JPH05277302A - Freezing and concentrating method and apparatus for high-moisture material - Google Patents

Abstract

(57) [Summary] [Purpose] To increase the efficiency of separation of concentrated liquid and ice by causing large spherical ice crystals to be generated when freezing high-moisture materials. [Structure] The high-moisture material is enclosed in a material container 6 and installed in a pressure vessel-shaped crystallizer 1. The pressure inside the crystallizer 1 is controlled by a high-pressure pump 12. The material that has been supercooled in the crystallizer 1 is
By pressurizing the inside of the crystallizer 1 and then releasing the pressure, the supercooled state is released and the crystal is frozen. And
By pressurizing the inside of the crystallizer 1 again, a part of the produced ice crystals is thawed to become granular ice crystals. Therefore, the pressure is removed and the granular ice crystals are grown. This gives large spherical ice crystals free of concentrate.

Description

Detailed Description of the Invention

[0001]

The present invention relates to liquid foods, cosmetics,
Alternatively, the present invention relates to a method and apparatus for concentrating a high-moisture material such as a pharmaceutical product, and more particularly to a freeze-concentration method and apparatus for concentrating a high-moisture material by freezing it and separating only water in it as ice. ..

[0002]

2. Description of the Related Art There are various methods for concentrating a material containing a large amount of water, and a freeze concentration method is known as one of them. The freeze-concentration method is a method of partially freezing high-moisture materials and separating water, which is a solvent, as pure ice crystals to condense it, and to prevent microbial contamination, deterioration of solutes, and dissipation of volatile aromatic components. It has the feature that it can be suppressed to a low level. Therefore, it is considered to be the most ideal method for concentrating high-grade foods, cosmetics, or pharmaceuticals that emphasizes nutritional components, colors, aromas, flavor components, and the like. An apparatus for performing such freeze concentration is
Generally, it comprises a cooler for precooling the feed, a crystallizer for producing and growing ice crystals, and a separator for separating the concentrate and ice crystals. There are two types of crystallizers, one is a direct cooling type and the other is an indirect cooling type. There is an indirect cooling method. The indirect cooling type crystallizer has an internal cooling crystallizer that performs heat exchange through a wall surface and an external cooling crystallizer that supplies cold heat by a material under adiabatic conditions, both of which are wine, beer, It is used for concentrating coffee.

By the way, when freeze concentration is carried out by such an apparatus, it is required that the ice crystal is grown and matured in a crystallizer sufficiently large in order to easily separate water as ice crystals from the concentrated liquid. Be done. Therefore, conventionally, in the crystallizer, the generation and growth of ice have been controlled mainly by the cooling temperature.

[0004]

However, in the case of controlling the generation and growth of ice by the cooling temperature as described above, it is required to lower the cooling temperature in order to accelerate the generation and growth of the ice. It is easy to become. Then, if the high-moisture material in the supercooled state is frozen, the ice crystals generated by the primary nucleation are likely to have a dendrite shape. Therefore, the ice obtained by growing the ice nuclei has many dendrites. Dendritic crystals tend to include solutes between crystals. Therefore, the ice produced by the crystallizer becomes ice crystals containing the concentrated liquid, and the separation efficiency between the concentrated liquid and the ice crystals in the separator deteriorates. In addition, the control based on the cooling temperature has problems such as poor responsiveness and difficulty in fine control.

The present invention has been made in view of the above problems, and an object thereof is to provide a method and an apparatus for freeze-concentrating a high-moisture material which produces ice crystals which can be easily separated from a concentrate. It is to be.

[0006]

In order to achieve this object, in the present invention, in addition to the control by cooling temperature, the change of the freezing point under pressure is utilized to control the formation of ice nuclei and the growth of ice crystals. I am trying to do it. That is, the method for freeze-concentrating a high-moisture material according to the present invention comprises freezing the high-moisture material in a supercooled state, applying a static pressure to the ice to partially thaw it, and then using the ice as a nucleus under normal pressure. It is characterized by growing ice crystals and separating the obtained ice. Freezing of the super-moisture material in the supercooled state can be performed by applying static pressure to the high-moisture material and then removing the static pressure. Further, in the freeze concentration device according to the present invention, the crystallizer for freezing the high-moisture content material and for growing the ice crystals is used as a pressure vessel, and the pressurizing device capable of controlling the pressure in the crystallizer is provided. It is characterized by being.

