Method for producing freeze-dried food and method for improving restoration properties of freeze-dried food

Abstract

To provide a method for producing freeze-dried food that enables the production of the freeze-dried food, including food containing solid ingredients, with superior restorability by a simple method, as well as a method for improving the restoration properties of the freeze-dried food.SOLUTION: A method for producing freeze-dried food includes: a contact step of contacting food containing solid ingredients with a treatment liquid; a freezing step of freezing the food containing the solid ingredients after contact with the treatment liquid; and a freeze-drying step of freeze-drying the food containing the solid ingredients frozen in the freezing step, together with a frozen seasoning material.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing a freeze-dried food and a method for improving the reconstitution property of a freeze-dried food. [Background technology]

[0002] Due to changes in lifestyles and diversifying tastes, the demand for freeze-dried instant foods (hereinafter sometimes referred to as "freeze-dried foods"), which are produced by a method including a freeze-drying process and can be eaten simply by pouring hot water over them and waiting a short time, has been increasing in recent years. Various developments regarding freeze-dried foods have been carried out.

[0003] For example, as a method for providing freeze-dried dried meat with good reconstitution and flavor, a method for producing freeze-dried meat has been proposed in which heat-treated meat is perforated on the surface with multiple holes, which is then treated with superheated steam and freeze-dried (see, for example, Patent Document 1).

[0004] In addition, as a dried food that is highly creative and can be easily restored to an edible state in a short time, a dried food has been proposed that includes a first block of food ingredients such as a hamburger steak and a second block of food ingredients such as demi-glace sauce, in which the second block is made up of food ingredients that have a higher fluidity in an edible state than the first block, and is contained within a container body such that the first block is located closer to the inlet / outlet of the container than the second block (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2014-135918 A [Patent Document 2] JP 2022-147879 A Summary of the Invention [Problem to be solved by the invention]

[0006] With the recent increase in demand for instant foods, consumers are also demanding higher levels of reconstitution. In addition, freeze-dried foods that combine solid ingredients such as hamburger steak with seasonings such as demi-glace sauce do not have sufficient reconstitution. Therefore, there is a strong demand for the rapid provision of technology that can improve the reconstitution of freeze-dried foods.

[0007] The present invention aims to solve the above-mentioned problems in the prior art and to achieve the following objectives: That is, the present invention aims to provide a method for producing a freeze-dried food, including a food containing solid ingredients, which has good reconstitution properties, by a simple method, and a method for improving the reconstitution properties of a freeze-dried food. [Means for solving the problem]

[0008] In order to solve the above problems, the inventors conducted extensive research and discovered that it is possible to easily improve the reconstitution of a freeze-dried food comprising a food containing solid ingredients and a seasoning by carrying out a contact step in which the food containing solid ingredients is brought into contact with a treatment liquid, followed by freezing, and then freeze-drying the frozen food together with a frozen seasoning.

[0009] The present invention is based on the findings of the present inventors, and the means for solving the above problems are as follows. <1> a contacting step of contacting a food containing solid ingredients with a treatment liquid; a freezing step of freezing the food containing the solid food material that has been contacted with the treatment liquid; a freeze-drying step of freeze-drying the food containing the solid food material frozen in the freezing step together with a frozen seasoning; The present invention relates to a method for producing a freeze-dried food, the method comprising the steps of: <2> The freeze-drying step is a step of freeze-drying the food containing the solid food material frozen in the freezing step in a state where the frozen seasoning is located on the food containing the solid food material frozen in the freezing step. <1> A method for producing the freeze-dried food described above. <3> The freeze-drying step is a step of freeze-drying the food containing the solid food material frozen in the freezing step in a state where the food is located on top of the frozen seasoning. <1> A method for producing the freeze-dried food described above. <4> The freezing step is a step of freezing the food containing the solid ingredient while immersed in the processing liquid. <1> from <3> The present invention relates to a method for producing a freeze-dried food according to any one of the above. <5> The freezing step is a step of freezing the food containing the solid food material that has been contacted with the treatment liquid and then drained. <1> from <3> The present invention relates to a method for producing a freeze-dried food according to any one of the above. <6> The treatment liquid contains a sugar alcohol. <1> from <5> The present invention relates to a method for producing a freeze-dried food according to any one of the above. <7> A contacting step of contacting a food containing solid ingredients with a treatment liquid; a freezing step of freezing the food containing the solid food material that has been contacted with the treatment liquid; a freeze-drying step of freeze-drying the food containing the solid food material frozen in the freezing step together with a frozen seasoning; The present invention relates to a method for improving the reconstitution property of a freeze-dried food, the method comprising the steps of: <8> The freeze-drying step is a step of freeze-drying the food containing the solid food material frozen in the freezing step in a state where the frozen seasoning is located on the food containing the solid food material frozen in the freezing step. <7> This is a method for improving the reconstitution property of the freeze-dried food described in the above. <9> The freeze-drying step is a step of freeze-drying the food containing the solid food material frozen in the freezing step in a state where the food is located on top of the frozen seasoning. <7> This is a method for improving the reconstitution property of the freeze-dried food described in the above. <10> The freezing step is a step of freezing the food containing the solid ingredient while immersed in the processing liquid. <7> from <9> The present invention relates to a method for improving the reconstitution property of a freeze-dried food according to any one of the above. <11> The freezing step is a step of freezing the food containing the solid food material that has been contacted with the treatment liquid and then drained. <7> from <9> The present invention relates to a method for improving the reconstitution property of a freeze-dried food according to any one of the above. <12> The treatment liquid contains a sugar alcohol. <7> from <11> The present invention relates to a method for improving the reconstitution property of a freeze-dried food according to any one of the above. Effect of the Invention

[0010] According to the present invention, it is possible to solve the above-mentioned problems in the conventional art, achieve the above-mentioned objective, and provide a method for producing freeze-dried foods, including foods containing solid ingredients, which have good reconstitution properties in a simple manner, and a method for improving the reconstitution properties of freeze-dried foods. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] (Method for producing freeze-dried food, method for improving the reconstitution of freeze-dried food) The method for producing a freeze-dried food of the present invention includes at least a contacting step, a freezing step (1), and a freeze-drying step, and may further include other steps as necessary. The method for improving the reconstitution property of a freeze-dried food of the present invention includes at least a contacting step, a freezing step (1), and a freeze-drying step, and may further include other steps as necessary. Since the method for improving the reconstitution property of a freeze-dried food of the present invention can be carried out in the same manner as the method for producing a freeze-dried food of the present invention, the method for producing a freeze-dried food of the present invention and the method for improving the reconstitution property of a freeze-dried food of the present invention will be described together below.

[0012] <Food containing solid ingredients> The food containing the solid food ingredients (hereinafter sometimes referred to as "solid food ingredient-containing food") contains at least a solid food ingredient, and may further contain other ingredients as necessary.

[0013] The solid food material is not particularly limited and can be appropriately selected depending on the purpose. Examples of the solid food material include meat, seafood, vegetables, and food materials that imitate these. The solid food materials may be used alone or in combination of two or more kinds. The content of the solid ingredients in the solid ingredient-containing food is not particularly limited and can be appropriately selected depending on the purpose. The solid ingredient-containing food may be composed of only solid ingredients.

[0014] The meat is not particularly limited as long as it can be used in foods and can be appropriately selected depending on the purpose. Examples of the meat include chicken, beef, pork, mutton, horse meat, wild boar, wild boar and pork, duck meat, crossbreed duck meat, turkey meat, and domestic duck meat.

