JP2019017276A - Fresh food product freeze dry production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a freeze-dry manufacturing method for suppressing color fading on the surface of fresh food such as vegetables and fruits. SOLUTION: This is a manufacturing method 10 for freeze-drying fresh foods such as vegetables and fruits while suppressing surface discoloration, which is a freezing step 20 in which the fresh foods are put in a freezer at -20°C to be frozen, The fresh food thus prepared is put into a vacuum dryer, a vacuum pressure is applied until the inside of the vacuum dryer reaches -30°C, and then the inside of the vacuum dryer is raised in a vacuum state by +5°C at every predetermined time to 3 to 6 First-stage vacuum drying step 30 to reach ±0° C. over a period of time, and medium-term vacuum drying step 40 to raise the temperature in the vacuum dryer by +5° C. at a predetermined time every 2 hours to reach 50° C. And the latter stage vacuum drying step 50 of maintaining the inside of the vacuum dryer in a vacuum state at 50° C. for 2 to 4 days. [Selection diagram] Figure 1

Description

  The present invention relates to a method for freeze-drying fresh food, and more particularly to a method for freeze-drying fresh food such as vegetables and fruits while suppressing discoloration of the surface.

  The traditional freeze-dried food manufacturing method employs a method in which water-containing foods and food materials are rapidly frozen at about minus 30 ° C., further reduced in pressure to sublimate and dry the water. In recent years, it has been widely used for emergency foods and portable foods, and in recent years it has evolved in various ways as health foods and functional foods. Traditionally, foods suitable for drying such as dried seafood and agricultural products have been used, but they require careful preparation and long-term complex manufacturing processes, so they are suitable as ingredients for making dried fish. Is limited to some ingredients such as dried eggs and dried potatoes, and the conventional drying technology leaves quality problems such as texture and discoloration compared to non-dry ingredients that are generally distributed, The development of a method for freeze-drying that would solve these problems was awaited.

  In recent years, freeze-drying methods for foods have little change in form such as shrinkage and cracking due to drying, little change in nutritional components and flavors such as vitamins, and are porous and easily invaded by water and hot water. In addition, freeze-dried products have been developed that have many advantages such as being light and excellent in transportability due to its low moisture content, and being able to be stored for a long period of time by inhibiting the action of enzymes and microorganisms. On the other hand, textures such as texture and color change depending on the ingredients, and there are still problems such as large capital investment and energy cost compared to other dry food technologies.

  As a specific proposal of the freeze-drying method for conventional foods, for example, by forming a zein film on the outer surface of the fruit that has been freeze-dried from food, while using the fruit freeze-dried as a raw material, It has toughness that does not cause chipping, exhibits excellent water resistance and non-hygroscopicity even when used in contact with moisture or moisture, and makes use of the original shape, color, and flavor of the fruit. A possible “coated dry food” (Patent Document 1) has been proposed and has become a publicly known technique.

  However, since the proposal of such a “coated dry food” employs a means for forming a zein film on the outer surface of the freeze-dried fruit, the tactile sensation and taste inherent in the food are impaired by the outer surface being coated. It was a proposal that left the problem of being lost.

  Moreover, the 1st process of vacuum-freeze-drying the fruit which provided the arbitrary tastes, maintaining the original fruit structure and color structure of a fruit, and the 2nd process of impregnating and seasoning arbitrary dried liquids with the obtained dried fruit, And the third step of vacuum freeze-drying the dried fruit that has been impregnated with the seasoning liquid again, and maintaining the original pulp structure and color structure and allowing arbitrary flavoring. "Dried fruit and method for producing the same" (Patent Document 2) has been proposed and is a known technique.

  However, since the proposal of such “dried fruit and method for producing the same” employs a means for impregnating and seasoning the dried fruit with an arbitrary seasoning liquid, the tactile sensation inherent in food by impregnating the seasoned seasoning liquid It was a proposal that left the problem that the functionality as a natural food was impaired while the taste and taste were impaired.

  Also, after drying with hot air until the water content reaches 85 to 40% by weight, it is lyophilized so that it has excellent texture and has the original color of vegetables, fruits, etc. without adding colorants. A “dried food production method” (Patent Document 3) capable of obtaining food is proposed and has become a publicly known technique.

  However, since the proposal of the “method for producing a dried food” employs means for drying with hot air until the water content reaches 85 to 40% by weight, the dry texture and the freshness of the pulp by the conventional freeze-drying method are adopted. It was a proposal that left the problem that the degree would be lost.

  The present applicant pays attention to the problem of discoloration of the surface of fresh food by the conventional freeze-drying method, and under the idea of whether or not it is possible to provide a freeze-drying method that hardly loses the color of the original fresh food, A freeze-drying manufacturing method that suppresses discoloration of the surface of fresh foods such as vegetables and fruits has been developed, leading to the proposal of the “freeze-drying manufacturing method for fresh foods” in the present invention.

