JPH0253434A - Packed food - Google Patents

Abstract

PURPOSE:To prevent the loss of water from a food and to keep good quality over a long period by filling a food in a primary packaging bag and sealing the primary bag together with a hydrated highly water-absorbing resin in a secondary packaging container. CONSTITUTION:A primary packaging bag having an oxygen permeability of <=1ml/m<2>.24hr at 20 deg.C in dry state and filled with a food such as shavings of dried bonito is sealed together with a highly water-absorbing resin containing >=0.7 pts.wt. of water based on 1 pt.wt. of dry resin (e.g., alkali-neutralized and crosslinked ethylene-maleic anhydride copolymer) in a secondary packaging container made of a hydrophobic thermoplastic resin (e.g., PE) having a gas- barrier resin layer (e.g., PVA) having a thickness of 5-30mum.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Industrial Applications The present invention includes a method for preventing moisture loss in packaging bags for foods, especially ``Kebushi'', and maintaining good quality over a long period of time, and the packaging bags. It relates to food packaging.

In general, food packaging has various purposes and functional missions, both large and small, but these can be summarized into three: - Preservation of contents - Convenience of handling - Promotion of sales. . Furthermore, regarding the protective function of the contents, the purpose of packaging is to prevent food deterioration factors listed below (■ biological deterioration factors such as microorganisms, pests, animals, and enzymes contained in the food itself; ■ fats and oils contained in food; dye,
Chemical alteration factors such as oxidation, decomposition, and polymerization of ingredients such as vitamins, and reactions between each ingredient, ■ Moisture absorption, drying, assimilation, damage, crystallization of ingredients, dissipation of aroma ingredients, adsorption of foreign odors, etc. This consists in eliminating physical alteration factors). In order to satisfy the protective function of the contents in food packaging, it goes without saying that packaging materials and packaging techniques must be appropriately selected depending on the target food. As mentioned above, prevention of moisture absorption and release during storage and distribution of contents is one of the major issues in food packaging, and the present invention is also related to this. For this discussion, three items are necessary: ■ Moisture barrier properties of packaging materials, moisture absorption and release properties of foods, and allowable range of moisture absorption and release of foods. The moisture barrier properties of packaging materials can be easily determined by commonly used evaluation methods, and the moisture barrier properties of various packaging materials currently in use are already known. The hygroscopic properties of foods can be determined from the relationship between moisture content, water activity, and relative humidity.Each food has a unique relationship between moisture content and water activity, and many reports have already been published on typical foods. There is an example. Approximate values of the allowable moisture absorption and desorption range of foods have already been determined empirically and serve as a guideline for selecting packaging materials and packaging techniques.

Now, when we give the moisture content at the time of packaging and the critical moisture content at which the food can maintain its commercial value on the moisture content-water activity relationship curve, the corresponding water activity value, that is, the commercial value after packaging, is maintained. The relative humidity within the container during the possible storage period is given. Two different cases occur depending on the level of humidity inside the container. The first case is when the humidity inside the container is lower than the storage environment humidity, in which case moisture enters the container through the packaging material and is absorbed by the food, resulting in quality deterioration. The second case is when the humidity inside the container is higher than the storage environment humidity, and in this case, moisture evaporates outside the container through the packaging material, causing a similar deterioration in quality. The purpose of food packaging is to extend the period until the critical moisture content is reached, that is, the shelf life, as much as possible.From the standpoint of fulfilling the packaging purpose and ideally achieving this, it is necessary to prevent moisture permeation. Packaging materials that can be blocked are needed. In practice, packaging materials that incorporate aluminum foil in ideal conditions fall under this category, but transparent packaging materials are used to satisfy the general consumer desire to "observe and confirm the contents before making a purchase." is insufficient in most cases.

