478 BUTTER DEFECTS 



Yeast cells require a relatively high temperature, approach- 

 ing that of the animal body, for their greatest development. 

 When on the farm, or in transit, or both, the cream is exposed 

 sufficiently long to summer heat, so that the cream itself be- 

 comes warm, the development of the yeast cells becomes very 

 pronounced and very intense. Often it is accompanied by vio- 

 lent gas production, frequently causing the lids of the cans to 

 blow off and the cream to foam over. In this condition the 

 cream gives off a very decided and objectionable yeasty flavor 

 similar to baker's yeast, that follows the product into the fin- 

 ished butter. 



If the cream is cooled promptly and properly on the farm 

 when it leaves the separator and is kept cool until shipped, it 

 usually reaches the creamery before it has a chance to become 

 yeasty and foamy. On the other hand, if the cream is not 

 cooled on the farm, the yeast cells become active at once and 

 when this fermentation has once commenced, it goes on rapidly 

 and is stopped with difficulty only. 



It is obvious also that the number of yeast cells present 

 in the cream to start with, has a great deal to do with the rapid- 

 ity and extent to which this defect develops. Contamination 

 of the cream through such channels as impure water, unclean 

 utensils, unclean separators and cans, should be avoided as 

 much as possible, and the cream producer should be instructed 

 to pay close attention to the following precautions : 



Prevention of Yeasty and Foamy Cream. 



1. Wash and scald all milk utensils, such as strainers, 

 pails, dippers, cans, etc., after each use. 



2. Wash and scald all parts of the cream separator that 

 come in contact with milk and cream, after each use. 



3. Cool the cream as soon as it leaves the separator to as 

 low a temperature as possible, preferably below 60 F. 



4. Use a cream cooling tank and keep the cream in cold 

 water until it leaves the farm. 



5. Protect the cream cans in transit from summer heat by 

 covering them with wet blankets. 



6. Do not allow the cans to stand on the station platform 

 exposed to the sun in hot weather- 



