combination of propionic and acetic acids and
carbon dioxide gas. The acids’ aromatic
sharpness, together with buttery diacetyl,
contributes to the distinctive flavor of
Emmental, and the carbon dioxide forms
bubbles, or the characteristic “holes.” The
propionibacteria grow slowly, and the
cheesemaker must coddle them along by
ripening the cheese at an unusually high
temperature — around 75ºF/24ºC — for
several weeks. This need for warmth may
reflect the cheese propionibacteria’s original
home, which was probably animal skin. (At
least three other species of propionibacteria
inhabit moist or oily areas of human skin, and
P. acnes takes advantage of plugged oil
glands.)
The Smear Bacteria The bacterium that gives
Münster, Epoisses, Limburger, and other
strong cheeses their pronounced stink, and
contributes more subtly to the flavor of many