Wine Fault

Acetaldehyde

Additional

Acetaldehyde is an oxidative compound producing bruised apple, nutty, or Sherry-like aromas when elevated in table wines. Sherry flor yeast deliberately manages acetaldehyde; in still table wine it signals uncontrolled oxidation.

Also known as: Ethanal, Aldehyde fault, Sherry-like taint

Typical severity: Medium

Cause

Ethanol oxidation to acetaldehyde under aerobic conditions, often with acetobacter co-occurrence.

How it occurs

Oxygen ingress during aging, weak SO₂, and microbial activity raise acetaldehyde. It can bind as bisulfite adducts, masking detection until wine is aerated.

Prevention

SO₂ management, oxygen-minimal handling, and monitoring aldehyde levels during élevage and before bottling.

Descriptors created

Descriptors reduced

Commonly confused with

Common wine styles

Common grape varieties

Common regions

Related winemaking techniques

Serving implications

Beginner explanation

Acetaldehyde smells like bruised apple or nail polish at high levels — in Sherry it's intentional; in Chardonnay it's a fault.

FAQ

Does decanting reveal acetaldehyde?
Aeration can release bound aldehydes, making the fault more apparent after swirling or decanting.
Is acetaldehyde always bad?
In Fino Sherry and flor-aged wines it defines style. In fresh table wines it indicates oxidative fault.

Related ontology entities

See also

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