246 MANUAL OF MILK PRODUCTS 



Amount of starter to use. — The amount of starter which 

 should be used with any given lot of cream will vary with the 

 age of the cream, the percentage of fat, and the time during 

 which the ripening process is to take place. The fresher the 

 cream is when the starter is added, the greater the opportunity 

 to control the ripening process, due to the fact that lactic acid 

 bacteria soon develop sufficiently to hold in check the growth 

 of the undesirable species which may be present. Also the 

 fresher and sweeter the cream, the smaller the per cent of starter 

 needed. On the other hand, if the cream is old and partly 

 ripened, a larger per cent may be desirable. Under some condi- 

 tions, as low as 2 per cent of starter may be used in sweet or 

 pasteurized cream, but under ordinary conditions, from 10 to 

 20 per cent will give good results. If higher percentages than 

 this are used, it involves considerable labor in the preparation 

 of the starter and a larger percentage of buttermilk to handle 

 and the loss of fat in churning may also be increased. If the 

 butter-maker knows the quality of his cream and the length of 

 time during which the ripening process should take place, he 

 can judge very accurately the amount of starter which should be 

 used. 



Quality of starter. — It is of the greatest importance that the 

 starter used should be of the best possible quality. While it is 

 not absolutely necessary that the starter should be a pure 

 culture, the more nearly pure it is, the better the results which 

 will be obtained. It is also necessary that the bacteria be in 

 an active, vigorous condition in order that they may develop 

 rapidly in the cream. There are many strains of the lactic 

 acid producing organisms, and some strains give better results 

 than others, especially in the flavor of the butter. The com- 

 mercial cultures which are on the market contain strains which 

 have been carefully tested and can be relied on to give satis- 

 factory results if they are properly prepared. In the prepara- 

 tion of the starter, it is of the greatest importance that the skim- 



