CREAM-RIPENING. 195 
The optimum temperature, or the temperature at which they 
grow best is, according to Russell, from 90° to 95° F. At this 
temperature the germs which cause undesirable results also grow 
most rapidly in cream. Cream contains germs both of the 
desiarble and the undesirable type. At a comparatively low 
temperature (between 60° and 70° F.) the greatest relative 
growth of the desirable germs is produced. Bacteriologists also 
Fic. 128.—Cream-ripening room in the Model Creamery at the 
World’s Exposition, St. Louis, Mo. 
tell us that the casein ferments as a rule thrive better at a 
lower temperature than do the lactic-acid ferments at the same 
temperature. This, keeping in mind that better results are 
obtained by ripening at lower temperatures (60° to 70° F.), 
seems to indicate that the flavoring substances are not formed 
entirely by the action of certain germs producing lactic acid, 
but that the flavoring substances are probably due to the 
joint action of several species. Lactic acid itself does not have 
