Reduction
/ree-DUK-shun/Sulfur compounds from lack of oxygen, creating off-odors.
Full Definition
Reduction is the opposite of oxidation - chemical reactions in oxygen-absent conditions producing sulfur compounds. Mild reduction smells of struck match or rubber; severe reduction of rotten eggs or sewage. It can occur from screwcap closure, minimal oxygen winemaking, or sulfur residues. Often blows off with aeration.