190 THE BOOK OF CHEESE 



schools of makers has varied from an acidity of 0.20 of 

 1 per cent or even slightly higher percentage titrated 

 as lactic acid, to about 0.17 of 1 per cent as now preferred 

 by some of the most successful groups of workers. The 

 ripeness of the milk can also be determined by the use of 

 the rennet test. 



The milk may be ripened by allowing the lactic organisms 

 already present in the milk to develop naturally. This 

 requires considerable time and while the lactic acid-forming 

 bacteria are developing, other and undesirable fermenta- 

 tions may be taking place, so that the good results which 

 should follow the uninterrupted development of the lactic 

 acid-forming organisms are lost. Starter is commonly used 

 to produce the desired ripening of the milk. (For the 

 preparation of starter see Chapter IV.) 



Some makers put the starter into the empty vat (Fig. 

 31) and add the milk as it is received; others add it to 



FIG. 31. Steel cheese vat. 



the total volume of cold milk and then begin to heat it. 

 Whenever the starter is used, it should be strained to 

 remove lumps. These lumps might cause a mottled 

 color in the cheese. The best practice calls for an acidity 

 or a rennet test of the mixed milk after it has been 

 brought to the setting temperature in the vat. With 

 milk tested at this stage and the volume of milk in the 



