JP5049169B2 - Agricultural product pre-cooling method and package - Google Patents

Description

  The present invention mainly relates to a method for precooling vegetables and other agricultural products such as fruits and fruits and a package.

  For example, vegetables and fruits such as vegetables and fruits that require freshness among agricultural products are stored in a foamed synthetic resin container such as polystyrene foam, and pre-cooled and packaged in a closed state. For such pre-cooling, so-called vacuum pre-cooling is generally used in which the inside of the container is evacuated (low pressure) through a vent hole provided in the lid, and the stored fruits and vegetables are evaporated to remove latent heat and cool. At this time, vegetables having a small surface area such as asparagus, which are pre-cooled fruits and vegetables, have a drawback that they cannot be efficiently cooled to a predetermined temperature unless the pre-cooling time is set long because the surface has a small amount of moisture adhering.

  As a solution to such a problem, for example, a vacuum cooling container disclosed in Patent Document 1 or a container such as a vacuum cooling cardboard box disclosed in Patent Document 2 has been proposed.

  The vacuum cooling container disclosed in Patent Document 1 (Japanese Utility Model Publication No. 4-32972) has a gap between the outer box and the metal inner box, and a gauze, sponge, etc. The moisture absorbing / releasing member is placed in a container in a wet and water-retained state, set in a container, and vacuum precooled to evaporate the moisture contained in the moisture absorbing / releasing member and cool the inner box itself with its latent heat. The stored items such as fruits and vegetables inside the container are cooled.

  In this case, moisture-absorbing / releasing members such as gauze and sponge are not easy to handle in a wet and water-retaining state, are difficult to set, and use various materials as moisture-absorbing / releasing members. Sorted collection from the viewpoint is also troublesome. In addition, when used for vacuum precooling of fruits and vegetables with a small surface area relative to the weight, the fruits and vegetables are cooled by heat transfer from the cooled inner box, so that the temperature unevenness and cooling unevenness in the container increase. There was a problem.

  Moreover, in the corrugated cardboard box for vacuum cooling disclosed in Patent Document 2 (Japanese Utility Model Publication No. 4-32971), a waterproof sheet is attached to the inside of the cardboard box, and a moisture absorbing / releasing member such as gauze or paper towel is attached on the inside. Then, after wetting the moisture-absorbing / releasing member with water, putting the fruits and vegetables to be stored inside, closing the lid and reducing the pressure in the chamber of the vacuum precooling chamber, the moisture contained in the moisture-releasing / releasing member is By evaporating, the fruits and vegetables of the contents are cooled.

  In this proposal, the hygroscopic member uses gauze, paper towels, hygroscopic resin, etc., but these hygroscopic members are attached after protecting the inner surface of the cardboard box with a waterproof sheet. It is necessary to keep it on, and the setting work is troublesome. In addition, since the moisture absorbing / releasing member is affixed to the inner surface of the box, it is difficult to wet the moisture absorbing / releasing member to absorb water, and the operation of measuring the amount of water absorbed is complicated. In addition, if the moisture absorbing / releasing member contains a sufficient amount of water, the surface of the moisture absorbing / releasing member becomes excessively wet, or water drops from the moisture absorbing / releasing member, The cardboard box may get wet, and there is also a risk of getting wet agricultural products such as fruits and vegetables.

If the corrugated cardboard gets wet, the corrugated bar box itself becomes weak, and the container shape collapses and is easily deformed or damaged. In order to prevent this, sticking the waterproof sheet to the entire surface of the cardboard box is troublesome and increases costs. Further, when the fruits and vegetables stored as described above get wet with water, there is a risk that the portion will be damaged. For example, even in the case of vegetables such as asparagus stored so as to maintain the same standing posture as during growth, they become easily damaged when wet.
Japanese Utility Model Publication No. 4-32972 Japanese Utility Model Publication No. 4-32971

  The present invention has been made in view of the above, and in vacuum precooling in a state where agricultural products such as fruits and vegetables are stored in a heat insulating container, a continuous cell foam layer and a closed cell foam layer having water absorption are laminated. By using the water-absorbent foam sheet, it can be securely held inside the foam sheet without dripping the absorbed water, and the stored agricultural products can be easily set inside the container without getting wet with excess water, In addition, the present invention provides a pre-cooling method that can reliably evaporate water during vacuum pre-cooling and can cool in a short time, and can efficiently carry out vacuum pre-cooling of agricultural products, and a package of agricultural products that have been vacuum pre-cooled.

