JP2000262260A - Microwave device for heat-sterilizing food, and heat- sterilization of food - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microwave device equipped with a magnetron for sterilizing food with heating, and also to provide a method for sterilizing a food with. SOLUTION: This device is equipped with a microwave irradiation chamber 11; upper wave guide tubes 12a, 12a' with the open ends arranged above a food 19 and focus set at almost the food bottom; lower wave guide tubes 12b, 12b' with the open ends arranged below the food 19 and focus set at almost the food top; magnetrons 13 provided at the wave guide tube ends; transfer device 16 which transfers microwave-transmittable containers 14 orderly into the microwave irradiation chamber 11; and control device 18 which controls a driving unit for the transfer device 16 and irradiation timing for the magnetrons 13, wherein the transfer device 16 is provided with a means which allows it to intermittently transfer the containers 14 in such a way to position each of them at a given position relative to the wave guide tubes while the food is irradiated with microwaves, and irradiation of microwaves is timed so that the waves are directed simultaneously onto both upper and lower sides of the food.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave food heat sterilizer using a magnetron and a food heat sterilizer.

[0002]

2. Description of the Related Art There have been proposed many methods and apparatuses for irradiating foods with microwaves for heat sterilization.

[0003] As a conventional heat sterilizing apparatus for foods using microwaves, for example, as shown in a schematic configuration diagram of Fig. 7, a microwave irradiation chamber 1 (Fig. 7) integrally formed or connected in a tunnel shape. As described above, or a large room surrounded by a metal shielding plate, and a plurality of waveguides 2 for guiding microwave energy into the microwave irradiation chamber 1. A plurality of endless magnetrons 3 disposed at one end of the waveguide 2, and a plurality of microwave-permeable plastic containers 4 (including those filled in bags) which contain and seal the food to be sterilized. A transfer device 6 arranged at predetermined intervals on a transfer line of a transfer belt 5 and sequentially transferring the microwave so as to continuously pass through the inside of the microwave irradiation chamber 1; and a drive control of a drive motor 7 of the transfer device 6; Magnetro And a control device 8 for controlling the irradiation timing of 3. The typical example is a microwave food heating and sterilizing apparatus 10 including several tens of seconds to several minutes until the food finally reaches a heating temperature of about 100 ° C. to 130 ° C. For example, a method of irradiating food with microwaves may be used.

[0004] In the apparatus and method for heating and sterilizing food by microwaves, mainly water molecules contained in the food itself to be sterilized by heat and bacteria existing in the food directly absorb microwave energy to generate molecular motion and generate internal movement. Since it generates heat (dielectric heating), it is heat-sterilized in a short time together with the sterilization effect of the high-frequency electric field itself, and heat medium such as boiling water is compared with an external food heat sterilization method using hot water or high-temperature steam. Since it is not required, it has advantages such as easy handling of the sterilization treatment.

[0005]

However, heat sterilization using microwaves as described above has a disadvantage that it is generally difficult to uniformly heat the entire food due to the concentration of the electric field of the microwaves. Therefore, conventionally, as a countermeasure against this uneven heating, (a) a reflection method in which a high temperature portion of the target food is shielded by a metal plate or the like and microwaves are reflected, or (b) water with a low water content ,
An absorption (attenuation) method that partially changes the absorption efficiency of food by adding a microwave energy absorber such as alcohol,
Furthermore, a method of (c) irradiating microwaves of different wavelengths (permeation depth changes) has been proposed.

However, the measures against uneven heating by the above methods (a) and (b), on the other hand, cause a decrease in the absorption efficiency of microwave energy, and the initial purpose of heat sterilization in a short time is not achieved. was there.

The microwave frequency used for microwave ovens is set at 2450 MHz according to the current Radio Law, and it is practically difficult to use other frequencies. Originally, the allocated frequency 2450 of the microwave oven
Since the microwave of MHz is compatible with the natural frequency of water molecules, and the penetration depth into the food is about 5 to 7 cm from the surface, it is just a good frequency for dielectric heating of foods about the size of heating in a microwave oven. is there. If the oscillation frequency of the microwave is higher than this, the penetration depth becomes too shallow, and if the oscillation frequency is low, it penetrates deeply but passes through almost without being exchanged with heat. Cannot be adopted. Thus, there is a need for an apparatus and method that can enhance the absorption efficiency, enable heat sterilization in a short time, and achieve uniform heating of food.

