562 



ANNUAL REPORT OF THE 



Off. Doc. 



in water. It is present io milk in amounts varjing from 4.5 to 5.5 

 per cent., and averaging 5 per cenj:. Its importance in dairy manu- 

 facture, especially in connection with butter and cheese, comes from 

 the readiness with which it is converted into lactic acid by various 

 organisms. This action will be studied in detail in the next chapter. 



6. The Salts of Milk (or Ash). 



The salts of milk, also called the mineral matter, or ash, are im- 

 portant constituents, though they are present in only small quan- 

 tities, varying from 0.50 to 0.90 per cent., and averaging about 0.70 

 per cent., as expressed by the ash. The elements which go to make 

 up the salts of milk, stated in the order of their abundance, are the 

 following: Phosphorus, potassium, calcium, chlorine, sodium, mag- 

 nesium, sulphur and iron. The calcium is probably present in the 

 form of calcium phosphates; the sodium, as sodium chloride; the 

 potassium, as potassium phosphate, chloride and citrate. 



7. The Gases of Milk. 



Milk contains more or less oxygen and nitrogen, some portions of 

 these gases being carried into it mechanically from the air in the pro- 

 cess of milking. It contains also carbon dioxide wheci freshly drawn, 

 probably between 3 and 4 per cent., a portion of which escapes at once 

 while being milked under usual conditions. 



We have now seen, in some detail, how many and what different 

 compounds are contained in milk. There are certain arbitrary divi- 

 sions of these compounds made for the sake of convenience. One 

 such division makes two classes of the compounds of milk — (1) water 

 and (2) solids, or milk-solids, or total solids, these including fat, 

 casein, albumin, milk-sugar and salts, or ash, of milk. Another divi- 

 sion is on the basis of the milk-fat, into (1) fat and (2) milk-serum, 

 this including all the milk except the fat, that is, water, casein, albu- 

 min, milk-sugar and ash. Separator skim-milk is nearly pure milk 

 serum. Then, again, the milk-solids themselves are divided into (1) 

 fat and (2) solids-not-fat, the solids-not-fat including the milk serum 

 less the water. 



Analvses of Milk. 



V 



Average of 5,552 American analyses com- 

 piled by the writer 87.10 



Average cheese-factory milk for the season 

 (May to November) In New York State,.., 87.40 



12.90 

 12.60 



3.90 

 3.75 



2.50 

 2.45 



0.70 

 0.70 



5.10 

 E.OO 



0.70 

 0.70 