  In order to solve the above-mentioned problems, the present invention provides a water-absorbing communication bubble when storing agricultural products in a heat insulating container comprising a foamed synthetic resin container main body and a lid and performing vacuum precooling and packaging. A plate-like water absorption sheet in which a large number of small holes are formed from the surface of the closed cell foam layer to the open cell foam layer. The foamed foam sheet is stored in the container together with the agricultural products in a state where water is absorbed in the open cell foam layer, and moisture in the open cell foam layer is evaporated through the small holes during vacuum precooling. It is characterized by pre-cooling.

  According to this pre-cooling method for agricultural products, during vacuum pre-cooling, the inside of the water-absorbent foam sheet having a laminated structure of an open-cell foam layer having water absorption and a closed-cell foam layer having almost no water absorption, in particular, water absorption. In a state where water is sufficiently absorbed in the open-cell foamed layer, the container is charged into a container and set at a predetermined position. During this setting operation, the water-absorbing foam sheet can be held without dripping water, and there is no possibility of wetting the inner surface of the container or wetting the stored agricultural products with excess moisture. In addition, the water-absorbent foam sheet itself has a moderately rigid plate shape having a shape-retaining property, and is easy to handle and can be set easily.

  When the vacuum is precooled, the water absorbed in the open cell foam layer is gradually sucked and evaporated through a large number of small holes formed in the closed cell foam layer. It can be cooled efficiently using latent heat.

  In particular, the water-absorbent foam sheet has a skin layer having a low degree of open cells on the surface of the open cell type foam layer, and moisture in the open cell type foam layer is opposite to the closed cell type foam layer. By preventing evaporation from the surface, water absorbed in the open cell foam layer may ooze out not only on the surface of the closed cell foam layer other than the small holes but also on the open cell foam layer. There is no risk of getting wet with excess moisture even if the agricultural product is in contact with the surface of the water absorbent foam sheet. On the other hand, when vacuum precooling is performed, moisture can be gradually sucked out from a large number of small holes in the closed-cell foamed layer and evaporated as described above, thereby efficiently cooling.

  By arranging the water-absorbent foam sheet along the inner wall surface of the container with the closed cell foam layer having the small holes facing inward, the latent heat of evaporation from the small holes is used for cooling the agricultural products. It can be used effectively and the cooling effect is enhanced.

  The water-absorbent foam sheet may be formed into a shape corresponding to the storage form of the agricultural product to be packaged. In this case, with the water absorbent foam sheet set inside the container, it can be stored in a state suitable for maintaining the form of various agricultural products such as fruits and vegetables. As a result, the entire agricultural product stored inside the container is well balanced. Cooling can be performed without causing uneven cooling.

  In addition, a large number of the small holes formed at a predetermined interval over the entire surface of the water-absorbent foam sheet has good water absorption when absorbing water, and a large number of small holes over the entire surface during vacuum cooling. By evaporating from the holes all at once, the cooling efficiency is further enhanced.

  Further, the present invention is a package packaged by vacuum precooling by the precooling method of any one of the above inventions, wherein the open cell foam layer having water absorption and the closed cell foam layer are laminated. A plate-like water-absorbent foam sheet, which is a resin foam sheet, in which small holes are formed from the surface of the closed-cell foam layer to the open-cell foam layer, and is stored inside the container together with agricultural products. And

  In this package, agricultural products such as fruits and vegetables that have been precooled and cooled as described above can be well kept in a cooled state. Moreover, even if the water absorbed in the water-absorbent foam sheet for vacuum precooling remains, the water can be reliably retained in the water-absorbent foam sheet, and the inside of the container and agricultural products are not wetted. In addition, the water-absorbent foam sheet has a moderately rigid and shape-retaining plate shape, so that it is not easily deformed or bent during transportation and is stored in the agricultural product. There is no risk of damage.

  Further, when the water absorbent foam sheet is disposed along the inner wall surface of the container with the closed cell foam layer having the small holes facing inward, it is generated by the respiratory heat of agricultural products during transportation. It can also absorb condensed water.

