Method for manufacturing freeze-dried food and method for improving restorability of freeze-dried food

Abstract

To provide a method for manufacturing a freeze-dried food that can manufacture a freeze-dried food having preferable restorability and containing a food including a solid food material with a simple method, and to provide a method for improving restorability of a freeze-dried food.SOLUTION: A method for manufacturing a freeze-dried food includes: a contact step of bringing a solid food material-containing food product into contact with a sugar-alcohol-containing liquid; a freezing step of freezing the solid food material-containing food product that has been brought into contact with the sugar-alcohol-containing liquid; and a freeze-drying step of freezing and drying the solid food material-containing food product that has been frozen in the freezing step.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, there has been an increasing demand in recent years for freeze-dried instant foods (hereinafter sometimes referred to as "freeze-dried foods") that can be eaten simply by pouring hot water over them and waiting a short time. These foods are manufactured using a method that includes a freeze-drying process, and 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 properties and flavor, a method for producing freeze-dried meat has been proposed in which heat-treated meat is perforated from the surface with multiple holes, then the meat is treated with superheated steam and freeze-dried (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-135918 Summary of the Invention [Problem to be solved by the invention]

[0005] With the recent increase in demand for instant foods, consumers' expectations for reconstitution have also increased. Therefore, there is a strong demand for a technology that can produce freeze-dried foods with better reconstitution properties.

[0006] The present invention aims to solve the above-mentioned problems of 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, that 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]

[0007] In order to solve the above-mentioned problems, the inventors conducted extensive research and discovered that the reconstitution of freeze-dried foods, including foods containing solid ingredients, can be easily improved by carrying out a contact process in which a food containing solid ingredients is brought into contact with a sugar alcohol-containing liquid (hereinafter sometimes referred to as a "treatment liquid"), followed by freezing and freeze-drying.

[0008] The present invention is based on the above 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 a solid food ingredient with a sugar alcohol-containing liquid; a freezing step of freezing the food containing the solid food material that has been contacted with the sugar alcohol-containing liquid; a freeze-drying step of freeze-drying the food containing the solid food material frozen in the freezing step; The method for producing a freeze-dried food is characterized by comprising the steps of: <2> The sugar alcohol content in the sugar alcohol-containing liquid is 1 to 10% by mass. <1> This is a method for producing the freeze-dried food described above. <3> The freezing step is a step of freezing the food containing the solid food material while immersed in the sugar alcohol-containing liquid. <1> or <2> This is a method for producing the freeze-dried food described above. <4> The freezing step is a step of freezing the food containing the solid food material that has been contacted with the sugar alcohol-containing liquid and then drained. <1> or <2> This is a method for producing the freeze-dried food described above. <5> a contacting step of contacting a food containing a solid food ingredient with a sugar alcohol-containing liquid; a freezing step of freezing the food containing the solid food material that has been contacted with the sugar alcohol-containing liquid; a freeze-drying step of freeze-drying the food containing the solid food material frozen in the freezing step; The method for improving the reconstitution property of freeze-dried food is characterized by comprising the steps of: <6> The sugar alcohol content in the sugar alcohol-containing liquid is 1 to 10% by mass. <5> This is a method for improving the reconstitution property of the freeze-dried food described in the above. <7> The freezing step is a step of freezing the food containing the solid food material while immersed in the sugar alcohol-containing liquid. <5> or <6> This is a method for improving the reconstitution property of the freeze-dried food described in the above. <8> The freezing step is a step of freezing the food containing the solid food material that has been contacted with the sugar alcohol-containing liquid and then drained. <5> or <6> This is a method for improving the reconstitution property of the freeze-dried food described in the above. [Effects of the Invention]

[0009] According to the present invention, it is possible to solve the above-mentioned problems in the prior art, achieve the above-mentioned object, 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 INVENTION

[0010] (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, 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, and a freeze-drying step, and may further include other steps as necessary. The method for improving the reconstitution property of freeze-dried foods of the present invention can be carried out in the same manner as the method for producing freeze-dried foods of the present invention, so below we will explain both the method for producing freeze-dried foods of the present invention and the method for improving the reconstitution property of freeze-dried foods of the present invention together.

[0011] <Foods 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 needed.

[0012] The solid food material is not particularly limited and can be appropriately selected depending on the purpose. Examples 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. 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 consist of only solid ingredients.

[0013] The meat is not particularly limited as long as it can be used in food products, and can be appropriately selected depending on the purpose. Examples include chicken, beef, pork, lamb, horse meat, wild boar, wild boar and pork, duck, crossbred duck, turkey, and domestic duck.

[0014] 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 sea cucumber.

[0015] The parts of the meat and seafood to be used are not particularly limited and can be appropriately selected depending on the purpose.

[0016] 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 include sweet potato, taro, carrot, pumpkin, burdock, cabbage, and broccoli.

[0017] The part of the vegetable to be used is not particularly limited and can be appropriately selected depending on the purpose.

