JP2019082297A - Continuous freezer - Google Patents

Abstract

To cool the whole or each portion of an object to be frozen to an optional desired temperature while reducing the time in freezing the object to be frozen which requires a freezing step.SOLUTION: A nozzle and a control valve for spraying liquid nitrogen are provided in correspondence with each of stirring fans 12 provided in a freezing container 11 so that a spray amount can be controlled for each of the stirring fans 12. A rapid freezing zone LTZ and a temperature averaging zone HTZ are set, and in order to control the inside of the zones at a desired temperature, openings of the control valves in the respective zones are automatically adjusted on the basis of a measurement result by an LTZ side temperature sensor 20a and an HTZ side temperature sensor 20b, and an amount of the liquid nitrogen sprayed to each of the zones is controlled. Further, conveyance speeds of an LTZ side conveyance conveyor 18a and an HTZ side conveyance conveyor 18b for conveying an object to be frozen are determined by considering a set temperature of each of the zones. Both of a surface and an inside of the object to be frozen are cooled to the desired temperature in a downstream end of the temperature averaging zone HTZ.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a continuous freezer, and more particularly to a continuous freezer for cooling an object to be frozen under two or more continuous low temperature atmospheres of liquid nitrogen.

  Among various types of food products, some food products include a freezing process in their production process. For example, a cake production process is composed of a baking process of dough, a slicing process of dough, a decoration process, a freezing process, and a cutting process in chronological order. In the freezing step in the cake production process, all of the produced cake is frozen to a predetermined low temperature range. The reason why the above freezing step is necessary in the cake production process is as follows.

  In the cutting process, a unique cutter is used to finish the cut surface neatly. Therefore, when the temperature of the cake is lower than a predetermined temperature (experimental value: -28 ° C), the cake is too hard, so the cutter may be damaged at the time of cutting or the appearance defect occurs at the cake at the time of cutting. There is a case. On the other hand, if the product temperature is higher than the specified temperature (experimental value: -13 ° C), the cake (especially cream) does not harden, so the unfrozen cream adheres to the cutter at the time of cutting, and appearance defects occur at the time of recutting. May occur and product failure. Furthermore, if the temperature of the cake is uneven, the hardness may vary and the cutter may be damaged.

  Conventionally, a batch-type mechanical freezer has been mainly used as an apparatus for freezing food in the freezing step. For example, Patent Document 1 and Patent Document 2 disclose examples of mechanical freezers.

  In Patent Document 1, the cold air is jetted to the frozen food (F) by the high air pressure fan (52) and the cold air jet slit (71) to break the mirror film on the surface of the frozen food to enable rapid freezing. ing.

  Moreover, in patent document 2, to-be-frozen thing (scallops pillars) (20) is conveyed by the conveyor belt (15), and the cold wind is supplied from the upper surface side and lower surface side of a conveyor. Cold air is supplied so that the inside of the cooling space is at or below -38 ° C, and it is possible to freeze the frozen matter uniformly and efficiently by adjusting the air volume on the upper surface side and the lower surface side.

  However, in the mechanical freezer represented by the disclosure of each of the above patent documents, the freezing time is prolonged without sufficiently lowering the cooling temperature, and the productivity and the quality are lowered. Specifically, when a food is generally stored in a freezer for a long time, water is evaporated from the surface of the food (freeze-baked), and lipids in the food are oxidized by oxygen in the air (oil-burned).

  Also, in order to increase the cooling speed, a method of increasing the speed of cold air, a method of using brine, and the like are employed. However, the method of increasing the speed of the cold air has the disadvantage that the decoration scatters. On the other hand, the method using brine is not preferable from the viewpoint of safety and the impact on taste and texture because the product absorbs the brine.

  In addition, since a mechanical freezer requires additional equipment (heat exchangers, compressors, expanders, etc.), the installation space is large, and the maintainability and the washability are reduced.

  By the way, also from the above-mentioned viewpoint, recently, it is desired to shorten the time of the freezing process to shorten the production process and to improve the production amount and the quality. For example, in the above steps of the cake production process, one day in the baking process of the dough, one day in the slicing process of the dough, one day in the decoration process, one day in the freezing process and one day in the cutting process Was required.

