Dried food manufacturing method

Abstract

To avoid manufacturing of a product in which drop off, crack and chipping of an ingredient drying part is likely to occur with respect to dried food which freezes and dries food mixture mixing liquid food material and ingredients.SOLUTION: An ingredient freezing step S2 which freezes at least a part of ingredients when freezing and drying food mixture mixing liquid food material and ingredients to manufacture dry food, an ingredient freezing step S3 for defrosting the ingredients frozen at the ingredient freezing step S2, and a freezing drying step S6 for freezing and drying the food mixture mixing the ingredients with the liquid food material are performed in this order to manufacture dried food.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a dried food by freeze-drying a mixed food material obtained by mixing a liquid food material and an ingredient. [Background technology]

[0002] Some dried foods, such as instant miso soup, are manufactured by filling a container with a mixed foodstuff made by mixing liquid foodstuffs and ingredients, and then freeze-drying the mixed foodstuff, so that the parts where the liquid foodstuffs are dried and the parts where the ingredients are dried are integrated. In this case, when a food product containing ingredients that are prone to settling or floating in the liquid foodstuff is packed into multiple containers in succession with a portion of the mixed foodstuff produced in large quantities, the amount of ingredients packed into each container (the ratio of ingredients to liquid foodstuffs in each container) is likely to vary. For this reason, when packing foodstuffs containing such ingredients into containers, a manufacturing method is widely used in which the ingredients are packed into the containers separately from the liquid foodstuff, thereby avoiding variation in the amount of ingredients packed into each container.

[0003] Meanwhile, the following patent document discloses a method for producing instant miso soup that allows a fixed amount of ingredients to be easily filled into a container. In this method, the "ingredients" are cooked separately from the "broth" in the "miso soup", and then the "ingredients" are formed into a plate and frozen. The plate-shaped frozen ingredients are then chopped into pieces of any size according to the amount to be filled into the container, and the chopped frozen ingredient pieces are placed in the container. Then, the soup cooked separately from the ingredients is poured into the container. This results in the container being filled with frozen ingredient pieces (fixed amount of ingredients) and soup. The ingredients (frozen ingredient pieces) and soup in the container are then freeze-dried to complete the instant miso soup. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 61-26346 (pages 1-2) Summary of the Invention [Problem to be solved by the invention]

[0005] However, the instant miso soup manufacturing method disclosed in the above patent document has the following problems to be solved. Specifically, the manufacturing method disclosed in the above patent document employs a method in which the ingredients are cooked individually, then formed into a flat plate and frozen, and the frozen ingredients are chopped into pieces of any size and then placed in a container. This makes it easier to chop the flat frozen ingredients and place the chopped frozen ingredients in a container than to fill (place) an ingredient that has fluidity in an unfrozen state in a container, making it possible to easily quantify the ingredients to be filled in the container.

[0006] On the other hand, the applicant produced a prototype of "bamboo shoot soup (dried food that can be eaten by rehydrating in hot water)" using the same manufacturing method as disclosed in the above patent document, and was able to easily quantify the amount of ingredients per dried food, as disclosed in the above patent document. However, it was confirmed that among the completed "bamboo shoot soup" (hereinafter also referred to as "dried bamboo shoot soup"), cracks or chips occurred in the part where the "bamboo shoot (ingredient)" was dried (hereinafter also referred to as the "dried ingredient part"), and gaps occurred between the part where the "soup (liquid ingredient)" was dried (hereinafter also referred to as the "dried liquid ingredient part") and the dried ingredient part, resulting in the dried ingredient part detaching from the dried liquid ingredient part, or the dried ingredient part being in a state where it is easily detached from the dried liquid ingredient part (brittle state).

