JP2009039000A - Food drying method, and storehouse equipped with food drying means - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drying method for easily drying food such as vegetables, meat and fish in a household at a high quality while controlling propagation of bacteria and nutritive value of food. <P>SOLUTION: This drying method comprises changing pressure in a gas space in contact with a food 103 by a freezing atmosphere, increasing the quantity of saturated water vapor in the gas space when decompressing the gas space in contact with the food 103 so as to promote gasification of moisture on the surface of the food 103 and evaporate moisture in the food 103, and further repeating pressure changing treatment to further decrease moisture in the food 103, and promoting drying up to make a moisture content adequate so as to easily obtain a high-quality dried food. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a drying method for reducing moisture retained by food while maintaining quality in fresh foods such as vegetables, fruits, meat, and fish and cooked products (meal).

  In recent years, the need for bulk purchases has increased with the increase in the number of dual-income families and the number of nuclear families accompanying the advancement of women into the society. It is anxious to do.

  As a method for preserving fresh food in high quality for a long period of time, frozen storage is most commonly performed for reasons such as suppressing the growth of adhering bacteria and suppressing the self-digestion of food. However, since it takes time and time for thawing when cooking, frozen storage is not desirable considering the convenience of cooking. In addition, there is a concern that the quality of the food may be deteriorated due to a drip outflow that occurs when the frozen product is thawed, a thawing unevenness when thawing the microwave oven, or a partial boil by excessive heating. Furthermore, when vegetables and fruits are frozen, the cell membrane is destroyed, causing water outflow upon thawing, resulting in significant quality degradation.

  On the other hand, as a long-term preservation method, there is a method of drying food. For example, it is a food such as dried fish that opens and closes seafood to create a hard film on the surface, enhances storage stability, and further has a unique texture and flavor (see Patent Document 1). ).

  FIG. 3 shows a schematic diagram of a conventional food drying apparatus. As shown in FIG. 3, a heat radiating plate 2 is provided on the ceiling of the drying chamber 1, and an electric heating heating element 3 and an air heating chamber 4 with the heating element 3 as a bottom surface are arranged on the upper surface of the heat radiating plate 2. The warm air heated in the air heating chamber 4 is supplied into the drying chamber 1 and circulated.

  On opposite wall surfaces of the drying chamber 1, porous walls 5 and 5 a are respectively provided so as to form dispersion chambers 6 and 6 a behind them. The drying chamber 1 is pressurized by a blower 7 and temperature-adjusted by an air conditioning device 8 (air heating device) is supplied through a duct 9 to a dispersion chamber 6 formed along the wall surface. Is dispersed as a whole and is ejected laterally into the drying chamber 1 as external circulation heating air hg from a large number of small holes, and passes through the drying plates 11 supported in multiple stages in the carriage 10 so as to face each other. It flows into the dispersion chamber 6a behind the many holes in the wall 5a and returns to the blower 7 through the duct 9a.

  Further, a dehumidifying device 13 provided with a cooling device is connected to the duct 9a through a valve 14 so that the flow rate can be adjusted, and the heated air (circulated air) flowing in the duct 9a is cooled to remove humidity. ing.

  Further, an exhaust blower 15 and an air supply fan 16 are connected to the drying chamber 1, and the air inside the drying chamber 1 is exhausted by the exhaust blower 15 and kept at a predetermined reduced pressure state, and fresh air is generated by the air supply fan 16. It comes to supply. Depending on the design of the apparatus, the entire amount of heated air passing through the duct 9 may be allowed to pass through the dehumidifying device 13 so that the total amount of humidity can be adjusted.

  The heat radiating plate 2 provided on the ceiling surface is composed of a metal plate 2a having a ceramic layer formed on the lower surface facing the inside of the drying chamber 1, and a heater 2b disposed on the back surface thereof. The air heating chamber 4 is formed. Therefore, the heater 2b emits far infrared rays R from the lower surface, and heats the air passing through the air heating chamber 1 on the upper surface.

  In addition, an intake port 4a is provided on one side of the heat radiating plate 2, and an exhaust port 4b is provided on the other side. A powerful sirocco fan 4c is provided in the vicinity of the intake port 4a. Then, the air in the drying chamber 1 is sucked, pressurized by the fan 4c, and heated by the heater 2b while passing through the air heating chamber 4 to become hot air h having a predetermined temperature from the exhaust port 4b. It is discharged at high speed so as to reach the vicinity of the inner floor surface.

