JPH11332458A - Storage of food and storage case - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for storing fresh foods of e.g. fruits, vegetables or meat at subfreezing temperatures without a possibility of freeze, besides, for a long period at a low cost, and to provide a case therefor. SOLUTION: This case comprises: a case main body 1 surrounded with a heat-insulating material; and a transcalent liquid tank 4 receiving a liquid 5 with a freezing point of <=0 deg.C and designed to penetrate into the top surface or any side surface of the case main body 1. The other objective method is conducted by storing any food 3 in the case and setting the case in a refrigerator having a mean temperature of <0 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and a container for storing food. In particular, the present invention relates to a method of storing fresh vegetable or animal food in an electric refrigerator at a temperature as low as possible, near freezing, without causing freezing, and a storage container therefor.

[0002]

2. Description of the Related Art In order to extend the storage period of fruits and vegetables,
Storage in refrigerators is widely practiced. Fruit and vegetable cells are alive after harvest and ripen during refrigeration. Since the progress of ripening is generally suppressed at lower temperatures, the lower the temperature, the longer the storage period. However, when frozen, many of the cells are destroyed by ice crystals generated inside and outside the cells, and the quality after thawing is significantly inferior to fresh ones. For example, it becomes extremely soft and has a watery taste, and on standing, sap (called drip) exudes. For this reason, it is necessary to keep the fruits and vegetables from freezing during refrigeration.

[0003] Although there are frozen foods of vegetables, most of them are cooked products, and the types of fresh frozen foods are extremely limited, and they are also subjected to surface heating treatment (called blanching).

There are so-called "ice storage" and "ice temperature storage" as a method of storing at a low temperature that does not cause freezing. However, in order to prevent freezing, the average temperature in the refrigerator was set to -1 ° C to 2 ° C (except in some cases, where the fig was hard to freeze, the temperature was set to -2 ° C).

Although the freezing temperature of fruits is -2 to -5 ° C, the reason why the average temperature in the refrigerator is -1 ° C or higher is that both in the direct cooling system and the cold air circulation system, Since intermittent operation generally causes temperature fluctuations of ± 2 ° C or more, if the average temperature in the refrigerator is set to less than -1 ° C, the freezing temperature of the food is reached when the temperature fluctuates to a lower temperature, and at least a portion of the food is at least partially frozen. This is because freezing occurs.

In the case of the brine circulation system, the time variation of the temperature inside the refrigerator is slightly small and is about ± 1.5 ° C. However, since there is a problem of temperature unevenness depending on the location in the refrigerator, the average temperature in the refrigerator is reduced by -−. It was still difficult to lower it below 1 ° C. The brine circulation system has the further disadvantage of high equipment costs.

[0007] In the case of animal food such as animal meat, fish meat, etc., cells are in a dead state unlike plant foods. Fish meat is widely stored frozen. However, fish meat is also refrigerated (non-frozen) after thawing, and some animal meat is stored without freezing (for example, horse meat), depending on the type, because of the dislike of freezing and alteration due to thawing. Even in refrigeration, the lower the temperature, the longer the storage period can be, but if the temperature is lowered and partial freezing occurs, the quality such as taste and tongue deteriorates.

If perishable foods such as fruits, vegetables and raw meat can be stored at an average temperature of less than -1 ° C. without freezing, the storage period in a refrigerator can be further extended compared to ice temperature storage. be able to.

An object (1) of the present invention is to provide a method for storing fresh foods such as fruits, vegetables, meats and the like in a refrigerator for a long time without freezing. It is an object of the present invention to provide a method of storing at a temperature as low as possible below the freezing point without fear.

The object (2) of the present invention is that fruits, vegetables,
Provided is a container for storing fresh food such as meat in a refrigerator for a long time without freezing, particularly a container for storing a fresh vegetable food at a temperature as low as freezing below the freezing point without fear of freezing in a refrigerator. Is to provide.

[0010]

According to the present invention, the above object (1) is achieved by storing a container body made of a heat insulating material for storing food to be stored and a solid or liquid having a freezing point of 0 ° C. or less. And a liquid tank made of a heat conductor.
This liquid tank stores food in a storage container provided through at least one surface selected from the top surface and the side surface of the container main body, and stores the food in a refrigerator having an average temperature of less than 0 ° C or more than -5 ° C. Achieved by the method.