  When the water-absorbent foam sheet is formed into a shape corresponding to the storage form of the agricultural product to be packaged, as described above, the agricultural product can be stored in a state suitable for protecting the agricultural product and being stored. It is also possible to suppress movement during transportation of agricultural products and to provide good protection.

  In the present invention, the open cell foam layer refers to a foam layer having an open cell ratio of 50% or more and substantially water absorption, and the closed cell foam layer refers to the open cell ratio. Of 30% or less, which indicates substantially closed cell characteristics and hardly absorbs water.

  According to the method for precooling agricultural products of the present invention, by using a water absorbent foam sheet formed by laminating an open cell foam layer and a closed cell foam layer having water absorption, It is easy to absorb water, and there is no risk of wetting agricultural products such as the inner surface of the container or the stored fruits and vegetables. The whole agricultural product can be cooled efficiently without unevenness.

  In addition, in the package packaged as described above, it can be kept in a cooled state and there is no risk of wetting agricultural products stored during transportation, and the stored agricultural products such as fruits and vegetables are well protected. Can be made.

  Next, embodiments of the present invention will be described based on examples shown in the drawings.

  FIG. 1 is a perspective view showing a container body and a cover body of a heat insulating container used in the pre-cooling method of the present invention separately from a water absorbent foam sheet, FIG. 2 is a sectional view of the same, and FIG. 3 is a water absorbent used in the present invention. 4 is an enlarged cross-sectional view of a part of the expandable foam sheet, FIG. 4 is an enlarged cross-sectional view of a vent hole portion for vacuum pre-cooling of the heat insulation container, FIG. 5 is a cross-sectional view when storing agricultural products, and FIG. FIG.

  The heat insulating container A1 in this embodiment is a foamed synthetic resin container, and as shown in the figure, basically a container body 10 having a substantially rectangular plane that opens upward, and an opening 11 of the container body 10. And a lid 20 to be attached. In this invention, in order to raise the cooling efficiency at the time of vacuum pre-cooling, the water absorbing foam sheet 30 mentioned later is used together with said heat insulation container A1.

  The container main body 10 and the lid 20 of the heat insulating container A1 are formed of foamed synthetic resin into a shape suitable for storing the agricultural product according to the type of agricultural product to be stored, in addition to a relatively simple flat rectangular box shape. The For example, in the case of the illustrated embodiment, a container used for storing asparagus, pre-cooling in a vacuum and shipping is illustrated.

  Normally, asparagus grows slightly during transportation after being stored in the container body, so that the state in which the asparagus is stood up (standing position) is maintained while being stored in the container. Treated. Therefore, the container body 10 of the heat insulating container 1 according to the illustrated embodiment is formed with a receiving portion 13 for receiving the stem portion 51 of the asparagus 50 accommodated in the bottom portion 12 as shown in FIG. . Since the asparagus 50 to be stored becomes thicker toward the lower side of the stem portion 51, the receiving portion 13 is inclined lower toward the side receiving the lower portion of the stem portion 51 of the asparagus 50, and stores a predetermined amount of asparagus 50. Then, in the state where the heat insulating container A1 is rotated 90 degrees sideways as shown in FIG. 6, the receiving portion 13 is formed to serve as a support for holding the asparagus 50 in a standing posture. .

  Further, as a fitting structure for attaching the lid 20 to the opening 11 of the container body 10, an upward protruding edge 11a is formed on the inner surface side of the opening 11 of the container body 10, and the On the lower surface side of the peripheral edge portion 21 of the lid 20, a fitting groove 21 a that fits into the protruding edge 11 a is provided.

  In order to enable vacuum precooling on the lower surface of the peripheral portion 21 having the fitting groove 21a of the lid body 20, as shown in an enlarged view in FIG. At a plurality of locations such as opposite sides, a ventilation groove 22 that opens to the outer periphery of the lid 20 and extends from the lower surface along the fitting groove 21a to the inside of the container around the protruding edge 11a is provided. In the state where the lid 20 is attached to the container main body 10, the inside and outside of the container communicate with each other through the ventilation groove 22 to allow air flow. The ventilation groove 22 may be formed by bending the inner and outer opening end positions in the circumferential direction by bending the crank groove in the circumferential direction at the inner bottom portion of the fitting groove 21a. As means for communicating the inside and outside of the container for vacuum pre-cooling, various other structures can be used. For example, an openable / closable communication port portion can be formed.