[0007] The applicant also produced prototypes of dried bamboo shoot soup using a conventional method, i.e., a method in which "bamboo shoots (ingredients)" are filled into a container without freezing, and then "soup (liquid ingredient)" is filled into the container and freeze-dried, and a method in which a mixed ingredient (not frozen) of "bamboo shoots (ingredients)" and "soup (liquid ingredient)" is filled into a container and freeze-dried, and compared the prototypes with dried bamboo shoot soup produced by the manufacturing method disclosed in the above patent document. However, it was confirmed that the dried bamboo shoot soup produced by either manufacturing method had a state in which the dried ingredient part was detached from the dried liquid ingredient part, or was in a state in which the dried ingredient part was easily detached from the dried liquid ingredient part (brittle state), just like the dried bamboo shoot soup produced by the manufacturing method disclosed in the above patent document.

[0008] The applicant has also confirmed that the same phenomenon as that confirmed in the dried bamboo shoot soup occurs in "dried foods freeze-dried from mixed ingredients of liquid ingredients and ingredients" other than dried bamboo shoot soup. The applicant has also confirmed that the more fibrous ingredients such as the bamboo shoots, chrysanthemum greens, root vegetables, radishes, carrots, and asparagus are used as ingredients, the more likely the dried ingredient part will become detached from the dried liquid ingredient part, or the dried ingredient part will become easily detached from the dried liquid ingredient part (brittle state).

[0009] In this case, when a dried food product is manufactured in which the dried ingredient portion has detached from the dried liquid ingredient portion, the detached dried ingredient portion may not be accommodated in the package at the time of shipment, resulting in a defective product with insufficient capacity (total amount of product may be small). Even if the detachment of the dried ingredient portion does not occur immediately after production, a dried food product that is prone to such detachment (fragile) may have the dried ingredient portion detached and the product may crack or chip within the package. This not only impairs the aesthetic appearance of the dried food product and reduces its product value, but also leaves a part of the dried food product (the detached or chipped part) remaining in the package when the dried food product is removed from the package for consumption, resulting in waste, as the remaining part is discarded together with the package without being eaten.

[0010] Therefore, in order to prevent the above-mentioned defective products from being shipped, it is necessary to carefully inspect whether there are any products in which the dried ingredient portion has come off or which are prone to such detachment, cracking, or chipping, and not only is such work cumbersome, but the product yield will decrease to the extent that defective products are discarded, which may lead to an increase in production costs. Thus, the manufacturing methods disclosed in the above patent documents and the conventional manufacturing methods have the problem that it is difficult to manufacture dried foods that are high in commercial value and do not cause waste at low cost.

[0011] The present invention has been made in consideration of the above-mentioned problems to be solved, and its main object is to provide a method for producing dried foods which can avoid the production of products prone to detachment of the dried ingredients and cracks or chips when produced by freeze-drying a mixed ingredient comprising a mixture of liquid ingredients and ingredients. [Means for solving the problem]

[0012] In order to achieve the above-mentioned object, the dried food manufacturing method described in claim 1 produces a dried food by freeze-drying a mixed food material obtained by mixing liquid food materials and ingredients, by carrying out, in this order, an ingredient freezing process for freezing at least a portion of the ingredients, an ingredient thawing process for thawing the ingredients frozen in the ingredient freezing process, and a freeze-drying process for freeze-drying the mixed food material obtained by mixing the ingredients with the liquid food materials.

[0013] The dried food manufacturing method described in claim 2 is the dried food manufacturing method described in claim 1, in which the ingredients thawed in the ingredient thawing process are dehydrated to a weight within a range of 70% to 95% of the weight of the ingredients before the ingredient freezing process began, and then mixed with the liquid food material.

[0014] A method for producing dried food according to claim 3 is the method for producing dried food according to claim 1, wherein the ingredient is frozen within a temperature range of -25°C or higher and -5°C or lower in the ingredient freezing step.

[0015] A method for producing dried food according to a fourth aspect of the present invention is the method for producing dried food according to the third aspect of the present invention, wherein the ingredients are frozen in the ingredient freezing step within a temperature range of -15°C or higher and -10°C or lower.

