JPH07264975A - Packing material for retaining freshness of vegetable and fruit and method for retaining freshness of vegetable and fruit with the same - Google Patents

Abstract

PURPOSE:To provide the packing material for preserving the freshness of vegetables and fruits, capable of retaining the freshness of the vegetables and fruits for long periods without lowering oxygen permeability even when water drops are adhered to the inner surface of the packing material, by forming penetrated holes, etc., from the outer layer side of a film so that the oxygen permeability of the packing material is in a specific range. CONSTITUTION:This packing material for retaining the freshness of vegetables and fruits is produced by forming penetrated holes and non-penetrated holes or only the non-penetrated holes in a multi-layered film having a thermally fusing resin layer as at least the innermost layer from the outside layer side of the film so that the oxygen permeability of the packing material in which numerous fine penetrated holes and numerous non-penetrated holes each having a hole diameter of several mum to 100mum or only the non-penetrated holes are formed and which is used for retaining the freshness of the vegetables and the fruits is in a number value range of 1 to 1.1 times that of an oxygen permeability set by the equation (the oxygen permeability of the packing material: cm<3>/m<2>.day.atm; the respiration volume of the vegetables and the fruits: cm<3>/kg.day; the weight of the vegetables or the fruits: kg; the surface area of the packing material: m<2>; the inner equilibrium oxygen fraction pressure of the packing material: atm). The oxygen permeability of the packing material is preferably <=50000cm<3>/ m2.day.atom, and the vegetables and the fruits are preferably packed with the packing material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packaging material for keeping freshness of fruits and vegetables which can be maintained for a long period of time, and a freshness keeping method for hermetically packaging fruits and vegetables using the packaging material.

[0002]

2. Description of the Related Art As a freshness-keeping package for fruits and vegetables, there is a method for maintaining the freshness of fruits and vegetables by adjusting the gas composition in the package. This is because fruits and vegetables are generally lower in oxygen than normal air,
It utilizes the property that freshness is maintained when placed in a high carbon dioxide gas composition. Based on the balance of oxygen consumption and carbon dioxide generation by the above and the gas permeability of the packaging material, the gas composition in the package is balanced at a constant concentration (partial pressure) to maintain the freshness of fruits and vegetables.

In order to maintain a constant composition of oxygen and carbon dioxide in the package, it is important to set the gas permeability of the packaging material according to the respiration rate of fruits and vegetables. At this time, the gas permeability of the packaging material is It is determined by the respiration rate of fruits and vegetables, the weight of fruits and vegetables, the surface area of packaging material, and the target gas composition (equilibrium gas partial pressure). The respiration rate of fruits and vegetables here is not the respiration rate in the atmosphere at the storage temperature, but the expected respiration rate in the gas composition in the target packaging, and is generally the respiration rate in the atmosphere. The respiratory volume is 1/3 to 1/2 of the volume. The inventors
Up to now, the oxygen permeability of the packaging material in the freshness-keeping packaging of fruits and vegetables has been set by using the following (Equation 2) as an equation for setting the gas permeability of the packaging material.

[0004]

[Equation 2]

On the other hand, as a method of processing the packaging material so as to have a required gas permeability, the method described in JP-A-4-2499 and JP-A-5-38765 discloses a film having a pore size of several μm to 100 μm. There is a method of forming a large number of through holes or non-through holes.

However, freshness of fruits and vegetables was maintained by using a packaging material having such fine pores (hereinafter referred to as a fine pore packaging material) having a gas permeability set in (Equation 1). In this case, there is a problem that the oxygen partial pressure in the package becomes lower than the target equilibrium oxygen partial pressure, and the expected freshness-retaining effect cannot be obtained. This is because in a micropore packaging material, generally, fine pores are formed from the inner surface side of the packaging material, so when the fruits and vegetables are packaged, the pores are blocked by water droplets (or a water thin film) that adheres to the inner surface of the packaging material. This is because the gas permeability decreases.

That is, in the microporous packing material, the water permeability (or the water thin film) is attached, so that the oxygen permeability is 1/5 to 4/5 of that in the case where the water droplet (or the water thin film) is not attached. Is reduced. Therefore, when using a micropore packing material, as shown in Japanese Patent Application No. 6-3606, the oxygen permeability of the packing material is set by using the following (expression 3) instead of (expression 2). Had to do.

