UNSWEETENED CONDENSED MILK DEFECTS 253 



returned milk is often manufactured into plain condensed bulk 

 milk. This defect can be avoided by neutralizing the milk before 

 heating, with an alkali (sodium bicarbonate or lime water), heat- 

 ing less intensely, or by not carrying the condensing process quite 

 so far. If the plain condensed bulk milk comes from the pan in 

 lumpy condition, it can usually be reduced to a smooth body by 

 passing it through an ice cream freezer at ordinary temperatures. 



Lumps of Curd in Evaporated Milk. The danger of lump- 

 iness, or curdiness in evaporated milk is greatly augmented by 

 the fact that, in addition to the causes named under plain con- 

 densed bulk milk, the sterilizing process must be dealt with. 

 The high sterilizing temperature used, tends to precipitate the 

 proteids of milk, and the temperature cannot be reduced below 

 certain limits without impairing the keeping quality of the pro- 

 duct. Most of the evaporated milk, after sterilization, is sub- 

 jected to the shaking process in which the coagulum in the cans 

 is reduced to a homogeneous creamy fluid, provided that the curd 

 is not too hard. A curd will form in the sterilizer in the majority 

 of cases. If it is soft enough, so that it can be completely broken 

 up, no harm is done. If it is so firm that mechanical shaking 

 fails to cause it to disappear, then the evaporated milk will reach 

 the market in lumpy condition and is difficult to sell. 



Effect of Quality of Fresh Milk. The quality of fresh milk 

 is all important in preventing lumpy evaporated milk. The milk 

 must come from healthy cows in good, normal physical condition. 

 It must not contain colostrum milk nor be stripper milk and it 

 must receive the best of care on the farm and reach the factory 

 perfectly sweet. Milk that is not of high quality in every respect 

 should not be received at the factory. 



The acidity of milk due to acid fermentation, lowers the 

 curdling point of the milk, partly by changing the reaction and 

 partly by lowering the citric acid content. High acidity there- 

 fore is one of the causes of curd formation in evaporated milk. 

 If abnormal curdling is to be prevented, one of the first and fun- 

 damental essentials is that the milk reach the condensery in as 

 fresh and sv/eet a condition as possible. 



Effect of Relation of Mineral Constituents of Milk. More 

 recent studies of the heat coagulation of milk, however, by Som- 



