JP2001063754A - Package for reserving freshness of fruit and vegetables - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a package for reserving freshness of fruit and vegetables, which is produced in a productivity equivalent to that of a normal packaging material film and has an excellent freshness-reserving effect which is not found in a conventional package. SOLUTION: In a bag-shaped package formed of a multi-layer film which is constituted by laminating an ethylene-vinyl acetate copolymer containing 15 to 30 wt.% of vinyl acetate on a polystyrene film, the ethylene-vinyl acetate copolymer layer contains 0.2 wt.% or more of organic or inorganic additive. Then, the multi-layer film has one or more fine hole per bag-shaped package, wherein one open area of the opening is 0.05 mm2 or lower. After a fruit and vegetables are put in this bag-shaped package, and a sealing is done, by the breathing of the content fruit and vegetables themselves, the concentration of carbon dioxide in the package becomes higher than the atmosphere, and the oxygen concentration in the package becomes lower than the atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an MA (Modified A)
tomosphere) to maintain the freshness of fruits and vegetables.
The present invention relates to a package for keeping freshness of fruits and vegetables in a bag-like package in which a film obtained by laminating a blend of a vinyl acetate copolymer and polyethylene is used in whole or in part.

[0002]

2. Description of the Related Art In recent years, a freshness maintaining material for fruits and vegetables having an MA (Modified Atomosphere) effect has been developed, and is mainly used for distribution. Fruits and vegetables continue to breathe even after harvesting, and when placed in an environment where the oxygen concentration is lower than the atmosphere (oxygen about 21%, carbon dioxide about 0.04%) and carbon dioxide concentration is high, respiration is suppressed and freshness is maintained. It is known that this is possible. However, if the package is in an environment of excessively low oxygen and high carbon dioxide, the fruits and vegetables will cause respiratory disorders and accelerate deterioration, and conversely, the oxygen concentration is too high or the carbon dioxide concentration is too low And a sufficient freshness retaining effect cannot be obtained. Also, if the humidity inside the package is too high, water droplets may form inside the package, making it difficult to see inside the package, causing mold or fruit and vegetables to rot.If the humidity is too low, the package may wilter or dry. Not preferred. That is, it is extremely important to control the inside of the package to an appropriate oxygen concentration, carbon dioxide concentration, and humidity. Here, since the amount of respiration of fruits and vegetables is completely different depending on the kind, temperature, cutting method, and the like, it is necessary to adjust the gas permeation amount and the moisture permeability of the packaging material according to them. When fruits and vegetables are hermetically sealed using a polymer film such as stretched polypropylene or polyethylene, which is commonly used for packaging of fruits and vegetables, the oxygen inside the package is consumed by respiration and the oxygen concentration becomes too low, resulting in poor freshness. Would. For this reason, films made by multiple manufacturers that produce micropores (pore diameter of several hundred μm or less) or scratches to maintain the freshness of fruits and vegetables by MA and increase the amount of oxygen gas permeation depending on the number and size of the films Is being developed. In any of these methods, the oxygen permeability, carbon dioxide permeability, and moisture permeability are determined by the material and thickness of the film, and the number and size of the micropores and scratches. This means that it is impossible to set oxygen permeability, carbon dioxide permeability, and moisture permeability independently and freely. For example, when a low moisture permeable resin such as stretched polypropylene is used, if the pores are made to have a predetermined oxygen permeability, there is a problem that moisture permeability is insufficient, water droplets are formed in the package, and mold grows. May occur. When the number of micropores is increased in order to increase the moisture permeability, the oxygen permeability becomes too high, and the preservability of the contents deteriorates. Therefore, it is necessary to use a highly moisture-permeable packaging material. General-purpose resins include polystyrene, polyvinyl alcohol, ethylene-vinyl acetate copolymer, and polyamide resin.

