JP2004357627A - Vacuum steam thawing machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vacuum steam thawing machine capable of carrying out high-quality thawing in a short time. <P>SOLUTION: This vacuum steam thawing machine is equipped with a treating tank 1 which can store a material to be thawed and hermetically seal the material, depressurizing means 3 and 4 for depressing the interior of the treating tank, steam-supplying means 8 and 9 for supplying steam to the interior of the depressurized treating tank, a pressure sensor 3 for measuring pressure in the treating tank and a means (a control part) 19 for determining a treating amount or a surface temperature of the material to be thawed by a pressure-raising rate in the treating tank in steam supply by the steam supplying means or a pressure-lowering rate in the treating tank accompanying steam condensation by the material to be thawed. The vacuum steam thawing machine is constituted so that reduction of pressure by subsequent pressure-reducing means and feed of steam by the steam-supplying means are controlled based on the determined treated amount of the material to be thawed or the surface temperature. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a vacuum steam thawing machine (low-pressure steam thawing apparatus) for thawing a frozen product.
[0002]
[Prior art]
A vacuum steam thawing machine is known as an apparatus for thawing a frozen product. The vacuum steam thawing machine is a device that evacuates the inside of a processing tank in which a frozen product is stored, and supplies the steam into the processing tank to thaw by the latent heat of condensation of the steam. For example, as shown in Patent Literature 1 below, after the inside of a treatment tank is evacuated, saturated steam is supplied at a controlled temperature, and the frozen product is raised to a predetermined temperature and thawed.
[0003]
[Patent Document 1]
JP-A-10-179019
[Problems to be solved by the invention]
However, the conventional vacuum steam thawing machine could not determine the throughput. In addition, when the operation time is fixed, there is a possibility that if the processing amount is small, over-thawing occurs, and if the processing amount is large, the thawing is insufficient. Further, even if the operation time can be changed, it does not change according to the amount of the material to be thawed. Since the control does not follow the change in the processing amount, the thawing time may be long. For this reason, in the conventional vacuum steam thawing machine, a large amount of drip (taste component) is generated, and there is a possibility that the quality is significantly impaired.
[0005]
Further, in the conventional vacuum steam thawing machine, the temperature of the object to be thawed is detected and controlled by a temperature sensor. The temperature sensor is used by piercing the object to be thawed, but it is difficult to pierce the temperature sensor because of the frozen material. In addition, it is conceivable to simply install a temperature sensor in the treatment tank without sticking the temperature sensor into the object to be thawed. However, such a method is affected by the temperature around the installation location and has low reliability. there were.
[0006]
The present invention has been made in view of the above circumstances, and a main object thereof is to provide a vacuum steam thawing machine that realizes high-quality thawing in a short time.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a vacuum steam thawing machine according to the present invention includes the following constituent features (A) to (E).
(A) A treatment tank capable of containing an object to be thawed and hermetically sealed.
(B) Decompression means for decompressing the inside of the processing tank.
(C) Steam supply means for supplying steam into the depressurized processing tank.
(D) A pressure sensor for measuring the pressure in the processing tank.
(E) Means for determining the processing amount or surface temperature of the object to be defrosted based on the rate of pressure increase in the processing tank during steam supply by the steam supply means or the rate of pressure decrease in the processing tank due to vapor condensation by the object to be defrosted. .
[0008]
And preferably, in addition to the above configuration, a vacuum steam thawing machine in which the decompression by the decompression means and the steam supply by the steam supply means are performed a plurality of times, based on the determined processing amount or surface temperature of the object to be defrosted. A vacuum steam thawing machine characterized in that the pressure reduction by the pressure reducing means and the steam supply by the steam supply means are controlled thereafter.
[0009]
In addition, preferably, in addition to the above configuration, based on the determined processing amount or surface temperature of the object to be defrosted, the operation time, the reduced pressure amount or the amount of steam supply, the operation timing of the reduced pressure or the steam supply, the operation time of the reduced pressure or the steam supply. A vacuum steam thawing machine characterized in that any one or more of the number of operations is determined and the subsequent operation is performed. Here, the determination of the processing amount or surface temperature of the object to be thawed and the operation adjustment based on the determination may be performed a plurality of times during operation.
