JP2014008492A - Interface advancing freeze concentration apparatus and interface advancing freeze concentration method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an interface advancing freeze concentration apparatus and an interface advancing freeze concentration method which are capable of increasing yield of concentrated liquid and suppressing quality deterioration by preventing supercooling and by shortening concentration time.SOLUTION: An interface advancing freeze concentration apparatus 10 is equipped with at least: a stirring mechanism 30 which stirs solution 1 in a container 20 in which a seed crystal 3 is arranged; a cooling mechanism 40 which cools down the solution 1 in the container 20 by cooling medium; an ice crystal removing mechanism 60 which removes generated ice crystal to obtain concentrated liquid, in which the apparatus is equipped with: a temperature adjusting mechanism 70 which adjusts temperature of the cooling medium such that temperature of the solution gradually drops while the ice crystal is being generated.

Description

  The present invention relates to an interfacial forward freeze concentration apparatus and an interfacial forward freeze concentration method for producing a concentrate by cooling and freezing various solutions such as sake and fruit juice and removing ice crystals.

Conventionally, concentrated concentrates of raw materials have been used in various fields such as foods and pharmaceuticals, and freeze concentration methods are known as one of the methods for producing concentrated liquids.
Compared with evaporative concentration and membrane concentration methods, freeze concentration methods enable high-quality concentration of the raw material solution, and are superior as a method for crystallization of thermally unstable solutes due to the low-temperature concentration feature. Yes.

Of the freeze concentration methods, the interfacial forward freeze concentration method involves placing a solution of fruit or the like in a container and submerging the container in a refrigerant while stirring. Then, the ice phase generated on the cooling surface at the bottom of the container is grown, that is, the interface between the unfrozen solution phase and the ice phase is advanced to the unfrozen solution phase side, thereby creating one ice crystal. A concentrated liquid is produced in the upper part.
Since this method produces one large ice crystal, solid-liquid separation is extremely easy compared to the conventional freezing method (suspension crystal method), and the system can be simplified. Solutes (nutrients and flavors) Since the component) is excellent in preservability, there is an advantage that flavors such as sake and fruit juice can be enhanced.

  However, supercooling may occur at the beginning of the concentration process, that is, when generating ice crystals serving as nuclei. As a result, a part of the solute is incorporated into the ice crystals due to the supercooling, resulting in a loss of the solute and an increase in yield. There is a problem of lowering.

Thus, for example, Patent Document 1 discloses a forward freeze concentration method in which a large number of small holes are provided on the bottom surface inside a container.
In this method, the solution is gradually submerged in the coolant while stirring the solution, so that a temperature gradient is first generated in the solution in each small hole, and ice crystals serving as nuclei are generated in the deepest part in each small hole. . Then, by gradually growing the ice crystals as the core in each small hole, the ice crystals are spread out in a thin film over the entire bottom surface of the container, and new ice crystals are sequentially generated on the ice crystals. To obtain one large ice crystal.
According to this method, by first generating ice crystals serving as nuclei, ice crystals can be generated at a high temperature before reaching supercooling, so that the occurrence of supercooling can be suppressed to some extent.

  Also, for example, in Patent Document 2, a heat exchanger is arranged around a container, and the surface layer of ice crystals obtained in the concentration step is heated and melted to separate and recover the solute taken into the surface layer. A concentrator is disclosed.

JP-A-11-216301 JP 2000-334203 A

However, the conventional techniques as disclosed in the above patent documents have the following problems.
That is, the technique of Patent Document 1 generates only one ice crystal in a container, and since it takes time to generate ice crystals, there is a problem that it is difficult to mass-produce the concentrate industrially, and oxidation. There was a problem that the quality deteriorated due to the above.
Further, there is a problem that supercooling is likely to occur if the temperature of the refrigerant is lowered in order to accelerate the generation time of ice crystals.

