JP2000060511A - Thermal sterilization - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for thermal sterilization by applying microwaves and superheated steam decompressed to a pressure near to the atmospheric pressure to target articles to sterilize the articles. SOLUTION: This method for thermal sterilization comprises decompressing saturated steam B1 supplied from a boiler 57 and having a pressure of about 5-10 kg/cm2 G to a pressure of about 0.1-0.7 kg/cm2 G by the use of a pressure- reducing valve 59, heating the obtained steam B1 with a heater 60 up to a temperature of about 110-300 deg.C to produce a superheated steam B2, transferring the superheated steam B2 into a microwave heating chamber 50, and subsequently quickly heating target articles A with the superheated steam and microwaves in the microwave heating chamber 50 to sterilize the articles A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat sterilization method for sterilizing an object to be sterilized, which is a granular food, by applying microwaves and superheated steam.

[0002]

2. Description of the Related Art Grain, gen buckwheat, beans,
There are spices, dried vegetables, health foods, etc., but there are many types, and their shapes and particle sizes are various, and 3 to 15%.
Many have a certain amount of water.

[0003] Since such a granular food is generally processed by obtaining processing steps such as drying, ripening and crushing, it may be extremely contaminated. For example, spices, gen buckwheat, etc. are extremely polluted with soil fungi and the number of bacteria is 10 ⁵ to 10 ⁸
It can also be (pieces / g).

For the sterilization of the above-mentioned powdery or granular food, an air flow type sterilizer utilizing superheated steam having a high sterilizing effect is widely used.

This air flow type sterilizer uses a steam air flow for transporting and heating powdery or granular materials. Specifically, superheated steam having a sterilization pressure of 1 to 3 Kg / cm ² G and a temperature of about 120 to 260 ° C. is circulated in the pipe at a high speed with a flow rate of 10 to 30 m / sec, and the powder in the pipe is granulated. Objects are transported and heated while floating.

Further, a retort sterilizer is used for heat sterilization of retort foods in which foods are packed and sealed in pouches (bags) or molded containers to which plastic films are attached.

This retort sterilizer puts the retort food in a pressure cooker and heats the food in the pauge or the container by steam or hot water introduced into the pressure cooker, and the temperature of the food is, for example, 3 at 120 ° C. Heat sterilize the food by keeping it for a minute.

[0008]

The sterilization method using the above-mentioned air flow type sterilization apparatus is said to be a sterilization method capable of rapid heating and having a high sterilization effect.

However, in order to carry out this sterilization method, a pressure system such as a means for supplying the granular material into the pressurizing system or a mechanism for separating the granular material from the vapor and collecting it outside the pressurizing system is used. However, the sterilizer has an expensive system configuration. Further, since the powdery or granular material is conveyed by the air flow, bulky foods such as retort foods cannot be sterilized.

The sterilization method using the above-mentioned retort sterilization apparatus is a method for sterilizing heat from steam or hot water introduced into the pressure cooker to the center from the surface of the food through the page and the molding container.

Therefore, for example, it takes about 40 minutes to raise the temperature to 120 ° C., so that the surface of the food is exposed to a high temperature for a long time.
There is a problem that the quality such as aroma and texture deteriorates.

Further, since the sterilization method using the retort sterilization apparatus is a pressure heating method using a pressure cooker, continuous sterilization of the powder and granules is difficult, which is a problem in the production of the powder and granular foods. There is. Furthermore, since the pressure cooker is used, maintenance, inspection and management are difficult in terms of safety.

In view of the above-mentioned circumstances, the present invention has an object of proposing a heat sterilization method for sterilizing an object to be sterilized in a short time by using superheated steam near atmospheric pressure (atmospheric pressure) and microwaves together. .

[0014]

In order to achieve the above object, the present invention relates to a heat sterilization method in which microwave energy and water vapor energy are applied to an object to be sterilized in a microwave heating chamber.

In the present invention, the pressure of the steam is reduced to near atmospheric pressure, and the temperature of the steam is set to 11
The temperature is raised to about 0 to 300 ° C. to bring the microwave heating chamber into an atmosphere of superheated steam, and microwaves and steam are applied to the sterilization object for heat sterilization.

Further, the present invention has a structure in which hot air is sent into the microwave chamber to keep the superheated steam in the microwave heating chamber warm.

[0017]

According to the present invention, saturated steam having a temperature of about 100 to 110 ° C. is depressurized to near atmospheric pressure (normal pressure), and the steam is utilized by a heat source such as an electric heater or a gas heater. The temperature is raised to 110 to 300 ° C. Due to this temperature rise, the inside of the microwave heating chamber is brought into an overheated steam atmosphere.