On the other hand, as for a magnetron which oscillates microwaves, a magnetron of 2450 MHz (power of about 400 W to 800 W) used in a microwave oven is easily available at a low cost, and it is obvious that the magnetron is also used in a microwave food heating and sterilizing apparatus. It is desirable in terms of cost to use a magnetron for a range.

[0009] In addition, industrially, it is essential that a large amount of food can be sterilized efficiently in a short time. At the end of the day, it is required to have a sufficient competitiveness with respect to other sterilization methods in terms of cost and processing capacity (processing capacity of about several hundred pieces / hour).

However, looking down on the current microwave food heating and sterilizing apparatus, an apparatus and method satisfying the above requirements have not yet been realized. For example, a food delicate to a temperature such as tofu (a suitable temperature range as a heat sterilization temperature is a narrow range of 65 to 80 ° C., and 90 ° C.
If it is heated to near, it will solidify excessively and will not be a product. ), A relatively large volume of food requires particularly uniform heat sterilization. However, at this stage, microwave heat sterilization enables uniform heating and efficient mass heat sterilization in a short time. The device and the heat sterilization method have not yet been realized.

The present invention has been made in view of the problems of the above-described conventional apparatus and method for heating and sterilizing food by microwaves, and provides an apparatus and method which sufficiently satisfy the above-mentioned requirements.

[0012]

SUMMARY OF THE INVENTION The present invention provides the following apparatuses (1) to (5) for solving the problems of the conventional microwave food heating and sterilizing apparatus and method.

(1) A microwave irradiation chamber integrally formed or connected in a tunnel shape, a plurality of waveguides for guiding microwave energy into the microwave irradiation chamber, and one end of the waveguide A magnetron, and a transport device for transporting a plurality of microwave-permeable containers containing foods arranged in a row on a transport line so as to sequentially pass through the microwave irradiation chamber, and a drive control of the transport device and the transport device. And a control device for controlling irradiation timing of the magnetron, wherein the conveying device is configured such that the container holding the food is fixed at a predetermined position with respect to the waveguide during the microwave irradiation. Means for intermittently conveying the food, wherein the control device sequentially performs a plurality of microwave irradiation steps in which each container containing the food is subjected to microwave irradiation for a predetermined time. In each microwave irradiation step, the opening end is disposed above the food so that the maximum point (focal point) of the microwave electric field strength is located substantially on the bottom surface of the food. And a lower waveguide whose opening end is disposed below the food so that the maximum point (focal point) of the microwave electric field strength is located substantially on the upper surface of the food. Wherein the control device performs timing control such that microwaves are simultaneously irradiated from above and below the food in each microwave irradiation step.

(2) In the microwave food heating and sterilizing apparatus according to the above (1), a microwave irradiation step (main irradiation step) for mainly heating the central part of the food and a corner part of the food are mainly heated. A microwave food heating and sterilizing apparatus comprising a magnetron and a waveguide for performing a microwave irradiation step (sub-irradiation step).

(3) In the microwave food heating and sterilizing apparatus according to the above (2), the waveguide in the main irradiation step is a straight pipe, and the waveguide in the sub irradiation step is an R-tube that is bent at approximately 90 degrees. A microwave food heat sterilizer, characterized in that:

(4) In the microwave food heating and sterilizing apparatus according to (1), (2) or (3),
After the main irradiation step and the sub irradiation step, the temperature of the food is detected by the non-contact temperature sensor and heated to within the proper sterilization temperature range, and the food that exceeds the proper sterilization temperature range,
While sorting out foods that are below the proper sterilization temperature range,
A microwave food heating and sterilizing apparatus, comprising a magnetron for performing an additional microwave irradiation step on food having a temperature lower than the proper sterilization temperature range and a waveguide thereof.

(5) At least five main irradiation steps for mainly heating the center of the food and four sub-irradiation steps for mainly heating the corners of the food are sequentially performed, and the final heating temperature is set at 65 ° C. A method for heat-sterilizing food by the microwave food-heat sterilizer according to any one of the above (1) to (4), wherein the method is controlled at a temperature of from -80 ° C.

