JP2003024040A - Agitation tank for storing yeast slurry, method for producing fermented foods such as beer by using the same agitation tank, and agitating vane provided in the same agitation tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformly agitate and mix the entire yeast slurry in an agitation tank in a short time without causing poor mixing of the yeast slurry which is a non-Newtonian fluid, as well as protect yeast from damages and hence prevent the deterioration of the biological activity, in the agitation tank for storing yeast slurry mainly used in a beer production process, to provide a method for producing a fermented food such as beer by using the agitation tank and an agitating vane provided in the agitation tank. SOLUTION: In this agitation tank for storing yeast slurry to be supplied to the fermentation tank where the fermented food such as beer is fermented, the agitation vane is constructed so that a maximum diameter of a rotation body formed in the rotation of the agitation vane is 60-90% based on the inner diameter of the agitation tank and the height of the rotation body is 90-120% based on a standard depth of the yeast slurry normally stored in the agitation tank.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a stirring tank for storing yeast liquid, a method for producing fermented foods using the stirring tank, a stirring blade provided in the stirring tank, and more specifically, mainly beer. The present invention relates to a yeast liquid storage stirring tank used in a manufacturing process, a method for producing fermented food such as beer using the yeast liquid storage stirring tank, and a stirring blade provided in the yeast liquid storage stirring tank.

[0002]

2. Description of the Related Art Generally, in a process for producing a fermentation product such as beer, yeast recovered from a fermentation tank is stored in a storage stirring tank and returned to the fermentation tank as seed yeast for reuse.

The yeast stored in the storage stirring tank settles in the lower part of the storage stirring tank with the lapse of time, resulting in uneven yeast concentration and cooling temperature in the storage stirring tank. In order to eliminate this, it is necessary to stir the yeast solution.

However, the yeast liquid is a non-Newtonian fluid similar to butter, soap, etc., and such a non-Newtonian fluid has a large stirring force unlike the Newtonian fluid in which the stirring effect is improved in proportion to the stirring force. However, it is known that the stirring effect proportional to that is not necessarily obtained.

On the other hand, although it is necessary to stir in order to make the yeast concentration and the temperature of the yeast solution uniform as described above, it is also necessary that the stirring does not damage the yeast.

In such a beer manufacturing process, conventionally, blades such as inclined paddle blades and propeller blades have been mainly used as stirring blades provided in the stirring tank for storing the yeast liquid supplied to the fermentation tank. It was

[0007]

However, when a yeast solution which is a non-Newtonian fluid is agitated by using such an agitating blade, there is a problem that the whole cannot be uniformly mixed by the low speed agitation.

On the other hand, in order to eliminate this improper mixing and increase the yeast concentration and the temperature uniformity of the yeast liquid, high-speed strong stirring damages and destroys the yeast and reduces its biological activity. There is a point.

The present invention has been made in order to solve such contradictory problems, and uniformly stirs and mixes the whole tank in a short time without causing defective mixing of the yeast liquid which is a non-Newtonian fluid. It is an object of the present invention that it is possible to do so, and that it does not damage the yeast and does not reduce its biological activity.

[0010]

In order to solve such problems, the present invention provides a stirring tank for storing yeast liquid, a method for producing fermented foods such as beer using the stirring tank, and stirring the same. What was made as a stirring blade provided in the tank, and the characteristic of the stirring tank for storing yeast liquid is that the stirring tank for storing yeast liquid stores the yeast liquid to be supplied to the fermentation tank for fermenting fermented foods such as beer. In the tank, the maximum diameter of the rotor formed when the stirring blade is rotated is 60 to 90% of the tank diameter, and the height of the rotor is 90 to 120% of the liquid depth at the standard storage of the yeast liquid. It is composed.

