JP5086000B2 - Method for producing frozen sushi package - Google Patents

Description

  The present invention relates to a method for producing a frozen sushi package that can provide sushi after thawing without impairing the freshness before thawing.

  Conventionally, raw fish (fresh fish) and sushi containing raw fish have been frozen and preserved as a method of preserving their freshness over a long period of time. However, after thawing, changes in the color of raw fish, deterioration of taste, and drip (The outflow of liquid from the raw fish at the time of thawing) or the like occurs, and it is the actual situation that deterioration of quality and freshness cannot be prevented. In particular, tuna, which is a sushi item preferred by many Japanese, has such problems when stored for a long time even if it is frozen at -20 ° C.

  Further, white rice constituting the sushi lump of sushi is often frozen and stored, for example, when a large amount is cooked in the home, but generally it is kept at a temperature of 10 ° C. or less (particularly 8 ° C.) for a long time. Even if it is stored, it becomes senile, and even if it is frozen and stored for a long period of time, there is a problem that aging occurs after thawing after 1 to 2 months.

  Especially in the logistics industry related to frozen foods, it takes a long time for a product to reach from the place of manufacture to the place of sale, especially when the country of manufacture differs from the place of sale. However, due to the problems described above, Japanese people who prefer tuna sushi lived around the world, but it was difficult to freeze and export tuna sushi.

  Here, to-be-frozen objects such as raw fish and shrimp lump can freely move in the to-be-frozen object without being bound by the above-mentioned bound water bound by molecules such as proteins constituting the to-be-frozen object. Has a large amount of water, such as free water. When freezing, the free water freezes, and ice crystals are generated and grow and grow coarse, destroying the structure of cells in the raw fish and shrimp mass. Due to the structure, drip is generated, and it becomes difficult to restore the object to be frozen to a fresh state before freezing.

  In general, the coarsening of ice crystals as described above occurs when the time for passing through the ice crystal formation temperature range is long during freezing. In view of this point, various refrigeration apparatuses and refrigeration methods that do not impair the freshness before thawing after thawing have been proposed. For example, by immersing the object to be frozen in a liquid refrigerant or by spraying the liquid refrigerant on the object to be frozen, it is rapidly cooled to quickly pass through the ice crystal generation temperature range, and the ice crystals are coarsened. A method of suppressing it is conceivable.

  However, in the method of immersing the object to be frozen in the liquid refrigerant or spraying the liquid refrigerant on the object to be frozen, the surface layer of the object to be frozen can be rapidly cooled, but a frozen layer is formed only on the surface layer. Tend to be. The cooling of the inside of the object to be frozen is limited by the heat transfer from the surface, but it is delayed because the heat transfer is hindered by the presence of the surface frozen layer, and the ice crystals are coarse in the object to be frozen. There is a problem that it cannot be effectively prevented.

For such a problem, for example, Patent Document 1 discloses a step of supplying a deoxidized material, a step of manufacturing a vacuum pack including an object to be frozen together with the deoxidized material, a step of heating the vacuum pack, and the vacuum pack. A freezing method including a step of freezing the object to be frozen while supplying a static magnetic field in a substantially vertical direction and supplying a radio wave in a substantially horizontal direction to the vacuum pack is disclosed.
Utility Model Registration No. 3126049 Specification

  However, even with the technique described in Patent Document 1, the actual situation is that after the thawing, the color change of the raw fish, the deterioration of the taste, the drip, etc. occur, and the deterioration of the quality and freshness cannot be sufficiently prevented. .

  In addition, conventional frozen foods are distributed and sold in the market by packaging a plurality of items to be frozen in aluminum vapor deposition packs or packaging individual items to be frozen in vacuum packs, etc. In the aluminum vapor deposition pack, raw foods come off from the shrimp lump when transported, and in the above vacuum pack, raw foods come off from the shrimp lump at the time of opening, and if you try to eat a large number of sushi during meals, the opening work is troublesome. There is also the problem of being.

  Therefore, the present invention does not cause a change in color tone, deterioration of taste, drip, etc. even when naturally thawed after long-term frozen storage, and can sufficiently prevent deterioration in quality and freshness. An object of the present invention is to provide a sushi package, particularly a frozen sushi package that is not deformed during transport and opening.

