JP6915226B2 - Heat treatment method of microorganisms - Google Patents

Description

The present invention relates to a method for heat-treating microorganisms, and more particularly to a method for heat-treating microorganisms that can be used for foods and drinks, pharmaceuticals, and the like.

Probiotic foods are foods containing microorganisms such as bacteria that are said to have a positive effect on the human body when taken into the human body. For example, probiotic foods include yogurt containing live lactic acid bacteria.

Since the dead cells of microorganisms that can be used in probiotic foods contain active ingredients that have a positive effect on the human body depending on the type of microorganisms, the microorganisms contained in probiotic foods are dead cells. There may be. In addition, when the microorganism contained in the probiotic food is a dead cell, the microorganism does not act in the probiotic food, so that there is an advantage that the quality of the probiotic food can be kept stable. be.

For example, Japanese Patent Application Laid-Open No. 2008-245569 discloses Lactobacillus paracasei KW311 strain, which is a kind of lactic acid bacterium, as a bacterium that can be used in probiotic foods. Japanese Unexamined Patent Publication No. 2008-245569 discloses that foods and drinks having an antiallergic function can be produced by blending killed cells of the heat-sterilized Lactobacillus paracasei KW311 strain into foods and drinks.

Killed cells of microorganisms used in probiotic foods are obtained, for example, by heat sterilizing living microorganisms (live bacteria). However, when live bacteria are sterilized by heating, dead cells and the like aggregate to form aggregates in a liquid containing live bacteria. When the agglomerates formed by heat sterilization are added to the probiotic food as it is, the consumer may feel roughness due to the agglomerates and the texture of the probiotic food may be deteriorated.

In order to prevent deterioration of texture in probiotic foods, it is desirable to suppress the progress of aggregation of live bacteria during heat sterilization to prevent the formation of huge aggregates. The smaller the agglomerates, the less likely the consumer will feel the roughness due to the agglomerates, and thus the deterioration of the texture of the probiotic food can be prevented. In order to suppress the progress of aggregation, the temperature at the time of heat sterilization may be set to, for example, a temperature of 100 ° C. or lower. By lowering the temperature during heat sterilization, it is possible to suppress the progress of denaturation of proteins that form microorganisms, which is the cause of the formation of aggregates.

When the sterilization temperature is 100 ° C. or lower, hot water heating is used. Hot water heating is, for example, a method of heating an object to be heated by circulating hot water heated to a predetermined temperature (100 ° C. or less) around the object to be heated. Note that heat sterilization includes steam heating using steam at 100 ° C. or higher, but the method using steam heating is not appropriate from the viewpoint of preventing the progress of aggregation.

However, hot water heating has a problem that it takes time to heat the object to be heated to a predetermined temperature, and the efficiency of heat sterilization is poor. Further, when the liquid containing live bacteria is sterilized by heating using hot water heating, the substantially heating time of the liquid containing live bacteria may become long, and the formation of agglomerates containing dead cells or the like may proceed. ..

Japanese Unexamined Patent Publication No. 2008-2455569

Therefore, an object of the present invention is to provide a method for heat-treating microorganisms that can prevent the formation of aggregates.

The method for heat-treating microorganisms according to the present disclosure includes a) step and b) step. a) In the step, the liquid containing microorganisms is heated to a predetermined sterilization temperature using vacuum vapor. In the b) step, the temperature of the liquid containing the microorganisms heated by the a) step is maintained at the sterilization temperature using vacuum steam for a predetermined time.

Preferably, the method for heat treating microorganisms according to the present disclosure further comprises step c). c) The step is to culture the microorganisms. In the a) step, the liquid containing the microorganisms cultured in the c) step is heated.

Preferably, in the method for heat-treating microorganisms according to the present disclosure, the c) step includes a c-1) step and a c-2) step. In step c-1), the medium is inoculated with microorganisms and the microorganisms inoculated in the medium are cultured. In step c-2), a concentrated solution of microorganisms is produced from the medium containing the microorganisms cultured in step c-1). a) The step heats the concentrate.

Preferably, in the method for heat-treating microorganisms according to the present disclosure, the a) step includes a-1) step and a-2) step. In the step a-1), when the temperature of the liquid containing microorganisms is a predetermined intermediate temperature lower than the sterilization temperature, the liquid containing microorganisms is heated using vacuum steam having a temperature equal to or higher than the intermediate temperature and lower than the sterilization temperature. In the a-2) step, when the temperature of the liquid containing microorganisms is equal to or higher than the intermediate temperature and lower than the sterilization temperature, the liquid containing microorganisms is heated using vacuum vapor having a temperature equal to or higher than the sterilization temperature.

Preferably, the intermediate temperature is the agglomerate formation temperature at which agglomerates are formed in a liquid containing microorganisms.

Preferably, in the method for heat-treating microorganisms according to the present disclosure, the steps a) and b) adjust the temperature of the vacuum steam by changing the air pressure of the vacuum steam.

Preferably, in the method for heat-treating microorganisms according to the present disclosure, step a) uses a jacket tank including a tank portion into which a liquid containing microorganisms is charged and a jacket portion having an internal space to which vacuum vapor is supplied. , The liquid containing microorganisms is heated and the internal space is depressurized to a pressure lower than the atmospheric pressure before supplying the vacuum vapor to the internal space.

According to the present disclosure, it is possible to prevent the formation of agglomerates when the microorganisms are heat-treated.