Further, a characteristic of the method for producing fermented foods such as beer is that the method for producing fermented foods such as beer has a step of stirring the yeast liquid in a yeast liquid storage stirring tank. A stirring blade such that the maximum diameter of the rotating body formed during rotation is 60 to 90% of the tank diameter and the height of the rotating body is 90 to 120% of the liquid depth during standard storage of the yeast liquid in the stirring tank. And stirring the yeast liquid by rotating the stirring blade at a rotation speed of 1 to 30 rpm.

Further, a characteristic of the stirring blade is that the stirring blade is provided in a yeast liquid storage stirring tank for storing the yeast liquid for supplying to a fermentation tank for fermenting fermented foods such as beer. The maximum diameter of the rotating body that is sometimes formed is
The height of the rotor is 60 to 90%, which is 90 to 120% of the liquid depth of the standard storage of the yeast liquid.

Here, the maximum diameter of the rotating body refers to the dimension (diameter) of the largest diameter portion of the rotating body formed when the stirring blade rotates. Further, the standard storage time of the yeast solution means a state in which the yeast solution is stored in an amount set on the design of the stirring tank for storing the yeast solution and the experience of operation management, and the yeast solution is stored according to the stirring tank. The standard storage amount of liquid is uniquely determined.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a schematic front view schematically showing a yeast liquid storage stirring tank as an embodiment.

In FIG. 1, reference numeral 1 is a tank body, a body 2 is formed in a substantially cylindrical shape, and a bottom 3 is formed in an inverted conical shape.

Reference numeral 4 denotes a rotary shaft vertically provided at substantially the center of the tank main body 1. The rotary shaft 4 has two upper and lower paddle blades.
5a and 5b are mounted vertically.

Then, the upper and lower paddle wings 5a and 5b, respectively.
Are arranged at an intersection angle of 45 degrees as shown in FIG.

The stirring blade 5 composed of both paddle blades 5a and 5b is set such that the maximum diameter of the rotor formed when the stirring blade 5 rotates is 60 to 90% of the tank diameter. .

The height of the rotating body is set to 90 to 120% of the liquid depth of the standard storage of the yeast liquid.

Further, the lower surface side of the lower paddle blade 5b is formed in a sloped shape so as to match the inverted conical bottom portion 3 of the tank body 1.

As shown in FIG. 3, the yeast tank-storing agitation tank 6 having the above-described structure is a main fermentation tank 7 for beer production.
It is used by being arranged in the latter stage.

That is, the beer production process includes a malt saccharification process and a yeast fermentation process. In the yeast fermentation process, a part of the yeast discharged from the main fermentation tank 7 is used for storing the yeast liquid. It is stored in the stirring tank 6 and returned to the main fermentation tank 7 as seed yeast for reuse.

Then, the yeast needs to be uniformly stirred in the stirring tank 6 for storing the yeast liquid.

By using the stirring tank for storing the yeast liquid as in the above embodiment, it is possible to stir at a low rotation speed that does not damage the yeast, and to stir and mix the whole uniformly.

In this case, since the upper and lower paddle blades 5a and 5b are arranged, discharge flows are generated from the respective paddle blades 5a and 5b, and the upper and lower discharge flows do not interfere with each other. The flow of yeast liquid can be smoothly connected.

Further, since the maximum diameter of the rotating body formed by the rotation of the stirring blade 5 is set to 60 to 90% of the tank diameter, the yeast liquid flows even in the vicinity of the inner wall of the tank body 1. It does not cause damage to yeast.

That is, the maximum diameter of the rotating body is 60% of the tank diameter.
If the following, because the yeast liquid near the inner wall of the tank does not flow,
The yeast solution is not uniformly stirred, and the yeast is destroyed by the shearing force at the sliding surface between the non-fluid part and the flowing part. On the other hand, when it is 90% or more, the gap between the blade and the inner wall of the tank decreases, and the blade This is because a high shearing force may be generated between the inner walls of the tank and the yeast may be damaged, and the effect of vertically mixing is reduced, so that uniform mixing cannot be performed.

