What is reductive nose in wine?

Reductive nose is one of those wine faults that sounds worse than it usually is. It occurs when wine develops in an oxygen-starved environment, allowing volatile sulphur compounds (VSCs) to accumulate. The main culprits are hydrogen sulphide (H₂S, rotten eggs), methanethiol (cooked cabbage), and dimethyl sulphide (canned corn, truffle).

Why does it happen? Several reasons. Yeasts that are starved of nitrogen during fermentation produce more H₂S. Wines aged on their lees (dead yeast cells) without regular stirring can go reductive. And closures that block oxygen -- screw caps especially -- can trap these compounds in the bottle.

Here is the good news: mild reduction often disappears with aeration. Pour the wine into a decanter or even just swirl it aggressively in your glass for a few minutes. If the off-smell lifts and reveals clean fruit underneath, you are fine. A persistent stink after 30 minutes of air? That is a more serious fault involving mercaptans and disulphides, which are much harder to blow off.

Sommeliers have a quirky trick for stubborn reduction: drop a clean copper coin into the decanter. Copper reacts with H₂S to form odourless copper sulphide. It actually works for mild cases, though purists may raise an eyebrow.

Interestingly, a touch of reduction can be a positive thing. Those gunflint and struck-match notes in a great Chablis or Sancerre? That is controlled reduction adding complexity. The line between 'interesting minerality' and 'unpleasant fault' is razor-thin.