[0015] The seafood is not particularly limited as long as it can be used in foods, and can be appropriately selected depending on the purpose. Examples include shrimp; squid; octopus; fish meat such as salmon, cod, tuna, trout, rockfish, sea bream, Spanish mackerel, yellowtail, turbot, bonito, horse mackerel, sardine, pacific saury, and mackerel; and shellfish such as clams, scallops, and italy shellfish.

[0016] The parts of the meat and seafood to be used are not particularly limited and can be appropriately selected depending on the purpose.

[0017] The vegetables are not particularly limited as long as they can be used in foods and can be appropriately selected depending on the purpose. Examples of the vegetables include sweet potato, taro, carrot, pumpkin, burdock, cabbage, and broccoli.

[0018] The part of the vegetable to be used is not particularly limited and can be appropriately selected depending on the purpose.

[0019] The above-mentioned ingredients that imitate these refer to ingredients that can produce food products that have the same texture, etc. as the above-mentioned meat, seafood, or vegetables when cooked. The food materials that imitate these are not particularly limited, and any known food materials can be appropriately selected. For example, food materials produced using plant-based raw materials such as soybean protein and wheat protein can be mentioned.

[0020] The solid food-containing food is not particularly limited as long as it contains a solid food, and can be appropriately selected according to the purpose, and examples thereof include hamburger steak, pork cutlet, chicken cutlet, shrimp tempura, etc. These may be used alone or in combination of two or more kinds.

[0021] <Freeze-dried foods> The freeze-dried food contains at least the solid ingredient-containing food and a seasoning, and further contains other ingredients as necessary. The freeze-dried food may consist of the solid ingredient-containing food and the seasoning.

[0022] The seasoning material is used to season the food containing the solid ingredients, and examples of the seasoning material include demi-glace sauce, curry sauce, and tempura sauce. The seasoning material also includes liquid seasonings such as miso soup. The seasoning material may contain solid ingredients.

[0023] Other ingredients in the freeze-dried food are not particularly limited, and may be appropriately selected depending on the purpose from ingredients that are usually used in freeze-dried instant foods that are reconstituted with hot water.

[0024] The freeze-dried food is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include miso katsu, chicken cutlet curry, pork cutlet curry, shrimp tempura bowl ingredients, miso soup, and the like.

[0025] The shape, structure, and size of the freeze-dried food are not particularly limited and can be appropriately selected according to the purpose. For example, the shape can be a block shape. In addition, the structure can be a multi-layer structure of at least two layers including a layer of the solid food-containing food and a layer of the seasoning. The layer of the solid food-containing food and the layer of the seasoning may be stacked in the vertical direction when the freeze-dried food is placed, or may be arranged side by side in the horizontal direction.

[0026] The present invention includes at least a contact step, a freezing step (1), and a freeze-drying step, and may further include other steps as necessary. The other steps are not particularly limited as long as they do not impair the effects of the present invention, and may be appropriately selected depending on the purpose. For example, the other steps include a solid food-containing food preparation step, a seasoning filling step, and a freezing step (2).

[0027] <Food preparation process containing solid ingredients> The solid ingredient-containing food preparation step is a step of preparing food containing solid ingredients.

[0028] The treatment in the solid foodstuff-containing food preparation step is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include cutting, drilling, oiling, filling, and sterilization.

[0029] The cutting process is a step of cutting the solid ingredient-containing food. The thickness, shape, structure and size of the solid food material are not particularly limited and may be appropriately selected depending on the purpose. The solid food material may be frozen and then thawed before use, or may be unfrozen and used as is.

[0030] The hole making process is a process of making holes in the solid ingredient-containing food product. The method for making the holes is not particularly limited, and any known method can be appropriately selected. For example, a method using a meat tenderizer can be mentioned. The number of holes is not particularly limited and can be appropriately selected depending on the purpose. The size (diameter), depth, and spacing of the holes are not particularly limited and can be appropriately selected depending on the purpose. The holes do not need to penetrate the thickness of the target, but may penetrate the target. The holes may be formed on only one side of the solid ingredient-containing food product or on both sides. The hole punching may be performed in a plurality of places at once, or in a plurality of steps.

[0031] The oil-frying process is a step of oil-frying the solid ingredient-containing food (hereinafter, sometimes referred to as "frying" or "deep-frying"). The method and conditions for the oil adjustment are not particularly limited and can be appropriately selected depending on the purpose.

[0032] The filling process is a step of filling a container with the solid ingredient-containing food product. The container is not particularly limited as long as it is a container that can be used for producing freeze-dried foods, and can be appropriately selected depending on the purpose.

[0033] The sterilization treatment is a treatment for sterilizing the solid ingredient-containing food. The sterilization method is not particularly limited and may be appropriately selected from known methods, such as steaming and boiling. The conditions for the sterilization are not particularly limited and can be appropriately selected depending on the purpose.

[0034] The order in which the above-mentioned processes are carried out is not particularly limited and can be appropriately selected depending on the purpose.

[0035] <Contact process> The contacting step is a step of contacting the solid ingredient-containing food with a treatment liquid.

[0036] - Processing fluid - The treatment liquid may consist of only an aqueous solvent that can be used in foods, such as water, or may contain a sugar alcohol. Among these, the treatment liquid containing a sugar alcohol is preferred in that it can improve the reconstitution property. The treatment liquid may contain other components as necessary.

[0037] The sugar alcohol is not particularly limited as long as it can be used in foods, and can be appropriately selected depending on the purpose, and examples thereof include reduced starch syrup, sorbitol, xylitol, erythritol, mannitol, maltitol, lactitol, reduced palatinose, etc. These may be used alone or in combination of two or more kinds. Among the above sugar alcohols, reduced starch syrup and sorbitol are preferred in that more excellent effects can be obtained.

[0038] The content of the sugar alcohol in the processing solution is not particularly limited and may be appropriately selected depending on the purpose, but is preferably 1 to 10% by mass, more preferably 1.5 to 5% by mass, and particularly preferably 2 to 4% by mass. If it is within the above preferred range, it is advantageous in that both the reconstitution property and the flavor are excellent.

[0039] The other components in the treatment liquid are not particularly limited as long as they do not impair the effects of the present invention and can be appropriately selected depending on the purpose, and examples thereof include antioxidants, etc. These may be used alone or in combination of two or more. The antioxidant is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include vitamin E and vitamin C. These may be used alone or in combination of two or more kinds. The content of the other components in the treatment liquid is not particularly limited and can be appropriately selected depending on the purpose.

[0040] The method of contact is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include a method of immersing the solid ingredient-containing food in the treatment liquid, a method of applying or spraying the treatment liquid onto the solid ingredient-containing food, etc. For example, the treatment liquid can be filled into a container containing the solid ingredient-containing food and brought into contact with the solid ingredient-containing food.

[0041] The amount of the treatment liquid used for the solid food-containing food is not particularly limited and can be appropriately selected depending on the purpose. For example, in the case of immersion, an amount sufficient to immerse the solid food-containing food entirely can be used, and in the case of application or spraying, an amount sufficient to bring the solid food-containing food entirely into contact with the treatment liquid can be used.

[0042] The contact time is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 10 minutes or more, more preferably 20 minutes or more, and particularly preferably 30 minutes or more.

[0043] The solid foodstuff-containing food may be drained after the contacting step, or may be directly subjected to the step described below without draining the liquid.

[0044] <Freezing process (1)> The freezing step (1) is a step of freezing the solid ingredient-containing food that has been contacted with the treatment liquid.

[0045] The mode of the freezing step (1) is not particularly limited and can be appropriately selected depending on the purpose. For example, (a) the solid ingredient-containing food is frozen while immersed in the treatment liquid, or (b) the solid ingredient-containing food is contacted with the treatment liquid and then the liquid is drained off and then frozen.

