JPH09278926A - Gas-permeable film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply and readily obtain a gas-permeable film, useful for preserving vegetables and fruits, etc., in a high-quality state and capable of regulating the gas permeability by passing an aqueous solution containing alginic acid and a water-soluble compound through the formation of a film. SOLUTION: This gas-permeable film is obtained by forming a film of an aqueous solution containing (A) alginic acid and (B) a water-soluble compound, bringing the resultant film into contact with (C) an aqueous solution of a polyvalent metallic salt, such as a calcium salt, insolubilizing the component A, providing a coagulated alginic acid film, washing the insolubilized film with water, dissolving the component B and regulating the gas permeability with the dissolved component B. The component B preferably includes any of natural polysaccharides such as pullulan or starch, sucrose, glucose, an oligosaccharide (cyclodextrin), polyvinyl alcohol and monovalent salts without making the component A get and the component C preferably includes any of metallic salts such as calcium chloride, barium chloride, aluminum sulfate, zinc sulfate, copper sulfate and strontium chloride.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a gas permeable film used for storing fruits and vegetables, processed foods and the like in a high quality state.

[0002]

Films with adjustable gas permeability can be used in a variety of applications to optimize the environment of the packaged article. For example, when used for packaging fruits and vegetables, it can be stored in a high quality state. This is because the breathing action of fruits and vegetables can be suppressed to bring the external environment closer to the ideal. Even after being harvested, fruits and vegetables breathe, evaporate water,
It also has other chemical and physiological life functions.
Vegetables and fruits break down sugars and organic acids to breathe, and acquire chemical energy to sustain life activities. When the respiratory action becomes active, sugar and organic acids are consumed and the taste deteriorates. Therefore, it is necessary to control the respiratory action to an ideal state in order to store and package it in high quality. Furthermore, the plant ages while releasing the gas hormone ethylene.
Ethylene released from plants accelerates plant ripening. Therefore, it is important to control the ethylene amount to the optimum value.

In order to keep fruits and vegetables for a long time, the environment of the packaging container is set to an environment suitable for keeping freshness.
packaging has been developed. As a packaging material used for MA packaging, for example, a technique has been developed in which a film layer such as an aluminum foil or a plastic film is laminated on the surface of cardboard paper to adjust gas permeability. Corrugated cardboard paper with a plastic film adhered suppresses the permeation of carbon dioxide gas and oxygen by the plastic film, and the environment inside the packaging container can be optimized for maintaining the freshness of fruits and vegetables.

For example, a container for packing rapeseed can be kept highly fresh by keeping the carbon dioxide concentration inside the container at 5% and the oxygen concentration at about 2 to 3%. The plastic film stretched on the cardboard paper is required to have gas permeability capable of controlling the storage environment within the above range. In the case of rape blossoms, if the gas permeability of the plastic film is too high, flowers will bloom in 2-3 days and the commercial value will be lost. This is because rape blossoms do not become commercial products when flowers bloom.
On the other hand, if the gas permeability is too low, it will be damp and rot inside the packaging container. Therefore, even if the gas permeability is too high or too low, the internal environment of the packaging container cannot be optimized to keep the freshness, and high quality MA packaging cannot be achieved. Not only rapeseed but also other fruits and vegetables tend to have the same tendency, and a comfortable gas permeability is required for MA packaging.

Plastic films for adjusting gas permeability are described in, for example, the following publications. JP-A-6-165636 JP-A-6-209701 JP-A-6-248100 JP-A-7-102081

[0006] The above-mentioned publication describes a film in which a non-porous resin layer is laminated on a perforated film or a polymethylpentene film to adjust the gas permeability of oxygen, carbon dioxide, etc. of the entire film. It Further, in the publication, a mixture of EEA, 4MIP and an unsaturated carboxylic acid modified polyolefin is used to provide oxygen in a packaging atmosphere,
A method for optimizing carbon dioxide concentration is described.

[0007]

Although these plastic films can adjust the gas permeability, they have the drawback of high disposal cost. This is because the damage to the incinerator is large when incinerated. Further, the plastic film whose gas permeability can be adjusted has a drawback that the cardboard box cannot be effectively reused when it is adhered to the cardboard box. This is because the plastic film adhered to the cardboard box hinders the recycling of cardboard paper. The cardboard paper to which the plastic film is adhered cannot be recycled as paper pulp by recycling it.

Furthermore, plastic films cannot be manufactured with simple manufacturing equipment. It must be manufactured using an expensive molding machine. Further, the plastic film having the adjusted gas permeability has a drawback that it is time-consuming to bond the plastic film to a corrugated box, for example, when the plastic film is used by being adhered to a corrugated box.