In order to solve the above problems, the present invention provides:
(1) A step of cooking sushi including a shrimp lump and raw ingredients placed on the shri lump;
(2) A step of freezing the sushi to obtain frozen sushi while supplying radio waves propagating in a direction substantially perpendicular to the direction of the magnetic field lines in a static magnetic field including unidirectional and substantially uniform magnetic field lines;
(3) A step of placing the frozen sushi in a container having an opening on the upper surface; and (4) a shape of the frozen sushi covered on the thermoplastic film by covering the upper surface of the container with a heated thermoplastic film in a reduced-pressure atmosphere. Forming a recessed portion having substantially the same shape as the above and storing the frozen sushi in the recessed portion and holding it on the upper surface;
Including
In the step (2), the magnetic flux density of the static magnetic field is 100 gauss to 150 gauss, the average magnetic flux density is 110 gauss to 130 gauss, the frequency of the radio wave is 500 kHz, and the ambient temperature is −35 ° C. to −40 ° C. and about -20 ° C. the sushi core temperature during freezing, the temperature of about -22 ° C. and be Rukoto between the raw food material and the shari mass during freezing,
A method for producing a frozen sushi package characterized by the above.

  According to such a configuration, even when the food is naturally thawed after long-term frozen storage, there is no change in the color tone of raw ingredients made of raw fish, deterioration of the taste, drip, etc., and the deterioration of quality and freshness is sufficiently prevented. It is possible to reliably provide frozen sushi that can be carried out, in particular, frozen sushi that does not deform during transportation and opening.

  Here, the “shari chunk” is a chunk of rice for sushi (sushi rice), and is usually obtained by mixing vinegar with rice. In this invention, there is no limitation in particular in the kind of the said cooked rice, the said vinegar, and the said sushi rice obtained by these, What is generally used for sushi can be used.

  “Raw food” placed on the shari lump means raw fish (including partially baked food) used mainly as so-called sushi material, and other raw meat (partially baked food, etc.) And raw vegetables (including partially baked foods).

  In addition, the “static magnetic field including unidirectional and substantially uniform magnetic field lines” will be described in detail later, but within the static magnetic field, the magnetic flux density of the magnetic field lines is substantially constant, and the magnetic field lines are substantially in one direction. It means running almost linearly.

  According to the present invention, even when natural thawing is performed after long-term frozen storage, the color tone of raw ingredients, taste deterioration, drip and the like do not occur, and the freezing that can sufficiently prevent deterioration in quality and freshness. It is possible to provide a sushi package, particularly a frozen sushi package that is not deformed during transportation and opening.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. However, the following embodiments are merely representative, and the present invention is not limited to these. FIG. 1: is the perspective view which made one part transparent the structure which shows the structure of the freezing apparatus used in process (2) among the manufacturing methods of the frozen sushi package which concerns on this invention.

Process (1)
First, in step (1), sushi is cooked that includes a shrimp lump and raw ingredients arranged on the shri lump. This step may be performed by a conventionally known method. In addition, examples of the raw food include those described above, but the remarkable effects of the present invention can be obtained particularly in the case of raw fish such as tuna, yellowtail, hamachi, amberjack and skipjack.

Process (2)
Next, as the step (2), the sushi is frozen while supplying radio waves propagating in a direction substantially perpendicular to the direction of the magnetic force lines in a static magnetic field including unidirectional and substantially uniform magnetic force lines. Get frozen sushi.

  A freezer 1 shown in FIG. 1 includes a freezer 4 for freezing sushi 2, a static magnetic field consisting of lines of magnetic force that run in a substantially vertical direction with respect to sushi 2 in the freezer 4 (that is, the direction indicated by arrow X in FIG. 1). A static magnetic field generator 6 for generating a unidirectional static magnetic field including substantially uniform magnetic lines), and a substantially horizontal direction with respect to the sushi 2 in the freezer 4 (a direction substantially perpendicular to the direction of the magnetic lines, ie, 1 includes at least a radio wave supply device 8 that supplies radio waves propagating in a direction indicated by an arrow Y in FIG.

  The freezer 4 included in the refrigeration apparatus 1 constitutes the internal space of the refrigeration apparatus 1 and has a refrigeration function in the present embodiment. In addition, although the freezer 4 in FIG. 1 is a rack type batch type, any of a tunnel type, a spiral type, etc. may be sufficient and can be used for this invention in each case.

  The freezer 4 includes refrigeration means, and the refrigeration means includes a compressor, a condenser, an expansion valve, a cooling pipe (evaporator), etc., which are not shown in the figure, and is a generally known quick refrigeration cycle device that circulates refrigerant. Etc. can be used. The expansion valve and the cooling pipe (evaporator) are installed in the internal space of the freezer 4 and contribute to the generation of cold air.