[0008]

[Equation 3]

However, in (Equation 3), the coefficient a is used to correct the decrease in the oxygen permeability of the micropore packing material due to the water droplet (or water thin film). The rate of decrease in oxygen permeability fluctuates depending on the adhesion state of the water thin film), so the value of the coefficient a fluctuates. Therefore, the coefficient a
It was difficult to accurately set the value of, and even if there was no problem in maintaining the freshness, it was not possible to maintain the optimum freshness maintaining state.

[0010]

In order to solve the above problems, according to the present invention, when vegetables and fruits are packaged, even if water droplets (or water thin films) adhere to the inner surface of the packaging material, the oxygen permeability is almost reduced. Therefore, it is an object of the present invention to provide a freshness-keeping packaging material for fruits and vegetables in which the oxygen permeability can be accurately set by using (Equation 2), and a freshness-keeping method for fruits and vegetables using the packaging material.

[0011]

The freshness-maintaining packaging material for vegetables and fruits of the present invention is a multilayer film in which at least the innermost layer is made of a heat-fusible resin such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, The film has a pore size of several μm to 10 μm so that the target oxygen permeability can be obtained in the film.
It is a micropore packing material in which innumerable 0 μm fine non-through holes and through holes or only non-through holes are formed. As a method of forming fine holes, a method represented by the methods described in JP-A-4-2499 and JP-A-5-38765 may be used.

Here, when forming fine pores in the above-mentioned multilayer film, by forming pores from the outer layer side of the film, water drops (or water) attached to the inner surface when used as a freshness-keeping packaging material for fruits and vegetables. The thin film prevents the oxygen permeability from being extremely decreased by blocking the pores. At this time, the fine pores formed in the film have a pore diameter of several μm to
As long as it is within the range of 100 μm, it may be only the non-through holes, or the through holes and the non-through holes may be mixed, and it is not limited.

Further, oxygen required for the above-mentioned fine pore packing material.
Permeability is the weight of the fruits and vegetables that are packaged, the respiration rate of the fruits and vegetables,
From surface area of packaging material and target gas composition (equilibrium gas partial pressure)
It may be set according to (Equation 2). Call of vegetables and fruits here
As described above, the amount of gas absorbed is not the value in the atmosphere but the target gas.
Respiratory volume expected in the composition, generally at storage temperature
The respiration rate of 1/2 to 1/3 of the respiration rate in the atmosphere is set.
Set. However, when processing from the outer surface side of the multilayer film
In this case, the non-penetrating hole is a water drop (or water film) attached to the inner surface.
Not affected, but the through holes are affected, so high acid
It is a micropore packing material with a high ratio of through holes that requires elementary permeability.
Is caused by water droplets (or water film) attached to the inner surface of the packaging material.
When the through hole is closed and a fine hole is formed from the inner layer side
Similarly, the oxygen permeability of the packaging material is greatly reduced. Therefore,
In such a case, it is shown in Japanese Patent Application No. 6-3606.
Thus, using (Equation 3) instead of (Equation 2), the acid of the packaging material is
The elemental transparency should be set and the hole should be
(Formula 2) can be applied to form oxygen permeation
Approximately 50,000 cm³/ M ²・ Day ・ atm
In the following cases.

Further, in practice, it was set from (Equation 2).
Make the oxygen permeability of the microporous packing material perfectly match the oxygen permeability.
Is difficult to achieve, and the oxygen permeability is 50,000.
cm ³/ M²・ Even if it is less than day ・ atm,
To completely eliminate the effect of water droplets (or water film) that adhere
However, the oxygen permeability is reduced by several percent. Therefore, fine
The oxygen permeability of the pore packing material depends on the water drop (or water thin film)
1 to 1.1 times the value set from (Equation 2) without
It should be in the numerical range. Note that (Equation 2) or (Equation
The oxygen permeability of the packaging material in 3) depends on the storage temperature of fruits and vegetables.
The oxygen permeability of the microporous packing material of the present invention.
Excessive temperature hardly affects the storage temperature.
It does not have to be the oxygen permeability of
It can be substituted.

Further, according to the present invention, the fruits and vegetables are hermetically packaged by a micropore packaging material having an oxygen permeability of 50,000 cm ³ / m ² · day · atm or less set by (Equation 2). The gas composition of can be maintained at a gas composition suitable for the fruits and vegetables, and the freshness of the fruits and vegetables can be maintained for a long period of time.

