Lees are a common factor in the weight and flavor of white and sparkling wines. They’re leftover yeast particles that appear during fermentation.
When a wine ferments, yeast particles break down during a process called autolysis, which yields sugars and amino acids that can affect a wine’s flavor, aroma, and body. The impact of lees on a white or sparkling wine is desirable – they can contribute to the wine’s creaminess and depth by adding flavors of toast, smoke, clove or vanilla, depending on the process, length of time a wine is left “on the lees,” and the type of barrel in which the wine is aged.
Wines can be aged on the lees for anywhere from a few months to several years. You’ll usually see longer lees aging in Champagnes versus, for example, a Chardonnay.
If you’re curious, and you’d like to taste the depth of flavor of a wine left “on the lees,” Check out these selections: