JPS594110B2 - How to preserve food - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves packaging uncooked, semi-cooked, or cooked foods and frozen foods using a polyester film having heat-sealing properties, and then cooking and sterilizing them at high temperatures. The purpose is to significantly extend the storage period.

Traditionally, food preservation methods include disinfectants, preservatives,
Methods such as adding fungicides to food were used, but
The effects of these chemicals on the human body cannot be ignored, and food must be sealed in containers or film and boiled or exposed to high-temperature, high-pressure water without adding disinfectants, preservatives, or fungicides. The so-called retort method of sterilization has come to be used, but the temperature of the atmosphere used in these cases is from 80°C to 135°C at the highest, and it is difficult to completely sterilize.
It takes a long time to fully sterilize the food, and even if the purpose of sterilization is achieved, it is not possible to cook the food sufficiently, and this is combined with the hygroscopic nature of the film and water intrusion into the interior due to pinholes. Cooking and sterilization may be incomplete, and the contents may collapse due to vibrations of water or steam. 5. The present invention is a packaging method that eliminates these drawbacks, and is a method for preserving food by packaging and sealing the food with a polyethylene terephthalate film having a heat-sealable note and sterilizing the food by cooking at high temperatures.

The polyethylene terephthalate film used in the present invention refers to an unstretched, uniaxially stretched or biaxially stretched film formed into a sheet from polyethylene terephthalate obtained by condensation polymerization from terephthalic acid and ethylene glycol. A sheet laminated to paper or other heat-resistant -5 material can also be used. Depending on the purpose, dibasic acid components such as isophthalic acid, 2,6-naphthalene dicarboxylic acid, hydroxyisophthalic acid, '0 sulfoisophthalic acid, adipic acid, and sebacic acid may be used within the range that does not significantly change the properties of polyethylene terephthalate. , dodecanedioic acid, etc. may be copolymerized, and glycol components include propylene glycol, butanediol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, neopentyl glycol,
Cyclohexaline methanol or the like may be copolymerized. Depending on the purpose, polyester, nylon, 10 polycarbonate, polystyrene, polyolefin, etc., which are condensed from the above-mentioned raw materials, may be blended within a range that does not significantly change the properties of polyethylene terephthalate. For the purpose of heat resistance, highly polymerized polyethylene terephthalate obtained by solid phase polymerization of polyethylene terephthalate obtained by ordinary polycondensation in a high temperature vacuum is used. In the present invention, the polyester resin on which at least one side of the polyethylene terephthalate film is laminated has a glass transition point of 25°C to 130°C, preferably 45°C to 120°C, as measured by a differential calorimeter DSC. A suitable material has a softening point of 120°C to 230°C, preferably 140°C to 200°C, as measured by the ring and ball method of JIS-K-2531-60.

Polyester resins with a glass transition point of 25°C or lower and a softening point of 120°C or lower are already soft at room temperature and have high heat sealing strength at room temperature when combined with a film, but the sealing strength at high temperatures decreases significantly. . Glass transition point is 1
Polyester resins with a softening point of 230°C or higher and a temperature of 30°C or higher require high temperatures when they are combined with a film and then heat-sealed for food packaging, making it difficult to heat-seal, and the resin is too hard. Not suitable for the purpose of the present invention. Such polyester resin has a glass transition point of 25
The softening point according to JIS-K-2531-60 (ring and ball method) is 120KC to 230℃ at a temperature of and isophthalic acid)
A linear copolymerized polyester (hereinafter simply referred to as linear copolymerized polyester) consisting of a residue and a glycol residue is preferable.

A more preferable linear copolymerized polyester has a terephthalic acid residue or a residue consisting of terephthalic acid and isophthalic acid accounting for 95 to 50 mol% as a dibasic acid component, and one or more types forming a glycol component. It can be obtained by appropriately determining the composition ratio of glycol residues so as to satisfy the above-mentioned ranges of softening point and glass transition point. 20 to 70 moles of glycol component? is preferably composed of ethylene glycol residues and/or 1,4-butanediol residues. Here, the remainder of the dibasic acid component is one or two types of aliphatic dibasic acids such as succinic acid, adipic acid, sebacic acid, and azelaic acid, and aromatic dibasic acids such as orthophthalic acid and diphenyldicarboxylic acid. It is composed of the above residues, and the glycol component is
In addition to ethylene glycol and 1,4-butadiol, 1
, 2-propylene glycol, 1,3-propylene glycol, 1,6-hexanediol, diethylene glycol, triethylene glycol, dipropylene glycol, neopentyl glycol, alkylene oxide adduct of bisphenol A or its hydride, etc. Consists of one or more of the following. In addition, residues of oxyacids such as hydroxybenzoic acid may be present. The linear copolymerized polyester used in the present invention is preferably soluble in organic solvents.