  And the static magnetic field generator 6 which can arrange | position the sushi 2 to the static magnetic field containing a substantially uniform magnetic force line in the freezer 4 is the plate-shaped upper part installed facing in parallel in the substantially horizontal direction. It includes a magnetic member 6a and a lower magnetic member 6b, and a support 6c that supports the upper magnetic member 6a and the lower magnetic member 6b.

  More specifically, each of the upper magnetic member 6a and the lower magnetic member 6b includes a plate-like permanent magnet, and the static magnetic field generating means 6 has the above structure, so that the upper magnetic member 6a By arranging the sushi 2 between the lower magnetic member 6b, a static magnetic field composed of magnetic field lines that are unidirectional and substantially uniform in a substantially vertical direction through a fixed space between the two by the support 6c. It is formed.

Further, as the permanent magnets, for example, it is preferable to use ferrite magnets, the effect of the between the upper magnetic member 6a and the lower magnetic member 6b, the present invention if caused to generate a static magnetic field of 1 00-150 gauss It can be obtained more reliably. The average magnetic flux density is preferably 110 to 130 gauss, especially about 120 gauss.

  The spacing between the upper magnetic member 6a and the lower magnetic member 6b, the specifications, number and spacing of the permanent magnets included in the upper magnetic member 6a and the lower magnetic member 6b, the configuration of the holder used to hold the permanent magnets, and the like are desired. A person skilled in the art can select as appropriate on the condition that the static magnetic field is generated in a substantially vertical direction (that is, the direction indicated by the arrow X in FIG. 1) in consideration of the strength and uniformity of the static magnetic field. it can.

A radio wave supply device 8 that supplies radio waves in the freezer 4 to the sushi 2 in a substantially horizontal direction (that is, a direction indicated by an arrow Y in FIG. 1) includes radio wave transmitters 8a and 8b and an amplifier (not shown). ) and is configured de, 3 00kHz~600kHz, particularly preferably supplies radio waves included in a region of radio wave having a frequency of about 500 kHz.

  By supplying such long-wave radio waves to sushi 2, the position of water molecules (protons) contained in the sushi mass and raw ingredients of sushi 2 can be shaken without significant change. Thus, the arrangement of water molecules during freezing can be realized more reliably. Conventionally known radio wave transmitters 8a and 8b and amplifiers as described above can be used. For example, as the radio wave transmitters 8a and 8b, for example, a coil antenna can be used.

  In this step (2), the temperature in the freezer 4 (atmosphere temperature of sushi 2) is preferably set to -35 ° C to -45 ° C (particularly -40 ° C). Within this temperature range, the sushi 2 can be frozen (frozen) rapidly for several minutes to several tens of minutes, preferably 15 minutes to 30 minutes, without further damaging the shaving lump or raw food.

  Among them, the center temperature of sushi 2 (that is, the temperature measured at the substantially central portion of the sushi block by inserting a thermometer inside the sushi block) is about −20 ° C. It is preferable that the ambient temperature (that is, a temperature measured by inserting a thermometer between the sushi 2's shards and raw ingredients) is about -22 ° C.

  In addition to the freezer 4 and the static magnetic field generator 6, the freezer 1 may be provided with a cold air circulation device 10 that circulates cold air (cold air) that cools the sushi 2 contained in the internal space of the freezer 4. . According to such a configuration, it is possible to prevent cold air from being unevenly distributed in the freezer 4, and the sushi 2 arranged in the freezer 4 can be more reliably and uniformly frozen.

Process (3)
Next, in the step (3), the frozen sushi is placed in a container having an opening on the upper surface. As a container which can be used here, various things can be used if sushi can be arrange | positioned on an upper surface and it can package with a thermoplastic film, The material and shape are not specifically limited, either.

  However, from the viewpoint of excellent adhesion to the thermoplastic film used in the step (4) described later, it is preferable to use a container made of polypropylene or polystyrene. Here, FIG. 2 is a schematic perspective view of the container 12 that can be suitably used in the method for producing a frozen sushi package according to the present invention. As shown in FIG. 2, it is preferable to use a container 12 having a space 12a in which a thermoplastic film can be more reliably heat-sealed.

  Further, the number of frozen sushi to be arranged is not particularly limited, but as will be described later, the thermoplastic resin film used in the present invention is formed with a recess having a shape substantially the same as the shape of each frozen sushi. And the said frozen sushi is accommodated in the said recessed part, and it is especially preferable when arrange | positioning two or more frozen sushi.

