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. Tf the plain condensed bulk milk comes from the pan in 
lumpy condition, it can usually be reduced to a smooth bee 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, 1s 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 sweet a condition as possible. 
Effect of Relation of Mineral Constituents of Milk.— More 
recent studies of the heat coagulation of milk, however, by Som- 
