JP2006101763A - Method for producing dried slice of citrus fruit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing dried slices of citrus fruit solving such defects that slices of citrus fruit such as lemon slices currently served as drink and food are not suitable for long preservation because fresh sliced fruits are used as they are, and the dried slices require any freezing devices for their preservation so as to produce well flavored slice products preservable under normal temperatures and having good restoration properties with water or hot water. <P>SOLUTION: The method for producing dried slices of citrus fruit comprises soaking sliced citrus fruit such as lemon in trehalose solution followed by subjecting the sliced fruit to decompressing treatment, bringing the sliced fruit back to a normal-pressure condition, and keeping the sliced fruit in such a condition for a certain period of time to freeze-dry the sliced fruit. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention provides dried citrus fruit slices such as freeze-dried lemon slices that can be easily restored to the original state with water or hot water, etc., and can be stored without using preservatives even at room temperature.

It is already known that food is impregnated with a liquid component in the food after being subjected to reduced pressure treatment or in contact with a liquid component or a gas component in a reduced pressure state (see, for example, Patent Document 1). However, the impregnation treatment under reduced pressure is performed for the purpose of soaking the liquid component in the food in a short time or seasoning it in a short time, and using trehalose as in the present invention, further drying by freeze drying. It does not relate to the production of citrus slices such as dried lemon slices that have excellent restorability and good storage stability when combined with the method.
JP 2003-174850 A

  Citrus fruit slices such as lemon slices and orange slices are frequently used in various foods and drinks such as tea, juice, cocktails, and salads. And citrus fruit slices, such as lemon slices currently used for food and drink, are used as they are by slicing fruits and vegetables, and are not suitable for long-term storage. There is also a method of freezing storage, but freezing equipment is required for storage, which is inferior in terms of convenience. In addition, when the sliced lemon is processed as it is by a drying method such as air drying or freeze drying, the skin part shrinks and hardens, and when immersed in a liquid, the restorability is poor, making it unsuitable for consumption. There were drawbacks. In addition, the dried ones often have the lemon crumple crushed, and there are few savory lemon slices, and improvement of this point has been desired.

  In order to meet the above-mentioned demands of the industry, the present invention newly develops a dried product of citrus fruit slices such as lemon slices that can be stored at room temperature, has excellent resilience with water and hot water, and has a good flavor. It was made for the purpose.

  In order to achieve the above-mentioned object, the present inventors have studied from various directions. As a result, the raw material is impregnated with a sugar solution, and then freeze-dried. In that case, an aqueous solution of trehalose is used as the sugar solution, and The impregnation treatment is carried out under reduced pressure, and further, after the reduced pressure treatment, the pressure is returned to normal pressure and maintained for a certain period of time, thereby succeeding for the first time in producing the desired dried citrus fruit slice and completing the present invention. It was.

  That is, the method of the present invention comprises the following steps. Ingredient preparation, sugar solution preparation, decompression, maintenance of reduced pressure state, return to normal pressure, immersion, draining, recovery of ingredients, freeze drying process. In the above, the step of preparing the sugar solution to maintaining the reduced pressure state may be a step of reducing the pressure, maintaining the reduced pressure state, and injecting the sugar solution.

More specifically, the method of the present invention comprises the following steps.
(1) Slice fruit (2) Immerse in trehalose solution (3) Reduce pressure and hold for a certain period of time (4) Return to normal pressure and hold for a certain period of time (5) Drain the trehalose solution and collect the fruit slice (6) Perform freeze-drying process In the above process, the order of (2) and (3) may be interchanged.

  Hereinafter, the present invention will be described in detail by taking a lemon as an example of a citrus fruit.

(1) Slice the lemon-Lemon slice thickness; 1-10 mm, preferably 2-5 mm
・ Slicing method: A slicer usually used may be used.
If desired, in addition to slices, that is, so-called round slices, slices can be sliced at right angles or at an angle to the round slices, and the slices can be of an appropriate size and shape. Is also possible. Therefore, in the present invention, these are all called slices.

(2) Immerse in trehalose solution-Concentration of trehalose solution; 10-20%, preferably 10-15%
At this time, in order to prevent the lemon slice from floating in the airtight container, an undesired net or the like is placed on the surface of the lemon slice.

