Mercaptans

Mercaptans, or spoilage thiols, refer to sulfur compounds formed when hydrogen sulfide reacts with ethanol and other wine constituents. Heavier and less volatile than the parent gas, they carry aromas of onion, cooked garlic, rubber and drains. Unlike simple reduction, frequently corrected through aeration, this advanced stage resists decanting and requires a controlled copper treatment in the cellar, applied under strict analytical monitoring to avoid stripping desirable thiols.