  An arrow 23 indicating the vertical direction of the asparagus 50 to be stored is provided on the upper surface of the lid 20, and the arrow 23 is attached in the vertical direction of the asparagus 50 in a state in which the asparagus 50 is stored. This facilitates the work of standing the heat insulating container A1 sideways as described above.

  The water-absorbing foam sheet 30 used in combination with the heat insulating container A1 is basically composed of an open-cell foam layer 31 having water absorbency and a closed-cell foam having substantially no water absorption. This is a thermoplastic resin foam sheet that is laminated with the layer 32 and has a plate shape that has moderate rigidity and is capable of self-supporting, and can be easily formed into any shape by means such as vacuum molding or press molding. In addition, a large number of small holes 33 are formed by mechanical processing from the surface of the closed cell foam layer 32 to the open cell foam layer 31. In particular, it is desirable that the open cell foam layer 31 has a water retention capacity that allows water to appropriately ooze out from the small holes 33 when pressed.

  The water-absorbent foam sheet 30 may be various thermoplastic resin foam sheets as long as it has a laminated structure of the open-cell foam layer 31 and the closed-cell foam layer 32 and forms a plate shape having shape retention. However, in practice, it is desirable to use a foamed sheet of polystyrene resin that is reasonably rigid and excellent in moldability and shape retention.

  For example, a resin composition containing 0.5 to 5 parts by weight of a surfactant with respect to 100 parts by weight of a mixed resin obtained by adding a hydrogenated product of a copolymer of styrene and a conjugated diene to a styrene resin and a polyolefin resin. A so-called open-cell foam layer 31 having water absorption obtained by foaming a product, and a so-called closed-cell foam layer 32 having mainly water-absorbing and almost no water-absorption obtained by foaming a styrene resin. A foamed sheet of polystyrene-based resin is used.

  The open cell foam layer 31 is made of an aliphatic or alicyclic hydrocarbon such as butane, pentane, etc., in a polystyrene resin, for example, the mixed resin, introduced into an extruder and melted by heating. Open air bubbles by mixing a foaming agent consisting of a kind of resin and setting the resin containing the foaming agent to a resin temperature 10 ° C. higher than that of the closed-cell foamed layer and extruding it from the die at the end of the extruder into the atmosphere. It can be obtained by forming a foamed layer having a high rate.

  As a method of laminating the open cell foam layer 31 and the closed cell foam layer 32, for example, it is preferable to laminate while extruding both foam layers by a co-extrusion method using one extruder, but they are extruded individually. Both foamed layers can be laminated by adhesion or heat fusion means.

  FIG. 4 is an enlarged view of a part of the water absorbent foam sheet 30 obtained as described above. On the surfaces of the open cell foam layer 31 and closed cell foam layer 32 laminated, A skin layer with fine bubbles is formed by quenching during extrusion foaming. Reference numeral 35 denotes a skin layer on the surface of the open cell foam layer 31, and the skin layer 35 suppresses water absorption on the surface of the open cell foam layer 31.

  When the open cell ratio of the open cell foam layer 31 is lower than 50%, the water absorption due to the open cell is low, and the cooling efficiency expected at the time of vacuum precooling cannot be obtained. Further, when the open cell ratio of the closed cell foam layer 32 is higher than 30%, the shape retention and moldability are lowered even when a polystyrene resin foam sheet is used. Accordingly, the open cell rate of the open cell foam layer 31 is 50% or more, more preferably 50 to 80% including the skin layer, and the open cell rate of the closed cell type foam layer 32 is 30% or less, preferably Is 20% or less.

  The small hole 33 is provided on the closed cell foam layer 32 side, opens to the surface of the closed cell foam layer 32 and penetrates from the surface to the open cell foam layer 31. And preferably, a part is formed so as to enter the open cell foam layer 31. In particular, the small holes 33 are required over the entire surface of the water-absorbent foamed sheet 3 as shown in FIG. 1 in consideration of water absorption at the time of vacuum precooling and cooling efficiency due to moisture evaporation. It is preferable to form them so as to form an arrangement with a substantially uniform density at intervals. In addition, the small holes 33 may be formed in a scattered manner in addition to being arranged in a regular manner with their positions shifted vertically and horizontally or diagonally as shown in FIG. Furthermore, it can also form partially in the one part area | region of the said water absorbing foam sheet 3 according to the storage form of agricultural products.