  As trehalose, both α, α-trehalose and α, β-trehalose can be used. Usually, α, α-trehalose is used, and water-containing or anhydrous crystal powder (for example, crystalline anhydrous trehalose, non- Crystalline anhydrous trehalose or the like) can be used as appropriate. Commercially available products can also be used. For example, high-purity water-containing crystal trehalose (produced by Hayashibara Shoji Co., Ltd., registered trademark “Trehaose”) that is industrially produced from starch by an enzymatic method can be advantageously used. Trehalose may be mixed by directly sprinkling a solid such as a powder or crystal on a lemon slice, but is usually used in the form of a solution such as an aqueous solution as described above.

(3) Depressurize and hold for a certain period of time Pressure of decompression treatment: Pressure of decompression treatment or decompressed state is 5,000 to 12,000 Pa, preferably 5,000 to 10,000 Pa, more preferably 8,000 to 10,000 Pa.

  When the pressure is lowered from 5,000 Pa, the solution may be boiled even at room temperature, and therefore it is preferable to perform the treatment at a pressure that does not cause the solution to boil. If the raw material collapses due to boiling, the lemon canopy collapses, or it is inferior to that which is not dried when the dried lemon slice is restored (under conditions of 4,200 Pa, the water is 30 ° C. Boil.)

-Decompression treatment time: 5 to 20 minutes, preferably 7 to 10 minutes.
If it is less than 5 minutes, there is a case where the permeation cannot be sufficiently performed in the next step of returning to the normal pressure and holding it.
Since it only needs to penetrate sufficiently in the next step of holding back to normal pressure, it is not necessary to perform decompression for a long time (20 minutes or more), but infiltration is incomplete when holding normal pressure in the next step In this case, it is preferable to lengthen the decompression processing time.
Note that there is no problem even if the steps (2) and (3) are reversed.

(4) Return to normal pressure and hold for a certain period of time-If the pressure is rapidly returned to normal pressure, the liquid surface of the trehalose solution tends to shake and the shape tends to collapse, so return to normal pressure so that the shape of the lemon slice does not change. For example, the cock provided in the upper part of the container which has airtightness is opened, it returns to a normal pressure, and it hold | maintains as it is for the following time.

-Holding time after normal pressure: 2 to 60 minutes, preferably 5 to 20 minutes.
Within 2 minutes, the trehalose solution cannot be sufficiently retained. As a guideline, it is desirable that the albedo portion of the lemon slice is slightly transparent because the trehalose solution does not sufficiently penetrate if the albedo portion remains white.
It is preferable that the trehalose solution can be sufficiently permeated and retained, and it may be permeated for a long time. However, if the penetration rate does not change even if it penetrates for a long time, it is not necessary to penetrate further. As a guide, it is preferably within 60 minutes.
The temperature to hold is set appropriately. Normal temperature is acceptable.

(5) Drain the trehalose solution and collect the lemon slices.
• Drain the trehalose solution: Ensure that the lemon slice does not deform.
Care should be taken to maintain the shape of the saw.
The recovered trehalose solution may be used as a solution to be dipped again. However, when the trehalose concentration in the solution is less than 10%, it is necessary to discard it or add trehalose to increase the concentration.

(6) Perform freeze-drying The usual processing used for drying food may be used. For example, before drying, the lemon slice obtained above is frozen. The freezing temperature may be such that the lemon slice is frozen, and usually it is preferably frozen at -18 ° C or lower.

The frozen lemon slice is put into a freeze-drying apparatus and vacuum freeze-dried.
The treatment time may be set as appropriate, and the smaller the moisture content of the lemon slice, the better. Therefore, the treatment time is preferably 5% or less, and preferably 3% or less.

  The dried lemon slice obtained in this way is a novel food and has the following characteristics.

(I) Easy to return to water and hot water, and can be easily eaten up to the skin.
As mentioned above, the penetration of water and hot water is better than products processed with existing technology. Therefore, it returns to the softness that the whole can be easily eaten in about 1 minute.
(B) Easy long-term storage.
Basically, the features of ordinary freeze-dried products are maintained. If high temperature and high humidity conditions are avoided, it can be stored for about one year.
(C) It is possible to maintain a good shape while being sliced.
Compared with other drying methods, the shrinkage of the white part of the skin can be suppressed.
This makes it possible to maintain a good shape as a whole slice.