The heat-killing condition of general bacteria is, for example, 5 minutes at 60 ° C. for Shigella, and usually 6 hours.
It can be roughly sterilized at 5 ° C to 80 ° C for 1 to 2 minutes. Originally, it is considered that heat sterilization by microwaves is substantially more relaxed than the above conditions due to the sterilization effect of the high-frequency electric field.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a microwave food heat sterilization apparatus and a heat sterilization method according to the present invention will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram for explaining the overall configuration of a microwave food heating and sterilizing apparatus according to the present invention.
FIG. 2 is a view for explaining the positional relationship between the waveguide of the microwave food heat sterilizing apparatus according to the present invention and the container containing the food. FIG. 3 is a diagram for explaining a heating experiment and a measurement result for tofu of the microwave food heat sterilizing apparatus according to the present invention. 4 and 5 are diagrams showing measurement results under other conditions of the heating experiment. FIG. 6 is a diagram showing a heat sterilization method employed by the microwave food heat sterilization apparatus of the present invention and a measurement result of the heating temperature.

Referring to FIG. 1, the structure of the microwave food heating and sterilizing apparatus 20 is briefly described. The microwave irradiation chamber 11 is integrally formed or connected in a tunnel shape, and microwave energy is supplied into the microwave irradiation chamber 11. .., 12b... And R curved to approximately 90 degrees.
, 12b '..., A magnetron 13 disposed at one end of each of the waveguides, and a plurality of microwave-permeable containers 14 containing foods are arranged on a transport line. And a transfer device 16 (drive motors 15a and 1a) which are sequentially transferred so as to pass through the microwave irradiation chamber 11.
5b) and a control device 18 for controlling the drive of the transport device 16 and controlling the irradiation timing of the magnetron 13. The conventional microwave food heating and sterilizing device 10 shown in FIG. Is almost the same as
In particular, the transport device 16 is not a device that continuously and continuously transports the container 14 containing the food like the endless transport belt 5 that has been widely used in the related art. During irradiation, the waveguides 12a,.
.., 12a ′,..., 12b ′.
This enables a so-called shuttle or tact transfer.

Further, the control device 18 performs one microwave irradiation step K (1) in which each container 14 containing food is subjected to microwave irradiation for a predetermined time (usually set to about 8 to 20 seconds) by a microcomputer. ) Is controlled in a plurality of steps, that is, K1, K2, K3,... Arranged in a line, and the microwave irradiation step K1, K2, K3
As shown in the schematic diagram of FIG. 2 (a) using a straight pipe or (b) using an R-tube waveguide, a container having an open end containing a food 19 is shown in FIG. The upper waveguide 12 disposed above the upper waveguide 12 such that the maximum point (focus) Fa of the electric field strength of the microwave oscillated by the magnetron 13 is located on the substantially bottom portion 19 b of the food 19 in the container 14.
a or 12a 'and a lower waveguide whose opening end is disposed below the food 19 so that the maximum point (focal point) Fb of the microwave electric field strength is located substantially on the upper surface 19a of the food 19. 12b or 12b ', and the control device 18 in FIG. 1 continuously detects the presence of the food 19 by a sensor (not shown) provided at the entrance of the microwave irradiation chamber 11 and continuously performs the microwave irradiation step K1. , K2
In the configuration, the magnetron 13 is controlled so that microwaves are continuously and simultaneously irradiated from above and below the food.

In the present apparatus, the magnetron 13
From the viewpoint of cost, it is preferable to directly use a magnetron (output of 400 W to 800 W, particularly output of 500 W is widely used) used in a general microwave oven. The waveguides 12a and 12b are metal tubes having a square or circular cross section, and as shown in FIGS. 2A and 2B, the bottom portion 19b or the top portion 19a of the food 19 from each magnetron 13. The wavelength λ of the microwave having a waveguide distance X to 2450 MHz (= 123
mm), 5/4, 7/4, 9/4, 11/4 times
Are set so that the maximum points (focal points) Fa and Fb of the electric field strength of the microwave satisfy the overlapping arrangement condition as shown in the figure.