A technique for maintaining freshness of fruits and vegetables using a polystyrene film is disclosed in, for example, Japanese Patent Application Laid-Open No. 8-230933.
And Japanese Patent Application Laid-Open No. 10-117677.
These include a polystyrene film and an ethylene-vinyl acetate copolymer (Japanese Unexamined Patent Publication No.
No. 30933, JP-A-10-117677), or a perforated film of polyolefin (JP-A-6-117).
No. 219465) to obtain the required high moisture permeability. However, in the MA packaging of fruits and vegetables, the optimal oxygen concentration, carbon dioxide concentration, and humidity for keeping freshness vary greatly for all fruits and vegetables, and also vary depending on the temperature. For example, in a film using stretched polystyrene and an ethylene-vinyl acetate copolymer as disclosed in Japanese Patent Application Laid-Open No. 8-230933, although the moisture permeability is suitable, the oxygen permeation amount is too small for most vegetable packaging materials and the freshness is low. No retention effect is obtained. Further, in a method of laminating a perforated film of a stretched polystyrene film and a perforated film of a polyolefin as disclosed in JP-A-6-219465, in order to obtain optimal moisture permeability for vegetables, the porosity of the polyolefin film is extremely increased, and The polyolefin layer must be extremely thin, and it is difficult to say that it is practical from the viewpoint of production technology and material properties such as seal strength.
In order to solve this problem, as described in JP-A-10-117677, a microporous film having an average diameter of 100 to 800 μm is formed on a film bag formed by extrusion-coating an ethylene-vinyl acetate copolymer on a stretched polystyrene film. Opening less than one month was done. However, in such a large hole, the control of the amount of oxygen permeation cannot be performed with high accuracy, and the types of vegetables that can obtain the effect of maintaining freshness are limited. Further, in order to obtain such high moisture permeability, the proportion of vinyl acetate in the ethylene-vinyl acetate copolymer must be increased, and the material itself becomes considerably soft. MA packaging of fruits and vegetables can be roughly classified into two types of packaging methods. One is a type in which a bag-made product is manufactured in advance, and sealing is performed after filling the contents. In a broad sense, this includes a case where fruits and vegetables are manually packed into the bag-made product and hand-sealed. The other type is a type in which a film is supplied to a packaging machine in the form of a film roll and processed into a bag shape and filled and sealed in the packaging machine. Such a film obtained by laminating an ethylene-vinyl acetate copolymer having a high ratio of polystyrene and vinyl acetate has a high risk of causing problems such as blocking and wrinkling when applied to a bag making machine or a packaging machine. Furthermore, if the ethylene-vinyl acetate copolymer protrudes a little from the polystyrene film side when opening the micropores, the ethylene-vinyl acetate adheres to each other over time after winding and unwinds when used. There was a serious problem that the film was cut off from there. This problem is that the film cannot be wound up and stored in a roll shape in a state in which the fine holes are formed, which means that it cannot be actually used in a packaging machine of a type supplied by a film roll. In addition, it can be said that it is difficult to preserve the raw material in the state after the fine pores even when bag making is performed.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a freshness preserving package for fruits and vegetables which has the same level of productivity as a conventional packaging material film and has an unprecedented freshness preserving effect.

[0005]

According to the present invention, a polystyrene film is used as a base material and vinyl acetate is contained in an amount of 15 to 30% by weight.
By providing micropores in the film laminated with the ethylene-vinyl acetate copolymer contained, it becomes possible to keep the oxygen concentration and the humidity optimum for the fruits and vegetables to be packaged. In addition, the problem of blocking and wrinkling occurring in a packaging machine and a bag making machine caused by an ethylene-vinyl acetate copolymer, and the problem of breaking of a film caused by piercing a fine hole and storing it in a film roll is added to an organic or inorganic substance. This has been solved by adding an agent, and it has become possible to obtain a freshness-preserving package for fruits and vegetables having good freshness-retaining effect and productivity. That is, the present invention provides a polystyrene film with 15 to 30 vinyl acetate.
In a bag-like package consisting of a multilayer film obtained by laminating an ethylene-vinyl acetate copolymer containing 0.2% by weight of an ethylene-vinyl acetate copolymer, the ethylene-vinyl acetate copolymer layer contains at least 0.2% by weight of an organic or inorganic additive, The multilayer film has one or more micropores per one bag having an opening area of 0.05 mm ² or less per bag, and the fruits and vegetables are put in the bag-like package and hermetically sealed. Thereafter, the freshness holding package of fruits and vegetables has a carbon dioxide concentration in the package higher than that in the atmosphere due to the respiration of the fruits and vegetables themselves, and an oxygen concentration in the package lower than the atmosphere. Preferably,
A freshness-retaining package in which the oxygen concentration in the package becomes 0.2 to 17% within at least 48 hours after hermetically sealing. As a preferred embodiment, the fruits and vegetables using a bag-like package composed of only the multilayer film, a film different from the package, or a bag-like package composed of two or more types of sheet-like materials are used. This is a freshness maintaining package. In addition, the freshness maintaining package for fruits and vegetables, wherein the additive is a polyolefin resin, calcium carbonate or a silicate compound.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The polystyrene film used in the present invention may be a styrene homopolymer or a copolymer of styrene and another monomer, or may be a stretched one. The ethylene-vinyl acetate copolymer used in the present invention must have a vinyl acetate component of 15 to 30% by weight. If it is less than 15% by weight, the moisture permeability is too low and the freshness maintaining effect of the fruits and vegetables is not sufficient. If it exceeds 30% by weight, it is difficult to process the film, and even if the additive according to the present invention is added, the film cannot be practically used. As an additive to be added to the ethylene-vinyl acetate copolymer layer, a polyolefin resin such as polyethylene and polypropylene, and an inorganic substance such as calcium carbonate and a silicate compound are preferable.
These may be used alone or in combination of two or more. The amount added must be at least 0.2% by weight. Less than 0.2% by weight has no effect. In addition to these additives, other additives such as an antifogging agent and an antistatic agent may be blended. These may be used after being coated on a film.

