JP2024098186A - Resin film and packaging bag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a packaging bag capable of suppressing the occurrence of black spots on surfaces of root vegetables during storage of the root vegetables at a room temperature, and a resin film for constituting the packaging bag.

SOLUTION: Provided is a resin film 1 for suppressing the occurrence of black spots on surfaces of root vegetables when the root vegetables are packaged and stored. The resin film 1 has 1 to 40 through holes 12 having an average diameter of 8,000 μm or less per m², wherein a water vapor transmission rate of the resin film 1 in an atmosphere of 90% RH is 50 g/m² day or more. A packaging bag 101 is constructed by using the resin film 1.

SELECTED DRAWING: Figure 5

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a resin film and a packaging bag.

When storing and preserving foods such as fruits and vegetables that have not been heat-treated, packaging bags are required to be able to maintain the freshness of the foods without losing their freshness.
When fruits and vegetables are stored in a packaging bag, there is a problem that the concentrations of oxygen gas and carbon dioxide gas in the packaging bag change due to the fact that the fruits and vegetables continue to breathe during storage. It is known that fruits and vegetables respire actively and are consumed when the oxygen gas concentration is high in the packaging bag. Therefore, in order to prevent such problems, various packaging bags and packaging methods have been studied.

For example, a packaging bag for vegetable and other plant materials has been disclosed that has a specific range of water vapor permeability that is specific to the film material that constitutes the packaging bag, and further has a specific range of oxygen permeability due to holes in the film (see Patent Document 1).

Among fruits and vegetables, black spots may appear on the surface during storage, particularly in the case of root vegetables such as radishes. This is particularly noticeable when stored at room temperature. Figure 1 shows image data of a radish with black spots on its surface. It is known that the number of such black spots gradually increases during storage of the radish. This is presumably because the radish's tissues stop functioning when some deterioration occurs on the surface of the radish exposed to the external environment. However, since the black spots only appear on the surface (surface layer), there is no problem with the quality of the parts deeper than the surface (surface layer), and if these surface areas are removed, there is no problem in using the radish for consumption.

Special Publication No. 7-94263

However, no means have been disclosed to date for preventing the occurrence of such black spots during storage at room temperature. If it were possible to prevent the occurrence of black spots in root vegetables stored at room temperature, it would be of great significance as it would reduce the amount of food waste.

The present invention aims to provide a packaging bag that can prevent the occurrence of black spots on the surface of root vegetables during storage at room temperature, and a resin film for forming the packaging bag.

In order to solve the above problems, the present invention employs the following configuration.
[1] A resin film for suppressing the occurrence of black spots on the surface of root vegetables when the root vegetables are packaged and stored, the resin film having 1 to 40 through holes per square meter with an average diameter of 8,000 μm or less, and a water vapor transmission rate of the resin film of 50 ^g / ^m2 ·day or more in an atmosphere of 90% RH.
[2] The resin film according to [1], wherein the root vegetable is Japanese radish.
[3] A packaging bag made using the resin film according to [1] or [2].

[4] The packaging bag described in [3], in which the root vegetables are stored in the storage section of the packaging bag under atmospheric conditions, and then the opening of the packaging bag is sealed to produce a sealed packaging bag, and when the sealed packaging bag is stored at room temperature for 24 hours, the oxygen gas concentration in the storage section of the sealed packaging bag is 5 volume % or less and the carbon dioxide gas concentration is 15 volume % or more.
[5] The packaging bag according to [3] or [4], wherein when the opening of the packaging bag is closed, the capacity of the packaging bag is 30 L or less.

The present invention provides a packaging bag that can suppress the occurrence of black spots on the surface of root vegetables during storage at room temperature, and a resin film for constituting the packaging bag.

This is image data of a radish with black spots on its surface. 1 is a perspective view showing a schematic diagram of an example of a packaging bag according to an embodiment of the present invention. FIG. 11 is a perspective view showing a schematic diagram of another example of a packaging bag according to one embodiment of the present invention. 1 is a perspective view showing an example of a state in which root vegetables are packaged using a packaging bag according to one embodiment of the present invention. FIG. 1 is a cross-sectional view showing an example of a state in which root vegetables are packaged using a packaging bag according to one embodiment of the present invention. FIG. 10 is a perspective view showing another example of a state in which root vegetables are packaged using a packaging bag according to one embodiment of the present invention. FIG. 10 is a cross-sectional view showing another example of a state in which root vegetables are packaged using a packaging bag according to one embodiment of the present invention. FIG. FIG. 2 is a schematic diagram showing the evaluation criteria when evaluating the effect of suppressing the occurrence of black spots on packaging bags in Example 1 and Comparative Example 1. 1 is a graph showing the evaluation results of the effect of suppressing the occurrence of black spots on packaging bags in Example 1 and Comparative Example 1.