[0007]

As described above, when a high-moisture material in a supercooled state is frozen, dendrites or pleated ice formed by combining a plurality of dendrites is formed. And
When pressure is applied to the ice crystals, due to the freezing point depression due to the pressure, the dendritic or pleated portions of the generated ice crystals, such as the dendritic portion or the fold-shaped portion, are thawed preferentially and instantly to form granular ice. It becomes a crystal. When the pressure is removed when the ice crystals become granular in this way, and the ice is grown using the ice crystals as ice nuclei, the ice grown with the ice crystals as granules tends to have a spherical shape. The ice contained in the ice will have many spherical crystals. At this time, if the cooling temperature is appropriately controlled, large ice crystals can be grown. Then, the suspension containing the grown ice crystals is transferred to a separator, and the ice crystals are separated from the suspension, whereby a concentrated liquid can be obtained. In that case, the generated ice crystals become pure ice containing almost no concentrate, and since they become large spherical ice crystals, the separation efficiency between the concentrate and ice crystals is extremely high, and the operating cost is kept low. be able to.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. In the figure, FIG. 1 is a vertical side view showing an embodiment of a crystallizer used in a freeze concentration apparatus according to the present invention. As is clear from this figure, this crystallizer 1 is provided with a thick-walled cylindrical body 2 whose upper end is open and whose lower end is closed by a bottom wall. At the upper end opening of the crystallizer main body 2, a material take-out cap 4 fixed to the main body 2 by tightening a ground nut 3 is provided. An O-ring 5 is attached to the outer peripheral surface of the material extraction cap 4, and the O-ring 5 liquid-tightly seals between the crystallizer main body 2 and the material extraction cap 4. . The crystallizer 1 is thus formed as a pressure vessel which is sealed by the material extraction cap 4.

A material container 6 which is inserted into the internal space of the main body 2 of the crystallizer main body 2 when the upper end opening of the crystallizer main body 2 is closed by the cap 4 is attached to the lower surface of the material take-out cap 4. The material container 6 is in the form of a thin-walled pipe made of tetrafluoroethylene resin or the like, and its upper and lower ends are sealed by rubber stoppers 7 and 8, respectively. The upper rubber stopper 7 is fixed to the lower surface of the material extraction cap 4 by adhesion or the like. Therefore, by fitting the rubber stopper 7 to the upper end of the material container 6, the material container 6 can be attached to the material take-out cap 4.

A material temperature measuring thermocouple 9 is attached to the material take-out cap 4. That thermocouple 9
Penetrates through the material take-out cap 4 and the upper rubber stopper 7, and projects into the inside of the material container 6. In this way, the temperature of the material in the material container 6 is measured from the outside of the crystallizer 1. Further, on the upper part of the crystallizer main body 2, a pressure gauge 10 for detecting the pressure inside the main body 2 is provided.
Is attached.

On the other hand, a pressure pump pipe 11 communicating with the inside of the crystallizer main body 2 is connected to the lower portion of the crystallizer main body 2. A high pressure pump 12 is provided at the tip of the pressure pump pipe 11.
Is provided. In this way, by injecting a static pressure medium such as ethanol into the inside of the crystallizer main body 2 using the high pressure pump 12, a pressure is applied to the inside thereof. That is, the high-pressure pump 12 is the crystallizer 1
It is a pressurizing device that controls the internal pressure.

A cooling jacket 1 is provided on the outer circumference of the crystallizer main body 2.
3 is provided. The cooling jacket 13 has a refrigerant inlet 14 and a refrigerant outlet 15, and the temperature inside the crystallizer main body 2 is controlled by circulating the refrigerant through the inlet 14 and the outlet 15.

In addition to the crystallizer 1 and the high-pressure pump 12 as described above, the freeze concentrator is composed of a precooler for precooling the material and a separator for separating the concentrate and ice. Since these coolers and separators may be ordinary ones, their explanations are omitted here.

Next, the procedure for concentrating the high-moisture material using the freeze concentrator thus constructed will be described along with its operation. For example, when concentrating the solution, the solution is previously cooled to 2 to 0 ° C. using a precooler. Then, the solution is put into a material container 6 whose lower end is sealed with a rubber stopper 8. At this time, the material container 6 is slightly depressed so that air bubbles do not enter the solution and the solution does not leak out of the material container 6 even when the solution is frozen and volume-expanded. Then, the upper end of the material container 6 is fitted into the rubber stopper 7 fixed to the material take-out cap 4 and sealed. Thereby, the material container 6 is attached to the material take-out cap 4. On the other hand, the inside of the crystallizer main body 2 is filled with a static pressure medium such as ethanol having a low freezing temperature. In addition, the cooling jacket 13 of the crystallizer 1 circulates a refrigerant of −2 to −15 ° C.,
The inside of the main body 2 is kept at −2 to −15 ° C. And
At the upper end opening of the crystallizer main body 2, a material take-out cap 4 having a material container 6 attached is attached, and a gland nut 3 is attached.
Tighten and seal with.

