STARTERS 233 



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 this should not 

 happen. 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 F., or lower if possible. This prevents any 

 further growth of germs and the sample can thus 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 list. 



By putting from, 2 per cent to 5 per cent 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 con- 

 taminated. 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 

 without 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 

 for inoculation are the same from day to day, the starter will 

 be ripe at nearly the same hour every day, and, consequently, 

 more uniform ripening results can be obtained. The noticeable 

 coagulation of the starter when milk or skim-milk is used will 

 usually take place' when there is about .6 per cent of acidity. 

 A slight coagulation will take place when there is about .5 per 

 cent of acidity, but it is hardly noticeable. The coagulation- 

 point may vary with different samples of milk. 



If a mother-starter is to be kept any length of time it should 

 be inoculated into a sample of good fresh pasteurized milk about 