<<Resin film>>
A resin film according to one embodiment of the present invention is intended to suppress the occurrence of black spots on the surface of root vegetables when the root vegetables are packaged and stored, and the resin film has 1 to 40 through holes per square ^meter with an average diameter of 8,000 μm or less, and the water vapor transmission rate of the resin film in an atmosphere of 90% RH is 50 g/ ^m2 ·day or more.
By packaging root vegetables in a packaging bag made using the resin film of this embodiment, the occurrence of black spots on the surface of the root vegetables during storage at room temperature can be suppressed.

In this specification, "room temperature" means a temperature that is neither cooled nor heated, i.e., a normal temperature, such as a temperature between 15 and 25°C.

Examples of the root vegetables include Japanese radish, carrot, taro, and burdock.
Among them, it is preferable that the root vegetable is Japanese radish, since this has a higher effect of suppressing the occurrence of black spots.

Examples of resins contained in the resin film include polyolefins such as polyethylene (PE) and polypropylene (PP); polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), and polybutylene naphthalate (PBN); polyamides such as nylon; ethylene-vinyl alcohol copolymers (EVOH) and other ethylene-based copolymers (copolymers having structural units derived from ethylene and other structural units); polyvinyl resins such as polyvinyl chloride (resins having structural units derived from monomers having a vinyl group (ethenyl group)); polycarbonates, etc.

Among the resins contained in the resin film, examples of the polyethylene include low density polyethylene (LDPE), linear low density polyethylene (LLDPE), metallocene-catalyzed linear low density polyethylene (metallocene LLDPE), medium density polyethylene (MDPE), and high density polyethylene (HDPE).

In this specification, the density of the low density polyethylene, linear low density polyethylene, and metallocene-catalyzed linear low density polyethylene is 0.910 g/cm ³ or more and less than 0.945 g/cm ³ .
The density of the medium density polyethylene is equal to or greater than 0.945 g/cm ³ and less than 0.955 g/cm ³ .
The density of high density polyethylene is 0.955 g/ ^cm3 or more.

Among the resins contained in the resin film, examples of the polypropylene include homopolypropylene (hPP), propylene-ethylene random copolymer (also known as polypropylene random copolymer, sometimes referred to as "rPP" in this specification), and propylene-ethylene block copolymer (also known as polypropylene block copolymer, sometimes referred to as "bPP" in this specification).

The resin film may contain only one type of resin, or two or more types. If there are two or more types, the combination and ratio of the resins can be selected as desired depending on the purpose.

The resin film may contain other components in addition to the resin. That is, the resin film may be composed of the resin and the other components.

The resin film may contain only one type of other component, or two or more types. If there are two or more types, the combination and ratio of these components can be selected as desired depending on the purpose.

The other components are not particularly limited as long as they are non-resin components, and can be arbitrarily selected depending on the purpose.
Examples of the other components that are non-resin components include additives known in the art.

Examples of the additives include antifogging agents, antiblocking agents, antioxidants, antistatic agents, crystal nucleating agents, inorganic particles, viscosity reducers, thickeners, heat stabilizers, lubricants, infrared absorbers, and ultraviolet absorbers.

In the resin film, the ratio of the content of the other components to the total mass of the resin film ([content of other components of resin film (parts by mass)]/[total mass of resin film (parts by mass)]×100) is preferably 20% by mass or less, more preferably 10% by mass or less, and may be, for example, any of 5% by mass or less, 3% by mass or less, and 1% by mass or less. When the ratio of the content of the other components is equal to or less than the upper limit, the effect obtained by the resin film containing the resin is enhanced.
On the other hand, the content of the other components is 0 mass % or more.

In other words, in the resin film, the ratio of the resin content (parts by mass) to the total mass (parts by mass) of the resin film ([resin content (parts by mass) of resin film]/[total mass (parts by mass) of resin film]×100) is preferably 80% by mass or more, more preferably 90% by mass or more, and may be, for example, any one of 95% by mass or more, 97% by mass or more, and 99% by mass or more.
On the other hand, the content of the resin is 100% by mass or less.
The ratio of the resin content is usually the same as the ratio of the resin content (parts by mass) to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming a resin film described below ([resin content (parts by mass) of composition for forming a resin film] / [total content (parts by mass) of components that do not vaporize at room temperature in composition for forming a resin film] x 100).

In the resin film, the ratio of the total content (parts by mass) of the polyolefin, polyester, polyamide, polyvinyl resin, and polycarbonate to the content (parts by mass) of the resin ([total content (parts by mass) of polyolefin, polyester, polyamide, polyvinyl resin, and polycarbonate in the resin film]/[resin content (parts by mass) in the resin film]×100) is preferably 80% by mass or more, more preferably 90% by mass or more, and may be, for example, any one of 95% by mass or more, 97% by mass or more, and 99% by mass or more. When the ratio of the total content is equal to or more than the lower limit, the effect of suppressing the occurrence of black spots on the surface of root vegetables when the root vegetables are packaged and stored in a packaging bag manufactured using the resin film is enhanced.
On the other hand, the total content is 100% by mass or less.
The ratio of the total content is usually the same as the ratio of the total content (parts by mass) of the polyolefin, polyester, polyamide, polyvinyl resin and polycarbonate to the resin content (parts by mass) in the composition for forming a resin film described below ([total content (parts by mass) of polyolefin, polyester, polyamide, polyvinyl resin and polycarbonate in the composition for forming a resin film] / [resin content (parts by mass) in the composition for forming a resin film] × 100).
Here, for resins among polyolefins, polyesters, polyamides, polyvinyl resins and polycarbonates that are not contained in the resin film and the composition for forming a resin film, the content of that resin in the resin film and the composition for forming a resin film is 0 parts by mass.