Step (4)
In step (4), the upper surface of the container is covered with a heated thermoplastic film in a reduced-pressure atmosphere, a recess having a shape substantially the same as the shape of the frozen sushi is formed in the thermoplastic film, and the frozen sushi is It is accommodated in the recess and held (packaged) on the upper surface.

  The thermoplastic film used here can be softened by heating to form a recess having the same shape as that of the frozen sushi, and the frozen sushi and the upper surface of the container are packaged under a reduced pressure atmosphere (ie, under vacuum). Anything that can be packaged (that is, vacuum packaging or vacuum contact packaging) may be used. Examples thereof include olefin resins such as low density polyethylene, high density polyethylene, polypropylene, ethylene-α-olefin copolymer, and polymethylpentene.

  Especially, it has a certain amount of flexibility even after packaging, and when opening the obtained frozen sushi package, it is preferable that the sushi is not damaged. Moreover, it is suitable for vacuum packaging or vacuum contact packaging, and it is preferable to use a gas-impermeable thermoplastic film from the viewpoint that the obtained frozen sushi package does not adversely affect sushi as much as possible from outside air.

  A particularly preferable thermoplastic film is a thermoplastic film having a three-layer structure including an ethylene vinyl alcohol film, an ionomer film, and an ethylene vinyl acetate film. Such a thermoplastic film is softened by heating and forms a recess having a shape substantially the same as the shape of frozen sushi when vacuum-packed or vacuum-tightly wrapped, and securely holds the frozen sushi by the above container, and is packaged. Since it has some flexibility afterwards, it will not damage the sushi when opened.

  Here, the reduced pressure atmosphere in this step (4) (that is, the degree of vacuum in the vacuum chamber used for vacuum packaging or vacuum tight packaging) is the size and shape of the container, the number and shape of frozen sushi, the temperature of the container and frozen sushi. As a result of intensive studies by the present inventors, it has been found that -0.05 MPa to -0.20 MPa and -0.05 MPa to -0.10 MPa are preferable.

  Further, the heating temperature of the thermoplastic film used for vacuum packaging or vacuum contact packaging varies depending on the material of the thermoplastic film and the degree of vacuum at the time of packaging, but in the case of the thermoplastic film having the above three-layer structure, it is about 100. What is necessary is just -150 degreeC (preferably 130 degreeC).

  In this way, a frozen sushi package 20 according to the present invention as shown in FIG. 3 can be obtained. FIG. 3 is a schematic longitudinal sectional view showing an embodiment of the frozen sushi package 20 obtained by the method for producing a frozen sushi package according to the present invention.

  The frozen sushi package 20 shown in FIG. 3 includes three frozen sushi pieces 22 including a shrimp lump 22a and raw food material 22b, and is a thermoplastic that accommodates the frozen sushi piece 22 in a recess having substantially the same shape as the frozen sushi piece 22. The top surfaces of the frozen sushi 22 and the container 26 are packaged by the resin film 24.

  In the frozen sushi package obtained by the method for producing a frozen sushi package according to the present invention, first, the peripheral portion of the thermoplastic resin film is opened, and the outside air is slowly taken in from the lower portion of the frozen sushi 22 and thawed. Can do.

  In this way, since the raw food 22b can be thawed while being gradually thawed from the shank lump 22a and suppressing the attachment of condensed water from the outside air to the raw food as much as possible, the color tone of the raw food at the time of thawing Change, taste deterioration, drip and the like do not occur, and deterioration of quality and freshness can be sufficiently prevented.

  In addition, when a plurality of frozen sushi is included, the thermoplastic resin film has flexibility, has a plurality of concave portions having substantially the same shape as each frozen sushi, and each frozen sushi Since it accommodates in a recessed part, a shaving lump and a raw material do not collapse at the time of conveyance and opening, and deformation | transformation of frozen sushi or sushi can be suppressed effectively.

  As mentioned above, although typical embodiment of this invention was described, this invention is not limited only to these. For example, the frozen sushi package may contain one or more frozen sushi. Moreover, in the frozen sushi package, the frozen sushi may be arranged in parallel, arranged in series, or arranged in a combination of parallel and series.

"Example"
First, shari lump was made with sushi rice obtained by mixing vinegar with cooked rice, and raw tuna fillets were placed on top of it to cook a plurality of tuna sushi (step (1)). Next, a plurality of these tuna sushi were placed in a BU-150 type full-use freezer manufactured by Ryoho Freeze Co., Ltd. and rapidly frozen for about 30 minutes (step (2)).