[0010]
Further, the vacuum steam thawing machine of the present invention includes the following constitutional requirements (A) to (C), in which the pressure reduction by the pressure reducing means and the steam supply by the steam supply means are performed plural times, and the processing amount of the material to be thawed (the above-mentioned amount). The decompression by the decompression unit and the supply of steam by the steam supply unit are controlled based on automatic determination or manual setting.
(A) A treatment tank capable of containing an object to be thawed and hermetically sealed.
(B) Decompression means for decompressing the inside of the processing tank.
(C) Steam supply means for supplying steam into the depressurized processing tank.
[0011]
In addition, in the present invention, in addition to any one of the above configurations, the pressure reducing means includes a steam ejector having a suction port connected to the treatment tank, and a vacuum pump connected to an outlet of the steam ejector via a heat exchanger. And a vacuum steam thawing machine characterized by comprising:
[0012]
Further, according to the present invention, there is provided a vacuum steam thawing machine characterized in that the supply of steam to the processing tank is performed at a constant pressure and a constant flow rate in addition to any one of the above configurations.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the vacuum steam thawing machine of the present invention will be described in more detail based on embodiments.
FIG. 1 is a schematic structural view showing one embodiment of the vacuum steam thawing machine of the present invention.
[0014]
As shown in this figure, a vacuum steam thawing machine according to the present invention comprises a processing tank 1 comprising a sealable pressure-resistant container in which an object to be thawed (frozen material to be thawed) is housed, and the inside of this processing tank 1 is decompressed. A pressure reducing means (3, 4), a steam supply means (8, 9) for supplying steam into the depressurized processing tank 1, and a pressure sensor 2 for measuring a pressure in the processing tank 1 as main parts.
[0015]
As the decompression means, a vacuum pump, a steam ejector, a water ejector, or the like can be used. These can be used in combination of a plurality of types. In the present embodiment, the steam ejector 3 and the vacuum pump 4 are combined to constitute a pressure reducing means. In this case, the suction port of the steam ejector 3 is connected to the processing tank 1, and a vacuum pump 4 is connected to the outlet of the steam ejector 3 via a heat exchanger 5 and a check valve 6. Therefore, by injecting steam from the inlet to the outlet of the steam ejector 3 while driving the vacuum pump 4 to perform cooling and condensation by the heat exchanger 5, the inside of the processing tank 1 to which the suction port is connected is formed. Air can be sucked out and discharged to reduce the pressure inside the processing tank 1.
[0016]
Therefore, the steam from the boilers 8 and 9 can be supplied to the inlet of the steam ejector 3 via the ejector steam supply valve 7. A water ring vacuum pump 4 is connected to an outlet of the steam ejector 3 via a heat exchanger 5 and a check valve 6. Water is supplied to the vacuum pump 4 through a sealed water supply valve 10, and drainage from the vacuum pump 4 is discharged to a drain port. Further, cooling water is also supplied to the heat exchanger 5 via the strainer 11 and the heat exchange water supply valve 12, and is drained to a drain port. The sealed water supply valve 10 for supplying water to the vacuum pump 4 is opened in conjunction with the vacuum pump 4.
[0017]
The steam supply unit is a unit that supplies (steams) the steam from the boiler 9 into the decompressed processing tank. The steam supply line is provided with a steam pressure adjusting means including a reduced pressure steam supply valve 13 and a steam orifice 14. In the present embodiment, both the reduced-pressure steam supply valve 13 and the steam orifice 14 are provided, and the pressure and the flow rate of the steam from the boiler 9 can be adjusted. Thereby, the steam supplied into the processing tank 1 can be set to a constant pressure and a constant flow rate. Such a constant-pressure and constant-flow steam supply enables stable and accurate thawing. This constant pressure and constant flow rate steam supply means is not limited to this embodiment. The supply pressure of the boiler 9 is controlled to be constant, and a constant flow rate means such as the orifice 14 is provided at the outlet side of the boiler 9. It can also be realized by:
[0018]
By the way, there is a possibility that rust and rust preventives in the pipes may be mixed in the steam generated by the general boiler 8. However, the steam supplied into the processing tank 1 directly contacts the object to be thawed, and the object to be thawed may be a frozen food. Therefore, it is desirable to supply cleaner steam to the processing tank 1. Therefore, in the present embodiment, pure water or soft water is heated by the stainless steel heat exchanger 15 using the steam from the boiler 8 as a heat source, and safe and clean steam can be used. That is, clean steam is supplied into the processing tank 1 using the secondary boiler (reboiler) 9.