As a result, the substance to be sterilized in the microwave heating chamber is heated from the surface by the steam, and at the same time, the interior of the microwave heating chamber is heated by the irradiation of microwaves. As a result, the object to be sterilized can be rapidly heated uniformly from inside and outside to sterilize it. It should be noted that the present invention is not limited to human food, and can similarly sterilize animal food.

Further, according to the present invention, the temperature of the superheated steam is lowered to the saturation temperature or lower, the substance to be sterilized absorbs moisture, and the inner wall surface of the microwave heating chamber and the microwave heating chamber for putting in and out the substance to be sterilized. In order to prevent water droplets from adhering to the inner wall of the opening, a means for sending hot air into the microwave heating chamber using a hot air generator with adjustable temperature is adopted.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a mechanism diagram showing a heat sterilization apparatus for carrying out the heat sterilization method of the present invention.

In the figure, reference numeral 50 designates a microwave heating chamber having a heat insulating structure. On the left and right sides of the heating chamber 50, there are openings 51 with a filter for preventing microwave leakage,
52 is provided.

Further, the microwave heating chamber 50 is provided with a conveyor belt 53 for transferring the sterilization object A from the openings 51 to 52. The conveyor belt 53 is driven by the motor 54.

Further, the opening 5 of the microwave heating chamber 50
Exhaust ducts 55 and 56 for superheated steam are connected to 1 and 52, and the exhaust amount is adjusted by using these exhaust ducts 55 and 56 as manual dampers. If necessary, an exhaust blower may be connected for forced exhaust.

On the other hand, 5 to 10 sent from the boiler 57
Saturated water vapor B of about (Kg / cm ² G) (gauge pressure)
1 has a configuration in which the pressure is reduced to about 0.1 to 0.7 (Kg / cm ² G) by the pressure reducing valve 59 for pressure adjustment via the gate valve 58.

Further, the saturated steam B1 thus depressurized is heated at a temperature of 110 to 300 ° C. by a heat exchange type heating heater 60 composed of an electric heater or a gas heater.
The temperature is raised to a certain degree to generate superheated steam B2. The superheated steam B2 is used in the microwave heating chamber 50 and the heating heater-6.
Temperature sensor 6 provided in a part of the pipe 61 for connecting to 0
According to the detection signal of No. 2, the temperature is adjusted to a preset temperature.

The superheated steam B2 thus generated is blown into the microwave heating chamber 50 through the blowout holes 63a, 63b, 63c of the pipes, and the heating chamber 50 is filled with the microwave heating chamber 50.

On the other hand, on the bottom side of the microwave heating chamber 50, a heat-resistant circulation fan 64 connected to a return duct.
A hot air generator including a heating heater 65 and a hot air temperature sensor 66 provided in a part of the blowing duct is provided.

The circulating hot air temperature of the hot air generator is controlled according to the detection signal of the hot air temperature sensor 66 so as to reach a preset temperature. From this, the superheated steam in the microwave heating chamber 50 is supplemented with heat while being circulated by the hot air of the hot air generator, and the temperature of the superheated steam is kept warm.

The microwave is generated by the microwave oscillator 67.
The microwave is oscillated and is irradiated into the microwave heating chamber 50 through the irradiation opening at the tip of the waveguide 68. A seal plate 69 made of a material such as Teflon, ceramics, or quartz glass is provided at the microwave irradiation port to prevent the superheated vapor from entering the waveguide 68.

Next, a sterilization method using the above-mentioned heat sterilization apparatus will be described. First, before the object A to be sterilized is carried into the microwave heating chamber 50, the circulating fan 64 and the heating heater 65 are operated to operate the hot air generator, and the openings in the microwave heating chamber 50 and the left and right sides thereof are opened. The inner walls of the parts 51 and 52 are heated.

This is to prevent water droplets generated by the heat of the superheated steam being taken away when the temperature of the inner wall of the microwave heating chamber 50 or the object to be sterilized is low and the temperature of the superheated steam lowering. .

Then, the sluice valve 58 is opened and saturated water vapor B is added.
1 is sent to the pressure reducing valve 59, and the water vapor B1 is reduced to a predetermined pressure by the pressure reducing valve 59. The saturated steam B1 thus depressurized is sent to the heating heater 60, and the heating heater 60 causes the heating heater 60 to reach a predetermined temperature (110 to 30).
The superheated steam B2 heated to 0 ° C.) is sent out from the pipe 61.

The superheated steam B2 thus sent out is
As already mentioned, 0.1-0.7 (Kg / cm ² G)
At a pressure of 110 to 300 ° C., this superheated steam B2 is blown out by the blowout ports 63a, 63b, 63c ...
-More radiated into the microwave heating chamber 50.