  At this time, in the youthful freezer, a static magnetic field atmosphere of 100 to 150 gauss was formed in the space where tuna sushi was placed, radio waves having a frequency of about 300 kHz to about 600 kHz were propagated, and the temperature was set to −40 ° C. . In addition, a thermometer is inserted into the sushi chunk and the temperature measured at the substantially central portion of the sushi chunk is about −20 ° C. A thermometer is inserted between the sushi chunk and raw ingredients. The measured temperature was about -22 ° C.

  The above three frozen sushi pieces are placed on a polypropylene tray having the shape shown in FIG. 2 (step (3)), and Hipack E film (ethylene) is used with Hipack vacuum contact packaging machine HI-750. A three-layer film of a vinyl alcohol film, an ionomer film and an ethylene vinyl acetate film) is heated to about 130 ° C. to be softened, and the upper surface of the container is vacuum-sealed and packed with frozen sushi at a vacuum degree of −0.09 MPa. Sushi package A was obtained (step (4)).

《Comparative example》
A frozen sushi package B was obtained in the same manner as in the above example except that the sushi was frozen in a commercial freezer.

[Evaluation]
After storing the frozen sushi package A obtained in the above example and the frozen sushi package B obtained in the above comparative example in a commercial freezer, a part of the thermoplastic resin film is cut so that the outside air enters the inside. And left in a room at about 30 ° C. After 3 hours, all the tuna sushi contained in the frozen sushi package A and the frozen sushi package B were thawed, but the tuna sushi in the frozen sushi package A did not have any tuna color change or drip. Although the taste was also delicious, the tuna sushi of the frozen sushi package B had a color change and drip, and the taste was poor.

  According to the present invention, even when thawed after freezing for a long period of time, frozen sushi that can sufficiently prevent deterioration in quality and freshness without causing a change in color tone, deterioration in taste, drip, etc. It is possible to provide a package, particularly a frozen sushi package that is not deformed during transportation and opening. Therefore, the frozen sushi package obtained in the present invention is suitable for export to remote places such as overseas.

It is the perspective view which made one part transparent the structure which shows the structure of the freezing apparatus used in the process (2) among the manufacturing methods of the frozen sushi package which concerns on this invention. It is a schematic perspective view of the container 12 which can be used suitably for the manufacturing method of the frozen sushi package which concerns on this invention. It is a schematic longitudinal cross-sectional view which shows one Embodiment of the frozen sushi package 20 obtained by the manufacturing method of the frozen sushi package which concerns on this invention.

1 ... Refrigeration equipment,
2 ... Sushi,
4 ... Freezer
6 ... Static magnetic field generator,
8: Deoxidizing material supply device,
10 ... cold air circulation device,
12, 26 ... containers,
12a space
20 ... Frozen sushi package,
22 ... Frozen sushi,
22a ... Shari lump,
22b ... raw food (material),
24: Thermoplastic resin film.

Claims (5)

(1) A step of cooking sushi including a shrimp lump and raw ingredients placed on the shri lump;
(2) A step of freezing the sushi to obtain frozen sushi while supplying radio waves propagating in a direction substantially perpendicular to the direction of the magnetic field lines in a static magnetic field including unidirectional and substantially uniform magnetic field lines;
(3) A step of placing the frozen sushi in a container having an opening on the upper surface; and (4) a shape of the frozen sushi covered on the thermoplastic film by covering the upper surface of the container with a heated thermoplastic film in a reduced-pressure atmosphere. And forming a recess having substantially the same shape as the above and storing the frozen sushi in the recess and holding it on the upper surface;
In the step (2), the magnetic flux density of the static magnetic field is 100 gauss to 150 gauss, the average magnetic flux density is 110 gauss to 130 gauss, the frequency of the radio wave is 500 kHz, and the ambient temperature is −35 ° C. to −40 ° C. and about -20 ° C. the sushi core temperature during freezing, the temperature of about -22 ° C. and be Rukoto between the raw food material and the shari mass during freezing,
The manufacturing method of the frozen sushi package characterized by this. The container in the step (3) is made of polypropylene or polystyrene;
The manufacturing method of the frozen sushi package of Claim 1 characterized by these. The thermoplastic film in the step (4) is gas-impermeable,
The manufacturing method of the frozen sushi package of Claim 1 or 2 characterized by these. The thermoplastic film has a three-layer structure containing ethylene vinyl alcohol, ionomer, and ethylene vinyl acetate;
The manufacturing method of the frozen sushi package in any one of Claims 1-3 characterized by these. The method for producing a frozen sushi package according to any one of claims 1 to 4 , wherein the atmosphere in the step (4) is reduced to -0.05 MPa to -0.20 MPa.

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