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 other cheeses, is Brevibacterium linens. As a group, the brevibacteria appear to be natives of two salty environments: the seashore and human skin. Brevibacteria grow at salt concentrations that inhibit most other microbes, up to 15% (seawater is just 3%). Unlike the starter species, the brevibacteria don’t tolerate acid and need oxygen, and grow only on the cheese surface, not inside. The cheesemaker encourages them by wiping the cheese periodically with brine, which causes a characteristic sticky, orange-red “smear” of brevibacteria to develop. (The color comes from a carotene-related pigment; exposure to light usually intensifies the color.) They contribute a more subtle complexity to cheeses that are wiped for only part of the ripening (Gruyère) or are ripened in humid conditions (Camembert). Smear cheeses are so reminiscent of cloistered human skin because both B. linens and its human cousin, B. epidermidis, are very active at breaking down protein into molecules with fishy, sweaty, and garlicky aromas (amines, isovaleric acid, sulfur compounds). These small molecules can diffuse into the cheese and affect both flavor and texture deep inside.