6 SCIENCE AND PRACTICE OF CHEESE-MAKING 



utensils made of tin, unless great care in cleaning is 

 used, contain dirt that holds large numbers of bacteria. 

 Rust and imperfect soldering of joints furnish places 

 for dirt to get out of easy reach. Without prompt 

 ^r .^^.w^nd extreme care, strainers easily become filthy and 

 i^sv'/^/^are then simply breeding places for bacteria. When 

 ,^^c^^ milk cans are used for carrying back whey to the farm 

 from the cheese-factory, the cans often are not cleaned 

 promptly, and, when finally attended to, are not treated 

 with proper thoroughness. Through the medium of 

 a dirty whey-vat, filth, as well as disease, germs 

 may be distributed throughout the whole neighbor- 

 hood. Even epidemics of typhoid fever have been 

 traced to this source of infection; certain diseases 

 have been similarly distributed among farm ani- 

 mals, as, for example, tuberculosis in calves and 

 hogs. 



Unclean surroundings after milking. — Milk, even 

 when drawn under the cleanest possible conditions, 

 very easily becomes contaminated by being kept, even 

 for a short time, in any place that is not clean. 



Keeping milk cool. — At temperatures above 60° 

 F., milk more rapidly undergoes fermentation changes 

 than at lower temperatures (p. 290). 



ABSORPTION OF FLAVORS 



Milk, particularly when warm, possesses remarkable 

 ability to absorb and retain odors present in the sur- 

 rounding air. The most common sources of such 

 odors are the manure in unclean stables and any 

 strong-smelling food present in the stable during milk- 

 ing-time. Among the most common conditions under 



