340 CHEESE 



In some cases cheese is made without rennet, by simply allowing 

 the milk or cream to turn sour and thus bring about the coagulation 

 of the casein. This method is chiefly used for the preparation of cream 

 cheese. 



Soft cheeses are made by coagulating with rennet at a low tempera- 

 ture (about 25 to 30). They always contain a considerable quantity 

 of water. Brie, Camembert and Neufchatel are types of this class. 



Hard cheeses are formed when the coagulation takes place at about 

 35. 



The quality of a cheese largely depends upon the amount of fat in 

 it. Some hard cheeses are made from enriched milk, i.e., milk to 

 which additional cream has been added. Stilton cheese is an example. 



From whole milk, Cheddar, Cheshire and Wensleydale, Gruy^re, 

 Edam and Gorgon zola cheeses are made. 



From mixtures of whole milk and skimmed milk, Gloucester, 

 Leicester and (sometimes) Cheddar, also Parmesan and (often) Edam 

 cheeses are derived. 



From skimmed milk, various poor cheeses, e.g., Limburg and Dan- 

 ish, are produced, but are of little value or importance. 



Roquefort cheese is made from sheep's milk, as are several other 

 varieties. 1 



The general practice in making a cheese is to hasten the ripening 

 of the milk by the addition of a " starter," consisting of sour milk con- 

 taining large numbers of the lactic bacterium, or a pure culture of the 

 lactic ferment. When lactic fermentation has proceeded far enough, 

 i.e., when the proportion of lactic acid in the milk reaches a certain 

 amount (determined most safely by titration with standard soda solu- 

 tion, and often about 0'2 per cent lactic acid) it is ready for curdling. 

 By trial with a small quantity of the milk at about 30, the amount of 

 rennet required to cause coagulation in the desired time is then deter- 

 mined, and this quantity is then added to the main mass. If the 

 cheese be wanted to cure rapidly, the rennet should cause coagulation 

 in about 20 minutes ; if a slow curing be desired, in about 40 minutes. 

 When the curd is solid, the temperature is raised to about 37 and 

 kept constant until a hot iron, placed in contact with the curd and 

 drawn away, pulls off threads about half an inch in length. This usu- 

 ally occurs in about one or two hours after the milk is heated to 37. 



The whey is then run off and the curd stirred and turned, to allow 

 the whey to escape. The curd is next reduced in -a mill, salted and 

 pressed in moulds. The cheeses are then stored away at a tempera- 

 ture of 15 to 18 and allowed to ripen. 2 



The changes which occur during ripening are little understood, 

 although recently, an enormous number of researches have been made 

 on the subject. Considerable loss of water occurs, the milk sugar of 

 the whey left adhering to the curd is converted into lactic acid, but 

 the most obscure changes are those which affect the proteid matter. 

 The original casein is converted into other more digestible and 



1 Sartori, Jour. Chem. Soc., 1891, Abstracts, 951. 



2 For a detailed account of Cheddar cheese-making, see a Report by Lloyd, 

 published by the Board of Agriculture, 1899. 



