JPS6158569A - Sterilization of food package with microwaves - Google Patents

Abstract

PURPOSE:A food package is put in a specific support which is made of a material transmitting microwaves and has pressing parts along the edges and irradiated with microwaves to enable continuous sterilization of food packages under normal pressure without scorching, uneven heating and bursting. CONSTITUTION:A food package is put in a support which is made of a microwave-permeating material and has 2 side walls forming the containing part whose form is almost same as that of the food package at the center and has the pressing parts on its edges whose inner periphery comes more inside than the sealing part of the package and held so that the 2 side walls may not come into close contact with a space of several millimeters, then sterilization is carried out. The pouch is sealed roundly on its corners except the deaeration part 11. In case of a tray, the tray 12 is covered with a lid 13 and sealed along the edges except the deaeration part 14.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for sterilizing food packaging by microwave irradiation, and in particular, the packaging does not rupture even when sterilized continuously under normal pressure. The present invention relates to a method for microwave sterilization of food packages that does not cause damage or severe deformation.

[Conventional technology]

Currently, in order to distribute sealed food packages at room temperature for long periods of time, food is sterilized using the retort sterilization method.

However, this retort sterilization method uses a heat medium of 100'C or higher and heat sterilizes under pressure, so the sterilization time is
I wore it for a long time, 20 to 60 minutes.

Therefore, it has the disadvantage of impairing the texture, taste, aroma, color, etc. of the food to be sterilized.

Since this retort sterilization method performs sterilization under pressure, advanced technology is required to adjust the pressure to prevent the package from breaking.

This changed to the tort sterilization method, and a sterilization method using a microfluid that can be heated in a short time attracted attention, and the United States Army Research Institute announced a method of sterilization using microwave irradiation under pressure, similar to the retort sterilization device. It was done. However, since this method uses microwave irradiation under pressure, it is difficult to adjust the pressure like the retort sterilization method, and the sterilization equipment is complicated and expensive, making it not suitable for general use.

In addition, as a sterilization method using microwaves,
As shown in Japanese Patent Application No. 26949, there is a method in which a package containing an object to be sterilized is sealed in a pressure-resistant container made of a material suitable for microwave sterilization, and sterilization is performed by irradiating microwaves from outside the pressure-resistant container. I have a suggestion.

According to this method, sterilization can be achieved by sealing the package in a pressure reduction container and irradiating it with microwaves, but since microwaves are irradiated all at once, uneven heating tends to occur, and foods with low moisture content can be sterilized. In some cases, burns may occur.

Further, if the method of degassing is not disclosed and the degassing is not sufficiently facilitated, temperature unevenness may occur in the package, and the bag may break.

Furthermore, since the sealing force type filter is used, it takes time to store and take out food packages, and it is difficult to sterilize them continuously. So, the food is a liquid or a solid.
It can be held and held by the side walls of the sheet, but if the food is small such as a piece of meat, 1-1- is in a swollen state and 'f(), and it is difficult to seal the food package with the support made of two side walls in close contact with the presser part.

[Problem that the invention attempts to solve]

That is, an object of the present invention is to provide a sterilization method that allows continuous microwave sterilization under normal pressure and does not cause uneven heating, burning of the food, or bag breakage. Another object of the present invention is to provide a sterilization method that can be applied to food packages that are difficult to be brought into close contact with a support made of two side walls.

[Means for solving problems]

The present invention involves filling a bag or tray sealed on three sides with a food product with a moisture content of 20% or more, and then pressing a package with a thickness of 35 rfrrn or less, which is sealed around the periphery with degassing holes left in some parts, to the periphery. The inner periphery of the presser part is located at the periphery of the food package. The structure is such that the degassing part is placed inside the support made of a material that can transmit microwaves, with the degassing part facing upward, and the holding parts of the two side walls are placed in close contact with each other for a few minutes.
After sandwiching the package with a gap of rn, microwaves are first irradiated from the outside of the support to bring the internal temperature of the package to io.

After heating and degassing to a temperature of ~105°C, the degassing part of the package was sealed, and microwaves were irradiated from the outside of the support in the same manner as above to raise the internal temperature of the package to 125°C or higher. After heating and holding for a certain period of time to sterilize the food,
This is a microwave sterilization method for cooling food packages.

The material of the bag or tray to be filled with the cooked food is a microwave-permeable material, and the inner surface is made of a heat-sealable laminate material 1'4, and its thickness is preferably 0.65 mm or less.