Therefore, in order to more reliably satisfy the purpose of packaging, some kind of auxiliary method is required, and it is a well-known fact that in the first case, the method of enclosing a desiccant in the container is generally used in combination. It is. However, as in the second case, there are no effective supplementary measures available for foods whose commercial value is significantly impaired by evaporation of water under normal storage or distribution conditions, and in the end, as much as possible is transparent. Currently, there is no effective countermeasure other than using materials with low humidity. In this case, in order to approach the packaging purpose, strict requirements are consequently imposed on the packaging material, which inevitably becomes extremely expensive.

Before describing the details of the present invention, the term "keribushi" as used in the present invention will be defined below.

“Kerifushi” is the same as defined in the “Japanese Agricultural Standards for Kerifushi” and has the following contents. ■
Fish such as bonito, mackerel, and tuna have their heads, internal organs, etc. removed, are boiled to coagulate their proteins, are then cooled, and dried to a moisture content of 26% or less (hereinafter referred to as ``fushi''). ) or in the case of bonito flakes, the surface of which has been shaved) with mold of No. 2 mold or higher (hereinafter referred to as "Garebushi J") which has been shaved into flakes, thick flakes, or strings; ■ Fish such as sardines and horse mackerel are boiled to coagulate the protein and then dried (hereinafter referred to as "sardines"), or these fish are boiled to coagulate the protein, then squeezed to remove the fish oil and dried. (hereinafter referred to as "pressed dried sardines") shaved into flakes, thick flakes, or threads;
■There are three types, which are a mixture of the first two.

Since "keribushi" is shaved into flakes, thick flakes, or threads as described above, it is susceptible to oxidation by oxygen. To prevent this, gas exchange packaging using nitrogen gas is used for packaging, and the oxygen permeability in dry conditions at 20°C is 1 nnl/rr? - Packaging materials that are resistant to 24 hours or less must be used. On the other hand, the Japanese Agricultural Standards stipulate that the moisture content of ``Keribushi'' in packages filled with nitrogen gas is 9% or more and 21% or less. Generally, about 18 to 20% is considered to be a desirable range in terms of flavor and texture, and the moisture content is also generally adjusted to 18 to 20% during production. The water activity value at that time is around 0.8, and the normal storage and distribution conditions are mostly when the environmental humidity is 80% or less.
Moisture permeates to the outside of the bag through the packaging material, and the drying of the ``Keribushi'' progresses. As drying progresses, the flavor and texture will be impaired, and if it becomes less than 15%, the ``Kebushi'' will turn into powder, further impairing its commercial value. The role of packaging materials is to ensure that the amount of carbon dioxide does not fall below 15%.

To explain in more detail the packaging form of “Keribushi”,
Immediately after production, in most cases, products are packaged with gas exchange using various transparent packaging materials, then stored as they are in cardboard cases, etc., and then secondary wrapped and shipped according to the respective sales route.

There are also various forms of secondary packaging, and in the case of ``bonito shavings'', which is a typical ``shaved shavings'' product, about 20 bags containing 5g each are placed in a metal can with a lid and placed in a presentation box. Examples include cases in which the products are mainly sold as gifts, and cases in which five to six 5g bags are further packaged in a transparent packaging material and sold at mass retailers such as supermarkets. Other ``kegeribushi'' may be packaged in secondary packaging, similar to ``bonito flakes,'' or may be sold in primary packaging immediately after production. From the perspective of reducing moisture content, the following are cases where sales channels are different. First of all, when sold at mass retailers such as supermarkets, the secondary packaging material is heat-sealed using a material with low moisture permeability, and it is common for it to go on sale shortly after production. In addition, because the turnover rate at stores is fast, there are relatively few problems with poor quality due to a decrease in moisture content. On the other hand, if it is sold as a gift, it is basically sold twice a year (midyear gift and year-end gift).
Because of the peak demand, products that are planned to be produced throughout the year are stored for a certain period of time and then packed into a predetermined number of metal cans and shipped. Because they are stored in primary packaging under severe temperature and humidity conditions, and because the period from when they are sold until when they are consumed is relatively long, quality deterioration is likely to occur due to a decrease in moisture content.

