108 Dairy Bacteriology. 



To insure these conditions the jars must be thoroughly 

 -cleaned and then sterilized just before use by placing 

 them in cold water and bringing them to the boiling 

 point, or sterilized by a thorough steaming. The sample 

 of milk of a patron must be taken so as to avoid contam- 

 ination from the milk of the other patrons. This can 

 best be done by filling the jars as the milk is poured 

 from the patron's can into the weigh can. In cutting 

 the curds, the knife used must be dipped in hot water 

 between each test to cleanse the same. In short, the 

 test should be carried out with great care so that the 

 tester is certain of the results obtained. 



Other tests for the bacteriological condition of milk 

 will be described in Chapter IX. 



Overcoming abnormal fermentations. The lactic 

 -acid bacteria are often looked upon as normal to milk, 

 and it is certain that they are to be classed as harmful, 

 only as they injure the keeping qualities of milk. In 

 milk designed for butter and cheese their presence is 

 necessary. At times these desirable forms of bacteria 

 may disappear, and be replaced by less desirable 

 types. In one case it was observed that the usual lactic 

 "bacteria had been replaced in a cheese factory supply by 

 an acid-forming organism that produced an intensely 

 fitter taste in the milk, thus rendering the cheese of no 

 value. When such harmful forms appear, they must be 

 overcome, and the normal types of bacteria replaced. A 

 thorough cleaning of the milk utensils, attention to the 

 cattle and all places from which such bacteria may find 

 their way into the milk is often sufficient to cause a dis- 

 appearance of the trouble. If the acid-forming bacteria 

 liave disappeared, the inoculation of the milk with cul- 

 tures in ways later to be discussed is often of advantage. 



