JP2939263B2 - Manufacturing method of retort food - Google Patents

Description

The present invention relates to a method for producing a retort food.

[Related Art] In recent years, saponified ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVOH) has been widely used as a packaging material for retort foods in order to prevent deterioration of the quality of contents due to oxygen. Such EVOH is excellent in oxygen barrier properties, transparency, thermal stability, melt processability, etc., but has the disadvantage that it easily absorbs moisture during retort treatment, and when moisture is absorbed, the oxygen barrier properties are reduced, and the recovery of oxygen barrier properties is slow. Therefore, it is generally used in the form of a laminate having a polyolefin having a high water barrier property as an outer layer for the purpose of compensating for the disadvantage.

In such a structure, the polyolefin layer generally has a low moisture permeability at room temperature, and therefore, when left to dry after retort treatment, conversely, excess moisture absorbed in the retort is present in the EVOH layer for a long time, which indicates that the EVOH layer Since the oxygen barrier of the layer is lowered and the food is deteriorated, for example, in JP-A-61-228878, the moisture content in the EVOH layer is rapidly reduced by forcibly drying the laminated film after retorting. In the method of decreasing the oxygen barrier property and recovering the oxygen barrier property more quickly, and in JP-A-62-122923, by performing drying in an inert gas atmosphere, it is possible to prevent oxygen from permeating into the container during drying and increasing the amount. How to prevent,
Further, Japanese Patent Application Laid-Open No. 60-159043 discloses that the outer layer is made as thin as possible than the inner layer, and the moisture absorbed in the intermediate layer EVOH by the retort treatment is promoted to pass through the outer layer by forced drying and escape. It proposes a method for promoting recovery of the oxygen barrier property of EVOH in the intermediate layer.

Further, as described above, in addition to the method of using forced drying to prevent the quality deterioration of retort foods, attempts have been made to solve such a problem from the viewpoint of the laminate structure, and JP-A-53-35778 discloses Filed an application for a multilayer laminate structure of a biaxially stretched film with improved water barrier properties as a packaging material for retort foods using EVOH, including a heat seal layer / EVOH biaxially stretched film layer / nylon biaxially stretched film layer. Is shown.

[Problems to be Solved by the Invention] However, JP-A-61-228878 and JP-A-53-35778
In the inventions disclosed in JP-A-62-122923 and JP-A-60-159043, the oxygen barrier property recovery rate is not always sufficient.
In the invention disclosed in Japanese Patent Application Laid-Open Publication No. H10-163, there is no conventional technology that can sufficiently satisfy all of the devices, operability, and effects.

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the problems, and as a result, a container having a multilayer structure manufactured by an extrusion molding method, wherein a base material used for an outer layer is an inner layer If the moisture permeability is higher than the substrate used for the retort treatment and the forced drying is performed after the retort treatment, the oxygen barrier property of the EVOH layer after the retort treatment is maintained while maintaining the conventional method in terms of equipment and operability. The present inventors have found a method which can be rapidly recovered and which has no fear of causing a deterioration in the quality of food, thereby completing the present invention.

That is, the present invention, `` filling the contents obtained from the multilayer structure produced by the extrusion molding method, after sealing, subjected to retort treatment, and then forcibly dried to produce a retort food,
Outer layer (A) as a multilayer structure; moisture permeability at a film thickness of 30μ is 20-400 g / m ²
・ A film layer of nylon or polyethylene terephthalate having a melting point of 130-300 ° C. on day, a thickness of 15-250 μm, an intermediate layer (B); a film layer of saponified ethylene-vinyl acetate copolymer, an inner layer (C) ; Moisture permeability at a film thickness of 30μ is 20g / m ²・ day
Below, the thickness of the polymer whose melting point is 100-180 ° C
A structure comprising a film layer of 50 μm or more, wherein the thickness of the outer layer (A) is smaller than the thickness of the inner layer (C), and the thickness of the outer layer (A) is larger than the thickness of the intermediate layer (B). A structural method for a retort food, characterized by using an object. It is.

The feature of the present invention is that a substrate having a higher moisture permeability than the inner layer (C) is used for the outer layer (A) as described above, and the thickness of the outer layer (A) is made smaller than the thickness of the inner layer (C). In addition, a layer structure in which the thickness of the outer layer (A) is larger than the thickness of the intermediate layer (B) is used. Thus, the drying rate of the EVOH layer (intermediate layer (B)) after the retort treatment is increased, that is, the oxygen barrier property can be rapidly recovered. When a substrate having high moisture permeability is used for the outer layer, deterioration of the food is expected due to moisture absorption during the retort treatment.However, the present inventor rapidly recovers the barrier property by drying after the retort treatment. It has been confirmed that this has a great influence on the suppression of the deterioration of the base material of the present invention.