C1 Problems to be Solved by the Invention The present inventors have studied from various angles the requirements for packaging materials and storage requirements to ensure that the moisture content does not fall below 15% even during long-term storage or distribution under severe conditions. As a result, assuming a storage or distribution period of one year under the most severe conditions that are normally considered, as long as current transparent packaging materials are used,
We have come to the conclusion that it is almost impossible to maintain the moisture content of ``Kerebushi'', which has been reduced to 18%, at 15% or more. Therefore, the present invention was developed as a result of extensive research into a low-cost and easily applicable method for preventing moisture loss during storage and distribution stages. As mentioned above, the method of enclosing a desiccant (hygroscopic agent) is generally adopted as an auxiliary method to prevent moisture absorption in food products where moisture absorption impairs commercial value. is based on a completely different idea. In other words, by maintaining the relative humidity inside the secondary packaging container (or secondary packaging bag) at a level as close as possible to that inside the primary packaging bag, regardless of the environmental humidity during storage or distribution, Second, it is intended to prevent a decrease in the moisture content of foods, especially ``Kebushi''.

As a result of considering various methods based on the idea of 02 methods for solving the problem, we decided to use a super absorbent resin containing water inside the secondary packaging container together with the food, especially the primary packaging bag for "Keribushi". By enclosing the food, the relative humidity inside the secondary packaging container, that is, the outside of the food, especially the shavings packaging bag, can be maintained at a level close to the relative humidity inside the primary packaging bag, regardless of storage and distribution conditions. In this way, a food packaging body in which a secondary packaging container is filled with a water-containing super absorbent resin along with a primary packaging bag filled with food, especially ``shaved rice'', is as follows. It has many advantages. In other words, the superabsorbent resin does not come into direct contact with food, especially ``Kebushi'', and since water is adsorbed by the superabsorbent resin, the ``Kebushi'' packaging bag does not become excessively wet, and the type of superabsorbent resin By appropriately selecting the amount of moisture and the amount of moisture, it is possible to provide any desired humidity within the secondary packaging container. Furthermore, as the name suggests, superabsorbent resin can hold water several hundred times its own weight, so a small amount of superabsorbent resin can affect the water permeability of the secondary packaging container or the degree of water dispersion. Therefore, the relative humidity inside the secondary packaging container can be maintained at a level close to the relative humidity inside the primary packaging bag.

