1 66 Condensed Milk and Milk Powder 



different degrees of concentration, and then decide how much evap- 

 oration it will stand without developing subsequently a permanent 

 curd in the sterilizer. 1 



Effect of Sterilization. — The coagulum is formed in the steril- 

 izer. The higher the temperature, other conditions being the same, 

 the firmer the curd. The lowest temperature that will efficiently 

 sterilize the evaporated milk should, therefore, be used. Since the 

 sterilizing temperature to be maintained cannot be modified below 

 certain limits, it is necessary, when the milk is very sensitive to 

 the heat, to lower the degree of concentration. In some factories 

 fractional sterilization is resorted to with batches of milk that are 

 suspicious. By so doing, lower temperatures 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 temperature 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 safe- 

 guard against the formation of excessive curd in the sterilizer. 



Effect of Homogenising Evaporated Milk. — Excessive pressure 

 in the homogenizer tends to so change the physical properties of 

 the casein as to render it more sensitive to the sterilizing 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 pounds 

 or below. 2 



Acid Elux 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 manufac- 

 ture and sealing of the cans. 



1 For detailed discussion ol relation of concentration to curdiness of evaporated milk 

 see Chapter IX on "Manufacture ol Evaporated Milk," "Striking," p. 83 



2 For detailed discussion of the effect of homogenizing on curdiness see Chapter X on 

 "Homogenizing" and Chapter XXIV on "Separated and Churned Evaporated Milk," p. 167 