[0018] The above-mentioned ingredients that imitate these refer to ingredients that can be used to produce food products that have the same texture as the above-mentioned meats, seafood, or vegetables when cooked. The food materials that imitate these are not particularly limited, and known food materials can be appropriately selected, for example, food materials produced using plant-derived raw materials such as soy protein and wheat protein.

[0019] The solid food-containing food is not particularly limited as long as it contains solid food ingredients and can be appropriately selected depending on the purpose, and examples include hamburger steak, pork cutlet, chicken cutlet, shrimp tempura, etc. These may be used alone or in combination of two or more.

[0020] <Freeze-dried foods> The freeze-dried food contains at least the solid ingredient-containing food and, if necessary, further contains other ingredients. The freeze-dried food may consist solely of the solid ingredient-containing food.

[0021] The other ingredients in the freeze-dried food are not particularly limited, and ingredients that are usually used in freeze-dried instant foods that are reconstituted in hot water can be appropriately selected depending on the purpose.

[0022] The freeze-dried food is not particularly limited and can be appropriately selected depending on the purpose.

[0023] The shape, structure, and size of the freeze-dried food are not particularly limited and can be appropriately selected depending on the purpose. For example, the shape may be a block.

[0024] The present invention includes at least a contacting step, a freezing step, 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 can be appropriately selected depending on the purpose, such as a step of preparing a food containing solid ingredients.

[0025] <Food preparation process containing solid ingredients> The solid ingredient-containing food preparation step is a step of preparing food containing solid ingredients.

[0026] The treatment in the solid foodstuff-containing food preparation step is not particularly limited and can be appropriately selected depending on the purpose. Examples include cutting, punching, oiling, filling, and sterilization.

[0027] 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 can 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.

[0028] 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. 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 through. The holes may be formed on only one side of the solid foodstuff-containing food product or on both sides. The holes may be drilled at multiple locations at once, or may be drilled in multiple steps.

[0029] The oil-frying process is a step of oil-frying (hereinafter, sometimes referred to as "frying" or "deep-frying") the solid ingredient-containing food. The method and conditions for adjusting the oil are not particularly limited and can be appropriately selected depending on the purpose.

[0030] The filling process is a step of filling the solid ingredient-containing food into a container. The container is not particularly limited as long as it can be used for producing freeze-dried foods, and can be appropriately selected depending on the purpose.

[0031] The sterilization treatment is a treatment for sterilizing the food containing solid ingredients. The sterilization method is not particularly limited, and any known method can be appropriately selected, such as steaming or boiling. The conditions for the sterilization are not particularly limited and can be appropriately selected depending on the purpose.

[0032] The order in which the above-mentioned processes are carried out is not particularly limited and can be appropriately selected depending on the purpose.

[0033] <Contact process> The contacting step is a step of contacting the solid ingredient-containing food with a sugar alcohol-containing liquid.

[0034] -Sugar alcohol-containing liquid- The solvent used for the sugar alcohol-containing liquid is not particularly limited as long as it is an aqueous solvent such as water that can be used in foods, and can be appropriately selected depending on the purpose. The sugar alcohol-containing liquid may contain other components in addition to the sugar alcohol, if necessary.

[0035] 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. Among the sugar alcohols, reduced starch syrup and sorbitol are preferred in that they provide more excellent effects.

[0036] The content of the sugar alcohol in the sugar alcohol-containing liquid is not particularly limited and can 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. A content within the above preferred range is advantageous in that both reconstitution property and flavor are excellent.

[0037] The other components in the sugar alcohol-containing solution 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. The content of the other components in the sugar alcohol-containing liquid is not particularly limited and can be appropriately selected depending on the purpose.

[0038] The contact method 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 sugar alcohol-containing liquid, a method of applying or spraying the sugar alcohol-containing liquid onto the solid ingredient-containing food, etc. For example, the sugar alcohol-containing liquid can be filled into a container containing the solid ingredient-containing food and then brought into contact with the solid ingredient-containing food.

[0039] The amount of the sugar alcohol-containing liquid used for the solid food material-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 entire solid food material-containing food can be used, and in the case of application or spraying, an amount sufficient to bring the entire solid food material-containing food into contact with the sugar alcohol-containing liquid can be used.

[0040] 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.

[0041] The solid food material-containing food may be drained after the contacting step, or may be subjected to the steps described below without being drained.

[0042] <Freezing process> The freezing step is a step of freezing the solid ingredient-containing food that has been brought into contact with the sugar alcohol-containing liquid.

[0043] The form of the freezing process is not particularly limited and can be selected appropriately depending on the purpose. For example, (a) the solid ingredient-containing food is frozen while immersed in the sugar alcohol-containing liquid, or (b) the solid ingredient-containing food is contacted with the sugar alcohol-containing liquid and then drained and frozen.

[0044] The freezing conditions are not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include leaving the mixture to stand at −10° C. or below until it is completely frozen. The freezing temperature may be constant, or the mixture may be frozen stepwise at different temperatures.

[0045] <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. The freeze-drying step may be performed after the freezing step, and another step may be included between the freezing step and the freeze-drying step.

