THE PRODUCTS OF THE DAIRY. 191 



in large dairies and creameries, though the cost of the 

 separator and the power required to run it have pre- 

 vented its rapid adoption in the small home dairy. 



The various large machines have now reached a remark- 

 able degree of perfection ; and it is only a question of time 

 before those adapted for the small dairy, both in point 

 of cost and power, will be available. 



Butter. — Butter consists of the fat globules of milk 

 gathered into a solid form. Like other products of the 

 dairy, it is subject to wide variations in composition and 

 quality. Good butter should contain at least eighty-five 

 per cent of pure butter fat, not more than twelve per cent 

 of moisture, and less than one per cent of casein. The 

 content of ash, or mineral salts, depends upon methods 

 of salting, though it should not exceed one and one-half 

 per cent. 



The yield of butter from a given quantity of milk de- 

 pends chiefly upon the amount of fat in the milk, and the 

 composition of the product secured. If milk is bought 

 for butter-making, it should be paid for on the basis of 

 content of butter fat, rather than by weight or volume. 

 The yield of butter from a given quantity of fat in differ- 

 ent lots of milk also varies slightly, since the fat in all 

 milks cannot be uniformly recovered as butter even under 

 uniform methods of treatment. This is believed to be 

 largely due to differences in the size of the fat globules ; 

 the larger the globule the greater the proportion of 

 fat recovered; in practice, however, this point is largely 

 disregarded. 



The properties of butter which determine its edible 

 quality and appearance are flavor, keeping quality, solid- 



