358 SCIENCE AND PRACTICE OF CHEESE-MAKING 



of a neutral salt. These substances are chiefly lime 

 compounds or compounds containing calcium as a 

 base. Over one-half and, probably, about three- 

 fourths, of the calcium compounds in milk are in such 

 form as enable them to combine with lactic acid. A 

 considerable part of the calcium in milk is in com- 

 bination with phosphoric acid in the form of insoluble 

 compounds, probably dicalcium phosphate in large 

 part, which is held in suspension in the form of very 

 minute, solid particles. Some believe that the cal- 

 cium phosphate is in direct combination with casein 

 in milk. The action that probably takes place can be 

 represented as follows : 



Lactic acid -f- insoluble calcium phosphate = cal- 

 cium lactate -f- soluble calcium phosphate (mono or 

 acid-calcium phosphate). Now, mono-calciimi phos- 

 phate is an. acid salt ; it neutralizes alkalis and tastes 

 sour. Therefore, when we talk about lactic acid in 

 cheese-making, we really mean the products formed 

 by the action of lactic acid — calcium lactate and cal- 

 cium acid phosphate. 



The first effect of the formation of these soluble 

 lime salts is to promote the coagulating effect of 

 rennet; and the particular thing accomplished by 

 ripening milk for cheese-making is the formation in 

 small, but sufficient, quantities of cakium lactate and 

 soluble calcium phosphate. The succeeding changes 

 in curd, the formation of a superficial film on each 

 small piece of curd, the shrinking with the simul- 

 taneous expulsion of whey, the stringing on a hot 

 iron, the change in texture of curd to the softer, 

 velvety form, resembling the meat of a chicken's 

 breast, the plastic condition — these changes all 



