2 CHEESE MAKING. 
be filtered through a porcelain filter it will leave a gelatinons 
mass on the filter, which is the casein; or, if skim milk be re- 
volved for a long time in a separator bowl, a layer of casein 
will be deposited on the walls of the towl. Casein is dissolved 
in solutions of borax, scdium phosphate, and alkalies. It is used 
commercially as a sizing for paper. 
Albumen. The casein makes up abcut three-fourths of the 
proteids of milk. When milk has been coagulated by rennet the 
casein is precipitated. If the whey be heated to 180° F. another 
proteid will be thrown down, viz., the albumen. This is much 
like the white of an egg which is coagulated by heat. It is in 
solution until the heat precipitates it. Albumen is not incor- 
porated in Cheddar cheese in the ordinary method of manu- 
facture, and cannot apparently be so incorporated without re- 
sulting in the making of sour cheese. 
In addition to the casein and albumen of the milk, small 
amounts of other nitrogenous components are always present, 
but our knowledge of these substances is as yet incomplete. 
4. Ash. 
The ash is the bone-forming part of the milk and consists 
largely of phosphates of calcium and potash, with some chlor- 
ides. Although the ash is present only in small quantities in 
the milk it is of great importance in cheese making. <A part cf 
the calcium salts is supposed to be suspended as fine particles 
in the milk or held in combination with the casein, but a part 
is certainly held in solution and on this solubility of calcium 
salts depends the property of coagulation by rennet. If am- 
monium oxalate be added to milk in sufficient quantity, the 
soluble calcium salts will be changed to insoluble calcium ox- 
alate, and the milk will not curdle with rennet. Similar results 
can be obtained by heating the milk to 180° F. When a soluble 
calcium salt is added to such milk, the rennet will again act, in 
fact it will work faster than before because of the increase in the 
soluble calcium salts in the milk. 
5. Milk Sugar. 
The sugar of milk crystallizes in hard crystals; it is not as 
sweet as common cane sugar. It caramelizes at a hi h tempera- 
ture, giving the peculiar scalded taste to the milk. It is sepa- 
