MILK 297 



' ' After the casein has been removed there remains 

 nothing but a transparent liquid that might be taken 

 for water slightly tinted with yellow. This liquid 

 is called whey. It contains little besides water with 

 a small quantity of sugar of milk which gives it a 

 slightly sweet taste. It is especially in Switzerland 

 that sugar of milk is obtained on a large scale by 

 the evaporation of the liquid that remains after re- 

 moving the cream and curds from the milk. In spite 

 of its name this substance has nothing in common 

 with ordinary sugar, the white loaf-sugar we use ; it 

 is a dull-white substance, rather hard, crunching 

 under the teeth, and of a slightly sugary taste. It 

 is used only in pharmacy. 



" Cream and casein constitute the nutritive ingre- 

 dients of milk, and determine its food value. The 

 milk that is richest in these constituents is sheep's 

 milk, next comes goats' milk, and last of all cows' 

 milk. Although of little value to us, sugar of milk 

 claims our attention for a moment on account of the 

 change it undergoes to the great detriment of the 

 milk itself. Little by little, especially when exposed 

 to the heat of summer, this sugary matter sours 

 and becomes an acid. That is what makes milk 

 sour if kept too long. Of course when this sourness 

 shows itself the milk soon curdles. Coagulation 

 takes place as if an acid had been added to the 

 milk. Hence, to keep milk for some time and prevent 

 its turning sour of its own accord, this acidulation 

 of the sugar of milk must be delayed. This is done 

 by taking care to boil the milk a little every day." 



