THE RELATION O'F MICROORGANISMS TO BUTTER. 345 



that there is a decomposition of the glycerides with a resulting increase in 

 free acids. It has been shown that this does not always occur; that a 

 butter may be in an advanced state of decomposition and its content in 

 volatile acids not be higher than when fresh. Two types of changes are 

 usually distinguished, rancidity and the appearance of a tallow-like odor. 

 The latter may be due to purely chemical factors, while the former is 

 quite certainly biological. 



Moldy butter is a frequent trouble encountered by the butter maker. 

 Butter itself is not a good substratum for mold growth, but the parch- 

 ment paper in which the butter is wrapped and with which the containers 

 are lined, is an excellent substratum. Air and moisture favor mold 

 growth; hence if the papers and containers are contaminated with mold 

 spores, the butter is likely to reach the market in an objectionable con- 

 dition. Butter tubs are scalded, steamed, soaked in brine, or treated 

 with a dilute solution of formaldehyde, in order to destroy the mold 

 spores present. The most "efficient treatment is to coat the inside of the 

 container with paraffin. This prevents trouble from the container but not 

 from the paper, which, if suspected as the source of trouble, may be treated 

 by heating in water. 



PATHOGENIC BACTERIA IN BUTTER. 



If the milk contains pathogenic bacteria, they are certain to pass into 

 the cream and be incorporated in the butter. It is not believed that 

 butter is an important agent in the distribution of the organisms of 

 tuberculosis and typhoid fever, although both are able to exist in salted 

 butter for over two months. Foot-and mouth-disease may be caused in 

 humans by the use of butter made from the milk of infected animals. 