JP-A-6-284875 JP 2004-121136 A Japanese Patent Laid-Open No. 6-153782

  This invention makes it a subject to provide the freeze-drying manufacturing method which suppresses the discoloration of the surface of fresh foods, such as vegetables and fruits, in view of the said problem.

  In order to solve the above problems, the present invention is a manufacturing method for freeze-drying fresh foods such as vegetables and fruits while suppressing discoloration of the surface, and the fresh foods are put into a freezer at −20 ° C. and frozen. Freezing process and frozen fresh food are put into a vacuum dryer, vacuum pressure is applied until the inside of the vacuum dryer reaches −30 ° C., and then the inside of the vacuum dryer is increased by + 5 ° C. every predetermined time in a vacuum state. The first stage vacuum drying process to reach ± 0 ° C. over 3 to 6 days, and the middle period to increase the inside of the vacuum dryer by + 5 ° C. every predetermined time in a vacuum state to reach 50 ° C. over 2 to 3 days A means comprising a vacuum drying step and a late vacuum drying step of maintaining the inside of the vacuum dryer in a vacuum state at 50 ° C. for 2 to 4 days is adopted.

  Further, the present invention provides that the temperature in the vacuum dryer is set to -20 to -30 ° C for 1 to 2 times when the temperature in the vacuum dryer reaches -10 ° C in the previous vacuum drying step. Take measures to return.

  Further, according to the present invention, the latter vacuum drying step maintains a state of 30 ° C. for about 30 minutes every predetermined time, whereby a state of 50 ° C. for a predetermined time and a state of 30 ° C. for about 30 minutes are alternately repeated. Take the means.

  According to the freeze-drying method for fresh food according to the present invention, the vacuum drying process is divided into three stages, the first period, the middle period, and the second period, and the vacuum drying temperature is several times to several tens of times longer than the conventional one, and every predetermined time. By finely setting the temperature, it is possible to produce a dried food that can maintain the gorgeous color inherent in fresh food for a long time.

  In addition, according to the freeze-drying method for fresh food according to the present invention, the food surface is not coated with colorants or sugars as in the past, so that the taste inherent in fresh food is not impaired, and the appearance on the appearance is It has an excellent effect that a dry food that is almost the same as a fresh food before processing can be produced.

  Furthermore, according to the freeze-drying method for fresh food according to the present invention, there is an excellent effect that the nutritional value of the food is not impaired, and the functionality as a natural food is not impaired.

  Furthermore, according to the freeze-drying method for fresh food according to the present invention, compared to the conventional freeze-drying method for fresh food, there is almost no change in form such as shrinkage or cracking due to drying, so food samples and souvenirs It has an excellent effect that it can be provided in a wide variety of situations, such as goods, objects that can be eaten in restaurants, and dessert dishes.

  Furthermore, according to the freeze-drying method for fresh food according to the present invention, the temperature control is programmed and fully automated so that there is no variation in the quality of the product and the labor savings can be achieved. Play.

It is explanatory drawing which shows 1st embodiment of the freeze-drying manufacturing method of the fresh food concerning this invention. (Example 1) It is explanatory drawing which shows 2nd embodiment of the freeze-drying manufacturing method of the fresh food concerning this invention. (Example 2) It is explanatory drawing which shows 3rd embodiment of the freeze-drying manufacturing method of the fresh food concerning this invention. Example 3

The freeze-drying production method 10 for fresh food according to the present invention includes a freezing step 20, a first-stage vacuum drying step 30, a middle-term vacuum drying step 40, and a second-stage vacuum drying step 50. The greatest feature is that a means of freeze-drying while suppressing the above is adopted.
Hereinafter, an embodiment of a freeze-drying manufacturing method 10 for fresh food according to the present invention will be described with reference to the drawings.

  In addition, the freeze-drying manufacturing method 10 of the fresh food concerning this invention is not limited to the Example described below, The process, method, etc. which can exhibit the same effect within the range of the technical idea of this invention. Within the range, it can be appropriately changed.

FIG. 1 is an explanatory view showing a first embodiment of a freeze-drying manufacturing method 10 for fresh food according to the present invention, wherein (a) is a chart showing manufacturing steps, and (b) is a time series of manufacturing steps. FIG.
The freeze-dried manufacturing method 10 for fresh food according to the present embodiment includes a freezing step 20, an early vacuum drying step 30, an intermediate vacuum drying step 40, and a late vacuum drying step 50.