  Therefore, in general, consider a liquid nitrogen type freezer capable of quick freezing rather than a mechanical freezer to shorten the freezing process. For example, consider that it is assumed that all processes of the decoration process, the freezing process, and the cutting process are completed in one day.

Here, examples of liquid nitrogen freezers are disclosed, for example, in Patent Literature 3 and Patent Literature 4.
Patent Document 3 discloses that rapid freezing can be performed by using liquid nitrogen (4) as a premise, but in particular, for example, as in chocolate, depending on the item to be frozen (3), only its surface is rapidly There are some that are solidified by freezing and there is no need to solidify the inside, so after solidifying the surface by rapid freezing with liquid nitrogen, it is expensive by keeping the temperature low at a freon cooler (5) It is disclosed that it saves various liquid nitrogen.

  Further, in Patent Document 4, although liquid nitrogen is also used to freeze food (115) in principle, liquid nitrogen after cooling the food is further added for the purpose of saving the liquid nitrogen. It is disclosed for use in cooling the gaseous refrigerant of a mechanical refrigeration system (122).

Patent No. 3438164 gazette Patent No. 4318699 gazette Japanese Patent Application Laid-Open No. 8-296938 JP 2002-257452 A

  As described above, since the cooling temperature can be lowered by using a liquid nitrogen freezer as compared with a mechanical freezer, it is expected to shorten the time in the freezing step.

  However, it is impossible to spray liquid nitrogen directly onto a frozen object such as a cake in order to prevent the occurrence of cracks and cracks on the surface. Further, as in the case of the mechanical freezer, if the cold air velocity is too fast, the decoration will be scattered if it is a cake, resulting in a product failure. Therefore, even if a liquid nitrogen type freezer is adopted, it is necessary to freeze the object to be frozen not by direct spraying of liquid nitrogen but by atmosphere cooling with low temperature nitrogen gas that has vaporized liquid nitrogen.

  From another point of view, the faster the cooling rate (the shorter the freezing time), the more the surface of the material to be frozen gets excessively cold, resulting in a temperature difference with the inside, and the whole becomes uneven. In particular, when the surface is too cold, problems such as breakage of the cutter at the time of cutting and appearance defects of the object to be frozen at the time of cutting occur. Therefore, even if a liquid nitrogen type freezer is used, a quick freezing step for freezing the object to be frozen in a short time and a temperature equalizing step for making the overall temperature of the object to be frozen uniform within a predetermined temperature range Since it is necessary to eliminate temperature unevenness occurring in the rapid freezing step, two units having different set temperatures are required, or one unit must be repeatedly used with different temperature control.

On the other hand, from the viewpoint of production speed and installation space and freezing time, the freezing time is limited by the processing speed of the cutting process (for example, 30 seconds / sheet) and the allowable installation space of the apparatus body (for example, 7 m at maximum). Therefore, in the case of this example, the freezing time needs to be within 14 minutes.
From the above, it was necessary to find a new freezing method / freezer in order to simultaneously reduce the freezing time and equalize the product temperature.

  The present invention has been made in view of the above circumstances, and when freezing an object to be frozen which requires a freezing step, while shortening the time, the whole or each part of the object to be frozen can be any desired. It is an object of the present invention to provide a continuous freezer that can be brought to a temperature.

In order to solve the above-mentioned subject, the present invention comprises the following composition.
[1] A conveyer for conveying an object to be frozen
Two or more cooling spaces for cooling the objects to be frozen on the transfer conveyor by a low temperature atmosphere;
Two or more of the cooling spaces are provided continuously on the transfer conveyor, and at least the transfer surface of the transfer conveyor is exposed in the cooling space,
Continuous freezer in which the temperature of the low temperature atmosphere of the adjacent cooling space differs.
[2] The cooling space has a cooling device for maintaining the low temperature atmosphere,
The continuous freezer according to [1], wherein the cooling device has one or more stirring fans for stirring an atmosphere in the cooling space, and one or more nozzles for spraying liquid nitrogen onto the stirring fans. .
[3] The continuous freezer according to [1] or [2], wherein the cooling space has an exhaust port for forcibly exhausting the atmosphere in the cooling space.