[0016]

In the past, the microporous film had micropores formed from the innermost layer side, but in the present invention, by processing from the outer layer side of the multilayer film, water drops (or water thin film) adhere to the inner surface of the packaging material. It is possible to prevent the decrease of the oxygen permeability due to, and therefore, even when the oxygen permeability is set, the correction by the uncertain coefficient a as shown in (Equation 3) is not necessary, and it is used conventionally (Equation 2). The oxygen permeability can be set using. Further, by sealingly packaging the fruits and vegetables with the packaging material of the present invention, it becomes possible to extend the freshness keeping period of the fruits and vegetables.

[0017]

EXAMPLES Examples of the present invention will be shown below.

Example 1 Stretched polypropylene 20 μm
And polyethylene 20 μm, from the stretched polypropylene side of the laminated polypropylene, an infinite number of fine pores with a pore size of several μm to 100 μm are formed, and the oxygen permeability in the state where water droplets (or water thin film) does not adhere is approximately 4,000 to 50. , 0
When 6 kinds of micropore packing materials a to d shown in the following (Table 1) are prepared so that it becomes 00 cc / m ² · day · atm and no water droplet (or water thin film) is attached to the polyethylene side Then, the oxygen permeability when adhered was measured. As shown in (Table 1), in the microporous packaging material of this example, the rate of decrease in oxygen permeability due to the attachment of water droplets (or water thin film) was 10% or less.

[0019]

[Table 1]

Comparative Example 1 Stretched polypropylene 20 μm
From the stretched polypropylene side of the laminated film of polyethylene and 20 μm, innumerable fine holes having a pore size of several μm to 100 μm are formed, and the oxygen permeability in a state where water droplets are not attached is approximately 55,000 and 80,000 cm ^3.
/ M ² · day · atm, the two kinds of micropore packing materials of e and f shown in (Table 1) above and the same laminated film in which a myriad of micropores are formed from the polyethylene side. Three types of micropore packing materials g to i shown in (Table 1) were prepared, and the oxygen permeability was measured when the water droplets were not attached to the polyethylene side and when they were attached.
As shown in (Table 1), in the microporous packaging material of this comparative example, the rate of decrease in oxygen permeability due to the attachment of water droplets (or water thin film) was more than 10%.

Example 2 Palm freshness-keeping packaging was also performed under the following conditions (Table 2). When the oxygen permeability of the packaging material is set using (Equation 2), it is 4,150 cm ³ / m ² · day.
・ Atm. When the bean sprouts were sealed and stored under the conditions of (Table 2) using the microporous packing material a of (Table 1), good storage results were obtained.

[0022]

[Table 2]

Example 3 Enoki mushrooms were freshly packed under the following conditions (Table 3). When the oxygen permeability of the packaging material is set using (Equation 1), 13,500 cm ³ / m ² · d
It becomes ay ・ atm. When the enoki mushrooms were sealed and stored under the conditions of (Table 3) using the microporous packing material b of (Table 1), good storage results were obtained.

[0024]

[Table 3]

[0025]

When the freshness-keeping packaging material for fruits and vegetables according to the present invention is used to maintain the freshness, the gas permeability of the packaging material does not decrease due to the influence of water droplets, as described above. As described above, it is not necessary to determine the oxygen permeability of the packaging material in consideration of the influence of water droplets, and by using this packaging material, freshness of fruits and vegetables can be favorably maintained.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B65D 65/40 A 81/24 A

Claims (3)

[Claims] 1. A fruit or vegetable comprising a multi-layer film having at least the innermost layer made of a heat-fusible resin layer, innumerable fine through-holes having a pore diameter of several μm to 100 μm and non-through holes or only non-through holes. In the packaging material for keeping freshness, the oxygen permeability of the packaging material is 1 of the oxygen permeability set by the following (Equation 1).
A packaging material for keeping freshness of fruits and vegetables, wherein through-holes and non-through holes or only non-through holes are formed from the outer layer side of the film so as to fall within a numerical range of 1.1 times. [Equation 1] 2. Oxygen permeability of 50,000 cm ³ / m ² ·
The packaging material for keeping freshness of fruits and vegetables according to claim 1, which has a value of not more than day · atm. 3. A freshness-retaining method for hermetically packaging fruits and vegetables using the packaging material for keeping freshness of fruits and vegetables according to claim 1 or 2.