  Further, the technique of Patent Document 2 is a mechanism in which a solute is recovered by heating after being taken into the surface layer of ice crystals, and there is a problem that overcooling cannot be actively prevented.

  In view of such problems, the present invention provides an interfacial forward freeze concentration apparatus and an interfacial forward freeze concentration method that can prevent overcooling and shorten the concentration time to increase the yield of the concentrate and suppress quality degradation. The purpose is to do.

  The interfacial forward freeze concentration apparatus of the present invention includes a stirring mechanism for stirring the solution in the container in which the seed crystals are arranged, a cooling mechanism for cooling the solution in the container with a refrigerant, and the generated ice crystals are removed to remove the concentrated liquid. An interface forward freeze concentration apparatus comprising at least an ice crystal removal mechanism to be obtained, further comprising a temperature adjustment mechanism for adjusting the temperature of the refrigerant so that the temperature of the solution gradually falls during the formation of ice crystals.

In addition, an ice crystal scraping mechanism for continuously scraping the ice crystals generated on the inner surface of the container during the ice crystal generation is provided.
In addition, a pre-cooling mechanism is provided that cools the solution within a temperature range that does not freeze before the solution is put into the container.
Further, the ice crystal removing mechanism is characterized in that ice crystals in the solution are removed by filtration.

  The interfacial forward freeze concentration method of the present invention includes a seed crystal placement step of placing a seed crystal in a solution, a stirring step of stirring the solution in the container, a cooling step of cooling the solution in the container with a refrigerant, In the interfacial forward freeze concentration method comprising at least an ice crystal generation step for generating ice crystals on the inner surface and an ice crystal removal step for removing the ice crystals in the solution to obtain a concentrate, the temperature of the solution in the ice crystal generation step A temperature adjusting step of adjusting the temperature of the refrigerant so as to gently fall.

The ice crystal generation step further includes an ice crystal scraping step of continuously scraping the ice crystals generated on the inner surface of the container.
In addition, a pre-cooling step of cooling the solution within a temperature range that does not freeze is provided before the cooling step.
In the ice crystal removing step, ice crystals in the solution are removed by filtration.

  According to the interfacial forward freeze concentration apparatus and the interfacial forward freeze concentration method of the present invention, supercooling is achieved by using a seed crystal and adjusting the temperature of the refrigerant so that the temperature of the solution gradually decreases during ice crystal formation. In addition, the concentration time can be shortened. Therefore, it is possible to increase the yield of the concentrated liquid and to suppress quality deterioration.

In this specification, “adjusting the temperature of the refrigerant so that the temperature of the solution gently decreases” means adjusting the temperature of the refrigerant so that overcooling does not occur while measuring the temperature of the solution. It means that the temperature of the solution is gradually lowered.
The temperature at which supercooling occurs changes every moment depending on various conditions such as the type and concentration of the solution.
During the formation of ice crystals, the solute that has not been taken into the ice phase moves to the solution side, and the concentration of the solution gradually increases with time, so the temperature at which supercooling occurs also changes with time. Also, the solidification temperature of the solution decreases as the concentration increases.

In the present invention, the temperature of the solution is measured during the formation of ice crystals, and if the sign of supercooling such as a rapid increase in the rate of decrease in the solution temperature per unit time is detected or predicted, the temperature of the refrigerant is decreased slightly. As a result, the temperature of the solution is adjusted so that it gradually decreases by dynamically changing the rate of decrease of the refrigerant temperature per hour. As a result, it is possible to shorten the concentration time by shortening the generation time of ice crystals while preventing supercooling.
As described above, when the temperature of the solution is slowly lowered while adjusting the temperature of the refrigerant so that the supercooling does not occur, the difference between the solution temperature and the refrigerant temperature is lowered while being almost constant. The present invention is characterized in that the temperature of the refrigerant is not adjusted so as to make the temperature difference between them constant, but the temperature of the refrigerant is dynamically changed so as not to cause overcooling.

