Method for manufacturing compressed freeze-dried foods

Abstract

This invention provides compressed freeze-dried foods with excellent shape retention properties, particularly for ingredients with high moisture content, such as vegetables. [Solution] A compressed freeze-dried food comprising at least one ingredient selected from the group consisting of fruits and vegetables, mushrooms, and seaweed, and gelatin and / or pregelatinized dextrin. Preferably, it comprises two or more ingredients selected from the group consisting of fruits and vegetables, mushrooms, and seaweed. Preferably, the total volume of the ingredients when restored is 4.8 times or more and 7.2 times or less the volume of the compressed freeze-dried food before restoration.

Description

Technical Field

[0001] The present invention relates to a freeze-dried food obtained by compressing fruits and vegetables with a high water content rate.

Background Art

[0002] Conventionally, dried vegetable blocks have been used as vegetables for various processed foods such as instant soups. Ingredients such as vegetables with a high water content rate have a very low bulk density after drying. Therefore, dried vegetable blocks are generally manufactured by trimming raw vegetables to an appropriate size, blanching them, increasing the bulk density by compression molding, and then subjecting them to vacuum freeze-drying. Dried vegetable blocks are restored by pouring hot water during eating.

[0003] Patent Document 1 describes a method for manufacturing a dried vegetable block at low cost without using an excipient, in which hot-air dried vegetables are pressed into a block shape and then vacuum freeze-dried. Patent Document 2 describes a method for manufacturing a compression-molded dried food in which an excipient is mixed with ingredients such as blanched vegetables, subjected to hot-air drying treatment, subjected to compression molding treatment, and then subjected to freeze-drying treatment. Patent Document 3 describes a method for manufacturing a compressed food in which a humidified gas is supplied to dried vegetables to uniformly humidify them, compression molded, and then dried again. In the examples, the initial drying and re-drying are performed by the vacuum freeze-drying method.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the methods described in Patent Documents 1 and 2 have problems in that browning of ingredients such as vegetables due to hot air drying is unavoidable, and the shape retention of the product is insufficient. In Patent Document 1, no excipients are used, and in Patent Document 2, although excipients are used, sugars such as glucose and lactose are used as excipients, so in both cases the shape retention of the product is insufficient, and the blocks are prone to losing their shape during transportation. In the method described in Patent Document 3, browning can be suppressed by vacuum freeze-drying, but since no excipients are used, the shape retention of the product is still insufficient.

[0006] This invention was made in consideration of the above, and aims to provide compressed freeze-dried foods with a high moisture content per unit volume and excellent shape retention for ingredients with a high moisture content, such as vegetables. [Means for solving the problem]

[0007] The compressed freeze-dried food of the present invention comprises at least one ingredient selected from the group consisting of fresh fruits and vegetables, mushrooms and seaweed, and gelatin and / or pregelatinized dextrin. Here, pregelatinized dextrin includes both low-molecular-weight pregelatinized starch and pregelatinized dextrin.

[0008] Preferably, the compressed freeze-dried food contains two or more ingredients selected from the group consisting of fresh produce, mushrooms, and seaweed.

[0009] Preferably, the compressed freeze-dried food described above has a total volume of ingredients that, when restored, is 4.8 times or more and 7.2 times or less than the volume of the compressed freeze-dried food before restoration.

[0010] The present invention provides a method for producing compressed freeze-dried food, comprising: a mixing step of mixing at least one ingredient selected from the group consisting of fresh produce, mushrooms, and seaweed with a binding solution containing gelatin and / or pregelatinized dextrin; a molding step of shaping the mixture obtained in the mixing step into a block or plate shape; a first drying step of vacuum freeze-drying the molded product obtained in the molding step; a humidifying step of humidifying the molded product after the first drying step; a compression step of compressing the molded product after the humidifying step; and a second drying step of vacuum freeze-drying the molded product after the compression step.

[0011] Preferably, in the method for producing the compressed freeze-dried food described above, the mixing step is a step of mixing two or more ingredients selected from the group consisting of fresh fruits and vegetables, mushrooms and seaweed with the binding liquid.