The freezing process 20 is a process in which fresh food is put into a freezer at −20 ° C. and frozen.
In general, the freeze-drying method uses a technique in which moisture is sublimated and dried by vacuum, but the boiling point of moisture is lowered by lowering the atmospheric pressure by vacuum. Therefore, if fresh food is put into a vacuum dryer at room temperature, the internal moisture will boil at a low temperature, and the original flavor of the food will be impaired. Therefore, the fresh food to be processed is frozen in advance, and then put into a vacuum dryer to apply a vacuum pressure, thereby drying in a state where the boiling point of moisture is lowered. This step of freezing fresh food in advance is the main freezing step 20.

In the first vacuum drying step 30, the fresh food frozen in the freezing step 20 is put into a vacuum dryer, a vacuum pressure is applied until the inside of the vacuum dryer reaches −30 ° C., and then the inside of the vacuum dryer is in a vacuum state. In this step, the temperature is raised by + 5 ° C. every predetermined time and finally reached ± 0 ° C.
When the fresh food frozen to -20 ° C in the freezing step 20 is put into a vacuum dryer and a vacuum pressure is applied, the solidified (icified) water inside the fresh food is directly vaporized without passing through the liquefied state. (Steamed) and released to the outside of food. This is the so-called sublimation phenomenon in the freeze drying process. During this sublimation, the heat of vaporization is taken away, so that the temperature of the food is gradually lowered. Also in this embodiment, by applying a vacuum pressure, the heat of vaporization is deprived from fresh food frozen at −20 ° C., and eventually reaches −30 ° C. Thereafter, the temperature in the vacuum dryer is adjusted, and the temperature is increased by + 5 ° C. every predetermined time, and finally reached ± 0 ° C.

  By the way, if the temperature rises suddenly in a vacuum state, the temperature rises before the moisture inside the food is sufficiently vaporized, and the color and flavor of the food are affected by the boiling of residual moisture. Changes, and also causes a loss of nutritional value. Therefore, the first vacuum drying step 30 is performed slowly over 3 to 6 days throughout. That is, the first vacuum drying step 30 is a step of increasing by + 5 ° C. every predetermined time and finally reaching ± 0 ° C. over 3 to 6 days. It should be noted that increasing from -30 ° C. by + 5 ° C. to reach ± 0 ° C., in other words, the timing of increasing + 5 ° C. is 6 times in total (−30 ° C. → −25 ° C./−25° C. → −20 C / -20 ° C → -15 ° C / -15 ° C → -10 ° C / -10 ° C → -5 ° C / -5 ° C → ± 0 ° C). At this time, the predetermined time for increasing by + 5 ° C. is exemplified as follows.

・ When raised every 12 hours → reached ± 0 ° C in 3 days ・ When raised every 18 hours → reached ± 0 ° C in 4 days and 12 hours ・ When raised every 20 hours → 5 When reaching ± 0 ° C in days and increasing every 24 hours → reaching ± 0 ° C in 6 days As shown in the above example, when this vacuum drying step 30 is performed over 3 to 6 days, + 5 ° C each The predetermined time for raising is in the range of 12 to 24 hours. The predetermined time is not particularly limited as long as it is appropriately determined within the range depending on the type of fresh food to be dried. It is also possible to change the time taken for the rise at each timing.

Next, the medium-term vacuum drying step 40 is a step of raising the inside of the vacuum dryer by + 5 ° C. every predetermined time in a vacuum state and finally reaching 50 ° C.
In the previous vacuum drying step 30, the fresh food is subjected to a sublimation effect by increasing the temperature by + 5 ° C. every predetermined time from −30 ° C. and finally reaching ± 0 ° C. while the vacuum pressure is applied. Vacuum drying is almost complete. This medium-term vacuum drying step 40 is performed for the purpose of further sucking and sublimating minute moisture remaining in the food and moisture in the vacuum dryer by raising the temperature by + 5 ° C. every predetermined time in a vacuum state. Is.

  The adverse effects of a rapid temperature increase in a vacuum state are as described above, and the medium-term vacuum drying step 40 is also performed slowly over 2 to 3 days throughout. That is, the middle-term vacuum drying step 40 is a step of increasing by + 5 ° C. every predetermined time and finally reaching 50 ° C. over 2 to 3 days. In addition, it is increased by + 5 ° C from ± 0 ° C to reach 50 ° C. In other words, the timing of increasing + 5 ° C is 10 times in total (± 0 ° C → 5 ° C / 5 ° C → 10 ° C / 10 ° C → 15 ℃ / 15 ℃ → 20 ℃ / 20 ℃ → 25 ℃ / 25 ℃ → 30 ℃ / 30 ℃ → 35 ℃ / 35 ℃ → 40 ℃ / 40 ℃ → 45 ℃ / 45 ℃ → 50 ℃) become. At this time, the predetermined time for increasing by + 5 ° C. is exemplified as follows.