It is a flowchart which shows the heat treatment method of the microorganism which concerns on embodiment of this invention. It is the schematic of the structure of the heating apparatus used in the heating step shown in FIG. It is a graph which shows the time change of the temperature in the concentrated solution of bifidobacteria which concerns on Example 2 of this invention. It is a graph which shows the time change of the temperature in the concentrated solution of bifidobacteria which concerns on Comparative Example 2 of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are designated by the same reference numerals, and the description thereof will not be repeated.

In the method for heat-treating microorganisms according to the present embodiment, the microorganisms are cultivated to generate a culture solution, the produced culture solution is concentrated to generate a concentrated solution, and the microorganisms contained in the concentrated solution are subjected to vacuum steam. It is a method of heating.

Since the microorganisms contained in the concentrate are sterilized by heating the concentrate of microorganisms using the method for heat-treating microorganisms according to the present embodiment, the heat-treated concentrate can be added to foods and drinks. can.

In this embodiment, the microorganism is a microorganism that can be used in probiotic foods and pharmaceuticals. That is, in the present embodiment, the microorganism to be heat-treated is a microorganism that is considered to have a positive effect on the human body by being taken into the human body.

Microorganisms that can utilize the method for heat-treating microorganisms according to the present embodiment are, for example, bacteria such as lactic acid bacteria and bifidobacteria. Examples of lactic acid bacteria include Lactobacillus, Streptococcus, and Lactococcus, which are mainly used for producing fermented milk. Examples of lactic acid bacteria include Leuconostoc and Pediococcus, which are used in the production of meat products and dairy products other than fermented milk. Bifidobacterium is a bacterium belonging to the genus Bifidobacterium.

Vacuum steam is a type of water vapor. Specifically, vacuum steam refers to steam having a temperature of less than 100 ° C. and a pressure lower than atmospheric pressure. In the present embodiment, the atmospheric pressure means the standard atmospheric pressure (1 atm = 101325 Pa). That is, in the present embodiment, since the concentrated liquid is heated at a temperature lower than 100 ° C., the formation of agglomerates is suppressed in the concentrated liquid.

FIG. 1 is a flowchart showing a method for heat-treating microorganisms according to the present embodiment. As shown in FIG. 1, the method for heat-treating microorganisms according to the present embodiment includes a culture step (step S1), a concentration step (step S2), and a heat treatment step (step S3).

Hereinafter, each step shown in FIG. 1 will be described in detail by taking the case where the microorganism is bifidobacteria as an example.

{Culture step (step S1)}
First, in the culturing step (step S1), bifidobacteria are cultivated. The medium used for culturing bifidobacteria may contain a nutrient source capable of growing bifidobacteria. The medium may contain at least one of milk-derived components, yeast extract, soybean extract, peptone, sugars, and minerals.

Milk-derived components include, for example, whey, casein, skim milk powder, whey protein concentrate (WPC), whey protein isolate (WPI) and the like. Peptone is, for example, trypticase soybeans. Examples of saccharides include monosaccharides such as glucose and disaccharides such as lactose. As the mineral, for example, whey mineral or the like can be used. The medium is sterilized, for example, at 121 ° C. or higher for 1 to 10 minutes. Then, the sterilized medium is inoculated with bifidobacteria, and the bifidobacteria are neutralized and cultured. When the bifidobacteria are neutralized and cultured, the temperature of the medium and the pH of the medium are not particularly limited as long as they are suitable for the growth of the bifidobacteria.

In cultures of bifidobacteria after the culture with culture process (step S1), the concentration of bifidobacteria, ^{preferably, 10 7 ~10 11 cfu / mL} .

When culturing a microorganism other than bifidobacteria, a medium suitable for the growth of the microorganism to be cultured may be selected. Regarding the temperature and pH at the time of culturing, it is sufficient to maintain the conditions suitable for the growth of the microorganism to be cultivated.

{Concentration step (step S2)}
After the culturing step (step S1), the culture solution of bifidobacteria is concentrated to produce a concentrated solution of bifidobacteria (step S2).

Centrifugation is used to concentrate the culture of bifidobacteria. For centrifugation, for example, after cooling the bifidobacteria culture solution to a temperature of 10 ° C., a centrifugal force of 5,000 to 20,000 × G is applied to the bifidobacteria culture solution, and the residence time is about 2 to 10 minutes. Do as.

The centrifuge used in the concentration step (step S2) is preferably a continuous type in order to efficiently centrifuge a large amount of bifidobacteria culture solution. Specifically, the continuous centrifuge provides liquid supply (supply of bifidobacteria culture solution), deflation (acquisition of bifidobacteria-concentrated lower layer bifidobacteria culture solution), and discharge (bifidobacterium culture solution). It is possible to carry out in parallel with the discharge of the supernatant of the bacterial culture solution). It should be noted that this embodiment does not prevent the use of a centrifuge other than the continuous type.

By the concentration step (step S2), the bifidobacteria culture solution is separated into a lower layer bifidobacteria culture solution containing bifidobacteria at a high concentration and an upper layer light solution (supernatant) containing almost no bifidobacteria. By recovering the lower layer bifidobacteria culture solution as a bifidobacteria concentrate, it is possible to recover the bifidobacteria contained in the bifidobacteria culture solution with high efficiency.

