Reduction

When Wine Gets Funky
Ever heard of gunpowder or struck matchstick in wine descriptions? It's a thing. Reduction in wine refers to aromas and flavors that develop when wines are exposed to very little oxygen, resulting in the formation of volatile sulfur compounds (VSCs). While sometimes intentional, reduction can also occur as an unwanted fault.

The Science:
During fermentation, stressed yeasts (particularly when lacking nutrients or oxygen) produce hydrogen sulfide and other sulfur compounds. These compounds can evolve during aging, sometimes appearing and disappearing mysteriously. Importantly, reduction isn't simply the opposite of oxidation—wines can actually be both reduced and oxidized simultaneously. These compounds often develop in oxygen-poor environments, with stainless steel tanks being a common culprit due to their completely sealed, oxygen-free nature.

The Good Kind Of Reduction:
Not all reduction is negative. Some winemakers intentionally work with mild reduction to add complexity, such as the prized "matchstick" character in certain Chardonnays. This is sometimes referred to as the Coche-Dury Effect, named after the ultra rare Burgundian producer's signature reductive style. Some VSCs contribute positive elements to traditional method sparkling wines and barrel-aged wines.

Too Much Of A Good Thing:
Common markers of excessive reduction include rotten egg aromas, rubber or burnt match notes, and onion or garlic scents, often accompanied by a hard, angular finish on the palate. Winemakers prevent these issues through proper oxygen management during fermentation. Once present, reduction can sometimes be addressed through aeration or careful use of copper sulfate. For wine drinkers, decanting may help with mild cases, though more severe reduction usually requires professional intervention.

To Sum It All Up...
Reduction in wine is complex and sometimes desirable in small doses, adding complexity and character. However, excessive reduction is considered a fault that can significantly impact wine quality. Understanding reduction helps both winemakers and consumers better appreciate the delicate balance required in quality winemaking.