[0046] The freeze-drying method is not particularly limited, and any known method can be appropriately selected.

[0047] The vacuum freeze-drying can be carried out using a known freeze-dryer. The method of 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 moisture 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.

[0048] According to the method of the present invention, freeze-dried foods with good reconstitution properties can be produced in a simple manner. [Example]

[0049] The present invention will be specifically explained below with reference to test examples, but the present invention is not limited to these test examples.

[0050] (Test Example 1) <Test Example 1-1> Using hamburger as an example of a food containing solid ingredients, a freeze-dried food was produced as follows.

[0051] -Hamburg steak preparation- The cooked frozen hamburger steak was thawed and then cut into 2 cm cubes. It was then steamed (stopped when the temperature reached 90°C) and sterilized. The recipe for the cooked frozen hamburger steak was as follows: -Prepared frozen hamburger recipe- · 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

[0052] -contact- Sterilized hamburger steak (50.0 g) was immersed in 100.0 g of a treatment liquid (water containing 2% by mass of reduced starch syrup (MU-45, manufactured by Ueno Food Techno Co., Ltd.)), left to stand overnight in a refrigerator, and then drained.

[0053] -frozen- The drained hamburger steaks were hand-packed into individual serving containers, and the individual serving containers were left to stand in a freezer at -25°C for 8 hours or more until frozen.

[0054] -Lyophilization- The frozen hamburger steak, together with the individual serving container, was subjected to vacuum freeze-drying using a freeze-dryer (manufactured by Kyowa Vacuum Engineering Co., Ltd.) at a pressure of 60 Pa. This resulted in a freeze-dried food product (water content of 5% by mass or less) in the form of a dry block.

[0055] <Test Example 1-2> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 1-1, except that the content of reduced starch syrup in the treatment solution for contact treatment was set to 5% by mass.

[0056] <Test Example 1-3> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 1-1, except that the content of reduced starch syrup in the treatment solution for contact treatment was set to 10% by mass.

[0057] <Test Example 1-4> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 1-1, except that the treatment liquid for contact treatment was changed to water.

[0058] <Test Example 1-5> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 1-1, except that the contact treatment was not carried out.

[0059] <Evaluation> The freeze-dried food was added with 80 mL of boiling water, and after 30 seconds, it was eaten. The reconstitution and flavor were evaluated according to the following criteria. The results are shown in Table 1. The evaluation was carried out by four trained evaluators. In Test Example 2 and onwards, the evaluation was carried out by three or four evaluators. The evaluation results for reconstitution were shown as the average of the evaluation results from each evaluator, and the evaluation results for flavor were consistent among all evaluators (the same applies to Test Example 2 and onward).

[0060] [Evaluation criteria] -Resilience- 5 points: Reconstituted and very soft in texture. 4 points: Reconstituted and soft in texture. 3 points: Restored. 2 points: The exterior has been restored, but the center has not. 1 point: Not restored.

[0061] -flavor- ○: No sweetness is detected. △: Slightly sweet. ×: Very sweet.

[0062] [Table 1]

[0063] (Test Example 2) <Test Example 2-1> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 1-1, except that the treatment liquid for contact treatment was replaced with water containing 1.5% by mass of reduced starch syrup A (MU45, manufactured by Ueno Food Techno Co., Ltd.).

[0064] <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 the content of reduced starch syrup A in the treatment solution for contact treatment was set to 2.0% by mass.

[0065] <Test Example 2-3> 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 the treatment liquid for contact treatment was changed to water containing 1.0% by mass of sorbitol.

[0066] <Test Example 2-4> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 2-3, except that the sorbitol content in the treatment solution for contact treatment was set to 1.5% by mass.

[0067] <Test Example 2-5> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 2-3, except that the sorbitol content in the treatment solution for contact treatment was set to 2.0% by mass.

[0068] <Test Example 2-6> A freeze-dried food (water content of 5% by mass or less) was obtained in the same manner as in Test Example 2-1, except that the treatment liquid for contact treatment was replaced with water containing 1.0% by mass of reduced starch syrup B (SE 30, manufactured by Bussan Food Science Co., Ltd.).

[0069] <Test Example 2-7> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 2-6, except that the content of reduced starch syrup B in the treatment solution for contact treatment was set to 1.5% by mass.

[0070] <Test Example 2-8> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 2-6, except that the content of reduced starch syrup B in the treatment solution for contact treatment was set to 2.0% by mass.

[0071] <Test Example 2-9> A freeze-dried food (water content of 5% by mass or less) was obtained in the same manner as in Test Example 2-1, except that the treatment liquid for contact treatment was replaced with water containing 1.5% by mass of reduced starch syrup C (SE 600, manufactured by Bussan Food Science Co., Ltd.).

[0072] <Test Example 2-10> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 2-9, except that the content of reduced starch syrup C in the treatment solution for contact treatment was set to 2.0% by mass.

[0073] <Test Example 2-11> 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 the treatment liquid for contact treatment was changed to water containing 2.0% by mass of granulated sugar.