  The shape of the small hole 33 is not limited to a circular hole, and may be an elliptical or rounded square hole, a long hole such as a slit, and other various hole shapes. Moreover, it can also be set as the shape which spreads outward on the inclined surface at the side opened to the surface. Moreover, although the magnitude | size of the small hole 33 changes with the arrangement | positioning space | intervals etc., for example, in the case of a circular hole, internal diameter 0.1-7 mm, in the case of an ellipse, short diameter 0.1-7 mm, long diameter 0.2 -14 mm. Moreover, the arrangement | positioning space | interval of the said small hole 33 shall be 1-70 mm, for example. Of course, implementation outside the above range is also possible.

  The size and shape of the water-absorbent foam sheet 30 may be set to cover the substantially entire surface of the bottom 12 of the container body 10 and the substantially entire surface of the opening 11 depending on the type of agricultural product to be stored. In the case of agricultural products that are easily damaged, such as the tip, shorten the length so that it does not contact the easily damaged portion such as the tip, or cut out a part so that it does not contact the tip. It is preferable to form it like this.

  The thickness of the water-absorbent foam sheet 30 is preferably 1.0 to 8.0 mm, but can be appropriately set according to the usage mode such as the type of agricultural products and the capacity of the heat insulating container A1. Moreover, it is preferable that the open cell foam layer 31 is usually set so as to occupy 1/2 to 4/5 of the thickness of the water absorbent foam sheet 30. In particular, since the amount of water absorption can be controlled by the thickness of the open-cell foamed layer 31, it is preferable to appropriately change and set the thickness within the above range in accordance with the type of agricultural products to be vacuum precooled.

  Further, by laminating the closed cell foam layer 32 on the open cell foam layer 31, the closed cell type foam layer has shape retention and moldability that cannot be obtained by the open cell foam layer alone. The foam layer 32 is preferably 1/5 to 1/2 the thickness of the water absorbent foam sheet 30. That is, if the thickness of the closed cell foam layer 32 becomes too thin, shape retention and moldability deteriorate, so it is preferable to set the range within the above range in relation to the water absorption of the open cell foam layer 31.

  A case will be described in which the water-absorbent foam sheet 30 is used in combination with the heat insulating container A1 to perform vacuum precooling of asparagus, for example, as an agricultural product.

  The asparagus 50 to be precooled is accommodated in the container main body 10 of the heat insulating container A1 as shown in FIG. 6, but in the state in which the water absorbent foam sheet 30 has previously absorbed water, for example, the bottom of the container main body 10 12 is loaded and set on the receiving portion 13 of the device 12. At this time, the water absorbent foam sheet 30 is set with the closed cell foam layer 32 having the small holes 33 facing upward, that is, inward. In this setting operation, the water absorption amount of the water absorbent foam sheet 30 is determined by the thickness of the open cell foam layer 31. For example, the water absorbent foam sheet 30 is immersed in water in a container such as a bucket for several seconds. As a result, a predetermined amount of water corresponding to the thickness of the open cell foam layer 31 is absorbed through the numerous small holes 33 provided in the closed cell foam layer 32. Therefore, it is not necessary to measure the amount of water to be absorbed. In addition, since the water-absorbent foam sheet 30 can be held without dripping the absorbed water, the water-absorbed water does not drop and wet the inner surface of the container, and the water-absorbent foam sheet itself has shape retention. Because it has a certain plate shape, it is easy to handle and can be set easily.

  As shown in FIG. 5, asparagus, which is an agricultural product to be stored, for example, a plurality of asparagus 50 in a bundle is stored on the water absorbent foam sheet 30. At this time, the tip of the asparagus 50 is stored so as not to hit the inner wall surface of the water absorbent foam sheet 30 on the receiving portion 13. After the predetermined amount of asparagus 50 is stored, the water-absorbing foam sheet 30 that has absorbed water in the same manner as described above is also placed on the stored asparagus 50 downward on the side having the small holes 33, that is, on the inner side of the container. Insert and set it up. Thus, in a state where the lid 20 is fitted and attached to the open end 11 of the container body 10, as shown in FIG. 6, the stored asparagus 50 maintains a standing posture with the tip side up. Rotate 90 ° to stand sideways. In this state, the water absorbent foam sheet 30 is loaded and set on both sides of the standing asparagus 50.