The resin film may be made of one layer (single layer) or may be made of two or more layers. When the resin film is made of multiple layers, these multiple layers may be the same or different, and the combination of these multiple layers is not particularly limited as long as it does not impair the effects of the present invention.

In this specification, not only in the case of the resin film, "multiple layers may be the same or different" means "all layers may be the same, all layers may be different, or only some layers may be the same," and further, "multiple layers are different" means "at least one of the constituent materials and thicknesses of each layer is different from each other."

When the resin film is made up of multiple layers, one of the outermost layers may be a sealant layer. The sealant layer may be a known one.

The thickness of the resin film is not particularly limited, but is preferably 15 to 40 μm, and more preferably 20 to 30 μm.
Here, the "thickness of the resin film" means the thickness of the entire resin film. For example, the thickness of a resin film consisting of multiple layers means the total thickness of all layers constituting the resin film.

The resin film has through-holes with an average diameter (mean size) of 8000 μm or less.
The shape of the opening of the through hole on the surface of the resin film and the shape of the opening of the through hole in a cross section perpendicular to the longitudinal direction are not particularly limited, and may be, for example, any of a circular shape, an elliptical shape, a polygonal shape such as a triangular shape or a rectangular shape, a shape in which two or more shapes selected from the group consisting of a circular shape, an elliptical shape and a polygonal shape are combined, etc. However, from the viewpoint of ease of forming the through hole, the shape is preferably a circular shape.
In this specification, unless otherwise specified, the "opening of the through hole" means both the opening of the through hole on the surface of the above-mentioned resin film and the opening of the through hole in a cross section perpendicular to its longitudinal direction.

If the shape of the opening of the through hole is other than circular, the diameter of the through hole means the longest length (maximum diameter) of the lengths of the line segments connecting two different points of the opening.

The average diameter of the through holes is preferably 50 to 8000 μm, more preferably 60 to 4500 μm, and particularly preferably 70 to 1000 μm, and may be, for example, either 70 to 700 μm or 70 to 300 μm. By having the average diameter of the through holes in this range, when an object to be packaged (e.g., the root vegetables) is placed and stored in the storage section of a packaging bag manufactured using the resin film, the concentrations of oxygen gas, carbon dioxide gas, and water vapor in the storage section can be adjusted in a balanced manner to a more suitable range. Furthermore, by having the average diameter of the through holes be equal to or greater than the lower limit, the production of the resin film becomes easier.

The number of the through holes in the resin film (the number of through holes per unit area of the resin film) is 1 to 40/m ² , preferably 2 to 30/m ² , more preferably 3 to 20/m ² , and particularly preferably 4 to 10/m ^2. By having the number of through holes in such a range, when an object to be packaged (e.g., the root vegetables) is housed and stored in a storage section of a packaging bag manufactured using the resin film, the concentrations of oxygen gas, carbon dioxide gas, and water vapor in the storage section can be adjusted in a balanced manner to a more suitable range.

The number of through holes in the resin film, i.e., the number of through holes per unit area (1 ^m2 ) of the resin film, can be adjusted by adjusting either or both of the area of the resin film and the number of through holes per resin film.

The position of the through holes in the resin film is not particularly limited, but it is preferable that the through holes are in an area other than the heat-sealed area, the cut area, or the heat-sealed area during the manufacture of the packaging bag described below. In this way, all of the through holes in the resin film can be made to function effectively in the packaging bag.

The water vapor transmission rate of the resin film in an atmosphere of 90% RH (relative humidity 90%) is 50 g/ ^m2 ·day or more, preferably 70 g/ ^m2 ·day or more, more preferably 80 g/ ^m2 ·day or more, and particularly preferably 100 g/ ^m2 ·day or more. When the water vapor transmission rate of the resin film is equal to or more than the lower limit, a sufficient effect is obtained that the packaged object (e.g., the root vegetables) can be stored in a fresh state without losing its freshness by using a packaging bag manufactured using the resin film.

There is no particular limitation on the upper limit of the water vapor transmission rate of the resin film in an atmosphere of 90% RH (relative humidity 90%).
For example, when an item to be packaged (e.g., the root vegetables) is placed and stored in a storage section of a packaging bag manufactured using a resin film, the water vapor transmission rate is preferably 400 g/ ^m2 ·day or less, since this increases the effect of preventing the item to be packaged from drying and wilting.
In one embodiment, the water vapor permeability of the resin film may be, for example, any one of 50 to 400 g/ ^m2 ·day, 70 to 400 g/ ^m2 ·day, 80 to 400 g/ ^m2 ·day, and 100 to 400 g/ ^m2 ·day, although these are only examples of the water vapor permeability.