[0046] The freezing conditions are not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include leaving the mixture at −10° C. or lower until it is completely frozen. The freezing temperature may be constant, or the mixture may be frozen stepwise at different temperatures.

[0047] <Seasoning filling process> The seasoning filling step is a step of filling a container with the seasoning.

[0048] The method of filling the seasoning is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include a method of filling a container with unfrozen seasoning, a method of filling a container with frozen seasoning, etc. Specifically, examples thereof include (c) a method of filling a container with unfrozen seasoning such as liquid seasoning on top of the solid ingredient-containing food frozen in the freezing step (1) or (d) a method of placing a frozen seasoning on top of the solid ingredient-containing food frozen in the freezing step (1) or in the container. In the method (c), the seasoning can be frozen in the freezing step (2) described below.

[0049] The amount of the seasoning used is not particularly limited and can be appropriately selected depending on the type of the solid ingredient-containing food.

[0050] <Freezing process (2)> The freezing step (2) is a step of freezing the seasoning material packed in the container.

[0051] The freezing step (2) may be carried out either before or after the solid ingredient-containing food is frozen. The mode of the freezing step (2) is not particularly limited and can be appropriately selected depending on the purpose. Examples include (e) a mode in which a seasoning material filled in a container that does not contain the solid ingredient-containing food is frozen, and (f) a mode in which unfrozen seasoning material is filled on top of the solid ingredient-containing food in a container that contains the frozen solid ingredient-containing food, and then frozen.

[0052] The freezing conditions are not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include leaving the mixture at −5° C. or lower until it is completely frozen. The freezing temperature may be constant, or the mixture may be frozen stepwise at different temperatures.

[0053] Instead of the freezing step (2), a frozen seasoning may be prepared and then packed into the container.

[0054] <Lyophilization process> The freeze-drying step is a step of freeze-drying (hereinafter sometimes referred to as "vacuum freeze-drying") the solid ingredient-containing food frozen in the freezing step together with frozen seasonings. The freeze-drying step may be carried out after the freezing step (1), and another step may be included between the freezing step (1) and the freeze-drying step.

[0055] The freeze-drying mode is not particularly limited and can be appropriately selected depending on the purpose. Examples of the freeze-drying mode include (i) freeze-drying in a state where the frozen seasoning is located on top of the solid ingredient-containing food frozen in the freezing step (1), and (ii) freeze-drying in a state where the solid ingredient-containing food frozen in the freezing step (1) is located on top of the frozen seasoning.

[0056] The freeze-drying method is not particularly limited, and any known method can be appropriately selected.

[0057] The vacuum freeze-drying can be carried out using a known freeze-drying machine. The method for the vacuum freeze-drying is not particularly limited and any known method can be appropriately selected, but it is preferable to perform the vacuum freeze-drying by reducing the pressure to a vacuum of 90 Pa or less and raising the temperature. The water content of the freeze-dried food after the vacuum freeze-drying is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 5% by mass or less.

[0058] According to the method of the present invention, it is possible to produce a freeze-dried food that contains the solid ingredient-containing food and the seasoning, has a layer structure of two or more layers, and is a freeze-dried food that integrates the solid ingredient-containing food and the seasoning, and has good reconstitution properties.

[0059] In order to obtain better reconstitution properties, it is preferable that when eating, boiling water is poured onto the solid ingredient-containing food so that the boiling water comes into contact with the solid ingredient-containing food. EXAMPLES

[0060] The present invention will be specifically explained below by way of test examples, but the present invention is not limited to these test examples.

[0061] (Test Example 1) Hamburger steak was used as an example of a food containing solid ingredients, and a freeze-dried food was produced as follows.

[0062] <Step A: Preparation of hamburger steak> After thawing the cooked frozen hamburger steak, holes were made physically using a meat tenderizer, and then the steak was steamed (stopped when the temperature reached 90°C) and sterilized. The recipe for the cooked frozen hamburger steak was as follows: -Preparation of pre-cooked frozen hamburger steak- · Beef ··· 40.0% by mass Onion: 20.0% by mass Binder (breadcrumbs, liquid egg white) 9.0% by mass · Granular soy protein ··· 5.0% by mass · Milk protein ··· 1.0% by mass Salt: 1.0% by mass Fruit seasoning: 0.5% by mass · Spices ··· 0.2% by mass pH adjuster: 0.3% by mass · Water ··· 23.0% by mass Total 100.0% by mass

[0063] <Process B: Contact> Sterilized hamburger steaks (90.0 g) were manually packed into individual serving containers. Next, 70.0 g of treatment liquid (water or water containing sugar alcohol) (enough to immerse the hamburger steaks; see Tables 1 and 2 for details of the treatment liquid) was added and the containers were left to stand for a certain period of time (hereinafter sometimes referred to as the "contact time"; see Tables 1 and 2 for the contact time).

[0064] <Process C: Freezing> After leaving the hamburger steaks for a certain period of time, each individual serving container was placed in a freezer at -25°C for 8 hours or more to freeze the hamburger steaks.

[0065] <Process D: Seasoning liquid filling> After freezing, 100.0 g of seasoning liquid (demi-glace sauce) was poured onto the hamburger steak.

[0066] <Process E: Freezing> The individual serving containers were then placed again in a freezer at -5°C or below for at least 8 hours to freeze, resulting in a two-layer laminated structure in which the frozen seasoning liquid was located on top of the frozen hamburger steak (including the frozen processing liquid).

[0067] <Process F: Freeze drying> The laminated structure was subjected to vacuum freeze-drying together with the individual food container using a freeze-dryer (manufactured by Kyowa Vacuum Engineering Co., Ltd.) at a pressure of 60 Pa. This resulted in a freeze-dried food (water content 5% by mass or less) that was a dry block having a two-layer structure of a seasoning layer and a hamburger steak layer.

[0068] <Evaluation> The freeze-dried food obtained was placed on a plate with the hamburger steak side up, 160 mL of boiling water was poured onto the hamburger steak side, and the food was eaten after mixing for 2 minutes, and the reconstitution and flavor were evaluated according to the following evaluation criteria. The results are shown in Tables 1 and 2. The evaluation was carried out by three trained evaluators. The evaluation result of the reconstitution is the average value of the evaluation results by the three evaluators. The evaluation results of the flavor were consistent among the three evaluators (the same applies to Test Example 2 and onwards).

[0069] [Evaluation Criteria] -Resilience- 5 points: Reconstituted and very soft in texture. 4 points: Reconstituted and soft in texture. 3 points: Restored. 2 points: The outside has been restored, but the center has not. Score 1: Not restored.

[0070] -flavor- ○: No sweetness is felt. △: Slightly sweet. ×: Very sweet.

[0071] [Table 1]

[0072] [Table 2]

[0073] From the above results, it was confirmed that the method of the present invention can produce a freeze-dried food with good restorability, which can be restored to an edible state in a short time of less than 2 minutes, even when the food containing solid ingredients and the seasoning are stacked and integrated into a block. Furthermore, the method of the present invention can simplify the production process compared to producing the food containing solid ingredients and the seasoning as separate blocks.

[0074] (Test Example 2) <Test Example 2-1> Steps A to F were carried out in the same manner as in Test Example 1-3 to obtain a freeze-dried food (water content: 5% by mass or less) that was a dry block having a two-layer structure of a seasoning layer and a hamburger steak layer.

[0075] <Test Example 2-2> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 2-1, except that step B was not performed. The freeze-dried food in this Test Example had a single-layer structure in which the hamburger steak portion and the seasoning portion were located in the same layer.

[0076] <Test Example 2-3> -Process 1- The individual serving containers were filled with 100.0 g of seasoning liquid (demi-glace sauce).