The recovery rate of bifidobacteria in the concentration step (step S2) is preferably 95% or more. The concentration of bifidobacteria in the concentrate of bifidobacteria produced in the concentration step (step S2) is, for example, 10 ⁸ to 10 ¹² cfu / mL.

When the culture solution of a microorganism other than bifidobacteria is subjected to centrifugation, the conditions for centrifugation may be changed as appropriate. Specifically, the centrifugal force and the residence time applied to the culture solution of the microorganisms other than bifidobacteria may be appropriately changed so that the microorganisms other than bifidobacteria can be concentrated at a recovery rate of 95% or more.

{Heating step (step S3)}
As shown in FIG. 1, the concentrated solution of bifidobacteria produced in the concentration step (step S2) is heat-treated using vacuum steam (step S3). The heating step (step S3) is a step of heating the concentrated solution of bifidobacteria to a predetermined target temperature and maintaining the concentrated solution of bifidobacteria heated to a predetermined target temperature for a predetermined time. The target temperature is, for example, a sterilization temperature at which bifidobacteria contained in the concentrate can be sterilized. As a result, the bifidobacteria contained in the concentrate are sterilized, and a concentrate of dead bifidobacteria is produced. Bifidobacterium killed cell concentrates are used as raw materials for probiotic foods and pharmaceuticals.

FIG. 2 is a schematic diagram of the configuration of the heat treatment apparatus 100 used in the heating step (step S3) shown in FIG. As shown in FIG. 2, the heat treatment device 100 includes a vacuum steam generator 1, a jacket tank 2, pipes 3 to 5, and a control device 6.

The vacuum steam generator 1 is a device that generates vacuum steam. The jacket tank 2 is a container for heat-treating the concentrated solution of bifidobacteria. The pipe 3 connects the vacuum steam generator 1 and the internal space 22A of the jacket portion 22 in the jacket tank 2. One end of the pipe 4 is connected to the bottom of the internal space 22A of the jacket portion 22. Although not shown in FIG. 2, the other end of the pipe 4 is a discharge port for discharging aggregated water in the internal space 22A. One end of the pipe 5 is connected to a joint (not shown) provided in the pipe 4, and the other end of the pipe 5 is connected to the vacuum steam generator 1. The pipe 5 is used for the vacuum steam generator to recover the vacuum steam that has flowed into the pipe 4. The control device 6 is a vacuum steam from the vacuum steam generator 1 to the internal space 22A based on the temperature of the concentrated solution of Bifizus bacteria measured by the temperature sensor 24 and the atmospheric pressure of the vacuum steam measured by the pressure sensor 25. Control the supply of. The temperature sensor 24 and the pressure sensor 25 will be described later.

The jacket tank 2 includes a tank portion 21, a jacket portion 22, a stirring device 23, a temperature sensor 24, and a pressure sensor 25.

The tank portion 21 is a cylindrical container into which a concentrated solution of bifidobacteria is charged. The jacket portion 22 is a hollow container that covers the outer peripheral side surface and the bottom surface of the tank portion 21. The hollow portion of the jacket portion 22 is the internal space 22A. In the internal space 22A, the vacuum steam supplied from the vacuum steam generator 1 condenses in water. The tank portion 21 and the jacket portion 22 are made of a metal having high thermal conductivity or the like, and are thermally connected to each other.

The stirring device 23 is a stirring blade that stirs the concentrated solution of bifidobacteria charged into the tank portion 21. The temperature sensor 24 measures the temperature of the concentrated solution of bifidobacteria charged into the tank unit 21. The pressure sensor 25 is arranged in the internal space 22A and measures the air pressure of the vacuum steam supplied to the internal space 22A.

As shown in FIG. 1, the heating step (step S3) includes a charging step (step S31), a depressurizing step (step S32), a temperature raising step (step S33), and a temperature maintaining step (step S34). .. Hereinafter, the heating step (step S3) will be described in detail with reference to FIGS. 1 and 2 by taking as an example a case where the concentrated solution of bifidobacteria is maintained at 80 ° C. for 10 minutes.

{Charging step (step S31) and depressurizing step (step S32)}
First, the concentrated solution of bifidobacteria produced in step S2 is charged into the tank section 21 (step S31). The internal space 22A of the jacket portion 22 is decompressed to a pressure lower than the atmospheric pressure by using a decompression device or a vacuum steam generator 1 (not shown) (step S32).

When the internal space 22A is not depressurized, the influence of the atmosphere (nitrogen and oxygen) on the atmospheric pressure and temperature in the internal space 22A becomes large, so that it becomes difficult to adjust the temperature of the vacuum steam in the internal space 22A. By decompressing the internal space 22A in advance, it becomes easy to adjust the temperature of the vacuum steam in the internal space 22A to a desired temperature.

{Temperature rise step (step S33)}
After depressurizing the internal space 22A of the jacket portion 22 in step S32, vacuum vapor is supplied to the internal space 22A to heat the concentrated solution of bifidobacteria charged into the tank portion 21 (step S33). In step S33, the temperature of the bifidobacteria concentrate is raised to the target temperature (80 ° C.). Further, in step S33, the concentrated solution of bifidobacteria is stirred by rotating the stirring blade of the stirring device 23. By stirring the bifidobacteria concentrate, the bifidobacteria concentrate charged into the tank portion 21 can be heated substantially uniformly.