In the case of a bag, the laminated material is suitably a film composed of stretched nylon/unstretched polypropylene or stretched nylon/unstretched nylon/unstretched polypropylene with a total thickness of approximately 80 to 120 microns.

In the case of a tray, in addition to the above configuration, the lid material can also be a laminated film of polyethylene terephthalate/stretched nylon/unstretched polypropylene, and the container body can be made of unstretched polypropylene, unstretched nylon/unstretched polypropylene, or unstretched polypropylene. / saponified ethylene-vinyl acetate copolymer / unstretched polypropylene, unstretched polypropylene / unstretched nylon / saponified ethylene-vinyl acetate copolymer, / unstretched polypropylene. It is appropriate that the thickness be 3 or less.

On the other hand, the support is made of a heat-resistant, pressure-resistant, and microwave-transmissible material, specifically, polycarbonate, Teflon, ceramic, wood, or a material in which glass fiber is mixed with the polycarbonate or Teflon.

Then, the structures of the bag, tray, and support will be explained according to the drawings.

As shown in Figure 1, before sterilization, the bag is a bag whose corners are sealed in an arc shape, leaving a degassing part (11) at the mouth part 00).
The width of this deaeration section (11) is suitably in the range of 3 to 7 gates.

In the case of a tray, as shown in Figures 2 and 6, the container body (+2) and the cover material (13) are combined and sealed, leaving a surrounding degassing part (14). So, deaeration R41
! 11 of f141] is suitably in the range of 6 to 7 mm as described above.

Figure 4(a) shows the state in which this package is housed in the support.
(1)) and shown in FIG. Fig. 4 (al and (1)) are the same drawings, but in Fig. 4 (a) the sealing part of the package is shaded, and in Fig. 4 (1)) the holding part of the support is shaded. are shaded. Figure 5 is similar to Figure 4 (a
This is an explanatory cross-sectional view of l at B-B (Z).

As can be seen, the support has a holding part (21) around the periphery, and two side walls (161 (+ ,7)
A window (181 (191) for hermetically sealing the deaeration section of the package at the upper part of the side wall, and a measurement port (191) for temperature inspection to detect the heating state of the package at least on one side wall. 20), and the inner periphery of the presser part (21) is located inside the inner periphery of the sealing part of the package.

The two side walls have a structure in which the holding portions (2) do not come into close contact with each other, and a gap of several 111 l is provided to sandwich the package.

Furthermore, it is a matter of course that the two side walls are held down with fasteners or the like so that they do not expand even if the package expands due to heating.

If the measurement ports for the January temperature test are provided on both side walls, water or air will flow better in the next cooling process, and the cooling effect will be even better.

In the present invention, the first heating time is 6 out of 2 heating times.
The next heating period can be done within 4 minutes.

In the final cooling step, the package is cooled from the outside of the support body containing the package to 70 to 75° C. with cold air or cold water, and then the package is taken out from the support body.

[Effect]

According to the method of the present invention, not only the initial heating but also the initial heating ensures that the package is degassed, so that the subsequent heating for sterilization can also be performed under normal pressure.

Since it can be operated under normal pressure in this way, it is easy to operate and the sterilizer can be downsized.

Continuous sterilization is possible by providing a large number of supports in the device and feeding them continuously, and sterilization conditions can be easily changed by adjusting the transfer speed and microwave output.

Because the heating time for the package is less than 10 minutes, it is now possible to sterilize beefsteaks, grilled fish, meatballs, etc., which could not be manufactured using conventional retort sterilization methods, and can be used for a wide range of foods containing 20% or more moisture. It became possible to apply to

Since the support has a structure in which the two side walls are not brought into close contact with each other and a gap of several mm is provided, there is no need to tightly hold the food package when taking it in and out, so the operation is easy.

In addition, even if the support has a structure with a gap, the inside of the presser part of the support is located inside the seal part of the food package, so the seal part of the food package may peel off or turn white. It's unlikely that I'll be able to do that.

〔Example〕

Example 1 A laminated film of stretched nylon film (15μ)/unstretched polypropylene film (70μ) was made of 130μ
120g in a bag sealed on three sides of X170B Inugisa
30g of seasoned meat dumplings are the first after filling with sauce.
As shown in the figure, the package is sealed with the opening part leaving the degassing in 5H, and is made of Teflon containing glass fiber, and is made of two sheets with a gap of 5 mm as shown in Figures 4 and 5. It is housed in a support body consisting of side walls with a measurement port for temperature testing in the center and a window for sealing at the top.

