Stirred tank for storing yeast slurry, method of manufacturing fermented foods such as beer using the stirred tank, and stirring impeller provided in the stirred tank

Abstract

According to the present invention, there is provided a stirred tank for storing yeast slurry to be supplied to fermentation tanks where fermented foods such as beer are fermented, is characterized in that a stirring impeller is provided within the stirred tank and so constructed that a maximum diameter of a rotation body defined by the rotation of the stirring impeller is 60-90% of the inner diameter of the stirred tank, and the height of the rotation body is 70% or more of a standard depth of the yeast slurry normally stored in the stirred tank.

1 . A method of manufacturing beer including the process of storing in a stirred tank a part of yeast slurry discharged from fermentation tanks where beer is fermented, and then returning the part of yeast slurry from the stirred tank to the fermentation tanks for reuse, comprising: 
 providing a stirring impeller made up of vertically oriented surfaces with no main stirring surface that is slanted from vertical, having a shape and a size varied in a vertical orientation, which variation is configured to achieve vertical flow of the yeast slurry, and positioned within a tank body of the stirred tank, said tank body having a substantially cylindrical shape with a bottom portion of an inverted cone shape, and so constructed that a maximum diameter of a rotation body defined by the rotation of the stirring impeller is 60-90% of the inner diameter of the stirred tank, and the height of the rotation body is 70% or more of a depth of the part of yeast slurry stored in the stirred tank, and a jacket disposed on a periphery of the tank body within which a cooling medium is circulated so as to cool the yeast slurry; and    stirring the yeast slurry by rotating the stirring impeller at a rotational speed of 1-30 rpm, while setting a concentration of the yeast slurry within the tank body to 30-60%.    
   
   
       2 . A method of manufacturing beer according to  claim 1 , wherein the maximum diameter of the rotation body defined by the rotation of the stirring impeller is 70-90% of the inner diameter of the stirred tank.  
   
   
       3 . A method of manufacturing beer according to  claim 1 , wherein the height of the rotation body defined by the rotation of the stirring impeller is 90-120% of the depth of the yeast slurry.  
   
   
       4 . A method of manufacturing beer according to  claim 1 , wherein the stirring impeller is rotated at a rotational speed of 1-20 rpm.  
   
   
       5 . A method of manufacturing beer according to  claim 2 , wherein the height of the rotation body defined by the rotation of the stirring impeller is 90-120% of the depth of the yeast slurry.  
   
   
       6 . A method of manufacturing beer according to  claim 2 , wherein the stirring impeller is rotated at a rotational speed of 1-20 rpm.  
   
   
       7 . A method of manufacturing beer according to  claim 3 , wherein the stirring impeller is rotated at a rotational speed of 1-20 rpm.  
   
   
       8 . A method of manufacturing beer according to  claim 5 , wherein the stirring impeller is rotated at a rotational speed of 1-20 rpm.  
   
   
       9 . A method of manufacturing beer according to  claim 1 , wherein the stirring impeller has no hole or opening.  
   
   
       10 . A method of manufacturing beer including the process of storing in a stirred tank a part of yeast slurry discharged from fermentation tanks where beer is fermented, and then returning the part of yeast slurry from the stirred tank to the fermentation tanks for reuse, comprising: 
 providing a stirring impeller including vertically flat surfaced paddle blades with no main stirring surface that is slanted from vertical, the stirring impeller being positioned within a tank body of the stirred tank, said tank body having a substantially cylindrical shape with a bottom portion of an inverted cone shape, and so constructed that a maximum diameter of a rotation body defined by the rotation of the stirring impeller is 60-90% of the inner diameter of the stirred tank, and the height of the rotation body is 70% or more of a depth of the part of yeast slurry stored in the stirred tank, and a jacket disposed on a periphery of the tank body within which a cooling medium is circulated so as to cool the yeast slurry; and    stirring the yeast slurry by rotating the stirring impeller at a rational speed of 1-30 rpm, while setting a concentration of the yeast slurry within the tank body to 30-60%.    
   
   
       11 . A method of manufacturing beer according to  claim 1  wherein the stirring impeller includes a rotational shaft, a first paddle blade, and a second paddle blade, wherein the first paddle blade and the second paddle blade are affixed to the rotational shaft, and wherein the first paddle blade is affixed to the rotational shaft at an angle offset from the second paddle blade.  
   
   
       12 . A method of manufacturing beer according to  claim 11 , wherein the first paddle blade is affixed to the rotational shaft at a horizontal elevation above the second paddle blade.  
   
   
       13 . A method of manufacturing beer according to  claim 12 , wherein a portion of the first paddle blade and a portion of the second paddle blade overlap each other in the horizontal elevation.  
   
   
       14 . A method of manufacturing beer according to  claim 10 , wherein the stirring impeller includes a rotational shaft, a first paddle blade, and a second paddle blade, wherein the first paddle blade and the second paddle blade are affixed to the rotational shaft, and wherein the first paddle blade is affixed to the rotational shaft at an angle offset from the second paddle blade.  
   
   
       15 . A method of manufacturing beer according to  claim 14 , wherein the first paddle blade is affixed to the rotational shaft at a horizontal elevation above the second paddle blade.  
   
   
       16 . A method of manufacturing beer according to  claim 15 , wherein a portion of the first paddle blade and a portion of the second paddle blade overlap each other in the horizontal elevation.