88 CREAMERY BUTTER MAKING 



which, together with their by-products, is fatal to their 

 development. 



The chief difference in the three cultures prepared by 

 these men lies in the intensity of acid produced. The 

 "lactic" is the most vigorous, and the "Boston" the least 

 vigorous acid producing culture, while the "duplex" 

 seems to take an intermediate position. Sometimes, how- 

 ever, it is difficult to distinguish between these cultures. 



Erricson's culture has only recently been placed upon 

 the market but is already popular. It is sent out in the 

 form of a liquid (also as a powder) which appears to con- 

 sist of sterilized milk to which some sugar has been added. 



Hansen's lactic ferment is put up in the form of a 

 powder which consists chiefly of sterilized milk with 

 possibly slight additions of casein and starch. In this 

 dry powdery medium the germs remain in a dormant 

 condition. When held a long time in this condition their 

 vitality seems to become impaired. 



Preparation. Most of the commercial cultures are 

 sent out in one ounce bottles which are hermetically 

 sealed. The method of making starters from them is the 

 same for all whether they are obtained in the liquid or 

 in the dry form. 



In making the first batch of commercial starter, the 

 entire contents of the bottle is put into a quart of skim- 

 milk, sterilized by keeping it at a temperature of 200 F. 

 for two hours, and then cooling to 80 which temperature 

 should be maintained until the starter has thickened. A 

 new starter is now prepared by introducing the quart of 

 starter into fifty pounds of skim-milk, pasteurized by 

 keeping it at a temperature of 170 to 185 for thirty 

 minutes and then cooling to 65 F. All subsequent starters 

 are prepared in the same way except that the amount of 