The water vapor permeability of the resin film is preferably the water vapor permeability in an atmosphere of 40°C and 90% RH.

The water vapor permeability of the resin film can be adjusted, for example, by adjusting the size or number of the through holes, or the type or thickness of the components contained in each layer constituting the resin film.

The water vapor permeability of the resin film can be measured in accordance with JIS K 7129B.

<<Method of manufacturing resin film>>
The resin film can be produced by a known method using a resin film-forming composition containing the components for constituting the resin film.
The composition for forming a resin film may be produced by adjusting the type and content of the components so that the resin film contains the desired components in the desired content. For example, the ratio of the contents of the components that do not vaporize at room temperature in the composition for forming a resin film is usually the same as the ratio of the contents of the components in the resin film.

The resin film-forming composition may be, for example, a resin composition containing the resin, and optionally the other components, and optionally a solvent.

Use of the solvent may improve the handleability of the resin film-forming composition.
In this specification, unless otherwise specified, the term "solvent" is used as a concept that includes not only a substance that dissolves a target component, but also a dispersion medium that disperses the target component.
Examples of the solvent include organic solvents and water.

The resin film-forming composition may contain only one type of solvent, or may contain two or more types of solvents. When two or more types of solvents are contained, the combination and ratio thereof can be selected arbitrarily.
The content of the solvent in the composition for forming a resin film is not particularly limited, and may be appropriately selected depending on, for example, the types of components other than the solvent.

The resin film can be produced, for example, by using an extruder to melt-extrude and mold a resin film-forming composition to produce an unprocessed resin film that does not have the through holes, and then forming the through holes in the unprocessed resin film.
When producing a resin film consisting of one layer (single layer), an unprocessed resin film consisting of one layer can be produced by the above-mentioned method. When producing a resin film consisting of multiple layers, for example, several extruders can be used to co-extrude and mold the respective resin film forming compositions for forming each layer, thereby producing an unprocessed resin film consisting of multiple layers.

An unprocessed resin film consisting of multiple layers can also be produced, for example, by separately producing or preparing in advance two or more films for constituting any two or more of the layers, laminating these two or more films together using a thermal lamination method or the like without using an adhesive, and further laminating other layers as necessary so as to achieve the desired arrangement.

An unprocessed resin film consisting of multiple layers can also be produced by, for example, producing or preparing a film that will form one or more of the layers in advance, coating or drying a resin film-forming composition for constituting the other layers in the unprocessed resin film onto this film to form a laminated structure of two or more layers, and, if necessary, further laminating the other layers so as to form the desired arrangement.

Unprocessed resin films consisting of one layer (single layer) or multiple layers can also be produced in the form of a tube by, for example, an inflation method using a resin film-forming composition.

Methods for forming the through holes in the raw resin film include known methods such as piercing the raw resin film with a needle or irradiating it with a laser.

<<Packaging bag>>
A packaging bag according to one embodiment of the present invention is formed using the resin film according to one embodiment of the present invention described above.
Since the packaging bag of this embodiment is constructed using the resin film, when root vegetables are packaged and stored using the packaging bag of this embodiment, the occurrence of black spots on the surface of the root vegetables during storage at room temperature can be suppressed.

FIG. 2 is a perspective view showing a schematic diagram of an example of the packaging bag of the present embodiment.
The packaging bag 101 shown here is configured using the resin film 1 according to one embodiment of the present invention described above. Note that through holes in the resin film 1 are omitted in Fig. 2.

The overall shape of the packaging bag 101 is a thin bag shape, and the opening area of the opening 10 of the packaging bag 101 is narrow.
The two main surfaces of the packaging bag 101 have a rectangular planar shape. At least one of a first side 101a, a second side 101b opposite thereto, and a third side 101c connecting the first side 101a and the second side 101b in the packaging bag 101 is formed by heat sealing. Among the first side 101a, the second side 101b, and the third side 101c, the sides that are not formed by heat sealing are formed by folding the resin film 1.

The item to be packaged (e.g., root vegetables) can be packaged by placing it in the storage section 11 through the opening 10 of the packaging bag 101 and then closing the opening 10.

In this specification, not limited to the case of the packaging bag 101, blocking the opening means an operation of closing the opening to an extent that it is possible to prevent the insertion and removal of items into and from the storage section of the packaging bag, and includes, for example, an operation of sealing the entire area of the opening to hermetically seal the items in the storage section, and an operation of narrowing the opening area of the opening to an extent that it prevents the passage of items without sealing the entire area or a part of the opening. The operation of narrowing the opening area of the opening includes an operation of twisting the opening. When the operation of narrowing the opening area of the opening is performed, a jig such as a tie may be attached to the closing section in order to maintain the narrowed state of the opening area.