In the food drying apparatus configured as described above, a drying cycle comprising a heating drying process that causes at least hot air to act on the food to be dried, and a cooling air drying process that is brought into contact with cold air at room temperature or lower following this heating drying process. By aging and drying a food that is repeated several times, the overall effect of the operation of accelerating the drying rate by heat drying and the cold air drying process of applying cold air at room temperature or less occurs, Thus, it has become possible to provide a drying method with improved aging without requiring a long time.
JP 2003-225077 A

  However, in the above-described conventional configuration, the drying degree is increased by repeating a drying process consisting of a heating and drying process in which warm air is applied and a cooling and drying process in which the heating and drying process is brought into contact with cold air at a room temperature or lower, several times. However, by contacting the food with warm air in the temperature range where the growth of bacteria at about 35 to 45 ° C. is most active, it is possible to promote the decay of food due to significant growth of the bacteria attached to the food. There was a problem of high nature. In addition, by repeating the heat drying step and the cold air drying step a plurality of times, there is also a problem that moisture is removed and the food is dried too much, and the food becomes hard and the texture becomes poor. Furthermore, there is a problem that a heating device that acts with hot air and a cooling device that acts with cold air must be used in combination, and the device is large and cannot be used easily at home.

  The present invention solves the above-described conventional problems, and suppresses the growth of bacteria and dries foods while maintaining freshness. It is simple and automatic not only at home but also at food processing sites. The present invention provides a method for drying a food product that can be dried.

  In order to solve the above conventional problems, the present invention provides a freezing step for freezing food, a transformation step for changing the pressure of a gas space in contact with the food in the freezing step in a freezing atmosphere, and the transformation step. A drying step of detecting the moisture content of the food and drying the food until a predetermined moisture content is reached.

  As a result, when the gas space in contact with the food is decompressed, the amount of saturated water vapor in the gas space increases, and vaporization of moisture on the food surface is promoted. And the water | moisture content in a foodstuff evaporates, and also by repeating such a pressure fluctuation process in a freezing atmosphere, the water | moisture content of a foodstuff further reduces and drying is accelerated | stimulated until it becomes a moderate water content.

  According to the method of drying food by repeatedly performing the decompression step under the freezing atmosphere of the present invention, the freezing atmosphere is a temperature that can suppress the growth of bacteria and self-digestion of the food during drying, thereby suppressing deterioration. Furthermore, it is possible to appropriately evaporate the water content of the food while suppressing the deactivation of nutrients such as vitamins of the food. As a result, the obtained food has effects such as improvement of storage stability, maintenance of nutrition, concentration of umami, and maintenance of flavor. In addition, as an effect of improving cooking properties, effects such as shortening of cooking time and promotion of penetration of taste can be obtained. By reducing the pressure, a low oxygen atmosphere is obtained, and lipid oxidation can be suppressed.

  The invention according to claim 1 includes a freezing step for freezing food, a transformation step for changing the pressure of a gas space in contact with the food in the freezing step in a freezing atmosphere, and a moisture content of the food in the transformation step. And a drying step of drying until a predetermined water content is reached.

  First, when the gas space in contact with food is depressurized, the amount of saturated water vapor in the gas space increases, and the vaporization of moisture on the food surface is promoted. Thereby, by repeating such a pressure fluctuation process in a frozen atmosphere, the water content of the food is further reduced and drying is promoted.

  By detecting the moisture content, it is possible to provide a dry state with a moisture content desired by the user, such as suppressing excessive drying by controlling the drying level.

  By drying until reaching a predetermined moisture content, the effect of improving the storage stability and umami condensation occurs. In particular, by carrying out in a freezing atmosphere, the growth of microorganisms can be mitigated, and the storage stability is improved. Moreover, by applying pressure fluctuation, a load is applied to the microbial cell membrane, and by rupturing the microbial cell membrane, an effect of suppressing the growth of microorganisms is produced, and the storage stability is further improved.