[0019]
Specifically, as shown in FIG. 1, using the heat of the steam from the primary boiler 8, the secondary boiler 9 converts pure water or soft water into clean steam, and converts the clean steam into a strainer 16. It is supplied to the processing tank 1 via such as. Further, in the illustrated example, the steam supplied to the inlet of the steam ejector 3 also uses the steam from the secondary boiler 9. That is, the steam from the secondary boiler 9 can be used for both steam supply to the inlet of the steam ejector 3 and steam supply to the treatment tank 1 by the steam supply means. The switching can be performed by opening and closing the ejector steam supply valve 7 and the reduced pressure steam supply valve 13. In addition, using only the primary boiler 8, the steam of the boiler can be used for supply to the ejector 3 and the processing tank 1, clean steam is supplied to the processing tank 1, and steam of the primary boiler 8 is supplied to the ejector 3. Of course, it can be configured to supply.
[0020]
By the way, outside air can be introduced into the processing tank 1 so that the reduced pressure state can be broken. In this embodiment, the processing tank 1 can communicate with the outside air via the outside air introduction valve 17 and the filter 18. Therefore, when the outside air introduction valve 17 is opened, the inside of the processing tank 1 is opened to the atmospheric pressure, and outside air is introduced into the processing tank 1 through the filter 18 so that the pressure can be restored. Depending on the degree of opening of the outside air introduction valve 17, the pressure inside the processing tank 1 can be gradually increased.
[0021]
Further, the vacuum steam thawing machine is provided with a controller 19 for controlling a pressure reducing means, a steam supplying means (steam pressure adjusting means), an outside air introducing means and the like, and the controller 19 detects the detected pressure from the pressure sensor 2. Based on the above, each means is controlled. That is, the pressure sensor 2, the vacuum pump 4, the ejector steam supply valve 7, the sealed water supply valve 10, the heat exchange water supply valve 12, the reduced pressure steam supply valve 13, the outside air introduction valve 17, and the like are connected to the controller 19, The controller enables the following operation.
[0022]
FIG. 2 is a diagram illustrating an example of an operation flow of the vacuum steam thawing machine according to the present embodiment, and illustrates a pressure change in the processing tank 1. FIGS. 3A and 3B are flowcharts for executing the operation. FIG. 3A is a main process, FIG. 3B is a holding process in the second pressure range during the main process, and FIG. 3 shows a steam supply-pressure reduction pulse process.
[0023]
When the object to be thawed is to be thawed by the vacuum steam thawing machine of this embodiment, the object to be thawed is accommodated in the processing tank 1 and the processing tank 1 is sealed. Thereafter, as shown in FIG. 2, the pressure in the processing tank is reduced to the first pressure range P1 using a pressure reducing means (ST1). That is, the inside of the processing tank 1 is depressurized by opening the ejector steam supply valve 7, the sealed water supply valve 10, and the heat exchange water supply valve 12, and driving the steam ejector 3 and the vacuum pump 4.
[0024]
In addition, the first pressure range P1 and a second pressure range P2 described later may be a certain pressure range or a certain predetermined pressure. In the illustrated example, for example, 8 hPa is adopted as the first pressure P1 in consideration of current hardware restrictions. Further, in the second pressure range P2, for example, 18 to 22 hPa is adopted in consideration of the fact that if the temperature is too high, the temperature rises and there is a possibility that various bacteria may propagate. It is needless to say that the first pressure range P1 and the second pressure range P2 (the upper limit pressure P2U and the lower limit pressure P2L) can be appropriately changed.
[0025]
After reducing the pressure to the first pressure P1, the pressure reducing means is stopped, and steam is supplied into the processing tank 1 by the steam supply means (ST2). That is, while the ejector steam supply valve 7 and the like are closed, the decompression steam supply valve 13 is opened, and steam is supplied into the processing tank 1. As a result, the pressure in the processing tank 1 increases, but in this case, steam is supplied to the upper limit pressure P2U (22 hPa) of the second pressure range P2 (18 to 22 hPa). Then, in the second pressure range P2, a predetermined time T1 is maintained (ST3). For this purpose, the timer starts counting from the time point when the pressure reaches the second pressure range P2 (the upper limit pressure P2U in the illustrated example) for the first time, and the pressure in the processing tank is kept at the second level until the timer reaches the predetermined time T1. The pressure is maintained in the pressure range P2 (ST31 to ST37).