  As described above, the heat insulation container A1 is placed sideways in a vacuum precooling chamber, and vacuum precooling is performed by evacuating the interior to a low pressure. At this time, the air in the heat insulation container A1 is, for example, a lid. Moisture absorbed by the open cell foam layer 31 of the water absorbent foam sheet 30 as it is sucked through the ventilation groove 22 in the fitting portion of the body 20 and the inside of the container is evacuated to a low pressure is independent. By gradually sucking out and evaporating through each of the small holes 33 formed in the bubble-type foamed layer 32, the asparagus 50 can be cooled using latent heat generated by the evaporation. In particular, since the large number of small holes 33 are directed toward the inner side of the container, latent heat due to water evaporation from the small holes 33 can be effectively used, and as a result, the entire asparagus 50 as the stored agricultural product is cooled. Cooling can be performed efficiently without causing unevenness.

  When the vacuum pre-cooling is completed in this way, the storage state is maintained and the product is shipped and transported. At this time, even if the water absorbed in the water absorbent foam sheet 30 remains, the water can be reliably retained in the water absorbent foam sheet 30 and does not wet the inside of the container, asparagus, or the like. Moreover, since the water-absorbent foam sheet 30 has a shape-retaining plate shape, the water-absorbent foam sheet 30 is not deformed or bent during transportation, and may be damaged by coming into contact with the stored agricultural products. Absent. Moreover, when taking out the contents at the transportation destination, the water absorbent foam sheet 30 can be easily taken out, and the water absorbent foam sheet 30 does not interfere with the take-out of the contents.

  The plate-like water-absorbent foam sheet 30 used in the present invention can be formed into a shape corresponding to the storage form of the agricultural product to be packaged using its formability. FIGS. 8 and 9 show the water absorbent foam sheet 30 as shown in FIG. 7 in the case where the agricultural product to be shipped after pre-vacuum cooling is asparagus 50 in the same manner as the above-described embodiment of FIGS. The example in the case of shape | molding and using also as the receiving part 13 in the container main body 10 of an above-described Example is shown.

  In the embodiment of FIG. 8, the structure of the heat insulating container A2 is basically the same as that of the above-described embodiment, and the same components are denoted by the same reference numerals and the description thereof is omitted. The receiving part which receives the stem part 51 of the asparagus 50 is not formed. Then, the water absorbent foam sheet 30 formed in the form of FIG. 7 along the bottom portion 12 is set in a water absorption state, and further on the stored asparagus 50, that is, on the lid 20 side as well. A water absorbent foam sheet 30 is disposed. Also in this embodiment, the asparagus 50 is stored with the opening 11 of the container body 10 facing upward, and the cover 20 is attached after the storage, and the state shown in FIG. In this state, it is subjected to vacuum precooling.

  In the embodiment of FIG. 9, the heat insulating container A <b> 3 includes a container body 15 having an opening 16 on the tip side of the asparagus 50 housed as shown in the figure, and a lid attached to the opening 16. 25. The fitting structure of the lid 25 that is attached to the opening 16 of the container body 15 and the communication path inside and outside the container have substantially the same configuration as that of the above-described embodiment. The same reference numerals are used and the description thereof is omitted. Also in the case of this embodiment, the water absorbent foam sheet 30 formed as shown in FIG. 7 is loaded and set on both sides of the asparagus 50 accommodated in the container body 15 so that the lid 25 is covered. It is worn. In this state, it is subjected to vacuum precooling.

  The water-absorbent foam sheet 30 used in the embodiment of FIGS. 8 and 9 has a laminated structure of the open-cell foam layer 31 and the closed-cell foam layer 32 as described in the above-described embodiment, and is closed-cell. A large number of small holes 33 are formed in the mold foam layer 32, and as shown in FIG. 7, a supporting convex portion 37 having an inclined side of the closed cell foam layer 32 having the small holes 33 is formed. The convex portion 37 is used with its side facing the inner side of the container. As shown in FIG. 7, the small hole 33 can be formed only on the inclined surface 37a of the convex portion 37 on the inner side of the container, or can be formed over the entire surface. In practice, it is preferable to form it over the entire surface because the work of absorbing water during use becomes easy.

