IX] 



factory article, no doubt necessary, since without 

 their help butter tastes flat. Yet butter made 

 without their aid is still capable of being used. On 

 the other hand, in cheese -making, bacteria are 

 absolutely indispensable, since there can be no doubt 

 whatever that what imparts to a cheese its char- 

 acteristic properties, and indeed renders it so 

 desirable an article of food, viz. its flavour, is due 

 to the action of the different kinds of bacteria or 

 classes of bacteria. The proper flavour of cheese is 

 the result of a ripening process in which the chief 

 agents are bacteria. This ripening process goes on 

 at different rates in different cheeses, and may last 

 for weeks or months. To the cheese-maker, there- 

 fore, the assistance which the bacteriologist is likely 

 to afford is of the very highest importance. 



Conditions determining Quality of Cheese. 

 As fat is the chief constituent of butter, so casein is 

 the chief constituent of cheese ; but while fat pre- 

 dominates in butter over all other ingredients, in 

 many cheeses the amount of fat present may be quite 

 equal to, and, indeed, largely exceed, the amount of 

 casein. Although this is the case, it is the changes 

 which go on in the ripening process in the casein that 

 are of chief importance. The means taken to produce 

 different kinds of cheeses are various. The nature of 

 the cheese will be determined by a number of con- 

 ditions, among which may be mentioned the method 