[0026]
At this time, after the steam is first supplied to the upper limit pressure P2U (22 hPa) of the second pressure range, the reduced-pressure steam supply valve 13 is closed, and the supply of the steam into the processing tank 1 is stopped. If left as it is, the vapor in the processing tank 1 is condensed by the material to be thawed. Thus, the pressure in the processing tank 1 gradually decreases without using the pressure reducing means. When the pressure falls below the lower limit pressure P2L (18 hPa) of the second pressure range, the steam supply means is driven again to supply steam into the processing tank 1. Then, when the pressure reaches the upper limit pressure P2U (22 hPa) of the second pressure range, the process of stopping the steam supply is repeated.
[0027]
Specifically, as shown in FIGS. 3A and 3B, after the pressure is reduced from the atmospheric pressure to the first pressure P1 (ST1), steam is supplied to the second pressure range upper limit pressure P2U (ST2 (= ST32 + ST33). )). When the pressure reaches the second pressure range upper limit pressure P2U, the steam supply is stopped (ST34). As described above, the pressure in the processing tank 1 gradually decreases as the vapor condenses. When the pressure falls below the second pressure range lower limit pressure P2L (ST35), unless the predetermined time T1 has elapsed (ST36), steam is again supplied to the second pressure range upper limit pressure P2U (ST32, ST33). Thus, using the output from the pressure sensor 2, the pressure in the processing tank 1 is maintained between the upper limit pressure P2U and the lower limit pressure P2L of the second pressure range for a predetermined time T1 (for example, 15 minutes). Next, the controller 19 controls the steam supply means. By holding the predetermined time T1 in the second pressure range P2, the thawing time can be shortened. In addition, when the operation is performed at the beginning of the operation, the temperature of the object to be defrosted is low, so that the surface of the object to be defrosted is also prevented from burning.
[0028]
After maintaining for a predetermined time T1 in the second pressure range P2 (ST3), the pressure is reduced again to the first pressure P1 (ST4), and maintained at the first pressure P1 for a predetermined time T2 (for example, 2 minutes) (ST5). After maintaining the first pressure P1 for a predetermined time (ST5), the following steam supply-pressure reduction pulse control is performed (ST6). In this steam supply-pressure reduction pulse control, as shown in FIG. 3C, first, steam is supplied to a second pressure range (here, the upper limit pressure P2U) (ST61). After reaching the second pressure range upper limit pressure P2U, the pressure is reduced to the first pressure P1 (ST62), and is maintained at the first pressure P1 for a predetermined time T2 (for example, 2 minutes) (ST63). Such a cycle of the steam supply to the second pressure range P2, the pressure reduction to the first pressure range P1, and the holding in the first pressure range P1 is repeated a predetermined number of times (ST64). Then, after the steaming-decompression pulse is executed a predetermined number of times (ST6), it is kept in the first pressure range P1 (ST7), so that the material to be thawed is kept cool.
[0029]
By the way, in the controller 19, the pressure is increased in the processing tank 1 when the steam is supplied by the steam supply means, or the pressure is reduced in the processing tank 1 due to the vapor condensation by the thawing material. The processing amount (or surface temperature) of the obtained thawing object can be determined. Note that these speeds can be grasped from a change in the output value of the pressure sensor 2 and the time required for the change.
[0030]
For example, after the pressure is reduced to the first pressure P1 by the pressure reducing means at the beginning of the operation, when the steam is supplied to the second pressure range P2, the processing amount can be determined by grasping the rate of pressure increase in the processing tank 1. is there. Assuming that the materials to be thawed are simply different in weight from the same material, when the amount of the processed material to be thawed is large, the supplied steam is cooled and easily condensed, so that the rate of pressure increase in the processing tank 1 becomes slow. That is, in FIG. 2, the line L1 from the first pressure P1 to the second pressure range P2 has a small rising angle with respect to the horizontal direction, and lies in the horizontal direction. Conversely, when the processing amount of the material to be thawed is small, the pressure rising speed in the processing tank 1 increases, and the line L1 has a large rising angle with respect to the horizontal direction and stands in the vertical direction. That is, the pressure in the processing tank quickly increases to the set pressure.