Regarding the generation of ice crystals, only one ice crystal may be generated in the lower part of the container, or the ice crystals generated on the inner surface of the container may be scraped continuously.
When scraping ice crystals continuously, the scraped granular ice crystals grow in a floating state in the solution, so that compared with the case where only one ice crystal is formed, ice crystals Since the contact area with the solution increases, the generation rate of ice crystals increases, and the time required for the concentration step can be further shortened.

In addition, by stirring the solution, the solution having a high concentration existing around the ice crystal is excluded from the periphery of the ice crystal, that is, the osmotic pressure is lowered by lowering the solution concentration around the ice crystal. It is possible to suppress the solute from being taken into the ice crystal.
Further, by pre-cooling the solution within a temperature range in which the solution is not frozen before putting the solution into the container, the concentration step can be made more efficient than when no pre-cooling is performed.

Schematic diagram showing the configuration of the interfacial forward freeze concentration apparatus Schematic diagram showing the configuration of the interfacial forward freeze concentration apparatus

[First Embodiment]
A first embodiment of the interfacial forward freeze concentration apparatus 10 of the present invention will be described.
As shown in FIGS. 1 and 2, the interface forward freeze concentration apparatus 10 includes a container 20, a stirring mechanism 30, a cooling mechanism 40, a preliminary cooling mechanism 50, an ice crystal scraping mechanism 60, a temperature adjusting mechanism 70, and an ice crystal removing mechanism. 80.
The container 20 has a bottomed shape with an open top, and the solution 1 is placed inside. Although the kind of solution 1 is not limited, For example, aqueous solutions, such as liquor and fruit juice, can be used. In this embodiment, sake is used.

Sake includes brewed liquor (for example, Japanese sake (including raw sake and water adjusted), beer, wine, cider, etc.), distilled liquor (rice shochu, whiskey, brandy, koji shochu, rum), mixed liquor (synthetic sake, synthetic sake, Mirin, sweet fruit liquor, liqueurs, miscellaneous liquor, sparkling liquor, fruit beer, etc.).
Examples of the aqueous solution include fruit juice, coffee (water extract of roasted coffee beans), tea (water extract of various tea leaves), milk, and soup stock. Tea leaves may be used alone, or a plurality of types of tea leaves may be combined. Examples of the milk include pasteurized milk and processed milk. Dashi soup includes kombu dashi, bonito dashi, bouillon, umami extract, Japanese dashi, Western dashi, Chinese dashi, and so on. In these aqueous solutions, water-insoluble components may be suspended or dispersed. The aqueous solution may be frozen and concentrated as it is, or may be freeze-concentrated after filtering water-insoluble components.
Examples of the fruit juice include common fruit juices such as lemon juice, orange juice, and apple juice.

Although the material of the container 20 is not specifically limited, It is preferable to use a material with high heat conductivity, for example, stainless steel and glass can be used.
The shape of the container 20 is not particularly limited, but a shape that can efficiently transfer the heat of the external refrigerant 42 to the solution 1 is preferable. For example, a cylindrical shape having a small diameter with respect to the entire length can be given. Further, in consideration of scraping off the ice crystals 3 (see FIG. 2) generated on the inner surface of the container 20 by an ice crystal scraping mechanism 60 described later, a cylindrical shape is preferable.

A seed crystal 2 is disposed in the lower part of the container 20.
The seed crystal 2 is for preventing overcooling of the solution 1 and promoting crystallization. In this embodiment, seed ice is used, but ice nucleoprotein or the like may be used.
By arranging the seed crystal 2, the occurrence of supercooling can be prevented, and the amount of solute adhering to the ice crystal 3 (the amount of incorporation) can be suppressed. When the solution 1 is sake, the amount of alcohol as a solute adhering to the ice crystals 3 can be suppressed, so that the alcohol concentration in the solution 1 can be increased.