According to the continuous freezer of the present invention, the space on the conveyer can be divided into arbitrary regions having different temperatures. Therefore, when freezing an object to be frozen which requires a freezing step, the time is shortened. The whole or each part of the object to be frozen can be set to any desired temperature. If similar measures and effects are to be achieved with a mechanical freezer, multiple freezers with individual temperature adjustments are required. In addition, throughput can be improved because continuous transportation is possible. Furthermore, since the atmosphere is frozen, the object to be frozen can be applied even if it is a delicate food.
In addition, the space on the transport conveyor can be divided into arbitrary regions of different temperatures by providing a plurality of sets of nozzles for spraying liquid nitrogen and a stirring fan, and individually controlling the spray amount and the rotation speed of the stirring fan. Is surely realized.
Furthermore, by providing an exhaust port corresponding to each cooling space, mixing of nitrogen gas between the cooling spaces can be avoided, and temperature control can be reliably performed.

It is a top view of a continuous freezer which is one embodiment to which the present invention is applied. It is sectional drawing seen from the side direction of the continuous-type freezer which is one Embodiment to which this invention is applied.

  Hereinafter, the configuration of a continuous freezer, which is an embodiment to which the present invention is applied, will be described in detail with reference to the drawings, together with a method of operating the continuous freezer. In the drawings used in the following description, in order to make the features easy to understand, the features that are the features may be enlarged for the sake of convenience, and the dimensional ratio of each component may be limited to the same as the actual Absent.

  First, the configuration of a continuous freezer that is an embodiment to which the present invention is applied will be described. Here, FIG. 1 is a plan view of an embodiment of the continuous freezer according to the present invention, and FIG. 2 is a side sectional view thereof.

As shown in FIG. 1 and FIG. 2, the continuous freezer 1 of this embodiment has a freezing container 11, and the desired temperature of the object to be frozen is obtained by passing the object to be frozen through its hollow. Frozen. Stirring fans 12 are suspended at equal intervals on the inner wall ceiling portion of the freezing container 11, and specifically, a total of 22 stirring fans 12 _{1 to} 12 ₂₂ are provided in two rows of eleven in a row. ing.

Further, corresponding to each of the agitation fan 12, the outer wall upper portion of the refrigeration container 11, the fan drive motors _{131-134 22} for driving each of the stirring fan 12 is provided. Therefore, the rotational speed of each stirring fan 12 can be individually inverter controlled by each fan drive motor 13. In order to avoid interference between the stirring fans 12 adjacent to each other in the transport direction, the fan partition plate 14 is provided between the stirring fans 12.

  In addition, the continuous freezer 1 is provided with a liquid nitrogen supply unit 15, and from there through the liquid nitrogen supply pipe 16 to each nozzle (not shown) provided in the portion of each stirring fan 12 (LN: Liquid Nitrogen ) Is supplied. Since the liquid nitrogen supplied to each nozzle and sprayed from them is vaporized to low temperature nitrogen gas by the wind by the rotation of the stirring fan 12, the liquid nitrogen is not directly sprayed to the object to be frozen, and the atmosphere is cooled Is possible. Thereby, the crack of the surface of the object to be frozen can be avoided.

  The nozzle affects the liquid nitrogen spray amount, and the nozzle diameter is preferably about φ1.1 mm. When the nozzle diameter is too small, the liquid nitrogen spray amount decreases, and the temperature in the freezing container 11 does not fall to the target temperature, or the cooling time from the normal temperature to the target temperature becomes long. On the other hand, when the nozzle diameter is too large, the liquid nitrogen spray amount increases, and the cooling time from the normal temperature to the target temperature in the cold storage becomes faster, but the running cost increases.