[0031]
In order to determine the processing amount of the material to be thawed, not only the pressure rising speed from the first pressure P1 to the second pressure range P2, but also the second pressure range upper limit pressure P2U when holding in the second pressure range P2. It is also possible to use the pressure reduction rate accompanying the vapor condensation up to the lower limit pressure P2L. Further, for example, even when the pressure increasing speed from the first pressure P1 to the second pressure range P2 is used, the steam supply step immediately after the pressure reduction at the beginning of the operation may be used, or any of the steam supply and the pressure reduction pulse processing. Which process is used is appropriately set, for example, such a steam supply process can be used.
[0032]
In the case of using the pressure decrease rate accompanying the vapor condensation from the upper limit pressure P2U of the second pressure range to the lower limit pressure P2L when the pressure is held in the second pressure range P2, the surface temperature of the material to be defrosted can be estimated. . That is, when the steam supply is stopped, the pressure in the processing tank decreases because the steam continues to be condensed into the defrosted product. By observing the slope, it can be determined whether the surface temperature has increased. When the surface temperature is low, a large amount of vapor in the processing tank can be condensed, so that the pressure in the processing tank rapidly decreases. Conversely, when the surface temperature rises, the temperature difference between the inside temperature of the processing tank and the surface temperature becomes small, so that the amount of condensed water decreases and the decrease in the pressure inside the processing tank becomes slow. When there is a time (slope) in which the pressure in the processing tank decreases, it is determined that the surface temperature has increased, and the holding time T1 in the second pressure range and the number of pulses can be changed.
In addition, the determination of the surface temperature can be performed by using the pressure increasing speed from the first pressure P1 to the second pressure P2 in the steam supply-decompression pulse processing.
[0033]
In this manner, the processing amount of the object to be defrosted is determined. Based on the determined estimated processing amount of the object to be defrosted, the subsequent pressure reduction by the pressure reducing means and the steam supply by the steam supply means are controlled. In other words, the controller determines the operation time, the pressure reduction amount or the steam supply amount (the pressure in the first pressure range or the second pressure range), the operation timing of the pressure reduction or the steam supply ( One or more of the operation timing, the holding time T2 in the first pressure range, the holding time T1 in the second pressure range), the number of decompression or steaming operations (the number of pulses of steaming-decompression pulse processing), and the like. Is determined and the subsequent operation is controlled.
[0034]
In the present embodiment, the holding time T1 in the second pressure range P2 and the number of pulses of the steam supply-pressure reduction pulse processing are determined. However, as described above, it is conceivable to make the holding pressure in the holding step in the second pressure range P2 or the second pressure in the steaming-decompression pulse step variable.
[0035]
The determination of the processing amount of the object to be thawed and the operation adjustment based on the determination may be performed a plurality of times during operation. For example, the holding time in the second pressure range P2 is determined based on the pressure increase rate at the time of steam supply at the beginning of the operation, and the number of subsequent steaming-decompression pulses is determined. It is also possible to correct this with the pressure rise rate at the time of steam supply in.
[0036]
It goes without saying that the operation flow is not limited to FIG. In particular, in the step of supplying steam to the second pressure range P2 after reducing the pressure to the first pressure P1 at the beginning of the operation, it is conceivable to appropriately change the subsequent steps in the same manner as in FIG. For example, it is conceivable that the upper limit pressure P2U and the lower limit pressure P2L of the second pressure range P2 are changed stepwise, or the pressure of the second pressure range P2 is reduced so as to approach the first pressure P1 over time. .
