BACTERIA AND BUTTER-MAKING 2(X) 



day's churning. In this way some starter is reserved each day 

 to be used in the cream collected for the day, and thus the or- 

 iginal starter is carried on from churning to churning. After 

 some days, however, it is necessary to resort once more to a 

 new pure culture built up in the same way. The reason for this 

 is that the miscellaneous bacteria in the cream may develop in 

 larger numbers each day, until eventually the cream contains 

 too many of the undesirable organisms. How long a starter 

 may be carried from day to day before a fresh one must be 

 substituted cannot be definitely stated. It is customary to con- 

 tinue the same starter for a week, sometimes for two weeks, 

 but rarely for a longer period than this. 



THE USE OF A STARTER 



In Ordinary Cream. In this case, the starter prepared as 

 above described is simply added to the cream of a day's collec- 

 tion, in proportions which experience has found to be most use- 

 ful, without previous treatment of the cream. In using the 

 starter thus it is evidently desirable that the cream should be 

 as fresh as possible, because the fresher the cream the smaller 

 the number of bacteria in it, and the greater the chance that 

 the starter will overcome them and produce its desired effect. 



The use of starters in this way is open to a theoretical ob- 

 jection. The cream that has been brought to the creamery al- 

 ready contains bacteria in large numbers and, ordinarily, in 

 considerable variety. These bacteria would themselves produce 

 the ripening of cream, even without any starter, although it 

 would be a slower process than when the starter was added. 

 The effect of the starter added to the cream already filled with 

 bacteria in great numbers will evidently not always be uniform. 

 It may be that the bacteria already present will produce their 

 own effect in ripening quite independent of the starter. It may 

 be, on the other hand, that the starter added in considerable 

 quantity will quite overcome the effect of the smaller number 