  The stirring mechanism 30 is for stirring the solution 1 in the container 20, and in the present embodiment, a ribbon screw 32 (screw conveyor) having spiral blades around the rotating shaft 31 is used as a rotary motor (illustrated). It is configured to rotate around the rotation shaft 31. The rotation speed and rotation time of the rotary motor can be adjusted by a controller (not shown).

In general, during cooling, the concentration of the solution increases around the ice crystals. This is because, when the water around the ice crystals changes into ice crystals, the solute that has not been incorporated into the ice crystals remains around the ice crystals.
Therefore, the solution 1 is stirred and the solute remaining around the ice crystal 3 is dispersed in the solution 1, thereby reducing the concentration of the solution 1 around the ice crystal 3 and lowering the osmotic pressure on the surface of the ice crystal 3. Therefore, the amount of solute taken into the ice crystal 3 can be suppressed. In addition, since the temperature of the solution around the ice crystal 3 is low, the temperature of the entire solution can be efficiently lowered by stirring and mixing the solution around the ice crystal 3 with the entire solution. As a result, the concentration time can be shortened while preventing overcooling.
The stirring condition is preferably 100 rpm or more, more preferably 500 rpm or more, although it depends on the arrangement interval of the blades, the shape of the blades, the shape of the container 20, and the like.
In the present embodiment, the stirring mechanism 30 also serves as an ice crystal scraping mechanism 60 described later.

The cooling mechanism 40 is for cooling the solution 1 in the container 20, and generally includes a refrigerant tank 41, a refrigerant 42, a cooling pipe 43, a cooling device main body 44, and the like.
The refrigerant tank 41 has a bottomed box shape with an open top, and the inside is filled with the refrigerant 42. As the refrigerant 42, known ones such as methanol, ethanol, isopropyl alcohol, and naybrine can be used.

The cooling pipe 43 is stretched around the inner surface of the refrigerant tank 41, and both ends thereof are connected to the cooling device main body 44.
As the cooling device main body 44, for example, a well-known device such as a rapid cooling device using cold air such as a blast chiller can be used.
The cooling air sent from the cooling device main body 44 passes through the cooling pipe 43, whereby the refrigerant 42 and the container 20 are cooled, and the ice crystals 3 are generated on the inner surface of the container 20.
Regarding the rate of formation of ice crystals 3, an excessively high rate is not preferable because the amount of solute components taken into the ice crystals increases, and an excessively low rate is not preferable from the viewpoint of recovery.

The pre-cooling mechanism 50 is for cooling the solution 1 within a temperature range in which the solution 1 is not frozen in the pre-cooling container 51 before putting the solution 1 into the container 20. The refrigerant tank 52, the precooling refrigerant 53, the precooling cooling pipe 54, the cooling device main body 55 (also used as the cooling device main body 44), and the like are roughly configured.
The cooling method is the same as that of the cooling mechanism 40, and the cooling air sent from the cooling device main body 55 passes through the cooling pipe 54 for preliminary cooling, whereby the preliminary cooling refrigerant 53 and the preliminary cooling container 51 are cooled. The temperature of the pre-cooling refrigerant 53 is set to a temperature at which the solution 1 does not freeze. For example, when the solution 1 is sake, it is maintained at about −5 ° C. to −8 ° C.

The ice crystal scraping mechanism 60 is for continuously scraping the ice crystals 3 generated on the inner surface of the container 20 during the ice crystal generation. In the present embodiment, the ice crystal scraping mechanism 60 also functions as the stirring mechanism 30 as described above. ing.
That is, the ice crystal scraping mechanism 60 includes a ribbon screw 61, and the ice crystal 3 generated on the inner surface of the container 20 by a spiral blade is rotated by rotating a rotating shaft with a rotary motor (not shown). It has a scraping mechanism.
The ice crystal 3 is scraped off by the ribbon screw 61 and grows in a granular form while floating in the solution 1.