[0074] <Test Example 2-12> 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 the treatment liquid for contact treatment was changed to water.

[0075] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 2.

[0076] [Table 2]

[0077] From the above results, it was confirmed that the method of the present invention makes it possible to produce freeze-dried foods with good reconstitution properties that can be reconstituted to a edible state in a short period of time using a simple method.

[0078] (Test Example 3) Pork (loin) was used as an example of a food containing solid ingredients, and a freeze-dried food was produced as follows.

[0079] <Test Example 3-1> -Preparation of pork (loin)- Pork (loin) was cut into 15 mm thick slices, and then physically pierced with a meat tenderizer. It was then boiled (stopped at 90°C) and sterilized.

[0080] -contact- Sterilized pork (40.0 g) was manually packed into a single-serving container. Next, 40.0 g (enough to immerse the pork) of a treatment solution (water containing sugar alcohol (reduced starch syrup concentration 2% by mass)) was poured into the container and allowed to stand for 30 minutes.

[0081] -frozen- After the above contact treatment, the pork was placed in a container in a freezer at -25°C for at least 8 hours and frozen.

[0082] -Lyophilization- The frozen pork (including the frozen processing liquid) was vacuum freeze-dried together with the individual serving containers using a freeze dryer (manufactured by Kyowa Vacuum Engineering Co., Ltd.) at a pressure of 60 Pa. This resulted in a freeze-dried food product (with a moisture content of 5% by mass or less) in the form of a dry block.

[0083] <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 was not carried out.

[0084] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 3.

[0085] [Table 3]

[0086] (Test Example 4) Beef (round) was used as an example of a food containing solid ingredients, and a freeze-dried food was produced as follows.

[0087] <Test Example 4-1> -Beef (Thigh) Preparation- The beef (thigh) was cut into 5mm thick slices and physically pierced with a meat tenderizer. It was then boiled (stopped at 90°C) and sterilized.

[0088] -contact- Sterilized beef (20.0 g) was manually packed into individual serving containers. Next, 40.0 g (enough to immerse the beef) of a treatment solution (sugar alcohol-containing water (reduced starch syrup concentration 2% by mass)) was poured into the containers and allowed to stand for 30 minutes.

[0089] -frozen- After the contact treatment, the beef was frozen in its container at −25°C for at least 8 hours.

[0090] -Lyophilization- The frozen beef (including the frozen treatment liquid) was vacuum freeze-dried together with the individual serving containers using a freeze dryer (manufactured by Kyowa Vacuum Engineering Co., Ltd.) at a pressure of 60 Pa. This resulted in a freeze-dried food product (water content of 5% by mass or less) in the form of a dry block.

[0091] <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 was not carried out.

[0092] <Test Example 4-3> A freeze-dried food (water content of 5% by mass or less) was obtained in the same manner as in Test Example 4-1, except that the beef was not perforated.

[0093] <Test Example 4-4> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 4-3, except that the contact treatment was not carried out.

[0094] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 4.

[0095] [Table 4]

[0096] (Test Example 5) Chicken meat (breast) was used as an example of a food containing solid ingredients, and a freeze-dried food was produced as follows.

[0097] <Test Example 5-1> -Preparation of chicken breast- Chicken meat (breast) was cut into 20 mm thick pieces, and then physically pierced with a meat tenderizer. It was then boiled (stopped at 90°C) and sterilized.

[0098] -contact- Sterilized chicken meat (30.0 g) was manually packed into individual serving containers. Next, 40.0 g (enough to immerse the chicken meat) of a treatment solution (water containing sugar alcohol (reduced starch syrup concentration 2% by mass)) was poured into the containers and allowed to stand for 30 minutes.

[0099] -frozen- After the contact treatment, the chicken meat was frozen in its container at −25° C. for at least 8 hours.

[0100] -Lyophilization- The frozen chicken meat (including the frozen processing liquid) was vacuum freeze-dried together with the individual serving containers using a freeze dryer (manufactured by Kyowa Vacuum Engineering Co., Ltd.) at a pressure of 60 Pa. This resulted in a freeze-dried food product in the form of a dry block (water content of 5% by mass or less).

[0101] <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 the contact treatment was not carried out.

[0102] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 5.

[0103] [Table 5]

[0104] (Test Example 6) Shrimp was used as an example of a food containing solid ingredients, and a freeze-dried food was produced as follows.

[0105] <Test Example 6-1> -Preparing shrimp- After peeling the shrimp, they were physically pierced using a meat tenderizer, then boiled (stopped at 90°C) and sterilized.

[0106] -contact- Sterilized shrimp (35.0 g) were manually packed into individual serving containers. Next, 40.0 g (enough to submerge the shrimp) of a treatment solution (water containing sugar alcohol (reduced starch syrup concentration 2% by mass)) was poured into the containers and allowed to stand for 30 minutes.

[0107] -frozen- After the above contact treatment, the shrimp was placed in a container in a freezer at -25°C for at least 8 hours and frozen.