[0007] The laminated film is provided with micropores in order to match the oxygen permeability to the fruits and vegetables to be packaged. In order to appropriately control the oxygen concentration in the package, it is necessary that the opening area of at least one opening is 0.05 mm ² or less. If it is larger than this, the amount of transmission per opening becomes too large, and it becomes difficult to control the atmosphere in the package. It is desirable that the micropores have a diameter of preferably 0.01 mm ² or less, more preferably 0.005 mm ² or less, because the atmosphere in the package can be controlled with higher precision. When processing into a bag-like shape, or when filling and sealing the contents, any means such as heat sealing, high frequency sealing, and ultrasonic sealing may be used. What is important is that the permeation of gas from the seal is practically negligible. These seals may be partially processed to be easily opened.

[0008] In order to obtain the effect of maintaining freshness, the oxygen concentration in the package is set within the range of 0.2 to 17% depending on the contents within 48 hours after packaging, and the state is stably maintained. Is preferred. For example, broccoli is 5
15%, 8-17% for carrots, 1 for soybean sprouts
10% is preferred. Means such as gas replacement may be used to quickly bring the gas concentration in the package to a predetermined range.
What is important is to control the oxygen permeation rate of the whole package according to the respiration rate of the fruits and vegetables in the contents. Hereinafter, the present invention will be described with reference to examples.

[0009]

EXAMPLES Example 1 A 20 μm thick film obtained by adding 5% by weight of polyethylene to an ethylene-vinyl acetate copolymer containing 20% by weight of vinyl acetate was laminated on a stretched polystyrene film having a thickness of 15 μm. The sucrose fatty acid ester-based antifogging agent was previously applied to the ethylene-vinyl acetate copolymer. In this film, about 0.02 holes / cm ² of fine holes having an opening area of about 0.02 mm ² were formed.
And stored at 35 ° C. for one month in a rolled state. After that, the film roll was set in an automatic packaging machine, 10 okras (about 100 g) were put therein, sealed and packaged, and stored at 12 ° C. At this time, there was no breakage of the film, and the packaging was performed without any problem. Bag size is 140 × 1
It was 60 mm. The oxygen concentration of the package after 48 hours had elapsed was 10.7% on average, and the package was stored until the 6th day, but the appearance and odor remained almost unchanged with no change. During the storage period, almost no water droplets adhered to the inside of the package, and the contents were always visible and good. << Comparative Example 1 >> The laminated film of Example 1 was not subjected to microfabrication, and was stored at 35 ° C. for one month, and then 10 okras were packaged by an automatic packaging machine as in Example 1. Packaging was performed without any problem, but the oxygen concentration in the package after 48 hours was 0.1 0.1 on average.
On the 5th day, the odor was quite offensive, and the storage condition was not good. Comparative Example 2 A stretched polystyrene film having a thickness of 15 μm was laminated with a 20 μm thick film obtained by adding 0.1% by weight of polyethylene to an ethylene-vinyl acetate copolymer containing 20% by weight of vinyl acetate. This ethylene
The vinyl acetate copolymer was previously coated with a sucrose fatty acid ester-based antifog agent. This film was processed so as to open micropores having a hole area of about 0.025 mm ² at a rate of about 0.02 / cm ² , and stored in a rolled state at 35 ° C. for one month. After that, it was set in an automatic packaging machine and 10 okras (about 100 g) were put in the container to manufacture a sealed package.