In the above configuration, if the predetermined position is set so that the center of the container 14 is located directly below or directly above the open ends of the straight waveguides 12a and 12b during microwave irradiation, it is efficient. A large area near the center of the food can be heated. In this regard, in the continuous conveyance method using an endless belt conventionally used for conveying food, microwave irradiation is constantly moving relative to the food and is not constant, and as a result, energy absorption efficiency is reduced. is there.

Next, the transport device 16 and its control will be described in more detail.
The position to be irradiated (for example, the center) of the container 14 is accurately moved to a position just below or directly above the open ends of the waveguides 12a and 12b to be in a stationary state, and the control device 18 turns on the magnetron 13 And then simultaneously irradiate the microwaves from above and below for 10 seconds, and drive control by the control device 18 so that all the containers 14 placed on the transport line are moved by a predetermined distance (for one tact) to the next tact in 2 seconds. (Shuttle system or tact system).

In consideration of cost, the transport device 16 for realizing the shuttle type or tact type transport is a conventional endless transport belt 5 or an endless chain connected to a tray on which food is loaded. 7 can be realized by intermittently driving the vehicle. However, in the microwave food heating and sterilizing apparatus 20, the waveguides 12a, 12b
Since it is desirable to accurately position the container 14 with respect to the opening end of the opening, the position control by turning on / off the drive motor 7 becomes weak in the conventional method of intermittently operating the transfer device 6 or the like. .

If high-precision positioning is required, as a shuttle-type transporting means with improved transporting positional accuracy, a motor is mounted on a fixed mounting table supported on the left and right sides of the bottom surface of the container 14 containing the food. -A shuttle hand (moving table) that periodically moves up and down by about 10 mm by cam drive and reciprocates a predetermined distance in the horizontal direction by a rack and pinion mechanism is disposed between the mounting tables described above, and is moved up and forward ( By adopting a transport mechanism as shown in FIG. 1 which reciprocates up and down with one turn of down, slide in the reverse direction as one turn, highly accurate shuttle-type transport can be realized. That is, the drive motor 15a drives the motor / cam drive for vertically moving the shuttle hand, and the drive motor 15b drives the rack and pinion mechanism for horizontally sliding the shuttle hand. In other words, every time the microwave irradiation step (one tact) is completed, the operation of repeatedly lifting all the containers 14 in each step with the shuttle hand, moving the container 14 to the next step, placing it on the mounting table, and returning to the original position is performed. By repeating periodically, the shuttle mechanism becomes accurate. Note that the shuttle system itself as a means for transporting articles is a known technique employed in an automobile manufacturing line or the like, and it is needless to say that various means for realizing the technique can be considered other than the mechanism described above.

Next, the means and method for uniformly heating the food 19 will be described in detail below, based on a heating experiment on tofu, which is a typical example of the food 19 to which the microwave food heating / sterilizing apparatus 20 has a range.

As shown in FIG. 3A, a substantially rectangular parallelepiped container 14 containing one tofu is placed in a microwave irradiation chamber.
The distance (focal length) F at which the electric field intensity becomes maximum is set so that the waveguide distance X from the magnetron 13 (output 500 W) to the center of the tofu is 2.75λ (= 338 mm). The waveguides 12a 'and 12b' of the R tube are disposed so as to be centered, and an oscillation frequency of 2450 M
When a heating experiment of tofu by microwave irradiation at Hz was performed, the measurement result of FIG. 3B was obtained. The frames in the table below show the tofu 23 viewed from the plane, each of the nine divided columns shows the position of the center and four corners of the plane, and the three temperature data (° C.) ) Indicates the temperature of the tofu (lower, middle, upper) at each of the above locations.

As a result of the above experiment, a short microwave irradiation of 60 seconds was enough for the center to reach 65 ° C. or higher. However, as can be seen from FIG. The result is considerably low in some parts, and uniform heating is not realized.

Next, as shown in FIG. 2B, the open end is disposed above the food 19 (hereinafter referred to as tofu 23), and the maximum point (focal point) Fa of the microwave electric field intensity is changed to the tofu. 23
And the upper end (waveform) 12b 'of the upper R tube which is positioned substantially at the center of the bottom surface, and the open end is disposed below the tofu, and the maximum point (focus) Fb of the microwave electric field intensity is substantially equal to the tofu. When the lower R-waveguide 12b 'was disposed so as to be located at the center of the upper surface and the focal points were overlapped, the measurement result of FIG. 4 was obtained.

