JPH0638724A - Vacuum thawer for frozen material - Google Patents

Abstract

PURPOSE:To obtain a thawer capable of rapidly thawing a frozen material at a prescribed temperature or below without causing partial heating by controlling the interior of a hermetically sealed container under a pressure within a prescribed range in a thawer utilizing microwaves under a reduced pressure. CONSTITUTION:The thawer is constructed from a hermetically sealed container 1 capable of housing a frozen material 2, a magnetron 5 for irradiating the frozen material 2 with microwaves, a vacuum pump 8 for decompressing the interior of the hermetically sealed container 1 and a pressure sensing means 9 for sensing a prescribed pressure and capable of controlling the vacuum pump 8 and the magnetron 5 based on a signal from the pressure sensing means 9 and thereby controlling the frozen material 2 under a pressure within a prescribed range and thawing the frozen material 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum thawing apparatus for thawing a frozen body under reduced pressure.

[0002]

2. Description of the Related Art Conventionally, as a method for thawing a frozen body such as a frozen product, a natural thawing method that is left at room temperature and a thawing apparatus that is left in a refrigerator or using running water have been used. So-called microwave ovens using microwaves are used because they are small and can be rapidly thawed.

Further, Japanese Patent Laid-Open No. 63-79581 proposes a method of irradiating a frozen product with microwaves after depressurizing the inside of the closed container to a predetermined decompressing state and thawing at a predetermined temperature or lower.

[0004]

However, the thawing method that naturally thaws or uses a refrigerator and running water has a problem that it takes a long time to thaw and sufficient thaw quality cannot be obtained. It was

Further, in the defrosting method using microwaves such as a microwave oven, the defrosting can be performed more rapidly than the above-mentioned defrosting method, but the microwave is intermittently irradiated or the microwave output is changed. At present, it is thawed by complicated microwave control such as control, and if the thaw time and microwave control are inadequate due to the type, size, shape, etc. of the frozen body, the frozen body will partially The problem remains that it heats up.

Further, in the thawing method in which the pressure is reduced to a predetermined pressure and microwaves are used, when partial thawing of the frozen body proceeds, water vapor is generated and the pressure in the closed container starts to rise and is maintained at the predetermined pressure. It is impossible to thaw, and there remains a problem that it cannot be thawed below a temperature corresponding to a predetermined pressure.

The present invention has been made to solve the above-mentioned problems, and in a decompressor utilizing microwaves under reduced pressure, the pressure reducing means and microwaves are controlled to set a predetermined pressure inside the closed container. It is an object of the present invention to provide a vacuum thawing device capable of rapidly thawing a frozen body at a temperature equal to or lower than a predetermined temperature without controlling partial heating of the frozen body by controlling the range.

[0008]

In order to achieve this object, a vacuum thawing device of the present invention comprises a closed container in which a frozen body can be stored, and a microwave for irradiating the frozen body in the closed container with microwaves. A generator, a decompression means for decompressing the inside of the closed container, and a pressure detection means for detecting a predetermined pressure, and by controlling the decompression means and the microwave generator based on the signal of the pressure detection means, The frozen body stored in the container is thawed by controlling it within a predetermined pressure range.

[0009]

In the vacuum thawing apparatus of the present invention having the above structure, by thawing the frozen body stored in the closed container while controlling the inside of the closed container to a predetermined pressure range,
The frozen body in the closed container is rapidly thawed at a temperature equal to or lower than the predetermined temperature without being heated above the temperature corresponding to the saturated vapor pressure at the predetermined pressure.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic block diagram of the present invention.

A closed container 1 having a door 3 and a pressure reducing means (for example, vacuum pump) 8 are housed in one frame, and a microwave generator (for example, magnetron) 5 is provided in the closed container 1 through a waveguide. Are connected, and the space between the closed container 1 and the waveguide is sealed by a plate-shaped partition plate 4 having high radio wave transmission. Further, the closed container 1 is provided with a pressure detecting means 9,
The degree of vacuum inside can be measured. Further, a vacuum pump 8 is communicated with the closed container 1, and a vacuum exhaust valve 6 is provided in the communication part. With the above apparatus, the frozen container 2 of foods such as seafood and meat can be thawed by irradiating the closed container 1 with microwaves.

Next, the decompression method will be described.

After storing the frozen body 2 in the closed container 1, a vacuum exhaust valve 6 provided in a communication portion between the closed container 1 and the vacuum pump 8.
The vacuum pump 8 with the vacuum release valve 7 closed.
Is activated to reduce the pressure in the closed container 1 to a predetermined pressure, and the vacuum pump 8 is stopped based on a signal from the pressure detection means 9. The magnetron 5 is actuated at the same time as the depressurization is started to irradiate the inside of the closed container 1 with microwaves to start thawing the frozen body 2.

