JP2006006269A - Method for preserving dried food - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for preserving a food, in which a dried food is stored in a container which uses a transparent resin composition having oxygen-absorbing ability as at least a part of constituents and has transparency. <P>SOLUTION: This method for preserving the food comprises receiving the dried food in the container which has the transparency and is formed out of an oxygen-absorbing multi-layer material containing a layer composed of the resin composition having the oxygen-absorbing ability. Thus, quality of the food is maintained for an extremely long period in such a state that the dried food in the container is visually confirmed. Further, the dried food is prevented from oxidative deterioration, while maintaining the food in a dried state. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for preserving dried food. More specifically, the present invention relates to a method for preserving foods that prevents deterioration due to oxidation of dried foods by making the storage atmosphere oxygen-free.

  Conventionally, a large number of food preservation methods have been proposed in order to extend the period during which a harvested or processed food can be safely ingested, or to satisfy the demand for ease of cooking. In general, the deterioration of food quality is caused by microbial reproduction and insect damage, and oxidative alteration of food ingredients. Proliferation of microorganisms and insect damage make food incapable of being eaten directly, and oxidative alteration of food components mainly destroys nutrients and adversely affects the flavor. Reduce. Many preservation methods that have been passed down to the present since ancient times have focused on preventing the growth of microorganisms and insect damage, sterilization and insecticide by heating and ultraviolet irradiation, and drying, freezing refrigeration, salt storage, sugar storage, acid addition, soot, Furthermore, the addition of preservatives and bactericides has made it difficult to grow microorganisms, and food from microorganisms and insects has been separated by canning and bottled.

In addition to this, food preservation methods that control the storage atmosphere typified by oxygen-free packaging in recent years also play a role in maintaining the flavor and color tone of foods by having an antioxidant function. Oxygen-free packaging is a sachet-type oxygen scavenger (for example, trade name “AGELESS”, Mitsubishi Gas Chemical Co., Ltd.) that is filled with oxygen-absorbing compositions such as powdered or granular iron powder or ascorbic acid. And a container made of a gas non-permeable (gas barrier) packaging material that can be sealed. As a packaging material, a transparent synthetic resin film having advantages such as light weight and visible contents is mainly used.
On the other hand, from the viewpoint of protecting foods from damage caused by microorganisms and imparting storability, a method of removing moisture from foods rich in moisture is important. When the water activity of the food is 0.90 or less, general spoilage bacteria can hardly grow, and when the water activity is 0.80 or less, mold is difficult to grow. Therefore, the water activity of many dry foods is 0.80 or less.

However, the method for preserving foods that uses oxygen scavengers such as iron powder and ascorbic acid to make oxygen in the packaging container is oxygen-free when these oxygen scavengers absorb oxygen. May not be suitable for dry foods. When using an oxygen scavenger with water added to the composition so that it can function even under dry conditions, the deoxygenation function stops due to the moisture transferring to the dry food, and the dry food becomes damp was there. Further, when a small bag type oxygen absorber is used for anaerobic packaging of food, it is necessary to fix the oxygen absorber with an adhesive or the like if there is a risk of accidental eating. In addition, when storing colored foods, the effects of oxygen remaining in containers and foods even after nitrogen substitution and vacuum degassing, and the minute amounts of oxygen that permeate the film cannot be ignored when synthetic resin films are used. In order to avoid discoloration of foods involving oxygen and light energy, an opaque container is often used, and the contents are not visible.
In recent years, as disclosed in Patent Documents 1 to 3, oxygen scavenging resin films have been developed.
JP-A-2003-521552 Japanese Patent No. 3334056 Japanese Patent No. 3183704

  As described above, it has been extremely difficult to store dried foods in an oxygen-free state while being kept in a dry state. An object of the present invention is to solve the above-described problems in the prior art, to provide a method for preserving foods that prevents oxidative deterioration of dried foods, that the contents can be seen, and that there is no risk of accidentally eating foreign substances.

As a result of intensive studies in view of the above-mentioned problems of the prior art, the inventors of the present invention can prevent oxidative alteration of food components by storing dried food in a transparent container having oxygen absorption ability even under drying. The present inventors have found that the food inside can be seen, and that there is no fear of eating foreign substances by mistake, and the present invention has been achieved.
That is, the present invention relates to a method for preserving food, characterized in that the dried food is stored in a transparent container having at least part of a transparent resin composition having oxygen absorption ability. The present invention also relates to a method for preserving food, characterized in that the dried food is stored in a container made of a deoxygenating multilayer body including a layer made of a resin composition having transparency and having an oxygen absorption ability. is there.