[0077] -Process 2- The seasoning liquid was placed in individual serving containers in a freezer at or below -5°C for at least 8 hours and frozen.

[0078] -Process 3- A hamburger steak was prepared in the same manner as in step A of Test Example 2-1.

[0079] -Process 5- The hamburger steak was placed on top of the frozen seasoning liquid, and the individual serving container was again placed in a freezer at -25°C for 8 hours or more to freeze, forming a two-layer laminate structure in which the frozen hamburger steak was placed on top of the frozen seasoning liquid. Note that the hamburger steak in this test example was not subjected to a contact step in which it was brought into contact with a treatment liquid.

[0080] -Process 6- Freeze-drying was carried out in the same manner as in step F of Test Example 2-1 to obtain a freeze-dried food (water content: 5% by mass or less) that was a dry block having a two-layer structure of a hamburger steak layer and a seasoning layer.

[0081] <Test Example 2-4> -Process 1- The individual serving containers were filled with 100.0 g of seasoning liquid (demi-glace sauce).

[0082] -Process 2- The seasoning liquid was placed in individual serving containers in a freezer at or below -5°C for at least 8 hours and frozen.

[0083] -Process 3- A hamburger steak was prepared in the same manner as in step A of Test Example 2-1.

[0084] -Process 4- A sterilized hamburger steak (90.0 g) was immersed in 70.0 g of a treatment liquid (water containing 2% by mass of reduced starch syrup), left to stand for 30 minutes, and then drained.

[0085] -Process 5- The hamburger steak was placed on top of the frozen seasoning liquid, and the individual serving container was again placed in a -25°C freezer for 8 hours or more until it was frozen, forming a two-layer laminated structure in which the frozen hamburger steak was located on top of the frozen seasoning liquid.

[0086] -Process 6- Freeze-drying was carried out in the same manner as in step F of Test Example 2-1 to obtain a freeze-dried food (water content: 5% by mass or less) that was a dry block having a two-layer structure of a hamburger steak layer and a seasoning layer.

[0087] <Test Example 2-5> -Process 1- The individual serving containers were filled with 100.0 g of seasoning liquid (demi-glace sauce).

[0088] -Process 2- The seasoning liquid was placed in individual serving containers in a freezer at or below -5°C for at least 8 hours and frozen.

[0089] -Process 3- A hamburger steak was prepared in the same manner as in step A of Test Example 2-1.

[0090] -Process 4- The sterilized hamburger steak (90.0 g) was manually packed on top of the frozen seasoning liquid. Next, the processing liquid (water containing 2% by mass of reduced starch syrup) was added to the container until the hamburger steak was submerged, and the container was left to stand for 30 minutes.

[0091] -Process 5- After leaving it to stand for 30 minutes, the individual serving containers were again left to stand in a -25°C freezer for more than 8 hours until they were frozen, forming a two-layered structure in which the frozen hamburger steak (including the frozen processing liquid) was located on top of the frozen seasoning liquid.

[0092] -Process 6- Freeze-drying was carried out in the same manner as in step F of Test Example 2-1 to obtain a freeze-dried food (water content: 5% by mass or less) that was a dry block having a two-layer structure of a hamburger steak layer and a seasoning layer.

[0093] <Evaluation> The obtained freeze-dried foods were evaluated in the same manner as in Test Example 1. The results are shown in Table 3. Note that in Test Examples 2-2 and 2-3, the foods were not reconstituted, and therefore the flavor could not be evaluated (indicated by "*" in the table).

[0094] [Table 3]

[0095] From the results of Test Examples 2-1, 2-4, and 2-5, it was confirmed that freeze-dried foods with good reconstitution properties can be produced according to the method of the present invention, even when the production process is changed.

[0096] (Test Example 3) Pork cutlet was used as an example of a food containing solid ingredients, and a freeze-dried food was produced as follows.

[0097] <Test Example 3-1> -Preparation of pork cutlet- The pork cutlet was fried at 180-185°C for 3 minutes, cut into 4 equal pieces, and hand-packed into containers (70.00g).

[0098] -contact- Next, 40.00 g (enough to immerse the pork cutlet) of a treatment liquid (sugar alcohol-containing water (reduced starch syrup concentration 0.64% by mass) was filled into the container and left to stand for 30 minutes.

[0099] -Steamed- Next, steaming treatment (3 minutes after reaching a temperature of 90°C) was carried out to sterilize the mixture.

[0100] -frozen- After steaming, the pork cutlets were placed in a container in a freezer at -25°C for 8 hours or more and frozen.

[0101] -Seasoning liquid filling- After freezing, 103.00 g of seasoning liquid (miso cutlet sauce) was poured on top of the pork cutlet.

[0102] -frozen- The container was then placed again in a freezer at -5°C or below for at least 8 hours to freeze, forming a two-layered structure in which the frozen seasoning liquid was located on top of the frozen pork cutlet (including the frozen processing liquid).

[0103] -Lyophilization- The laminated structure was subjected to vacuum freeze-drying together with the container using a freeze-dryer (manufactured by Kyowa Vacuum Engineering Co., Ltd.) at a pressure of 60 Pa. This resulted in a freeze-dried food (water content 5% by mass or less) that was a dry block having a two-layer structure of a seasoning layer and a pork cutlet layer.

[0104] <Test Example 3-2> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 3-1, except that the contact treatment and steam-cooking treatment were not performed.

[0105] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 4.

[0106] [Table 4]

[0107] (Test Example 4) Chicken cutlet was used as an example of a food containing solid ingredients, and a freeze-dried food was produced as follows.

[0108] <Test Example 4-1> -Preparation of chicken cutlet- The chicken cutlets were fried at 180-185°C for 3 minutes, cut into 4 equal pieces, and hand-packed into containers (75.00g).

[0109] -contact- Next, 20.00 g (enough to immerse the chicken cutlet) of a treatment liquid (sugar alcohol-containing water (reduced starch syrup concentration 1.3% by mass) was filled into the container and allowed to stand for 30 minutes.

[0110] -Steamed- Next, steaming treatment (3 minutes after reaching a temperature of 90°C) was carried out to sterilize the mixture.

[0111] -frozen- After steaming, the chicken cutlets were placed in a container in a freezer at -25°C for 8 hours or more and frozen.

[0112] -Seasoning liquid filling- After freezing, 145.00 g of seasoning liquid (chicken cutlet curry sauce) was filled on top of the chicken cutlet.

[0113] -frozen- The container was then placed again in a freezer at -5°C or below for at least 8 hours to freeze, forming a two-layered structure in which the frozen seasoning liquid was placed on top of the frozen chicken cutlets (including the frozen processing liquid).

[0114] -Lyophilization- The laminated structure was subjected to vacuum freeze-drying together with the container using a freeze-dryer (manufactured by Kyowa Vacuum Engineering Co., Ltd.) at a pressure of 60 Pa. This resulted in a freeze-dried food (water content 5% by mass or less) that was a dry block with a two-layer structure of a seasoning layer and a chicken cutlet layer.

[0115] <Test Example 4-2> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 4-1, except that the contact treatment and steam-cooking treatment were not performed.

[0116] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 5.

[0117] [Table 5]

[0118] (Test Example 5) Shrimp tempura was used as an example of a food containing solid ingredients, and a freeze-dried food was produced as follows.

[0119] <Test Example 5-1> -Preparation of shrimp tempura- Frozen shrimp tempura was thawed and immersed for 5 seconds in a liquid containing 0.1% by mass of vitamin E. It was then sterilized by steaming (stopping when the temperature reached 90°C).