Further, when the superheated steam discharged into the microwave heating chamber 50 touches a cold part, dew condensation occurs,
The circulation fan 64 and the heating heater 65 are constantly operated to supply heat so as to keep the set superheat temperature without lowering the temperature of the superheated steam.

In this manner, the sterilized object A is placed on the conveyor belt 53 in the microwave heating chamber 50 in the superheated steam atmosphere, and is sequentially fed from the opening 51. As a result, the substance A to be sterilized is heated from the outer surface by superheated steam, and molecular vibration is generated by the irradiation of microwaves to generate heat from the inside. Therefore, the inside and outside of the substance A to be sterilized are uniformly heat-sterilized at high speed. It

The sterilized sterilized product is successively conveyed from the opening 52, and then cooled through a cooling step as needed.

Further, in this heat sterilizer, the left and right exhaust ducts 55 and 56 constantly discharge the superheated steam B2 supplied to the microwave heating chamber 50 by the amount. From this, the pressure of the superheated steam is slightly high (0.1 to 0.7K
g / cm ² G) even if present, microwave heating chamber 50
Is opened, a pressure seal and a pressurizing structure are not required, and continuous heat sterilization using the conveyor belt 53 is possible.

Next, the experimental equipment and the experimental data for the actual sterilization using the heat sterilization method of the present invention will be described. Experimental equipment Microwave heating device Microwave maximum output: 0 to 1.5KW x 2 units (0 to 3KW) Oven dimensions: 800W x 830L x 850Hmm Rotation table: 600φ stirrer fan: Radio wave stirrer Hot air circulation generator : Heater capacity 5 kW (with automatic temperature control circuit) Heat-resistant circulation fan 4 m ³ / min Circulation amount: With manual damper Exhaust air: φ100 mm With manual damper 〇 Superheated steam supply boiler: Maximum evaporation amount 60 kg / Hr maximum pressure 5.5 Kg / cm ² G scan - Pa - heat - data -: heat - data - capacity 6KW (with automatic temperature control circuit) superheated steam pressure up to 0.7 Kg / cm ² G 〇 measuring instruments thermometer: light Fiber-thermometer Anritsu instrument AMOTH FX8000 Weighing scale: SINKO DENSI SG-10K 〇 Experimental raw material experiment example 1 Product name: Gen buckwheat (with buckwheat shell) Number of pre-treatment bacteria: 2.8 × 10 ⁶ cells / g Experimental example 2 Product name: Number of bacteria before buckwheat treatment: 4.5 × 10 ⁵ cells / g

Experimental data

[Equation 1]

Experimental Results No discoloration was observed in the appearance of buckwheat flour in the whole buckwheat flour covered with buckwheat flour, and also in buckwheat flour C, which is the most severe condition of buckwheat flour drawn into flour. There was no moisture absorption and rather a slight dryness, which was a very good result. About buckwheat flour I actually smashed soba and tried it,
The result was that the scent and tenacity were moderate.

[0041]

As described above, according to the heat sterilization method of the present invention, the substance to be sterilized is placed in the microwave heating chamber under the atmosphere of superheated steam having a pressure close to the atmospheric pressure, and the substance to be sterilized Since sterilization is performed by irradiating waves, it is possible to rapidly sterilize the object to be sterilized by heating it from inside and outside.

As a result, in addition to high-speed sterilization, heat-sensitive foods and foods whose outer shape is packaged in a pauge or molded container can be sufficiently sterilized.

Further, even if the superheated steam is used, the pressurizing structure is not formed, so that there is no need for a pressure structure or a seal countermeasure, and in this respect, the heat sterilization method is advantageous in cost, management and safety.

[Brief description of drawings]

FIG. 1 is a mechanism diagram showing a heat sterilization apparatus showing an embodiment of a heat sterilization method of the present invention.

[Explanation of symbols]

50 microwave heating chamber 53 Conveyor belt 55, 56 Exhaust duct 57 Boiler 58 Gate valve 59 Pressure reducing valve 60 heating heater 63a, 63b, 63c ... Outlet of superheated steam 64 circulation fan 65 heating heater 67 Microwave oscillator A sterilizer B1 saturated steam B2 superheated steam

Claims (2)

[Claims] 1. In a heat sterilization method in which microwave energy and water vapor energy are applied to an object to be sterilized in a microwave heating chamber, the pressure of the water vapor is reduced to near atmospheric pressure and the temperature of the water vapor is controlled. 110-300 ° C
A heat sterilization method comprising heating to a certain degree to bring the inside of a microwave heating chamber into an atmosphere of superheated steam, and applying microwaves and steam to an object to be sterilized for heat sterilization. 2. The heat sterilization method according to claim 1, wherein hot air is sent into the microwave chamber to keep the superheated steam as an atmosphere in the microwave heating chamber warm.