Bacteriology 13 



Adding the Ctdture. 



After being pasteurized, the milk should be cooled 

 to a temperature of 80° F. — a suitable temperature 

 for the development of the lactic acid-forming or- 

 ganisms. The commercial or pure culture is added 

 to the milk and mixed thoroughly by shaking the 

 bottle. The shaking should be repeated four or five 

 times every fifteen or twenty minutes. The milk 

 should be placed in a room or incubator with a tem- 

 perature as near 80° F. as possible. A uniform 

 temperature is necessary for the growth of the or- 

 ganisms. The bacteria in the pure culture are more 

 or less dormant, so that this higher temperature is 

 necessary to stimulate their activity. The milk 

 should be coagulated in eighteen to twenty-four 

 hours, depending largely on the uniformity of the 

 temperature maintained in the incubator. 



"Mother" Starter, or Startolme. 



The thickened sour milk obtained by inoculating 

 the sweet pasteurized milk with the pure culture of 

 lactic acid-forming bacteria is known as " Mother " 

 starter, or Startoline. Its physical properties, odor 

 and taste should be examined carefully. 



Sometimes the first few inoculations from a new 

 culture will show signs of gas, but ordinarily this 

 will quickly disappear and have no injurious effect 

 on the starter. It should have a clean. sour-cream 

 odor and be smooth, thick and creamy, entirely free 

 from lumps, whey, and gas pockets. This starter 

 may have an objectionable flavor, due to the media 

 in which the organisms were growing when shipped. 

 In such cases it is necessary to carry one or two 

 propagations to overcome the flavor, to enliven the 

 micro-organisms and to secure the quantity desired. 



