SWEETENED CoNDENSED Mink DEFECTS 243 
duction of milk and factory conditions, gain access to the con- 
densed milk, are largely inhibited and do not ferment the sweet- 
ened condensed milk, there are certain specific forms of bacteria 
and yeast whose growth is not retarded by the concentrated 
sugar solution of this product. Contamination of the condensed 
milk with these specific organisms is usually the result of highly 
unsanitary conditions in the handling of the condensed mulk. 
The products of fermentation depend on the particular type 
and species of micro-organisms involved. In most cases the 
sucrose is the chief constituent attacked, but the lactose, also, 
is capable of gaseous fermentation, though instances of lactose 
fermentation in sweetened condensed milk are not common. 
The gaseous fermentation of lactose is largely caused by 
bacteria, yeast and molds which contain the lactose-splitting 
enzyme “lactase,” which has the power of hydrolizing the lac- 
tose. While the species of organisms which cause lactic acid 
fermentation from lactose are very numerous, those containing 
the enzyme lactase and thereby causing gaseous termentation 
from lactose, are less frequent, at least, as far as their access to 
milk and condensed milk is concerned. It is generally under- 
stood, though not experimentally proven, that species of micro- 
organisms which do not contain the enzyme lactase have no 
gvas-producing action on lactose. 
The great majority of cases of gaseous fermentation ol 
sweetened condensed milk are the result of the action of micro- 
organisms on the sucrose, especially those which contain the 
enzyme “invertase.” The majority of yeasts secrete invertase 
and ferment sucrose, producing alcohol and carbon dioxide to 
the same extent as in the case of glucose fermentations. The 
process is considerably slower, however, especially at the start, 
owing to the fact that inversion of the sucrose must precede 
fermentation. For this reason gaseous fermentations of sweet- 
ened condensed milk do not become noticeable until the product 
is one or several weeks old, 
Contamination with Yeast on the Farm.—-Jn most cases of 
yeast fermentations of sweetened condensed milk, the source of 
contamination lies in the factory. While such contamination 
may and often does occur on the farm, the veast cells, though 
they may be spore-bearing, are destroved by the heat to which 