  A control valve (on / off valve or proportional control valve) (not shown) is provided in each path after branching to each nozzle of the liquid nitrogen supply pipe 16, and with this configuration, liquid nitrogen for each stirring fan 12 It is possible to control the supply amount. For example, a piping portion shown by a dotted line in FIG. 1 is a portion in which the supply of liquid nitrogen is stopped by closing the corresponding control valve.

  From the above configuration, the inside of the freezing container 11 is divided into two or more zones in the transport direction of the object to be frozen, and temperature control can be performed for each zone.

  In the present embodiment shown in the drawing, a total of 22 stirring fans 12 are provided in two rows of 11 in a row, but the number of rows and the number thereof are not limited to this. At this time, if the control valve is provided corresponding to each stirring fan 12 (nozzle) as described above, the supply amount of liquid nitrogen can be controlled for each stirring fan 12 (nozzle). In order to control the temperature by division in the direction, it is sufficient if the supply amount of liquid nitrogen can be controlled at least for each row in the cross sectional direction of the freezing container 11. The stirring fans 12 are generally provided at equal intervals in the conveying direction. However, the stirring fans 12 may be provided together with the fan drive motor 13 if they can be detachable or movable by a predetermined distance in the conveying direction. The transport direction width of each zone can be made flexible.

  Therefore, in the present embodiment shown in FIG. 1 and FIG. 2, a rapid freezing zone (LTZ: Low Temperature) is provided upstream of the transport path, taking the case of evenly cooling the cake as the object to be frozen in a short time as an example. The case of forming two zones of Zone (approximately -100 ° C.) and a temperature equalization zone (HTZ: High Temperature Zone) (approximately -10 ° C. to 0 ° C.) downstream thereof will be described. The rapid freezing zone LTZ literally means a zone for rapid freezing of the cake in a short time, and the temperature equalization zone HTZ freezes the cake surface as a result of cooling in the rapid freezing zone LTZ. It is a zone to eliminate the uneven temperature condition that the inside of things is relatively warm.

  In the present embodiment, as a conveyer for conveying the cake in the freezing container 11, the LTZ side conveyer 18a and the HTZ side conveyer 18b are provided corresponding to the rapid freezing zone LTZ and the temperature equalizing zone HTZ, respectively. It is provided. The conveyer may be a single one corresponding to the upstream end to the downstream end of the freezing container 11, but this causes the conveyor belt to move back and forth between the two zones, thereby causing heat exchange and causing the two zones to There is a risk that the temperature difference may not be properly secured. Therefore, as in the present embodiment, it is preferable to provide a dedicated conveyer in each zone. This is the same as when three or more zones are provided.

  The LTZ-side transport conveyor 18a and the HTZ-side transport conveyor 18b are respectively driven by the LTZ-side transport conveyor drive motor 19a and the HTZ-side transport conveyor drive motor 19b, and the LTZ-side transport conveyor 18a and the HTZ-side transport conveyor 18b The transport speed of can be individually controlled by inverter. Moreover, it becomes applicable to various products by changing the width | variety and length of each conveyance conveyor according to the processing amount, the shape, etc. of a product (object to be frozen).

  In the rapid freezing zone LTZ and the temperature equalization zone HTZ, an LTZ side temperature sensor 20a and an HTZ side temperature sensor 20b for measuring the temperature in each zone are provided. The temperature of each zone can be controlled to a desired temperature by controlling the spray amount of liquid nitrogen by adjusting the degree of opening of the control valve based on the measurement results of these temperature sensors. In addition, it is not necessary to necessarily be one temperature sensor in each zone, and a plurality of temperature sensors may be installed at desired positions.

  Moreover, in order to suppress frost formation in each zone in the freezing container 11, it is preferable to provide an exhaust port in each zone. In the embodiment shown in FIGS. 1 and 2, the LTZ side exhaust port 21a is provided at the upstream end corresponding to the rapid freezing zone LTZ, and the HTZ side exhaust port at the downstream end corresponding to the temperature equalization zone HTZ. 21b is provided. At this time, it is preferable to provide a blower at each of the LTZ-side exhaust ports 21a and 21b. Thereby, in the rapid freezing zone LTZ, the flow is in the upstream direction, and in the temperature equalization zone HTZ, it is in the downstream direction, and mixing of nitrogen gas with different temperatures at the zone boundary can be avoided. Note that the displacement of each blower can be individually inverter controlled.