[0120] -contact- 74.00 g of the sterilized shrimp tempura was manually packed into a container. Next, 20.10 g (enough to immerse the shrimp tempura) of a treatment liquid (sugar alcohol-containing water (reduced starch syrup concentration 0.5% by mass) was added to the container and allowed to stand for 30 minutes.

[0121] - Hand-packed with Mitsuba leaves - Next, thawed mitsuba (4.00 g) was hand-stuffed on top of the shrimp tempura.

[0122] -frozen- The shrimp tempura was placed in a container in a freezer at -25°C for 8 hours or more and frozen.

[0123] -Seasoning liquid filling- After freezing, 129.97 g of seasoning liquid (shrimp tempura sauce) was poured on top of the shrimp tempura.

[0124] -frozen- The container was then placed again in a -25°C freezer for more than 8 hours to freeze, creating a two-layered structure in which the frozen seasoning liquid was located on top of the frozen shrimp tempura (including frozen processing liquid and mitsuba).

[0125] -Lyophilization- The laminated structure was subjected to vacuum freeze-drying together with the individual food container using a freeze-dryer (manufactured by Kyowa Vacuum Engineering Co., Ltd.) at a pressure of 60 Pa. This resulted in a freeze-dried food (water content 5% by mass or less) that was a dry block with a two-layer structure of a seasoning layer and a shrimp tempura layer.

[0126] <Test Example 5-2> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 5-1, except that no contact treatment was performed and the amount of seasoning liquid was changed to 145.00 g.

[0127] <Test Example 5-3> A freeze-dried food (moisture content: 5% by mass or less) was obtained in the same manner as in Test Example 5-1, except that the immersion time in the vitamin E-containing liquid in the shrimp tempura preparation process was changed to 10 seconds, the amount of treatment liquid used in the contact treatment was changed to 30.00 g, the reduced starch syrup concentration was changed to 2% by mass, the amount of mitsuba was changed to 3.20 g, and the amount of seasoning liquid was changed to 120.00 g.

[0128] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 6.

[0129] [Table 6]

[0130] (Test Example 6) As an example of a food containing solid ingredients, sweet potato slices were used and a freeze-dried food was produced as follows.

[0131] <Test Example 6-1> -Preparation of sweet potatoes- The sweet potatoes were cut into gingko-like slices (5 mm thick), and then physically pierced with a meat tenderizer. They were then steamed (at 90°C for 3 minutes) and sterilized.

[0132] -contact- Sterilized sweet potatoes (40.0 g) were manually packed into individual serving containers. Next, 40.0 g (enough to immerse the sweet potatoes) of a treatment liquid (water containing sugar alcohol (reduced starch syrup concentration 2% by mass) was added to the container and allowed to stand for 30 minutes.

[0133] -frozen- After the above contact treatment, the sweet potatoes were placed in a container in a freezer at -25°C for 8 hours or more to freeze them.

[0134] -Seasoning liquid filling- After freezing, 80.0 g of seasoning liquid (demi-glace sauce) was poured on top of the sweet potatoes.

[0135] -frozen- The container was then placed again in a freezer at -5°C or below for at least 8 hours to freeze, forming a two-layered structure in which the frozen seasoning liquid was located on top of the frozen sweet potatoes (including the frozen treatment liquid).

[0136] -Lyophilization- The laminated structure was subjected to vacuum freeze-drying together with the container using a freeze-dryer (manufactured by Kyowa Vacuum Engineering Co., Ltd.) at a pressure of 60 Pa. This resulted in a freeze-dried food (water content 5% by mass or less) that was a dry block with a two-layer structure of a seasoning layer and a sweet potato layer.

[0137] <Test Example 6-2> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 6-1, except that the contact treatment was not performed.

[0138] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 7.

[0139] [Table 7]

[0140] (Test Example 7) As an example of a food containing solid ingredients, sweet potato cut into strips was used to produce a freeze-dried food in the following manner.

[0141] <Test Example 7-1> -Sweet potato preparation- The sweet potatoes were cut into strips (5 mm thick) and then physically pierced with a meat tenderizer. They were then steamed (at 90°C for 3 minutes) and sterilized.

[0142] -contact- Sterilized sweet potatoes (40.0 g) were manually packed into individual serving containers. Next, 40.0 g (enough to immerse the sweet potatoes) of a treatment liquid (water containing sugar alcohol (reduced starch syrup concentration 2% by mass) was added to the container and allowed to stand for 30 minutes.

[0143] -frozen- After the above contact treatment, the sweet potatoes were placed in a container in a freezer at -25°C for 8 hours or more to freeze them.

[0144] -Seasoning liquid filling- After freezing, 80.0 g of seasoning liquid (demi-glace sauce) was poured on top of the sweet potatoes.

[0145] -frozen- The container was then placed again in a freezer at -5°C or below for at least 8 hours to freeze, forming a two-layered structure in which the frozen seasoning liquid was located on top of the frozen sweet potatoes (including the frozen treatment liquid).

[0146] -Lyophilization- The laminated structure was subjected to vacuum freeze-drying together with the container using a freeze-dryer (manufactured by Kyowa Vacuum Engineering Co., Ltd.) at a pressure of 60 Pa. This resulted in a freeze-dried food (water content 5% by mass or less) that was a dry block with a two-layer structure of a seasoning layer and a sweet potato layer.

[0147] <Test Example 7-2> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 7-1, except that the contact treatment was not performed.

[0148] <Test Example 7-3> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 7-1, except that no hole-making treatment was performed in the preparation of the sweet potatoes.

[0149] <Test Example 7-4> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 7-3, except that the contact treatment was not performed.

[0150] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 8.

[0151] [Table 8]

[0152] (Test Example 8) Taro was used as an example of a food containing solid ingredients, and a freeze-dried food was produced as follows.

[0153] <Test Example 8-1> - Preparation of taro root - The frozen taro was thawed, cut into pieces 5 mm thick, and then boiled (at 90°C for 90 seconds) and sterilized.

[0154] -contact- Sterilized taro (40.0 g) was manually packed into individual serving containers. Next, 40.0 g (enough to immerse the taro) of a treatment liquid (water containing sugar alcohol (reduced starch syrup concentration 2% by mass)) was added to the container and allowed to stand for 30 minutes.

[0155] -frozen- After the above contact treatment, the taro was placed in a container in a freezer at -25°C for 8 hours or more to freeze.

[0156] -Seasoning liquid filling- After freezing, 80.0 g of seasoning liquid (demi-glace sauce) was poured on top of the taro.

[0157] -frozen- The container was then placed again in a freezer at -5°C or below for at least 8 hours to freeze, forming a two-layered structure in which the frozen seasoning liquid was placed on top of the frozen taro (including the frozen treatment liquid).

[0158] -Lyophilization- The laminated structure was subjected to vacuum freeze-drying together with the container using a freeze-dryer (manufactured by Kyowa Vacuum Engineering Co., Ltd.) at a pressure of 60 Pa. This resulted in a freeze-dried food (water content 5% by mass or less) that was a dry block with a two-layer structure of a seasoning layer and a taro layer.

[0159] <Test Example 8-2> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 8-1, except that the contact treatment was not performed.

[0160] <Test Example 8-3> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 8-1, except that miso soup was used as the seasoning liquid.

[0161] <Test Example 8-4> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 8-3, except that the contact treatment was not performed.

[0162] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 9.

[0163] [Table 9]

[0164] (Test Example 9) Carrots were used as an example of a food containing solid ingredients, and a freeze-dried food was produced as follows.

[0165] <Test Example 9-1> - Preparation of carrots - The carrots were cut into 15 mm cubes, then physically pierced with a meat tenderizer, and then boiled (at 90°C for 10 minutes) to sterilize them.