FIG. 3 is a perspective view that illustrates a schematic diagram of another example of the packaging bag of the present embodiment.
In FIG. 3 and subsequent figures, the same components as those shown in the figures already described are given the same reference numerals as in the figures already described, and detailed description thereof will be omitted.
The packaging bag 102 shown here is also configured using the resin film 1 according to one embodiment of the present invention described above. Also in Fig. 3, through holes in the resin film 1 are omitted from illustration.

The overall shape of the packaging bag 102 is a wide bag shape, and the opening area of the opening 20 of the packaging bag 102 is large. Furthermore, the packaging bag 102 has a bottom 102a.

The item to be packaged (e.g., root vegetables) can be packaged by placing it in the storage section 21 through the opening 20 of the packaging bag 102 and then closing the opening 20.

The shape of the packaging bag of this embodiment is not limited to that shown in FIGS. 2 and 3, so long as it is bag-shaped.
For example, the packaging bag 101 shown in Figure 2 has a rectangular planar shape when closed, and the packaging bag 102 shown in Figure 3 has an overall shape like a basket, but the packaging bag of this embodiment may have other shapes such as a bottomed cylindrical shape (a cylindrical shape with a bottom at one end that is closed), or it does not have to have a clearly definable shape like these.

Figure 4 is a schematic perspective view of an example of root vegetables packaged using the packaging bag of this embodiment, and Figure 5 is a cross-sectional view.

The packaging bag 101 shown here is made of a resin film 1 as explained above, and ten root vegetables 9 are stored in the storage section 11 of the packaging bag 101 .
More specifically, five root vegetables 9 are aligned in a row with their length directions and orientations all aligned in the storage section 11. Furthermore, on top of this row (five root vegetables) of root vegetables 9, five more root vegetables 9 are similarly aligned in a row with their length directions and orientations all aligned, stacked on top of the five root vegetables 9. That is, in the storage section 11 of the packaging bag 101, two rows of five root vegetables 9 are stacked on top of each other, and all ten root vegetables are arranged with their length directions and orientations aligned in the same way.

FIG. 5 is a cross-sectional view of the packaging bag in which root vegetables are packaged, taken along a direction perpendicular to the longitudinal direction of the root vegetables.
As shown in Fig. 5, the resin film 1 is provided with a plurality of through holes 12 that extend from one surface (the surface opposite to the storage section 11 side) 1a to the other surface (the surface on the storage section 11 side) 1b, penetrating the resin film 1 in the thickness direction. Note that the through holes are not shown in the resin film 1 in Fig. 4.

After the root vegetables 9 are stored in the packaging bag 101, the opening 10 is twisted and this state is maintained by using a fastener 8, and the opening 10 of the packaging bag 101 is closed to become a closed opening 10'.
When the packaging bag 101 is looked down from above and from a position overlooking the entire length of the root vegetables 9, the closed opening 10' (opening 10) is positioned in a position that does not overlap with the root vegetables 9 (more specifically, in a position away from one end of the root vegetables 9 on the opposite side to the root vegetables 9).

Although the fastener 8 is ring-shaped, in this embodiment, the shape and the closing (binding) method of the fastener are not particularly limited as long as the fastener is a jig that can maintain the closure of the opening 10.
For example, in this embodiment, a cable tie may be used as the tie to tie the opening 10 of the packaging bag 101 with the cable tie to close the opening 10, or a string may be used as the tie to tie the opening 10 of the packaging bag 101 with the string to close the opening 10, or a rubber band may be used as the tie to tighten the opening 10 of the packaging bag 101 with the rubber band to close the opening 10. However, these are only examples of a method of closing the opening with a tie. Also, in this embodiment, the opening 10 may be closed by tying a portion of the packaging bag 101 closer to the storage section 11 than the opening 10 without using a tie.

Figure 6 is a perspective view showing another example of root vegetables packaged using the packaging bag of this embodiment, and Figure 7 is a cross-sectional view.

The packaging bag 102 shown here is made of the resin film 1 as explained above, and ten root vegetables 9 are stored in the storage section 21 of the packaging bag 102 .
The manner in which the ten root vegetables 9 are stored in the storage section 21 of the packaging bag 102 is similar to the manner in which the ten root vegetables 9 are stored in the storage section 11 of the packaging bag 101, and in the storage section 21 of the packaging bag 102, two rows of five root vegetables 9 are stacked together, and all ten root vegetables are arranged with the length direction and orientation aligned.

FIG. 7 is a cross-sectional view of the packaging bag in which root vegetables are packaged, taken in a direction perpendicular to the longitudinal direction of the root vegetables, similar to FIG.
As shown in Fig. 7, the resin film 1 has a plurality of through holes 12 formed therein, similar to the case shown in Fig. 5. Note that the through holes are not shown in the resin film 1 in Fig. 6.