[0037]
Specifically, as shown in FIG. 4, after the pressure is reduced to the first pressure P1 by the pressure reducing means, steam is supplied to the second pressure range P2 by the steam supply means, and the upper limit pressure P2U and the lower limit pressure of the second pressure range P2. The supply of steam and the reduction in pressure due to the condensation of steam are repeatedly performed so as to be maintained within the range of P2L, but the upper limit pressure P2U and the lower limit pressure P2L of the second pressure range P2 are changed stepwise. That is, the set pressure for turning on and off the reduced pressure steam supply valve is changed stepwise. In the illustrated example, the upper limit pressure P2U and the lower limit pressure P2L of the second pressure range P2 gradually decrease over time so as to approach the first pressure P1. For example, a setting is used in which steam is initially supplied to 22 hPa, and then steamed again at 18 hPa after the stop of steaming, and then steamed to 18 hPa, and then steamed again to 14 hPa after the steaming is stopped. Thus, the second pressure range P2 is gradually decreased to approach the first pressure P1.
[0038]
Further, after the pressure is reduced to the first pressure P1 at the beginning of the operation, the steam is supplied to the second pressure range P2, and after maintaining for a certain time, the process of reducing the pressure to the first pressure P1 is the same as that in FIG. It is also conceivable to change it as follows. That is, in FIG. 2, the pressure is reduced immediately after the supply of steam to the second pressure P2. However, as shown in FIG. 5, the pressure is kept at the set pressure, and the pressure of the keep is gradually reduced.
[0039]
In other words, it can be said that the following cycle is performed after the pressure is reduced to the first pressure P1 at the beginning of the operation. That is, after the steam is supplied from the first pressure P1 to the second pressure range P2, and is maintained in the second pressure range P2 so as to be maintained within the range of the upper limit pressure P2U and the lower limit pressure P2L of the second pressure range P2. The process of reducing the pressure to the first pressure range P1 by the pressure reducing means is repeated. In the example of FIG. 4, the second pressure range P2 is changed for each cycle (P21, P22, P23). That is, the upper limit pressure P2U and the lower limit pressure P2L of the second pressure range P2 are gradually reduced to the first pressure side each time the cycle changes.
[0040]
Further, the pressure fluctuation amount of the second pressure range P2 may be changed. For example, each time the cycle changes, the difference between the upper limit pressure P2U and the lower limit pressure P2L of the second pressure range P2 may be different.
[0041]
Further, outside air may be introduced into the processing tank 1. In the embodiment of FIG. 5 described above, the total pressure (the partial pressure of air in the processing tank + the partial pressure of steam) during the steam supply is reduced stepwise, and accordingly, the partial pressure of the steam in the processing tank 1 is also reduced. As shown in FIG. 6, the steam partial pressure is gradually reduced, but the total pressure may be gradually increased.
[0042]
FIG. 6A shows the relationship between the time and the partial pressure of the vapor in the processing tank in this case, and FIG. 6B shows the relationship between the time and the total pressure in the processing tank. As shown in FIG. 6A, the vapor partial pressure in the processing tank is set to decrease similarly to FIG. In addition, here, the pressure is gradually decreased even during the holding step in the second pressure area P2 in each cycle, and the second pressure area P2 is decreased linearly. Further, in the present embodiment, as shown in FIG. 6B, the total pressure in the processing tank is increased.
[0043]
The reason for this is to prevent the pack surrounding the material to be thawed from expanding and causing heat transfer obstruction by reducing the pressure in the processing tank. As shown in FIG. 6B, when air is introduced from the middle, the total pressure in the processing tank increases, but the partial pressure (ratio) of the steam decreases. By doing so, the swelling of the pack of the object to be defrosted can be suppressed and the amount of heat input can be suppressed, so that the surface temperature of the object to be defrosted can be controlled to the optimum temperature. By changing the target value of the vapor partial pressure in the processing tank, the surface temperature of the object to be thawed can be optimally controlled.
[0044]
According to the vacuum steam thawing machine of each of the above-mentioned embodiments, the product temperature (core temperature, surface temperature) of the material to be thawed is monitored by monitoring the pressure in the processing tank at the time of depressurization and steam supply with a pressure sensor. Can be thawed without. Further, since the control is performed by the pressure in the processing layer, the reliability is higher than the case of using a temperature sensor, without being affected by the surrounding atmosphere. In addition, the object to be thawed is frozen at, for example, -30 ° C., so that it is difficult to pierce the temperature sensor. In addition, the control based on the pressure can be set in consideration of not only the processing amount of the object to be thawed but also the size and type.
