198 BACTERIA IN BUTTER. 



cooled rapidly. After it has cooled to a temperature of 70- 

 80 the quart of prepared culture is poured into it, stirred 

 thoroughly and the whole set aside, carefully covered up, for 

 a further growth of the microorganisms. The bacteria 

 develop, and in the course of two days there are obtained sev- 

 eral gallons of a culture well impregnated with the bacteria 

 in question. This material is used as the " starter " for 

 inoculating the body of the cream which is to be ripened. 



This process of building up is, of course, somewhat 

 troublesome. It requires a more or less constant attention on 

 the part of the butter-maker, and has had much to do 

 with preventing the wider extension of the use of pure 

 cultures. For this reason there has been, in recent years, 

 an attempt to put upon the market a form of pure cul- 

 ture which can be used directly in the cream, without this 

 previous building-up process. One or two such commercial 

 products have been introduced to the butter-makers in 

 Europe, the makers claiming that they can be added directly 

 to the cream without any previous cultivation. The tests of 

 such cultures, however, have not been satisfactory. They 

 appear to be made up largely of lactic acid, and the bacteria 

 are not present in sufficient abundance to accomplish very 

 much. At the present time there is no reason for believing 

 that such pure cultures for direct use are of any practical 

 value, and the use of pure cultures at the present time still 

 depends upon this building-up process. 



The starter prepared by this building-up process is added 

 to the cream to be ripened, in proportion of about 10%. 

 After the cream has ripened and is ready for churning a few 

 gallons are removed, to be used as a starter for the next day's 

 cnurning. In this way the starters are carried from day to 

 day for several days. About once a week it is commonly 

 found desirable to build up a new starter from the com- 

 mercial pure culture. 