In the present invention, the object (2) is provided so that a container body surrounded by a heat-insulating material for storing food and at least one surface selected from a top surface and a side surface of the container body are penetrated. A liquid tank made of a heat conductor, provided with a liquid or solid having a freezing point of 0 ° C. or less.
Achieved by food storage containers.

Although the shape of the container body is not particularly limited, a rectangular parallelepiped is preferable from the viewpoint of the efficiency of use of the space in the refrigerator. Foamed plastics are useful as the heat insulating material, for example, foamed polyurethane and foamed polystyrene. The thickness of the heat insulating material is desirably 5 mm or more, preferably 15 mm or more. Although the heat insulation performance is slightly inferior, a box such as a step ball or a step plastic (plastic step ball-shaped material) can be used. The container body may have a door, a sliding door, a hanging curtain, etc. that can be opened and closed on at least a part of the top or side surface so that food can be taken in and out. The container body may be in the form of a flat dish or tray-shaped body covered with a deep lid. The container body may be made of a flexible material, and a liquid tank may be placed on the food, and the food may be wrapped using an air-filled plastic sheet (commonly called an air pack).

The liquid tank is made of a good conductor. The good thermal conductor is, for example, aluminum or copper. Aluminum is preferred from the viewpoint of rust toxicity. Copper may be plated with nickel, chromium, or the like. A stainless steel plate, a zinc iron plate or the like may be used, and a thin plastic film may be used. It is not necessary to constitute the entire liquid tank with a good conductor, but it is preferable to constitute the entire or most of the portion where the liquid tank is exposed inside or outside the container body with a good heat conductor. A part of the wall surface facing the inside and outside of the container body may be made of a good thermal conductor. When providing a liquid tank through the top surface of the container body,
A part of the side surface of the liquid tank may be exposed outside the container, and at least a part of the liquid tank may be formed of a good heat conductor.

The shape of the liquid tank is not particularly limited, but when the liquid tank is provided on the top surface of the container main body, it is preferably circular or square, shallow pan-shaped or dish-shaped. When the liquid tank is provided on the side surface of the container body, a thin container in which the side walls exposed inside and outside the container body are parallel to each other is preferable. The liquid tank may have an open top surface, but preferably has a structure for preventing a change in components due to evaporation of the aqueous solution in the tank, and is preferably provided with a lid or, in the case of an open container, provided with a floating lid. . Materials such as lids and floating lids to prevent evaporation of the aqueous solution
For example, it is preferable to use an aluminum plate.

The liquid tank does not need to occupy the entire top surface or side surface of the container body in which it is provided, but may occupy only a part of the surface. The liquid tank is preferably provided on the top or the upper side of the container body, since the temperature distribution in the container is reduced.

The liquid having a freezing point of 0 ° C. or lower (solid below the freezing point) may be either an organic substance or an inorganic substance. Although an aqueous solution of an organic substance or an inorganic substance is practical, it is preferable that the composition be hardly rotted and resistant to mold. For example, it is an aqueous solution of ethyl alcohol, 1,2-propanediol or the like. However, if a volatile component such as ethyl alcohol is used, the freezing point of the solution may change. The freezing point of the liquid is preferably -20 ° C or higher, especially -1 ° C.
Below, it is preferred that it is -4 ° C or more. For storage of fresh vegetable foods such as vegetables and fruits, it is particularly preferable to use such a liquid and place the container in a refrigerator having an average or midpoint temperature of less than -1 ° C. Glycerin, 1,2-propanedio-
Aqueous solution of 3 to 15% by weight of glycols such as 1,3-propanediol, monosaccharides such as glucose and fructose, disaccharides such as sucrose and trehalose, and fructooligosaccharides. An aqueous solution of about 12 to 33% (by weight) of such a saccharide such as an oligosaccharide can be used. These include
It preferably contains a fungicide (eg, ethyl alcohol, isopropyl alcohol).

Table 1 shows the freezing points of main aqueous solutions having a freezing point of -1 ° C or lower and -4 ° C or higher. [Table 1] Solute concentration (% by weight) Freezing point (° C) 1,2-propanediol 4.5-1.7 6-2.4 Glycerin 6-2.18-2.9 Sucrose 15-1. 7 24 -2.6

As the liquid in the liquid tank, although the temperature buffering effect is slightly inferior, water may be used, or a liquid having a freezing point lower than -4 ° C., for example, a 10% by volume or more aqueous glycerin solution may be used.

