

WATER FOR MICRO-ORGANISMS. 



is to attribute somewhat too bad a character to the samples 

 of air and water examined. 



There are two points at which cold water is employed in 

 the brewery in large quantities, but without its coming into 

 direct contact with the wort or with the beer. I refer to the 

 yeast vessels in the fermenting cellar and to the steep-water 

 in the malt-house. 



A practice frequently adopted is to keep the yeast covered 

 with cold water. In some breweries pieces of ice are put 

 directly into the yeast ; in others greater care is employed, 

 and the ice is placed in the cover of the yeast tub ; in all 

 cases care is taken to maintain a low temperature. If this 

 were not done, most species of the water bacteria would in 

 all probability find a favourable medium in the yeast-mass. 

 As a rule, the yeast remains under the conditions named for 

 12-24 hours only, rarely 48 hours. When introduced into 

 the tub with cold water, the temperature of the mass is about 

 10 C, but when the cover with the ice has been placed over 

 it, the temperature sinks in a few hours to about 6 C. 



I have examined yeast thus treated frequently and at 

 different seasons, but when the cooling with ice was sufficiently 

 ensured I never found that the bacteria multiplied to an 

 appreciable extent ; and as soon as the yeast is introduced 

 into the wort the activity of most of the bacteria in the water 

 becomes completely suspended, as has just been shown. It 

 will, therefore, be of no importance if such species multiply 

 even to a fairly considerable extent in the viscous mass 

 occurring between the yeast cells. This is, in fact, a favour- 

 able medium for the development of by far the larger number 

 of bacteria. That the multiplication of injurious bacteria at this 

 point is also to be feared, is self-evident. In the above we 

 have spoken of such species under the general name of wort 

 bacteria. When these are present in the water which comes 

 in contact with the yeast, they will, as a rule, multiply like 

 the water bacteria, especially if the yeast mass has been 