[0012] Preferably, in any of the above methods for producing compressed freeze-dried food, the compression step is a step of compressing the molded product so that the volume of the molded product after compression is 1 / 4.8 or less and 1 / 7.2 or more of the total volume of the ingredients used in the mixing step. [Effects of the Invention]

[0013] The compressed freeze-dried food of the present invention has increased bulk density due to compression, allowing it to contain more ingredients per unit volume. Furthermore, by including gelatin and / or pregelatinized dextrin as a binding agent, it has excellent shape retention and is resistant to deformation. According to the method for producing the compressed freeze-dried food of the present invention, a compressed freeze-dried food is obtained that contains more ingredients per unit volume, has excellent shape retention, and is resistant to deformation. [Brief explanation of the drawing]

[0014] [Figure 1] This is a production flow diagram of a compressed freeze-dried food product according to one embodiment. [Modes for carrying out the invention]

[0015] The compressed freeze-dried food of this embodiment contains ingredients selected from the group consisting of fresh produce, mushrooms, and seaweed, and gelatin and / or pregelatinized dextrin. The compressed freeze-dried food of this embodiment is manufactured by mixing these raw materials, molding them, and going through the processes of vacuum freeze-drying, compression, and vacuum freeze-drying. Details of the manufacturing method will be described later. The compressed freeze-dried food of this embodiment is consumed after being rehydrated with hot water, such as as an ingredient in instant food. Rehydration with hot water also includes rehydrating with soup or other ingredients containing components other than water. In the following, the compressed freeze-dried food of this embodiment may be simply referred to as "compressed freeze-dried food."

[0016] Compressed freeze-dried foods contain at least one ingredient selected from the group consisting of fresh produce, mushrooms, and seaweed. Fresh produce includes vegetables and fruits. Examples of vegetables include leafy vegetables such as cabbage, spinach, and broccoli, root vegetables such as carrots and radishes, and fruit vegetables such as cucumbers and eggplants. Examples of mushrooms include maitake, shiitake, and button mushrooms.

[0017] The compressed freeze-dried food preferably contains two or more, more preferably three or more, ingredients selected from the group consisting of fresh fruits and vegetables, mushrooms, and seaweed. This is because it improves the appearance of the compressed freeze-dried food when it is rehydrated with hot water. In particular, it is preferable to include green ingredients and red or yellow ingredients to add color.

[0018] The ingredients should have a high moisture content in their normal, undried state, preferably 80% or more. This is because a higher moisture content in the ingredients offers greater advantages in terms of the amount of ingredients per unit volume that can be achieved with the compressed freeze-dried food of this embodiment.

[0019] The compressed and freeze-dried food may contain ingredients not included in the group consisting of fruits and vegetables, mushrooms, and seaweeds. Even in such a case, it is preferable that the ingredients included in the group consisting of fruits and vegetables, mushrooms, and seaweeds account for 80% by volume or more, and more preferably 90% by volume or more, of the total ingredients in the compressed and freeze-dried food. Also, for instant food applications, it is preferable that vegetables account for 80% by volume or more, and more preferably 90% by volume or more, of the total ingredients in the compressed and freeze-dried food.

[0020] The ratio of the volume of all ingredients in the compressed and freeze-dried food (hereinafter referred to as the volume ratio of the ingredients) is preferably 60% by volume or more. If the volume ratio of the ingredients is too low, the amount of the restored ingredients per unit volume of the compressed and freeze-dried food will be reduced. On the other hand, the volume ratio of the ingredients is preferably 90% by volume or less, and more preferably 85% by volume or less. This is because if the volume ratio of the ingredients is increased too much, the tissue of the ingredients is likely to be damaged in the compression process during production.

[0021] Gelatin and / or pregelatinized dextrin are added as binders to improve the shape retention of the compressed and freeze-dried food. Gelatin and pregelatinized dextrin are viscous and form a network structure of polymers, and the ingredients are mechanically retained in the network structure, so they are excellent as binders.

[0022] There are several types of gelatin, such as those derived from porcine skin collagen, but the type of gelatin is not particularly limited. Gelatin has a great effect of enhancing the shape retention but is expensive, so the amount of use can be suppressed by using it in combination with pregelatinized dextrin.

[0023] Pregelatinized dextrin is obtained by reducing the molecular weight of gelatinized (gelatinized) starch by enzymatic decomposition with amylase or the like, or by gelatinizing dextrin, which is a starch hydrolyzate. Powdered products of pregelatinized dextrin are commercially available.