After the root vegetables 9 are stored in the packaging bag 102, the opening 20 is twisted and this state is maintained by using a fastener 8, so that the opening 20 of the packaging bag 102 is closed to become a closed opening 20'.
When the packaging bag 102 is viewed from above and from a position overlooking the entire length of the root vegetables 9, the closed opening 20' (opening 20) is located at a position overlapping the root vegetables 9.

The opening 20 of the packaging bag 102 can be closed in the same manner as the opening 10 of the packaging bag 101, including the use or non-use of a fastener.

The packaging form of root vegetables in the packaging bag of this embodiment is not limited to those shown in Figs.
For example, in Figures 4 to 7, ten root vegetables are stored in one packaging bag, but the number of root vegetables stored in one packaging bag can be adjusted as appropriate depending on the size of the packaging bag, the type of root vegetables, etc.
For example, in Figures 4 to 7, the root vegetables are arranged in two rows in the storage section of the packaging bag, but they may be arranged in any number of rows other than two. Also, in Figures 4 to 7, the length directions and orientations of all the root vegetables are the same, but the length directions and orientations of some of the root vegetables may be different, or the length directions of all the root vegetables may be the same and the orientations of some of the root vegetables may be opposite to those of the other root vegetables.
For example, in Figures 4 to 7, multiple root vegetables are arranged with their length directions aligned, but the arrangement of multiple root vegetables can be adjusted as desired according to the shape of the root vegetables and is not particularly limited. If the length direction of the root vegetables cannot be clearly defined, the arrangement of the root vegetables does not need to be defined.

The number of through holes in the region forming the storage section of the packaging bag (the number of through holes per unit area of the storage section forming region) is preferably 1 to 40/ ^m2 , more preferably 2 to 30/ ^m2 , even more preferably 3 to 20/ ^m2 , and particularly preferably 4 to 10/ ^m2 . By setting the number of through holes in the storage section forming region within such a range, the concentrations of oxygen gas, carbon dioxide gas, and water vapor in the storage section can be adjusted in a balanced manner to a more suitable range. Furthermore, the effect of suppressing the occurrence of black spots on the surface of root vegetables during storage at room temperature is further enhanced.

When the opening of the packaging bag (e.g., opening 10 shown in FIG. 2, opening 20 shown in FIG. 3) is closed, the capacity of the packaging bag (e.g., the capacity of storage section 11 when opening 10 shown in FIG. 2 is closed opening 10', and the capacity of storage section 21 when opening 20 shown in FIG. 3 is closed opening 20') is preferably 1 L or more, and may be, for example, 5 L or more, 10 L or more, or 15 L or more. In this way, the effect of suppressing the occurrence of black spots on the surface of root vegetables during storage of the root vegetables at room temperature is enhanced.
In this specification, unless otherwise specified, the capacity of a packaging bag means the capacity of the storage section when the opening of the packaging bag is closed and it is assumed that there are no items (items to be packaged) present in the storage section.

On the other hand, the capacity of the packaging bag when the opening of the packaging bag is closed is not particularly limited. For example, in order to improve the handleability of the packaging bag containing root vegetables, it is preferable that the capacity of the packaging bag when the opening of the packaging bag is closed be 30 L or less.
In one embodiment, when the opening of the packaging bag is closed, the capacity of the packaging bag may be, for example, any one of 1 to 30 L, 5 to 30 L, 10 to 30 L, and 15 to 30 L. However, these are only examples of the capacity of the packaging bag 101.

In particular, packaging bags of this capacity are preferred when the total mass of the root vegetables to be stored is 5 to 30 kg, and more preferably when it is 7 to 15 kg. When these conditions are met, the effect of suppressing the occurrence of black spots on the surface of the root vegetables during storage at room temperature is particularly high.

When root vegetables are stored in the storage section of the packaging bag of this embodiment under atmospheric conditions, and then the opening of the packaging bag is sealed to produce a sealed packaging bag, and the sealed packaging bag is stored at room temperature for 24 hours, it is preferable that the oxygen gas concentration in the gas inside the storage section of the sealed packaging bag is 5% by volume or less and the carbon dioxide gas concentration is 15% by volume or more. By storing packaged root vegetables in this environment where the oxygen gas concentration is low and the carbon dioxide gas concentration is high, the effect of suppressing the occurrence of black spots on the surface of the root vegetables stored at room temperature is further enhanced. This is presumably because the respiration of the root vegetables during storage is suppressed to a low level within a more appropriate range, and the metabolism of the root vegetables is suppressed within a more appropriate range.

On the other hand, as described above, when the closed packaging bag is stored at room temperature for 24 hours, it is preferable that the oxygen gas concentration in the gas inside the storage section of the closed packaging bag is 1% by volume or more and the carbon dioxide gas concentration is 25% by volume or less. By making the oxygen gas concentration equal to or more than the lower limit and the carbon dioxide gas concentration equal to or less than the upper limit, the effect of suppressing the occurrence of black spots on the surface of root vegetables stored at room temperature and the effect of storing the root vegetables without losing their freshness and maintaining their freshness are both enhanced.

