JP6836893B2 - Porous dried food manufacturing method and porous dried food manufacturing equipment - Google Patents

Description

The present invention relates to a method for producing a dried food, particularly a porous dried food in which a large number of micropores are formed, and an apparatus for producing a porous dried food.

Various techniques have been developed to process foods such as vegetables, fruits, meats and fish into dried foods. In particular, in recent years, dried foods that are suitable for eating as they are as snack foods have become widespread, and in addition to taste and nutritional value, texture is also important. Porous dried foods with many fine pores formed in the foods have a crispy texture and are suitable for eating as they are.

For example, Patent Document 1 discloses a method for producing a porous dried food, which is obtained by subjecting foods such as vegetables and fruits to an enzyme treatment and then drying them in a reduced pressure environment. In this production method, it is possible to produce a porous dried food having an excellent texture by forming a large number of pores in the food by destroying cells constituting the food by enzyme treatment.

JP-A-8-210

The method for producing a dried pore food described in Patent Document 1 requires enzyme treatment as described above, and it is said that the enzyme acts on cellulose in the cell wall. Therefore, it cannot be similarly applied to foods other than vegetables and fruits such as meat and fish. As a result of studies, the present inventors have developed a technique for producing a porous dried food that does not require enzyme treatment and can be applied to various foods.

In view of the above circumstances, an object of the present invention is to provide a method for producing a porous dried food having an excellent texture and an apparatus for producing a porous dried food.

In order to achieve the above object, the method for producing a porous dried food according to one embodiment of the present invention includes a freezing step, a first heating and drying step, a vacuum drying step, and a second heating and drying step.
In the above freezing step, the object which is a food is frozen.
In the first heat-drying step, the frozen object is heated and dried so that a dry layer is formed on the surface of the object.
In the vacuum drying step, the object dried in the first heat drying step is dried in a reduced pressure environment.
In the second heat drying step, the object dried in the vacuum drying step is heated and dried.

In this production method, the structure of the object is destroyed by freezing the object in the freezing step, and the water content is adjusted by the first heating and drying step. By performing vacuum drying in this state, the object is expanded (swelled), and the remaining water is removed by the second heating and drying step. As a result, it is possible to produce a porous dried food having a large number of fine pores and having an excellent texture.

In the freezing step, the temperature of the object may be maintained in the maximum ice crystal formation temperature zone for 30 minutes or more.

A freezing method that maintains the temperature of an object in the maximum ice crystal formation temperature range (-1 to -5 ° C) for 30 minutes or more is called slow freezing, and is distinguished from quick freezing that passes through the same temperature range in less than 30 minutes. To. By freezing the object by slow freezing, the size of the ice crystals contained in the object is increased, and the cells constituting the object are destroyed. Thereby, it is possible to improve the texture of the object.

In the first drying step, the object may be dried so that the water content of the object is 45 wt% or more and 65 wt% or less. Moisture content refers to the ratio of the weight of water to the total weight of the object, and is expressed as a percentage here.

If the removal of water by the first step is insufficient and the target contains more than 65 wt% of water, the target expands in the vacuum drying step and the target is destroyed. Further, if the water content of the object is less than 45 wt% due to excessive removal of water by this step, the expansion width is small or expansion does not occur. Therefore, the water content in the first heating and drying step is preferably 45 wt% or more and 65 wt% or less.

In the first heating and drying step, the object may be heated so that the temperature of the object is 50 ° C. or higher and 60 ° C. or lower.

If the temperature of the object exceeds 60 ° C, the removal of water proceeds too much, and if it is less than 50 ° C, the drying time becomes long. Therefore, the temperature of the object in the first heating and drying step is preferably 50 ° C or more and 60 ° C or less. Is.

In the first heating and drying step, the object may be heated by applying warm air to the object in an atmospheric pressure environment.

In the first heating and drying step, the object may be heated by using a heater in an atmospheric pressure environment or a reduced pressure environment.

In the second heat-drying step, the object may be dried so that the water content of the object is 20 wt% or less.

If the object contains water with a moisture content of more than 20 wt%, a crispy texture cannot be obtained and the storage stability of the food due to drying is impaired. Therefore, the moisture content in the second heating and drying step is 20 wt. % Or less, particularly 15 wt% or less is preferable.

In the second heat-drying step, the object may be heated and dried in a reduced pressure environment.

