142 MAINE AGRICULTURAL EXPERIMENT STATION. 



One reason why there has been more risk in handling cream 

 than milk is the greater value of the cream, involving greater 

 loss when it fails to reach the market in good condition. 



As is very generally known at the present time, the souring of 

 cream is due to the growth of minute organisms or plants called 

 bacteria. These bacteria are not present in the milk while it is 

 yet in the udder of the cow, but they are so universally distrib- 

 uted, especially in warm weather, about the barns and in the 

 dust of the air, that the milk has scarcely reached the pail on its 

 way from the udder of the cow before it is contaminated with 

 them. Under favorable conditions for their growth they will 

 cause the milk or cream separated from it to sour and no ordin- 

 ary straining or even passing the milk through a cream sepa- 

 rator will remove them. After the bacteria that cause souring 

 of milk and cream are once introduced, they will multiply rap- 

 idly and soon do their work unless they are destroyed or held in 

 check, that is, their growth and multiplying prevented. 



METHODS OF DESTROYING THE GERMS. 



There seem to be but three methods of preventing this growth 

 and consequent souring of the cream: First, by means of cold; 

 second, addition to the milk or cream of some germicide like 

 boric or salicylic acid; or third, by subjecting the cream to a 

 sufficiently high temperature to destroy the germs. Each of 

 these methods has its advantages and disadvantages when put 

 to practical use, and it is the purpose of this bulletin to show 

 which of them has the most to recommend it. 



USE OF COLD. 



In this climate during steady cold weather there can be but lit- 

 tle objection to the use of cold as a preservative in shipping 

 cream to local markets. Cream that is kept at a temperature 

 below 45 F. will remain sweet for a long time, but in warm 

 weather and when it has to be shipped to a distant point in warm 

 cars, the necessary cold is secured by the use of ice, which is an 

 unsatisfactory method on account of expense, although the qual- 

 ity of the cream brought to market by this method is of the 

 highest. ; .. 