Examples of the organic solvent include chloroform, dioxane, tetrahydrofuran, methyl ethyl ketone, ethyl acetate, benzene, toluene, and xylene. As mentioned above, the dihydrochloric acid component of the linear copolymerized polyester used in the present invention preferably contains 40 mol% or more of terephthalic acid residues or residues consisting of terephthalic acid, isophthalic acid, and terephthalic acid. If the oil content is 40 mol%, the degree of polymerization will be low and the softening point will also be low, making it unsuitable for the purpose of the present invention.

Also, there are 70 moles of glycol component erectile glycol residue? Or over 20 moles? If it is less than this, the solubility of the linear copolymerized polyester in organic solvents may decrease. The molecular weight of the linear copolymerized polyester used in the present invention is 0 in intrinsic viscosity (measured at 80°C in phenol/tetrachloroethane = 60/40 (weight ratio)).
．． 15 to 1.2 d1/9 is suitable.

In addition, linear copolymerized polyesters have two different glass transition points.
More than seeds may be blended. When cooking food at high temperatures, the sealing strength of the film must be sufficiently maintained even at high temperatures, and is 50g/15 at 100℃
Seal strength of mm or more is required. Glass transition point 2
The sealing strength of a heat-sealable polyethylene terephthalate film composited with a polyester resin with a softening point of 120°C or less at room temperature of 5°C or lower is 509/15 mm or higher at room temperature, but it becomes 509/15 mm or lower at 100°C, which is not practical. . On the other hand, the glass transition point is 25°C~1
The sealing strength of heat-sealable polyethylene terephthalate film, which is a composite of polyester resin with a softening point of 120 to 230°C at 30°C, is 509/1 even at 100°C.
It is 5 mTIL or more and is practical. Here, the heat seal strength (9/15mm) means width 15mm 1 length 1
The heat-sealed surfaces of two 50-meter samples were put together, and the film was heat-sealed for 1 second at a pressure of 1 kg/(V7!) using a heating plate. After leaving the film in an atmosphere of 20°C and 65% RH for 24 hours, the film was heated to Toyo Seiki Co., Ltd. This is the force required to peel off the film at a speed of 200 mm/min in one direction using Tensilon manufactured by the company.The method of compounding polyester resin on at least one side of polyethylene terephthalate film involves applying a solution or melt of polyester resin. The so-called part-coat method, in which the entire surface is coated or only the sealed area is coated, the co-extrusion method of polyethylene terephthalate and polyester resin, the in-line lamination method, the extrusion lamination method, and the lamination of a film made of polyethylene terephthalate and polyester resin. Refers to methods etc.

The coating amount of the resin on the surface of the polyethylene terephthalate film is in the range of 0.05 to 59/m in terms of solid content, preferably in the range of 0.1 to 1.09/m. The thickness of the terephthalate film is 3 to 5.
In the case of 0μ, the coating thickness of the resin is 2 to 30% of the above film.
, preferably 5 to 10%, is applied to one or both sides of the film. The thus obtained heat-sealable polyethylene terephthalate film preferably has a heat-sealing strength above room temperature that is greater than or at least the same as the heat-sealing strength at room temperature. The heat-sealing strength is such that it can be easily opened, and the heat-sealing strength is greatly reduced by high temperatures during high-temperature cooking, so the overall strength is required to prevent the package from being opened.

At 100℃, the heat-sealed part is strong enough not to be easily opened due to expansion due to internal gas pressure during high-temperature cooking, or strong enough that the seal does not open completely and gas escapes due to gaps in some parts. A seal strength of 509/15 mm or more is practical. Here, for reference, how the glass transition point and softening point of the polyester resin affect the seal strength and temperature will be described.