[0108] -Lyophilization- The frozen shrimp (including the frozen treatment liquid) was vacuum freeze-dried 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 product in the form of a dry block (water content of 5% by mass or less).

[0109] <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 carried out.

[0110] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 6.

[0111] [Table 6]

[0112] (Test Example 7) Salmon was used as an example of a food containing solid ingredients, and a freeze-dried food was produced as follows.

[0113] <Test Example 7-1> -Preparing salmon- The salmon was cut into 20 mm thick pieces, physically pierced with a meat tenderizer, and then boiled (at 90°C for 3 minutes) to sterilize it.

[0114] -contact- Sterilized salmon (35.0 g) was manually packed into individual serving containers. Next, 40.0 g (enough to immerse the salmon) of a treatment solution (water containing sugar alcohol (reduced starch syrup concentration 2% by mass)) was poured into the containers and allowed to stand for 30 minutes.

[0115] -frozen- After the contact treatment, the salmon was placed in a container in a freezer at -25°C for at least 8 hours to freeze.

[0116] -Lyophilization- The frozen salmon (including the frozen treatment liquid) was vacuum freeze-dried 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 product in the form of a dry block (water content of 5% by mass or less).

[0117] <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 carried out.

[0118] <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 the salmon was not perforated.

[0119] <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 carried out.

[0120] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 7.

[0121] [Table 7]

[0122] (Test Example 8) Yellowtail was used as an example of a food containing solid ingredients, and a freeze-dried food was produced as follows.

[0123] <Test Example 8-1> -Preparing yellowtail- The yellowtail was cut into 10 mm thick pieces, then boiled (at 90°C for 3 minutes) to sterilize it.

[0124] -contact- Sterilized yellowtail (45.0 g) was manually packed into individual serving containers. Next, 40.0 g (enough to immerse the yellowtail) of a treatment solution (water containing sugar alcohol (reduced starch syrup concentration 2% by mass)) was poured into the container and allowed to stand for 30 minutes.

[0125] -frozen- After the contact treatment, the yellowtails were placed in a container in a freezer at -25°C for at least 8 hours to freeze.

[0126] -Lyophilization- The frozen yellowtail (including the frozen processing solution) was subjected to vacuum freeze-drying together with the individual serving containers using a freeze-dryer (manufactured by Kyowa Vacuum Engineering Co., Ltd.) at a pressure of 60 Pa. This resulted in a freeze-dried food product in the form of a dry block (water content of 5% by mass or less).

[0127] <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 carried out.

[0128] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 8.

[0129] [Table 8]

[0130] (Test Example 9) As an example of a food containing solid ingredients, bonito was used, and a freeze-dried food was produced as follows.

[0131] <Test Example 9-1> -Preparation of bonito- The bonito was cut into 20 mm thick pieces, and then physically pierced with a meat tenderizer. It was then boiled (at 90°C for 3 minutes) and sterilized.

[0132] -contact- Sterilized bonito (60.0 g) was manually packed into a single-serving container. Next, 40.0 g (enough to immerse the bonito) of a treatment solution (water containing sugar alcohol (reduced starch syrup concentration 2% by mass)) was poured into the container and allowed to stand for 30 minutes.

[0133] -frozen- After the contact treatment, the bonito was placed in a container in a freezer at -25°C for at least 8 hours to freeze.

[0134] -Lyophilization- The frozen bonito (including the frozen treatment liquid) was vacuum freeze-dried 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 product (water content of 5% by mass or less) in the form of a dry block.

[0135] <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 carried out.

[0136] <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 bonito was not perforated.

[0137] <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 carried out.

[0138] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 9.

[0139] [Table 9]

[0140] (Test Example 10) Scallops were used as an example of a food containing solid ingredients, and a freeze-dried food was produced as follows.

[0141] <Test Example 10-1> -Preparation of scallops- The shucked scallops were physically pierced using a meat tenderizer, then boiled (at 90°C for 3 minutes) to sterilize them.

[0142] -contact- Sterilized scallops (20.0 g) were manually packed into individual serving containers. Next, 40.0 g (enough to submerge the scallops) of a treatment solution (water containing sugar alcohol (reduced starch syrup concentration 2% by mass)) was poured into the containers and allowed to stand for 30 minutes.

[0143] -frozen- After the contact treatment, the scallops were placed in a container in a freezer at -25°C for at least 8 hours to freeze.

[0144] -Lyophilization- The frozen scallops (including the frozen treatment liquid) were vacuum freeze-dried 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 product in the form of a dry block (water content of 5% by mass or less).

[0145] <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 carried out.

[0146] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 10.

[0147] [Table 10]

[0148] (Test Example 11) Squid was used as an example of a food containing solid ingredients, and a freeze-dried food was produced as follows.

[0149] <Test Example 11-1> -Preparation of squid- The frozen squid was thawed and cut into 10 mm thick pieces, which were then physically pierced using a meat tenderizer.Then, the pieces were boiled (at 90°C for 3 minutes) and sterilized.