In the second heat-drying step, the object may be dried in a reduced pressure environment of 10 kpa or less.

The method for producing a porous dried food may further include a slicing step of slicing the object to a thickness of 2 mm or more and 10 mm or less before the step of freezing the object.

When the thickness of the object is less than 2 mm, the water content of the object is small and the swelling in the vacuum drying step does not proceed. Further, when the thickness of the object exceeds 10 mm, a large amount of heat energy and time are required to remove water in the drying step. Therefore, the thickness of the object is preferably 2 mm or more and 10 mm or less.

In order to achieve the above object, the porous dried food manufacturing apparatus according to one embodiment of the present invention includes a drying chamber, a vacuum pump, a hot air generator, and a control unit.
The drying chamber can accommodate an object that is food.
The vacuum pump is connected to the drying chamber and evacuates the drying chamber.
The hot air generator is connected to the drying chamber and supplies hot air to the drying chamber.
The control unit controls the hot air generator, heats the frozen object, dries it so that a dry layer is formed on the surface of the object, controls the vacuum pump, and controls the vacuum pump in the drying chamber. Is vacuum exhausted to dry the object in a reduced pressure environment.

According to this configuration, it is possible to realize the above-mentioned method for producing a porous dried food.

As described above, according to the present invention, it is possible to provide a method for producing a porous dried food having an excellent texture and an apparatus for producing a porous dried food.

It is a schematic diagram of the porous dried food production apparatus which concerns on embodiment of this invention. It is a flowchart which shows the manufacturing process of the porous dried food manufacturing method which concerns on embodiment of this invention. It is a graph for demonstrating the slow freezing used in the porous dry food production method which concerns on embodiment of this invention.

[About porous dried food manufacturing equipment]
The porous dried food production apparatus according to the embodiment of the present invention will be described. The porous dried food manufacturing apparatus according to the present embodiment is an apparatus for processing a food into a porous dried food. The food (object) to be processed is not particularly limited, and is any food such as fruits, vegetables, root vegetables, fish, meat, etc., and may be uncooked or cooked.

FIG. 1 is a schematic view showing the configuration of the porous dried food manufacturing apparatus 100 according to the present embodiment. As shown in the figure, the porous dried food manufacturing apparatus 100 includes a drying chamber 101, a vacuum pump 102, a hot air generator 103, a drying shelf 104, and a control unit 105. The drying chamber 101, the vacuum pump 102, and the hot air generator 103 are each connected by a pipe, and the pipe is provided with a vacuum valve V.

The drying chamber 101 is a vacuum chamber capable of maintaining a vacuum environment. The vacuum pump 102 is connected to the drying chamber 101 so that the inside of the drying chamber 101 can be evacuated.

The hot air generator 103 is connected to the drying chamber 101 and supplies hot air into the drying chamber 101. The drying shelf 104 is provided in the drying chamber 101 on which the object is placed. The control unit 105 is connected to the vacuum pump 102, the hot air generator 103, the vacuum valve V, and the like, and controls them.

The porous dried food production apparatus 100 has the above configuration. The configuration of the porous dried food production apparatus 100 is not limited to that shown here, and any device may be used as long as it can realize the method for producing a porous dried food described later.

[About the manufacturing method of porous dried foods]
A method for producing a porous dried food according to an embodiment of the present invention will be described.

FIG. 2 is a flowchart showing a process flow of the method for producing a porous dried food according to the present embodiment.

First, the object is sliced to a predetermined thickness (slicing step: St101). This thickness is, for example, 2 mm or more and 10 mm or less, more preferably 3 mm or more and 8 mm or less, and particularly preferably 7 mm. When the thickness of the object is less than 2 mm, the water content of the object is small and the swelling described later is unlikely to proceed. Further, when the thickness of the object exceeds 10 mm, it takes a relatively large amount of heat energy and time to remove water in each drying step described later. Therefore, the thickness of the object is preferably 2 mm or more and 10 mm or less, and more preferably 3 mm or more and 8 mm or less. If the thickness of the object is thin, this step can be omitted.

Subsequently, the object is frozen by slow freezing (slow freezing step: St102). FIG. 3 is a graph showing the difference between slow freezing and quick freezing. As shown in the figure, slow freezing is a freezing method in which the temperature of the object is gradually lowered, and the temperature of the object is in the maximum ice crystal formation temperature range (D in the figure) of -1 ° C to -5 ° C for 30 minutes. It passes over the above. As shown in the figure, quick freezing is a freezing method in which the maximum ice crystal formation temperature zone is passed in less than 30 minutes.