A large number of supports are mounted on a belt conveyor, and the structure is such that the supports can be continuously moved at a speed of 0.4 m/min.

A 1.2 m long container with six 600 W microwave oscillators (manufactured by Sanyo Electric) that irradiates microwaves in waveguides on both sides of the support body with this package stored therein.
was passed through the first heating section to perform deaeration work. This first
The passage time through the heating section was 3 minutes, and the temperature inside the package was measured with an infrared sensor through the measurement port on the support.
00~1020C.

Next, the package was degassed 1] and sealed, and then a length 12
．． was passed through the second heating to perform sterilization. The passage time through this second heating section was 6 minutes, and the temperature of the package was measured in the same manner as above and found to be 1280C.

Furthermore, the support containing the package was allowed to pass through the holding part for 1 minute, and then cooled for a minute with cold air at 5°C. When the temperature of the package reached 70 to 75°C, the package was removed from the support. I took it out and finished sterilizing it.

No abnormalities such as whitening or peeling were observed in the seal portion of this package.

On the other hand, when this package was stored in a constant temperature bath at 60°C and 60°C for 2 weeks, the state of the package was inspected, and the number of viable bacteria was as follows.
100 pieces/g or less or no gas generation was observed within the package.

Example 2 A container body made of unstretched polypropylene (thickness Q, 5 + nm) with a depth of 2.5 fl and a capacity of 200 d was filled with 200 I of sesame tofu, and stretched nylon film (15 μ) / unstretched polypropylene. Film (70μ)
After storing the package whose periphery was sealed with a lid material consisting of Il]6 fl leaving a degassing section in a support body having the same structure as in Example 1, it was placed in the same first heating section as in Example 1. The sample was passed through the second heating section to continuously perform deaeration and sterilization.

A large number of supports are placed on a belt conveyor, which moves continuously at a speed of 0.37n, 7 minutes, and can transport 12'0 pieces/hour.

The temperature of the package that passed through the first heating section and the second heating section for about minutes was measured using the same method as in Example 1.
The temperatures were 104°G and 125°C, respectively.

No abnormality was observed in the sealed portion of the package sterilized as described above, and the taste of the sesame tofu was better than that of the sesame tofu that had been sterilized by retort. The number of viable bacteria was also less than 100 cells/g.

〔effect〕

The sterilization method of the present invention continuously performs heat sterilization at 100'C or higher under normal pressure, compared to the conventional 17tort method.
Since it can be sterilized in a short time of 5 to 1/10, the taste and texture,
Does not impair taste or color (can be sterilized).

In addition, the initial heating fills the package with water vapor, which allows for more complete deaeration than the page empty deaeration method, provides a more uniform temperature distribution within the package, and eliminates the problem of microwave half-life depth. (There is no uneven heating and uniform heat sterilization is possible.

Furthermore, if there are pinholes in the package during the first heating, the temperature will not rise to a predetermined level, so that the presence or absence of pinholes in the package can be checked at the same time as the first heating.

Since the support body has a structure in which two side walls are not brought into close contact with each other and a gap is provided between the bottom parts, it is possible to store the food package even if its shape is slightly deformed. Ensure that the side walls are tightly clamped (or simply to prevent the support from opening due to expansion of the food package).
It is easy to move food packages in and out, and continuous operation is possible.

On the other hand, even when there is a gap, the inner circumference of the holding part of the support
Since the structure is located inside the inner periphery of the seal part of the food package, peeling of the seal part due to heating expansion of the food package will be prevented.
The inner periphery of the presser part can suppress the expansion of the package at the inner periphery of the package seal, preventing whitening of the seal and
Fig. 2 is an explanatory drawing showing another example of the package; Fig. 3 is an explanatory cross-sectional view of Fig. 2 A, -A'; Fig. 4 (, 1) (b) ) is an explanatory view of the support, and FIG. 5 is an explanatory cross-sectional view of FIG. 4 (alB-B').

Claims (1)

[Claims] It consists of two side walls that are made of a material that can transmit microwaves and have a holding part around the periphery, and form a storage part that has approximately the same shape as the outer shape of the food package to be stored in the center, and the inner periphery of the holding part is A food package made by storing a food package inside a support that is located inside the seal around the food package, sandwiching the two side walls with a gap of several millimeters between them, and then irradiating them with microwaves. How to sterilize your body with microwaves.