  Furthermore, by reducing the pressure of the gas space in contact with the food, a low oxygen atmosphere is obtained, so that lipid oxidation can be suppressed.

  Furthermore, in the cooking of food dried by the above method, effects such as shortening the cooking time and increasing the penetration of taste when seasonings are added occur.

  According to a second aspect of the present invention, the step of varying the pressure variation includes a pressure reduction step and an atmospheric pressure introduction step. By making the pressure fluctuation into these two steps, it is possible to simplify the freezing apparatus and save space.

  The invention described in claim 3 is characterized in that the humidity of the gas introduced by the atmospheric pressure introduction step is lower (low humidity) than the humidity of the gas introduction destination. As a result, it is possible to easily and efficiently evaporate water from the food more efficiently.

  According to a fourth aspect of the present invention, the pressure reducing step includes means for selectively adsorbing a food-specific odor. For example, by moving the gas from the inside of the storage to the outside of the storage, such as through a means for selectively adsorbing only the N-type gas specific to the fishy odor, a specific cause of bad odor in the storage It is possible to remove various gases. It is also possible to selectively adsorb ethylene gas, which causes aging of vegetables.

  The invention according to claim 5 includes at least one step of changing the pressure of the gas space in contact with the food and freezing the food in any process until the food reaches a predetermined moisture content. The food product is dried, and the food product has a food drying function. With this storage, it is possible to make dry foods with a predetermined moisture content, and by simply evaporating the moisture of foods easily and moderately at home, it improves storage, shortens cooking time, concentrates flavor, maintains flavor, etc. The effect is obtained.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same reference numerals are given to the same configurations as those of the conventional example or the embodiments described above, and detailed descriptions thereof will be omitted. The present invention is not limited to the embodiments.

(Embodiment 1)
Embodiments of the present invention will be described with reference to the drawings.

  1 is a cross-sectional view of a vacuum drying apparatus according to Embodiment 1 of the present invention. FIG. 2 is a flowchart showing control of the case internal pressure and the first on-off valve and the second on-off valve.

  As shown in FIG. 1, a case 104 that is pulled out by a door 102 and stores food 103 therein and a lid 105 that seals the case 104 when the door 102 is closed are provided inside the main body 101. ing. A packing (not shown) is provided at the joint between the case 104 and the lid 105, and the door 102 is in a closed state so that the internal vacuum is maintained when the inside of the case 104 is decompressed. Yes.

  The lid 105 is instructed and fixed in the main body 101 by a stopper (not shown), and when the user pulls out the door 102, only the case 104 is pulled out with the top opened. In addition, the food 103 placed in the case 104 is placed in a state where it is placed in a food container 106 made of, for example, foamed resin, having an upper opening.

  A suction pipe 107 for sucking the air in the case 104 is connected to the lid 105 with an introduction portion sealed by welding or a sealing material so that there is no leakage from the case 104. The suction pipe 107 connects the case 104 and a pump 108 that depressurizes the inside of the case 104, and a first on-off valve 109 is provided in the middle path between the case 104 and the pump 108, and the amount of air sucked in the case 104 Is adjusted.

  The suction pipe 107 is provided with an adsorbent 110 that selectively adsorbs the gas odor generated from the food 103 in the case 104. Furthermore, although not shown here, when the food 103 in the case 104 is a fish or meat with a lot of bacteria attached, when the air in the case 104 is inhaled, the fungus contained in the food 103 is sucked up. Therefore, since there is a concern that the bacteria may grow in the suction pipe 107 and grow, a means for sterilizing the adhered fungi is attached. The means for sterilization is not particularly limited, but since it is highly versatile and preferably small, an LED having a wavelength in the ultraviolet wavelength region or an LED having a blue wavelength is installed in the suction pipe 107 and inhaled. Means for killing the fungi contained in the atmosphere in the case 104 by irradiating them continuously or blinking is also conceivable. A suction pipe 107 connected to the pump 108 discharges air sucked from the case 104 by the pump 108.

  Further, the exhaust pipe 111 branches in the middle of the first on-off valve 109 and the case 104, and the second on-off valve 112 is provided in the branch pipe. When the inside of the case 104 is in a decompressed state, the second on-off valve 112 can adjust the amount of air flowing into the case 104 and change the pressure in the case 104 to atmospheric pressure.

