(WineFolly) - You might have seen the words “sur lie” on a bottle of Loire white wine. Sur lie translates to “on the lees,” but what exactly are wine lees and what do they do?

What are wine lees?

Lees are leftover yeast particles from autolysis which is the self-destruction of yeast cells by enzymes created from fermentation. As strange as this may seem, lees are used in white and sparkling wines to add beneficial textures and flavors.

What do lees do?

As the yeast cells start to break down during the process of autolysis, they release tiny amounts of sugars (called polysaccharides) and amino acids. The presence of these compounds is sensed on our tongues and palates as a textural weightiness or increased body in the wine. White and sparkling wines that are aged on the lees are often described as creamier, richer, fuller-bodied or with a greater depth and complexity of flavor.

What do lees taste like?

Besides the added textural creaminess, the release of fatty acids (which come from the breakdown of the yeast cell wall) add to the aromas/flavors in wine.

• Sparkling Wines: Traditional method sparkling wines that are aged for extended periods on the lees will have increased flavors of toast, bread-like aromas, cheese or buttermilk-like aromas, floral elderflower-like aromas and sometimes sweet, nutty aromas.
• White Wines: Still white wines will also have increased yeast-like flavors similar to sparkling wines. Additionally, lees aging in oak barrels will extract additional aroma compounds from the wood including sweet, caramel-like notes, smoke-like flavors, clove flavors, umami or meaty flavors, and vanilla.

How long are wines aged on lees?

Depending on the wine, lees aging can occur for as little as 3–4 months or as long as several years...