As can be seen from FIG. 4, in the irradiation for 60 seconds, the center is about 60 ° C., but the corner is also heated to a temperature close to or higher than the center. In addition, although irradiation for 90 seconds was necessary to bring the temperature of the central portion to about 70 ° C., it can be said that substantially uniform heating was realized as a whole. This is, on the one hand, the waveguides 12a ', 12
The heating means in which b 'is disposed so that the focal points Fa and Fb are vertically overlapped and simultaneously irradiates microwaves has a lower heating efficiency than the case of straight waveguides 12a and 12b to be described later. Suggest that it can be used to provide gentle and uniform heating.

Next, the same experiment was performed with the straight waveguides 12a and 12b as shown in FIG. 2A, and the measurement results shown in FIG. 5 were obtained.

As can be seen from FIG. 5, the lower portion of the central portion was heated to 70 ° C. by microwave irradiation for 60 seconds, but the temperature was low overall, and the temperature difference between the central portion and the corner portion was smaller than that of the R tube. Big. That is, even in the method of simultaneously irradiating with overlapping, in the case of the straight waveguides 12a and 12b, only the central portion is efficiently heated, but the heating of the corner portion is slow.

From the above experimental results, the inventor of the present application has proposed, as a microwave heat sterilization method for simultaneously improving the heating efficiency of heat sterilization and uniform heating, for example, that the temperature of all portions of the tofu 23 to be heated is reduced. As shown in FIG. 1, first, the center portion of the food 19 is quickly and efficiently illuminated by irradiating the straight waveguides 12 a and 12 b with the upper and lower overlaps so that the temperature is in the range of 65 ° C. to 80 ° C. Microwave irradiation steps K1 to K6 to be heated (referred to as a main irradiation step), and then microwaves are irradiated mainly on the corners of the food 19 with the upper and lower overlapping portions of the R-tube waveguides 12a 'and 12b'. Microwave irradiation step K for gentle heating
I recalled that it could be realized by a combination of 7 to K10 (referred to as a sub-irradiation step).

FIG. 6 shows focal points Fa and F as shown in FIG.
b is a straight waveguide 12a, 1
2b for 60 seconds, and then R waveguides 12a 'and 12b' with focal points Fa and Fb vertically overlapped (the irradiation center was shifted 35 mm left and right in the direction of travel from the center of food 19, that is, the tofu. (Disposed on the side close to the corner part), the heating temperature measurement results of each microwave irradiation for 20 seconds around the left and right corner parts, and the result of irradiation for 25 seconds with the R tube waveguide under the same conditions as above is there.

FIG. 6 shows that the total area of food (tofu) was 6%.
Generally uniform heating is realized within a heating temperature range of 5 ° C. to 75 ° C., and the main irradiation step (K1 to K6) is performed.
It can be seen that uniform and efficient heating of the tofu by microwave irradiation can be realized by the combination of and the sub-irradiation step (K7 to K10).

Thus, it is clear that the above-mentioned heat sterilization apparatus 30 by microwave or the above-mentioned heat sterilization method using this apparatus can be applied not only to tofu but also to various other foods. For example, there are no particular restrictions on microwave oven-permeable containers or bags of a predetermined size, prepared side dishes or spaghetti, retorted foods, etc., but there is no particular limitation, but in the present invention, it is important to keep in mind tofu that temperature control is difficult. It should be added that the invention has been made.

Incidentally, the initial temperature of the food before the heat sterilization treatment is not always constant, and the heating temperature of each food after the microwave irradiation step may vary. Therefore, at the time of microwave heating sterilization, the initial temperature of the food as the initial condition is set at the center or the upper limit of the expected initial temperature range (for example, 30 ° C. to 40 ° C.) in consideration of the temperature variation of the actual food. It is necessary to determine the irradiation time in the microwave irradiation step by setting the temperature to a close temperature. In the case of tofu that is delicate to the heating temperature as described above, if it is heated to around 90 ° C. beyond the appropriate heat sterilization temperature range of 65 ° C. to 80 ° C., it will solidify excessively and become a product. There is no. But,
Even if the initial conditions are properly set, it is undeniable that some may deviate from the desired heat sterilization temperature range.

