Wine Fault

Brettanomyces

Microbial

Brettanomyces is a spoilage yeast that produces earthy, leathery, and barnyard-like aromas in wine. At low levels some drinkers accept subtle savory notes in Rhône and Burgundy reds, but pronounced Brett reads as a microbial fault that masks fruit and terroir.

Also known as: Brett, Brett yeast, Dekkera

Typical severity: Medium

Cause

Spoilage yeast (Brettanomyces bruxellensis and related strains) metabolizing hydroxycinnamic acids into volatile phenols.

How it occurs

Brett survives in barrel wood, transfer lines, and unsanitized equipment. It grows slowly during aging when alcohol, pH, and free SO₂ are insufficient to suppress it — especially in wines with residual sugar or low intervention.

Prevention

Rigorous cellar hygiene, steam-cleaning barrels, maintaining adequate free SO₂, pH management, and early detection via sensory and lab testing. Some producers sterile-filter before bottling.

Descriptors created

Descriptors reduced

Commonly confused with

Common wine styles

Common grape varieties

Common regions

Related winemaking techniques

Serving implications

Beginner explanation

Brett smells like barnyard, leather, or band-aids — not the same as intentional earthy terroir. A little divides opinion; a lot is clearly faulty.

FAQ

Can you smell Brett before opening the bottle?
Often yes — barnyard or leather notes are apparent on the nose once the wine is poured, though low levels can be subtle.
Is Brett always a fault?
In formal judging, yes at high levels. Some traditional styles tolerate trace Brett, but it remains a microbial spoilage organism.

Related ontology entities

See also

Fault identification guidance reflects common wine education practice and may vary by wine style, age, and context.