JPS60244274A - Microwave sterilization of food - Google Patents

Abstract

PURPOSE:To enable the sterilization of a packed food without deteriorating its taste, by filling a food in a top-opened bag, sealing the top leaving an evacuation port, putting the package in a supporting member, heating and evacuating the bag, sealing the evacuation port, sterilizing with heat, and cooling the product. CONSTITUTION:A food having a water-content of >=20% is filled in a top-opened bag 1 or tray, and the top of the bag, etc. is sealed leaving the evacuation port 11 to obtain the package having a thickness of <=35mm.. The package is put into the supporting member 2 made of a microwave-transmitting material (e.g. Teflon) and having a holding part 11 having a volume sufficient to receive the package and nearly the same shape as that of the package, in a manner to direct the evacuation port 11 upward. The food is irradiated with microwave radiation from the outside of the supporting member 2 until the inner temperature of the package reaches 100-105 deg.C, when the content of the package is evacuated and the evacuation port 11 is sealed. Thereafter, similar to the above procedure, the food is irradiated with microwave radiation from the outside of the package until the inner temperature of the package reaches >=125 deg.C. The package is maintained in the above state for a definite time to effect the sterilization of the food, and then cooled to finish the procedure.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a method of sterilizing food by microwave irradiation, and in particular, even if sterilization is performed continuously under normal pressure, the package does not burst or deform. This relates to a microwave sterilization method for food that does not cause serious damage.

[Prior art and its problems]

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 2.
It took a long time, from 0 to 60 minutes.

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

This retort sterilization method performs sterilization under pressure.
Therefore, sophisticated technology was required to adjust the pressure in order to prevent the package from breaking.

As an alternative to the retort sterilization method, a sterilization method using a microfluid that can be heated in a short time has attracted attention, and the United States Army Research Institute has announced a method that sterilizes by irradiating microwaves under pressure, similar to the retort sterilizer. 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 difficult to use for general use.

In addition, as a sterilization method using microwaves,
As shown in Japanese Patent No. 26949, a method has been proposed in which a package containing an object to be sterilized is sealed in a pressure-resistant container made of a material that can transmit microwaves, and the material is sterilized by irradiating it with a microphone off from outside the pressure-resistant container. ing.

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

Further, there is no disclosure regarding the deaeration method, and if deaeration is not performed sufficiently, temperature unevenness may occur in the package, and the bag may break.

Furthermore, since it is a closed system, it takes time to store and take out packages of objects to be sterilized, making it difficult to sterilize them continuously.

is housed in a support made of a microwave-transmissible material that has a volume that accommodates this package and has a storage part of approximately the same shape, with the degassing part facing upward, and first irradiates microwaves from the outside of the support. and the internal temperature of the package is 100-105℃
After heating and deaerating the package, the degassing part of the package is sealed, and microwaves are irradiated from the outside of the support in the same manner as above until the internal temperature of the package reaches 125°C or higher. This is a microwave sterilization method for food in which the food is heated to a certain temperature, held for a certain period of time, sterilized, and then cooled.

In this case, it is preferable to cover the material of the bag or tray filled with food.

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 addition to the above-mentioned structure, for the tray, 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,
Suitable materials include 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 wall thickness after molding is 3 mm 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 with the corners sealed in an arc shape, leaving a degassing part at the 5-mouth part 00, and the width of this degassing part is 5 to 7 mm. The range of the camp is appropriate.

In the case of a tray, as shown in Fig. 2 and Fig. 6, the lid material (131) is overlapped with the container body 1121, and the deaeration part (14) is sealed leaving the surrounding area. )
As mentioned above, it is appropriate that the width is in the range of 3 to 7 scales.

As shown in FIG. 4 and FIG.
It consists of a side wall +161 (17), and a window (181Q
9! Furthermore, at least one side wall is provided with a measurement port (2) for temperature inspection to detect the heating state of the package. Of course, the two side walls have a sandwiching structure so that the package does not open even if it expands due to heating.

Here, if measurement ports for temperature testing are provided on both side walls,
In the next cooling process, there is a good flow of water or air.
The cooling effect will be even better.

Of the two heatings in the present invention, the first heating time is 6
within minutes, and the subsequent heating time 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 non-inventive person i1/n, the first heating is of course.