The present invention was developed for the purpose of solving such drawbacks. An important object of the present invention is to provide a gas permeable film which can easily and easily adjust the gas permeability to an ideal state and can be manufactured without using an expensive manufacturing apparatus. Further, another important object of the present invention is to provide a gas permeable film that can simplify the disposal process and can effectively reuse the bonded cardboard box or the like if necessary.

[0010]

The gas-permeable film of the present invention is formed by forming a film with an aqueous solution containing alginic acid and a water-soluble compound, and contacting this film with an aqueous solution of a polyvalent metal salt such as calcium salt. It is characterized in that alginic acid is insolubilized to form an alginic acid coagulated film, the insolubilized alginic acid coagulated film is washed with water to dissolve the water-soluble compound, and the gas permeability is adjusted by the dissolved water-soluble compound.

As the aqueous solution containing alginic acid which forms a film, an aqueous solution in which alginic acid is dissolved in an acid or an alkali, or an aqueous solution in which alginate such as sodium alginate, potassium alginate or ammonium alginate is dissolved in water can be used.

Water-soluble compounds added to alginic acid include natural polysaccharides such as pullulan and starch, sucrose, glucose, oligosaccharide (cyclodextrin),
Does not gel polyvinyl alcohol and alginic acid 1
Valuable salts are used.

Further, as the polyvalent metal salt, metal salts such as calcium chloride, barium chloride, aluminum sulfate, zinc sulfate, copper sulfate and strontium chloride are used.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. However, the embodiments described below exemplify the gas permeable film for embodying the technical idea of the present invention, and the present invention does not specify the gas permeable film as the following.

The gas-permeable film of the present invention forms a film with an aqueous solution containing alginic acid and a water-soluble compound, and the film is coagulated with a polyvalent metal salt such as calcium salt to give an insolubilized alginic acid coagulated film, The gas permeability is adjusted by washing the alginic acid coagulated film with water. An aqueous solution containing alginic acid and a water-soluble compound is applied to the surface of an object to be coated such as a cardboard box or food to form a film, or extruded from a slit into an aqueous solution of a polyvalent metal to form a film.

The film applied to the object to be coated can be adjusted by the concentration of alginic acid. The viscosity of an aqueous solution containing alginic acid increases as the concentration of alginic acid increases. When an aqueous solution containing highly viscous alginic acid is used, the film thickness attached to the surface of the object to be coated becomes thick. For example, an aqueous solution of sodium alginate has a higher viscosity as the concentration is higher. , Form a thick film on the surface of the object to be coated.

The coating thickness of the aqueous solution containing alginic acid is adjusted to an optimum value depending on the application. A gas permeable film having a low gas permeability, in other words, a gas permeable film through which a gas easily permeates, reduces the concentration of an aqueous solution of alginic acid to thin the film. Although the concentration of the aqueous solution containing alginic acid is not constant depending on the type of alginic acid, for example, sodium alginate has a concentration of 0.5 wt%.
-6 wt%, preferably 1-5 wt% is set.

Further, the gas permeable film of the present invention comprises
The gas permeability is adjusted by adding a water-soluble compound to the aqueous solution of alginic acid. When the amount of the water-soluble compound added is increased, the gas permeable film has a low gas permeability, and in other words, the gas becomes permeable to gas. Alginic acid coagulates, but water-soluble compound does not coagulate, so in the coagulated state of alginic acid, the water-soluble compound can be removed by washing with water, and micropores can be provided in the water-soluble compound part to allow gas to permeate. Is.

[0019]

【Example】

Example 1 A gas permeable film is manufactured by the following steps. An aqueous solution containing 1 wt% alginic acid and 1 wt% pullulan is applied to one side of a 5 × 5 cm corrugated cardboard liner to form a film of an aqueous solution containing alginic acid and pullulan, a film thickness of 500 μm, on the surface of the corrugated cardboard liner. A 5 wt% calcium chloride aqueous solution is sprayed on the aqueous solution of alginic acid and pullulan applied to the surface of the corrugated board liner to solidify the alginic acid. Then, the alginic acid coagulated film is washed with water to dissolve the water-soluble compound and adjust the gas permeability. The gas permeability of the gas permeable film which is solidified on the surface of the corrugated board liner and whose gas permeability is adjusted is measured.
However, the gas permeability was measured in a state where a coating film was laminated on a corrugated cardboard liner having a gas permeability of 70 seconds.

When the gas permeability of the gas permeable film produced in the above steps was measured, it was 250 seconds. However, the gas permeability is in accordance with JIS P8117, 20 ℃,
It was conducted under the condition of 65%. For the gas permeability test, a B-type Gurley type densometer manufactured by Toyo Seiki Seisakusho Co., Ltd. was used.