If the liquid tank is composed of two or more parts, each part containing liquids having different freezing points, the freezing of food can be more reliably prevented over a wider temperature range of the refrigerator. It is preferable that the difference between the freezing points of the liquids is 1 to 2 ° C. Each part may face the inside and outside of the food container, but the first part (the liquid with the lower freezing point) faces the outside of the liquid tank, and the second part is inside the first part. It is advantageous to form a double structure such as

In the food container, together with fresh food to be stored, means for preventing the food from drying, for example, having a freezing point of -5 ° C.
It is preferable to accommodate a lower aqueous solution or humidifier. For example, a glass containing a 15% by volume aqueous solution of 1,2-propanediol or a 12% by volume aqueous solution of glycerin is placed in a food container. The antifreeze placed in the food container preferably contains a fungicide (for example, 2% by volume of ethyl alcohol).

In the food container, volatile, harmless alcohols (for example, ethyl alcohol, isopropyl alcohol, hinoxythiol), liquids, solids, solutions, Alternatively, it is preferable to provide a source of alcohol vapor such as an adsorbent on silica or nonwoven fabric. A benzoate or a solution thereof can also be used.

The storage container having the above-mentioned structure containing the food is stored in a normal operation state other than during defrosting so that the average temperature is less than 0 ° C.
Store in a refrigerator set at 5 ° C or higher. This temperature zone is a temperature zone at a maximum of 4 ° C. lower than the conventional ice temperature storage, and the storage period of the food by freezing and refrigeration can be extended as compared with the conventional one. The average temperature of the refrigerator is selected in consideration of the fluctuation range of the internal temperature and the freezing temperature of the stored food. For example, the temperature is between −2 ° C. and −3 ° C. for pork, −2 ° C. to −3.5 ° C. for tuna, and −2 ° C. to −4 ° C. for grapes. However, since the freezing temperature is determined by the content of sugars and organic acids in the same varieties of fruits, and by the fat content in meats, the above is only a guide.
When it is difficult to measure the average temperature, the midpoint temperature (the midpoint between the highest temperature and the lowest temperature in the normal operation state) may be substituted.

[0023]

The food is accommodated in a container provided with a liquid tank containing a liquid having a freezing point of 0 ° C. or less and penetrating the top surface or the like. When stored in a refrigerator having a temperature of not less than 0 ° C., the liquid having a freezing point of 0 ° C. or less in the liquid tank is cooled by the cool air in the refrigerator. As the temperature of the liquid in the liquid tank decreases, the temperature in the container body also decreases. When the temperature in the refrigerator drops below 0 ° C., the temperature of the liquid in the liquid tank also drops, reaching the freezing point. Once the temperature of the liquid reaches the freezing point, the temperature drop almost stops once due to the latent heat of water freezing. When the whole liquid in the liquid tank is solidified, the temperature is reduced again. In many cases, however, the refrigerator in the refrigerator or the cold air source is stopped before that, so that the temperature in the refrigerator is stopped for a while.

When the temperature inside the refrigerator rises due to the invasion of heat from the outside, heat corresponding to the temperature difference is also applied to the partially solidified liquid in the liquid tank. Since this heat is consumed due to the latent heat of melting of the solid phase (such as ice), the temperature of the liquid hardly changes until all the solid phase is melted. In the meantime, the refrigerator operates again, and the temperature in the refrigerator decreases. Thereafter, this is repeated. As described above, the liquid (particularly, aqueous solution) containing the solid phase in the liquid tank is thermally buffered by the latent heat, and the temperature is kept near the freezing point. The temperature inside the container body, which is surrounded by a heat insulating material except for the liquid tank, is strongly controlled by the temperature of the liquid in the liquid tank, and is always maintained at a temperature near its freezing point.

When the temperature in the refrigerator continues to decrease even after all of the liquid in the liquid tank has solidified, the temperature buffering action by the latent heat of solidification does not work. Is suppressed by the cool air, and the temperature is buffered by this factor.

Even when the liquid in the liquid tank does not solidify at the lowest temperature in the refrigerator, the viscosity of the liquid increases at low temperatures near the freezing point, and heat transfer by convection is restricted. Buffered.