[0166] -contact- Sterilized carrots (30.0 g) were manually packed into individual serving containers. Next, 40.0 g (enough to immerse the carrots) of a treatment liquid (water containing sugar alcohol (reduced starch syrup concentration 2% by mass)) was added to the container and allowed to stand for 30 minutes.

[0167] -frozen- After the above contact treatment, the carrots were placed in a container in a freezer at -25°C for 8 hours or more to freeze them.

[0168] -Seasoning liquid filling- After freezing, 80.0 g of seasoning liquid (demi-glace sauce) was poured on top of the carrots.

[0169] -frozen- The container was then placed again in a freezer at -5°C or below for at least 8 hours to freeze, forming a two-layered structure in which the frozen seasoning liquid was located on top of the frozen carrots (including the frozen processing liquid).

[0170] -Lyophilization- The laminated structure was subjected to vacuum freeze-drying together with the container using a freeze-dryer (manufactured by Kyowa Vacuum Engineering Co., Ltd.) at a pressure of 60 Pa. This resulted in a freeze-dried food (water content 5% by mass or less) that was a dry block having a two-layer structure of a seasoning layer and a carrot layer.

[0171] <Test Example 9-2> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 9-1, except that the contact treatment was not performed.

[0172] <Test Example 9-3> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 9-1, except that the carrots were not perforated.

[0173] <Test Example 9-4> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 9-3, except that the contact treatment was not performed.

[0174] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 10.

[0175] [Table 10]

[0176] (Test Example 10) Pumpkin was used as an example of a food containing solid ingredients, and a freeze-dried food was produced as follows.

[0177] <Test Example 10-1> -Pumpkin preparation- The pumpkin was cut into 5mm pieces and steamed (at 90°C for 3 minutes) to sterilize it.

[0178] -contact- The sterilized pumpkin (20.0 g) was manually packed into an individual serving container. Next, 40.0 g (enough to immerse the pumpkin) of a treatment liquid (water containing sugar alcohol (reduced starch syrup concentration 2% by mass) was poured into the container and left to stand for 30 minutes.

[0179] -frozen- After the above contact treatment, the pumpkin in the container was left to stand in a freezer at -25°C for 8 hours or more to freeze.

[0180] -Seasoning liquid filling- After freezing, 80.0 g of seasoning liquid (demi-glace sauce) was poured onto the pumpkin.

[0181] -frozen- The container was then placed again in a freezer at -5°C or below for at least 8 hours to freeze, creating a two-layer structure in which the frozen seasoning liquid was located on top of the frozen pumpkin (including the frozen treatment liquid).

[0182] -Lyophilization- The laminated structure was subjected to vacuum freeze-drying together with the container using a freeze-dryer (manufactured by Kyowa Vacuum Engineering Co., Ltd.) at a pressure of 60 Pa. This resulted in a freeze-dried food (water content 5% by mass or less) that was a dry block with a two-layer structure of a seasoning layer and a pumpkin layer.

[0183] <Test Example 10-2> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 10-1, except that the contact treatment was not performed.

[0184] <Test Example 10-3> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 10-1, except that miso soup was used as the seasoning liquid.

[0185] <Test Example 10-4> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 10-3, except that the contact treatment was not performed.

[0186] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 11.

[0187] [Table 11]

[0188] (Test Example 11) Burdock was used as an example of a food containing solid ingredients, and a freeze-dried food was produced as follows.

[0189] <Test Example 11-1> - Preparation of burdock root - The burdock root was cut to a thickness of 5 mm, and then physically pierced with a meat tenderizer. It was then boiled (at 90°C for 10 minutes) to sterilize it.

[0190] -contact- Sterilized burdock (15.0 g) was manually packed into an individual serving container. Next, 20.0 g (enough to immerse the burdock) of a treatment liquid (water containing sugar alcohol (reduced starch syrup concentration 2% by mass) was added to the container and left to stand for 30 minutes.

[0191] -frozen- After the above contact treatment, the burdock was placed in a container in a freezer at -25°C for 8 hours or more to freeze.

[0192] -Seasoning liquid filling- After freezing, 80.0 g of seasoning liquid (demi-glace sauce) was poured on top of the burdock.

[0193] -frozen- The container was then placed again in a freezer at -5°C or below for at least 8 hours until it was frozen, forming a two-layered structure in which the frozen seasoning liquid was placed on top of the frozen burdock (including the frozen processing liquid).

[0194] -Lyophilization- The laminated structure was subjected to vacuum freeze-drying together with the container using a freeze-dryer (manufactured by Kyowa Vacuum Engineering Co., Ltd.) at a pressure of 60 Pa. This resulted in a freeze-dried food (water content 5% by mass or less) that was a dry block with a two-layer structure of a seasoning layer and a burdock layer.

[0195] <Test Example 11-2> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 11-1, except that the contact treatment was not performed.

[0196] <Test Example 11-3> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 11-1, except that the burdock root was not perforated.

[0197] <Test Example 11-4> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 11-3, except that the contact treatment was not performed.

[0198] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 12.

[0199] [Table 12]

[0200] (Test Example 12) Cabbage was used as an example of a food containing solid ingredients, and a freeze-dried food was produced as follows.

[0201] <Test Example 12-1> - Preparation of cabbage - Cabbage cut into 30 mm cubes was boiled (95°C or higher for 2 minutes) and sterilized.

[0202] -contact- Sterilized cabbage (40.0 g) was manually packed into an individual serving container. Next, 40.0 g (enough to immerse the cabbage) of a treatment liquid (water containing sugar alcohol (reduced starch syrup concentration 2% by mass) was added to the container and allowed to stand for 30 minutes.

[0203] -frozen- After the above contact treatment, the cabbages were placed in a container in a freezer at -25°C for 8 hours or more to freeze them.

[0204] -Seasoning liquid filling- After freezing, 80.0 g of seasoning liquid (demi-glace sauce) was poured onto the cabbage.

[0205] -frozen- The container was then placed again in a freezer at -5°C or below for at least 8 hours to freeze, forming a two-layered structure in which the frozen seasoning liquid was placed on top of the frozen cabbage (including the frozen processing liquid).

[0206] -Lyophilization- The laminated structure was subjected to vacuum freeze-drying together with the container using a freeze-dryer (manufactured by Kyowa Vacuum Engineering Co., Ltd.) at a pressure of 60 Pa. This resulted in a freeze-dried food (water content 5% by mass or less) that was a dry block with a two-layer structure of a seasoning layer and a cabbage layer.

[0207] <Test Example 12-2> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 12-1, except that the contact treatment was not performed.

[0208] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 13.

[0209] [Table 13]

[0210] (Test Example 13) As an example of a food containing solid ingredients, squid was used and a freeze-dried food was produced as follows.

[0211] <Test Example 13-1> -Preparation of squid- The frozen squid was thawed and cut into pieces 10 mm thick, then physically pierced with a meat tenderizer.Then, the squid was boiled (at 90°C for 3 minutes) and sterilized.

[0212] -contact- Sterilized squid (50.0 g) was manually packed into an individual serving container. Next, 40.0 g (enough to immerse the squid) of a treatment liquid (water containing sugar alcohol (reduced starch syrup concentration 2% by mass)) was poured into the container and left to stand for 30 minutes.

[0213] -frozen- After the above contact treatment, the squid was placed in a container in a freezer at -25°C for at least 8 hours and frozen.

[0214] -Seasoning liquid filling- After freezing, 80.0 g of seasoning liquid (demi-glace sauce) was poured on top of the squid.

