Casu marzu or casu fràzigu

Casu marzu o casu frazigu. Foto di Alessandro Sanna, Laore Sardegna

Casu fràzigu—commonly spelled casu marzu, meaning "rotten cheese"—is a distinctive product of the Sardinian dairy industry, characterized by a unique maturation process. It is a pecorino cheese colonized by the larvae of the cheese fly (Piophila casei). Once eggs are laid on the cheese, the larvae hatch and feed on the cheese, triggering intense proteolysis that transforms the cheese's internal structure into a fluid, amber-yellow cream with a strong, pungent flavor. Maturation occurs during the warm months, when the insect's cycle is active; the cheese is opened by removing the top, known as su tappu.

The name varies depending on the area of the island: casu mùchidu, casu modde, casu bèiu, casu fatitu, among others. Similar productions occur throughout the Mediterranean, from the Corsican casgiu merzu to other European regional traditions.

From a regulatory perspective, the production and marketing of casu fràzigu are prohibited by Italian and European regulations—Article 5 of Law No. 283 of 30 April 1962, and the subsequent "Hygiene Package" (EC Regulations Nos. 852, 853, and 854 of 2004 and No. 2073 of 2005)—due to the potential health risks associated with the presence of larvae. To preserve its heritage, the product has been included in the list of Traditional Agri-food Products.

Bibliography

Formaggio e pastoralismo in Sardegna. Storia, cultura, tradizione e innovazione. Nuoro, Ilisso, 2015.
Regione Autonoma della Sardegna, Elenco dei Prodotti Agroalimentari Tradizionali (PAT), 2025.

Update

11/9/2026 - 15:42