Therefore, the temperature of the food in the container body is kept substantially constant, and the food is kept at a temperature lower than 0 ° C. and higher than the freezing temperature as long as the composition of the liquid in the liquid tank, that is, the coagulation temperature is appropriately selected. Stored and stored without freezing.

[0028]

FIG. 1 shows an example of a storage container used in the food storage method of the present invention. The container body 1 is surrounded by a heat insulating layer 2 and stores the food 3 therein. Top 1a of container body 1
Is provided with a shallow dish-shaped liquid tank 4. The liquid tank 4 contains an antifreezing liquid 5 and a floating lid 6 is floated on the liquid surface. The heat insulating layer 2 is a foamed polystyrene layer having a thickness of about 2 cm. The liquid tank 4 and the floating lid 6 are made of aluminum having a thickness of about 0.5 mm, and the antifreezing liquid 5 is a 7% by volume aqueous solution of 1,2-propanediol. The container body 1 also contains an antifreeze 7
Is placed. The antifreeze 7 is a 15% aqueous solution of glycerin containing 2% ethyl alcohol (concentration in volume%). This container is housed in a refrigerator having a midpoint temperature of less than -1 ° C and at least -5 ° C during normal operation except during defrosting.

FIG. 2 shows another example of the food storage container used in the storage method of the present invention. Container body 1, heat insulation layer 2, food 3,
The antifreeze 7 and the cup 8 are the same as in the above example. A shallow dish-shaped double liquid tank 4A, 4B is provided at the top 1a of the container body 1. The liquid tanks 4A and 4B contain antifreeze liquids 5A and 5B, respectively, and the liquid tank 4B is covered with an aluminum foil 6B (the periphery is reinforced by a polyethylene frame (not shown)). The liquid tanks 4A and 4B are both made of aluminum having a thickness of about 0.5 mm, and the antifreeze liquids 5A and 5B are 8% and 6% 1,2-propanediol aqueous solutions, respectively.
A cup 8 in the container body 1 contains a 15% aqueous solution of 1,2-propanediol as an antifreeze 7. This food storage container is stored in a refrigerator having an average temperature of less than -1 ° C and not less than -5 ° C.

Another example of the food storage container used in the storage method of the present invention is shown in FIG. Container body 1, heat insulation layer 2, food 3,
The antifreeze 7 and the cup 8 are the same as in the above example. A sealed liquid tank 4C having parallel side walls is provided on the side wall 1b of the container body 1.
Is provided and contains the antifreezing liquid 5C. The liquid tank 4C is made of aluminum having a thickness of about 0.5 mm and is sealed. The antifreeze solution 5C is a 7% by volume aqueous solution of 1,2-propanediol. The antifreeze 7 contained in the glass 8 is a 15% by volume aqueous solution of 1,2-propanediol. This container is stored in a refrigerator having an average temperature of less than -1 ° C and not less than -5 ° C.

Another example of the food storage container used in the storage method of the present invention is shown in FIG. Container body 1, heat insulation layer 2, food 3,
The antifreeze 7 and the cup 8 are the same as in the above example. A liquid tank 4D is provided on the upper part of the side wall 1b of the container main body 1, and contains an antifreezing liquid 5D. The liquid tank 4D is made of aluminum having a thickness of about 0.5 mm, and is sealed with a polyethylene lid 4d. Antifreeze solution 5D is 7% by volume of 1,2-propanedio-
Aqueous solution. Antifreeze 7 in glass 8 is ethanol
50% by volume aqueous solution. The container was heated to an average temperature of -1
Store in refrigerator below ℃, above -5 ℃.

FIG. 5 shows another example of a food storage container used in the storage method of the present invention. The heat insulating layer 2, the food 3, the antifreeze 7, and the glass 8 are the same as in the above example. The container body 1 comprises a flat saucer 1c and a lid 1d. A liquid tank 4E made of an aluminum foil bag laminated with a polyethylene film is placed on the top 1e of the lid 1d, and the liquid tank 4E has an antifreezing liquid 5E. Is contained. The antifreeze solution 5E is an 8% by weight glycerin aqueous solution. The antifreeze 7 contained in the cup 8 is a 50% by volume aqueous solution of ethanol. In the container main body 1, there is further placed a cup 8E containing the antiseptic liquid 7E. This container is stored in a refrigerator having an average temperature of less than -1 ° C and not less than -5 ° C.