  According to the present invention, the dried food in the container can maintain its quality such as nutrients and color tone for a very long time in a state that can be visually confirmed while maintaining its dry state.

  The food preservation method of the present invention is to store the dried food in a container having at least a part of a constitution of a resin having transparency and oxygen absorbing ability. The resin having transparency and oxygen absorption performance is composed of an easily oxidizable thermoplastic resin, a transition metal catalyst, and a photosensitizer.

  As the easily oxidizable thermoplastic resin, an organic polymer compound having a portion in which carbon and carbon are bonded by a double bond or an organic polymer compound having a hydrogen atom bonded to a tertiary carbon atom can be used. The carbon-carbon double bond in the organic polymer compound having a portion in which carbon and carbon are bonded by a double bond may be in the polymer main chain or in the side chain. Representative examples include styrene butadiene rubber and ethylene / methyl acrylate / cyclohexenylmethyl acrylate copolymer. An example of an organic polymer compound having a hydrogen atom bonded to a tertiary carbon atom is a hydrogenated styrene butadiene rubber.

  The transition metal catalyst is a metal compound such as a salt or oxide of a transition element metal. Manganese, iron, cobalt, nickel and copper are preferred, and manganese, iron and cobalt are particularly preferred because they exhibit excellent catalytic action. Examples of the metal salt of the transition element metal include a mineral salt and a fatty acid salt of the transition element metal, such as a hydrochloride, sulfate, nitrate, acetate, or higher fatty acid salt of the transition element metal. Representative examples include cobalt octylate, manganese octylate, manganese naphthenate, and iron naphthenate.

  A transition metal catalyst preferable from the viewpoint of ease of handling is a supported catalyst in which a salt of a transition element metal is supported on a support. Although the kind of support | carrier is not specifically limited, A zeolite, diatomaceous earth, calcium silicates, etc. can be used. In particular, an agglomerate having a size of 0.1 to 200 μm at the time of catalyst preparation and after preparation is preferable because of good handling properties. In particular, a carrier having a thickness of 10 to 100 nm when dispersed in a resin is preferable because it gives a transparent resin composition when blended in the resin. An example of such a carrier is a synthetic calcium silicate compound. The blending ratio of the transition metal catalyst is preferably 0.001 to 10 wt% as a metal atomic weight in the resin composition having transparency and oxygen absorption from the oxygen absorption performance, physical strength, and economy. ˜1 wt% is particularly preferred.

  A photosensitizer is a substance that causes photosensitization. Photosensitization is a phenomenon in which excited molecules generated by photoexcitation do not react themselves but activate other molecules to cause a reaction. Representative examples of the photosensitizer include benzophenone and derivatives thereof, thiazine dyes, metal porphyrin derivatives, anthraquinone derivatives, and the like. Preferably, it is a benzophenone derivative containing a benzophenone skeleton structure. The blending ratio of the photosensitizer is preferably 0.001 to 10 wt%, particularly preferably 0.01 to 1 wt%.

  The above readily oxidizable thermoplastic resin, transition metal catalyst and photosensitizer are formed into a pellet-like, film-like or sheet-like oxygen-absorbing resin composition by melt-kneading using an extruder for resin or the like. be able to. Moreover, it can also be set as the oxygen absorptive resin composition which the oxygen absorptive resin composition disperse | distributed in the other thermoplastic resin by adding another thermoplastic resin and melt-kneading.

  The oxygen-absorbing resin composition that is a feature of the present invention has transparency. Furthermore, this oxygen-absorbing composition can be used as a packaging material having oxygen-absorbing ability in part or all of a packaging bag or packaging container as it is or by laminating with an appropriate packaging material. For example, by co-extrusion and co-extrusion lamination, the oxygen-absorbing resin composition is used as an oxygen-absorbing layer, and a thermoplastic resin such as polyolefin having high oxygen permeability and heat fusion properties is packaged on the stored food side. A film or sheet-shaped oxygen-absorbing multi-layer body, which is laminated as a gas barrier layer by laminating as a gas barrier layer, laminating as a separating layer from the contents, and laminating a resin such as polyester or polyamide vapor-deposited silica or alumina having low oxygen permeability on the outside air side It can be. 1-300 micrometers is preferable and, as for the thickness of the oxygen absorption layer in this oxygen-absorbing multilayer body, 10-200 micrometers is more preferable.

