424 MILK AND MILK PRODUCTS 
The undesirable flavors in butter may be due to absorbed odors or 
to products formed in the butter after manufacture. Dyer (1916) 
showed that the undesirable flavors developing in butter held in eold 
storage at a temperature of 0° C. were not due to an oxidation of the fat 
itself. Gas analyses indicated that the quantity of buttermilk left in 
2 3 4 5 6 7 8 
Months in Storage 
Fic. 72.—Diagram Showing Decrease in Bacterial Content of Butter Stored at Dif- 
ferent Temperatures (After Mohler, Washburn and Rogers, 1909.) 
the butter has a relation to the quantity of carbon dioxide formed. 
Rancidity is probably the algebraic sum of a number of factors. 
Milk in the fresh condition is a very suitable medium for bacteria. 
Northrup (1911) studied the longevity of B. typhi in sour milk. Before 
these organisms were destroyed Bacterium lactis acidi had to produce 
