Castoreum

Leather, birch-tar smoke, warm phenolic. On dilution a dried-fruit sweetness and a bark-like woodiness appear. Harsh when concentrated; at trace level it rounds and warms a base.

Castoreum is not named in the index of the IFRA Standards, 51st Amendment. Any restricted constituent it contains still counts toward the limit for each product category.

In the United States castoreum appears in the GRAS list of natural extractives at 21 CFR 182.50.

The material comes from animals trapped or hunted for fur. Lots need traceability documents for origin and legality. Store dark, sealed and cool.

Beavers carry two castor sacs near the cloaca. These are distinct from the anal glands. The secretion marks territory, and its make-up follows the diet: beavers eat willow and aspen bark, so the secretion is rich in phenolic compounds derived from that bark.

The sacs are dried in air or over smoke, then macerated in ethanol for a tincture or solvent-extracted for a resinoid and absolute. Tinctures are usually aged for months; harshness drops and the leather and dried-fruit notes come forward.

The two sources are the North American beaver (Castor canadensis) and the Eurasian beaver (Castor fiber). Canadian material has long dominated the market. Both species are listed as Least Concern by IUCN, but supply is tied to fur trapping.

In perfumery castoreum anchors leather and chypre structures. Most producers now use reconstitutions built from synthetic molecules. It has also been used in tiny amounts as a food flavouring in the United States, although that use is rare today.