The maximum ice crystal formation temperature zone is a temperature zone in which the volume of ice crystals grows, and in slow freezing, the passage time of the same temperature zone is long, so that the volume of ice crystals becomes large. On the other hand, in quick freezing, the transit time in the same temperature range is short, so the volume of ice crystals is smaller than in slow freezing.

In the present embodiment, the object is frozen by slow freezing to increase the volume of ice crystals and destroy the cells constituting the object. This softens the object. The freezing time of slow freezing is preferably 6 hours or more.

Subsequently, the slowly frozen object is heated and dried (first heat-drying step: St103). As a result, after thawing the object, water is removed. In the first heat-drying step, the object is dried so that the moisture content of the object is 45 wt% or more and 65 wt% or less.

This step can be performed by placing the slowly frozen object on the drying shelf 104 and supplying hot air from the hot air generator 103 into the drying chamber 101 under atmospheric pressure. At this time, it is preferable to heat the object so that the temperature of the object is 50 ° C. or higher and 60 ° C. or lower. This is because if the temperature of the object exceeds 60 ° C, the removal of water proceeds too much, and if it is less than 50 ° C, the drying time becomes long. Instead of hot air, the object may be heated by a heater such as an infrared lamp.

Further, this heating and drying may be performed by reducing the pressure in the drying chamber 101 to 20 kPa or more and 50 kPa or less, heating the object with a heater (not shown), and setting the temperature of the object to 45 ° C or more and 60 ° C or less. .. The heating temperature and heating time can be adjusted according to the type and thickness of the object, and the water content can be 45 wt% or more and 65 wt% or less.

In this heating and drying step, when the moisture evaporates from the surface of the object, the moisture moves from the inside of the object to the surface. As the drying progresses, the moisture inside decreases and the rate of movement of moisture from the inside to the surface decreases, so that a dry layer is formed on the surface of the object. In this state, some water is contained inside the object, but this heating and drying step is completed at this point.

Subsequently, the object is dried by vacuum drying (vacuum drying step: St104). This step can be performed by reducing the pressure in the drying chamber 101 to 10 kPa or less. By rapidly evacuating the inside of the drying chamber 101, the moisture contained in the object reaches the vapor pressure and vaporizes. At this time, the volume of the object increases, and the object expands (expands).

Subsequently, the object is heated and dried (second heating and drying step: St105). As a result, the object is dried until the moisture content is 20 wt% or less, preferably 15 wt% or less.

In this step, drying can be performed by evacuating the inside of the drying chamber 101 with a vacuum pump 102. Further, the inside of the drying chamber 101 may be heated by a heater or the like to dry it. The heating temperature and heating time can be adjusted according to the type and thickness of the object, and the water content can be reduced to 15 wt% or less.

By the above steps, the food of the object becomes a porous dried food. The object is softened by the slow freezing step (St102), the water content is adjusted by the first heating and drying step (St103), the object is expanded by the vacuum drying step (St104), and further, the second heating and drying step (St103). By removing the water with St105), the object can be made porous. This makes it possible to produce a porous dried food having a crispy texture.

The above manufacturing method may be carried out by the user, or may be carried out by the control unit 105 controlling the vacuum pump 102, the hot air generator 103, the vacuum valve V, and the like. The control unit 105 can proceed with each of the above steps based on, for example, a change in the weight of the object.

[About water content]
As described above, in the first heating and drying step, the object is dried so that the moisture content is in the range of 45 wt% or more and 65 wt% or less.

If the removal of water by this step is insufficient and the object contains more than 65 wt% of water, the object expands in the vacuum drying step (St104) and the object is destroyed. Further, if the water content of the object is less than 45 wt% due to excessive removal of water by this step, the expansion width is small or expansion does not occur. Therefore, the water content in the first heating and drying step is preferably 45 wt% or more and 65 wt% or less.

Further, as described above, in the second heat drying step, the product is dried until the moisture content becomes 15 wt% or less. If the removal of water by this step is insufficient and the object contains water with a moisture content of more than 20 wt%, a crispy texture cannot be obtained and the food can be preserved by drying. It is impaired. Therefore, the water content in the second heating and drying step is preferably 15 wt% or less.

