I08 MODERN METHODS OF TESTING MILK 



peated at intervals of 30 to 40 minutes for 8 hours 

 or more. Under the favorable conditions of tempera- 

 ture, similar to those employed in cheese-making, the 

 organisms present develop readily and reveal their 

 presence in dififerent characteristic ways. The jars 

 are finally opened, any whey present is drained oflf, 

 and the following tests are applied : ( i ) The curd is 

 cut into two pieces. The curd will be solid and free 

 from holes on the cut surfaces, if the milk is not 

 tainted. If it is sjiongy and full of holes, it con- 

 tains those undesirable organisms that produce gases 

 in the curd and injure it for cheese-making, showing 

 in the form of "fioating curds" and "hufify" cheese. 

 The holes arc usually small, their common name be- 

 ing "pin-holes." (2) The curd is examined with ref- 

 erence to any marked disagreeable odors that may 

 be present. Some undesirable organisms reveal their 

 presence by smell without making spongy curd. This 

 may, perhaps, be best perceived by smelling of a 

 freshly cut surface of the curd. Offensive odors are, 

 of course, an undesirable indication. S]:)ecial a])]:)ara- 

 tus for perforniing the test is furnished by dairy-sup- 

 ply houses, but pint fruit-jars and other home-made 

 appliances will answer satisfactorily. 



By this method one can learn what particular lot 

 of milk among several is responsible for undesirable 

 fermentations. Moreover, having traced the source of 

 contamination to a single herd of cows, it is easily 

 possible, by applying the test to single cows, to ascer- 

 tain which individual or individuals may be the source 

 of trouble. 