  In addition, the above oxygen-absorbing composition is mixed with at least one selected from a desiccant, an adsorbent, an antibacterial agent, and a colorant to form a composition having both an oxygen absorption function and a drying function. be able to. Moreover, it can also be set as the multilayer body containing the layer of an oxygen absorptive composition, and the layer containing 1 or more types chosen from a desiccant, an adsorbent, an antibacterial agent, and a coloring agent.

  A dried food is a food that is originally dried, or a food that has been dehydrated for the purpose of imparting storage and transportability, rationalizing cooking, producing cooking ingredients, and creating new foods. The present invention is applicable to all foods, but foods having a water activity of 0.80 or less, particularly foods having a water activity of 0.60 or less, and water activity of 0.30, to which conventional oxygen scavengers were difficult to apply. It can be suitably used for the following foods. Specifically, as dried foods with a water activity of 0.80 or less, herbal medicines, spices, boiled and dried fish, cuts, rice and millet, dried noodles, dried meat and delicacies, squid, shrimp and shellfish and other dried fish, dried fish Examples include mushrooms such as shiitake mushrooms, seaweeds such as kombu and wakame, beans such as azuki and soy beans, and dry foods with a water activity of 0.60 or less. Examples of dried foods having a water activity of 0.30 or less include dried vegetables, snacks such as coffee (powder and beans), crackers and potato chips, powder seasonings, and oils.

Further, the atmospheric humidity in the container can be in an oxygen-free state in the entire range, but it is a dry atmosphere in which a conventional oxygen scavenger is difficult to apply, 80% RH or less, particularly 60% RH or less, Can be preferably made oxygen-free at 30% RH or less. It is also preferable to enclose a desiccant in the form of a sachet or a sheet when the dried food is stored in a container made of an oxygen-absorbing multilayer having the oxygen-absorbing layer.

  Whether or not the dried food is suitably stored can be determined by the color tone of the food and the acid value and peroxide value. Changes in the color of the food can be easily determined by visual inspection, and discoloration is considered to have deteriorated in quality. The acid value is the number of mg of potassium hydroxide required to neutralize free fatty acids contained in 1 g of fats and oils, and foods with high acid values are evaluated as having poor quality. Fresh fats and oils generally have a very low acid value, but free fatty acids are produced by oxidation during storage and processing, resulting in a high acid value. The peroxide value is a value obtained by reacting peroxide in food with potassium iodide and expressing the liberated iodine by the number of milliequivalents per 1 kg of food, and an increase in peroxide value indicates a decrease in food quality. It becomes an indicator. In general, since fats and oils form peroxides at the beginning of oxidation, the peroxide value represents the degree of oxidation in the initial stage of fats and oils.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1
A transition metal catalyst obtained by impregnating a synthetic calcium silicate (trade name “Microcell E”, manufactured by Celite) with a manganese octylate solution (manufactured by Nippon Chemical Industry Co., Ltd.) and drying under reduced pressure, A phenylbenzophenone sensitizer is mixed and melted and kneaded at 180 ° C. with a low-density polyethylene and a twin screw extruder, resulting in a manganese atom content of 1.2 wt% and a synthetic calcium silicate (average particle size of 2 μm). Was prepared from a resin composition having a weight of 7.5 wt% and a phenylbenzophenone content of 2.1 wt%.

  This masterbatch and an easily oxidizable thermoplastic resin, ethylene / methyl acrylate / cyclohexenylmethyl acrylate copolymer (trade name “OSP500R”, manufactured by Chevron Phillips Chemical Company LP), are melt-mixed at a weight ratio of 1: 9. Then, a transparent multilayer film using this as an oxygen absorbing layer was produced by coextrusion lamination. As a result, an isolation layer also serving as a heat-fusibility was laminated on one side of the oxygen absorbing layer, and a reinforcing layer, an adhesive layer, and a gas barrier layer were laminated on the other side in this order. A linear low density polyethylene was used for the separating layer and the reinforcing layer, a maleic acid-modified polyethylene adhesive resin was used for the adhesive layer, and a silica-deposited polyethylene terephthalate film was used for the gas barrier layer. The thickness of each layer was 10 μm for the isolation layer, 20 μm for the oxygen absorption layer, 30 μm for the reinforcing layer, 10 μm for the adhesive layer, and 15 μm for the gas barrier layer. Using the obtained oxygen-absorbing multilayer film on both sides, a transparent oxygen-absorbing flat bag having a size of 200 mm × 300 mm was produced.