[0016] A method for producing a dried food according to a fifth aspect of the present invention is the method for producing a dried food according to any one of the first to fourth aspects, in which vegetables are used as the ingredients. Effect of the Invention

[0017] According to the method for producing dried food described in claim 1, by carrying out an ingredient freezing step and an ingredient thawing step before the freeze-drying step, the shrinkage of the ingredients that have been subjected to the ingredient freezing step and ingredient thawing step during the freeze-drying step can be reduced compared to the conventional method in which the freeze-drying step is carried out without carrying out the ingredient freezing step and ingredient thawing step, and therefore it is possible to preferably prevent the ingredient dried part from coming off the liquid food dried part in the produced dried food, the occurrence of cracks or chips, and the production of a product that is prone to cracks or chips. This makes it possible to sufficiently improve the commercial value of the produced dried food and sufficiently reduce its production cost.

[0018] In addition, according to the dried food manufacturing method described in claim 2, the ingredients thawed in the ingredient thawing process are dehydrated so that their weight is within the range of 70% to 95% of the weight of the ingredients before the ingredient freezing process began, thereby increasing the adhesion between the liquid food dried section and the ingredient dried section, thereby more effectively preventing the ingredient dried section from detaching, cracking or chipping, and the production of products that are prone to cracking or chipping.

[0019] In the method for producing dried foods according to claim 3, the ingredients are frozen in the ingredient freezing step at a temperature range of -25°C or more and -5°C or less. In the method for producing dried foods according to claim 4, the ingredients are frozen in the ingredient freezing step at a temperature range of -15°C or more and -10°C or less. Therefore, according to the method for producing dried foods according to claims 3 and 4, the moisture content of the ingredients can be suitably reduced, and the shrinkage of the ingredients can be sufficiently reduced, so that separation of the dried ingredients, cracks or chips, and the production of products that are prone to cracks or chips can be more suitably prevented. Furthermore, the time required for producing dried foods and the increase in power consumption during production can be avoided, and the production cost of dried foods can be sufficiently reduced.

[0020] According to the dried food manufacturing method described in claim 5, by using vegetables as the ingredients, which are rich in fiber, it is possible to produce dried foods with high commercial value by sufficiently reducing the frequency of such defects, even in dried foods that are prone to peeling off of the dried ingredients, cracking or chipping, and cracking or chipping when produced by conventional manufacturing methods. [Brief description of the drawings]

[0021] [Figure 1] 1 is a flowchart of a dried food production process 1. [Diagram 2] FIG. 2 is a photograph of dried bamboo shoot juice (dried food) produced according to the dried food production method of the present invention. [Diagram 3] FIG. 1 is a photograph of dried bamboo shoot soup (dried food) produced according to the production method disclosed in the above-mentioned patent document. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, an embodiment of the "dried food manufacturing method" will be described with reference to the accompanying drawings.

[0023] In the "dried food manufacturing method" according to the present invention, as an example, a "dried food obtained by freeze-drying a mixed food material obtained by mixing liquid food materials and ingredients" is manufactured by the dried food manufacturing process 1 shown in Fig. 1. The manufacturing method according to the present invention will be described below by taking as an example a method for manufacturing "bamboo shoot soup" as a "dried food" (a food similar to the dried food prototyped by the applicant using various manufacturing methods as described above) by the dried food manufacturing process 1.

[0024] 1-1. Ingredients used Ingredients Bamboo shoots (boiled bamboo shoots) 23.0% (an example of a "vegetable" as an "ingredient") Tofu (dried tofu) 1.1% Wakame (dried wakame) 0.6% · Soup (liquid ingredients) Dissolved water 50.2% Miso 18.7% Other seasonings 4.5% Starch 1.9% (The "%" indicates the percentage of each ingredient.)

[0025] 1-2. Preparation process S1 For example, when raw bamboo shoots are used as an ingredient, they are washed, peeled, de-soured, boiled, etc. In this example, boiled bamboo shoots that have already been subjected to these processes are used as an ingredient. In this example, tofu (dried tofu) and wakame (dried wakame) are added directly to the dissolving water in the subsequent cooking step S5. However, if these ingredients are to be added to the dissolving water in a reconstituted state, the reconstitution process is carried out at this point.