When the material container 6 is set in the crystallizer 1 kept at a low temperature below the freezing point in this way, the solution enclosed in the material container 6 is gradually cooled. Therefore, the solution is in a supercooled state. Therefore, the temperature of the solution detected by the thermocouple 9 for measuring the material temperature is −
When the temperature reaches 0.5 to -10 ° C, the high pressure pump 12 is used to inject a static pressure medium into the crystallizer main body 2 to increase the internal pressure to 100 to 1500 kg / cm ² . Then, after about 1 minute in that state, the pressure is released. Then, the solution is stimulated by the pressure change, and the supercooled state is released. Therefore, the solution freezes rapidly,
Ice crystals are produced. The ice becomes crystals with many dendrites and folds. When ice is generated, the temperature of the material temperature measuring thermocouple 9 is 0 ° C. due to the heat generated by the ice. Then, the ice is aged for 3 to 20 minutes.

Next, the high pressure pump 12 is used to inject the static pressure medium into the crystallizer 1 again, and the internal pressure thereof is set to 100 to 1
Keep it at 500 kg / cm ² for 2 to 20 minutes. When the pressure in the crystallizer main body 2 is increased, the frozen solution in the material container 6 arranged inside the crystallizer main body 2 is pressurized. Then, since the freezing point is lowered by the pressure, a part of the produced ice crystal is instantly thawed. In that case, the tip portion of the ice crystal, that is, the dendritic portion or the pleated portion is preferentially thawed.
Therefore, the ice becomes granular ice crystals without dendrites or folds. After 2-20 minutes the pressure is suddenly released and the ice is allowed to grow again. When granular ice crystals are grown as ice nuclei, the grown ice tends to be large granular crystals, that is, spherical crystals. Then, solutes are unlikely to be contained in such spherical ice crystals. Therefore, the resulting ice will be ice crystals of pure water containing almost no solute.

After the ice has grown in this way, the gland nut 3 is loosened, and the material extraction cap 4 is removed from the crystallizer main body 2. Further, the material container 6 attached to the material extraction cap 4 is pulled out from the rubber stopper 7, and the suspension of the concentrated liquid and the ice crystals in the material container 6 is transferred to a separator. Then, it is filtered and washed to separate it into a concentrated liquid and ice crystals. In that case, since the generated ice crystals are spherical as described above, the concentrated liquid rarely adheres to the ice crystals. Therefore, the separation is extremely efficient.

Thus, according to this freeze concentration method,
Part of the dendritic ice crystals generated by freezing is thawed to form granular crystals, and ice is grown using the granular ice crystals as nuclei, so spherical ice crystals containing no concentrate are obtained. be able to. Moreover, since the ice crystals, which are the ice nuclei, are thawed by the pressure, the thawing does not take time unlike the case of using the temperature. And since spherical and large ice crystals are obtained, simple filtration,
The concentrated liquid can be easily separated by washing or the like. Therefore, the efficiency of separating the concentrated liquid and the ice crystals can be significantly increased. Further, according to the freeze-concentrating apparatus, it is possible to perform from the formation of ice nuclei to the thawing and the growth of ice crystals only by controlling the pressure in the crystallizer 1 by the high-pressure pump 12, so the above-mentioned freezing is performed. The device for carrying out the concentration method can be very simple.

[0019] Such a freeze concentrator was actually prototyped,
The concentration experiment was conducted using it. A coffee liquid prepared by dissolving commercially available instant coffee in distilled water was used as the material to be concentrated. Then, in order to measure the coffee liquid concentration, first, the absorbance of coffee liquid of various concentrations was measured by a spectrophotometer, and a calibration curve of the coffee liquid concentration and the absorbance was obtained. The calibration curve was as shown in FIG. As is clear from this figure, the concentration of the coffee liquor and the value of the absorbance are proportional to each other, and the distilled water having a concentration of 0 has an absorbance of 0,
The higher the concentration, the higher the absorbance. This relationship also holds for ice. A coffee liquid having a concentration of 3% was prepared as a concentrated raw material. The crystallizer main body 2 had an inner diameter of 30 mm and a length of 250 mm, and the material container 6 was a tube of tetrafluoroethylene resin having a diameter of 20 mm and a length of 170 mm. A 50% ethanol solution was used as the static pressure medium, and the ethanol solution was filled in the crystallizer main body 2. On the other hand, a 30% ethylene glycol liquid was used as the refrigerant, and the cooling jacket 13 was circulated at a flow rate of 17 liters per minute. The temperature of the refrigerant is -4 ° C and -5 ° C.
Pre-circulate the crystallizer 1 at -4 ° C or -5 ° C.
I kept it.