As described above, the maximum diameter of the rotating body is 60 of the tank diameter.
Although it is set to be ~ 90%, it is more preferably 70 to 90%, further preferably 75 to 90% and 80 to 90%.

When it is 70% or more, the fluctuation of the yeast concentration is reduced, and the yeast is stirred more uniformly.
As described above, when it is 80% or more, the fluctuation of the yeast concentration is further reduced, and the uniform stirring effect of the yeast is further improved.

Further, the height of the rotor formed by the rotation of the stirring blade is 90 to 120 which is the liquid depth at the standard storage of the yeast liquid.
Since it is set so as to be%, no defective mixing occurs.

Further, if it is 90% or more, since the top of the stirring blade exists near the liquid surface during the standard storage of the yeast liquid, it means that the yeast liquid can be stirred and mixed more uniformly from the standard storage to the discharge of the entire amount. There is also an effect that the foaming sometimes occurs disappears immediately after stirring.

On the other hand, if it is 120% or less, since the top of the stirring blade is slightly above the liquid surface during standard storage, there is an effect that more uniform stirring and mixing can be performed and bubbling also disappears.

Here, the height H ₁ of the rotating body means the distance between the upper end of the rotating body formed by the rotation of the stirring blade 5 and the lower end of the rotating body as shown in FIG.

The liquid depth H ₂ at the standard storage of the yeast liquid is
As shown in FIG. 4, between the liquid level of the yeast liquid when the yeast liquid is stored in the tank body 1 (at the time of storage) and the lowest portion of the bottom portion 3 of the tank body 1 (the apex of the inverted triangle). Of the standard liquid volume, that is, a state in which the amount of yeast liquid set in the design of the stirring tank for storing yeast liquid and the experience of operation management is stored, Therefore, the standard storage amount of the yeast solution is uniquely determined.

The space above the liquid surface during standard storage is a space for expansion during foaming. Therefore, the standard storage amount referred to here indicates the volume for liquid and yeast only.

Furthermore, the lower end of the rotating body and the bottom portion 3 of the tank body 1
Distance H ₃ between the lowermost, upon stirring the yeast solution, which distance is provided for uniformly stirring and mixing without damaging the yeast. If this distance is too short, the yeast will be damaged during stirring, and if the distance is too large, uniform stirring will not be possible.

Further, the stirring blade is stirred at a rotation speed of 1 to 30 rpm.

This is because if it is less than 1 rpm, it is difficult to stir and mix the yeast solution, and if it exceeds 30 rpm, the torque sharply increases and the yeast is damaged by the shearing force.

Particularly, when the rotation speed is set to 1 to 20 rpm, damage of yeast due to shearing force can be prevented more reliably. When the yeast solution that has completely settled and separated is uniformly dispersed, cooled rapidly, or when foaming is suppressed, agitation is performed at 10 rpm or more for a short time, and when maintaining temperature, at an extremely low speed close to 1 rpm. Continuous operation or intermittent operation at a low speed of 1 to 10 rpm can prevent damage to the yeast. In particular, since the yeast can be homogenized by stirring from the state where the yeast have been separated by sedimentation, it is desirable to maintain the yeast at a necessary low speed intermittent operation after cooling without fear of sedimentation of the yeast.

Further, since the upper and lower paddle blades 5a and 5b are arranged at an intersecting angle of 45 degrees when viewed from the plane, this phase shift causes a smooth upward and downward flow of the yeast liquid. Becomes

By the above-mentioned actions, a uniform stirring and mixing effect in the stirring tank 6 for storing the yeast liquid can be obtained.

(Other Embodiments) In the above embodiment, the paddle blades are arranged in two upper and lower stages, but it is also possible to arrange them in three or more stages.

Further, in this embodiment, the upper and lower paddle blades are arranged at an intersection angle of 45 degrees when viewed from the plane, but this intersection angle is not limited to this embodiment either.