As described above, when the closed packaging bag is stored at room temperature for 24 hours, if the oxygen gas concentration in the gas inside the storage section of the closed packaging bag is 5% by volume or less and the carbon dioxide gas concentration is 15% by volume or more, these oxygen gas and carbon dioxide gas concentrations are maintained even after 24 hours from the start of storage. For example, an oxygen gas concentration of 5% by volume or less and a carbon dioxide gas concentration of 15% by volume or more can be maintained for up to 120 hours from the start of storage of the closed packaging bag.

As described above, when the sealed packaging bag is stored at room temperature for 24 hours, the oxygen gas concentration and carbon dioxide gas concentration in the gas inside the storage section of the sealed packaging bag can be adjusted, for example, by adjusting the manner in which the through holes are provided in the resin film, the type and content of the main components of the resin film, etc.

The sealed packaging bags are then packed in a known storage box such as a cardboard box or a plastic box, but it is preferable to store the storage box without sealing it after the sealed packaging bags have been packed in. This not only prevents black spots from appearing on the surface of the root vegetables during storage at room temperature, but also prevents damage to the root vegetables during storage.

<<Manufacturing method of packaging bags>>
The packaging bag can be produced by a known method.
For example, a packaging bag can be produced by folding a single sheet of the resin film at a desired location, and then heat-sealing opposing peripheral edges to form the opening and storage section.
For example, a packaging bag can be produced by using two of the above-mentioned resin films and heat-sealing the opposing peripheral edges to form the opening and the storage portion.
Such a manufacturing method is suitable as a manufacturing method for the packaging bag shown in FIG. 2, for example.

For example, a packaging bag can be produced by producing a tubular raw resin film by an inflation method, forming through holes in the raw resin film to produce a tubular resin film, cutting the tubular resin film to the desired length, and heat welding the cut portions.
For example, a packaging bag can be manufactured by producing a tubular unprocessed resin film by an inflation method, cutting the tubular unprocessed resin film to the desired length, heat-sealing the cut portions, and forming the through holes in the unprocessed resin film after cutting and heat-sealing.
Such a manufacturing method is suitable as a manufacturing method for the packaging bag shown in FIG. 3, for example.

<<How to package items>>
The items to be packaged, such as the root vegetables, can be packaged by known methods.
For example, as described above, the object to be packaged (e.g., root vegetables) can be packaged by placing the object to be packaged in the storage section through the opening of the packaging bag and then closing the opening.
The method for closing the opening is as described above.

It is preferable that the storage of the packaged object in the storage section of the packaging bag and the closing of the opening of the packaging bag are both performed under atmospheric conditions. This makes it easier to maintain the oxygen gas concentration of 5 volume % or less and the carbon dioxide gas concentration of 15 volume % or more in the gas in the storage section of the closed packaging bag when the closed packaging bag is stored at room temperature for 24 hours and when it is subsequently stored.

By adjusting the resin film, which is the raw material for producing the sealed packaging bag, and the method of sealing the opening of the packaging bag, it is preferable that when the sealed packaging bag is stored at room temperature for 24 hours or more, and preferably when it is stored continuously after 24 hours, the oxygen gas concentration in the storage section of the sealed packaging bag is 5 volume % or less and the carbon dioxide gas concentration is 15 volume % or more. Storing root vegetables in this manner increases the effect of suppressing the occurrence of black spots on the surface of root vegetables stored at room temperature.

The present invention will be described in more detail below with reference to specific examples. However, the present invention is not limited to the examples shown below.

[Example 1]
<<Manufacturing of packaging bags>>
The resin film prepared had a two-layer structure in which a polyamide layer (thickness 27 μm) and an ethylene-vinyl alcohol copolymer layer (thickness 3 μm) were laminated, had 6 through holes/ ^m2 with an average diameter of 120 μm, was 30 μm thick, and had a water vapor transmission rate of 150 g/ ^m2 -day in an atmosphere of 40°C and 90% RH.
This resin film was folded with the ethylene-vinyl alcohol copolymer layer on the inside and two opposing sides were heat-sealed (the ethylene-vinyl alcohol copolymer layers were heat-sealed together) to produce a packaging bag with an opening and dimensions of 1000 mm x 1000 mm (surface area of 2 x 10 ⁶ mm ² ).
The number of through holes in the storage section forming area of the obtained packaging bag was 6 per ^square meter.

<<Evaluation of packaging bags>>
Under atmospheric conditions and at room temperature, five radishes immediately after harvest were arranged in a row in the storage section of the packaging bag obtained above, and five more radishes immediately after harvest were similarly arranged in a row on top of the first row of radishes, resulting in a total of ten radishes arranged in two rows and stored as shown in Figures 4 and 5. However, all ten radishes were aligned in the same length direction, but some were reversed. These radishes were produced in Choshi City, Chiba Prefecture, and each radish weighed 0.9 to 1.5 kg, with the total mass of these radishes being 12 kg.
After storing these 10 radishes, the opening of the packaging bag was twisted and further maintained in this state using a tie to close the opening of the packaging bag and package the 10 radishes. At this time, the capacity of the packaging bag (storage section) was about 25 L.