The food storage container shown in FIGS.
Lower the concentration of antifreeze liquid, average temperature less than 0 ℃ -1 ℃
It may be stored in the above refrigerator.

[0034]

[Example 1] An example of the result of low-temperature refrigeration of Kyoho grape using the container of Fig. 2 is shown. Grapes were stored in the container body 1, a temperature sensor (not shown) was inserted into the container body, and the grape was stored in a low-temperature refrigerator (cool air circulation system) having an average temperature or a midpoint temperature of about -4 ° C. Temperature sensor in refrigerator
(Not shown) was inserted, and the respective temperatures in the container body and the refrigerator were recorded. The temperature in the refrigerator fluctuated ± 3 ° C., but the temperature fluctuation in the container body was ± 1.2 ° C. The stored grapes can be stored at 5
Even after storage for months, the flavor, color, and hardness were the same as fresh products.

[Example 2] A stew was prepared using the container shown in FIG.
An example of the result of low-temperature refrigeration of Ben grapes is shown. Grapes were stored in the container body 1, a temperature sensor (not shown) was inserted into the container body, and the grape was stored in a low-temperature refrigerator (cool air circulation system) having an average or midpoint temperature of about -3.5 ° C. A temperature sensor (not shown) was also inserted in the refrigerator, and each temperature in the container body and the refrigerator was recorded. The temperature in the refrigerator showed a fluctuation of ± 2.5 ° C., but the temperature in the container body fluctuated ± 0.7 ° C. The stored grapes do not show any damage due to freezing.
Even after storage for months, the flavor, color, and hardness were the same as fresh products.

Example 3 An example of the result of low-temperature refrigeration of tuna sashimi fillets using the container of FIG. 5 is shown. Container body 1
The tuna was housed, a temperature sensor (not shown) was inserted into the container body, and housed in a low-temperature refrigerator (cool air circulation system) having an average or middle point temperature of about -4 ° C. A temperature sensor (not shown) was also inserted in the refrigerator, and each temperature in the container body and the refrigerator was recorded. The temperature in the refrigerator showed a fluctuation of ± 1.5 ° C., but the average temperature in the container body was about −3.5 ° C., and the temperature fluctuation was only ± 0.3 ° C. The stored tuna did not freeze and kept the same taste, color and appearance as fresh after storage for 2 weeks. The tuna stored directly in the refrigerator was frozen and had a watery taste after thawing. Average temperature 5 ℃
The tuna stored in the refrigerator for the same period became discolored and the freshness was significantly reduced.

Example 4 An example of the result of low-temperature refrigeration of a strawberry using the container of FIG. 5 is shown. Strawberries were housed in the container body 1, a temperature sensor (not shown) was inserted into the container body, and housed in a small low-temperature refrigerator (cool air circulation system) having an average or midpoint temperature of about -1.2 ° C. Temperature sensor in refrigerator
(Not shown) was inserted, and the temperatures in the container body and the refrigerator were recorded. The temperature in the refrigerator showed a fluctuation of ± 0.8 ° C., but the temperature in the container body was about −1.2 ° C. on average, and the fluctuation was only ± 0.1 ° C. The stored strawberries did not freeze and kept the same taste, color and appearance as fresh after storage for 2 weeks. Strawberries stored directly in the refrigerator were frozen and thawed to a watery taste.

[0038]

According to the storage method of the present invention, fresh foods such as fruits, vegetables, meats, etc. can be refrigerated for a long time at low cost without freezing even in a refrigerator having an average temperature of less than 0 ° C. . In particular, the present invention makes it possible to refrigerate fruits and vegetables for a long period of time without fear of freezing even at temperatures lower than the conventional ice temperature storage, that is, below -1 ° C. ADVANTAGE OF THE INVENTION According to the storage container of this invention, fresh foods, such as a fruit, a vegetable, and meat, can be refrigerated at low cost for a long period of time without freezing even in a refrigerator with an average temperature of less than 0 degreeC. In particular, it makes it possible to refrigerate fruits and vegetables for a long time without fear of freezing, at an average internal temperature of less than -1 ° C. The storage method or storage container of the present invention is not only vegetable, fresh food such as fruits and vegetables, but also meat,
It is also useful for fresh animal foods such as fish and cooked foods.