The temperature of the vacuum steam in the internal space 22A of the jacket portion 22 is adjusted according to the temperature of the concentrated solution of bifidobacteria charged into the tank portion 21. Specifically, when the temperature of the bifidobacteria concentrate charged into the tank section 21 is below the intermediate temperature, which is lower than the target temperature, vacuum vapor having a temperature above the intermediate temperature and below the target temperature is used. Use to heat the bifidobacteria concentrate. Then, when the temperature of the bifidobacteria concentrate becomes equal to or higher than the intermediate temperature, the bifidobacteria concentrate is heated by using vacuum vapor having a target temperature or higher. In this way, after heating with vacuum steam at an intermediate temperature, the concentrated solution of Bifizus bacterium is quickly heated by heating with vacuum steam having a temperature equal to or higher than the intermediate temperature and lower than the target temperature. At the same time, it becomes easy to maintain the temperature of the concentrated solution of Bifizus bacterium at the target temperature.

The intermediate temperature is preferably the agglomerate formation temperature (for example, 60 ° C.) at which agglomerates are formed in the concentrated solution of bifidobacteria. This makes it possible to prevent the temperature rise of the bifidobacteria from slowing down near the agglomerate formation temperature when the concentrated solution of the bifidobacteria is heated. When heating the bifidobacteria concentrate, the heating time near the agglomerate formation temperature can be shortened, so that the formation of agglomerates can be prevented when the bifidobacteria concentrate is heated.

In the present embodiment, the target temperature is set to 80 ° C. and the intermediate temperature is set to 60 ° C. at the start of heating the concentrated solution of bifidobacteria. At the start of heating the bifidobacteria concentrate, the temperature of the bifidobacteria concentrate is below the intermediate temperature (60 ° C.), so the temperature of the vacuum vapor in the internal space 22A of the jacket portion 22 is 60 ° C. or higher and 65 ° C. or lower. Is adjusted to. When the temperature of the concentrated solution of bifidobacteria becomes an intermediate temperature (60 ° C.) or higher, the temperature of the vacuum vapor in the internal space 22A is adjusted to 80 ° C. or higher and 85 ° C. or lower.

The setting of the target temperature (80 ° C.) and the intermediate temperature (60 ° C.) in the heat treatment of the concentrated solution of bifidobacteria is an example, and a temperature different from the above temperature may be set as the target temperature and the intermediate temperature.

Hereinafter, the temperature adjustment of the vacuum steam in the internal space 22A of the jacket portion 22 will be specifically described. The internal space 22A of the jacket portion 22 is controlled to a pressure lower than the atmospheric pressure by a decompression device or a vacuum steam generator 1 (not shown). Since the condensation temperature of the vacuum vapor is uniformly determined by the atmospheric pressure, when the vacuum vapor is put into the space where the pressure is controlled, the temperature of the vacuum vapor becomes the condensation temperature at that pressure.

Therefore, the temperature of the vacuum steam in the internal space 22A can be adjusted by controlling the air pressure in the internal space 22A of the jacket portion 22. The air pressure in the internal space 22A is controlled by adjusting the flow rate of the vacuum steam supplied to the internal space 22A.

Next, the principle that the concentrated solution of bifidobacteria is heated by vacuum steam will be described in detail. The concentrated solution of bifidobacteria charged into the tank portion 21 is heated by the latent heat released when the vacuum vapor is condensed into the liquid water in the internal space 22A of the jacket portion 22.

The temperature of the concentrated solution of bifidobacteria charged into the tank portion 21 is, for example, 4 ° C. at the start of heating (immediately after centrifugation). Since the tank portion 21 and the jacket portion 22 are in thermal contact with each other, the vacuum vapor is cooled by the concentrated solution of bifidobacteria charged into the tank portion 21 in the internal space 22A of the jacket portion 22. As the vacuum vapor cools, it releases latent heat and condenses into liquid water. The latent heat released by the condensation of the vacuum vapor is transmitted to the tank portion 21 and heats the concentrated solution of bifidobacteria.

The liquid water generated by the condensation of the vacuum vapor moves to the bottom of the internal space 22A of the jacket portion 22 and is discharged from the pipe 5. The condensation of vacuum steam acts to lower the air pressure in the internal space 22A and lower the temperature in the internal space 22A. However, as described above, the air pressure in the internal space 22A is controlled by adjusting the flow rate of the vacuum steam. Therefore, since the supply of the vacuum steam to the internal space 22A is continued, the heating of the concentrated solution of bifidobacteria is continued by the latent heat released from the vacuum steam.

The bifidobacteria concentrate is heated by the latent heat released from the vacuum steam, but the temperature of the steam is lower than 100 ° C. Therefore, the concentrated solution of bifidobacteria is not heated at a temperature of 100 ° C. or higher. In addition to the heating method using vacuum steam, there is hot water heating as a method of heating the concentrated solution of bifidobacteria to a temperature of 100 ° C. or lower. However, by using the latent heat released from the vacuum steam to heat the concentrated solution of bifidobacteria, it is possible to heat the concentrated solution of bifidobacteria in a shorter time than when heating the concentrated solution of bifidobacteria by hot water heating. The reason will be explained.

Latent heat is, for example, the thermal energy released or absorbed when a substance changes from one phase (eg, gas) to another (eg, liquid). When the vacuum vapor undergoes a phase transition to liquid water, latent heat is released from the vacuum vapor. The latent heat released from the vacuum vapor varies depending on the pressure of the vacuum vapor, but is larger than the sensible heat of liquid water and is about five times or more the sensible heat of liquid water. The sensible heat of liquid water is the heat released when the temperature of liquid water drops, or the heat absorbed when the temperature of liquid water rises.