A dry food preservation test using this oxygen-absorbing flat bag was conducted. After irradiating the produced flat bag with ultraviolet light (16.7 mW / cm ² ) using a 400 W high-pressure mercury lamp as a light source, put butter peanut (water activity 0.37) as a food with a calcium oxide desiccant in a sachet, 500 mL This was sealed in a container together with oxygen-reduced air having an oxygen concentration of 2% and left in a constant temperature room at 25 ° C. under a fluorescent lamp with an illuminance of 4500 lux. After 2 days of standing, it was confirmed that the oxygen concentration in the container was in an oxygen-free state of less than 0.1 vol%. Furthermore, it was stored under a fluorescent lamp with an illuminance of 4500 lux in a constant temperature room at 25 ° C. The acid value of the butter peanut before storage was 0.5 mg / g, and the peroxide value was 0.5 meq / kg.
On the seventh day of storage, the color of butter peanuts and the crispy dry texture did not change at all. In addition, the acid value of butter peanut after 7 days was 0.5 mg / g, and the peroxide value was as small as 1.0 meq / kg.

Example 2
In the same manner as in Example 1, a transparent oxygen-absorbing flat bag was produced, and a dry food storage test using the same was conducted. As a food, freeze-dried cut (water activity 0.26) was sealed.
On the seventh day of storage, the freeze-dried color and smooth fluidity were not changed at all.

Example 3
In the same manner as in Example 1, a transparent oxygen-absorbing flat bag was produced, and a dry food storage test using the same was conducted. Matcha (water activity 0.38) was sealed as a food.
On the 7th day of storage, the green tea color was slightly faded, but the green color was maintained, and the smooth fluidity did not change at all.

Example 4
In the same manner as in Example 1, a transparent oxygen-absorbing flat bag was produced, and a dry food storage test using the same was conducted. Tea buckwheat noodles (water activity 0.56) were sealed as food.
On the 7th day of storage, the color tone and hardness of the tea buckwheat noodles did not change at all.

Example 5
In the same manner as in Example 1, a transparent oxygen-absorbing flat bag was produced, and a dry food storage test using the same was conducted. Dried shrimp (water activity 0.65) was sealed as food.
On the 7th day of storage, the color of dried shrimp and the crispy dry texture did not change at all.

Reference example 1
In the same manner as in Example 1, a transparent oxygen-absorbing flat bag was produced, and a dry food storage test using the same was conducted. Baby salami (water activity 0.83) was sealed as food.
On the seventh day of storage, the color and texture of the baby salami did not change at all.

Comparative Example 1
A dry food storage test was conducted in the same manner as in Example 1 except that a flat bag (trade name “PTS bag”, manufactured by Mitsubishi Gas Chemical Co., Ltd.) made of a multilayer film having transparency and high gas barrier properties was used. It was. Butter peanut (water activity 0.37) was sealed as food.
The acid value of the butter peanut on the 7th day of storage was 0.5 mg / g, the peroxide value was 24.3 meq / kg, and the peroxide value indicating a decrease in food quality compared to Example 1 was greatly increased. .

Comparative Example 2
In the same manner as in Comparative Example 1, a transparent flat bag was produced, and a dry food storage test using the same was conducted. As a food, freeze-dried cut (water activity 0.26) was sealed.
On the seventh day of storage, the color of freeze-drying was faded on the seventh day of storage.

Comparative Example 3
In the same manner as in Example 1, a transparent flat bag was produced, and a storage test for dried foods using the same was conducted. Matcha (water activity 0.38) was sealed as a food.
Significant fading was observed in the color tone of Matcha on the second day of storage.

Comparative Example 4
In the same manner as in Example 1, a transparent flat bag was produced, and a storage test for dried foods using the same was conducted. Tea buckwheat noodles (water activity 0.56) were sealed as food.
On the second day of storage, significant fading was observed in the color tone of the dried noodles.