Therefore, in the microwave food heating and sterilizing apparatus 30 shown in FIG. 1 of the present invention, the main irradiation step (K1 to K1) is performed.
After the completion of the sub-irradiation step (Tact of K7 to K10) and the sub-irradiation step (Tact of K7 to K10), the temperature of the food is measured by the non-contact temperature sensor 21 with the tact of K11, and the control device 18 is heated to within the proper sterilization temperature range. Food, the food that exceeds the proper sterilization temperature range (defective product), and the food that is less than the appropriate sterilization temperature range, and additional microwave irradiation is applied to the food that is less than the appropriate sterilization temperature range. It is desirable that the magnetron 13 performing the process (the tact of K12 and K13) and the waveguides 12a 'and 12b' thereof be additionally provided. In the final step (tact of K14), the temperature of the food is measured again by the non-contact temperature sensor 21 in the same manner as described above, and the final sorting is automatically performed by a sorting machine (not shown) attached to the microwave irradiation chamber 11. It is desirable.

As described above, tofu has been described in detail as an example of food to be subjected to heat sterilization. However, the microwave food heat sterilization apparatus of the present invention has a relatively low heating temperature and a narrow appropriate heating temperature range like tofu. It will be appreciated that it is particularly beneficial for sensitive foods.

Finally, according to the design of the inventor, the output 5
In the case of using a 00W magnetron, in the case of a tofu sealed in a general container having a capacity of about one, in view of its mass productivity, the processing capacity should be reduced to at least the main irradiation step of mainly heating the central part of the food (for 10 seconds). 1 irradiation / step), preferably 6 steps as shown in FIG. 1, and 4 sub-irradiation steps (irradiation / step for 10 seconds) for mainly heating the corners of the food.
Steps (two steps for each of the left corner and the right corner) are sequentially performed, and two additional steps of the additional microwave irradiation (preferably a sub-irradiation step in which the waveguide is an R tube) are preferably performed in the final step (FIG. K12 and K13 tacts) are arranged, and additional irradiation is appropriately performed on foods having a temperature lower than the proper sterilization temperature range. The final heating temperature is measured by the non-contact temperature sensor 21 at the final K14 tact, and the food is sorted. C. to 80.degree. A small radiation thermometer is used as the non-contact temperature sensor 21, and the temperature measurement is inserted as one step (K11, K14 tact) before and after the additional microwave irradiation steps K12, K13 as described above. It is convenient to do so.

In the above configuration, one tact is reduced to the required time 12
Transported in 2 seconds, 2400 units / line
It has a processing capacity of 8 hours.
A processing capacity of 800 to 5,000 / 8 hours can be realized. If there are six rows of transfer lines, the processing capacity is 1800 pieces / hour. This is a processing capacity that is industrially sufficient as a processing capacity for heat sterilization of foods such as tofu. Of course, if the required time of one tact is further shortened, the processing capacity is further increased, but the number of irradiation steps needs to be increased, so that the apparatus scale becomes large. Therefore, it is important to keep the balance in consideration of various conditions such as the heat sterilization temperature, the processing capacity, the equipment cost, and the installation conditions. According to the estimation of the inventor, the sterilization process or the sterilization process for the tofu is configured as a six-row transfer line (tact transfer line).
It has been found that securing a processing capacity of about 2000 pieces / hour is realistic in terms of the above balance.

[0044]

The microwave food heat sterilization apparatus and heat sterilization method of the present invention have the following effects.

(1) Heat sterilization by uniform microwaves with small heating unevenness can be realized for the whole food in a short time.

(2) There is an excellent effect that the processing capacity is high and the productivity is excellent.

(3) Appropriate control of the heating temperature range by microwaves for tofu can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram for explaining the overall configuration of a microwave food heating and sterilizing apparatus according to the present invention.

FIG. 2 is a diagram illustrating a positional relationship between a waveguide of a microwave food heat sterilizing apparatus according to the present invention and a container containing food.