・ When raised every 5 hours → reached 50 ℃ in 2 days and 2 hours ・ When raised every 6 hours → reached 50 ℃ in 2 days and 12 hours ・ When raised every 7 hours → Reaching 50 ° C. in 2 days and 22 hours As shown in the above example, when the intermediate vacuum drying step 40 is performed over 2 to 3 days, the predetermined time for increasing by + 5 ° C. is about 5 to 7 hours. Become. The predetermined time is not particularly limited as long as it is appropriately determined within the range depending on the type of fresh food to be dried. It is also possible to change the time taken for the rise at each timing.

Next, the late vacuum drying step 50 is a step of maintaining the inside of the vacuum dryer in a vacuum state at 50 ° C. for 2 to 4 days.
In the medium-term vacuum drying step 40, the fresh food is subjected to + 5 ° C. every predetermined time from ± 0 ° C. while reaching a vacuum pressure, and finally reaches 50 ° C. It can be said that the suction and sublimation of the water in the vacuum dryer and the vacuum dryer are almost complete. The latter vacuum drying step 50 is performed for the purpose of completely sucking and sublimating moisture remaining in the food and moisture in the vacuum dryer by maintaining the vacuum drying step 50 at 50 ° C. in a vacuum state. The latter vacuum drying step 50 is performed slowly over 2 to 4 days throughout. The number of days is not particularly limited as long as it is appropriately determined within the range depending on the type of fresh food to be dried.

In the present embodiment, the food to be dried is not particularly limited, and can be applied to any food as long as it is a fresh food such as vegetables and fruits. Among them, fruits and vegetables suitable for freeze-drying are conventionally used, and the fruits include strawberries, blueberries, cranberries, kiwis, pineapples, grapes, mandarin oranges, loquats, apples and bananas that are characterized by a flesh structure or color structure. Fig, peach, oyster, watermelon, melon, lemon, pear, ume, cherry, mango, mangosteen, papaya, pomegranate, etc. are suitable. For vegetables, root vegetables such as sweet potatoes and burdock, and fruit vegetables such as tomatoes and cucumbers are suitable. For leaf vegetables, stem vegetables such as garlic and bamboo shoots are applicable, but so-called leaves such as cabbage and lettuce. Vegetables are not very suitable.
In addition, it is desirable that large foods such as watermelons, melons, and moss are sliced to an appropriate size before freezing and then transferred to each step in view of deep drying.

A specific example of the freeze-drying manufacturing method 10 for fresh food according to the present embodiment will be described below in the order of the manufacturing process.
(1) Put fresh food at room temperature into a -20 ° C freezer and freeze it.
(2) The frozen fresh food is put into a vacuum dryer, and vacuum pressure is applied until the inside of the vacuum dryer reaches −30 ° C.
(3) Increase the vacuum dryer by + 5 ° C. every 12-24 hours while maintaining the vacuum state, and reach ± 0 ° C. over 3 to 6 days.
(4) Thereafter, while the vacuum dryer is kept in a vacuum state, the temperature is increased by + 5 ° C. every 5 to 7 hours and allowed to reach 50 ° C. over 2 to 3 days.
(5) Further, the inside of the vacuum dryer is kept under vacuum at 50 ° C. for 2 to 4 days for vacuum drying.
(6) Take out from the vacuum dryer and cool naturally.

  According to the freeze-dried manufacturing method 10 for fresh food according to the present embodiment configured as described above, the vacuum drying process is divided into three stages, the first period, the middle period, and the second period, and from the freezing process until the freeze-dried food is finally completed. The period is set to several times to about ten times longer than the usual method of about 10 days (7 to 13 days), and the temperature is set finely every predetermined time, so that the original fresh food has It is possible to provide a freeze-dried food that can maintain a gorgeous color for a long time and that does not impair the nutritional value.

Next, 2nd embodiment of the freeze-drying manufacturing method 10 of the fresh food concerning this invention is described. Parts similar to those of the first embodiment are omitted.
FIG. 2 is an explanatory view showing a second embodiment of the freeze-drying manufacturing method 10 for fresh food according to the present invention, and is a graph showing a time series of manufacturing steps.

In the freeze-drying manufacturing method 10 for fresh food according to the present embodiment, when the temperature in the vacuum dryer reaches −10 ° C. in the previous vacuum drying step 30, the temperature in the vacuum dryer is set once or twice. The structure which returns to the state of -20 to -30 degreeC is employ | adopted.
In the drawing, for convenience of explanation, the case where the temperature in the vacuum dryer is returned from −10 ° C. to −20 ° C. only once in the previous vacuum drying step 30 is shown.