[0150] -contact- Sterilized squid (10.0 g) was manually packed into a single-serving container. Next, 40.0 g (enough to immerse the squid) of a treatment solution (water containing sugar alcohol (reduced starch syrup concentration 2% by mass)) was poured into the container and allowed to stand for 30 minutes.

[0151] -frozen- After the contact treatment, the squid was frozen in its container at −25° C. for 8 hours or more.

[0152] -Lyophilization- The squid to be frozen (including the frozen treatment liquid) was vacuum freeze-dried 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 product (water content of 5% by mass or less) in the form of a dry block.

[0153] <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 carried out.

[0154] <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 squid was not perforated.

[0155] <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 carried out.

[0156] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 11.

[0157] [Table 11]

[0158] (Test Example 12) Tuna was used as an example of a food containing solid ingredients, and a freeze-dried food was produced as follows.

[0159] <Test Example 12-1> -Preparation of tuna- The tuna was cut into 20mm cubes, then physically pierced with a meat tenderizer, and then boiled (at 90°C for 3 minutes) to sterilize it.

[0160] -contact- Sterilized tuna (25.0 g) was manually packed into individual serving containers. Next, 40.0 g (enough to immerse the tuna) of a treatment solution (water containing sugar alcohol (reduced starch syrup concentration 2% by mass)) was poured into the container and allowed to stand for 30 minutes.

[0161] -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.

[0162] -Lyophilization- The frozen tuna (including the frozen treatment liquid) was vacuum freeze-dried 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 product (water content of 5% by mass or less) in the form of a dry block.

[0163] <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 carried out.

[0164] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 12.

[0165] [Table 12]

[0166] (Test Example 13) As an example of a food containing solid ingredients, italy shellfish was used, and a freeze-dried food was produced as follows.

[0167] <Test Example 13-1> - Preparation of Itayagai - After thawing the frozen mushrooms, they were boiled (at a temperature of 90°C for 3 minutes) and sterilized.

[0168] -contact- Sterilized scallops (15.0 g) were manually packed into individual containers. Next, 40.0 g (enough to immerse the scallops) of a treatment solution (water containing sugar alcohol (reduced starch syrup concentration 2% by mass)) was poured into the container and allowed to stand for 30 minutes.

[0169] -frozen- After the contact treatment, the shellfish were placed in a container in a freezer at -25°C for 8 hours or more to freeze.

[0170] -Lyophilization- The frozen shellfish (including the frozen treatment solution) 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 product (water content of 5% by mass or less) in the form of a dry block.

[0171] <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 carried out.

[0172] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 13.

[0173] [Table 13]

[0174] (Test Example 14) As an example of a food containing solid ingredients, amberjack was used and a freeze-dried food was produced as follows.

[0175] <Test Example 14-1> -Preparation of amberjack- The amberjack was cut into 15mm cubes, then physically pierced with a meat tenderizer. It was then boiled (at 90°C for 3 minutes) and sterilized.

[0176] -contact- Sterilized amberjack (20.0 g) was manually packed into individual serving containers. Next, 40.0 g (enough to immerse the amberjack) of a treatment solution (water containing sugar alcohol (reduced starch syrup concentration 2% by mass)) was poured into the container and allowed to stand for 30 minutes.

[0177] -frozen- After the contact treatment, the amberjack were placed in a container in a freezer at -25°C for at least 8 hours to freeze.

[0178] -Lyophilization- The frozen amberjack (including the frozen processing solution) was vacuum freeze-dried 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 product in the form of a dry block (water content of 5% by mass or less).

[0179] <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 carried out.

[0180] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 14.

[0181] [Table 14]

[0182] (Test Example 15) As an example of a food containing solid ingredients, sweet potato slices were used, and a freeze-dried food was produced as follows.

[0183] <Test Example 15-1> -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.

[0184] -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 solution (water containing sugar alcohol (reduced starch syrup concentration 2% by mass)) was poured into the containers and allowed to stand for 30 minutes.

[0185] -frozen- After the contact treatment, the sweet potatoes were placed in a container in a freezer at -25°C for 8 hours or more to freeze them.

[0186] -Lyophilization- The frozen sweet potatoes (including the frozen treatment liquid) were vacuum freeze-dried 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 product (with a moisture content of 5% by mass or less) in the form of a dry block.

[0187] <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 carried out.

[0188] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 15.

[0189] [Table 15]

[0190] (Test Example 16) As an example of a food containing solid ingredients, sweet potato slices were used and freeze-dried food was produced as follows.

[0191] <Test Example 16-1> -Preparation of sweet potatoes- 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.

[0192] -contact- Sterilized sweet potatoes (20.0 g) were manually packed into individual serving containers. Next, 40.0 g (enough to immerse the sweet potatoes) of a treatment solution (water containing sugar alcohol (reduced starch syrup concentration 2% by mass)) was poured into the containers and allowed to stand for 30 minutes.

[0193] -frozen- After the contact treatment, the sweet potatoes were placed in a container in a freezer at -25°C for 8 hours or more to freeze them.