  Furthermore, in order to suppress the inflow of low temperature nitrogen gas from the rapid freezing zone LTZ to the temperature equalization zone HTZ, it is preferable to provide a zone partition plate 17 at the boundary.

  The temperature equalization zone HTZ is susceptible to the influence of low temperature nitrogen gas from the rapid freezing zone LTZ. Therefore, in order to enhance the temperature control accuracy of the temperature equalization zone HTZ, a heater or a room temperature gas may be used in the zone. It is desirable to provide a mechanism that can heat. At that time, it is desirable that the normal temperature gas be an inert gas to prevent oxidation and be dry to prevent frost formation.

Next, an operation method of the continuous freezer 1 of the present embodiment will be described.
As an operation of the continuous freezer 1 of the present embodiment, measurement results by the LTZ side temperature sensor 20a and the HTZ side temperature sensor 20b in order to control the respective temperatures in the rapid freezing zone LTZ and the temperature equalization zone HTZ to desired temperatures. The amount of liquid nitrogen sprayed in each zone is controlled by automatically adjusting the degree of opening of each control valve in each zone.

  Since the amount of liquid nitrogen sprayed to rapid freezing zone LTZ is larger than that of temperature uniforming zone HTZ, the rotational speed of stirring fan 12 in rapid freezing zone LTZ is usually within temperature uniforming zone HTZ. The blower displacement of the LTZ-side exhaust port 21a is larger than that of the HTZ-side exhaust port 21b. Further, the transport speed of each conveyor of the LTZ-side transport conveyor 18a and the HTZ-side transport conveyor 18b is determined by the balance between the cake production amount as the object to be frozen and the effective area of each conveyor.

  As a result, when the object to be frozen (cake) introduced into the freezing container 11 reaches the downstream end of the rapid freezing zone LTZ by the conveyance by the LTZ-side conveyance conveyor 18a of the desired speed, the desired temperature difference is desired. It will have a surface temperature and a desired center temperature. Then, when the object to be frozen is further introduced into the temperature equalization zone HTZ and reaches the downstream end of the temperature equalization zone HTZ by conveyance by the HTZ-side conveyance conveyor 18b of a desired speed, the surface temperature and the center temperature are substantially equal. It will be in a state of being

  As described above, according to the continuous freezer 1 of the present embodiment, a plurality of sets of the nozzle for spraying liquid nitrogen and the stirring fan 12 are provided, and the spraying amount thereof and the rotational speed of the stirring fan 12 are individually controlled. Thus, the rapid freezing zone LTZ and the temperature equalization zone HTZ are continuously provided, and further, the flow of low temperature nitrogen gas is controlled by the exhaust ports 21a and 12b to achieve temperature control of those zones.

  According to this configuration, in the rapid freezing zone LTZ, the cake is rapidly frozen in a short time, and the temperature difference between the surface and the interior generated at that time is equalized to the tolerance in the subsequent temperature equalization zone HTZ. The process time can be shortened, the production volume can be increased, and the workload of workers can be reduced.

  Specifically, the time of the freezing step is reduced to about 14 minutes from the conventional overnight. In addition, when the final end (the most downstream) of the temperature equalization zone HTZ is reached, the surface temperature is -13 to -28 ° C and the center temperature is -13 to -21 ° C. In addition, cracking of the cake surface and scattering of decoration do not occur.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the present invention. For example, in the above-mentioned embodiment, although the configuration in which the two zones of the quick freezing zone LTZ and the temperature equalization zone HTZ are divided is taken as an example, it is not limited thereto, and it is divided into three or more zones. May be For example, another temperature zone may be provided after the temperature equalization zone HTZ in the above-described embodiment. In this case, zone dividers are provided at the boundaries of each zone. Also, an exhaust port is provided in each zone. Here, when three or more zones are provided, the position of the exhaust port in the intermediate zone other than the both end zones is preferably the boundary position between the intermediate zone and the both end zones in the transport direction of the zones. This is because the mixing of nitrogen gas at the boundary of both ends of the zone can be efficiently prevented.

