JPH03175963A - Method for thermal sterilization of food - Google Patents

Abstract

PURPOSE:To thermally sterilize a complex food with microwaves without using a retainer and destroying the food by packaging the complex food with a heat-shrinkable film, primarily heating the packaged food and then heating the resultant food with microwaves. CONSTITUTION:A complex food such as croquette, 'GYOZA' (fried dumpling stuffed with minced pork) or 'DAIFUKU' (rice cake stuffed with bean jam) having the skin and contents is contained in a tray-like container and packaged with a heat shrinkable film having a gas discharging means formed by providing slits, etc., or sealing the film partially leaving an unsealed part, etc. The packaged food is then primarily dried with hot air or an oven, irradiated with infrared rays, etc., to shrink the heat shrinkable film. Sterilization of the package is further carried out by heating with microwaves.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for heat sterilization of foods, and particularly to a method for heat sterilization of composite foods having a skin and a content.

<Conventional technology> Heat sterilization using microwaves has been widely used as a conventional means of sterilizing food, and is a method in which food is continuously supplied to a sterilization section such as a pipe prepared in an apparatus, and the food is packaged after sterilization. (Japanese Unexamined Utility Model Publication No. 58-117892) and a method of sterilizing food by throwing it into an apparatus (Japanese Unexamined Patent Publication No. 60-78568) are known as boat fishing. When food is pre-packaged, there is a risk that the container may be destroyed by the water vapor generated from the food if it is sealed, so to prevent this, degassing holes are provided in the container (Japanese Patent Laid-Open No. 62-282556).
JP-A No. 60-78568), or a technique using a glue retainer to prevent damage (Japanese Patent Application Laid-Open No. 60-78568).

<Problems to be Solved by the Invention> By the way, among various foods that have been sterilized, it has been found that when heat sterilizing composite foods that have a skin and a content such as shark roe, croquettes, and daifuku, the food may burst inside the device. It could be destroyed.

Examining the cause of this, microwaves have excellent permeability and can penetrate into the inside of the food, causing the contents of the composite food to heat up and generate water vapor. However, this water vapor is suppressed from being released by the epidermis, and this accumulates and eventually becomes It turned out that it would explode.

The above-mentioned destruction can be prevented by using the retainer. However, it is extremely difficult to create a retainer that matches the shape of each food, and the food expands to some extent when heated. However, when a retainer is used, the retainer completely suppresses expansion, so in the case of composite foods, the skin part is crushed and becomes hard, which is a drawback.

Therefore, the present invention provides microwave sterilization of composite foods.
To provide a heat sterilization method that does not use a retainer and does not destroy food.

Means for Solving the Problems> That is, the present invention stores a composite food having a skin and contents in a tray-like container, wraps it with a heat-shrinkable film to form an exhaust means, and then heat-shrinks it by primary heating. This is a method for heat sterilization of foods, which is characterized by shrinking a film and then performing microwave heat sterilization.

<Function> In the present invention, the food is compressed by wrapping and shrinking the food with a heat-shrinkable film. When this package is heated with microwaves, water vapor is generated inside the food, but the food is wrapped and pressed with a heat shrink film.
Rupture of the epidermis is prevented.

Furthermore, although water vapor is generated on the surface of the food, drying is prevented because the food is wrapped in a heat-shrinkable film. Moreover, excess water vapor is discharged by the formed exhaust means, so that the heat-shrinkable film packaging will not burst.

<Example> Next, the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing a food package (A) according to the present invention.

The food to which the present invention is applied includes an epidermis (11) and a content (
12), and specifically includes several side dishes such as croquettes, minced meat cutlets, and fried shrimp, skin-on side dishes such as shark roe, shumai, and Chinese steamed buns, and Japanese sweets such as daifuku and monaka. An example is the department. This composite food (1) is stored in a tray-shaped container (2) and wrapped with a heat shrink film (3).