The temperature adjustment mechanism 70 is for adjusting the temperature of the refrigerant 42 so that the temperature of the solution 1 gradually falls during the formation of ice crystals, and includes a solution temperature sensor 71, a refrigerant temperature sensor 72, and a control device 73. It is roughly composed of
The solution temperature sensor 71 is disposed in the container 20 to measure the temperature of the solution 1, and the refrigerant temperature sensor 72 is disposed in the refrigerant tank 41 to measure the temperature of the refrigerant 42.
The control device 73 receives the temperature information of the solution 1 and the refrigerant 42 output from the solution temperature sensor 71 and the refrigerant temperature sensor 72, and cools the main body of the cooling device so that the temperature of the solution 1 gradually falls during the generation of ice crystals. 44 is controlled to adjust the temperature drop rate of the refrigerant 42.
Since the solidification temperature decreases as the concentration of the solution 1 increases and the concentration increases, it is necessary to lower the temperature of the refrigerant 42 in order to efficiently generate the ice crystals 3. At this time, the temperature of the solution 1 gently By dynamically adjusting the temperature of the refrigerant 42 so as to descend, overcooling can be prevented, the solution 1 can be adjusted to a desired concentration, and the amount of solute adsorbed on the ice crystals 3 can be suppressed. it can.

The ice crystal removal mechanism 80 is for removing the generated ice crystals 3 to obtain the concentrated liquid 4 (see FIG. 2). In this embodiment, the ice crystal removal mechanism 80 uses a filter medium 81 and a filter container 82 as shown in FIG. It comprises a filter 83. In addition to filtration, a centrifugal separation method, a pressure separation method, or the like can be used.
After completion of the freeze concentration operation in the container 20, the solution 1 in the container 20 is put into the filter 83, whereby the ice crystals 3 are removed by the filter medium 81 and only the concentrated liquid 4 that has passed through the filter medium 81 is obtained. It is structured.

The concentrated liquid 4 is obtained by removing a part of the water in the solution 1 as ice crystals 3, and can be used for the purpose of producing food and drink such as fruit juice, coffee, tea, milk, and soup depending on the type of the solution 1. . The concentrated solution 4 has an advantage that it can reduce the transportation cost and the storage cost as compared with the case where the solution 1 containing a large amount of water is transported or stored as it is, and is mainly prepared for that purpose. However, it can also be used as it is added to other foods and drinks.
Moreover, when the solution 1 is sake, the sugar content as a solute remains in the concentrate 4 due to concentration, so that the degree of sake can be reduced (sweetened).

In the above embodiment, the interfacial forward freeze concentration apparatus 10 is provided with the preliminary cooling mechanism 50. However, the preliminary cooling of the solution 1 is performed using the cooling mechanism 40 and the container 20 without including the preliminary cooling mechanism 50. You may decide to do it.
Further, if a plurality of cooling mechanisms 40 are prepared, the cooling process can be performed in parallel by the plurality of cooling mechanisms 40, so that the concentration work can be made efficient.
Further, although the stirring mechanism 30 also serves as the ice crystal scraping mechanism 60, the stirring mechanism 30 and the ice crystal scraping mechanism 60 may be provided separately.

Next, the interface forward freeze concentration method of the present invention will be described.
First, the refrigerant tank 41 is filled with the refrigerant 42, the solution 1 is placed in the container 20, and the seed crystal 2 is arranged (seed crystal arrangement step).
And while starting the temperature measurement of the solution 1 and the refrigerant | coolant 42, stirring of the solution 1 is started (stirring process and cooling process).
Further, it is preferable to measure the concentration of the solution 1 if possible.
In addition, it is preferable to perform preliminary cooling so that the temperature of the solution 1 at the start is about −5 ° C. and the temperature of the refrigerant 42 is about −10 ° C.

Although the temperature of the solution 1 during cooling should just be below a freezing point, the range of 0--40 degreeC is desirable, More preferably, it is -10-30 degreeC. When the cooling temperature is lower than the above range, cooling is performed more than necessary, resulting in an increase in power consumption. On the other hand, when the above range is exceeded, there is a possibility that the moisture will be insufficiently frozen due to the influence of the freezing point depression of the solution 1 described above.
During the cooling, it is necessary to adjust the temperature of the refrigerant 42 so that the temperature of the solution 1 gradually decreases (temperature adjustment step).