[0024] The gelatin content of the compressed freeze-dried food is preferably 0.29% by mass or more, more preferably 0.58% by mass or more, preferably 19.1% by mass or less, and more preferably 15.3% by mass or less. The pregelatinized dextrin content of the compressed freeze-dried food is preferably 1.9% by mass or more, more preferably 3.2% by mass or more, preferably 18.1% by mass or less, and more preferably 16.0% by mass or less. Furthermore, the total content of gelatin and pregelatinized dextrin of the compressed freeze-dried food is preferably 2.7% by mass or more, more preferably 4.1% by mass or more, preferably 23.8% by mass or less, and more preferably 20.3% by mass or less. If there is too little of these binding agents, sufficient shape retention cannot be obtained. On the other hand, if there is too much of these binding agents, the resilience of the compressed freeze-dried food will decrease. However, the use of gelatin and pregelatinized dextrin is subject to the condition that the sum of their volumes in relation to the compressed freeze-dried food (the volume percentage of the binding agent) does not exceed 100% when added to the volume percentage of the ingredients.

[0025] Compressed freeze-dried foods may contain additives other than the above-mentioned ingredients, gelatin, and pregelatinized dextrin. For example, compressed freeze-dried foods may contain ungelatinized dextrin. Compressed freeze-dried foods may also contain trehalose, which is added to maintain the color of the ingredients during blanching, or thickeners, which improve the flavor when reconstituted with soup. Compressed freeze-dried foods may also contain various seasonings. However, since compressed freeze-dried foods are often cooked after reconstitution or reconstituted with seasoned soup, etc., the compressed freeze-dried foods themselves do not need to contain seasonings.

[0026] An important characteristic of compressed freeze-dried foods is the ratio of the volume of the food obtained when restored to a unit volume of the compressed freeze-dried food. The volume of the food obtained when restored is the volume of the food itself, not its bulk density. Preferably, the volume of the food when restored is 4.8 times or more the volume of the compressed freeze-dried food before restoration. This ensures that the compressed freeze-dried food has sufficient volume when restored. On the other hand, the volume of the food when restored is preferably 7.2 times or less, more preferably 6.8 times or less the volume of the compressed freeze-dried food before restoration. If this value is too high, the tissue of the food is likely to be damaged during the compression process in manufacturing. One of the objectives of the compressed freeze-dried food in this embodiment is to contain more food per unit volume, and the compressed food expands when restored. The effect of this compression can be directly evaluated by the ratio of the volume of the restored food to the volume of the compressed freeze-dried food before restoration.

[0027] Compressed freeze-dried foods preferably contain 4% or more by volume, and more preferably 10% or more by volume, of voids. This is to prevent damage to the structure of the ingredients during the compression process in manufacturing. Since voids are the parts of the compressed freeze-dried food that do not contain ingredients or binders, the upper limit of the preferred range of voids is determined by the preferred value of the volume percentage of the raw materials.

[0028] The bulk density of freeze-dried foods is influenced by many factors, including the type of food (especially density and moisture content), the amount of ingredients, binders, and additives used. The density of fruits, vegetables, mushrooms, and seaweed is approximately 1.1 g / cm³. 3 Assuming a moisture content of approximately 90% by mass, the bulk density of compressed freeze-dried food is 0.7-1.1 g / cm³. 3 It is to that extent.

[0029] The shape of the compressed freeze-dried food is not particularly limited, but is preferably a rectangular block. The size of the compressed freeze-dried food can be determined according to its intended use and is not particularly limited. When used as an ingredient in instant food, the size is preferably 3cm x 3cm x 0.5cm to 10cm x 10cm x 2cm, depending on the size of the container.

[0030] Next, the method for producing the compressed freeze-dried food according to this embodiment will be explained following the flowchart in Figure 1.

[0031] In the manufacturing method of this embodiment, the ingredients and binding liquid are mixed and molded, and compressed freeze-dried food is produced through a first vacuum freeze-drying, humidification of the molded product, compression, and a second vacuum freeze-drying.

[0032] Prepare the ingredients. The ingredients shall include at least materials selected from the group consisting of fruits and vegetables, mushrooms, and seaweed. Preferred types of materials are as previously described with respect to compressed freeze-dried foods. The ingredients shall be cut to appropriate sizes as needed and blanched. Blanching is performed by briefly heating the ingredients in hot water or steam at a high temperature to inactivate the oxidizing enzymes in the ingredients to prevent deterioration and discoloration, and to soften the tissue to prevent tissue damage due to freezing. Blanching can be performed by known methods.