  The operations of the pump 108, the first on-off valve 109, and the second on-off valve 112 are controlled by the control base 114 by the pressure sensor 113 in the case 104.

  The series of operations is performed repeatedly until the initial weight of the food container 106 is detected by the weight sensor 115 and reaches a predetermined weight reduction, and is controlled by the control board 114.

  The main body 101 has a cooling cycle for cooling the inside of the case 104. The cooling cycle includes a compressor, a condenser, and a capillary tube (not shown), and has a structure in which the inside of the case 104 can be cooled by the forced convection evaporator 116. The cold air cooled by the forced convection evaporator 116 is forcibly ventilated into the main body 101 by the blower 117. A damper thermo 118 provided between the blower 117 and the main body adjusts the inflow amount of cold air inside the main body 101, receives electrical input from a main body switch, a temperature sensor, etc., and is driven by the driving force of the motor 119. The damper thermo 118 is configured to open and close.

  The cold air supplied from such a refrigeration apparatus is supplied to the inside of the main body 101 from the outlet 120 and gently cools the inside from the outer periphery of the case 104 by indirect cooling. The cool air supplied from the outlet 120 and having cooled the outer periphery of the case 104 is returned to the cooler through the suction duct 121 joined to the main body 101, cooled again, and supplied into the main body 101. In this embodiment, the refrigeration cycle is formed in this way.

  FIG. 2 is a flowchart of the operation of the vacuum drying apparatus in the present embodiment.

  A drying operation by the reduced pressure drying apparatus in the present embodiment will be described with reference to FIG.

  First, the process until the food 103 is charged will be described. First, if the food 103 is a vegetable, remove the dirt, and if it needs to be peeled off, put it in a food container 106 such as a tapper after performing the pretreatment and cutting it into an appropriate size. Keep the lid and wrap off.

  Also, in the case of fish or meat, when seasoning with a seasoning such as salt or pepper in advance, after the operation is performed first, it is generally used when selling at stores such as supermarkets It puts into food containers 106, such as a resin container and a tapper, and is made into the state where a lid and a wrap were removed. If no pre-operation is required, the food container 106 is left unwrapped.

  The door 102 is pulled out, and the food container 106 containing the food 103 is installed in the case 104. At the same time as the door 102 is completely closed, the lid 105 in the main body 101 covers the case, and a sealed structure is formed by packing or the like.

  Next, the user selects the type of the food 103, and further selects a dry state (dry mode) according to the purpose of use. For example, suppose that food 3 is raw squid, and in recent years there is a tendency for consumers to enjoy both taste and texture. We want to avoid drying too much by lightly draining water, such as raw drying or drying overnight. If so, select soft drying mode.

  On the other hand, for example, when the food 3 is a sweet potato, if you want to make a dried rice cake, select the soft drying mode if you want to leave the softness and finish, and if you want to finish it hard, the hard drying mode Can be set to select, and the same applies to other foods.

  Next, when the user presses the start button, after the weight sensor 115 measures the initial weight of the food container 106, the operation of the refrigeration cycle, the start of the operation of the pump 108, the opening of the first on-off valve 109, the second The on-off valve 112 is closed from the control board 114. As a result, air in the case 104 is sucked out from the suction pipe 107 connected to the lid 105, passes through the opened first on-off valve 109, is sucked into the pump 108, and the pressure in the case 104 is reduced. Starts. This operation is repeated until the weight sensor 115 reaches a predetermined weight reduction based on the food selected by the user and the drying mode, and is controlled by the control board 114.

  The air drawn into the pump 108 passes through the exhaust pipe 111 and is released to the outside air. At this time, since the second on-off valve 112 is in a closed state, air in the case 104 does not leak through the second on-off valve 112, and outside air does not flow into the case 104.

  Further, when the operation of the refrigeration cycle is started and the compressor, the condenser, and the capillary tube are operated, the cool air cooled by the forced convection evaporator 116 is forcibly ventilated into the main body 101 by the blower 117. Immediately after the start of cooling, the damper thermo 118 is opened as much as possible, but when the temperature sensor detects that the inside of the case 104 or the food 103 has reached a predetermined freezing temperature, it is input from the control board 114, and the opening degree is Get smaller. The cold air supplied by such a refrigeration cycle is supplied into the main body 101 from the outlet 120, and the inside is gently cooled from the outer periphery of the case 104 by indirect cooling. Thereby, the food 103 accommodated in the case 104 is rapidly cooled until it reaches a predetermined temperature.