Comparative Example 5
In the same manner as in Example 1, a transparent flat bag was produced, and a storage test for dried foods using the same was conducted. Dried shrimp (water activity 0.65) was sealed as food.
A slight fading was observed in the color of dried shrimp on the second day of storage, and the color was clearly faded on the seventh day of storage.

Comparative Example 6
In the same manner as in Example 1, a transparent oxygen-absorbing flat bag was produced, and a dry food storage test using the same was conducted. Baby salami (water activity 0.83) was sealed as food.
Slight fading was observed in the color of the baby salami on the second day of storage, and the color fading was apparent on the seventh day of storage.

Example 6
A masterbatch (trade name “OSP100M”, manufactured by Chevron Philips Chemical Company LP) and a copolymer of ethylene / methyl acrylate / cyclohexenylmethyl acrylate (trade name “OSP500R”, each containing 1.0 wt% of cobalt and a photosensitizer. )) Was melt-mixed at a weight ratio of 1: 9, and a transparent multilayer film having this as an oxygen-absorbing layer was produced by coextrusion. As a result, an isolation layer also serving as a heat fusible layer was laminated on one surface of the oxygen absorbing layer, and an adhesive layer, a gas barrier layer, and a protective layer were laminated on the other surface in this order. Linear low density polyethylene is used for the separating layer, modified polyethylene adhesive resin is used for the adhesive layer, ethylene / vinyl alcohol copolymer is used for the gas barrier layer, and nylon 6 / nylon 12 is used for the protective layer. Coalescence was used. The thickness of each layer was 10 μm for the separating layer, 20 μm for the oxygen absorbing layer, 10 μm for the adhesive layer, 15 μm for the gas barrier layer, and 10 μm for the protective layer.

Using the obtained oxygen-absorbing multilayer film, a flat bag having a size of about 200 mx 300 m was prepared, and a dry food storage test using the same was conducted in the same manner as in Example 1. Butter peanut (water activity 0.37) was sealed as food.
On the seventh day of storage, the color of butter peanuts and the crispy dry texture did not change at all. In addition, the acid value of butter peanut after 7 days was 0.5 mg / g, and the peroxide value was as small as 1.0 meq / kg.

Example 7
In the same manner as in Example 6, a transparent oxygen-absorbing flat bag was produced, and a dry food storage test using the same was conducted. As a food, freeze-dried cut (water activity 0.26) was sealed.
On the seventh day of storage, the freeze-dried color and smooth fluidity were not changed at all.

Example 8
In the same manner as in Example 6, a transparent oxygen-absorbing flat bag was produced, and a dry food storage test using the same was conducted. Matcha (water activity 0.38) was sealed as a food.
On the 7th day of storage, the green tea color was slightly faded, but the green color was maintained, and the smooth fluidity did not change at all.

Example 9
In the same manner as in Example 6, a transparent oxygen-absorbing flat bag was produced, and a dry food storage test using the same was conducted. Tea buckwheat noodles (water activity 0.56) were sealed as food.
On the 7th day of storage, the color tone and hardness of the tea buckwheat noodles did not change at all.

Example 10
In the same manner as in Example 6, a transparent oxygen-absorbing flat bag was produced, and a dry food storage test using the same was conducted. Dried shrimp (water activity 0.65) was sealed as food.
On the 7th day of storage, the color of dried shrimp and the crispy dry texture did not change at all.

Reference example 2
In the same manner as in Example 1, a transparent oxygen-absorbing flat bag was produced, and a dry food storage test using the same was conducted. Baby salami (water activity 0.83) was sealed as food.
On the seventh day of storage, the color and texture of the baby salami did not change at all.

Claims (5)

A method for preserving dried food, which comprises storing the dried food in a container having transparency that includes at least part of a resin composition having transparency and oxygen absorption ability. A method for preserving dried food, which comprises storing the dried food in a container made of an oxygen-absorbing multilayer including a layer made of a resin composition having transparency and an oxygen-absorbing ability. The dry food storage according to claim 1 or 2, wherein the resin composition having transparency and having an oxygen absorption capacity comprises an easily oxidizable thermoplastic resin, a transition metal catalyst, and a photosensitizer. Method. 4. The method for preserving food according to claim 3, wherein the transition metal catalyst comprises a transition metal salt supported on an inorganic carrier. The dry food storage method according to claim 1 or 2, wherein the dry food is a colored food.