  The adverse effects of a rapid temperature increase in a vacuum state are as described above, and the first vacuum drying step 30 is performed slowly over 3 to 6 days throughout. That is, the vacuum drying process 30 in the first half is increased by + 5 ° C. every predetermined time, returned to −20 to −30 ° C. once or twice when the temperature reaches −10 ° C., and again every predetermined time. The temperature is increased by + 5 ° C. and finally reaches ± 0 ° C. over 3 to 6 days. Incidentally, when the temperature is increased from −30 ° C. by + 5 ° C. to −10 ° C., it is allowed to reach ± 0 ° C. once or twice while returning to −20 ° C. to −30 ° C., in other words, + 5 ° C. The rising timing is at least 8 times in total (−30 ° C. → −25 ° C./−25° C. → −20 ° C./−20° C. → −15 ° C./−15° C. → −10 ° C./−20° C. → −15 ° C. / −15 ° C. → −10 ° C./−10° C. → −5 ° C./−5° C. → ± 0 ° C.), maximum 14 times (−30 ° C. → −25 ° C./−25° C. → −20 ° C./−20° C. → −15 ° C./−15° C. → −10 ° C./−30° C. → −25 ° C./−25° C. → −20 ° C./−20° C. → −15 ° C./−15° C. → −10 ° C./−30° C. → −25 C / -25 ° C. → -20 ° C./−20° C. → −15 ° C./−15° C. → −10 ° C./−10° C. → −5 ° C./−5° C. → ± 0 ° C.). At this time, the predetermined time for increasing by + 5 ° C. is exemplified as follows.

<< When returning to -20 ℃ once >>
・ When raised every 10 hours → ± 0 ℃ reached in 3 days and 8 hours ・ When raised every 12 hours → ± 0 ℃ reached in 4 days ・ When raised every 16 hours → 5 When it reaches ± 0 ° C in 8 days and when it is raised every 18 hours → It reaches ± 0 ° C in 6 days << Returning to -20 ℃ twice / Returning to -30 ℃ once >>
・ When raised every 8 hours → reached ± 0 ℃ in 3 days and 8 hours ・ When raised every 10 hours → reached ± 0 ℃ in 4 days and 4 hours ・ Raised every 12 hours In case of reaching ± 0 ° C in 5 days ・ In case of increasing every 14 hours → In case of reaching ± 0 ° C in 5 days and 20 hours << When returning to -30 ℃ twice >>
・ When raised every 6 hours → reached ± 0 ℃ in 3 days and 12 hours ・ When raised every 8 hours → reached ± 0 ℃ in 4 days and 16 hours ・ Raised every 10 hours Case → reach ± 0 ° C in 5 days and 20 hours As shown in the above example, when the vacuum drying step 30 is performed over 3 to 6 days, the predetermined time for increasing by + 5 ° C is about 6 to 18 hours. It becomes the range. Such a predetermined time and the number of times of returning to -20 to -30 ° C are not particularly limited as long as they are appropriately determined within the range depending on the type of fresh food to be dried. It is also possible to change the time taken for the rise at each timing.

  In the present embodiment, as described above, a mode is adopted in which the temperature in the vacuum dryer is returned to the state of -20 to -30 ° C once or twice when it reaches -10 ° C in the previous vacuum drying step 30. The reason for this is to use the change in the degree of vacuum due to a change in temperature and the change in the degree of dryness associated therewith. Specifically, by returning the temperature in the vacuum dryer to a state of -20 to -30 ° C, the degree of vacuum in the device becomes stronger than when the temperature is -10 ° C. Therefore, the color fading is suppressed and the coloring is improved.

About the specific example of the freeze-drying manufacturing method 10 of the fresh food concerning this embodiment, the case where the temperature in a vacuum dryer is returned from -10 degreeC to -20 degreeC in the case shown in FIG. For example, the order of the manufacturing process will be described below.
(1) Put fresh food at room temperature into a -20 ° C freezer and freeze it.
(2) The frozen fresh food is put into a vacuum dryer, and vacuum pressure is applied until the inside of the vacuum dryer reaches −30 ° C.
(3) While the vacuum dryer is kept in a vacuum state, the temperature is increased by + 5 ° C. every 10 to 18 hours. When the temperature reaches −10 ° C., the temperature is once returned to −20 ° C. and again increased by + 5 ° C. every 10 to 18 hours. And reach ± 0 ° C. over a total of 3 to 6 days.
(4) Thereafter, while the vacuum dryer is kept in a vacuum state, the temperature is increased by + 5 ° C. every 5 to 7 hours and allowed to reach 50 ° C. over 2 to 3 days.
(5) Further, the inside of the vacuum dryer is kept under vacuum at 50 ° C. for 2 to 4 days for vacuum drying.
(6) Take out from the vacuum dryer and cool naturally.