[0194] -Lyophilization- The frozen sweet potatoes (including the frozen treatment liquid) were vacuum freeze-dried 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 product (with a moisture content of 5% by mass or less) in the form of a dry block.

[0195] <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 carried out.

[0196] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 16.

[0197] [Table 16]

[0198] (Test Example 17) Pumpkin was used as an example of a food containing solid ingredients, and a freeze-dried food was produced as follows.

[0199] <Test Example 17-1> -Pumpkin preparation- Pumpkins were cut into 5mm thick slices and physically pierced with a meat tenderizer. They were then steamed (at 90°C for 3 minutes) to sterilize them.

[0200] -contact- Sterilized pumpkin (50.0 g) was manually packed into a single-serving container. Next, 40.0 g (enough to immerse the pumpkin) of a treatment solution (water containing sugar alcohol (reduced starch syrup concentration 2% by mass)) was poured into the container and allowed to stand for 30 minutes.

[0201] -frozen- After the contact treatment, the pumpkin was placed in a container in a freezer at -25°C for 8 hours or more to freeze.

[0202] -Lyophilization- The frozen pumpkin (including the frozen treatment liquid) was vacuum freeze-dried 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 product (water content of 5% by mass or less) in the form of a dry block.

[0203] <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 carried out.

[0204] <Test Example 17-3> 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 pumpkin was not perforated.

[0205] <Test Example 17-4> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 17-3, except that the contact treatment was not carried out.

[0206] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 17.

[0207] [Table 17]

[0208] (Test Example 18) Taro was used as an example of a food containing solid ingredients, and a freeze-dried food was produced as follows.

[0209] <Test Example 18-1> -Preparation of taro- The frozen taro was thawed and cut into 5 mm thick pieces, which were then physically pierced with a meat tenderizer.The pieces were then boiled (at 90°C for 90 seconds) and sterilized.

[0210] -contact- Sterilized taro (30.0 g) was manually packed into a single-serving container. Next, 40.0 g (enough to immerse the taro) of a treatment solution (water containing sugar alcohol (reduced starch syrup concentration 2% by mass)) was poured into the container and allowed to stand for 30 minutes.

[0211] -frozen- After the above contact treatment, the taro was left in the container in a freezer at -25°C for 8 hours or more to freeze.

[0212] -Lyophilization- The frozen taro (including the frozen treatment liquid) 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 product (water content of 5% by mass or less) in the form of a dry block.

[0213] <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 carried out.

[0214] <Test Example 18-3> 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 taro was not perforated.

[0215] <Test Example 18-4> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 18-3, except that the contact treatment was not carried out.

[0216] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 18.

[0217] [Table 18]

[0218] (Test Example 19) Carrots were used as an example of a food containing solid ingredients, and freeze-dried food was produced as follows.

[0219] <Test Example 19-1> -Preparing carrots- The carrots were cut into gingko-shaped slices (10 mm thick), and then physically pierced with a meat tenderizer. They were then boiled (at 90°C for 6 minutes) and sterilized.

[0220] -contact- Sterilized carrots (20.0 g) were manually packed into individual serving containers. Next, 40.0 g (enough to submerge the carrots) of a treatment solution (water containing sugar alcohol (reduced starch syrup concentration 2% by mass)) was poured into the container and allowed to stand for 30 minutes.

[0221] -frozen- After the contact treatment, the carrots were placed in a container in a freezer at -25°C for 8 hours or more to freeze them.

[0222] -Lyophilization- The frozen carrots (including the frozen treatment liquid) were vacuum freeze-dried 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 product (water content of 5% by mass or less) in the form of a dry block.

[0223] <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 carried out.

[0224] <Test Example 19-3> 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 carrots were not pierced.

[0225] <Test Example 19-4> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 19-3, except that the contact treatment was not carried out.

[0226] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 19.

[0227] [Table 19]

[0228] (Test Example 20) Carrots were used as an example of a food containing solid ingredients, and freeze-dried food was produced as follows.

[0229] <Test Example 20-1> -Preparing carrots- The carrots were cut into 15mm cubes, then physically pierced with a meat tenderizer, and then boiled (at 90°C for 10 minutes) to sterilize them.

[0230] -contact- Sterilized carrots (25.0 g) were manually packed into individual serving containers. Next, 40.0 g (enough to immerse the carrots) of a treatment solution (water containing sugar alcohol (reduced starch syrup concentration 2% by mass)) was poured into the container and allowed to stand for 30 minutes.

[0231] -frozen- After the contact treatment, the carrots were placed in a container in a freezer at -25°C for 8 hours or more to freeze them.

[0232] -Lyophilization- The frozen carrots (including the frozen treatment liquid) were vacuum freeze-dried 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 product (water content of 5% by mass or less) in the form of a dry block.

[0233] <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 carried out.

[0234] <Test Example 20-3> 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 carrots were not pierced.

[0235] <Test Example 20-4> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 20-3, except that the contact treatment was not carried out.

[0236] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 20.

[0237] [Table 20]

[0238] (Test Example 21) Broccoli was used as an example of a food containing solid ingredients, and a freeze-dried food was produced as follows.