[0026] 1-3. Ingredients freezing process S2 The bamboo shoots are frozen at a temperature in the range of -25°C to -5°C, preferably at a temperature in the range of -15°C to -10°C (for example, -11°C). (An example of the process of "freezing at least a part of the ingredients")

[0027] 1-4. Thawing process for ingredients S3 The bamboo shoots frozen in the ingredient freezing step S2 are thawed. At this time, as an example, the ingredients contained in the container are thawed under running water.

[0028] 1-5. Ingredient dehydration process S4 The bamboo shoots thawed in the ingredient thawing step S3 are placed in a perforated container (a colander or a basket) and left for a while with a weight or the like placed on top of them to dehydrate them. At this time, the bamboo shoots are dehydrated so that their weight is within a range of 70% to 95% (for example, about 93%) of the weight of the bamboo shoots before the ingredient freezing step S2 began.

[0029] 1-6.Cooking process S5 Tofu (dried tofu), wakame (dried wakame), miso and other seasonings are added to the dissolving water in a heating container and cooked.

[0030] 1-7. Freeze-drying process S6 As an example, after filling the container with bamboo shoots (part of the ingredients), the cooking liquid (liquid ingredients and other ingredients such as tofu and wakame seaweed) cooked in cooking step S5 is poured into the container (an example of a state in which "mixed ingredients mixed with liquid ingredients" are contained within the container body). The container filled with bamboo shoots and juice is then freeze-dried. This completes the dried bamboo shoot soup. The specific content (processing procedure) of this freeze-drying is publicly known, so a detailed explanation will be omitted.

[0031] 1-8. Packaging process S7 The block of dried bamboo shoot juice is placed in a packaging container and sealed. This completes the product.

[0032] In this case, when ingredients are frozen in the freeze-drying process during the production of dried foods, the moisture contained in the ingredients turns into ice blocks that are scattered throughout the ingredients, and when the ice blocks in the ingredients are sublimated, voids are created in the areas where the ice blocks were previously located.

[0033] Here, in the freeze-drying step S6, when ingredients with a high water content and liquid ingredients are respectively filled into the container, the water contained in the ingredients (water that does not contain seasonings, etc.) seeps out from the ingredients into the liquid ingredients due to the difference in concentration with the surrounding liquid (liquid ingredients that contain seasonings, etc.), and a "layer of water seeping out from the ingredients" is generated around the ingredients. This phenomenon becomes more pronounced as the amount of water contained in the ingredients increases. Also, the more water seeps out of the ingredients, the greater the shrinkage of the ingredients themselves due to the freeze-drying step S6. Therefore, particularly for foods that use ingredients with a high fiber content (such as vegetables), the layer of water that is generated around the ingredients before the freeze-drying step S6 tends to become large, and as this layer of water is frozen and sublimated, large voids are likely to occur around the dried ingredients.

[0034] For this reason, in dried bamboo shoot soup produced by a conventional method that does not include the ingredient freezing step S2, ingredient thawing step S3, and ingredient dehydration step S4, the ingredients have a high moisture content at the start of the freeze-drying step S6, which results in large gaps being formed between two dried ingredient sections where adjacent ingredients in the ingredients have been dried, large gaps (cracks) occurring within one dried ingredient section, and large gaps being formed between the dried liquid ingredient section and the dried ingredient section, as shown in Figure 3. The dried bamboo shoot soup shown in the figure was produced using the same ingredients as the dried bamboo shoot soup in the above example, in the same blending ratio, and in the figure and Figure 2, which will be referred to later, the near-white areas are the dried ingredient sections, and the near-black areas are the dried liquid ingredient sections.

[0035] On the other hand, in the dried bamboo shoot soup produced according to the above-mentioned dried food production process 1, the moisture content of the ingredients at the start of the freeze-drying step S6 was reduced, so that no large gaps were formed between the two ingredient dried sections where adjacent ingredients in the ingredients were dried, no large gaps (cracks) were formed within one ingredient dried section, and no large gaps were formed between the liquid ingredient dried section and the ingredient dried section, as shown in Figure 2. Thus, despite using the same ingredients at the same blending ratio, no large gaps were formed like in the dried bamboo shoot soup produced by the conventional method, because the ingredient freezing step S2, ingredient thawing step S3, and ingredient dehydration step S4 were carried out prior to the freeze-drying step S6.

