CREAM RIPENING 111 



Each package costs about 75 cts. So long as the average 

 person on the farm is not trained in starter propagation, 

 the best starter to use in making dairy butter is one of 

 the natural sorts. Usually buttermilk is the most con- 

 venient. Natural starter is not good enough to employ 

 regularly in a creamery. 



81. Artificial starter. — Artificial starter is a pure 

 culture of lactic acid-producing bacteria. These micro- 

 organisms are isolated from milk and are cultivated on a 

 medium that can readily be put in good form for trans- 

 portation. There are two general forms of media in which 

 artificial starter is shipped, the powdered and liquid. 

 The powdered condition, in which there is very little 

 moisture, holds the bacteria in the active stage longer 

 than the liquid medium. The powder forms may be held 

 at room temperature, while the liquid cultures must be 

 put in the refrigerator. The liquid culture, which con- 

 tains bacteria not quite so dormant as those in the 

 powder culture, must be used before the expiration of 

 the time that is stamped on each bottle. 



Usually it is necessary to set a new starter every three 

 or four weeks. This depends largely on the carefulness 

 of the operator. Often a very careful butter-maker will 

 carry a starter over a j^ear without renewal. In case a 

 liquid starter is employed, the company supplying the 

 cultures has a standing order to send a bottle of starter 

 at regular intervals. When the powder form is used, 

 several samples are purchased at one time. 



82. Apparatus. — In the cultivation of starter, the 

 usual practice is to carry the starter from day to day in a 

 small quantity, which is more carefully handled. This 

 small amount is termed " mother starter." The choice 

 of containers for mother starter depends largely on condi- 