[Brief description of the drawings]

FIG. 1 is a sectional view of a storage container used in the present invention.

FIG. 2 is a sectional view of a storage container used in the present invention.

FIG. 3 is a sectional view of a storage container used in the present invention.

FIG. 4 is a sectional view of a storage container used in the present invention.

FIG. 5 is a sectional view of a storage container used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Container main body 1a Top part of container main body 1b Side wall of container main body 1c Receiving tray 1d Lid 1e Top part of lid 2 Thermal insulation layer 3 Food 4 Liquid tank 4A, 4B, 4C, 4D, 4E Liquid tank 4d Lid 5 Antifreeze liquid 5A, 5B, 5C, 5D, 5E Antifreeze liquid 6 Floating lid 6B Aluminum foil 7 Antifreeze liquid 8 cups 7E Anticorrosion liquid 8E cup

Claims (21)

[Claims] 1. A container body for containing food to be stored, which is surrounded by a heat-insulating material, and a liquid tank made of a hot conductor containing a solid or liquid having a freezing point of 0 ° C. or less. The liquid tank stores food in a container provided through at least one surface selected from the top surface and the side surface of the container body, and the container in which the food is stored has an average temperature or a midpoint temperature. 0
A method for storing food, comprising storing in a refrigerator at a temperature lower than -5 ° C or lower than -5 ° C. 2. The food storage method according to claim 1, wherein said liquid tank is provided so as to penetrate a top surface of said container body. 3. The method for storing food according to claim 1, wherein the liquid tank is provided so as to penetrate an upper side portion of the container body. 4. The food storage method according to claim 1, wherein said container body is made of an air-filled plastic sheet. 5. The method according to claim 5, wherein the container has an average temperature or a midpoint temperature of -1.
The method for storing food according to any one of claims 1 to 4, wherein the food is stored in a refrigerator at a temperature lower than -5C or higher than -5C. 6. The method for storing food according to claim 5, wherein the liquid tank contains a liquid having a freezing point of -1 ° C or lower and -4 ° C or higher. 7. The food storage method according to claim 1, wherein water is contained in the liquid tank. 8. The liquid tank has a floating lid of a good conductor.
The method for storing food according to claim 1, 2, 5, or 6. 9. The method according to claim 1, wherein the liquid tank is composed of two parts, and the first part contains a liquid having a lower freezing point than the second part. 10. The method according to claim 9, wherein the difference between the freezing points of the liquids of the first part and the second part is 0.5 ° C. to 2 ° C. 11. The method for storing food according to claim 1, wherein the liquid has a composition that is resistant to spoilage and mold. 12. The method for storing food according to claim 11, wherein the liquid is an aqueous solution of an organic substance containing ethyl alcohol or isopropyl alcohol. 13. The container according to claim 1, wherein an aqueous solution that does not freeze at −5 ° C. is stored in said container body together with said food.
2. Any one of the food storage methods. 14. An ethyl alcohol,
The method for storing food according to any one of claims 1 to 13, wherein an isopropyl alcohol or hinoxythiol vapor generator is accommodated together with the food. 15. A container for storing food at a temperature of less than 0 ° C., comprising: a container body surrounded by a heat insulating material for containing the food; and a top surface and side surfaces of the container body. A food storage container, comprising: a liquid tank made of a good heat conductor, the liquid tank being provided so as to penetrate at least one selected surface thereof, and containing a liquid or a solid having a freezing point of 0 ° C. or less. 16. The food storage container according to claim 15, wherein said liquid tank is provided through a top surface of said container body. 17. The food storage container according to claim 15, wherein the liquid tank is provided so as to penetrate an upper side portion of the container body. 18. The food storage container according to claim 15, wherein said container body comprises an air-filled plastic sheet. 19. The food storage container according to claim 15, wherein the liquid tank contains a liquid having a freezing point of -1 ° C. or lower. 20. The liquid tank has a freezing point of -1 ° C or lower and -4 ° C or lower.
17. The food storage container of claim 16 containing the liquid. 21. The food storage container according to claim 15, wherein the liquid tank has two parts, and the first part contains a liquid having a lower freezing point than the second part.