[0036] Specifically, in the above-mentioned dried food manufacturing process 1, the moisture contained in the ingredients is frozen in the ingredient freezing step S2, resulting in ice blocks being scattered in various parts of the ingredients, and then the ice blocks in the ingredients are thawed and changed to a liquid phase in the ingredient thawing step S3. Therefore, due to the expansion caused by the freezing of the moisture and the contraction caused by the melting of the ice blocks, elements other than moisture in the ingredients (such as fiber) are slightly damaged. As a result, some of the moisture contained in the ingredients seeps out from the ingredients, and the moisture content of the ingredients is reduced before the start of the freeze-drying step S6 compared to before the start of the ingredient freezing step S2. Therefore, it is presumed that the "layer of water seeping out from the ingredients" that occurs around the ingredients when the ingredients and liquid ingredients are filled into the container in the freeze-drying step S6 is prevented from becoming excessively large, and large voids are less likely to be formed around the dried parts of the ingredients after the freeze-drying step S6.

[0037] In addition, as described above, by carrying out the ingredient freezing step S2 and the ingredient dehydrating step S4, elements other than the moisture in the ingredients (such as fiber) are slightly destroyed, which weakens the contraction force caused by the internal stress of the ingredients themselves, and prevents the ingredients from excessively contracting during sublimation (drying). This is also presumably one of the reasons why large voids are unlikely to form in the dried bamboo shoot soup. In this case, in the ingredient dehydrating step S4 after the ingredient thawing step S3 in the above-mentioned dried food manufacturing process 1, the thawed ingredients are dehydrated and some of the moisture is removed. As a result, the amount of water that seeps out from the ingredients when mixed with the liquid food material is even smaller. This is also a reason why large voids are unlikely to form in the dried bamboo shoot soup.

[0038] Furthermore, by carrying out the ingredient freezing step S2, ingredient thawing step S3, and ingredient dehydration step S4 prior to the freeze-drying step S6, the amount of moisture contained in the ingredients is sufficiently reduced, so that when the ingredients and liquid ingredients are mixed in the freeze-drying step S6, the liquid ingredients cling to the surface of the ingredients, and the adhesion between the dried ingredient portion and the dried liquid ingredient portion is strengthened, which is presumably one of the reasons why large voids are unlikely to form in the dried bamboo shoot soup. As a result, the dried ingredient portion is prevented from coming off and cracking or chipping occurs in the dried bamboo shoot soup produced by the above-mentioned dried food production process 1.

[0039] In addition, in foods that use multiple types of ingredients such as bamboo shoots, tofu, and wakame seaweed, such as in the example of dried bamboo shoot soup above, it has been confirmed that even if the ingredient freezing step S2, ingredient thawing step S3, and ingredient dehydrating step S4 are only performed on a portion of these ingredients (only bamboo shoots in the example of dried bamboo shoot soup), separation of the dried ingredients and the occurrence of cracks and chips can be effectively prevented.

[0040] In this case, it is preferable that the "at least some of the ingredients" for which steps S2, S3, and S4 are performed are "ingredients with a high fiber content" among the multiple ingredients, or "ingredients with a high blending ratio (main ingredients)" among the multiple ingredients. Specifically, since "ingredients with a high fiber content" have a high water content and are prone to shrinkage due to the presence of "elements other than water," it is preferable to perform steps S2, S3, and S4 on these ingredients. Also, by performing steps S2, S3, and S4 on the "main ingredients" with a high water content, separation of the dried portion of the ingredients and cracks and chips can be suitably avoided even if steps S2, S3, and S4 are not performed on the other ingredients.

[0041] In addition, it is possible to target not only "several of a plurality of types of ingredients" but also "a portion of the total amount of one type of ingredient." In other words, it is possible to manufacture a dried food by mixing one type of ingredient with one that has undergone each of steps S2, S3, and S4 and one that has not. Even in this manufacturing method, if the amount of the ingredient that undergoes each of steps S2, S3, and S4 is sufficiently large, it is possible to effectively prevent the dried portion of the ingredient from coming off and the occurrence of cracks and chips.