The outer layer (A) of the present invention has a moisture permeability of 20-
400g / m ² · day, preferably 50-300g / m ² · day, mp 13
There is no particular limitation as long as it is a polymer having a temperature of 0 to 300 ° C, preferably 150 to 270 ° C. Specifically, various kinds of nylon such as 6-6, 6-, 6, 10-, etc., polycarbonate, polyethylene terephthalate, amorphous Polyethylene terephthalate or the like is preferable, and is used as a film layer having a thickness of 15 to 250 μm.

When the moisture permeability of the resin is less than 20 g / m ² · day, the moisture permeability of the film layer is too low, and the recovery speed of the oxygen barrier property of the EVOH layer is slow. On the other hand, whitening of the EVOH layer to be observed in the retorting products also becomes irreversible after drying a resin exceeds 300g / m ² · day, the transparency of the container is deteriorated, and unrecoverable barrier reduction is observed preferably Absent.

If the melting point is lower than 130 ° C., there is a risk of fusing at the time of retort, and a polymer exceeding 300 ° C. is difficult to mold with a general-purpose molding machine and is not practical.

If the thickness of the outer layer (A) constituting the container is less than 15 μm, the film layer cannot withstand the harsh conditions at the time of the retort treatment,
Deformation is likely to occur. If it exceeds 250 μm, it takes time to dry the EVOH layer, and the recovery of the oxygen barrier property of the EVOH layer is undesirably slow.

The composition of the EVOH of the intermediate layer (B) of the present invention is not particularly limited as long as it can be used as a packaging material for a retort food, but the ethylene content is 25 to 55 mol%, preferably 28 to 50 mol%, The degree of saponification of the vinyl acetate component is at least 95 mol%, preferably at least 99 mol%. If the ethylene content is less than 25 mol%, the water resistance is insufficient and the oxygen barrier property is greatly reduced. If the ethylene content exceeds 55 mol%, the oxygen barrier property is insufficient. Also, when the saponification degree of the vinyl acetate component is less than 95 mol%, the water resistance is insufficient and the oxygen barrier property is also insufficient.

Further, a small amount of propylene, isobutene, α-octene, α-dodecene, α-octadecene and other α-olefins, unsaturated carboxylic acids or salts thereof, partial alkyl esters, complete alkyl esters, nitriles, etc.
A comonomer such as amide / anhydride, unsaturated sulfonic acid or a salt thereof may be contained as a component.

The inner layer (C) of the present invention has a moisture permeability of 20 g /
m ² · day or less, preferably less 15 g / m ² · day, mp 10
There is no particular limitation as long as the polymer has a temperature of 0 to 180 ° C, preferably 130 to 165 ° C. Specifically, high-density polyethylene,
Polypropylene, ethylene-propylene copolymer and the like are preferable, and are used as a film layer having a thickness of 50 μ or more.

In the case of a polymer having a water vapor transmission rate exceeding 20 g / m ² · day, the oxygen barrier property of the EVOH layer is affected by the moisture content.

If the melting point is less than 100 ° C, there is a risk of fusing at the time of retort, and a polymer exceeding 180 ° C has too high a heat sealing temperature and is not practical.

When the thickness of the inner layer (C) is less than 50μ, the moisture content is EV
It permeates into the OH layer and causes a decrease in the oxygen barrier properties of the EVOH layer.

Further, in the present invention, it is essential to use a multilayer structure in which the thickness of the outer layer (A) is smaller than the thickness of the inner layer (C). If these conditions are not satisfied, moisture in the contents is supplied to the EVOH layer during forced drying, so that the drying efficiency of the EVOH layer deteriorates and the recovery of oxygen barrier properties also slows.

Although the structure of the present invention is based on the constitution of (A) / (B) / (C), practically, the adhesive layer (D) and the anchor coat agent layer ( E) is provided.

As the adhesive layer (D), various materials such as polyolefin, polyester, and acrylic are all suitably used, but preferably acid-modified polyolefin, more preferably carboxylic acid (for example, maleic anhydride) -modified polypropylene, Acid-modified ethylene-vinyl acetate copolymers are practical. The thickness of the adhesive layer is usually 5 to 5 so as not to affect the effect of the outer layer (A).
Make 50μ.

As the anchor coating agent, any of various types such as an organic titanium type, an isocyanate type, a polyethylene imine type, and a polybutadiene type are preferably used.
-2μ is used after coating.

An extrusion molding method is used as a melt molding method for producing the multilayer structure of the present application. Among these, as the extrusion molding method, any of the known dry lamination method, extrusion coating method, co-injection molding method, multilayer inflation molding method, multilayer T-die extrusion molding method, multilayer hollow molding method, multilayer pipe extrusion method, etc. are employed. As the joining method of the molten resin layer, an inner die joining method and an outer die joining method can be adopted.