Hot water heating is a heating method using the sensible heat of liquid water. Specifically, it is a method of heating a concentrated solution of bifidobacteria by filling the internal space 22A of the jacket portion 22 with hot water having a predetermined temperature. be. As mentioned above, the latent heat of vacuum steam is much larger than the sensible heat of hot water. Therefore, the method of heating using the latent heat released from the vacuum steam can quickly heat the concentrated solution of bifidobacteria in a shorter time than the method of heating using sensible heat (hot water heating). Become.

Further, when heating is performed using vacuum steam, the stirring load can be reduced. The reason for this will be described below.

As described above, hot water heating requires more time to reach the target temperature than heating with vacuum steam. When hot water heating is used, the temperature of the concentrated solution of bifidobacteria becomes close to the agglomerate formation temperature for a long time, so that agglomerate formation proceeds. That is, when hot water heating is used, huge aggregates are likely to be generated in the concentrated solution of bifidobacteria. In order to crush the huge agglomerates produced, it is necessary to increase the agitation load. That is, when hot water heating is used, it is necessary to set the tip speed of the stirring blade to a speed at which the agglomerates can be crushed.

On the other hand, when the bifidobacteria are heated using vacuum steam, as described above, the time around the agglomerate formation temperature is shortened, so that the agglomerate formation is suppressed. Since it is not necessary to crush the agglomerates by stirring, the stirring load can be reduced (the tip speed of the stirring blade can be reduced). For example, by heating with vacuum steam, it becomes possible to heat a concentrated liquid having a high viscosity that cannot be agitated under a high load.

{Temperature maintenance step (step S34)}
When the bifidobacteria concentrate charged into the tank portion 21 rises to the target temperature by the temperature raising step (step S33), the bifidobacteria concentrate is kept at the target temperature for a predetermined time while continuing the rotation of the stirring blade. Maintain (step S34). In the present embodiment, the air pressure of the vacuum vapor in the internal space 22A of the jacket portion 22 is controlled so that the concentrated solution of bifidobacteria maintains the target temperature of 80 ° C. for 10 minutes.

As described above, vacuum steam is also used in the temperature maintenance step (step S34). As a result, it becomes easier to maintain the temperature of the concentrated solution of bifidobacteria at 80 ° C. as compared with the case of using hot water heating. Hereinafter, the reason will be described by taking the case where the target temperature is set to 80 ° C. as an example.

In hot water heating, when the temperature of the concentrated solution of bifidobacteria heated to the target temperature (80 ° C.) exceeds 80 ° C., hot water having a temperature of 80 ° C. or lower is supplied to the jacket portion 22 to provide hot water in the internal space 22A. It is necessary to lower the temperature of. However, since the temperature of the hot water in the internal space 22A changes due to the convection of the hot water, it takes time for the temperature of the hot water to reach 80 ° C. or lower in the entire internal space 22A.

On the other hand, when vacuum steam is used, the temperature of the vacuum steam in the internal space 22A is controlled by controlling the air pressure of the vacuum steam in the internal space 22A. Since the vacuum steam is a gas, the change in the air pressure of the vacuum steam in the internal space 22A is much faster than the change in the temperature of the hot water when the internal space 22A is filled with hot water. The temperature of the vacuum vapor in the internal space 22A can be diligently adjusted according to the temperature of the concentrated solution of bifidobacteria. Therefore, when vacuum steam is used, it becomes easier to maintain the temperature of the concentrated solution of bifidobacteria at the target temperature (80 ° C.) as compared with the case where hot water heating is used.

In the temperature maintenance step (step S34), the heating step (step S3) is completed by maintaining the temperature of the concentrated solution of bifidobacteria at the target temperature for a predetermined time. The concentrated solution of bifidobacteria after the heating step (step S3) is used as a raw material for probiotic foods and pharmaceuticals.

When the concentrated solution of microorganisms other than bifidobacteria is heated by the heating step (step S3), the heating temperature of the concentrated solution of microorganisms other than bifidobacteria and the time for maintaining the concentrated solution at the heating temperature are set to the concentrated solution. It is appropriately changed depending on the type of microorganisms contained. For example, when the concentrated solution of microorganisms is sterilized by the heating step (step S3), the conditions under which the microorganisms are sterilized by heating differ depending on the microorganisms.

As described above, in the method for heat-treating microorganisms according to the present embodiment, vacuum steam is used to heat the microbial concentrate, and vacuum steam is used to set the temperature of the microbial concentrate at a predetermined temperature for a certain period of time. maintain.

Since the vacuum vapor supplied to the internal space 22A of the jacket portion 22 has a temperature lower than 100 ° C., the microbial concentrate is not heated to 100 ° C. or higher in the heating step (step S3). Therefore, since it is possible to suppress the progress of heat-induced denaturation of the protein forming the microorganism and the protein derived from the medium, it is possible to suppress the progress of the formation of aggregates in the concentrated solution of the microorganism.

Further, by using the latent heat released by the condensation of vacuum steam, the concentrated solution of microorganisms can be heated to a target temperature more quickly than when it is used by heating with hot water. As a result, the substantially heating time of the concentrated solution of bifidobacteria can be shortened, so that the formation of agglomerates can be further prevented.