Further, when the gas permeability was changed by changing the concentrations of alginic acid and pullulan, the gas permeability of the gas permeable film changed as shown in FIGS. When the amount of the water-soluble compound added to alginic acid was increased, the gas permeability of the gas permeable film decreased. 1 is a gas permeable film to which 25 parts by weight of pullulan, which is a water-soluble compound, is added to 75 parts by weight of sodium alginate, and FIG. 2 is 5 parts to 50 parts by weight of sodium alginate.
FIG. 3 shows the gas permeability of a gas permeable film to which 0 part by weight of pullulan was added, and FIG. 3 shows a gas permeable film to which 75 parts by weight of pullulan was added to 25 parts by weight of sodium alginate. In these figures, the horizontal axis represents the concentration of the added additive of sodium alginate and pullulan, which is a water-soluble compound.

As shown in FIGS. 1 to 3, the gas permeability of the gas permeable film decreases as the amount of pullulan, which is a natural polysaccharide added as a water-soluble compound, increases. Furthermore, the higher the concentrations of sodium alginate and pullulan, the higher the gas permeability of the gas permeable film. Further, in these figures, □ indicates the gas permeability of the non-washed alginic acid coagulated film, and ○ indicates the gas permeability of the washed alginic acid coagulated film. When the coagulated film of alginic acid to which pullulan, which is a water-soluble compound, has been added, is washed with water, the gas permeability decreases as indicated by the circles, and the gas easily permeates.

Example 2 The gas permeability of the gas permeable film changes depending on the type of polyvalent metal salt that solidifies the aqueous solution containing alginic acid. For example, when an aqueous solution containing 1 wt% sodium alginate and 1 wt% pullulan is coagulated with the following polyvalent metal salts of ,, the gas permeability of the gas permeable film is as follows. It was However, the concentration of the polyvalent metal salt is 5 wt%,
A gas permeable film was manufactured in the same manner as in Example 1.

Copper sulfate: 270 seconds strontium chloride: 290 seconds Barium chloride: 240 seconds Aluminum sulfate: 130 seconds

[Example 3] Furthermore, the gas permeability of the gas permeable film varies depending on the type of water-soluble compound added to alginic acid. For example, in a water-soluble compound added to 1 wt% sodium alginate,
The gas-permeable film obtained by dipping an aqueous solution containing alginic acid and a water-soluble compound in a 5 wt% calcium chloride aqueous solution to coagulate alginic acid uses water-soluble compounds of Became. However,
The amount of the water-soluble compound added was 1 wt%, and a gas permeable film was manufactured by the same method as in Example 1.

Starch: 280 seconds Sucrose: 110 seconds Cyclodextrin: 230 seconds Sodium chloride: 90 seconds

From the above, the gas permeable film of the present invention is adjusted in gas permeability by adjusting the amount and type of the water-soluble compound added to the aqueous solution containing alginic acid and the type of polyvalent metal salt. Can be adjusted to an optimum value.

The surface of food was directly coated with the gas permeable film of the present invention, and its storage condition was observed.

Example 4 Sudachi was immersed in an aqueous solution in which 1 wt% sodium alginate and 1 wt% pullulan were dissolved and taken out.
An aqueous solution film is formed on the entire surface. The easiest way to immerse Sudachi in an aqueous solution of alginic acid and pullulan is
A film of an aqueous solution of alginic acid and pullulan can be formed on the surface of Sudachi. However, a film can be formed by spraying an aqueous solution of alginic acid and pullulan on the surface of Sudachi. Sudachi coated with an aqueous solution of sodium alginate and pullulan is immersed in a 5 wt% calcium chloride aqueous solution to coagulate alginic acid for 3 minutes. Alginic acid is partially insolubilized with calcium to coagulate and become an insolubilized alginic acid coagulated film. Remove Sudachi from the aqueous calcium chloride solution and wash with water. In this step, the pullulan contained in the alginic acid coagulated film is dissolved and the gas permeability is adjusted. After that, it is dried to obtain a gas permeable film.

As described above, the Sudachi whose surface was covered with the gas permeable film was subjected to 5
When stored for a day, the results shown in Table 1 were obtained.

[0031]

[Table 1]

As is apparent from this table, in the Sudachi whose surface is covered with the gas permeable film, the green color did not change even after 5 days, and no mold was generated. On the other hand, in the case of untreated Sudachi whose surface was not covered with the gas permeable film, after 5 days, 35 were mostly discolored yellow and 6 were moldy on the surface.

