614 MILK 



quality of the milk he purchases. The sediment test for dirty 

 milk, the Babcock test for fat, and the Hart test for casein are 

 easily made, and furnish the cheese maker with the necessary 

 information about the quality of the milk to be used for cheese 

 making. ' The Babcock and Hart tests also furnish an equitable 

 basis for valuation of the milk. 



It is claimed that exceptionally pure milk is not suitable for 

 cheese making because it is so poor in bacteria that cultures of 

 micro-organisms must be used to produce results. On the other 

 hand, some bacteria commonly present in unclean milk may cause 

 abnormal flavors or objectionable gas formation. Pasteurized 

 milk has the advantage of containing but few bacteria, and 

 when it is used, pure cultures of cheese-forming bacteria can be 

 inoculated into the milk. However, there are some drawbacks 

 to the use of pasteurized milk which as yet have been only par- 

 tially overcome. The first objection to be raised is the retarda- 

 tion of rennet action upon the casein. This is due to the precipita- 

 tion of calcium salts by heat, and can be rectified by addition 

 of calcium chlorid or some other soluble calcium salt. The sec- 

 ond objection is the softness of the curd produced with the use of 

 pasteurized milk. No universal remedy for this trouble has 

 been found and, therefore, pasteurized milk is not as suitable for 

 the making of hard cheeses as for the manufacture of soft ones. 

 However, Sammis and Bruhn have succeeded in making a satis- 

 factory Cheddar cheese from pasteurized milk. Instead of using 

 sour milk they added hydrochloric acid to produce coagulation. 

 The product scored better than cheese made from the same milk- 

 supply in the usual manner, and the yield was nearly 5 per cent, 

 greater. It is confidently expected that some means will be dis- 

 covered which will correct the consistency of the curd from 

 pasteurized milk so that pasteurized milk can become the basis 

 of all kinds of cheese. When this can be done the cheese maker's 

 work will be facilitated, since under present conditions his milk- 

 supply varies from day to day in bacterial content, coming, as it 

 does, from a number of producers, and therefore constituting a 

 mixed product. Pasteurization would make the quality of the 

 milk fairly constant and the results would be uniform with the use 

 of cultures of micro-organisms. There would be established a regu- 

 lar routine of work which is unheard of under present conditions. 



Milk for cheese making has been sterilized by the use of hydro- 

 gen peroxid and then inoculated with cheese-ripening cultures in 

 order to avoid the detrimental influence of the many bacteria 

 usually present in . milk. However, the process is confined to 

 special kinds of cheese and has been only partially successful. 

 - It is true that the use of pure cultures for cheese making is 



