152 MARKET DAIRYING 



are now in vogue : ( I ) the discontinuous method by which 

 every particle of milk and cream is heated from ten to 

 thirty minutes according as the temperature is high or 

 low; (2) the continuous method by which milk and cream 

 are permitted to pass in a constant stream through the 

 pasteurizer and are subjected on an average less than 

 one minute to the pasteurizing temperature. 



In general the most efficient pasteurization is obtained 

 with the discontinuous method. 



Pasteurizing Temperatures. Obviously where milk 

 is heated only a minute or less, a higher temperature 

 must be employed than where it is heated for a much 

 longer period of time. With the continuous method 

 the temperature varies from 160° to i8o° F. With 

 the discontinuous method the temperature varies 

 from 140° to 155° F. Exposing milk or cream to 

 a temperature of 145° F. for twenty minutes results 

 in very satisfactory pasteurization. ^The temperature and 

 time of exposure should always be such as to insure the 

 destruction of the tubercle bacillus, which is one of the 

 most resistant of the disease bacteria most commonly 

 "found in milk. 



Quiclc Cooling. In pasteurising the heating must be 

 quickly followed by thorough cooling. This is an ex- 

 tremely important part of the pasteurizing process. It is 

 desirable that the temperature be reduced at once to 45" 

 F. or below. 



Viscogin. Thorough pasteurization reduces the vis- 

 cosity or whipping property of cream. To restore the 

 original viscosity a solution (jf sucrate of lime is added, 

 which is known as viscogin. This solution is made by 

 adding an excess of slaked lime to three parts of sugar 

 dissolved in five parts of water. The mixture is al- 



