74 Agricultural Bacteriology. 



milk also facilitates the coagulation of the curd. The 

 whey is removed from the curd by straining. The cheese 

 is then salted and is ready for use. Its flavor is that 

 of sour milk, or butter milk, as it is really a concentrated 

 form of sour milk. It contains, of course, an immense- 

 number of lactic acid bacteria. Cottage cheese has poor 

 keeping qualities, since mold soon begins to grow on the 

 surface of the moist mass of curd. 



As representative of the second group, the typical 

 American cheddar and the Swiss cheese are the best 

 known. In these types the casein is curdled by the ad- 

 dition of rennet extract, the curdling action being de- 

 pendent upon the coagulating enzymes contained in this 

 animal extract. By cutting the curd mass and warming 

 the same, the whey is rapidly expressed, leaving a firm 

 solid curd, which is formed into various shapes by plac- 

 ing the same in moulds. The fresh curd is tough, rub- 

 bery, tasteless, and practically insoluble in water, but 

 when placed under proper curing conditions, becomes in 

 time, soft, plastic, high in flavor, and a large part of it is 

 soluble in water. A "ripe" or cured cheese is easily di-, 

 gested while green cheese is indigestible. 



There are at least four hundred different kinds of 

 cheese, but those which are of importance in the markets 

 of the world do not exceed twelve to fifteen. The re- 

 mainder have merely a local market in the districts 

 where made. All varieties are produced from milk and 

 yet the resulting product is far different. This in- 

 dicates that the conditions of manufacture and curing 

 of the product, directly or indirectly, play an important 

 part in determining the type of cheese. 



Milk for cheese making. It is very important that 

 the milk for cheese shall be normal in all respects and 



