2O8 PRACTICAL DAIRY BACTERIOLOGY 



through the cream. 2. The lactic acid bacteria which are espe- 

 cially desired in the cream appear to be most vigorous just be- 

 fore the souring. Before the milk has soured or after it has 

 curdled, they do not seem to have so much power as they do 

 just before curdling. Care should be taken never to allow the 

 material to cool to a temperature much below 65. If it does, 

 undesirable bacteria are liable to grow, and the growth of the 

 desired organisms is checked. 



If a larger amount of starter is needed, for a creamery where 

 there are hundreds of gallons to be ripened, the preparation of 

 a starter must be continued farther. The starter is prepared 

 in exactly the same way up to the last step. Meantime several 

 gallons of cream or skim-milk have been pasteurized, the 

 amount depending upon the size of the churning. This should 

 be cooled to 80 at about the time when the starter prepared 

 according to the last paragraph has become soured. This starter 

 is then poured into the new lot of pasteurized milk or cream, 

 the mixture is covered to keep out the dust, placed at a temper- 

 ature of about 65, and when it has become well soured, it is a 

 starter of sufficient quantity to be used in a vat of hundreds of 

 gallons of cream. This process is spoken of as a "building up 

 process." Evidently the whole process is only a means of in- 

 creasing the number of bacteria by growing the culture in a 

 considerable amount of pasteurized milk. 



The starter thus prepared is added to the cream in varying 

 proportions, the larger the amount the quicker the ripening, a 

 quick ripening being, however, generally undesirable. 1 Some- 

 times as much as I part of the starter to 10 parts of cream is 

 used; in other cases a smaller amount is used and sometimes 

 more. After the cream in the vat, into which the starter has 

 been inoculated, has been ripened for the proper length of time 

 and is ready to churn, a certain quantity of it is removed, placed 

 in a clean can, and set aside to serve as a starter for the next 



1 Dean. Ont. Agr. Col. Exper. Sta., Farm. Rep., 1901. 