The heat-shrinkable film (3) is a uniaxially or biaxially stretched plastic film made of resin such as polyethylene, polypropylene, polystyrene, polyethylene terephthalate, polyvinyl chloride, polyvinylidene chloride, etc., and shrinks when heated to a predetermined temperature. be. The heat-shrinkable film (3) is made into a bag or tube shape in advance.If the heat-shrinkable film (3) is made into a bag-like shape, the heat-shrinkable film (3) is used to absorb exhaust air during heat shrinkage and water vapor generated from food during microwave heating. In order to prevent the bag from bursting due to the heat shrink film (3), the exhaust means (4) should be formed by providing holes, slints, etc. in the heat shrink film (3), or sealing it with some parts left unsealed. In the case of a shape, the open end serves as an exhaust means and can be exhausted.

The food package (A) described above is first heated.

This heating is for shrinking the heat shrink film (3) and pressing the food, and at the same time preheating the food.

This preheating makes the microwave heating in the next step more uniform and enables stable sterilization.

The means for primary heating is generally by hot air, but it is also possible to use methods such as an oven or irradiation of infrared rays containing a large amount of far infrared rays.

The heat-shrinked food package (A) is then sterilized by microwave heating. The supply to the microwave heating may be performed immediately after the first heating, or may be held for an appropriate period of time so that the heating by the first heating is uniform. Microwave heating is performed under conditions that completely sterilize the food. The specific conditions are determined depending on the type and amount of food, but -M is set so that the food undergoes a thermal history of about 3 to 5 minutes at 100°C. Although water vapor is generated from the surface of the food due to microwave heating, the food is wrapped in a heat shrink film so it does not dry out, and since an appropriate exhaust means (4) is formed,
The packaging of the heat shrink film (3) will not be damaged. Water vapor is also generated inside the food, but since the food is wrapped and pressed with a heat shrink film (3), explosive release of water vapor is suppressed and damage to the food is prevented.

In addition, the heat-shrinkable film (3) is flexible and stretches to some extent even when the food expands due to heating, so it does not crush the skin (11).

The food package (A) that has been heated and sterilized is either hermetically packaged with other packaging material to prevent subsequent contamination, or
The exhaust means (4) is sealed by suitable means (for example, sealing with a sealing member, sealing with heat sealing of the opening). Then, it is usually manufactured into a product through a cooling process.

Test example> Two pieces of Korofuke as a composite food were stored in a tray-shaped container made of polypropylene, and a container made of polypropylene with a thickness of 20 mm was placed.
It was packaged with μm heat shrink film.

This food package was placed in a hot air tunnel at a temperature of 200″C for two
First heating was performed for 5 seconds. The food temperature at this time was 40-50''C (outlet temperature).

Next, it was supplied to a microwave heating chamber and heated by irradiating microwaves at 4Kw for 1 minute (Example 1).
For comparison, heating was performed under the same conditions as above except that the product was not wrapped in a heat shrink film (Comparative Example 1). Table 1 shows the results of observing the appearance, taste, and temperature of the food after heating.

Two Chinese litté heads were placed as a composite food in a tray-shaped container made of polypropylene, and the container was wrapped with a heat-shrinkable polypropylene film having a thickness of 20 μm.

This food package was subjected to primary heating for 10 minutes in a far-infrared hot air tunnel at a temperature of 140°C. The food temperature at this time was 60 to 70°C (outlet temperature).Then, the food was supplied to a microwave heating chamber and heated at 2Kw.

Heating was performed by irradiating microwaves for 3 minutes (Example 2)
In addition, for comparison, heating was performed under the same conditions as above except that the product was not wrapped in a heat shrink film (Comparative Example 2). Table 2 shows the results of observing the appearance, taste, and temperature of the food after heating.

Table <Effects of the Invention> As described above, according to the present invention, heat sterilization of complex foods using microwaves, which was previously impossible, is now possible using a retainer.
It is now possible to do this without using food and without destroying the food.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a food package (A) according to the present invention. (1) ... Composite food (2) ... Tray-shaped container (3) ... Heat-shrinkable film (4) ... Exhaust means (11) ... Skin (12) ... Contents (A )...Food packaging patent application Hitotoppan Printing Co., Ltd. Representative Kazuo Suzuki

Claims (1)

[Claims] A composite food with a skin and contents is stored in a tray-shaped container.
After wrapping with heat shrink film to form exhaust means,
A method for heat sterilization of foods, which comprises shrinking a heat-shrinkable film through primary heating, and then performing microwave heat sterilization.