STARTERS. 221 



powder thoroughly mixed with the milk than it is to get the 

 liquid cultures mixed. If anything is used with which to stir 

 the sample, it should be sterihzed before coming in contact 

 with the milk. This appUes in the preparation of all cultures. 

 In testing or sampling the mother-starters, nothing should be 

 allowed to come in contact with it unless it has previously been 

 thoroughly sterilized. The powder cultures are usually more 

 vigorous in their effect than most of the liquid cultures now 

 on the market. The powder cultures usually coagulate the 

 sample in about twenty-four hours, and if the operator is used 

 to handling the liquid cultures, he should watch the mother- 

 starters prepared from powder cultures, so that they do not 

 get overripe. It is very essential that the starters do not get 

 overripe. The time when the germs are most numerous and 

 most active in the starter is about the time when the sample 

 coagulates. As soon as this stage has been reached, or just 

 previous to coagulation, the starter should be cooled down to 

 at least 50° ¥., or lower if possible This prevents any further 

 growth of germs and the sample can be kept a short time 

 without injury. 



Directions usually accompany each of the cultures, but the 

 above will be found to produce good results with all of those 

 mentioned in the above outhne. 



By inoculating from 2% to 5% or more of the mother- 

 starter into a large sample of pasteurized milk, any desired 

 amount of starter can be prepared. In selecting this amount 

 of milk, as much care as possible should be taken in order to 

 select the best kind of milk, and keep it from being contaminated. 

 When this large sample of starter is at the proper stage of 

 coagulation, it should be used at once, or else cooled down to 

 about 50° F. The amount of mother-starter with which to 

 inoculate the large sample of starter may vary a little with- 

 out any bad effects. If the large sample of starter is to be 

 ready for use in a short time, a larger portion of the mother- 

 starter can be used for inoculation. If the temperature at 

 which the starter is set and the amount of mother-starter used 