[0239] <Test Example 21-1> - Preparation of broccoli - After thawing the pre-cut frozen broccoli, holes were physically pierced using a meat tenderizer, and then boiled (at 90°C for 2 minutes) to sterilize it.

[0240] -contact- Sterilized broccoli (25.0 g) was manually packed into individual serving containers. Next, 40.0 g (enough to submerge the broccoli) of a treatment solution (water containing sugar alcohol (reduced starch syrup concentration 2% by mass)) was poured into the containers and allowed to stand for 30 minutes.

[0241] -frozen- After the contact treatment, the broccoli was placed in a container in a freezer at -25°C for 8 hours or more to freeze.

[0242] -Lyophilization- The frozen broccoli (including the frozen treatment liquid) was vacuum freeze-dried 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 product (with a moisture content of 5% by mass or less) in the form of a dry block.

[0243] <Test Example 21-2> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 21-1, except that the contact treatment was not carried out.

[0244] <Test Example 21-3> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 21-1, except that the broccoli was not perforated.

[0245] <Test Example 21-4> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 21-3, except that the contact treatment was not carried out.

[0246] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 21.

[0247] [Table 21]

[0248] (Test Example 22) Cabbage was used as an example of a food containing solid ingredients, and a freeze-dried food was produced as follows.

[0249] <Test Example 22-1> -Preparation of cabbage- Cabbage cut into 3cm cubes was boiled (over 95°C for 2 minutes) and sterilized.

[0250] -contact- Sterilized cabbage (25.0 g) was manually packed into individual serving containers. Next, 40.0 g (enough to immerse the cabbage) of a treatment solution (water containing sugar alcohol (reduced starch syrup concentration 2% by mass)) was poured into the container and allowed to stand for 30 minutes.

[0251] -frozen- After the contact treatment, the cabbages were placed in a container in a freezer at -25°C for 8 hours or more to freeze them.

[0252] -Lyophilization- The frozen cabbage (including the frozen treatment liquid) 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 product (water content of 5% by mass or less) in the form of a dry block.

[0253] <Test Example 22-2> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 22-1, except that the contact treatment was not carried out.

[0254] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 22.

[0255] [Table 22]

[0256] (Test Example 23) Burdock root was used as an example of a food containing solid ingredients, and a freeze-dried food was produced as follows.

[0257] <Test Example 23-1> - Preparation of burdock root - The burdock root was cut into 5 mm thick pieces, and then physically pierced with a meat tenderizer. It was then boiled (at 90°C for 10 minutes) to sterilize it.

[0258] -contact- Sterilized burdock (15.0 g) was manually packed into a single-serving container. Next, 40.0 g (enough to immerse the burdock) of a treatment solution (water containing sugar alcohol (reduced starch syrup concentration 2% by mass)) was poured into the container and allowed to stand for 30 minutes.

[0259] -frozen- After the contact treatment, the burdock roots were placed in a container in a freezer at -25°C for 8 hours or more to freeze.

[0260] -Lyophilization- The frozen burdock (including the frozen treatment solution) was vacuum freeze-dried 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 product (water content of 5% by mass or less) in the form of a dry block.

[0261] <Test Example 23-2> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 23-1, except that the contact treatment was not carried out.

[0262] <Test Example 23-3> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 23-1, except that the burdock root was not perforated.

[0263] <Test Example 23-4> A freeze-dried food (water content: 5% by mass or less) was obtained in the same manner as in Test Example 23-3, except that the contact treatment was not carried out.

[0264] <Evaluation> The obtained freeze-dried food was evaluated in the same manner as in Test Example 1. The results are shown in Table 23.

[0265] [Table 23]

[0266] 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 various types of solid food ingredients are used.

Claims

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

2. 2. The method for producing a freeze-dried food according to claim 1, wherein the sugar alcohol content in the sugar alcohol-containing liquid is 1 to 10% by mass.

3. 3. 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 sugar alcohol-containing liquid.

4. 3. 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 that has been contacted with the sugar alcohol-containing liquid and then drained of liquid.

5. a contacting step of contacting a food containing a solid food ingredient with a sugar alcohol-containing liquid; a freezing step of freezing the food containing the solid food material that has been contacted with the sugar alcohol-containing liquid; a freeze-drying step of freeze-drying the food containing the solid food material frozen in the freezing step; A method for improving the reconstitution of freeze-dried food, comprising:

6. 6. The method for improving the reconstitution property of a freeze-dried food according to claim 5, wherein the sugar alcohol content in the sugar alcohol-containing liquid is 1 to 10% by mass.

7. 7. The method for improving the reconstitution property of freeze-dried food according to claim 5, wherein the freezing step is a step of freezing the food containing the solid food material while immersed in the sugar alcohol-containing liquid.

8. 7. The method for improving the reconstitution property of freeze-dried food according to claim 5, wherein the freezing step is a step of freezing a food containing the solid food material that has been contacted with the sugar alcohol-containing liquid and then drained.

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