[0215] -frozen- The container was then placed again in a freezer at -5°C or below for at least 8 hours to freeze, forming a two-layered structure in which the frozen seasoning liquid was located on top of the frozen carrots (including the frozen processing liquid).

[0216] -Lyophilization- The laminated structure was subjected to vacuum freeze-drying together with the container using a freeze-dryer (manufactured by Kyowa Vacuum Engineering Co., Ltd.) at a pressure of 60 Pa. This resulted in a freeze-dried food (water content 5% by mass or less) that was a dry block having a two-layer structure of a seasoning layer and a squid layer.

[0217] <Test Example 13-2> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 13-1, except that the contact treatment was not performed.

[0218] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 14.

[0219] [Table 14]

[0220] (Test Example 14) Tuna was used as an example of a food containing solid ingredients, and a freeze-dried food was produced as follows.

[0221] <Test Example 14-1> - Preparation of tuna - The tuna was cut into cubes of 20 mm square, and then physically pierced with a meat tenderizer. It was then boiled (at 90°C for 3 minutes) to sterilize it.

[0222] -contact- The pasteurized tuna (30.0 g) was manually packed into an individual serving container. Next, 40.0 g (enough to immerse the tuna) of a treatment liquid (water containing sugar alcohol (reduced starch syrup concentration 2% by mass) was added to the container and allowed to stand for 30 minutes.

[0223] -frozen- After the above contact treatment, the tuna was placed in a container in a freezer at -25°C for at least 8 hours and frozen.

[0224] -Seasoning liquid filling- After freezing, 80.0 g of seasoning liquid (demi-glace sauce) was poured on top of the tuna.

[0225] -frozen- The container was then placed again in a freezer at -5°C or below for at least 8 hours to freeze, creating a two-layered structure in which the frozen seasoning liquid was placed on top of the frozen tuna (including the frozen treatment liquid).

[0226] -Lyophilization- The laminated structure was subjected to vacuum freeze-drying together with the container using a freeze-dryer (manufactured by Kyowa Vacuum Engineering Co., Ltd.) at a pressure of 60 Pa. This resulted in a freeze-dried food (water content 5% by mass or less) that was a dry block with a two-layer structure of a seasoning layer and a tuna layer.

[0227] <Test Example 14-2> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 14-1, except that the contact treatment was not performed.

[0228] <Test Example 14-3> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 14-1, except that no hole-making process was performed in the preparation of the tuna.

[0229] <Test Example 14-4> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 14-3, except that the contact treatment was not performed.

[0230] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 15.

[0231] [Table 15]

[0232] (Test Example 15) Salmon was used as an example of a food containing solid ingredients, and a freeze-dried food was produced as follows.

[0233] <Test Example 15-1> -Preparation of salmon- The salmon was cut into cubes of 20 mm square, and then physically pierced with a meat tenderizer. It was then boiled (at 90°C for 3 minutes) to sterilize it.

[0234] -contact- The pasteurized salmon (50.0 g) was manually packed into an individual serving container. Next, 40.0 g (enough to immerse the salmon) of a treatment liquid (water containing sugar alcohol (reduced starch syrup concentration 2% by mass) was poured into the container and allowed to stand for 30 minutes.

[0235] -frozen- After the above contact treatment, the salmon was placed in a container in a freezer at -25°C for at least 8 hours and frozen.

[0236] -Seasoning liquid filling- After freezing, 80.0 g of seasoning liquid (demi-glace sauce) was poured onto the salmon.

[0237] -frozen- The container was then placed again in a freezer at -5°C or below for at least 8 hours until frozen, forming a two-layered structure in which the frozen seasoning liquid was located on top of the frozen salmon (including the frozen processing liquid).

[0238] -Lyophilization- The laminated structure was subjected to vacuum freeze-drying together with the container using a freeze-dryer (manufactured by Kyowa Vacuum Engineering Co., Ltd.) at a pressure of 60 Pa. This resulted in a freeze-dried food (water content 5% by mass or less) that was a dry block with a two-layer structure of a seasoning layer and a salmon layer.

[0239] <Test Example 15-2> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 15-1, except that the contact treatment was not performed.

[0240] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 16.

[0241] [Table 16]

[0242] (Test Example 16) As an example of a food containing solid ingredients, bonito was used and a freeze-dried food was produced as follows.

[0243] <Test Example 16-1> - Preparation of bonito - The bonito was cut into cubes of 20 mm square, and then physically pierced with a meat tenderizer. It was then boiled (at 90°C for 3 minutes) and sterilized.

[0244] -contact- Sterilized bonito (40.0 g) was manually packed into an individual serving container. Next, 40.0 g (enough to immerse the bonito) of a treatment liquid (water containing sugar alcohol (reduced starch syrup concentration 2% by mass)) was added to the container and allowed to stand for 30 minutes.

[0245] -frozen- After the above contact treatment, the bonito was placed in a container in a freezer at -25°C for 8 hours or more to freeze it.

[0246] -Seasoning liquid filling- After freezing, 80.0 g of seasoning liquid (demi-glace sauce) was poured on top of the bonito.

[0247] -frozen- The container was then placed again in a freezer at -5°C or below for at least 8 hours until it was frozen, forming a two-layered structure in which the frozen seasoning liquid was located on top of the frozen bonito (including the frozen processing liquid).

[0248] -Lyophilization- The laminated structure was subjected to vacuum freeze-drying together with the container using a freeze-dryer (manufactured by Kyowa Vacuum Engineering Co., Ltd.) at a pressure of 60 Pa. This resulted in a freeze-dried food (water content 5% by mass or less) that was a dry block with a two-layer structure of a seasoning layer and a bonito layer.

[0249] <Test Example 16-2> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 16-1, except that the contact treatment was not performed.

[0250] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 17.

[0251] [Table 17]

[0252] (Test Example 17) Shrimp was used as an example of a food containing solid ingredients, and a freeze-dried food was produced as follows.

[0253] <Test Example 17-1> -Preparation of shrimp- After peeling the shrimp, they were physically pierced with a meat tenderizer, then boiled (at 90°C for 3 minutes) to sterilize them.

[0254] -contact- Sterilized shrimp (30.0 g) were manually packed into individual serving containers. Next, 40.0 g (enough to immerse shrimp) of treatment liquid (sugar alcohol-containing water (reduced starch syrup concentration 2% by mass) was poured into the container and left to stand for 30 minutes.

[0255] -frozen- After the above contact treatment, the shrimp were placed in a container in a freezer at -25°C for at least 8 hours and frozen.

[0256] -Seasoning liquid filling- After freezing, 80.0 g of seasoning liquid (demi-glace sauce) was poured onto the shrimp.

[0257] -frozen- The container was then placed again in a freezer at -5°C or below for at least 8 hours to freeze, forming a two-layer structure in which the frozen seasoning liquid was placed on top of the frozen shrimp (including the frozen processing liquid).

[0258] -Lyophilization- The laminated structure was subjected to vacuum freeze-drying together with the container using a freeze-dryer (manufactured by Kyowa Vacuum Engineering Co., Ltd.) at a pressure of 60 Pa. This resulted in a freeze-dried food (water content 5% by mass or less) that was a dry block with a two-layer structure of a seasoning layer and a shrimp layer.

[0259] <Test Example 17-2> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 17-1, except that the contact treatment was not performed.

[0260] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 18.

[0261] [Table 18]

[0262] (Test Example 18) As an example of a food containing solid ingredients, scallops were used and a freeze-dried food was produced as follows.

[0263] <Test Example 18-1> - Preparation of scallops - The shucked scallops were physically pierced with a meat tenderizer, then boiled (at 90°C for 3 minutes) to sterilize them.