E. More details about the super absorbent resin used in the Japanese invention (1)
An α-olefin such as ethylene, propylene, 1-butene, isobutylene or diisobutylene, preferably an α-olefin having 2 to 12 carbon atoms, and maleic anhydride or a derivative thereof (e.g. maleic acid, maleic acid amide, maleic acid imide), or a crosslinked product of its alkali neutralized product (a method for producing such a super absorbent resin is already known as JP-A-56-36504), (2) methyl vinyl ether, A copolymer of a polymerizable vinyl compound such as vinyl acetate or styrene and maleic anhydride or its derivative, or a crosslinked product of its alkali neutralized product (the method for producing such a super absorbent resin is as described in (1) above). (3) Polymers of acrylic acid or methacrylic acid, copolymers mainly composed of them, or crosslinked products of alkali-neutralized products of these (co)polymers; 4) Self-crosslinking type alkali metal acrylate polymer obtained from alkali metal acrylate or alkali metal methacrylate (
Such a super absorbent resin is disclosed in, for example, Japanese Patent Application Laid-Open No. 53-463.
(manufactured by the method disclosed in the specification of Publication No. 89, etc.)
, (5) Saponified copolymers of vinyl esters and methacrylic esters or acrylic esters (such super absorbent resins are produced, for example, by the method disclosed in Japanese Patent Publication No. 53-37994) Also, commercially available products include "Sumikagel" by Sumitomo Chemical ■)
, (6) an alkali neutralized product of starch-polyacrylonitrile graft copolymer or polyacrylonitrile graft copolymer (such super absorbent resins are
9-43395 (disclosed in the specification etc.),
(7) Cross-linked starch or cellulose-addition polymerizable water-soluble monomer (maleic anhydride, acrylic acid) graft polymer.
This is used in No. 46199 and No. 53-46200. As a commercially available product, Sanyo Chemical Industries■
(8) Others (
Cross-linking agents such as "Aqualon" (carboxymethyl cellulose) on the Bercules side, etc., can be mentioned, but the above-mentioned (1)
A copolymer of α-olefin and maleic anhydride or an alkali-neutralized product thereof, a copolymer of the polymerizable vinyl compound and maleic anhydride of (2) above, or a crosslinked product of an alkali-neutralized product thereof. , a copolymer containing a polymer of acrylic acid or methacrylic acid as described in (3) above and a monomer thereof, or a crosslinked product of an alkali neutralized product of the (co)polymer thereof, the acrylic acid as described in (4) above. A self-crosslinking alkali metal salt polymer obtained from an acid alkali metal salt and the above (
Saponified copolymers of vinyl ester and methacrylic ester or acrylic ester (5) are preferably used. Among them, a crosslinked product of the alkaline neutralized product of the copolymer of α-olefin and maleic anhydride described in (1) above, specifically, a neutralized product of sodium hydroxide of the inbutylene-maleic anhydride copolymer, A crosslinked product obtained by reacting an epoxy compound or a polyvalent amine is preferably used. This alkali-neutralized crosslinked product of a copolymer of α-olefin and maleic anhydride is produced by combining α-olefin such as ethylene, propylene, 1-butene, imbutylene, or diisobutylene with maleic anhydride using a radical polymerization catalyst or the like. The resulting copolymer is treated with an alkali metal hydroxide, ammonia or an alkaline substance, particularly preferably an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide, for example in the form of an aqueous solution. It is produced by making it an alkali neutralized product and then reacting it with a crosslinking agent such as an epoxy compound or a polyvalent amine. The superabsorbent resin referred to in the present invention may be a resin composition, a mixture, or a composite material, and the manufacturing method thereof is not particularly limited.

In the present invention, a superabsorbent resin having the ability to absorb water at least 10 times its own weight is preferable because the amount of resin to be encapsulated is small. Note that the water absorption capacity of super absorbent resin means that 1 g of super absorbent resin is 500 c, c,
After immersing the sample in distilled water for 30 minutes or more, the sample was placed on a 200-mesh filter cloth to drain the water, the weight was measured, and the value was calculated as follows.

Weight after water absorption - Original weight Water absorption capacity = Original weight The water content when the superabsorbent resin is sealed in a secondary packaging container is calculated as follows: During the distribution period, the food in the primary packaging bag loses moisture during packaging. This is the amount of water that maintains the relative humidity within the secondary packaging container so that it can be maintained. The moisture content at the time of sealing is determined by the permissible moisture absorption and desorption range of the food in the primary packaging bag and the moisture permeability of the secondary packaging container. Or, assuming the distribution period, when maintaining the moisture content of the ``shaved shavings'' in the primary packaging bag at 15% or more, the moisture content is 8 to 30% by weight, preferably 10 to 25% by weight, based on the ``shaved shavings''.

The water content of the superabsorbent resin during the storage period is 0 of its own weight.
．． It needs to be 7 times or more. When the water content of the superabsorbent resin becomes 0.7 times or less than its own weight, the relative humidity inside the secondary packaging container becomes 80% or less, causing the food in the primary packaging bag to dry out and reduce its commercial value. Note that the water content of the super absorbent resin refers to the water content of the super absorbent resin when 10 g of the super absorbent resin is heated at 105°C, 4
The value was calculated as follows after drying for a period of time and measuring the weight.

