UNSWEETENED CONDENSED MII^K DEFECTS 217 



batches of milk that are suspicious. By so doing, lower tem- 

 peratures can be used effectively, but this process calls for much 

 more labor, increases the cost of manufacture and decreases the 

 capacity of the factory. 



Effect of Fractional Curdling. Experience has shown that, 

 if the proteids in evaporated milk are partly precipitated by heat 

 before the milk reaches the sterilizer, the curd, or lumps formed 

 in the sterilizer are less firm and can be shaken out more readily. 

 It is, therefore, advisable to heat the milk in the forewarmers to 

 as near the boiling point as possible and to hold it at that tem- 

 perature for at least five minutes before it is drawn into the pan. 

 The superheating of the evaporated milk before it leaves the pan 

 is an additional safeguard against the formation of excessive curd 

 in the sterilizer. 



Effect of Homogenizing Evaporated Milk. Excessive pres- 

 sure in the homogenizer tends to so change the physical prop- 

 erties of the casein as to render it more sensitive to the steriliz- 

 ing process. Evaporated milk, homogenized under excessive 

 pressure almost invariably forms a firm, unshakable curd in the 

 sterilizer. The homogenizing pressure should be kept down to 

 one thousand to fifteen hundred pounds. 2 



Acid Flux in the Cans Causes Lumps. Similar as in the case 

 of the sweetened condensed milk, the presence of acid flux in the 

 cans of evaporated milk causes lumpiness. The acid that reaches 

 the interior of the cans causes the milk coming in contact with 

 the seams to curdle. Only acid-free flux should be used in the 

 manufacture and sealing of the cans. 



Grainy Evaporated Milk 



General Description. This term is sometimes applied to 

 lumpy milk, in which case it means the same. By grainy milk, 

 however, is generally understood milk which contains a sediment 

 of a white granular appearance, which is insoluble. 



Causes and Prevention. This granular sediment is largely 

 found in the hermetically sealed cans after the sterilizing process. 

 It is due to excessively high sterilizing temperatures or too long 



1 For detailed discussion of relation of concentration to curdiness of evap- 

 orated milk see Chapter VIII on "Striking." 



8 For detailed discussion of the effect of homogenizing on curdiness see 

 Chapter IX on "Homogenizing" and Chapter XXIV on "Separated and Churned 

 Evaporated Milk." 