[0033] A binding solution is prepared by mixing gelatin and / or pregelatinized dextrin with other additives as needed and dissolving them in water at approximately 85°C. The amounts of gelatin and pregelatinized dextrin used are preferably within the aforementioned ranges in the compressed freeze-dried food product.

[0034] The ingredients and binding agent are mixed, and the resulting mixture is molded. The mixture may be molded into a block in the amount equivalent to one compressed freeze-dried food product, but preferably, the amount equivalent to multiple compressed freeze-dried food products is molded into a large plate. The mixture may be molded by placing it directly into a mold, or it may be placed in a plastic bag and then placed in the mold with the bag inside. Hereafter, the molded product will be referred to as the molded product. At this stage, the molded product contains many voids and has an extremely low bulk density.

[0035] The molded product is sterilized by heating. Sterilization can be carried out by known methods. For example, the molded product can be sterilized by holding it at 70°C for 15 minutes or more.

[0036] The sterilized molded product is pre-frozen and then subjected to the first vacuum freeze-drying. Pre-freezing and vacuum freeze-drying can be carried out by known methods. In vacuum freeze-drying, only volatile components such as water are removed from the molded product by sublimation, and the volume of the molded product and the food itself does not change.

[0037] The molded product is humidified after vacuum freeze-drying. Humidifying the molded product gives it mechanical flexibility, which prevents the food from breaking during the next compression process. Humidification is done by spraying hot water onto the molded product or by placing the molded product in a steamer. Preferably, an appropriate amount of hot water is sprayed onto the molded product, and then it is placed in a steamer for humidification. This is because spraying hot water shortens the humidification time, and humidifying in a steamer at the end allows for uniform humidification of the molded product and precise control of the moisture content of the molded product after humidification. One humidification method is to spray hot water equivalent to about 20% of the weight of the molded product, and then hold it in a steamer with 100% humidity for 10 to 40 minutes while controlling the surface temperature to 30 to 50°C.

[0038] A weight is placed on the humidified molded product to compress it. Compression can increase the bulk density of the molded product. Compression is carried out so that the volume of the molded product after compression is preferably 1 / 4.8 or less, preferably 1 / 7.2 or more, and more preferably 1 / 6.8 or more, of the total volume of the ingredients used in the mixing process. Compression reduces the volume of the molded product, and also reduces the volume of the ingredients themselves that have lost moisture. If the volume ratio of the ingredients is 50% by volume, the volume of the ingredients will decrease by approximately the same ratio as the volume of the molded product.

[0039] If the mixture is formed into a large sheet containing the amount needed for multiple compressed freeze-dried food products during the molding process, it should be cut into individual portions after compression.

[0040] The compressed molded product is pre-frozen, and then subjected to a second vacuum freeze-drying. Pre-freezing and vacuum freeze-drying can be carried out by known methods. The volume of the molded product and the food itself does not change even after the second vacuum freeze-drying.

[0041] As described above, the compressed freeze-dried food of this embodiment is obtained. When this compressed freeze-dried food is restored by rehydrating it with hot water, the ingredients expand and return to their original state as they were when mixed. [Examples]

[0042] The compressed freeze-dried food product of this embodiment and its manufacturing method will be described in more detail by reference to examples. Compressed freeze-dried food products were prepared by changing the composition of the binding liquid and using the following methods.

[0043] The ingredients used were spinach, broccoli, and carrots. Frozen cut spinach was used after being fully thawed. Broccoli was used after the stems were removed and frozen cut broccoli was fully thawed. Shredded air-dried carrots were rehydrated in boiling water and then drained. The approximate density and moisture content of the ingredients were 1.1 g / cm³ for spinach. 3 And 82.4% by mass, broccoli is 1.1 g / cm³ 3 And 86.2% by mass, with carrots at 1.2 g / cm³. 3 This is 89.6% by mass. The amount of ingredients used per compressed freeze-dried food was calculated as follows: 35.00g of spinach, 75.00g of broccoli, and 10.37g of carrots, using the ingredients for 20 compressed freeze-dried foods.

[0044] A binding solution was prepared by dissolving gelatin, pregelatinized dextrin (Nippon Denko Chemical Co., Ltd., Amicol TP), and dextrin in 85°C water. Of these, the ungelatinized dextrin does not have the effect of binding the food ingredients, but it does have the effect of reducing cracking and chipping of dried products. The amount of binding solution was also prepared for 20 freeze-vacuum dried food products. The amount of each component per freeze-vacuum dried food product is shown in Tables 1 and 2.