  Moreover, in the above-mentioned embodiment, although the example in the case of setting a zone in the order of the rapid freezing zone LTZ and the temperature equalization zone HTZ from the upstream side and raising the temperature toward the downstream side has been described, Alternatively, the temperature may be lowered stepwise toward the downstream side. As described above, by appropriately selecting the number of divisions of the temperature zone, the set temperature, the configuration order, and the like, it is possible to reduce the time and to set the entire or each part of the object to be frozen to any desired temperature.

Hereinafter, the effects of the present invention will be described in detail using specific examples.
(1) Comparative Example 1 (Conventional freezing method)
Object to be frozen: Cake (W400 × D300 × H30 mm 1.2 kg)
Freezing device: liquefied nitrogen type freezer (Magic cube MC-350)
Freezing method: Atmosphere cooling by low temperature nitrogen gas Cooling temperature: -120 ° C
(result)
When the inside of the product reached the target temperature, the surface became lower than the target temperature (supercooling), and the surface was too hard to be cut. When the product surface reached the target temperature, the inside was in the state of higher than the target temperature (not frozen), and the appearance defect occurred in the product at the time of cutting.

(2) Comparative example 2 (conventional freezing method)
Object to be frozen: Cake (W400 × D300 × H30 mm 1.2 kg)
Freezing device: Liquefied nitrogen type freezer (Magic Freeze MF-100SD)
Freezing method: Atmosphere cooling with low temperature nitrogen gas + liquid nitrogen direct spray cooling temperature: -120 ° C
(result)
The product surface was in the state of below the target temperature (supercooling), and the surface was too hard to cut. In addition, the product surface cracked after freezing due to the fast cooling rate (sprayed with liquid nitrogen).

(3) Example 1
Object to be frozen: Cake (W400 × D300 × H30 mm 1.2 kg)
Freezing device: Liquefied nitrogen type freezer (Magic Freeze MF-500SD special order specification)
Freezing method: Atmosphere cooling by low temperature nitrogen gas Cooling temperature: -100 ° C (rapid freezing zone LTZ)
Isothermal temperature: -10 ° C (isothermal zone HTZ)
(result)
The product could be frozen to a target temperature range with a freezing time of 14 minutes. There were no appearance problems such as breakage of the product surface after freezing.

  The continuous freezer of the present invention can be employed, for example, as a freezing step in a cake production process.

DESCRIPTION OF SYMBOLS 1 ... Continuous freezer 11 ... Refrigeration container 12 ... Stirring fan 13 ... Motor for fan drive 14 ... Fan partition plate 15 ... Liquid nitrogen supply unit 16 ... Liquid nitrogen supply piping LTZ: rapid freezing zone HTZ: temperature equalization zone 17: zone partition plate 18a: LTZ side transport conveyor 18b: HTZ side transport conveyor 19a: LTZ side transport conveyor drive motor 19b ... HTZ side transport conveyor drive motor 20a ... LTZ side temperature sensor 20b ... HTZ side temperature sensor 21a ... LTZ side exhaust port 21b ... HTZ side exhaust port

Claims (3)

A conveyer for conveying an object to be frozen;
Two or more cooling spaces for cooling the objects to be frozen on the transfer conveyor by a low temperature atmosphere;
Two or more of the cooling spaces are provided continuously on the transfer conveyor, and at least the transfer surface of the transfer conveyor is exposed in the cooling space,
Continuous freezer in which the temperature of the low temperature atmosphere of the adjacent cooling space differs. The cooling space has a cooling device for maintaining the low temperature atmosphere,
The continuous freezer according to claim 1, wherein the cooling device has one or more stirring fans for stirring an atmosphere in the cooling space, and one or more nozzles for spraying liquid nitrogen to the stirring fans. .   The continuous freezer according to claim 1 or 2, wherein the cooling space has an exhaust port for forcibly evacuating the atmosphere in the cooling space.

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