JPS6254691B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for processing heat-sterilized sealed packages. Containers such as cups and trays made of thermoplastic synthetic resin are filled with contents such as food and medical instruments, then sealed and packaged with a lid, and the package is then heat sterilized. However, during the heat sterilization described above, the container body and lid may be deformed due to expansion of the contents due to heating or expansion of air within the package. Conventionally, deformation of the container body has been prevented by appropriately selecting its shape, material, wall thickness, etc., and deformation of the lid material has been prevented by using a heat-shrinkable film for the lid material, or by using a packaging material. This was prevented by heating and sterilizing the product while it was inverted. However, when packaging contents with high porosity or air content, or when packaging contents with a large void left in the package without filling the container body completely, it is necessary to use a lid. Even if a heat-shrinkable film is used for the material, the expansion force of the contents and gas inside the package is greater than the shrinkage force of the heat-shrinkable film, so the lid material expands and deforms significantly, causing cooling of the package. Even after the gas inside the package has contracted, the lid material does not shrink in the same manner as the shape, so unevenness due to sagging appears on the surface of the lid material, which deteriorates the appearance. It becomes difficult to stack. As a result of intensive research to solve the above problems, the present inventors have come up with an invention that uses a simple method to remove the slack in the lid of a package caused by heat sterilization. . In other words, the present invention involves filling a container body made of a thermoplastic synthetic resin with contents, sealing the package with a lid made of a heat-shrinkable film, and heat-sterilizing the package at a temperature of 60 to 100°C. A heat sterilized sealed package characterized in that the package is cooled, and then only the lower lid part of the package is brought into contact with hot water of 100°C or less for 2 seconds to 3 minutes with the lid of the package facing downward. This is a processing method. The heat-shrinkable film of the lid material in this invention is
A stretched film made of thermoplastic resin such as polyamide, polypropylene, polyester, polystyrene, polyvinylidene chloride, etc., stretched uniaxially or biaxially, or a heat-shrinkable multilayer film made by laminating the above stretched film on another film as a surface layer. be. Examples of the film for the back layer of the multilayer film include polypropylene, polyethylene, polyamide, partially saponified ethylene/vinyl acetate copolymer, ethylene ethyl acrylate, polyvinyl alcohol, polyolefin such as ionomer, polystyrene, polyethylene terephthalate, and polyalkylene terephthalate. It is a stretched or unstretched film formed from a block copolymer of polyalkylene glycol and polyalkylene glycol, polyamide such as nylon 6 and nylon 66, polyvinylidene chloride, and the like. This film may be provided with a printed layer, a metal vapor deposited layer, etc., if necessary. The above heat-shrinkable film preferably has a wet heat shrinkage rate of at least 2% when immersed in hot water at 85°C for 30 minutes. Further, the thickness of the heat-shrinkable film is preferably 10 to 500μ, preferably 30 to 150μ. As the lid material, a heat-shrinkable multilayer film using a heat-shrinkable nylon film as the surface layer is particularly suitable. The lid material is sealed to the container body by heat fusion or adhesive bonding. The contents of the package are heat sterilized by immersing the package in hot water at a temperature of 60 to 100°C for 10 to 120 minutes. If the temperature of heat sterilization exceeds 100°C, it is not preferable because it not only deforms the container body but also deteriorates the quality of the contents depending on the type of contents. Due to the heat sterilization described above, the lid material of the package swells due to the expansion of the contents or gas inside the package, which causes slack in the lid material when it is cooled, and this slack is removed. Therefore, the lid material is heat-treated again. To heat-treat the lid of the package again, with the lid of the package facing downward, heat only the lid part of the package in hot water at 100°C or below, preferably 60 to 100°C, for 2 seconds or more. Contact is allowed for 3 minutes, preferably 2 seconds to 1 minute. As a means of bringing only the lid material portion of the package into contact with hot water, for example, the packaging bodies are arranged in a wire mesh basket with the lid material facing downward, and the basket is immersed to a depth of 1 to 5 mm below the surface of the hot water; Also, 1 from the hot water surface of the hot water tank.
It is appropriate to provide a wire mesh at a depth of ~5 mm and arrange the packages on this wire mesh with the lid facing down. Alternatively, the wire mesh may be moved using an endless belt system, and the packages may be sequentially placed on the wire mesh for continuous processing. The depth at which the lid portion of the package is immersed in hot water is preferably as shallow as possible, and a deeper immersion portion is not preferred because the contents will be heated. If the temperature of the hot water for shrinking the lid material exceeds 100°C or if the contact time exceeds 3 minutes, the contents may be heated and expand, or the container body may be deformed, which is not preferable. On the other hand, the hot water temperature
If the temperature is less than 60℃ or the contact time is less than 2 seconds,
The shrinkage of the lid material is insufficient and the slack is not removed. Note that the hot water temperature for shrinking the lid material is preferably slightly higher than the temperature during heat sterilization. Furthermore,
When heat sterilization is performed using hot water, the above-mentioned heat sterilization tank may be used to remove slack from the lid material. The present invention will be specifically explained below with reference to Examples. Example A cup with a capacity of 80 c.c. formed by deep drawing a polypropylene sheet was filled with jelly with the filling amount changed as shown in the table below. Biaxially stretched nylon film (moist heat shrinkage rate 12%, thickness 15μ)
A heat-shrinkable two-layer film (wet heat shrinkage rate: 6%) laminated with the above was sealed as a lid, and the package was sterilized in a hot water sterilization tank at 85°C for 30 minutes, then transferred to a cooling tank and cooled in water. did. Next, a wire mesh was provided at a position 3 mm below the water surface of the hot water sterilization tank, and the packages were arranged on the wire mesh with the lid material facing downward, and heated at 85°C.
The cap material was immersed in hot water for the time shown in the table below, then taken out from the hot water layer, cooled, and observed for sagging, and the results are shown in the table below.

[Table] The sagging state of the lid material is shown as 1 for no sagging, and 2, 3, 4, and 5 as the degree of sagging increases. As can be seen in the table above, the lower the filling rate, the greater the sagging of the lid after sterilization, and the sagging of the lid will not be removed if the hot water treatment time to remove the sag of the lid is 1 second; If the time is longer than 5 minutes, sagging will occur due to expansion of the contents and gas. If the hot water treatment time is 1 minute, the slack will be completely removed even if the filling rate is small.

Claims (1)

[Scope of Claims] 1. A container body made of thermoplastic synthetic resin is filled with contents and then sealed with a lid made of a heat-shrinkable film. The package is then heat sterilized at a temperature of 60 to 100°C. After that, it is cooled, and then the lower lid part of the sealed package is brought into contact with hot water at 60 to 100°C for 2 seconds to 3 minutes with the lid material facing downward. How to dispose of sealed packages. 2. The method for processing a heat-sterilized sealed package according to claim 1, wherein the heat-shrinkable film of the lid material is a stretched nylon film.