Under such preparations, the concentrated 3% coffee liquid was precooled to 0.5 ° C. in advance, and the coffee liquid was put into the material container 6 stoppered with the rubber stopper 8. The amount was about 45 g. Then, the material container 6 was set in the crystallizer 1 filled with the ethanol solution. Then, the change of the coffee liquid temperature was monitored by the thermocouple 9 for measuring the material temperature. Thermocouple 9 for material temperature measurement-
When the temperature reached 2.5 ° C., the ethanol solution was injected into the crystallizer 1 using the high-pressure pump 12, and the pressure in the crystallizer 1 was increased to 700 kg / cm ² . After the pressure was maintained for about 1 minute, the pressure was released to bring the inside of the crystallizer 1 to atmospheric pressure. Further, after 5 to 10 minutes, the ethanol solution was injected again into the crystallizer 1 by using the high-pressure pump 12, and the pressure in the crystallizer 1 was adjusted to 700 kg / cm ² . And it hold | maintained in that state for 5 minutes. Then, the pressure was suddenly released, and ice was grown under normal pressure. After a lapse of 10 to 40 minutes, the material container 6 was taken out, the material inside thereof was transferred to a separator, suction-filtered by the separator, and washed with 10 ml of water at 0 ° C. In this way, the concentrate was separated into ice crystals. Then, with respect to the obtained ice, its production amount and absorbance were measured. For comparison, the same experiment was conducted without applying static pressure by the high-pressure pump 12. The results are shown in Table 1.

[0021]

[Table 1]

The low absorbance of ice means that the amount of coffee incorporated in the ice crystals is small. Therefore, it can be said that the larger the amount of the obtained ice crystals and the lower the absorbance thereof, the more pure the ice and the more efficiently the ice was separated from the concentrated liquid. As is clear from Table 1, the amount of ice generated in the one thawed using pressure is slightly smaller than that in the case where pressure is not used, but the separation efficiency of the concentrated liquid and the obtained ice The quality is extremely good. For example, a case of cooling to -4 ° C and treating for 40 minutes without applying pressure, a case of applying pressure for 45 minutes, or a treatment at -5 ° C for 20 minutes without applying pressure. The amount of ice generated is almost the same in the case and the case where the pressure is applied for 25 minutes, but the absorbance is much smaller when the pressure is applied. That is, it can be seen that almost pure ice is separated and the concentration efficiency is enhanced even with the same treatment time.

It should be noted that, in the above-mentioned embodiments, the freeze-concentration device was described as a laboratory device, but in industrial implementation, for example, a large number of material containers are installed in one crystallizer and a large amount of them are simultaneously prepared. It goes without saying that the material is processed, and the pre-cooling and the separation are continuously performed. In such a case, it may be possible to use a cooling fluid as a static pressure medium introduced into the crystallizer so that pressurization and cooling of the material are performed simultaneously.

[0024]

As is apparent from the above description, according to the present invention, after freezing a high-moisture material, a part of the ice crystals is once thawed to form granular ice crystals, which are then used as ice nuclei. Since ice crystals are allowed to grow as described above, the obtained ice crystals are spherical crystals that do not easily contain a concentrated liquid within and between the crystals. Therefore, the efficiency of separating the concentrated liquid and the ice crystals is increased, and the cost for the separation can be significantly reduced. Moreover, since the ice crystals, which are the ice nuclei, are thawed by applying pressure, the thawing is instantaneously performed. Therefore, the processing does not take much time. Further, since a pressure vessel is used in place of the conventional crystallizer and the pressure in the crystallizer may be controlled by a high-pressure pump or the like, the structure of the freeze concentration device does not become complicated. Therefore, the device can be obtained at low cost.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view showing an example of a crystallizer used in a freeze concentration apparatus according to the present invention.

FIG. 2 is a graph showing the relationship between the solute concentration and the absorbance, which was determined for an experiment performed using the crystallizer.

[Explanation of symbols]

 1 Crystallizer 2 Crystallizer main body 4 Material extraction cap 6 Material container 9 Thermocouple for measuring material temperature 10 Pressure gauge 12 High pressure pump 13 Cooling jacket

Claims (3)

[Claims] 1. A high-moisture material in a supercooled state is frozen, and static pressure is applied to the ice to partially thaw it, and then ice crystals are grown under normal pressure using the ice as a nucleus to obtain ice crystals. A method for freeze-concentrating a high-moisture material, characterized in that the high-moisture material is concentrated by separating ice. 2. The high-moisture material in the supercooled state is frozen by applying static pressure to the high-moisture material and then removing the static pressure. Freeze concentration method. 3. A freeze concentration apparatus comprising a crystallizer for freezing a high-moisture material and growing ice crystals thereof, and a separator for separating the ice crystals from a concentrated liquid; the crystallizer being a pressure vessel. And a freeze-concentrator for high-moisture material, which is provided with a pressurizing device capable of controlling the pressure in the crystallizer.