[0045]
Further, according to the vacuum steam thawing machine of each of the embodiments, the product temperature of the thawed product is not excessively increased, the quality can be maintained, and the thawing time can be shortened. In particular, this is achieved by pressure keeping at a predetermined pressure or by steam supply and pressure reduction pulse control. In addition, since the surface temperature can be raised as quickly as possible, the thawing time can be reduced. For example, when thawing 100 kg of chicken from -30 ° C to 0 ° C, it can be thawed in 120 minutes. In addition, dripping after thawing can be suppressed without adding excessive heat, and thawing can be performed while maintaining quality.
[0046]
Note that the present invention is not limited to a vacuum steam thawing machine, and is applicable to other devices that condense steam and transfer heat. Also, thawing is not limited to thawing up to 0 ° C, but can be applied to thawing up to -3 ° C, for example.
[0047]
The present invention is not limited to the above embodiment. In the above embodiment, the decompression is stopped and the steam supply is performed. However, the pressure may be reduced during the steam supply, that is, the steam may be supplied while the pressure is reduced. By doing so, it is possible to keep at a pressure close to the first pressure P1, and to perform thawing at a lower temperature. Further, since the surface temperature of the defrosted product is kept below the saturation temperature in the treatment tank, the upper limit of the surface temperature can be controlled by changing the setting of the second pressure range P2.
[0048]
【The invention's effect】
As described above, according to the vacuum steam thawing machine of the present invention, high-quality thawing can be realized in a short time.
[Brief description of the drawings]
FIG. 1 is a schematic structural view showing one embodiment of a vacuum steam thawing machine of the present invention.
FIG. 2 is a view showing one example of an operation flow of the vacuum steam thawing machine in FIG. 1, and shows a pressure change in a processing tank.
FIGS. 3A and 3B are flowcharts for executing the operation of FIG. 2; FIG. 3A is a main process, FIG. 3B is a holding process in a second pressure range during the main process, and FIG. 3 shows a steam supply-pressure reduction pulse process.
FIG. 4 is a diagram showing a modification of the operation flow of FIG. 2;
FIG. 5 is a diagram showing another modification of the operation flow of FIG. 2;
FIG. 6 is a diagram showing a modification of the operation flow of FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Processing tank 2 Pressure sensor 3 Steam ejector 4 Vacuum pump 5 Heat exchanger 7 Ejector steam supply valve 8, 9 Boiler 13 Reduced pressure steam supply valve 17 Outside air introduction valve

Claims (6)

A treatment tank that can accommodate the material to be thawed and that can be sealed;
Decompression means for decompressing the inside of the processing tank,
Steam supply means for supplying steam into the depressurized processing tank,
A pressure sensor for measuring the pressure in the processing tank,
Means for determining the processing amount or surface temperature of the object to be defrosted, based on the rate of pressure increase in the processing tank during steam supply by the steam supply means or the rate of pressure decrease in the processing tank due to vapor condensation by the object to be defrosted. A vacuum steam thawing machine characterized in that: A vacuum steam thawing machine in which the pressure reduction by the pressure reducing means and the steam supply by the steam supply means are performed a plurality of times,
The vacuum steam thawing machine according to claim 1, wherein the subsequent reduction in pressure by the pressure reducing means and the supply of steam by the steam supply means are controlled based on the determined processing amount or surface temperature of the object to be thawed. Based on the processing amount or surface temperature of the determined object to be defrosted, the operation time, the amount of pressure reduction or steaming, the operation timing of pressure reduction or steaming, the number of times of operation of pressure reduction or steaming, etc., at least one of which The vacuum steam thawing machine according to claim 2, wherein the following operation is performed. The vacuum steam thawing machine according to claim 3, wherein the determination of the processing amount or the surface temperature of the object to be thawed and the operation adjustment based thereon are performed a plurality of times during operation. A treatment tank that can accommodate the material to be thawed and that can be sealed;
Decompression means for decompressing the inside of the processing tank,
Steam supply means for supplying steam into the depressurized processing tank,
A vacuum steam thawing machine characterized in that pressure reduction by the pressure reducing means and steam supply by the steam supplying means are performed a plurality of times, and pressure reduction by the pressure reducing means and steam supply by the steam supplying means are controlled based on the throughput of the material to be thawed. . The vacuum steam thawing machine according to any one of claims 1 to 5, wherein the supply of steam to the processing tank is performed at a constant pressure and a constant flow rate.

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