JPH0630694A - Freshness retaining film and method for maintaining freshness using the same - Google Patents

Abstract

PURPOSE:To preserve broccoli without reducing freshness. CONSTITUTION:A freshness retaining film consists of three or more layers wherein the middle layer comprises an ethylene-vinyl acetate copolymer or an ethylene-ethyl acrylate copolymer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a freshness-keeping film and a freshness-keeping method using the same. More specifically, broccoli is packaged in a packaging bag and the atmosphere is filled with O ₂ and C.
The present invention relates to a hermetically sealed film for optimizing O ₂ concentration and keeping freshness, and a method for keeping fresh broccoli after harvesting using the film.

[0002]

2. Description of the Related Art In recent years, consumers' needs for freshness of fruits and vegetables and flowers are high, and how to keep the freshness after harvesting is very important together with the cultivation technique of fruits and vegetables. In order to meet such demands, development of a packaging film focused on keeping freshness is under way, and for example, a method of removing ethylene which causes aging of plants (Japanese Patent Laid-Open No. 63-
309137, JP-A-63-110186), a method of activating cells by generating far infrared rays (JP-A-62-62).
210973) and humidity control inside the bag (Japanese Patent Laid-Open No. 58-193).
678), a method based on the antifogging effect (Japanese Patent Laid-Open No. 62-1104).
9), a method based on an antibacterial effect (Japanese Patent Laid-Open No. 61-14823)
Various measures such as 6) have been proposed. However, an effective freshness-keeping method for various kinds of fruits and vegetables has not been found. In other words, although a freshness-retaining effect can be seen in each individual special case, it is very difficult to obtain the same effect with other fruits and vegetables.

Broccoli, in particular, has a high need for keeping freshness because its freshness decreases in a very short time after harvesting, and yellowing progresses, an offensive odor occurs, and a cut edge is slimmed. At present, various films are being investigated, and the freshness preservation and distribution are optimized by improving the packaging form (for example, hermetic packaging, folding packaging, corrugated cardboard box, styrofoam box, etc.) and the distribution temperature. Insufficient to retain, and the freshness is remarkably reduced especially at normal temperature.

The optimum O ₂ and CO ₂ concentrations (this is called the CA storage condition) for maintaining the freshness of broccoli have been studied in the past, for example, “Food Distribution Technology 19 (8). ) P62 to P64 ", O ₂ concentration is 3 to 6%, CO ₂ concentration is 6%, no offensive odor is generated, and storage at 22 ° C. for 4 days is reported, but this condition is 20 μm. Low density polyethylene (LDP
E) It is the value achieved with the film, and there is a problem in practical strength. Further, this combination of O ₂ and CO ₂ concentrations happens to be a value achieved from the balance of gas permeability and respiration of the film, and this value cannot be said to be optimum.

[0005]

[Problems to be Solved by the Invention] Even if the broccoli is hermetically packaged in a bag, O ₂ , C in the bag can be distributed even at normal temperature.
O ₂ concentration is optimized to keep freshness, suppresses yellowing,
Until now, no freshness-preserving film that suppresses the generation of off-flavors has been proposed.

[0006]

SUMMARY OF THE INVENTION The gist of the present invention consists of a multilayer film of three or more layers, the intermediate layer of which is an ethylene-vinyl acetate copolymer or an ethylene-ethyl acrylate copolymer, and both inner and outer surface layers. Is low density polyethylene, linear low density polyethylene, ethylene-vinyl acetate copolymer having a vinyl acetate content of 8% by weight or less, ethylene-ethyl acrylate copolymer having an ethyl acrylate content of 8% by weight or less, polypropylene, polystyrene And a freshness-retaining film for broccoli, and a method for maintaining freshness, which comprises packaging broccoli with the freshness-retaining film.

The multi-layer film used in the present invention is 3
An intermediate layer made of ethylene-vinyl acetate copolymer (EVA) or ethylene-ethyl acrylate copolymer (EEA) and an inner surface layer, an outer surface layer made of another resin, and, if necessary, those layers Has an adhesive layer for adhering. The thickness ratio is preferably in the range of intermediate layer / sum of layers other than intermediate layer = 1/1 to 5/1.

The EVA used in the intermediate layer preferably has a vinyl acetate content (VA) of 8 to 40% by weight, and an EEA ethyl acrylate content (EA) of preferably 8 to 40% by weight. To use. V on both inner and outer surface layers
Any of EVA, low density polyethylene, linear low density polyethylene, polypropylene, polystyrene having A of 8% by weight or less, or a mixture thereof is used. The main function of both the inner and outer surface layers is to prevent blocking. When the adhesiveness between the intermediate layer and the inner and outer surface layers is poor in practical use, an adhesive layer is provided between them. For the adhesive layer, unsaturated carboxylic acid-modified polyolefin can be preferably used.

The unsaturated carboxylic acid modified polyolefin is preferably a polyolefin graft-modified with an unsaturated carboxylic acid such as acrylic acid, methacrylic acid, maleic acid, fumaric acid or itaconic acid or a derivative thereof. The grafting amount of unsaturated carboxylic acid is polyolefin 100
0.01 to 5 parts by weight, preferably 0.0
2 to 0.5 parts by weight. The unsaturated carboxylic acid-modified polyolefin has a melt index of 0.
5 to 20 g / 10 minutes, preferably 1.0 to 10 g / 10
Minutes are good.

When polypropylene, polystyrene, or polybutadiene is used for the surface layer, EVA or an unsaturated carboxylic acid-modified polyolefin based on EEA is preferably used as an adhesive agent for its adhesive effect.