  According to the freeze-dried manufacturing method 10 for fresh food according to the present embodiment configured as described above, the vacuum drying process is divided into three stages, the first period, the middle period, and the second period, and from the freezing process until the freeze-dried food is finally completed. The period is set several times to several tens of times longer than the usual method of about 10 days (7 to 13 days), and the temperature is set finely every predetermined time, and in accordance with the dryness of fresh food. To provide freeze-dried foods that can maintain the gorgeous color of the original fresh food for a long time and return to the prescribed temperature once or twice and repeatedly perform vacuum drying, while maintaining the nutritional value. It is something that can be done.

Next, 3rd embodiment of the freeze-drying manufacturing method 10 of the fresh food concerning this invention is described. Portions similar to those in the first and second embodiments are omitted.
FIG. 3 is an explanatory view showing a third embodiment of the freeze-drying manufacturing method 10 for fresh food according to the present invention, and is a graph showing the time series of the manufacturing process.

The freeze-dried manufacturing method 10 for fresh food according to the present embodiment maintains the state of 30 ° C. for about 30 minutes every predetermined time in the latter vacuum drying step 50, so that the state of 50 ° C. for the predetermined time and about 30 minutes are maintained. A configuration in which the 30 ° C. state is repeated alternately is employed.
In the drawing, the case where the state of 30 ° C. for about 30 minutes is provided about 6 times in the late vacuum drying step 50 is shown.

  The adverse effects of a rapid temperature increase in a vacuum state are as described above, but in the late vacuum drying step 50, there is almost no moisture in the food or in the vacuum dryer. Therefore, even if the temperature fluctuates suddenly, the effect on the color, flavor and nutritional value of the food is not so great. Therefore, there is no particular problem even if the temperature is changed alternately between the state of 50 ° C. and the state of 30 ° C. as in the latter vacuum drying step 50. The latter vacuum drying step 50 is performed slowly over 2 to 4 days throughout. That is, in the latter vacuum drying step 50, the temperature is lowered from 50 ° C. to 30 ° C. every predetermined time, the state of 30 ° C. is maintained for about 30 minutes, and the temperature is raised again to 50 ° C. for 2 to 4 days. It is the process of repeating alternately. At this time, the predetermined time for lowering the temperature from 50 ° C. to 30 ° C. may be appropriately determined depending on the type of fresh food to be dried and the drying condition, and is not particularly limited. Further, the timing for lowering the temperature from 50 ° C. to 30 ° C. can be performed by changing the required time for each timing. The required time and the total number of days (2 to 4 days) of the late vacuum drying step 50 determine how many times the 30 ° C. state is provided.

  In the present embodiment, as described above, the reason for adopting the aspect of maintaining the state of 30 ° C. for about 30 minutes every predetermined time in the late vacuum drying step 50 is as follows. The point is to use the change of. Specifically, by returning the temperature in the vacuum dryer to a state of 30 ° C., the degree of vacuum in the machine becomes stronger than when it is 50 ° C., and by repeating this, the remaining moisture of the input fresh food is squeezed out. In addition to complete drying, the degree of dryness of the surface progresses and becomes hard, and the color is fixed.

About the specific example of the freeze-drying manufacturing method 10 of the fresh food concerning this embodiment, in the case shown in FIG. 3, ie, the case where the 30 degreeC state of about 30 minutes was provided about 6 times in the latter stage vacuum drying process 50, a manufacturing process This will be explained below in order.
(1) Put fresh food at room temperature into a -20 ° C freezer and freeze it.
(2) The frozen fresh food is put into a vacuum dryer, and vacuum pressure is applied until the inside of the vacuum dryer reaches −30 ° C.
(3) Increase the vacuum dryer by + 5 ° C. every 12-24 hours while maintaining the vacuum state, and reach ± 0 ° C. over 3 to 6 days.
(4) Thereafter, while the vacuum dryer is kept in a vacuum state, the temperature is increased by + 5 ° C. every 5 to 7 hours and allowed to reach 50 ° C. over 2 to 3 days.
(5) Further, while the vacuum dryer is kept in a vacuum state, the temperature is lowered from 50 ° C. to 30 ° C. every about 7 to 14 hours, the state of 30 ° C. is maintained for about 30 minutes, and the temperature is raised again to 50 ° C. This is vacuum dried while repeating 6 times alternately over 2 to 4 days.
(6) Take out from the vacuum dryer and cool naturally.

  According to the freeze-dried manufacturing method 10 for fresh food according to the present embodiment configured as described above, the vacuum drying process is divided into three stages, the first period, the middle period, and the second period, and from the freezing process until the freeze-dried food is finally completed. The period is set several times to several tens of times longer than the usual method of about 10 days (7 to 13 days), and the temperature is set finely every predetermined time, and in accordance with the dryness of fresh food. By repeatedly vacuum drying alternately at a temperature of 50 ° C for a predetermined time and at a temperature of 30 ° C for about 30 minutes, the gorgeous color of the original fresh food can be maintained for a long time and the nutritional value is also impaired. Freeze-dried food that can be provided.