When a predetermined time elapses, layered crystallization of water in the solution 1 is performed on the inner surface of the container 20 to generate ice crystals 3 (ice crystal generation step).
Since the solution 1 is agitated during the formation of the ice crystals, the solute contained in the solution 1 around the ice crystals 3 is not taken into the ice crystals 3 at the solid-liquid interface, and sufficient mass transfer is performed.
In addition, the ice crystals 3 generated on the inner surface of the container 20 are continuously scraped (ice crystal scraping step) to grow the ice crystals 3 while floating in the solution 1.
Then, when a predetermined time has elapsed, the cooling is terminated, and the concentrated liquid 4 is obtained by removing the ice crystals 3 in the solution 1 by filtration or the like (ice crystal removal step).
When the concentration of the solution 1 is being measured, the cooling may be terminated when the predetermined concentration is reached.

各実施例（実施例１〜５）及び比較例（比較例１〜３）におけるサンプル量、たね氷の有無、冷却開始時の冷媒温度（冷媒開始温度）、冷媒降下温度の設定条件（降下設定温度）、リボンスクリューの回転数を表２及び表３に示す。

Next, examples of the interface forward freeze concentration apparatus and the interface advance freeze concentration method of the present invention will be described.
Table 1 shows the apparatus configuration.

Sample amount in each Example (Examples 1 to 5) and Comparative Example (Comparative Examples 1 to 3), presence / absence of ice cubes, refrigerant temperature at the start of cooling (refrigerant start temperature), setting conditions for refrigerant fall temperature (fall setting) Table 2 and Table 3 show the temperature) and the rotation speed of the ribbon screw.

各実施例及び比較例における経過時間と温度変化を示すグラフを表５及び表６に示す。

なお、表５の実施例１のグラフに表しているように、グラフの上の線がサンプル（溶液）温度を示し、下の線が冷媒温度を示している。表６も同様である。 The sake used was sake and sake. Table 4 shows the alcohol concentration, sake degree and specific gravity of both.

Tables 5 and 6 show graphs showing elapsed time and temperature change in each Example and Comparative Example.

As shown in the graph of Example 1 in Table 5, the upper line of the graph indicates the sample (solution) temperature, and the lower line indicates the refrigerant temperature. The same applies to Table 6.

The results are shown in Table 7 and Table 8.

[Example 1]
Sake was used as the solution, and the stirring device 2 (see Table 1) was used as the stirring mechanism.
The temperature difference between the refrigerant and the solution was controlled, the temperature of the refrigerant was gradually lowered, and the test was terminated when the target alcohol concentration was reached.
Although the temperature difference started at −3 ° C., the temperature did not decrease at all, so the temperature difference was changed to −4 ° C.
Alcohol adsorption to ice crystals was reduced by increasing the rotational speed compared to Comparative Example 1. This is thought to be because the osmotic pressure on the ice phase was lowered by stirring and the adsorption of ice was suppressed. Moreover, the alcohol concentration rate also became very large. However, if the temperature difference is −3 to −4 ° C., the concentration time takes 6 and a half hours or more, so it can be said that the working efficiency is not so good.

[Example 2]
Sake was used as the solution, and the stirring device 2 was used as the stirring mechanism.
When the temperature difference was set to −5 ° C., the concentration time was significantly shortened to less than 2 hours.
The amount of concentrated liquid recovered was 200 ml, and the yield was 50%.
This shows that the stirring method and temperature difference management are important.