Example 5 The surface of the mandarin orange was coated with the gas permeable film in the same manner as in Example 4 except that the mandarin orange was used instead of the sudachi covered with the gas permeable film. The oranges treated by this method are entirely covered with a coating film having a controlled gas permeability.

As described above, the mandarin orange whose entire surface was coated with the coating film had a temperature of 25 ° C. and a humidity of 60.
Even after storing at 30% for 30 days, no mold was generated on the surface.

[Example 6] The entire surface of the banana is coated with a gas permeable film in the same manner as in Example 4 except that the food is changed from Sudachi to banana. The banana treated by this method is entirely covered with a gas permeable film whose gas permeability is adjusted with a water-soluble compound. In this way, the banana whose entire surface was covered with the gas permeable film was stored at a temperature of 25 ° C. and a humidity of 60% for 5 days, and the black-brown area was extremely small as compared with the conventional storage method. The banana, which was not covered with the gas permeable film, was stored under the same conditions and had a black-brown area of 14.7%, but the banana coated in this example had a black-brown area slightly over the entire surface. It was reduced to 1.4%. That is, in the banana coated with the gas-permeable film of the present invention, the appearance of black-brown spots was delayed as compared with the untreated one, and the maturity could be controlled.

[Embodiment 7] Except for changing sudachi into rice cake,
In the same manner as in Example 4, the entire surface of the rice cake was covered with the gas permeable film. The rice cake treated by this method is entirely covered with a gas permeable film having a gas permeability adjusted with a water-soluble compound. In this way, rice cake with the entire surface covered with a gas permeable film and untreated rice cake with no treatment,
Each of them was inoculated with a mold derived from rice cake and subjected to a culture test. The culture test was conducted for 4 days at a temperature of 20 ° C. and a humidity of 60%. As a result, the rice cake coated with the gas permeable film was suppressed in the growth of mold as compared with the untreated rice cake, and the excellent preservation effect was observed.

[0037]

The gas permeable film of the present invention has a feature that it can be simply and easily adjusted to an ideal gas permeability suitable for various uses. This is because the water-soluble compound is added to the aqueous solution of alginic acid to coagulate the alginic acid, and then the water-soluble compound is washed and removed to adjust the gas permeability at the portion where the water-soluble compound is removed.

Further, the gas permeable film of the present invention comprises
For example, the gas permeability can be adjusted to an ideal state by directly adhering to the surface of the food or directly onto the surface of a packaging material such as a cardboard box for packaging the food. Therefore, unlike a plastic film, there is no need to bond it to the surface of a food or packaging material after forming it into a film shape, and it can be used very conveniently for this type of application.

Furthermore, the gas-permeable film of the present invention has a feature that it can be produced, for example, by adhering to the surface of a food or packaging material without using an expensive production apparatus like a plastic film.

Further, since the gas permeable film of the present invention is obtained by coagulating alginic acid, it does not damage the incinerator when incinerated and discarded like a plastic film. This is because the gas permeable film obtained by solidifying alginic acid has an extremely small amount of heat generated when incinerated, which is about 1/4 that of plastic.

Further, since the gas permeable film obtained by coagulating alginic acid can be eaten as it is, it is possible to eat the food without removing the gas permeable film directly packaged in the food. Therefore, unlike a plastic film, there is no need to peel and remove the gas permeable film, and there is a feature that handling is easy.

[Brief description of drawings]

FIG. 1 is a graph showing the gas permeability with respect to the concentrations of sodium alginate and a water-soluble compound.

FIG. 2 is a graph showing gas air permeability with respect to concentrations of sodium alginate and a water-soluble compound.

FIG. 3 is a graph showing gas air permeability with respect to concentrations of sodium alginate and a water-soluble compound.

Claims (3)

[Claims] 1. A film is formed from an aqueous solution containing alginic acid and a water-soluble compound, and the film is brought into contact with an aqueous solution of a polyvalent metal salt such as a calcium salt to insolubilize alginic acid to form an alginic acid coagulated film, which is the insolubilized alginic acid coagulated film. A gas-permeable film, which comprises washing the film with water to dissolve the water-soluble compound and adjusting the gas permeability with the water-soluble compound to be dissolved. 2. Water-soluble compounds added to alginic acid include natural polysaccharides such as pullulan and starch, sucrose, glucose, oligosaccharides (cyclodextrin),
Does not gel polyvinyl alcohol and alginic acid 1
The gas permeable film according to claim 1, comprising any one of valent salts. 3. The gas permeable film according to claim 1, wherein the polyvalent metal salt contains any of metal salts such as calcium chloride, barium chloride, aluminum sulfate, zinc sulfate, copper sulfate, and strontium chloride.