Example 2 A stretched polystyrene film having a thickness of 15 μm was laminated with a 20 μm thick film obtained by adding 2% by weight of calcium carbonate to an ethylene-vinyl acetate copolymer containing 20% by weight of vinyl acetate. The sucrose fatty acid ester-based antifogging agent was previously applied to the ethylene-vinyl acetate copolymer. In this film, about 0.03 micro pores having an opening area of about 0.02 mm ² /
It was perforated at a rate of cm ² and stored at 35 ° C. for 1 month in a wound state. After that, it was set on an automatic packaging machine, filled with about 200 g of edamame, hermetically sealed and stored at 5 ° C. At this time, there was no breakage of the film, and the packaging was performed without any problem. The bag size was 150 × 200 mm. The oxygen concentration of the package after 48 hours was 13% on average, and the package was stored until the 8th day. However, the package and the odor remained almost unchanged with little change in appearance and odor. During the storage period, almost no water droplets adhered to the inside of the package, and the contents were always visible and good. << Comparative Example 3 >> No vinyl acetate was added to a stretched polystyrene film having a thickness of 15 μm.
A 20 μm-thick ethylene-vinyl acetate copolymer containing 10% by weight was laminated. The sucrose fatty acid ester-based antifogging agent was previously applied to the ethylene-vinyl acetate copolymer. The aperture area of this film is about 0.02mm
^Two micropores were perforated at a rate of about 0.03 / cm ² , and stored in a rolled state at 35 ° C. for one month. After that, it was set in an automatic packaging machine and about 200 g of edamame was put into it and tried to be packaged in a sealed manner. << Comparative Example 4 >> Thickness 2 obtained by adding 2% by weight of calcium carbonate to an ethylene-vinyl acetate copolymer containing 10% by weight of vinyl acetate in a stretched polystyrene film having a thickness of 15 μm.
A 0 μm film was laminated. The sucrose fatty acid ester-based antifogging agent was previously applied to the ethylene-vinyl acetate copolymer. This film was stored in a rolled state at 35 ° C. for one month without fine processing. After that, it was set on an automatic packaging machine, filled with about 200 g of edamame, hermetically sealed and stored at 5 ° C. At this time, there was no breakage of the film, and the packaging was performed without any problem. After 48 hours, the package had an oxygen concentration of 0.1% on average. At that time, when the package was opened for quality confirmation, an odor caused by the anaerobic respiration of the bean was found.

[0011]

According to the present invention, a package for keeping freshness of fruits and vegetables which has few troubles in a packaging machine or a bag making machine and has good preservability can be obtained.

Claims (7)

[Claims] 1. A bag-like package comprising a multilayer film obtained by laminating an ethylene-vinyl acetate copolymer containing 15 to 30% by weight of vinyl acetate on a polystyrene film, wherein the ethylene-vinyl acetate copolymer layer is The multilayer film contains an organic or inorganic additive in an amount of 0.2% by weight or more, and the multilayer film has one or more micropores per bag having an opening area of 0.05 mm ² or less per bag. After putting the fruits and vegetables in the bag-shaped package and sealing it tightly, the respiration of the fruits and vegetables in the contents causes the carbon dioxide concentration in the package to be higher than that in the atmosphere, and the oxygen concentration in the package to be higher than that in the atmosphere. A freshness-retaining package for fruits and vegetables, characterized in that it has a lower concentration than that of (1). 2. The package according to claim 1, wherein the oxygen concentration in the package becomes 0.2 to 17% within at least 48 hours after the hermetically sealing. 3. The package for preserving freshness of fruits and vegetables according to claim 1, wherein the package comprises a bag-like package consisting of the multilayer film alone. 4. The package for preserving freshness of fruits and vegetables according to claim 1, wherein a bag-like package comprising two or more kinds of said multilayer film and a film different therefrom or a sheet-like material is used. 5. The package for preserving freshness of fruits and vegetables according to claim 1, wherein said additive is a polyolefin resin. 6. The package for preserving freshness of fruits and vegetables according to claim 1, wherein said additive is calcium carbonate. 7. The method according to claim 1, wherein said additive is a silicate compound.
4. The package for maintaining freshness of fruits and vegetables according to 4.