Original weight - Weight after drying Weight after drying Weight after drying The super absorbent resin can be used as it is in powder form, or mixed with an appropriate binder, pulp, etc. if necessary. A method of applying or impregnating a film or sheet-like material (e.g., paper, non-woven fabric, etc.) with super-absorbent resin; Examples include a method of inserting and laminating resin powder and fixing it by pressing, heat fusion, adhesion, etc. Further, it is preferable that these super absorbent resins be placed in a bag made of a moisture permeable material and then sealed in a secondary packaging container. Examples of moisture permeable materials include woven fabrics made of natural fibers, chemical fibers, or mixtures thereof, nonwoven fabrics such as natural fibers, chemical fibers, or mixtures thereof, and plastic tapes and yarns, and paper.

As the secondary packaging container that can be used in the present invention, airtight containers υ
For example, commonly used substantially air-impermeable containers with lids (e.g. metal cans, plastic containers) are suitable, but cardboard cases alone or in combination with plastic film bags may also be used. It is possible.

Here, the plastic container that is the secondary packaging container is:
A material having at least one moisture-proof horse chestnut layer is preferably used. Moisture-proof resins include vinylidene chloride resin,
Examples include vopropylene, polyethylene, polyethylene terephthalate, polyvinyl chloride, and ethylene-vinyl alcohol copolymer. This secondary packaging container may be a single layer or a multilayer composite made with other plastics. The multilayer body can be obtained by laminating films or sheets, or by coextrusion blowing, coinjection blowing, coextrusion lamination, etc., using an interlayer adhesive if necessary.

As the secondary packaging bag, a multilayer packaging bag having a gas barrier sugar layer, preferably a gas barrier resin layer in the middle, is suitably used. Here, as the gas barrier resin, vinyl alcohol resin (polyvinyl alcohol, ethylene-vinyl alcohol copolymer (EVOH)
) l, vinylidene chloride resin, polyamide resin containing metaxylylene diamine or isophthalic acid,
Examples include acrylonitrile resins and polyester resins containing isophthalic acid. Examples of the resin provided on one or both sides of the gas barrier resin layer include thermoplastic resins, particularly hydrophobic thermoplastic resins such as polyethylene terephthalate, polyolefins (polyethylene, polypropylene), polyvinyl chloride, polystyrene, polyamide, etc. . These multilayer packaging bags are obtained by dry lamination, extrusion lamination, coextrusion lamination, etc., using interlayer adhesives if necessary.

The thickness of each layer of the multilayer packaging bag, which is the primary packaging bag, is that the gas barrier resin layer has a thickness of 5 to 30μ, and the thermoplastic resin provided on one or both sides of the gas barrier resin layer has a thickness of (both sides). If provided on pi, its total thickness) 40-1
00μ.

In the present invention, the food to be filled into the primary packaging bag includes:
The most typical example is shavings, but it can also be applied to other items that require a moderate amount of moisture.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples in any way. Furthermore, the definitions of terms used in the Examples are as follows unless otherwise specified.

a) OP: Biaxially stretched polypropylene film with a thickness of 25μ b) XL: Biaxially stretched Eval ■ film with a thickness of 12μ c) PE: Low density polyethylene film with a thickness of 50μ d) Super absorbent resin pack: Isobutylene-maleic anhydride co 2 g of a super absorbent resin made of a crosslinked product of alkali neutralized polymer (the water absorption capacity of this super absorbent resin was 200 times its own weight) packed in a pouch made of breathable nonwoven fabric. e) Super absorbent resin sheet: super absorbent resin made of a crosslinked product of alkali neutralized inbutylene-maleic anhydride copolymer (the water absorption capacity of this super absorbent resin was 200 times its own weight) 5g of sheets impregnated and assimilated with Danko Kanpetsu Example-1 20 commercially available "bonito shavings" packs filled with 5g in small bags with material composition of OP/XL/P E were placed in a gift metal can. Then, add one "super absorbent resin pack" containing 25g of water, close the lid, and heat at 20℃-60%RH.
After storing No. 1 for a year under the following conditions, the can was opened, the ``bonito shavings'' pack was taken out, the weight was measured using a balance, and the rate of change in moisture content was determined from the amount of change in weight.

