Condensed Milk and Milk Powder 171 



affects the casein, that the latter is more prone to curdle in the 

 sterilizer. However, experience has amply shown that the maximum 

 pressure required to prevent fat separation in the finished product, 

 is not great enough to seriously affect the behavior of the casein 

 during sterilization. Hence, the proper regulation of the pressure 

 and the intelligent use of the homogenizer, furnish a satisfactory 

 and reliable means to prevent fat separation. Under average con- 

 ditions, the use of sufficient pressure to reduce the fat globules to 

 one-third of their original size, practically destroys the power of the 

 fat globules to rise to the surface. A pressure of approximately 

 one thousand pounds per square inch, makes possible this reduction 

 of the size of the fat globules. 1 



Fermented Evaporated Milk 



General Description. — Fermented evaporated milk is evap- 

 orated milk, which after sterilization, has undergone fermentation. 

 The type of fermentations found in this product varies with locality, 

 season of year and factory conditions. The contents of the cans 

 may have soured with curd formation, or a curd may have formed 

 without acid development, or the fermentation may be gaseous, in 

 which case the cans bulge, and these gaseous fermentations may be 

 accompanied by acid formation or by putrefactive products. In all 

 cases of fermented milk the product is entirely worthless. These 

 defects are usually, though not always, detected during the period 

 of incubation. 



Fermented evaporated milk is the result, either of incomplete 

 sterilization, or of leaky cans. The causes of fermented evaporated 

 milk differ with the specific type of fermentations produced; they 

 will be discussed separately and as relating to the respective types 

 of fermentations. 



Acid Fermentation, Sour, Curdled, Evaporated Milk 



General Description. — Upon opening the cans the contents 

 are found to be sour and curdy. 



Causes and Prevention. — This condition is the result of the 

 presence of acid producing species of micro-organisms, usually of 

 the lactic acid type, which sour the milk, and the acid produced 

 curdles the casein. Since the majority of the lactic acid bacteria 



1 For details on the use of homogenizer see Chapter X on "Homogenizing," p. 85 