[0042] Next, the relationship between the freezing temperature of the ingredients in the ingredient freezing step S2 in the dried food production process 1, whether or not the ingredient dehydrating step S4 is performed, and the state of the produced dried food will be described.

[0043] Using the same procedure as that of the above-mentioned dried food manufacturing process 1, various types of "dried food (dried bamboo shoot soup)" were produced with different freezing temperatures of the ingredients in the ingredient freezing step S2 and with or without the ingredient dehydration step S4, and were evaluated for the detachment of the dried part of the ingredients, the presence or absence of cracks or chips, and brittleness (ease of breaking). The results of the evaluation are shown in [Table 1]. Note that the types and blending ratios of ingredients used, and the sequence of steps from the preparation step S1 to the freeze-drying step S6 in the dried food manufacturing process 1 (except for the presence or absence of the ingredient freezing step S2, the ingredient thawing step S3, and the ingredient dehydration step S4) are the same as those in the above-mentioned examples, so duplicated explanations will be omitted. In addition, in this example for the purpose of evaluation, the packaging step S7 is not performed.

[0044] [Table 1]

[0045] In this case, as shown in [Table 1], when food 1 was produced, the ingredient freezing step S2 and the ingredient thawing step S3 were not carried out, when food 2A and 2B were produced, the freezing temperature of the ingredients in the ingredient freezing step S2 was -10°C, when food 3A and 3B were produced, the freezing temperature of the ingredients in the ingredient freezing step S2 was -15°C, when food 4A and 4B were produced, the freezing temperature of the ingredients in the ingredient freezing step S2 was -25°C, and when food 5A and 5B were produced, the freezing temperature of the ingredients in the ingredient freezing step S2 was -50°C. Also, when food 2A to 5A was produced, the ingredient dehydrating step S4 was not carried out, and when food 2B to 5B was produced, the ingredient dehydrating step S4 was carried out to dehydrate the ingredients to a weight within a range of 70% to 95% (in this example, 93%) of the weight of the ingredients before the start of the ingredient freezing step S2 (after the preparation step S1 for food 1 was completed). It should be noted that if the ingredient freezing step S2 and the ingredient thawing step S3 were not performed, it would not be possible to perform the ingredient dehydrating step S4 so that the weight of the ingredient would be within a range of 95% or less of the weight of the ingredient.

[0046] Here, the "Evaluation" column in [Table 1] indicates suitability for shipping as a product with "◎", "○", "△" or "×" based on the occurrence of falling off of the dried ingredient part from the liquid ingredient part, chipping or cracking, and the rate of breakage (crumbling) when an external force of a light pinch is applied. Specifically, foods with almost no defects as described above (foods with sufficiently high product value) are marked with "◎", foods with defects but with very low levels of defects (foods with minor defects that do not reduce the product value) are marked with "○", foods with a certain number of foods unsuitable for shipping (foods that may reduce the product value) are marked with "△", and foods with many foods unsuitable for shipping are marked with "×". The "Ease of manufacturing" column was evaluated from the perspectives of the time and power consumption required for manufacturing, ease of dehydration, etc.

[0047] As shown in "Table 1", in Food 1, in which the ingredient freezing step S2 and the ingredient thawing step S3 were not carried out before the freeze-drying step S6, many foods unsuitable for shipping were confirmed. In contrast, in Foods 2A to 5A and 2B to 5B, in which the ingredient freezing step S2 and the ingredient thawing step S3 were carried out before the freeze-drying step S6, a certain number of defective products were confirmed in some cases, regardless of the freezing temperature or whether the ingredient dehydrating step S4 was carried out or not, but many foods unsuitable for shipping were not confirmed. Therefore, it can be understood that by carrying out the ingredient freezing step S2 and the ingredient thawing step S3 prior to the freeze-drying step S6, it is possible to preferably avoid the production of defective products.