{Modification example}
In the above embodiment, an example of heat sterilizing the microorganisms contained in the concentrate has been described. However, the microorganisms contained in the concentrate may be inactivated by using the method for heat-treating microorganisms according to the above embodiment.

In the above embodiment, an example of heating a concentrated solution of microorganisms using vacuum steam has been described, but the present invention is not limited to this. In the heat treatment step (step S3), the culture solution of the microorganism may be heated as it is using vacuum steam without being subjected to centrifugation. That is, the liquid containing the cultured microorganisms may be heated using vacuum vapor. Alternatively, a liquid in which foods and drinks containing microorganisms are dispersed in water at a constant concentration may be heated using vacuum steam. That is, the liquid heated in the heating step (step S3) may be a liquid containing microorganisms.

In the above embodiment, an example in which the temperature of the vacuum steam is adjusted in two stages of the intermediate temperature or more and the target temperature or less and the target temperature or more in the temperature raising step (step S33) has been described. However, in the temperature raising step (step S33), the temperature of the vacuum steam may be adjusted in three or more steps, or the temperature of the vacuum steam may be adjusted to the target temperature from the beginning.

In the above embodiment, microorganisms (lactic acid bacteria, bifidobacteria, etc.) that can be used as raw materials for probiotic foods and pharmaceuticals have been described as examples, but the present invention is not limited to this. The liquid containing microorganisms such as other bacteria may be heat-treated by the heating step (step S3).

In the concentration step (step S2) of the above embodiment, an example in which a centrifugation method is used to generate a concentrate of bifidobacteria from the culture solution of bifidobacteria after culturing has been described, but the present invention is not limited thereto. If a concentrated solution of bifidobacteria can be produced from the culture solution of bifidobacteria after culturing, a method other than the centrifugation method (for example, a membrane separation method or the like) may be used.

In the above embodiment, an example of heat sterilizing a concentrated solution of bifidobacteria has been described. However, when heating a concentrate containing microorganisms other than bifidobacteria, the target temperature (sterilization temperature) is appropriately changed according to the type of microorganisms contained in the concentrate. When the intermediate temperature is set to the agglomerate formation temperature, the intermediate temperature may be appropriately changed based on the type of microorganisms contained in the concentrated solution, the components contained in the concentrated solution, and the like.

In the above embodiment, in the culture step (step S1) and the concentration step (step S2), a concentrate containing only bifidobacteria is prepared, and in the heating step (step S3), the target temperature of the concentrate is sterilized. The case of temperature has been described. However, the concentrate may contain two or more types of microorganisms. In this case, in the heating step (step S3), the target temperature of the concentrate may be a temperature at which at least one of the microorganisms contained in the concentrate is sterilized. Further, the target temperature may be a temperature at which at least one of the microorganisms contained in the concentrate is inactivated.

Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited to the following examples.

[Evaluation test 1]
The size of the agglomerates when the microbial concentrate was heated using vacuum vapor was verified. Specifically, the result of Example 1 in which the concentrated solution of bifidobacteria is heated using vacuum steam of less than 100 ° C. and Comparative Example 1 in which the concentrated solution of bifidobacteria is heated using ordinary steam of 100 ° C. or higher. Was compared with the results of.

{Example 1}
A heat-treated concentrate of bifidobacteria was produced according to the procedure shown below.

1) A culture solution of bifidobacteria was obtained by neutralizing and culturing a bifidobacteria OLB6378 strain, which is a type of bifidobacteria, using a casein decomposition medium. The casein decomposition medium is a medium using enzymatically decomposed casein as a protein source. The Bifidobacterium OLB6378 strain is a Bifidobacterium bifidum OLB6378 strain, which has been deposited at the National Institute of Technology and Evaluation Patent Microorganisms Depositary Center under the accession number "NITE BP-31".

2) Using a centrifuge (model name: CFD130) manufactured by GEA Westfalia Separator, 1500 kg of a culture solution of bifidobacteria was centrifuged (at 4 ° C. and 10,000 G for 3 minutes). As a result, 1457 kg of the supernatant was removed from 1500 kg of the culture solution of bifidobacteria to obtain a cell concentrate fraction (43 kg).

The bacterial cell concentrate fraction obtained by centrifugation corresponds to the bifidobacteria concentrate before heat treatment according to Example 1. In the concentrated solution of bifidobacteria before the heat treatment according to Example 1, the cell concentration of bifidobacteria was 2 × 10 ¹¹ cfu / mL. The cell concentration of bifidobacteria was measured using the method described in "Food Sanitation Inspection Guideline Microorganisms Edition (1990)" published by the Japan Food Sanitation Association.

3) The concentrated solution of bifidobacteria before heat treatment according to Example 1 was put into a 50 L tank manufactured by Osaka Sanitary Co., Ltd. The temperature of the bifidobacteria concentrate according to Example 1 was 6.2 ° C. before the start of heating.

Then, vacuum steam was charged into the jacket portion of the 100 L tank, and the concentrated solution of bifidobacteria according to Example 1 was heated to 80 ° C. while stirring the concentrated solution of bifidobacteria charged into the 100 L tank. The stirring conditions were that the rotational speed of the rotor was 120 rpm and the tip speed of the rotor was 0.88 m / sec. In heating the concentrated solution of bifidobacteria according to Example 1, the temperature of the vacuum vapor in the jacket portion was adjusted to 60 ° C. or higher and 65 ° C. or lower until the temperature of the concentrated solution reached 60 ° C. When the temperature of the concentrated solution was 60 ° C. or higher and 80 ° C. or lower, the temperature of the vacuum vapor in the jacket portion was adjusted to 80 ° C. or higher and 85 ° C. or lower.