However, in order to cause the yeast liquid to flow up and down to a certain extent, it is preferably within the range of 30 ° to 90 °.

Furthermore, the structure of the stirring tank 6 for storing the yeast liquid is also
As in the above-described embodiment, upper and lower multistage paddle blades are attached to the rotary shaft 4.
The structure is not limited to the structure in which 5a, 5b, ... Are arranged, and the structure is not limited.

For example, a large flat plate blade having a large number of holes such as the stirring blade disclosed in Japanese Patent Laid-Open No. 7-786, or Japanese Patent Laid-Open No. 61-200842 and Japanese Patent Laid-Open No. 8-200842. -281089, such as the stirring blades disclosed in the publication, a plurality of large vertical plate blades are provided at different angles,
Like the stirring blade disclosed in Japanese Utility Model Publication No. 7-34928,
It is also possible to use a substantially trapezoidal large vertical flat plate with a plate-shaped auxiliary wing attached to the back surface thereof with a gap.

However, the stirring blade of the present invention has changes in shape, size, and mounting method in the vertical direction, compared with simple anchor blades, paddle blades, and lattice blades, and it is possible to move the liquid up and down by these changes. A stirring blade that can be used is desirable.

Further, in a stirring tank such as brewer's yeast which is required to have a sanitary property, it is desirable that there is no blade inclination or hole that would be a blind spot in the cleaning work during tank cleaning. It is desirable to use a stirring blade without openings.

In other words, it is preferable to use a stirring blade which is free from bolts and joints in the stirring tank and has a smooth curved surface without a horizontal surface which impairs the cleaning property and a vertical surface.

In addition, since such a stirring blade can sufficiently mix the yeast solution without any baffle plate, it is not necessary to attach a baffle plate to impair the washability of the tank.

By using such a stirring blade, a sufficient cleaning effect can be obtained and an accident such as microbial contamination does not occur.

Further, in the above embodiment, the case where the yeast stirring tank is used for beer production has been described, but the use is not limited to this, and it can be used for stirring yeast other than beer. is there.

A yeast solution having a concentration of 30 to 60% is mainly used.

Here, the concentration of the yeast solution means the volume% of yeast to the solution.

[0056]

Example 1 In this example, the correlation between the stirring time and the fluctuation of the pH of the yeast solution was tested.

In this embodiment, the stirring tank has a volume of 4
m ³ , the inner diameter of the tank was 1900 mm, and the maximum diameter of the stirring blade was 60% of the tank diameter.

Further, the height of the rotating body formed when the stirring blade was rotated was set to be 1490 mm. As a result, the height of this rotating body was 97% of the liquid depth during standard storage, and the top of the stirring blade was located approximately 50 mm above the liquid surface during standard storage of the yeast liquid.

Further, the stirring blades are the paddle blades provided above and below, intersecting each other at an angle of 45 degrees as in the above embodiment.
It has 5a and 5b.

Further, in this example, the stirring was carried out at a low rotation speed of 20 rpm.

On the other hand, an inclined paddle blade was used as a comparative example.

This inclined paddle blade has a maximum diameter of 800 mm when rotated and an inner diameter of the tank of 2200 mm. Therefore, the maximum diameter of the rotor formed when the rotating shaft is rotated is equal to the tank diameter. It will be about 36%.

In the comparative example, the rotation speed was 58 rpm.

The results are shown in FIG.

As is clear from FIG. 5, in the comparative example,
While the pH of the yeast solution fluctuated remarkably with the change in the stirring time, the pH fluctuation in this example was smaller than that in the comparative example.

From this result, it can be judged that the damage of yeast was less in this example than in the comparative example.

The state of the yeast after stirring was observed with an electron microscope. As shown in Reference Photo 1, when stirring was performed with the inclined paddle blade of the comparative example, the yeast was clearly damaged. I was able to confirm that

On the other hand, the yeast solution stirred using the stirring tank of this example was in a good condition with no damage to the yeast as shown in Reference Photo 1.