Example 2 The moisture content of a hot potato using a "super absorbent resin sheet" containing 20 g of water instead of the "super absorbent resin pack" was determined in the same manner as in Example 1.

Example-3 500 commercially available bonito shavings packs, the same as those used in Example-1, were placed in a cardboard case with a volume of 0.05rn', and an additional 50g of water was added to make a "super absorbent resin pack". Add 10 pieces, close the lid, and heat at 30℃-60%RH.
After 1 was stored for a year under the following conditions, the package was opened, the ``bonito shavings'' pack was taken out, the weight was measured using a balance, and the moisture content was determined from the amount of change in weight.

Example 4 500 commercially available bonito shavings j-packs and 410 super absorbent resin packs containing 25 g of water were prepared using low-density polyethylene with a thickness of 60 μm. Place it in a bag with a surface area of about 1 I, heat seal the opening, store it for one year at 30'C and 60% RH, then open it and take out the ``bonito shavings'' pack, and weigh it on a balance. The moisture content was determined from the weight change.

Comparative Example-1 The moisture content after one year of storage was determined in the same manner as in Example-1, except that the [super absorbent resin bag] containing 25 g of water was not added.

Comparative Example 2 The moisture content after one year of storage was determined in the same manner as in Example 3, except that the "super absorbent resin pack" containing 50 g of water was not added.

Comparative Example 3 The moisture content after one year of storage was determined in the same manner as in Example 4, except that the "super absorbent resin pack" containing 25 g of water was not added.

Table 1 shows the moisture content of ``bonito shavings'' after one year of storage determined in each case.

With conventional preservation methods, the moisture content of ``bonito shavings'' was below a desirable level, whereas in the examples according to the present invention, ``bonito shavings'' were stored for one year.
It is clear that even if the moisture content increases or decreases slightly, it is not a problem and shows an excellent preservation effect.

Table 1: Moisture content (double weight %) The ``kegeribushi'' prepared in Examples 1 to 4 after being stored for one year are moderately moisturized and have good aroma and flavor. On the other hand, the "Kegeribushi" prepared in Comparative Examples 1 to 3 after being stored for one year were not sufficiently moisturized, so their flavor and texture were impaired.

The super absorbent resin does not come into direct contact with food, and since moisture is adsorbed by the super absorbent resin, it does not overly wet the primary packaging bag filled with food, and it is highly absorbent. By appropriately selecting the type and water content of the water-absorbing resin, it is possible to provide any humidity within the secondary packaging container. Furthermore, as the name suggests, superabsorbent resin can hold water hundreds of times its own weight, so a small amount of superabsorbent resin can affect the water permeability or water dispersion rate of the secondary packaging container. Regardless, the relative humidity within the secondary packaging container can be maintained at a level close to the relative humidity within the primary packaging bag.

Patent applicant: Kuraray Co., Ltd. Agent: Patent Attorney Ken Honda

Claims (1)

[Scope of Claims] (1) A food packaging body in which a hydrated super absorbent resin is sealed in a secondary packaging container together with a primary packaging bag filled with food. (2) The food container of claim 1, wherein the secondary packaging container is a substantially air-impermeable lidded container. (3) The food package according to any one of claims 1 to 2, wherein the food is "shaved". (4) The food package according to any one of claims 1 to 3, wherein the superabsorbent resin contains water equal to or more than 0.7 times its own weight. (5) The food container according to any one of claims 1 to 4, wherein the super absorbent resin is contained in a bag made of a breathable material. (6) The food package according to any one of claims 1 to 5, wherein the super absorbent resin is formed in a film or sheet shape. (7) The food package according to any one of claims 1 to 5, wherein the superabsorbent resin is applied or impregnated onto a sheet. (8) The food package according to any one of claims 1 to 5, wherein the super absorbent resin is sandwiched between porous sheets. (9) A method for maintaining the quality of a food package, characterized in that a super absorbent resin containing water is sealed in a container together with the package filled with the food.