For example, 43 moles of terephthalic acid? , 7 moles of sebacic acid? , 30 moles of ethylene glycol? , 20 moles of neopentyl glycol? Polyester resin A, which was condensed and polymerized, has a glass transition point of 62°C and a softening point of 173°C, and the sealing strength and temperature of a heat-sealable film coated with a thickness of 2μ on a biaxially stretched polyethylene terephthalate film with a thickness of 30μ. The relationship is shown by curve A in Figure 1, and according to this, the seal strength is small at temperatures below 60°C, increases at temperatures above 80°C, and even at high temperatures of 180°C, it maintains the same seal strength as at room temperature. However, it is suitable for the purpose of the present invention. On the other hand, terephthalic acid 3
0 mole? , 20 moles of sebacic acid? , Neopen 1,000 glycol 30 mol%, ethylene glycol 20 mol? Polyester resin B (glass transition point 7°C,
The relationship between the sealing strength and temperature of a heat-sealable film coated with a thickness of 2μ on a biaxially stretched polyethylene terephthalate film with a softening point of 120°C and a thickness of 30μ is shown by curve B in Figure 1, and according to this, Although the sealing strength is high at room temperature below 30°C, it becomes very small at high temperature above 80°C, making it unsuitable for the purpose of the present invention.
In order to improve the machining properties and appearance of polyethylene terephthalate film composited with polyester resin, apply a release agent, antistatic agent, slip agent, anti-blocking agent, anti-fog agent, etc. to the surface as necessary. Alternatively, it may be incorporated into a polyester resin layer or a polyethylene terephthalate film layer.

In order to further improve the surface activity, a chemical treatment such as corona treatment, flame treatment, acid or alkali octaoxidizing agent may be performed. Depending on the type of food that is packaged and heated and cooked, some of the food sticks to the inner surface of the film, and some of the food may stick to the film surface when the food is opened and eaten after cooking.

In order to minimize the adhesion of food to the surface of the film, the surface of the film that comes into contact with the food should be treated as a release treatment.
Liquid or solid mold release agents, such as rapeseed oil, sesame oil, cottonseed oil, soybean oil, corn oil, olive oil, salad oil, animal and vegetable oils and fats such as marcarin, butter, lard, and head, inorganic powders such as silica, silicone oil, and sugar esters. It is effective to apply polyvinyl alcohol, sugar, flour, calcium stearate, and mixtures thereof, or to apply nonwoven fabric, woven fabric, thin paper, etc. made of paper and synthetic resins such as polyester, nylon, and polypropylene. It is. These release agents, release cloth, and release paper may be used alone or in combination, and may be applied or attached to the entire surface, but should not be applied or attached to the heat-sealed area. It is more effective. Foods that can be packaged by the method of the present invention include bread, hotcakes, gastella, kutsukiichi, bisget, manjiyu, rice crackers, arare, mochi, Western sweets, pizza pie, potatoes, pilaf, bread perk, shiyuumai, and giyo. It refers to the dough for meatballs, rice dishes, etc., semi-baked products, cooked products, or frozen products of these.

The sealed packaging method of the present invention includes overlap packaging,
Any method may be used, such as single-sided seal packaging, pillow-type packaging, packaging with both ends bent downward without heat bonding, and twist packaging. It refers to the state of being Furthermore, in order to facilitate opening, a tear tape may be attached to the area where the package is to be opened. Means for high-temperature cooking sterilization in the present invention include electric ovens, gas ovens, infrared cookers, microwave ovens, etc. The cooking sterilization temperature can range from 80°C or higher to the melting point of polyethylene terephthalate film. , preferably from 135°C or higher to 10°C below the melting point of the polyethylene terephthalate film.

When uncooked, semi-cooked, cooked, frozen food, etc. is packaged with the film of the present invention, heat-sealed, and cooked in an oven at a temperature of 80°C or higher, preferably 135°C or higher, the food inside is There may be burnt marks on the surface of the food when it is cooked, but because the adhesive strength of the film is high even at high temperatures, gases such as water vapor released when food is cooked can increase the internal pressure appropriately. ,
The sealed portion does not completely rupture, and if the internal pressure becomes too high, gas will escape from a portion of the sealed portion, but once the gas is released and the internal pressure falls, the sealed portion will return to its original state. Foods packaged with a polyethylene terephthalate film composited with a polyester resin with a glass transition point of 25°C or lower and a softening point of 120°C or lower, which is heat-sealed, remain well sealed at room temperature; When cooking in an oven or the like at a temperature of 135°C or higher, preferably 135°C or higher, the heat sealing strength at high temperatures is low, so gases such as water vapor released when food is cooked can cause the internal pressure to increase. If the temperature rises, the seal part will break and the gas inside will be released, and even if the internal pressure drops after the gas has escaped, the seal part will not return to its original state, and even after cooking is finished, the seal part will remain wide open. , the condition is not suitable for food storage. According to the method of the invention,
A polyester resin having a glass transition point of 25°C to 130°C and a softening point of 120°C to 230°C is formed on at least one side of a polyethylene terephthalate film, and the sealing strength at 100°C is 509/15m71.
The food is packaged and sealed with a polyethylene terephthalate laminated film having a heat sealing property of t or more, and then,
By cooking and sterilizing at high temperatures, the contents are sterilized and preserved or cooked while retaining their food form in a sealed state.Even after cooking and sterilization are completed, the sealed contents are effectively maintained, preventing spoilage bacteria and oxygen. This made it difficult for people to enter the area, making it possible to significantly extend the shelf life of food.