[0264] -contact- Sterilized scallops (40.0 g) were manually packed into individual serving containers. Next, 40.0 g (enough to immerse the scallops) of treatment liquid (water containing sugar alcohol (reduced starch syrup concentration 2% by mass)) was added to the container and left to stand for 30 minutes.

[0265] -frozen- After the above contact treatment, the scallops were placed in a container in a freezer at -25°C for at least 8 hours and frozen.

[0266] -Seasoning liquid filling- After freezing, 80.0 g of seasoning liquid (demi-glace sauce) was poured onto the scallops.

[0267] -frozen- The container was then placed again in a freezer at -5°C or below for at least 8 hours to freeze, creating a two-layered structure in which the frozen seasoning liquid was placed on top of the frozen scallops (including the frozen treatment liquid).

[0268] -Lyophilization- The laminated structure was subjected to vacuum freeze-drying together with the container using a freeze-dryer (manufactured by Kyowa Vacuum Engineering Co., Ltd.) at a pressure of 60 Pa. This resulted in a freeze-dried food (water content 5% by mass or less) that was a dry block with a two-layer structure of a seasoning layer and a scallop layer.

[0269] <Test Example 18-2> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 18-1, except that the contact treatment was not performed.

[0270] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 19.

[0271] [Table 19]

[0272] (Test Example 19) As an example of a food containing solid ingredients, a freeze-dried food was produced using a mussel shellfish as follows.

[0273] <Test Example 19-1> - Preparation of the itayagai - After thawing the frozen mushrooms, they were boiled (at 90°C for 3 minutes) to sterilize them.

[0274] -contact- Sterilized oyster shells (20.0 g) were manually packed into individual serving containers. Next, 40.0 g (enough to immerse the oyster shells) of a treatment liquid (water containing sugar alcohol (reduced starch syrup concentration 2% by mass)) was poured into the container and left to stand for 30 minutes.

[0275] -frozen- After the above contact treatment, the container containing the oysters was placed in a freezer at -25°C for 8 hours or more to freeze them.

[0276] -Seasoning liquid filling- After freezing, 80.0 g of seasoning liquid (demi-glace sauce) was poured on top of the frozen yams.

[0277] -frozen- The container was then placed again in a freezer at -5°C or below for at least 8 hours to freeze, forming a two-layered structure in which the frozen seasoning liquid was placed on top of the frozen oyster shells (including the frozen treatment liquid).

[0278] -Lyophilization- The laminated structure was subjected to vacuum freeze-drying together with the container using a freeze-dryer (manufactured by Kyowa Vacuum Engineering Co., Ltd.) at a pressure of 60 Pa. This resulted in a freeze-dried food (water content 5% by mass or less) that was a dry block with a two-layer structure of a seasoning layer and a ginger layer.

[0279] <Test Example 19-2> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 19-1, except that the contact treatment was not performed.

[0280] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 20.

[0281] [Table 20]

[0282] (Test Example 20) As an example of a food containing solid ingredients, amberjack was used and a freeze-dried food was produced as follows.

[0283] <Test Example 20-1> -Preparation of Amberjack- The amberjack was cut into cubes of 20 mm square, and then physically pierced with a meat tenderizer. It was then boiled (at 90°C for 3 minutes) to sterilize it.

[0284] -contact- The pasteurized amberjack (30.0 g) was manually packed into an individual serving container. Next, 40.0 g (enough to immerse the amberjack) of the treatment liquid (water containing sugar alcohol (reduced starch syrup concentration 2% by mass)) was poured into the container and left to stand for 30 minutes.

[0285] -frozen- After the above contact treatment, the amberjacks were placed in a container in a freezer at -25°C for more than 8 hours and frozen.

[0286] -Seasoning liquid filling- After freezing, 80.0 g of seasoning liquid (demi-glace sauce) was poured on top of the amberjack.

[0287] -frozen- The container was then placed again in a freezer at -5°C or below for at least 8 hours until it was frozen, forming a two-layered structure in which the frozen seasoning liquid was placed on top of the frozen amberjack (including the frozen processing liquid).

[0288] -Lyophilization- The laminated structure was subjected to vacuum freeze-drying together with the container using a freeze-dryer (manufactured by Kyowa Vacuum Engineering Co., Ltd.) at a pressure of 60 Pa. This resulted in a freeze-dried food (water content 5% by mass or less) that was a dry block with a two-layer structure of a seasoning layer and an amberjack layer.

[0289] <Test Example 20-2> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 20-1, except that the contact treatment was not performed.

[0290] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 21.

[0291] [Table 21]

[0292] As described above, it was confirmed that freeze-dried foods with good reconstitution properties can be produced according to the method of the present invention, even when the type of solid food material is changed.

Claims

1. A contacting step of contacting a food containing solid ingredients with a treatment liquid; a freezing step of freezing the food containing the solid food material that has been contacted with the treatment liquid; a freeze-drying step of freeze-drying the food containing the solid food material frozen in the freezing step together with a frozen seasoning; A method for producing a freeze-dried food, comprising the steps of:

2. 2. The method for producing a freeze-dried food according to claim 1, wherein the freeze-drying step is a step of freeze-drying in a state in which the frozen seasoning is located on top of the food containing the solid food material frozen in the freezing step.

3. 2. The method for producing a freeze-dried food according to claim 1, wherein the freeze-drying step is a step of freeze-drying in a state in which the food containing the solid ingredients frozen in the freezing step is located on top of the frozen seasoning.

4. 4. The method for producing a freeze-dried food according to claim 1, wherein the freezing step is a step of freezing the food containing the solid food material while immersed in the treatment liquid.

5. 4. The method for producing a freeze-dried food according to claim 1, wherein the freezing step is a step of freezing a food containing the solid food material that has been contacted with the treatment liquid and then drained of liquid.

6. The method for producing a freeze-dried food according to claim 1 , wherein the treatment liquid contains a sugar alcohol.

7. The method for producing a freeze-dried food according to claim 4, wherein the treatment liquid contains a sugar alcohol.

8. The method for producing a freeze-dried food according to claim 5 , wherein the treatment liquid contains a sugar alcohol.

9. A contacting step of contacting a food containing solid ingredients with a treatment liquid; a freezing step of freezing the food containing the solid food material that has been contacted with the treatment liquid; a freeze-drying step of freeze-drying the food containing the solid food material frozen in the freezing step together with a frozen seasoning; A method for improving the reconstitution of freeze-dried food, comprising the steps of:

10. 10. The method for improving the reconstitution of a freeze-dried food according to claim 9, wherein the freeze-drying step is a step of freeze-drying in a state in which the frozen seasoning is located on top of the food containing the solid food ingredients frozen in the freezing step.

11. 10. The method for improving the reconstitution of a freeze-dried food according to claim 9, wherein the freeze-drying step is a step of freeze-drying in a state in which the food containing the solid ingredients frozen in the freezing step is positioned on top of the frozen seasoning.

12. 12. The method for improving the reconstitution property of a freeze-dried food according to claim 9, wherein the freezing step is a step of freezing the food containing the solid food material while immersed in the treatment liquid.

13. 12. The method for improving the reconstitution of a freeze-dried food according to claim 9, wherein the freezing step is a step of freezing a food containing the solid food material that has been contacted with the treatment liquid and then drained of liquid.

14. The method for improving the reconstitution property of a freeze-dried food according to any one of claims 9 to 11, wherein the treatment liquid contains a sugar alcohol.

15. The method for improving the reconstitution property of a freeze-dried food according to claim 12, wherein the treatment liquid contains a sugar alcohol.

16. The method for improving the reconstitution property of a freeze-dried food according to claim 13, wherein the treatment liquid contains a sugar alcohol.

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