  In the case of the embodiments shown in FIGS. 8 and 9, as in the case of the above-described embodiment, the work of setting the water absorbent foam sheet 30 and the work of absorbing water are easy, and the inner surface of the container or the asparagus 50 accommodated therein. Therefore, it is possible to satisfactorily cool the entire stored agricultural product without any unevenness by using the latent heat of vaporization of the water absorbed in the water absorbent foam sheet 30.

  In each of the above-described embodiments, the case where the agricultural product to be stored is asparagus has been described. However, the present invention is not limited to this and can be applied to vacuum cooling of other various agricultural products such as fruits and vegetables. In addition, depending on the type of agricultural product, the water absorbent foam sheet 30 can be loaded and set along the inner surface of all the four side walls of the container body or on the bottom or the opening side.

  In the present invention, the foam synthetic resin that is a constituent material of the container bodies 10 and 15 and the lid bodies 20 and 25 of the heat insulating containers A1, A2 and A3 includes styrene-modified polyolefin resin, polystyrene, high impact polystyrene, styrene-ethylene. Polystyrene resins such as copolymers, styrene-maleic anhydride copolymers, styrene-acrylonitrile copolymers, polyolefin resins such as polyethylene, polypropylene, ethylene-vinyl acetate copolymers, polyester resins such as polyethylene terephthalate, etc. Various synthetic resin foams can be used. Especially, the molded object by the bead foaming of a styrene modified polyolefin resin is used suitably.

  In particular, when the heat-insulating container is made of a styrene-based resin foam, by using a polystyrene-based resin foam sheet as the water-absorbent foam sheet 30, both are made of the same material, and collection work for recycling is facilitated. .

[Example]
In order to confirm the effect of cooling by vacuum pre-cooling using a water-absorbent foam sheet, vacuum pre-cooling was carried out for asparagus as agricultural products as follows.

  As a container for performing vacuum precooling, a heat insulating container A1 having a ventilation groove in the fitting portion of the lid was used in the form shown in FIGS.

  Further, as the water-absorbent foam sheet, an open cell foam layer 31 having a open cell ratio of 70% and a thickness of 2.2 mm and a closed cell foam layer 32 having a open cell ratio of 10% and a thickness of 0.6 mm are laminated, In addition, a plate-like water-absorbent foam sheet of polystyrene resin in which a large number of elliptical small holes 33 having a minor axis of 1.0 mm are formed at intervals of 10 mm in the closed cell foam layer 32 is made to have a size of 200 mm in length and width. 2 sheets were used.

  In a state where the water-absorbing foam sheet is immersed in water and absorbed in the open cell foam layer, the water-absorbent foam sheet is placed on the receiving portion 13 at the bottom in the container body 10 of the heat insulating container A1 as shown in FIG. The asparagus 4 kg (40 bundles of 100 g of one bundle) is placed on the water absorbent foam sheet 30 and the same as described above. The water-absorbing foam sheet that had been absorbed in was inserted with the side having the small holes facing downward, and the lid 20 was attached to the container body 10. Thereafter, the container was rotated 90 ° so that the tip of the asparagus faced upward, and the container was placed sideways, and a predetermined number was placed on the pallet and placed in a vacuum precooling chamber to perform precooling.

  In the pre-cooling process, after pre-cooling the vacuum pre-cooling chamber by roughing for a certain time (about 17 minutes from the start), intermittent operation is performed so that the internal pressure is kept below a certain level by main pulling by a vacuum pump. Pre-cooling treatment was performed while controlling.

  In this pre-cooling treatment, three points (a, b, and c in FIG. 6) are provided on the back side (bottom side), the center portion, and the near side (lid side) of the asparagus stem portion inside the container. At three points), a thermometer was inserted and fixed to the core of each asparagus, and the temperature during the precooling treatment was measured over time. The measurement results are shown in FIG. 10 for the back side (point a), in FIG. 11 for the central portion (point b), and in FIG. 12 for the near side (point c).