Next, the present invention will be further explained with reference to Examples and Comparative Examples.

Example 1 35 moles of terephthalic acid was added to one side of a biaxially stretched polyethylene terephthalate film (melting point 255 °C) with a thickness of 30 μm. , 15 moles of isophthalic acid? , 30 mol% neopentyl glycol, 20 mol ethylene glycol? A taloloform solution of a polyester resin having a softening point of 181° C. and a glass transition point of 76° C. obtained by condensation polymerization was applied thereto to obtain a heat-sealable polyester film (1) having a polyester resin layer of 2 μm.

Separately, polyethylene terephthalate and the above polyester resin were extruded by a two-layer coextrusion method, and biaxially stretched.
A heat-sealable polyester film () having a polyethylene terephthalate layer of 30 μm and a polyester resin layer of 4 μm was obtained.

A kutsuki dough prepared by dissolving commercially available kutsuki mix powder in water was wrapped in horizontal pillow heat seal packaging with films (1) and () as shown in FIG. 2, and baked in an oven at 190°C for 15 minutes.

The package expands due to the gas and water vapor generated during baking, but a gap is created in a part of the heat-sealed area between the two, allowing the gas to escape, and the package as a whole remains sealed without tearing. was. Items taken out after 15 minutes and left to cool remain completely sealed at 30°C and 85%
No abnormalities were observed in either product after being stored in a humid room for more than a year, but after baking Kutsuki I without wrapping it in film, I wrapped it in film I and film, respectively.
When left in a room at 30°C and 85% humidity, mold developed after 36 days.

Example 2 Commercially available Gastera was wrapped in horizontal pillow-heat seal packaging as shown in FIG. 2 using the films (1) and () of Example 1, respectively, and heated in an oven at 180°C for 10 minutes.

Even during heating, the sealed portion remained sealed without being torn. When taken out after 10 minutes and left to cool, it remained completely sealed and was placed in a room at 30°C and 85% humidity.
Although they were stored for more than a year, no abnormalities were observed in any of them.

Commercially available Gastera was not heat-treated and was wrapped in horizontal pillow-heat-sealed film.
When I left it in a room at 0°C and 85% humidity, mold developed after 25 days. Comparative Example 1 On one side of a biaxially stretched polyethylene terephthalate film (melting point 255°C) with a thickness of 30 μm, 35% of terephthalic acid was applied.
A chloroform solution of a polyester resin with a softening point of 123°C and a glass transition point of 16°C obtained by condensation polymerization from 15 mol% of adipic acid, 20 mol% of neopentyl glycol, and 30 mol% of ethylene glycol was applied. A heat-sealable polyester film having a polyester resin layer of 2 μm was obtained.

This film was used to wrap the shoelace dough, and it was wrapped in a horizontal pillow heat-seal package as shown in Figure 2. It was placed in an oven at 190°C and baked for 15 minutes, but the heat-sealed part was widely opened, and after 15 minutes, it was taken out and left to cool. However, if the package was left open and left in a room at 30°C and 85% humidity, the temperature would rise to 32.
Mold appeared after a few days.

Similarly, this film was used to package a commercially available Gastella in a horizontal pillow heat-seal package and it was heated in an oven at 1800C for 10 minutes, but the seal opened during the heating, and although it was taken out after 10 minutes and left to cool, the package remained open. When it was left in a room at 30°C and 85% humidity, mold developed after 21 days.

[Brief explanation of the drawings] Figure 1 is a diagram showing the relationship between seal strength and temperature.
FIG. 2 shows an embodiment of the packaging aspect of the present invention. A...Temperature dependence of seal strength of polyester resin A (2μ) coating polyethylene terephthalate film (30μ), B...Polyester resin B (2μ) coating polyethylene terephthalate film (30μ) Temperature dependence of seal strength.

Claims (1)

[Claims] 1 A polyester resin having a glass transition point of 25°C to 130°C and a softening point of 120°C to 230°C is formed on at least one side of a polyethylene terephthalate film, and has a seal strength of 50 g/1 at 100°C.
A method for preserving food, which comprises packaging and sealing the food with a polyethylene terephthalate laminated film having heat-sealing properties of 5 mm or more, and then sterilizing the food by cooking at a high temperature.