(Example 2) In this example, the fluctuation of the yeast concentration when the yeast solution was dispensed was measured.

In this embodiment, the stirring tank has a volume of 5
m ^3, was used having an inner diameter of 2200mm tank.

The maximum diameter of the rotating body formed by the stirring blades when the rotating shaft was rotated was set to be about 83% of the tank diameter.

Further, the height of the rotating body formed when the stirring blade was rotated was set to 1993 mm. As a result, the height of this rotating body was 93% of the liquid depth during standard storage, and the top of the stirring blade was approximately 50 mm from the liquid surface during standard storage of yeast liquid.
It is in a high position.

In this example, stirring was carried out at the rotational speeds of 20 rpm (Example 2-1) and 5 rpm (Example 2-2).

On the other hand, as Comparative Example 2-1, a stirring tank equipped with a propeller type stirring blade was used.

The inner diameter of the tank is 2800 mm, and the maximum diameter of the rotor formed by rotating the propeller type stirring blade is
It was 1600 mm. Therefore, the maximum diameter of the rotating body is about 57% of the tank diameter. The rotation speed was 70 rpm.

As Comparative Example 2-2, an inverted trapezoidal frame-shaped blade was used.

The inner diameter of the tank was 2500 mm, and the maximum diameter of the rotor formed by rotating the inverted trapezoidal frame type stirring blade was 1400 mm. Therefore, the maximum diameter of the rotating body is about 56% of the tank diameter. The rotation speed was 70 rpm.

The results of these tests are shown in FIG.

As is clear from FIG. 6, in each comparative example, the yeast concentration fluctuated within the range of 15%, whereas in this example, the yeast concentration fluctuated within 5%.

From this result, it can be judged that the yeast was uniformly stirred in this example as compared with the comparative example.

Example 3 In this example, the correlation between the number of times yeast was discharged from the tank and the pH was tested.

After the yeast was stored in the stirring tank, a fixed amount was discharged every 3 hours, and the discharge was performed 8 times.
The variation of H was measured.

More specifically, 10 rpm for 10 minutes before discharge
The pH of the discharged yeast liquid was measured by stirring at the number of revolutions.

As the stirring tank, the maximum diameter of the rotor formed by the stirring blades when the rotating shaft is rotated is about the tank diameter.
The one used was 83%.

The height of the rotator was set so as to be 93% of the standard storage of the yeast solution in each case.

The test results are shown in FIG. As is clear from FIG. 7, both Example 3-1 and Example 3-2
Although the discharge work was performed eight times for 24 hours, the fluctuation in pH was within 0.2.

From these results, Example 3-1 and Example 3-
It was confirmed that in both, almost no damage to the yeast was observed.

(Example 4) In this example, the correlation between the number of times yeast was discharged from the tank and the yeast concentration was tested.

After containing the yeast in the stirring tank, a fixed amount was discharged every 3 hours in the same manner as in Example 3, and the discharging was performed 8 times.
Changes in yeast concentration with the number of discharges were measured.

The fluctuation of the yeast concentration was measured by the change of the viable cell sensor value.

Yeast is positively charged when it is alive and negatively charged when it is dead.

When the permittivity of the yeast liquid is measured, the state of yeast life and death can be confirmed, and this can be detected by a sensor to be converted into yeast concentration.

As the stirring tank, the maximum diameter of the rotor formed by the stirring blades when the rotating shaft is rotated is about the tank diameter.
60% (Example 4-1), the maximum diameter of the rotating body was about 75% of the tank diameter (Example 4-2), and the maximum diameter of the rotating body was about 83% of the tank diameter. Naruto (Example 4-3)
3 types were used.

The height of the rotator was set to 93% of that in the standard storage of the yeast solution in each case.

The test results are shown in FIG.