The film of the present invention is characterized by the intermediate layer, which has a large carbon dioxide permeability ratio to oxygen permeability of 5 or more, and also has a large absolute value of oxygen permeability, thus sealing broccoli having a large respiration rate. Even if it is packaged, it does not suffocate, and since the O ₂ concentration in the bag is 2 to 5%, yellowing is suppressed and freshness can be maintained. Therefore, the thickness ratio between the intermediate layer and the other layers is preferably 1/1 to 5/1. If it is 1/1 or less, the influence of the characteristic value of the intermediate layer on the whole multilayer film is too small, and if it is 5/1 or more, problems such as film formability and strength are large. Also, the thickness of the film depends on the mass of broccoli in the package and the ambient temperature,
Practically, the thickness is 15 to 50 μm, preferably 25 to 40 μm.

A known method can be used as a method for forming a film. In order to obtain a multilayer film, an inflation method of multilayer coextrusion, a method of forming by a T-die method, or a multilayer formation by lamination can be adopted. Incidentally, a plasticizer, a heat stabilizer, which is usually added to the resin,
Antioxidants, fillers, lubricants, antiblocking agents, UV absorbers, colorants, modifiers and the like may be used as necessary. Also, an antibacterial agent, which is important for maintaining freshness,
It is also possible to add antifungal agents, antifog agents, ethylene removing agents, and the like.

A method of packaging broccoli using the above-mentioned film is to put the broccoli in the film, bind the mouth of the film, tie it with a rubber band, or heat-seal the broccoli in a hermetically sealed manner. There is no particular limitation, including a method of putting this in a cardboard box or a method of putting a cardboard box containing broccoli in the present film and hermetically packaging by the above-mentioned method. Also,
Even in the folded packaging, if the folding amount is increased and the packaging form is close to the hermetically sealed packaging, there is a considerable effect. With this film, the storage temperature ranges from low temperature (0 to 10 ° C) to normal temperature (1
It has a freshness-retaining effect in a wide range of 0 to 30 ° C.) and is not particularly limited.

[0014]

The present invention will be described below with reference to examples, but the present invention is not limited to these examples. still,
The PCO _{2 and} PO _{2 in} the examples were measured by a pressure type gas permeability measurement method (using JASCO Corporation Gasperm-100 type).
Was performed at 23 ° C.

Example 1 Low density polyethylene (LDPE) (F131 manufactured by Mitsubishi Kasei) for the outermost layer, and EVA (V5 manufactured by Mitsubishi Yuka Co., Ltd.) for the middle layer.
No. 05, vinyl acetate content 25% by weight), a three-layer film having a thickness of 30 μm was formed by a three-layer coextrusion inflation method. The thickness ratio of each layer was 1/8/1. When the O ₂ and CO ₂ transmittances PO ₂ and PCO ₂ of this film are measured

[0016]

## EQU1 ## PO ₂ = 13500 [cc / m ² .Day.atm] PCO ₂ = 79000 [cc / m ² .Day.atm].

Example 2 Except that EEA (A710 manufactured by Mitsui DuPont, ethyl acrylate content 15% by weight) was used for the intermediate layer.
A 30 μm thick film was formed in the same manner as in Example 1. The transmittance is

[0018]

## EQU00002 ## PO ₂ = 14600 [cc / m ² .Day.atm] PCO ₂ = 82000 [cc / m ² .Day.atm].

Comparative Example 1 LDPE (manufactured by Mitsubishi Kasei Co., F13
1) A 30 μm thick film was formed. The transmittance is

[0020]

[Equation 3] PO ₂ = 5600 [cc / m ² · Day · atm] PCO ₂ = 22300 [cc / m ² · Day · atm].

A broccoli storage test was carried out using the above films. Nine pieces of broccoli (1980 g) were packed in a 50 cm × 60 cm bag and stored at 25 ° C. Three
The test results after day are shown in Table-1. The packaging form was bag-like, heat-sealed and hermetically packaged.

Comparative Examples 2 and 3 The film used in Example 2 was formed into a sheet, and broccoli was folded (not sealed) and packaged and stored. The test results after 3 days are shown in Table 1.

[0023]

[Table 1]

[0024]

The present invention provides a broccoli freshness-preserving film in which the O ₂ and CO ₂ concentrations in the bag are optimized for keeping freshness only by hermetically packaging broccoli, yellowing is suppressed, and no offensive odor is generated. be able to.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C08L 23/08 LDJ 7107-4J

Claims (4)

[Claims] 1. A multi-layer film having three or more layers, an intermediate layer of which is an ethylene-vinyl acetate copolymer or an ethylene-ethyl acrylate copolymer, and inner and outer surface layers of which are low-density polyethylene and linear low-density polyethylene. From ethylene-vinyl acetate copolymer having a vinyl acetate content of 8% by weight or less, ethylene-ethyl acrylate copolymer having an ethyl acrylate content of 8% by weight or less, polypropylene, polystyrene, polybutadiene, or a mixture thereof. A freshness-preserving film for broccoli, which is characterized by 2. The freshness-preserving film according to claim 1, wherein the multilayer film has a thickness constitution of intermediate layer / sum of layers other than intermediate layer = 1/1 to 5/1. 3. The ethylene-vinyl acetate copolymer of the intermediate layer has a vinyl acetate content of 8 to 40% by weight, and the ethylene-ethyl acrylate copolymer has an ethyl acrylate content of 8 to 40% by weight. The freshness-preserving film according to claim 1 or 2. 4. A freshness-retaining method, which comprises packaging broccoli with the freshness-retaining film according to any one of claims 1 to 3.