Which fungus is used to make the blue cheese Roquefort?

Penicillium roqueforti is the fungus used to make the blue cheese Roquefort.

This blue-green mold is a widespread saprotrophic species in the genus Penicillium. Cheese makers introduce selected cultures into the curd, then pierce the developing cheese so oxygen can reach the mold. P. roqueforti grows along these air channels, creating Roquefort’s characteristic blue veins and contributing much of its sharp aroma and flavor.

Roquefort is made from sheep’s milk and aged in the natural caves of Roquefort-sur-Soulzon in southern France. The cheese’s protected designation means that the name Roquefort is reserved for cheese produced under specified regional and manufacturing conditions. A traditional legend says that mold transformed an abandoned piece of sheep’s-milk cheese in a cave, though the story is folklore rather than established history.

A common mix-up is assuming every blue cheese uses the same mold. Stilton and several other cheeses also use P. roqueforti, while some cheeses, including certain Gorgonzolas, use Penicillium glaucum instead. Despite its name, this fungus does not produce penicillin.