[Example 3]
Sake was used as the solution, and the stirring device 2 was used as the stirring mechanism.
The temperature difference was set to -4.5 ° C. Compared with the temperature difference of Example 5 of −5 ° C., the test time was increased from 2 hours 30 minutes to 2 hours 45 minutes, but the alcohol concentration absorbed in the ice crystals was low. However, since there is no big difference between the yields, it is possible that the adsorbed alcohol can be recovered by the suction method after the end of the test even at -5 ° C.

[Example 4]
The solution was changed from sake with a high water content to raw sake.
In the case of raw alcohol with a high alcohol concentration, the concentration time can be greatly shortened because the concentration difference to the target is reduced. The yield is about 50%, which is almost the same as the sake result.
However, it seems that alcohol adsorption to ice crystals increases due to rapid ice formation.

[Example 5]
Raw liquor was used as the solution.
When the temperature difference was set to 4.5 ° C. through the results of Example 4, the measurement time and the yield were not substantially affected.
Alcohol adsorption on ice was slightly suppressed by setting the temperature difference to 4.5 ° C. Alcohol adsorption on ice seems to be still high, but as can be seen from the results of Example 1, the solution temperature hardly falls at a temperature difference of 3 to 4 ° C.

[Comparative Example 1]
The stirring device 1 was used as a stirring mechanism.
The higher the alcohol concentration of sake, the lower the coagulation temperature. When the temperature of the refrigerant is kept at -8 ° C, the temperature of the solution will hardly decrease. The temperature was lowered and concentrated.
In addition, seed ice made on the bottom surface was grown to form single ice crystals, which were separated into solid and liquid.
It turns out that it is hardly concentrated numerically. Also, alcohol adsorption on ice is very high at 12%, indicating that this method has very poor concentration efficiency.

[Comparative Example 2]
The stirring device 1 was used as a stirring mechanism.
The temperature of the refrigerant was kept at -15 ° C.
The purpose was to grow seed ice on the bottom surface to form a single ice crystal and separate it into solid and liquid, but sherbet-like ice was formed within 10 minutes. It can be seen that although the alcohol concentration is increased, the adsorption to ice crystals is very high. This is thought to be because quick freezing occurred and it was quickly cooled in a short time.
In this method, it is possible to concentrate alcohol in a shorter time, but on the other hand, there is much loss and inefficiency.

[Comparative Example 3]
The stirring device 2 was used as a stirring mechanism.
Since no seed ice was placed in the container, the temperature of the solution dropped rapidly, making it difficult to maintain a temperature difference of 5 ° C. from the refrigerant.
When the solution temperature was around −10 ° C., it became almost a sherbet, and the concentrated solution could not be recovered. Probably because of rapid freezing caused by supercooling. Looking at the graph, it can be seen that the temperature rapidly increased around −10 ° C., and heat of solidification was generated by rapid freezing.
Alcohol adsorption to the ice crystal part is very high at 11.7%, and the yield is poor. It was reconfirmed that seed ice as the core of ice was necessary.

[Discussion]
[Improvement of solid-liquid separation method]
Comparative Examples 1 and 2 were methods in which seed ice made on the bottom surface was grown to form a single ice crystal and solid-liquid separation. However, it was found that the ice crystals adhering to the seed ice were scraped off with a ribbon screw as in each of the examples, and the granular ice crystals were grown in the solution in a short time and with good yield. In addition, it is possible to prevent the quality of sake from deteriorating by implementing it in a short time.

[Necessity of seed ice]
As can be seen from Comparative Example 3, seed ice serving as a solid core is indispensable for the freeze concentration method. When there is no seed ice, the inside of the solution is cooled at once, causing rapid freezing, and the entire solution is hardened in a sherbet shape. As a result, the yield of the liquid is almost lost, and the rate of alcohol adsorption on ice increases due to rapid cooling.

[Reduction of osmotic pressure by stirring]
In the interfacial forward freezing concentration, there is a concern that the yield may decrease due to the adsorption of alcohol on ice. Therefore, it was found that the adsorption of alcohol to ice crystals can be suppressed by stirring the solution with a ribbon screw rotating at high speed and lowering the osmotic pressure of the floating ice surface.
It was also found that the entire solution was evenly mixed by high-speed rotation and could be concentrated in a shorter time.