The temperature conditions for performing these melt moldings are desirably about 160 to 250 ° C., and if necessary, known additives such as fillers, coloring agents, stabilizers, and foaming agents may be added in appropriate amounts. is there.

The structure obtained as described above is molded as a container having an arbitrary shape such as a bag, a bolt, a cup, or a tube, and then filled with food and subjected to retort treatment.

The retort treatment of the present invention includes not only steam sterilization at high temperature and high pressure but also boil sterilization, and may be performed not only in the atmosphere but also in an inert gas such as nitrogen. Specifically, the retort treatment is performed at a steam or hot water temperature of 80 to 150 ° C. and a heating time of 10 seconds to 60 minutes.

After the retort processing is completed, forced drying is performed. As the forced drying of the present invention, various methods such as hot air spray drying and infrared heating drying are possible, and the forced drying may be performed in an inert gas atmosphere such as nitrogen, carbon dioxide, or a mixed gas thereof.
The drying conditions such as the drying temperature and the drying time are determined according to the layer structure of the multilayer structure content of the present invention, retort treatment conditions, and required EV.
It may be appropriately selected depending on the oxygen barrier property of the OH layer, etc., and usually, the drying is carried out at a drying temperature of 80 to 150 ° C. and a drying time of 5 seconds to 60 minutes. The drying is desirably performed until the water absorption of the EVOH layer becomes 5% by weight or less.

The production method of the present invention requires complete sterilization, such as boiled beans, tsukudani, delicacies, frozen cooked foods, pickles, miso, spaghetti, stewed poultry vegetables, komaki, hamburger steak,
It is suitable as a method for producing various retort foods such as fish and shellfish, meat sauce, curry, stew, and sour pork.

[Action] In the present invention, by using a polymer having a high moisture permeability for the outer layer and using a container made of a multilayer structure having EVOH as the intermediate layer, the drying speed of the EVOH layer is increased at the time of forced drying after the retort treatment. Has the effect of increasing the recovery speed of oxygen barrier properties.

[Examples and Controls] Next, the present invention will be further described with reference to Examples. In addition, the measurement was performed as follows.

Oxygen permeability According to ASTM D 3985, OX manufactured by Modern Control
-Measured at 25 ° C and 75% RH using TRAN100.

In accordance with JIS Z 0208, a film having a thickness of 30 μm was measured at a temperature of 40 ° C. and a relative humidity of 90%.

Example 1 Outer layer (A-1); 6-nylon intermediate layer (B-1); saponified ethylene-vinyl acetate copolymer inner layer (C-1); ethylene-propylene copolymer adhesive layer (D -1): The layer structure and the film thickness (μ) of each resin of maleic anhydride-modified polypropylene were (A-1) /
A four-layer laminated structure of (B-1) / (D-1) / (C-1) = 50/20/15/80 was produced by an extrusion molding method under the following conditions.

The die temperature was 250 ° C.

A bag having a size of 10 × 10 (cm unit) is prepared from the obtained multilayer structure, filled with ion-exchanged water, the bag is closed by heat sealing, and the bag is retorted at 120 ° C. for 30 minutes. Fifteen
Minutes for forced drying. The oxygen permeability was measured before the retort treatment and one day after the retort treatment, and is shown in Table 1.

Comparative Example 1 Outer layer (a-1) and inner layer (c-1); polypropylene Intermediate layer (b-1); saponified ethylene-vinyl acetate copolymer adhesive layer (d-1); maleic anhydride-modified polypropylene Using each resin, the layer configuration and film thickness (μ) are (a-1) / (d-1) / (b-1) / d-1) / (c-
1) A five-layer laminated structure of 140/10/20/10/300 was produced by an extrusion molding method under the following conditions.

The die temperature was 220 ° C.

Using the obtained multilayer structure, an experiment was performed in the same manner as in Example 1.

 The results are shown in Table 1.

Comparative Example 2 An experiment was conducted in the same manner as in Example 1 except that the forced drying was omitted, and the results are shown in Table 1.

Comparative Example 3 An experiment was conducted in the same manner as in Example 1 except that the layer structure shown in Table 1 was used, and the results were also shown.

Example 2 Outer layer (A-3); polyethylene terephthalate intermediate layer (B-3); saponified ethylene-vinyl acetate copolymer inner layer (C-3); ethylene-propylene copolymer adhesive layer (D- 3); maleic anhydride-modified polypropylene anchor coating agent (E-3); layer constitution and film thickness (μ) using each of polyurethane isocyanate resins (A-3) / (E-3) / (B- 3) / (D-3) = 30
A four-layer laminated structure of / 1/20/13/100 was produced by a coextrusion coating method.

