404 MANUAL OF MILK PRODUCTS 



they are filled full, it is difficult to prevent contamination from 

 the covers, which are hard to sterilize when the pasteurization 

 is done in hot water. 



4. Protect the containers with regular covers (caps or 

 tops) . 



5. Pasteurize by heating to a temperature of 180 to 200 F. 

 for thirty minutes or longer, and then cool to ripening tempera- 

 ture of 60 to 75 F. Pasteurization may be accomplished by 

 tying a string about the necks of the bottles and suspending 

 them in a pail or vat heated by steam or in a kettle or dish 

 heated on a stove. (If pasteurized over a fire, do not let the 

 bottles rest on the bottom of the receptacle.) Other supports 

 may be used to keep the containers from tipping over. If 

 glass containers are used, the temperature should be raised and 

 reduced slowly in order to prevent breaking. 



6. After pasteurization the milk is ready for inoculation. 

 Inoculate in a quiet place where the wind cannot blow dirt and 

 bacteria into this clean seed bed. With dry fingers remove 

 the cover and place it in a clean spot. Pour in all of the com- 

 mercial culture, or two to ten per cent from the previous day's 

 culture. 1 



7. Ripen at about 60 to 75 F. The first inoculation from 

 the commercial culture should be ripened at about 70 to 85 F. 

 The smaller inoculations require higher temperatures than do 

 the larger inoculations. By experience an operator can soon 

 learn what inoculation and temperature should be used to ripen 

 his starter in a given time. Usually a 1 to 8 per cent inocula- 



1 The amount of ripened starter for inoculation can be measured 

 accurately in a vessel, such as a sterilized cup or spoon, or it can be 

 determined rather closely by the eye. Place the thumb above the 

 milk line in the bottle to be inoculated, in this way measuring the 

 amount to add, and raise the milk line to that mark by pouring in the 

 ripened starter. Be sure that the curd from the previous day is well 

 broken. After inoculation, shake the freshly inoculated sample so as 

 to distribute the bacteria. 