As is clear from FIG. 8, Example 4-1
And, although the discharge work was performed 8 times in Example 4-2 and 4 times in Example 4-3, the fluctuation of the yeast concentration was within 8%.

Particularly, in the case of Example 4-2 in which the maximum diameter of the rotating body was about 75% of the tank diameter, the fluctuation of the yeast concentration was about 5%, and the maximum diameter of the rotating body was about the tank diameter. In the case of Example 4-3 in which the concentration was 83%, the variation in yeast concentration was about 3%.

From these results, it was confirmed that yeast damage was small in each Example, and that particularly yeast damage was hardly observed in Examples 4-2 and 4-3.

It was also confirmed that 70% or more, and even 80% or more of the maximum diameter of the rotating body was uniformly agitated.

Example 5 In this example, the temperature change at each point in the tank was measured.

In this example, the same stirring tank as in Example 1 was used.

That is, the stirring tank of this embodiment has a volume of 4
It was installed so that the maximum diameter of the rotor (blade diameter) was 1140 mm and the height of the rotor was 1490 mm, using a m ³ tank with an inner diameter of 1900 mm. As a result, the height of this rotating body is 97% of the liquid depth during standard storage.

The yeast liquid was stirred at 1 rpm and 20 in such a stirring tank.
The temperature at the time of stirring at rpm was measured over time.

Specifically, the temperature change in the stirring tank when the stirring blade in the stirring tank was rotated at 1 rpm and 20 rpm while changing the rotation speed was measured with a temperature sensor over time, and the stirring was performed. Confirmed the effect of.

The results are shown in FIGS. 9 and 10.

The temperature measurement site in the stirring tank is the point described in FIG.

As shown in FIGS. 9 to 11, it can be seen that there is little variation in temperature depending on the measurement site in the tank, and there is almost no variation when stirring at 20 rpm.

From this, it can be seen that the temperature in the tank was uniformly stirred and maintained at a constant temperature even at a very low speed of 1 to 20 rpm.

(Example 6) In this example, the temperature followability in the tank was tested.

Also in this embodiment, as in the case of the above-mentioned first embodiment, a volume of 4 m ³ and an inner diameter of the tank of 1900 mm are used, and the maximum diameter of the rotor is set to 1140 mm and the height of the rotor is set to 1490 mm. did. The height of the rotating body is 97% of the liquid depth during standard storage.

The stirring blade was stirred at 20 rpm. As a comparative example, a two-stage paddle blade as shown in FIG. 12 was used and stirring was performed at 53 rpm. The results are shown in Fig. 13.

In general, the storage temperature of the yeast liquid is controlled according to a time chart, and the refrigerant is flowed through the jacket around the stirring tank until the temperature in the tank reaches the set temperature, and the yeast in the tank is cooled. The liquid is cooling.

Therefore, if the temperature following property in the tank is poor, the yeast solution in the center of the tank remains uncooled even though the yeast solution near the outer peripheral surface is rapidly cooled, and Therefore, a temperature difference occurs, and the cooling efficiency of the tank deteriorates.

FIG. 13 shows the results of measuring the trackability of the temperature inside the yeast solution when the yeast solution was stirred using the stirring tank of the Example and when the yeast solution was stirred using the stirring tank of the Comparative Example. Becomes

As shown in FIG. 13, even if the stirring speed is as low as 20 rpm, the temperature followability is better in this embodiment than in the comparative example, and uniform stirring can be achieved in a short time without high speed stirring. I understand. In addition, the temperature of the yeast is appropriately controlled because it closely follows the delicate temperature setting.

Example 7 In this example, the viable cell rate of yeast was measured.

Specifically, using three types of stirring tanks described later, the viable cell ratio before and after stirring yeast was determined.

For the measurement of the viable cell rate, yeast stained with methylene blue was observed with a microscope, and the viable cells were counted using a hemacytometer.