Since the initial heating ensures that the packaging is degassed,
Heating for subsequent 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.

Since the package can be heated within 10 minutes, it is now possible to sterilize beefsteak, grilled fish, etc., which could not be produced using conventional retort sterilization methods, and can be applied to a wide range of foods containing moisture content of 11 or more. became.

〔Example〕

Example 1 A laminated film of stretched nylon film (15μ)/unstretched polypropylene film (70μ) was made of Lanali, 130
In a bag with the size of x170m sealed on three sides [120g
After filling the beef steak and 30 g of seasoning with sauce, the package was sealed with a 5 trr M width of degassing at the mouth as shown in Figure 1, and was made of glass fiber-containing Teflon. As shown in Fig. 5, it is housed in a support body consisting of two 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 placed on a belt conveyor.

It has a structure that allows it to move continuously at a speed of K 0.4 m 7 minutes.

With this package stored, the support passed through a first heating section with a length of 1.2 m each equipped with three 600 W microwave oscillators (manufactured by Sanyo Electric) that irradiated microwaves in waveguides on both sides. and deaeration work was performed. The passage time through this first heating section was 3 minutes, and the temperature inside the package was measured with an infrared sensor through the measurement port of the support.
The temperature was 0 to 102°C.

Next, the deaeration port of the package was sealed, and then the same microwave oscillator as the first heating section was installed on each side.
The sample was sterilized by passing through a second heating step of 100 m. The passage time through this second heating section was 3 minutes.

The temperature of the package was measured in the same manner as above and found to be 128°C.

Furthermore, after passing the support containing the package through the holding part for 1 minute, it was cooled with cold air at 5℃ for 3 minutes, and when the temperature of the package reached 70 to 75℃, the package was removed from the support. I took it out and finished sterilizing it.

The beefsteak in this package was not in a Yamato-like state as in the case of retort sterilization, and had a flavor close to well-done.

On the other hand, when this package was stored in a constant temperature bath at 60°C for 2 weeks, the state of the package was inspected and the number of viable bacteria was found to be .

100 pieces/g or less, and no gas generation was observed within the package.

Example 2 An unstretched polypropylene sheet with a thickness of 3 mm was stored in a container body with a depth of 25 cm and a capacity of 200 cm, and 200 g of sesame tofu was filled into the container body, and a stretched nylon film (15μ)/unstretched polypropylene film was formed. After storing the package whose periphery was sealed with a lid material made of (70μ) leaving a degassing part with a width of 6ro+ in a support having the same structure as in Example 1,
The sample was passed through a first heating section and a second heating section similar to the above, and was continuously degassed and sterilized.

A large number of supports are placed on a belt conveyor and are continuously [
It moves at a speed of 0.37 Ft/min and can transfer 120 pieces/hour.

The temperature of the package that passed through the first heating section and the second heating section for 6 minutes was measured in the same manner as in Example 1, and was 104°G and 125°C, respectively.

The taste of the sesame tofu in the package that had been 5π sterilized as described above 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 pressurized heat sterilization at 100°C or higher under normal pressure.
It can be sterilized in 1/10 of a short time, so the texture, taste,
Don't spoil the color (be sure to sterilize it).

Also, due to the initial heating, water vapor is created inside the package. Uniform heat sterilization is possible.

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

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of the package at the time of initial heating;
FIG. 2 is an explanatory diagram showing another example of the package, FIG. 3 is an explanatory cross-sectional diagram taken along the line A-A' in FIG. 2, and FIG. 4 is an explanatory diagram. The explanatory diagram of the support body, FIG. 5, is a cross-sectional explanatory diagram of FIG. 4 BB'. Patent applicant Figure 3〕2 Figure 5

Claims (1)

[Claims] After filling the food into bags or trays that are sealed on three sides,
A package sealed with a degassing part left in a part is placed inside a support made of a microwave-transparent material that has a volume that accommodates the package and has a storage part of approximately the same shape, with the degassing part on top. First, microwaves are irradiated from the outside of the support to bring the internal temperature of the package to 100 to 105℃.
After heating and degassing for 5 ic, and sealing the degassing part of the package, microwave is irradiated from the outside of the support again and heated so that the internal temperature of the package becomes 125 ° C. or higher. 1. A microwave sterilization method for food, which involves sterilizing food and then cooling it.