  10 to 12, the conventional example in which the vacuum precooling was performed in the same manner as in the example of the present invention except that the asparagus gas was accommodated in the container without using the water absorbent foam sheet was similarly provided in the same three points as described above. The results of measuring the temperature are also shown.

Table 1 below shows the amount of water absorption and the amount of residual water and the amount of evaporation during water-containing and after pre-cooling by measuring the weight of the water-absorbent foam sheet before and after the pre-cooling treatment.

  As is clear from FIGS. 10 to 12, in the case of the embodiment of the present invention, the temperature drop at each of the three points is faster than the conventional example, and the temperature is lowered to a lower temperature than the conventional example. The intended low temperature (7-8 ° C.) was obtained in a short time.

  The present invention can be suitably used for vacuum precooling of fruits and vegetables such as vegetables and fruits and other various agricultural products.

It is the perspective view which partly lacked and shown the container main body of the heat insulation container used in the pre-cooling method of this invention, a cover body, and a water absorbing foam sheet. It is sectional drawing same as the above. It is a partial expanded sectional view of the water absorbing foam sheet used by this invention. It is an expanded sectional view of the vent hole part for the vacuum precooling of the heat insulation container. It is sectional drawing at the time of storage operation of agricultural products. It is sectional drawing at the time of the vacuum precooling of agricultural products. It is the perspective view which a part of which showed the example which shape | molded the water absorbing foam sheet was missing. It is sectional drawing which shows the other Example of this invention. It is sectional drawing which shows other Example of this invention. It is a temperature change graph of the back | inner side (point a) during a pre-cooling process. It is a temperature change graph of the center part (b point) during a pre-cooling process. It is a temperature change graph of the near side (point c) during a pre-cooling process.

Explanation of symbols

  A1, A2, A3 ... heat insulating containers, 10, 15 ... container main body, 11, 16 ... opening, 11a ... projecting edge, 12 ... bottom, 13 ... receiving part, 20, 25 ... lid, 21 ... peripheral part, 21a DESCRIPTION OF SYMBOLS ... Fitting groove, 22 ... Ventilation groove, 23 ... Arrow, 30 ... Water-absorbing foam sheet, 31 ... Open-cell foam layer, 32 ... Closed-cell foam layer, 33 ... Small hole, 35 ... Skin layer, 37 ... Convex part, 37a ... inclined surface, 50 ... asparagus, 51 ... stem part.

Claims (6)

In the heat insulation container consisting of a foamed synthetic resin container body and lid, the agricultural products are stored and vacuum precooled for packaging.
A thermoplastic resin foam sheet in which a water-absorbing open-cell foam layer and a closed-cell foam layer are laminated, and a large number of small holes are formed from the surface of the closed-cell foam layer to the open-cell foam layer. The plate-like water-absorbing foam sheet is stored in the container together with the agricultural products in a state where the open-cell foam layer absorbs water, and the water in the open-cell foam layer is preliminarily vacuum-cooled. A method for pre-cooling agricultural products, characterized in that pre-cooling is performed while evaporating the water through the small holes.   The water-absorbent foam sheet has a skin layer having a low degree of open cells on the surface of the open cell type foam layer, and moisture in the open cell type foam layer from the surface opposite to the closed cell type foam layer. The method for precooling agricultural products according to claim 1, wherein evaporation is not performed.   The method for precooling agricultural products according to claim 1 or 2, wherein the water-absorbent foam sheet is disposed along the inner wall surface of the container with the closed cell foam layer having the small holes facing inward.   The method for precooling agricultural products according to any one of claims 1 to 3, wherein the water-absorbent foam sheet is formed into a shape corresponding to a storage form of agricultural products to be packaged.   The method for precooling agricultural products according to any one of claims 1 to 4, wherein a large number of the small holes are formed at predetermined intervals over the entire surface of the water-absorbent foam sheet.   A packaging body in which agricultural products are stored in a heat insulating container made of a foam synthetic resin container body and a lid, and vacuum precooling is performed by the precooling method according to any one of claims 1 to 5. And a thermoplastic resin foam sheet in which an open cell type foam layer and a closed cell type foam layer are laminated, and a plate-like shape in which small holes are formed from the surface of the closed cell type foam layer to the open cell type foam layer. A packaging body for agricultural products, wherein the water-absorbent foam sheet is housed in a container together with agricultural products.