Wine Fault

Reduction

Chemical

Reduction refers to volatile sulfur compounds formed under oxygen-poor conditions, producing rubber, struck match, or cabbage-like aromas. Mild reduction can blow off with aeration; severe cases indicate a chemical fault.

Also known as: Reductive notes, Reductive winemaking fault, Stinky ferment

Typical severity: Medium

Cause

Volatile sulfur compounds (H₂S, mercaptans, disulfides) formed when yeast or wine chemistry lacks adequate oxygen during fermentation or aging.

How it occurs

Overly reductive fermentations, deficient yeast nutrients, heavy lees contact without oxygen, and stainless-steel aging without racking can trap sulfur compounds. Bottle closure can preserve mild reduction.

Prevention

Adequate yeast nutrition, controlled oxygen at key stages, copper fining when appropriate, and early sensory monitoring during fermentation.

Descriptors created

Descriptors reduced

Commonly confused with

Common wine styles

Common grape varieties

Common regions

Related winemaking techniques

Serving implications

Beginner explanation

A struck-match smell on a young white may blow off with decanting — that's mild reduction, not always a permanent fault.

FAQ

Will decanting fix reduction?
Mild reduction often dissipates with aeration. Severe mercaptans or disulfides may persist or worsen with exposure.
Is reductive winemaking always a fault?
Deliberate low-oxygen handling is a technique. The fault is when sulfur compounds exceed acceptable sensory thresholds.

Related ontology entities

See also

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