Using the obtained multilayer structure, an experiment was performed in the same manner as in Example 1.

 The results are shown in Table 1.

Example 3 (Co-extrusion molding method) An experiment was carried out in accordance with Example 1, except that the layer configuration was as shown in Table 1, and the results were also shown.

(Note) Outer layer (A-1); 6 nylon moisture permeability 260 g / m ² · day, melting point 218 ° C (A-2); polycarbonate moisture permeability 150 g / m ² · day, melting point 220-240 ° C (A-3) ); Polyethylene terephthalate moisture permeability 25 g / m ² · day, melting point 263 ° C (A-4); amorphous polyethylene terephthalate (manufactured by Eastman, trade name PETG 6763) moisture permeability 55 g / m ² · day, melting point 245 ° C (A-1): Polypropylene moisture permeability 8 g / m ² · day, melting point 164 ° C (a-2); 6-nylon moisture permeability 260 g / m ² · day, melting point 218 ° C. Intermediate layer (ethylene-vinyl acetate copolymer) (B-1); ethylene content 30 mol%, saponification degree 99.3 mol% (B-2); ethylene content 42 mol%, saponification degree 99.1 mol% (B-3); ethylene content 32 mol% , Saponification degree 99.7 mol% (B-4); ethylene content 46 mol%, saponification degree 99.4 mol% (b-1); ethylene content 30 mol% Saponification degree 99.3 mol% [same as (B-1)] (b-2); ethylene content 30 mol%, saponification degree 99.3 mol% [same as (B-1)] Inner layer (C-1); Propylene polymer Moisture permeability 8 g / m ² · day, melting point 164 ° C (C-2); High density polyethylene Moisture permeability 6 g / m ² · day, melting point 135 ° C (C-3); Ethylene-propylene copolymer Ethylene content 5 mol%, moisture permeability 11 g / m ² · day, melting point 153 ° C. (C-4); ethylene-propylene copolymer, ethylene content 5 mol%, moisture permeability 11 g / m ² · day, melting point 153 ° C. (c-1) ); Polypropylene moisture permeability 8 g / m ² · day, melting point 164 ° C (c-2); Propylene copolymer moisture permeability 8 g / m ² · day, melting point 164 ° C [(C-
Same as 1)] Adhesive layer (D-1); maleic anhydride-modified polypropylene (Mitsubishi Yuka, trade name Modick P-310F) (D-2); maleic anhydride-modified ethylene-vinyl acetate copolymer ( (Mitsubishi Yuka, trade name Novatic AP 240H) (D-3); maleic anhydride-modified polypropylene (Mitsubishi Yuka, trade name Novatic AP-196P) (D-4); maleic anhydride-modified ethylene-acetic acid Vinyl copolymer (Mitsui Petrochemical, trade name Admer VF-600) (D-4) '; maleic anhydride-modified polypropylene (Mitsubishi Yuka, trade name Modick P-310F) (d-1); anhydrous maleic Acid-modified polypropylene (Mitsubishi Yuka, trade name Novatic AP-196P) (d-2); Maleic anhydride-modified polypropylene (Mitsubishi Yuka, trade name Modick P-310F) [Same as (D-1) Anchor coating agent (E-3); polyurethane polyisocyanate (Takeda Chemical Co., trade name Takelac A-36)
9) * Moisture permeability: measured at a film thickness of 30μ.

[Effect] The method for producing a retort food according to the present invention employs a polymer having a high moisture permeability for the outer layer, and a multilayer structure containing EVOH as an intermediate layer. The drying speed is increased, and the recovery speed of the oxygen barrier property is increased. As a result, it has the effect of preventing the quality of the contents from deteriorating due to oxygen.

Claims (1)

(57) [Claims] 1. A container obtained from an extrusion-molded multilayer structure is filled with contents, sealed, subjected to a retort treatment, and then forcibly dried to produce a retort food. The outer layer (A) has a moisture permeability of 20-400 g / m ² · d at a thickness of 30 μm.
ay, 15-250 μm thick film layer made of nylon or polyethylene terephthalate having a melting point of 130-300 ° C., intermediate layer (B); film layer of saponified ethylene-vinyl acetate copolymer, inner layer (C) ; Moisture permeability at a film thickness of 30μ is 20g / m ²・ day
Below, the thickness of the polymer whose melting point is 100-180 ° C
A structure comprising a film layer of 50 μ or more, wherein the thickness of the outer layer (A) is smaller than the thickness of the inner layer (C), and the thickness of the outer layer (A) is larger than the thickness of the intermediate layer (B). A method for producing a retort food, comprising using a product.