The moisture content of the object can be measured by a dry weight loss method using an infrared moisture meter. As the infrared moisture meter, for example, FD-610 (manufactured by Kett Science Institute Headquarters) can be used.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made.

Examples and comparative examples of the present invention will be described.

[Example 1]
Raw bananas were peeled, sliced to a thickness of 7 mm, and frozen for 6 hours or more (slow freezing). The banana was moved to a drying chamber in a frozen state, and the chamber was heated and dried with warm air (first heating and drying).

The dried (first heat-dried) banana shrank to a thickness of about 4 mm, the surface was dried, and water remained inside (moisture content: 50 to 60 wt%). In this state, the pressure in the drying chamber was reduced from atmospheric pressure to 5 kPa or less. As a result, the moisture inside the banana was vaporized, and the banana expanded from 4 mm to 10 mm in thickness (expansion rate ((thickness after drying / thickness before drying) × 100) 150%).

It was dried in the expanded state (second heat drying) to obtain a porous dried banana having a moisture content of about 10 wt%. When the inside of the porous dried banana was observed with a microscope (VHX5000: manufactured by KEYENCE CORPORATION), a large number of voids having a diameter of about 0.5 mm were confirmed. When I ate it, it had a crispy texture.

[Example 2]
Raw bananas were peeled, sliced to a thickness of 7 mm, and frozen for 6 hours or more (slow freezing). The banana was moved to a drying chamber in a frozen state and heated and dried (first heat drying) with an infrared heater while adjusting the pressure in the chamber under reduced pressure (50 kPa to 20 kPa).

The dried (first dried) banana shrank to a thickness of about 4 mm, the surface was dried, and water remained inside (moisture content: 50 to 60 wt%). In this state, the pressure in the drying chamber was reduced to 5 kPa or less. As a result, the water inside the banana was vaporized, and the banana expanded from 4 mm to 10 mm in thickness (expansion rate: 150%).

It was dried in the expanded state (second heat drying) to obtain a porous dried banana having a moisture content of about 10 wt%. When the inside of the porous dried banana was observed with a microscope (VHX5000: manufactured by KEYENCE CORPORATION), a large number of voids having a diameter of about 0.5 mm were confirmed. When I ate it, it had a crispy texture.

[Example 3]
Raw bananas were peeled and sliced to a thickness of 10 mm. Hereinafter, it was produced in the same manner as in Example 1 above. After the second heat-drying step, the water content of the obtained porous dried banana was about 5% higher than that of Example 1, and the crispy texture was slightly inferior to that of Example 1. By further drying for 2 hours, the same texture as in Example 1 was obtained.

[Example 4]
Raw bananas were peeled and sliced to a thickness of 2 mm. Hereinafter, it was produced in the same manner as in Example 1 above. At the time of the first heating and drying step, the water content inside the banana was reduced, and the degree of expansion due to the vacuum drying step was smaller than that of Example 1. After the second heat-drying step, the obtained porous dried banana had a slightly inferior crispy texture as compared with Example 1.

[Example 5]
Raw bananas were peeled and sliced to a thickness of 7 mm. After slow freezing in the same manner as in Example 1, the first heat drying was carried out under the condition for a longer time than in Example 1 to set the moisture content of the banana to 40 wt%. After that, vacuum drying and second heat drying were performed under the same conditions as in Example 1. The obtained porous dried banana had a thick and hard dry layer formed on the surface as compared with Example 1, and the expansion rate due to swelling was about 70%. The internal structure was slightly finer and the crispy texture was slightly inferior to that of Example 1.

[Example 6]
Raw bananas were peeled and sliced to a thickness of 7 mm. After slow freezing in the same manner as in Example 1, the first heat drying was carried out under the condition of a shorter time than in Example 1 to set the moisture content of the banana to 66 wt%. After that, vacuum drying and second heat drying were performed under the same conditions as in Example 1. The surface condition of the obtained porous dried banana was similar to that of Example 1, but the water content was slightly higher than that of Example 1. The expansion rate due to swelling was about 150%, and rupture occurred in some places. When it was eaten, the crispy texture was slightly inferior to that of Example 1.