(Example 7-1) The stirring tank of this example had a volume of 5 m ³ and an inner diameter of 2100 mm, and the maximum diameter of the rotor (blade diameter) was 1745 mm and the height of the rotor was 1993 mm. It was installed so that the standard solution of yeast solution had a liquid depth of 93%.

This yeast solution was stored at 5 rpm for a storage time in a stirring tank.
The viable cell rate was measured when the mixture was stirred for 36 hours.

(Embodiment 7-2) The stirring tank of this embodiment had a volume of 5 m ³ and an inner diameter of 2100 mm, and the maximum diameter (blade diameter) of the rotor of the stirring blade was 1745 mm and the height of the rotor was high. Was set to be 1993 mm, and the liquid depth during standard storage of the yeast liquid was 93%.

The yeast solution was kept at 5 rpm for a residence time in the stirring tank.
The viable cell rate when stirred for 33 hours was measured.

(Example 7-3) The stirring tank of this example had a volume of 5 m ³ and an inner diameter of 2100 mm, and the maximum diameter (blade diameter) of the rotor of the stirring blade was 1745 mm and the height of the rotor was high. Was set to be 1993 mm, and the liquid depth during standard storage of the yeast liquid was 93%.

The yeast solution was kept at 5 rpm for the residence time in the stirring tank.
The viable cell rate was measured when the mixture was stirred for 39 hours.

When stirring is carried out under the above conditions,
Figure 14 shows the results of measuring the viable cell ratio of yeast before and after stirring.
Shown in.

As is clear from FIG. 14, there was almost no difference in the viable cell ratio in this example before and after stirring. This shows that the yeast cells were not damaged by stirring.

(Embodiment 8) In this embodiment, the correlation between the rotational speed of the stirring blade and the shaft torque was tested using the stirring tank of the above-mentioned Embodiment 7. The liquid depth at the standard storage of the yeast liquid was also tested in the same state as in Example 7.

[0128] The correlation was determined by using the yeast immediately after recovery, recovery 24
The yeast and known Newtonian fluid after the passage of time are shown in FIG.

As shown in FIG. 15, the axial torque required for the yeast immediately after the recovery is larger than the axial torque required for the yeast 24 hours after the recovery.

In FIG. 15, the intersection of the line showing the data of yeast and the line showing the data of Newtonian fluid indicates that the apparent viscosity of the yeast liquid at that rotation speed is equal to the viscosity of the Newtonian fluid.

It can be understood that the apparent viscosity of the yeast liquid changes from 30000 cp to 1000 cp with respect to the rotation speed from 2 rpm to 20 rpm, and it is a non-Newtonian fluid.

Further, the stirring torque of the yeast slurry is 10 rp.
Below m, it tends to be almost constant regardless of the rotation speed. This tendency is a characteristic observed in Bingham fluid, and the data in FIG. 15 shows that the yeast solution is Bingham fluid. Bingham fluid has a yield stress, and the fluid does not move even when a force below the yield stress acts.

From this fact, the yeast liquid is not a general fluid which can be mixed relatively easily, but a special fluid which requires special consideration for fluidizing the whole and uniformly mixing it. Is estimated.

[0134]

As described above, according to the present invention, as the stirring blade of the yeast liquid storage stirring tank, the maximum diameter of the rotating body which can be obtained by rotating the stirring blade is 60 to 90% of the tank diameter, Since the height of the rotor is 90 to 120% of the depth of the standard storage of yeast liquid, and the stirring blade is rotated at a rotation speed of 1 to 30 rpm for stirring, Can be mixed almost uniformly, and the effect of mixing and stirring is significantly better than that of a yeast stirring tank equipped with a general inclined paddle blade and the like.

Further, the maximum diameter of the rotor formed by the rotation of the stirring blade is 60 to 90% of the tank diameter, and the height of the rotor is 90 to 120% of the liquid depth at the standard storage of the yeast liquid. As a result, a good stirring effect can be obtained even with a relatively low rotation speed of 1 to 30 rpm, and as a result, there is no risk of damaging or destroying the yeast and reducing its biological activity.