  Therefore, according to the present invention, the following remarkable effects are exhibited.

・ No special equipment such as freezing is required, and long-term storage is possible without using preservatives at room temperature.
・ Provides dried lemon slices with little browning or shape change.
-Good water return and hot water return, and it is possible to eat the whole.
-It is suitable as a health ingredient because it can be eaten up to the part of the skin that contains a large amount of functional ingredient eriocitrin.
・ When there is a large amount of harvest, this method allows you to store and use the harvest without wasting it, and it is easy to process in the production area. Can be done at low cost.
・ You can enjoy dried slices of various shapes and sizes.
・ Because it is sliced in advance, it is not necessary to slice fruits and vegetables every time it is used, and it is very convenient.

  In the following, the present invention will be described in detail by taking lemon as a representative example, but the present invention is not limited to only examples, and in addition to lemon, orange, yuzu, kabosu, sudachi, lime, daidai, mandarin orange and others The present invention can be widely applied to citrus fruits. Even citrus fruits are particularly suitable for those having a thick albedo portion.

Example 1
(1) Slice of lemon raw material 404 g of sliced lemon fruits and vegetables were used. For slicing, an ECA-201 slicer (manufactured by Emura Sales Co., Ltd.) was used. For this, other products could be used if uniform slicing was possible.
The slice thickness can be adjusted within a certain range by changing the parts. In this example, the slice was set to a thickness of 3 to 4 mm.

(2) Immersion treatment of trehalose solution In this example, a 15% aqueous solution of trehalose (obtained from Hayashibara Corporation) was used. 3 L of trehalose solution was used.

First, the sliced lemon was placed in a container and covered with a lid. At this time, a colander (a plate having a hole in a mesh shape) was previously covered so that the shape of the lemon did not change in the next operation.
Next, the air in the container is degassed with a vacuum pump, and the pressure is reduced (pressure: 9300 Pa). Deaeration was continued for about 8 minutes.
Then open the top of the container (with a spout on the lid) and pour the trehalose solution. At this time, treatment was performed so that air did not flow together with the trehalose solution.
After pouring the liquid, the upper cock was opened, the pressure was returned to normal pressure, and held there for 5 minutes.
Then, the poured liquid was discharged | emitted from the lower cock, and the immersion process was completed.

(3) Freeze-drying treatment Before performing freeze-drying, the lemon slice obtained in step (2) was frozen at -20 ° C.
For freeze-drying treatment, an RLE-103 type vacuum freeze dryer (manufactured by Kyowa Vacuum Technology Co., Ltd.) was used, and the conditions were set at a temperature of 30 ° C. and the treatment was performed for 48 hours. The weight before and after the treatment and the temperature and pressure during the treatment are shown in Tables 1 and 2 below.

(Table 1)
Change in weight before and after processing ―――――――――――――――――
weight-----------------
Before impregnation 100.0
After impregnation 106.9
(Tray load) 105.7
After FD 17.0
―――――――――――――――――
(Weight is 100 before impregnation)

(Table 2)
Changes in temperature and pressure during freeze-drying process ――――――――――――――――――――――――
At the beginning After the end ――――――――――――――――――――――――
Shelf temperature 9.2 33.0
Product temperature (upper stage) -2.2 30.9
Product temperature (middle) -11.4 29.3
Product temperature (lower) -10.9 30.7
In-vessel pressure (Pa) 101300 13
――――――――――――――――――――――――

  The freeze-dried lemon slice thus obtained maintained the shape of a normal lemon slice, and the shape of the lemon slice was maintained without being crushed. The moisture content of this dried slice lemon was 2.8%.

(Example 2)
This was also performed when the immersion order of Example 1 was changed.

  In the same manner as in Example 1, sliced lemon was charged into a container, and then a net was laid and a trehalose solution was injected. Next, the air in the container was deaerated with a vacuum pump in a sealed state. After deaeration was continued for about 8 minutes and the reduced pressure state was maintained, the upper cock of the container was opened and the pressure was slowly returned to normal pressure. It was kept as it was for 5 minutes, the trehalose solution was discharged, and a soaked lemon slice was obtained. This was freeze-dried in the same manner as in Example 1.

