Fermentations of Milk. 



59 



The greatest amount of trouble with slimy milk occurs 

 during the warmest weather and in bottled milk that has 

 been kept in a refrigerator. The cream is often slimy, 

 while the lower layers are apparently normal. In other 

 cases the entire mass of milk be- 

 comes thick and viscous. The bac- 

 teria producing the first type are 

 aerobic and grow best at low tem- 

 peratures. Outbreaks of this trou- 

 ble do not usually persist for any 

 length of time, if care is taken to 

 sterilize thoroughly the milk uten- 

 sils. The bacteria causing the trou- 

 ble do not form acid. 



The second type in which the en- 

 tire mass of milk becomes slimy is 

 usually due to bacteria that form 

 acid. The milk is curdled, but the 

 curd instead of b^ ing easily broken 

 up as in the normal acid fermenta- 

 tion is very ropy. This type of fer- 

 mentation is rare. Tn Norway slimy 

 milk is prepared for human food. 

 It has an agreeable acid taste much 

 like the taste of butter-milk. It is 

 very ropy and appears unappetiz- 

 FIG. 11. SLIMY MILK. i ng to one not accustomed to it. In 

 Holland ropy whey, which is pro- 

 duced by much the same kind of bacteria as the Norwe- 

 gian "ropy milk, is used in the making of Edam cheese in 

 order to overcome trouble in handling poor milk, just 

 as the American cheese maker uses lactic acid bacteria 