Here, the principle of decompression will be explained. For example,
When the pressure is reduced to 30 Torr, the water boils at about 29 ° C and maintains this boiling point as long as water is present. That is, when the pressure in the closed container 1 is reduced to 30 Torr, the object to be thawed is thawed while being maintained at a temperature of about 29 ° C. or less, which is particularly suitable for thawing raw products.

However, in practice, when the frozen body 2 is heated and partial thawing proceeds, steam is generated and the closed container 1
Since the internal pressure starts to rise, the boiling point consequently rises and the temperature of the frozen body 2 rises, so that a good thawing result cannot be obtained. Therefore, in order to realize good thawing as described above, it is necessary to control the pressure inside the closed container 1 to a predetermined value.

However, maintaining a constant pressure requires a very complicated control. Considering the boiling point, for example, as shown in FIG. 2, when the pressure rises from 25 Torr to 30 Torr, the temperature of the boiling point is about 26 ° C.
To 29 ° C., and this temperature range is a range that does not cause any problems in actual thawing. As a result, it is not necessary to maintain the pressure constant, and if the pressure is controlled within a predetermined pressure range, a sufficient thawing result can be obtained.

A method of controlling the pressure within the predetermined pressure range according to the present invention will be described with reference to the timing chart of FIG.

After reducing the pressure to P0, the vacuum pump is stopped. As the thawing progresses, the pressure inside the closed container 1 starts to rise for the reason described above. When the pressure reaches P1, the vacuum pump 8 is operated again by the signal of the pressure detecting means 9. When the pressure returns to the predetermined pressure P0, the vacuum pump 8 is stopped. Further, while the vacuum pump 8 of T2-T3 is operating, the generation of water vapor is suppressed by stopping the magnetron 5 and stopping the irradiation of microwaves.
It is possible to shorten the time for reducing the pressure of -T3. By stopping the microwave irradiation, the generation of water vapor stops,
On the other hand, the generated water vapor is condensed in the low temperature part, so that the pressure starts to drop. As a result, the depressurization time of T2-T3 is further shortened.

After that, the above operation is repeated until the defrosting is completed.

After the thawing is completed, the vacuum release valve 7 is opened, the inside of the closed container 1 is returned to atmospheric pressure, the door 3 is opened, and the frozen body 2 is taken out.

As described above, the frozen body 2 can be well thawed at a predetermined temperature or lower by controlling the temperature within a predetermined pressure range and thawing.

Of course, as a pressure control method, in FIG.
The vacuum pump 8 may be operated continuously during thawing and controlled only by the vacuum exhaust valve 6.

Further, in the above-mentioned embodiment, the method of stopping the operation of the magnetron 5 to stop the irradiation of the microwave during the time T2-T3 and T4-T5 when the vacuum pump 8 is operated has been described. The generation of water vapor is suppressed even if the microwave is switched to the weak output without stopping the operation of (1), and the same effect as that of the above-described embodiment can be obtained.

Further, in the above-described embodiment, the control of starting the operation of the vacuum pump 8 when the pressure in the closed container reaches P1 and stopping the operation of the vacuum pump 8 when the pressure returns to the predetermined pressure P0 is simply repeated ( Even if the microwave is continuously output), the effect similar to that of the above-described embodiment can be obtained.

[0026]

As is apparent from the above description, according to the vacuum thawing apparatus of the present invention, the closed container containing the frozen body is controlled within the predetermined pressure range by controlling the depressurizing means and the microwave generator. By irradiating with microwaves in a controlled state, the frozen body is thawed rapidly below a predetermined temperature, so thawed products can be thawed quickly and with stable quality without partial heating. effective.

[Brief description of drawings]

FIG. 1 is a structural schematic diagram of a vacuum defrosting apparatus.

FIG. 2 is a relationship diagram between pressure and boiling point of water.

FIG. 3 is a timing chart of the vacuum thawing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Airtight container 2 Frozen body 3 Door 4 Partition plate 5 Microwave generator 6 Vacuum exhaust valve 7 Vacuum release valve 8 Pressure reducing means 9 Pressure detecting means

Claims (1)

[Claims] 1. A closed container in which a frozen body can be stored, a microwave generator for irradiating the frozen body in the closed container with microwaves, a decompression means for reducing the pressure in the closed container, and a predetermined pressure. It is composed of a pressure detecting means for detecting, and by controlling the pressure reducing means based on the signal of the pressure detecting means, the frozen body stored in the closed container is thawed by controlling it within a predetermined pressure range. Vacuum defroster for frozen bodies.