4) After heating the concentrated solution of bifidobacteria to 80 ° C., the concentrated solution of bifidobacteria was held at 80 ° C. for 10 minutes. As a result, a concentrated solution of bifidobacteria after the heat treatment according to Example 1 was obtained.

{Comparative example 1}
As Comparative Example 1, a heat treatment of a concentrated solution of bifidobacteria was performed using ordinary steam at 100 ° C. or higher.

1) Bifidobacterium bifidum OLB6378 strain, which is a kind of bifidobacteria used in Example 1, was cultured by the culture method described in Example 1 above, and the bifidobacteria according to Comparative Example 1 were cultured. A culture solution was obtained.

2) Using the centrifugation method described in Example 1, a cell concentrate fraction (43 kg) according to Comparative Example 1 was obtained from the culture solution of bifidobacteria according to Comparative Separation 1. The bacterial cell concentrate fraction according to Comparative Example 1 corresponds to the bifidobacteria concentrate before heat treatment according to Comparative Example 1. In the concentrated solution of bifidobacteria before the comparative treatment according to Comparative Example 1, the cell concentration was 2 × 10 ¹¹ cfu / mL. The method for measuring the cell concentration in Comparative Example 1 is the same as the method for measuring the cell concentration in Example 1.

The concentrated solution of bifidobacteria before heat treatment according to Comparative Example 1 was put into a 50 L tank manufactured by Iwai Kogyo Co., Ltd. The temperature of the concentrated solution of bifidobacteria according to Comparative Example 1 was 6.2 ° C. before the start of heating.

Steam of 110 ° C. or higher and 130 ° C. or lower is charged into the jacket portion of the 50L tank, and the concentrated solution of bifidobacteria according to Comparative Example 1 is heated to 80 ° C. while stirring the concentrated solution of bifidobacteria charged in the 50L tank. did. The stirring conditions were that the rotational speed of the rotary blade was 250 rpm and the tip speed of the rotary blade was 1.31 m / sec.

After heating the concentrated solution of bifidobacteria according to Comparative Example 1 to 80 ° C., the concentrated solution of bifidobacteria according to Comparative Example 1 was held at 80 ° C. for 10 minutes. As a result, a concentrated solution of bifidobacteria after heat treatment according to Comparative Example 1 was obtained.

{evaluation}
Aggregates in each of the concentrated solution of bifidobacteria before heat treatment according to Example 1, the concentrated solution of bifidobacteria after heat treatment according to Example 1, and the concentrated solution of bifidobacteria after heat treatment according to Comparative Example 1. The size was measured.

A method for measuring agglomerates will be described by taking as an example a concentrated solution of bifidobacteria after heat treatment according to Example 1. A dispersion was obtained by dispersing the concentrated solution of bifidobacteria after the heat treatment according to Example 1 in water. Using a laser diffraction type particle size distribution meter (SALD-2000, manufactured by Shimadzu Corporation), the average diameter, medium diameter, and most frequent diameter of the agglomerates contained in the dispersion were measured.

Table 1 shows the concentrated solution of bifidobacteria before heat treatment according to Example 1, the concentrated solution of bifidobacteria after heat treatment according to Example 1, and the concentrated solution of bifidobacteria after heat treatment according to Comparative Example 1. The size of the agglomerates in.

As shown in Table 1, the concentrated solution of bifidobacteria before heat treatment according to Example 1 is the smallest in any of the average diameter, the medium diameter, and the most frequent diameter. In the concentrated solution of bifidobacteria before heat treatment according to Example 1, the average diameter, the medium diameter, and the mode diameter are 1 to 1.7 μm, and these values correspond to the size of the bifidobacteria. .. That is, it can be seen that agglomerates are not formed in the concentrated solution of bifidobacteria before the heat treatment according to Example 1.

The average diameter, medium diameter, and mode of the agglomerates contained in the concentrated solution of Bifizus bacteria after the heat treatment according to Example 1 are contained in the concentrated solution of Bifizus bacteria before the heat treatment according to Example 1. Greater than the average, median, and mode of agglomerates. That is, it can be seen that the formation of aggregates has progressed to some extent by heat-treating the concentrated solution of bifidobacteria according to Example 1.

However, the aggregates contained in the heat-treated bifidobacteria concentrate according to Example 1 are smaller than the aggregates contained in the heat-treated bifidobacteria concentrate according to Comparative Example 1. That is, by performing the heat treatment using vacuum steam on the concentrated solution of bifidobacteria according to Example 1, the progress of the formation of aggregates is suppressed as compared with the case where the heat treatment is performed at a temperature of 100 ° C. or higher. It became clear that it could be done.

The tip speed of the rotary blade in Example 1 is about two-thirds that of the rotary blade in Comparative Example 1, but the agglomerates contained in the concentrated solution of bifidobacteria after the heat treatment according to Example 1 are present. It is smaller than the agglomerates contained in the concentrated solution of bifidobacteria after the heat treatment according to Comparative Example 1. That is, it was clarified that when the heat treatment using vacuum steam was performed, the formation of huge agglomerates could be suppressed without stirring for crushing the agglomerates.