  The freeze-drying method for fresh food according to the present invention is an inherent advantage of freeze-dried food, that is, it is porous and easy to infiltrate water and hot water, so it has good restorability and solubility, and it has low moisture and is lightweight and transportable. Compared to the conventional freeze-drying method, the freshness of the product is higher than that of conventional freeze-drying methods. It is possible to keep the gorgeous color inherent in food for a long time, there is no change in form such as shrinkage and cracking due to rapid drying, and there are few changes in the original taste and flavor of fresh food, and vitamins Nutritional ingredients such as food samples and souvenirs, objects that can be eaten in restaurants, dessert dishes, etc. It is those that can be use. Therefore, the industrial applicability of the “freeze-dried process for producing fresh food” according to the present invention is considered to be extremely large.

10 Freeze Drying Process 20 Freezing Process 30 Early Vacuum Drying Process 40 Medium Vacuum Drying Process 50 Late Vacuum Drying Process

The present invention relates to a freeze-drying process for fresh foods, and more particularly to a process for freeze-drying fresh foods made of vegetables and fruits while suppressing discoloration of the surface.

The present applicant pays attention to the problem of discoloration of the surface of fresh food by the conventional freeze-drying method, and under the idea of whether or not it is possible to provide a freeze-drying method that hardly loses the color of the original fresh food, A freeze-drying manufacturing method that suppresses discoloration of the surface of fresh foods composed of vegetables and fruits has been developed, leading to the proposal of the “freeze-drying manufacturing method for fresh foods” in the present invention.

In view of the above problems, an object of the present invention is to provide a freeze-drying manufacturing method that suppresses discoloration of the surface of a fresh food made of vegetables and fruits .

In order to solve the above-mentioned problems, the present invention is a manufacturing method for freeze-drying a fresh food consisting of vegetables and fruits while suppressing discoloration of the surface, and the fresh food is put into a −20 ° C. freezer and frozen. The frozen process and the frozen fresh food are put into a vacuum dryer, and a vacuum pressure is applied until the inside of the vacuum dryer reaches −30 ° C. Then, the inside of the vacuum dryer is + 5 ° C. every predetermined time in a vacuum state. The first vacuum drying step of raising the temperature to ± 0 ° C. over 3 to 6 days and the inside of the vacuum dryer at + 5 ° C. every predetermined time in a vacuum state to reach 50 ° C. over 2 to 3 days The medium vacuum drying step and the latter vacuum drying step of maintaining the inside of the vacuum dryer in a vacuum state at 50 ° C. for 2 to 4 days are adopted.

Further, according to the present invention, the latter vacuum drying step maintains a state of 30 ° C. for about 30 minutes every predetermined time, whereby a state of 50 ° C. for a predetermined time and a state of 30 ° C. for about 30 minutes are alternately repeated. Take the means.

In the present embodiment, the food to be dried is not particularly limited, and can be applied to any food as long as it is a fresh food composed of vegetables and fruits . Among them, fruits and vegetables suitable for freeze-drying are conventionally used, and the fruits include strawberries, blueberries, cranberries, kiwis, pineapples, grapes, mandarin oranges, loquats, apples and bananas that are characterized by a flesh structure or color structure. Fig, peach, oyster, watermelon, melon, lemon, pear, ume, cherry, mango, mangosteen, papaya, pomegranate, etc. are suitable. For vegetables, root vegetables such as sweet potatoes and burdock, and fruit vegetables such as tomatoes and cucumbers are suitable. For leaf vegetables, stem vegetables such as garlic and bamboo shoots are applicable, but so-called leaves such as cabbage and lettuce. Vegetables are not very suitable.
In addition, it is desirable that large foods such as watermelons, melons, and moss are sliced to an appropriate size before freezing and then transferred to each step in view of deep drying.

Freeze-dried preparation 10 of fresh food according to the present embodiment, the in the later vacuum drying step 50, to maintain the state of 30 ° C. approximately 30 minutes at every predetermined time, the predetermined time 50 ° C. state substantially 30 minutes A configuration in which the 30 ° C. state is repeated alternately is employed.
In the drawing, the case where the state of 30 ° C. for about 30 minutes is provided about six times in the late vacuum drying step 50 is shown.

