of 6.2 g/ ^m² ·day (NY/EVOH/NY/PE-based EP, 150 μm thick) was used as the bottom material, and a film with an oxygen permeability of 2.5 mL/ ^m² ·day·atm and a moisture permeability of 8.0 g/ ^m² ·day (NY/EVOH/NY/PE, 80 μm thick) was used as the lid material, and the PE-based EP of the bottom material and the PE of the lid material were used as the innermost layers, except that the procedure was the same as in Example 1.

[Comparative Example 2]
In Example 3, instead of the bottom material and lid material, a film with an oxygen permeability of 1.5 mL/ ^m² ·day·atm and a moisture permeability of 4.3 g/ ^m² ·day (PP//NY/PE-based EP, 150 μm thick) was used as the bottom material, and a film with an oxygen permeability of 3.7 mL/ ^m² ·day·atm and a moisture permeability of 4.7 g/ ^m² ·day (PP//NY/EVOH/NY/PE, 80 μm thick) was used as the lid material, with the PE lid material serving as the innermost layer. The procedure was carried out in the same manner as in Example 3. Note that "PP//NY/EVOH/NY/PE" is a laminate of PP film and NY/EVOH/NY/PE film.

[Comparative Example 3]
In Example 3, instead of the bottom material and lid material, a film with an oxygen permeability of 1.1 mL/ ^m² ·day·atm and a moisture permeability of 2.9 g/ ^m² ·day (NY/EVOH/NY/PE-based EP, 250 μm thick) was used as the bottom material, and a film with an oxygen permeability of 2.2 mL/ ^m² ·day·atm and a moisture permeability of 7.4 g/ ^m² ·day (NY/EVOH/NY/PE, 100 μm thick) was used as the lid material, with the PE of the lid material being the innermost layer. The procedure was carried out in the same manner as in Example 3.

[Reference example 1]
In Comparative Example 2, the procedure was carried out similarly, except that high-pressure treatment was not performed.

Table 1 shows the laminate structure, film thickness, oxygen permeability, and moisture permeability used in the Examples, Comparative Examples, and Reference Example 1, and Table 2 shows the results of the high-pressure treatment.

The meanings of the abbreviations in Table 1 are as follows:
PP: Polypropylene EVOH: Ethylene vinyl alcohol copolymer (ethylene vinyl acetate copolymer keene)
NY: Nylon Barrier NY: Organic Acid Coated Barrier Nylon KNY: Polyvinylidene Chloride Coated Nylon PE: Polyethylene LLDPE: Linear Low-Density Polyethylene PE-based EP: Polyethylene-based Easy Peel Film

A comparison between Reference Example 1 and Comparative Example 2 revealed that the material in Reference Example that was deep-drawn and packaged without high-pressure treatment did not show discoloration, while the material that underwent high-pressure treatment did.

In Example 5, where an oxygen absorption layer was provided in the intermediate layer, no discoloration of the treated material occurred even after high-pressure treatment, suggesting that oxygen is influencing the discoloration of the treated material.

Materials treated with a laminate having an oxygen permeability of 1.0 mL/ ^m² ·day·atm or less as the base material showed no discoloration for 75 days or more, regardless of the treatment time (Examples 1-5). In contrast, materials treated with a laminate having an oxygen permeability exceeding 1.0 mL/ ^m² ·day·atm as the base material showed discoloration (Comparative Examples 1-3).

<Test 2: Evaluation of color changes using a color difference system>
Next, the color changes over time were evaluated for the deep-drawn packaged foods of Example 5, Comparative Example 2, and Reference Example 1 using a colorimeter. Measurements were taken from the outside of the deep-drawn packaged foods in their original state. A "CR-400" colorimeter (manufactured by Konica Minolta Japan, Inc.) was used. The color difference ΔE* was calculated from the L*a*b* value of the deep-drawn packaged food immediately after high-pressure processing or after packaging, and from the L*a*b* value of the packaged food after a predetermined number of storage days. The change in ΔE* was evaluated as the change in color of the deep-drawn packaged food. The results are shown in Figure 3.

Referring to Figure 3, in conventional packaged foods using laminates, there was no change in color in the untreated (Reference Example 1) product, whereas in the treated (Comparative Example 2) product, the color of the ham changed significantly.
Furthermore, it can be seen that even when packaged food using the laminate of the present invention (Example 5) is subjected to high-pressure treatment, there is no change in the color of the ham being treated, just as with packaged food using a conventional laminate that has not been subjected to high-pressure treatment.

<Test 3: Visual evaluation of the color of the treated object (2)>
In addition to Examples 1-5 and Comparative Examples 1-3, packaged foods were manufactured in the same manner as in Example 1 of Test 1 for Examples 6-10 and Comparative Examples 4 and 5 shown in Table 3. For Examples 6-10 and Comparative Examples 4 and 5, laminates with the oxygen permeability and moisture permeability shown in Table 3 were used as the base material, and the same laminate as in Example 3 shown in Table 1 was used as the lid material. Next, the color changes of the obtained packaged foods were visually evaluated. The evaluation results are shown in Table 3.
Examples 1-5 and Comparative Examples 1-3 shown in Table 3 represent the results of Test 1.

Referring to Table 3, when the ratio of moisture permeability to oxygen permeability (moisture permeability/oxygen permeability) was 3.5 or higher, no discoloration occurred for 75 days or more (Examples 1-10). In contrast, treated materials using a laminate with a ratio of moisture permeability to oxygen permeability (moisture permeability/oxygen permeability) of less than 3.5 as the base material experienced discoloration (Comparative Examples 1-5).