[Temperature control of solution and refrigerant]
As the concentration of the solution increases and the concentration increases, the solidification temperature decreases, so the cooling temperature must be lowered. In each of the examples, it was found that the temperature of the solution and the refrigerant were respectively controlled, and the solution was cooled so that the temperature of the solution gradually decreased, so that it could be concentrated to a target alcohol concentration to some extent.
It was also found that alcohol adsorption on ice crystals can be further suppressed by narrowing the temperature difference between the solution and the refrigerant. In this test, a glass container was used, so the ideal temperature range was 4.5 to 5.0 ° C.

[Improve efficiency by concentrating raw sake]
It was found that the concentration of the original sake can be concentrated in a shorter time and the efficiency is higher than the concentration of the sake (thinned with water) again. Moreover, the yield was hardly changed, and it was found that the concentration of the raw liquor can be concentrated to a desired alcohol concentration.
In addition, it turns out that sake degree becomes small (it becomes sweet) by concentration.
In addition, sake was used as a solution this time, but it can be assumed that almost the same effect can be obtained with an aqueous solution such as fruit juice.

  The present invention relates to an interface forward freeze concentration apparatus and an interface advance freeze concentration method that can prevent overcooling and shorten the concentration time to increase the yield of the concentrate and suppress quality degradation. Has availability.

DESCRIPTION OF SYMBOLS 1 Solution 3 Ice crystal 4 Concentrated liquid 10 Interface forward freezing concentration apparatus 20 Container 30 Stirring mechanism 40 Cooling mechanism 50 Precooling mechanism 60 Ice crystal scraping mechanism 70 Temperature control mechanism 80 Ice crystal removal mechanism

Claims (8)

A stirring mechanism for stirring the solution in the container in which the seed crystals are arranged;
A cooling mechanism for cooling the solution in the container with a refrigerant;
In an interface forward freezing and concentrating device comprising at least an ice crystal removing mechanism that removes the generated ice crystals to obtain a concentrated liquid,
An interface forward freezing and concentrating apparatus comprising a temperature adjusting mechanism for adjusting a temperature of a refrigerant so that a temperature of a solution is gently lowered during ice crystal formation.   The interface forward freezing and concentrating apparatus according to claim 1, further comprising an ice crystal scraping mechanism that continuously scrapes the ice crystals generated on the inner surface of the container during the ice crystal generation.   3. The interface forward freezing and concentrating apparatus according to claim 1, further comprising a pre-cooling mechanism that cools the solution within a temperature range that does not freeze before the solution is put into the container.   The interface forward freeze concentration apparatus according to any one of claims 1 to 3, wherein the ice crystal removal mechanism removes ice crystals in the solution by filtration. A seed crystal placement step of placing a seed crystal in the solution;
A stirring step of stirring the solution in the container;
A cooling step of cooling the solution in the container with a refrigerant;
An ice crystal generation process for generating ice crystals on the inner surface of the container;
In the interface forward freeze concentration method comprising at least an ice crystal removal step of removing ice crystals in the solution to obtain a concentrated solution,
An interfacial forward freeze concentration method comprising a temperature adjustment step of adjusting the temperature of the refrigerant so that the temperature of the solution gradually falls in the ice crystal generation step.   6. The interface forward freezing and concentrating method according to claim 5, further comprising an ice crystal scraping step of continuously scraping ice crystals generated on the inner surface of the container during the ice crystal generation step.   The interface forward freeze concentration method according to claim 5 or 6, further comprising a preliminary cooling step of cooling the solution within a temperature range in which the solution is not frozen before the cooling step.   In the said ice crystal removal process, the ice crystal in a solution is removed by filtration, The interface advance freeze concentration method as described in any one of Claims 5-7 characterized by the above-mentioned.

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