[0045] The above ingredients and binding agent were mixed, and the resulting mixture was placed in a plastic bag. The plastic bag was then placed on a tray and molded into a block measuring 30cm x 24cm x 4cm. The tray was heated with steam, and the core temperature of the molded material was maintained at 70°C or higher for 15 minutes to sterilize it. The molded material, still in its bag, was pre-frozen in a freezer at -25°C or below, and then freeze-dried in a vacuum freeze-dryer at a vacuum of 133 Pa or less for 36 hours (first drying step). Hot water equivalent to about 20% of its weight was sprayed onto the freeze-dried molded material, and it was placed in a steamer. After humidifying at 70°C and 100% humidity for 10 minutes, the steamer door was closed and left for 30 minutes to allow further humidification. A weight of 20-100 kg was placed on the humidified molded material and compressed until its thickness was 0.5 cm. The compressed molded material was cut into pieces measuring 6cm x 6cm x 0.5cm. The cut molded products were pre-frozen in a freezer at -25°C or below, and then freeze-dried in a vacuum freeze-dryer at a vacuum of 133 Pa or less for 12 hours (second drying process).

[0046] The shape retention and rehydration properties of the prepared compressed freeze-dried food were evaluated.

[0047] Shape retention was determined by dropping 10 compressed freeze-dried foods from a height of 10 cm and counting the number of items that completely broke, according to the following criteria. A: Number of completely broken specimens: 0-1 B: Number of completely broken pieces: 2-4 C: The number of completely broken specimens is 5 or more.

[0048] The rehydration properties were determined by rehydrating the product in boiling water for 3 minutes and then evaluating it according to the following criteria. A: It will rehydrate completely and spread throughout the container. B: If you loosen it with a spoon or similar utensil, it will rehydrate and spread throughout the container. C: Hot water hardly penetrates compressed freeze-dried foods.

[0049] Tables 1 and 2 show the ingredient ratios and evaluation results of the compressed freeze-dried foods produced. The ingredient weights are shown as the weight per compressed freeze-dried food unit. In the tables, "dried food" refers to compressed freeze-dried foods.

[0050] [Table 1]

[0051] [Table 2]

[0052] Tables 1 and 2 show that increasing the amount of binder improves the shape retention of compressed freeze-dried foods but worsens their rehydration properties, while decreasing the amount of binder worsens shape retention but improves rehydration properties. Experiments 2-7, 10-14, and 16 achieved a rating of B or higher for both shape retention and rehydration properties, indicating that they were sufficiently good for practical use. Experiments 3-5, 11-12, and 16 achieved a rating of A or higher for both shape retention and rehydration properties, indicating particularly excellent shape retention and rehydration properties.

[0053] The present invention is not limited to the embodiments or examples described above, and various modifications are possible within the scope of its technical concept.

Claims

1. At least one food ingredient selected from the group consisting of fruits and vegetables, mushrooms and seaweed, Containing gelatin and / or pregelatinized dextrin, Compressed freeze-dried food.

2. It includes two or more ingredients selected from the group consisting of fruits and vegetables, mushrooms and seaweed. The compressed freeze-dried food according to claim 1.

3. The total volume of the ingredients after restoration is 4.8 times or more and 7.2 times or less the volume of the compressed freeze-dried food before restoration. The compressed freeze-dried food according to claim 1.

4. A mixing step of mixing at least one food ingredient selected from the group consisting of fruits and vegetables, mushrooms and seaweed with a binding solution containing gelatin and / or pregelatinized dextrin, A molding step is performed to form the mixture obtained in the mixing step into a block or plate shape. A first drying step involves vacuum freeze-drying the molded product obtained in the molding step, A humidification step in which the molded product after the first drying step is humidified, A compression step in which the molded product after the humidification step is compressed, A second drying step involves vacuum freeze-drying the molded product after the compression step, A method for producing compressed freeze-dried food having the following characteristics.

5. The mixing step is a step of mixing two or more ingredients selected from the group consisting of fruits and vegetables, mushrooms and seaweed with the binding liquid. A method for producing compressed freeze-dried food according to claim 4.

6. The compression step is a step of compressing the molded product so that the volume of the molded product after compression is 1 / 4.8 or less and 1 / 7.2 or more of the total volume of the ingredients used in the mixing step. A method for producing compressed freeze-dried food according to claim 4.

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