The adverse effects of a rapid temperature increase in a vacuum state are as described above, but in the late vacuum drying step 50, there is almost no moisture in the food or in the vacuum dryer. Therefore, even if the temperature fluctuates suddenly, the effect on the color, flavor and nutritional value of the food is not so great. Therefore, there is no particular problem even if the temperature is changed alternately between the state of 50 ° C. and the state of 30 ° C. as in the latter vacuum drying step 50. The latter vacuum drying step 50 is performed slowly over 2 to 4 days throughout. That is, in this latter vacuum drying step 50, the temperature is lowered from 50 ° C. to 30 ° C. every predetermined time, the state of 30 ° C. is maintained for about 30 minutes, and the temperature is raised again to 50 ° C. for 2 to 4 days. It is the process of repeating alternately. At this time, the predetermined time for lowering the temperature from 50 ° C. to 30 ° C. may be appropriately determined depending on the type of fresh food to be dried and the drying condition, and is not particularly limited. Further, the timing for lowering the temperature from 50 ° C. to 30 ° C. can be performed by changing the required time for each timing. The required time and the total number of days (2 to 4 days) of the late vacuum drying step 50 determine how many times the 30 ° C. state is provided.

In the present embodiment, as described above, the reason why the state in which the state of 30 ° C. is maintained for about 30 minutes every predetermined time in the late vacuum drying step 50 is as follows is the change in the degree of vacuum due to the temperature change and the degree of drying associated therewith. The point is to use the change of. Specifically, by returning the temperature in the vacuum dryer to a state of 30 ° C., the degree of vacuum in the machine becomes stronger than when it is 50 ° C., and by repeating this, the remaining moisture of the input fresh food is squeezed out. In addition to complete drying, the degree of dryness of the surface progresses and becomes hard, and the color is fixed.

A specific example of a freeze-dried preparation 10 of fresh food according to the present embodiment, as an example a case in which a state of 30 ° C. for approximately 30 minutes about 6 times in the later vacuum drying step 50 that is, shown in FIG. 3, the manufacturing process This will be explained below in order.
(1) Put fresh food at room temperature into a -20 ° C freezer and freeze it.
(2) The frozen fresh food is put into a vacuum dryer, and vacuum pressure is applied until the inside of the vacuum dryer reaches −30 ° C.
(3) Increase the vacuum dryer by + 5 ° C. every 12-24 hours while maintaining the vacuum state, and reach ± 0 ° C. over 3 to 6 days.
(4) Thereafter, while the vacuum dryer is kept in a vacuum state, the temperature is increased by + 5 ° C. every 5 to 7 hours and allowed to reach 50 ° C. over 2 to 3 days.
(5) Further, while the vacuum dryer is kept in a vacuum state, the temperature is lowered from 50 ° C. to 30 ° C. every about 7 to 14 hours, the state of 30 ° C. is maintained for about 30 minutes, and the temperature is raised again to 50 ° C., This is vacuum dried while repeating 6 times alternately over 2 to 4 days.
(6) Take out from the vacuum dryer and cool naturally.

According to the freeze-dried manufacturing method 10 for fresh food according to the present embodiment configured as described above, the vacuum drying process is divided into three stages, the first period, the middle period, and the second period, and from the freezing process until the freeze-dried food is finally completed. The period is set several times to several tens of times longer than the usual method of about 10 days (7 to 13 days), and the temperature is set finely every predetermined time, and in accordance with the dryness of fresh food. By repeatedly vacuum drying alternately at a temperature of 50 ° C for a predetermined time and at a temperature of 30 ° C for approximately 30 minutes, the gorgeous color of the original fresh food can be maintained for a long time and the nutritional value is also impaired. Freeze-dried food that can be provided.

Claims (3)

A method for freeze-drying fresh foods such as vegetables and fruits while suppressing discoloration of the surface,
A freezing process in which fresh food is put into a -20 ° C freezer and frozen;
Frozen fresh food is put into a vacuum dryer, a vacuum pressure is applied until the inside of the vacuum dryer reaches −30 ° C., and then the inside of the vacuum dryer is increased by + 5 ° C. every predetermined time in a vacuum state. The previous vacuum drying step to reach ± 0 ° C over 6 days;
A medium-term vacuum drying step in which the inside of the vacuum dryer is increased by + 5 ° C. every predetermined time in a vacuum state to reach 50 ° C. over 2 to 3 days;
A late vacuum drying step of maintaining the inside of the vacuum dryer in a vacuum state at 50 ° C. for 2 to 4 days;
A method for freeze-drying fresh food, characterized by comprising:   In the previous vacuum drying step, when the temperature in the vacuum dryer reaches −10 ° C., the temperature in the vacuum dryer is returned to the −20 to −30 ° C. state once or twice. The freeze-drying manufacturing method of the fresh food of Claim 1.   The latter vacuum drying step is characterized in that the state of 50 ° C. for a predetermined time and the state of 30 ° C. for about 30 minutes are alternately repeated by maintaining a state of 30 ° C. for about 30 minutes every predetermined time. The freeze-drying manufacturing method of the fresh food of Claim 1 or Claim 2.