  Even if the step of injecting the trehalose solution and the step of reducing the pressure were interchanged, the same dried lemon slice as in Example 1 could be produced.

(Comparative test)
(A) Comparison with air dry (hot air drying) The sliced lemon was placed on a metal mesh and dried with hot air at 100 ° C. for 3 hours. The moisture content was estimated to be about 84% from the residual weight in the freeze-drying process, and the point where the weight decreased to that extent was used as a measure for the drying end point.
As a result, the white part (albedo) of the skin shrunk during drying, and the lemon slices were remarkably accelerated by hot air during drying.
Before seeing water reconstitution and hot water reconstitution, the dry lemon slices obtained in the examples were of low quality so that they could not be compared.

  As described above, (raw material) → (impregnated with sugar solution) → (air dry treatment) is a drying treatment performed at a high temperature such as air dry, so that lemons are drastically browned and deformed. Absent. On the other hand, in the freeze-drying process, it was confirmed that browning and deformation can be minimized in order to suppress the amount of heat applied to the raw material.

(B) Comparison with reduced-pressure drying (at room temperature) The lemon slice subjected to the immersion treatment, which was performed in the same manner as in the Examples until the impregnation treatment with the trehalose solution, was directly dried under reduced pressure. Drying conditions were performed at a shelf temperature of 30 ° C. for 24 hours.
As a result, the skin was contracted, although it was better than the air-dried product. When this was returned with water or hot water, the skin was still hard, and the texture was far from the lemon sliced lemon.
It has been found that it is preferable to perform freeze-drying after the immersion treatment.

That is, as described above, (raw material) → (impregnated with sugar solution) → (vacuum drying treatment) can be processed at a lower temperature than air drying,
-Deformation due to application of a certain temperature-Disturbance of shape due to sudden boiling of liquid components during decompression is inevitable.
On the other hand, with freeze drying, since the temperature rise can be minimized, deformation of the raw material is minimized, and it is confirmed that there is no risk of bumping because the raw material is frozen. It was done.

  Note that (raw material) → (impregnated with sugar solution) → (not dried (after impregnation, freezing, etc.)) does not perform the drying process, and therefore there is no merit by performing the impregnation process. Therefore, preservability is not improved, and even if immersed in a sugar solution, there is almost no difference from ordinary freezing treatment.

  Further, in the present invention, it is necessary to use a trehalose solution, perform an impregnation treatment under reduced pressure, return to normal pressure, and hold for a certain period of time.

In ordinary freeze-drying treatment, the albedo (white part) around the lemon slice shrinks and becomes hard, and when it is restored with water, it is difficult to absorb water, and the dryness and hot water return properties of the dried product are not good.
On the other hand, when this treatment is performed, the impregnation of the trehalose solution suppresses the shrinkage of the albedo portion during drying, so that the dried product has good water return and hot water return properties.
Furthermore, since the state in which the trehalose solution is immersed in the gaps in the albedo portion can be preserved by holding for a certain period of time after the pressure reduction, a remarkable effect is obtained that shrinkage hardly occurs even if this is freeze-dried.

Claims (10)

  A method for producing a dried citrus fruit slice, comprising immersing a sliced citrus fruit in a trehalose solution, performing a reduced pressure treatment, returning to normal pressure, discharging the immersion liquid, and performing freeze drying.   Dried citrus fruit slice characterized by maintaining sliced citrus fruit under reduced pressure, adding trehalose solution to it and immersing it, then returning to normal pressure, discharging the immersion liquid, and performing freeze drying Manufacturing method.   The method according to claim 1 or 2, wherein the trehalose solution is 10 to 20% by weight.   The method according to any one of claims 1 to 3, wherein the trehalose is α, α-trehalose.   The method according to any one of claims 1 to 4, wherein the decompression treatment conditions are 5,000 to 12,000 Pa and 5 to 20 minutes.   The method according to any one of claims 1 to 5, wherein the holding time until the immersion liquid is discharged after returning to normal pressure is 2 to 60 minutes.   The method according to any one of claims 1 to 6, characterized by slicing to a thickness of 1 to 10 mm.   The method according to any one of claims 1 to 7, wherein the citrus fruit is lemon.   A dried citrus fruit slice produced by the method according to any one of claims 1 to 8.   A dried lemon slice produced by the method according to any one of claims 1 to 8.