Noble mould on dry sausages

Noble mould on dry sausages (noble mold, white mould on salami) is the thin white coat of Penicillium moulds on the casing. The FAO meat-processing manual calls it harmless to health and says it gives the sausage its typical look and flavour. But FAO warns straight away that not all moulds are safe: some produce toxins.

The French call this coat «fleur», the flower. The Saucisson de l'Ardèche specification explains why it is there: the fleur slows and evens out drying, keeps a light film of moisture on the casing and prevents a hard crust. It may settle naturally or be added by dipping, and the finished saucisson may be brushed clean.

What happens on the casing? A 2024 review in the journal Foods describes how Penicillium nalgiovense is applied to sausages as a suspension of spores. It forms a thin layer of mycelium that creates a microclimate and limits moisture loss, shields the meat from light and oxygen, slows rancidity and crowds out unwanted microbes. The species most often found on fermented sausages are P. nalgiovense, P. salami, P. chrysogenum and P. nordicum. The first two produce no toxins, while P. nordicum can produce ochratoxin A.

The coat is the rule, not the exception. Spain's RD 474/2014 defines Fuet by its whitish coat, and Chorizo de Cantimpalos in its achorizado and cular formats wears a floury white flora. Lacaune saucisson is sold with or without its fleur, and Auvergne saucisson with a white fleur or in ash. The white film on Polish krakowska sucha, though, is coagulated protein, not mould, and a little surface oil keeps it from forming.

How do you tell normal from spoiled? USDA FSIS calls a thin white coat on dry salami safe, as long as no other mould is present. Black, green or grey patches mean spoilage. For hard salami and dry-cured country hams, FSIS says to scrub the mould off the surface. The 2024 review adds a caution: toxins can migrate inside, so removing the layer does not guarantee safety if toxin-producing species have grown. The EU still sets no mycotoxin limits for meat products.

Why this matters to you: an even white coat on Saucisson sec or fuet is a sign of proper drying, so do not rush to throw it away. Coloured patches are another matter. For more on these sausages see Dry-cured sausages.