The closed packaging bag was then packed into a cardboard box measuring 575 mm x 343 mm x 156 mm, and the opening of the cardboard box was folded to form a box shape, but the folded area was not sealed. In this state, the closed packaging bag inside the cardboard box was stored in air at a temperature of 25°C.

Using a gas concentration measuring device (MOCON Europe's "CheckPoint"), the concentrations of oxygen gas and carbon dioxide gas in the storage compartment of the sealed packaging bag after some time had passed since the start of storage were measured. As a result, it was confirmed that the oxygen gas concentration was stable at 4% by volume and the carbon dioxide gas concentration was stable at 17% by volume 24 hours after the start of storage and thereafter.

After some time had passed since the start of storage, the sealed packaging bags were removed from the cardboard box, and each of the 10 radishes was visually observed through the packaging bag. The number of black spots observed on the surface of the radishes was then classified into one of five levels using the criteria shown in Figure 8, and an evaluation score was given to each radish. The average of the 10 evaluation scores was then used as the evaluation score for the effect of suppressing the occurrence of black spots on the packaging bag. After evaluation, the sealed packaging bags were packed back into the cardboard box and continued to be stored, and such evaluations were performed at multiple times. The evaluation results at this time are shown in Figure 9.

<<Production and evaluation of packaging bags>>
[Comparative Example 1]
After storing 10 radishes, the packaging bag was manufactured and evaluated in the same manner as in Example 1, except that the opening of the packaging bag was not twisted and the bag was packed in a cardboard box with the opening left open. The radishes used were produced in Choshi City, Chiba Prefecture, and each radish weighed 0.9 to 1.5 kg, with the total weight of the radishes being 12 kg. The evaluation results are shown in Figure 9.
In this comparative example, the concentrations of oxygen gas and carbon dioxide gas in the storage portion of the unsealed packaging bag after a certain period of time had passed since the start of storage were measured in the same manner as in Example 1. As a result, it was confirmed that the oxygen gas concentration was stable at 21% by volume and the carbon dioxide gas concentration was stable at 0% by volume (below the detection limit) at 24 hours after the start of storage and thereafter.

As is clear from Figure 9, in Example 1, even five days after the start of storage, the evaluation score was at a high level of about 3 points. Five days after the start of storage, the number of black spots was only a few (less than 10) in all 10 radishes, and the ratio of the area where black spots were observed to the surface area of the radishes was less than 5%. Thus, the packaging bag of Example 1 was highly effective in suppressing the occurrence of black spots on the surface of the radishes during storage.

It was speculated that the reason why the packaging bag of Example 1 showed such results was because the opening of the packaging bag was sealed with the resin film. As a result, it was speculated that the oxygen gas concentration was kept low and the carbon dioxide gas concentration was kept high in the storage section of the sealed packaging bag during storage at room temperature, suppressing the respiration of the radish to a low level and suppressing the metabolism of the radish.

In contrast, in Comparative Example 1, the evaluation score continued to decrease immediately after the start of storage, and after five days, the number of black spots had increased dramatically in all ten radishes, with the ratio of the area where black spots were observed to the surface area of the radishes exceeding 50%. Thus, the packaging bag of Comparative Example 1 did not suppress the occurrence of black spots on the surface of the radishes during storage at room temperature.

It is speculated that the reason why the packaging bag of Comparative Example 1 showed such results is because the opening of the packaging bag was not sealed, even though the resin film was used. As a result, it is speculated that the gas composition in the storage section of the packaging bag during storage became closer to that of the atmosphere, the oxygen gas concentration was high, and the carbon dioxide gas concentration was maintained low, so that the respiration of the radish was not inhibited and the metabolism of the radish was not inhibited.

This invention can be used as a packaging bag for root vegetables.

1: Resin film 11, 21: Storage section of packaging bag 12: Through hole 9: Root vegetables 10, 20: Opening of packaging bag 101, 102: Packaging bag

Claims (5)

A resin film,
The resin film is intended to suppress the occurrence of black spots on the surface of root vegetables when the root vegetables are packaged and stored,
The resin film has through holes having an average diameter of 8000 μm or less in a number of 1 to 40 per ^square meter,
A resin film having a water vapor transmission rate of 50 g/ ^m2 ·day or more in an atmosphere of 90% RH. The resin film according to claim 1, wherein the root vegetable is Japanese radish. A packaging bag constructed using the resin film according to claim 1 or 2. The packaging bag according to claim 3, in which the root vegetables are stored in the storage section of the packaging bag under atmospheric conditions, and then the opening of the packaging bag is closed to produce a closed packaging bag, and when the closed packaging bag is stored at room temperature for 24 hours, the oxygen gas concentration in the storage section of the closed packaging bag is 5 volume % or less and the carbon dioxide gas concentration is 15 volume % or more. The packaging bag according to claim 3, wherein the volume of the packaging bag is 30 L or less when the opening of the packaging bag is closed.

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