[0048] In this case, compared with foods 2A to 5A in which the ingredient dehydration step S4 was not carried out after the ingredient thawing step S3, foods 2B to 5B in which the ingredient dehydration step S4 was carried out had a lower frequency of defective products and were evaluated favorably. Therefore, it can be understood that by carrying out the ingredient dehydration step S4 after the ingredient thawing step S3 to dehydrate the ingredients and sufficiently reduce the water content, it is possible to more suitably avoid the production of defective products. In addition, the applicant has produced prototype foods by processing the ingredients in the ingredient dehydration step S4 so that the weight of the ingredients is less than 70% or more than 95% of the weight of the ingredients before the start of the ingredient freezing step S2. However, when dehydration was carried out to a weight of less than 70% (when the amount of dehydration was large), the appearance of some ingredients may be distorted or the taste may be impaired, and when dehydration was carried out to a weight of more than 95% (when the amount of dehydration was small), no change due to the presence or absence of the ingredient dehydration step S4 was confirmed.

[0049] On the other hand, by carrying out the ingredient freezing step S2 and the ingredient thawing step S3 before the freeze-drying step S6, the frequency of defective products can be sufficiently reduced, but the lower the freezing temperature in the ingredient freezing step S2, the smaller the size of the ice blocks generated in the ingredients during freezing, and the smaller the degree of "destruction of elements other than water in the ingredients (fiber, etc.)" caused by freezing and thawing. Therefore, ingredients frozen at an excessively low temperature (a temperature below -25°C) are less likely to seep out of the ingredients when thawed, and if the ingredients are dehydrated to an appropriate moisture content in the ingredient dehydration step S4, there is a risk of excessive destruction of "elements other than water in the ingredients (fiber, etc.)", which may impair the texture and appearance of the ingredients. For this reason, if the freezing temperature in the ingredient freezing step S2 is excessively low, it becomes difficult to carry out the ingredient dehydration step S4. Furthermore, the lower the freezing temperature in the ingredient freezing step S2, the more power consumption is required to lower the temperature inside the freezer, and the longer the time required to thaw the ingredients in the ingredient thawing step S3.

[0050] Therefore, as shown in Table 1, food 1, which does not undergo ingredient freezing step S2 and ingredient thawing step S3, is the easiest to manufacture, while foods 5A and 5B, which have the lowest freezing temperature in ingredient freezing step S2, are the least easy to manufacture. The applicant has prototyped foods using a freezing temperature of -5°C in ingredient freezing step S2, but has confirmed that it takes a very long time to freeze the ingredients and that it is difficult to adopt a manufacturing method at this freezing temperature.

[0051] As described above, in order to avoid the production of defective products and ensure sufficient ease of production in the dried food production method, it is preferable to set the freezing temperature in the ingredient freezing step S2 within a temperature range of −25° C. to −5° C., and preferably within a temperature range of −15° C. to −10° C. In addition, it can be seen that the frequency of production of defective products can be further reduced by carrying out the ingredient dehydration step S4 after the ingredient thawing step S3.

[0052] Thus, according to the dried food manufacturing method by the dried food manufacturing process 1, by performing the ingredient freezing step S2 and the ingredient thawing step S3 before the freeze-drying step S6, the shrinkage amount of the ingredients that have been subjected to the ingredient freezing step S2 and the ingredient thawing step S3 in the freeze-drying step S6 can be reduced compared to the conventional manufacturing method in which the ingredient freezing step S2 and the ingredient thawing step S3 are not performed, and therefore it is possible to preferably prevent the ingredient dried part from coming off the liquid food dried part in the manufactured dried food, cracks or chips, or the manufacture of a product that is prone to cracks or chips. This makes it possible to sufficiently improve the commercial value of the manufactured dried food and sufficiently reduce its manufacturing cost.

[0053] Furthermore, according to the dried food manufacturing method using this dried food manufacturing process 1, by carrying out an ingredient dehydration process S4 in which the ingredients thawed in the ingredient thawing process S3 are dehydrated to a weight within a range of 70% to 95% of the weight of the ingredients before the ingredient freezing process S2 began, the adhesion between the liquid food dried section and the ingredient dried section can be increased, thereby more effectively preventing the ingredient dried section from detaching, cracking or chipping, and the production of products that are prone to cracking or chipping.