FIG. 3 is a diagram for explaining a heating experiment and a measurement result for tofu of the microwave food heat sterilizing apparatus according to the present invention.

FIG. 4 is a diagram showing measurement results under other conditions of the above-mentioned tofu heating experiment.

FIG. 5 is a diagram illustrating a measurement result under other conditions of the heating experiment of the tofu.

FIG. 6 is a diagram showing a heat sterilization method employed by the microwave food heat sterilization apparatus of the present invention and a measurement result of the heating temperature.

FIG. 7 is a schematic configuration diagram of a conventional microwave food heating and sterilizing apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1, 11 Microwave irradiation room 2 Waveguide 3 Magnetron 4, 14 Container 5 Endless transport belt 6, 16 Transport device 7 Drive motor 8, 18 Control device 10, 20 Microwave food heating and sterilizing device 12a, 12b Straight pipe Waveguide 12a ', 12b' Waveguide of R tube 13 Magnetron 15a, 15b Drive motor 19 Food 19a Top 19b Bottom 21 Non-contact temperature sensor 23 Tofu Fa, Fb Focus K, K1, K2, K3, micro Wave irradiation process (1 tact) X Waveguide distance

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masashi Sakairi 5-14-18 Ishikuracho, Maebashi-shi, Gunma Japan F-term in Hicom Corporation (reference) 4B021 LA13 LA24 LA25 LP06 LT02 LT03 LT06

Claims (5)

[Claims] 1. A microwave irradiation chamber integrally formed or connected in a tunnel shape, a plurality of waveguides for guiding microwave energy into the microwave irradiation chamber, and one end of the waveguide. A magnetron, a conveying device for arranging a plurality of microwave-permeable containers containing foods in a line on a conveying line, and sequentially conveying the containers so as to pass through the microwave irradiation chamber, a drive control of the conveying device, and the magnetron And a control device for controlling the irradiation timing of the microwave food heating and sterilizing apparatus, wherein the transport device is such that the container containing the food is fixed at a predetermined position with respect to the waveguide during the microwave irradiation. Means for intermittently conveying, wherein the control device is configured to sequentially convey a plurality of microwave irradiation steps in which each container containing the food is subjected to microwave irradiation for a predetermined time; Dynamic control, and in each microwave irradiation step, the opening end is disposed above the food so that the maximum point (focal point) of the microwave electric field strength is located substantially on the bottom surface of the food. A waveguide, and a lower waveguide whose opening end is disposed below the food so that the maximum point (focal point) of the microwave electric field strength is located substantially on the upper surface of the food. In the microwave food heating and sterilizing apparatus, the control device performs timing control so that microwaves are simultaneously irradiated from above and below the food in each microwave irradiation step. 2. The microwave food heating and sterilizing apparatus according to claim 1, wherein a microwave irradiation step (main irradiation step) for mainly heating a central portion of the food and a microwave for mainly heating a corner portion of the food. A microwave food heating and sterilizing apparatus, comprising a magnetron for performing an irradiation step (sub-irradiation step) and a waveguide thereof. 3. The microwave food heating and sterilizing apparatus according to claim 2, wherein the waveguide in the main irradiation step is a straight pipe,
A microwave food heating and sterilizing apparatus, wherein the waveguide in the sub-irradiation step is an R-tube curved at approximately 90 degrees. 4. The method according to claim 1, 2 or 3.
In the microwave food heat sterilization device according to the above, after the main irradiation step and the sub-irradiation step, the temperature of the food is detected by a non-contact temperature sensor and heated to within the proper sterilization temperature range, and the appropriate sterilization temperature range Exceeding food and food below the proper sterilization temperature range, and sorting, and that the magnetron and the waveguide to perform an additional microwave irradiation step on the food below the appropriate sterilization temperature range. Characteristic microwave food heat sterilizer. 5. A main irradiation step of mainly heating at least the central part of the food in five steps and a sub-irradiation step of mainly heating the corner part of the food in four steps sequentially, and the final heating temperature is 65 ° C. The method for heat-sterilizing food by the microwave food-heat sterilizer according to any one of claims 1 to 4, wherein the temperature is controlled to 80 ° C.