  Further, the cool air supplied from the outlet and having cooled the outer periphery of the case 104 is returned to the cooler through the suction duct 121 joined to the main body 101, cooled again, and supplied into the main body 101.

  When the pressure sensor 113 detects that the inside of the case 104 has been reduced to a predetermined pressure, the pump 108 is stopped and the first on-off valve 109 is closed through the control board 114. Thereby, the inside of the case 104 having a completely sealed structure is maintained in a predetermined reduced pressure state.

  In this state, first, if the food 103 is non-frozen, water droplets and moisture adhering to the periphery of the food 103 are generated by the decompression in the case 104, so that the water of the food 103 is removed and dried. Promotes.

  Further, when the food 103 is slightly frozen, the freezing of the food 103 occurs from the surface. Therefore, by performing a pressure reduction process in a state where the surface of the food 103 is covered with an ice film, the ice film on the surface of the food 103 is sublimated. And drying can be promoted.

  Subsequently, the arrival of a predetermined pressure inside the case 104 is detected, and after a predetermined time has elapsed, an input is generated from the control base 114, the second on-off valve 112 is opened, and the case 104 is entered from the suction pipe 107. Rapid introduction of outside air occurs. At this time, convection of the air layer occurs in the case 104 due to the outside air introduced, and the food 103 that has received the convection is in a state where drying is further promoted by the wind pressure. In addition, since the outside air introduced at this time is lower than the humidity in the case 104, the drying efficiency is further improved. The method of setting the outside air introduced into the case 104 to be lower than the humidity inside the case 104 is not particularly limited here, but the outside air introduced into the case 104 may be lower than the temperature inside the case 104. A method using a water absorption film or the like for removing moisture from the outside air in the suction pipe 107 can be considered.

  Thereafter, if the weight sensor 115 can detect that the food 103 has reached a predetermined weight according to the type of food and the selection of the drying mode, the series of operations of the vacuum drying apparatus is terminated and stored at a predetermined temperature. It becomes possible. For example, when the drying mode is selected as the soft drying mode, the food 103 produced by this method has a relatively high moisture content and thus needs to be refrigerated, so it can be stored at a temperature of 10 degrees or less. desirable. On the other hand, when the hard drying mode is selected, since the moisture content is small, it can be stored at room temperature without refrigerated storage.

  However, if the predetermined weight has not been reached, a series of operations are repeated until the predetermined weight is reached.

  After reaching the predetermined weight, it can be stored in the vacuum drying apparatus as it is, and after the food 103 reaches the predetermined weight, the case 104 can be maintained at a predetermined temperature and a reduced pressure state. In this case, the optimality of the predetermined temperature differs depending on the type of food 103 and the water content. For example, in the case of a vegetable with a high water content, the cell membrane is destroyed by freezing and dehydration occurs, resulting in poor texture. Therefore, it is desirable to store at a temperature above the temperature at which the food 103 is slightly frozen.

  As described above, in the reduced-pressure drying apparatus of the present embodiment, in the process of freezing the food 103, the atmosphere in contact with the food 103 is given at least one cycle of reduced pressure and air introduction. Thereby, drying of the food 103 can be promoted. It is possible to dry while suppressing the growth of bacteria and the like adhering to the food 103, and it is possible to produce a high-quality dried food. Therefore, the number of storage days is also increased, and long-term storage is possible.

  In addition, many of the nutrients such as vitamins and flavors that are the basis of the flavor of the food 103 are very unstable to heat, and there is concern that they may be deactivated by the action of warm air. However, in the reduced pressure drying apparatus of the present embodiment, since the drying process is performed in a frozen atmosphere, it is possible to maintain nutrients and odor components.

  Furthermore, since it can be stored in a depressurized state after drying, that is, in a low oxygen state, there is also an effect of suppressing lipid oxidation such as fish and meat, and an effect of suppressing discoloration due to the formation of myoglobin. It is possible to preserve and preserve the flavor and quality. Furthermore, it is possible to maintain a high-quality dry state over a long period of time by periodically applying pressure fluctuations during storage.