[0054] Furthermore, according to the method for producing dried foods by this dried food production process 1, the ingredients are frozen in the ingredient freezing step S2 within a temperature range of -25°C or higher and -5°C or lower, preferably within a temperature range of -15°C or higher and -10°C or lower, thereby suitably reducing the moisture content of the ingredients and sufficiently reducing the amount of shrinkage of the ingredients, thereby more suitably preventing the detachment of the dried ingredient portion, cracks or chips, and the production of products that are prone to cracks or chips. Furthermore, the time required for producing dried foods and the increase in power consumption during production are avoided, and the production cost of dried foods can be sufficiently reduced.

[0055] In addition, according to the dried food manufacturing method using this dried food manufacturing process 1, by using vegetables as ingredients, which are high in fiber, it is possible to produce dried foods with high commercial value by sufficiently reducing the frequency of such defects, even in dried foods that are prone to peeling off of the dried ingredients, cracking or chipping, and cracking or chipping when produced by conventional methods.

[0056] It should be noted that the "dried food manufacturing method" is not limited to the above-mentioned examples of manufacturing methods.

[0057] For example, in the ingredient dehydration step S4, an example has been given in which weights are placed on the ingredients (bamboo shoots) to dehydrate them, but depending on the type of ingredient, it is also possible to dehydrate the ingredients by absorbing moisture from the ingredients using a water absorbent (such as absorbent paper or a sponge), by using a centrifugal dehydrator, or by leaving the ingredients in a drying cabinet for a while.

[0058] Also, while an example of a manufacturing method for manufacturing "dried bamboo shoot soup" as a "dried food" using "bamboo shoots" as the main "ingredient" has been described, various "dried juices" and "dried soups" can be manufactured using various "ingredients" other than "bamboo shoots", for example "vegetables" such as lotus root, carrots, radish and asparagus, in the same manner as in the above-mentioned dried food manufacturing process 1. Also, an example of performing the ingredient dehydration step S4 after the ingredient thawing step S3 has been described, but when the moisture content of the ingredients can be suitably reduced by performing the ingredient freezing step S2 and the ingredient thawing step S3, dried foods can also be manufactured without performing the ingredient dehydration step S4.

[0059] In addition, although the above description uses an example of a manufacturing method for dried foods in which moisture (hot water, etc.) is absorbed when the food is eaten, the above-mentioned dried food manufacturing method can also be used to produce high-value products when producing "dried foods that can be eaten in a dry state," such as snack foods and dried topping ingredients. [Explanation of symbols]

[0060] 1. Dry food manufacturing process S1 Preparation process S2 Ingredients freezing process S3 Thawing process S4 Ingredient dehydration process S5 Cooking process S6 Freeze drying process S7 Packaging process

Claims

1. When producing a dried food by freeze-drying a mixed food material obtained by mixing liquid food materials and ingredients, An ingredient freezing step of freezing at least a portion of the ingredients; An ingredient thawing process for thawing the ingredient frozen in the ingredient freezing process; a freeze-drying step of freeze-drying the mixed food material obtained by mixing the ingredients with the liquid food material, in this order to produce the dried food.

2. 2. A method for producing a dried food product as described in claim 1, wherein the ingredient thawed in the ingredient thawing process is dehydrated to a weight within a range of 70% to 95% of the weight of the ingredient before the ingredient freezing process began, and then mixed with the liquid food material.

3. 2. The method for producing a dried food according to claim 1, wherein the ingredient is frozen at a temperature within the range of -25°C or higher and -5°C or lower in the ingredient freezing step.

4. 4. The method for producing a dried food according to claim 3, wherein the ingredient is frozen at a temperature within the range of -15°C or higher and -10°C or lower in the ingredient freezing step.

5. 5. The method for producing a dried food according to claim 1, wherein the ingredients are vegetables.

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