Next, for the laminates of Examples 1-10 and Comparative Examples 1-5, the relationship between oxygen permeability and water permeability was plotted in Figure 4, with oxygen permeability on the X-axis and water permeability on the Y-axis. The plot marks are indicated by symbols representing the evaluation of color fading.

Referring to Figure 4, it was found that Examples 1-10 and Comparative Examples 1-5 have different distributions. Analyzing these distributions, three straight lines (A) to (C) were drawn.
(A) From Examples 1 to 10, a straight line was drawn passing through Examples 4 and 9 (gray circles), which had a small ratio of water vapor permeability to oxygen vapor permeability (water vapor permeability / oxygen vapor permeability). This straight line was given by the following equation (A).
Formula (A): Y=4.2X+0.68
(B) Next, equation (A) was slid along the Y-axis to draw a straight line passing through comparative example 3. This straight line was given by the following equation (B).
Formula (B): Y=4.2X-1.72
(C) Also, a straight line was drawn that was midway between equations (A) and (B). This straight line was given by the following equation (C).
Formula (C): Y=4.2X-0.52

From these results, it can be concluded that no discoloration occurred because the oxygen permeability (mL/ ^m² ·day·atm) and moisture permeability (g/ ^m² ·day) satisfied the conditions of the following formula (1).
Y>4.2X+z Formula (1)
(However, X represents oxygen permeability, Y represents water vapor permeability, and z is -1.5.)

The packaged food of the present invention is used for products to be sterilized or disinfected by a high-pressure processing method. In particular, it is preferably used for meat products and seafood products.
The packaging material of the present invention is used for sealing and packaging objects to be processed in high-pressure processing methods.
The laminate of the present invention is intended for use as packaging material for objects to be processed in high-pressure processing methods.

1 Laminated body, 2 Outermost layer, 3 Intermediate layer, 4 Innermost layer, 10 Packaged food, 11 Packaging material, 11A Bottom material, 11B Lid material, 12 Packaged object

Claims (11)

A packaged food comprising a product to be processed and a packaging material for packaging the product to be processed,
The aforementioned packaging material is
The oxygen permeability is 1.0 mL/ ^m² /day·atm or less.
The moisture permeability is 1.0 to 10 g/m² ^· day.
The laminate comprises (a) an outermost layer, (b) an intermediate layer, and (c) an innermost layer.
The (b) intermediate layer comprises at least one of a layer selected from a layer containing a resin having oxygen gas barrier properties and a layer containing an oxygen absorber.
A packaged food product characterized in that the product to be processed is subjected to pressure treatment while sealed with the packaging material. A packaged food comprising a product to be processed and a packaging material for packaging the product to be processed,
The aforementioned packaging material is
The ratio of water vapor permeability (g/ ^m² ·day) to oxygen permeability (mL/ ^m² ·day·atm) (water vapor permeability/oxygen permeability) is 3.5 or higher.
The moisture permeability is 1.0 to 10 g/m² ^· day.
The laminate comprises (a) an outermost layer, (b) an intermediate layer, and (c) an innermost layer.
The (b) intermediate layer comprises at least one of a layer selected from a layer containing a resin having oxygen gas barrier properties and a layer containing an oxygen absorber.
A packaged food product characterized in that the product to be processed is subjected to pressure treatment while sealed with the packaging material. A packaged food comprising a product to be processed and a packaging material for packaging the product to be processed,
The aforementioned packaging material is
The oxygen permeability (mL/ ^m² ·day·atm) and moisture permeability (g/ ^m² ·day) satisfy the following conditions in equation (1):
The moisture permeability is 1.0 to 10 g/m² ^· day.
The laminate comprises (a) an outermost layer, (b) an intermediate layer, and (c) an innermost layer.
The (b) intermediate layer comprises at least one of a layer selected from a layer containing a resin having oxygen gas barrier properties and a layer containing an oxygen absorber.
A packaged food product characterized in that the product to be processed is subjected to pressure treatment while sealed with the packaging material.
Y>4.2X+z Formula (1)
(However, X represents oxygen permeability, Y represents water vapor permeability, and z is -1.5.) The packaged food according to any one of claims 1 to 3, wherein the oxygen permeability of the packaging material is 0.5 mL/ ^m² /day·atm or more and 1.0 mL/ ^m² /day·atm or less. The oxygen permeability (mL/m³) of the aforementioned packaging material ² Moisture permeability (g/m) relative to day/atm ² The packaged food according to any one of claims 1 to 4, wherein the ratio of (water permeability/oxygen permeability) of day is 4.0 or higher. The packaged food according to any one of claims 1 to 5, characterized in that the pressure of the pressurization treatment is 50 MPa or more and 1000 MPa or less, and the temperature during the pressurization treatment is 5°C or more and 60°C or less. The packaged food according to any one of claims 1 to 6, characterized in that the processed material is a meat product. The packaged food according to any one of claims 1 to 7, characterized in that the processed product is a sliced food product. The packaged food according to any one of claims 1 to 8, characterized in that the innermost layer (c) is a layer made of a heat-sealable resin or resin composition. A packaging material characterized by its use in packaged food products as described in any one of claims 1 to 9. A laminate characterized by its use in the packaging material described in claim 10.