  In addition, by selecting the type of food 103 and the drying mode in advance, it is possible to automatically perform drying according to the user's preference, thereby improving convenience and cooking ability.

  In the case of cooking by using the dried food 103 obtained by the reduced pressure drying apparatus according to the present embodiment, for example, when the food 103 is a vegetable, the vegetable having moderately reduced moisture is increased in sweetness due to the component concentration effect. The texture is also improved. Furthermore, since the water content of the food 103 is reduced, there is not much outflow of water even when fried vegetables, and it is possible to make a stir-fried vegetable without stickiness. Furthermore, since the network structure of the cells of the food 103 is slightly larger, it has high permeability such as seasonings, can be easily cooked, and has the effect of shortening the cooking time. In addition, in other words, the cooking time can be shortened, so that the heating energy can be reduced and an energy saving effect can be obtained.

  It is also possible to dry side dishes such as fried foods. In this case, it is possible to preserve | save, maintaining a crispy feeling because the water | moisture content of a clothes dries moderately. Even when thawing with a microwave oven or the like, since the moisture is uniform, high-quality thawing can be performed, and the taste of freshly fried can be reproduced.

  In the present embodiment, the electric pump 108 is used as the pressure reducing means, but these are not particularly specified. For example, it is possible to reduce the pressure by using a manual pump or by providing an oxygen adsorbent or a nitrogen adsorbent. Moreover, it is also possible to use the pump 108 and the gas adsorbent in combination, thereby complementing the deterioration of the performance with time of the pump 108 and the adsorbent, so that the refrigeration apparatus can be used for a long time.

  In the present embodiment, the moisture content is correlated with the weight reduction rate obtained by dividing the difference between the weight of the initial food container 106 and the weight of the food container 106 during or after the drying operation by the weight of the initial food container 106. However, the method is not limited to this method. Therefore, in the present embodiment, the moisture content of the food 103 is detected using the weight sensor 115, but the detecting means is not particularly limited, and may be controlled using, for example, a time sequence. .

  In addition, the predetermined pressure in the depressurization step is not particularly specified, but by performing the depressurization step in a freezing atmosphere, a sufficient water removing effect can be obtained by setting the pressure to about 0.08 to 0.03 MPa from the atmospheric pressure. Can be obtained.

  In addition, according to this embodiment, compared with the method of making by sun-drying or hot-air drying, high-quality dried food is suppressed in a hygienic environment while suppressing self-digestion such as bacterial growth and lipid oxidation. It is possible to make.

  As described above, the method for drying a food according to the present invention appropriately controls the water content of the food while suppressing the growth of bacteria during drying and the deterioration of the food due to self-digestion and inactivation of heat-sensitive nutrients such as vitamins. Can be evaporated. As a result, the resulting foods have the effects of improving shelf life, shortening cooking time, concentrating umami, and maintaining flavor, and can be applied to commercial or household refrigeration equipment and household refrigerators. It is.

Sectional drawing of the reduced pressure drying apparatus in Embodiment 1 of this invention Flowchart of operation of vacuum drying apparatus in Embodiment 1 of the present invention Diagram showing conventional food drying equipment

Explanation of symbols

103 Food 109 Adsorbent 115 Weight sensor

Claims (5)

  A freezing step for freezing food, a transformation step for changing the pressure of the gas space in contact with the food in the freezing step in a freezing atmosphere, and detecting the moisture content of the food in the transformation step to a predetermined moisture content A method for drying a food product, the method comprising a drying step of drying until reaching.   The food drying method according to claim 1, wherein the step of changing the pressure variation includes a pressure reduction step and an atmospheric pressure introduction step.   The method for drying food according to claim 1 or 2, wherein the humidity of the gas introduced in the atmospheric pressure introduction step is lower than the humidity of the gas introduction destination.   The method for drying a food according to any one of claims 1 to 3, further comprising means for selectively adsorbing a food-specific odor in the decompression step.   The store | warehouse | chamber provided with the drying means of the foodstuff using the drying method of the foodstuff as described in any one of Claim 1 to 4.

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