[Comparative Example 1]
Raw bananas were peeled and sliced to a thickness of 7 mm. Slow freezing was not carried out, and thereafter, first heat drying, vacuum drying and second heat drying were carried out under the same conditions as in Example 1. The banana did not soften because it was not slowly frozen, and the expansion rate due to vacuum drying was about 50% due to the effect. The texture was also harder than that of Example 1, and a porous dried banana could not be obtained.

[Comparative Example 2]
Raw bananas were peeled and sliced to a thickness of 7 mm. After slow freezing in the same manner as in Example 1, the surface was vacuum-dried in the same manner as in Example 1 under the condition that the moisture content of the banana was 75 wt% and no dry layer was formed on the surface without first heating and drying. Porous dried bananas could not be obtained because they were foamed and destroyed.

Table 1 shows the production conditions and evaluation results of the porous dried food production methods according to Examples 1 to 6 and Comparative Examples 1 and 2.

As described above, according to Examples 1 to 6, it was possible to produce a porous dried banana having an excellent texture. Further, it was confirmed that the thickness of the food by slicing is preferably 3 mm or more and 8 mm or less, and the water content in the first heat-drying step is preferably 45 wt% to 65 wt%.

By applying the present invention, in addition to bananas, porous dried foods were obtained from the following foods.
Fruits: Strawberries, citrus fruits (lemon, ponkan, tankan, kinkan), apples, pine apples, kiwi fruits, grapes, avocados, mangoes, watermelons, melons Vegetables: Leafy vegetables (horensou, komatsuna, turnips), root vegetables (Carrots, turnips, radishes, gobos), earthenware (sweet potatoes, potatoes, onions), fruit vegetables (tomatoes, pumpkins, bitter melons, okura), spicy sardines (togarashi)
Beans: Natto Fish: Eva miscellaneous fish (migratory fish)

100 ... Porous dry food manufacturing equipment 101 ... Drying room 102 ... Vacuum pump 103 ... Hot air generator 104 ... Drying shelf 105 ... Control unit

Claims (10)

The freezing process that freezes the object that is food,
A first heat-drying step of heating the frozen object and drying it so that a dry layer is formed on the surface of the object.
A vacuum drying step of drying the object dried in the first heat drying step in a reduced pressure environment, and a vacuum drying step.
Wherein heating the object to be dried in a vacuum drying process, possess a second heat drying step of drying,
A method for producing a porous dried food in which the pressure is reduced to 20 kPa or more and 50 kPa or less in the first drying step. The method for producing a porous dried food according to claim 1.
A method for producing a porous dried food in which the temperature of the object is maintained in the maximum ice crystal formation temperature zone for 30 minutes or more in the freezing step. The method for producing a porous dried food according to claim 1 or 2.
In the first heat-drying step, a method for producing a porous dried food, in which the object is dried so that the water content of the object is 45 wt% or more and 65 wt% or less. The method for producing a porous dried food according to any one of claims 1 to 3.
In the first heat-drying step, a method for producing a porous dried food, in which the object is heated so that the temperature of the object is 50 ° C. or higher and 60 ° C. or lower. The method for producing a porous dried food according to any one of claims 1 to 4.
Wherein in the first heat drying step, the method of producing a porous dry food for heating the object using the heat Ta. The method for producing a porous dried food according to any one of claims 1 to 5.
In the second heat-drying step, a method for producing a porous dried food, in which the object is dried so that the water content of the object is 20 wt% or less. The method for producing a porous dried food according to any one of claims 1 to 6.
In the second heat-drying step, a method for producing a porous dried food, in which the object is heated and dried in a reduced pressure environment. The method for producing a porous dried food according to claim 7.
In the second heat-drying step, a method for producing a porous dried food, in which the object is dried in a reduced pressure environment of 10 kpa or less. The method for producing a porous dried food according to any one of claims 1 to 8.
A method for producing a porous dried food, further comprising a slicing step of slicing the object to a thickness of 2 mm or more and 10 mm or less before the step of freezing the object. A drying room that can accommodate food objects and
A vacuum pump connected to the drying chamber and evacuating the drying chamber,
A heater provided in the drying chamber to heat the object,
The heater and controls the vacuum pump, dried as a layer and dried surface before Symbol object of frozen the object is heated at 50kPa under less pressure environment than 20kPa is formed, it is dried A porous dried food production apparatus including a control unit for drying the object in a reduced pressure environment and further heating and drying the dried object.

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