Further, since the height of the rotor formed by the rotation of the stirring blade is 90 to 120% of the liquid depth of the standard storage of the yeast liquid, the yeast liquid can be uniformly stirred and mixed, and the yeast liquid is generated during the charging. There is an effect that the generated foaming disappears immediately after stirring.

[Brief description of drawings]

FIG. 1 is a schematic front view schematically showing a yeast agitation tank as one embodiment.

FIG. 2 is a schematic plan view showing an arrangement state of paddle blades of a yeast stirring tank.

FIG. 3 is a schematic block diagram showing a positional relationship between a yeast stirring tank and a main fermentation tank.

FIG. 4 is a schematic front view showing the height of the rotating body and the liquid depth of the yeast liquid during standard storage.

FIG. 5 is a graph showing a correlation between stirring time and pH of yeast solution.

FIG. 6 is a graph showing changes in yeast concentration.

FIG. 7 is a graph showing a correlation between the number of times yeast is discharged from a tank and pH.

FIG. 8 is a graph showing the correlation between the number of times yeast is discharged from the tank and the yeast concentration.

FIG. 9 is a graph showing the correlation between the temperature in the tank and the stirring time.

FIG. 10 is a graph showing the correlation between the temperature in the tank and the stirring time.

FIG. 11 is an explanatory view showing a temperature measurement position in the stirring tank.

FIG. 12 is an explanatory view showing a stirring blade of a comparative example.

FIG. 13 is a graph showing the correlation between the temperature in the tank and the elapsed time.

FIG. 14 is a graph showing the viable cell rate of yeast.

FIG. 15 is a graph showing a correlation between rotation speed and shaft torque.

[Explanation of symbols]

1 ... Tank main body 5 ... Stirring blade

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yukichi Okamoto             4-8 Tsutsujigaoka, Tarumi-ku, Kobe-shi, Hyogo             No. 1 Azalea Hill Hill 3140 No. 2 (72) Inventor Kawamura             1-1 South 4-chome, Nango-dori, Shiroishi-ku, Sapporo-shi, Hokkaido               Asahi Breweries, Ltd. Hokkaido factory (72) Inventor Eiichi Jimbo             21-1 Midori, Moriya-cho, Kitasoma-gun, Ibaraki Prefecture             Asahi Breweries, Ltd. F term (reference) 4B029 AA02 BB07 CC01 DA10 DB19                       DF08 DF09

Claims (3)

[Claims] 1. In a yeast liquid storage stirring tank for storing a yeast liquid for supplying a fermenting tank for fermenting fermented foods such as beer, the maximum diameter of the rotor formed when the stirring blade is rotated is the tank diameter. A stirring tank for storing yeast liquid, wherein the stirring blade is configured such that the height of the rotating body is 90 to 120% of the liquid depth at the time of standard storage of the yeast liquid at 60 to 90%. 2. A method for producing fermented foods such as beer having a step of stirring yeast liquid in a yeast liquid storage stirring tank, wherein the yeast liquid storage stirring tank has a maximum diameter of a rotor formed during rotation. Is equipped with a stirring blade such that 60 to 90% of the tank diameter and the height of the rotating body is 90 to 120% of the liquid depth at the time of standard storage of the yeast liquid, and the stirring blade has a rotation speed of 1 to 30 rpm. A method for producing fermented foods such as beer, which comprises rotating the yeast liquid and stirring the yeast liquid. 3. A stirring blade provided in a yeast liquid storage stirring tank for storing a yeast liquid for supplying to a fermenter for fermenting fermented foods such as beer, comprising a rotating body formed during rotation. An agitating blade characterized in that the maximum diameter is 60 to 90% of the tank diameter and the height of the rotating body is 90 to 120% of the liquid depth at the standard storage of the yeast liquid.