[Evaluation test 2]
The time change when the microbial concentrate was heated using vacuum vapor at 100 ° C. or lower was investigated. In Example 2, the time change in the temperature of the bifidobacteria concentrate when vacuum steam was used was measured, and in Comparative Example 2, the time change in the temperature of the bifidobacteria concentrate when hot water heating was used. Was measured.

{Example 2}
By the same procedure as in Example 1 above, 50 kg of a concentrated solution of bifidobacteria according to Example 2 was obtained. 50 kg of the concentrated solution of bifidobacteria according to Example 2 was put into a 100 L tank manufactured by Osaka Sanitary Co., Ltd., and vacuum steam was supplied to the jacket portion of the 100 L tank for heating. At the time of heating, 50 kg of the concentrated solution of bifidobacteria according to Example 2 was stirred by rotating the stirring blade. The stirring conditions were that the rotation speed of the stirring blade was 120 rpm and the tip speed of the stirring blade was 0.88 m / sec. While adjusting the temperature of the vacuum vapor in the jacket portion according to the temperature rise of the bifidobacteria, the time change of the temperature of 50 kg of the concentrated solution of the bifidobacteria was measured.

FIG. 3 is a graph showing the time change of the temperature of the concentrated solution of bifidobacteria in this example. As shown in FIG. 3, the set value of the temperature of the vacuum steam supplied to the jacket portion of the 100 L tank is changed according to the temperature rise of the concentrated solution of bifidobacteria. When 50 kg of the bifidobacteria concentrate was heated using vacuum steam, it took 80 minutes for the temperature of 50 kg of the bifidobacteria concentrate to reach 80 ° C.

{Comparative example 2}
By the same procedure as in Example 1 above, 100 kg of a concentrate of bifidobacteria according to Comparative Example 2 was obtained. 100 kg of the concentrated solution of bifidobacteria according to Comparative Example 2 was put into a 250 L tank manufactured by Skanima Co., Ltd., and hot water was supplied to the jacket portion of the 250 L tank for heating. At the time of heating, the concentrated solution of bifidobacteria was stirred by a stirring blade and a scraper provided in a 250 L tank. The stirring conditions were that the rotation speed of the stirring blade was 350 rpm and the tip speed of the stirring blade was 1.85 m / sec. While adjusting the temperature of the hot water supplied to the jacket portion according to the temperature rise of the bifidobacteria concentrate, the time change of the temperature of 100 kg of the bifidobacteria concentrate was measured.

FIG. 4 is a graph showing the time change of the temperature of the concentrated solution of bifidobacteria in this example. As shown in FIG. 4, the temperature of the hot water supplied to the jacket portion of the 250 L tank is changed according to the temperature rise of the concentrated solution of bifidobacteria. When 100 kg of the bifidobacteria concentrate was heated with warm water, it took 180 minutes for the temperature of 100 kg of the bifidobacteria concentrate to reach 80 ° C.

Although the embodiments of the present invention have been described above, the above-described embodiments are merely examples for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiment, and the above-described embodiment can be appropriately modified and implemented within a range that does not deviate from the gist thereof.

100 Heat treatment device 1 Vacuum steam generator 2 Jacket tank 3, 4 Piping 5 Control device 21 Tank section 22 Jacket section 23 Stirrer 24 Temperature sensor 25 Pressure sensor

Claims (6)

a) A step of heating a liquid containing microorganisms to a predetermined sterilization temperature using vacuum steam, and
b) A step of maintaining the temperature of the liquid containing microorganisms heated by the step a) at the sterilization temperature for a predetermined time using vacuum steam.
With
The step a) is
a-1) The agglomerate formation temperature or higher and the sterilization temperature or lower until the temperature of the liquid containing the microorganism becomes lower than the sterilization temperature and reaches the agglomerate formation temperature at which agglomerates are formed in the liquid containing the microorganism. The step of heating the liquid containing the microorganisms using vacuum steam at the temperature of
a-2) A step of heating the liquid containing the microorganisms using vacuum vapor having a temperature equal to or higher than the sterilization temperature after the temperature of the liquid containing the microorganisms reaches the agglomerate formation temperature.
A method of heat treatment of microorganisms , including. The heat treatment method according to claim 1, further
c) Step of culturing the microorganism,
With
The step a) is a method for heat-treating microorganisms that heats a liquid containing the microorganisms cultured in the step c). The heat treatment method according to claim 2.
The step c) is
c-1) A step of inoculating the medium with the microorganism and culturing the microorganism inoculated in the medium, and
c-2) Including a step of producing a concentrated solution of microorganisms from a medium containing microorganisms cultured in the above step c-1).
The step a) is a method for heat-treating a microorganism that heats the concentrated solution. The method for heat-treating a microorganism according to any one of claims 1 to 3.
The steps a) and b) are heat treatment methods for microorganisms that adjust the temperature of the vacuum vapor by changing the atmospheric pressure of the vacuum vapor. The method for heat-treating a microorganism according to any one of claims 1 to 4.
In the step a), the liquid containing the microorganism is heated by using a jacket tank including a tank portion into which the liquid containing the microorganism is charged and a jacket portion having an internal space to which the vacuum vapor is supplied. A method for heat-treating microorganisms that reduces the pressure of the internal space to a pressure lower than the atmospheric pressure before supplying the vacuum vapor to the internal space. A production method for producing a probiotic food to which a microorganism heat-treated by the method for heat-treating a microorganism according to any one of claims 1 to 5 is added.

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