BUTTER AND CHEESE 139 



been extensively advertised as an ice-cream producer which did 

 not require the use of cream or of ice. 



Occasionally it may become necessary to examine sour milk 

 and buttermilk for the presence of toxins and objectionable bac- 

 teria and other undesirable organisms. Because of the careless 

 and more or less promiscuous handling of buttermilk before it 

 reaches the consumer, it is especially liable to the invasion of 

 foreign organisms. The routine examination of buttermilk is 

 largely limited to a direct microscopical inspection. Mold spores 

 and yeast cells should be sparingly present and the predominating 

 bacilli should be small 1 (lactic acid formers) and of irregular and 

 rather indefinite outline. Mold and cocci should be very sparingly 

 present. 



To examine butter for the presence of bacteria (direct micro- 

 scopical method) and other contaminations, place i gram of the 

 butter in 10 cc. of ether and shake until all of the butter fat is 

 dissolved. Pour the solution into the special centrifugal tube 

 and centrifugalize for 5 min. Wash the contents of the i cc. 

 end tube into 10 cc. of ether and again shake and centrifugalize. 

 Pour off the ether and add 2 cc. of a 2 per cent, sodic hydrate 

 solution and shake until the casein is dissolved. The sodic hydrate 

 solution emulsifies the small amount of fat present. Examine 

 the emulsion for bacteria, counting the bacteria and body cells 

 by means of the hemacytometer. 



Butter and cheese made from the milk of animals suffering 

 from foot-and-mouth disease have transmitted this disease to 

 humans. The bovine type of tuberculosis has resulted from the 

 consumption of milk, cream and butter. Tubercle bacilli have 

 been found in the more quickly ripened cheeses. Tubercle bacilli 

 do, however, not survive long in soured cream or milk, perhaps 

 not over 2 or 3 days. 



The following are some of the more important organisms con- 

 cerned in the ripening of cheese. 



1 The Bacillus bulgarius is comparatively large (i X 6/0- 



